Phase-change material layers, methods of forming the same, phase-change memory devices having the same, and methods of forming phase-change memory devices

PRIORITY STATEMENT

0001This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 2006-65562 filed on Jul. 12, 2006 in the Korean Patent Office, the entire contents of which are herein incorporated by reference.

BACKGROUND

00021. Field

0003Example embodiments may relate to phase-change material layers, methods of forming a phase-change material layer, and/or methods of manufacturing a memory device including a phase-change material layer. For example, example embodiments may relate a phase-change material layer that may be formed by using a plasma at a relatively lower temperature, a method using a plasma at a relatively lower temperature, and/or a method of manufacturing a phase-change memory device including a phase-change material layer using a plasma.

00042. Description of the Related Art

0005Semiconductor memory devices may be generally divided into volatile semiconductor memory devices such as dynamic random access memory (DRAM) devices or static random access memory (SRAM) devices, and non-volatile semiconductor memory devices such as flash memory devices or electrically erasable programmable read only memory (EEPROM) devices. The volatile semiconductor memory device may lose stored data if power is discontinued. The non-volatile semiconductor memory device may retain stored data even though power is discontinued.

0006Among related art non-volatile semiconductor memory devices, flash memory devices have been used in various electronic apparatuses such as digital cameras, cellular phones, MP3 players, and/or similar devices. Programming and/or reading may require relatively longer amounts of time for flash memory devices. Semiconductor memory device such as a magnetic random access memory (MRAM) device, a ferroelectric random access memory (FRAM) device, and/or a phase-change random access memory (PRAM) device may require smaller amounts of time to program and/or read.

0007The phase-change memory device may store information by exploiting resistance differences between amorphous phases and crystalline phases of a phase-change material layer including a chalcogenide compound such as germanium-antimony-tellurium (GST) or the like. The PRAM device may store data as “0” and “1” using a reversible phase transition of the phase-change material layer. An amorphous phase of the phase-change material layer may have a larger resistance than a crystalline phase of the phase-change material layer. In the PRAM device, a transistor formed on a substrate may provide a phase-change material layer with a reset current (I_reset) for changing the phase of the phase-change material layer from a crystalline state into an amorphous state. The transistor may also supply the phase-change material layer with a set current (I_set) for changing the phase of the phase-change material layer from the amorphous state into the crystalline state. Related art PRAM devices and related art methods of manufacturing a PRAM device may include forming a phase-change material layer of GST through a sputtering process and/or an evaporation process.

0008In related art method of manufacturing the PRAM device, the phase-change material layer including GST may be formed by a physical vapor deposition (PVD) process such as a sputtering process and/or an evaporation process, but phase-change material formation rate in these processes may not be properly controlled. Phase-change material layers may not have a dense crystalline structure and/or not have a face centered cubic (FCC) crystalline structure, such an FCC structure providing better electrical characteristics. Further, concentration ratios among germanium, antimony, and/or tellurium may not be adequately controlled if the phase-change material layer is formed by the PVD process. The phase-change material layers formed by the PVD process may not have adequate phase transition if a set current is applied to the phase-change material layer. Phase-change material formation rate may be relatively slower such that manufacturing cost and time may be higher.

SUMMARY

0009Example embodiments may provide a phase-change material layer having a composition obtained using a plasma at a low temperature to ensure improved characteristics.

0010Example embodiments may provide a method of forming a phase-change material layer using a plasma at a low temperature.

0011Example embodiments may provide a method of manufacturing a phase-change memory device having improved electrical characteristics using a plasma at a low temperature.

0012Example embodiments may provide a method of forming a phase-change material layer including loading an object into a reaction chamber, generating a plasma including, for example, helium, in the reaction chamber, forming a first material layer on the object by providing a first source gas including a first material in the reaction chamber, and/or forming a first composite material layer on the object by providing a second source gas including a second material in the reaction chamber. The first composite material layer may include the first material and/or the second material. A third material layer may then be formed on the first composite material layer by providing a third source gas including a third material in the reaction chamber. A second composite material layer may be formed on the first composite material layer by providing a fourth source gas including a fourth material in the reaction chamber. The second composite material layer may include the third material and/or the fourth material.

0013Generating a plasma in example embodiments may include introducing, for example, a helium gas may be into the reaction chamber. The helium gas may be pre-heated, and then the pre-heated helium gas may be stabilized. A helium plasma may be generated from the stabilized helium gas. For example, the helium gas may be pre-heated for about 30 seconds to about 90 seconds, and the pre-heated helium gas may be stabilized for about 1 second to about 4 seconds. The helium plasma may be generated by applying a power of about 20 Watts to about 200 Watts to the stabilized helium gas for about 5 seconds to about 15 seconds.

0014In example embodiments, the plasma may further include, for example, an argon plasma. The argon plasma may be generated by simultaneously introducing, for example, an argon gas and a helium gas into the reaction chamber. Flow rate ratio between the helium gas and the argon gas may be in a range of about 1.0:0.06 to about 1.0:1.5.

0015In example embodiments, the first material may include germanium (Ge) and/or the third material may include antimony (Sb). For example, the first material may include Ge(iso-Propane)₃H, GeCl₄, Ge(Methane)₄, Ge(Methane)₄N₃, Ge(Ethane)₄, Ge(Methane)₃N(Ethane)₂, Ge(iso-Butane)₃H, Ge(n-Butane)₄, Sb(GeEthane₃)₃and/or Ge(Cyclopropane)₂. These may be used alone or in combination. Additionally, the third material may include Sb(iso-Butane)₃, SbCl₃, SbCl₅, Sb(Methane₃), Sb(Ethane)₃, Sb(iso-Propane)₃, Sb(t-Butane)₃, Sb[N(Methane)₂]₃and/or Sb(Cyclopropane)₃. These may be used alone or in combination.

0016In example embodiments, the first source gas may be heated to about 100° C. to about 300° C. for about 0.1 second to about 2.0 seconds. The first material layer may be formed by applying a power of about 20 Watts to about 200 Watts at a pressure of about 1 Torr to about 5 Torr.

0017In example embodiments, the first through fourth source gases may each be provided with carrier gases including, for example, argon.

0018In example embodiments, a first purge gas including helium, argon, and/or another noble gas may be introduced into the reaction chamber before providing the second source gas.

0019In example embodiments, the second and/or fourth material may include tellurium (Te). For example, the second and/or the fourth materials may each include Te(iso-Butane)₂, TeCl₄, Te(Methane)₂, Te(Ethane)₂, Te(n-Propane)₂, Te(iso-Propane)₂and/or Te(t-Butane)₂. These may be used alone or in any combination.

0020In example embodiments, the second and the fourth source gases may be heated to about 100° C. to about 300° C. for about 0.1 second to about 1 second. Additionally, the first and the second composite material layers may be formed by applying a power of about 20 Watts to about 200 Watts at a pressure of about 1 Torr to about 5 Torr.

0021In example embodiments, the third source gas may be heated to about 100° C. to about 300° C. for about 0.1 second to about 1 second. The third material layer may be formed by applying a power of about 20 Watts to about 200 Watts at a pressure of about 1 Torr to about 5 Torr.

0022In example embodiments, a second purge gas including helium, argon, and/or another noble gas may be introduced into the reaction chamber before providing the third and fourth source gas.

0023In example embodiments, a fourth purge gas including helium, argon, and/or another noble gas may be introduced into the reaction chamber after forming the second composite material layer.

0024In example embodiments, the first material may include antimony and the third material may include germanium.

0025In example embodiments, the first composite material and the second composite material layer may be repeated at least once. The first composite material and the second composite material layer may be alternately formed.

0026Example embodiments may provide a method of forming a phase-change material layer including germanium-antimony-tellurium. In example methods of forming phase-change material layers, a germanium layer may be formed on a substrate loaded in a reaction chamber by placing a substrate in a first source gas including germanium under an atmosphere including a helium, argon, and/or other noble gas plasma. A germanium-tellurium layer may be formed by providing a second source gas including tellurium. An antimony layer may be formed on the germanium-tellurium layer by a third source gas including antimony interacting with the germanium-tellurium layer. An antimony-tellurium layer may be formed on the germanium-tellurium layer by a fourth source gas including tellurium interacting with the antimony layer.

0027In example embodiments, the helium, argon, and/or other noble gas plasma may be generated by introducing a helium, argon, and/or other noble gas into a reaction chamber, pre-heating the gases, stabilizing the pre-heated gases, and/or generating the plasma from the stabilized gases.

0028In example embodiments, a first purge gas including helium, argon, and/or other noble gas may be introduced into the reaction chamber for about 0.1 second to about 2 seconds before providing the second source gas. A second purge gas including helium, argon, and/or other noble gas may be introduced into the reaction chamber for about 0.1 second to about 2 seconds before providing the third source gas. A third purge gas including helium, argon, and/or other noble gas may be introduced into the reaction chamber for about 0.1 second to about 2 seconds before providing the fourth source gas. A fourth purge gas including helium, argon, and/or other noble gas may be introduced into the reaction chamber for about 0.1 second to about 2 seconds after forming the antimony-tellurium layer.

0029In example embodiments, the second source gas may be substantially similar to the fourth source gas.

0030In example embodiments, the phase-change material layer may include about 1 to about 6 percent by weight carbon, about 15 to about 30 percent by weight germanium, about 15 to about 25 percent by weight antimony, and/or tellurium for the remaining weight percentage.

0031Example embodiments may provide a phase-change material layer including carbon-germanium-antimony-tellurium. The phase-change material layer may include about 1 to about 6 percent by weight carbon, about 15 to about 30 percent by weight germanium, about 15 to about 25 percent by weight antimony, and/or tellurium for the remaining weight percentage.

0032In example embodiments, the phase-change material layer may have a face centered cubic (FCC) crystalline structure grown along a plane of (200).

0033In example embodiments, the phase-change material layer may include uniform grains having sizes of about 2 mm to about 15 mm.

0034Example embodiments may provide a method of manufacturing a phase-change memory device. In example methods of manufacturing phase-change memory devices, a lower electrode may be formed on a substrate. A phase-change material layer including a germanium-antimony-tellurium (GST) compound may be formed on the lower electrode. An upper electrode may be formed on the phase-change material layer. The phase-change material layer may include a first layer formed on the lower electrode by a first source gas including a first material on the lower electrode under an atmosphere including, for example, a helium, argon, and/or other noble gas plasma. A first composite material layer may be formed on the lower electrode by a second source gas including a second material on the first layer. The first composite material layer may include the first material and the second material. A third material layer may be formed on the first composite material layer by a third source gas including a third material on the first composite material layer. A second composite material layer may be formed on the first composite material layer by a fourth source gas including a fourth material on the third layer. The second composite material layer may include the third material and the fourth material.

0035In example embodiments, a contact region may be formed on a portion of the substrate. The lower electrode may be electrically connected to the contact region.

0036Example embodiments may include a phase-change material layer including carbon that may be formed at a lower temperature under a helium, argon, and/or other noble gas plasma environment by providing source gases for layer formation. A phase-change material layer including carbon may have a crystalline structure such as an FCC structure. The phase-change material layer including carbon may have improved electrical characteristics, for example, a lower reset current and/or an improved set resistance. Manufacturing costs and/or time may be reduced because the phase-change material layer including carbon may be obtained by a simpler process.

BRIEF DESCRIPTION OF THE DRAWINGS

0037The above and/or other features and advantages of example embodiments will become more apparent by describing them in detail with reference to the attached drawings. The accompanying drawings are intended to depict example embodiments and should not be interpreted to limit the intended scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.

0038<figref idref="DRAWINGS">FIG. 1</figref> is a flow chart illustrating an example method of forming a phase-change material layer.

0039<figref idref="DRAWINGS">FIG. 2</figref> is a timing diagram illustrating an example method of forming the phase-change material layer.

0040<figref idref="DRAWINGS">FIG. 3</figref> is a graph illustrating content peaks in three different example embodiment phase-change material layers formed by differing flow rates of helium gas and pressures for forming a helium plasma.

0041<figref idref="DRAWINGS">FIG. 4</figref> is a graph comparing crystalline structures of related art phase-change material layers and phase-change material layers in example embodiments.

0042<figref idref="DRAWINGS">FIG. 5</figref> illustrates electron microscopic pictures showing plan crystalline structures of carbon-containing phase-change material layers according to example embodiments.

0043<figref idref="DRAWINGS">FIG. 6</figref> illustrates electron microscopic pictures showing cross-sectional crystalline structures of carbon-containing phase-change material layers in example embodiments.

0044<figref idref="DRAWINGS">FIG. 7</figref> is a graph illustrating resistances of the carbon-containing phase-change material layers versus flow rate of Helium in example embodiments.

0045<figref idref="DRAWINGS">FIG. 8</figref> illustrates electron microscopic pictures showing plan crystalline structures of carbon-containing phase-change material layers of further example embodiments.

0046<figref idref="DRAWINGS">FIG. 9</figref> illustrates electron microscopic pictures showing cross-sectional crystalline structures of the carbon-containing phase-change material layers of further example embodiments.

0047<figref idref="DRAWINGS">FIG. 10</figref> is a graph illustrating resistances of the carbon-containing phase-change material layers versus pressure in further example embodiments.

0048FIGS. <b>11</b> to <b>18</b> are cross-sectional views illustrating example methods of manufacturing a phase-change memory device.

0049FIGS. <b>19</b> to <b>23</b> are cross-sectional views illustrating a further example methods of manufacturing a phase-change memory device.

DESCRIPTION OF EXAMPLE EMBODIMENTS

0050Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

0051Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures.

0052It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

0053It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).

0054The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

0055It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon functionality and/or acts involved.

0056The present invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.

0057It will be understood that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like reference numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

0058It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

0059Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

0060The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

0061Example embodiments are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present invention.

0062Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

0063<figref idref="DRAWINGS">FIG. 1</figref> is a flow chart illustrating an example method of forming a phase-change material layer, and <figref idref="DRAWINGS">FIG. 2</figref> is a timing diagram illustrating the example method of forming the phase-change material layer in <figref idref="DRAWINGS">FIG. 1</figref>.

0064As shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, after loading an object into a reaction chamber, a plasma may be generated in the reaction chamber in step S<b>10</b>. A phase-change material layer may be formed on the object, which may be a semiconductor substrate such as a silicon substrate, a silicon-on-insulator (SOI) substrate, a single crystalline metal oxide substrate, and/or any suitable object. For example, the object may be a single crystalline aluminum oxide (Al₂O₃) substrate and/or a single crystalline strontium titanium oxide (SrTiO₃) substrate. The object may include an electrode, a conductive layer, a conductive pattern, an insulation layer, an insulation pattern, and/or any other suitable electronic component. The phase-change material layer may be formed to contact the object or may be formed to not contact the object by interposing the electrode, the conductive layer, the conductive pattern, the insulation layer, the insulation pattern, and/or any other component between the object and phase-change material layer.

0065In example embodiments, the plasma formed over the object may include a helium (He) plasma. In order to generate the helium plasma in the reaction chamber, a helium gas may be introduced into the reaction chamber at a flow rate of about 200 standard cubic centimeters per minute (sccm) to about 800 sccm. For example, the helium gas may be provided onto the object at a flow rate of about 300 sccm to about 500 sccm.

0066In example embodiments of the present invention, the plasma formed in the reaction chamber may include an argon (Ar) and helium plasma. An argon gas may be introduced into the reaction chamber at a flow rate of about 50 sccm to about 300 sccm to thereby generate the argon plasma over the object in the reaction chamber. Flow rate ratio between the helium gas and the argon gas may be in a range of 1:0.06 to about 1:1.5. For example, the flow rate ratio between the helium gas and the argon gas may be about 1:0.1 to about 1:1.

0067Helium/argon gas introduced to the reaction chamber may be pre-heated for about 30 to about 90 seconds and then stabilized for about 1 second to about 3 seconds. For example, the helium/argon gas may be pre-heated for about 60 seconds, and the pre-heated helium/argon gas may then be stabilized for about 2 seconds. A power of about 20 Watts to about 200 Watts may be applied to the stabilized helium/argon gas for about 5 to about 15 seconds, thereby generating the helium/argon plasma over the object in the reaction chamber. For example, a power of about 30 Watts to about 50 Watts may be applied to the stabilized helium/argon gas for about 10 seconds to generate the helium/argon plasma in the reaction chamber. The method illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref> may be referred as a plasma-assisted chemical vapor deposition (CVD) method, in which a plasma is continuously applied in the reaction chamber during formation of various layers on an object. The helium/argon plasma may be continuously formed in the reaction chamber during formation of the phase-change material layer on the object.

0068A purge gas may be introduced into the reaction chamber after forming the helium/argon plasma in the reaction chamber. The purge gas may include a helium gas and/or an argon gas. The purge gas may remove remaining helium/argon plasma from the reaction chamber. The purge gas may be provided into the reaction chamber for about 1 second to about 3 seconds. For example, the purge gas may be introduced into the reaction chamber for about 2 seconds.

0069As illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in step S<b>20</b>, the object may be exposed to a first source gas introduced into the reaction chamber including a first material for a first time T<b>1</b> after forming the helium/argon plasma in the reaction chamber. The first source gas may be provided from a first source gas canister together with a first carrier gas. The first source gas canister may be kept at a room temperature.

0070The first carrier gas may include an inactive gas such as argon, nitrogen, and/or any noble gas. The first carrier gas may be introduced to the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the flow rate of the first carrier gas may be in a range of about 100 sccm.

0071The first source gas including the first material may be introduced to the reaction chamber for the first time T<b>1</b>, which may be in a range of about 0.1 second to about 2 seconds. For example, the object may be exposed to the first source gas for about 1 second. The first material in the first source gas may be chemically absorbed, deposited, and/or chemisorbed onto the object under a relatively lower pressure of about 1 Torr to about 5 Torr by applying a power of about 20 Watts to about 200 Watts. For example, the first material may be chemisorbed on the object under a relatively lower pressure of about 3 Torr by applying a power of about 30 Watts to about 50 Watts. Because the first material in the first source gas may be chemisorbed on the object using the helium/argon plasma, the first material may be chemisorbed on the object at a low temperature of about 100° C. to about 300° C. For example, the first material in the first source gas may be chemisorbed onto the object at a lower temperature of about 200° C. In chemisorbing the first material onto the object, the reaction chamber may have a temperature of about 100° C. to about 200° C. For example, the reaction chamber may have a temperature of about 150° C. while chemisorbing the first material on the object.

0072The first material in the first source gas may include, for example, germanium (Ge) and/or Antimony (Sb). For example, the first material may include Ge(iso-Propane)₃H, GeCl₄, Ge(Methane)₄, Ge(Methane)₄N₃, Ge(Ethane)₄, Ge(Methane)₃N(Ethane)₂, Ge(iso-Butane₃)H, Ge(n-Butane)₄, Sb(GeEthane₃)₃, Ge(Cyclopropane)₂, and/or another suitable material. These materials may be used alone or in any combination. Table 1 shows types and characteristics of different materials that include germanium if used as the first material employed in example embodiments. <tables id="TABLE-US-00001" num="1"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217PT" align="center" /><thead><row><entry namest="1" nameend="1" align="center">TABLE 1</entry></row></thead><tbody valign="top"><row><entry /></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>(Values are approximate)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="49PT" align="left" /><colspec colname="2" colwidth="28PT" align="center" /><colspec colname="3" colwidth="28PT" align="center" /><colspec colname="4" colwidth="35PT" align="center" /><colspec colname="5" colwidth="77PT" align="left" /><tbody valign="top"><row><entry /><entry>Melting</entry><entry>Boiling</entry><entry /><entry /></row><row><entry /><entry>Point</entry><entry>Point</entry><entry>Molecular</entry></row><row><entry>Type</entry><entry>[° C.]</entry><entry>[° C.]</entry><entry>Weight</entry><entry>Property</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="49PT" align="left" /><colspec colname="2" colwidth="28PT" align="char" char="." /><colspec colname="3" colwidth="28PT" align="char" char="." /><colspec colname="4" colwidth="35PT" align="center" /><colspec colname="5" colwidth="77PT" align="left" /><tbody valign="top"><row><entry>GeCl₄</entry><entry>−49.5</entry><entry>83.1</entry><entry>214.40</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(Me)₄</entry><entry>−88.0</entry><entry>43.4</entry><entry>132.73</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(Me)₄N₃</entry><entry>−65.0</entry><entry>136.0</entry><entry>159.71</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(Et)₄</entry><entry>−90.0</entry><entry>165.0</entry><entry>188.84</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(Me)₃NEt₂</entry><entry>&lt;10.0</entry><entry>138.0</entry><entry>189.82</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Sb(GeMe₃)₃</entry><entry>12.0</entry><entry>—</entry><entry>474.83</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(i-Bu)4</entry><entry>−73.0</entry><entry>225.0</entry><entry>301.05</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Sb(GeEt₃)₃</entry><entry>&lt;10.0</entry><entry>157.0</entry><entry>683.71</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Ge(Cp)₂</entry><entry>25.0&lt;</entry><entry>—</entry><entry>202.78</entry><entry>Yellow solid</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0073If the first material in the first source gas includes germanium, the first material may be chemisorbed onto the object so that a germanium layer may be formed as a first material layer on the object. Similarly, if the first material in the first gas source includes antimony, the first material may be chemisorbed onto the object so that an antimony layer may be formed as the first material layer on the object.

0074As illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in step S<b>30</b>, a first purge gas may be introduced into the reaction chamber for a second time T<b>2</b> after forming the first material layer on the object. The first purge gas may be introduced into the reaction chamber for the second time T<b>2</b>, which may be in a range of about 0.1 second to about 2 seconds. The first purge gas may include an inactive gas such as argon, nitrogen, and/or another inert gas. For example, the first purge gas may be introduced into the reaction chamber for about 1.0 second. The first purge gas may be introduced into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the first purge gas may be introduced into the reaction chamber at a flow rate of about 100 sccm.

0075The first purge gas may remove any remaining, non-chemisorbed first material and first gas from the reaction chamber. For example, the first purge gas may remove a portion of the first material merely physically absorbed, or physisorbed, and not chemisorbed and may further remove any stray portion of the first material from the reaction chamber.

0076In step S<b>40</b>, the first material layer formed on the object may be exposed to a second source gas introduced into the reaction chamber including a second material for about a third time T<b>3</b> after providing the first purge gas. The second source gas may be provided from a second source gas canister. The second source gas canister may have a temperature of about 30° C. to about 40° C. The second source gas may be introduced with a second carrier gas. The second carrier gas may be introduced into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the second carrier gas may be introduced into the reaction chamber at a flow rate of about 100 sccm. The second carrier gas may include, for example, an argon gas and/or another inert gas.

0077The second material in the second source gas may include tellurium (Te). The second source gas may be introduced and flow for the third time T<b>3</b>, which may be in a range of about 0.1 second to about 1 second. For example, the third time T<b>3</b> may be about 0.4 to about 0.8 seconds. Examples of the second material may include Te(iso-Butane)₂, TeCl₄, Te(Methane)₂, Te(Ethane)₂, Te(n-Propane)₂, Te(iso-Propane)₂, Te(t-Butane)₂, and/or another suitable material. These materials may be used alone or in any combination. Table 2 shows types and characteristics of different materials that include tellurium if used as the first material employed in example embodiments. <tables id="TABLE-US-00002" num="2"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217PT" align="center" /><thead><row><entry namest="1" nameend="1" align="center">TABLE 2</entry></row></thead><tbody valign="top"><row><entry /></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>(Values are approximate)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="OFFSET" colwidth="14PT" align="left" /><colspec colname="1" colwidth="35PT" align="left" /><colspec colname="2" colwidth="70PT" align="center" /><colspec colname="3" colwidth="49PT" align="center" /><colspec colname="4" colwidth="49PT" align="center" /><tbody valign="top"><row><entry /><entry /><entry>Melting Point</entry><entry>Boiling Point</entry><entry>Molecular</entry></row><row><entry /><entry>Type</entry><entry>[° C.]</entry><entry>[° C.]</entry><entry>Weight</entry></row><row><entry /><entry namest="OFFSET" nameend="4" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="OFFSET" colwidth="14PT" align="left" /><colspec colname="1" colwidth="35PT" align="left" /><colspec colname="2" colwidth="70PT" align="char" char="." /><colspec colname="3" colwidth="49PT" align="center" /><colspec colname="4" colwidth="49PT" align="center" /><tbody valign="top"><row><entry /><entry>TeCl₄</entry><entry>−224</entry><entry>380</entry><entry>269.41</entry></row><row><entry /><entry>Te(Me)₂</entry><entry>−10</entry><entry>—</entry><entry>157.68</entry></row><row><entry /><entry>Te(Et)₂</entry><entry>—</entry><entry>—</entry><entry>185.72</entry></row><row><entry /><entry>Te(nPr)₂</entry><entry>—</entry><entry>—</entry><entry>213.77</entry></row><row><entry /><entry>Te(tBu)₂</entry><entry>—</entry><entry>—</entry><entry>241.83</entry></row><row><entry /><entry>Te(iPr)₂</entry><entry>—</entry><entry>—</entry><entry>213.77</entry></row><row><entry /><entry namest="OFFSET" nameend="4" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0078The second material in the second source gas may chemically react with the first material layer at a relatively lower temperature of about 100° C. to about 300° C. and a relatively lower pressure of about 1 Torr to about 5 Torr. A first composite material layer including the first material and the second material may be formed on the object due to the reaction between the second material and the first material layer.

0079The first composite material layer may further include carbon by providing an additional source gas including carbon together with the second source gas. Alternatively, an organic ligand included in the first material and/or the second material may correspond to carbon included in the first composite material layer.

0080When the second material chemically reacts with the first material layer, a power of about 20 Watts to about 200 Watts may be applied to the reaction chamber. For example, the first composite material layer may be formed by applying a power of about 20 Watts to about 50 Watts.

0081If the first material includes germanium and the second material contains tellurium, the first composite material layer may include germanium-tellurium (Ge—Te) by a chemical reaction between tellurium in the second material and germanium in the first material. Thus, the first composite material layer including the first and the second materials may correspond to a germanium-tellurium layer. Alternatively, the first composite material may correspond to a carbon-containing germanium-tellurium layer.

0082The first time T<b>1</b> of the first source gas and the third time T<b>3</b> of the second source gas may be adjusted to control concentration ratio of germanium and tellurium in the first composite material layer. A concentration ratio between germanium and tellurium included in the first composite material layer may be controlled by the flow rate of the helium gas that forms the helium plasma in the reaction chamber.

0083As illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in step S<b>50</b>, a second purge gas may be introduced into the reaction chamber for a fourth time T<b>4</b> after forming the first composite material layer on the object. The second purge gas may be provided into the reaction chamber for the fourth time T<b>4</b>, which may be in a range of about 0.1 second to about 2 seconds. For example, the second purge gas including an argon gas and/or a helium gas may be introduced into the reaction chamber for about 1 second. The second purge gas may be introduced into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the second purge gas may be provided into the reaction chamber at a flow rate of about 100 sccm.

0084The second purge gas may remove non-reacted second material from the reaction chamber. That is, the second purge gas may remove any of the second material that is not chemically reacted with the first material layer.

0085In step S<b>60</b>, a third source gas including a third material may be introduced to the reaction chamber for a fifth time T<b>5</b> after introducing the second purge gas to the reaction chamber. The first composite material layer may be exposed to the third source gas, which may be supplied from a third source gas canister together with a third carrier gas. The third source gas canister may have a temperature of about 30° C. to about 50° C. The third carrier gas may include an inactive gas such as argon, nitrogen, and/or another inert gas. The third carrier gas may flow into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the third carrier gas may flow into the reaction chamber at a flow rate of about 100 sccm.

0086The first composite material layer may be exposed to the third source gas for the fifth time T<b>5</b>, which may be in a range of about 0.1 second to about 2 seconds, thereby forming a third material layer on the first composite material layer. For example, the third source gas may be introduced into the reaction chamber for about 0.4 to about 0.8 seconds. Additionally, the third material layer may be formed on the first composite material layer at a relatively lower pressure of about 1 Torr to about 5 Torr by applying a power of about 20 Watts to about 200 Watts. For example, the third material layer may be formed on the first composite material layer under a relatively lower pressure of about 3 Torr by applying a power of about 30 Watts to about 50 Watts.

0087As described above, because the third material may chemically react with the first composite material layer using the helium/argon plasma, the third material layer may be formed on the first composite material layer at a relatively lower temperature of about 100° C. to about 300° C. For example, the third material layer may be formed on the first composite material layer at a relatively lower temperature of about 200° C. During formation of the third material layer, the reaction chamber may have a temperature of about 100° C. to about 200° C. For example, the interior of the reaction chamber may have a temperature of about 150° C.

0088The third material in the third source gas may include antimony (Sb). For example, the third material may include Sb(iso-Butane)₃, SbCl₃, SbCl₅, Sb(Methane)₃, Sb(Ethane)₃, Sb(n-Propane)₃, Sb(t-Butane)₃, Sb[N(Methane)₂]₃, Sb(Cyclopropane)₃, and/or another suitable antimony material. These materials may be used alone or any combination. The following Table 3 shows approximate types and characteristics of different materials that may include antimony and may be used as the third material in the present embodiment. <tables id="TABLE-US-00003" num="3"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217PT" align="center" /><thead><row><entry namest="1" nameend="1" align="center">TABLE 3</entry></row></thead><tbody valign="top"><row><entry /></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>(Values approximate)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="49PT" align="left" /><colspec colname="2" colwidth="28PT" align="center" /><colspec colname="3" colwidth="28PT" align="center" /><colspec colname="4" colwidth="35PT" align="center" /><colspec colname="5" colwidth="77PT" align="left" /><tbody valign="top"><row><entry /><entry>Melting</entry><entry>Boiling</entry><entry /><entry /></row><row><entry /><entry>Point</entry><entry>Point</entry><entry>Molecular</entry></row><row><entry>Type</entry><entry>[° C.]</entry><entry>[° C.]</entry><entry>Weight</entry><entry>Property</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="49PT" align="left" /><colspec colname="2" colwidth="28PT" align="char" char="." /><colspec colname="3" colwidth="28PT" align="char" char="." /><colspec colname="4" colwidth="35PT" align="center" /><colspec colname="5" colwidth="77PT" align="left" /><tbody valign="top"><row><entry>SbCl₃</entry><entry>73.4</entry><entry>283</entry><entry>228.11</entry><entry>—</entry></row><row><entry>SbCl₅</entry><entry>2.8</entry><entry>79</entry><entry>299.02</entry><entry>—</entry></row><row><entry>Sb(Me)₃</entry><entry>−87.6</entry><entry>80.6</entry><entry>166.86</entry><entry>Pyrophoric</entry></row><row><entry>Sb(Et)₃</entry><entry>—</entry><entry>156</entry><entry>208.94</entry><entry>Pyrophoric</entry></row><row><entry>Sb(nPr)₃</entry><entry>—</entry><entry>100</entry><entry>251.02</entry><entry>Pyrophoric</entry></row><row><entry>Sb(tBu)₃</entry><entry>&lt;10</entry><entry>102</entry><entry>293.10</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Sb[N(Me)₂]₃</entry><entry>—</entry><entry>32</entry><entry>253.99</entry><entry>Sensitive to air/moisture</entry></row><row><entry>Sb(Cp)₃</entry><entry>56</entry><entry>—</entry><entry>—</entry><entry>Sensitive to air/moisture</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0089If the third material in the third source gas includes antimony, the third material layer formed on the first composite material layer may be an antimony layer. Alternatively, if the first material and the third material include antimony and germanium, respectively, the third material in the third source gas may include germanium, and the third material layer may be a germanium layer.

0090As illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in step S<b>70</b>, a third purge gas may be introduced to the reaction chamber for a sixth time T<b>6</b> after forming the third material layer on the first composite material layer. The third purge gas may flow into the reaction chamber for the sixth time T<b>6</b>, which may be in a range of about 0.1 second to about 2 seconds. For example, the third purge gas including an argon and/or helium gas may be flow into the reaction chamber for about 1 second. The third purge gas may flow into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the third purge gas may flow into the reaction chamber at a flow rate of about 100 sccm. The third purge gas may remove any non-chemisorbed third material from the reaction chamber. That is, the third purge gas may purge any excess portion of the third material that has not chemically reacted with the first composite material layer.

0091In step S<b>80</b>, the third material layer may be exposed to a fourth source gas including a fourth material introduced into the reaction chamber for a seventh time T<b>7</b> after purging the reaction chamber using the third purge gas. The fourth material in the fourth source gas may include tellurium. Examples of the fourth material may include Te(iso-Butane)₂, TeCl₄, Te(Methane)₂, Te(Ethane)₂, Te(n-Propane)₂, Te(iso-Propane)₂, Te(t-Butane)₂, and/or another tellurium material. These materials may be used alone or in any combination. The fourth source gas may be provided from a fourth source gas canister having a temperature of about 30° C. to about 40° C. The second and the fourth source gases may be provided from the same source gas canister. The fourth source gas may be fed into the reaction chamber together with a fourth carrier gas. The fourth carrier gas may be introduced into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the fourth carrier gas including, for example, an argon gas may be introduced into the reaction chamber at a flow rate of about 100 sccm.

0092The third material layer may be exposed to the fourth source gas for the seventh time T<b>7</b>, which may be in a range of about 0.1 second to about 1 second. For example, the fourth source gas including the fourth material may be introduced into the reaction chamber for about 0.4 to about 0.8 seconds. The fourth material may chemically react with the third material layer at a relatively lower temperature of about 100° C. to about 300° C. and a relatively lower pressure of about 1 Torr to about 5 Torr, and a second composite material layer including the third and/or the fourth materials may be formed on the first composite material layer. During formation of the second composite material layer, a power of about 20 Watts to about 200 Watts may be applied to the reaction chamber. For example, the second composite material layer may be formed on the first composite material layer by applying a power of about 30 Watts to about 50 Watts.

0093When the third material includes antimony and the fourth material includes tellurium, the second composite material layer may include antimony-tellurium due to a chemical reaction between antimony in the third material layer and tellurium in the fourth source gas. Alternatively, the second composite material layer may include carbon substantially similar to the first composite material layer. The second composite material layer may be a carbon-containing antimony-tellurium layer. The phase-change material layer including germanium-antimony-tellurium and/or carbon-containing germanium-antimony-tellurium may thus be formed on an object.

0094In example methods, the concentration of antimony and/or tellurium in the second composite material layer may be easily adjusted by controlling the fifth time T<b>5</b> of the third source gas and/or the seventh time T<b>7</b> of the fourth source gas. Additionally, carbon concentration in the second composite material layer may be adjusted by controlling the flow rate of the helium gas for forming the helium plasma.

0095The phase-change material layer may include, for example, about 1 to about 6 percent by weight of carbon, about 15 to about 30 percent by weight of germanium, about 15 to about 25 percent by weight of antimony, and about 39 to about 69 percent by weight of tellurium.

0096As illustrated in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, in step S<b>90</b>, a fourth purge gas may be introduced into the reaction chamber for an eighth time T<b>8</b> after forming the phase-change material layer on the object. The fourth purge gas may be introduced into the reaction chamber for the eighth time T<b>8</b>, which may be in a range of about 0.1 second to about 2 seconds. For example, the fourth purge gas including, for example, an argon gas, may flow into the reaction chamber for about 1 second. The fourth purge gas may flow into the reaction chamber at a flow rate of about 50 sccm to about 200 sccm. For example, the fourth purge gas may flow into the reaction chamber at a flow rate of about 100 sccm. The fourth purge gas may remove any remaining non-reacted fourth material from the reaction chamber. For example, the fourth gas may purge a portion of the fourth material that has not chemically reacted with the third material layer.

0097It should be understood that this description is for illustration purposes, and is not intended to limit the scope of the present general inventive concept. The materials including germanium, antimony, and tellurium may be applied in other orders and/or sequences. For example, a material including antimony may be applied first, a material including tellurium second, a material including germanium third, and the material including tellurium fourth. Other orders may also be used.

0098Germanium, tellurium, and antimony concentration ratios in the phase-change material layer containing carbon may be adjusted by controlling the feeding time T<b>1</b> of the first source gas, the feeding time T<b>3</b> of the second source gas, the feeding time T<b>5</b> of the third source gas, and/or the feeding time T<b>7</b> of the fourth source gas. Further, carbon content of the phase-change material layer may be controlled by adjusting the flow rate of the helium gas for the helium plasma and/or the pressure for generating the helium plasma. For example, carbon content of the phase-change material layer may increase if the flow rate of the helium gas for the helium plasma increases. A carbon content of the phase-change material layer may decrease if the pressure for forming the helium plasma increases.

0099The carbon-containing phase-change material layer may include germanium, antimony, and tellurium at a concentration ratio of about 2:2:5 if the feeding time of the source gas including antimony is about 0.6 to about 0.8 seconds and the feeding time of the source gas including tellurium is about 0.6 to about 0.8 seconds. If the carbon-containing phase-change material layer has about a 2:2:5 concentration ratio among germanium, antimony, and tellurium, the phase-change material layer may have a FCC crystalline structure and/or improved electrical characteristics. The carbon-containing phase-change material layer may also undergo phase transition if the carbon-containing phase-change material layer includes germanium, antimony, and tellurium in a concentration ratio of about 2:2:5.

0100<figref idref="DRAWINGS">FIG. 3</figref> is a graph illustrating content peaks in three different phase-change material layers formed by differing flow rates of helium gas and pressures for forming a helium plasma. In <figref idref="DRAWINGS">FIG. 3</figref>, “AX” indicates content peaks of carbon, germanium, antimony and tellurium in a first phase-change material layer formed under process conditions including a pressure of about 2 Torr, a flow rate of a helium gas of about 600 sccm, and a power of about 30 Watts. “BX” represents content peaks of carbon, germanium, antimony, and tellurium in a second phase-change material layer formed under process conditions including a pressure of about 3 Torr, a flow rate of a helium gas of about 500 sccm, and a power of about 30 Watts. “CX′” denotes content peaks of carbon, germanium, antimony, and tellurium in a third phase-change material layer formed under process conditions including a pressure of about 2 Torr, a flow rate of a hydrogen gas of about 500 sccm, and a power of about 30 Watts.

0101As illustrated in <figref idref="DRAWINGS">FIG. 3</figref>, the first and the second phase-change material layers AX and BX may include above 2 percent by weight of carbon if the first and the second phase-change material layers are formed using helium plasmas. However, the third phase-change material layer CX may not include carbon because the third phase-change material layer is formed using a hydrogen plasma. The first phase-change material layer may include about 2.91 percent by weight of carbon, and the second phase-change material layer may include about 2.69 percent by weight of carbon. Thus, the content of carbon in the phase-change material layer may increase as the flow rate of the helium gas increases, whereas pressure for forming the helium plasma decreases. If carbon content of the phase-change material layer increases, the phase-change material layer may have improved set resistance.

0102As described above, example embodiment phase-change material layers including the first and the second composite material layers may be formed on the object using example methods described with reference to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>. As illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, the phase-change material layer may achieve a thickness and adjusted concentration ratio by repeating a first unit process I to form the first composite material layer and a second unit process II to form the second composite material layer. For example, if the first unit process I and the second unit process II are alternately repeated about fifty times, example embodiment phase-change material layers may have a thickness of about 1,000 Å.

0103The first unit process I and the second unit process II may be alternately repeated. Alternatively, more than one first unit process I and/or more than one second unit process II may be alternately repeated. For example, the first unit process I, the second unit process II the first unit process I, and/or the second unit process II may be sequentially executed. In other example methods, the first unit process I, the first unit process I, the second unit process II, the first unit process I, the first unit process I, and the second unit process II may be sequentially executed. In further example methods, the second unit process II, the first unit process I, the second unit process II, and the first unit process I may be sequentially executed. Alternatively, for example, the second unit process II, the second unit process II, the first unit process I, the second unit process II, the second unit process II, and the first unit process I may be sequentially executed. Other sequences of the first and second unit processes I and II may also be performed.

0104The phase-change material layer may have a crystalline structure that may be different from that of the conventional phase-change material layer.

0105Example embodiment phase-change material layers formed through the above-described example method may include about 1 to about 6 percent by weight of carbon, about 15 to about 30 percent by weight of germanium, about 15 to about 25 percent by weight of antimony, and about 39 to about 69 percent by weight of tellurium. Example embodiment phase-change material layers having this composition may have a crystalline structure different from that of related art phase-change material layer. Example embodiment phase-change material layers may have a reduced reset current and/or a decreased set current.

0106<figref idref="DRAWINGS">FIG. 4</figref> is a graph contrasting crystalline structures of related art phase-change material layers and example embodiment phase-change material layers. In <figref idref="DRAWINGS">FIG. 4</figref>, the crystalline structures of the phase-change material layers may be detected using an X-Ray diffractometer. In <figref idref="DRAWINGS">FIG. 4</figref>, “XXV” represents the crystalline structure of related art phase-change material layer, and “XXVI” indicates the crystalline structure of example embodiment phase-change material layers.

0107As illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, example embodiment phase-change material layer XXVI may have a crystalline structure that includes a dominant FCC structure, which may be grown along a (200) plane. FCC structures grown along a (200) plane may not be dominant in related art phase-change material layers XXV. Example embodiment phase-change material layers XXVI may include uniformly grown minute grains to provide improved electrical characteristics. Uniform grains in example embodiment phase-change material layer XXVI may have a denser structure so as to not cause a contact failure in an electrode. For example, the minute grains in example embodiment phase-change material layer XXVI may have sizes in a range of about 2 nm to about 15 nm.

0000Analysis of Crystalline Structures of Phase-Change Material Layers

0108The following example embodiment phase-change material layers were subjected to various experiments with results detailed below.

EXAMPLES 1-4

0109Four different plasmas generated by example process conditions shown in the following Table 4 were used to create each of Examples 1-4, in which a substrate was exposed to a first source gas including germanium for about 1.0 second. Then the substrate was exposed to a second source gas including tellurium for about 0.2 seconds to form a first composite material layer on the substrate in accordance with example methods.

0110The first composite material layer was then exposed to a third source gas including antimony for about 0.4 seconds, and then the first composite layer was exposed to a fourth source gas including tellurium for about 0.2 seconds, forming a second composite layer. In accordance with example methods, a carbon-containing phase-change material layer including germanium, antimony and tellurium was formed on the substrate. <tables id="TABLE-US-00004" num="4"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="4"><colspec colname="OFFSET" colwidth="42PT" align="left" /><colspec colname="1" colwidth="105PT" align="center" /><colspec colname="2" colwidth="28PT" align="center" /><colspec colname="3" colwidth="42PT" align="center" /><thead><row><entry /><entry namest="OFFSET" nameend="3" align="center">TABLE 4</entry></row></thead><tbody valign="top"><row><entry /><entry /></row><row><entry /><entry namest="OFFSET" nameend="3" align="center" rowsep="1" /></row><row><entry /><entry>Flow Rate of Gas for a Plasma</entry><entry>Pressure</entry><entry>RF Power</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="OFFSET" colwidth="42PT" align="left" /><colspec colname="1" colwidth="49PT" align="center" /><colspec colname="2" colwidth="56PT" align="center" /><colspec colname="3" colwidth="28PT" align="center" /><colspec colname="4" colwidth="42PT" align="center" /><tbody valign="top"><row><entry /><entry>Ar [sccm]</entry><entry>He [sccm]</entry><entry>[Torr]</entry><entry>[W]</entry></row><row><entry /><entry namest="OFFSET" nameend="4" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="42PT" align="left" /><colspec colname="2" colwidth="49PT" align="char" char="." /><colspec colname="3" colwidth="56PT" align="char" char="." /><colspec colname="4" colwidth="28PT" align="center" /><colspec colname="5" colwidth="42PT" align="center" /><tbody valign="top"><row><entry>Example 1</entry><entry>300</entry><entry>0</entry><entry>3</entry><entry>30</entry></row><row><entry>Example 2</entry><entry>250</entry><entry>100</entry><entry>3</entry><entry>30</entry></row><row><entry>Example 3</entry><entry>150</entry><entry>300</entry><entry>3</entry><entry>30</entry></row><row><entry>Example 4</entry><entry>50</entry><entry>500</entry><entry>3</entry><entry>30</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0111<figref idref="DRAWINGS">FIG. 5</figref> illustrates electron microscope images of crystalline structures of carbon-containing phase-change material layers in Examples 1 to 4. <figref idref="DRAWINGS">FIG. 6</figref> illustrates electron microscope images of cross-sectional crystalline structures of the carbon-containing phase-change material layers in Examples 1 to 4. In <figref idref="DRAWINGS">FIG. 5</figref>, “XXA,” “”XXB,” “XXC” and “XXD” indicate the plan crystalline structures of carbon-containing phase-change material layers in Examples 1, 2, 3, and 4, respectively. In <figref idref="DRAWINGS">FIG. 6</figref>, “XXa,” “XXb,” “XXc” and “XXd” represent the cross-sectional crystalline structures of carbon-containing phase-change material layers in Examples 1, 2, 3 and 4, respectively.

0112As illustrated in <figref idref="DRAWINGS">FIGS. 5 and 6</figref>, the carbon-containing phase-change material in Examples 3 and 4 may include uniformly grown minute grains and/or have uniform surfaces because the flow rate of the helium gas may be larger than that of the argon gas to allow improved electrical characteristics. If the flow rate of the argon gas is larger than that of the helium gas, the carbon-containing phase-change material layers shown in Examples 1 and 2 may not have uniform minute grains and/or uniform surfaces, and their electrical characteristics may not be improved. Example embodiment carbon-containing phase-change material layers may have an increasingly uniform surface and/or uniformly grown minute grains as the flow rate of the helium gas for forming the plasma increases.

0113<figref idref="DRAWINGS">FIG. 7</figref> is a graph illustrating resistances of the carbon-containing phase-change material layers in Examples 1 to 4.

0114As illustrated in <figref idref="DRAWINGS">FIG. 7</figref>, the carbon-containing phase-change material layers in Examples 1 and 2 have resistances below about 60 mΩ-cm, whereas the carbon-containing phase-change material layers according to Examples 3 and 4 have resistivity above about 100 mΩ-cm. That is, a carbon-containing phase-change material layer may have an increased resistivity as flow rate of helium gas increases because of an increase in carbon content in the carbon-containing phase-change material layer.

EXAMPLES 5 to 8

0115In accordance with example methods, Examples 5 to 8 discussed below were formed by conditions detailed in Table 5 below by generating a plasma over a substrate under process conditions shown in the following Table 5, the substrate was exposed to a first source gas including germanium for about 1 second. Then the substrate was exposed to a second source gas including tellurium for about 0.2 seconds to form a first composite material layer on the substrate.

0116The first composite layer was exposed to a third source gas including antimony was for about 0.4 seconds, and then a second composite material layer was formed on the substrate by a fourth source gas including tellurium exposed to the substrate for about 0.2 seconds. An example embodiment carbon-containing phase-change material layer including germanium, antimony, and tellurium was thus formed on the substrate. <tables id="TABLE-US-00005" num="5"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217PT" align="center" /><thead><row><entry namest="1" nameend="1" align="center">TABLE 5</entry></row></thead><tbody valign="top"><row><entry /></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>(values are approximate)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="4"><colspec colname="OFFSET" colwidth="42PT" align="left" /><colspec colname="1" colwidth="105PT" align="center" /><colspec colname="2" colwidth="28PT" align="center" /><colspec colname="3" colwidth="42PT" align="center" /><tbody valign="top"><row><entry /><entry>Flow Rate of Gas for a Plasma</entry><entry>Pressure</entry><entry>RF Power</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="OFFSET" colwidth="42PT" align="left" /><colspec colname="1" colwidth="49PT" align="center" /><colspec colname="2" colwidth="56PT" align="center" /><colspec colname="3" colwidth="28PT" align="center" /><colspec colname="4" colwidth="42PT" align="center" /><tbody valign="top"><row><entry /><entry>Ar [sccm]</entry><entry>He [sccm]</entry><entry>[Torr]</entry><entry>[W]</entry></row><row><entry /><entry namest="OFFSET" nameend="4" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="5"><colspec colname="1" colwidth="42PT" align="left" /><colspec colname="2" colwidth="49PT" align="center" /><colspec colname="3" colwidth="56PT" align="center" /><colspec colname="4" colwidth="28PT" align="center" /><colspec colname="5" colwidth="42PT" align="center" /><tbody valign="top"><row><entry>Example 5</entry><entry>50</entry><entry>500</entry><entry>2</entry><entry>30</entry></row><row><entry>Example 6</entry><entry>50</entry><entry>500</entry><entry>3</entry><entry>30</entry></row><row><entry>Example 7</entry><entry>50</entry><entry>500</entry><entry>4</entry><entry>30</entry></row><row><entry>Example 8</entry><entry>50</entry><entry>500</entry><entry>5</entry><entry>30</entry></row><row><entry namest="1" nameend="5" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

0117<figref idref="DRAWINGS">FIG. 8</figref> shows electron microscope pictures of plan crystalline structures of carbon-containing phase-change material layers of Examples 5 to 8. <figref idref="DRAWINGS">FIG. 9</figref> shows electron microscope pictures of cross-sectional crystalline structures of the carbon-containing phase-change material layers in Examples 5 to 8.

0118In <figref idref="DRAWINGS">FIG. 8</figref>, “XXE,” “”XXF,” “XXG” and “XXH” show the plan crystalline structures of carbon-containing phase-change material layers in Examples 5-8, respectively. In <figref idref="DRAWINGS">FIG. 9</figref>, “XXe,” “XXf,” “XXg” and “XXh” show the cross-sectional crystalline structures of carbon-containing phase-change material layers in Examples 5-8, respectively.

0119As illustrated in <figref idref="DRAWINGS">FIGS. 8 and 9</figref>, the carbon-containing phase-change material layers in Examples 5 and 6 may have uniform surfaces and/or include uniformly grown minute grains because the pressure is relatively lower. If pressure for forming the plasma is relatively higher, the carbon-containing phase-change material layers shown in Examples 7 and 8 may not have uniform minute grains and/or uniform surfaces, and may have inferior electrical characteristics. A carbon-containing phase-change material layer may have a uniform surface and/or uniformly grown minute grains if the carbon-containing phase-change material layer is formed at a relatively lower pressure.

0120<figref idref="DRAWINGS">FIG. 10</figref> is a graph illustrating resistivity of the carbon-containing phase-change material layers in Examples 5 to 8.

0121As illustrated in <figref idref="DRAWINGS">FIG. 10</figref>, the carbon-containing phase-change material layers in Examples 7 and 8 have resistivity below about 60 mΩ-cm, whereas the carbon-containing phase-change material layers in Examples 5 and 6 have resistivity above about 100 mΩ-cm. Hence, a carbon-containing phase-change material layer may have an increased resistance if the carbon-containing phase-change material layer is formed at a low pressure. That is, carbon content in the carbon-containing phase-change material layer may increase when the carbon-containing phase-change material layer is formed at the relatively lower pressure.

0122FIGS. <b>11</b> to <b>18</b> are cross-sectional views illustrating an example method of manufacturing a phase-change memory device including the example phase change layer described above.

0123As illustrated in <figref idref="DRAWINGS">FIG. 11</figref>, an isolation layer <b>303</b> may be formed on a semiconductor substrate <b>300</b> to define an active region and a field region. The isolation layer <b>303</b> may be formed by an isolation process such as a shallow trench isolation (STI) process, a thermal oxidation process, and/or another suitable process. For example, the isolation layer <b>303</b> may be formed using an oxide such as silicon oxide.

0124Agate insulation layer (not illustrated), a gate conductive layer (not illustrated), and/or a gate mask layer (not illustrated) may be sequentially formed on the active region of the semiconductor substrate <b>300</b>. The gate insulation layer may be formed using an oxide and/or a metal oxide having a higher dielectric constant. For example, the gate insulation layer may be formed using silicon oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium oxide, tantalum oxide, aluminum oxide, and/or another suitable material. The gate insulation layer may be formed by a thermal oxidation process, a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or any other suitable process.

0125The gate conductive layer may be formed using doped polysilicon, a metal, and/or a metal silicide. For example, the gate conductive layer may be formed using tungsten, aluminum, titanium, tantalum, tungsten silicide, titanium silicide, cobalt silicide, and/or another suitable material. The gate conductive layer may be formed by a CVD process, a PECVD process, an ALD process, a sputtering process, and/or another suitable process.

0126The gate mask layer may be formed using a material that may have an etching selectivity relative to the gate conductive layer and/or the gate insulation layer. For example, the gate mask layer may be formed using silicon nitride, silicon oxynitride, and/or titanium oxynitride. The gate mask layer may be formed by a CVD process, a PECVD process, a sputtering process, an ALD process, and/or another suitable method.

0127The gate mask layer, the gate conductive layer, and/or the gate insulation layer may be patterned to form a gate insulation layer pattern <b>306</b>, a gate electrode <b>309</b>, and a gate mask <b>312</b> on the semiconductor substrate <b>300</b>.

0128A first insulation layer (not illustrated) may be formed on the semiconductor substrate <b>300</b> to cover the gate mask <b>312</b>. The first insulation layer may be anisotropically etched to form a gate spacer <b>315</b> on sidewalls of the gate insulation layer pattern <b>306</b>, the gate electrode <b>309</b>, and/or the gate mask <b>312</b>. The gate structure <b>318</b> may include the gate insulation layer pattern <b>306</b>, the gate electrode <b>309</b>, the gate mask <b>312</b>, and/or the gate spacer <b>315</b>.

0129A first contact region <b>321</b> and/or a second contact region <b>324</b> may be formed in portions of the semiconductor substrate <b>300</b> adjacent to the gate structures <b>318</b> by an ion implantation process using the gate structure <b>318</b> as an ion implantation mask. A transistor including the first contact region <b>321</b>, the second contact region <b>324</b>, and the gate structure <b>318</b> may thus be formed on the semiconductor substrate <b>300</b>. For example, the first and the second contact regions <b>321</b> and <b>324</b> may correspond to source/drain regions of the transistors, respectively.

0130As shown in <figref idref="DRAWINGS">FIG. 12</figref>, a first insulating interlayer <b>327</b> may be formed on the semiconductor substrate <b>300</b> to cover the transistor. The first insulating interlayer <b>327</b> may be formed using an oxide such as PSG, BPSG, USG, SOG, TEOS, PE-TEOS, FOX, HDP-CVD oxide, and/or any suitable oxide. The first insulating interlayer <b>327</b> may be formed by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or any suitable process.

0131The first insulating interlayer <b>327</b> may be partially etched by a photolithography process or the like so that first and second lower contact holes <b>330</b> may be formed through the first insulating interlayer <b>327</b>. The first and the second lower contact holes <b>330</b> may expose the first and the second contact regions <b>321</b> and <b>324</b>, respectively.

0132A first conductive layer <b>336</b> may be formed on the first insulating interlayer <b>327</b> to fill up the first and the second lower contact holes <b>330</b>. The first conductive layer <b>336</b> may be formed using doped polysilicon, a metal, a conductive metal nitride, and/or another conductive material. The first conductive layer <b>336</b> may be formed by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a pulse laser deposition (PLD) process, and/or another suitable process. The first conductive layer <b>336</b> may be formed using, for example, tungsten, titanium, titanium nitride, tantalum, tantalum nitride, aluminum, aluminum nitride, titanium aluminum nitride, tungsten nitride, and/or another suitable material. These materials may be used alone or in any combination.

0133As shown in <figref idref="DRAWINGS">FIG. 13</figref>, the first conductive layer <b>336</b> may be partially removed by a chemical mechanical polishing (CMP) process and/or an etch-back process until the first insulating interlayer <b>327</b> is uniformly exposed. Thus, a first lower contact <b>339</b> and a second lower contact <b>342</b> may be formed in the first and the second lower contact holes <b>330</b>, respectively. The first lower contact <b>339</b> may be on the first contact region <b>321</b>, and/or the second lower contact <b>342</b> may be formed on the second contact region <b>324</b>.

0134A second conductive layer <b>345</b> may be formed on the first insulating interlayer <b>327</b> and the first and/or the second lower contacts <b>339</b> and <b>342</b>. The second conductive layer <b>345</b> may be formed using doped polysilicon, a metal, and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable process.

0135After a second insulation layer (not illustrated) is formed on the second conductive layer <b>345</b>, the second insulation layer may be partially etched by a photolithography process or the like. Thus, a first insulation layer pattern <b>348</b> and a second insulation layer pattern <b>349</b> may be formed on the second conductive layer <b>345</b>. The second insulation layer may be formed using a nitride and/or an oxynitride by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process. The first insulation layer pattern <b>348</b> may be formed on a portion of the second conductive layer <b>345</b> under which the first lower contact <b>339</b> may be located. The second insulation layer pattern <b>349</b> may be formed on a portion of the second conductive layer <b>345</b> where the second lower contact <b>342</b> may be located.

0136As illustrated in <figref idref="DRAWINGS">FIG. 14</figref>, the second conductive layer <b>345</b> may be partially etched using the first and the second insulation layer patterns <b>348</b> and <b>349</b> as etching masks, to thereby form combined pads and lower wirings <b>351</b> and <b>352</b>. The pad and lower wiring <b>351</b> may be located on the first lower contact <b>339</b> and/or the first insulating interlayer <b>327</b>. The pad and lower wiring <b>352</b> may be on the second lower contact <b>342</b> and/or the first insulating interlayer <b>327</b>. The pad and lower wiring <b>351</b> may be electrically connected to the first contact region <b>321</b> through the first lower contact <b>339</b>, and/or the pad and lower wiring <b>352</b> may be electrically connected to the second contact region <b>352</b> through the second lower contact <b>342</b>.

0137A second insulating interlayer <b>354</b> may be formed on the first insulating interlayer <b>327</b> and may cover the first and/or the second insulation layer patterns <b>348</b> and <b>349</b>. The second insulating interlayer <b>354</b> may be formed using, for example, an oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process. For example, the second insulating interlayer <b>354</b> may be formed using PSG, BPSG, USG, SOG, TEOS, PE-TEOS, FOX, HDP-CVD oxide, and/or another suitable process.

0138The second insulating interlayer <b>354</b> may be partially removed by an etch-back process and/or a CMP process until the first and the second insulation layer patterns <b>348</b> and <b>349</b> are exposed. For example, the second insulating interlayer <b>354</b> may be etched using a slurry that includes an abrasive such as ceria having a higher etching selectivity between an oxide and a nitride. The first and/or the second insulation layer patterns <b>348</b> and/or <b>349</b> may serve as polishing stop layers. If the second insulating interlayer <b>354</b> is partially removed, the first insulation layer pattern <b>348</b>, and/or the pad <b>351</b> may be buried in the second insulating interlayer <b>354</b>. The second insulation layer pattern <b>349</b> and the lower wiring <b>352</b> may be simultaneously buried in the second insulating interlayer <b>354</b>.

0139A third insulation layer <b>357</b> may be formed on the second insulating interlayer <b>354</b>, the first insulation layer pattern <b>348</b>, and/or the second insulation layer pattern <b>349</b>. The third insulation layer <b>357</b> may be formed using a nitride and/or an oxynitride by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0140A sacrificial layer <b>360</b> including an oxide may be formed on the third insulation layer <b>357</b>. The sacrificial layer <b>360</b> may be formed using oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0141As shown in <figref idref="DRAWINGS">FIG. 15</figref>, the sacrificial layer <b>360</b>, the third insulation layer <b>357</b>, and/or the first insulation layer pattern <b>348</b> may be partially etched by a photolithography process or the like so that an opening <b>361</b> exposing the pad <b>351</b> may be formed.

0142A fourth insulation layer (not illustrated) may be formed on a sidewall of the opening <b>361</b>, the pad <b>351</b>, and/or the sacrificial layer <b>360</b> to fill up the opening <b>361</b>. The fourth insulation layer may be anisotropically etched to form a preliminary spacer <b>363</b> on the sidewall of the opening <b>361</b>. For example, the fourth insulation layer may be formed using silicon nitride and/or another suitable material.

0143A third conductive layer <b>366</b> may be formed on the pad <b>351</b> and the sacrificial layer <b>360</b> to fill up the opening <b>361</b>. The third conductive layer <b>366</b> may be formed using doped polysilicon, a metal, and/or a conductive metal nitride. For example, the third conductive layer <b>366</b> may be formed using tungsten, tungsten nitride, titanium, titanium nitride, tantalum, tantalum nitride, molybdenum nitride, niobium nitride, titanium silicon nitride, aluminum, titanium aluminum nitride, titanium boron nitride, zirconium silicon nitride, tungsten silicon nitride, tungsten boron nitride, zirconium aluminum nitride, molybdenum silicon nitride, molybdenum aluminum nitride, tantalum silicon nitride, tantalum aluminum nitride, and/or any other suitable material. The third conductive layer <b>366</b> may be formed by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable process.

0144As illustrated in <figref idref="DRAWINGS">FIG. 16</figref>, the third conductive layer <b>366</b> may be partially removed by a CMP process or the like until the sacrificial layer <b>360</b> is exposed, thereby forming a preliminary lower electrode <b>372</b> that fills up the opening <b>361</b>. The preliminary spacer <b>369</b> may be between the sidewall of the opening <b>361</b> and a sidewall of the preliminary lower electrode <b>372</b>.

0145The sacrificial layer <b>360</b> may be removed by an etch-back process and/or a CMP process to expose the second insulation layer <b>357</b>. If the sacrificial layer <b>360</b> is removed, the preliminary spacer <b>369</b> and/or the preliminary lower electrode <b>372</b> may each protrude from the second insulation layer <b>357</b> as pillar-like shapes.

0146As illustrated in <figref idref="DRAWINGS">FIG. 17</figref>, upper portions of the preliminary spacer <b>369</b> and the preliminary lower electrode <b>372</b> may be removed by a CMP process to form a lower electrode <b>375</b> and/or a spacer <b>378</b> on the pad <b>351</b>. For example, the lower electrode <b>375</b> and the spacer <b>378</b> may be formed using a slurry that includes an abrasive containing ceria. The CMP process may remove the second insulation layer <b>357</b> and form the lower electrode <b>375</b> and the spacer <b>378</b>.

0147A phase-change material layer <b>384</b> containing carbon may be formed on the second insulation layer <b>357</b>, the lower electrode <b>375</b>, and/or the spacer <b>378</b>. The carbon-containing phase-change material layer <b>384</b> may include a plurality of first composite material layers <b>381</b><i>a </i>and <b>381</b><i>b </i>and a plurality of second composite material layers <b>382</b><i>a </i>and <b>382</b><i>b</i>. Each of the first composite material layers <b>381</b><i>a </i>and <b>381</b><i>b </i>may include germanium, tellurium, and/or carbon, and each of the second composite material layers <b>382</b><i>a </i>and <b>382</b><i>b </i>may include antimony, tellurium, and/or carbon, or vice versa. The carbon-containing phase-change material layer <b>384</b> may thus include germanium-antimony-tellurium. The phase-change material layer <b>384</b> may include about 1 to about 6 percent by weight of carbon, about 15 to about 30 percent by weight of germanium, about 15 to about 25 percent by weight of antimony, and/or about 39 to about 69 percent by weight of tellurium. The phase-change material layer <b>384</b> may be formed by processes substantially similar to the processes described with reference to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>. Although <figref idref="DRAWINGS">FIGS. 17 and 18</figref> may show the first and the second composite layers as physically identifiable, the first and the second composite layers may not be physically identifiable. In other words, the phase-change material layer <b>384</b> may appear as a substantially homogenous layer having a substantially uniform GST concentration.

0148As illustrated in <figref idref="DRAWINGS">FIG. 18</figref>, a fourth conductive layer (not illustrated) may be formed on the phase-change material layer <b>384</b>. The fourth conductive layer may be formed of doped polysilicon, a metal, and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable process. The fourth conductive layer and/or the phase-change material layer <b>384</b> may be partially etched by a photolithography process or the like so that a phase-change material layer pattern <b>387</b> and/or an upper electrode <b>390</b> may be stacked on the lower electrode <b>378</b> and the second insulation layer <b>357</b>. The phase-change material layer pattern <b>387</b> may be on the lower electrode <b>378</b>, the spacer <b>375</b>, and/or the second insulation layer <b>357</b>. The upper electrode <b>390</b> may be on the phase-change material layer pattern <b>387</b>.

0149A third insulating interlayer <b>393</b> may be formed on the second insulation layer <b>357</b> to cover the upper electrode <b>390</b>. The third insulating interlayer <b>393</b> may be formed using an oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0150An upper contact hole <b>394</b> that may expose the upper electrode <b>390</b> may be formed through the third insulating interlayer <b>393</b> by partially etching the third insulating interlayer <b>393</b> through a photolithography process or the like.

0151An upper contact <b>396</b> may be formed on the upper electrode <b>390</b> in the upper contact hole <b>394</b>, and an upper wiring <b>399</b> may be formed on the upper contact <b>396</b> and/or the third insulating interlayer <b>393</b>. The upper contact <b>396</b> and the upper wiring <b>399</b> may be integrally formed. The upper contact <b>396</b> and the upper wiring <b>399</b> may be formed using a metal and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or any other suitable process.

0152FIGS. <b>19</b> to <b>23</b> are cross-sectional views illustrating an example method of manufacturing a phase-change memory device having an example embodiment phase-change layer as described above.

0153As illustrated in <figref idref="DRAWINGS">FIG. 19</figref>, an isolation layer <b>403</b> may be formed on a semiconductor substrate <b>400</b> to define an active region of the semiconductor substrate <b>400</b>.

0154Agate insulation layer (not illustrated), a gate conductive layer (not illustrated), and a gate mask layer (not illustrated) may be sequentially formed on the active region of the semiconductor substrate <b>400</b>. The gate insulation layer, the gate conductive layer, and/or the gate mask layer may be partially etched to form a gate insulation layer pattern <b>406</b>, a gate electrode <b>409</b>, and a gate mask <b>412</b> on the semiconductor substrate <b>400</b>. The gate electrode <b>409</b> may include a single layer structure that has a doped polysilicon layer, a metal layer, and/or a conductive metal nitride layer. Alternatively, the gate electrode <b>409</b> may have a multi-layered structure that includes doped polysilicon layer, a metal layer, a conductive metal nitride layer, and/or a metal silicide layer. The gate mask <b>412</b> may be formed using a material that may have an etching selectivity relative to the gate electrode <b>409</b> and/or the gate insulation layer pattern <b>406</b>.

0155After a first insulation layer (not illustrated) is formed on the semiconductor substrate <b>400</b> to cover the gate mask <b>412</b>, the first insulation layer may be anisotropically etched to form a gate spacer <b>415</b> on sidewalls of the gate insulation layer pattern <b>406</b>, the gate electrode <b>409</b>, and/or the gate mask <b>412</b>. Thus, gate structure <b>418</b> may be formed on the semiconductor substrate <b>400</b>. The gate structure <b>418</b> may include the gate insulation layer pattern <b>406</b>, the gate electrode <b>409</b>, and/or the gate mask <b>412</b>.

0156A first contact region <b>421</b> and/or a second contact region <b>424</b> may be formed at portions of the semiconductor substrate <b>400</b> adjacent to the gate structure <b>418</b>. The first contact region <b>421</b> and the second contact region <b>424</b> may be formed by an ion implantation process using the gate structures <b>418</b> as implantation masks. A transistor including the first contact region <b>421</b>, the second contact region <b>424</b>, and the gate structures <b>418</b> may be thus formed on the semiconductor substrate <b>400</b>.

0157A first insulating interlayer <b>427</b> may be formed on the semiconductor substrate <b>400</b> and may cover the gate structures <b>418</b>. The first insulating interlayer <b>427</b> may be formed using an oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0158The first insulating interlayer <b>427</b> may be partially etched by a photolithography process to form a first lower contact hole (not illustrated) and/or a second lower contact hole (not illustrated) that may partially expose the first contact region <b>421</b> and/or the second contact region <b>424</b>, respectively.

0159A first conductive layer (not illustrated) may be formed on the first insulating interlayer <b>427</b> to fill up the first and/or the second lower contact holes. The first conductive layer may be formed using doped polysilicon, a metal, and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable process.

0160The first conductive layer may be partially removed by a CMP process and/or an etch-back process until the first insulating interlayer <b>427</b> may be exposed such that a first lower contact <b>439</b> and a second lower contact <b>442</b> may be formed in the first lower contact hole and the second lower contact hole. The first lower contact <b>439</b> may be on the first contact region <b>421</b>, and the second lower contact <b>442</b> may be on the second contact region <b>424</b>.

0161As illustrated in <figref idref="DRAWINGS">FIG. 20</figref>, a second conductive layer (not illustrated) and a second insulation layer (not illustrated) may be stacked on the first lower contact <b>439</b>, the second lower contact <b>442</b>, and the first insulating interlayer <b>427</b>. The second insulation layer may be formed using a nitride and/or an oxynitride by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process. The second conductive layer may be formed using doped polysilicon, a metal, and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable process.

0162The second insulation layer may be partially etched by a photolithography process or the like to simultaneously form a first insulation layer pattern <b>445</b> and/or a second insulation layer pattern <b>446</b>. The first insulation layer pattern <b>445</b> may be formed on a portion of the second conductive layer under which the first lower contact <b>439</b> may be located. The second insulation layer pattern <b>446</b> may be formed on a portion of the second conductive layer under which the second lower contact <b>442</b> may be located.

0163The second conductive layer may be etched using the first and/or the second insulation layer patterns <b>445</b> and/or <b>446</b> as etching masks, thereby forming a lower electrode <b>448</b> and/or a lower wiring <b>449</b>. The lower electrode <b>448</b> may be on the first lower contact <b>439</b> and may be electrically connected to the first contact region <b>421</b> through the first lower contact <b>439</b>. The lower wiring <b>449</b> may be formed on the second lower contact <b>442</b> and/or may be electrically connected to the second contact region <b>424</b> through the second lower contact <b>442</b>.

0164A second insulating interlayer <b>451</b> may be formed on the first insulating interlayer <b>427</b> and may cover the first and/or the second insulation layer patterns <b>445</b> and/or <b>446</b>. The second insulating interlayer <b>451</b> may be formed using an oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0165The second insulating interlayer <b>451</b> may be partially removed by an etch-back process and/or a CMP process until the first and the second insulation layer patterns <b>445</b> and <b>446</b> may be exposed. For example, the second insulating interlayer <b>451</b> may be partially removed using a slurry that includes an abrasive containing ceria. The first and/or the second insulation layer patterns <b>445</b> and/or <b>446</b> may serve as polishing stop layers.

0166As illustrated in <figref idref="DRAWINGS">FIG. 21</figref>, a third insulation layer <b>454</b> may be formed on the second insulating interlayer <b>451</b>, the first insulation layer pattern <b>445</b>, and/or the second insulation layer pattern <b>446</b>. The third insulation layer <b>454</b> may be formed using a nitride and/or an oxynitride by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or a similar process.

0167A sacrificial layer <b>457</b> may be formed on the third insulation layer <b>227</b>. The sacrificial layer <b>457</b> may be formed using oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable process.

0168The sacrificial layer <b>457</b>, the third insulation layer <b>451</b>, and/or the first insulation layer pattern <b>445</b> may be partially etched by a photolithography process or the like, thereby forming an opening <b>458</b> that may expose the lower electrode <b>448</b>.

0169After a fourth insulation layer (not illustrated) may be formed on the lower electrode <b>448</b>, a sidewall of the opening <b>458</b>, and/or the sacrificial layer <b>457</b> fill up the opening <b>458</b>. The fourth insulation layer may be anisotropically etched to form a preliminary spacer <b>466</b> on the sidewall of the opening <b>458</b>.

0170A carbon-containing phase-change material layer <b>463</b> may be formed on the lower electrode <b>448</b> and/or the sacrificial layer <b>457</b> to fill up the opening <b>458</b>. The carbon-containing phase-change material layer <b>463</b> may be formed by processes substantially the same as those described with reference to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>. The carbon-containing phase-change material layer <b>463</b> may include a plurality of first composite material layers <b>460</b><i>a </i>and <b>460</b><i>b</i>, and/or a plurality of second composite material layers <b>461</b><i>a </i>and <b>461</b><i>b</i>. Each of the first composite material layers <b>460</b><i>a </i>and <b>460</b><i>b </i>may include germanium, tellurium, and/or carbon, and each of the second composite material layers <b>461</b><i>a </i>and <b>461</b><i>b </i>may include antimony, tellurium and/or carbon, or vice versa. The carbon-containing phase-change material layer <b>463</b> may thus include germanium-antimony-tellurium. FIGS. <b>21</b> to <b>23</b> may show the first and the second composite layers as distinctly identifiable, but the first and second composite layers may not be distinctly identifiable. In other words, the carbon-containing phase-change material layer <b>463</b> may be a substantially homogenous layer having a substantially uniform GST concentration.

0171As illustrated in <figref idref="DRAWINGS">FIG. 22</figref>, the carbon-containing phase-change material layer <b>463</b> may be partially removed by a CMP process until the sacrificial layer <b>457</b> may be exposed so that a preliminary phase-change material layer pattern <b>469</b> may be formed on the lower electrode <b>448</b> in the opening <b>458</b>. The preliminary spacer <b>466</b> may be between the sidewall of the opening <b>458</b> and a sidewall of the preliminary phase-change material layer pattern <b>469</b>.

0172The sacrificial layer <b>457</b> may be removed by an etch-back process and/or a CMP process to expose the third insulation layer <b>454</b>. When the sacrificial layer <b>457</b> is removed, the preliminary spacer <b>466</b> and the preliminary phase-change material layer pattern <b>469</b> may protrude from the third insulation layer <b>454</b> as pillar-like shapes.

0173As illustrated in <figref idref="DRAWINGS">FIG. 23</figref>, upper portions of the preliminary spacer <b>466</b> and/or the preliminary phase-change material layer pattern <b>469</b> may be removed by a CMP process and/or an etch-back process, thereby forming a spacer <b>472</b> and a carbon-containing phase-change material layer pattern <b>475</b> on the lower electrode <b>448</b>. For example, the spacer <b>472</b> and/or the carbon-containing phase-change material layer pattern <b>475</b> may be formed using a slurry that includes an abrasive containing as ceria. When forming the spacer <b>472</b> and the carbon-containing phase-change material layer pattern <b>475</b>, the third insulation layer <b>454</b> may serve as a polishing stop layer and/or an etch stop layer. The CMP process may remove the third insulation layer <b>454</b> while forming the spacer <b>472</b> and the carbon-containing phase-change material layer pattern <b>475</b>.

0174An upper electrode <b>478</b> may be on the third insulation layer <b>454</b>, the spacer <b>472</b>, and/or the carbon-containing phase-change material layer pattern <b>475</b>. The upper electrode <b>478</b> may be formed of doped polysilicon, a metal, and/or a conductive metal nitride by a sputtering process, a CVD process, an ALD process, an electron beam evaporation process, a PLD process, and/or another suitable method.

0175A third insulating interlayer <b>481</b> may be formed on the third insulation layer <b>454</b> and may cover the upper electrode <b>478</b>. The third insulating interlayer <b>481</b> may be formed using oxide by a CVD process, a PECVD process, an ALD process, an HDP-CVD process, and/or another suitable method.

0176After an upper contact hole may expose the upper electrode <b>478</b> through the third insulating interlayer <b>481</b> by partially etching the third insulating interlayer <b>481</b>, an upper contact <b>484</b> may be formed on the upper electrode <b>478</b> in the upper contact hole. An upper wiring <b>487</b> may be formed on the upper contact <b>484</b> and/or the third insulating interlayer <b>481</b>. The upper contact <b>484</b> and the upper wiring <b>487</b> may be integrally and simultaneously formed using doped polysilicon, a metal, and/or a conductive metal nitride.

0177Example embodiments may provide a phase-change material layers including carbon that may be more easily and/or more quickly formed at a lower temperature under a helium/argon plasma environment by providing source gases for various feeding times. Additionally, example embodiment phase-change material layers including carbon may have a desired crystalline structure such as an FCC crystalline structure. Example embodiment phase-change material layers including carbon may have improved electrical characteristics such as a lower reset current and/or an improved set resistance. Further, manufacturing cost and time may be reduced because the phase-change material layer including carbon may be fabricated by a simplified series of processes.

0178Example embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the intended spirit and scope of example embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.