Method of forming multi-level tungsten features

Abstract

A method of forming a structure on a substrate includes forming a tungsten nucleation layer within at least one opening within a multi-level portion of the substrate. The method includes exposing the nucleation layer to a nitrogen trifluoride-containing gas to inhibit growth of the nucleation layer at the 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 packed layer over the nucleating 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 inhibit growth of a portion of the fill layer along the at least one opening.

Description

[0001] field

[0002] Embodiments herein relate to methods used in electronic device fabrication, and more particularly, to methods for forming tungsten features in semiconductor devices. Background Art

[0003] Related technical description

[0004] Tungsten (W) is widely used in integrated circuit (IC) device manufacturing to form conductive features where relatively low electrical 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, interconnect structures (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 the dielectric material layer).

[0005] Due to its relatively low resistivity, tungsten is also commonly used to form bit lines and word lines, which are used to address individual memory cells in a memory cell array of a three-dimensional NAND (3D NAND) device. A 3D NAND structure includes a horizontal array of levels that can be stacked by depositing layers in sequence. A channel can be formed by stacking films and filling the channel with tungsten. In some cases, the channel sidewall width can vary between levels. During the filling of the channel, due to the variation in the 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 faster in the upper portion of the channel than in the lower portion. This can result in the formation of voids in portions of the channel, particularly those disposed in a structure having two or more levels (and particularly high aspect ratio features).

[0006] Therefore, there is a need for processes for filling contact features that are free or substantially free of voids and seams and have low resistivity for a variety of film thicknesses within vias in multi-level structures. Summary of the invention

[0007] 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 cyclically alternated to form a nucleation layer in 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 inhibit the growth of the nucleation layer at a narrow portion in the at least one opening. The method includes exposing at least one opening to a tungsten-containing precursor gas to form a filling layer above the nucleation layer in 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 inhibit the growth of a portion of the filling layer along the at least one opening.

[0008] 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 that is less 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 cyclically alternated to form a nucleation layer in at least one opening of the substrate. The method includes exposing the opening to the tungsten-containing precursor gas to form a portion of a filling layer above the nucleation layer in the at least one opening. The method includes: exposing the opening of the substrate to a nitrogen trifluoride-containing gas or a nitrogen-containing plasma and exposing the opening to a tungsten-containing precursor gas to form a filling layer in the at least one opening. The method includes exposing the opening of the substrate to a nitrogen trifluoride-containing gas to inhibit the growth of the filling layer in the at least one opening.

[0009] In some embodiments, a method of forming a structure on a substrate is provided. The method includes forming a tungsten nucleation layer in at least one opening formed in a multi-level portion of the substrate. The method includes exposing the tungsten nucleation layer to a nitrogen-containing plasma to inhibit growth of the nucleation layer at a narrow portion of the at least one opening and exposing the at least one opening to a tungsten-containing precursor gas to form a fill layer above the nucleation layer in the at least one opening. The method includes exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas to inhibit growth of a portion of the fill layer along the at least one opening.

[0010] In some embodiments, a structure is provided on a substrate. The structure includes an opening in the substrate. The opening includes a plurality of levels stacked vertically from a bottom of the opening to a surface of the opening. A tungsten-containing layer is disposed in the opening, the tungsten-containing layer including a nucleation layer disposed along a sidewall of the opening. The nucleation layer includes boron and tungsten. The structure includes a filling layer disposed above the nucleation layer in the opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to be able to understand in detail the manner in which the above-mentioned features of the present disclosure are achieved, the present disclosure briefly summarized above may be described in more detail by reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered as limiting the scope of the embodiments, and other equivalent embodiments may be recognized.

[0012] Figure 1 is a schematic cross-sectional view of a portion of a substrate illustrating undesirable voids or seams in conventionally formed tungsten features.

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

[0014] Figure 2B According to an embodiment 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 simplified process flow for 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 a method described herein according to one embodiment.

[0017] Figure 4B is a schematic cross-sectional view of a portion of a substrate including a substrate processed by a method described herein according to one embodiment.

[0018] 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

[0019] Embodiments herein relate generally to electronic device manufacturing, and more particularly, embodiments herein relate to systems and methods for forming low-resistivity tungsten features in semiconductor device manufacturing schemes.

[0020] Figure 1 1 is a schematic cross-sectional view of a substrate 101 illustrating an undesirable void 20 formed during a conventional tungsten deposition process. Here, the substrate 101 includes a patterned surface 11 disposed in a plurality of hierarchical layers, such as a first hierarchical layer 12A and a second hierarchical layer 12B. In some embodiments, the first hierarchical layer 12A is a first dielectric layer (e.g., silicon oxide (SiO x)), and the second hierarchical layer is composed of a second dielectric layer (e.g., silicon nitride (SiN)). 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 a portion filled with tungsten layer 15); barrier material layer 14, which is deposited on hierarchical layers 12A, 12B to align the opening; and tungsten layer 15, which is deposited on barrier material layer 14. Figure 1 The illustrated tungsten layer 15 is formed using a conventional deposition process, such as a chemical vapor deposition (CVD) or atomic layer deposition (ALD) process, in which 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 forms a cover of material (tungsten cover layer 15C) on the field of the patterned surface 11.

[0021] exist Figure 1 , the opening has a non-uniform profile that is wider at the surface of the substrate 101 and tapers as the opening extends from the surface inward into the second layer 12B. At the interface 25 of the first and second level layers, the width of the second level is narrower than the width of the first level disposed inward from the second level. As shown, the interface portion of the conformal tungsten layer 15 has grown together to block or "pinch off" the entrance of the opening disposed in the first level layer 12A before the opening is completely filled, thereby producing an undesirable void 20, i.e., an absence of tungsten material, in the tungsten feature 15A. In addition to the voids, undesirable seams (e.g., 24) may also appear in the tungsten features, as shown in the second level layer 12B using a conventional tungsten deposition process. The voids 20 and seams 24 are susceptible to corrosion by chemically active components of the tungsten chemical mechanical polishing fluid, and if the seams 24 and / or voids 20 are exposed during the chemical mechanical polishing process, it may result in an undesirable loss of tungsten material from the features 15A, 15B.

[0022] Thus, embodiments herein provide a processing system configured to perform a combination of various aspects of the method without transferring substrates between processing chambers, thereby improving the overall substrate processing throughput and production capacity of the tungsten gap fill processing scheme described herein. The methods and systems provided herein are particularly suitable 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. Aspect ratio refers to the ratio of the total height of a feature to the average width or diameter.

[0023] Typically, a gap fill processing scheme includes: forming a differential tungsten deposition inhibition profile in a feature opening formed in a surface of a substrate; filling the opening with a tungsten material according to the inhibition profile; and depositing a blanket of tungsten on the field surface of the substrate. Forming the tungsten deposition inhibition profile typically includes: forming a tungsten nucleation layer; and treating the tungsten nucleation layer using a nitrogen trifluoride-containing gas, an active nitrogen species (e.g., treating free radicals), or a combination thereof. Nitrogen from the nitrogen trifluoride, active nitrogen species, or a combination thereof is introduced into portions of the nucleation layer, such as by adsorption of nitrogen and / or by reacting with metallic tungsten in the nucleation layer to form tungsten nitride (WN). The adsorbed nitrogen and / or nitrided surface of the tungsten nucleation layer ideally delays (inhibits) tungsten nucleation, and thus delays subsequent tungsten deposition on the tungsten nucleation layer.

[0024] In some embodiments, by using a remote plasma source coupled to the substrate processing chamber fluid, a process radical is formed at a remote substrate processing chamber. By controlling the processing conditions in the processing chamber, such as temperature and pressure, and controlling the concentration, flux and energy of the process radicals at the substrate surface, the desired suppression effect on the field of the patterned surface and the desired suppression profile formed in the opening in the patterned surface are achieved. Typically, the process radicals are formed by a non-halogen nitrogen-containing gas (such as N2, NH3, NH4 or a combination thereof). In some embodiments, a nitrogen trifluoride-containing gas is provided to the processing chamber without conveying the substrate. Without being bound by theory, it is believed that nitrogen trifluoride suppresses the growth in the opening at the interface of the hierarchical layer to fully fill the bottom of the opening and prevent pinching off at the interface. It has been found that the process radicals can provide enhanced suppression at the surface closer to the opening, while nitrogen trifluoride can suppress at a deeper position in the opening. Therefore, in some embodiments, voids may be prevented from forming during the filling process by performing a process that combines exposing portions of the nucleation layer and / or portions of the tungsten fill layer to nitrogen trifluoride (NF3) and nitrogen radicals during their respective process steps. The process may include adjusting the relative amounts of exposure to nitrogen trifluoride (NF3) and nitrogen radicals during the deposition process. By adjusting the relative amounts of exposure to nitrogen trifluoride (NF3) and nitrogen radicals during a cyclic deposition process for forming the nucleation layer and / or the tungsten fill layer, a desired deposition profile will be allowed to be produced in the feature during the deposition process. During the cyclic deposition process, exposure to nitrogen trifluoride (NF3) and nitrogen radicals may be done simultaneously or sequentially, in one example, first exposing the deposited layer to nitrogen trifluoride (NF3) in sequence, and then exposing the deposited layer to nitrogen radicals before depositing subsequent layers of the nucleation layer and / or the fill layer on the deposited layer. In another example, the deposited layer is first exposed to nitrogen radicals and then exposed to nitrogen trifluoride (NF3) in sequence before depositing subsequent layers of nucleation layer and / or fill layer on the deposited layer.

[0025] The tungsten nucleation and deposition process of the gap fill process scheme generally includes: flowing a tungsten-containing precursor and a reducing agent into a process chamber and exposing a substrate surface to the tungsten-containing precursor and the reducing agent. 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 on the surface of the substrate.

[0026] The processing systems described herein are configured to periodically perform chamber cleaning operations in which undesirable tungsten residues are removed from interior surfaces of a processing chamber using a cleaning chemistry, such as a cleaning chemistry including active halogen species (e.g., fluorine or chlorine (cleaning) radicals) formed remotely from the processing chamber.

[0027] The chamber cleaning operation generally includes: flowing halogen cleaning radicals into the processing chamber; reacting the cleaning radicals with tungsten residues to form volatile tungsten species; and exhausting the volatile tungsten species from the processing chamber through an exhaust device. The chamber cleaning operation is usually performed between substrate processing, that is, after removing a processed substrate from the processing chamber and before a subsequent processed substrate to be processed is received in the processing chamber.

[0028] FIG. 2A to FIG. 2B 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 is configured to provide desired different processing conditions for each of the nucleation process, the inhibition process, the selective gapfill process, and the cap deposition process within a single processing chamber 202 (i.e., without transferring the substrate between multiple processing chambers).

[0029] like Figure 2A As shown, the processing system 200 includes: a processing chamber 202; a gas delivery system 204, the gas delivery system being fluidically coupled to the processing chamber 202; and a system controller 208. The processing chamber 202 (eg, Figure 2A 2 (shown in cross-section in FIG. 1 ), 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 device 217 (such as one or more vacuum pumps) for maintaining the processing volume 215 under sub-atmospheric conditions and exhausting process gases and process byproducts from the processing volume.

[0030] 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 space 219 together with the lid plate. Here, the lid plate 216 is maintained at a desired temperature using one or more heaters 229 thermally coupled to the lid plate. The showerhead 218 faces a substrate support assembly 220 disposed in the processing space 215. As described below, the substrate support assembly 220 is configured to move a substrate support 222 between an elevated substrate processing position (as shown) and a lowered substrate transfer position (not shown), and thus move a substrate 230 disposed on the substrate support 222. When the substrate support assembly 220 is in the elevated substrate processing position, the showerhead 218 and the substrate support 222 define a processing area 221.

[0031] By providing a gas inlet 223 ( Figure 2B ) couples the gas delivery system 204 to the process chamber 202. The process or cleaning gas delivered by the gas delivery system 204 flows through the gas inlet 223 into the gas distribution space 219 and through the plurality of openings 232 ( Figure 2B ) is distributed into the processing region 221. In some embodiments, the chamber lid assembly 210 further includes a perforated baffle 225 disposed between the gas inlet 223 and the showerhead 218. In these embodiments, the gas flowing into the gas distribution space 219 is first diffused by the baffle 225 to provide a more uniform or desired distribution of gas flow into the processing region 221 together with the showerhead 218.

[0032] Process gases and process byproducts are exhausted radially outward from the process region 221 through an annular passage 226 surrounding the process 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 process chamber 202 includes one or more second liners 228, which are used to protect the inner surface of the one or more sidewalls 212 or the chamber base 214 from corrosive gases and / or undesirable material deposition.

[0033] 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 pedestal 214 surrounding the support shaft 262. The purge gas may be used to create a positive pressure region (compared to the pressure in the processing region 221) below the substrate support 222 during substrate processing. Typically, the purge gas introduced through the chamber pedestal 214 flows upward from the chamber pedestal and around the edge of the substrate support 222 to be exhausted from the processing volume 215 through the annular channel 226. The purge gas reduces undesirable material deposition on surfaces below the substrate support 222 by reducing and / or preventing material precursor gases from flowing into the substrate support.

[0034] 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 disposed on the movable support shaft 262. To facilitate transferring 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 a lift pin ring 268 or are disposed to engage with a lift pin hoop. The plurality of lift pins 267 are movably disposed in openings formed through the substrate support 222. When the substrate support 222 is disposed in a lowered substrate transfer position (not shown), the plurality of lift pins 267 extend above a substrate receiving surface of the substrate support 222 to lift the substrate 230 from the substrate receiving surface and provide access to a backside (inactive) surface of the substrate 230 through 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 are lowered beneath the substrate receiving surface of the substrate support 222 to allow the substrate 230 to be placed on the substrate receiving surface.

[0035] The substrate 230 is transferred to and from the substrate support 222 through a door 271 (e.g., 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 (e.g., openings in a door housing) are fluidly coupled to a purge gas source 237 (e.g., an Ar gas source). The purge gas is used to prevent process gases and cleaning gases from contacting and / or decomposing seals surrounding the door, thereby extending the useful life of the door.

[0036] The substrate support 222 is configured for vacuum chucking, wherein the substrate 230 is secured to the substrate support 222 by applying a vacuum to an interface between the substrate 230 and the substrate receiving surface. The vacuum is applied using a vacuum source 272 fluidly coupled to one or more channels or ports formed in the substrate receiving surface of the substrate support 222. In other embodiments, for example, where the processing chamber 202 is configured for direct plasma processing, the substrate support 222 may be configured for electrostatic chucking. In some embodiments, the substrate support 222 includes one or more electrodes (not shown) coupled to a bias voltage power source (not shown), such as a continuous wave (CW) RF power source or a pulsed RF power source, which provides a bias voltage to the one or more electrodes.

[0037] As shown, the substrate support assembly 220 features a dual-zone temperature control system to provide independent temperature control in different areas of the substrate support 222. The different temperature control areas of the substrate support 222 correspond to different areas of the substrate 230 disposed on the substrate support. Here, the temperature control system includes a first heater 263 and a second heater 264. The first heater 263 is disposed in a central area of ​​the substrate support 222, and the second heater 264 is disposed radially outward from the central area to surround the first heater 263. In other embodiments, the substrate support 222 may have a single heater or more than two heaters.

[0038] In some embodiments, the substrate support assembly 220 further includes an annular shadow ring 235 for preventing undesirable deposition of material on the circumferential beveled edge of the substrate 230. During the transfer of substrates to and from the substrate support 222, i.e., when the substrate support assembly 220 is disposed in a lowered position (not shown), the shadow ring 235 is placed on an annular flange within the processing volume 215. When the substrate support assembly 220 is disposed in the raised or processing position, the radially outward 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 shape of the shadow ring 235 is such that the radially inward portion of the shadow ring 235 is disposed over the beveled edge of the substrate 230 when the substrate support assembly 220 is in the raised substrate processing position.

[0039] In some embodiments, the substrate support assembly 220 further includes an annular purge ring 236 disposed on the substrate support 222 to surround the substrate 230. In these embodiments, a shadow ring 235 may be disposed on the purge ring 236 when the substrate support assembly 220 is in the elevated substrate processing position. Typically, the purge ring 236 features a plurality of radially inward openings that are in fluid communication 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 beveled edge of the substrate 230 to prevent process gas from entering the annular region and causing undesirable deposition of material on the beveled edge of the substrate 230.

[0040] In some embodiments, the processing chamber 202 is configured for direct plasma processing. In these embodiments, the showerhead 218 can be electrically coupled to a first power source 231 (such as an RF power source) that supplies power to ignite and maintain a plasma of a process gas flowing into the processing region 221 through capacitive coupling with the showerhead. 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.

[0041] The processing system 200 is advantageously configured to perform each of the tungsten nucleation, inhibition, and bulk tungsten deposition processes of the void-free and seamless tungsten gapfill process recipe without removing the substrate 230 from the processing chamber 202. Gases used to perform the various processes of the gapfill process recipe and to clean residues from the interior surfaces of the processing chamber are delivered to the processing chamber 202 using a gas delivery system 204 fluidly coupled to the processing chamber.

[0042] Typically, the gas delivery system 204 includes one or more remote plasma sources, here first and second radical generators 206A-206B, a deposition gas source 240, and a conduit system 294 (e.g., 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. The gas delivery system 204 further includes a plurality of isolation valves, here 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.

[0043] Each of the free radical generators 206A-206B features a chamber body 280 that defines respective first and second plasma chamber spaces 281A-281B ( Figure 2B ). Each of the radical generators 206A to 206B is coupled to a corresponding power source 293A to 293B. The power sources 293A to 293B are used to ignite and maintain a plasma 282A to 282B of a gas delivered to the plasma chamber space 281A to 281B from a corresponding first gas source or a second gas source 287A to 287B fluidly coupled to the plasma chamber space. In some embodiments, the first radical generator 206A generates radicals for a differential inhibition process. For example, the first radical generator 206A can be used to ignite and maintain a treatment plasma 282A from a halogen-free gas mixture delivered from the first gas source 287A to the first plasma chamber space 281A. The second radical generator 206B can be used to generate cleaning radicals for a chamber cleaning process by igniting and maintaining a cleaning plasma 282B from a halogen-containing gas mixture delivered from the second gas source 287B to the second plasma chamber space 281B.

[0044] Typically, nitrogen treatment radicals have a relatively short lifetime (compared to halogen cleaning radicals) and may exhibit relatively high sensitivity to recombination resulting from collisions with surfaces in the gas delivery system 204 and / or with other species of the process plasma effluent. Therefore, 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 short travel distance from the first plasma chamber space 281A to the process region 221.

[0045] In some embodiments, the first radical generator 206A is further fluidly coupled to a second gas source 287B that delivers a halogen-containing adjustment gas to the first plasma chamber space 281A for a plasma source adjustment process. In these 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 space 281A.

[0046] Suitable remote plasma sources that may be used for one or both of the free radical generators 206A-206B include a radio frequency (RF) or very high radio frequency (VHRF) capacitively coupled plasma (CCP) source, an inductively coupled plasma (ICP) source, a microwave induced (MW) plasma source, an electron cyclotron resonance (ECR) chamber, or a high density plasma (FIDP) chamber.

[0047] As shown, the first radical generator 206A is fluidly coupled to the processing chamber 202 by using first and second conduits 294A-294B, which extend upward from the gas inlet 223 to connect with the outlet of the first plasma chamber space 281A. A first valve 290A disposed between the first and second conduits 294A-294B is used to selectively fluidly isolate the first radical generator 206A from the processing chamber 202 and other parts of the gas delivery system 204. Typically, during the chamber cleaning process, the first valve 290A is closed to prevent the active cleaning gas (e.g., halogen radicals) from flowing into the first plasma chamber space 281A and damaging the surface of the first plasma chamber space.

[0048] The second free radical generator 206B is fluidly coupled to the second conduit 294B and, therefore, to the processing chamber 202 by using the third and fourth conduits 294C-294D. The second free radical generator 206B is selectively isolated from the processing chamber 202 and other portions of the gas delivery system 204 by using a second valve 290B disposed between the third and fourth conduits 294C-294D.

[0049] A deposition gas (e.g., a tungsten-containing precursor and a reducing agent) is delivered from the deposition gas source 240 to the processing chamber 202 using a fifth conduit 294E. As shown, the fifth conduit 294E is coupled to the second conduit 294B at a location proximate to the gas inlet 223, so that the first valve and the second valve 290A-290B can be used to isolate the first radical generator and the second radical generator 206A-206B from the deposition gas introduced into the processing chamber 202, respectively. In some embodiments, the gas delivery system 204 further includes a sixth conduit 294F, which is coupled to the fourth conduit 294D at a location proximate to the second valve 290B. The sixth conduit 294F is fluidly coupled to a purge gas source 237 (e.g., an argon (Ar) gas source), which can be used to periodically purge portions of the gas delivery system 204 for undesirable residue cleaning, suppression, and / or deposition gases.

[0050] The system controller 208 facilitates the operation of the processing system 200. 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 setting, such as a programmable logic controller (PLC), for controlling various chamber components and subprocessors. The memory 296 coupled to the CPU 295 facilitates the operation of the processing chamber. The support circuits 297 are typically coupled to the CPU 295 and include caches, clock circuits, input / output subsystems, power sources, etc., and combinations thereof coupled to the various components of the processing system 200 to facilitate control of substrate processing operations thereby.

[0051] 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 by a computer system. The program(s) of the program product define the functionality of the embodiments (including the methods described herein). Therefore, the computer-readable storage medium is an embodiment of the present disclosure when it carries computer-readable instructions that direct the functionality of the methods described herein.

[0052] The processing system 200 described above may be used to perform each of nucleation, suppression, and gap fill deposition, thereby providing a single chamber seamless tungsten gap fill solution.

[0053] Figure 3 is a diagram illustrating a simplified process flow for processing a substrate, which may be performed using a processing system 200 , according to some embodiments. FIG. 4A to FIG. 4B is a schematic cross-sectional view of a portion of a substrate 400 illustrating aspects of different stages of a void-free and seamless tungsten interstitial process scheme.

[0054] Substrate 400 features a patterned surface 401, the patterned surface including a first hierarchical layer 412A and a second hierarchical layer 412B, in which a plurality of openings 405 (one is shown) are formed. 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 about 200 nm to about 300 nm), 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 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, each opening 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 opening includes 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 and the second level openings together form a single continuous opening 405. The uppermost portion of the first level opening 402A meets the lowermost portion of the second level opening 402B at the interface 406.

[0055] At the interface, 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, the width 407 is about 5% to about 100% greater than the width 410, such as about 10% to about 50%. For example, the width 410 can be about 50 nm to about 300 nm, such as about 75 nm to about 125 nm, and the width 407 can be about 70 nm to about 400 nm, such as about 150 nm to about 250 nm. In some embodiments, for each level, the widest portion of the level (such as the uppermost portion 414 of the second level 402B) is about 5% to about 100% greater than the narrowest portion of the level (such as the lowermost portion 410 of the second level 402B), such as about 10% to about 50%. In some embodiments, the height of the first level opening 402A is substantially equal to, less than, or greater than the height of the 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 clamping effect. The methods described herein enable growth behavior that fills the openings without forming voids.

[0056] like Figure 4BAs shown, patterned surface 401 includes a barrier or adhesion layer 403, such as a titanium nitride (TiN) layer, deposited on first level layer 412A and second level layer 412B to conformally align openings 405 and facilitate subsequent deposition of tungsten nucleation layer 404. In some embodiments, adhesion layer 403 is deposited to a thickness between about 20 angstroms (Å) and about 150 Å, such as about 30 Å to about 100 Å.

[0057] Nucleation layer deposition

[0058] As depicted by activity 302, each of process flows 300A, 300B, 300C, 300D, 300E, and 300F includes forming a nucleation layer 404 over substrate 400. The nucleation layer may be formed using any process capable of forming a tungsten nucleation layer. In some embodiments, prior to forming the nucleation layer 404, the substrate is exposed to a boron-containing gas (e.g., B2H2), such as for an immersion time of about 5 seconds or longer, such as about 10 seconds or longer, such as about 20 seconds to 30 seconds. In some embodiments, the nucleation layer 404 is deposited over the adhesion layer 403.

[0059] The nucleation layer may be formed using an atomic layer deposition (ALD) or physical vapor deposition (PVD) process of a tungsten-containing nucleation layer. Forming the nucleation layer includes exposing the substrate 400 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 includes boron and is introduced into the processing chamber at a reducing agent flow rate. In some embodiments, the tungsten-containing precursor gas and the reducing agent are cyclically alternating to form a nucleation layer above the substrate in at least one opening of the substrate at the reducing agent flow rate. In some embodiments, the reducing agent and the tungsten-containing precursor gas are cyclically alternating starting with the reducing agent or the tungsten-containing precursor gas and ending with the same starting gas or ending with a gas different from the starting gas. In some embodiments, the reducing agent or the tungsten-containing precursor gas is cyclically alternating starting with the tungsten-containing precursor gas and ending with the reducing agent. Figure 4B Schematically illustrated in FIG. 4 is a portion of an exemplary substrate 400 having a nucleation layer 404 formed thereon.

[0060] In some embodiments, the nucleation layer 404 is deposited using an atomic layer deposition (ALD) process. The ALD process includes repeated 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 between the alternating exposures. In some embodiments, the processing region 221 is purged continuously. Examples of suitable tungsten-containing precursors include tungsten halides, such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), or combinations thereof. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent includes a boron-containing reagent, such as B2H6. In some embodiments, the tungsten-containing precursor includes an organometallic precursor and / or a fluorine-free precursor, such as methylcyclopentadienyl-dicarbonyl nitroso-tungsten (MDNOW), ethylcyclopentadienyl-dicarbonyl nitroso-tungsten (EDNOW), hexacarbonyl tungsten (W(CO)6), or combinations thereof.

[0061] During the nucleation process, the processing space 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 into the processing region 221 at a flow rate of about 100 sccm or less, such as about 10 sccm to about 60 sccm or 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 between about 300 sccm and about 750 sccm.

[0062] It should be noted that the flow rates for the various deposition and treatment processes described herein are for a processing system 200 configured to process substrates having a diameter of 300 mm. Appropriate scaling may be used for processing systems configured to process substrates of different sizes.

[0063] 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 may be purged between 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 may be delivered from the deposition gas source 240 or from the purge gas source 237. Typically, repeated cycles of the nucleation process continue 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. The nucleation layer 404 is disposed along the sidewalls of the opening 405, such as over the barrier or adhesion layer 403.

[0064] In some embodiments, immediately following each nucleation activity 302, in activity 306, a tungsten gap fill material 408 ( Figure 4B ) is at least partially deposited into the plurality of openings 405. The need for optional activity 306 immediately following the nucleation activity 302 is determined based on the profile of the openings, such as the relative heights of the levels. As an example, for a lower level that is much longer than an upper level, the interface between the levels (referred to herein as a "necking point") may be located close to the surface of the opening, so the opening may be at least partially filled with tungsten interstitial material 408 prior to introducing the growth inhibitor. In some embodiments, the optional activity 306 is performed when the minimum width of the opening is within a range of about 50% or less of the maximum width of the opening, such as within a range of 30% or less, such as within a range of 20% or less. Other profiles may determine the need for the optional activity 306, such as lower aspect ratio features that may benefit from the optional operation and features with wide openings at the surface. Without being bound by theory, it is believed that the optional activity 306 can improve yield prior to the inhibition operation.

[0065] In one embodiment, the tungsten gap fill material 408 is formed using a chemical vapor deposition (CVD) process, the CVD process comprising: simultaneously flowing (co-flowing) a tungsten-containing precursor gas and a reducing agent into the processing region 221; and exposing the substrate 400 to the tungsten-containing precursor gas and the reducing agent. The tungsten-containing precursor and the reducing agent used in the tungsten gap fill CVD process may include any combination of the tungsten-containing precursor and the reducing agent described with reference to activity 302. In some embodiments, the tungsten-containing precursor includes WF6, and the reducing agent includes hydrogen. In some embodiments, the tungsten gap fill material 408 partially fills the plurality of openings 405.

[0066] The tungsten-containing precursor flows 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 sccm, or between about 100 sccm and about 900 sccm. The reducing agent flows into the processing region 221 at a rate greater than about 500 sccm, such as greater than about 750 sccm, greater than about 1000 sccm, or between about 500 sccm and about 10000 sccm, such as between about 1000 sccm and about 9000 sccm or between about 1000 sccm and about 8000 sccm.

[0067] In some embodiments, the tungsten gap fill CVD process conditions are selected to provide a tungsten feature with relatively low residual film stress compared to a conventional tungsten CVD process. For example, in some embodiments, the tungsten gap fill CVD process includes heating the substrate to about 250° C. or higher, such as about 300° C. or higher, or between about 250° C. and about 600° C., or between about 300° C. and about 500° C. During the CVD process, the processing space 215 is typically maintained at a pressure of less than about 500 Torr, less than about 600 Torr, less than about 500 Torr, less than about 400 Torr, or between about 1 Torr and about 500 Torr (such as between about 1 Torr and about 450 Torr, or between about 1 Torr and about 400 Torr, or, for example, between about 1 Torr and about 300 Torr).

[0068] In another embodiment, an atomic layer deposition (ALD) process is used to deposit the tungsten gapfill material 408 at operation 306. The tungsten gapfill ALD process includes repeated cycles of alternately exposing the substrate 400 to a tungsten-containing precursor gas and a reducing agent and purging the processing region 221 between alternating exposures.

[0069] 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 is typically purged between alternating exposures by flowing an inert 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 may be delivered from the deposition gas source 240 or from the purge gas source 237.

[0070] In other embodiments, the tungsten gapfill material 408 is deposited using a pulsed CVD method that includes repeated cycles of alternatingly exposing the substrate 400 to a tungsten-containing precursor gas and a reducing agent without purging the process region 221. The processing conditions for the tungsten gapfill pulsed CVD method may be the same, substantially the same, or within the same range as the processing conditions described above for the tungsten gapfill ALD process.

[0071] In some embodiments, the nucleation layer 404 and the fill layer 408 are monolithic and have 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 adhesion layer and the nucleation layer to the center of the fill layer 408.

[0072] After forming the nucleation layer 404 and the optional tungsten gap fill material 408, a differential inhibition profile is formed by exposing the sidewalls of the opening to a nitrogen trifluoride containing gas, an active species of a process gas (such as a nitrogen containing gas), or a combination thereof. Several combinations of processes are described with reference to processes 300A, 300B, 300C, 300D, 300E, and 300F. Other combinations have also been accomplished.

[0073] Process 300A - Nitrogen Trifluoride Treatment

[0074] like Figure 3 As shown, process 300A includes, in activity 304, after forming a nucleation layer (e.g., as described in activity 302), treating an outer surface of nucleation layer 404 or tungsten gap fill material 408 (e.g., after optional activity 306) to inhibit tungsten deposition on field surfaces of substrate 400 at interfaces (e.g., necking points) between adjacent levels. Activity 304 forms differential inhibition profiles in a plurality of openings 405 using a differential inhibition process. Forming the differential inhibition profiles includes exposing sidewalls of the openings to a nitrogen trifluoride-containing gas.

[0075] Exposing the opening to the nitrogen trifluoride-containing gas includes flowing the nitrogen trifluoride-containing gas for 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 flows 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 nitrogen trifluoride gas to inert carrier gas is about 1:10,000 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.

[0076] After processing described in activity 304, a tungsten gap fill material 408 is formed in the opening at activity 306. In some embodiments, as shown in process 300A, activities 304 and 306 (eg, together C1) may be repeated one or more times, such as once or twice, until the opening is filled.

[0077] Process 300B - Nitrogen Trifluoride Treatment + Additional Nucleation

[0078] Similar to process 300A, process 300B includes activity 302 (with optional activity 306 immediately following activity 302), activity 304, and activity 306 (eg, together C2). After activity 306, one or more cycles of activities 302, 304, and 306 may be repeated (eg, C2).

[0079] Process 300C - Nitrogen trifluoride treatment + active substance treatment

[0080] 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 a reactive species of a process gas (e.g., a process radical from a remote plasma source). Suitable process gases that can be used for the suppression process include N2, H2, NH3, NH4, O2, CH4, or a combination thereof. In some embodiments, the process gas includes nitrogen, such as N2, H2, NH3, NH4, or a combination thereof, and the reactive species includes nitrogen radicals, such as atomic nitrogen. In some embodiments, the process gas is combined with an inert carrier gas (such as Ar, He, or a combination thereof) to form a process gas mixture.

[0081] In some embodiments, starting with nitrogen trifluoride or starting with a treatment radical, the nitrogen trifluoride of activity 304 alternates with the treatment radical of activity 305. Between each treatment (nitrogen trifluoride or nitrogen), a tungsten gap fill material 408 is at least partially deposited into one or more openings (e.g., activity 306). In process 300C, the nitrogen trifluoride treatment of activities 304 and 306 (together C1) is followed by the active material treatment of activities 305 and 306 (together C3). Depending on the desired inhibition profile, after C3, another iteration of C1, C2, C3, or a combination 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., repeat C1+C3).

[0082] The order between nitrogen trifluoride and the treatment free radical, the exposure time and the ratio of gas flow rate are determined based on the profile of the opening. For example, for a necking point that is deeper in the opening, a longer exposure of nitrogen trifluoride relative to the treatment free radical is used. For a necking point with a small width and for very high aspect ratio features, a longer exposure of nitrogen trifluoride is used relative to the process treated with free radicals. The duration of nitrogen trifluoride relative to the duration of the free radical treatment can be about 20:1 to about 1:20, such as about 5:1 to about 1:1 or about 1:2 to about 1:6.

[0083] Without being bound by theory, it is believed that the reactive nitrogen species formed during the treatment with free radicals are incorporated into portions of the nucleation layer 404 by adsorbing the reactive nitrogen species and / or by reacting with the metallic 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 (inhibits) further tungsten nucleation and thus retards subsequent tungsten deposition on the tungsten nucleation layer.

[0084] In some embodiments, exposing the nucleation layer 404 to the process radicals includes: using the first radical generator 206A to form a process plasma 282A of a substantially halogen-free process gas mixture and flowing the effluent of the process plasma 282A into the process region 221. In some embodiments, the flow rate of the process gas mixture entering the first radical generator 206A and thus the flow rate of the process plasma effluent (such as nitrogen) entering the process region 221 is about 1 sccm and about 3000 sccm, such as about 1 sccm and about 2500 sccm, such as about 1 sccm and about 2000 sccm, such as about 1 sccm and about 1000 sccm, such as about 1 sccm and about 500 sccm, such as about 1 sccm and about 250 sccm, such as about 1 sccm and about 100 sccm, such as about 1 sccm and about 75 sccm, such as about 1 sccm and about 50 sccm.

[0085] In some embodiments, the inhibiting treatment process includes exposing the substrate 400 to the treatment radicals for about 2 seconds or more, 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.

[0086] In some embodiments, the concentration of the substantially halogen-free process gas in the process gas mixture is about 0.1 vol% to about 50 vol%, such as about 0.2 vol% to about 40 vol%, about 0.2 vol% to about 30 vol%, about 0.2 vol% and about 20 vol%, or for example, such as about 0.2 vol% and about 10 vol%, such as about 0.2 vol% and about 5 vol%.

[0087] In other embodiments, a remote plasma (not shown) may be used to form the process radicals, the remote plasma being ignited and maintained in a portion of the process volume 215 that is separated from the process region 221 by the showerhead 218, such as between the showerhead 218 and the cover plate 216. In these embodiments, the reactive process gas may flow through an ion filter to remove substantially all ions from the ion filter before the process radicals reach the process region 221 and the surface of the substrate 400. In some embodiments, the showerhead 218 may be used as an ion filter, and in other embodiments, the plasma used to form the process radicals is an in-situ plasma formed in the process region 221 between the showerhead 218 and the substrate 400. In some embodiments, for example, when an in-situ process plasma is used, the substrate 400 may be biased to control the directionality and / or accelerate ions, such as charged process radicals, formed from the process gas toward the substrate surface.

[0088] In some embodiments, the inhibition treatment process includes maintaining the processing space 215 at a pressure of less than about 100 Torr while flowing the reactive process gas into the processing space. For example, during the inhibition treatment process, the processing space 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.

[0089] Process 300D - Nitrogen trifluoride treatment + additional nucleation + active material treatment

[0090] Process 300D includes activity 302 (with optional activity 306 immediately following activity 302), activity 304, and activity 306 (together C2). After activity 306, additional nucleation activity 302 is performed, followed by active material processing of activity 305, and then activity 306 (together C4). Additional iterations of C1, C2, C3, C4, and combinations thereof are also contemplated thereafter. 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., repeat C2+C4).

[0091] Process 300E - Active Substance Treatment + Nitrogen Trifluoride Treatment

[0092] Process 300E includes activity 302 (with optional activity 306 immediately following activity 302), activity 305, and activity 306 (together C4). After activity 306, the nitrogen trifluoride treatment of activity 304 is performed, followed by the CVD tungsten gap fill of activity 306 (together C1). Additional iterations of C1, C2, C3, C4, and combinations thereof are contemplated thereafter. In some embodiments, one or more C4 cycles may be completed, followed by one or more C1 cycles, and then both cycles may be repeated (e.g., repeat C4+C1).

[0093] Process 300F - Active substance treatment + Nitrogen trifluoride treatment

[0094] Process 300F includes activity 302 (with optional activity 306 immediately following activity 302), activity 305, and activity 306 (together C4). After activity 306, an additional nucleation activity 302 is performed, followed by a nitrogen trifluoride treatment activity 304, and then a CVD tungsten gap fill of activity 306 (together C2). Additional iterations of C1, C2, C3, C4, and combinations thereof are also contemplated thereafter. In some embodiments, one or more C4 cycles may be completed, followed by one or more C2 cycles, and then both cycles may be repeated (e.g., repeating C4+C2).

[0095] Although not depicted in the figures, in some embodiments, activities 304 and 305 follow one another without intervening activities, such as activity 306 .

[0096] In a typical semiconductor manufacturing scheme, after depositing the tungsten gapfill material 408 into the opening 405 , a chemical mechanical polishing (CMP) process may be used to remove the blanket of tungsten material (and a barrier layer disposed beneath the blanket) from the field surfaces of the substrate.

[0097] 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 of the disclosure, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A method for forming a structure on a substrate, the method comprising: exposing at least one opening formed in the multi-level 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 comprising boron at a reducing agent flow rate, wherein the tungsten-containing gas and the reducing agent are cyclically alternating to form a nucleation layer within the at least one opening of the substrate; exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas to inhibit growth of the nucleation layer at a narrow portion within the at least one opening; exposing the at least one opening to a tungsten-containing precursor gas to form a fill layer over the nucleation layer within the at least one opening; as well as The at least one opening of the substrate is exposed to the nitrogen trifluoride-containing gas or nitrogen-containing plasma to inhibit growth of a portion of the fill layer along the at least one opening.

2. The method of claim 1, wherein exposing the at least one opening to the tungsten-containing precursor gas comprises a chemical vapor deposition process. 3 . The method of claim 1 , wherein exposing the at least one opening to the nitrogen trifluoride containing gas and the nitrogen containing plasma comprises alternating the nitrogen trifluoride containing gas and the nitrogen containing plasma.

4. The method of 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 prior to exposing to the nitrogen trifluoride-containing gas.

5. The method of 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 prior to exposing to the nitrogen-containing plasma.

6. The method of claim 1 , further comprising determining a first interval for exposing the at least one opening of the substrate to the nitrogen trifluoride and a second interval for exposing the substrate to the nitrogen-containing plasma based on: a location of an interface between a first level and a second level of the multi-level portion along a length of the at least one opening; a width of the at least one opening at an interface of two adjacent levels of the multi-level portion; a width of the at least one opening at a surface of the opening; a ratio between a minimum width along said at least one opening and said maximum width along said opening; an aspect ratio of the at least one opening; or A combination of the above.

7. A method for forming a structure on a substrate, the method comprising: 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 comprises a lower portion and an upper portion, wherein the upper portion comprises a width that is less than a width of the lower portion; exposing the at least one opening of the substrate to a reducing agent comprising boron at a reducing agent flow rate, wherein the tungsten-containing precursor gas and the reducing agent are cyclically alternating to form a nucleation layer within the at least one opening of the substrate; exposing the at least one opening to the tungsten-containing precursor gas to form a portion of a fill layer above the nucleation layer within 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 the filling layer in the at least one opening; as well as The at least one opening of the substrate is exposed to the nitrogen trifluoride-containing gas to inhibit growth of the filling layer within the at least one opening.

8. The method of claim 7, wherein the at least one opening further comprises a middle portion between the upper portion and the lower portion, wherein the middle portion comprises a width that is smaller than the width of the upper portion and the width of the lower portion.

9. The method of claim 7, further comprising determining a first interval for exposing the substrate to the nitrogen trifluoride and a second interval for exposing the substrate to the nitrogen-containing plasma based on: an interface location of the upper portion and the lower portion along the length of the at least one opening; a width of the opening at an interface of the upper portion and the lower portion; a width of the opening at a surface of the opening; a ratio between a minimum width along said opening and said maximum width along said opening; and an aspect ratio of the opening; or a combination thereof.

10. The method of claim 7, wherein the opening is disposed in two or more hierarchical layers, wherein an upper hierarchical layer is connected to a lower hierarchical layer at an interface, wherein a width of the opening in the upper hierarchical layer at the interface is narrower than a width of the opening in the lower hierarchical layer at the interface.

11. The method of claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas comprises flowing the nitrogen trifluoride-containing gas for about 1 second to about 30 seconds.

12. The method of claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas comprises heating the substrate to a temperature of about 200°C to about 600°C.

13. The method of claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride containing gas comprises flowing the nitrogen trifluoride containing gas at a rate of about 0.5 seem to about 500 seem.

14. The method of claim 7, wherein exposing the at least one opening of the substrate to a nitrogen trifluoride-containing gas comprises co-flowing the nitrogen trifluoride gas with an inert carrier gas to form a nitrogen trifluoride mixture.

15. The method of claim 7, wherein the nitrogen trifluoride-containing gas comprises a volumetric gas flow ratio of nitrogen trifluoride gas to inert carrier gas of about 1:10,000 to about 1:

10.

16. A method of forming a structure on a substrate, the method comprising: forming a tungsten nucleation layer within at least one opening formed in the multi-level portion of the substrate; exposing the tungsten nucleation layer to a nitrogen-containing plasma to inhibit growth of the nucleation layer at a narrow portion within the at least one opening; exposing the at least one opening to a tungsten-containing precursor gas to form a fill layer over the nucleation layer within the at least one opening; as well as The at least one opening of the substrate is exposed to a nitrogen trifluoride-containing gas to inhibit growth of a portion of the fill layer along the at least one opening. 17 . The method of claim 16 , forming a second nucleation layer over the filling layer before exposing the at least one opening of the substrate to the nitrogen trifluoride-containing gas. 18 . The method of claim 16 , forming a second filling layer 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 of claim 18 , further comprising exposing the second filling layer within the at least one opening to the nitrogen trifluoride-containing gas or the nitrogen-containing plasma to inhibit growth of the second filling layer.

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

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