Nonvolatile semiconductor memory and semiconductor memory device

The present invention relates to a non-volatile semiconductor memory using a resistance changing material, and more particularly to a non-volatile semiconductor memory in which an additive element is introduced into a resistance changing film and a semiconductor storage device using this memory.

In recent years, the demand for small and large-capacity information recording / playback devices (storage devices) has been rapidly expanding. Among them, NAND flash memory and small HDD (hard disk drive) have undergone rapid evolution of recording density and have formed a large market. Under these circumstances, some new memory ideas have been proposed with the aim of significantly exceeding the limit of recording density. Among them, a non-volatile semiconductor memory using a resistance changing material having a low resistance state and a high resistance state has attracted attention (see, for example, Non-Patent Documents 1 and 2).

In this type of memory, a voltage pulse can be applied to the resistance changing material to repeatedly change the low resistance state and the high resistance state, and these two states correspond to binary data "0" and "1". Let me record the data. It is expected that multi-value recording will be possible and the recording density will be further increased.

However, when the multi-valued storage or the recording density is increased, there arises a problem that the probability of erroneous switching, in which erroneous information is written when writing or erasing information, increases. In addition, there is an example of introducing an additive element into a film containing carbon as a main component (see, for example, Patent Document 1), but this example is for incorporating Ti in a carbon nanotube, and is described below. The method of introducing the additive element is completely different from the configuration of the present invention described.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-166591</text></patcit><nplcit num="1"><text>P. Vettiger, G. Cross, M. Despont, U. Drechsler, U. Durig, B. Gotsmann, W. Haberle, MA Lants, HE Rothuizen, R. Stutz and GK Binnig, IEEE Trans. Nanotechnology 1, 39 (2002) )</text></nplcit><nplcit num="2"><text>P. Vettiger, T. Albrecht, M. Despont, U. Drechsler, U. Durig, B. Gotsmann, D. Jubin, W. Haberle, MA Lants, HE Rothuizen, R. Stutz, D. Wiesmann and GK Binnig, P Bachtold, G. Cherubini, C. Hagleitner, T. Loeliger, A. Pantazi, H. Pozidis and E. Eleftheriou, in Technical Digest, IEDM03 pp.763-766</text></nplcit>

<p> An object of the present invention is to provide a non-volatile semiconductor memory capable of high-density recording and low power consumption operation, and capable of reducing the probability of erroneous switching, and a semiconductor storage device using this memory.</p>

<p> The non-volatile semiconductor memory according to one aspect of the present invention includes a resistance changing film whose electrical resistivity changes by applying a voltage or energization, and an electrode provided with the resistance changing film sandwiched from the film thickness direction. The changing film is characterized in that at least one additive element selected from hydrogen, boron, nitrogen, fluorine, silicon, and titanium is solid-dissolved in a film containing carbon as a main component. And.</p><p> Further, in the non-volatile semiconductor memory according to another aspect of the present invention, a resistance changing film whose electrical resistivity changes by applying a voltage or energization and an electrode provided by sandwiching the resistance changing film from the film thickness direction are provided. The resistivity change film is formed by solid-dissolving at least one additive element selected from boron, nitrogen, fluorine, silicon, and titanium in a film containing carbon as a main component, and the addition thereof. It is characterized in that the content of additive elements other than hydrogen among the elements is 0.01 to 5 [at.%].</p><p> Further, in the non-volatile semiconductor memory according to another aspect of the present invention, a resistance changing film whose electrical resistivity changes by applying a voltage or energization and an electrode provided by sandwiching the resistance changing film from the film thickness direction are provided. The resistance change film is provided in a film containing carbon as a main component, and Mn, Fe, Co, Cu, Mo, Sr, Ba, Ce, Pr, Nd, Sm, Eu, CrO.₃, AlCl₃, CuCl₂, FeCl₂, FeCl₃, MnCl₂, CrCl₃, ZrCl₂, HfCl₄, ZnCl₂, ZnCl₂, SbCl₅, SbF₅, BiCl₄At least one kind of additive selected from the above is introduced as an interlayer compound of graphite, and the content of the additive is 0.01 to 20 [at.%].</p><p> Further, the semiconductor storage device according to still another aspect of the present invention includes a plurality of word lines arranged in parallel, a plurality of bit lines arranged in parallel so as to intersect the word lines, and the word lines. A resistance changing film, which is provided at each intersection of a word and a bit wire and whose electrical resistivity changes depending on an applied voltage or energization, is provided, and the resistance changing film is composed of hydrogen and boron in a film containing carbon as a main component. , At least one additive element selected from nitrogen, fluorine, silicon, and titanium dissolved in solid form, or Mn, Fe, Co, Cu, Mo, Sr, Ba, Ce, Pr, Nd, Sm, Eu, CrO₃, AlCl₃, CuCl₂, FeCl₂, FeCl₃, MnCl₂, CrCl₃, ZrCl₂, HfCl₄, ZnCl₂, ZnCl₂, SbCl₅, SbF₅, BiCl₄At least one kind of additive selected from the above is introduced as an interlayer compound of graphite, and the content of the additive element or the additive is 0.01 to 20 [at.%]. Further, a non-linear resistance element, a diode, a transistor, or the like is used to select a desired element from a plurality of bit lines and word lines.</p>

<p> According to the present invention, by introducing the above-mentioned additive element into a film containing carbon as a main component, high recording density and low power consumption operation can be realized, and the probability of erroneous switching can be reduced. .. Therefore, there are great industrial merits as a next-generation technology that breaks down the barrier of recording density of the current non-volatile memory.</p>

Hereinafter, the details of the present invention will be described with reference to the illustrated embodiments.

[Construction] FIG. 1 is a diagram showing a circuit configuration of a cross-point type non-volatile semiconductor storage device according to an embodiment of the present invention.

Multiple word lines WL (WLi-1, WLi, WLi + 1) and multiple bit lines BL (BLj-1, BLj, BLj + 1) are arranged in parallel, and the word line WL extends in the X direction. The bit line BL extends in the Y direction. Although only three lines are shown in the figure, a large number of word line WLs and bit line BLs are actually arranged.

One end of the word line WL is connected to the word line driver &amp; decoder 11 via the MOS transistor RSW as the selection switch, and one end of the bit line BL is connected to the bit line via the MOS transistor CSW as the selection switch. It is connected to the driver &amp; decoder &amp; read circuit 12.

A selection signal R (Ri-1, Ri, Ri + 1) for selecting one word line (low) is input to the gate of the MOS transistor RSW, and one is input to the gate of the MOS transistor CSW. The selection signal C (Cj-1, Cj, Cj + 1) for selecting the bit line (column) is input.

Memory cells are arranged at each intersection of the word line WL and the bit line BL. That is, it has a so-called cross-point type cell array structure in which the memory cells 13 are arranged at the intersections of the word line WL and the bit line BL. Further, the memory cell 13 uses a resistance changing material, and a diode 14 for preventing a sneak current during recording / playback is connected in series to the memory cell 13.

FIG. 2 shows the structure of the memory cell array section used in the semiconductor storage device of FIG.

A word line WL and a bit line BL are arranged on the semiconductor substrate 20, and a memory cell 13 and a diode 14 are arranged at the intersection of these wirings. The feature of such a cross-point type cell array structure is that it is not necessary to individually connect MOS transistors to the memory cells 13, which is advantageous for high integration. For example, as shown in FIGS. 3 and 4, memory cells 13 can be stacked to form a memory cell array in a three-dimensional structure.

As shown in FIG. 5, for example, the memory cell 13 is composed of a stack structure of a recording layer 131, a heater layer 132, and a protective layer 133. One memory cell 13 stores 1-bit data. Further, the diode 14 is arranged between the word line WL and the memory cell 13. It is preferable to omit the diode 14 when the set / reset is changed only by the direction of the voltage.

[Write / Erase / Read operation] The write / erase / read operation of the semiconductor storage device of this embodiment will be described with reference to FIGS. 1 to 5.

Here, it is assumed that the memory cell surrounded by the dotted line A in FIG. 1 is selected and the write / erase / read operation is executed for this memory cell.

In the write operation (set operation), a voltage is applied to the selected memory cell, a potential gradient is generated in the memory cell, and a current pulse is passed. Therefore, for example, the potential of the word line WLi is changed to the potential of the bit line BLj. Relatively higher than. If the bit line BLj is a fixed potential (for example, the ground potential), a positive potential may be given to the word line WLi.

The resistance-changing film containing carbon (C) as the main component, which is a recording film, has a graphite component having a fine crystal grain size and a so-called amorphous carbon or amorphous carbon in which the crystal structure without long-range order is disturbed. It is a mixture of carbon materials and exhibits a structure in which a predetermined additive is dispersed in these carbon materials or inserted between carbon lattices or between graphite layers.

Specifically, the resistance changing film of the present embodiment is obtained by solid-solving at least one kind of additive element selected from the following additive element group in a film containing carbon as a main component.

Additive element group: H, B, N, F, Si, Ti Configuration example: CH, CB, CN, CF, C-Si, C-Ti, CHB, CHN, BF₃, SiF₄ These elements are elements that partially dissolve in a film containing carbon as a main component. Solid solution is a state in which even if another atom enters the crystal structure of a certain metal, it retains the shape of the original crystal structure and is mixed in a solid state. The amount of the limit at which other elements can enter as a solid solution is called the solid solution limit, and the solid solution limit depends on the film forming method, the post-formation treatment method, and the like.

Here, the desirable range for the content of the additive element is 0.01 to 20 [at.%]. Further, the desirable range of the content of the additive element other than hydrogen among the additive elements is 0.01 to 5 [at.%].

Further, the resistance change film may be one in which at least one kind of additive selected from the following additives is introduced as an interlayer compound of graphite into a film containing carbon as a main component.

Additives: Mn, Fe, Co, Cu, Mo, Sr, Ba, Ce, Pr, Nd, Sm, Eu, CrO₃, AlCl₃, CuCl₂, FeCl₂, FeCl₃, MnCl₂, CrCl₃, ZrCl₂, HfCl₄, ZnCl₂, ZnCl₂, SbCl₅, SbF₅, BiCl₄ These elements are elements, molecules, and compounds that form so-called graphite interlayer compounds (GICs) that do not dissolve in solid solution and enter between graphite layers. The elements, molecules, and compounds that form GIC with carbon are called intercarrants. GIC is known to form a so-called stage structure. The first stage is a structure in which one layer of graphite, so-called graphene and intercarrant, is alternately laminated, the structure in which two layers of graphene and intercarrant are alternately laminated is the second stage, and the structure in which graphene is three layers and intercar The structure in which the runts are alternately laminated is called the third stage, and the same applies hereinafter.

The concentration of intercarrant is highest in the first stage, and the concentration of intercarrant decreases as the number of stages increases. The concentration varies depending on the atom, molecule, and compound of the intercarland, but 0.01 to 20 [at.%] Was preferable. The stage structure may be a single stage or several stages may be mixed. The analysis of the stage structure can be evaluated by XRD, cross-sectional TEM, etc. Since it is difficult to make a rigorous evaluation using only ultra-thin thin films, we determined the fabrication conditions using bulk graphite and applied those conditions to each thin film.

There are several methods for evaluating the ratio of the graphite component to the amorphous carbon component. For example, evaluation by Raman spectroscopy or direct observation by TEM observation, electrical resistivity, electron spin resonance (ESR), and X-ray diffraction There is a method of estimating from (XRD) and so on.

The graphite component may be a so-called carbon nanotube (CNT) or fullerene in part or in whole. Conversely, part or all of the amorphous material may be so-called carbon nanotubes (CNTs) or fullerenes. CNTs have structures such as single wall (SWCNT), double wall (DWSNT), and multi-wall (MWCNT), and CNTs may contain fullerenes and other elements. Graphene may be used as the graphite component or the amorphous component. Graphene is also known as so-called two-dimensional (2D) graphite.

Since the amorphous component has a lattice constant between the lattice planes of graphite, that is, in the c-axis direction, which is larger than that of graphite, it can be said that it is an aggregate of graphene having a small crystal grain size, but various characteristics may differ. .. Graphene or 2D graphite is ideally a semiconductor or semimetal with a zero bandgap, and the density of states near the Fermi energy changes sharply, so that various properties can change significantly. This was particularly remarkable in the recording film containing carbon (C) containing the additive element of the present embodiment as a main component. Graphene may exhibit properties as a semiconductor having a band gap depending on the shape and periodicity of the end of the crystal lattice. Some CNTs, especially single-walled CNTs (SWCNTs), exhibit metallic properties and some exhibit semiconducting properties.

The electrical resistivity of graphite is known to be very sensitive to its crystallinity. Therefore, the crystal grain size is one of the important factors. Graphite has anisotropy in its crystal structure and various properties in the so-called in-plane direction (xy direction), in which hexagonal lattices with relatively strong bonds are connected, and in the c-axis direction perpendicular to this. Generally, the electrical resistivity in the in-plane direction is very small as compared with that in the c-axis direction. In addition, graphite has a weak binding force in the c-axis direction and cleaves relatively easily between lattice planes in the c-axis direction. The film density is determined by X-ray reflectivity measurement (XRR) or the like. With XRR, the density distribution in the film thickness direction of the film can also be measured. Therefore, the distribution in the film thickness direction can also be evaluated. The densities shown below basically indicate the densities of most regions in the membrane. For example, the interface between the film and the film, the surface of the film, and the like may have different densities from other parts.

Graphite interlayer compounds (GIC) are also positioned as synthetic metals and synthetic conductors, which have a different band structure from graphite in an electronic state. In particular, the low stage structure has a lower electrical resistivity than graphite, and although it is not monotonous, it gradually approaches that of graphite as the number of stages increases. Changes in the proportion of stages in the membrane also appear as changes in the electrical resistivity of the membrane.

At this time, in the selected memory cell surrounded by the dotted line A, the movement of the added element or the vacancies, the change of the band structure, or the combined action of these occurs due to the application of voltage or current. In the case of the former two, for example, the electrical resistivity of the film changes by changing the Fermi energy while keeping the band structure substantially. In extreme cases, the electrical resistivity of the film also changes when the additive elements are localized or vice versa. In the latter case, which is related to the former two, the electrical resistivity of the film changes due to the deformation of the band structure due to the application of voltage or current. As a result, the memory cell changes from the high resistance state to the low resistance state, and the set operation (write) is completed.

At the time of writing, it is preferable that the unselected word lines WLi-1, WLi + 1 and the non-selected bit lines BLj-1, BLj + 1 are all biased to the same potential. Further, it is preferable to precharge all word lines WLi-1, WLi, WLi + 1 and all bit lines BLj-1, BLj, BLj + 1 during standby before writing.

The erase operation (reset operation) uses the Joule heat generated by passing a large current pulse through the selected memory cell and its residual heat, the applied voltage, or the energy of the current itself. Therefore, for example, the potential of the word line WLi. Is relatively higher than the potential of the bit line BLj. If the bit line BLj is a fixed potential (for example, the ground potential), a positive potential may be given to the word line WLi.

At this time, in the selected memory cell surrounded by the dotted line A, a change opposite to the recording state occurs, and the original state is restored again. As a result, the memory cell changes from the low resistance state to the high resistance state, and the reset operation (erasure) is completed.

The read operation is performed by sending a current pulse to a selected memory cell surrounded by the dotted line A and detecting the resistance value of the memory cell. However, the current pulse needs to be a small value so that the material constituting the memory cell does not change the resistance.

For example, the read current (current pulse) generated by the read circuit is passed from the bit line BLj to the memory cell surrounded by the dotted line A, and the resistance value of the memory cell is measured by the read circuit. If the new material already explained is adopted, the difference in resistance value in the set / reset state is 10³The above can be secured.

[Summary] According to the semiconductor storage device using such a non-volatile semiconductor memory, it is possible to realize higher recording density and lower power consumption than the current hard disk and flash memory.

[Other] Although only the semiconductor storage device has been described in this embodiment, the materials and principles proposed in this embodiment can be applied to current recording media such as hard disks and DVDs.

[Example] Next, an example in which some samples are prepared and the resistance difference between the reset (erase) state and the set (write) state is evaluated will be described. Since set reset is a name, other definitions may be used.

As a sample, in addition to the pillar-type cross-point array structure shown in FIGS. 2 to 4, for example, a resistance changing element (nonvolatile semiconductor memory) having an embedded type structure shown in FIG. 6 is used. The results of pillar-type cross-point array structures, embedded-type structures, etc. are illustrated below.

A lower electrode 61 is provided on the Si substrate (semiconductor substrate) 60, and a resistance change film 62 containing carbon as a main component is provided on a part of the electrode 61. An insulating film 63 is embedded in the side portion of the resistance changing film 62. An upper electrode 64 is provided on the resistance changing film 62 and the insulating film 63, and a conductive film 65 is provided on the electrode 64.

For evaluation, a probe pair with a tip diameter of 10 nm or less is used for the electrode pad portion of about 100 μmφ of the sample.

The probe pair is brought into contact with the electrode pad connected to the device, and writing / erasing is performed using one of them. Writing is performed by applying a voltage pulse of 1 to 10 V to the recording layer, for example, with a width of 10 nsec to 100 msec. Erasing was performed by applying a voltage pulse of 0.2 to 8 V to the recording layer, for example, with a width of 50 nsec to 100 μsec. The optimum values for these write and erase pulse widths differ depending on the sample material and structure. Alternatively, it may differ slightly depending on the number of switchings, and optimized conditions are used as the measured characteristics. In addition, DC evaluation is also possible like a semiconductor parameter analyzer.

It also performs a read with the other one of the probe pairs between writes / erases. Reading is performed by applying a voltage pulse having a width of 10 to 1000 nsec and about 0.1 to 0.5 V to the recording layer and measuring the resistance value, current, voltage, etc. of the recording layer (recording bit).

(First Example) In the resistance changing element having the structure shown in FIG. 6, TiN is used as the electrodes 61 and 64 for applying a voltage or current, and SiO is used as the insulating film 63.₂A membrane was used. The upper and lower electrodes 61 and 64 are connected to the measurement pad by W and Al wiring. TiN, W, Al are formed by the sputtering method, and the SiO of the insulating film 63 is formed.₂The film was formed by using the CVD method.

Specifically, as shown in FIG. 7A, a TiN film 61 is formed on the Si substrate 60 by the sputtering method, and SiO is formed on the TiN film 61 by the CVD method.₂After depositing the film 63, SiO is used by the RIE method as shown in FIG. 7 (b).₂A circular opening is provided in a part of the film 63. Subsequently, as shown in FIG. 7 (c), the resistance changing film 62 is deposited by the CVD method or the sputtering method, and then the resistance changing film 62 is polished by the CMP method as shown in FIG. 7 (d) to perform SiO.₂Leave only in the opening of the membrane 63. After that, the resistance change film 62 and SiO₂By depositing the TiN film 64 on the film 63 by a sputtering method and further forming the Al film 65 on the TiN film 64, the structure shown in FIG. 6 can be obtained.

A CVD method, a sputtering method, or the like can be used for forming the resistance changing film 62 having carbon as a main component, which is a resistance changing portion. When forming a resistance change film 62 containing carbon as a main component, a hydrocarbon (CH) -based gas is often used as a reaction gas in the CVD method. Hydrogen H may remain in the film. The residual amount of hydrogen could be varied in the range of 0.01 [at.%] To 20 [at.%], Although it varies depending on the film forming conditions. Further, a desired element can be added to the membrane by mixing the gas containing the element to be added with the reaction gas.

The reaction gas is acetylene (C).₂H₂), Propylene (C₃H₆) Etc. are used, and it can be added to the membrane by partially reacting with hydrogen, nitrogen, oxygen, etc., and added elements using carrier gases such as He, Ar, nitrogen, etc. Can also be introduced. There are several CVD methods, but the plasma CVD (PECVD) method is preferable because it can form a film at a relatively low temperature.

The electrical resistivity of the thin film formed by the CVD method depends on the film formation conditions.^-3It will be more than the order of [Ω cm]. In particular, it is sensitive to the film formation temperature, and a high resistance film can be obtained when the film formation temperature is low. With carbon alone, it is practically difficult to reduce the electrical resistivity of the film by annealing after thin film formation. If this is done, heating of at least 1000 ° C is required, and there is a high risk of damage to other parts of the device. On the other hand, when the above-mentioned elements are added to the carbon (C) of the present embodiment, the electrical resistivity of the film at the time of film formation can be easily lowered, and the resistance can be lowered by annealing. Carbon nanotubes (CNTs) can also be produced using the CVD method, and of course it is easy to add various additives.

On the other hand, when the film is formed by the sputtering method, the sputtering target usually made of graphite or the like is sputtered with an inert gas. Since an inert gas such as Ar is usually used as the sputter gas, hydrogen does not remain in the membrane. When hydrogen is added, it is carried out by mixing hydrogen or a gas containing hydrogen, for example, the above-mentioned hydrocarbon gas, as the reaction gas with the reaction gas. It is possible to mix the elements to be added to the target, and these can be used to add to the membrane. There are several sputtering methods, but magnetron sputtering is excellent in mass productivity. If a graphite-based sputtering target is used, either DC or RF film formation is possible. Depending on the added element and its amount, the material may have high electrical resistance. In such a case, the RF sputtering method can be used. The electrical resistivity of the thin film formed by the sputtering method depends on the film forming conditions.^-1~10^-2It will be more than the order of [Ω cm]. After all, it is sensitive to the film formation temperature, and when the film formation temperature is low, a high resistance film can be obtained.

Boron (B) could be added to carbon (C) from 0.0005 to 20 [at.%] In the resistance change part that changes the electrical resistivity, but from 0.01 [at.%] To 5.0 [at.%] ], Good SW characteristics were obtained. In this example, 0.1 [at.%] Of boron (B) was added to carbon (C). The diameter of the resistance change portion in this embodiment is 0.5 μmφ and the height is 50 nmt. The resistance change part of this embodiment is SiO.₂Since it is embedded in the insulator film of, it has a slightly tapered shape in the vertical direction.

The electrodes include nitrides, carbides or oxides selected from at least one of the following group A, or a mixture of nitrides and oxides, a mixture of nitrides and carbides, and oxides and carbides. It may be composed of a mixture, a nitride, or a mixture of a carbide and an oxide.

Group A: Ti-N, Ti-Si-N, Ta-N, Ta-Si-N, Si-N, Ti-C, Ta-C, Si-C, WN Further, as the electrode, a material composed of at least one of the following group B may be used.

Group B: W, Ta, Si, Ir, Ru, Au, Pt, Pd, Mo, Ni, Cr, Co Further, the electrode may be a laminated film of at least one type of group A and at least one type of group B.

Further, it is desirable that the film thickness of the resistance change film is 5 nm or more and 70 nm or less.

Switching (SW) characteristics were evaluated in a sample of this specification. As a result, the resistance value in the reset state is 10⁷[Ω] stand, resistance value in the set state is 10⁴A good result of [Ω] level was obtained. This means that the probability of false switches can be reduced. We also confirmed that the cycle life can be 10,000 cycles or more. Membrane density is 1.6 [g / cm³]Met.

As described above, in the CVD method, a hydrocarbon (CH) -based gas is often used as the reaction gas, but in this case, hydrogen (H) may remain in the film depending on the film forming conditions. is there. The residual amount of hydrogen varies depending on the film forming conditions, but can be varied in the range of 0.01 at.% To 20 at.%. The same applies to the following examples, but hydrogen (H) is contained in the above range together with an additive element such as boron (B).

(Second Example and Comparative Example) In the configuration of the first embodiment, the amount of boron (B) added is variable to 0.0005,0.01,0.05,0.2,0.5,1.0,5.0,10.0 [at.%], And the diameter of the resistance change portion is 30,2. , 0.2,0.1,0.05 μmφ was prepared and the SW characteristics were evaluated. As shown in (Table 1) below, good SW characteristics were obtained except when the diameter of the resistance change part was large. In the sample in which the amount of boron (B) added is 0.0005 [at.%], There is a large variation between the samples, that is, there is a large variation in the set / reset resistance, set / reset voltage, etc., so that the effect of the invention is as follows. , It is presumed that it is not enough. Further, in the sample in which the amount of boron (B) added is 10.0 [at.%], The amount of precipitation of B is large, and it is difficult to form a film having uniform electrical resistivity or a film having uniform characteristics, which is good. I couldn't get the SW characteristics.<tables num="1"><img file="JP2010141046A_D0001.tif" /></tables>

In (Table 1), NG means that the switch could not be performed, and good means that good set / reset resistance, voltage, etc. were obtained as in the first embodiment. From this result, it can be seen that it is possible to use a resistance change portion having a smaller diameter. When the minimum element size was obtained, the direction in which the current and voltage were applied was about 20 nm, and the direction perpendicular to this was about 10 nm in diameter.

Here, the principle of resistance change of the resistance change film containing carbon (C) as a main component changes depending on various mechanisms depending on the added element and its addition form. Here, for example, the case where boron (B) is added will be described. FIG. 8 shows the dependence of the electrical resistivity at room temperature on the boron (B) concentration when boron (B) is added to carbon (C). As can be seen from this figure, the electrical resistivity increases according to the concentration of boron (B) and shows a maximum value near 0.07 to 1.0 [at.%]. That is, the doped boron (B) has a contribution of forming holes and increasing carriers, and a contribution of lowering the Fermi level by forming carriers and increasing the bandgap. These contributions initially outweigh the contributions that increase the bandgap, thus increasing the electrical resistivity. After that, the electrical resistivity decreases according to the concentration of boron (B), and gradually approaches a constant value.

Therefore, the most desirable amount of boron (B) added is in the range of 0.07 to 1.0 [at.%]. Although this example is an example of boron (B), the additive element that replaces the carbon atom has the same tendency. On the other hand, atoms or molecules of the type inserted between lattice planes in the c-axis direction show different behavior.

In a conventional resistance changing element, a so-called filament path is formed by the inflow and outflow of ions, and the resistance is changed by the movement of ions or the like in the filament or in a portion in contact with another layer. In the case of the resistance change film containing carbon (C) as a main component of the present embodiment, the constituent elements are the same as ionization, and the movement of charged atoms or the like, or the change of the band structure without the movement of atoms, or The main factor is the composite form of both. In the former case, the movement of pores and replacement with additive elements are also included. The resistance changing element naturally becomes smaller due to the miniaturization of the semiconductor element. Therefore, the influence on the electrical resistivity due to the movement of the additive element or the like becomes large.

When boron (B) is added, the lattice constant of the resistance change film containing carbon (C) as a main component expands slightly depending on the concentration of addition. By changing the concentration of B, it is possible to change the stress state with the film in contact. As a result, it is possible to improve the adhesion with other films. Since other additive elements also exhibit similar behavior, this can be used to improve the stress state of the film and the adhesion to other films. The membrane density is 1.3 to 3.0 [g / cm] for a suitable sample.³]Met. Membrane density is 1.3 [g / cm²], The film density changed significantly due to heating during the process, and good characteristics could not be obtained. In addition, the film density is 3.0 [g / cm.³], In the case of more than that, the graphite component is small, so that the electrical resistivity of the film is too high and the resistance cannot be changed. The same was true for the following examples.

(Third Example and Comparative Example) In the configurations of the first and second examples, a sample was prepared in which the amount of hydrogen contained was varied and the diameter of the resistance changing portion was 0.5 μmφ, and the SW characteristics were evaluated. Good SW characteristics were obtained in the range of 0.01 to 20 [at.%] For the hydrogen content. The membrane density is 1.4 to 2.9 [g / cm] for a suitable sample.³]Met.

(Fourth Example and Comparative Example) In the configuration of the first embodiment, the amount of titanium (Ti) added was varied to 0.0005,0.01,0.05,0.5,1.0,5.0 [at.%], And a sample was prepared in which the diameter of the resistance change portion was 0.2 μmφ. Then, the SW characteristics were evaluated. Good SW characteristics were obtained when the amount of added elements was in the range of 0.01 [at.%] To 1.0 [at.%]. The membrane density of a suitable sample is 1.4 to 2.8 [g / cm].³]Met.

In addition, in the sample in which the amount of Ti added is 0.0005 [at.%], The variation between the samples is large, that is, the set / reset resistance, the set / reset voltage, etc. are greatly varied, so that the effect of the invention is not sufficient. I decided. In addition, in a sample with a Ti addition amount of 5.0 [at.%], The amount of Ti deposited increases, the resistance decreases, and it is difficult to form a film with uniform electrical resistivity or a film with uniform characteristics. , Good SW characteristics could not be obtained.

(Fifth Example and Comparative Example) In the configuration of the first embodiment, the amount of silicon (Si) added was varied to 0.0005,0.01,0.05,0.2,1.0,5.0 [at.%], And a sample was prepared in which the diameter of the resistance change portion was 0.2 μmφ. Then, the SW characteristics were evaluated. Good SW characteristics were obtained when the amount of added elements was in the range of 0.01 [at.%] To 1.0 [at.%]. The membrane density is 1.3 to 3.0 [g / cm] for a suitable sample.³]Met.

In addition, in the sample in which the amount of Si added is 0.0005 [at.%], The variation between the samples is large, that is, the set / reset resistance, the set / reset voltage, etc. are greatly varied, so that the effect of the invention is not sufficient. I decided. In addition, in the sample in which the amount of Si added is 5.0 [at.%], The amount of Si deposited is large, and it is difficult to form a film with uniform electrical resistivity or a film with uniform characteristics, and good SW characteristics. I couldn't get it.

(6th Example and Comparative Example) In the configuration of the first embodiment, the amount of nitrogen (N) added was varied to 0.0005,0.01,0.05,0.2,1.0,5.0,10.0 [at.%], And the diameter of the resistance change portion was set to 0.2 μmφ. Was prepared and the SW characteristics were evaluated. The results are the same as in (Table 1), but as shown in (Table 2), good SW characteristics were obtained in the range of 0.01 [at.%] To 5.0 [at.%]. The membrane density is 1.4 to 3.0 [g / cm] for a suitable sample.³]Met.

In the sample in which the amount of nitrogen (N) added is 0.0005 [at.%], There is a large variation between the samples, that is, there is a large variation in the set / reset resistance, set / reset voltage, etc. I decided it wasn't enough. In addition, in the sample in which the amount of nitrogen (N) added is 10.0 [at.%], The amount of N deposited is large, and it is difficult to form a uniform film or a film with uniform characteristics, resulting in good SW characteristics. I couldn't get it.

As an example of improving the stress state of the film and the adhesion with other films by adding nitrogen (N), when the concentration of nitrogen (N) near the portion in contact with the other film is increased, it is concrete. The adhesion of the film was evaluated with and without the addition of 5.0 [at.%] In the region of 1 to 4 nm near the part in contact with other films. A uniform film laminate was formed on the substrate, and the adhesion of the film was measured. The concentration added to the entire film is 1.0 [at.%] Or less. As a result, it was found that when the concentration of nitrogen N in the vicinity of the portion in contact with other membranes was increased, the adhesion of the membrane was improved by 10 times or more as compared with the case where it was not. The film thickness of the portion where the concentration of nitrogen (N) was increased in the vicinity of the portion in contact with the other film was preferably 1 to 20 [%] of the total film thickness. A more suitable region was a film thickness of 1 to 5 [%] of the total film thickness. As the film in contact with the film containing carbon (C) as the main component, Si, SiO₂, TiN, W, etc. were examined and it was good.<tables num="2"><img file="JP2010141046A_D0002.tif" /></tables>

(7th Example and Comparative Example) In the configuration of the first example, the amount of fluorine (F) added was varied to 0.0005,0.01,0.05,0.2,1.0,5.0 [at.%], And a sample was prepared in which the diameter of the resistance change part was 0.5 μmφ. , SW characteristics were evaluated. Good SW characteristics were obtained when the amount of added elements was in the range of 0.01 [at.%] To 1.0 [at.%]. The membrane density is 1.3 to 2.9 [g / cm] for a suitable sample.³]Met.

In the sample in which the amount of fluorine (F) added is 0.0005 [at.%], There is a large variation between the samples, that is, there is a large variation in the set / reset resistance, set / reset voltage, etc., so that the effect of the invention is as follows. , Judged not enough. In addition, in the sample in which the amount of fluorine (F) added is 5.0 [at.%], The amount of precipitation of F is large, the electrical resistivity becomes too high, or it is difficult to form a film with uniform characteristics, which is good. I couldn't get the SW characteristics.

When fluorine (F) is added, the resistance tends to increase. In particular, by increasing the fluorine concentration near the side wall rather than near the center of the resistance change part, the region where the current flows can be made smaller, so a large resistance change can be made. Obtainable. As a result, an element with lower power consumption can be manufactured. If the distance from the center to the side wall is 1 and the distance from the side wall is up to 30% in the region near the side wall where the fluorine concentration is increased, it is difficult for the concentration to become uniform even if the temperature is changed by another process.

As a method of adding fluorine (F), there is a method of adding fluorine (F) to the reaction gas, but there is a case where a fluorine F-based gas is used as the RIE gas. For example CF₄, CHF₃For example, when processing an element, it is possible to react from the side wall at the same time as processing. In this case, it is also possible not to include fluorine (F) in the resistance change portion containing carbon (C) produced first. In this case, the concentration of fluorine (F) gradually changes from the side wall toward the center.

(8th Example and Comparative Example) In the configuration of the first embodiment, SbCl as an intercarant₅Was prepared under the conditions for forming the 1st to 5th stages as GIC. In addition, SbCl₅A sample was prepared in which the diameter of the resistance change part was 0.2 μmφ by varying the concentration of, and the SW characteristics were evaluated. The membrane density is 1.3 to 2.9 [g / cm] for a suitable sample.³]Met. SbCl₅Good SW characteristics were obtained in the range of 0.01 to 20 [at.%].

The compound (intercarrant) that forms the graphite interlayer compound is SbCl.₅Not limited to CrO₃, AlCl₃, CuCl₂, FeCl₂, FeCl₃, MnCl₂, CrCl₃, ZrCl₂, HfCl₄, ZnCl₂, ZnCl₂, SbCl₅, SbF₅, BiCl₄Etc. can be used. In this case as well, good SW characteristics were obtained in the range of 0.01 to 20 [at.%] For the content of the additive.

Further, not limited to the compound, Mn, Fe, Co, Cu, Mo, Sr, Ba, Ce, Pr, Nd, Sm, Eu and the like can be added. In this case as well, good SW characteristics were obtained in the range of 0.01 to 20 [at.%] For the content of the additive element.

As described above, in any of the samples of the first to eighth embodiments, information is recorded (written) and reproduced (read) by controlling the characteristics of the resistance changing film as a non-volatile semiconductor memory. Was made. In addition, it was possible to make it finer than before, it was possible to achieve low power consumption, and it was remarkably excellent in terms of cycle characteristics.

As described above, according to the semiconductor storage device of the present embodiment, high recording density and low power consumption operation can be realized by introducing the above-mentioned additive element into the resistance change film containing carbon as a main component. Moreover, the probability of erroneous switching can be reduced. In addition, the resistance in the ON state is greatly increased, the ON current is also significantly reduced, and operation with extremely small power consumption per cell is possible. This enables simultaneous parallel processing of a large number of cells, and can realize extremely high-speed operation per chip.

Therefore, despite the extremely simple mechanism, it is possible to record information with a recording density that cannot be reached by the conventional technology, and at the same time, it is possible to realize high-speed operation. Therefore, there are great industrial merits as a next-generation technology that breaks down the barrier of recording density of the current non-volatile memory.

(Modification example) The present invention is not limited to the above-described embodiments and examples, and each component can be modified and embodied without departing from the gist thereof. In addition, various inventions can be constructed by appropriately combining a plurality of components disclosed in the above-described embodiment. For example, some components may be deleted from all the components disclosed in the above-described embodiment, or components of different embodiments may be combined as appropriate.

<figref num="1">The figure which shows the circuit structure of the cross-point type non-volatile semiconductor storage device which concerns on one Embodiment of this invention.</figref><figref num="2">The perspective view which shows the structure of the memory cell array part used for the semiconductor storage device of FIG.</figref><figref num="3">The perspective view which shows the example which the memory cells are stacked and the memory cell array is arranged three-dimensionally.</figref><figref num="4">The perspective view which shows the example which the memory cells are stacked and the memory cell array is arranged three-dimensionally.</figref><figref num="5">FIG. 5 is a cross-sectional view showing a configuration of a memory cell including a stack structure of a recording layer, a protective layer, and a heater layer.</figref><figref num="6">FIG. 5 is a cross-sectional view showing a structural example of a sample of a non-volatile semiconductor memory according to an embodiment of the present invention.</figref><figref num="7">The cross-sectional view which shows the manufacturing process of the sample structure example of FIG.</figref><figref num="8">A characteristic diagram showing the relationship between the added element and the amount of change in electrical resistivity.</figref>

Code description

11 ... Wordline Driver &amp; Decoder 12 ... Bit line driver &amp; decoder &amp; read circuit 13 ... memory cell 14 ... diode 20,60 ... Semiconductor substrate 61 ... TiN film (lower electrode) 62 ... Resistance change film 63 ... SiO₂Membrane (insulating film) 64 ... TiN film (upper electrode) 65 ... Al film (conductive film) 131 ... Recording layer 132 ... Heater layer 133 ... Protective layer WL (WLi-1, WLi, WLi + 1) ... word line BL (BLj-1, BLj, BLj + 1) ... bit line