Low stress tungsten layer deposition

Abstract

A method of forming a structure on a substrate includes forming a nucleation layer within an opening of the substrate within a processing chamber. The method further includes forming a passivation layer on at least a portion of the nucleation layer by introducing a free radical treatment into the processing chamber. The method further includes forming a tungsten filled layer over the passivation layer and the nucleation layer within the opening, wherein the tungsten filled layer is formed by a plurality of treatment cycles. Each treatment cycle includes pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas through the substrate, and purging the first gas and the second gas by flowing a purge gas through the substrate for a purge time duration.

Description

Background Art

[0001] field

[0002] Embodiments of the present disclosure relate generally to methods used in electronic device fabrication and, more particularly, to methods for forming tungsten features in semiconductor devices.

[0003] Related technical description

[0004] Tungsten (W) is widely used in integrated circuit (IC) device fabrication to form conductive features where relatively low resistance and relatively high electromigration resistance are desired. For example, tungsten can be used as a metal fill material to form source contacts, drain contacts, metal gate fills, gate contacts, interconnects (e.g., horizontal features formed in the surface of a dielectric material layer), and vias (e.g., vertical features formed through a dielectric material layer to connect other interconnect features disposed above and below it).

[0005] Due to its relatively low resistivity, tungsten is also commonly used to form bit lines and word lines for addressing individual memory cells in a memory cell array of a three-dimensional NAND (3D NAND) device. A 3D NAND structure comprises a horizontal array of levels that can be stacked by sequentially depositing layers. A channel can be formed through the stack of films and filled with tungsten. In some cases, the channel sidewall width can vary between levels. During channel filling, due to the varying channel sidewall width and the higher concentration of the precursor gas used to deposit the tungsten fill layer, the tungsten fill layer can be deposited more quickly in the upper portion of the channel than in the lower portion. This can result in the formation of voids within portions of the channel, particularly for channels arranged in a structure having two or more levels, and particularly for high aspect ratio features. Additionally, conventional methods for depositing tungsten within the channel result in tungsten gapfills with high internal stress. This stress can cause the substrate to deform (e.g., warp, bow, crack).

[0006] Therefore, there is a need for a process for depositing tungsten gapfill within channels in multi-level structures that is free or substantially free of voids and seams and has low resistivity. There is also a need in the art for depositing tungsten gapfill with low to no internal stress. Summary of the Invention

[0007] Embodiments described herein generally relate to systems and methods for forming tungsten features in semiconductor devices. More specifically, embodiments herein provide processes and methods for forming low-stress tungsten structures.

[0008] In one embodiment, a method of forming a structure on a substrate includes forming a nucleation layer within an opening of the substrate within a processing chamber. The method further includes forming a passivation layer on at least a portion of the nucleation layer by introducing a free radical treatment into the processing chamber. The method further includes forming a tungsten fill layer above the passivation layer and the nucleation layer within the opening, wherein the tungsten fill layer is formed by a plurality of treatment cycles. Each treatment cycle includes pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas through the substrate, and purging the first gas and the second gas by flowing a purge gas through the substrate for a purge time duration.

[0009] In one embodiment, a method of forming a structure on a substrate includes depositing a tungsten fill layer into an opening of the substrate, the tungsten fill layer having an internal stress of less than 200 MPa. The tungsten fill layer is formed by a plurality of treatment cycles, each treatment cycle comprising pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas through the substrate, and purging the first and second gases by flowing a purge gas through the substrate for a purge time duration.

[0010] In one embodiment, a method of 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 of the substrate, and a second portion of the nucleation layer is deposited on a field region of the substrate. The method further includes forming a passivation layer on the nucleation layer by exposing the nucleation layer to a free radical treatment. The passivation layer prevents tungsten from being deposited on the second portion of the nucleation layer. The method further includes forming a tungsten fill layer over the passivation layer and the nucleation layer within the opening. The tungsten fill layer is formed by a plurality of treatment cycles, each treatment cycle including pulsing a first gas to the substrate for a pulse time duration while concurrently flowing a second gas through the substrate, and purging the first gas and the second gas by flowing a purge gas through the substrate for a purge time duration. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order that the manner in which the above-recited features of the present disclosure may be understood in detail, a more particular description of the present disclosure, briefly summarized above, may be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only exemplary embodiments of the present disclosure and are therefore not to be considered limiting of the scope of the present disclosure, as the disclosure may admit to other equally effective embodiments.

[0012] Figure 1is a schematic cross-sectional view of a portion of a substrate illustrating undesirable void or seam formation in a conventionally formed tungsten feature.

[0013] Figure 2A is a schematic diagram of a processing system that can be used to implement the methods described herein, according to one embodiment.

[0014] Figure 2B yes Figure 2A A close-up cross-sectional view of a portion of a processing system is shown.

[0015] Figure 3 is a diagram illustrating a method of processing a substrate according to one embodiment.

[0016] Figure 4A is a schematic cross-sectional view of a portion of a substrate, including a substrate to be processed by the methods described herein, according to one embodiment.

[0017] Figure 4B is a schematic cross-sectional view of a substrate showing an adhesion layer deposited thereon according to one embodiment.

[0018] Figure 4C is a schematic cross-sectional view of a substrate showing a nucleation layer deposited on an adhesion layer according to one embodiment.

[0019] Figure 4D is a schematic cross-sectional view of a substrate showing a passivation layer formed on a nucleation layer according to one embodiment.

[0020] Figure 4E is a schematic cross-sectional view of a substrate showing a tungsten gapfill layer according to one embodiment.

[0021] Figure 5 Graphs illustrating the stress of different tungsten gapfill layers deposited on a substrate formed by different processes are shown.

[0022] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0023] Embodiments herein are directed generally to electronic device fabrication, and more particularly, to systems and methods for forming low-resistivity tungsten features in semiconductor device fabrication schemes.

[0024] Figure 11 is a schematic cross-sectional view of a substrate 101 illustrating undesirable voids 20 formed during a conventional tungsten deposition process. Here, substrate 101 includes a patterned surface 11 disposed within a plurality of hierarchical layers, such as a first hierarchical layer 12A and a second hierarchical layer 12B. In some embodiments, first hierarchical layer 12A is a first dielectric layer, and second hierarchical layer 12B is a second dielectric layer. In some embodiments, substrate 101 includes a plurality of alternating first hierarchical layers and second hierarchical layers. Patterned surface 11 includes at least one opening having a high aspect ratio opening formed therein (shown as being filled with a portion of tungsten layer 15), an adhesion layer 14 deposited on hierarchical layers 12A, 12B to line the opening, and a tungsten layer 15 deposited on adhesion layer 14. Figure 1 The illustrated tungsten layer 15 is formed using a conventional deposition process (e.g., chemical vapor deposition (CVD) or atomic layer deposition (ALD) process), wherein tungsten is conformally deposited (grown) on the patterned surface 11 to fill the opening. The tungsten layer 15 forms tungsten features 15A in the first level layer 12A, tungsten features 15B in the second level layer 12B, and a material via (tungsten via 15C) on the field region of the patterned surface 11. In one example, the first dielectric layer and the second dielectric layer may include silicon oxide (SiO x ) and / or silicon nitride (SiN).

[0025] exist Figure 1 1. In the embodiment of the present invention, 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 level layers, the width of the second level layer 12B is narrower than the width of the first level layer 12A disposed inward from the second level layer 12B. As shown, the interfacial portions of the conformal tungsten layer 15 have grown together to block or "pinch off" the entrance of the opening disposed in the first level 12A before the opening can be completely filled, thereby resulting in an undesirable void 20 in the tungsten feature 15A, i.e., a lack of tungsten material. In addition to voids, undesirable gaps (e.g., 24) may appear in the tungsten features, as shown, appearing within the second level 12B using conventional tungsten deposition processes. Voids 20 and crevices 24 are susceptible to corrosion from chemically active components of a tungsten chemical mechanical polishing (CMP) polishing fluid, which can result in undesirable loss of tungsten material from features 15A, 15B if crevices 24 or 20 are exposed during the CMP process. Additionally, conventional tungsten deposition processes result in a tungsten layer 15 having high internal stresses that can deform the first and second level layers 12A, 12B of substrate 101. For example, the stress can be approximately or exceed 1600 MPa.

[0026] The embodiments described herein form tungsten gap fillers deposited from the bottom up within an opening in a substrate with reduced stress and reduced void instances. The methods and systems provided herein are particularly useful for achieving tungsten gap fillers with 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). The aspect ratio refers to the ratio of the total height of the feature to the average width or diameter. Additionally, embodiments herein provide a processing system that is 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 for the tungsten gap fill processing scheme described herein.

[0027] Figure 2A A processing system 200 that can be used to perform the bottom-up tungsten gapfill substrate processing method described herein is schematically illustrated. Here, the processing system 200 is configured to provide the different processing conditions required to form an adhesion layer, a nucleation layer, a passivation layer, and a tungsten gapfill layer on a substrate within a single processing chamber 202, i.e., without transferring the substrate between multiple processing chambers.

[0028] like Figure 2A As shown, 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 ( Figure 2A 1 and 2) includes a chamber lid 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 217, such as one or more vacuum pumps, for maintaining the processing volume 215 at a process pressure, such as sub-atmospheric conditions, and for evacuating process gases and process byproducts therefrom.

[0029] The chamber lid assembly 210 includes a lid plate 216 and a showerhead 218 coupled to the lid plate 216 to define a gas distribution volume 219. The lid plate 216 is maintained at a desired temperature by one or more heaters 229 thermally coupled thereto. The showerhead 218 faces a substrate support assembly 220 disposed within the processing volume 215. As discussed below, the substrate support assembly 220 is configured to move a substrate support 222, and thereby a substrate 230 disposed thereon, between a raised substrate processing position (as shown) and a lowered substrate transfer position (not shown). When the substrate support assembly 220 is in the raised substrate processing position, the showerhead 218 and the substrate support 222 define a processing region 221.

[0030] The gas delivery system 204 is fluidly coupled to the processing chamber 202 via a gas inlet 223 disposed through the lid plate 216. Process or cleaning gas delivered using the gas delivery system 204 flows through the gas inlet 223 into the gas distribution volume 219 and is distributed into 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 baffle plate 225 disposed between the gas inlet 223 and the showerhead 218. In those embodiments, gas flowing into the gas distribution volume 219 is first diffused by the baffle plate 225 to provide, in conjunction with the showerhead 218, a more uniform or desired distribution of gas into the processing region 221.

[0031] Process gases and process byproducts are evacuated radially outward from the processing region 221 through an annular passage 226 that surrounds the processing region 221. The annular passage 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 that are used to protect the inner surfaces of the one or more sidewalls 212 or the chamber base 214 from corrosive gases and / or deposition of undesirable materials.

[0032] In some embodiments, a purge gas source 237 in fluid communication with the processing volume 215 is used to flow a chemically inert purge gas, such as argon (Ar), into a region disposed 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 positive pressure region below the substrate support 222 (compared to the pressure in the processing region 221) during substrate processing. Typically, the purge gas introduced through the chamber base 214 flows upward therefrom and around the edge of the substrate support 222 to evacuate the processing volume 215 through the annular channel 226. The purge gas reduces the deposition of undesirable materials on surfaces below the substrate support 222 by reducing and / or preventing the inflow of material precursor gases therein.

[0033] 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 an area below the chamber base 214, and a substrate support 222 that is seated 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 that are coupled to or seated in engagement with a lift pin ring 268. The plurality of lift pins 267 are movably seated in openings formed through the substrate support 222. When the substrate support 222 is disposed in the lowered substrate transfer position (not shown), the plurality of lift pins 267 extend above the substrate receiving surface of the substrate support 222 to lift the substrate 230 therefrom and enable a substrate handler (not shown) to contact the back (inactive) surface of the substrate 230. When the substrate support 222 is in the raised or processing position (as shown), the plurality of lift pins 267 retract below the substrate receiving surface of the substrate support 222 to allow the substrate 230 to rest thereon.

[0034] The substrate 230 is transferred to and from the substrate support 222 through a door 271, such as a slit valve disposed in one of the one or more sidewalls 212. Here, one or more openings in an area surrounding the door 271, such as an opening in a door housing, are fluidly coupled to a purge gas source 237, such as an argon source. The purge gas is used to prevent process and cleaning gases from contacting and / or degrading the seals surrounding the door, thereby extending its useful life.

[0035] 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. The vacuum is applied using a vacuum source 272 fluidically 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 can be configured for electrostatic clamping. In some embodiments, the substrate support 222 includes one or more electrodes (not shown) coupled to a bias voltage source (not shown), such as a continuous wave (CW) RF power source or a pulsed RF power source, which supplies a bias voltage thereto.

[0036] As shown, the substrate support assembly 220 is equipped with a dual-zone temperature control system to provide independent temperature control in different zones of the substrate support 222. The different temperature-controlled zones of the substrate support 222 correspond to different zones of the substrate 230 positioned thereon. Here, the temperature control system includes a first heater 263 and a second heater 264. The first heater 263 is positioned in the central zone of the substrate support 222, and the second heater 264 is positioned radially outward from the central zone to surround the first heater 263. In other embodiments, the substrate support 222 may have a single heater or more than two heaters.

[0037] In some embodiments, the substrate support assembly 220 further includes an annular shadow ring 235 for preventing undesirable material from being deposited on the circumferential beveled edge of the substrate 230. During transfer of the substrate to and from the substrate support 222, i.e., when the substrate support assembly 220 is positioned in a lowered position (not shown), the shadow ring 235 rests on the annular edge within the processing volume 215. When the substrate support assembly 220 is positioned 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 positioned on the substrate support 222. Here, the shadow ring 235 is shaped such that a radially inward portion of the shadow ring 235 rests on the beveled edge of the substrate 230 when the substrate support assembly 220 is in the raised substrate processing position.

[0038] In some embodiments, the substrate support assembly 220 further includes an annular purge ring 236 positioned on the substrate support 222 to surround the substrate 230. In those embodiments, a shadow ring 235 can be positioned on the purge ring 236 when the substrate support assembly 220 is in the elevated substrate processing position. Typically, the purge ring 236 has a plurality of radially inward openings that are 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 beveled edge of the substrate 230 to prevent process gas from entering the annular region and causing undesirable material to be deposited on the beveled edge of the substrate 230.

[0039] In some embodiments, the processing chamber 202 is configured for direct plasma processing. In those embodiments, the showerhead 218 can be electrically coupled to a first power source 231, such as an RF power source, which supplies power to ignite and sustain a plasma of the process gas flowing into the processing region 221 through capacitive coupling therewith. In some embodiments, the processing chamber 202 includes an inductive plasma generator (not shown) and forms the plasma by inductively coupling RF power to the process gas.

[0040] refer to Figure 2A and 2B , the gas delivery system 204 includes one or more remote plasma sources, here a first radical generator 206A and a second radical generator 206B, a deposition gas source 240, and a conduit system 294 (e.g., a plurality of conduits 294A-294F) that fluidly couple the radical generators 206A-206B and the deposition gas source 240 to the lid assembly 210. Although the gas delivery system 204 shown includes two radical generators 206A-206B, the processes described herein can also be implemented using a gas delivery system 204 having only a single radical generator 206A. The gas delivery system 204 further includes a plurality of isolation valves, here a first valve 290A and a second valve 290B, each disposed between the radical generators 206A-206B and the lid plate 216, which can be used to fluidically isolate each radical generator 206A-206B from the processing chamber 202 and from each other.

[0041] Each of the radical generators 206A-206B has a chamber body 280 that defines a respective first plasma chamber volume 281A and a second plasma chamber volume 281B ( Figure 2B Each free radical generator 206A-206B is coupled to a respective power source 293A-293B. The power sources 293A-293B are used to ignite and maintain a plasma 282A-282B of a gas delivered to the plasma chamber volumes 281A-281B from a respective first gas source 287A or second gas source 287B fluidly coupled thereto. The first free radical generator 206A can be used to ignite and maintain a treatment plasma 282A from a non-halogen-containing gas mixture delivered from the first gas source 287A to the first plasma chamber volume 281A. In some embodiments, the first free radical generator 206A generates activated species, such as treatment radicals, that are used to treat a substrate to inhibit tungsten deposition thereon, such as by forming a passivation layer. The treatment radicals can be a non-halogen nitrogen-containing gas, such as nitrogen (N2), ammonia (NH3), or other nitrogen-containing gases. The treatment radicals can be a combination of different non-halogen-containing nitrogen gases. In some embodiments, the treatment radical may be a nitrogen-containing gas including a halogen, such as nitrogen trifluoride (NF3). The second radical generator 206B may be used to generate cleaning radicals for a chamber cleaning process by igniting and maintaining a cleaning plasma 282B via a halogen-containing gas mixture delivered from a second gas source 287B to the second plasma chamber volume 281B.

[0042] Typically, nitrogen treatment radicals have a relatively short lifetime (compared to halogen cleaning radicals) and may exhibit relatively high sensitivity to collisions with surfaces in the gas delivery system 204 (such as the conduit system 294) and / or recombination with other species of the treatment plasma effluent. Thus, in 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 shorter travel distance from the first plasma chamber volume 281A to the processing region 221. In some embodiments, the first radical generator 206A and the first gas source 287A are attached to the chamber lid assembly 210 or an upper structure of the processing chamber 202.

[0043] In some embodiments, the first radical generator 206A is also fluidly coupled to a second gas source 287B that delivers a halogen-containing conditioning gas to the first plasma chamber volume 281A for use in a plasma source conditioning process. In those embodiments, the gas delivery system 204 may 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.

[0044] Suitable remote plasma sources that may be used for one or both of the free 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.

[0045] As shown, the first radical generator 206A is fluidly coupled to the processing chamber 202 using a first conduit 294A and a second conduit 294B that extend 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 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, during a chamber cleaning process, the first valve 290A is closed to prevent activated cleaning gases, such as halogen radicals, from flowing into the first plasma chamber volume 281A and damaging its surfaces.

[0046] The second radical generator 206B is fluidly coupled to the second conduit 294B, and thereby to the processing chamber 202, using a third conduit 294C and a fourth conduit 294D. The second radical generator 206B is selectively isolated from the processing chamber 202 and other portions of the gas delivery system 204 using a second valve 290B disposed between the third conduit 294C and the fourth conduit 294D.

[0047] Deposition gas, such as a tungsten-containing precursor and a reducing agent, is delivered from deposition gas source 240 to processing chamber 202 using fifth conduit 294E. As shown, fifth conduit 294E is coupled to second conduit 294B near gas inlet 223, such that first valve 290A and second valve 290B can be used to isolate first radical generator 206A and second radical generator 206B, respectively, from deposition gas introduced into processing chamber 202. Third valve 290C is positioned in fifth conduit 294E to selectively isolate deposition gas source 240 from first radical generator 206A and second radical generator 206B, and selectively allow a certain amount of deposition gas to flow through fifth conduit 294E and into processing region 221. In some embodiments, gas delivery system 204 further includes sixth conduit 294F, which is coupled to 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) gas source, which may be used to periodically purge portions of the gas delivery system 204 of undesirable residual cleaning, suppression, and deposition gases.

[0048] In some embodiments, deposition gas source 240 is attached to chamber lid assembly 210 or the upper structure of processing chamber 202. In some embodiments, deposition gas source 240 is a plurality of different deposition gas reservoirs connected to conduit system 294 via separate conduits, and each respective deposition gas reservoir may have an associated flow control valve. Each separate deposition gas reservoir may be attached to chamber lid assembly 210 or the upper structure of processing chamber 202.

[0049] The operation of the processing system 200 is controlled by the system controller 208 ( Figure 2A) facilitates. The system controller 208 includes a programmable central processing unit, here a CPU 295, which is operable in conjunction with a memory 296 (e.g., non-volatile memory) and support circuits 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. 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 caches, clock circuits, input / output subsystems, power supplies, etc., coupled to various components of the processing system 200, and combinations thereof, to facilitate control of its substrate processing operations.

[0050] The instructions in the memory 296 are in the form of a program product, such as a program that implements the method of the present disclosure. In one example, the present disclosure can be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program of the program product defines the functions of the embodiments (including the methods described herein). Thus, when carrying computer-readable instructions that direct the functions of the methods described herein, the computer-readable storage medium is an embodiment of the present disclosure.

[0051] Figure 3 is a diagram illustrating a process 300 for processing a substrate, which may be performed using the processing system 200 , according to some embodiments. Figures 4A to 4E is a schematic cross-sectional view of a portion of an exemplary substrate 400 illustrating aspects of the process 300 at various stages.

[0052] After the substrate 400 is placed on the substrate receiving surface of the substrate support 222 within the processing chamber 202, an adhesion layer 422 is formed on the substrate 400, as depicted in activity 302. Then, a nucleation layer 424 is deposited on the adhesion layer 422, as depicted in activity 304. Next, the substrate 400 is subjected to a radical treatment, wherein the substrate 400 is treated with a treatment gas including activated species to form a passivation layer 426, as depicted in activity 306. Then, a tungsten gapfill layer 428 is deposited by pulsed CVD, as depicted in activity 308. The tungsten gapfill layer 428 is deposited from the bottom up and is substantially or completely free of voids or seams. Process 300 will be explained in more detail below.

[0053] Figure 4AAn exemplary substrate 400 is illustrated. Substrate 400 comprises a patterned surface 401 including a first hierarchical layer 412A and a second hierarchical layer 412B having a plurality of openings 405 (one shown) formed therein. In some embodiments, the plurality of openings 405 include one or a combination of high-aspect-ratio via or trench openings having a width (e.g., each of 407 and 414) of about 100 nm to about 400 nm (e.g., about 200 nm to about 300 nm) and a depth (e.g., each of 402A or 402B, or either of 402A or 402B) of about 2 μm to about 8 μm (e.g., about 3 μm to about 6 μm). In some embodiments, the plurality of openings includes at least one opening having a width 410 of the narrowest portion of the opening of about 50 nm to about 200 nm, such as about 75 nm to about 125 nm. In some embodiments, the individual openings 405 may have an aspect ratio (depth to width ratio) of about 10:1 or greater (such as about 25:1 or greater, such as about 30:1 to about 100:1, such as about 40:1 to about 60:1). In some embodiments, the via or trench openings include an aspect ratio of about 20:1 to about 40:1. The openings disposed within the first level 412A are referred to as first-level openings 402A, and the openings disposed within the second level 412B are referred to as second-level openings 402B. The first-level openings 402A and the second-level openings 402B together form a single connected opening 405. The uppermost portion of the first-level opening 402A abuts the lowermost portion of the second-level opening 402B at an interface 406.

[0054] At interface 406, the width 407 of the uppermost portion of the first-level opening is greater than the width 410 of the lowermost portion of the second-level opening 402B. In some embodiments, width 407 is approximately 5% to approximately 100% greater than width 410, such as approximately 10% to approximately 50%. For example, width 410 may be approximately 50 nm to approximately 300 nm, such as approximately 75 nm to approximately 125 nm, and width 407 may be approximately 70 nm to approximately 400 nm, such as approximately 150 nm to approximately 250 nm. In some embodiments, for each level, the widest portion of that level (such as uppermost portion 414 of second level 402B) is approximately 5% to approximately 100% greater than the narrowest portion of that level (such as lowermost portion 410 of second level 402B), such as approximately 10% to approximately 50%. In some embodiments, the height of first-level opening 402A is substantially the same as, less than, or greater than the height of second-level opening 402B. Without being bound by theory, it is believed that the abrupt difference in opening width at the interface may cause a pinch-off effect when the tungsten gapfill layer is deposited.The process 300 described herein enables the formation of a tungsten gapfill layer 428 that fills the opening 405 without forming voids.

[0055] As in Figure 3 Activity 302 shown in and referenced Figure 4B The process 300 begins by depositing an adhesion layer 422 on the patterned surface 401 within the processing chamber 202. The adhesion layer 422 is composed of a material that, in addition to promoting the nucleation of tungsten, prevents or limits the diffusion of tungsten into the underlying material. The adhesion layer 422 may be a titanium nitride (TiN) layer. Figure 4B As shown, patterned surface 401 includes an adhesion layer 422 deposited on first level layer 412A and second level 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 depth of approximately 20 angstroms. With The thickness between, such as about to about Adhesion layer 422 may be formed by processing system 200 using an atomic layer deposition (ALD), physical vapor deposition (PVD) process, or a chemical vapor deposition (CVD) process. For example, adhesion layer 422 may be a titanium nitride layer formed using a titanium-containing precursor and a nitrogen-containing precursor flowing from deposition gas source 240 into processing region 221. For example, adhesion layer 422 may be formed by flowing titanium tetrachloride (TiCl4) and ammonia (NH3) from deposition gas source 240 into processing region 221 to react therein to form titanium nitride.

[0056] As shown in activity 304 , a nucleation layer 424 is deposited on the adhesion layer 422 . Figure 4C Schematically illustrates a portion of an exemplary substrate 400 having a nucleation layer 424 formed thereon. 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 a cycle of repeatedly 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 the alternating exposures. In some embodiments, the processing region 221 is continuously purged. Examples of suitable tungsten-containing precursors include tungsten halides, such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), or combinations thereof. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent can be a boron-containing reagent, 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 dicarbonyl nitrosyl tungsten), EDNOW (ethylcyclopentadienyl dicarbonyl nitrosyl tungsten), tungsten hexacarbonyl (W(CO)6), or a combination thereof.

[0057] For example, the tungsten-containing precursor and the reducing agent are each flowed into the processing region 221 for a duration 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 the alternating exposures by flowing a purge gas, such as argon (Ar) or hydrogen, into the processing region 221 for a duration 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 delivered from the deposition gas source 240 or from the bypass gas source 238. Typically, the cycle of repeating the nucleation process continues until the nucleation layer 424 has a thickness between about 10 angstroms and about 200 angstroms, such as between about 10 angstroms and about 150 angstroms, or between about 20 angstroms and about 150 angstroms. The nucleation layer 424 is disposed along the sidewalls of the opening 405, such as above the adhesion layer 422. During the nucleation process, the processing volume 215 can be maintained at a pressure of 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 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 from about 10 sccm to about 60 sccm, or from about 20 sccm to 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 about 200 sccm to about 1000 sccm, such as from about 300 sccm to about 750 sccm.

[0058] At activity 306, the substrate 400 is subjected to a free radical treatment to Figure 4D A passivation layer 426 is formed on the nucleation layer 424 within the illustrated opening 405. The passivation layer 426 inhibits, and in some embodiments, completely inhibits, tungsten nucleation on the passivation layer 426. The radical treatment 306 includes flowing an activated species (such as an activated nitrogen species, such as N2, NH3, or a combination thereof) formed in the first radical generator 206A into the processing region 221. In some embodiments, the activated species is mixed with an inert carrier gas (such as Ar, He, or a combination thereof) to form a radical treatment gas mixture. Without intending to be bound by theory, it is believed that nitrogen from the activated nitrogen species is incorporated into portions of the nucleation layer 424, for example, by adsorption of nitrogen or by reacting with the metallic tungsten of the nucleation layer 424 to form a tungsten nitride (WN) passivation layer 426. The passivation layer 426 desirably delays (inhibits) further tungsten nucleation and, thereby, delays subsequent tungsten deposition thereon.

[0059] In some embodiments, the passivation layer 426 only partially covers the nucleation layer 424, wherein a portion of the nucleation layer 424 near the bottom of the opening 405 is uncovered. The field portion 426a of the passivation layer 426 can optionally be formed on the field region 403, and the opening portion 426b is formed on the surface of the opening 405. For example, the field portion 426a can be formed to prevent a large amount of tungsten from being deposited on the field region 403 of the substrate 400. Reducing or eliminating tungsten deposition on the field region 403 reduces material costs and reduces the time required to perform operations for removing the overlayer. The opening portion 426b is a tungsten deposition inhibition profile that facilitates the deposition of the tungsten gap fill layer 428 in the opening 405 in activity 308 without forming a void. As Figure 4D As shown, opening portion 426b may extend partially from second-level opening 402B into first-level opening 402A. Opening portion 426b may terminate at or near pinch-off point 430 of nucleation layer 424, which is the narrowest point within opening 405 near interface 406 after nucleation layer 424 is deposited. In some embodiments, opening portion 426b may extend beyond pinch-off point 430. A desired suppression effect on field portion 426a and a desired suppression profile in opening 405 are achieved by controlling processing conditions (such as temperature and pressure) within processing chamber 202 and controlling the concentration, flux, and energy of treatment radicals directed toward the substrate surface.

[0060] For example, the radical treatment may produce a passivation layer 426 that inhibits the deposition of tungsten more strongly nearer the beginning of the opening 405 than nearer the bottom of the opening 405. The passivation layer 426 is formed to achieve the desired inhibitory effect to promote the bottom-up deposition of a void-free and seam-free tungsten gap fill portion 428 within the opening 405. The passivation layer 426 also mitigates the pinch-off effect to avoid the formation of voids. For example, the passivation layer 426 may prevent a large amount of tungsten from being deposited on the opening portion 426b until the tungsten has filled the first level opening 402A. Once the first level opening 402A is filled with tungsten, additional tungsten is deposited on the tungsten filling the first level opening 402A to fill the second level opening 402B to form the tungsten gap fill layer 428. As Figure 4E As shown, the portion of the tungsten gap-fill layer 428 in the second opening 402B is formed over the opening portion 426 b of the passivation layer 428 .

[0061] The passivation layer 426 can be formed with a non-uniform thickness within the opening 405 so that the suppression effect is non-uniform. For example, the passivation layer 426 can be tapered so that the suppression effect decreases with the depth of the opening 405, so that tungsten nucleates at different rates on different portions of the passivation layer 426 to control the formation of the tungsten gapfill layer 428. For example, the tungsten nucleation rate increases with the depth of the opening 405, so that a faster tungsten nucleation rate occurs on the exposed portion of the nucleation layer 424 at the bottom of the opening 405.

[0062] In some embodiments, exposing the nucleation layer 424 to the treat radicals includes using the first radical generator 206A to form a treat plasma 282A of a substantially halogen-free treat gas mixture, and flowing the effluent of the treat plasma 282A into the processing region 221. In some embodiments, the flow rate of the treat gas mixture into the first radical generator 206A, and thus the flow rate of the treat plasma effluent (such as nitrogen) 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 105 sccm, such as between about 1 sccm and about 75 sccm, such as between about 1 sccm and about 50 sccm.

[0063] In some embodiments, the free radical treatment includes exposing the substrate 400 to the treatment radicals for about 2 seconds or longer, such as about 2 seconds to about 30 seconds, such as about 5 seconds to about 20 seconds, such as about 10 seconds to about 15 seconds.

[0064] In some embodiments, the concentration of activated radical species within the radical treatment gas mixture is from about 0.1 vol% to about 50 vol%, such as from about 0.2 vol% to about 40 vol%, from about 0.2 vol% to about 30 vol%, from about 0.2 vol% to about 20 vol%, or for example, such as from about 0.2 vol% to about 10 vol%, such as from about 0.2 vol% to about 5 vol%.

[0065] In other embodiments, the treatment radicals may be formed using a remote plasma (not shown) that is ignited and maintained in a portion of the processing volume 215 that is separated from the processing region 221 by the showerhead 218, such as between the showerhead 218 and the cover plate 216. In those embodiments, the activated treatment gas may be passed through an ion filter to remove substantially all ions from the treatment radicals before they reach the processing region 221 and the surface of the substrate 400. In some embodiments, the showerhead 218 may function 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, for example, when an in-situ treatment plasma is used, the substrate 400 may be biased to control the directionality of ions (e.g., charged treatment radicals) formed from the treatment gas toward the substrate surface and to accelerate these ions.

[0066] In some embodiments, free radical treatment includes maintaining the processing volume 215 at a pressure of less than about 100 Torr while flowing the activated treatment gas into the processing volume 215. For example, during free radical treatment, the processing volume 215 can be maintained at a pressure of about 20 Torr or less, such as about 0.5 Torr to about 10 Torr, such as about 1 Torr to about 5 Torr.

[0067] Activity 308 represents the use of pulsed chemical vapor deposition ("pulsed CVD") to Figure 4E A tungsten gap filler 428 is shown formed in the opening 405. It has been found that reducing pressure and increasing temperature can improve the stress formed in the tungsten gap filler. However, the effect of simply increasing temperature and reducing pressure is reduced. For example, low pressure (such as vacuum conditions) affects the quality of the gap fill and interferes with the suction of the substrate 400 to the substrate support assembly 220. Some temperatures may degrade or adversely affect other features formed on the substrate 400. Additionally, some temperatures promote degradation of components of the processing system 200, resulting in increased maintenance costs. The pulsed CVD process shown as activity 308 includes processing the substrate 400 at low pressure at medium to high temperatures to take advantage of their stress reduction benefits. However, pulsed CVD 308 results in improved tungsten gap fill and lower stress than can be achieved by adjusting temperature and pressure parameters alone.

[0068] The pulsed CVD process, represented by 308, includes cyclically pulsing a first gas for a pulse time duration while concurrently flowing a second gas into the processing region 221, and then purging the first gas and the second gas from the processing region 221 with a purge gas for a purge time duration. The first gas and the second gas are supplied to the processing region 221 by a deposition gas source 240. The pressure within the processing volume 215 is between about 0.7 Torr and about 15 Torr, such as 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, and 14.5 Torr. The temperature within the processing region 221 may be between 400° C. and 500° C., and heat may be supplied by the heater 229 , the first heater 263 , and / or the second heater 264 .

[0069] In some embodiments, the first gas is a tungsten-containing precursor, such as tungsten hexafluoride. In some embodiments, the first gas is hydrogen. In some embodiments, the first gas is a mixture of a tungsten-containing precursor and hydrogen, such as a mixture of tungsten hexafluoride and hydrogen. The pulse duration can be between about 0.3 seconds and about 2 seconds, such as about 0.5 seconds, about 1 second, and about 1.5 seconds.

[0070] In some embodiments, when the first gas comprises a tungsten-containing precursor, the second gas is a mixture of hydrogen and an inert gas (such as argon). 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, when the first gas is a mixture of a tungsten-containing precursor and hydrogen, the second gas is an inert gas.

[0071] 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 gases having the same components but different concentrations. In some embodiments, the purge gas may be supplied to the processing region 221 from a purge gas source 237. The purge gas may be supplied by a deposition gas source 240 because, after the first gas pulse ceases, the processing region 221 is purged by continuing to flow the second gas into the processing chamber 202, which causes the first gas to flow out of the processing region 221 and out of the exhaust 217. The pulse duration may be between about 0.5 seconds and about 5 seconds, such as about 1 second, such as about 1.5 seconds, such as about 2 seconds, such as about 2.5 seconds, such as about 3 seconds, such as about 3.5 seconds, such as about 4 seconds, and such as about 4.5 seconds.

[0072] Without being bound by theory, it is believed that fluorine impurities in the tungsten gapfill 428 contribute to stress. Without being bound by theory, it is believed that purging with a purge gas that does not include fluorine after each pulse reduces the formation of fluorine impurities, such as by reducing the time available for tungsten hexafluoride to interact with the forming tungsten gapfill. Additionally, it is believed that reducing stress in the tungsten gapfill results in smaller grain size.

[0073] In one embodiment, the first gas is tungsten hexafluoride, and the second gas is a mixture of hydrogen and argon. For example, tungsten hexafluoride is pulsed into the processing region 221 at between about 50 sccm and 1200 sccm for a pulse duration into a concurrently flowing mixture of hydrogen at between about 200 sccm and 6000 sccm and argon at between about 350 sccm and about 8000 sccm. The processing region 221 is then purged with the hydrogen and argon mixture.

[0074] In one embodiment, the first gas is hydrogen and the second gas is a mixture of tungsten hexafluoride and argon. For example, hydrogen gas between about 200 sccm and 6000 sccm is pulsed into the processing region 221 over a pulse time duration into a concurrently flowing mixture of tungsten hexafluoride between about 50 sccm and 1200 sccm and argon between about 350 sccm and about 8000 sccm. The processing region 221 is then purged with the mixture of tungsten hexafluoride and argon. For example, the processing region 221 can be purged with a mixture of argon between 3000 sccm and about 8000 sccm and tungsten hexafluoride between 100 sccm and 900 sccm. Without being bound by theory, it is believed that pulsing tungsten hexafluoride into the flowing hydrogen gas allows the deposition reaction to be more complete, which reduces the formation of fluorine impurities in the deposited tungsten gapfill layer 428.

[0075] In one embodiment, the first gas is a mixture of tungsten hexafluoride and hydrogen, and the second gas is argon. For example, a mixture of tungsten hexafluoride at between about 50 sccm and 1200 sccm and hydrogen at between about 200 sccm and 6000 sccm is pulsed into the processing region 221 into the concurrently flowing argon at between about 350 sccm and about 8000 sccm for a pulse duration. The processing region 221 is then purged with argon. For example, the processing region 221 may be purged with 3000 sccm to about 8000 sccm of argon.

[0076] It has been observed that the pulsed CVD process 308 including a first gas of hydrogen and a second gas that is a mixture of tungsten hexafluoride and argon has improved gapfill, 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 gapfill quality compared to tungsten gapfill deposited by conventional techniques.

[0077] The pulsed CVD process 308 may be performed in 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, as 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.

[0078] The pulsed CVD process 308 results in a tungsten gapfiller 428 having reduced stress. In some embodiments, the tungsten gapfiller 428 formed by the pulsed CVD process 308 has an internal stress between about 0 MPa and 200 MPa, such as between 0 MPa and 150 MPa, such as between 0 MPa and 100 MPa, such as between about 0 MPa and 50 MPa, such as between about 0 MPa and 40 MPa, such as between about 0 MPa and 30 MPa, such as between about 0 MPa and 20 MPa, such as between about 0 MPa and 10 MPa, such as between about 0 MPa and 5 MPa, such as between about 0 MPa and 1 MPa, such as between about 0 MPa and about 0.5 MPa. In some embodiments, the tungsten gapfiller 428 has a neutral (e.g., 0 MPa) or substantially neutral internal stress.

[0079] A chemical mechanical polishing (CMP) process may be used to remove overlayer materials such as adhesion layer 422 , nucleation layer 424 , passivation layer 426 , and portions of tungsten gapfill layer 428 that extend over field region 403 of substrate 400 after tungsten gapfill layer 428 is deposited into opening 405 .

[0080] The processing system 200 is configured to perform each activity of the process 300 to form a tungsten gapfill having low stress, voids, and seams. The process 300 can be performed without removing the substrate 400 from the processing system 200. The separate processes used to perform the process 300 and the treat gases used to clean residues from the interior surfaces of the processing chamber 202 are delivered to the processing chamber using a gas delivery system 204 fluidly coupled to the processing chamber 202. In other embodiments, each activity in the process 300 can be performed in a different processing system, such as in a cluster tool having multiple processing systems 200.

[0081] In some embodiments, process 300 is performed on a substrate having a single level of layers rather than multiple levels of layers.

[0082] Figure 5 A bar graph 500 is included that illustrates approximately 12,000 angstroms of etched metal formed on a substrate under various process conditions. Figure 2 depicts stress in thick tungsten features (e.g., tungsten gapfill). The Y-axis represents stress in megapascals (MPa) in the 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.

[0083] The tungsten feature 501 is deposited by a conventional CVD tungsten deposition process that includes concurrently flowing tungsten hexafluoride and hydrogen at 400° C. and 300 Torr. Figure 5 As shown, tungsten feature 501 has a stress of approximately 1600 MPa. Tungsten feature 502 is formed using a CVD process that includes concurrently flowing tungsten hexafluoride and hydrogen 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 is formed using a CVD process that includes concurrently flowing tungsten hexafluoride and hydrogen at 450°C and 5 Torr, resulting in a stress of approximately 1000 MPa. Compared to tungsten feature 502, tungsten feature 503 has a lower stress due to a 50°C increase in temperature. Tungsten feature 504 is formed using a CVD process that includes concurrently flowing tungsten hexafluoride and hydrogen at 540°C and 5 Torr, resulting in a stress of approximately 350 MPa. Compared to tungsten features 502 and 503, tungsten feature 504 has an even lower stress due to the further increase in temperature.

[0084] Feature 505 is formed using a pulsed CVD process 308 performed at 500° C. and a pressure of approximately 0.8 Torr. The first gas comprises a mixture of 50 sccm of tungsten hexafluoride and 200 sccm of hydrogen. The second gas comprises argon at 350 sccm. The pulse duration of the first gas is 0.5 seconds. Process region 221 is purged with 350 sccm of argon for a purge duration of 2 seconds. Tungsten feature 505 has a stress of approximately 0 MPa. Thus, pulsed CVD process 308 further reduces the stress of the tungsten feature in addition to the stress reduction benefits provided by the low pressure and high temperature.

[0085] While the foregoing 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 to be determined by the claims which follow.

Claims

1. A method for forming a structure on a substrate, the method comprising: forming a nucleation layer within an opening of a substrate within a processing chamber; forming a passivation layer on at least a portion of the nucleation layer by introducing free radical treatment into the processing chamber; as well as forming a tungsten fill layer over the passivation layer and the nucleation layer within the opening, wherein the tungsten fill layer is formed by a plurality of treatment cycles, each treatment cycle comprising: pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas across the substrate; as well as The first gas and the second gas are purged by flowing the purge gas through the substrate for a purge time duration.

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

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

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

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

7. The method of claim 1, wherein the first gas is hydrogen, 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. 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. The method of claim 1, wherein the pulse time duration is between about 0.3 seconds and about 2 seconds, and the purge time duration is between about 0.5 seconds and about 5 seconds.

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

11. A method of forming a structure on a substrate, the method comprising: A tungsten fill layer is deposited into the opening of the substrate, the tungsten fill layer having an internal stress of less than 200 MPa, wherein the tungsten fill layer is formed by a plurality of treatment cycles, each treatment cycle comprising: pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas across the substrate; and The first gas and the second gas are purged by flowing the purge gas through the substrate for a purge time duration.

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

13. The method of claim 11, wherein the first gas is hydrogen, 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. 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. The method of claim 11, wherein the pulse time duration is between about 0.3 seconds and about 2 seconds, and the purge time duration is between about 0.5 seconds and about 5 seconds.

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

17. A method of forming a structure on a substrate, the method comprising: forming a nucleation layer on a substrate, wherein a first portion of the nucleation layer is deposited in the opening of the substrate and a second portion of the nucleation layer is deposited on a field region of the substrate; forming a passivation layer on the nucleation layer by exposing the nucleation layer to a free radical treatment, wherein the passivation layer prevents tungsten from being deposited on the second portion of the nucleation layer; as well as forming a tungsten fill layer over the passivation layer and the nucleation layer within the opening, wherein the tungsten fill layer is formed by a plurality of treatment cycles, each treatment cycle comprising: pulsing a first gas toward the substrate for a pulse time duration while concurrently flowing a second gas across the substrate; as well as The first gas and the second gas are purged by flowing the purge gas through the substrate for a purge time duration.

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

19. The method of claim 17, wherein the first gas is hydrogen, 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. The method of claim 17, wherein the tungsten fill layer has a stress between 0 MPa and 200 MPa.

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