Gas flow sequences for molybdenum deposition

Abstract

Provided herein are methods and related apparatus for deposition of a molybdenum in a feature by atomic layer deposition processes. In some embodiments, molybdenum precursor and inert gas are co-flowed into a charge volume continuously during an ALD cycle. In some embodiments, a two-step purge process is performed after discharge of a charge volume into a process chamber.

Description

Atorney Docket No. LAM1P078WO-12131-1WO GAS FLOW SEQUENCES FOR MOLYBDENUM DEPOSITIONINCORPORATION BY REFERENCE

[0000] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in their entireties and for all purposes.BACKGROUND

[0001] Deposition of conductive materials an integral part of many semiconductor fabrication processes. These materials may be used for horizontal interconnects, vias between adjacent metal layers, contacts between metal layers and devices, and as lines in memory' devices.

[0002] The background description provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admited as prior art against the present disclosure.SUMMARY

[0003] Provided herein are methods and related apparatus for deposition of a moly bdenum in a feature. Related apparatuses are also provided.

[0004] In one aspect of the embodiments herein, a method is provided for depositing molybdenum, the method including: providing a substrate including features to be filled in a process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process includes one or more cycles of: (a) flowing a molybdenum precursor and an inert gas into the process chamber; (b) flowing a first purge gas into the process chamber; (c) flowing a reactant into the process chamber; and (d) flowing a second purge gas into the process chamber; wherein (b) includes: (i) a first flow rate purge; and (ii) a second flow rate purge, wherein the second flow rate purge has a higher flow rate than the first flow rate purge.

[0005] In some embodiments, the first flow rate purge is performed at a flow rate less than about 4000 seem. In some embodiments, the process chamber has a reactive cavity defined at least in part by the substrate and a showerhead above the substrate and having a first volume, and the first flow rate purge flows a second volume of inert gas that is less than about 2 times larger than the first volume. In some embodiments, the second flow rate purge flows a third volume of inert gasAtorney Docket No. LAM1P078WO-12131-1WO that is at least about 20 times larger than the first volume. In some embodiments, a second flow rate purge is performed at a flow rate greater than about 10 slm. In some embodiments, purge gas is flowed through a mass flow controller (MFC) during the first flow rate purge, and is flowed from a charge volume during the second flow rate purge. In some embodiments, (a) includes discharging the molybdenum precursor and inert gas into the process chamber from a charge volume. In some embodiments, the charge volume is not discharged into the process chamber during (b)-(d). In some embodiments, molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process. In some embodiments, molybdenum precursor is flowed into the charge volume from a molybdenum precursor source via a restrictive flow orifice plate, and the flow of molybdenum precursor into the charged volume is a choked flow. In some embodiments, a pressure in the charge volume prior to discharge is less than about half a pressure of a molybdenum precursor source. In some embodiments, the purge gas and the inert gas includes argon, helium, nitrogen, or any combinations thereof. In some embodiments, the molybdenum precursor is a molybdenum oxyhalide. In some embodiments, the reactant is a hydrogen-containing reactant. In some embodiments, the ALD process is a non-plasma thermal process. In some embodiments, the ALD process is a plasma-enhanced process. In some embodiments, (d) comprises: (A) a third flow rate purge: and (B) a fourth flow rate purge, wherein the fourth flow rate purge has a higher flow rate than the third flow rate purge.

[0006] In another aspect of the embodiments herein, a method for depositing molybdenum is provided, the method including: providing a substrate including features to be filled in a process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process includes one or more cycles of: (a) flowing a molybdenum precursor and an inert gas into the process chamber from a charge volume; (b) flowing a first purge gas into the process chamber; (c) flowing a reactant into the process chamber; and (d) flowing a second purge gas into the process chamber; wherein molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process. In some embodiments, the charge volume is not discharged into the process chamber during (b)-(d). In some embodiments, molybdenum precursor is flowed into the charge volume from a molybdenum precursor source via a restrictive flow orifice plate, and the flow of molybdenum precursor into the charged volume is a choked flow. In some embodiments, a pressure in the charge volume prior to discharge is less than about half a pressure of a molybdenum precursor source.

[0007] In another aspect of the embodiments herein, an apparatus for depositing molybdenum is provided, the apparatus including: a process chamber having one or more stations each configured to hold a substrate; one or more process gas inlets for coupling to a hydrogen (H2) gasAtorney Docket No. LAM1P078WO-12131-1WO source, a molybdenum precursor gas source, and an inert purge gas source; and a controller for controlling operations in the apparatus, the controller including non-transitory machine-readable instructions for: providing a substrate including features to be filled in a process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process includes one or more cycles of: (a) flowing a molybdenum precursor and an inert gas into the process chamber from a charge volume; (b) flowing a first purge gas into the process chamber; (c) flowing a reactant into the process chamber; and (d) flowing a second purge gas into the process chamber; wherein molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process.

[0008] These and other aspects of the disclosure are described in more detail below with reference to the Figures.BRIEF DESCRIPTION OF DRAWINGS

[0009] Figures 1A and IB are schematic examples of material stacks that include Mo layers according to various embodiments.

[0010] Figures 2A-2L are schematic examples of various structures into which molybdenum may be deposited in accordance with disclosed embodiments.

[0011] Figure 3 is a process diagram show operations in a deposition-etch-deposition method of filling wordline features of a 3D NAND structure.

[0012] Figure 4 illustrates certain operations of the process of Figure 3.

[0013] Figure 5 is a process flow diagram illustrating example operations in a method for interconnect metallization.

[0014] Figure 6 shows cross-sectional representations of a feature during various stages of the process of Figure 5.

[0015] Figure 7A shows an example of molybdenum deposition by an atomic layer deposition (ALD) process.

[0016] Figures 7B-7C are timing diagrams of examples of ALD processes.

[0017] Figure 8 shows a graph of Mo Torr-seconds for two different ALD processes described herein.

[0018] Figures 9A-9B show graphs of wafer canty mole fraction and Langmuirs for different ALD processes described herein.

[0019] Figure 10 provides an example of a precursor delivery stem.

[0020] Figure 11 depicts a schematic illustration of an embodiment of an ALD process station.

[0021] Figure 12A-12B show examples of semiconductor processing tools.Atorney Docket No. LAM1P078WO-12131-1WODETAILED DESCRIPTION

[0022] In the following description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed embodiments. While the disclosed embodiments will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments.

[0023] The subscripts ‘N” and “y” are used throughout the disclosure to denote a number greater than 0 that forms a stable compound. However, it should be noted that the lack of an “x” or other subscript (e.g., in titanium nitride (TiN) or titanium oxynitride (TiON)) does not imply a particular atomic ratio.

[0024] Provided herein are methods of filling features with molybdenum (Mo) that may be used for logic and memory applications. The Mo films may be deposited in semiconductor substrate features such as vias and trenches. The Mo films may be deposited to line features as liner layers and / or to fill features.

[0025] In some embodiments, the methods involve botom-up deposition of Mo in a feature. Botom-up deposition refers to growth that is mostly or wholly from a feature botom relative to the feature sidewalls. Botom-up deposition is distinguished from filling a feature by nucleation and growth on all feature surfaces. This results in conformal growth and can result in the formation of a void and / or seam in the feature. For example, a void may form as growth at the top of the feature can pinches off the feature. A seam can form in the center of a feature as film grows inward from the sidewalls. Botom-up deposition can avoid formation of voids and seams in the feature during the fill process. References to botom-up deposition can include be inside-out deposition for horizontally-oriented features in which growth proceeds from the interior of a feature outw ard.

[0026] While described chiefly in the context of Mo, the methods may be used for deposition of other metals including W, Co, and Ru. For some applications, molybdenum offers several benefits over other metals such as cobalt (Co), ruthenium (Ru), and tungsten (W): (i) barrier-less and linerless molybdenum film deposition is more feasible on oxides and nitrides as compared to deposition of cobalt, ruthenium, and tungsten, (ii) Mo resistivity scaling is better than that of tungsten, (iii) Mo intermixing with underlying Co is not expected compared to Ru intermixing with Co at temperatures less than 450°C, and (iv) there is relatively easy Mo integration into current W schemes compared to copper and ruthenium.

[0027] Deposition of molybdenum may be performed by atomic layer deposition (ALD) processes, which in some embodiments may be plasma enhanced ALD (PEALD). ALD is aAtorney Docket No. LAM1P078WO-12131-1WO surface-mediated deposition technique in which doses of a precursor and a reactant are sequentially introduced into a deposition chamber. One or more cycles of sequential doses of a molybdenum precursor and reactant may be used to deposit Mo. Deposition by ALD may be advantageous for complex architectures, as described below, as it may conformally deposit within features. However, ALD processes may be limited by diffusion into features; the complex architecture may require additional time for species to diffuse and adsorb / react within features. Thus, it is desirable to improve the deposition of molybdenum ALD processes to decrease cycle time and / or increase grow th rate per cycle.

[0028] Figures 1A and IB are schematic examples of material stacks that include Mo layers according to various embodiments. Figures 1 A and IB illustrate the order of materials in examples of particular stacks and may be used with any appropriate architecture and application, as described further below'. Figure 1A shows a first material stack 111 featuring a substrate 102 and a molybdenum layer 108 deposited thereon. The substrate 102 may be a silicon or other semiconductor wafer, e.g., a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer, including w afers having one or more layers of material, such as dielectric, conducting, or semi-conducting material deposited thereon. In some embodiments, the substrate 102 may be or include silicon (Si) or silicon germanium (SiGe). The methods may also be applied to form metallization stack structures on other substrates, such as glass, plastic, and the like.

[0029] The stack 111 has a dielectric layer 104 on the substrate 102. The dielectric layer 104 may be deposited directly on a semiconductor surface (e.g., a Si or SiGe surface) of the substrate 102, or there may be any number of intervening layers. For example, the substrate 102 may include any number of layers deposited in various arrangements on a semiconductor surface.

[0030] Examples of dielectric layers include doped and undoped silicon oxide, silicon nitride, and aluminum oxide layers, with specific examples including doped or undoped layers of silicon nitride (SiN), silicon dioxide (SiCh), and aluminum oxide (AI2O3). The stack 111 has a layer 106 disposed between the molybdenum layer 108 and the dielectric layer 104. The layer 106 may be a diffusion barrier and / or an adhesion layer, for example. A diffusion barrier is a layer that prevents diffusion of species between layers. An adhesion layer is a layer that promotes adhesion of a layer to an underlying layer. Examples of diffusion barrier and adhesion layers include titanium nitride (TiN), titanium / titanium nitride (Ti / TiN), tungsten (W), tungsten nitride (WN), and tungsten carbon nitride (WCN). The molybdenum layer 108 is the main conductor of the structure. In some embodiments, the molybdenum layer 108 may include multiple bulk layers deposited at different conditions. The molybdenum layer 108 may or may not include a molybdenum nucleation layer. In the depicted example of Figure 1A, the molybdenum layer 108 is deposited directly on the layer 106. In other embodiments (not depicted), the molybdenum layerAtorney Docket No. LAM1P078WO-12131-1WO 108 may be deposited on a separate layer such as a growth initiation layer that includes another material, such as a tungsten (W) or W-containing growth initiation layer. The growth initiation layer may be used to facilitate nucleation and grow th of the molybdenum layer 108.

[0031] Figure IB shows another example of a stack 121. In this example, the stack 121 includes the substrate 102, dielectric layer 104, with molybdenum layer 108 deposited directly on the dielectric layer 104, without an intervening diffusion barrier or adhesion layer. The molybdenum layer 108 is as described with respect to Figure 1 A. By using molybdenum as the main conductor, low resistivity thin films can be obtained. Examples of low resistivity thin films include films with resistivity less than 40 uOhm-cm at 60 angstroms thickness and less than 15 uOhm-cm at 200 angstroms thickness.

[0032] In some embodiments, a stack (not shown) may include the substrate, a conductive layer, and a molybdenum layer deposited onto the conductive layer. As used herein, a conductive layer is a layer having a conductivity of at least 104Q'l-cm-1at room temperature. Examples include molybdenum on a metal layer (e.g., a W layer, or another Mo layer). In these embodiments, there is no dielectric layer betw een the molybdenum layer and the conductive layer. Similarly, the stack may include molybdenum deposited directly on a metal compound layer. Examples include molybdenum on a metal nitride layer (e.g., TiN, WN, or MoN). In still some other embodiments of a stack (not shown), the stack may include a substrate and a molybdenum layer deposited directly on the substrate, including directly on a semiconducting surface, on a dielectric surface, or on a conductive surface. Figures 1A and IB illustrate examples of the order of materials in a particular stack and may be used with any appropriate architecture and application, with examples described further below.

[0033] The methods described herein are performed on a substrate that may be housed in a chamber. The substrate may be a silicon or other semiconductor wafer, including w afers having one or more layers of material, such as dielectric, conducting, or semiconducting material deposited thereon. The methods are not limited to semiconductor substrates and may be performed to fill any feature with molybdenum.

[0034] Substrates may have features such as vias or contact holes, which may be characterized by one or more narrow^ and / or re-entrant openings, constrictions w ithin the feature, and high aspect ratios. A feature may be formed in one or more of the above-described stacks or layers within a stack. For example, the feature may be formed at least partially in a dielectric layer. In some embodiments, a feature may have an aspect ratio of at least about 2:1, at least about 4:1, at least about 6: 1, at least about 10: 1, at least about 25: 1, or higher. One example of a feature is a hole or via in a semiconductor substrate or a layer on the substrate.

[0035] Figure 2A depicts a schematic example of a DRAM architecture, including a Mo buriedAtorney Docket No. LAM1P078WO-12131-1WO wordline (bWL) 208 in a silicon substrate 202. The Mo bWL is formed in a trench etched in the silicon substrate 202. Lining the trench is a conformal barrier layer 206 and an insulating layer 204. The conformal barrier layer 206 is disposed between the insulating layer 204 and the silicon substrate 202. In this example, the insulating layer 204 may be a gate oxide layer formed from a high-k dielectric material such as a silicon oxide or silicon nitride material. In some embodiments disclosed herein, the conformal barrier layer 206 is TiN or a tungsten-containing layer, such as WN or WCN layer. In some embodiments, a conformal tungsten-containing grow th initiation layer (not shown) may be present between the conformal barrier layer 206 and the molybdenum bWL 208. Alternatively, the molybdenum bWL 208 may be deposited directly on a TiN or other diffusion barrier. In some embodiments, one or both of layers 204 and 206 is not present.

[0036] The bWL structure shown in Figure 2A is one example of an architecture that includes a molybdenum fill layer. During fabrication of the bWL, molybdenum is deposited into a feature that may be defined by an etched recess in the silicon substrate 202 that is conformally lined with layers 206 and / or 204, if present.

[0037] Figures 2B-2H are additional schematic examples of various structures into which molybdenum may be deposited in accordance with disclosed embodiments. Figure 2B shows an example of a cross-sectional depiction of a vertical feature 201 to be filled with Mo. The feature can include a feature hole 205 in a silicon substrate 202. The feature hole 205 may have an underlayer 203 lining the sidewall or interior of the feature hole 205 and may form the interior surfaces. The feature hole 205 or other feature may have a dimension near the opening, e.g., an opening diameter or line width of between about 10 nm to 500 nm, for example, betw een about 25 nm and about 300 nm. The feature hole 205 can be referred to as an unfilled feature or simply a feature. The vertical feature 201, and any feature, may be characterized in part by an axis 218 that extends through the length of the feature, with vertically -oriented features having vertical axes and horizontally-oriented features having horizontal axes. The underlayer 203 can be, for example, a diffusion barrier layer, an adhesion layer, a nucleation layer, a combination of thereof, or any other applicable material. Non-limiting examples of underlayers can include dielectric layers and conducting layers. Examples of dielectric materials include oxides, such as SiCh and AI2O3; nitrides, such as SiN; carbides, such as nitrogen-doped silicon carbide (NDC) and oxy gen-doped silicon carbide (ODC); and low k dielectrics, such as carbon-doped SiCh. In particular implementations, an underlayer can be one or more of titanium, titanium nitride, tungsten nitride, titanium aluminide, tungsten, and molybdenum. In some embodiments, the under-layer is tungsten-free. In some embodiments, the underlayer is molybdenum-free.

[0038] In some embodiments, features are wordline features in a 3D NAND structure. For example, a substrate may include a wordline structure having an arbitrary number of wordlinesAtorney Docket No. LAM1P078WO-12131-1WO (e.g.. 50 to 450) with vertical channels at least 200A deep. Examples of wordline features are described further below. Another example of a feature is a trench in a substrate or layer. Features may be of any depth. In various embodiments, the feature may have an underlayer, such as a barrier layer or adhesion layer. Non-limiting examples of underlayers include dielectric layers and conducting layers, e.g., silicon oxides, silicon nitrides, silicon carbides, metal oxides, metal nitrides, metal carbides, and metal layers.

[0039] Figure 2C shows an example of a vertical feature 201 that has a re-entrant profile. A reentrant profile is a profile that narrows from a botom, closed-end, or interior of the feature to the feature opening. According to various implementations, the profile may narrow gradually and / or include an overhang at the feature opening. Figure 2C shows an example of the later, with an underlayer 213 lining the sidewall or interior surfaces of the feature hole 205. Similar to Figure 2B, the underlayer 213 can be a diffusion barrier layer, an adhesion layer, a nucleation layer, a combination of thereof, or any other applicable material. Non-limiting examples of under-layers can include dielectric layers and conducting layers. The underlayer 213 forms an overhang 215 such that the underlayer 213 is thicker near the opening of the vertical feature 201 than inside the vertical feature 201.

[0040] In some implementations, features having one or more constrictions within the feature may be filled. Figure 2D shows examples of views of various filled features having constrictions. Each of the examples (a), (b), and (c) in Figure 2D includes a constriction 209 at a midpoint within the feature. The constriction 209 can be, for example, between about 15 nm-20 nm wide. Constrictions can cause pinch off during deposition of molybdenum in the feature using conventional techniques, with deposited metal blocking further deposition past the constriction before that portion of the feature is filled, resulting in voids in the feature. Example (b) further includes an overhang 215 (such as, a liner / barrier overhand) at the feature opening. Such an overhang could also be a potential pinch-off point. Example (c) includes a constriction 212 further away from the field region than the overhang 215 in example (b).

[0041] Horizontal features, such as in 3-D memory structures, can also be filled. Figure 2E shows an example of a horizontal feature 250 that includes a constriction 251. For example, horizontal feature 250 may be a word line in a 3-D NAND (also referred to as vertical NAND or VNAND) structure. In some implementations, the constrictions can be due to the presence of pillars in a 3D NAND or other structure. Figure 2F presents a cross-sectional side view of a 3-D NAND structure 210 (formed on a silicon substrate 202) having 3-D NAND stacks (left 225 and right 226), central vertical structure 230, and a plurality of stacked horizontal wordline features 220 with openings 222 on opposite sidewalls 240 of central vertical structure 230. Note that Figure 2F displays two “stacks” of the exhibited 3-D NAND structure 210, which together form theAtorney Docket No. LAM1P078WO-12131-1WO “trench-like” central vertical structure 230. However, in certain embodiments, there may be more than two such stacks arranged in sequence and running spatially parallel to one another, the gap between each adjacent pair of stacks forming a central vertical structure 230, like that explicitly illustrated in Figure 2F. In this embodiment, the horizontal wordline features 220 are 3-D memory' wordline features that are fluidically accessible from the central vertical structure 230 through the openings 222. Although not explicitly indicated in the figure, the horizontal wordline features 220 present in both the 3-D NAND stacks 225 and 226 shown in Figure 2F (i.e., the left 3-D NAND stack 225 and the right 3-D NAND stack 226) are also accessible from the other sides of the stacks (far left and far right, respectively) through similar vertical structures formed by additional 3-D NAND stacks (to the far left and far right, but not shown). Each 3-D NAND stack 225, 226 contains a stack of wordline features that are fluidically accessible from both sides of the 3-D NAND stack through a central vertical structure 230. In the particular example schematically illustrated in Figure 2F, each 3-D NAND stack contains 6 pairs of stacked wordlines. How ever a 3-D NAND memory layout may contain any number of vertically stacked pairs of wordlines.

[0042] The wordline features in a 3-D NAND stack can be formed by depositing an alternating stack of silicon oxide and silicon nitride layers, and then selectively removing the nitride layers leaving a stack of oxides layers having gaps betw een them. These gaps are the wordline features. Any number of wordlines may be vertically stacked in such a 3-D NAND structure so long as there is a technique for forming them available, as well as a technique available to successfully accomplish (substantially) void-free fills of the vertical features. Thus, for example, a VNAND stack may include betw een 2 and 512 horizontal w ordline features, betw een 2 and 256 horizontal wordline features, between 8 and 128 horizontal yvordline features, or between 16 and 64 horizontal wordline features, and so forth (the listed ranges understood to include e the recited endpoints).

[0043] Figure 2G presents a cross-sectional top-down view of the same 3-D NAND structure 210 shown in the side view in Figure 2F with the cross-section taken through the horizontal section 260 as indicated by the dashed horizontal line in Figure 2F. The cross-section of Figure 2G illustrates several rows of pillars 255, which are shown in Figure 2F to run vertically from the base of the substrate 202 to the top of the 3-D NAND structure 210. In some embodiments, the pillars 255 are formed from a polysilicon material and are structurally and functionally significant to the 3-D NAND structure 210. In some embodiments, such polysilicon pillars may serve as gate electrodes for stacked memory cells formed within the pillars. The top-view of Figure 2G illustrates that the pillars 255 form constrictions in the openings 222 to wordline features 220. Fluidic accessibility' of wordline features 220 from the central vertical structure 230 via openings 222 (as indicated by the arrows in Figure 2G) is inhibited by pillars 255. In some embodiments,Atorney Docket No. LAM1P078WO-12131-1WO the size of the horizontal gap between adjacent poly silicon pillars is between about 1 and 20 nm. This reduction in fluidic accessibil ity increases the difficulty of uniformly filling wordline features 220 with material. The structure of wordline features 220 and the challenge of uniformly filling them with molybdenum material due to the presence of pillars 255 is further illustrated in Figures 2H. 21, and 2J.

[0044] Figure 2H exhibits a vertical cut through a 3-D NAND structure similar to that shown in Figure 2F, but here focused on a single pair of wordline features 220 and additionally schematically illustrating a fill process which resulted in the formation of a void 275 in the filled wordline features 220. Figure 21 also schematically illustrates void 275, but in this figure illustrated via a horizontal cut through pillars 255, similar to the horizontal cut exhibited in Figure 2G. Figure 2J illustrates the accumulation of molybdenum material around the constrictionforming pillars 255, the accumulation resulting in the pinch-off of openings 222, so that no additional molybdenum material can be deposited in the region of voids 275. Apparent from Figures 2H and 21 is that void-free molybdenum fill relies on migration of sufficient quantities of deposition precursor down through central vertical structure 230, through openings 222, past the constricting pillars 255, and into the furthest reaches of wordline features 220, prior to the accumulated deposition of molybdenum around pillars 255 causing a pinch-off of the openings 222 and preventing further precursor migration into wordline features 220. Similarly, Figure 2J exhibits a single wordline feature 220 viewed cross-sectionally from above and illustrates how a generally conformal deposition of molybdenum material begins to pinch-off the interior of wordline feature 220 due to the fact that the significant width of pillars 255 acts to partially block, and / or narrow, and / or constrict what would otherwise be an open path through wordline feature 220. (It should be noted that the example in Figure 2J can be understood as a 2-D rendering of the 3-D features of the structure of the pillar constrictions shown in Figure 21, thus illustrating constrictions that would be seen in a plan view rather than in a cross-sectional view.)

[0045] Three-dimensional structures may need longer and / or more concentrated exposure to precursors to allow the innermost and botommost areas to be filled. Three-dimensional structures can be particularly challenging when employing molybdenum halide and / or molybdenum oxyhalide precursors because of their proclivity to etch, with longer and more concentrated exposure allowing for more etch as parts of the structure.

[0046] Figures 2K and 2L show examples of an asymmetric trench structure DRAM bWL. Some fill processes for DRAM bWL trenches can distort the trenches such that the final trench width and resistance Rs are significantly non-uniform. Figure 2K shows an unfilled feature 261 and filled feature 265 that exhibits line bending after fill. In this example, the features are a narrow asymmetric trench structure DRAM bWL. As shown, multiple features 283 are depicted on aAtorney Docket No. LAM1P078WO-12131-1WO substrate. These features 283 are spaced apart, and in some embodiments, adjacent features have a pitch between about 20 nm and about 60 nm or between about 20 nm and 40 nm. The pitch is defined as the distance between the middle axis of one feature to the middle axis of an adjacent feature. The unfilled features 261 may be generally V-shaped, as shown in feature 283, having sloped sidewalls where the width of the feature narrows from the top of the feature to the botom of the feature. The features widen from the feature botom 273b to the feature top 273a. After some fill operations, line bending may be observed within the filled feature 265. In some situations, a cohesive force between opposing surfaces of a trench pulls the trench sides together, as depicted by arrows 267. This phenomenon is illustrated in Figure 2L and may be characterized as “zipping up” the feature. As the feature 283 is filled, more force is exerted from a center axis 299 of the feature 283, causing line bending. For example, molybdenum may be deposited on the sidewalls of the feature 283. Deposited molybdenum 284a and 284b on sidewalls of feature 283 thereby interact in close proximity, where molybdenum-molybdenum bond radius r is small, thereby causing cohesive interatomic forces between the smooth growing surfaces of molybdenum and pulling the sidewalls together, thereby causing line bending.

[0047] Provided below are methods of filling features with molybdenum. The methods described herein include surface treatment and deposition operations, which may be used to fill substrate features such as those described above. As described above, molybdenum offers several benefits over other metals. Examples of feature fill for horizontally-oriented and vertically-oriented features are described below. It should be noted that in at least most cases, the examples are applicable to both horizontally-oriented and vertically-oriented features. Horizontally-oriented features generally refer to features oriented such that the feature axis is parallel to the plane of the substrate surface. Vertically-oriented features generally refer to features oriented such that the feature axis is orthogonal to the plane of the substrate surface.

[0048] In some embodiments, methods of filling features that include exposing a feature to a metal halide, e.g., a molybdenum halide, prior to feature fill are described. The metal halide can etch, deposit, and / or otherwise treat material on the feature bottom and / or sidewalls.Interconnect Metallization

[0049] Figure 5 is a process flow diagram illustrating example operations in a method for interconnect metallization. The process begins with an operation 501 in which a feature having dielectric sidewalls and a metal-containing contact is provided. The metal-containing contact may be at the botom of the feature with the dielectric sidewalls extending from the feature opening to the metal-containing contact. The feature may be provided to a processing chamber. In some embodiments, one or more processing operations may occur in the processing chamber to formAtorney Docket No. LAM1P078WO-12131-1WO the feature having dielectric sidewalls and a metal-containing containing contact.

[0050] Examples of dielectric sidewalls include silicon-containing layers such as oxides and nitrides. Examples of metal-containing contacts include metals and metal compound films. The metal-containing contact may be generally conductive, having a conductivity of at least 104Q1-cm1at room temperature. Examples include TiN, TiAlC, W. Co, Mo, Ru, Cu. Ni. Rh. Ir, Ta, Ti, TiSix, RuSix, NiPtSix, TiSiN, MoSix, CoSix. and TaN.

[0051] In some embodiments, a surface oxide is present on the metal-containing contact. Still further, in some embodiments, a layer containing other impurities is present on the metalcontaining contact.

[0052] In some embodiments, an etch operation to remove a liner layer from at least the sidewalls of the feature is performed prior to operation 501. For example, a feature may include a TiN liner layer conformally coating the botom and sidewalls. An etch may be performed to remove the TiN layer from the sidewalls, exposing dielectric material. The sidewall surfaces are then silicon oxide or other dielectric material.

[0053] In an operation 503, a pre-treatment is performed. Operation 503 can remove surface oxide and / or etch residue, for example. Examples of etch residue include fluorocarbons and hydrocarbon polymers. According to various embodiments, operation 503 involves exposure to a molybdenum halide gas and / or a plasma clean.

[0054] A plasma clean may be remotely generated or generated in-situ. In some embodiments, operation 503 involves exposure to a reducing plasma such as a EE plasma. In some embodiments, operation 503 treats the dielectric sidewalls. For example, it may remove organic materials and / or reduce oxygen in the dielectric sidewalls. This can improve subsequent Mo growth selectivity on a metal -containing surface with respect to the sidewalls.

[0055] In some embodiments, the clean involves exposure to a molybdenum halide gas, e.g., MoCIs. This may be a plasma-free operation. Plasma-free refers to the operation performed without activating a plasma. Exposure to a molybdenum halide can remove impurities from the metal contact. For example, in embodiments in which an amorphous Mo-containing layer is present, it can remove all or at least a portion of the layer. In the same or other embodiments, exposure to a molybdenum halide inhibits nucleation on the dielectric sidewall surfaces.

[0056] In some embodiments, a molybdenum chloride compound is used. Molybdenum-containing compounds are also referred to herein as Mo-containing precursors or Mo precursors. Molybdenum chlorides are given by the formula MoClx, where x is 2, 3, 4, 5, or 6, and include molybdenum dichloride (MoCh), molybdenum trichloride (MoCk), molybdenum tetrachloride (MoCty), molybdenum pentachloride (MoCh), and molybdenum hexachloride (MoCle). In some embodiments, M0CI5 or MoCle are used. While the description chiefly refers to MoCkAtorney Docket No. LAM1P078WO-12131-1WO compounds, in other embodiments, other molybdenum halides may be used. Molybdenum halide precursors are given by the formula MoXz, where X is a halogen (fluorine (F), chlorine (Cl), bromine (Br), or iodine (I)) and z is 2, 3, 4, 5, or 6. Examples of MoXzprecursors include molybdenum fluoride (MoFe). In some embodiments, a non-fluorine-containing MoXz precursor is used to prevent fluorine etch or incorporation. In some embodiments, anon-bromine-containing and / or a non-iodine-containing MoXzprecursor is used to prevent etch or bromine or iodine incorporation.

[0057] In some embodiments, operation 503 involves exposure to the molybdenum halide compound without a co-reactant gas. In such embodiments, the molybdenum halide may be pulsed or delivered in a continuous dose. For examples, MoCls may be pulsed with argon (Ar) other inert gas for a certain number of cycles. Alternatively, a continuous dose of Mods can be delivered followed by an Ar purge.

[0058] In some embodiments, operation 503 involves exposure to the molybdenum halide compound with a co-reactant gas to deposit Mo. The co-reactant is generally H2, though other reducing agents as described below may be used. In one example sequence, M0CI5 pulses are alternated with H2 pulses with interv ening purge gas pulses. In another example, M0CI5 pulses are alternated with H2 pulses with no interv ening purge gas pulses. In another example sequence, M0CI5 pulses are alternated with H2 pulses with a purge gas pulse directly after only one of the reactant gases in each cycle. In another example sequence, M0CI5 is flowed with H2. In the further example sequence, the co-flowed reactants are pulsed with an alternating Ar pulse. In another example sequence, H2 gas may be flowed into the chamber and is continuously flowing into the chamber while M0CI5 is intermitently flowing into the chamber. In any of these examples, another molybdenum halide and / or another inert gas may be used instead of M0CI5 and Ar, respectively. In some embodiments, sequences with a co-reactant may be employed when metals besides Mo are at the feature botom. In such embodiments, a Mo surface layer may be formed facilitating subsequent Mo growth. For example, if a W, Co, or Ru layer is at the feature botom, operation 503 may be used to form a thin Mo surface layer.

[0059] In addition to or instead of any of the operations described above, operation 503 can involve an atomic layer clean with a chlorine-based plasma, a hydrogen fluoride (HF) vapor clean, an ammonium fluoride (NH4F) clean, or a treatment using other reducing agents. These operations may be used to reduce oxide off a feature surface.

[0060] The process continues at operation 505 with selective deposition of a Mo pre-fill layer on the metal-containing contact. The selective deposition deposits a layer on the metal-containing without significant deposition on the dielectric sidew alls.

[0061] In some embodiments, this operation involves reaction using a molybdenum halide or aAtorney Docket No. LAM1P078WO-12131-1WO molybdenum oxyhalide precursor. In some embodiments, M0CI5 is used as it has good selectivity as described below.

[0062] Process conditions such as the precursor gas, the reducing agent, substrate temperature, process pressure, and exposure time may affect the selectivity of the Mo film being deposited. Different precursor gases may have different process windows in which Mo film may be selectively deposited. For example, M0CI5 is selective while MoChChis not, i.e., under the same temperature and pressure conditions, the precursor gas of M0CI5 may deposit Mo only on a conductive surface and not on a dielectric surface while a precursor gas of MOO2CI2 will deposit Mo on both conductive and dielectric surfaces. Generally speaking, M0CI5 gas has a large process window, i.e., large temperature and pressure range, where the precursor gas retains its selectivity. For example, M0CI5 may be selectively deposited on a metal material with respect to a dielectric material where the process temperature is 300°C to 800°C. In some embodiments, the substrate temperature is 350°C to 550°C. Generally speaking, higher process temperatures and higher process pressures reduce the selectivity of the deposited film. For example, at higher temperatures, a precursor gas such as M0CI5 may lose its selectivity and deposit Mo film on both a metal surface and dielectric surface within a feature.

[0063] In some embodiments, operation 505 can be a thermal or plasma-based process. In some embodiments, operations 505 is a plasma-enhanced ALD (PEALD) or plasma enhanced CVD (PECVD) process using a molybdenum halide precursor. In some embodiments, the molybdenum halide precursor is M0CI5. Hydrogen (H2) or other reducing agent may be used for the PEALD or PECVD deposition.

[0064] In some embodiments, operation 505 can be a thermal process. It can be easier to achieve selectivity with a thermal process. In some such embodiments, operation 505 can involve a pulsed chemical vapor deposition (pulsed CVD) process.

[0065] Figure 6 shows cross-sectional representations of a feature during various stages of the process of Figure 5. The feature including a conductive botom material 602 and dielectric sidewalls 604 is provided to a processing tool, where it undergoes a pre-treatment operation as described with reference to operation 503 of Figure 5. After pretreatment, the surface of the conductive botom material may be free of oxide and other residues, for example. A selective deposition is then performed to deposit Mo 606 at the botom of the feature. The selective deposition forms Mo on the conductive botom material 602 without significant deposition on the dielectric sidewalls 604. This depicts an example of feature after operation 505 of Figure 5 with a layer of Mo is in the feature without deposition on the sidewalls above the layer.

[0066] Returning to Figure 5, a conformal Mo liner is deposited in an operation 507. The conformal Mo liner is deposited by a non-selective method that deposits on both the Mo pre-fillAtorney Docket No. LAM1P078WO-12131-1WO layer and the dielectric sidewalls. In some embodiments, MOO2CI2 may be used to deposit a conformal layer. The deposition may be a PEALD deposition using M0O2O2. Above about 400°C, thermal ALD may be used to deposit a conformal layer using MOO2CI2. In some embodiments, M0CI5 may be used with a PEALD to deposit the conformal layer. This is shown in Figure 6A. with conformal Mo liner 608 deposited in the feature.

[0067] Returning to Figure 5, the process may continue with fill of the feature with Mo in an operation 509. The same or different Mo precursor may be used for operations 507 and 509. Operation 509 may include one or more deposition, inhibition, and etch operations as described further below. The sequence of these operations as well as the precursor used can depend on the feature profile. For example, if the feature is re-entrant, one or more etch and / or inhibition operations may be used to tailor the fill. For less challenging structures, such as V-shaped structures, PEALD using MOO2CI2 may be used, for example. These structures may also be filled using a pulsed CVD process in some embodiments. Further description of possible fill techniques of re-entrant features is described below. Figure 6 shows the structure after the fill, with bulk Mo film 601 in the feature.Molybdenum Deposition

[0068] Deposition of molybdenum as described herein involves reacting a Mo-containing precursor, also referred to as a molybdenum precursor. In some embodiments, a molybdenum halide compound as described above is used. In methods including surface treatment using a molybdenum halide compound, the same or different compound may be used for deposition.

[0069] In some embodiments, a Mo precursor is a molybdenum chloride (MoClx) compound also referred to as a molybdenum chloride precursor or MoClx precursor. Molybdenum chloride precursors are given by the formula MoCk, where x is 2, 3, 4, 5, or 6, and include molybdenum dichloride (M0CI2), molybdenum trichloride (M0CI3), molybdenum tetrachloride (MoCk), molybdenum pentachloride (MoCk). and molybdenum hexachloride (MoCk). In some embodiments, MoCk or MoCk are used. While the description chiefly refers to MoCk precursors, in other embodiments, other molybdenum halide precursors may be used. Molybdenum halide precursors are given by the formula MoXz, where X is a halogen (fluorine (F), chlorine (Cl), bromine (Br), or iodine (I)) and z is 2, 3, 4, 5, or 6. Examples of MoXzprecursors include molybdenum fluoride (MoFe). In some embodiments, a non-fluorine-containing MoXz precursor is used to prevent fluorine etch or incorporation. In some embodiments, anon-bromine-containing and / or a non-iodine-containing MoXzprecursor is used to prevent etch or bromine or iodine incorporation.

[0070] In some embodiments, the feature may be filled using a molybdenum oxyhalideAtorney Docket No. LAM1P078WO-12131-1WO precursor. Molybdenum oxyhalide precursors are given by the formula MoOyXz, where X is a halogen (fluorine (F), chlorine (Cl), bromine (Br), or iodine (I)), and y and z are numbers greater than 0 such that MoOyXzforms a stable compound. Examples of molybdenum oxyhalides include molybdenum dichloride dioxide (MOO2CI2), molybdenum tetrachloride oxide (MoOCk), molybdenum tetrafluoride oxide (M00F4), molybdenum dibromide dioxide (MoChBn). and the molybdenum iodides MOO2I, and MO4O11I. It should be understood that as used herein the term molybdenum oxyhalide precursor may refer to a molybdenum oxyhalide precursor as described above or a molybdenum-containing oxyhalide precursor that includes molybdenum, oxygen, a halide and one or more other elements. In some embodiments, molybdenum oxyhalide or molybdenum-containing oxyhalides may include multiple different halogens (e.g., F and Cl and / or I and / or Br, etc.). A feature may be filled with molybdenum using a MoXxprecursor, MoOyXz precursor, or a combination thereof.

[0071] For deposition of molybdenum into the feature, the molybdenum precursor may be reacted with a co-reactant. Examples of co-reactants include hydrogen (H2), silane (SiFU), diborane (B2H6), germane (GeFL), ammonia (NFE), and hydrazine (N2H4). Ammonia and hydrazine may be used to deposit molybdenum nitrides or molybdenum oxynitrides.

[0072] In some embodiments, deposition of molybdenum may use a plasma-based process. Gas may be fed into a remote or in-situ plasma generator to generate plasma species. Examples of gas that may be used to generate plasma may be a hydrogen-containing gas, such as H2, nitrogencontaining gas, such as nitrogen (N2) and other gases, such as Ar and NHs. The plasma species may be inert or react with the molybdenum precursor to form a film.

[0073] A feature may be filled with molybdenum by atomic layer deposition (ALD) or chemical vapor deposition (CVD). Thermal ALD or plasma enhanced ALD (PEALD) may be used. Similarly, thermal CVD or plasma enhanced CVD (PECVD) may be used.

[0074] ALD is a surface-mediated deposition technique in which doses of a precursor and a reactant are sequentially introduced into a deposition chamber. One or more cycles of sequential doses of a molybdenum precursor and reactant may be used to deposit Mo. For example, in the deposition of an initial molybdenum layer (e.g., as in operation 505 or 507 of Figure 5), M0CI5 may be used as a precursor and H2 as a reducing agent. Doses of M0CI5 and H2 are sequentially introduced into the deposition chamber with a purge gas, such as argon, flowed between. For ALD. the temperature of the substrate and the pressure of the chamber may be controlled. For example, the substrate may be heated between 200°C and 800°C, e.g., between 250°C and 550°C or between 300°C and 500°C between 350°C and 450°C. In some embodiments, the chamber may be pressurized between 10 Torr and 200 Torr, e.g., between 50 Torr and 90 Torr. In some embodiments, the temperature and / or pressure may be used to control the rate of reactions. InAtorney Docket No. LAM1P078WO-12131-1WO some embodiments, the temperature and / or pressure may be used to control selectivity.

[0075] In some embodiments, the Mo precursor is a molybdenum fluoride (MoFx) compound, also referred to as a molybdenum fluoride precursor or MoFxprecursor. Molybdenum chloride precursors are given by the formula MoFx, where x is 4, 5, or 6, and include molybdenum tetrafluoride (M0F4). molybdenum pentafluoride (M0F5), and molybdenum hexafluoride (MoFe).

[0076] MoFe can be advantageous as it has a boiling point of 34°C. Being a gas at standard pressure and 35°C allows MoFe to be delivered through a mass flow controller (MFC) at room temperature, without heating and without condensing and forming particles. However MoFe is an aggressive etchant and exposure to MoFe during a process can result in etching instead of or in addition to Mo deposition. In some embodiments, deposition using MoFe involves providing a flow of MoFe in a process gas with the MoFe at a molar concentration of 0.01% or less. Concentration may be significantly lower in some embodiments, for example, 0.008% or less, 0.005% or less, or 0.004% or less. These values can also be expressed as parts per million (ppm) of a gas: 100 ppm (100 MoFe molecules per 1 million gas particles (atoms, molecules)) or less, 80 ppm or less, or 40 ppm or less. At temperatures between 200°C and 650°C, for example, a molar concentration at or below 0.004% results in CVD deposition when flowed with H2 and argon. Higher temperatures may be used to favor the deposition reaction and allow higher concentrations of MoFe, e.g., up to 0.01%. In some embodiments, concentrations may be 0.0039% or .0035% or less. In some embodiments, the MoFe concentration is at least 0.00004% or at least 0.0001%. Concentration may be very low with an exposed metal surface to grow on, for example.

[0077] Deposition using MoFe with H2 as reducing agent occurs only at unusually low concentration. As an example, for 0.5 seem of MoFe. a total flow rate of 13,500 seem may be used, for a MoFe concentration of 0.0037%. Deposition using metal halides and hydrogen generally involves much higher concentrations. For example, deposition of molybdenum using molybdenum hexachloride and hydrogen can be performed using concentrations 5 to 10 times higher than those used for MoFe.

[0078] In some embodiments. MoFe may be used at higher concentrations and lower temperatures with a reducing agent that is stronger than that of hydrogen. Lower temperatures can reduce or prevent etching with MoFe; however, at low temperatures H2 may not result in deposition. Stronger reducing agents such silane, disilane, polysilanes and diborane may be used for deposition at lower temperatures (e.g., below 200°C). The resulting films may not be pure molybdenum and in some cases are more resistive than those deposited using H2 as the reducing agent. For these reasons they may not be appropriate for some applications.

[0079] As described above, the methods described herein may be used to fill 3D NAND structures. Figure 3 is a process diagram show operations in a DED method of filling wordlineAtorney Docket No. LAM1P078WO-12131-1WO features of a 3D NAND structure. Figure 4 illustrates certain operations of the process of Figure 3. The method of Figure 3 begins with providing a 3D NAND structure having unfilled wordline features in an operation 301. Examples of such structures are described above with respect to Figures 2F-2J. Figure 4 shows a top-down view of pillars of an example of part of a 3D NAND structure. The outer pillars are adjacent to the slit from which the wordline feature are fluidically accessible. In the depicted example, 3 rows of staggered pillars are shown. According to various embodiments, the number of rows may be, e.g., 20 or more. As described above with reference to Figure 2F, there are slits on either side such that reaching the innermost wordlines of 20 rows of pillars involves diffusion through 10 rows of pillars from a slit. Referring back to Figure 2F, the critical dimension of the central vertical structure 230 may be on the order of hundreds of nanometers, with the depth more than 1 micron. The critical dimension of the wordline features prior to molybdenum deposition may be, e.g., 10-20 nm, or 12-16 nm. As described, it can be challenging to fill such features uniformly and void-free. A substrate that includes the 3D NAND structure may be provided to a semiconductor processing tool. As provided, the pillars may include a dielectric layer, e.g., an AI2O3 layer as shown in Figure 4.

[0080] Returning to Figure 3, the method includes depositing a conformal liner and thin film in the wordline features of the 3D NAND structure in an operation 303. An example of a conformal liner + film is shown in left panel of Figure 4. As shown, Mo is deposited conformally around each of the features, evenly from the exterior (slit side) to the interior (non-slit side). This partial fill deposition may be referred to as the Depl operation. In some embodiments, the conformal liner and thin film deposition may be a single film that is the result of multiple cycles of a single ALD process used to deposit a conformal film of about 4 to 6 nm. However, in some embodiments, a nucleation layer is deposited. This may be referred to as a liner layer. For example, molybdenum does not nucleation well on AI2O3 or other oxide surfaces. The nucleation layer may be deposited as described above. In some embodiments, ammonia is used as a reducing agent to deposit a molybdenum nitride or molybdenum oxynitride liner layer of less than 2 nm. This allows a subsequent process using hydrogen as the reducing agent to deposit on the liner layer to increase the total thickness, e g., to about 4 to 6 nm. The molybdenum nitride or molybdenum oxide nitride layer is converted to molybdenum during the Mo-containing precursor / ^ ALD process. The thicknesses of the liner layer and liner + thin film layer may be modified depending on the dimensions of the structure. The ALD process in Figure 3 is typically a thermal ALD process. This is because achieving lateral fill throughout the wordline feature is easier with a thermal process. Conformal fill throughout the complex structure is also facilitated by use of a molybdenum oxyhalide precursor such as MOO2CI2 rather than a molybdenum halide such as MoCh. This because molybdenum halides are stronger etchants. With a large and complexAtorney Docket No. LAM1P078WO-12131-1WO structure, a molybdenum halide may etch at the top of the structure while the precursor diffuses through the structure.

[0081] In some embodiments, a thermal ALD process using MOO2CI2 and NH3 is used to deposit a conformal liner at 350°C to 550°C. In some embodiments, a thermal ALD process using MOO2CI2 and H2 is used to deposit a conformal thin film on the liner at a higher temperature, e.g., 550°C to 615°C. To achieve top to bottom as well as lateral uniformity, charge volumes may be used for the precursor and / or reducing agent doses.

[0082] An optional etch pre-treatment may be performed in an operation 305. The pre-etch treatment makes it easier to etch in the subsequent operation. If performed, the pre-etch treatment may be conformal or non-conformal. In some embodiments, it is non-conformal, being preferentially applied to the outer wordlines relative to the inner wordlines. The pre-etch treatment may be an oxidation or nitridation of the molybdenum. The pre-etch treatment may be a plasma or thermal treatment. In some embodiments, a thermal pre-etch treatment may be easier to control the diffusion into the structure and extent of treatment.

[0083] For oxidation, the structure may be exposed to ozone. And, because relatively high temperatures (e.g., 450° to over 600°C), exposure to oxygen gas (O2) or water vapor may be used. For nitridation, ammonia may be used, or another nitrogen-containing gas or plasma. Operation 305 has top to botom uniformity. As in operation 303, charge volumes may be used to achieve this.

[0084] After the optional pre-etch treatment, an etch that is preferential to the molybdenum in the outer wordlines is performed in an operation 307. In the exterior portion of the wordline feature the oxide of the feature may be exposed. The interior portion of the wordline may be etched less such that molybdenum may remain on the interior features. This is illustrated in the middle panel of Figure 4, with the molybdenum on the outermost pillars removed, the molybdenum in the second row of pillars mostly removed, and the molybdenum on the third row of pillars intact. In some embodiments, the molybdenum is thinned but not completely removed from any portion of the wordline features.

[0085] The extent of etching may be determined based on how many pillars there are, the geometry of the structure, etc. For example, a first etch may be targeted such that molybdenum is removed from all but the innermost pillars, with a subsequent etch leaving molybdenum on the next innermost row, etc. The pre-etch treatment can be used to tune the etch profile. In addition or instead of the pre-etch treatment, concentration of the etchant and / or dose time can be used to control the diffusion into the structure and the extent of etching. Chamber pressure and pedestal temperature are the other parameters that can be varied to tune the etch profile. Chamber pressure is used to control chemical diffusion and temperature is used to control the reactivity of theAtorney Docket No. LAM1P078WO-12131-1WO chemical with the Mo surface.

[0086] Higher concentration (and thus higher partial pressure) of the etchant can be used to reach further into the structure. Similarly, a continuous dose or longer pulsed doses will facilitate diffusion. Lower partial pressures and / or shorter doses of etchant can be used to keep the etchant from extending further into the structure. Charge volumes may be used for top to botom uniformity. Examples of etch processes regimes include pressure ranging from lOOmT to 100T, temperature ranging from room temperature to 750°C, gas flows ranging from 50sccm to 50slm, dose times ranging from 10ms to 60s, and etchant concentrations ranging from 0.001% to 100%.

[0087] Examples of etch chemistries include halogen-containing compounds such as M0CI5, F2, NF3, MoF6, BCh, HC1, Ch, CIF3, CI2O, SF6, CF4, HF, HBr, WF6, and CC14. For 3D NAND structures, the etch is a thermal etch to avoid plasma damage. However, aspects of the method described in Figure 3 can be applied for logic applications for which a plasma etch may be used. An optional post-etch treatment may be performed in an operation 309. Such a treatment can be used to remove byproducts that can hinder subsequent etching and / or are unwanted in the device. For example, any of oxygen, chlorine, or boron may be removed. The post-etch treatment can involve a reducing soak (e.g., H2 soak) or exposure to a halosilane, for example, for ligand exchange. Other examples include exposure to argon.

[0088] Returning to Figure 3, a thin film is deposited by ALD in an operation 311. Generally, the same precursor and process ranges as used for the conformal thin film in operation 303 are used. Use of a different precursor or process range may be performed. This may be referred to as the Dep2 operation. In embodiments in which oxide is exposed during the etch on the outer portion of the features, the deposition may be selective to the molybdenum film remaining in the wordline features. Thus, the film deposited in the subsequent deposition may be deposited selective to the inner portion of the wordline feature. As molybdenum starts to grow and a nucleation delay is overcome (if present), the deposition may become conformal. As show n in Figure 4, after the subsequent deposition, the Mo film may be thicker on the inner portion of the feature compared to the outer portion of the feature. In embodiments in which there is no nucleation delay, the Mo film may be thicker on the inner portion of the feature compared to the outer portion of the feature of the greater thickness after the etch. The right panel of Figure 4 shows the structure after the Dep2 operation. In some embodiments, a liner described above or other nucleation layer may be part of the Dep2 operation.

[0089] Operations 305-311 may be repeated one or more times to fill more of the structure. The pre-treatment, etch, post-treatment, and deposition operations conditions may varied or the same for any tw o repetitions. For example, the etch in a subsequent iteration may be tailored to extend less into the structure.Atorney Docket No. LAM1P078WO-12131-1WO

[0090] In some embodiments, MOO2CI2 is used for the Depl partial fill and Dep2 selective deposition. In other embodiments, other molybdenum precursors may be used with the same or different precursor used for Depl and Dep2. Inhibition and de-inhibition operations as described above may be incorporated into the integration processes as described above.Molybdenum Deposition by ALD

[0091] In some embodiments, a feature may be filled using an ALD process. Figure 7A shows an example of molybdenum deposition by an atomic layer deposition (ALD) process. In the example of Figure 7A, a substrate is exposed to a process gas including a molybdenum-containing precursor in an operation 701. A purge operation is then performed in an operation 703. An adsorbed layer of molybdenum-containing precursor remains, with the gas phase precursor removed. The substrate is then exposed to a reactant in an operation 705. This is ty pically a reducing agent, e.g., hydrogen. In plasma processes using a direct plasma, the plasma is ignited during this operation. In plasma processes using a direct plasma, reactant includes plasma species (e.g., hydrogen radicals) generated remotely. The reactant reacts with the adsorbed precursor to form a layer of molybdenum. A purge operation is then performed in an operation 707. Operations 701-707 may then be repeated until the molybdenum film is at a target thickness in an operation 709.

[0092] Modifications of the process described in Figure 7A can include exposure to the reactant as the first operation in each cycle, followed by a purge, exposure to the molybdenum-containing compound, and purge. Further modifications can include each cycle forming less than a monolayer. This can be performed by limiting the amount of one or both reactants. In some embodiments, the ALD process may not be strictly self-limiting. For example, one or both of the purge operations may be omited or shortened such that some gas-phase reactant remains and reacts in the gas phase. This can increase deposition rate. Further modifications can include repeating operation 701 (with or without an intervening purge) prior to performing operation 705 within a cycle. In some embodiments, operation 705 is repeated one or more times within a cycle. Such modifications facilitate diffusion through a feature. Still further, in some embodiments, the reactant may be, e.g., nitrogen-containing such that a molybdenum nitride or molybdenum oxynitride layer is formed. The temperature of the substrate and pressure in the chamber may be controlled during an ALD operation.

[0093] Figures 7B and 7C show various process conditions during each phase. Five process conditions are depicted here but it will be understood that other gases, plasma, temperature, pressure, or other conditions may also be present and may vary or be the same across different phases and across different cycles. The process conditions shown in Figures 7B and 7C include:Atorney Docket No. LAM1P078WO-12131-1WO • a hydrogen-containing gas source (which may be a source of hydrogen gas (H2)),• an argon gas source(which may act as a purge gas, carrier gas, inert gas, or any combination thereof),• a charge volume (CV) that may be charged and discharged,• molybdenum-containing precursor gas source flowed into the CV, and• argon gas source flowed into the CV.

[0094] In the example of Figure 7B, deposition cycle 710A includes four phases - first phase 720A, first purge phase 740A, second phase 750A, and second purge phase 780A. During first phase 720A, the hydrogen source gas is turned on and the molybdenum precursor gas source is turned flowing into the charge volume. During this operation only hydrogen-containing gas sources may be flowed into the process chamber.

[0095] During first purge phase 740A, argon gas source may be turned on to purge the process chamber, and molybdenum precursor gas source may flow into the charge volume for some of the first purge phase. Prior to the end of the first purge phase, argon gas may be flowed into the charge volume and the molybdenum precursor gas source is turned off.

[0096] During second phase 750A, the charge volume is discharged into the process chamber. During the second phase 750A, argon gas may still be flowed into the charge volume and thus also flowed into the process chamber. During the second phase 750A the molybdenum precursor gas source is turned off.

[0097] During second purge phase 780A, argon gas source may be turned on, the charge volume is turned off (i.e., can accumulate more charge) and molybdenum precursor gas source is turned on to flow into the charge volume.

[0098] While this process flow shows a hydrogen source turned on followed by discharging a charge volume including molybdenum precursor and argon gas, it will be understood that the alternate may be used instead (e.g., discharge charge volume, then purge, then hydrogen source on, then purge).

[0099] Deposition cycle 710A is then repeated in deposition cycle 71 OB. Deposition cycle 71 OB includes four phases - first phase 720B, first purge phase 740B, second phase 750B, and second purge phase 780B. First phase 720B may be the same as or may be different from first phase 720A. In this example, first phase 720B is the same as first phase 720 A. During first phase 720B, the hydrogen source gas is turned on and the molybdenum precursor gas source is turned flowing into the charge volume. During this operation only hydrogen-containing gas sources may be flowed into the process chamber.

[0100] During first purge phase 740B, the hydrogen source is turned off, the argon gas sourceAtorney Docket No. LAM1P078WO-12131-1WO may be turned on to purge the process chamber, and molybdenum precursor gas source may flow into the charge volume for some of the first purge phase. Prior to the end of the first purge phase, argon gas may be flowed into the charge volume and the molybdenum precursor gas source is turned off.

[0101] During second phase 750B, the charge volume is discharged into the process chamber. Argon gas may still be flowed into the charge volume and thus also flowed into the process chamber. During the second phase 750B the molybdenum precursor gas source is turned off.

[0102] During second purge phase 780B, argon gas source may be turned on, the charge volume is turned off (i.e., can accumulate more charge) and molybdenum precursor gas source is turned on to flow into the charge volume.

[0103] Figure 7C shows an alternative deposition cycle scheme that may be used in some embodiments. Figure 7C shows a timing schematic illustration that shows various operations that may be performed in accordance with certain disclosed embodiments. Process 712 includes two deposition cycles 715A and 715B but it will be understood that only one cycle or more than two cycles may be performed in accordance with certain disclosed embodiments. In this example, deposition cycles 715 A and 715B include the same operations repeated in each cycle but it will be understood that in some embodiments, various operations, or a variety' of operations may be modified or combined with other operations, such as those described in Figure 7B.

[0104] Figure 7C shows various process conditions during each phase - five process conditions are depicted here but it will be understood that other gases, plasma, temperature, pressure, or other conditions may also be present and may vary or be the same across different phases and across different cycles. The process conditions shown in Figure 7C include:• a hydrogen-containing gas source (which may be a source of hydrogen gas (H2)),• an argon gas source (which may act as a purge gas, carrier gas, inert gas, or any combination thereof),• a charge volume (CV) that may’ be charged and discharged,• molybdenum-containing precursor gas source flowed into the CV, and• argon gas source flowed into the CV.

[0105] In this example, deposition cycle 715A includes four phases - first phase 725 A, first purge phase 745A, second phase 755A, and second purge phase 785A. Notably, molybdenum precursor and argon are flowing into the charge volume during all phases. While the CV may be discharged during the second phase 755A and 755B as discussed below, the co-flow of molybdenum precursor and argon into the charge volume is continuous throughout all phases, charging the charge volume outside of second phases 755A and 755B.Atorney Docket No. LAM1P078WO-12131-1WO

[0106] During first phase 725A, the hydrogen source gas is turned on. During this operation only hydrogen-containing gas sources may be flowed into the process chamber.

[0107] During first purge phase 745A, argon gas source may be turned on to purge the process chamber, and the hydrogen source gas is turned off.

[0108] During second phase 755A, the charge volume is discharged into the process chamber. During the second phase 755A, molybdenum precursor gas and argon gas may still be flowed into the charge volume and thus also flowed into the process chamber. Notably, the argon flow into the charge volume and the argon gas source may be distinct, in that the argon flowing into the charge volume has separate flow paths from the argon flowing into the process chamber.

[0109] During second purge phase 785A, argon gas source may be turned on and the charge volume is turned off (i.e., can accumulate more charge). Notably, turning on the argon source gas may be performed as a two-step purge process. In some embodiments, a two-step purge process as described herein may include flowing purge gas at a first flow rate followed by flowing purge gas at a second flow rate, wherein the second flow rate is higher than the first flow rate. During a first step, a low flow purge 713a is performed, followed by a second step high flow purge 717a. Tn some embodiments, the low flow purge may be a trickle purge that helps increase total exposure of the substrate to the molybdenum precursor. The high flow purge may then evacuate the molybdenum precursor from the process chamber. While a low flow purge and high flow purge are shown in Figure 7C, in some embodiments only a high flow purge is performed, similar to first purge phase 745A.

[0110] While this process flow shows a hydrogen source turned on followed by discharging a charge volume including molybdenum precursor and argon gas, it will be understood that the alternate may be used instead (e.g., discharge charge volume, then two-step purge, then hydrogen source on, then purge).

[0111] Deposition cycle 715A is then repeated in deposition cycle 715B. Deposition cycle 715B includes four phases - first phase 725B, first purge phase 745B, second phase 755B, and second purge phase 785B. First phase 725B may be the same as or may be different from first phase 725 A. In this example, first phase 725B is the same as first phase 725 A. While the CV may be discharged during the second phase 755 A and 755B as discussed below, the co-flow of molybdenum precursor and argon into the charge volume is continuous throughout all phases, charging the charge volume outside of second phases 755A and 755B.

[0112] During first phase 725B, the hydrogen source gas is turned on. During this operation only hydrogen-containing gas sources may be flowed into the process chamber.

[0113] During first purge phase 745B, argon gas source may be turned on to purge the process chamber, and the hydrogen source gas is turned off.Atorney Docket No. LAM1P078WO-12131-1WO

[0114] During second phase 755B, the charge volume is discharged into the process chamber. During the second phase 755B, molybdenum precursor gas and argon gas may still be flowed into the charge volume and thus also flowed into the process chamber. Notably, the argon flow into the charge volume and the argon gas source may be distinct, in that the argon flowing into the charge volume has separate flow paths from the argon flowing into the process chamber.

[0115] During second purge phase 785B, argon gas source may be turned on and flow from the charge volume is turned off (i.e., so it can accumulate charge). Notably, turning on the argon source gas may be performed as a two-step purge process. In some embodiments, a two-step purge process as described herein may include flowing purge gas at a first flow rate followed by flowing purge gas at a second flow rate, wherein the second flow rate is higher than the first flow rate. During a first step, a low flow purge 713b is performed, followed by a second step high flow purge 717b. In some embodiments, the low flow purge may be a trickle purge that helps increase total exposure of the substrate to the molybdenum precursor. The high flow purge may then evacuate the molybdenum precursor from the process chamber.

[0116] While this process flow shows a hydrogen source turned on followed by discharging a charge volume including molybdenum precursor and argon gas, it will be understood that the alternate may be used instead (e.g., discharge charge volume, then two-step purge, then hydrogen source on, then purge).

[0117] The hydrogen-containing source gas in various embodiments may be hydrogen gas. Although argon is described with respect to Figures 7A-7C, it will be understood that other inert gases may be used instead of argon, including and not limited to helium.

[0118] In some embodiments, the ALD processes described herein are thermal ALD processes. In some embodiments, the ALD processes described herein may also be plasma-enhanced (PEALD).

[0119] ALD deposition may be a generally slow film growth process compared to CVD, such that it is desirable to improve film growth rate and throughput without sacrificing film quality. For complex feature architecture, a single ALD cycle may be at least 6 seconds or more as additional time is required for species to diffuse and adsorb / react throughout the features. One metric for ALD deposition is the concentration and exposure of molybdenum precursors during an ALD dose step. Generally, higher concentration and exposure is preferable.

[0120] Two techniques are described herein to improve molybdenum film deposition by ALD. First, molybdenum precursor delivery may be improved by modifying the charge volume and flow scheme to continuously co-flow molybdenum precursors and argon gas into a charge volume. During an ALD cycle, molybdenum precursor may be flowed into a charge volume, which may then be discharged into the process chamber. In one embodiment, the molybdenum precursor isAtorney Docket No. LAM1P078WO-12131-1WO flowed into a charge volume to a first pressure, and then an inert gas, such as argon, is flowed into the charge volume to a second pressure higher than the first pressure. This may be referred to as a sequential flow process. Figure 7B illustrates a sequential flow process, where Mo precursor is flowed into a charge volume followed by flowing argon into the charge volume. While Figure 7B shows the flow of argon into the charge volume as occurring before and during second phases 750A and 750B, in some embodiments, argon may be flowed into the charge volume only during second phases 750A and 750B.

[0121] The first pressure may be based on an inlet pressure of the molybdenum precursor. For example, if the inlet pressure is about 150 Torr, then the first pressure is about 75 Torr, or about half the inlet pressure. In some embodiments, the inlet pressure of the molybdenum precursor is about 150 Torr, or at least about 100 Torr, or between about 100 and about 200 Torr, or between about 150 Torr and about 200 Torr. The first pressure and the inlet pressure are related by a factor of two based on the requirements for choked flow and the use of a restrictive flow orifice (RFO) for the molybdenum precursor source. An RFO is a type of orifice plate that may be used to control gas flow. Gas flow generally depends on the pressure difference between an upstream environment, or inlet, and a downstream environment, or outlet, where a larger pressure difference increases the flow rate. Choked flow is a flow condition where the mass flow does not increase with a further decrease to the downstream pressure. Generally, when the inlet pressure is at least two times the outlet pressure, the flow through an RFO is choked, i.e., the flow velocity is limited by the inlet pressure regardless of the outlet pressure (the exact ratio depends on the gas species). This may be desirable as the mass flow rate through the RFO may be calculated without consideration of the outlet pressure. However, when flowing gas into a charge volume, the pressure of the charge volume will increase. Thus, as the pressure of the charge volume increases, the outlet pressure eventually is half the inlet pressure, and choked flow no longer occurs. This can be undesirable as the calculation of mass flow becomes considerably more complex. Thus, for flowing molybdenum precursor, a charge volume may generally be charged with molybdenum precursor up to about half the inlet pressure of the molybdenum precursor source.

[0122] After filling with molybdenum precursor, the charge volume may be filled with an inert gas, such as argon. Inert gas may have a much higher inlet pressure than molybdenum precursors, such that choked flow into the charge volume may be maintained at pressures higher than the first pressure used for the molybdenum precursor. When the charge volume is then discharged into a process chamber, the pressure decreases. During discharge, inert gas may still be flowed into the charge volume and thus also into the process chamber. After a dose step to discharge the charge volume, the charge volume may be charged again in a sequence of molybdenum precursor followed by inert gas.Atorney Docket No. LAM1P078WO-12131-1WO

[0123] One issue with a sequential approach is that total dosage of the molybdenum precursor depends on the time available to charge the charge volume and the duration of the molybdenum dose step. Generally, a longer dose step will increase a deposition rate as more precursor may adsorb in features. However, if the duration of the dose step is increased without increasing the ALD cycle time, the molybdenum precursor has less time to flow into the charge volume, which can reduce the concentration of molybdenum precursor in the charge volume, negatively affecting the dose step and counteracting the longer dose step duration.

[0124] One solution to modify the molybdenum precursor delivery' so that molybdenum precursor is continuously flowed throughout an ALD cycle. Thus, modifying the duration of any single step of the ALD cycle, without modifying the total duration of an ALD cycle, will not decrease the concentration of molybdenum precursor. This may be accomplished by co-flowing molybdenum precursor and argon gas into a larger charge volume. Generally, if the charge volume is large enough, the molybdenum precursor may be flowed into the charge volume without increasing the charge volume pressure more than about half the inlet pressure of the molybdenum precursor, even while co-flowing argon. Furthermore, the flow of argon may also be controlled to maintain pressure in the charge volume of less than about half the inlet pressure of the molybdenum precursor, maintaining a choked flow of the molybdenum precursor. During discharge, the charge volume pressure may decrease, and then the pressure increases after discharging. In some embodiments, the charge volume pressure does not exceed half the inlet pressure of the molybdenum precursor.

[0125] In some embodiments, a larger charge volume may be used to facilitate a co-flow ALD process. In some embodiments, a charge volume may be about 2 L, or between about 1.5 L and about 2.5 L. A larger charge volume presents multiple advantages. First, it enables co-flowing reagents and inert gas while maintaining choked flow. Second, it can maintain greater flow into the process chamber. As a molybdenum precursor dose time increases, the duration of flow from the charge volume also increases, which decreases the pressure of the charge volume and negatively affects flow. By increasing the volume of the charge volume, the pressure drop from a longer dose time is mitigated and thus the flow into the process chamber may be maintained, which is desirable to increase total exposure.

[0126] In some embodiments, a co-flow scheme may charge a charge volume to a pressure higher than about half the inlet pressure of the molybdenum precursor. In some embodiments, the flow through an RFO plate may be calibrated at higher charge volume pressures using a calibration curve of RFO flow as a function of charge volume pressure. In some embodiments, this may control for flow of inert gas as well. In some embodiments, a MFC may be used to control flow of molybdenum precursor instead of an RFO plate, which may facilitate more precise control ofAtorney Docket No. LAM1P078WO-12131-1WO molybdenum precursor flow into the charge volume.

[0127] The second technique to improve molybdenum deposition by ALD is directed to purging the molybdenum precursor. During precursor purge, purge gas is flowed into the process chamber to evacuate any precursor species. However, some of the precursor species may still be able to diffuse into and adsorb within features of the substrate, particularly for complex 3D NAND architectures. Thus, a high flow purge may waste precursor species by evacuating them before they can sufficiently diffuse and adsorb. Figure 7B illustrates this process, as the second purge phases 780A and 780B have a high flow purge immediately after the second phase molybdenum precursor dose step.

[0128] An alternative technique is illustrated in Figure 7C, utilizing a low flow purge 713a and 713b prior to a high flow purge. In some embodiments a low flow purge may be a trickle purge. A trickle purge may be flowed from a source of inert gas to ensure a dow nstream flow of gas through flow paths towards a showerhead. This may prevent or inhibit the undesirable backflow of gases through valves and other flow paths. In some embodiments, a low flow purge may have a flow rate of about 1600 seem, less than about 4000 seem, or between about 1000 seem and about 4000 seem.

[0129] A low- flow' purge may push molybdenum precursor deeper into features, improving adsorption uniformity’. In some embodiments, a low flow purge may be equal to about one volume turn. A volume turn is related to the volume of the process chamber and may be defined by the volume betw een the showerhead and the substrate that is occupied by reactants, which may be called a reactive cavity . In some embodiments, a volume turn includes flowing a volume of gas equivalent to the volume of the reactive cavity. In some embodiments, a low flow purge may flow about 1 volume turn, less than about 2 volume turns, or between about 1 volume turn and about 2 volume turns. A volume turn may be determined by the flow rate and duration of flow. For example, for a low' flow' purge of about 250 ms and a flow' rate of about 1600 seem, about one half of the volume of a reactive cavity may be replaced. Doubling the duration or doubling the flow' rate would similarly double the volume turn. Thus, in some embodiments, increasing the flow rate may facilitate decreasing the duration of the low flow purge while still achieving about 1, about 2, or between about 1 and about 2 volume turns. In some embodiments, the duration of a low' flow' purge is less than about 250 ms, less than about 300 ms, between about 10 ms and 250 ms, or between about 50 ms and about 250 ms.

[0130] A low' flow purge may be distinguished from a high flow purge. A high flow purge may generally flow about 20 or more volume turns of purge gas into a process chamber. A low flow purge, by contrast, may flow' less than about 2 volume turns. A high flow purge may push all precursor species or reactants from the reactive cavity to be removed by a vacuum pump. A lowAtorney Docket No. LAM1P078WO-12131-1WO flow purge, by contrast, may push precursor species deeper into features without evacuating them from the reactive cavity. In some embodiments, a high flow purge has a flow rate of at least about 10 slm, or between about 10 slm and about 40 slm. In some embodiments, the duration of a high flow purge is at least about 0.3 seconds, between about 0.3 seconds and about 0.5 seconds, or between about 0.3 seconds and about 2 seconds.

[0131] A two-step purge presents several advantages. The low flow purge may push molybdenum precursor species deeper into features to increase exposure within features. This can increase deposition rate without having to increase the total flow of molybdenum precursor, thus increasing the efficiency of converting molybdenum precursor into a deposited film. This can reduce precursor waste and increase the deposition rate, increasing throughput. The high flow purge may then evacuate precursor species from the process chamber to avoid undesirable vapor phase interactions between precursor species and reactants.

[0132] In some embodiments, a two-step purge as described herein may be used after flowing a precursor species into a process chamber. In some embodiments, a two-step purge may also be used after flowing a reactant species into a process chamber. A two-step purge may be similarly beneficial for the reactant as the precursor, particularly in ensuring that reactant flows deeper into features to reactant with adsorbed precursor species. A two-step purge performed after flowing a reactant species may be performed using the same or similar techniques as described above. For example, in Figure 7C, first purge phases 745A and 745B may be performed using a two-step purge process as shown in second purge phases 785A and 785B.

[0133] Figure 8 presents a chart of Molybdenum Torr-seconds, or Langmuires, as a function of dose time for sequential flow and co-flow ALD deposition, corresponding to the timing diagrams of Figure 7B and 7C, respectively. For both processes, the total cycle time is constant at 6 seconds, but the dose time for discharging a charge volume containing molybdenum precursor and argon is changed. As shown in Figure 8, for a sequential How ALD process, increasing dose time may decrease exposure, as the charge volume has less time to accumulate molybdenum precursor. For a co-flow process, by contrast, total exposure time is less susceptible to dose time as molybdenum precursor is constantly flowing into the charge volume, even when the charge volume is discharging into the process chamber.

[0134] Figures 9A and 9B present additional charts showing simulations of mole fraction and Langmuirs as a function of time for different ALD processes. ALD process 901 uses 100% molybdenum precursor. ALD process 902 co-llows molybdenum precursor and argon at a 50: 100 seem ratio, respectively. ALD process 903 co-flows molybdenum precursor and argon at a 38: 100 seem ratio, respectively. ALD process 904 sequentially flows molybdenum precursor and argon with a dose step duration of 0.4 seconds, and ALD process 905 sequentially flows molybdenumAtorney Docket No. LAM1P078WO-12131-1WO precursor and argon with a dose step duration of 0.8 seconds.

[0135] In Figure 9A, the mole fraction increases by co-flowing compared to a sequential ALD process. Notably, ALD process 904 has a higher mole fraction than ALD process 905 as the charge volume may accumulate more molybdenum precursor before discharge, as noted above. ALD processes 902 and 903 similarly show higher mole fractions by co-flowing molybdenum precursor and argon. While ALD process 901 shows the highest mole fraction, it should be understood that the overall pressure in the CV is the lowest for ALD process 901, as argon is not being co-flowed, which reduces the overall exposure. Figure 9A does not reflect the pressure in the CV, which at low pressures will reduce the flow of molybdenum precursor into features.

[0136] In Figure 9B, Langmuirs are graphed as a function of time, starting with a dose and then a low flow purge at 0.8 seconds for ALD processes 901, 902, and 903. ALD processes 904 and 905 do not have a low flow purge. As shown in Figure 9B, the low' flow purge increases total exposure before the high flow purge. This benefit would also be present for sequential flow ALD processes, though a low flow purge was not performed for ALD processes 904 and 905. One the high flow purge is performed total exposure is maximized as the molybdenum precursor species are evacuated from the process chamber.Apparatus

[0137] Figure 10 depicts a schematic illustration of an embodiment of flow paths 1 100 for an ALD process station. A wafer may be supported by a pedestal and a showerhead may distribute process gases over the w afer. In some embodiments, a reactive cavity is defined by a cylinder having two parallel, circular bases that are co-planar with a showerhead and wafer, respectively, and a curved surface between the circular surfaces. Figure 10 depicts a reactive canty constrained by the showerhead, wafer, and dashed lines between them. The showerhead may be connected with various sources via valves, plates, or controllers. The example of Figure 10 shows three sources, a treatment gas source (e.g., FL), a molybdenum precursor source, and an inert gas source. In some embodiments, one or more gas sources may be connected to multiple charge vessels. The apparatus includes a gas manifold system, which provides line charges to the various gas distribution lines. The manifolds provide the treatment gases and inert gas to the deposition chamber through valved charged vessels. The various valves are opened or closed to provide a line charge, i.e., to pressurize the distribution lines.

[0138] Using charge vessels can enable delivering treatment gases to the botom of high aspect ratio structures, e.g.. to the botom wordline of 3D NAND structures. Pressurized gas flows through the showerhead and reaches the w afer or other workpiece that it to be treated.

[0139] In some embodiments, the Mo precursor source may use an restrictive flow' orifice plateAtorney Docket No. LAM1P078WO-12131-1WO (RFO) to control flow of molybdenum precursor into the charge volume. As discussed above, when the charge volume pressure is less than half the inlet pressure of the source, a choked flow occurs that can be used to readily measure the flow rate of molybdenum precursor.

[0140] Inert gas source may also be connected to the molybdenum charge volume as well as a separate inert gas charge volume and a MFC connected to the showerhead without a charge volume. The inert gas charge volume may be used during high flow purge steps to rapidly evacuate reactant species from the process chamber. The MFC, by contrast, may be used to facilitate a low flow purge by flowing a much smaller flow of inert gas. In some embodiments, the MFC may be in line with the inert gas charge volume or may have a separate connection to the inert gas source. In some embodiments, each of the sources may be from a location in a fabrication facility that is different from the location of the semiconductor processing tool, and the processing modules, to where the gases are flowed. For example, the semiconductor processing tool may be located on a fabrication floor that is a different level in the facility than where a source is located.

[0141] Each source may be controlled by a valve or other flow control mechanism. Flow control mechanisms may include throtle valves, mass flow controllers, RFO plates, bypass valves, etc.

[0142] Figure 11 depicts a schematic illustration of an embodiment of an ALD process station 1100 having a process chamber 1102 for maintaining a low-pressure environment. In some embodiments, a plurality of ALD process stations may be included in a common low-pressure process tool environment. For example. Figures 12A and 12B depict embodiments of a multi-station processing tool 1200. In some embodiments, one or more hardware parameters of ALD process station 1100, including those discussed in detail below, may be adjusted programmatically by one or more computer controllers 1250. In some other embodiments, a process chamber may be a single station chamber.

[0143] ALD process station 1100 fluidly communicates with reactant delivery system 11 Ola for delivering process gases to a distribution showerhead 1106. Reactant delivery system 1101a includes a mixing vessel 1104 for blending and / or conditioning process gases, such as a Mo precursor-containing gas, a hydrogen-containing gas, an argon or other carrier gas, or other reactant-containing gas, for delivery to showerhead 1106. One or more mixing vessel inlet valves 1120 may control introduction of process gases to mixing vessel 1104. In various embodiments, deposition of an initial Mo layer is performed in process station 1100 and in some embodiments, other operations such as in-situ clean or Mo gap fill may be performed in the same or another station of the multi-station processing tool 1200 as further described below with respect to Figure 12A.

[0144] As an example, the embodiment of Figure 11 includes a vaporization point 1103 for vaporizing liquid reactant to be supplied to the mixing vessel 1104. In some embodiments,Atorney Docket No. LAM1P078WO-12131-1WO vaporization point 1103 may be a heated vaporizer. In some embodiments, a liquid precursor or liquid reactant may be vaporized at a liquid injector (not shown). For example, a liquid injector may inject pulses of a liquid reactant into a carrier gas stream upstream of the mixing vessel 1104. In one embodiment, a liquid injector may vaporize the reactant by flashing the liquid from a higher pressure to a lower pressure. In another example, a liquid injector may atomize the liquid into dispersed microdroplets that are subsequently vaporized in a heated delivery pipe. Smaller droplets may vaporize faster than larger droplets, reducing a delay between liquid injection and complete vaporization. Faster vaporization may reduce a length of piping downstream from vaporization point 1103. In one scenario, a liquid injector may be mounted directly to mixing vessel 1104. In another scenario, a liquid injector may be mounted directly to showerhead 1106.

[0145] Reactant delivery system 1101a may also include one or more solid precursor delivery components including one or more on-board ampoules 1113 and / or bulk delivery components 1115. Figure 18 below provides an example of a bulk delivery system.

[0146] In some embodiments, a liquid flow controller (LFC) upstream of vaporization point 1103 may be provided for controlling a mass flow of liquid for vaporization and delivery' to process chamber 1102. For example, the LFC may include a thermal mass flow meter (MFM) located downstream of the LFC. A plunger valve of the LFC may then be adjusted responsive to feedback control signals provided by a proportional-integral-derivative (PID) controller in electrical communication with the MFM. However, it may take one second or more to stabilize liquid flow using feedback control. This may extend a time for dosing a liquid reactant. Thus, in some embodiments, the LFC may be dynamically switched between a feedback control mode and a direct control mode. In some embodiments, this may be performed by disabling a sense tube of the LFC and the PID controller.

[0147] Showerhead 1106 distributes process gases toward substrate 1112. In the embodiment shown in Figure 11, the substrate 1112 is located beneath showerhead 1106 and is shown resting on a pedestal 1108. Showerhead 1106 may have any suitable shape and may have any suitable number and arrangement of ports for distributing process gases to substrate 1112.

[0148] In some embodiments, pedestal 1108 may be raised or low ered to expose substrate 1112 to a volume betw een the substrate 1112 and the showerhead 1106. In some embodiments, pedestal 1108 may be temperature controlled via heater 1110. Pedestal 1108 may be set to any suitable temperature, such as between about 250°C and about 800°C during operations for performing various disclosed embodiments. It will be appreciated that, in some embodiments, pedestal height may be adjusted programmatically by a suitable computer controller 850. At the conclusion of a process phase, pedestal 1108 may be lowered during another substrate transfer phase to allow' removal of substrate 1112 from pedestal 1108.Atorney Docket No. LAM1P078WO-12131-1WO

[0149] In some embodiments, a position of showerhead 1106 may be adjusted relative to pedestal 1108 to vary a volume between the substrate 1112 and the showerhead 1106. Further, it will be appreciated that a vertical position of pedestal 1108 and / or showerhead 1106 may be varied by any suitable mechanism within the scope of the present disclosure. In some embodiments, pedestal 1108 may include a rotational axis for rotating an orientation of substrate 1112. It will be appreciated that, in some embodiments, one or more of these example adjustments may be performed programmatically by one or more suitable computer controllers 1150. The computer controller 1150 may include any of the features described below with respect to controller 1150 of Figure 11.

[0150] In some embodiments where plasma may be used as discussed above, showerhead 1106 and pedestal 1108 electrically communicate with a radio frequency (RF) power supply 1114 and matching netw ork 1116 for powering a plasma. In some embodiments, the plasma energy may be controlled by controlling one or more of a process station pressure, a gas concentration, an RF source power, an RF source frequency, and a plasma power pulse timing. For example. RF power supply 1114 and matching network 1116 may be operated at any suitable power to form a plasma having a desired composition of radical species. Likewise, RF power supply 1114 may provide RF power of any suitable frequency. In some embodiments, RF power supply 1114 may be configured to control high- and low-frequency RF power sources independently of one another. Example low-frequency RF frequencies may include, but are not limited to, frequencies between 0 kHz and 900 kHz. Example high-frequency RF frequencies may include, but are not limited to, frequencies between 1.8 MHz and 2.45 GHz, or greater than about 13.56 MHz, or greater than 27 MHz. or greater than 80 MHz, or greater than 60 MHz. It will be appreciated that any suitable parameters may be modulated discretely or continuously to provide plasma energy for the surface reactions.

[0151] In some embodiments, the plasma may be monitored in-situ by one or more plasma monitors. In one scenario, plasma power may be monitored by one or more voltage, current sensors (e.g.. VI probes). In another scenario, plasma density and / or process gas concentration may be measured by one or more optical emission spectroscopy sensors (OES). In some embodiments, one or more plasma parameters may be programmatically adjusted based on measurements from such in-situ plasma monitors. For example, an OES sensor may be used in a feedback loop for providing programmatic control of plasma power. It will be appreciated that, in some embodiments, other monitors may be used to monitor the plasma and other process characteristics. Such monitors may include, but are not limited to, infrared (IR) monitors, acoustic monitors, and pressure transducers.

[0152] In some embodiments, instructions for a controller 1150 may be provided viaAtorney Docket No. LAM1P078WO-12131-1WO input / output control (IOC) sequencing instructions. In one example, the instructions for seting conditions for a process phase may be included in a corresponding recipe phase of a process recipe. In some cases, process recipe phases may be sequentially arranged, so that all instructions for a process phase are executed concurrently with that process phase. In some embodiments, instructions for seting one or more reactor parameters may be included in a recipe phase. For example, a first recipe phase may include instructions for seting a flow rate of an inert and / or a reactant gas (e.g., a Mo precursor), instructions for seting a flow rate of a carrier gas (such as argon), and time delay instructions for the first recipe phase. A second, subsequent recipe phase may include instructions for modulating or stopping a flow rate of an inert and / or a reactant gas, and instructions for modulating a flow rate of a carrier or purge gas and time delay instructions for the second recipe phase. A third recipe phase may include instructions for modulating a flow rate of a second reactant gas such as H2, instructions for modulating the flow rate of a carrier or purge gas, instructions for igniting a plasma, and time delay instructions for the third recipe phase. A fourth, subsequent recipe phase may include instructions for modulating or stopping a flow rate of an inert and / or a reactant gas, and instructions for modulating a flow rate of a carrier or purge gas and time delay instructions for the fourth recipe phase. It will be appreciated that these recipe phases may be further subdivided and / or iterated in any suitable way within the scope of the present disclosure.

[0153] Further, in some embodiments, pressure control for process station 1100 may be provided by buterfly valve 1118. As shown in the embodiment of Figure 11, butterfly valve 1118 throtles a vacuum provided by a downstream vacuum pump (not shown). However, in some embodiments, pressure control of process station 1100 may also be adjusted by varying a flow rate of one or more gases introduced to the process station 1100.

[0154] Figure 12A and Figure 12B show examples of processing systems. Figure 12A shows an example of a processing system including multiple chambers. The system 1200 includes a transfer module 1203. The transfer module 1203 provides a clean, vacuum environment to minimize risk of contamination of substrates being processed as they are moved between various modules. Mounted on the transfer module 1203 is a multi-station chamber 1209 capable of performing in-situ clean and / or ALD processes described above. Surface treatment and / or initial Mo layer deposition may be performed in the same or different station or chamber as the subsequent Mo gap fill.

[0155] Chamber 1209 may include multiple stations 1211, 1213, 1215, and 1217 that may sequentially perform operations in accordance with disclosed embodiments. For example, chamber 1209 may be configured such that station 1211 performs an in-situ treatment using a MoClx precursor. Station 1213 may be configured to selectively treat the field region and upperAtorney Docket No. LAM1P078WO-12131-1WO sidewalls and stations 1215 and 1217 may be configured to perform ALD of bulk Mo using an molybdenum oxyhalide precursor and H2. In another example, chamber 1209 may be configured such that station 1211 performs in-situ clean, station 1213 performs ALD of an initial Mo layer, station 1213 selectively treats the layer, and 1214 deposition of bulk Mo. In another example, the chamber 1209 may be configured to do parallel processing of substrates, with each station performing multiple processes sequentially.

[0156] Two or more stations may be included in a multi-station chamber, e.g., 2-6, with the operations appropriately distributed. For example, a two-station chamber may be configured to perform ALD of an initial Mo layer in a first station followed by ALD of bulk Mo in a second station. Stations may include a heated pedestal or substrate support, one or more gas inlets or showerhead or dispersion plate.

[0157] Also mounted on the transfer module 1203 may be one or more single or multi-station modules 1207. In some embodiments, a preclean as described above may be performed in a module 1207, after which the substrate is transferred under vacuum to another module (e.g., another module 1207 or chamber 1209) for ALD. In another example, a module for selective treatment of a film may be mounted on the transfer module.

[0158] The system 1200 also includes one or more wafer source modules 1201, where wafers are stored before and after processing. An atmospheric robot (not shown) in the atmospheric transfer chamber 1219 may first remove wafers from the source modules 1201 to loadlocks 1221. A wafer transfer device (generally a robot arm unit) in the transfer module 1203 moves the wafers from loadlocks 1221 to and among the modules mounted on the transfer module 1203.

[0159] Referring to Figure 5, for example, in some embodiments, chamber 1209 is configured to perform pre-treatment, selective fill, conformal liner deposition, and final fill. In one example, station 1211 is configured to perform pre-treatment, station 1213 is configured to perform selective fill, station 1213 is configured to perform conformal liner deposition, and station 1215 is configured to perform final fill. In some embodiments, etch and / or inhibition processes may be performed. For example, station 1211 is configured to perform pre-treatment. station 1213 is configured to perform selective fill, station 1213 is configured to perform inhibition, and station 1215 is configured to perform final fill.

[0160] Figure 12B is an embodiment of a system 1200. The system 1200 in Figure 12B has wafer source modules 1201, a transfer module 1203, atmospheric transfer chamber 1219. and loadlocks 1221, as described above with reference to Figure 12A. The system in Figure 12B has three single station modules 1257a-1275c. The system 1200 may be configured to sequentially perform operations in accordance with disclosed embodiments. For example, the single station modules 1257a-1257c may be configured so that a first module 1257a performs a surfaceAtorney Docket No. LAM1P078WO-12131-1WO treatment, a second module 957b performs ALD of an initial Mo layer using a molybdenum halide precursor, and a third module 957c performs ALD of bulk Mo using a molybdenum oxyhalide precursor. In this example, an in-situ clean may be optionally performed in second module 1257b instead of or in addition to a preclean in first module 1257a. In another example, the single station modules 1257a-1257c may be configured so that a first module 1257a performs a deposition of an initial metal layer, a second module 1257b performs selective treatment, and a third module 1257c performs ALD of bulk Mo using a molybdenum oxyhalide precursor. In yet another example, one module may be configured for deposition, another module for selective treatment, and another module for etch.

[0161] Stations may include a heated pedestal or substrate support, one or more gas inlets or showerhead or dispersion plate as described above with reference to Figures 10 and 11.

[0162] Returning to Figure 12A and 12B, in various embodiments, a system controller 1229 is employed to control process conditions during deposition. The controller 1229 will typically include one or more memory devices and one or more processors. A processor may include a CPU or computer, analog and / or digital input / output connections, stepper motor controller boards, etc. Such a system controller may be employed in control of any of the processes and apparatus described herein.

[0163] The controller 1229 may control all the activities of the apparatus. The system controller 1229 executes system control software, including sets of instructions for controlling the timing, mixture of gases, chamber pressure, chamber temperature, wafer temperature, radio frequency (RF) power levels, wafer chuck or pedestal position, and other parameters of a particular process. Other computer programs stored on memory’ devices associated with the controller 1229 may be employed in some embodiments.

[0164] Typically, there will be a user interface associated with the controller 1229. The user interface may include a display screen, graphical software displays of the apparatus and / or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.

[0165] System control logic may be configured in any suitable way. In general, the logic can be designed or configured in hardware and / or software. The instructions for controlling the drive circuitry' may be hard coded or provided as software. The instructions may be provided by “programming.” Such programming is understood to include logic of any form, including hard coded logic in digital signal processors, application-specific integrated circuits, and other devices which have specific algorithms implemented as hardware. Programming is also understood to include software or firmware instructions that may be executed on a general-purpose processor. System control software may be coded in any suitable computer readable programming language.Atorney Docket No. LAM1P078WO-12131-1WO

[0166] The computer program code for controlling the Mo precursor pulses, hydrogen pulses, and argon flow, and other processes in a process sequence can be writen in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran, or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program. Also as indicated, the program code may be hard coded.

[0167] The controller parameters relate to process conditions, such as, for example, process gas composition and flow rates, temperature, pressure, cooling gas pressure, substrate temperature, and chamber wall temperature. These parameters are provided to the user in the form of a recipe and may be entered utilizing the user interface.

[0168] Signals for monitoring the process may be provided by analog and / or digital input connections of the system controller 1229. The signals for controlling the process are output on the analog and digital output connections of the deposition apparatus.

[0169] The system software may be designed or configured in many ways. For example, various chamber component subroutines or control objects may be written to control operation of the chamber components necessary to carry out the deposition processes in accordance with the disclosed embodiments. Examples of programs or sections of programs for this purpose include substrate positioning code, process gas control code, pressure control code, and heater control code.

[0170] In some implementations, a controller 1229 is part of a system, which may be part of the above-described examples. Such systems can include semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and / or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller 1229, depending on the processing requirements and / or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature setings (e.g., heating and / or cooling), pressure setings, vacuum setings, power setings, radio frequency (RF) generator settings in some systems, RF matching circuit setings, frequency setings, flow rate setings, fluid delivery' setings, positional and operation setings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0171] Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integratedAtorney Docket No. LAM1P078WO-12131-1WO circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual setings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0172] The controller 1229, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherw ise networked to the system, or a combination thereof. For example, the controller 1229 may be in the ‘"cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may¬ enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start anew process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and / or setings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. The parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, such as by including one or more discrete controllers that are networked together and w orking towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0173] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a PVD chamber or module, a CVD chamber or module, an ALD chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and / orAtorney Docket No. LAM1P078WO-12131-1WO manufacturing of semiconductor wafers.

[0174] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and / or load ports in a semiconductor manufacturing factory.

[0175] The controller 1229 may include various programs. A substrate positioning program may include program code for controlling chamber components that are used to load the substrate onto a pedestal or chuck and to control the spacing between the substrate and other parts of the chamber such as a gas inlet. A substrate tilt and rotation program may include for tilt and rotation. A process gas control program may include code for controlling gas composition, flow rates, pulse times, and optionally for flowing gas into the chamber prior to deposition in order to stabilize the pressure in the chamber. A pressure control program may include code for controlling the pressure in the chamber by regulating, e.g., a throtle valve in the exhaust system of the chamber. A heater control program may include code for controlling the current to a heating unit that is used to heat the substrate. Alternatively, the heater control program may control delivery' of a heat transfer gas such as helium to the w afer chuck.

[0176] Examples of chamber sensors that may be monitored during deposition include mass flow controllers, pressure sensors such as manometers, and thermocouples located in the pedestal or chuck. Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain desired process conditions.

[0177] The foregoing describes implementation of disclosed embodiments in a single or multichamber semiconductor processing tool. The apparatus and process described herein may be used in conjunction with lithographic paterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels, and the like. Typically, though not necessarily, such tools / processes will be used or conducted together in a common fabrication facility. Lithographic paterning of a film typically includes some or all of the following steps, each step provided with a number of possible tools: (1) application of photoresist on a workpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby patern it using a tool such as a wet bench; (5) transferring the resist patern into an underlying film or workpiece by using a dry' or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.

Claims

Atorney Docket No. LAM1P078WO-12131-1WOCLAIMSWhat is claimed is:

1. A method, comprising:providing a substrate comprising features to be fdled in a process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process comprises one or more cycles of:(a) flowing a molybdenum precursor and an inert gas into the process chamber; (b) flowing a first purge gas into the process chamber;(c) flowing a reactant into the process chamber; and(d) flowing a second purge gas into the process chamber;wherein (b) comprises:(i) a first flow rate purge; and(ii) a second flow rate purge, wherein the second flow rate purge has a higher flow rate than the first flow rate purge.

2. The method of claim 1 , wherein the first flow rate purge is performed at a flow rate less than about 4000 seem.

3. The method of claim 1. wherein the process chamber has a reactive cavity defined at least in part by the substrate and a showerhead above the substrate and having a first volume, and the first flow rate purge flows a second volume of inert gas that is less than about 2 times larger than the first volume.

4. The method of claim 3, wherein the second flow rate purge flows a third volume of inert gas that is at least about 20 times larger than the first volume.

5. The method of claim 1. wherein a second flow rate purge is performed at a flow rate greater than about 10 slm.

6. The method of claim 1, wherein purge gas is flowed through a mass flow controller (MFC) during the first flow rate purge, and is flowed from a charge volume during the second flow rate purge.

7. The method of claim 1, wherein (a) comprises discharging the molybdenum precursor and inert gas into the process chamber from a charge volume.Atorney Docket No. LAM1P078WO-12131-1WO 8. The method of claim 7, wherein the charge volume is not discharged into the process chamber during (b)-(d).

9. The method of claim 7. wherein molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process.

10. The method of claim 9, wherein molybdenum precursor is flowed into the charge volume from a molybdenum precursor source via a restrictive flow orifice plate, and the flow of molybdenum precursor into the charged volume is a choked flow.

11. The method of claim 7, wherein a pressure in the charge volume prior to discharge is less than about half a pressure of a molybdenum precursor source.

12. The method of claim 1, wherein the first purge gas, second purge gas, and the inert gas comprise argon, helium, nitrogen, or any combinations thereof.

13. The method of claim 1. wherein the molybdenum precursor is a molybdenum oxyhalide.

14. The method of claim 1, wherein the reactant is a hydrogen-containing reactant.

15. The method of claim 1, wherein the ALD process is a non-plasma thermal process.

16. The method of claim 1, wherein the ALD process is a plasma-enhanced process.

17. The method of claim 1, wherein (d) comprises:(A) a third flow- rate purge; and(B) a fourth How rate purge, wherein the fourth flow7rate purge has a higher flow7rate than the third flow rate purge.

18. A method, comprising:providing a substrate comprising features to be filled in a process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process comprises one or more cycles of:(a) flowing a molybdenum precursor and an inert gas into the process chamber from a charge volume;(b) flowing a first purge gas into the process chamber;(c) flowing a reactant into the process chamber; and(d) flowing a second purge gas into the process chamber;Atorney Docket No. LAM1P078WO-12131-1WO wherein molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process.

19. The method of claim 18, wherein the charge volume is not discharged into the process chamber during (b)-(d).

20. The method of claim 18, wherein molybdenum precursor is flowed into the charge volume from a molybdenum precursor source via a restrictive flow orifice plate, and the flow of molybdenum precursor into the charged volume is a choked flow.

21. The method of claim 18, wherein a pressure in the charge volume prior to discharge is less than about half a pressure of a molybdenum precursor source.

22. An apparatus, comprising:a process chamber having one or more stations each configured to hold a substrate; one or more process gas inlets for coupling to a hydrogen (H2) gas source, a molybdenum precursor gas source, and an inert purge gas source; anda controller for controlling operations in the apparatus, the controller comprising non-transitory machine-readable instructions for:providing a substrate comprising features to be filled in the process chamber; depositing molybdenum in the features using an ALD process, wherein the ALD process comprises one or more cycles of:(a) flowing a molybdenum precursor and an inert gas into the process chamber from a charge volume;(b) flowing a first purge gas into the process chamber;(c) flowing a reactant into the process chamber; and(d) flowing a second purge gas into the process chamber;wherein molybdenum precursor and inert gas are flowed into the charge volume continuously during the ALD process.

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