Fluorine-free tungsten atomic layer deposition for improved dielectric selectivity

Abstract

A method for selectively forming a tungsten metal film on a conductive surface relative to a dielectric surface is described. A substrate is exposed to first process conditions to deposit a tungsten-containing film on the substrate that does not contain tungsten metal. The tungsten-containing film is then converted to a tungsten metal film by exposure to second process conditions.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to the field of electronic device manufacturing, and in particular to integrated circuit (IC) manufacturing. In particular, embodiments of the present disclosure relate to a method for filling surface structures with a metal film. [Background technology]

[0002] Integrated circuits are made possible by processes that produce intricately patterned layers of material on substrate surfaces. Producing patterned materials on substrates requires controlled methods for depositing the desired materials. Depositing a film on one surface selectively relative to a different surface is useful for patterning and other applications.

[0003] Conventional methods for metal deposition often suffer from poor selectivity to dielectric surfaces, and can also suffer from low throughput for atomic layer deposition (ALD) processes in single wafer processing environments.

[0004] For high-k metal gates in FINFET technology, the features that need to be filled become extremely small as technology nodes move to 14nm and below. 6 ()-based chemical vapor deposition (CVD) / ALD tungsten films introduce fluorine and cannot be deposited directly on the gate without barrier and nucleation layers. As dimensions shrink, the barrier and nucleation layers take up most of the space in narrow features. The high resistivity of these films impacts the performance of the resulting device.

[0005] Therefore, there is a need for improved methods for selective metal deposition. Summary of the Invention

[0006] One or more embodiments of the present disclosure are directed to a method of treating a substrate. The substrate surface is exposed to first process conditions including a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film on the substrate surface. The tungsten-containing film is substantially free of tungsten metal. The tungsten-containing film is exposed to second process conditions including a flow of a second reducing agent to reduce the tungsten-containing film on the substrate surface to a metallic tungsten film.

[0007] Further embodiments of the present disclosure are directed to a method of forming a metallic tungsten film. A tungsten-containing film substantially free of tungsten metal is formed on a substrate. The substrate has a conductive surface and a dielectric surface, and the tungsten-containing film forms on the conductive surface selectively to the dielectric surface. The tungsten-containing film is formed by exposing the substrate to first process conditions including a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent. The fluorine-free tungsten precursor and the first reducing agent have a flow ratio in the range of 10:1 to 1:2.5. The tungsten-containing film is converted to a metallic tungsten film by exposing the substrate including the tungsten-containing film substantially free of tungsten metal to second process conditions including a flow of a second reducing agent.

[0008] Further embodiments of the present disclosure are directed to a method for forming a metallic tungsten film. A substrate having a dielectric surface and a conductive surface is sequentially exposed to a first process condition and a second process condition to selectively deposit a metallic tungsten film on the conductive surface. The first process condition includes a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film on the conductive surface. The tungsten-containing film is substantially free of tungsten metal. The second process condition includes a flow of a second reducing agent to reduce the tungsten-containing film on the conductive surface to a metallic tungsten film.

[0009] In order to allow the above-mentioned features of the present disclosure to be understood in detail, a more detailed description of the present disclosure, briefly summarized above, can be had by reference to the embodiments. Some embodiments are illustrated in the attached drawings. However, it should be noted that the attached drawings only illustrate typical embodiments of the present disclosure, since the present disclosure may admit of other equally effective embodiments, and therefore should not be considered as limiting the scope of the present disclosure. The embodiments described herein are illustrated in the attached drawings for purposes of illustration and not limitation, in which similar elements are indicated by similar reference numerals. [Brief description of the drawings]

[0010] [Figure 1] 1 illustrates an exemplary processing method in accordance with one or more embodiments of the present disclosure. [Diagram 2] 1A-1D show schematic cross-sectional views of a semiconductor device during a processing method according to one or more embodiments of the present disclosure. [Diagram 3] 1A-1D show schematic cross-sectional views of a semiconductor device during a processing method according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the accompanying drawings, similar components and / or features may have the same reference numerals. Furthermore, various components of the same type may be distinguished by a dash after the reference numeral and a second numeral that distinguishes between the similar components. If only a first numeral is used in the specification, the description of the specification may apply to any of the similar components having the same first numeral, regardless of the second numeral.

[0012] Before describing some example embodiments of the present disclosure, it is to be understood that the present disclosure is not limited to the details of construction or process steps set forth in the following specification, as the present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0013] As used herein, "substrate" refers to any substrate on which a film treatment is performed during a manufacturing process, or any material surface formed on a substrate. For example, substrate surfaces on which treatment may be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, but are not limited to, semiconductor wafers. Substrates may be exposed to pretreatment processes to polish, etch, reduce, oxidize, hydroxylate, anneal, and / or bake the substrate surface. In addition to performing film treatments directly on the surface of the substrate itself, in the present disclosure, any of the disclosed film treatment steps may be performed on an underlayer formed on the substrate, which is disclosed in more detail below, and the term "substrate surface" is intended to include such underlayers as the context indicates. Thus, for example, if a film / layer or partial film / layer is being deposited on a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0014] In this specification and the appended claims, the terms "precursor," "reactant," "reactive gas," and the like are used interchangeably to refer to any gas species capable of reacting with the substrate surface.

[0015] As used herein, the term "liner" refers to a layer conformally formed along at least a portion of the sidewalls and / or bottom surface of an opening, such that a substantial portion of the opening prior to deposition of the layer remains unfilled after deposition of the layer. In some embodiments, the liner may be formed along the entire sidewalls and bottom surface of the opening.

[0016] One or more embodiments of the present disclosure are directed to highly selective deposition processes. In some embodiments, deposition rates are high for metal fill applications. In some embodiments, fluorine-free metal precursors are used to improve selectivity and deposition rates. In some embodiments, a reducing agent is incorporated into the first ALD step to improve selectivity to the dielectric and also increase deposition rates with comparable film performance (e.g., step coverage, gap filling). Some embodiments provide highly selective fluorine-free tungsten deposition by a high throughput ALD process.

[0017] Some embodiments of the present disclosure provide atomic layer deposition methods that incorporate a reducing agent in the first ALD step. Without being bound to a particular theory of operation, it is believed that the inclusion of a reducing agent significantly enhances the reduction of the precursor by allowing the precursor to undergo pyrolysis into various derivatives of the precursor in the main reduction ALD step.

[0018] In one or more embodiments of the present disclosure, various gases (e.g., H 2 , SiH 4 , Si 2 H 6 , Si 4 H 10 , N.H. 3 ) is incorporated into the metal (e.g., tungsten (W)) precursor dose. In some embodiments, the incorporation of a reducing agent improves the selectivity of metal deposition relative to the dielectric and accelerates the rate of metal reduction.

[0019] In some embodiments, ALD fluorine-free tungsten (FFW) can be used to replace conventional high-resistance nucleation layers (e.g., SiH 4 Or B 2 H 6 ALD W, 20-30 Å) and thick fluorine barriers (e.g., TiN, 30-50 Å) are replaced and / or reduced. In some embodiments, FFW provides lower resistance, better step coverage, and superior fluorine barrier properties compared to conventional WF. 6It can be integrated with the base bulk W loading, in some embodiments improving throughput while maintaining acceptable film performance or other metrics (e.g., non-uniformity, step coverage, particles).

[0020] One or more embodiments of the present disclosure are directed to a method for high deposition rates of FFW films. 2 , SiH 4 , Si 2 H 6 , Si 4 H 12 , N.H. 3 A small coflow of a reducing agent such as is added to the W precursor ALD dosage step. In some embodiments, hydrogen (H 2 ) occurs at a suitable temperature (eg, in the range of 400° C. to 550° C., or 460° C. to 475° C.).

[0021] Tungsten precursors for growing the FFW include, but are not limited to, tungsten chloride and hydrogen as a reducing agent. In some embodiments, the FFW is grown on a conductive layer (e.g., a TiN or TiAl film). In one or more embodiments, the ALD process includes exposure to a W precursor dosage, which may range from 50 to 500 sccm of H 2 co-flow of W precursor, H 2 Administration, H 2 Purging involves: Argon (Ar) or other suitable inert gas is used for the precursor carrier and purging in some embodiments.

[0022] In some embodiments, the deposition rate of the FFW is increased by more than two times (2x) on TiN and TiAl films. In some embodiments, the increased deposition rate of the FFW results in increased film throughput. In some embodiments, a FFW nucleation layer is deposited followed by a FFW at a high deposition rate in the same chamber without an air break.

[0023] In one or more embodiments, a small amount of a reducing agent (H 2 ) does not show CVD W film growth. Without being bound to any particular theory of operation, it is believed that without sufficient reducing agent, the W precursor is not completely reduced to metallic W. Furthermore, with a small amount of reducing agent, a portion of the W precursor is reduced to various W precursor derivatives, which are less reactive and can be easily reduced by the addition of small amounts of H 2 It is believed that the tungsten precursor is not easily reduced to metallic W in the stream. The derivative of the tungsten precursor deposited on the substrate surface is reduced to metallic tungsten.

[0024] 1-3, one or more embodiments of the present disclosure are directed to a method 100 for depositing a metal film 240. Figure 2 illustrates the method 100 for depositing a metal film 240 on a surface 202 of a substrate 200, e.g., a blanket deposition process.

[0025] Figure 3 illustrates a selective deposition process in which a metal film 240 is preferentially deposited on one surface relative to a second surface. The substrate 200 illustrated in Figure 3 includes a first material (conductive material 204) that includes a first surface (conductive surface 205) and a second material (dielectric material 206) that includes a second surface (dielectric surface 207).

[0026] FIG. 3 illustrates a substrate 200 having a surface structure 212 formed thereon. The surface structure 212 can be any suitable structure, such as a via or a trench. In the illustrated embodiment, the structure 212 has a bottom formed by a conductive surface 205 and a sidewall formed by a dielectric surface 207. While FIG. 3 illustrates a substrate with a single feature for purposes of illustration, one skilled in the art will appreciate that there may be more than one feature. The shape of the feature can be any suitable shape, including, but not limited to, a peak, a trench, and a cylindrical via. In a particular embodiment, the feature is a trench. In another particular embodiment, the feature is a via. In this regard, the term "feature" refers to any intentional surface irregularity. Suitable examples of features include, but are not limited to, a trench having a top, two sidewalls, and a bottom, a peak having a top and two sidewalls extending upward from the surface, and a via having an open bottom and sidewalls extending downward from the surface. The features can have any suitable aspect ratio (ratio of feature depth to feature width). In some embodiments, the aspect ratio is equal to or greater than approximately 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40:1. In one or more embodiments, the aspect ratio is greater than 10:1.

[0027] The method 100 includes an atomic layer deposition (ALD) process 110 that includes four sub-processes. One skilled in the art will appreciate that more or less than four sub-processes can be included in the ALD process 110, and the present disclosure is not limited to the process shown. In the ALD process 110 shown in Figure 3, a substrate having a dielectric surface 207 and a conductive surface 205 is sequentially exposed to first process conditions 112 and second process conditions 116 to selectively deposit a metallic tungsten film 240 on the conductive surface 205.

[0028] In method 100, substrate 200 is exposed to first process conditions in process 112. The first process conditions include a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film 220 on substrate surface 202. Figure 3 illustrates the formation of tungsten-containing film 220 on a surface of a first material (conductive surface 205 of conductive material 204).

[0029] The tungsten-containing film 220 is substantially free of tungsten metal. As used in this manner, the term "tungsten metal" refers to zero-valent tungsten atoms in the tungsten-containing film 220. As used in this manner, the phrase "substantially free of tungsten metal" means that no more than 5%, 2%, 1%, or 0.5% of the tungsten atoms in the tungsten-containing film 220 are zero-valent tungsten atoms.

[0030] In some embodiments, the first process conditions include a fluorine-free tungsten precursor. In some embodiments, the fluorine-free tungsten precursor comprises or consists essentially of a tungsten halide. As used herein and in the appended claims, the phrase "consists essentially of" means that the active (or reactive) species comprises 95%, 98%, 99%, or 99.5% or more of the recited species on a molar basis. In some embodiments, the tungsten halide is tungsten pentachloride (WCl 5 ) or tungsten hexachloride (WCl 6 In some embodiments, the fluorine-free tungsten precursor comprises one or more of WOCl. 4 Or WO 2 Cl 2In another embodiment, the first process conditions include a tungsten precursor selected from the group consisting of a non-fluorine-containing halide tungsten precursor or a non-chlorine-containing halide tungsten precursor, such as tungsten pentabromide (WBr 5 ) or tungsten hexabromide (WBr 6 ).

[0031] The first process conditions include a first reducing agent that reacts with the tungsten precursor. The first reducing agent (also referred to as a first reducing substance) is hydrogen (H 2 ) or ammonia (NH 3 ) or hydrazine (N 2 H 4 ) and a reactive gas such as a hydrogen-containing gas, such as argon (Ar), helium (He), or nitrogen (N 2 and a carrier gas, such as hydrogen (H 2 O 4 ). In some embodiments, the carrier gas is an inert gas. In some embodiments, the first gas consists or consists essentially of a metallic tungsten precursor gas, a reactive gas, and a carrier gas. In some embodiments, the first gas consists or consists essentially of a chlorine-free halide tungsten precursor, a fluorine-free halide tungsten precursor, a hydrogen-containing gas, and an inert gas. In some embodiments, the first reducing agent is hydrogen (H 2 O 4 ). 2 ), silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ) or ammonia (NH 3 2. The method of claim 1 , comprising one or more of:

[0032] The tungsten precursor of some embodiments is flowed into the processing region of the processing chamber in a carrier gas. In the case of solid or liquid precursors, the precursor of some embodiments is held in an ampoule, and a flow of the carrier gas passes through the ampoule to carry the precursor. In some embodiments, the carrier gas comprises an inert gas. In some embodiments, the carrier gas comprises or consists essentially of one or more of helium, neon, argon, nitrogen, krypton, or xenon. As used herein, the flow rate of the metal precursor is the flow rate of the carrier gas that contains the metal precursor.

[0033] In some embodiments, the total flow rate into the processing region of the processing chamber is the combined flow rate of the metal precursor and the first reducing agent. In some embodiments, a make-up gas is flowed into the processing region, and the metal precursor and the first reducing agent are added to the make-up gas flow. In some embodiments, the make-up gas flow has a much higher flow rate than either the metal precursor or the first reducing agent. In some embodiments, the make-up gas flow has a flow rate that is greater than 10 times (10x) the flow rate of the precursor or the first reducing agent.

[0034] In some embodiments, the flow rates of the tungsten precursor and the first reducing agent are configured to provide a tungsten-containing film that is substantially free of tungsten metal. In some embodiments, the first reducing agent has a flow rate in the range of 50-500 sccm. As will be appreciated by those skilled in the art, the flow rate of the make-up gas does not change the ratio of the tungsten precursor to the first reducing agent. The make-up gas flow can change the overall concentration of the tungsten precursor and / or the first reducing agent.

[0035] In some embodiments, the first process conditions include a flow rate of the first reducing agent in a range of 5% to 70% of a flow rate of the fluorine-free tungsten precursor.

[0036] In some embodiments, the flow ratio of the fluorine-free tungsten precursor to the first reducing agent is within a range of 10:1 to 1:2.5.

[0037] The dielectric material 206 and the dielectric surface 207 of the dielectric material 206 may comprise any suitable dielectric material. In some embodiments, the dielectric material 206 and the dielectric surface 207 may comprise one or more of silicon nitride, silicon oxide.

[0038] The conductive material 204 and the conductive surface 205 of the conductive material 204 may comprise any suitable conductive material. In some embodiments, the conductive material 204 and the conductive surface 205 of the conductive material 204 may comprise one or more of titanium nitride, titanium aluminum, aluminum, or titanium.

[0039] In some embodiments, the method 100 includes a purge process 114 as part of the ALD process 110. The purge process 114 can be any suitable purge process that removes unreacted metal precursor or first reducing agent from the processing region of the processing chamber. In some embodiments, the purge process 114 includes flowing the same inert gas that is used as a carrier gas for the metal precursor.

[0040] The method 100 includes exposure to second process conditions 116 as part of the ALD process 110. The second process conditions 116 are configured to reduce the tungsten-containing film 220 on the substrate surface to a metallic tungsten film 240. In other words, in some embodiments, exposing the tungsten-containing film 220, which is substantially free of tungsten metal, to second process conditions that include a flow of a second reducing agent converts the tungsten-containing film 220 to a metallic tungsten film 240.

[0041] In some embodiments, the second process conditions include a second reducing agent. In some embodiments, the second reducing agent is the same species as the first reducing agent. In some embodiments, the second reducing agent is a different species than the first reducing agent. The concentration of the second reducing agent may be the same as the first reducing agent concentration, or may be different from the first reducing agent concentration.

[0042] In some embodiments, the second reducing agent is hydrogen (H 2 ), silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ) or ammonia (NH 3 )

[0043] In some embodiments, the method 100 includes a purge process 118 as part of the ALD process 110. The purge process 118 can be any suitable purge process that removes unreacted metal precursor or first reducing agent from the processing region of the processing chamber. In some embodiments, the purge process 118 includes flowing the same inert gas that was used as a carrier gas for the metal precursor. In some embodiments, the purge process 118 includes flowing the same inert gas as the purge process 114. In some embodiments, the inert gas used as the carrier gas for the metal precursor, the carrier / diluent gas for the reducing agent (if present), the make-up gas, and the purge gas include the same species.

[0044] In some embodiments, as shown in Figure 3, a metallic tungsten film 240 is formed on conductive surface 205 selectively to dielectric surface 207. In some embodiments, metallic tungsten film 240 fills structure 212 in a gap-fill process (as shown in Figure 3).

[0045] The metallic tungsten film 240 of some embodiments deposits at a rate that is at least twice as fast as the deposition rate of a substantially similar process without the first reducing agent under the first process conditions.

[0046] The temperature of the substrate 200 in some embodiments is maintained throughout the ALD process 110. In some embodiments, the temperature of the substrate 200 is maintained at a temperature in the range of 400° C. to 550° C. during the first process conditions 112 and the second process conditions 116. In some embodiments, the temperature of the substrate 200 during the ALD process 110 is maintained in the range of 400° C. to 550° C., or 425° C. to 525° C., or 450° C. to 500° C.

[0047] 2, an optional nucleation layer 230 is formed on the substrate surface 202 prior to exposure to the first process conditions 212. In some embodiments, the substrate surface 202 is not exposed to air between the formation of the nucleation layer 230 and the first process conditions 212.

[0048] In other embodiments, the metal precursor may form other suitable metal films. Suitable metal films include, but are not limited to, one or more of cobalt (Co), molybdenum (Mo), tungsten (W), tantalum (Ta), titanium (Ti), ruthenium (Ru), rhodium (Rh), copper (Cu), iron (Fe), manganese (Mn), vanadium (V), niobium (Nb), hafnium (Hf), zirconium (Zr), yttrium (Y), aluminum (Al), tin (Sn), chromium (Cr), lanthanum (La), iridium (Ir), or any combination thereof. The metal precursor selected for other metal films of some embodiments may comprise or consist essentially of a fluorine-free metal halide.

[0049] After completion of the ALD process 110, a decision point 120 is checked as part of the method 100 of some embodiments. If the deposited metallic tungsten film 240 reaches a predetermined thickness or a predetermined number of ALD cycles is reached, the method 100 ends or moves to an optional post-deposition process 130. If the predetermined conditions are not met, the method 100 repeats the ALD process 110.

[0050] In some embodiments, the post-deposition process 130 includes an annealing process.

[0051] In the preceding specification, embodiments of the present disclosure have been described with reference to certain exemplary embodiments of the present disclosure. It will be apparent that various modifications can be made to the exemplary embodiments without departing from the broader spirit and scope of the embodiments of the present disclosure as set forth in the following claims. Correspondingly, the specification and drawings should be regarded in an illustrative rather than a restrictive sense.

Claims

1. 1. A method comprising: exposing a substrate surface to first process conditions comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film on the substrate surface, wherein 5% or less of the tungsten atoms are zero-valent tungsten atoms; exposing the tungsten-containing film to second process conditions comprising a flow of a second reducing agent to reduce the tungsten-containing film on the substrate surface to a metallic tungsten film; Including, The first process conditions include a flow rate of the first reducing agent being within a range of 5% to 70% of a flow rate of the fluorine-free tungsten precursor; and The method, wherein the substrate surface comprises a dielectric surface and a conductive surface.

2. 2. The method of claim 1 , wherein the fluorine-free tungsten precursor consists essentially of a tungsten halide.

3. The fluorine-free tungsten precursor is tungsten pentachloride (WCl ５ ) or tungsten hexachloride (WCl ６ 10. The method of claim 1, further comprising one or more of the following:

4. The first reducing agent is hydrogen (H ２ ), silane (SiH ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ), tetrasilane (Si ４ H １０ ) or ammonia (NH ３ 10. The method of claim 1, further comprising one or more of the following:

5. The second reducing agent is hydrogen (H ２ ), silane (SiH ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ), tetrasilane (Si ４ H １０ ) or ammonia (NH ３ 10. The method of claim 1, further comprising one or more of the following:

6. The method of claim 1 , wherein the first reducing agent and the second reducing agent comprise the same reactive species.

7. The method of claim 1 , wherein the first reducing agent has a flow rate in the range of 50 to 500 sccm.

8. 2. The method of claim 1, wherein the metallic tungsten film is formed selectively on the conductive surfaces relative to the dielectric surfaces.

9. 2. The method of claim 1, wherein the substrate surface has a structure formed thereon having a bottom and a sidewall, the bottom of the structure comprising the conductive surface and the sidewall of the structure comprising the dielectric surface.

10. The method of claim 9 , wherein the metallic tungsten film fills the structure.

11. The method of claim 1 , wherein the dielectric surface comprises one or more of silicon nitride, silicon oxide.

12. The method of claim 1 , wherein the conductive surface comprises one or more of titanium nitride, titanium aluminum, aluminum, or titanium.

13. 10. The method of claim 1 further comprising purging between said first process condition and said second process condition.

14. 10. The method of claim 1, wherein the substrate surface is maintained at a temperature in the range of 400° C. to 550° C. during the first process conditions and the second process conditions.

15. 10. The method of claim 1, further comprising forming a nucleation layer on the substrate surface prior to exposure to the first process conditions, wherein the substrate surface is not exposed to air between the formation of the nucleation layer and the first process conditions.

16. 1. A method comprising: forming a tungsten-containing film on a substrate, wherein 5% or less of the tungsten atoms are zero-valent tungsten atoms, the substrate having a conductive surface and a dielectric surface, the tungsten-containing film forming on the conductive surface selectively to the dielectric surface, the tungsten-containing film being formed by exposing the substrate to first process conditions comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent, the flow rate of the first reducing agent being in the range of 5% to 70% of a flow rate of the fluorine-free tungsten precursor; converting the tungsten-containing film to a metallic tungsten film by exposing the substrate including the tungsten-containing film, wherein 5% or less of the tungsten atoms are zero-valent tungsten atoms, to second process conditions including a flow of a second reducing agent; A method comprising:

17. 1. A method comprising: sequentially exposing a substrate having a dielectric surface and a conductive surface to first and second process conditions to selectively deposit a metallic tungsten film on the conductive surface; the first process conditions include a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film on the conductive surface, wherein 5% or less of the tungsten atoms are zero-valent tungsten atoms, and the second process conditions include a flow of a second reducing agent to reduce the tungsten-containing film on the conductive surface to a metallic tungsten film. Selectively depositing a metallic tungsten film on said conductive surface. Including, the first process conditions include a flow rate of the first reducing agent being within a range of 5% to 70% of a flow rate of the fluorine-free tungsten precursor; method.

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