Low-stress tungsten layer deposition

Abstract

A method for forming a structure on a substrate includes forming a nucleation layer in an opening in the substrate in a processing chamber. The method further includes forming a passivation layer on at least a portion of the nucleation layer by introducing a radical process into the processing chamber. The method further includes forming a tungsten fill layer in the opening on the passivation layer and the nucleation layer, the tungsten fill layer being formed through a plurality of processing cycles. Each processing cycle includes pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration.

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments of the present disclosure relate generally to methods used in electronic device manufacturing, and more particularly to methods used to form tungsten features in semiconductor devices. [Background technology]

[0002] Tungsten (W) is widely used in integrated circuit (IC) device fabrication to form conductive features that require relatively low electrical resistance and relatively high resistance to electromigration. For example, tungsten can be used as a metal fill material to form source contacts, drain contacts, metal gate fill, gate contacts, interconnects (e.g., horizontal features formed on the surface of a dielectric material layer), and vias (e.g., vertical features formed through a dielectric material layer to connect other interconnect features located above and below the dielectric material layer).

[0003] Due to its relatively low resistivity, tungsten is also commonly used to form bitlines and wordlines used to address individual memory cells in the memory cell array of three-dimensional NAND (3D NAND) devices. 3D NAND structures include horizontal arrays of steps that can be stacked by sequentially depositing layers. Channels can be formed through a stack of films and filled with tungsten. In some cases, the channel sidewall widths may vary between steps. During channel filling, the tungsten fill layer may deposit faster in the upper portion of the channel than in the lower portion due to variations in channel sidewall width and a higher concentration of precursor gases used to deposit the tungsten fill layer. This can cause void formation within parts of the channel, especially in channels arranged in structures with two or more steps, and especially in high-aspect-ratio features. Additionally, conventional methods for depositing tungsten in channels result in tungsten gapfill with high internal stress. This stress can deform (e.g., warp, bend, or crack) the substrate.

[0004] Therefore, there is a need for a process for depositing tungsten gapfills in multi-tiered channels that are free or substantially free of voids and seams and have low resistivity. There is also a need in the art for depositing tungsten gapfills that have low to no internal stress. Summary of the Invention

[0005] FIELD OF THE INVENTION The embodiments described herein generally relate to systems and methods used to form tungsten features in semiconductor devices. More particularly, the embodiments herein provide processes and methods for forming low-stress tungsten structures.

[0006] In one embodiment, a method for forming a structure on a substrate includes forming a nucleation layer in an opening in the substrate in a processing chamber. The method further includes forming a passivation layer on at least a portion of the nucleation layer by introducing a radical treatment into the processing chamber. The method further includes forming a tungsten fill layer in the opening on the passivation layer and the nucleation layer, the tungsten fill layer being formed through a plurality of processing cycles. Each processing cycle includes pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration.

[0007] In one embodiment, a method for forming a structure on a substrate includes depositing a tungsten fill layer in an opening in a substrate having an internal stress of less than 200 MPa. The tungsten fill layer is formed by a plurality of process cycles, each process cycle including pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration.

[0008] In one embodiment, a method for forming a structure on a substrate includes forming a nucleation layer on the substrate. A first portion of the nucleation layer is deposited in an opening in the substrate, and a second portion of the nucleation layer is deposited in a field of the substrate. The method further includes forming a passivation layer on the nucleation layer by exposing the nucleation layer to a radical treatment. The passivation layer prevents tungsten deposition on the second portion of the nucleation layer. The method further includes forming a tungsten fill layer in the opening over the passivation layer and the nucleation layer. The tungsten fill layer is formed through multiple processing cycles, each processing cycle including pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration.

[0009] In order that the above-recited features of the present disclosure may be understood in detail, a more particular description of the above briefly summarized disclosure can be made with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure, since the present disclosure may admit of other equally effective embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a portion of a substrate illustrating undesirable void or seam formation in a conventionally formed tungsten feature. [Figure 2A] 1 is a schematic diagram of a processing system that can be used to perform the methods described herein, according to one embodiment. [Figure 2B] 2B is a close-up cross-sectional view of a portion of the processing system shown in FIG. 2A. [Figure 3] 1 illustrates a method of processing a substrate according to one embodiment. [Figure 4A]1 is a schematic cross-sectional view of a portion of a substrate, including a substrate to be processed by a method described herein, according to one embodiment. [Figure 4B] 1 is a schematic cross-sectional view of a substrate showing an adhesion layer deposited on the substrate, according to one embodiment. [Figure 4C] 1 is a schematic cross-sectional view of a substrate showing a nucleation layer deposited on an adhesion layer according to one embodiment. [Figure 4D] 1 is a schematic cross-sectional view of a substrate showing a passivation layer formed on a nucleation layer according to one embodiment. [Figure 4E] 1 is a schematic cross-sectional view of a substrate showing a tungsten gap fill layer according to one embodiment. [Figure 5] 1 is a graph showing the stress of different tungsten gap fill layers deposited on substrates formed by different processes. DETAILED DESCRIPTION OF THE INVENTION

[0011] For ease of understanding, where possible, identical reference numbers have been used to designate identical elements common to the figures. It is intended that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0012] FIELD Embodiments herein relate generally to electronic device manufacturing, and more particularly to systems and methods for forming low resistivity tungsten features in semiconductor device manufacturing processes.

[0013] FIG. 1 is a schematic cross-sectional view of a substrate 101 illustrating an undesired void 20 formed during a conventional tungsten deposition process. Here, substrate 101 includes a patterned surface 11 arranged in multiple step layers, such as first step layer 12A and second step layer 12B. In some embodiments, first step layer 12A is a first dielectric layer, and second step layer 12B is a second dielectric layer. In some embodiments, substrate 101 includes multiple alternating first and second step layers. Patterned surface 11 includes at least one opening (shown filled with a portion of tungsten layer 15) having a high aspect ratio opening formed therein, an adhesion layer 14 deposited on step layers 12A, 12B to line the opening, and a tungsten layer 15 deposited on adhesion layer 14. The tungsten layer 15 shown in FIG. 1 is formed using a conventional deposition process, such as a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process, 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 first step layer 12A, tungsten features 15B in the second step layer 12B, and an overburden of material (tungsten overburden layer 15C) on the fields of the patterned surface 11. In one example, the first and second dielectric layers are made of silicon oxide (SiO x ) and / or silicon nitride (SiN).

[0014] In FIG. 1 , the opening has a non-uniform profile that is wider at the surface of the substrate 101 and tapers as the opening extends inward from the surface into the second layer 12B. At the interface 25 between the first and second step layers, the width of the second step layer 12B is narrower than the width of the first step disposed inward from the second step layer 12B. As shown, the interface portions of the conformal tungsten layer 15 grow together and block or "pinch off" the entrance to the opening disposed in the first step 12A before the opening is completely filled, thereby causing an undesirable void 20, i.e., a lack of tungsten material, within the tungsten feature 15A. In addition to voids, using conventional tungsten deposition processes can result in undesirable seams (e.g., 24) in the tungsten feature, as shown in the second step 12B. The voids 20 and seams 24 are susceptible to corrosion from the chemically active components of tungsten chemical-mechanical polishing (CMP) polishing fluids, which can cause undesirable loss of tungsten material from the features 15A, 15B if the seams 24 or voids 20 are exposed during the CMP process. Additionally, conventional tungsten deposition processes result in a tungsten layer 15 with high internal stress that can deform the first and second step layers 12A, 12B of the substrate 101. For example, the stress can be about 1600 MPa or greater.

[0015] Embodiments described herein form bottom-up deposited tungsten gapfills in openings in substrates with reduced stress and reduced instances of voids. The methods and systems provided herein are particularly useful for tungsten gapfill for high aspect ratio features, such as about 25:1 or greater, such as about 30:1 to about 100:1, such as about 50:1 to about 80:1. Aspect ratio refers to the ratio of the overall height to the average width or diameter of the feature. Additionally, embodiments herein provide processing systems configured to perform a combination of individual aspects of the method without transferring the substrate between processing chambers, thereby improving the overall substrate processing throughput and capacity of the tungsten gapfill processing schemes described herein.

[0016] 2A schematically illustrates a processing system 200 that can be used to perform the bottom-up tungsten gap-fill substrate processing methods described herein, where processing system 200 is configured to provide different processing conditions desired for forming an adhesion layer, a nucleation layer, a passivation layer, and a tungsten gap-fill layer on a substrate within a single processing chamber 202, i.e., without transferring the substrate between multiple processing chambers.

[0017] 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 FIG. 2A) includes a chamber lid assembly 210, one or more sidewalls 212, and a chamber base 214, which collectively define a processing volume 215. The processing volume 215 is fluidly coupled to an exhaust 217, such as one or more vacuum pumps, that are used to maintain the processing volume 215 at a process pressure, such as subatmospheric conditions, and to evacuate processing gases and processing by-products therefrom.

[0018] The chamber lid assembly 210 includes a lid plate 216 and a showerhead 218 coupled to the lid plate 216, which together define a gas distribution volume 219. The lid plate 216 is maintained at a desired temperature using one or more heaters 229 thermally coupled thereto. The showerhead 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, and thus a substrate 230 disposed thereon, between an elevated substrate processing position (as shown) and a lowered substrate transfer position (not shown). When the substrate support assembly 220 is in the elevated substrate processing position, the showerhead 218 and the substrate support 222 define a processing region 221.

[0019] The gas supply system 204 is fluidly coupled to the processing chamber 202 via a gas inlet 223 disposed through the lid plate 216. Processing or cleaning gases supplied using the gas supply system 204 flow through the gas inlet 223 into the gas distribution volume 219 and are distributed to the processing region 221 through a plurality of openings 232 in the showerhead 218. In some embodiments, the chamber lid assembly 210 further includes a perforated blocker plate 225 disposed between the gas inlet 223 and the showerhead 218. In these embodiments, gases entering the gas distribution volume 219 are initially diffused by the blocker plate 225 and, in combination with the showerhead 218, provide a more uniform or desired distribution of gas flow into the processing region 221.

[0020] Process gases and process by-products are exhausted radially outward from the processing region 221 through an annular channel 226 that surrounds the processing region 221. The annular channel 226 may be formed in a first annular liner 227 disposed radially inward of the one or more sidewalls 212 (as shown), or may be formed in the one or more sidewalls 212. In some embodiments, the processing chamber 202 includes one or more second liners 228, which are used to protect the interior surfaces of the one or more sidewalls 212 or the chamber base 214 from corrosive gases and / or unwanted material deposition.

[0021] In some embodiments, a purge gas source 237 fluidly coupled to the processing volume 215 is used to flow a chemically inert purge gas, such as argon (Ar), into a region disposed directly below the substrate support 222, for example, through an opening in the chamber base 214 surrounding the support shaft 262. The purge gas can be used to create a region of positive pressure (compared to the pressure in the processing region 221) below the substrate support 222 during substrate processing. Generally, the purge gas flows through and upwardly from the chamber base 214, around the edge of the substrate support 222, and is exhausted from the processing volume 215 through the annular channel 226. The purge gas reduces unwanted material deposition on surfaces directly below the substrate support 222 by reducing and / or preventing the flow of material precursor gas thereto.

[0022] The substrate support assembly 220 includes a movable support shaft 262 that extends sealingly through the chamber base 214, such as surrounded by a bellows 265 in the region below the chamber base 214, and a substrate support 222 disposed on the movable support shaft 262. To facilitate transfer of substrates to and from the substrate support 222, the substrate support assembly 220 includes a lift pin assembly 266 that includes a plurality of lift pins 267 coupled to or disposed in engagement with a lift pin hoop 268. The plurality of lift pins 267 are movably disposed in openings formed through the substrate support 222. When the substrate support 222 is disposed in a lowered, substrate transfer position (not shown), the plurality of lift pins 267 extend above a substrate receiving surface of the substrate support 222 to lift a substrate 230 therefrom and enable access to a backside (inactive) surface of the substrate 230 by a substrate handler (not shown). When the substrate support 222 is in the raised or processing position (as shown), the plurality of lift pins 267 retract beneath the substrate receiving surface of the substrate support 222 to allow the substrate 230 to rest thereon.

[0023] Substrates 230 are transferred to and from the substrate support 222 through a door 271, e.g., a slit valve, located in one of the one or more side walls 212, where one or more openings in the area surrounding the door 271, e.g., an opening in the door housing, are fluidly coupled to a purge gas source 237, e.g., an Ar gas source. The purge gas is used to prevent process and cleaning gases from contacting and / or degrading the seal surrounding the door, thereby extending the useful life of the door.

[0024] The substrate support 222 is configured for vacuum chucking, in which 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. The vacuum is applied using a vacuum source 272 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, when the processing chamber 202 is configured for direct plasma processing, the substrate support 222 may be configured for electrostatic chucking. 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, that supplies a bias voltage thereto.

[0025] As shown, the substrate support assembly 220 features a dual-zone temperature control system for independent temperature control within different regions of the substrate support 222. The different temperature control regions of the substrate support 222 correspond to different regions 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 a 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 three or more heaters.

[0026] In some embodiments, the substrate support assembly 220 further includes an annular shadow ring 235 used to prevent unwanted material deposition on the circumferential bevel edge of the substrate 230. During substrate transfer to and from the substrate support 222, i.e., when the substrate support assembly 220 is disposed in a lowered position (not shown), the shadow ring 235 rests on an annular ledge within the processing volume 215. When the substrate support assembly 220 is disposed in a raised or processing position, a radially outer surface of the substrate support 222 engages the annular shadow ring 235 such that the shadow ring 235 surrounds the substrate 230 disposed on the substrate support 222. Here, the shadow ring 235 is shaped such that a radially inward-facing portion of the shadow ring 235 is disposed over the bevel edge of the substrate 230 when the substrate support assembly 220 is in the raised substrate processing position.

[0027] In some embodiments, the substrate support assembly 220 further includes an annular purge ring 236 disposed on the substrate support 222 to surround the substrate 230. In those embodiments, the shadow ring 235 may be disposed on the purge ring 236 when the substrate support assembly 220 is in the raised substrate processing position. Generally, the purge ring 236 features a plurality of radially inward-facing openings in fluid communication with a purge gas source 237. During substrate processing, purge gas flows into the annular region defined by the shadow ring 235, the purge ring 236, the substrate support 222, and the bevel edge of the substrate 230 to prevent process gas from entering the annular region and causing undesired material deposition on the bevel edge of the substrate 230.

[0028] In some embodiments, the processing chamber 202 is configured for direct plasma processing. In these embodiments, the showerhead 218 is electrically coupled to a first power source 231, such as an RF power source, that provides power to ignite and maintain a plasma of the processing gases flowing into the processing region 221 via capacitive coupling to the processing gases. In some embodiments, the processing chamber 202 includes an inductive plasma generator (not shown), and the plasma is formed via inductively coupling RF power to the processing gases.

[0029] 2A and 2B, the gas supply system 204 includes one or more remote plasma sources, here first and second radical generators 206A-206B, a deposition gas source 240, and a conduit system 294 (e.g., multiple conduits 294A-294F) that fluidly couples the radical generators 206A-206B and the deposition gas source 240 to the lid assembly 210. While the illustrated gas supply system 204 includes two radical generators 206A, 206B, the processes described herein may also be practiced using a gas supply system 204 having only a single radical generator 206A. The gas supply system 204 further includes a plurality of isolation valves, here first and second valves 290A-290B, respectively positioned between the radical generators 206A-206B and the lid plate 216, which can be used to fluidly isolate each of the radical generators 206A-206B from the processing chamber 202 and from each other.

[0030] Each of the radical generators 206A-206B features a chamber body 280 that defines a respective first and second plasma chamber volume 281A-281B (FIG. 2B). Each of the radical generators 206A-206B is coupled to a respective power source 293A-293B. The power sources 293A-293B are used to ignite and maintain plasmas 282A-282B of gases supplied to the plasma chamber volumes 281A-281B from a corresponding first gas source 287A or second gas source 287B fluidly coupled to the plasma chamber volumes 281A-281B. The first radical generator 206A can be used to ignite and maintain a processing plasma 282A from a non-halogen-containing gas mixture supplied to the first plasma chamber volume 281A from the first gas source 287A. In some embodiments, the first radical generator 206A generates activated species, e.g., treatment radicals, used to treat a substrate to inhibit tungsten deposition on the substrate, such as by forming a passivation layer. The treatment radicals can be a non-halogen nitrogen-containing gas, such as nitrogen gas (N), ammonia (NH), or other nitrogen-containing gases. The treatment radicals can also be a combination of different non-halogen nitrogen-containing gases. In some embodiments, the treatment radicals can be a nitrogen-containing gas containing a halogen, such as nitrogen trifluoride (NF). The second radical generator 206B can be used to generate cleaning radicals used in a chamber cleaning process by igniting and sustaining a cleaning plasma 282B from a halogen-containing gas mixture supplied from a second gas source 287B to the second plasma chamber volume 281B.

[0031] In general, nitrogen process radicals have a relatively short lifetime (compared to halogen cleaning radicals) and may exhibit a relatively high susceptibility to recombination from collisions with surfaces in the gas delivery system 204, such as the conduit system 294, and / or other species in the process plasma effluent. Accordingly, in embodiments herein, the first radical generator 206A is generally 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 process region 221. In some embodiments, the first radical generator 206A and the first gas source 287A are mounted to the chamber lid assembly 210 or the superstructure of the process chamber 202.

[0032] In some embodiments, the first radical generator 206A is also fluidly coupled to a second gas source 287B that supplies a halogen-containing conditioning gas to the first plasma chamber volume 281A for use in the plasma source conditioning process. In those embodiments, the gas delivery system 204 can further include a plurality of diverter valves 291 operable to direct the halogen-containing gas mixture from the second gas source 287B to the first plasma chamber volume 281A.

[0033] Suitable remote plasma sources that can be used in either or both of the radical generators 206A-206B include radio frequency (RF) or very high 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.

[0034] As shown, the first radical generator 206A is fluidly coupled to the processing chamber 202 using first and second conduits 294A-294B that extend upward from the gas inlet 223 and connect to the outlet of the first plasma chamber volume 281A. A first valve 290A disposed between the first conduit 294A and the second conduit 294B is used to selectively fluidly isolate the first radical generator 206A from the processing chamber 202 and other portions of the gas delivery system 204. Typically, the first valve 290A is closed during a chamber cleaning process to prevent activated cleaning gases, such as halogen radicals, from flowing into the first plasma chamber volume 281A and damaging its surfaces.

[0035] The second radical generator 206B is fluidly coupled to the second conduit 294B, and thus to the processing chamber 202, by using third and fourth conduits 294C-294D. The second radical generator 206B is selectively isolated from the processing chamber 202 and other portions of the gas delivery system 204 by using a second valve 290B disposed between the third conduit 294C and the fourth conduit 294D.

[0036] Deposition gas, such as a tungsten-containing precursor and a reducing agent, is supplied from the deposition gas source 240 to the processing chamber 202 using a fifth conduit 294E. As shown, the fifth conduit 294E is coupled to the second conduit 294B adjacent the gas inlet 223, such that the first and second valves 290A-290B can be used to isolate the first and second radical generators 206A-206B, respectively, from the deposition gas introduced into the processing chamber 202. A third valve 290C is positioned on the fifth conduit 294E to selectively isolate the deposition gas source 240 from the first radical generator 206A and the second radical generator 206B and selectively allow a quantity of deposition gas to flow through the fifth conduit 294E into the processing region 221. In some embodiments, the gas supply system 204 further includes a sixth conduit 294F coupled to the fourth conduit 294D at a location adjacent the second valve 290B. The sixth conduit 294F is fluidly coupled to a bypass gas source 238, such as an argon (Ar) gas source, which can be used to periodically purge a portion of the gas supply system 204 of undesired residue cleaning, inhibition, and deposition gases.

[0037] In some embodiments, the deposition gas source 240 is mounted to the chamber lid assembly 210 or to the superstructure of the processing chamber 202. In some embodiments, the deposition gas source 240 is a plurality of different deposition gas reservoirs connected to the conduit system 294 by separate conduits, and each respective deposition gas reservoir can have an associated flow control valve. Each separate deposition gas reservoir can be mounted to the chamber lid assembly 210 or to the superstructure of the processing chamber 202.

[0038] Operation of the processing system 200 is facilitated by a system controller 208 (FIG. 2A). The system controller 208 includes a programmable central processing unit, here a CPU 295, operable with memory 296 (e.g., non-volatile memory) and support circuits 297. The CPU 295 may be any form of general-purpose computer processor used in industrial environments, such as a programmable logic controller (PLC) to control various chamber components and sub-processors. The memory 296 coupled to the CPU 295 facilitates operation of the processing chamber. The support circuits 297 are conventionally coupled to the CPU 295 and include cache, clock circuits, input / output subsystems, power supplies, etc., and combinations thereof, coupled to the various components of the processing system 200 to facilitate control of substrate processing operations.

[0039] The instructions in memory 296 are in the form of a program product, such as a program that implements the methods of the present disclosure. In one example, the present disclosure may be embodied as a program product stored on a computer-readable storage medium for use with a computer system. The program in the program product defines the functions of the embodiments (including the methods described herein). Thus, a computer-readable storage medium, when it holds computer-readable instructions that direct the functions of the methods described herein, is an embodiment of the present disclosure.

[0040] 3 illustrates a process 300 used to process a substrate according to some embodiments, which may be performed using the processing system 200. FIGS. 4A-4E are schematic cross-sectional views of a portion of an exemplary substrate 400 illustrating aspects of the process 300 at different stages.

[0041] After the substrate 400 is placed on the substrate receiving surface of the substrate support 222 in the processing chamber 202, an adhesion layer 422 is formed on the substrate 400, as indicated by activity 302. A nucleation layer 424 is then deposited on the adhesion layer 422, as indicated by activity 304. The substrate 400 then undergoes a radical process in which the substrate 400 is treated with a process gas containing activated species to form a passivation layer 426, as indicated by activity 306. A tungsten gap-fill layer 428 is then deposited by pulsed CVD, as indicated by activity 308. The tungsten gap-fill layer 428 is deposited from bottom to top and is substantially or completely free of voids or seams. The process 300 is described in more detail below.

[0042] 4A illustrates an exemplary substrate 400. Substrate 400 features a patterned surface 401 including a first step layer 412A and a second step layer 412B having a plurality of openings 405 (one shown) formed therein. In some embodiments, the plurality of openings 405 comprises one or a combination of high aspect ratio via or trench openings having a width (e.g., each of 407, 414) of about 100 nm to about 400 nm, such as about 200 nm to about 300 nm, and a depth (e.g., each of 402A or 402B, or either 402A or 402B) of about 2 μm to about 8 μm, such as about 3 μm to about 6 μm. In some embodiments, the plurality of openings comprises at least one opening having a width 410 at its narrowest portion of about 50 nm to about 200 nm, such as about 75 nm to about 125 nm. In some embodiments, individual openings 405 can have an aspect ratio (depth to width) of about 10:1 or greater, e.g., about 25:1 or greater, e.g., about 30:1 to about 100:1, e.g., about 40:1 to about 60:1. In some embodiments, the via or trench opening comprises an aspect ratio of about 20:1 to about 40:1. The opening disposed within the first step 412A is referred to as the first step opening 402A, and the opening disposed within the second step 412B is referred to as the second step opening 402B. Together, the first and second step openings 402A and 402B form a single, continuous opening 405. The top portion of the first step opening 402A interfaces with the bottom portion of the second step opening 402B at interface 406.

[0043] A width 407 of the top portion of the first step opening is greater than a width 410 of the bottom portion of the second step opening 402B at the interface 406. In some embodiments, width 407 is about 5% to about 100% greater than width 410, such as about 10% to about 50% greater. For example, width 410 can be about 50 nm to about 300 nm, such as about 75 nm to about 125 nm, and width 407 can be about 70 nm to about 400 nm, such as about 150 nm to about 250 nm. In some embodiments, for each step, the widest portion of the step, such as top portion 414 of the second step 402B, is about 5% to about 100% greater, such as about 10% to about 50% greater, than the narrowest portion of the step, such as bottom portion 410 of the second step 402B. In some embodiments, the height of the first step opening 402A is substantially the same as, smaller than, or larger than the height of the second step opening 402B. Without being bound by theory, it is believed that the abrupt difference in opening width at the interface can cause a pinching effect when the tungsten gap fill layer is deposited. The process 300 described herein enables the formation of a tungsten gap fill layer 428 that fills the opening 405 without the formation of voids.

[0044] As indicated by activity 302 in FIG. 3 and with reference to FIG. 4B, process 300 begins by depositing an adhesion layer 422 on patterned surface 401 in processing chamber 202. Adhesion layer 422 is composed of a material that promotes tungsten nucleation as well as prevents or limits tungsten diffusion into underlying materials. Adhesion layer 422 can be a titanium nitride (TiN) layer. As shown in FIG. 4B, patterned surface 401 includes adhesion layer 422 deposited on first step layer 412A and second step layer 412B to conformally line opening 405 and facilitate subsequent deposition of tungsten nucleation layer 424. In some embodiments, adhesion layer 422 is deposited to a thickness between about 20 angstroms (Å) and about 150 Å, for example, about 30 Å to about 100 Å. Adhesion layer 422 can be formed by processing system 200 using atomic layer deposition (ALD), physical vapor deposition (PVD) processes, or chemical vapor deposition (CVD) processes. For example, adhesion layer 422 can be a titanium nitride layer formed by using a titanium-containing precursor and a nitrogen-containing precursor flowed from deposition gas source 240 into processing region 221. For example, adhesion layer 422 can be formed by flowing titanium tetrachloride (TiCl4) and ammonia (NH3) from deposition gas source 240 into processing region 221 and reacting therein to form titanium nitride.

[0045] As indicated by activity 304, a nucleation layer 424 is deposited on the adhesion layer 422. A portion of an exemplary substrate 400 with the nucleation layer 424 formed thereon is shown schematically in FIG. 4C. The nucleation layer 424 can be formed using any process capable of forming a tungsten nucleation layer. In some embodiments, the nucleation layer 424 is deposited using an atomic layer deposition (ALD) process. The ALD process includes repeating cycles of alternating between exposing the substrate 400 to a tungsten-containing precursor and exposing the substrate 400 to a reducing agent. In some embodiments, the processing region 221 is purged between alternating exposures. In some embodiments, the processing region 221 is purged continuously. Examples of suitable tungsten-containing precursors include tungsten halides, such as tungsten hexafluoride (WF), tungsten hexachloride (WCl), or combinations thereof. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent can be a boron-containing agent such as diborane (B2H6) or silane (SiH4). In some embodiments, the tungsten-containing precursor includes an organometallic precursor or a fluorine-free precursor, such as MDNOW (methylcyclopentadienyl-dicarbonylnitrosyl-tungsten), EDNOW (ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten), tungsten hexacarbonyl (W(CO)6), or a combination thereof.

[0046] For example, the tungsten-containing precursor and reducing agent are each flowed into the processing region 221 for a period between about 0.1 seconds and about 10 seconds, such as between about 0.5 seconds and about 5 seconds. The processing region 221 can be purged between alternating exposures by flowing a purge gas, such as argon (Ar) or hydrogen gas, into the processing region 221 for a period between about 0.1 seconds and about 10 seconds, such as between about 0.5 seconds and about 5 seconds. The purge gas can be supplied from the deposition gas source 240 or the bypass gas source 238. Generally, the repeated cycles of the nucleation process continue until the nucleation layer 424 has a thickness between about 10 Å and about 200 Å, such as between about 10 Å and about 150 Å, or between about 20 Å and about 150 Å. The nucleation layer 424 is disposed along the opening 405, such as on the adhesion layer 422. During the nucleation process, the processing volume 215 can be 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 between about 1 Torr and about 50 Torr. Exposing the substrate 400 to the tungsten-containing precursor includes flowing the tungsten-containing precursor from the deposition gas source 240 into the processing region 221 at a flow rate of about 100 sccm or less, such as between about 10 sccm and about 60 sccm, or between about 20 sccm and about 80 sccm. Exposing the substrate 400 to the reducing agent includes flowing the reducing agent from the deposition gas source 240 into the processing region 221 at a flow rate of between about 200 sccm and about 1000 sccm, such as between about 300 sccm and about 750 sccm.

[0047] In activity 306, the substrate 400 undergoes a radical treatment to form a passivation layer 426 on the nucleation layer 424 in the opening 405 shown in FIG. 4D. The passivation layer 426 inhibits, and in some embodiments, completely inhibits, tungsten nucleation at the passivation layer 426. The radical treatment 306 includes flowing activated species formed in the first radical generator 206A, such as activated nitrogen species such as N, NH, or a combination thereof, into the treatment region 221. In some embodiments, the activated species is combined with an inert carrier gas such as Ar, He, or a combination thereof to form a radical treatment gas mixture. Without being bound by theory, it is believed that nitrogen from the activated nitrogen species is incorporated into the nucleation layer 424, for example, by nitrogen adsorption or by reaction with the metallic tungsten of the nucleation layer 424, to form the tungsten nitride (WN) passivation layer 426. Passivation layer 426 desirably retards (inhibits) further tungsten nucleation and therefore subsequent tungsten deposition thereon.

[0048] In some embodiments, the passivation layer 426 only partially covers the nucleation layer 424, leaving a portion of the nucleation layer 424 near the bottom of the opening 405 uncovered. A field portion 426a of the passivation layer 426 may optionally be formed over the field 403, with an opening portion 426b formed over the surface of the opening 405. For example, the field portion 426a may be formed to prevent significant tungsten deposition on the field 403 of the substrate 400. Reducing or eliminating tungsten deposition on the field 403 reduces material costs and shortens the time required to perform the overburden removal operation. The opening portion 426b has a tungsten deposition suppression profile that aids in depositing the tungsten gap-fill layer 428 in the opening 405 without forming voids in activity 308. As shown in FIG. 4D , the opening portion 426b may extend partially from the second step opening 402B into the first step opening 402A. Opening portion 426b may terminate at or near pinch point 430 of nucleation layer 424, which is the narrowest point in opening 405 near interface 406 after nucleation layer 424 is deposited. In some embodiments, opening portion 426b may extend past pinch point 430. The desired suppression effect on field portion 426a and the desired suppression profile in opening 405 is achieved by controlling process conditions, such as temperature and pressure, in processing chamber 202 to control the concentration, flux, and energy of process radicals directed at the substrate surface.

[0049] For example, radical processing can create a passivation layer 426 that inhibits tungsten deposition more strongly near the open edges of opening 405 than at the bottom of opening 405. Passivation layer 426 is formed to achieve the desired inhibition effect to facilitate bottom-up deposition of tungsten gap-fill layer 428 within opening 405 that is void-free and seam-free. Passivation layer 426 also reduces the pinching effect to prevent void formation. For example, passivation layer 426 can prevent tungsten from depositing in significant amounts in opening portion 426b until tungsten fills first step opening 402A. After first step opening 402A is filled with tungsten, additional tungsten is then deposited on the tungsten filling first step opening 402A to fill second step opening 402B, thereby forming tungsten gap-fill layer 428. As shown in FIG. 4E, the portion of tungsten gap fill layer 428 in second opening 402B is formed over opening portion 426b of passivation layer 426.

[0050] Passivation layer 426 may be formed to a non-uniform thickness within opening 405 so that its suppression effect is non-uniform. For example, passivation layer 426 may be tapered so that its suppression effect decreases with the depth of opening 405 so that tungsten nucleates at different rates in different portions of passivation layer 426 to control the formation of tungsten gap fill layer 428. For example, the rate of tungsten nucleation increases with the depth of opening 405, such that a faster rate of tungsten nucleation occurs in the exposed portion of nucleation layer 424 at the bottom of opening 405.

[0051] In some embodiments, exposing the nucleation layer 424 to processing radicals includes forming a processing plasma 282A of a substantially halogen-free processing gas mixture using the first radical generator 206A and flowing effluents of the processing plasma 282A into the processing region 221. In some embodiments, the flow rate of the processing gas mixture into the first radical generator 206A, and therefore the flow rate of the processing plasma effluent, such as nitrogen gas, into the processing region 221 is between about 1 sccm and about 3000 sccm, such as between about 1 sccm and about 2500 sccm, such as between about 1 sccm and about 2000 sccm, such as between about 1 sccm and about 1000 sccm, such as between about 1 sccm and about 500 sccm, such as between about 1 sccm and about 250 sccm, such as between about 1 sccm and about 100 sccm, such as between about 1 sccm and about 75 sccm, such as between about 1 sccm and about 50 sccm.

[0052] In some embodiments, the radical treatment includes exposing the substrate 400 to the treatment radicals for a period of about 2 seconds or more, such as from about 2 seconds to about 30 seconds, such as from about 5 seconds to about 20 seconds, such as from about 10 seconds to about 15 seconds.

[0053] In some embodiments, the concentration of activated radical species in the radical treatment mixed gas is about 0.1 vol.% to about 50 vol.%, such as about 0.2 vol.% to about 40 vol.%, about 0.2 vol.% to about 30 vol.%, such as about 0.2 vol.% and about 20 vol.%, or such as about 0.2 vol.% and about 10 vol.%, such as about 0.2 vol.% and about 5 vol.%.

[0054] In other embodiments, the treatment radicals can be formed using a remote plasma (not shown) ignited and maintained in a portion of the process volume 215 separated from the processing region 221 by the showerhead 218, such as between the showerhead 218 and the lid plate 216. In these embodiments, the activated process gas can be flowed through an ion filter to remove substantially all ions from the activated process gas before the treatment radicals reach the processing region 221 and the surface of the substrate 400. In some embodiments, the showerhead 218 can be used as an ion filter. In other embodiments, the plasma used to form the treatment radicals is an in-situ plasma formed in the processing region 221 between the showerhead 218 and the substrate 400. In some embodiments, when an in-situ treatment plasma is used, the substrate 400 can be biased to directionally control and accelerate ions, e.g., charged treatment radicals, formed from the process gas toward the substrate surface.

[0055] In some embodiments, the radical treatment includes maintaining the process volume 215 at a pressure less than about 100 Torr while flowing an activated process gas through the process volume 215. For example, during the radical treatment, the process volume 215 can be maintained at a pressure of about 20 Torr or less, such as between about 0.5 Torr and about 10 Torr, such as between about 1 Torr and about 5 Torr.

[0056] Activity 308 represents using pulsed chemical vapor deposition (“pulsed CVD”) to form a tungsten gap fill layer 428 in the opening 405, as shown in FIG. 4E. It has been found that lowering the pressure and increasing the temperature improves the stress formed in the tungsten gap fill. However, simply increasing the temperature and lowering the pressure does not provide much payoff. For example, low pressures, such as vacuum conditions, affect the quality of the gap fill and prevent chucking of the substrate 400 to the substrate support assembly 220. At some temperatures, other features formed on the substrate 400 may be degraded or adversely affected. Additionally, at some temperatures, degradation of components of the processing system 200 may be accelerated, resulting in increased maintenance costs. The pulsed CVD process shown as activity 308 involves treating the substrate 400 at low pressures and moderate to high temperatures to take advantage of the stress reduction benefits. However, pulsed CVD 308 results in improved tungsten gap fill and reduced stress than can be achieved by adjusting the temperature and pressure parameters alone.

[0057] The pulsed CVD process, represented by 308, involves periodically pulsing a first gas for a pulse duration while simultaneously flowing a second gas into the processing region 221, and then purging the first and second gases from the processing region 221 with a purge gas for a purge duration. The first and second gases are supplied into the processing region 221 by a deposition gas source 240. The pressure in the processing volume 215 is between about 0.7 Torr and about 15 Torr, e.g., 1 Torr, 1.5 Torr, 2 Torr, 2.5 Torr, 3 Torr, 3.5 Torr, 4 Torr, 4.5 Torr, 5 Torr, 5.5 Torr, 6 Torr, 6.5 Torr, 7 Torr, 7.5 Torr, 8 Torr, 8.5 Torr, 9 Torr, 9.5 Torr, 10 Torr, 10.5 Torr, 11 Torr, 11.5 Torr, 12 Torr, 12.5 Torr, 13 Torr, 13.5 Torr, 14 Torr, 14.5 Torr, etc. The temperature in the processing region 221 can be between 400° C. and 500° C., and heat can be supplied by the heater 229, the first heater 263, and / or the second heater 264.

[0058] In some embodiments, the first gas is a tungsten-containing precursor, such as tungsten hexafluoride. In some embodiments, the first gas is hydrogen gas. In some embodiments, the first gas is a mixture of a tungsten-containing precursor and hydrogen gas, such as a mixture of tungsten hexafluoride and hydrogen gas. The pulse duration is between about 0.3 seconds and about 2 seconds, such as about 0.5 seconds, about 1 second, and about 1.5 seconds.

[0059] In some embodiments, the second gas is a mixture of hydrogen gas and an inert gas such as argon when the first gas contains a tungsten-containing precursor. In some embodiments, the second gas is a tungsten-containing precursor such as tungsten hexafluoride and an inert gas such as argon. In some embodiments, the second gas is an inert gas when the first gas is a mixture of a tungsten-containing precursor and hydrogen gas.

[0060] In some embodiments, the purge gas is an inert gas such as argon. Alternatively, the purge gas may be a second gas, or the purge gas may be composed of the same component gas but at a different concentration. In some embodiments, the purge gas may be supplied into the processing region 221 from the purge gas source 237. The purge gas may be supplied by the deposition gas source 240, in that after the first gas pulse ceases, the processing region 221 is purged by a continued flow of the second gas into the processing chamber 202, thereby causing the first gas to flow from the processing region 221 and out through the exhaust 217. The pulse duration may be between about 0.5 seconds and about 5 seconds, such as about 1 second, about 1.5 seconds, about 2 seconds, about 2.5 seconds, about 3 seconds, about 3.5 seconds, about 4 seconds, and about 4.5 seconds.

[0061] Without being bound by theory, it is believed that fluorine impurities in the tungsten gap fill layer 428 contribute to stress. Without being bound by theory, it is believed that purging with a fluorine-free purge gas after each pulse reduces the generation of fluorine impurities, such as by reducing the time available for tungsten hexafluoride to interact with the developing tungsten gap fill. Additionally, it is believed that reduced stress in the tungsten gap fill results in smaller grain sizes.

[0062] In one embodiment, the first gas is tungsten hexafluoride and the second gas is a mixture of hydrogen gas and argon. For example, between about 50 sccm and 1200 sccm of tungsten hexafluoride is pulsed into the processing region 221 for the pulse duration into a co-flowing mixture of about 200 sccm to 6000 sccm of hydrogen gas and about 350 sccm to about 8000 sccm of argon. The processing region 221 is then purged with the hydrogen gas and argon mixture.

[0063] In one embodiment, the first gas is hydrogen gas and the second gas is a mixture of tungsten hexafluoride and argon. For example, between about 200 sccm and 6000 sccm of hydrogen gas is pulsed into the processing region 221 for the pulse duration, followed by a co-flowing mixture of between about 50 sccm and 1200 sccm of tungsten hexafluoride and between about 350 sccm and about 8000 sccm of argon. The processing region 221 is then purged with the mixture of tungsten hexafluoride and argon. For example, the processing region 221 may be purged with a mixture of between 3000 sccm and 8000 sccm of argon and between 100 sccm and 900 sccm of tungsten hexafluoride. Without being bound by theory, it is believed that pulsing tungsten hexafluoride into flowing hydrogen gas allows for a more complete deposition reaction, thereby reducing the occurrence of fluorine impurities in the deposited tungsten gap fill layer 428.

[0064] In one embodiment, the first gas is a mixture of tungsten hexafluoride and hydrogen gas, and the second gas is argon. For example, a mixture of between about 50 sccm and 1200 sccm of tungsten hexafluoride and about 200 sccm to 6000 sccm of hydrogen gas is pulsed into the processing region 221 for the pulse duration, followed by about 350 sccm to about 8000 sccm of co-flowing argon. The processing region 221 is then purged with argon. For example, the processing region 221 can be purged with 3000 sccm to about 8000 sccm of argon.

[0065] The pulsed CVD process 308, which includes a first gas of hydrogen and a second gas that is a mixture of tungsten hexafluoride and argon, has been observed to have improved gap filling, e.g., fewer instances of voids, compared to other embodiments of the CVD process 308. However, other embodiments of the pulsed CVD process 308 have satisfactory gap filling quality compared to tungsten gap filling deposited by conventional techniques.

[0066] The pulsed CVD process 308 may be performed for one or more cycles, such as between 1 and 1000 cycles. The number of cycles may be based on the aspect ratio of the opening, since deeper openings may require more cycles. In some embodiments, the temperature and pressure may be maintained the same for each cycle. In some embodiments, the temperature and pressure may vary between cycles.

[0067] The pulsed CVD process 308 results in a tungsten gap fill layer 428 with reduced stress. In some embodiments, the tungsten gap fill layer 428 formed by the pulsed CVD process 308 has an internal stress between about 0 MPa and 200 MPa, e.g., between about 0 MPa and 150 MPa, such as between 0 MPa and 100 MPa, such as between about 0 MPa and about 50 MPa, such as between about 0 MPa and about 40 MPa, such as between about 0 MPa and about 30 MPa, such as between about 0 MPa and about 20 MPa, such as between about 0 MPa and about 10 MPa, such as between about 0 MPa and about 5 MPa, such as between about 0 MPa and about 1 MPa, or between about 0 MPa and about 0.5 MPa. In some embodiments, the tungsten gap fill layer 428 has a neutral, e.g., 0 MPa, or substantially neutral, internal stress.

[0068] A chemical mechanical polishing (CMP) process may be used after depositing tungsten gap fill layer 428 in opening 405 to remove overburden materials such as adhesion layer 422, nucleation layer 424, passivation layer 426, and portions of tungsten gap fill layer 428 that extend over field 403 of substrate 400.

[0069] The processing system 200 is configured to perform each activity of the process 300 to form a low-stress, void-free, and seam-free tungsten gapfill. The process 300 can be performed without removing the substrate 400 from the processing system 200. The process gases used to perform the individual processes of the process 300 and to clean residues from the interior surfaces of the processing chamber 202 are supplied to the processing chamber 202 using a gas supply system 204 fluidly coupled to the processing chamber 202. In other embodiments, each activity in the process 300 may be performed in a different processing system, such as in a cluster tool with multiple processing systems 200.

[0070] In some embodiments, the process 300 is performed on a substrate having a single layer rather than multiple layers.

[0071] 5 includes a bar graph 500 showing stress in approximately 12,000 angstrom (Å) thick tungsten features, such as tungsten gapfills, formed on a substrate under different process conditions. The y-axis represents stress in megapascals (MPa) in tungsten features labeled 501, 502, 503, 504, and 505 on the x-axis. Each tungsten feature 501, 502, 503, 504, and 505 is formed by a different process.

[0072] Tungsten feature 501 was deposited by a conventional CVD tungsten deposition process including co-flowing tungsten hexafluoride and hydrogen gas at 400°C and 300 Torr. As shown in FIG. 5 , tungsten feature 501 has a stress of approximately 1600 MPa. Tungsten feature 502 was formed by a CVD process including co-flowing tungsten hexafluoride and hydrogen gas at 400°C and 5 Torr, resulting in a stress of approximately 1300 MPa. Tungsten feature 502 has a lower stress than tungsten feature 501. Tungsten feature 503 was formed by a CVD process including co-flowing tungsten hexafluoride and hydrogen gas at 450°C and 5 Torr, resulting in a stress of approximately 1000 MPa. Compared to tungsten feature 502, tungsten feature 503 has lower stress, which was brought about by increasing the temperature by 50° C. Tungsten feature 504 was formed by a CVD process involving co-flowing tungsten hexafluoride and hydrogen gas at 540° C. and 5 Torr, which resulted in a stress of approximately 350 MPa. Tungsten feature 504 has lower stress compared to tungsten features 502, 503 as a result of the further increase in temperature.

[0073] The feature 505 was formed using a pulsed CVD process 308 performed at 500°C and a pressure of approximately 0.8 Torr. The first gas included a mixture of 50 sccm tungsten hexafluoride and 200 sccm hydrogen gas. The second gas included 350 sccm argon. The pulse duration of the first gas was 0.5 seconds. The processing region 221 was purged with 350 sccm argon, with a purge duration of 2 seconds. The tungsten feature 505 has a stress of approximately 0 MPa. Thus, the pulsed CVD process 308 further reduces stress in the tungsten feature beyond the benefits of stress reduction provided by the low pressure and high temperature.

[0074] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A method of forming a structure on a substrate, comprising: forming a nucleation layer in an opening in a substrate in a processing chamber; forming a passivation layer on at least a portion of the nucleation layer by introducing a radical treatment into the processing chamber; forming a tungsten fill layer in the opening over the passivation layer and the nucleation layer, the tungsten fill layer being formed by a plurality of processing cycles, each processing cycle comprising: pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate; and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration. forming, A method comprising:

2. The method of claim 1 , wherein the purge gas is the second gas.

3. The method of claim 1 , wherein the treating radical is an activated nitrogen-containing species.

4. The method of claim 1 , wherein the treatment radical is nitrogen gas.

5. 10. The method of claim 1, wherein forming the passivation layer comprises introducing the radical treatment into a processing region from a radical generator attached to a lid assembly of the processing chamber.

6. 2. The method of claim 1, wherein the first gas is tungsten hexafluoride, the second gas is a mixture of hydrogen gas and argon, and the purge gas is a mixture of hydrogen gas and argon.

7. 2. The method of claim 1, wherein the first gas is hydrogen gas, the second gas is a first mixture of tungsten hexafluoride and argon, and the purge gas is a second mixture of tungsten hexafluoride and argon.

8. 2. The method of claim 1, wherein the first gas is a mixture of tungsten hexafluoride and argon, the second gas is argon, and the purge gas is argon.

9. 10. The method of claim 1, wherein the pulse duration is between about 0.3 seconds and about 2 seconds, and the purge duration is between about 0.5 seconds and about 5 seconds.

10. 10. The method of claim 1, wherein the tungsten fill layer has a stress between 0 MPa and 200 MPa.

11. 1. A method of forming a structure on a substrate, comprising: depositing a tungsten fill layer into an opening in a substrate having an internal stress of less than 200 MPa, wherein the tungsten fill layer is formed by a plurality of processing cycles, each processing cycle comprising: pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate; and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration. depositing, including A method comprising:

12. 12. The method of claim 11, wherein the first gas is tungsten hexafluoride, the second gas is a mixture of hydrogen gas and argon, and the purge gas is a mixture of hydrogen gas and argon.

13. 12. The method of claim 11, wherein the first gas is hydrogen gas, the second gas is a first mixture of tungsten hexafluoride and argon, and the purge gas is a second mixture of tungsten hexafluoride and argon.

14. 12. The method of claim 11, wherein the first gas is a mixture of tungsten hexafluoride and argon, the second gas is argon, and the purge gas is argon.

15. 12. The method of claim 11, wherein the pulse duration is between about 0.3 seconds and about 2 seconds, and the purge duration is between about 0.5 seconds and about 5 seconds.

16. forming a passivation layer within the opening by injecting activated nitrogen species into a processing region of the processing chamber from a radical generator attached to the lid of the processing chamber; The method of claim 11 further comprising:

17. 1. A method of forming a structure on a substrate, comprising: forming a nucleation layer on a substrate, a first portion of the nucleation layer being deposited in an opening in the substrate and a second portion of the nucleation layer being deposited on a field in the substrate; forming a passivation layer on the nucleation layer by exposing the nucleation layer to a radical treatment, the passivation layer preventing tungsten deposition on the second portion of the nucleation layer; forming a tungsten fill layer in the opening over the passivation layer and the nucleation layer, the tungsten fill layer being formed by a plurality of processing cycles, each processing cycle comprising: pulsing a first gas to the substrate for a pulse duration while simultaneously flowing a second gas over the substrate; and purging the first gas and the second gas by flowing a purge gas over the substrate for a purge duration. forming, A method comprising:

18. 18. The method of claim 17, wherein the first gas is tungsten hexafluoride, the second gas is a mixture of hydrogen gas and argon, and the purge gas is a mixture of hydrogen gas and argon.

19. 18. The method of claim 17, wherein the first gas is hydrogen gas, the second gas is a first mixture of tungsten hexafluoride and argon, and the purge gas is a second mixture of tungsten hexafluoride and argon.

20. 18. The method of claim 17, wherein the tungsten fill layer has a stress between 0 MPa and 200 MPa.

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