Method for forming a multi-segment tungsten feature

Abstract

A method of forming a structure on a substrate includes forming a tungsten nucleation layer in at least one opening within a multi-step portion of the substrate. The method includes exposing the nucleation layer to a nitrogen trifluoride-containing gas to suppress growth of the nucleation layer in a narrow portion within the at least one opening. The method includes exposing the at least one opening to a tungsten-containing precursor gas to form a fill layer on the nucleation layer within the at least one opening. The method includes exposing at least one opening of the substrate to a nitrogen trifluoride-containing gas or a nitrogen-containing plasma to suppress growth of a portion of the fill layer along the at least one opening.

Description

Technical Field

[0001] Embodiments of the present specification relate to methods used in the manufacture of electronic devices, and more particularly, to methods used to form tungsten features in semiconductor devices.

Background Art

[0002] Tungsten (W) is widely used in the manufacture of integrated circuit (IC) devices 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 filling material to form source contacts, drain contacts, metal gate fills, 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 disposed above and below the dielectric material layer).

[0003] Due to its relatively low resistivity, tungsten is also commonly used to form bit lines and word lines used to address individual memory cells within a memory cell array of a three-dimensional NAND (3D NAND) device. The 3D NAND structure includes tiers of horizontal arrays that can be stacked by sequentially depositing layers. Channels can be formed through the stack of films and filled with tungsten. In some cases, the channel sidewall width may vary between tiers. During filling of the channel, the tungsten filling layer may deposit faster in the upper portion of the channel than in the lower portion due to the variation in channel sidewall width and the higher concentration of precursor gas used to deposit the tungsten filling layer. This can cause void formation within a portion of the channel, particularly in channels disposed in structures having two or more tiers, and particularly in high aspect ratio features.

[0004] Therefore, a process is needed to fill contact features having no or substantially no voids and seams and having a low resistivity for various film thicknesses within channels in a multi-level structure. SUMMARY OF THE INVENTION

[0005] In some embodiments, a method of forming a structure on a substrate is provided. The method includes exposing at least one opening formed in a multi-level portion of the substrate to a tungsten-containing gas at a precursor gas flow rate and exposing at least one opening of the substrate to a reducing agent containing boron at a reducing agent flow rate. The tungsten-containing gas and the reducing agent are periodically alternated to form a nucleation layer within at least one opening of the substrate. The method includes exposing at least one opening of the substrate to a nitrogen trifluoride-containing gas to suppress growth of the nucleation layer in a narrow portion within at least one opening. The method includes exposing at least one opening of the substrate to a tungsten-containing precursor gas to form a fill layer over the nucleation layer within at least one opening. The method includes exposing at least one opening of the substrate to a nitrogen trifluoride-containing gas or a nitrogen-containing plasma to suppress growth of a portion of the fill layer along at least one opening.

[0006] In some embodiments, a method of forming a structure on a substrate is provided. The method includes exposing at least one opening formed in the substrate to a tungsten-containing precursor gas at a precursor gas flow rate. The at least one opening includes a lower portion and an upper portion, and the upper portion includes a width smaller than the width of the lower portion. The method includes exposing at least one opening of the substrate to a reducing agent containing boron at a reducing agent flow rate. The tungsten-containing precursor gas and the reducing agent are periodically alternated to form a nucleation layer within at least one opening of the substrate. The method includes exposing the opening to the tungsten-containing precursor gas to form a part of a filling layer on the nucleation layer within the at least one opening. The method includes exposing at least one opening of the substrate to a nitrogen trifluoride-containing gas or a nitrogen-containing plasma, and exposing the opening to the tungsten-containing precursor gas to form a filling layer within the at least one opening. The method includes exposing the opening of the substrate to a nitrogen trifluoride-containing gas to suppress the growth of the filling layer within the at least one opening.

[0007] In some embodiments, a method of forming a structure on a substrate is provided. The method includes forming a tungsten nucleation layer within at least one opening formed in a multi-stage portion of the substrate. The method includes exposing the tungsten nucleation layer to a nitrogen-containing plasma to suppress the growth of the nucleation layer in a narrow portion within the at least one opening, and exposing at least one opening to a tungsten-containing precursor gas to form a filling layer on the nucleation layer within the at least one opening. The method includes exposing at least one opening of the substrate to a nitrogen trifluoride-containing gas to suppress the growth of a part of the filling layer along the at least one opening.

[0008] In some embodiments, a structure is provided on a substrate. The structure includes an opening in the substrate. The opening includes a plurality of steps stacked vertically from the bottom of the opening to the surface of the opening. A tungsten-containing layer is disposed within the opening, and the tungsten-containing layer includes a nucleation layer disposed along the sidewalls of the opening. The nucleation layer includes boron and tungsten. The structure includes a fill layer disposed over the nucleation layer within the opening.

[0009] To enable a more detailed understanding of the features enumerated above of the present disclosure, a more detailed description of the disclosure briefly summarized above can be made with reference to the embodiments, a part of which is shown in the accompanying drawings. However, it should be noted that the accompanying drawings show only exemplary embodiments and should not be considered as limiting its scope, and other equally effective embodiments can be recognized.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4A

Figure 4B

Modes for Carrying Out the Invention

[0011] For ease of understanding, where possible, the same reference numbers are used to designate the same elements common to the figures. It is intended that elements and features of one embodiment can be beneficially incorporated into other embodiments without further elaboration.

[0012] Embodiments herein generally relate to the manufacture of electronic devices, 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 showing undesirable voids 20 formed during a conventional tungsten deposition process. Here, the substrate 101 includes a patterned surface 11 disposed within a plurality of tiers such as a first tier 12A and a second tier 12B. In some embodiments, the first tier 12A is a first dielectric layer (e.g., silicon oxide (SiO x )) and the second tier consists of a second dielectric layer (e.g., silicon nitride (SiN)). In some embodiments, the substrate 101 includes a plurality of alternating first and second tiers. The patterned surface 11 includes at least one opening having a high aspect ratio opening formed therein (shown filled with a portion of a tungsten layer 15), a barrier material layer 14 deposited on the tiers 12A, 12B to line the opening, and a tungsten layer 15 deposited on the barrier material 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, and tungsten is conformally deposited (grown) on the patterned surface 11 to fill the opening. The tungsten layer 15 forms a tungsten feature 15A within the first tier 12A, a tungsten feature 15B within the second tier 12B, and an overburden of material (tungsten overburden layer 15C) on the field of the patterned surface 11.

[0014] In FIG. 1, the opening is wider at the surface of the substrate 101 and has a non-uniform profile that tapers as the opening extends inward from the surface to the second layer 12B. At the interface 25 between the first step and the second step, the width of the second step is narrower than the width of the first step disposed internally from the second step. As shown, the interface portion of the conformal tungsten layer 15 grows together and blocks or "pinches off" the entrance to the opening disposed in the first step 12A before the opening is completely filled, thereby causing an undesirable void 20 within the tungsten feature 15A, i.e., a lack of tungsten material. In addition to the void, using a conventional tungsten deposition process may result in an undesirable seam (e.g., 24) in the tungsten feature as shown within the second step 12B. The void 20 and the seam 24 are susceptible to corrosion from the chemical active components of the tungsten CMP polishing solution, such that when the seam 24 and / or the void 20 are exposed during the CMP process, an undesirable loss of tungsten material from the features 15A, 15B may be caused.

[0015] Accordingly, embodiments herein provide a processing system configured to perform a combination of the individual aspects of this method without transferring the substrate between processing chambers, thereby improving the overall substrate processing throughput and capacity of the tungsten gap fill processing scheme described herein. The methods and systems provided herein are particularly useful for tungsten gap fill 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. The aspect ratio refers to the ratio of the total height to the average width or diameter of the feature.

[0016] Generally, the gap fill process method includes forming a differential tungsten deposition suppression profile in an opening of a feature formed on a surface of a substrate, filling the opening with a tungsten material according to the suppression profile, and depositing a tungsten overburden on a field surface of the substrate. Forming the tungsten deposition suppression profile generally includes forming a tungsten nucleation layer and treating the tungsten nucleation layer using a nitrogen trifluoride-containing gas, an activated nitrogen nuclide, e.g., a processing radical, or a combination thereof. Nitrogen from the nitrogen trifluoride, the activated nitrogen nuclide, or a combination thereof is incorporated into a portion of the nucleation layer, e.g., by adsorption of the nitrogen nuclide and / or by reaction with metallic tungsten of the nucleation layer, to form tungsten nitride (WN). The adsorbed nitrogen and / or nitrided surface of the tungsten nucleation layer desirably delays (suppresses) tungsten nucleation, thereby delaying (suppressing) subsequent tungsten deposition thereon.

[0017] In some embodiments, the processing radicals are formed remotely from the substrate processing chamber by using a remote plasma source fluidly coupled to the substrate processing chamber. The desired suppression effect on the field of the patterned surface and the desired suppression profile of the openings formed in the patterned surface are achieved by controlling processing conditions in the processing chamber, e.g., temperature and pressure, and by controlling the concentration, flux, and energy of the processing radicals at the substrate surface. Generally, the processing radicals are N 2 , NH 3 , NH 4、or a combination thereof, such as a non-halogen nitrogen-containing gas. In some embodiments, the nitrogen trifluoride-containing gas is supplied to the process chamber without transferring the substrate. Without being bound by theory, nitrogen trifluoride is thought to suppress growth within the opening at the interface of the layer steps in order to sufficiently fill the bottom of the opening and prevent pinch-off at the interface. The processing radicals can enhance the suppression near the surface of the opening, while nitrogen trifluoride has been found to enable suppression at deeper locations within the opening. Therefore, in some embodiments, a process is performed that combines exposing a portion of the nucleation layer and / or a portion of the tungsten fill layer to nitrogen trifluoride (NF 3 ) and further to nitrogen radicals during their respective process steps to prevent the formation of voids during the fill process. This process can include adjusting the relative amounts of exposure to nitrogen trifluoride (NF 3 ) and further to nitrogen radicals during the deposition process. By adjusting the relative amounts of exposure to nitrogen trifluoride (NF 3 ) and further to nitrogen radicals during the periodic deposition process used to form either the nucleation layer and / or the tungsten fill layer, a desired deposition profile can be created in the feature during the deposition process. The exposure to nitrogen trifluoride (NF 3 ) and further to nitrogen radicals during the periodic deposition process may be completed simultaneously or sequentially. In one example, the deposited layer is first sequentially exposed to a first nitrogen trifluoride (NF 3 ), then to nitrogen radicals, and then a subsequent layer of the nucleation layer and / or the fill layer is deposited thereon. In another example, the deposited layer is first sequentially exposed to a first nitrogen radical, then to nitrogen trifluoride (NF 3 ), and then a subsequent layer of the nucleation layer and / or the fill layer is deposited thereon.

[0018] The tungsten nucleation and deposition process of the gap filling treatment method generally includes flowing a tungsten-containing precursor and a reducing agent into a processing chamber and exposing the substrate surface thereto. The tungsten-containing precursor and the reducing agent react on the surface of the substrate in one of a chemical vapor deposition (CVD) process, a pulsed CVD process, an atomic layer deposition (ALD) process, or a combination thereof to deposit a tungsten material thereon.

[0019] The processing system described herein is configured to periodically perform a chamber cleaning process, and undesirable tungsten residues are removed from the inner surface of the processing chamber using a cleaning chemistry such as a cleaning chemistry including activated halogen nuclides, such as fluorine or chlorine (cleaning) radicals, formed remotely from the processing chamber.

[0020] The chamber cleaning process generally includes flowing halogen cleaning radicals into the processing chamber, reacting the cleaning radicals with tungsten residues to form volatile tungsten nuclides, and exhausting the volatile tungsten nuclides from the processing chamber through an exhaust portion. The chamber cleaning process is generally performed during substrate processing, i.e., after the processed substrate is removed from the processing chamber and before the subsequent processed substrate to be processed is received in the processing chamber.

[0021] Figures 2A - 2B schematically show a processing system 200 that can be used to perform the bottom-up tungsten gap filling substrate processing method described herein. Here, the processing system is configured to provide different processing conditions desirable for each of a nucleation process, a suppression processing process, a selective gap filling process, and an overburden deposition process within a single processing chamber 202, i.e., without transferring the substrate between multiple processing chambers.

[0022] As shown in FIG. 2A, the processing system 200 includes a processing chamber 202, a gas supply 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 section 217, such as one or more vacuum pumps, used to maintain the processing volume 215 at near-atmospheric pressure conditions and to exhaust processing gases and processing by-products therefrom.

[0023] 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. Here, 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 on the substrate support 222, 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.

[0024] The gas supply system 204 is fluidly coupled to the processing chamber 202 via a gas inlet 223 (FIG. 2B) disposed through the lid plate 216. The processing gas or cleaning gas supplied by using the gas supply system 204 flows into the gas distribution volume 219 through the gas inlet 223 and is distributed to the processing region 221 through a plurality of openings 232 (FIG. 2B) of 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, the gas flowing into the gas distribution volume 219 is first diffused by the blocker plate 225 and the showerhead 218 is added to supply a more uniform or desired distribution of gas flow into the processing region 221.

[0025] The processing gas and processing by-products are discharged radially outward from the processing region 221 through an annular channel 226 surrounding the processing region 221. The annular channel 226 may be formed in a first annular liner 227 disposed radially inward of one or more sidewalls 212 (as shown), or may be formed in one or more sidewalls 212. In some embodiments, the processing chamber 202 includes one or more second liners 228, which are used to protect the inner surfaces of one or more sidewalls 212 or the chamber base 214 from corrosive gases and / or unwanted material deposition.

[0026] In some embodiments, a purge gas source 237 fluidly connected 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) under the substrate support 222 during substrate processing. Generally, the purge gas flows through the chamber base 214, upward therefrom, around the edge of the substrate support 222, and is discharged from the processing volume 215 through the annular channel 226. The purge gas reduces unwanted material deposition on the surface directly below the substrate support 222 by reducing and / or preventing the flow of material precursor gas thereto.

[0027] The substrate support assembly 220 includes a movable support shaft 262 that extends sealingly through the chamber base 214, such as one surrounded by a bellows 265 in a region below the chamber base 214, and a substrate support 222 disposed on the movable support shaft 262. To facilitate the 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 engaged 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 at a 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 allow access to the (inactive) surface on the back side 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 below the substrate receiving surface of the substrate support 222 to allow the substrate 230 to be placed thereon.

[0028] The substrate 230 is transferred to and from the substrate support 222 through a door 271, such as a slit valve, disposed on one of the one or more sidewalls 212. Here, one or more openings within the region surrounding the door 271, e.g., the opening of the door housing, are fluidly coupled to a purge gas source 237, such as an Ar gas source. The purge gas is used to prevent the process gas and the cleaning gas from contacting the seal surrounding the door and / or from deteriorating the seal surrounding the door, thereby extending the service life of the door.

[0029] The substrate support 222 is configured for a vacuum chuck by applying a vacuum at the interface between the substrate 230 and the substrate receiving surface to fix the substrate 230 to the substrate support 222. 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 directly for plasma processing, the substrate support 222 may be configured for an electrostatic chuck. In some embodiments, the substrate support 222 includes one or more electrodes (not shown) coupled to a bias voltage power source (not shown), such as a continuous wave (CW) RF power source or a pulsed RF power source that supplies a bias voltage thereto.

[0030] As shown in the figure, the substrate support assembly 220 features a dual-zone temperature control system for performing independent temperature control in 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 the central region of the substrate support 222, and the second heater 264 is disposed radially outward from the central region so as to surround the first heater 263. In other embodiments, the substrate support 222 may have a single heater or three or more heaters.

[0031] In some embodiments, the substrate support assembly 220 further includes an annular shadow ring 235 that is used to prevent unwanted material deposition on the circumferential bevel 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 in the 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 raised or in the processing position, the 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 when the substrate support assembly 220 is in the raised substrate processing position, the portion of the shadow ring 235 facing radially inward is disposed over the bevel edge of the substrate 230.

[0032] In some embodiments, the substrate support assembly 220 further includes an annular purge ring 236 disposed on the substrate support 222 so as 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 that are in fluid connection with a purge gas source 237. During substrate processing, the 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, preventing process gases from entering the annular region and causing unwanted material deposition on the bevel edge of the substrate 230.

[0033] In some embodiments, the processing chamber 202 is configured directly for plasma processing. In those embodiments, the showerhead 218 is electrically coupled to a first power source 231, such as an RF power source, which supplies power for igniting and maintaining a plasma of the process gas flowing into the processing region 221 via capacitive coupling with the process gas. In some embodiments, the processing chamber 202 includes an inductive plasma generator (not shown), and the plasma is formed by inductively coupling RF power to the process gas.

[0034] The processing system 200 is advantageously configured to perform each of a void-free and seam-free tungsten gap fill process scheme tungsten nucleation, suppression treatment, and bulk tungsten deposition process without removing the substrate 230 from the processing chamber 202. The gases used to perform the individual processes of the gap fill process scheme and to clean residues from the inner surface of the processing chamber are supplied to the processing chamber 202 using a gas supply system 204 fluidly coupled thereto.

[0035] Generally, the gas supply system 204 includes one or more remote plasma sources, here the first and second radical generators 206A - 206B, a deposition gas source 240, and a conduit system 294 (e.g., a plurality of conduits 294A - 294F) fluidly coupling the radical generators 206A - 206B and the deposition gas source 240 to the lid assembly 210. The gas supply system 204 further includes a plurality of isolation valves, here the first and second valves 290A - 290B, respectively disposed 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.

[0036] Each of the radical generators 206A - 206B features a chamber body 280 that defines respective first and second plasma chamber volume portions 281A - 281B (FIG. 2B). Each of the radical generators 206A - 206B is coupled to respective power supplies 293A - 293B. The power supplies 293A - 293B are used to ignite and sustain a plasma 282A - 282B of a gas supplied from a corresponding first gas source 287A or second gas source 287B that is fluidly coupled to the plasma chamber volume portions 281A - 281B. In some embodiments, the first radical generator 206A generates radicals used in a differential suppression process. For example, the first radical generator 206A can be used to ignite and sustain a process plasma 282A from a non - halogen - containing mixed gas supplied from the first gas source 287A to the first plasma chamber volume portion 281A. 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 mixed gas supplied from the second gas source 287B to the second plasma chamber volume portion 281B.

[0037] Generally, nitrogen treatment radicals have a relatively short lifetime (compared to halogen cleaning radicals) and can exhibit relatively high sensitivity to recombination from collisions with surfaces within the gas supply system 204 and / or other species of the process plasma emissions. Thus, in the embodiments of this specification, 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 portion 281A to the processing region 221.

[0038] In some embodiments, the first radical generator 206A is also fluidly coupled to a second gas source 287B, which 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 supply 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.

[0039] Suitable remote plasma sources that can be used in one or both of the radical generators 206A-206B include radio frequency (RF) or very high radio frequency (VHRF) capacitively coupled plasma (CCP) sources, inductively coupled plasma (ICP) sources, microwave induced (MW) plasma sources, electron cyclotron resonance (ECR) chambers, or high density plasma (HDP) chambers.

[0040] As shown, the first radical generator 206A is fluidly coupled to the processing chamber 202 by 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 supply system 204. Generally, the first valve 290A is closed during the chamber cleaning process to prevent an activation cleaning gas, e.g., a halogen radical, from flowing into the first plasma chamber volume 281A and damaging its surface.

[0041] 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 supply system 204 by using a second valve 290B disposed between the third conduit 294C and the fourth conduit 294D.

[0042] Deposition gases, such as tungsten-containing precursors and reducing agents, are supplied from a 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 at a location adjacent to the gas inlet 223, such that the first and second valves 290A-290B can each be used to separate the first and second radical generators 206A-206B from the deposition gases introduced into the processing chamber 202. In some embodiments, the gas supply system 204 further includes a sixth conduit 294F coupled to the fourth conduit 294D at a location adjacent to the second valve 290B. The sixth conduit 294F is fluidly coupled to a purge gas source 237, such as an argon (Ar) gas source, which can be used to perform unwanted residue cleaning, suppression, and / or periodically purge a portion of the gas supply system 204 related to the deposition gases.

[0043] The operation of the processing system 200 is facilitated by a system controller 208. The system controller 208 includes a programmable central processing unit, herein a CPU 295, operable by a memory 296 (e.g., non-volatile memory) and support circuitry 297. The CPU 295 is one of any form of general-purpose computer processor used in industrial environments, such as a programmable logic controller (PLC), that is programmable to control various chamber components and sub-processors. The memory 296 coupled to the CPU 295 facilitates the operation of the processing chamber. The support circuitry 297 conventionally includes a cache, clock circuit, input / output subsystem, power supply, etc., and combinations thereof, coupled to the CPU 295 and to various components of the processing system 200 to facilitate control of substrate processing operations.

[0044] The instructions in the memory 296 are in the form of a program product such as a program for implementing the method of the present disclosure. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use in a computer system. The program of the program product defines the functions of the embodiments (including the methods described herein). Therefore, a computer-readable storage medium is an embodiment of the present disclosure if it holds computer-readable instructions that direct the functions of the methods described herein.

[0045] The processing system 200 described above is used to perform each of nucleation, suppression, and gap-fill deposition, thereby providing a solution for single-chamber, seam-free tungsten gap-fill.

[0046] FIG. 3 is a diagram showing a simplified process flow used to process a substrate according to some embodiments that can be executed using the processing system 200. FIGS. 4A-4B are schematic cross-sectional views of a portion of a substrate 400 showing aspects at different stages of a void-free and seam-free tungsten gap-fill process scheme.

[0047] The substrate 400 features a patterned surface 401 that includes a first tier 412A and a second tier 412B having a plurality of openings 405 (one is 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, 414) of about 100 nm to about 400 nm, such as from 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, such as from about 3 μm to about 6 μm. In some embodiments, the plurality of openings include at least one opening where the width 410 of the narrowest portion of the opening is about 50 nm to about 200 nm, such as from about 75 nm to about 125 nm. In some embodiments, the individual openings 405 can have an aspect ratio (depth to width ratio) of about 10:1 or more, such as about 25:1 or more, such as from about 30:1 to about 100:1, such as from 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 opening disposed within the first tier 412A is referred to as the first tier opening 402A, and the opening disposed within the second tier 412B is referred to as the second tier opening 402B. The first and second tier openings together form a single continuous opening 405. The uppermost portion of the first tier opening 402A interfaces with the lowermost portion of the second tier opening 402B at the interface 406.

[0048] The width 407 of the uppermost part of the first-stage opening is larger than the width 410 of the lowermost part of the second-stage opening 402B at the interface. In some embodiments, the width 407 is about 5% to about 100% larger than the width 410, for example, about 10% to about 50% larger. For example, the width 410 can be about 50 nm to about 300 nm, for example, about 75 nm to about 125 nm, and the width 407 can be about 70 nm to about 400 nm, for example, about 150 nm to about 250 nm. In some embodiments, for each stage, the widest part of the stage, such as the uppermost part 414 of the second stage 402B, is about 5% to about 100% larger than the narrowest part of the stage, such as the lowermost part 410 of the second stage 402B, for example, about 10% to about 50% larger. In some embodiments, the height of the first-stage opening 402A is substantially the same as, smaller than, or larger than the height of the second-stage opening 402B. Without being bound by theory, a sudden difference in the opening width at the interface is thought to possibly cause a pinching effect. The methods described herein enable a growth behavior that fills the opening without forming voids.

[0049] As shown in FIG. 4B, the patterned surface 401 includes a barrier or adhesion layer 403, such as a titanium nitride (TiN) layer, deposited on the first-stage layer 412A and the second-stage layer 412B to conformally line the opening 405 and facilitate the subsequent deposition of the tungsten nucleation layer 404. In some embodiments, the adhesion layer 403 is deposited to a thickness between about 20 angstroms (Å) and about 150 Å, for example, a thickness of about 30 Å to about 100 Å.

[0050] Nucleation layer deposition Each of process flows 300A, 300B, 300C, 300D, 300E, and 300F includes forming a nucleation layer 404 on a substrate 400 shown as activity 302. The nucleation layer can be formed using any process that can form a tungsten nucleation layer. In some embodiments, before forming the nucleation layer 404, the substrate is exposed to a boron-containing gas such as B for a soak time of about 5 seconds or more, for example about 10 seconds or more, for example between about 20 seconds and 30 seconds. 2 H 2 In some embodiments, the nucleation layer 404 is deposited on an adhesion layer 403.

[0051] The nucleation layer can be formed using atomic layer deposition (ALD) of a tungsten-containing nucleation layer or a physical vapor deposition (PVD) process. Forming the nucleation layer includes exposing the substrate to a tungsten-containing precursor gas at a first precursor gas flow rate. In some embodiments, forming the nucleation layer includes exposing the substrate to a reducing agent. The reducing agent contains boron and is introduced into the process chamber at a reducing agent flow rate. In some embodiments, the tungsten-containing precursor gas and the reducing agent are periodically alternated to form the nucleation layer on the substrate within at least one opening of the substrate at a reducing agent flow rate. In some embodiments, the reducing agent and the tungsten-containing precursor gas are periodically alternated, starting with either the reducing agent or the tungsten-containing precursor gas and ending with the same first gas or a gas different from the first gas. In some embodiments, the reducing agent and the tungsten-containing precursor gas are periodically alternated, starting with the tungsten-containing precursor gas and ending with the reducing agent. A portion of an exemplary substrate 400 on which the nucleation layer 404 is formed is schematically shown in FIG. 4B.

[0052] In some embodiments, the nucleation layer 404 is deposited using an atomic layer deposition (ALD) process. The ALD process includes repeating cycles of alternately 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 during the alternate exposures. In some embodiments, the process region 221 is continuously purged. Examples of suitable tungsten-containing precursors include tungsten halides such as tungsten hexafluoride (WF 6 ), tungsten hexachloride (WCl 6 ), or combinations thereof. In some embodiments, the tungsten-containing precursor includes WF 6 , and the reducing agent includes a boron-containing agent such as B 2 H 6 . In some embodiments, the tungsten-containing precursor includes an organometallic precursor and / or a fluorine-free precursor, such as MDNOW (methylcyclopentadienyl-dicarbonylnitrosyl-tungsten), EDNOW (ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten), tungsten hexacarbonyl (W(CO) 6 ), or combinations thereof.

[0053] During the nucleation process, the processing volume 215 is 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 to the processing region 221 at a 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 to the processing region 221 at a flow rate between about 200 sccm and about 1000 sccm, such as between about 300 sccm and about 750 sccm.

[0054] Note that the flow rates of the various deposition and processing processes described herein are for a processing system 200 configured to process a 300 mm diameter substrate. Appropriate scaling may be used for processing systems configured to process substrates of different sizes.

[0055] The tungsten-containing precursor and the reducing agent are each flowed through the processing region 221 for a period between about 0.1 second and about 10 seconds, such as between about 0.5 second and about 5 seconds, for example. The processing region 221 can be purged during alternating exposures by flowing a purge gas, such as argon (Ar) or hydrogen gas, through the processing region 221 for a period between about 0.1 second and about 10 seconds, such as between about 0.5 second and about 5 seconds, for example. The purge gas can be supplied from the deposition gas source 240 or the purge gas source 237. Generally, the repetition of the cycle of the nucleation process continues until the nucleation layer 404 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, for example. The nucleation layer 404 is disposed along the sidewalls of the opening 405, such as on top of the 403 of the barrier or adhesion layer, for example.

[0056] In some embodiments, immediately following each nucleation activity 302, a tungsten gap-fill material 408 (FIG. 4B) is optionally deposited at least partially in the plurality of openings 405 in activity 306. The need for the optional activity 306 immediately following the nucleation activity 302 is determined based on the profile of the opening, such as the relative height of the steps. As an example, if the lower step is much longer than the upper step, an interface between the steps, herein referred to as a "constriction point", may be located adjacent to the surface of the opening, and thus the opening may be at least partially filled with the tungsten gap-fill material 408 before introducing the growth inhibitor. In some embodiments, the optional step 306 is performed if the minimum width of the opening is within about 50% or less, such as within 30% or less, such as within 20% or less, of the maximum width of the opening. Other profiles can determine the need for the optional activity 306, such as, for example, that low aspect ratio features can benefit from the optional step, features with wide openings on the surface, etc. Without being bound by theory, the optional activity 306 is thought to enable improving throughput prior to the inhibition step.

[0057] In one embodiment, the tungsten gap-fill material 408 is formed using a chemical vapor deposition (CVD) process that includes flowing a tungsten-containing precursor gas and a reducing agent simultaneously (in parallel flow) into the processing region 221 and exposing the substrate 400 thereto. The tungsten-containing precursor and reducing agent used in the tungsten gap-fill CVD process can include any combination of the tungsten-containing precursor and reducing agent described in connection with activity 302. In some embodiments, the tungsten-containing precursor includes WF 6 and the reducing agent includes hydrogen gas. In some embodiments, the tungsten gap-fill material 408 partially fills the plurality of openings 405.

[0058] The tungsten-containing precursor is flowed into the processing region 221 at a rate between about 10 sccm and about 1200 sccm, or greater than about 50 sccm, or less than about 1000 Torr, or between about 100 sccm and about 900 sccm. The reducing agent is flowed into the processing region 221 at a rate greater than about 500 sccm, such as greater than about 750 sccm, greater than about 1000 sccm, etc., or between about 500 sccm and about 10000 sccm, such as between about 1000 sccm and about 9000 sccm, or between about 1000 sccm and about 8000 sccm, etc.

[0059] In some embodiments, the tungsten gap-fill CVD process conditions are selected to provide tungsten features having a relatively low residual film stress as compared to conventional tungsten CVD processes. For example, in some embodiments, the tungsten gap-fill CVD process includes heating the substrate to a temperature of about 250 °C or greater, such as about 300 °C or greater, etc., or between about 250 °C and about 600 °C, or between about 300 °C and about 500 °C. During the CVD process, the processing volume 215 is generally maintained at a pressure of less than about 500 Torr, less than about 600 Torr, less than about 500 Torr, less than about 400 Torr, or between about 1 Torr and about 500 Torr, such as between about 1 Torr and about 450 Torr, or between about 1 Torr and about 400 Torr, etc., or for example, between about 1 Torr and about 300 Torr.

[0060] In another embodiment, the tungsten gap-fill material 408 is deposited in step 306 using an atomic layer deposition (ALD) process. The tungsten gap-fill ALD process includes repeating a cycle of alternately exposing the substrate 400 to a tungsten-containing precursor gas and a reducing agent and purging the processing region 221 between the alternate exposures.

[0061] The tungsten-containing precursor and the reducing agent are each flowed into the processing region 221 for a period between about 0.1 second and about 10 seconds, such as between about 0.5 second and about 5 seconds. The processing region 221 is generally purged by flowing an inert purge gas, such as argon (Ar) or hydrogen, into the processing region 221 for a period between about 0.1 second and about 10 seconds, such as between about 0.5 second and about 5 seconds, during the alternating exposures. The purge gas can be supplied from the deposition gas source 240 or the purge gas source 237.

[0062] In other embodiments, the tungsten gap fill material 408 is deposited using a pulsed CVD process that includes repeating cycles of alternately exposing the substrate 400 to the tungsten-containing precursor gas and the reducing agent without purging the processing region 221. The processing conditions of the tungsten gap fill pulsed CVD process can be the same, substantially the same, or within the same range as those described above for the tungsten gap fill ALD process.

[0063] In some embodiments, the nucleation layer 404 and the fill layer 408 are a single entity and there is no interface therebetween. The tungsten gap fill material 408 and the nucleation layer 404 together form a tungsten-containing layer. The thickness of the tungsten-containing layer is measured from the interface between the adhesive layer and the nucleation layer to the center of the fill layer 408.

[0064] After forming the nucleation layer 404 and the optional tungsten gap fill material 408, a differential etch profile is formed by exposing the sidewalls of the opening to an activation nuclide of a processing gas, such as a nitrogen trifluoride-containing gas, a nitrogen-containing gas, or a combination thereof. Some combinations of processes are described with reference to processes 300A, 300B, 300C, 300D, 300E, and 300F. Other combinations are also contemplated.

[0065] Process 300A - Nitrogen Trifluoride Treatment As shown in FIG. 3, after forming the nucleation layer in activity 304 (e.g., as described in activity 302), to suppress tungsten deposition on the field surface of the substrate 400 at the interface (e.g., the constriction point) between adjacent steps, the process 300A includes treating the outer surface of the nucleation layer 404 or the tungsten gap-fill material 408 (e.g., after optional activity 306). Activity 304 forms a differential suppression profile in a plurality of openings 405 by using a differential suppression process. Forming the differential suppression profile includes exposing the sidewalls of the openings to a nitrogen trifluoride-containing gas.

[0066] Exposing the openings to a nitrogen trifluoride-containing gas includes flowing the nitrogen trifluoride-containing gas for a period of about 1 second to about 90 seconds, such as about 1 second to about 30 seconds, such as about 3 seconds to about 20 seconds, such as about 7 seconds to about 15 seconds. In some embodiments, the temperature is maintained at about 200°C to about 600°C, such as about 300°C to about 500°C, such as about 400°C to about 450°C. In some embodiments, the nitrogen trifluoride-containing gas is flowed at a rate of about 0.5 sccm to about 1000 sccm, such as about 100 sccm to about 500 sccm, such as about 300 sccm to about 500 sccm, or about 600 sccm to about 800 sccm. In some embodiments, the thickness of the tungsten layer in the opening before the nitrogen trifluoride-containing gas is introduced into the opening is less than or equal to the thickness of the tungsten layer in the opening after the nitrogen trifluoride-containing gas is introduced. In some embodiments, the nitrogen trifluoride gas is combined with an inert carrier gas such as Ar, He, or a combination thereof to form a nitrogen trifluoride mixture. In some embodiments, the volumetric gas flow ratio of the nitrogen trifluoride gas to the inert carrier gas is about 1:10000 to about 1:10, such as about 1:5 to about 1:2, or about 1:4 to about 1:1, such as about 1:3 to about 1:2.

[0067] After the process described in Activity 304, tungsten gap fill material 408 is formed in the opening in Activity 306. In some embodiments, as shown in Process 300A, Activity 304 and Activity 306 (e.g., together as C1) can be repeated one or more times, such as one or two times, until the opening is filled.

[0068] Process 300B - Nitrogen Trifluoride Treatment + Additional Nucleation Similar to Process 300A, Process 300B includes Activity 302 (optional Activity 306 immediately following Activity 302), Activity 304, and Activity 306 (e.g., together as C2). After Activity 306, one or more cycles of Activities 302, 304, and 306 (e.g., C2) can be repeated.

[0069] Process 300C - Nitrogen Trifluoride Treatment + Activated Nuclei Treatment Similar to Process 300A, Process 300B includes Activity 302 (optional Activity 306 immediately following Activity 302), Activity 304, and Activity 306. In Activity 305, after Activity 306, the opening is treated with an activated nuclei of a processing gas, e.g., processing radicals from a remote plasma source. Suitable processing gases that can be used in the suppression process include N 2 , H 2 , NH 3 , NH 4 , O 2 , CH 4 , or combinations thereof. In some embodiments, the processing gas is N 2 such as nitrogen, H 2 , NH 3 , NH 4including, for example, nitrogen radicals such as atomic nitrogen, or combinations thereof. In some embodiments, the process gas is combined with an inert carrier gas such as Ar, He, or combinations thereof to form a process mixture gas.

[0070] In some embodiments, the nitrogen trifluoride of activity 304 is alternated with the processing radicals of activity 305, starting with nitrogen trifluoride or starting with the processing radicals. During each process (either nitrogen trifluoride or nitrogen), tungsten spacer material 408 is at least partially deposited into one or more of the openings (e.g., activity 306). In process 300C, after the nitrogen trifluoride treatment of activity 304 and activity 306 (collectively C1), the activated nuclide treatment of activity 305 and activity 306 (collectively C3) follows. Depending on the required suppression profile, after C3, another iteration of C1, C2, C3, or combinations thereof may be performed. In some embodiments, one or more C1 cycles may be completed, followed by one or more C3 cycles, and then both may be repeated (e.g., C1 + C3 may be repeated).

[0071] The order, exposure time, and ratio of the gas flow between nitrogen trifluoride and the processing radicals are determined based on the profile of the opening. For example, if the constriction point is deep within the opening, a longer exposure of nitrogen trifluoride is used compared to the processing radicals. For constriction points with a small width and for features with a very high aspect ratio, a longer exposure of nitrogen trifluoride is used compared to the process of treating with radicals. The nitrogen trifluoride period relative to the treatment period with radicals can be from about 20:1 to about 1:20, such as from about 5:1 to about 1:1, or from about 1:2 to about 1:6, etc.

[0072] Although not bound by theory, it is believed that the activated nitrogen nuclides formed during processing by radicals are incorporated into a portion of the nucleation layer 404 by adsorption of the activated nitrogen nuclides and / or by reaction with the metal tungsten of the nucleation layer 404 to form a tungsten nitride (WN) surface. The adsorbed nitrogen and / or nitrided surface of the tungsten nucleation layer 404 desirably retards (suppresses) further tungsten nucleation and thus subsequent tungsten deposition thereon.

[0073] In some embodiments, exposing the nucleation layer 404 to processing radicals includes forming a processing plasma 282A of a substantially halogen-free processing gas mixture using a first radical generator 206A and flowing the effluent of the processing plasma 282A into the processing region 221. In some embodiments, the flow rate of the processing gas mixture to the first radical generator 206A, and thus the flow rate of the processing plasma effluent such as nitrogen gas into the processing region 221, is from about 1 sccm and about 3000 sccm, such as from about 1 sccm and about 2500 sccm, such as from about 1 sccm and about 2000 sccm, such as from about 1 sccm and about 1000 sccm, such as from about 1 sccm and about 500 sccm, such as from about 1 sccm and about 250 sccm, such as from about 1 sccm and about 100 sccm, such as from about 1 sccm and about 75 sccm, such as from about 1 sccm and about 50 sccm.

[0074] In some embodiments, the suppression process includes exposing the substrate 400 to processing 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.

[0075] In some embodiments, the concentration of the substantially halogen-free processing gas in the processing mixed gas is from about 0.1% by volume to about 50% by volume, such as from about 0.2% by volume to about 40% by volume, from about 0.2% by volume to about 30% by volume, about 0.2% by volume and about 20% by volume, etc., or for example, such as about 0.2% by volume and about 10% by volume, such as about 0.2% by volume and about 5% by volume, etc.

[0076] In other embodiments, the processing radicals can be formed using a remote plasma (not shown) that is ignited and maintained, for example, between the showerhead 218 and the lid plate 216, which is a part of the processing volume 215 separated from the processing region 221 by the showerhead 218. In those embodiments, the activated processing gas can be passed through an ion filter to remove substantially all ions from the activated processing gas before the processing radicals reach the surface of the processing region 221 and the substrate 400. In some embodiments, the showerhead 218 may be used as an ion filter. In other embodiments, the plasma used to form the processing radicals is an in-situ plasma formed in the processing region 221 between the showerhead 218 and the substrate 400. In some embodiments, when using an in-situ processing plasma, a bias can be applied to the substrate 400 to control the directionality and / or accelerate ions, such as charged processing radicals, formed from the processing gas towards the substrate surface.

[0077] In some embodiments, the suppression processing process includes maintaining the processing volume 215 at a pressure of less than about 100 Torr while flowing the activated processing gas into the processing volume 215. For example, during the suppression processing process, the processing volume 215 can be maintained at a pressure of about 20 Torr or less, such as about 0.5 Torr and about 10 Torr, such as about 1 Torr and about 5 Torr.

[0078] Process 300D - Nitrogen trifluoride treatment + Additional nucleation + Activated nuclide treatment Process 300D includes activity 302 (optional activity 306 immediately following activity 302), activity 304, and activity 306 (collectively C2). After activity 306, an additional nucleation activity 302 is performed, followed by the activation nuclide treatment of activity 305, and then activity 306 follows (collectively C4). Thereafter, additional iterations of C1, C2, C3, C4, and combinations thereof are also contemplated. In some embodiments, one or more C2 cycles may be completed, followed by one or more C4 cycles, and then both may be repeated (e.g., C2 + C4 may be repeated).

[0079] Process 300E - Activation Nuclide Treatment + Nitrogen Trifluoride Treatment Process 300E includes activity 302 (optional activity 306 immediately following activity 302), activity 305, and activity 306 (collectively C4). After activity 306, the nitrogen trifluoride treatment of activity 304 is performed, followed by the CVD tungsten gap fill of activity 306 (collectively C1). Thereafter, additional iterations of C1, C2, C3, C4, and combinations thereof are also contemplated. In some embodiments, one or more C4 cycles may be completed, followed by one or more C1 cycles, and then both may be repeated (e.g., C4 + C1 may be repeated).

[0080] Process 300F - Activation Nuclide Treatment + Nitrogen Trifluoride Treatment Process 300F includes activity 302 (optional activity 306 immediately following activity 302), activity 305, and activity 306 (collectively C4). After activity 306, an additional nucleation activity 302 is performed, followed by a nitrogen trifluoride treatment activity 304, followed by CVD tungsten gap filling of activity 306 (collectively C2). Thereafter, additional iterations of C1, C2, C3, C4, and combinations thereof are also contemplated. In some embodiments, one or more C4 cycles may be completed, followed by one or more C2 cycles, and then both may be repeated (e.g., C4 + C2 may be repeated).

[0081] Although not depicted in the figures, in some embodiments, activities 304 and 305 are immediately subsequent to each other without an intervening activity such as activity 306.

[0082] In a typical semiconductor manufacturing process, a chemical mechanical polishing (CMP) process can be used to remove the tungsten overburden (and the barrier layer disposed thereunder) from the field surface of the substrate after depositing a tungsten gap fill material 408 into the opening 405.

[0083] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, and the scope of the present disclosure is determined by the following claims.

Claims

1. A method of forming a structure on a substrate, comprising: exposing at least one opening formed in a multi-step portion of the substrate to a tungsten-containing gas at a precursor gas flow rate; exposing the at least one opening of the substrate to a reducing agent containing boron at a reducing agent flow rate, wherein the tungsten-containing gas and the reducing agent are periodically and alternately interchanged to form a nucleation layer in the at least one opening of the substrate; exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas to suppress growth of the nucleation layer in a narrow portion within the at least one opening; exposing the at least one opening to the tungsten-containing precursor gas to form a filling layer on the nucleation layer within the at least one opening; exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas or nitrogen-containing plasma to suppress growth of a part of the filling layer along the at least one opening. A method comprising the above steps.

2. The method according to claim 1, wherein exposing the at least one opening to the tungsten-containing precursor gas comprises a chemical vapor deposition process.

3. The method according to claim 1, wherein exposing the at least one opening to the nitrogen trifluoride-containing gas and the nitrogen-containing plasma comprises alternately interchanging the nitrogen trifluoride-containing gas and the nitrogen-containing plasma.

4. The method according to claim 3, wherein exposing the at least one opening to the nitrogen trifluoride-containing gas and the nitrogen-containing plasma comprises exposing the substrate to the nitrogen-containing plasma before the nitrogen trifluoride-containing gas.

5. The method according to claim 3, wherein exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas and the nitrogen-containing plasma comprises exposing the substrate to the nitrogen trifluoride-containing gas before the nitrogen-containing plasma.

6. A first time interval for exposing the at least one opening of the substrate to nitrogen trifluoride and a second time interval for exposing the substrate to the nitrogen-containing plasma are at an interface location between a first stage and a second stage of the multi-step portion along the length of the at least one opening. The interface location between the first stage and the second stage of the multi-step portion along the length of the at least one opening. the width of the at least one opening at the interface of two adjacent stages of the multi-stage portion, the width of the at least one opening on the surface of the opening, the ratio of the minimum width along the at least one opening to the maximum width along the opening, the aspect ratio of the at least one opening, or a combination thereof The method according to claim 1, further comprising determining based on. **Claim 7** A method of forming a structure on a substrate, exposing at least one opening formed in the substrate to a tungsten-containing precursor gas at a precursor gas flow rate, wherein the at least one opening includes a lower portion and an upper portion, and the upper portion includes a width smaller than the width of the lower portion; exposing the at least one opening of the substrate to a reducing agent containing boron at a reducing agent flow rate, wherein the tungsten-containing precursor gas and the reducing agent are periodically and alternately interchanged to form a nucleation layer in the at least one opening of the substrate; exposing the at least one opening to the tungsten-containing precursor gas to form a part of a filling layer on the nucleation layer in the at least one opening; exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas or a nitrogen-containing plasma; exposing the at least one opening to the tungsten-containing precursor gas to form a filling layer in the at least one opening; exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas to suppress the growth of the filling layer in the at least one opening A method comprising. **Claim 8** The method according to claim 7, wherein the at least one opening further includes an intermediate portion between the upper portion and the lower portion, and the intermediate portion includes a width smaller than the width of the upper portion and the width of the lower portion. **Claim 9** The first time interval for exposing the substrate to nitrogen trifluoride and the second time interval for exposing the substrate to the nitrogen-containing plasma are at the interface location of the upper portion and the lower portion along the length of the at least one opening, the width of the opening at the interface of the upper portion and the lower portion, the width of the opening on the surface of the opening, the ratio of the minimum width along the opening to the maximum width along the opening, and determined based on the aspect ratio of the opening, or a combination thereof The method according to claim 7, further comprising determining based on **Claim 10** The method according to claim 7, wherein the opening is disposed in two or more layers, an upper layer interfaces with a lower layer at an interface, and a width of the opening in the upper layer at the interface is narrower than a width of the opening in the lower layer at the interface. **Claim 11** The method according to claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas includes flowing the nitrogen trifluoride-containing gas for about 1 second to about 30 seconds. **Claim 12** The method according to claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas includes heating the substrate to a temperature of about 200 °C to about 600 °C. **Claim 13** The method according to claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas includes flowing the nitrogen trifluoride-containing gas at a rate of about 0.5 sccm to about 500 sccm. **Claim 14** The method according to claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas includes co-flowing the nitrogen trifluoride gas with an inert carrier gas to form a nitrogen trifluoride mixture. **Claim 15** The method according to claim 7, wherein the nitrogen trifluoride-containing gas includes a volume gas flow ratio of nitrogen trifluoride gas to inert carrier gas of about 1:10,000 to about 1:

10. **Claim 16** A method of forming a structure on a substrate, comprising: forming a tungsten nucleation layer in at least one opening formed in a multi-level portion of the substrate; exposing the tungsten nucleation layer to a nitrogen-containing plasma to suppress growth of the nucleation layer in a narrow portion within the at least one opening; exposing the at least one opening to a tungsten-containing precursor gas to form a filling layer on the nucleation layer within the at least one opening; and exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas to suppress growth of a part of the filling layer along the at least one opening. A method comprising **Claim 17** The method according to claim 16, wherein a second nucleation layer is formed on the filling layer before exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas.

18. The method according to claim 16, wherein a second filling layer is formed in the at least one opening after exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas.

19. The method according to claim 18, further comprising exposing the second filling layer in the at least one opening to the nitrogen trifluoride-containing gas or the nitrogen-containing plasma to suppress growth of the second filling layer.

20. The method according to claim 19, further comprising forming a third filling layer in the at least one opening.

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