Method for treating titanium nitride film

Abstract

Embodiments herein relate to methods for forming titanium nitride films suitable for use as bulk fill materials for conductive features in semiconductor devices, such as capacitor electrodes and / or buried word lines in dynamic random access memory (DRAM) devices. In one embodiment, a method for forming a conductive feature in a semiconductor device is provided. The method includes thermally treating a substrate surface including at least a portion of a titanium nitride layer in the presence of hydrogen radicals. Thermally treating the substrate includes placing the substrate in a processing volume of a processing chamber, heating the substrate to a processing temperature greater than about 250°C, generating hydrogen radicals using a remote plasma source fluidly coupled to the processing volume, and simultaneously exposing at least a portion of the titanium nitride layer to the generated hydrogen radicals while maintaining the substrate at the processing temperature. Here, the substrate includes a field surface having a plurality of openings formed therein, and at least a portion of the titanium nitride layer is disposed within the plurality of openings.

Description

[Technical field]

[0001] background Field

[0001] Embodiments described herein relate generally to electronic device manufacturing, and more particularly to methods for forming titanium nitride fill materials for use as conductive features in semiconductor devices, such as for use as buried wordlines in dynamic random access memory devices. [Background technology]

[0002] 2. Description of Related Art

[0002] Tungsten (W) is commonly used as a fill material to form many of the conductive features of semiconductor devices. For example, tungsten is used to form low resistivity electrical connections in dielectric layers, i.e., horizontally disposed metal interconnects, vertical through vias between adjacent dielectric layers to connect horizontally disposed metal interconnects, and contacts between metal layers and devices formed on or in the underlying substrate. Because of its low resistivity, tungsten is also commonly used to form bitlines and wordlines used to address individual memory cells in the memory cell array of dynamic random access memory (DRAM) devices.

[0003] Typically, tungsten conductive features are formed by etching an opening, e.g., a hole or trench, in a material layer, lining the opening with a conductive barrier material, and depositing a layer of tungsten to fill the lined opening to form a conductive feature. Titanium nitride (TiN) is commonly used as the conductive barrier material or "barrier metal" covering the opening due to its ability to prevent the tungsten fill material from diffusing into the surrounding material layer and to promote adhesion between the tungsten fill material and the walls of the lined opening.

[0004]

[0004] Unfortunately, as circuit density increases and device features continue to shrink to meet the demands of next generation semiconductor devices, reliably manufacturing tungsten features is becoming increasingly problematic. Problems such as poor step coverage of titanium nitride layers in openings and voids in the deposited tungsten fill material are amplified as feature sizes shrink and can adversely affect device performance or device reliability and / or render the device inoperable.

[0005]

[0005] Therefore, there is a need in the art for improved bulk fill materials for forming conductive features in semiconductor devices and methods of forming the same. Summary of the Invention

[0006]

[0006] Embodiments herein are directed to methods of forming titanium nitride films suitable for use as bulk fill materials for conductive features of semiconductor devices, such as capacitor electrodes and / or buried wordlines of dynamic random access memory (DRAM) devices.

[0007] In one embodiment, a method for forming conductive features in an electronic device is provided. The method includes thermally treating a substrate surface including at least a portion of a titanium nitride layer in the presence of hydrogen radicals. Thermally treating the substrate includes placing the substrate in a processing volume of a processing chamber, heating the substrate to a processing temperature greater than about 250° C., generating hydrogen radicals using a remote plasma source fluidly coupled to the processing volume, and exposing at least a portion of the titanium nitride layer to the generated hydrogen radicals while simultaneously maintaining the substrate at the processing temperature. Wherein the substrate includes a field surface having a plurality of openings formed therein, and at least a portion of the titanium nitride layer is disposed in the plurality of openings.

[0008] In another embodiment, a method of forming a memory device includes heat treating a titanium nitride layer in the presence of hydrogen radicals. Heat treating the titanium nitride layer includes placing a substrate in a processing region of a first processing chamber, heating the substrate to a processing temperature greater than about 250° C., generating hydrogen radicals using a remote plasma source fluidly coupled to the processing region, and exposing the titanium nitride layer to the generated hydrogen radicals while simultaneously maintaining the substrate at the processing temperature, where the substrate features a field surface having a plurality of openings formed therein, and at least a portion(s) of the titanium nitride layer are disposed in the plurality of openings, where the at least a portion(s) of the titanium nitride layer disposed in the plurality of openings form buried wordlines of the memory device.

[0009] In another embodiment, a method of forming buried wordlines in a memory device is provided that includes: (a) disposing a substrate in a first processing region of a first processing chamber, where the substrate may include a field surface having a plurality of openings formed therein; (b) depositing a titanium nitride layer on the field surface of the substrate to at least partially fill the plurality of openings; (c) disposing the substrate in a second processing region of a second processing chamber connected to the first processing chamber; and (e) exposing the titanium nitride layer to hydrogen radicals generated using a remote plasma source fluidly coupled to the second processing region.

[0010]

[0010] So that the above features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present disclosure and therefore should not be considered as limiting its scope. [Brief description of the drawings]

[0011] [Figure 1A] 1 is a schematic cross-sectional view of an exemplary processing chamber that may be used to perform the methods described herein. [Figure 1B] 1 is a schematic cross-sectional view of an exemplary processing chamber that may be used to perform the methods described herein. [Diagram 2]

[0012] FIG. 1 is a schematic plan view of a multi-chamber processing system that can be used to perform the methods described herein. [Diagram 3]

[0013] 1 illustrates a method of forming conductive features of an electronic device according to one embodiment. [Figure 4A]

[0014] 4 is a schematic cross-sectional view of a semiconductor substrate illustrating one embodiment of the method of FIG. 3. [Figure 4B-4D] 4 is a schematic cross-sectional view of a semiconductor substrate illustrating an embodiment of the method of FIG. 3. [Figure 4E] 4 is a schematic cross-sectional view of a semiconductor substrate illustrating one embodiment of the method of FIG. 3. [Figure 4F] 4 is a schematic cross-sectional view of a semiconductor substrate illustrating one embodiment of the method of FIG. 3. [Figure 5A-5C]

[0015] 1 graphically illustrates various material properties of a titanium nitride (TiN) layer formed using the methods described herein. [Figures 6A-6D] 1 graphically illustrates various material properties of a titanium nitride (TiN) layer formed using the methods described herein. [Figure 7A-7D] 1 graphically illustrates various material properties of a titanium nitride (TiN) layer formed using the methods described herein. [Figure 8] 1 graphically illustrates various material properties of a titanium nitride (TiN) layer formed using the methods described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012]

[0016] For ease of understanding, wherever possible, like reference numbers have been used to designate identical elements that are common to several figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0013]

[0017] Embodiments herein are directed to methods of forming titanium nitride films suitable for use as bulk fill materials for conductive features of semiconductor devices, such as capacitor electrodes and / or buried wordlines of dynamic random access memory (DRAM) devices. Titanium nitride is a ceramic material that is sufficiently conductive to provide low ohmic contact between metal features and / or metal-semiconductor junctions, while acting as a barrier material to prevent reaction and interdiffusion between the respective materials. Thus, when used as a relatively thin barrier or liner for a conductive metal, titanium nitride is considered a "barrier metal."

[0014]

[0018] Typically, relatively thin layers of titanium nitride exhibit metallic-type electrical behavior, but the resistivity of titanium nitride layers formed by conventional methods is too high for the material to be useful as a bulk-fill conductive material in most semiconductor device applications. Accordingly, embodiments herein provide a hydrogen radical-assisted heat treatment of titanium nitride films to desirably reduce electrical resistivity. Beneficially, in addition to lowering the electrical resistivity of the deposited titanium nitride layer, the methods herein remove undesirable impurities therefrom, enhancing device performance and improving device reliability and yield.

[0015]

[0019] 1A illustrates a schematic diagram of an exemplary thermal processing system, a processing chamber 100, that can be used to perform aspects of the methods described herein. Here, the processing chamber 100 features a chamber body 102 that defines a processing region 104, a substrate support assembly 106 disposed within the processing region 104, a remote plasma source (RPS) 108 fluidly coupled to the processing region 104, and a system controller 110. The processing region 104 is fluidly coupled to a vacuum source, such as one or more dedicated vacuum pumps, that maintains the processing region 104 at subatmospheric conditions and evacuates process and other gases therefrom. The substrate support assembly 106 includes a substrate support 107 disposed on a support shaft 112 that extends sealingly through the base of the chamber body 102, such as surrounded by a bellows (not shown) in an area above or below the chamber base. Here, the substrate support 107 includes a heater 114, for example a resistive heating element, that is used to heat the substrate support 107, and thus bring a substrate 116 disposed on the substrate support 107, to a desired processing temperature.

[0016]

[0020] The RPS 108 is fluidly coupled to a hydrogen gas source 118 and is used to generate hydrogen radicals, which then flow into the processing region 104 through a conduit 120 fluidly coupled therebetween. In some embodiments, the conduit 120 features a dielectric liner 122, such as a quartz liner or an alumina liner, disposed therein. The dielectric liner 122 beneficially reduces recombination of radical species that might otherwise occur between the RPS 108 and the processing region 104.

[0017]

[0021] Generally, plasma excitation of hydrogen gas to form neutral hydrogen radicals also forms charged hydrogen ions, which can be accelerated toward the substrate 116 and cause undesired damage to features formed on the surface of the substrate. Thus, in some embodiments, the process chamber 100 further includes an ion filter 124 disposed between the RPS 108 and the substrate support 107. The ion filter 124 is used to remove hydrogen ions from the effluent of the RPS 108. Examples of suitable ion filters that can be used in the process chamber 100 include electrostatic filters, wire or mesh filters, plates with openings with relative aspect ratios (e.g., >2:1), and magnetic ion filters. In embodiments herein, the ion filter 124 removes substantially all of the generated ion radicals from the RPS effluent before the RPS effluent reaches the process region 104. As used herein, "substantially all of the generated hydrogen ions" means about 95% or more of the hydrogen ions generated by the RPS 108.

[0018]

[0022] Operation of the processing chamber 100 is facilitated by a system controller 110. The system controller 110 includes a programmable central processing unit, here a CPU 126, operable with a memory 128 (e.g., non-volatile memory) and support circuits 130. The CPU 126 may be any form of general-purpose computer processor used in an industrial environment, such as a programmable logic controller (PLC) for controlling the various chamber components and sub-processors. The memory 128 coupled to the CPU 126 is non-transitory and is in the form of a computer-readable storage medium (e.g., non-volatile memory) containing instructions which, when executed by the CPU 126, facilitate operation of the processing chamber. The support circuits 130 are conventionally coupled to the CPU 126 and include cache, clock circuits, input / output subsystems, power supplies, and combinations thereof coupled to the various components of the processing chamber 100 to facilitate control of substrate processing operations.

[0019]

[0023] Here, the instructions in the memory 128 are in the form of a program product, such as a program that performs the methods of the present disclosure. In one example, the present disclosure may be implemented as a program product stored in a computer-readable storage medium for use with a computer system. The program(s) of the program product define the functions of the embodiments, including the methods described herein. Thus, a computer-readable storage medium is an embodiment of the present disclosure when it carries computer-readable instructions that direct the functions of the methods described herein. In some embodiments, the processing chamber 100 can include any one or combination of the features of the processing system 150 described in FIG. 1B.

[0020]

[0024] FIG. 1B is a schematic cross-sectional view of a processing system 150 that can be used to perform the methods described herein, according to one embodiment. Here, the processing system 150 features tandem processing chambers 151A-151B having a chamber lid 152, one or more chamber walls 153, and a chamber base 154 that collectively define a first chamber region 155A and a second chamber region 155B. Here, the configurations of each of the processing chambers 151A-151B are substantially similar to one another to facilitate simultaneous processing of multiple substrates (not shown) under the same or substantially similar processing conditions. Either or both of the processing chambers 151A-151B can include any one or combination of the features of the processing chamber 100 described in FIG. 1A. In other embodiments, the configurations of the processing chambers 151A-151B, e.g., one or more features and components thereof, are different from one another.

[0021]

[0025] Each of the chamber regions 155A-151B has a respective substrate support assembly 156 disposed therein and a process kit 157 including one or more shields or liners used to shield processing components from the chamber regions 155A-151B and direct the flow of gases within the chamber regions. The chamber regions 155A-151B are fluidly coupled to a common vacuum source 158, such as one or more dedicated vacuum pumps, that is used to maintain the chamber regions 155A-151B at sub-atmospheric conditions and to evacuate process and other gases from the chamber regions. Process gases are supplied to the chamber regions 155A-151B, respectively, using a common gas supply system 159.

[0022]

[0026] Here, each substrate support assembly 156 includes a support shaft 160 movably disposed through the chamber base 154 and a substrate support 161 disposed on the support shaft 160. Generally, the substrate support 161 includes a heater 162, such as a resistive heating element, that is used to heat and maintain the substrate at a desired processing temperature. The chamber lid 152, the substrate support 161, and corresponding shields and liners of the process kit 157 collectively define a respective processing region 163A-163B when the substrate support 161 is in the raised position.

[0023]

[0027] As shown, each of the processing regions 163A-163B is fluidly coupled to a respective remote plasma source (RPS) 164 using a gas conduit 165 disposed therebetween. Each RPS 164 is fluidly coupled to one or more gas sources 166A-166B of a gas delivery system 159 to supply process gases and other gases thereto. In some embodiments, each of the gas conduits 165 includes a dielectric liner (not shown), such as the dielectric liner 122 described in FIG. 1A, and the processing system 150 further includes one or more ion filters 167 disposed between each RPS 164 and a substrate support 161 disposed within the processing regions 163A-163B. The ion filters 167 may be the same as or substantially similar to the ion filter 124 described in FIG. 1A. In other embodiments, a single remote plasma source may be used to supply activated species to each of the processing regions 163A-163B.

[0024]

[0028] Operation of the processing system is facilitated by a system controller 170 configured as described for system controller 110 of FIG. 1A and including a CPU 171, memory 172, and support circuits 173, which contain instructions in memory 172 for carrying out the methods described herein.

[0025]

[0029] FIG. 2 is a top-down cross-sectional view that illustrates a schematic of a multi-chamber processing system 200 that can be used to perform the methods described herein, according to one embodiment. Here, the multi-chamber processing system 200 includes one or more load lock chambers 202 for receiving a substrate into the multi-chamber processing system 200, a transfer chamber 204, and multiple processing systems 150A-150C, here a first processing system 150A, a second processing system 150B, and an optional third processing system 150C. Each of the processing systems 150A-150C are fluidly coupled to each other by a transfer chamber 204 disposed therebetween. The first processing system 150A is configured to perform the hydrogen radical processing methods described herein and may be the same as or substantially similar to the processing system 150 illustrated in FIG. 1B. The second processing system 150B includes one or more deposition chambers suitable for depositing titanium nitride, such as any one of a chemical vapor deposition (CVD) chamber, an atomic layer deposition (ALD) chamber, or a physical vapor deposition (PVD) chamber. The optional third processing system 150C is an etching system configured to remove excess titanium nitride from the field surface of the substrate, or a deposition system configured to deposit a dielectric material, such as silicon oxide or silicon nitride. The transfer chamber 204 includes a substrate handler 206 that facilitates transfer of substrates between the processing systems 150A-150C, where the transfer chamber 204 is maintained under vacuum, allowing substrates to be transferred between the processing systems 150A-150C to perform various aspects of the methods described herein without exposing the substrate to atmospheric conditions.

[0026]

[0030] 4A-4F illustrate a method for forming conductive features of a semiconductor device, according to one embodiment. Various aspects of method 300 are illustrated in FIG. 4A, which is a schematic isometric view of a portion of a substrate with a partially fabricated dynamic random access memory (DRAM) device formed thereon. FIGS. 4B-4F illustrate schematic formation of buried word lines (bWL) on the DRAM device. FIG. 4B is a cross-sectional view of FIG. 4A taken along line 4B-4B. It is contemplated that method 300, or various aspects thereof, may be performed using the processing chamber 100 and / or multi-chamber processing system 200 described above, although other suitable chambers may be used.

[0027]

[0031] Generally, the substrate 400 is formed of a semiconductor material, such as silicon, polysilicon, or silicon-germanium, and includes a plurality of shallow trench isolation (STI) regions 402 formed therein to define a plurality of spaced-apart, electrically isolated active areas 404. The STI regions 402 are formed of a dielectric material, such as silicon oxide, and are used to electrically isolate the active areas 404 from one another, thus preventing current leakage between them.

[0028]

[0032] In a partially fabricated DRAM device, a plurality of openings, here wordline trenches 406, are formed in a field surface 407 of a substrate 400. Each of the plurality of wordline trenches 406 extends through a portion of the STI region 402 and a portion of the active region 404, and separates source / drain doped regions 408 disposed on either side thereof (FIG. 4B). Here, the source / drain doped regions 408 are formed by implanting N-type or P-type dopants into the portion of the active region 404 of the substrate 400. Typically, the exposed portion of the active region 404 is oxidized after the buried wordline trenches 406 are formed therein, to provide a thin layer of dielectric material, e.g., silicon oxide 410, thereover.

[0029]

[0033] At activity 302, the method 300 optionally includes depositing a titanium nitride (TiN) layer 412 on the field surface 407 to fill or at least partially fill a plurality of openings, such as a plurality of wordline trenches 406. The TiN layer 412 (FIG. 4C) may be deposited using any suitable process, such as chemical vapor deposition (CVD), atomic layer deposition (ALD), or physical vapor deposition (PVD). For example, in one embodiment, the CVD process includes reacting a titanium precursor, such as TiCl4, and a nitrogen precursor, such as N2 or NH3, at the surface of the substrate. In another embodiment, the ALD process includes repeatedly exposing the surface of the substrate to alternating titanium precursors, such as TiCl4 or carbon-containing organotitanium precursors, and nitrogen precursors, such as N2 or NH3.

[0030]

[0034] Typically, one or both of the CVD or ALD processes are plasma enhanced, and the method includes forming a plasma of one or both precursors to form radical species thereof, and exposing a substrate to the plasma and / or the radical species formed therefrom. The plasma may be in situ (formed within the processing space) or may be formed remotely from the substrate, for example, by using a remote plasma source. In other embodiments, one or both of the CVD or ALD processes are thermal processes, for example, heating the substrate to promote reaction at its surface.

[0031]

[0035] In some embodiments, the TiN layer 412 is deposited using a plasma-enhanced PVD process in which plasma-excited species of a sputtering gas are used to bombard a titanium target and sputter titanium atoms therefrom. The titanium atoms are then deposited on the substrate surface in the presence of a nitrogen precursor, such as N2, to form the TiN layer 412. Here, the TiN layer 412 is deposited on the field surface 407 to a thickness sufficient to fill the openings, e.g., wordline trenches, formed therein. In some embodiments, the TiN layer 412 is deposited on the substrate disposed in a processing chamber of a multi-chamber processing system, and then the substrate is transferred to another processing chamber to perform a hydrogen radical heat treatment. In some embodiments, both the deposition of the TiN layer 412 and its hydrogen radical heat treatment are performed in the same processing chamber.

[0032]

[0036] In activity 304, the method 300 includes placing the substrate 400 with the TiN layer 412 deposited thereon (FIG. 4C) in a processing region of a processing chamber, where the processing region is maintained under vacuum conditions, such as less than atmospheric pressure, such as less than about 500 Torr, less than about 400 Torr, less than about 300 Torr, less than about 200 Torr, less than about 100 Torr, or less than about 50 Torr. In some embodiments, the processing region is maintained at a pressure between about 10 mTorr and about 50 Torr, such as between about 1 mTorr and about 10 mTorr.

[0033]

[0037] In activity 306, the method 300 includes heating the substrate 400 to a processing temperature of about 200° C. or greater, such as 250° C. or greater, about 300° C. or greater, about 350° C. or greater, about 400° C. or greater, or about 425° C. or greater, and maintaining the substrate 400 at that temperature. In some embodiments, the thermal processing temperature is in the range of about 200° C. to about 600° C., such as about 250° C. to about 600° C., about 250° C. to about 500° C., about 250° C. to about 500° C., about 300° C., or about 350° C. to about 550° C., such as about 400° C. to about 500° C., about 450° C. In some embodiments, the processing temperature is less than about 1000° C., such as less than about 900° C., less than about 800° C., less than about 700° C., or less than about 600° C.

[0034]

[0038] At activity 308, the method 300 includes exposing the heated substrate 400 to hydrogen radicals 413, where the hydrogen radicals 413 are formed by flowing hydrogen gas (H2) into a remote plasma source (RPS) fluidly coupled to the processing region and igniting and maintaining a plasma of the hydrogen gas to form radical species 413 thereof. The hydrogen radicals 413 then flow into the processing region and expose the surface of the TiN layer 412 of the heated substrate 400 thereto. Typically, the flow rate of hydrogen gas (H2) into the RPS for processing a 300 mm diameter substrate is between about 10 sccm and about 5000 sccm, such as between about 100 sccm and about 1500 sccm. Appropriate scaling can be used for substrates of different sizes. In other embodiments, a remote plasma can be formed in a portion of the processing region of the processing chamber separated from the portion of the processing region in which the substrate is located. For example, in those embodiments, the remote plasma may be formed in a portion of the processing region separated from the substrate processing portion by a showerhead.

[0035]

[0039] Typically, the effluent from the RPS is passed through an ion filter to remove substantially all ions from the hydrogen radicals before they reach the surface of the processing region and the substrate disposed therein. In embodiments in which a remote plasma is formed in a separate portion of the processing region, a showerhead disposed between the remote plasma and the substrate processing portion can be used as the ion filter.

[0036]

[0040] Here, activities 306 and 308 are performed simultaneously such that the substrate is maintained at a desired process temperature and a TiN layer 412 disposed thereon is simultaneously exposed to hydrogen radicals 413 for a desired process time. As described below, the sheet resistance of the TiN layer 412 formed according to method 300 desirably decreases with increasing process temperature and process time. In some embodiments, the process time, herein the amount of time that the substrate 400 is maintained at the process temperature while the TiN layer 412 is simultaneously exposed to hydrogen radicals from the RPS, is about 20 seconds or more, such as about 30 seconds or more, about 40 seconds or more, about 50 seconds or more, about 1 minute or more, about 1.5 minutes or more, about 2 minutes or more, about 2.5 minutes or more, even about 3 minutes, about 3.5 minutes or more, about 4 minutes or more, about 4.5 minutes or more, such as about 5 minutes or more.

[0037]

[0041] In activity 310, method 300 optionally includes a thermal bake process that includes maintaining the substrate at or near the processing temperature in the presence of hydrogen gas. Here, the thermal bake process includes flowing hydrogen gas into the processing region while simultaneously maintaining the substrate 400 at the processing temperature or heating the substrate 400 to a second temperature different from the processing temperature. Typically, flowing hydrogen gas into the processing region includes extinguishing a plasma formed in the RPS while continuing to flow hydrogen gas into the RPS. In activity 310, hydrogen gas can be flowed at approximately the same flow rate as during the hydrogen radical processing activities 306 and 308, or can be increased or decreased relative thereto. Activity 310 of method 300 can be performed in the same processing chamber as activities 306 and 308. In other embodiments, the substrate 400 can be transferred under vacuum to a second processing chamber of a multi-chamber processing system, and the thermal bake process can be performed in the second processing chamber. In some embodiments, the second temperature is about 1.10 times or more, such as about 1.2 times or more, about 1.3 times or more, about 1.4 times or more, about 1.5 times or more, about 1.6 times or more, about 1.7 times or more, about 1.8 times or more, about 1.9 times or more, or about 2 times or more, than the processing temperature at 306 and 308. In other embodiments, the second temperature is about 1.1 times or less, such as about 1.2 times or less, about 1.3 times or less, about 1.4 times or less, about 1.5 times or less, about 1.6 times or less, about 1.7 times or less, about 1.8 times or less, about 1.9 times or less, or about 2 times or less, than the processing temperature at 306 and 308.

[0038]

[0042] Here, activities 306, 308, and optionally 310 are performed after a TiN layer 412 has been deposited to a thickness sufficient to fill openings formed in the field surface 407, such as wordline trenches 406, as shown in Figure 4C. In another embodiment, the openings may be filled by alternating deposition of a relatively thin titanium nitride layer 414 (shown in phantom) in a first processing chamber, followed by heat treating the relatively thin titanium nitride layer 414 in the presence of hydrogen radicals until the accumulated thin titanium nitride layer fills the plurality of openings at least to the height of the field surface.

[0039]

[0043] Typically, once the openings are filled, the excess loads of TiN 416 are removed from the field surface 407, for example, by a chemical mechanical polishing (CMP) process or an etch-back process, as shown in FIG. 4D. In some embodiments, such as a DRAM manufacturing process, the excess loads of TiN 416 are removed from the field surface 407 using an etch-back process to form a plurality of buried wordlines 418 comprising and / or consisting essentially of titanium nitride, as shown in FIG. 4E. Typically, in these embodiments, the buried wordlines 418 are recessed from the field surface 407 to ensure electrical isolation from each other and / or from other adjacent conductive features. A dielectric layer 420 (FIG. 4F) is then deposited on the field surface 407 to electrically isolate the buried wordlines 418 and further protect them, for example, from exposure to atmospheric conditions. In some embodiments, the hydrogen radical thermal treatment method and the etch-back process are each performed in different process chambers of a multi-chamber processing system, for example, the multi-chamber processing system 200 of FIG. 2. In some embodiments, a hydrogen radical heat treatment is performed on the TiN layer 412 / buried wordlines 418 after the excess charge 416 is removed from the field surface, ie, after a CMP or etch-back process.

[0040]

[0044] Advantageously, the above hydrogen radical heat treatment method promotes the growth of titanium nitride grains, provides a desired crystallographic orientation to the titanium nitride surface, removes undesirable impurities therefrom, and improves (reduces) the resistivity of the conductive features.

[0041]

[0045] The hydrogen radicals of the heat treatment are believed to promote grain growth (an increase in the size of the crystallites of the material) in the as-deposited titanium nitride film layer by diffusing into the titanium nitride film and lowering the activation energy barrier required for grain boundary migration. The resulting larger grain (crystallite) size results in a decrease in the percentage (volume fraction) of grain boundary area in the titanium nitride layer. A decrease in the percentage of grain boundary area can be understood to result in a decrease in electron scattering at the surfaces of the grain boundaries and a corresponding decrease in the effective resistance of the conductive features formed therefrom.

[0042]

[0046] In addition to promoting grain growth, the methods described herein desirably promote grain fractionation during the grain growth stage, but it has been found that the resulting texture depends, at least in part, on the type of substrate used and the method of depositing the TiN layer thereon. In some embodiments, the treated TiN layer includes a textured surface with (111) and (222) crystal orientations that serve to further (desirably) reduce the resistivity of the resulting film.

[0043]

[0047] In addition to promoting grain growth and desirable crystal orientation of the titanium nitride material, the methods described herein desirably result in titanium nitride layers with fewer impurities compared to as-deposited films. Typically, the CVD, ALD, and PVD methods described above introduce undesirable process-induced impurities, such as chlorine or carbon, into the titanium nitride film. Hydrogen radicals from the processing methods react with the impurities to form volatile species, such as HCl and / or CHx, which are then outgassed from the titanium nitride film and exhausted from the processing region. Beneficially, hydrogen atoms introduced during the processing process that do not form volatile HCl and / or CHx species are driven out of the TiN as the grain size increases, since there are fewer grain boundary sites for the hydrogen atoms to occupy. As shown below, the higher the processing temperature, the lower the hydrogen concentration of the TiN layer after post-processing.

[0044]

[0048] 5A-5C are graphs showing the rate of change in resistivity (Rs) of titanium nitride films following processing methods described herein. In FIG. 5A, titanium nitride layer 500a was deposited using an ALD process in which the substrate was alternately exposed to TiCl4 and NH3. In FIG. 5B, titanium nitride layer 500b was deposited using an ALD process in which the substrate was alternately exposed to a titanium organic compound and a nitrogen precursor. In FIG. 5C, titanium nitride layer 500c was deposited using a PVD process in which titanium was sputtered from a titanium target onto a substrate placed in a nitrogen-rich environment. Each of titanium nitride layers 500a-c was deposited to a thickness of about 15 nm.

[0045]

[0049] Each of the titanium nitride layers 500a-c was heated and maintained at a temperature between 300° C. and 450° C. while simultaneously exposed to either molecular hydrogen (H2 gas) for 5 minutes (process condition 502), hydrogen radicals for 1 minute (process condition 504), or hydrogen radicals for 5 minutes (process condition 506). For each of process conditions 502, 504, and 506, the process region was maintained at a pressure of less than 5 Torr. Here, the resistivity reduction is characterized by the percent change in sheet resistance (Rs) between measurements before and after the heat treatment.

[0046]

[0050] As shown in Figures 5A-5C, for the 5 minute thermal treatment with molecular hydrogen (H2 gas) only (processing condition 502), no obvious resistivity (Rs) decrease is observed for the ALD, CVD, and PVD deposited films 502a-c, respectively. Instead, an increase in resistivity is observed, which may be due to the formation of TiOxNy due to air exposure after the substrate is removed from the processing system. For the hydrogen radical treatments 504, 506, the amount of Rs decrease increased with both the processing temperature and processing time. Among the various types of films, the largest resistivity decrease was observed for the metal-organic ALD deposited TiN layer (500b) under processing condition 506, where the substrate was maintained at about 450°C for 5 minutes while simultaneously exposed to hydrogen radicals. Under the same processing conditions, the TiCl4 ALD deposited and PVD deposited TiN layers 500a and 500c resulted in a resistivity decrease of 20.8% and 14.6%, respectively. Here, most of the decrease in Rs occurs during the initial stage of the hydrogen radical treatment. For example, for a TiCl4 deposited TiN layer 500a, maintaining the substrate at about 450° C. for 1 minute while simultaneously exposing it to hydrogen radicals (process condition 504) resulted in a 17.0% decrease in resistivity, while 5 minutes (process condition 506) resulted in a 20.8% decrease in Rs.

[0047]

[0051] Figures 6A-6B show chlorine concentration profile 600a and hydrogen concentration profile 600b of a TiCl4 ALD deposited TiN layer processed according to the methods described herein, where the TiCl4 ALD deposited TiN layer was deposited using the same process conditions as the TiCl4 ALD TiN layer of Figure 5A. Figures 6C-6D show carbon concentration profile 600c and hydrogen concentration profile 600d of a metal-organic ALD deposited TiN layer, where the metal-organic layer was deposited to the same thickness and under the same conditions as shown in Figure 5B.

[0048]

[0052] Here, Figures 6A-6D show the impurity profile of an as-deposited film 602 that was not processed using the methods described herein, a processing method 603 that involves simultaneously exposing the surface to molecular hydrogen while maintaining the substrate at a temperature of 450°C for 5 minutes, and processing methods 604-606 that involve simultaneously exposing the surface to hydrogen radicals while maintaining the substrate at temperatures of 300°C, 400°C, and 450°C for 5 minutes each.

[0049]

[0053] For chlorine impurities (FIG. 6A), the hydrogen radical treatment methods 604-606 show significant chlorine removal in the top 5 nm of the TiN layer when compared to the as-deposited TiN layer 602. The depth of impurity removal often depends on the quality and condition of the as-deposited film. For example, in FIG. 6A, the hydrogen treatment methods 604-606 show significant chlorine removal from the top 5 nm of the TiN layer when compared to the as-deposited TiN layer 602. For the other TiCl deposited films, significant chlorine removal was observed throughout substantially all of the treated TiN films, i.e., chlorine impurities were reduced throughout the majority of the treated TiN films. No significant chlorine removal is observed with the molecular hydrogen treatment method 603. In FIG. 6C, no significant removal of carbon impurities is observed between the as-deposited TiN layer 602 and the molecular hydrogen treatment method 603. In FIG. 6C, the hydrogen radical assisted heat treatment methods 604-606 result in carbon reduction both at the surface and inward therefrom, with increased carbon reduction observed at higher treatment temperatures. Both the TiCl4 ALD and metal-organic ALD TiN layers exhibited reduced hydrogen concentrations after processing method 603 compared to the as-deposited TiN layer 602, with a more pronounced reduction for the metal-organic ALD TiN layer.

[0050]

[0054] Here, the hydrogen radical treatment 604-606 incorporates hydrogen into both ALD deposited TiN layers (FIGS. 6B, 6D) with lower hydrogen concentrations observed under increased processing temperatures 604-606. In embodiments where hydrogen incorporation is undesirable, method 300 can further include a thermal bake process to remove undesirable hydrogen from the TiN layers, as described above in activity 310.

[0051]

[0055] Quantitative analyses of areal density based on secondary ion mass spectrometry (SIMS) results are shown in Figures 7A to 7D for the chlorine concentration 600a and hydrogen concentration 600b of the TiCl4 ALD deposited TiN layer, and the carbon concentration 600c and hydrogen concentration 600d of the treatment methods 602 to 606, respectively.

[0052]

[0056] FIG. 8 shows the X-ray diffraction analysis of the TiN layers of substrates 803a-e exposed to various treatment methods. Peak 801 indicates a (111) crystal orientation. Peak 802 indicates a (200) crystal orientation. The TiN layer of substrate 803a received no treatment and had the lowest intensity in both peaks 801 and 802. The TiN layer of substrate 803b was treated using a rapid thermal annealing process by heating and maintaining the substrate at about 850° C. for 1 minute in the presence of molecular nitrogen (N2) to have the highest intensity in peaks 801 and 802. The TiN layer of substrate 803c was treated using a rapid thermal annealing process by heating substrate 803 to about 550° C. in the presence of hydrogen radicals and maintaining the substrate for 1 minute to have the second highest intensity in peaks 801 and 802. The TiN layer of substrate 803d had the third highest intensity peak and was processed by heating substrate 803 to about 550° C. in the presence of hydrogen radicals and maintaining it at that temperature for four minutes. The TiN layer of substrate 803e had the fourth highest intensity peak and was processed by heating substrate 803e to about 550° C. and maintaining it in the presence of molecular hydrogen (H2) for one minute.

[0053]

[0057] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, which scope is determined by the appended claims.

Claims

1. 1. A method of forming conductive features in an electronic device, comprising: heat treating a substrate surface including at least a portion of the titanium nitride layer, said heat treating the substrate surface comprising: placing a substrate, the substrate including a field surface having a plurality of openings formed therein, and at least portions of the titanium nitride layer disposed within the plurality of openings, in a processing region of a first processing chamber; maintaining the processing region of the first processing chamber under vacuum conditions at a pressure between 10 mTorr and 50 Torr; heating the substrate to a first temperature of 300° C. or more and 850° C. or less; generating hydrogen radicals using a remote plasma source fluidly coupled to the processing region; and exposing said at least a portion of said titanium nitride layer to said generated hydrogen radicals while simultaneously maintaining said substrate at said first temperature for at least 1 minute and up to 5 minutes; A method comprising:

2. generating hydrogen radicals, Hydrogen gas (H ２ ) into the remote plasma source; igniting and maintaining a plasma of the hydrogen gas; and flowing an effluent of the remote plasma source containing the hydrogen radicals into the processing region; The method of claim 1 , comprising:

3. and flowing hydrogen gas into the processing region while simultaneously maintaining the substrate at a second temperature different from the first temperature. The method of claim 2.

4. 3. The method of claim 2, comprising using an ion filter to remove hydrogen ions from the remote plasma source effluent before the effluent flows into the processing region.

5. 2. The method of claim 1, wherein said titanium nitride layer is also disposed on said field surface, said titanium nitride layer filling said plurality of openings at least to the height of said field surface.

6. 2. The method of claim 1, wherein said titanium nitride layer forms a plurality of buried wordlines of a memory device.

7. 10. The method of claim 1, further comprising depositing the titanium nitride layer in a second processing chamber prior to transferring the substrate to the first processing chamber, the first processing chamber being connected to the second processing chamber by a transfer chamber disposed therebetween.

8. 8. The method of claim 7, further comprising alternating between depositing a titanium nitride layer in the second processing chamber and exposing the titanium nitride layer to hydrogen radicals in the first processing chamber until a plurality of titanium nitride layers fill the plurality of openings to at least the height of the field surface.

9. 1. A method of forming a memory device, comprising: heat treating the titanium nitride layer, wherein heat treating the titanium nitride layer comprises: placing a substrate in a processing region of a first processing chamber, the substrate including a field surface having a plurality of openings formed therein and at least portions of the titanium nitride layer disposed within the plurality of openings, the at least portions of the titanium nitride layer forming a plurality of buried wordlines; heating the substrate to a processing temperature of 300° C. or more and 850° C. or less; maintaining the processing region of the first processing chamber under vacuum conditions at a pressure between 10 mTorr and 50 Torr; generating hydrogen radicals using a remote plasma source fluidly coupled to the processing region; and exposing the titanium nitride layer to the generated hydrogen radicals while simultaneously maintaining the substrate at the treatment temperature for at least 1 minute and up to 5 minutes; A method comprising:

10. 10. The method of claim 9, wherein the memory device includes source and drain regions disposed on opposite sides of the buried wordline.

11. generating hydrogen radicals, Hydrogen gas (H ２ ) into the remote plasma source; igniting and maintaining a plasma of the hydrogen gas; and flowing an effluent of the remote plasma source containing the hydrogen radicals into the processing region; 10. The method of claim 9, comprising:

12. 12. The method of claim 11, further comprising removing generated hydrogen ions from the remote plasma source effluent by use of an ion filter before the effluent enters the processing region.

13. 10. The method of claim 9, wherein the titanium nitride layer is also disposed on the field surface, the titanium nitride layer filling the plurality of openings at least to the height of the field surface.

14. 10. The method of claim 9, further comprising depositing the titanium nitride layer in a second processing chamber prior to transferring the substrate to the first processing chamber, the first processing chamber being connected to the second processing chamber by a transfer chamber disposed therebetween.

15. 15. The method of claim 14, further comprising alternating between depositing a titanium nitride layer in the second processing chamber and exposing the titanium nitride layer to the generated hydrogen radicals in the first processing chamber while simultaneously maintaining the substrate at the processing temperature until a plurality of titanium nitride layers fill the plurality of openings at least to the height of the field surface.

16. 1. A method of forming a buried wordline in a memory device, comprising: (a) placing a substrate in a first processing region of a first processing chamber, the substrate including a field surface having a plurality of openings formed therein; (b) depositing a titanium nitride layer on the field surface of the substrate to at least partially fill the plurality of openings; (c) placing the substrate in a second processing region of a second processing chamber connected to the first processing chamber; (d) heating the substrate to a processing temperature of 300° C. or more and 850° C. or less; (e) maintaining the first processing region of the first processing chamber and the second processing region of the second processing chamber under vacuum conditions of between 10 mTorr and 50 Torr; (f) exposing the titanium nitride layer to hydrogen radicals generated using a remote plasma source fluidly coupled to the second processing region for a period of at least 1 minute and up to 5 minutes; A method comprising:

17. 17. The method of claim 16, further comprising sequentially repeating (a) through (f) until a plurality of said titanium nitride layers fill said plurality of openings to at least the height of said field surface.

18. generating hydrogen radicals, Hydrogen gas (H ２ ) into the remote plasma source; igniting and maintaining a plasma of the hydrogen gas; and flowing an effluent of the remote plasma source including the hydrogen radicals into the second process region; 17. The method of claim 16, comprising:

19. 20. The method of claim 18, further comprising removing hydrogen ions from the remote plasma source effluent by use of an ion filter before flowing the effluent into the second processing region.

20. 17. The method of claim 16, wherein the memory device includes source and drain regions disposed on opposite sides of the buried wordline.

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