Selective deposition of tungsten

Selective Deposition of Tungsten

SELECTIVE DEPOSITION OF TUNGSTEN

<b>[References to related patent applications]</b>

Statement of the Invention U.S. Provisional Application No. 62/364,185 filed on July 19, 2016 entitled "Selective Deposition of Tungsten" and U.S. Benefit of Provisional Application No. 62/414,408, both incorporated by reference.

The present invention generally relates to methods of manufacturing electronic devices. More specifically, the present invention relates to selective deposition by cyclic exposure or atomic layer deposition (ALD) with hot wire systems. In particular, the present invention relates to the formation of tungsten films by a hot wire cyclic exposure process.

Existing methods for selectively depositing tungsten use disilane (Si₂h₆) and tungsten hexafluoride (WF₆) as a precursor. Haukka et al. disclose such a method in US Pat. No. 8,956,971 in which deposition occurs at a temperature of about 150°C. This deposition may result in the formation of a tungsten layer on the copper surface.

Formation of tungsten by plasma is not yet feasible due to the negative effect of plasma on selectivity. Specifically, plasmons tend to form films on a variety of surfaces without distinguishing between different surfaces.

Formation of the tungsten film can be used to enhance electromigration (EM) resistance. Electromigration resistance can be achieved by forming a metal cap at the interface between the dielectric diffusion barrier layer and the metallic material. However, it is difficult to achieve good selectivity on metallic surfaces compared to dielectric surfaces. Several approaches, such as mild surface treatment including heat treatment or free radical treatment, have been taken to obtain the desired surface termination. However, mild surface treatment may not adequately prepare the desired surface for selective deposition.

Therefore, a method of depositing tungsten or other metal films with high selectivity is desired.

A method of selectively forming a tungsten film is disclosed in accordance with at least one embodiment of the present invention. The method comprises: providing a substrate comprising a first surface and a second surface for processing in a reaction chamber and a hot wire of an excitation species for generating a gas; performing a tungsten precursor pulse/purge step (pulse/purge step) onto the substrate, the step comprising: pulsing a tungsten precursor onto the substrate; and purging excess tungsten precursor from the reaction chamber; and performing a hydrogen precursor pulse/flush step onto the substrate, the step comprising: pulsing the hydrogen precursor material onto the substrate, wherein the hydrogen precursor is excited with a hot wire; and the excess hydrogen precursor is purged from the reaction chamber; wherein the tungsten precursor comprises at least one of the following: tungsten hexafluoride (WF₆); wherein the hydrogen precursor comprises at least one of the following: hydrogen (H₂); wherein the temperature of the filament is greater than about 1000° C.; and wherein the tungsten film is selectively formed on the first surface.

A method of selectively forming a metal-containing film is disclosed in accordance with at least one embodiment of the present invention. The method comprises: providing a substrate for processing in a reaction chamber and a wire element for contacting at least one gas; exposing the substrate to a metal precursor; and exposing the substrate to the gas that has been exposed adjacent to the wire; wherein The substrate includes at least two different materials and the metal film is selectively formed on one of the surfaces.

A method of forming a tungsten film is disclosed according to at least one embodiment of the present invention. The method comprises: providing a substrate for processing in a reaction chamber and a filament for passing at least one gas to the reaction chamber; flowing a tungsten precursor onto the substrate; and flowing a hydrogen precursor onto the substrate, wherein the hydrogen precursor is in contact with the hot wire; and wherein the reaction of the tungsten precursor with the hydrogen precursor in contact with the hot wire forms a tungsten film; and wherein the reaction chamber is a hot wall reaction chamber.

To summarize the objects and advantages achieved by the invention, some of the objects and advantages of the invention have been described above. Of course, it is to be understood that not necessarily all objects or advantages can be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the present invention can be realized or carried out in a manner that achieves or optimizes an advantage or group of advantages taught or suggested by the present invention without necessarily achieving the present invention. Other purposes or advantages that may be taught or suggested.

All such specific examples are intended to be within the scope of the invention disclosed herein. These and other embodiments will become apparent to those skilled in the art from the following detailed description of certain embodiments with reference to the accompanying drawings, the invention not being limited to any embodiment disclosed.

<p>10passivation or pretreatment steps</p><p>100Metal precursor flow steps</p><p>110Metal flow</p><p>120Inert gas flow as appropriate</p><p>200Non-metallic precursor flow steps</p><p>210Non-metal flow</p><p>220Inert gas flow as appropriate</p><p>300first path</p><p>310The second path</p><p>320The third path</p><p>400Structure</p><p>410substrate</p><p>420at least one channel</p><p>430Hot wire metal film</p><p>500structure</p><p>510substrate</p><p>520substrate tungsten insert</p><p>530Hot wire deposited tungsten layer</p><p>540Adhesive layer</p><p>600Metal oxide removal/conversion as the case may be</p><p>700Metal deposition</p><p>710hydrogen pulse/purging</p><p>720Metal Precursor Pulse/Purge</p><p>800Devices</p><p>810tungsten layer</p><p>820cobalt layer 820</p><p>830Silicon dioxide layer</p><p>900semiconductor device</p><p>91012nm W deposition</p><p>920alumina layer</p><p>930structure</p>

These and other features, aspects and advantages disclosed in the present invention are described below with reference to the drawings of certain specific examples, which are intended to illustrate rather than limit the invention.

Figure 1 illustrates a method according to at least one embodiment of the invention.

Figure 2 illustrates a method in accordance with at least one embodiment of the invention.

Figure 3 illustrates a method step in accordance with at least one embodiment of the invention.

Figure 4 illustrates a method step in accordance with at least one embodiment of the invention.

5A and 5B illustrate top views of a structure in accordance with at least one embodiment of the present invention.

6A and 6B illustrate cross-sectional views of a structure in accordance with at least one embodiment of the present invention.

Figure 7 illustrates a method in accordance with at least one embodiment of the invention.

Figure 8 illustrates a method in accordance with at least one embodiment of the invention.

Figure 9 illustrates a method in accordance with at least one embodiment of the invention.

10 illustrates a cross-sectional view of a structure in accordance with at least one embodiment of the invention.

11 illustrates a cross-sectional view of a structure in accordance with at least one embodiment of the present invention.

Although certain examples and embodiments are disclosed below, those skilled in the art will appreciate that the invention extends beyond the specifically disclosed examples and/or uses of the invention and obvious modifications and equivalents thereof. Accordingly, the scope of the disclosed invention should not be limited by the specific disclosed embodiments described below.

Deposition of films may be performed using equipment that utilizes a hot wire or heating filament to generate free radical species from a flowing precursor gas flowing along and near the hot wire. Apparatus as disclosed in US Patent Publication No. 2013/0337653 A, which is incorporated herein by reference. Other heating filaments are disclosed in US Patent Publication No. 2014/0120723 Al. The apparatus may include a reaction chamber, a substrate holder, a gas source, and a heating wire or filament for generating free radicals from a gas flowing along the wire, a heater for heating the substrate holder, and a heater for heating the reaction chamber Room wall heater.

Within the reaction chamber, a substrate holder is arranged to support a substrate. The gas source can provide precursor gas into the reaction chamber. There may also be hot wires or heating wires within the reaction chamber. A heating wire or heating wire may comprise a wire, ribbon or similar structure wound into a coil such that it comprises a plurality of windings extending helically about a central longitudinal axis. The heating wire or wire may comprise a metal such as tungsten or other suitable material capable of withstanding temperatures above 1000°C, above 1200°C, above 1300°C, or above 1500°C. According to at least one embodiment, the flowing gas may be in direct contact with a hot wire or heating wire that passes through a catalytic process of cracking the flowing gas.

The precursor gas may come into direct contact with the heating wire or filaments and then dissociate to form precursor gas radicals, which may then adsorb to the upper substrate or react with the adsorbed precursor on the substrate.

The substrate can comprise a variety of materials. When manufacturing integrated circuits, the substrate typically contains many thin films with different chemical and physical properties. By way of example and not limitation, a substrate may include a silicon-containing layer and a metal layer. In some embodiments, the substrate can include metal carbides. In some embodiments, the substrate can include a conductive oxide. In some embodiments, the substrate is a semiconductor wafer comprising silicon and having a diameter of about 100 mm to about 450 mm, about 200 to about 300 mm. In other embodiments, the substrate may comprise other types of substrates, such as glass; semiconductors; similar compound semiconductors, such as III-V or II-VI semiconductors; oxides; and various other types of substrates, such as non-planar or planar substrates.

In at least one specific example, the substrate may have a first surface comprising metal, which is referred to as a first metal surface or a first metallic surface in the present invention. The first surface may be substantially an elemental metal, such as Cu or Co. In other embodiments, the first surface can include metal nitrides or transition metals. The transition metal may be selected from the following group: Ti, V, Cr, Mn, Nb, Mo, Ru, Rh, Pd, Ag, Au, Hf, Ta, W, Re, Os, Ir and Pt. In some embodiments, the first surface can include noble metals such as Au, Pt, Ir, Pd, Os, Ag, Re, Rh, and Ru, for example. In other embodiments, metal films can be selectively deposited onto metal oxide surfaces relative to other surfaces, where the metal oxide surfaces can be, for example, WO_x, HfO_x,TiO_x, AlO_xor ZrO_xsurface. In some embodiments, the metal oxide surface can be an oxidized surface of a metallic material.

In at least one embodiment, the substrate may have a second surface, which is preferably a silicon-containing surface, which is referred to as a second silicon-containing surface or a second surface including silicon in the present invention. In some embodiments, the silicon-containing surface may include, for example, SiO₂. In some embodiments, the silicon-containing surface may comprise a material having Si-O bonds, such as SiO₂or based on SiO₂Low dielectric material (low-k material). In some embodiments, the second surface may include silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, silicon dioxide, or mixtures thereof. In some embodiments, the material comprising the second surface can be a porous material. In some embodiments, a porous material may contain pores that are connected to each other, while in other embodiments, the pores are not connected to each other. In some embodiments, the second surface can comprise a low-k material, which is defined as having a dielectric value or relative permittivity below about 4.0. In some embodiments, the low dielectric material may have a dielectric value or relative permittivity of less than about 3.5, less than about 3.0, less than about 2.5, or less than about 2.3.

Embodiments of the present invention may relate to selectively forming metallic films, films comprising transition metals, or metallic films comprising transition metals. In some embodiments, the film can comprise a metallic or metallic film comprising an element from Group IV, V, or VI of the Periodic Table of the Elements. In some embodiments, the film can comprise a metal film or metallic film comprising an element from Group V or VI of the Periodic Table of the Elements. In some embodiments, the film can comprise a metal film or metallic film comprising an element from Group VI of the Periodic Table of the Elements. In some embodiments, the film can be a film comprising tungsten or molybdenum. Embodiments of the invention can result in the formation of tungsten or molybdenum. In some embodiments, the formed film has a resistivity of less than about 200, less than about 100, less than about 50, less than about 30, less than about 20, or less than about 15 μΩcm. Typically, when the film is relatively thin, the resistivity may be higher than the bulk film (bulk film) or bulk material (bulk material); for example, a film with a thickness of less than 5 nm may exhibit a resistivity of less than about 200 μΩcm, while a thicker film of the same deposition procedure and conditions may exhibit a resistivity of less than about 20 μΩcm. For example, embodiments of the invention may involve the reaction of a tungsten precursor with a precursor comprising a reducing reactant, such as a precursor comprising hydrogen, eg a hydrogen precursor. In this particular example, a tungsten precursor or tungsten hexafluoride (WF6) can be reacted with a hydrogen precursor containing a hydrogen species such as excited species of hydrogen or atomic hydrogen in the following reaction: WF6+6HW+6HF at least In one embodiment, hydrogen can be an atomic species, or can become an excited or chemically activated species when exposed to a hot wire.

Embodiments of the invention may involve the selective deposition of metal on micron-scale (or smaller) features during integrated circuit fabrication. For example, the process flows described herein can be used to fabricate features having dimensions less than 100 microns, less than 1 micron, or less than 200 nm. With selective deposition of tungsten on copper for interconnects, feature or line width dimensions may be less than 1 micron, less than 200nm, less than 100nm, or less than 50nm or less than 30nm or less than 20nm. Those skilled in the art will recognize that selective deposition on larger features or smaller features, among other things, is possible using the disclosed methods.

Figure 1 illustrates a method according to at least one embodiment of the invention. The method includes a metal precursor flowing step 100 and a non-metallic flowing step 200, both of which may include a purge step. The non-metal flowing step 200 may occur such that the non-metal precursor is in contact with or near the hot wire. Each of these steps may be repeated via the first path 300 and the second path 310 as desired. The entire cycle can be repeated via the third path 320 as desired. The steps can be repeated to form a tungsten film of desired thickness.

The method can be performed under the following conditions. The pressure in the reaction chamber may be between about 0.001 mbar and about 1000 mbar, between about 0.01 mbar and about 100 mbar, or between about 0.05 mbar and 20 mbar. The substrate temperature may be between about 0 and about 800°C, between about 20 and about 500°C, between about 50 and about 450°C, between about 100 and about 400°C, between about Between 150 and about 350°C, between about 250 and about 300°C, or about 275°C. The substrate temperature can be maintained by heaters of the substrate holder. The filament temperature may be greater than about 1000°C, between about 1000 and about 2500°C, between about 1100 and about 2000°C, between about 1200 and about 1900°C, or between 1700 and 1800°C Between, or about 1750°C.

Additionally, one wall in the reaction chamber can be a hot wall or a cold wall. Hot wall reactors can be used in smaller volume reactors, but can also be used in larger volume reactors, such as batch furnace reactors. On the other hand, for large-volume reactors with volumes of the order of tens of liters, cold-wall reactors can be used, but cold-wall reactors can also be small-volume reactors, such as shower reactors designed with small volumes And/or possibly a reactor with a cooling system in the upper part of the reaction chamber. In a hot wall reactor, the wafer can be placed in a chamber where both the wafer holder and the lid placed over the wafer are heated, or in a reactor where all reaction chamber sections and/or The temperature of the wall is equal to or close to the temperature of the substrate. For hot walls, the temperature difference (positive or negative) of one or more reaction chamber walls and the substrate can be less than about 100°C, can be less than about 50°C, can be less than about 25°C, can be less than about 5°C, Or it can be around 0°C and can be maintained by a separate heater. For cold walls, the difference in temperature between one or more of the reaction chamber walls (cooler than the substrate) and the substrate (hotter than the chamber wall) can be greater than about 25°C, greater than about 50°C, greater than about 75°C, or higher at about 100°C.

Figure 2 illustrates a method in accordance with at least one embodiment of the invention. The method is the same as that shown in FIG. 1 , the difference is that the non-metal precursor flowing step 200 is before the metal precursor flowing step 100 , and both may include a purging step. Each of these steps may be repeated via the first path 300 and the second path 310 as desired. The entire cycle can be repeated via the third path 320 as desired. These steps can be repeated to form a metal film of desired thickness. The metal film may comprise at least one of: transition metal; metallic material; elemental transition metal film; elemental tungsten; elemental molybdenum.

The method can be performed under the following conditions. The pressure in the reaction chamber may be between about 0.001 mbar and about 1000 mbar, between about 0.01 mbar and about 100 mbar, or between about 0.05 mbar and 20 mbar, or in some cases about 0.05 mbar. The substrate temperature may be between about 0 and about 800°C, between about 20 and about 500°C, between about 50 and about 450°C, between about 100 and about 400°C, between about Between 150 and about 350° C., or between about 250 and about 300° C., and may be maintained by a heater of the substrate holder. The filament temperature may be greater than about 1000°C, between about 1000 and about 2500°C, between about 1100 and about 2000°C, between about 1200 and about 1900°C, or between 1700 and 1750°C between.

FIG. 3 illustrates a metal precursor flow step 100 comprising a metal flow 110 and an optional inert gas flow 120 . Metal flow 110 involves the flow, exposure or pulse of a metal precursor. The metal precursor may comprise at least one of the following: a transition metal element; a Group IV element; a Group V element; a Group VI element; a tungsten-containing precursor; a transition metal halide; a transition metal fluoride;₆); or molybdenum-containing precursors such as molybdenum fluoride (MoF₅or MoF₆), molybdenum chloride (MoCl₅), or other molybdenum halides. The flow rate of the metal precursor in flowing step 110 may be between about 1 and about 1000 seem, between about 3 and about 500 seem, or between about 5 and about 250 seem. In some embodiments, the flow rate of the metal precursor in the flowing step 110 may be about 3 sccm. The duration of metal precursor movement in flowing step 110 may be between 0.01 and 20 seconds, between 0.05 and 10 seconds, or between 0.1 and 5 seconds, or in some cases about 0.5 seconds. In the case of batch reactors with multiple substrates, for example, times may be longer and flow rates may be higher than previously described.

The optional inert gas flow 120 may comprise a purge gas flow. The purge gas can be one of: argon, nitrogen, helium, or other rare or inert gas. The flow rate of the optional inert gas flow 120 may be between about 25 and about 5000 seem, between about 50 and about 2500 seem, or between about 100 and about 2000 seem. The duration of the optional inert gas flow 120 may be between about 0.1 and 60 seconds, between about 0.5 and about 20 seconds, or between about 1 and 10 seconds, or in some cases about 7 seconds second. In at least one embodiment of the invention, there may be no flow of inert gas in optional inert gas flow 120 . In some cases, eg, in the case of batch reactors with multiple substrates, the time may be longer, eg, in excess of about 60 seconds and the flow rate may be higher than described above.

FIG. 4 illustrates a non-metal precursor flow step 200 comprising a non-metal flow 210 and an optional inert gas flow 220 . Non-metal flow 210 involves the flow, exposure or pulse of a non-metal precursor. Non-metal flow 210 may involve flowing a non-metal precursor so that it approaches or contacts a hot wire, resulting in the formation of excited, free radical or atomic species. The non-metallic precursor may comprise at least one of: a species comprising hydrogen, such as hydrogen (H₂). The flow rate of non-metallic flow 210 may be between about 1 and about 2000 seem, between about 5 and about 1000 seem, between about 50 and 500 seem, or in some cases about 50 seem. The duration of non-metallic flow 210 may be between about 0.1 and about 60 seconds, between about 0.5 and about 20 seconds, between about 1 and 10 seconds, or in some cases about 7 seconds. In some cases, for example, in the case of batch reactors with multiple substrates, the time may be longer, such as greater than about 60 seconds, and the flow rates higher than previously described.

The optional inert gas flow 220 may comprise a purge gas flow. The purge gas can be one of the following: argon, nitrogen, helium, or other noble gases. The flow rate of the optional inert gas flow 220 may be between about 25 and about 5000 seem, between about 50 and about 2500 seem, or between about 100 and about 2000 seem. The duration of the optional inert gas flow 220 may be between about 0.1 and 60 seconds, between about 0.5 and about 20 seconds, or between about 1 and 10 seconds, or in some cases about 7 seconds. second. In at least one embodiment of the invention, there may be no flow of inert gas in optional inert gas flow 220 . In some cases, eg, in the case of batch reactors with multiple substrates, the time may be longer, eg, in excess of about 60 seconds and the flow rate may be higher than described above.

In at least one embodiment of the invention, selective deposition can occur on a substrate. The substrate may include a first surface and a second surface. The first surface may comprise at least one of: a transition metal; an oxidized metal with an elemental metal conductive film or a metallic conductive film disposed thereunder; an elemental metal; a metallic surface; tungsten; copper; or cobalt. The second surface may comprise at least one of the following: silicon; silicon and oxygen; Si-O bonds; SiO₂; low dielectric material; silicon oxide; silicon nitride; silicon carbide; silicon oxynitride; silicon dioxide; or mixtures thereof. Selective deposition can be performed such that the deposited film is formed only on the first surface.

FIG. 5A illustrates a top view of structure 400 prior to deposition of tungsten by hot wire atomic layer deposition (ALD). The structure 400 includes a substrate 410 and at least one channel 420 . The substrate 410 may include at least one of the following: silicon dioxide (SiO₂), silicon (Si), silicon germanium (SiGe), or other suitable materials. At least one channel 420 may include at least one of: tungsten (W) or other metals.

The aforementioned hot wire ALD procedure may be applied to structure 400 such that deposited tungsten is formed on at least one channel 420 only. As shown in FIG. 5B , a film of the filament metal 430 may be formed only on the at least one channel 420 and not on the substrate 410 . The film of the filament metal 430 may include at least one of the following: tungsten (W) or other metals.

FIG. 6A illustrates a side view of a structure 500 in accordance with at least one embodiment of the present invention. The structure 500 includes a substrate 510 , a substrate tungsten insert 520 , a hot wire deposited tungsten layer 530 , and an adhesive layer 540 . The bonding layer 540 may not have any connection to the hot wire deposition process and may be used to allow the ability to perform cross-sectional analysis.

FIG. 6B illustrates an enlarged view of the structure 500 shown in FIG. 6A. The hot wire deposition process can achieve a hot wire deposited tungsten layer 530 with a film thickness of 16.92 nm.

In at least one embodiment, the temperature can be selected to promote selective deposition. If the surface area or volume per surface on the first surface (for example, /cm²or/cm³) is greater than the amount of deposited material per surface area or volume on the second surface, then deposition is generally defined as selective. The amount of material deposited on the surface can be determined by measuring the thickness of each layer. In some cases, thickness measurements may not be feasible due to discontinuous films. In some cases, selectivity can be determined by measuring deposited atoms per surface area or volume.

As mentioned above, selectivity can be expressed as the amount of material (A) formed on the first surface minus the amount of material (B) formed on the second surface and the amount of material (A) formed on the first surface. The ratio (ie, selectivity can be expressed as a percentage calculated by [(deposition on first surface)-(deposition on second surface)]/(deposition on first surface) or [(AB)/A]. Preferably, the selectivity is higher than about 70%, higher than about 80%, higher than about 90%, higher than about 95%, or higher than about 98%, or higher than about 99%, or about 100%. In some cases, a selectivity higher than 80% is acceptable for some applications. In some cases, a selectivity higher than 50% is acceptable for some applications. In some embodiments, selective deposition The temperature is such that the selectivity is greater than about 90%. In some embodiments, the deposition temperature can be selected such that a selectivity of about 100% is achieved.

In some embodiments, the selectively deposited film can have a thickness of less than about 100 nm, less than about 50 nm, about 25 nm or less than about 10 nm, about 0.5 nm to about 100 nm, or about 1 nm to about 50 nm. In some cases, however, a desired degree of selectivity, such as greater than 50%, greater than 50%, can be achieved by selectively depositing film thicknesses greater than about 2.5 nm, greater than about 5 nm, greater than about 10 nm, greater than about 25 nm, or greater than about 50 nm. Better than 80%.

In some embodiments, the selectively deposited film can have a growth rate of less than about 5 Å/cycle, less than about 2.5 Å/cycle, less than about 1.5 Å/cycle, or less than about 1.0 Å/cycle. In other embodiments, the selectively deposited film can have about 0.01 to about 5 Å/cycle, about 0.05 to about 2.5 Å/cycle, or about 0.1 to about 2 Å/cycle, or in some cases about 0.5 to about 1.5 Å/cycle cycle or about 1.1 Å/cycle. In some embodiments, the selectively deposited film can have a deposition rate on the first surface that is about two times, about five times, or about 10 times, or about 50 times the deposition rate on the second surface. In some embodiments, deposition can occur on the second surface, but the thickness of the deposition on the second surface can be reduced by etching that occurs during the film deposition process, e.g., etching on the second surface is greater than that on the second surface. One is more apparent on the surface. In some embodiments, deposition on the second surface may occur, but the deposited material may be almost completely or completely removed from the second surface during the deposition procedure.

In some embodiments, one or more pretreatment and/or passivation procedures or treatments of one or more surfaces of the substrate may be performed prior to selectively depositing the metal-containing film. FIG. 7 illustrates a passivation or pretreatment step 10 that occurs prior to the metal precursor flow 100 and the non-metal precursor flow 200 . Passivation or pretreatment can enhance selectivity and growth on desired surfaces, and can reduce or prevent (in some cases almost completely prevent) growth. In at least one embodiment according to the present invention, the pre-deposition of tungsten is exposed to air. In this case, the tungsten may have at least partially oxidized tungsten, ie tungsten oxide species with atomic hydrogen on the surface, which reduces the tungsten oxide species to metallic or elemental tungsten. This allows selective hot-filament atomic layer deposition of tungsten.

In some embodiments, the entire process flow can be performed in a single reaction chamber such as, for example, a single wafer module. However, in other embodiments, various steps can be performed in two or more reaction chambers. In some embodiments, a second, different reaction chamber may also be used to form the passivation layer therein. If optional annealing or thermal treatment is needed or desired, the substrate may be transferred to a second reaction chamber where thermal annealing or treatment (if used) and selective deposition are performed. In some embodiments, the annealing or heat treatment step can be performed in the second reaction chamber, and the substrate is transported back to the first reaction chamber, or transported to the third reaction chamber for selective deposition.

In some embodiments, the first surface treatment can be performed in a first reaction chamber and the selective deposition can be performed in a second, different reaction chamber without an annealing step between the first surface treatment and deposition steps. If desired, the substrates may be cooled for a period of time prior to transport. In some embodiments, cooling is performed at a pressure of vacuum to about 2 atm, or about 0.1 torr to about 760 torr, or about 1 torr to about 760 torr, for about 0 to 30 minutes, or about 0 to 10 minutes. The substrate can be, for example, under vacuum or at about 1 to 1000 torr under N₂(maybe some O₂) is transported in the presence of

In at least one embodiment of the present invention, low resistivity tungsten films of about 15 [mu][Omega]cm can be achieved. In some embodiments, the low-resistivity tungsten film can have a resistivity of less than about 100, less than about 50, less than about 30, less than about 20, or less than about 15 μΩcm. A low resistivity may be more likely to be achieved in a hot wall reactor, while a higher resistivity may be obtained in a cold wall reactor. In some embodiments, the low-resistivity tungsten film can include alpha-phase tungsten as characterized by X-ray diffraction (XRD). In some embodiments, the low-resistivity tungsten film can include greater than about 50% alpha-phase tungsten. In some embodiments, the low-resistivity tungsten film can include both alpha-phase tungsten and beta-phase tungsten. In some embodiments, the low-resistivity tungsten film can be entirely or almost entirely alpha-phase tungsten. In some embodiments, the deposition of low resistivity tungsten may not be selective. In other embodiments, the deposition of low resistivity tungsten is selective. In some embodiments, the deposition of low resistivity tungsten may be deposited on a substrate where only one material is present on the surface of the substrate. In some embodiments, the deposition of low resistivity tungsten can be deposited on a substrate having more than one material present on the surface.

In some embodiments, a transition metal film, such as a tungsten film, can comprise greater than about 75%, greater than about 85%, greater than about 90%, greater than about 95%, greater than about 98%, greater than about 99%, or greater than about 99.5% transition metals such as tungsten. In some embodiments, transition metal films, such as tungsten films, may contain impurities in the form of transition metals, hydrogen, or other metals other than halogens such as fluorine. Impurities may comprise less than about 25%, less than about 15%, less than about 10%, less than about 5%, less than about 2%, less than about 1%, or less than about 0.5%.

According to at least one embodiment of the present invention, selective deposition of metal or tungsten films can be inhibited or stopped by adding additional substances to the reactor. For example, selective deposition of tungsten can be achieved by adding nitride species such as N₂O or NH₃, until the reactor is completely stopped. In other examples, oxidizing species (such as O₂) can inhibit but not completely stop deposition, but appropriate treatment with an excited species of hydrogen such as hydrogen radicals or atomic hydrogen can allow deposition to proceed.

Figure 8 illustrates a method in accordance with at least one embodiment of the invention. The method pertains to the selective deposition of a metal, such as tungsten, on a first surface of a substrate comprising or having a layer of another metal, such as cobalt, opposite a second surface of the substrate, such as a silicon dioxide layer. The method may include optional metal oxide removal/conversion 600 and metal deposition 700 . Method steps can be repeated and the order of steps can be swapped as desired. According to at least one specific example, the optional metal oxide removal/conversion 600 can occur before or during the metal deposition 700, such as: before or during the first 50 cycles of the metal deposition 700; before or during a cycle; or before or during the first 10 cycles of metal deposition 700 .

Optionally, metal oxide removal/conversion 600 may partially or completely remove metal oxides. Optional metal oxide removal/conversion 600 may remove excess metal oxide or convert metal oxide to a metal film. The metal oxide removed in metal oxide removal/conversion 600 may optionally comprise tungsten oxide or cobalt oxide.

According to at least one embodiment of the invention, metal oxide removal/conversion 600 can optionally include flowing hydrogen contacting a hot wire before reaching a substrate in a reactor. The contact of hydrogen with the hot filament causes H2 to split into atomic H. The temperature of the reactor can be set between 100 and 400°C, between 200 and 350°C, or between 250 and 300°C. The pressure within the reactor may be greater than 0.01 mbar, greater than 0.05 mbar, or greater than 0.2 mbar. The hydrogen flow may be greater than 25 seem, greater than 50 seem, or greater than 75 seem. The filament temperature may be greater than about 1000°C, between about 1000 and about 2500°C, between about 1100 and about 2000°C, between about 1200 and about 1900°C, or between 1700 and 1750°C between. Optionally, metal oxide removal/conversion 600 may last for between 1 and 30 minutes, between 2 and 20 minutes, or between 5 and 15 minutes.

Optional metal oxide removal/conversion 600 may result in removal of the metal oxide, leaving a metal layer. On top of the cobalt layer, metal deposition 700 may deposit a layer of tungsten. FIG. 9 illustrates a metal deposition 700 in accordance with at least one embodiment of the invention. Metal deposition 700 may include hydrogen pulse/flush 710 and metal precursor pulse/flush 720 . The substrate temperature, which may be maintained by the substrate holder heater, may be between about 0 and about 800°C, between about 20 and about 500°C, between about 50 and about 450°C, between Between about 100 and about 400°C, between about 150 and about 350°C, or between about 250 and about 300°C, or about 275°C. The pressure in the reactor may be greater than 0.01 mbar, greater than 0.05 mbar, or greater than 0.2 mbar. Method steps can be repeated and the order of steps can be swapped as desired.

Hydrogen pulse/purge 710 may comprise a rate between 1 and 5000 seem, between 5 and 2000 seem, between 10 and 1000 seem, between 20 and 800 seem, or in some cases between 20 and A first flow of hydrogen between 80 seem, or between 40 and 60 seem. The hydrogen flow can continue to occur between 0.1 and 60 seconds, between 0.5 and 60 seconds, between 1 and 30 seconds, between 4 and 15 seconds, or between 7 and 10 seconds period. Hydrogen pulsing/purging 710 may also include flowing a purge gas to remove any excess hydrogen. The purge gas may contain, for example, nitrogen or argon. The flow of purge gas may occur for a period of between 0.1 and 60 seconds, between 1 and 20 seconds, between 4 and 15 seconds, or between 7 and 10 seconds. In some embodiments, the purge of 710 is not required or it may be less than 1.0 seconds.

Metal precursor pulse/purge 720 may include a first flowing metal precursor at a rate between 0.1 and 15 seem, between 1 and 10 seem, or between 3 and 7 seem. The metal precursor may comprise at least one of the following: a transition metal element; a Group IV element; a Group V element; a Group VI element; a tungsten-containing precursor; a transition metal halide; a transition metal fluoride;₆); or molybdenum-containing precursors, such as molybdenum fluoride, such as MoF₅or MoF₆. Metal precursor flow can occur for a period of between 0.1 and 10 seconds, between 0.2 and 5 seconds, or between 0.5 and 3 seconds. Metal pulsing/purging 720 may also include flowing a purge gas to remove any excess metal precursor. The purge gas may contain, for example, nitrogen or argon. The flow of purge gas may occur for a period of between 0.1 and 60 seconds, between 1 and 20 seconds, between 4 and 15 seconds, or between 7 and 10 seconds. In some embodiments, the purge of 720 is not required or it may be less than 1.0 seconds.

Figure 10 illustrates a device 800 formed in accordance with at least one embodiment of the present invention. Device 800 includes a tungsten layer 810 (shown as a black layer), a cobalt layer 820 (shown as a dark gray layer), and a silicon dioxide layer 830 (shown as a light gray layer). The use of a hot wire allows the tungsten layer 810 to be selectively deposited on the cobalt layer 820 rather than on exposed portions of the silicon dioxide layer 830 . Additionally, a titanium adhesion layer (not shown) may be disposed between the silicon dioxide layer 830 and the cobalt layer 820 .

FIG. 11 illustrates a semiconductor device 900 formed in accordance with at least one embodiment of the present invention. The semiconductor device 900 exhibits good conformality as a result of the hot-filament tungsten process on a three-dimensional structure with an aspect ratio of 40 (feature depth:width). Tungsten films are conformal in three-dimensional structure.

In the preparation of the sample shown in FIG. 11 , a layer of aluminum oxide 920 was formed on structure 930 followed by a 0.5 nm seed layer of amorphous silicon. The 12nm W deposition 910 uses the hot wire deposition method described in this invention. The sample is then covered with a thicker layer of amorphous silicon. In some embodiments, the hot wire deposited metal film (such as a selective or non-selective metal film, e.g., a tungsten film) has greater than about 50%, greater than about 80%, greater than about 90%, greater than about 95%, greater than about 98% %, greater than about 99% step coverage or an aspect ratio (depth:width) greater than about, greater than about 5, greater than about 10, greater than about 20, and in some cases even greater than about 40 or greater than about 80. It can be noted that for more complex structures than trenches or vias, the aspect ratio may be difficult to determine, but in the present invention, the aspect ratio can also be understood as the The ratio of the total surface area of a structure to the planar surface area of a wafer/substrate or part of a wafer/substrate.

Example

The examples listed below illustrate various aspects of illustrative embodiments of the invention. The compositions, methods and various parameters reflected therein are intended only to illustrate various aspects and specific examples of the invention, and are not intended to limit the scope of the claimed invention.

1. A method of forming a metal film comprising: providing a substrate for processing in a reaction chamber and a filament for passing at least one gas to the reaction chamber, wherein the surface of the substrate comprises cobalt; flowing a hydrogen precursor to the substrate, wherein the hydrogen precursor is in contact with the hot wire; flowing the metal precursor onto the substrate; and selectively forming on the surface comprising cobalt by the reaction of the metal precursor and the hydrogen precursor in contact with the hot wire. Metal or metallic film.

2. The method of embodiment 1, wherein the metal precursor comprises at least one of the following: transition metal elements; Group IV elements; Group V elements; Group VI elements; tungsten-containing precursors; transition metal halides; transition metals Fluoride; Tungsten Hexafluoride (WF₆); or molybdenum-containing precursors, such as molybdenum fluoride, such as MoF₅or MoF₆。

3. The method of any one of embodiments 1-2, wherein the hydrogen precursor comprises at least one of the following: hydrogen (H₂)。

4. The method of any of embodiments 1-3, wherein the surface comprises cobalt oxide and flowing a hydrogen precursor over the surface partially reduces the cobalt oxide.

5. The method of embodiment 4, wherein the hydrogen precursor is in contact with the hot wire.

6. The method of any one of embodiments 1-5, wherein the formed metal film comprises tungsten.

7. The method of any one of embodiments 1-6, wherein selectively forming the metal film comprises an ALD process.

8. The method of any one of embodiments 1-7, wherein selectively forming the metal film comprises a cyclic procedure.

9. The method of any one of embodiments 1-8, wherein selectively forming the metal film comprises a cyclic or sequential CVD process.

10. A reaction chamber configured to perform the method of any one of embodiments 1-9.

11. The method of any one of embodiments 1-10, wherein the substrate surface comprises cobalt oxide.

12. The method of example 11, wherein the cobalt oxide is at least partially reduced, reduced to metallic cobalt.

13. The method of any one of embodiments 1-12, wherein the substrate also comprises SiO₂the other surface.

14. The method as in embodiment 13, wherein relative to comprising SiO₂Another substrate, a metal film or a metallic film is selectively deposited onto the cobalt-containing surface.

15. The method of any one of embodiments 1-14, wherein the reaction chamber is a hot-walled reaction chamber.

16. A method of forming a metal film comprising: providing a substrate for processing in a reaction chamber and a filament for passing at least one gas to the reaction chamber, wherein the surface of the substrate comprises cobalt; exposing the substrate to a A hydrogen precursor in contact with a hot wire; exposing a substrate to a metal precursor; and selectively forming a metal or metallic film on a surface comprising cobalt by reaction of the metal precursor and the hydrogen precursor in contact with the hot wire .

17. The method of embodiment 16, wherein the metal precursor comprises at least one of the following: transition metal elements; Group IV elements; Group V elements; Group VI elements; Tungsten-containing precursors; Transition metal halides; Transition metals Fluoride; Tungsten Hexafluoride (WF₆); or molybdenum-containing precursors, such as molybdenum fluoride, such as MoF₅or MoF₆。

18. The method of embodiments 16-17, wherein the hydrogen precursor comprises at least one of the following: hydrogen (H₂)。

19. The method of any one of embodiments 16-18, wherein the surface comprises cobalt oxide and flowing a hydrogen precursor over the surface partially reduces the cobalt oxide.

20. The method of embodiment 19, wherein the hydrogen precursor is in contact with the hot wire.

21. The method of any one of embodiments 16-20, wherein the formed metal film comprises tungsten.

22. The method of any one of embodiments 16-21, wherein selectively forming the metal film comprises an ALD process.

23. The method of any one of embodiments 16-22, wherein selectively forming the metal film comprises a cyclic procedure.

24. The method of any one of embodiments 16-23, wherein selectively forming the metal film comprises a cyclic or sequential CVD process.

25. A reaction chamber configured to perform the method of any one of embodiments 16-24.

26. The method of embodiment 16, wherein the substrate surface comprises cobalt oxide.

27. The method of embodiment 26, wherein the cobalt oxide is at least partially reduced, reduced to metallic cobalt.

28. The method of any one of embodiments 16-27, wherein the substrate also comprises SiO₂the other surface.

29. The method of any one of embodiments 16-28, wherein relative to comprising SiO₂Another substrate, a metal film or a metallic film is selectively deposited onto the cobalt-containing surface.

30. The method of any one of embodiments 16-29, wherein the reaction chamber is a hot-walled reaction chamber.

31. A method of forming a metal film, comprising: providing a substrate having a three-dimensional structure for processing in a reaction chamber and a filament for passing at least one gas to the reaction chamber; flowing a hydrogen precursor to the substrate On, wherein the hydrogen precursor is in contact with the hot wire; making the metal precursor flow onto the substrate; and forming a metal film or metallic film on the three-dimensional structure by the reaction of the metal precursor and the hydrogen precursor in contact with the hot wire; And wherein the metallic or metallic film has a step coverage greater than about 50% in a three-dimensional structure having an aspect ratio greater than about 5.

32. The method of embodiment 31, wherein the metallic or metallic film has a step coverage greater than about 80% in a three-dimensional structure having an aspect ratio greater than about 5.

33. The method of any of embodiments 31-32, wherein the metallic or metallic film has greater than about 50% step coverage in the three-dimensional structure having an aspect ratio greater than about 20.

34. The method of any one of embodiments 31-33, wherein the metallic or metallic film comprises a transition metal film.

35. The method of any one of embodiments 31-34, wherein the metal or metallic film is a tungsten film.

36. The method of any one of embodiments 31-36, wherein the reaction chamber is part of a hot-walled reaction chamber.

37. A reaction chamber configured to perform the method of any one of embodiments 31-36.

38. A method of selectively forming a tungsten film, comprising: providing a substrate comprising a first surface and a second surface for processing in a reaction chamber and a filament for generating an excitation species of a gas; performing a tungsten precursor A substance pulsing/flushing step onto the substrate, the step comprising: pulsing a tungsten precursor onto the substrate; and purging excess tungsten precursor from the reaction chamber; and performing a hydrogen precursor pulsing/flushing step onto the substrate, the The steps include: pulsing a hydrogen precursor onto the substrate, wherein the hydrogen precursor is excited by a hot wire; and purging excess hydrogen precursor from the reaction chamber; wherein the tungsten precursor comprises at least one of the following: tungsten hexafluoride (WF₆); wherein the hydrogen precursor comprises at least one of the following: hydrogen (H₂); wherein the temperature of the filament is greater than about 1000° C.; and wherein the tungsten film is selectively formed on the first surface.

39. The method of embodiment 38, wherein one of the walls in the reaction chamber is a hot wall.

40. The method of embodiment 39, wherein the temperature difference between the hot wall and the substrate can be 100°C, can be less than about 50°C, can be less than about 25°C, can be less than about 5°C, or can be about 0°C.

41. The method of embodiment 38, wherein one of the walls in the reaction chamber is a cold wall.

42. The method of embodiment 41, wherein the temperature difference between the cold wall and the substrate can be less than about 100°C, can be less than about 50°C, can be less than about 25°C, can be less than about 5°C, or can be about 0 °C.

43. The method of any one of embodiments 38-42, wherein the pressure in the reaction chamber may be between 0.001 mbar and about 1000 mbar, between about 0.01 mbar and about 100 mbar, or between about 0.05 mbar and between 20mbar.

44. The method of any one of embodiments 38-43, wherein the purging of excess tungsten precursor comprises purging the reaction chamber with at least one of the following: nitrogen (N₂), argon (Ar), helium (He), or other rare or inert gases.

45. The method of any one of embodiments 38-42, wherein the purging of excess hydrogen precursor comprises purging the reaction chamber with at least one of the following: nitrogen (N₂), argon (Ar), helium (He), or other rare or inert gases.

46. A method of selectively forming a film comprising a metal, the method comprising: providing a substrate for processing in a reaction chamber and a filament element for contacting at least one gas; exposing the substrate to a metal precursor; and exposing the substrate to the gas that has been exposed to the vicinity of the filament; wherein the substrate comprises at least two different materials and a metal film is selectively formed on one of the surfaces.

47. The method of embodiment 46, wherein the metal precursor comprises a transition metal element.

48. The method of embodiment 46, wherein the metal precursor comprises group IV, V or VI elements.

49. The method of embodiment 46, wherein the metal precursor comprises a tungsten-containing precursor or a molybdenum-containing precursor.

50. The method of any one of embodiments 46-49, wherein the gas comprises a reducing gas.

51. The method of any one of embodiments 46-50, wherein the gas comprises hydrogen.

52. The method of embodiment 46, wherein the selectively formed film comprises a transition metal.

53. The method of any one of embodiments 46-52, wherein the selectively formed film comprises a metallic material.

54. The method of any one of embodiments 46-53, wherein the selectively formed film comprises an elemental transition metal film.

55. The method of any one of embodiments 46-54, wherein the selectively formed film comprises elemental tungsten or elemental molybdenum.

56. The method of any one of embodiments 46-55, wherein when the gas is exposed adjacent to the hot wire, the gas forms excited free radicals or atomic species.

57. The method of any one of embodiments 46-56, wherein when the gas is exposed adjacent to the hot wire, the gas forms excited free radicals or atomic species comprising hydrogen.

58. The method of any one of embodiments 46-57, wherein the substrate comprises a first surface and a second surface.

59. The method of embodiment 58, wherein the first surface comprises a transition metal.

60. The method of any one of embodiments 58-59, wherein the first surface comprises a metal oxide, and beneath the metal oxide is an elemental metal conductive film or a metallic conductive film.

61. The method of embodiment 58, wherein the second surface comprises silicon.

62. The method of embodiment 58, wherein the second surface comprises silicon and oxygen.

63. The method of embodiment 62, wherein the second surface comprises Si-O bonds.

64. The method of embodiment 58, wherein the second surface comprises SiO₂。

65. The method of embodiment 58, wherein the second surface comprises a low dielectric material.

66. The method of embodiment 58, wherein the second surface comprises silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, silicon dioxide, or mixtures thereof.

67. The method of embodiment 58, wherein the first surface comprises metal and the second surface comprises silicon and oxygen.

68. The method of embodiment 58, wherein the first surface comprises elemental metal and the second surface comprises silicon and oxygen.

69. The method of embodiment 58, wherein the first surface comprises a metallic surface and the second surface comprises silicon and oxygen.

70. The method of embodiment 58, wherein the first surface comprises W, Cu, or CO and the second surface comprises silicon and oxygen.

71. The method of any one of embodiments 58-70, wherein the film is selectively formed on the first surface.

72. The method of any one of embodiments 46-71, further comprising the step of exposing the substrate to a purge gas after the step of exposing the substrate to a metal precursor.

73. The method of any one of embodiments 46-72, further comprising the step of exposing the substrate to a purge gas after the step of exposing the substrate to gas passing through a hot wire.

74. The method of any one of embodiments 46-73, wherein the filament temperature is greater than 500°C.

75. The method of any one of embodiments 46-74, wherein the temperature of the filament is greater than 1000°C.

76. The method of any one of embodiments 46-75, wherein the filament temperature is greater than 1500°C.

77. The method of any one of embodiments 46-76, wherein the selectivity is greater than 50%.

78. The method of any one of embodiments 46-77, wherein the selectivity is greater than 90%.

79. The method of embodiment 46, wherein the temperature of the reaction chamber is maintained at about 0°C to about 800°C.

80. The method of any one of embodiments 46-79, wherein the film thickness is greater than 1 nm.

81. The method of any one of embodiments 46-80, wherein the film thickness is greater than 5 nm.

82. The method of any one of embodiments 46-81, wherein the film thickness is greater than 10 nm.

83. The method of any one of embodiments 46-82, wherein the film thickness is greater than 25 nm.

84. The method of embodiment 46, wherein one of the walls in the reaction chamber is a heated wall.

85. The method of embodiment 84, wherein the temperature difference between the hot wall and the substrate can be 100°C, can be less than about 50°C, can be less than about 25°C, can be less than about 5°C, or can be about 0°C.

86. The method of embodiment 46, wherein one of the walls in the reaction chamber is a cold wall.

87. The method of embodiment 86, wherein the temperature difference between the cold wall and the base plate can be less than about 100°C, can be less than about 50°C, can be less than about 25°C, can be less than about 5°C, or can be about 0 °C.

88. The method of any one of embodiments 46-87, wherein the pressure in the reaction chamber may be between 0.001 mbar and about 1000 mbar, between about 0.01 mbar and about 100 mbar, or between about 0.05 mbar and between 20mbar.

89. The method of any one of embodiments 46-88, wherein the purging of excess tungsten precursor comprises purging the reaction chamber with at least one of the following: nitrogen (N₂), argon (Ar), helium (He), or other rare gases.

90. The method of any one of embodiments 46-89, wherein the purging of excess hydrogen precursor comprises purging the reaction chamber with at least one of the following: nitrogen (N₂), argon (Ar), helium (He), or other rare gases.

91. The method of any one of embodiments 46-90, wherein selectively forming the film comprises an ALD procedure.

92. The method of any one of embodiments 46-91, wherein selectively forming the film comprises a cyclic procedure.

93. The method of any one of embodiments 46-92, wherein selectively forming the film comprises a cyclic or sequential CVD procedure.

94. A reaction chamber configured to perform the method of any one of embodiments 46-93.

95. A method of forming a tungsten film, comprising: providing a substrate for processing in a reaction chamber and a filament for passing at least one gas to the reaction chamber; flowing a tungsten precursor onto the substrate; and causing a hydrogen precursor is flowed onto the substrate, wherein the hydrogen precursor is in contact with a hot wire; and wherein the tungsten precursor and the reaction of the hydrogen precursor in contact with the hot wire form a tungsten film; and wherein the reaction chamber is a hot wall reaction chamber .

96. The method of embodiment 95, wherein the tungsten precursor comprises at least one of the following: tungsten hexafluoride (WF₆)。

97. The method of any one of embodiments 95-96, wherein the hydrogen precursor comprises at least one of the following: hydrogen (H₂)。

98. The method of any one of embodiments 95-97, wherein the filament temperature is about 1000°C, between about 1000 and about 2500°C, between about 1100 and about 2000°C, between about 1200 and Between about 1900°C, or between 1700 and 1750°C.

99. The method of any one of embodiments 95-98, further comprising: purging excess tungsten precursor from the reaction chamber.

100. The method of any one of embodiments 95-99, further comprising: purging excess hydrogen precursor from the reaction chamber.

101. The method of any one of embodiments 95-100, wherein the formed tungsten film has a resistivity of less than about 100 μΩcm.

102. The method of any one of embodiments 95-101, wherein the formed tungsten film has a resistivity of less than about 50 μΩcm.

103. The method of any of embodiments 95-102, wherein the formed tungsten film has a resistivity of less than about 15 μΩcm.

104. The method of any one of embodiments 95-103, wherein forming the tungsten film comprises an ALD process.

105. The method of any one of embodiments 95-104, wherein forming the tungsten film comprises a cyclic procedure.

106. The method of any one of embodiments 95-105, wherein forming the tungsten film comprises a cyclic or sequential CVD process.

107. A reaction chamber configured to perform the method of any one of embodiments 95-106.

The particular implementations presented and described are illustrative of the invention and its best mode and are not intended to limit the scope of the aspects and implementations in any way. In fact, well-known fabrication, connectivity, preparation and other functional aspects of the systems may not be described in detail for the sake of brevity. Furthermore, the connecting lines shown in the various figures are intended to represent illustrative functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may exist in an actual system, and/or may not exist in some specific instances.

It should be understood that the configurations and/or methods described herein are exemplary in nature and that these specific examples or embodiments are not to be considered limiting, as many variations are possible. The particular routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated may be performed in the order illustrated, in other orders, or in some cases omitted.

The subject matter of the present invention includes all novel and non-obvious combinations and subcombinations of the various procedures, systems and configurations, and other features, functions, acts and/or properties disclosed herein, and any and all equivalents thereof.