Processing system and methods for forming void-free and seam-free tungsten features

Abstract

The embodiments described herein are generally related to the manufacture of electronic components, and more specifically, to systems and methods for forming substantially void-free and seamless tungsten features in a semiconductor component manufacturing process. In one embodiment, the substrate processing system is characterized by a processing chamber and a gas delivery system fluidly coupled to the processing chamber. The gas delivery system includes a first radical generator for a differential suppression processing step and a second radical generator for a chamber cleaning process.

Description

[Technical Field]

[0001] The embodiments herein relate to systems and methods used in the manufacture of electronic components, and more specifically, to systems and methods for forming tungsten features in semiconductor components. [Previous Technology]

[0002] Tungsten (W) is widely used in the manufacture of integrated circuit (IC) components to form conductive features, where relatively low resistance and relatively high electromigration resistance are required. For example, tungsten can be used as a metal filler material to form source contacts, drain contacts, metal gate fillers, gate contacts, interconnects (e.g., horizontal features formed in the surface of a dielectric layer), and vias (e.g., vertical features of other interconnect features disposed above and below a dielectric layer via connections formed thereon). Due to its relatively low resistivity, tungsten is also commonly used to form bit lines and word lines, which are used to address individual memory cells in the memory cell array of a dynamic random-access memory (DRAM) element.

[0003] As circuit density increases and component features continue to shrink to meet the demands of next-generation semiconductor devices, the reliable production of tungsten features is becoming increasingly challenging. Problems such as voids and seams formed during conventional tungsten deposition processes are amplified as feature sizes decrease and may adversely affect device performance and reliability, or even render the device inoperable.

[0004] Therefore, this technology requires a processing system and method to solve the above problems. [Summary of the Invention]

[0005] The embodiments herein are generally related to the manufacture of electronic components, and more specifically, to systems and methods for forming substantially void-free and seamless tungsten features in semiconductor component manufacturing processes. In some embodiments, the systems and methods described herein provide a single-chamber processing solution with reduced substrate processing variability and increased substrate throughput to facilitate the reliable integration of seamless tungsten fillers into high-volume manufacturing lines.

[0006] In one embodiment, the substrate processing system includes a processing chamber comprising a chamber cover assembly, one or more chamber sidewalls, and a chamber base that collectively define a processing volume. The processing system also includes a gas delivery system fluidly coupled to the processing chamber, the gas delivery system including a first radical generator and a second radical generator, and a non-transitory computer-readable medium storing instructions for performing a method of processing a plurality of substrates when executed by a processor. The method includes: (a) receiving a substrate into the processing volume; (b) exposing the substrate to an activating processing gas comprising an effluent of a processing plasma formed in the first radical generator; (c) exposing the substrate to a first tungsten-containing precursor and a first reducing agent to deposit a tungsten interstitial material; (d) removing the substrate from the processing volume; and (e) repeating (a) to (d) when the number of substrates processed sequentially is less than or equal to a threshold value.

[0007] In one embodiment, a method of processing a substrate includes: (a) receiving the substrate into a processing volume of a processing system, the processing system including: a processing chamber including a chamber cover assembly, one or more chamber sidewalls and a chamber base that together define the processing volume; and a gas delivery system fluidly coupled to the processing chamber, the gas delivery system including a first free radical generator and a second free radical generator; (b) exposing the substrate to an activating processing gas, the activating processing gas including an effluent of processing plasma formed in the first free radical generator; (c) exposing the substrate to a first tungsten-containing precursor and a first reducing agent; (d) removing the substrate from the processing volume; and (e) repeating (a) to (d) when the number of substrates processed sequentially is less than or equal to a threshold value.

Implementation Method

[0019] The embodiments herein are generally related to the manufacture of electronic components, and more specifically, to systems and methods for forming substantially void-free and seamless tungsten features in a semiconductor component manufacturing process.

[0020] Typically, tungsten features in IC components are formed using a damascene (metal inlay) manufacturing process. The damascene process begins by depositing a dielectric material on a substrate surface, patterning the dielectric layer to form a plurality of openings, and depositing a tungsten material on the dielectric layer surface to fill the openings. Typically, before depositing the tungsten layer, a barrier or adhesive material such as titanium nitride (TiN) is deposited to line the openings. The deposition of the barrier layer and the tungsten layer creates a barrier and tungsten material capping layer on the substrate area, which is then removed using a chemical mechanical polishing (CMP) process.

[0021] The CMP process uses a combination of chemical and mechanical activity to planarize a tungsten capping layer from a region, which is at least partially provided by a polishing slurry. A typical tungsten CMP polishing slurry comprises an aqueous solution containing one or more chemically active components and suspended abrasive components (e.g., nanoparticles) to form a polishing slurry. The chemically active components soften the tungsten surface, for example, by forming a thin layer of tungsten oxide on the surface through oxidation, and the polishing components polish (remove) the tungsten oxide to expose the tungsten underneath. The oxidation and polishing cycles continue throughout the CMP process until the tungsten capping layer is removed from the dielectric layer region, leaving embedded tungsten features.

[0022] Typically, tungsten deposited using conventional methods is highly conformal to the patterned surface of the underlying layer. Unfortunately, as device features shrink and aspect ratios increase, the formation of undesirable voids and seams in tungsten features formed using conformal tungsten deposition methods is largely unavoidable. The resulting undesirable voids and seams (such as those shown in Figures 1A-1B) can lead to device performance and reliability issues, or even device failure.

[0023] Figure 1A is a schematic cross-sectional view of substrate 10A, illustrating undesirable voids 20 formed during a conventional tungsten deposition process. Here, substrate 10A includes a patterned surface 11, which includes a dielectric layer 12 (shown as a portion filled with a tungsten layer 15) in which high aspect ratio openings are formed, a barrier material layer 14 deposited on the dielectric layer 12 to line the openings, and a tungsten layer 15 deposited on the barrier material layer 14. The tungsten layer 15 is formed using a conventional deposition process, such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), in which tungsten is conformally deposited (grown) on the patterned surface 11 to fill the openings. The tungsten layer 15 forms tungsten features 15A in the openings and forms a material capping layer (tungsten capping layer 15B) on the region of the patterned surface 11.

[0024] In Figure 1A, the opening has an uneven profile, being narrower at the surface of the substrate 10A and widening (bending outwards) as it extends inwards into the dielectric layer 12. As shown, the overhang of the conformal tungsten layer 15 is grown together to block or "pinch off" the entrance to the opening before it can be fully filled, resulting in undesirable voids 20 in the tungsten feature 15A, i.e., a lack of tungsten material. If the voids 20 are opened (exposed) during a subsequent CMP process, polishing slurry may infiltrate the tungsten feature 15A, and the chemically active components of the polishing slurry can cause further loss of tungsten material therein, for example, through undesirable feature core-taking (primary vias) caused by corrosion of the tungsten material and / or static etching. Such undesirable tungsten loss can lead to device performance and reliability issues, or ultimately, complete device failure. Even without voids, undesirable seams in tungsten features are largely unavoidable using conventional tungsten deposition processes, as shown in Figure 1B.

[0025] Figure 1B is a schematic cross-sectional view of substrate 10B, illustrating an undesirable seam 24 formed during a conventional tungsten deposition process. Here, the patterned surface 11 includes an opening (a portion filled with tungsten layer 15) that has a substantially uniform profile as it extends from the surface of substrate 10B into dielectric layer 12. The opening is filled with tungsten, and no voids are formed. Nevertheless, the conformal growth of tungsten layer 15 from the wall of the opening outwards has resulted in an undesirable seam 24 extending through the center of tungsten feature 15A formed in the opening. Similar to the voids 20 shown in Figure 1A, seam 24 is susceptible to corrosion by the chemically active components of tungsten polishing slurry, which could lead to undesirable loss of tungsten material in feature 15A if seam 24 is exposed during a CMP process.

[0026] Fortunately, emerging technologies enabling selective tungsten deposition to provide bottom-up tungsten interstitial filling have shown promise in forming the substantially void-free and seam-free features required for next-generation devices. Typically, bottom-up tungsten interstitial filling processes involve substrate preparation and tungsten deposition processes, which are highly sensitive to even minor variations in substrate preparation conditions. This process sensitivity unevenly affects the selectivity of tungsten deposition across the substrate surface and / or leads to undesirable processing variations over time between multiple substrates processed in the same system or between substrates processed in different systems. Furthermore, due (at least in part) to the high process sensitivity to any changes in process conditions, different portions of the selective tungsten interstitial filling process are typically performed in different dedicated processing chambers, with the substrate being processed being moved one or more times during this process.

[0027] Unfortunately, compared to conventional tungsten deposition processes, the dedicated processing system and substrate processing requirements for selective tungsten interstitial filling undesirably increase the time and cost of forming tungsten features. Therefore, embodiments herein provide a processing system configured to combine individual samples of the method without transferring substrates between processing chambers, thereby improving the overall substrate throughput and capability of the tungsten interstitial filling processing scheme described herein.

[0028] Typically, the gap-filling treatment includes forming a differential tungsten deposition suppression distribution in a characteristic opening formed in the substrate surface, filling the opening with tungsten material according to the suppression distribution, and depositing a tungsten capping layer on the field surface of the substrate. Forming the tungsten deposition suppression distribution typically includes forming a tungsten nucleation layer and treating the tungsten nucleation layer with activated nitrogen species (e.g., treated radicals). Nitrogen treated radicals bind to portions of the nucleation layer, for example, by adsorption of nitrogen species and / or by reaction with metallic tungsten in the nucleation layer to form tungsten nitride (WN). The adsorbed nitrogen and / or nitrided surface of the tungsten nucleation layer ideally delay (suppress) tungsten nucleation and thus subsequent tungsten deposition thereon.

[0029] In some embodiments, the processed radicals are formed remotely from the substrate processing chamber using a distal plasma source fluidly coupled thereto. The desired suppression effect on the patterned surface region and the required suppression distribution in the openings formed in the patterned surface are achieved by controlling the processing conditions (e.g., temperature and pressure) within the processing chamber and controlling the concentration, flux, and energy of the processed radicals at the substrate surface. Typically, the processed radicals are formed from a non-halogenated nitrogen-containing gas, such as N2, NH3, NH4, or combinations thereof.

[0030] The tungsten nucleation and deposition process in the gap-filling treatment typically involves flowing a tungsten-containing precursor and a reducing agent into a processing chamber and exposing the substrate surface therein. The tungsten-containing precursor and reducing agent react on the substrate surface using one of the following processes: chemical vapor deposition (CVD), pulsed CVD, atomic layer deposition (ALD), or a combination thereof, to deposit tungsten material thereon.

[0031] Inevitably, tungsten and tungsten-related species (undesirable tungsten residues) also deposit on surfaces within the processing chamber other than the substrate surface. If not removed, these tungsten residues are a source of defects (particles), and if transferred to the substrate surface, may cause device failure. Therefore, the processing system described herein is configured to periodically perform a chamber cleaning operation, wherein undesirable tungsten residues are removed from the inner surfaces of the processing chamber using cleaning chemicals. Here, the cleaning chemicals contain activated halogen species, such as fluorine or chlorine (cleaning) radicals, that are located away from the processing chamber.

[0032] The chamber cleaning operation typically involves introducing halogenated cleaning radicals into the processing chamber, reacting the cleaning radicals with tungsten residues to form volatile tungsten species, and discharging the volatile tungsten species from the processing chamber via an exhaust port. The chamber cleaning operation is typically performed between substrate processing, i.e., after the processed substrate has been removed from the processing chamber and before the subsequently processed substrate has been received into the processing chamber.

[0033] In some embodiments, a distal plasma source fluidly coupled to the processing chamber is used to form cleaning radicals from a halogen-based cleaning gas, such as NF3. Forming cleaning radicals remotely from the processing chamber ideally avoids ion-based damage to chamber components, such as corrosion of the surfaces inside the processing chamber, which would otherwise occur if cleaning radicals were formed therein using in-situ plasma. Therefore, ion-based damage can ideally be contained on plasma-facing surfaces within the distal plasma source, which may have a halogen-based anti-plasma liner or coating to protect underlying materials from halogen-based plasma corrosion.

[0034] In some embodiments, the distal plasma source used to form the treatment radicals used in the suppression process is also used to form the cleaning radicals used in the chamber cleaning process. Unfortunately, when the same distal plasma source is used to provide radicals for both the suppression process and the chamber cleaning process, undesirable processing variations in the resulting suppression distribution have been observed. Undesirable processing variations include variations in the inter-substrate suppression distribution and / or non-uniform processing results across the substrate surfaces.

[0035] Without being bound by theory, it is believed that at least some undesirable processing variations are the result of surface damage within the distal plasma source caused by halogen-based cleaning plasma. It is further believed that at least some processing variations are caused by nitrogen adsorption and / or nitriding of surfaces within the distal plasma source exposed to nitrogen-based processing plasma. For example, it is believed that halogen-based damage and / or accumulation of halogen-based contaminants on the plasma-facing surface of the distal plasma source adversely affect the dissociation and recombination rates of nitrogen-based processing radicals subsequently formed therein. Variations in the dissociation and recombination rates of processing radicals formed using the distal cleaning plasma source can lead to variations in the concentration, flux, and energy of activated nitrogen species at the substrate surface, resulting in unstable processing outcomes. Therefore, the processing system provided herein is configured with at least two distal plasma sources, wherein a first distal plasma source is designated for and / or dedicated to generating processing radicals, and a second distal plasma source is designated for and / or dedicated to generating cleaning radicals during chamber cleaning operations.

[0036] As discussed below, using a specific plasma source for each suppression and chamber cleaning process provides improved suppression stability compared to a processing system that uses a common plasma source for both. Therefore, the embodiments described herein advantageously provide a relatively low-cost and high-volume single-chamber solution for joint suppression tungsten filling, such as the processing systems shown in Figures 2A-2B.

[0037] Figures 2A-2B schematically illustrate a processing system 200 that can be used to perform the bottom-up tungsten interstitial substrate processing method described herein. Here, the processing system is configured to provide the different processing conditions required for each of the nucleation process, suppression process, selective interstitial filling process, and capping layer deposition process within a single processing chamber 202, i.e., without the need to transfer the substrate between multiple processing chambers.

[0038] As shown in Figure 2A, the processing system 200 includes a processing chamber 202, a gas delivery system 204 fluidly coupled to the processing chamber 202, and a system controller 208. The processing chamber 202 (shown in cross-section in Figure 2A) includes a chamber cover assembly 210, one or more sidewalls 212, and a chamber base 214, which together define a processing volume 215. The processing volume 215 is fluidly coupled to an exhaust port 217, such as one or more vacuum pumps, for maintaining the processing volume 215 at sub-atmospheric pressure and discharging processing gases and processing byproducts therefrom.

[0039] The chamber cover assembly 210 includes a cover plate 216 and a spray head 218, which is coupled to the cover plate 216 to define a gas distribution volume 219 together. Here, the cover plate 216 is maintained at a desired temperature using one or more heaters 229 thermally coupled thereto. The spray head 218 faces a substrate support assembly 220 disposed in the processing volume 215. As discussed below, the substrate support assembly 220 is configured to move a substrate support 222 between an elevated substrate processing position (as shown) and a lowered substrate transport position (not shown), thereby moving a substrate 230 disposed on the substrate support 222. When the substrate support assembly 220 is in the elevated substrate processing position, the spray head 218 and the substrate support 222 define a processing area 221.

[0040] Here, the gas delivery system 204 is fluidly connected to the processing chamber 202 via a gas inlet 223 (Figure 2B), which is configured to pass through the cover plate 216. Processing or cleaning gas delivered by the gas delivery system 204 flows through the gas inlet 223 into the gas distribution volume 219 and is distributed into the processing area 221 via a plurality of openings 232 (Figure 2B) in the spray head 218. In some embodiments, the chamber cover assembly 210 further includes a perforated baffle plate 225 disposed between the gas inlet 223 and the spray head 218. In those embodiments, the gas flowing into the gas distribution volume 219 is first diffused by the baffle plate 225 to provide a more uniform or desired airflow distribution into the processing area 221, together with the spray head 218.

[0041] Here, the processing gas and processing byproducts are discharged radially outward from the processing region 221 via an annular channel 226 surrounding the processing region 221. The annular channel 226 may be formed in a first annular liner 227 disposed radially inside one or more sidewalls 212 (as shown), or may be formed in one or more sidewalls 212. In some embodiments, the processing chamber 202 includes one or more second liners 228 for protecting the inner surfaces of one or more sidewalls 212 or chamber base 214 from corrosive gases and / or unwanted material deposits.

[0042] In some embodiments, a purge gas source 237 in fluid communication with the processing volume 215 is used to allow a chemically inert purge gas, such as argon (Ar), to flow into a region disposed beneath the substrate support 222, for example, via an opening in the chamber base 214 surrounding the support shaft 262. During substrate processing, the purge gas can be used to create a positive pressure region beneath the substrate support 222 (compared to the pressure in the processing region 221). Typically, the purge gas introduced via the chamber base 214 flows upward therefrom and around the edge of the substrate support 222 to exit from the processing volume 215 via the annular channel 226. The purge gas reduces unwanted material deposition on the surface beneath the substrate support 222 by reducing and / or preventing the inflow of material precursor gases therein.

[0043] Here, the substrate support assembly 220 includes a movable support shaft 262 and a substrate support member 222. The support shaft extends hermetically through a chamber base 214, such as being surrounded by a bellows 265 in a region below the chamber base 214, and the substrate support member is disposed on the movable support shaft 262. To facilitate the transfer of the substrate to and from the substrate support member 222, the substrate support assembly 220 includes a lifting pin assembly 266, which includes a plurality of lifting pins 267 coupled to or configured to engage with a lifting pin clamp 268. The lifting pins 267 are movably disposed in openings formed through the substrate support member 222. When the substrate support 222 is positioned in the lowered substrate transfer position (not shown), the lifting pins 267 extend above the substrate receiving surface of the substrate support 222 to provide a pathway for lifting the substrate 230 and being provided by the substrate processor (not shown) to the back (non-active) surface of the substrate 230. When the substrate support 222 is in the raised or processing position (as shown), the lifting pins 267 retract below the substrate receiving surface of the substrate support 222 to allow the substrate 230 to rest on it.

[0044] Here, the substrate 230 is conveyed to and removed from the substrate support 222 via a door 271 (e.g., a slit valve disposed in one or more sidewalls 212). Here, one or more openings (e.g., openings in the door housing) in the area surrounding the door 271 are fluidly coupled to a purge gas source 237, such as an Ar gas source. The purge gas is used to prevent the processing and cleaning gases from contacting and / or degrading the seals surrounding the door, thereby extending their service life.

[0045] Here, the substrate support 222 is configured for vacuum clamping, wherein the substrate 230 is secured to the substrate support 222 by applying a vacuum to the interface between the substrate 230 and the substrate receiving surface. A vacuum is applied using a vacuum source 272, which is fluidly coupled to one or more channels or ports formed in the substrate receiving surface of the substrate support 222. In other embodiments, for example, where the processing chamber 202 is configured for direct plasma processing, the substrate support 222 may be configured for electrostatic clamping. In some embodiments, the substrate support 222 includes one or more electrodes (not shown) coupled to a bias voltage power supply (not shown), such as a continuous wave (CW) RF power supply or a pulsed RF power supply, which supplies the bias voltage.

[0046] As shown in the figure, the substrate support assembly 220 has a dual-zone temperature control system to provide independent temperature control in different areas of the substrate support 222. The different temperature control zones of the substrate support 222 correspond to different areas of the substrate 230 disposed thereon. Here, the temperature control system includes a first heater 263 and a second heater 264. The first heater 263 is disposed in the central region of the substrate support 222, and the second heater 264 is disposed radially outward from the central region to surround the first heater 263. In other embodiments, the substrate support 222 may have a single heater or more than two heaters.

[0047] In some embodiments, the substrate support assembly 220 also includes an annular shielding ring 235, which is used to prevent unwanted material from being deposited on the circumferential bevel of the substrate 230. During substrate transport to and from the substrate support 222, i.e., when the substrate support assembly 220 is in a lowered position (not shown), the shielding ring 235 rests on an annular boss within the processing volume 215. When the substrate support assembly 220 is in an elevated or processing position, the radially outward surface of the substrate support 222 engages with the annular shielding ring 235 such that the shielding ring 235 surrounds the substrate 230 disposed on the substrate support 222. Here, the shielding ring 235 is shaped such that when the substrate support assembly 220 is in the elevated substrate processing position, the radially inward portion of the shielding ring 235 is disposed on the bevel of the substrate 230.

[0048] In some embodiments, the substrate support assembly 220 further includes an annular purification ring 236 disposed on the substrate support 222 to surround the substrate 230. In those embodiments, a shielding ring 235 may be disposed on the purification ring 236 when the substrate support assembly 220 is in an elevated substrate processing position. Typically, the purification ring 236 has a plurality of radially inwardly facing openings in fluid communication with a purification gas source 237. During substrate processing, purification gas flows into the annular region defined by the shielding ring 235, the purification ring 236, the substrate support 222, and the bevel of the substrate 230 to prevent processing gas from entering the annular region and causing undesirable material deposition on the bevel of the substrate 230.

[0049] In some embodiments, the processing chamber 202 is configured for direct plasma processing. In those embodiments, the spray head 218 may be electrically coupled to a first power source 231, such as an RF power source, which provides power to ignite and sustain plasma flowing into the processing gas via capacitive coupling thereto. In some embodiments, the processing chamber 202 includes an inductively coupled plasma generator (not shown) and forms plasma by inductively coupling RF power to the processing gas.

[0050] Here, the processing system 200 is advantageously configured to perform each of the tungsten nucleation, suppression treatment, and main tungsten deposition processes in a gapless and seamless tungsten interstitial filling process scheme without removing the substrate 230 from the processing chamber 202. The gas used for the individual processes of the interstitial filling process scheme and for removing residues from the inner surface of the processing chamber is supplied to the processing chamber 202 via a gas delivery system 204 fluidly coupled to the processing chamber 202.

[0051] Typically, the gas delivery system 204 includes one or more remote plasma sources, here the first and second radical generators 206A-B, a deposition gas source 240, and a conduit system 294 (e.g., these conduits 294A-F) that fluidly couple the radical generators 206A-B and the deposition gas source 240 to the cover assembly 210. The gas delivery system 204 also includes a plurality of isolation valves, here the first and second valves 290A-B, each disposed between the radical generators 206A-B and the cover plate 216, which can be used to fluidly isolate each radical generator 206A-B from the processing chamber 202 and from each other.

[0052] Here, each of the radical generators 206A-B has a chamber body 280 that defines respective first and second plasma chamber volumes 281A-B (Figure 2B). Each radical generator 206A-B is coupled to a respective power source 293A-B. The power source 293A-B is used to ignite and sustain plasma 282A-B of a gas supplied to the plasma chamber volume 281A-B from a corresponding first or second gas source 287A-B fluidly coupled thereto. In some embodiments, the first radical generator 206A generates radicals used in the differential suppression process of activity 303 (Figure 3). For example, the first radical generator 206A can be used to ignite and sustain the processing plasma 282A from a halogen-free gas mixture supplied from the first gas source 287A to the first plasma chamber volume 281A. The second free radical generator 206B can be used to generate cleaning free radicals used in the chamber cleaning process, such as the active element 308 (Figure 3), by igniting and maintaining the cleaning plasma 282B from a halogen-containing gas mixture supplied from the second gas source 287B to the second plasma chamber volume 281B.

[0053] Typically, nitrogen-treated radicals have a relatively short lifetime (compared to halogen-cleaned radicals) and can exhibit relatively high sensitivity to recombination from collisions with surfaces in the gas delivery system 204 and / or with other species in the treated plasma effluent. Therefore, in the embodiments herein, the first radical generator 206A is typically positioned closer to the gas inlet 223 than the second radical generator 206B, for example, to provide a relatively short travel distance from the first plasma chamber volume 281A to the treatment area 221.

[0054] In some embodiments, the first free radical generator 206A is also fluidly coupled to a second gas source 287B, which delivers a halogen-containing conditioning gas to the first plasma chamber volume 281A for plasma source conditioning processes, such as those described in activity 309 of method 300. In those embodiments, the gas delivery system 204 may also include a plurality of diversion valves 291 operable to direct a halogen-containing gas mixture from the second gas source 287B to the first plasma chamber volume 281A.

[0055] Suitable distal plasma sources that can be used in one or both of the free radical generators 206A-B include radio frequency (RF) or very high radio frequency (VHRF) capacitively coupled plasma (CCP) sources, inductively coupled plasma (ICP) sources, microwave-induced (MW) plasma sources, electron cyclotron resonance (ECR) chambers, or high-density plasma (HDP) chambers.

[0056] As shown in the figure, the first free radical generator 206A is fluidly coupled to the processing chamber 202 via first and second conduits 294A-B extending upward from the gas inlet 223 to connect with the outlet of the first plasma chamber volume 281A. A first valve 290A disposed between the first and second conduits 294A-B is used to selectively fluidly isolate the first free radical generator 206A from the processing chamber 202 and other parts of the gas delivery system 204. Typically, the first valve 290A is closed during the chamber cleaning process (activity 308) to prevent the inflow of activating cleaning gases (e.g., halogen free radicals) into the first plasma chamber volume 281A and damage to its surface.

[0057] Here, the first free radical generator 206A, the first and second conduits 294A-B, and the first valve 290A are arranged and / or configured such that, for example by having bends in one or both of the conduits 294A-B, the processing plasma 282A is not in direct line of sight to the gas inlet 223. In other embodiments, the first plasma chamber volume 281A may be aligned with the gas inlet 223 to provide direct line of sight from the processing plasma 282A through the gas inlet 223 into the processing chamber 202. Direct line of sight can advantageously reduce unwanted recombination of processed free radicals by reducing gas phase collisions therebetween.

[0058] The second free radical generator 206B is fluidly coupled to the second conduit 294B via the third and fourth conduits 294C-D, and thus to the processing chamber 202. Here, the second free radical generator 206B is selectively isolated from the processing chamber 202 and other parts of the gas delivery system 204 by using the second valve 290B disposed between the third and fourth conduits 294C-D. As shown, the second free radical generator 206B, the third and fourth conduits 294C-D, and the second valve 290B are arranged such that the cleaning plasma 282B is not in direct line of sight with the second valve 290B or the processing chamber. Blocking the direct line of sight between the cleaning plasma 282B and the second valve 290B and the processing chamber 202 prevents damage to the components of the second valve 290B and the processing chamber 202 caused by halide ions, thus ideally extending their service life.

[0059] In some embodiments, the plasma-facing surface 283 of one or both of the plasma chamber volumes 281A-B is formed of a halogen-based anti-plasma material, such as alumina, aluminum nitride, silicon oxide, fused silica, quartz, sapphire, or combinations thereof. In some embodiments, the plasma-facing surface 283 of the plasma chamber volumes 281A-B comprises a tube or liner formed of a halogen-resistant plasma material. In other embodiments, the plasma-facing surface 283 has a coating or layer of a halogen-based anti-plasma material formed on the inner portion of the chamber body 280, such as an anodic aluminum oxide layer formed on the inner portion of an aluminum chamber body. In some embodiments, one or more of the conduits 294A-F are lined with a low-recombination dielectric material 292, such as fused silica, quartz, or sapphire, which ideally reduces the recombination of activated species in the distal plasma effluent as it is delivered to the processing chamber 202.

[0060] Here, a fifth conduit 294E is used to deliver deposited gas (e.g., containing tungsten precursors and reducing agents) from deposited gas source 240 to processing chamber 202. As shown, the fifth conduit 294E is coupled to a second conduit 294B near gas inlet 223, such that first and second valves 290A-B can be used to isolate the first and second free radical generators 206A-B from the deposited gas introduced into processing chamber 202. In some embodiments, gas delivery system 204 also includes a sixth conduit 294F, which is coupled to a fourth conduit 294D near second valve 290B. The sixth conduit 294F is fluidly coupled to a bypass gas source 238, such as an argon (Ar) source, which can be used to periodically purge unwanted residual cleaning, suppression, and / or deposited gas from portions of gas delivery system 204.

[0061] The operation of the processing system 200 is facilitated by a system controller 208. The system controller 208 includes a programmable central processing unit, here a CPU 295, which operates in conjunction with memory 296 (e.g., non-volatile memory) and support circuitry 297. The CPU 295 is one of any form of general-purpose computer processor used in an industrial environment, such as a programmable logic controller (PLC), for controlling various chamber components and subprocessors. Memory 296, coupled to the CPU 295, facilitates the operation of the processing chambers. Support circuitry 297 is conventionally coupled to the CPU 295 and includes cache, clock circuitry, input / output subsystems, power supplies, and combinations thereof, coupled to various components of the processing system 200 (or the multi-chamber processing system 800 of Figure 8) to facilitate the control board processing operation.

[0062] Here, the instructions in memory 296 are in the form of a program product, such as a program that implements the methods of this disclosure. In one instance, this disclosure may be implemented as a program product stored on a computer-readable storage medium for use by a computer system. The program of the program product defines the functionality of the embodiments (including the methods described herein). Therefore, a computer-readable storage medium is an embodiment of this disclosure when it carries computer-readable instructions that direct the functionality of the methods described herein.

[0063] Advantageously, the above-described processing system 200 can be used to perform each of the nucleation, suppression, interstitial deposition and capping layer deposition processes of the method 300 illustrated in Figure 3, thereby providing a single-chamber seamless tungsten interstitial solution.

[0064] Figure 3 is a diagram illustrating a method 300 for processing a substrate according to an embodiment, which can be performed using a processing system 200. Figures 4A-4D are schematic cross-sectional views of portions of the substrate 400, illustrating the state of method 300 at different stages of a gapless and seamless tungsten interstitial filling process.

[0065] In activity 301, method 300 includes receiving a substrate into a processing volume 215 of a processing chamber 202. In activity 302, method 300 includes forming a nucleation layer 404 on the substrate using a nucleation process. Figure 4A schematically illustrates a portion of an exemplary substrate 400 on which the nucleation layer 404 is formed.

[0066] Here, the substrate 400 has a patterned surface 401, which includes a dielectric material layer 402 in which a plurality of openings 405 (one shown in the figure) are formed. In some embodiments, these openings 405 include one or a combination of high aspect ratio vias or trench openings with a width of about 1 or less, such as about 800 nm or less, or about 500 nm or less, and a depth of about 2 or more, such as about 3 or more, or about 4 or more. In some embodiments, individual openings in the openings 405 may have an aspect ratio of about 5:1 or higher, such as about 10:1 or higher, 15:1 or higher, or between about 10:1 and about 40:1, such as between about 15:1 and about 40:1. As shown, the patterned surface 401 includes a barrier or adhesive layer 403, such as a titanium nitride (TiN) layer, which is deposited on the dielectric material layer 402 to conformally line the opening 405 and facilitate the subsequent deposition of the tungsten nucleation layer 404. In some embodiments, the adhesive layer 403 is deposited to a thickness between about 2 Å and about 100 Å.

[0067] In some embodiments, method 300 includes depositing an adhesive layer 403 using a second processing chamber of the multi-chamber processing system 800, as shown in Figure 8, before receiving the substrate into the processing chamber 202. In some embodiments, method 300 includes sequentially depositing the adhesive layer 403 and a nucleation layer 404 in the same processing chamber 202. In some embodiments, the adhesive layer 403 serves as a nucleation layer on which subsequent bulk tungsten deposition can be performed. In embodiments where the adhesive layer 403 serves as a nucleation layer, method 300 may not include activity 302.

[0068] In some embodiments, the nucleation layer 404 is deposited using an atomic layer deposition (ALD) process. Typically, an ALD process involves repeatedly exposing the substrate 400 alternately to a tungsten-containing precursor, exposing the substrate 400 to a reducing agent, and cleaning the treatment region 221 between the alternating exposures. Examples of suitable tungsten-containing precursors include tungsten halides, such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), or combinations thereof. Examples of suitable reducing agents include hydrogen (H2), boranes (e.g., B2H6), and silanes (e.g., SiH4, Si2H6, or combinations thereof). In some embodiments, the tungsten-containing precursor comprises WF6, and the reducing agent comprises B2H6, SiH4, or combinations thereof. In some embodiments, the tungsten-containing precursor comprises an organometallic precursor and / or a fluorine-free precursor, such as MDNOW (methylcyclopentadienyl-dicarbonylnitroso-tungsten), EDNOW (ethylcyclopentadienyl-dicarbonylnitroso-tungsten), hexacarbonyltungsten (W(CO)6), or a combination thereof.

[0069] During the nucleation process, the processing volume 215 is typically maintained at a pressure less than about 120 Torr, such as between about 900 mTorr and about 120 Torr, between about 1 Torr and about 100 Torr, or for example, between about 1 Torr and about 50 Torr. Exposing the substrate 400 to the tungsten-containing precursor includes allowing the tungsten-containing precursor to flow from the deposition gas source 240 into the processing region 221 at a flow rate exceeding about 10 sccm, such as between about 10 sccm and about 1000 sccm, such as between about 10 sccm and about 750 sccm, or between about 10 sccm and about 500 sccm. Exposing the substrate 400 to the reducing agent includes allowing the reducing agent to flow from the deposition gas source 240 into the processing region 221 at a flow rate between about 10 sccm and about 1000 sccm, such as between about 10 sccm and about 750 sccm. It should be noted that the flow rates for the various deposition and processing procedures described herein are for a processing system 200 configured to process substrates with a diameter of 300 mm. Appropriate scaling can be used for processing systems configured to process substrates of different sizes.

[0070] Here, the tungsten-containing precursor and the reducing agent each flow into the processing zone 221 for a duration of approximately 0.1 seconds to approximately 10 seconds, such as a duration of approximately 0.5 seconds to approximately 5 seconds. The processing zone 221 can be purified between alternating exposures by allowing an inert purge gas, such as argon (Ar), to flow into the processing zone 221 for a duration of approximately 0.1 seconds to approximately 10 seconds, such as a duration of approximately 0.5 seconds to approximately 5 seconds. The purge gas can be supplied from the deposition gas source 240 or from the bypass gas source 238. Typically, the repeated cycles of the nucleation process continue until the thickness of the nucleation layer 404 is between approximately 10 Å and approximately 200 Å, such as between approximately 10 Å and approximately 150 Å, or between approximately 20 Å and approximately 150 Å.

[0071] At activity 303, method 300 includes treating nucleation layer 404 to suppress tungsten deposition on the field surface of substrate 400 and forming a differential suppression distribution in the openings 405 by using a differential suppression process. Typically, forming a differential suppression distribution includes exposing nucleation layer 404 to an activated species of a process gas, such as process radical 406 shown in Figure 4B. Suitable process gases that can be used for the suppression process include N2, H2, NH3, NH4, O2, CH4, or combinations thereof. In some embodiments, the process gas contains nitrogen, such as N2, H2, NH3, NH4, or combinations thereof, and the activated species contains nitrogen radicals, such as atomic nitrogen. In some embodiments, the process gas is combined with an inert carrier gas, such as Ar, He, or combinations thereof, to form a process gas mixture.

[0072] Without being bound by theory, it is believed that activated nitrogen species (treated free radicals 406) are incorporated into portions of the nucleation layer 404 by adsorption of activated nitrogen species and / or by reaction with metallic tungsten of the nucleation layer 404 to form a tungsten nitride (WN) surface. The adsorbed nitrogen and / or nitride surface of the tungsten nucleation layer 404 ideally delays (inhibits) further tungsten nucleation and thus subsequent tungsten deposition thereon.

[0073] Typically, the diffusion of treated radicals 406 into these openings 405 is controlled to generate the desired suppression gradient within the feature openings 405. Here, the diffusion of treated radicals 406 is controlled such that the tungsten growth suppression effect on the walls of the openings 405 decreases with increasing distance from the region of the patterned surface 401 (Figures 4B-4C). As a result, tungsten nucleation is more easily established at or near the bottom of the feature, and once established, tungsten growth (deposition of interstitial material 408) within the openings 405 accelerates from the nucleation point (e.g., from the bottom of the openings 405 where there is no or low suppression) to provide seamless tungsten interstitial filling from bottom to top. The direction of the suppression gradient, from the high-suppression region to the unsuppressed or low-suppression region, is indicated by arrow 417 (Figure 4C). The diffusion of the treated radicals 406 into the opening 405 typically depends at least in part on the size and aspect ratio of the opening 405, and can be modulated by controlling, in particular, the energy, flux, and, in some embodiments, the directionality of the treated radicals 406 at the patterned surface 401.

[0074] In some embodiments, exposing the nucleation layer 404 to the processing radical 406 includes forming a processing plasma 282A that is substantially free of halogens using a first radical generator 206A and allowing the effluent of the processing plasma 282A to flow into the processing region 221. In some embodiments, the flow rate of the process gas mixture entering the first free radical generator 206A and thus the flow rate of the process plasma effluent entering the processing zone 221 are between about 1 sccm and about 3000 sccm, such as between about 1 sccm and about 2500 sccm, between about 1 sccm and about 2000 sccm, between about 1 sccm and about 1000 sccm, between about 1 sccm and about 500 sccm, between about 1 sccm and about 250 sccm, between about 1 sccm and about 100 sccm, or between about 1 sccm and about 75 sccm, for example, between about 1 sccm and about 50 sccm.

[0075] In some embodiments, the flow rate of the process gas mixture entering the first free radical generator 206A is between about 50 sccm and about 3000 sccm, such as between about 50 sccm and about 2500 sccm, between about 50 sccm and about 2000 sccm, between about 50 sccm and about 1000 sccm, between about 50 sccm and about 500 sccm, or between about 50 sccm and about 250 sccm. In some embodiments, the flow rate of the substantially halogen-free process gas (e.g., N2) is between about 1 sccm and about 200 sccm, such as between about 1 sccm and about 100 sccm, and the flow rate of the inert carrier gas is between about 50 sccm and about 3000 sccm, such as between about 50 sccm and about 2000 sccm, or between about 100 sccm and about 2000 sccm.

[0076] In some embodiments, the suppression process includes exposing the substrate 400 to the treatment free radicals 406 for about 5 seconds or longer, such as about 6 seconds or longer, about 7 seconds or longer, about 8 seconds or longer, about 9 seconds or longer, about 10 seconds or longer, or between about 5 seconds and about 120 seconds, such as between about 5 seconds and about 90 seconds, or between about 5 seconds and about 60 seconds, or between about 5 seconds and about 30 seconds, for example, between about 5 seconds and about 20 seconds.

[0077] In some embodiments, the concentration of the substantially halogen-free process gas in the process gas mixture is between about 0.5 vol.% and about 50 vol.%, such as between about 0.5 vol.% and about 40 vol.%, about 0.5 vol.% and about 30 vol.%, about 0.5 vol.% and about 20 vol.%, or for example, between about 0.5 vol.% and about 10 vol.%, such as between about 0.5 vol.% and about 5 vol.%.

[0078] In some embodiments, for example, when the substantially halogen-free process gas contains N2, NH3 and / or NH4, the first free radical generator 206A can be used to activate atomic nitrogen between about 0.02 mg and about 150 mg during the suppression process of a 300 mm diameter substrate, such as between about 0.02 mg and about 150 mg, or between about 0.02 mg and about 100 mg, between about 0.1 mg and about 100 mg, or between about 1 mg and about 100 mg. In some embodiments, the first radical generator 206A can be used to activate about 0.02 mg or more of atomic nitrogen during a suppression process on a 300 mm diameter substrate, such as about 0.2 mg or more, about 0.4 mg or more, about 0.6 mg or more, about 0.8 mg or more, about 1 mg or more, about 1.2 mg or more, about 1.4 mg or more, about 1.6 mg or more, about 1.8 mg or more, about 2 mg or more, about 2.2 mg or more, about 2.4 mg or more, about 2.6 mg or more, about 2.8 mg or about 3 mg or more. Appropriate scaling can be used in processing systems configured to process substrates of different sizes.

[0079] In other embodiments, the processed radicals 406 may be formed using a distal plasma (not shown) that is ignited and held in a portion of the processing volume 215 separated from the processing region 221 by the spray head 218, such as between the spray head 218 and the cover plate 216. In those embodiments, the activated processing gas may flow through an ion filter to substantially remove all ions therefrom before the processed radicals 406 reach the processing region 221 and the surface of the substrate 400. In some embodiments, the spray head 218 may be used as an ion filter. In other embodiments, the plasma for forming the processed radicals is an in-situ plasma formed in the processing region 221 between the spray head 218 and the substrate 400. In some embodiments, for example, when using an in-situ processing plasma, the substrate 400 may be biased to control directionality and / or accelerate ions, such as charged processed radicals, formed by the processing gas toward the substrate surface.

[0080] In some embodiments, the suppression process includes maintaining the processing volume 215 at a pressure of less than about 100 Torr while allowing activated processing gas to flow into it. For example, during the suppression process, the processing volume 215 may be maintained at a pressure of less than about 75 Torr, such as less than about 50 Torr, less than about 25 Torr, less than about 15 Torr, or between about 0.5 Torr and about 120 Torr, such as between about 0.5 Torr and about 100 Torr, or between about 0.5 Torr and about 50 Torr, or for example, between about 1 Torr and about 10 Torr.

[0081] At activity 304, method 300 includes selectively depositing tungsten interstitial material 408 (Figures 4C-4D) into the openings 405 according to the differential suppression distribution provided by the suppression treatment at activity 303. In one embodiment, the tungsten interstitial material 408 is formed using a low-stress chemical vapor deposition (CVD) process, which includes simultaneously flowing (co-flowing) a tungsten-containing precursor gas and a reducing agent into the processing region 221 and exposing the substrate 400 thereto. The tungsten-containing precursor and reducing agent used in the tungsten interstitial CVD process may include any combination of the tungsten-containing precursor and reducing agent described in activity 301. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent includes H2.

[0082] Here, the tungsten-containing precursor flows into the processing region 221 at a rate between about 50 sccm and about 1000 sccm, or greater than about 50 sccm, or less than about 1000 sccm, or between about 100 sccm and about 900 sccm. The reducing agent flows into the processing region 221 at a rate greater than about 500 sccm, such as greater than about 750 sccm, greater than about 1000 sccm, or between about 500 sccm and about 10000 sccm, such as between about 1000 sccm and about 9000 sccm, or between about 1000 sccm and about 8000 sccm.

[0083] In some embodiments, tungsten interstitial CVD process conditions are selected to provide tungsten characteristics with relatively low residual film stress compared to conventional tungsten CVD processes. For example, in some embodiments, the tungsten interstitial CVD process includes heating the substrate to a temperature of about 250°C or higher, such as about 300°C or higher, or between about 250°C and about 600°C, or between about 300°C and about 500°C. During the CVD process, the processing volume 215 is typically maintained at a pressure of less than about 500 Torr, less than about 600 Torr, less than about 500 Torr, less than about 400 Torr, or between about 1 Torr and about 500 Torr, such as between about 1 Torr and about 450 Torr, or between about 1 Torr and about 400 Torr, or for example, between about 1 Torr and about 300 Torr.

[0084] In another embodiment, tungsten interstitial material 408 is deposited at activity 304 using an atomic layer deposition (ALD) process. The tungsten interstitial ALD process includes repeatedly exposing substrate 400 alternately to a tungsten-containing precursor gas and a reducing agent, and purging treatment region 221 between the alternating exposures. The tungsten-containing precursor and reducing agent used in the tungsten interstitial ALD process may include any combination of the tungsten-containing precursor and reducing agent described in activity 301. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent includes H2.

[0085] Here, the tungsten-containing precursor and the reducing agent each flow into the processing zone 221 for a duration between approximately 0.1 seconds and approximately 10 seconds, such as a duration between approximately 0.5 seconds and approximately 5 seconds. The processing zone 221 is typically purified between alternating exposures by flowing an inert purging gas, such as argon (Ar), into the processing zone 221 for a duration between approximately 0.1 seconds and approximately 10 seconds, such as a duration between approximately 0.5 seconds and approximately 5 seconds. The purging gas can be supplied from the deposition gas source 240 or from the bypass gas source 238.

[0086] Exposing the substrate 400 to the tungsten-containing precursor may include allowing the tungsten-containing precursor to flow from the deposition gas source 240 into the processing region 221 at a flow rate between about 10 sccm and about 1000 sccm, such as between about 100 sccm and about 1000 sccm, between about 200 sccm and about 1000 sccm, between about 400 sccm and about 1000 sccm, or between about 500 sccm and about 900 sccm. Exposing the substrate 400 to the reducing agent may include allowing the reducing agent to flow from the deposition gas source 240 into the processing region 221 at a flow rate between about 500 sccm and about 10000 sccm, such as between about 500 sccm and about 8000 sccm, between about 500 sccm and about 5000 sccm, or between about 1000 sccm and about 4000 sccm.

[0087] In some embodiments, the tungsten interstitial ALD process includes heating the substrate to a temperature of about 250°C or higher, such as about 300°C or higher, or between about 250°C and about 600°C, or between about 300°C and about 500°C. In some embodiments, the ALD process includes maintaining the processing volume 215 at a pressure of less than about 150 Torr, less than about 100 Torr, less than about 50 Torr, for example less than about 30 Torr, or between about 0.5 Torr and about 50 Torr, such as between about 1 Torr and about 20 Torr.

[0088] In other embodiments, the tungsten interstitial material 408 is deposited using a pulsed CVD method, which involves repeatedly and alternately exposing the substrate 400 to a tungsten-containing precursor gas and a reducing agent without purging the treated area 221. The processing conditions of the tungsten interstitial pulsed CVD method may be the same as, substantially the same as, or within the same range as the processing conditions of the tungsten interstitial ALD process described above.

[0089] Advantageously, the above-described tungsten interstitial process provides relatively low residual stress in the tungsten material formed therefrom. Unbound by theory, it is believed that the increased energy provided by the relatively high substrate temperature (e.g., 250°C or higher) increases the diffusion rate of adsorbed atoms at open adsorption sites, while the relatively low processing pressure simultaneously slows down the tungsten interstitial deposition process. Compared to conventional conformal CVD processes, the increased diffusion rate of adsorbed atoms and the reduced deposition rate help improve the atomic arrangement in the deposited tungsten material (to achieve greater order), thereby advantageously resulting in lower residual film stress in the tungsten interstitial material. For example, in some embodiments, a tungsten blanket coating deposited using the above processing conditions to a thickness of about 1,200 Å has a residual film stress of less than about 1600 MPa, less than about 1500 MPa, less than about 1400 MPa, less than about 1300 MPa, less than about 1200 MPa, less than about 1100 MPa, less than about 1000 MPa, less than about 900 MPa, less than about 800 MPa, less than about 700 MPa, or in some embodiments, less than about 600 MPa.

[0090] In a typical semiconductor manufacturing process, chemical mechanical polishing (CMP) is used to remove a capping layer (and a barrier layer disposed thereunder) of tungsten material from the field surface of a substrate after depositing tungsten interstitial material 408 to openings 405. CMP processes typically rely on a combination of chemical and mechanical activity to facilitate uniform removal of the capping layer 410 and endpoint detection methods to determine when the tungsten capping layer has been removed from the field surface. Inhomogeneous removal of tungsten from the field surface or failure to detect the polishing endpoint can lead to undesirable over-polishing or under-polishing of at least some areas of the substrate surface. Over-polishing of tungsten can result in undesirable removal of tungsten from tungsten features (e.g., feature corering) because the polishing slurry in the CMP process is typically corrosive and can damage features during over-polishing. Under-polishing of tungsten can result in undesirable residual tungsten remaining on the field surface after CMP.

[0091] Unfortunately, the suppression process used to provide seamless and void-free tungsten features by promoting bottom-up tungsten growth also suppresses tungsten growth on the field surface to prevent the formation of a uniform tungsten capping layer during the main tungsten process. Therefore, embodiments herein may include a process for depositing a capping layer that differs from the process for depositing tungsten interstitial material 408 to provide a uniform tungsten thickness on the field surface of the substrate required for subsequent CMP processing.

[0092] In activity 305, method 300 may include forming a second nucleation layer 409 (Figure 4D) using a second nucleation process. In activity 306, method 300 includes forming a capping layer 410 using a capping layer process. The second nucleation process and / or capping layer process are used to reduce and / or eliminate tungsten growth inhibition on the field surface of the substrate, which is provided by the inhibition treatment process at activity 303. By reducing and / or reversing the inhibition effect, the field surface is prepared to allow the growth and / or deposition of a capping layer of tungsten material. The capping layer 410 may be used to facilitate uniform processing in subsequent chemical mechanical polishing (CMP) processes.

[0093] In some embodiments, the second nucleation layer 409 is deposited using an ALD process that is the same as or substantially similar to the ALD process used to form the (first) nucleation layer 404 in activity 302, or an ALD process having processing conditions within the range listed for the ALD process in activity 302. When used, the second nucleation layer 409 may be deposited to a thickness between about 5 Å and 100 Å, or between about 10 Å and 80 Å, or, for example, between about 20 Å and 60 Å.

[0094] The process used for depositing the capping layer 410 in activity 306 may be the same or substantially similar to the CVD or ALD process used for depositing the interstitial tungsten material in activity 304, or a process having the processing conditions within the range listed for the process in activity 302. In other embodiments, a CVD process with a processing pressure greater than that used for the tungsten interstitial process in activity 302 is used to deposit the capping layer. For example, in some embodiments, the ratio of the processing pressure used for depositing the capping layer 410 to the processing pressure used for depositing the tungsten interstitial material 408 is about 1.25:1 or greater, such as about 1.5:1 or greater, about 1.75:1 or greater, about 2:1 or greater, about 2.25:1 or greater, about 2.5:1 or greater, about 2.75:1 or greater, about 3:1 or greater, about 3.25:1 or greater, or about 3.5:1 or greater. The increased processing pressure of the capping layer process advantageously results in an increased deposition rate and a reduced substrate processing time. Here, the capping layer is deposited to a thickness between approximately 500 Å and approximately 6000 Å, such as between approximately 1000 Å and approximately 5000 Å.

[0095] In activity 307, method 300 includes transferring the processed substrate 400 out of processing chamber 202 and restarting at activity 301 by receiving the substrate to be processed into 202. In some embodiments, method 300 further includes periodically cleaning the processing chamber 202 between the processed substrates at activity 308 using a chamber cleaning process. The chamber cleaning process is used to remove unwanted process residues, such as accumulated tungsten residues, from the inner surface of the processing volume 215. In some embodiments, the chamber cleaning process is performed after the number of substrates sequentially processed in processing chamber 202 is greater than or equal to a threshold value, such as greater than or equal to 2 or more substrates, 3 or more substrates, 5 or more substrates, 7 or more substrates, 9 or more substrates, or 11 or more substrates.

[0096] In activity 308 of method 300, the chamber cleaning process typically includes activating a cleaning gas in a remote plasma source and allowing the activated cleaning gas to flow into the processing chamber 202. Typically, the cleaning gas mixture includes a halogen-containing gas and a carrier gas, such as argon or helium. Examples of suitable halogen-containing gases that can be used in the cleaning gas mixture include NF3, F2, SF6, Cl2, CF4, C2F6, C4F8, CHF3, CF6, CCl4, C2Cl6, and combinations thereof. In some embodiments, the cleaning gas further includes a diluent gas, such as Ar, He, or combinations thereof. For example, in one embodiment, the cleaning gas mixture includes NF3 and Ar or He. Typically, the activated species (e.g., halogen radicals) of the cleaning gas mixture react with tungsten residues accumulated on the surface of the processing chamber 205 to form volatile tungsten species. The volatile tungsten species are discharged from the processing volume 215 via exhaust port 217.

[0097] In some embodiments, the flow rate of the cleaning gas mixture entering the remote plasma source, and thus the flow rate of the activating cleaning gas mixture entering the processing volume 215, is about 500 sccm or greater, such as about 1000 sccm or greater, 1500 sccm or greater, about 2000 sccm or greater, or about 2500 sccm or greater. The concentration of halogen-containing gas in the cleaning gas mixture is typically between about 5 vol.% and about 95 vol.%, such as between about 5 vol.% and about 70 vol.%, about 10 vol.% and about 95 vol.%, or more than about 10 vol.%. In some embodiments, the activating cleaning gas mixture flows into the processing volume 215 for a duration of about 5 seconds or longer, about 10 seconds or longer, or about 15 seconds or longer. In some embodiments of the chamber cleaning process, for a processing chamber used to process substrates with a diameter of 300 mm, a distal plasma source can be used to activate about 5 mg or more atomic halogens, such as fluorine or chlorine, such as about 10 mg or more, about 15 mg or more, about 20 mg or more, about 25 mg or more, about 30 mg or more, about 35 mg or more, about 40 mg or more, about 45 mg or more, or for example, about 50 mg or more. Appropriate scaling can be used for the processing chamber, the size of which is suitable for processing substrates of different sizes.

[0098] Here, a remote plasma source (e.g., a second radical generator 206B) is used for the chamber cleaning process, which is different from the remote plasma source (e.g., a first radical generator 206A) used to generate treatment radicals at activity 303. For example, here, the chamber cleaning process includes flowing a cleaning gas mixture into the second radical generator 206B, igniting and maintaining a cleaning plasma 282B of the cleaning gas mixture, and flowing the effluent of the cleaning plasma 282B into the processing volume 215. Typically, performing a chamber cleaning operation after each substrate processed in the processing chamber 202 is undesirable due to the associated loss of substrate processing capacity. Therefore, the chamber cleaning operation is typically performed after a plurality of substrates have been processed in the chamber, such that the average number of substrates processed between chamber cleaning operations is about 2 substrates or more, such as about 5 substrates or more, about 10 substrates or more, about 15 substrates or more, or about 20 substrates or more.

[0099] Using a dedicated plasma source (first radical generator 206A) for the suppression process at activity 303 ideally provides improved processing stability compared to using a common plasma source for both the suppression process and the chamber cleaning process. This is likely because the corrosiveness of the plasma formed by the processing gas is significantly lower than that of the plasma formed by the halogen-based cleaning gas, and therefore, the ion-based damage to the surfaces within the first radical generator 206A is relatively low. Nevertheless, when using a processing plasma source dedicated to forming nitrogen-based processing radicals, at least some drift in processing performance is observed at the substrate edges; for example, a decrease in suppression performance at the substrate edges.

[0100] Without being bound by theory, it is believed that activated nitrogen species can adsorb onto the plasma-facing surface of the distal plasma source and onto the surface of the conduit between the distal plasma source and the processing chamber, and / or cause nitridation thereon. Adsorbed nitrogen and / or nitrided surface 407 can reduce processing plasma efficiency, for example, by reducing the dissociation rate of the processing gas and / or promoting the recombination of activated nitrogen species exposed thereon, thereby resulting in a decrease in the concentration and flux of free radicals at the substrate surface. Therefore, in some embodiments, the first free radical generator 206A is periodically regulated by igniting and sustaining the plasma from a relatively low flow rate and / or concentration of halogen-containing gas to remove adsorbed nitrogen and / or nitrides from the surfaces therein, as described in activity 309. A plasma source conditioning process is used to activate the surface of the first free radical generator 206A to extend the lifetime of processing free radicals subsequently formed therein. Generally, extending the lifetime of processing free radicals allows for an increase in the number of substrates that can be processed between chamber cleaning processes.

[0101] In Figure 3, the plasma source conditioning process is shown to be performed after the processed substrate is transferred from the processing chamber 202 and before the subsequent substrate to be processed is received therein. In other embodiments, the plasma source conditioning process may be performed while the substrate is positioned on the substrate support 222, for example, before the differential suppression process of activity 303 (as shown by the dashed line), after the differential suppression process of activity 303, or before, after, or simultaneously with any of the respective nucleation, gap-filling, and capping processes at activities 302, 304, 305, and 306.

[0102] In activity 309, method 300 includes flowing a conditioning gas mixture into a first free radical generator 206A and activating the conditioning gas mixture by igniting and maintaining its plasma. Here, the conditioning gas mixture comprises a halogenated gas and an inert carrier gas, such as Ar, He, or combinations thereof. Suitable halogenated gases that can be used for the conditioning gas mixture are described in activity 308. In some embodiments, the halogenated gas includes NF3.

[0103] In some embodiments, the halogen-containing gas comprises a conditioning gas mixture of about 0.1 vol.% to about 50 vol.%, such as between about 0.1 vol.% and about 40 vol.%, between about 0.1 vol.% and about 30 vol.%, between about 0.1 vol.% and about 25 vol.%, or, for example, between 0.1 vol.% and about 25 vol.%. The conditioning gas mixture flows into the first free radical generator 206A at a flow rate of about 100 sccm to about 2000 sccm, and the plasma of the conditioning gas mixture is ignited and maintained for a period of about 1 second to about 30 seconds, or about 1 second or longer, or about 30 seconds or less. In some embodiments, the halogen-containing gas may be introduced into the first free radical generator 206A at an effective flow rate between about 0.1 sccm and about 30 sccm, such as between about 0.1 sccm and about 20 sccm, between about 0.1 sccm and about 10 sccm, or between about 0.1 sccm and about 5 sccm. Here, the effective flow rate is equal to the flow rate of the conditioning gas mixture multiplied by the vol.% of the halogen-containing gas.

[0104] In some embodiments, the first radical generator 206A can be used to activate atomic halogens, such as fluorine or chlorine, between about 0.002 mg and about 40 mg during plasma source condition processes, such as between about 0.002 mg and about 35 mg, or between about 0.02 mg and about 30 mg, between about 0.02 mg and about 25 mg, between about 0.02 mg and about 20 mg, or between about 0.02 mg and about 15 mg. In some embodiments, the first radical generator 206A can be used to activate at least about 0.02 mg and no more than about 40 mg of atomic halogens, such as no more than about 35 mg, no more than about 30 mg, no more than about 25 mg, no more than about 20 mg, no more than about 15 mg, no more than about 10 mg, or at least about 0.02 mg and no more than about 8 mg of atomic halogens during plasma source condition processes.

[0105] In some embodiments, it may be necessary to limit the amount of halogen radicals exposed on the inner surface of the first radical generator 206A between plasma suppression processes. In those embodiments, for example, the weight ratio (fluorine (mg) / nitrogen (mg) or chlorine (mg) / nitrogen (mg)) of activated halogen species generated in the first radical generator 206A during the plasma source conditioning process to activated nitrogen radicals generated in subsequent suppression processes may not exceed about 5:1, such as not exceeding about 4:1, not exceeding about 3:1, or not exceeding about 2:1, for example not exceeding about 1:1.

[0106] As described above, the plasma source conditioning process advantageously improves the processing stability from substrate to substrate and the processing uniformity within the substrate. Unbound by theory, it is believed that activated nitrogen species used in the suppression process adsorb onto the surface of the conduit between the source and the chamber, and that the nitrided surface promotes the recombination rate of the activated nitrogen species subsequently flowing through it. The plasma source conditioning process advantageously removes nitrogen species from the surfaces between substrates, and thus helps to reduce the recombination rate and extend the lifetime of processed free radicals.

[0107] Figure 5 is a diagram illustrating a method 500 for processing a substrate according to another embodiment, which can be performed using the processing system 200 described in Figures 2A-2B. It is contemplated that any of the activities and / or processing conditions described in method 500 can be combined with or used in place of the activities and / or processing conditions described in method 300. Figures 6A-6D are schematic cross-sectional views of portions of substrate 400, illustrating various states of method 500 at different stages of a void-free and seamless tungsten interstitial filling process. Figure 6A schematically illustrates substrate 600 after activities 501-503 of method 500 are performed.

[0108] In activity 501, method 500 includes receiving substrate 600 into processing volume 215 of processing chamber 202. Substrate 600 has a patterned surface 401, which includes a dielectric material layer 402 having a plurality of openings 405 (one shown in the figure) formed therein, and may include any of the features and / or properties of substrate 400 described in figures 4A-4D, such as conformal adhesive layer 403.

[0109] In activity 502, method 500 includes depositing a first nucleation layer 404. The first nucleation layer 404 can be deposited using the nucleation process described in activity 302 of method 300.

[0110] In activity 503, method 500 includes depositing a conformal tungsten layer 605 on the first nucleation layer 404. The conformal tungsten layer 605 can be deposited using process and / or process conditions of any one or a combination of low-stress CVD, ALD, or pulsed CVD processes described in the selective gap-filling process of activity 304. Here, the tungsten layer 605 is deposited on the unsuppressed tungsten nucleation layer 404 and is therefore conformal to the patterned surface 401 of the substrate 600, for example, conformally lining an opening 405 formed therein. In some embodiments, the conformal tungsten layer 605 may be deposited to a thickness greater than about 50 angstroms (Å), such as between about 50 Å and about 1000 Å, or between about 50 Å and about 500 Å.

[0111] In activity 504, method 500 includes depositing a second nucleation layer 607 (Figure 6B) on a conformal tungsten layer 605. In some embodiments, the second nucleation layer 607 is formed using the same process as that used to form the first nucleation layer 404 or a different process within the same processing conditions.

[0112] At activity 505, method 500 includes processing the second nucleation layer 607 to suppress tungsten deposition on the field surface of substrate 600 and forming a differential suppression distribution in the openings 405 by using a differential suppression process. Activity 505 is illustrated in Figure 6B and can be performed using any of the processes or processing conditions described in activity 303 of method 300.

[0113] In some embodiments, method 500 includes performing a plasma source conditioning process (activity 509) after forming the second nucleation layer 607 in activity 504 and before performing a suppression process in activity 505. In those embodiments, the stacked layer of the first nucleation layer 404, the conformal tungsten layer 605, and the second nucleation layer 607 can protect the underlying surface from etching and / or damage caused by effluents (halogen radicals) exposed to the plasma source conditioning process.

[0114] At activity 506, method 500 includes selectively depositing a bulk tungsten filler material 408 (Figures 6C-6D) into the openings 405 according to the differential suppression distribution provided by the suppression treatment at activity 505. Activity 506 may be performed using any one or a combination of process or processing conditions of a selective gap-filling process as described in activity 304 for method 300.

[0115] At activity 507, method 500 includes transferring substrate 600 out of processing chamber 202, and in some embodiments, transferring substrate to be processed into processing chamber 202 and repeating method 500.

[0116] In some embodiments, method 500 also includes performing a chamber cleaning process at activity 508 and / or a plasma source condition process at activity 509. Activities 508 and 509 may be performed using any one or a combination of the processes, processing conditions and / or sequences of operations described in activities 308 and 309 of method 300, respectively.

[0117] In some embodiments, method 500 also includes forming a capping layer 609 of tungsten material on the field surface of substrate 600. In some embodiments, forming capping layer 609 includes continuing a gap-filling process in activity 506 until the inhibition effect on the field surface is overcome, and tungsten material may be deposited thereon. In other embodiments, capping layer 609 may be formed using one or a combination of the processes described in activities 305 and 306 of method 300.

[0118] The methods and systems provided above can be used to ideally reduce substrate-to-substrate process variability and improve the uniformity of processing within the substrate, while providing increased substrate throughput and reduced substrate processing costs. The experimental results shown in Figures 7A-7B demonstrate the increased processing stability and improved uniformity of processing within the substrate provided by the above systems and methods.

[0119] Figure 7A is graph 700A, illustrating the processing results of a plurality of substrates processed on a processing system without using the plasma source conditions described in activities 309 and 509. Figure 7B is graph 700B, illustrating the processing results of a plurality of substrates processed using the plasma source conditioning process described in activities 309 and 509. In each of Figures 7A-7B, a plurality of 300 mm diameter substrates (each substrate having a tungsten nucleation layer formed) are exposed to nitrogen-treated free radicals formed using a dedicated remote plasma source (e.g., a first free radical generator 206A), and then a layer of tungsten is deposited thereon using a tungsten interstitial process, as described in activity 304.

[0120] In Figure 7A, a plurality of substrates (300 substrates) are processed sequentially without using a plasma source conditioning process, such that the first radical generator 206A is not exposed to halogen-containing cleaning gases between suppression processes. In Figure 7B, a plurality of substrates (600 substrates) are processed sequentially using the same conditions as the substrates in Figure 7A, except that the distal plasma source (first radical generator 206A) is conditioned using the plasma source conditioning process of activity 309 between each suppression process. Tungsten thicknesses are measured at the center of each substrate and at radii of 50 mm (line 702A-B), 100 mm (line 704A-B), and 147 mm (line 706A-B). To reduce visual clutter, the tungsten thickness measurements at the center of each substrate are not shown, but are within approximately + / - 2.5% of the thickness measurements at radii of 50 mm (line 702A-B) and 100 mm (line 704A-B).

[0121] As shown in Figure 7A, the suppression effect at the edge of substrate 706A (as indicated by the thickness of the tungsten material deposited thereon) decreases in the first 50 sequentially processed substrates, while the suppression effect in the region radially inward from the edge remains relatively stable between substrates. Conversely, in Figure 7B, compared to the radially inward regions 702B and 704B, the suppression effect at the edge of substrate 706B remains relatively stable for more than 600 sequentially processed substrates.

[0122] In a typical processing system 200 where the gas inlet 223 is centrally located via the cover plate 216, activated nitrogen species used to process the substrate edge travel a greater distance to reach the substrate surface than activated species used to process surface regions disposed radially inward from the substrate edge. Without being bound by theory, it is believed that the greater travel distance can lead to a reduction in the excitation of activated species or an increase in the recombination of activated species at the substrate edge. It is believed that a non-ideal reduction in the concentration and flux of treated radicals at the substrate edge can lead to a corresponding reduction in the suppression effect received from them. Therefore, it is believed that the improvement in intra-substrate uniformity and the reduction in inter-substrate processing variability shown in Figures 7A-7B are the result of increased radical lifetime and / or the generation of at least metastable radical species achieved by the plasma source conditioning process. In the embodiments herein, the metastable radical species are radicals, such as nitrogen-treated radicals, having a lifetime of about 3 seconds or longer.

[0123] In some embodiments, the above method can be performed using a multi-chamber processing system 800, as shown in Figure 8. Here, the multi-chamber processing system 800 includes a plurality of system loading stations, here loading gates 802, for receiving substrates. Loading gates 802 may be hermetically sealed and typically coupled to a vacuum, such as one or more vacuum pumps, which can be used to evacuate air from there and maintain loading gates 802 at sub-atmospheric pressure. A substrate processor 830 disposed in a transfer chamber 811 is used to move substrate 230 between loading gates 802 and one or more processing chambers 812, 814, 202. Each processing chamber 812 and 814 may be configured to perform at least one of the substrate deposition processes, such as cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etching, degassing, pre-cleaning orientation, annealing, and other substrate processes. The processing system 200 is described in Figures 2A-2B and configured to perform the tungsten interstitial processing scheme described herein.

[0124] In some embodiments, one or more of the processing chambers 812, 814 are configured to perform a pre-cleaning process prior to a deposition process or a thermal annealing process on the substrate 230. In some embodiments, the aforementioned adhesive layer 403, for example, a TiN layer, is deposited in one of the processing chambers 812, 814 before the substrate 230 is transferred under vacuum (e.g., via transfer chamber 811) to a processing system 200 with which it is fluidly coupled.

[0125] Advantageously, the above-described processing systems 200 and 800 are configured to accommodate the different processing conditions required for each of the nucleation, suppression, interstitial deposition, and capping deposition processes within a single processing chamber 202, without removing the substrate from it. Processing system 200 is further configured to reduce processing variability, such as intra-substrate processing inhomogeneities and inter-substrate processing variations, thereby providing a wider processing window to achieve void-free, seamless, and / or low-stress tungsten features.

[0126] Although the foregoing content pertains to embodiments of this disclosure, other and further embodiments of this disclosure may be designed without departing from its basic scope, which is determined by the scope of the appended patent application. [Simplified Explanation of the Diagram]

[0008] In order to understand the above features of this disclosure in detail, a more specific description of the disclosure briefly summarized above can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings are merely illustrative embodiments and should therefore not be considered as limiting their scope, and other equivalent embodiments are permissible.

[0009] Figures 1A-1B are schematic cross-sectional views of a portion of the substrate, illustrating undesirable voids or seams in conventionally formed tungsten features.

[0010] Figure 2A is a schematic side view of a processing system that can be used to implement the methods described herein, according to one embodiment.

[0011] Figure 2B is a close-up cross-sectional view of a portion of the processing system shown in Figure 2A according to one embodiment.

[0012] Figure 3 is a diagram illustrating a substrate processing method according to an embodiment, which can be performed using the processing system shown in Figures 2A-2B.

[0013] Figures 4A-4D are schematic cross-sectional views of a portion of the substrate, illustrating various aspects of the method described in Figure 3.

[0014] Figure 5 is a diagram illustrating a substrate processing method according to another embodiment, which can be performed using the processing system shown in Figures 2A-2B.

[0015] Figures 6A-6D are schematic cross-sectional views of a portion of the substrate, illustrating various aspects of the method described in Figure 5.

[0016] Figures 7A-7B are graphs illustrating the results of substrate processing and substrate-to-substrate processing of films formed using the methods described herein.

[0017] Figure 8 is a schematic plan view of an exemplary multi-chamber processing system according to one embodiment, which can be used to perform the methods described herein.

[0018] For ease of understanding, the same element symbols are used where possible to indicate the same elements common to the figures. It is contemplated that elements and features of one embodiment can be advantageously incorporated into other embodiments without further description. [Biomaterial Storage]

[0128] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A substrate processing system comprising: a processing chamber including a chamber cover assembly, one or more chamber sidewalls, and a chamber base, the chamber cover assembly, the one or more chamber sidewalls, and the chamber base collectively defining a processing volume; a gas delivery system fluidly coupled to the processing chamber, the gas delivery system including a first radical generator and a second radical generator; and a non-transitory computer-readable medium storing instructions for performing a method of processing a plurality of substrates when executed by a processor, the method comprising the steps of: (a) receiving a substrate into the processing volume; (b) exposing the substrate to an activating processing gas containing an effluent of a processing plasma formed in the first radical generator; (c) exposing the substrate to a first tungsten-containing precursor and a first reducing agent to deposit a tungsten interstitial material; and (d) removing the substrate from the processing volume. (e) When the number of substrates processed sequentially is less than or equal to a threshold value, repeat (a) to (d); (f) When the number of substrates processed sequentially is greater than or equal to the threshold value, expose the chamber surface in the processing volume to an activating cleaning gas containing an effluent of a cleaning plasma formed in the second free radical generator; and (g) repeat (a) to (f).

2. The processing system as claimed in claim 1, wherein the method further comprises the following steps: depositing a tungsten nucleation layer after (a) and before (b), comprising the steps of: exposing the substrate to the first tungsten-containing precursor or a second tungsten-containing precursor and the first reducing agent or a second reducing agent to deposit the tungsten nucleation layer.

3. The processing system as claimed in claim 2, wherein the substrate includes a material layer having a plurality of openings formed therein, and the substrate is exposed to the activation processing gas to differentially suppress tungsten deposition on a field surface of the substrate relative to the surfaces within the plurality of openings.

4. The processing system as claimed in claim 2, wherein the step of depositing the tungsten nucleation layer comprises the following steps: repeatedly exposing the substrate alternately to the second tungsten-containing precursor and the second reducing agent in a cycle.

5. The processing system as claimed in claim 4, wherein the step of depositing the tungsten interstitial material comprises the following steps: repeatedly exposing the substrate alternately to the first tungsten-containing precursor and the first reducing agent in a cycle.

6. The processing system as claimed in claim 4, wherein the step of depositing the tungsten interstitial material comprises the following steps: heating the substrate to a temperature of about 250°C or higher while simultaneously allowing the first tungsten-containing precursor and the first reducing agent to flow into the processing volume.

7. The processing system as claimed in claim 1, wherein the gas delivery system further comprises: a first valve fluidly coupled between the first radical generator and the processing chamber; and a second valve fluidly coupled between the second radical generator and the processing chamber, wherein the step of exposing the surfaces of the chambers to the activating cleaning gas comprises the step of: isolating the first radical generator from the outflow of the cleaning plasma by using the first valve.

8. The processing system as claimed in claim 7, wherein the step of exposing the substrate to the activation processing gas comprises the following steps: isolating the second free radical generator from the outflow of the processing plasma by using the second valve.

9. The processing system as claimed in claim 7, wherein the cover assembly includes a cover plate and a spray head coupled to the cover plate, and the first and second free radical generators are configured to be in fluid communication with the processing volume via an air inlet formed through the cover plate.

10. The processing system of claim 9, wherein the effluent of the processing plasma travels a first distance from the first radical generator to the processing volume, and the effluent of the cleaning plasma travels a second distance from the second radical generator to the processing volume, wherein the first distance is less than the second distance.

11. A method of processing a substrate, comprising the steps of: (a) receiving a substrate into a processing volume of a processing system, the processing system comprising: a processing chamber including a chamber cover assembly, one or more chamber sidewalls and a chamber base that commonly define the processing volume; and a gas delivery system fluidly coupled to the processing chamber, the gas delivery system including a first free radical generator and a second free radical generator; (b) exposing the substrate to an activating processing gas, the activating processing gas including an effluent of a processing plasma formed in the first free radical generator; (c) exposing the substrate to a first tungsten-containing precursor and a first reducing agent; (d) removing the substrate from the processing volume; and (e) repeating (a) to (d) when a number of substrates processed sequentially is less than or equal to a threshold value. (f) When the number of substrates processed sequentially is greater than or equal to the threshold value, the surface of the chamber in the processing volume is exposed to an activating cleaning gas containing an effluent of a cleaning plasma formed in the second free radical generator; and (g) repeating (a) to (f).

12. The method as claimed in claim 11, wherein the step of exposing the substrate to the effluent of the processing plasma comprises the step of maintaining the processing volume at a pressure of about 50 Torr or less.

13. The method as described in claim 11 further comprises the following steps: depositing a tungsten nucleation layer after (a) and before (b), comprising the steps of: exposing the substrate to the first tungsten-containing precursor or a second tungsten-containing precursor and the first reducing agent or a second reducing agent to deposit the tungsten nucleation layer.

14. The method of claim 13, wherein the substrate comprises a material layer having a plurality of openings formed therein, and the substrate is exposed to the activation process gas to differentially suppress tungsten deposition on a field surface of the substrate relative to the surfaces within the plurality of openings.

15. The method of claim 11, wherein the gas delivery system also includes: a first valve fluidly coupled between the first radical generator and the processing chamber; and a second valve fluidly coupled between the second radical generator and the processing chamber, wherein exposing the chamber surfaces to the activating cleaning gas comprises isolating the first radical generator from the cleaning plasma effluent by using the first valve.

16. The method as claimed in claim 15, wherein the step of exposing the substrate to the activation process gas comprises the step of isolating the second free radical generator from the process plasma effluent by using the second valve.

17. The method of claim 16, wherein the cover assembly includes a cover plate and a spray head coupled to the cover plate, and the first and second free radical generators are configured to be in fluid communication with the processing volume via an air inlet formed through the cover plate.

18. The method of claim 17, wherein the effluent of the treated plasma travels a first distance from the first radical generator to the treated volume, and the effluent of the cleaning plasma travels a second distance from the second radical generator to the treated volume, wherein the first distance is less than the second distance.

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