Low-temperature deposition of protective material in a feature

Abstract

Methods and apparatuses for forming a protective material on a sidewall of a feature to protect the sidewall during subsequent etching and other operations are provided herein. The metal-containing protective layer is deposited thermally or using a plasma and may include forming an underlayer having a hydrogen-terminated surface prior to forming a metal-containing layer over the underlayer to form the protective material.

Description

LOW-TEMPERATURE DEPOSITION OF PROTECTIVE MATERIAL IN A FEATURECROSS REFERENCES

[0001] 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

[0002] Semiconductor device fabrication often involves etching of features. In some cases, during etching of a first material, certain other materials are also exposed to the etchants and the etchants may cause damage to some of these materials. It may be desirable to protect certain materials while other materials are being etched.

[0003] 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 admitted as prior art against the present disclosure.SUMMARY

[0004] One aspect involves a method of processing a semiconductor substrate, the method including: providing a substrate having a feature thereon, the feature having a feature opening and sidewalls; and forming a protective material on the sidewalls, whereby forming the protective material includes: forming an underlayer on the sidewalls, whereby the underlayer includes a hydrogen-terminated surface, and forming a metal-containing layer on the underlayer.

[0005] In various embodiments, the underlayer includes silicon. In various embodiments, the underlayer includes amorphous silicon. In various embodiments, the underlayer includes carbon. In various embodiments, the underlayer includes amorphous carbon. In various embodiments, the underlayer includes boron. In various embodiments, the underlayer includes phosphorous.

[0006] In various embodiments, the underlayer is deposited to a thickness of less than about 30% of a width of the feature opening at or near the feature opening.

[0007] In various embodiments, forming the underlayer further includes exposing the substrate to an underlayer precursor.

[0008] In some embodiments, the underlayer precursor is a hydrogen-containing precursor. In some embodiments, the hydrogen-containing precursor is selected from the group consisting of boranes, phosphides, hydrocarbons, hydrofluorocarbons, and carbon halides.

[0009] In some embodiments, the underlayer precursor is a halogen-containing precursor. In some embodiments, the halogen-containing precursor includes fluorine. In some embodiments, the halogen-containing precursor includes chlorine.

[0010] In some embodiments, forming the underlayer further includes exposing the substrate to a hydrogen gas.

[0011] In some embodiments, forming the underlayer further includes exposing the substrate to a hydrogen and igniting a plasma.

[0012] In some embodiments, the underlayer precursor is a carbon-containing precursor.

[0013] In some embodiments, the underlayer precursor is a halogen-containing and carbon- containing precursor.

[0014] In some embodiments, the underlayer precursor is a hydrogen-containing and carbon- containing precursor.

[0015] In various embodiments, the hydrogen-terminated surface is formed by exposing the substrate to an underlayer precursor having a hydrogen atom.

[0016] In various embodiments, the hydrogen-terminated surface is formed by exposing the substrate to an underlayer precursor and a hydrogen gas or hydrogen-containing plasma.

[0017] In some embodiments, the underlayer precursor is selected from the group consisting of silicon tetrafluoride, silicon tetrachloride, and carbon tetrachloride.

[0018] In some embodiments, the underlayer precursor is a non-silane.

[0019] In various embodiments, the metal-containing layer includes a metal selected from the group consisting of tungsten, cobalt, molybdenum, tin, titanium, hafnium, zirconium, ruthenium, and combinations thereof.

[0020] In various embodiments, the metal-containing layer includes elemental tungsten.

[0021] In various embodiments, the metal-containing layer includes elemental molybdenum.

[0022] In various embodiments, forming the metal-containing layer includes exposing the hydrogen-terminated surface to a metal-containing precursor. In some embodiments, the metalcontaining precursor includes a halogen atom. In some embodiments, the metal-containing precursor is selected from the group consisting of tungsten hexafluoride, tungsten pentafluoride, tungsten hexachloride, tungsten pentachloride, molybdenum dichloride, molybdenum trichloride, molybdenum tetrachloride, molybdenum pentachloride, molybdenum hexafluoride, and molybdenum hexachloride.

[0023] In various embodiments, at least one of the underlayer and the metal-containing layer are formed by plasma enhanced chemical vapor deposition.

[0024] In various embodiments, the method also includes igniting a plasma. In someembodiments, the plasma is ignited during forming the underlayer. In some embodiments, the plasma is ignited during forming the metal-containing layer.

[0025] In various embodiments, the underlayer is formed at a pressure of less than about 300 mTorr.

[0026] In various embodiments, the underlayer is formed at a temperature of less than about 300°C.

[0027] In various embodiments, the metal-containing layer is formed at a pressure of less than about 50 mTorr.

[0028] In various embodiments, the metal-containing layer is formed at a temperature of less than about 300°C.

[0029] In various embodiments, the plasma is ignited using a dual frequency plasma generator.

[0030] In various embodiments, the plasma is ignited during forming the underlayer and the plasma is ignited at a low power maintain a deposition rate that prevents pinch-off of material at or near the feature opening.

[0031] In various embodiments, the plasma is ignited during forming the underlayer and the plasma is ignited using a power of less than about 2500 W. In some embodiments, the plasma is ignited during forming the metal-containing layer and the plasma is ignited using a power of less than about 1000 W.

[0032] In various embodiments, a bias is not applied during igniting of the plasma.

[0033] In various embodiments, the method also includes applying a bias during igniting of the plasma using a first bias power. In some embodiments, the first bias power has a voltage of less than about 1 kV.

[0034] In various embodiments, the method also includes, after forming the protective material, etching a bottom of the feature by applying a second bias at a second bias power, whereby the first bias power is less than about 10% of the second bias power.

[0035] In various embodiments, the plasma is ignited using an inductively coupled plasma generator.

[0036] In various embodiments, the plasma is ignited using an capacitively coupled plasma generator.

[0037] In various embodiments, the protective material is formed in a plasma-free environment. In some embodiments, the protective material is formed at a temperature of less than about 500°C.

[0038] In various embodiments, the protective material is formed on the sidewalls from the feature opening to a depth of about 50% of a depth of the feature.

[0039] In various embodiments, the sidewalls include a surface having one or more materials selected from the group consisting of silicon oxide material, silicon nitride material, polysilicon material, and doped variations thereof.

[0040] In various embodiments, the doped variations thereof include dopants selected from the group consisting of boron and phosphorous.

[0041] In various embodiments, the protective material is formed on the sidewalls including alternating oxide and nitride material during 3D NAND fabrication.

[0042] In various embodiments, the method also includes after forming the protective material, etching a bottom of the feature to form a feature width at or near the bottom of the feature that is within about 10% of the width of a feature width at or near the feature opening.

[0043] These and other aspects are described further below with reference to the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a process flow diagram illustrating a method of processing a semiconductor substrate.

[0045] Figure 2 is a schematic illustration of a substrate.

[0046] Figure 3 is a process flow diagram illustrating a method of forming a protective material on the sidewalls of a feature.

[0047] Figure 4A provides an illustrative example of forming a protective material involving the ONON substrate.

[0048] Figure 4B shows schematic illustrations of an example of a feature during various operations that may be performed in accordance with certain disclosed embodiments.

[0049] Figure 5 shows a graph of normalized distribution of metal over features of the substrate at various chamber pressures during underlayer deposition and during protective layer deposition as resulting from an experiment.

[0050] Figure 6 provides examples of general structures for molybdenum precursors in accordance with certain disclosed embodiments.

[0051] Figure 7 provides examples of low valent molybdenum precursors of the formula Mo(L)e in accordance with certain disclosed embodiments.

[0052] Figure 8 provides examples of low valent dimolybdenum precursors that may be used in accordance with certain disclosed embodiments.

[0053] Figure 9 is a schematic view of a etch chamber that may be used in certain disclosed embodiments.DETAILED DESCRIPTION

[0054] In the following description, numerous specific details are set forth to provide athorough 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.

[0055] During semiconductor device fabrication processes, etching may sometimes be performed to form holes, lines, or other features. Some semiconductor device fabrication may involve etching materials, or a stack of materials. A film stack, including the alternating oxide and nitride layers, may be referred to as an ONON stack. In some embodiments, the film stack is a stack of alternating oxide and polysilicon bilayers (also known as “OPOP”). ONON layers may be used to fabricate structures such as for dynamic random access memory (DRAM) or three-dimensional NAND (3D-NAND). For 3D devices technology, advances may be driven by stack height and not necessarily feature shrink. Thus substrates may have increasingly thick material to be etched. For example, there may be a multitude of ONON bilayers to be etched (such as over 200 pairs of “ONON” bilayers, where each pair constitutes one layer of oxide and one layer of nitride). After such material is formed, a trench or feature may be etched into the thick material, and it may be challenging to etch thick material while preventing feature collapse, feature bowing, mask clogging, etch rate decrease, tapering, or other defects or issues as the substrate is exposed to etchants for longer durations or against harsher etching conditions. In some embodiments, anisotropic etching is performed for dielectric material to allow directional etching. In some embodiments, isotropic etching may be performed for sidewall etching. In some instances, etching may result in uneven etching - for example, tops of features may be etched to a given critical dimension but because it may be difficult for etchants to reach the bottoms of the features, the feature width at the bottom may not necessarily be the same as the feature width at the top, resulting in a tapered profile. It may be desirable to etch the bottoms of the feature such that the critical dimension delta between the top of the feature and the bottom of the feature is reduced, but because the top of the feature may be susceptible to further etching while etching the bottoms of the feature, it may be desirable to protect sidewalls near the top of the feature to prevent the feature width at the top from becoming even wider while the bottom of the feature is being etched.

[0056] Provided herein are methods and apparatuses for low-temperature deposition of the protective material on the sidewalls which may be used for various applications, including protecting sidewalls in high aspect ratio features to enable reduction of the delta of the criticaldimension at the top of the feature versus a bottom of the feature. The methods and apparatuses provided herein may be used to deposit protective material on the sidewalls of a feature in a substrate. The protective material may be used to control the critical dimension within a feature.

[0057] Figure 1 is a process flow diagram illustrating example operations in a method for processing a semiconductor substrate. The method for processing a semiconductor substrate 100 begins with operation 101, in which a substrate having a feature is provided. The feature may have a feature opening and sidewalls. In operation 103, a protective material is formed on the sidewalls of a feature.

[0058] Referring to Figure 1, method 100 begins with operation 101, i.e., providing a substrate having a feature thereon. In various embodiments, the substrate is a semiconductor substrate. The substrate may be a silicon wafer, e.g., a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer, including wafers having one or more layers of material, such as dielectric, conducting, or semiconducting material deposited thereon. In some embodiments, the substrate may be or include silicon (Si) or silicon germanium (SiGe). In some embodiments, the feature on the substrate is formed in silicon. In some embodiments, the feature on the substrate is formed in polysilicon.

[0059] In some embodiments, the substrate includes an oxide. An example oxide may be silicon oxide (SiCh). In some embodiments, the feature on the substrate is formed in an oxide material. In some embodiments, the feature on the substrate is formed in silicon oxide.

[0060] In some embodiments, the substrate includes a nitride. An example nitride may be silicon nitride (SisN4). In some embodiments, the feature on the substrate is formed in a nitride material. In some embodiments, the feature on the substrate is formed in silicon nitride.

[0061] In some embodiments, the substrate may be a film stack of alternating oxide and nitride film (“ONON”) deposited on the substrate. In various embodiments, the oxide layer is a silicon oxide layer. In various embodiments, the nitride layer is a silicon nitride layer. In some embodiments, the feature on the substrate is formed in an ONON stack.

[0062] In some embodiments, each oxide and nitride layer may be the same or different thickness. The thickness of each oxide and nitride layer may be between about 10 nm and about 100 nm, or about 35 nm in some embodiments.

[0063] Oxide and nitride layers for forming the alternating oxide and nitride film stack may be deposited using any suitable technique, such as atomic layer deposition (ALD), plasma-enhanced atomic layer deposition (PEALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or sputtering. In various embodiments, the oxide and nitride layers are deposited by PECVD.

[0064] The film stack may include up to but not limited to 512 layers of alternating oxide and nitride layers, whereby each oxide or each nitride layer constitutes one bilayer.

[0065] In some embodiments, the substrate may be a film stack of alternating oxide and polysilicon film (“OPOP”) deposited on the substrate. In various embodiments, the oxide layer is a silicon oxide layer. In some embodiments, the feature on the substrate is formed in an OPOP stack.

[0066] Figure 2 shows an example schematic illustration of a substrate 200 with alternating oxide (201) and nitride (202) films deposited on the substrate 200 and a feature 220 therein. Note that while the structure shown in Figure 2 shows an oxide deposited first, followed by nitride, oxide, nitride, etc., nitride may be deposited first, followed by oxide, nitride, oxide, etc. In some embodiments, the top of the ONON stack may also contain a thicker sacrificial oxide layer that is later removed during an integration step for the post etch structure.

[0067] In some embodiments, the substrate may be a film stack of alternating oxide and polysilicon layers deposited on the substrate. The film stack, including the alternating oxide and polysilicon layers, is referred to as an OPOP stack. OPOP stack may have an oxide deposited first, followed by polysilicon, oxide, polysilicon, etc., polysilicon may be deposited first, followed by oxide, polysilicon, oxide, etc.

[0068] In some embodiments, the substrate may be dielectric layers. Examples of dielectric layers include doped and undoped silicon oxide, silicon nitride, and aluminum oxide layers, with specific examples including doped or 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). In some embodiments, substrates may be doped or undoped with phosphorous or boron. For example, oxides and / or nitrides may be doped with other elements, such as but not limited to phosphorous (P) and / or boron (B) and / or arsenic (As). In some embodiments, nitrides may be doped with oxygen, or carbon, or both oxygen and carbon. In some embodiments, oxides may be doped with phosphorous, or boron, or both phosphorous and boron.

[0069] In some embodiments, the substrate may include any number of intervening layers. For example, a substrate may include any number of layers deposited in various arrangements on a semiconductor substrate.

[0070] In various embodiments, the substrate has a feature thereon. The feature may have a feature opening and sidewalls. The feature may be formed by using a carbon material which may be used as a carbon-containing hard mask to form the feature.

[0071] In various embodiments, the substrate includes a carbon-containing hard mask such asamorphous carbon material. The carbon-containing hard mask may be a blanket layer having no features etched thereon. The carbon-containing hard mask may be patterned to expose a dielectric material or ONON or OPOP stack. The carbon-containing hard mask may be used as a mask to pattern material underlying the mask. In various embodiments, this carbon-containing hard mask may be the material to be ultimately etched after forming appropriate hard masks over it with the desired pattern. The hard mask may be formed by plasma-enhanced chemical vapor deposition (PECVD) by introducing a hydrocarbon precursor gas to a processing chamber and igniting a plasma to deposit the carbon-containing hard mask on a substrate. Hydrocarbon precursors may have the chemical formula CxHy, where x is an integer from 2 to 10 and y is an integer from 2 to 24. Examples include methane, acetylene, ethylene, propylene, butane, cyclohexane, benzene, and toluene.

[0072] The carbon-containing hard mask may also vary in hardness such as material having a hardness between about 8 and about 12. The carbon material may also have any suitable modulus, such as between about 60 and about 160 GPa. In some embodiments, the percentage of sp3 bonds in the carbon material may be between about 15% and about 50%.

[0073] In various embodiments, the carbon-containing hard mask is between about 50 nm and about 500 nm thick for 3D NAND applications. The critical dimension of features to be etched in the amorphous carbon material depends on the application. In some embodiments, the features have a critical dimension between about 50 nm and about 120 nm for 3D NAND applications. In some embodiments, the features have a critical dimension between about 16 nm and about 22 nm for DRAM applications.

[0074] The substrate may have features such as vias or contact holes, which may be characterized by one or more narrow and / or re-entrant openings, constrictions within the feature, having sidewalls. In some embodiments, features may have 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, at least about 50: 1, or at least about 80: 1, or at least about 90:1, or at least about 100: 1, or at least about 150: 1, or at least about 200: 1, or higher. One example of a feature is a hole or via in a semiconductor substrate or a layer on the substrate. The feature may have a feature opening at or near the top of the feature of about 80 nm to about 150 nm, or 80 nm to about 120 nm, or about 100 nm.

[0075] Referring to operation 103, a protective material is formed on the sidewalls of a feature.

[0076] Figure 3 illustrates a method for forming a protective material on the sidewalls of afeature 110. The protective material may include an underlayer and a metal-containing layer. The method 110 begins with forming an underlayer 111, where the underlayer includes a hydrogen-terminated surface.

[0077] The protective material is non-conformal in various embodiments. The protective material may be primarily formed at or near the top of the feature or the feature opening, or more protective material may be formed at or near the top of the feature or the feature opening as compared to the bottom or deepest sidewall region of the feature. In some embodiments, the depth of the protective layer formed on the sidewall from the feature opening to a depth of about 50% of the feature. For example, for a feature having a sidewall depth of 7 pm from the feature opening, the protective layer may be formed on the sidewalls to a depth of about 3 pm to about 4 pm. In another example, for a feature having a sidewall depth of 9 pm from the feature opening, the protective layer may be formed on the sidewalls to a depth of about 4 pm to about 5 pm. In yet another example, for a feature having a sidewall depth of 12 pm from the feature opening, the protective layer may be formed on the sidewalls to a depth of about 5 pm to about 7 pm.

[0078] In some embodiments, the protective layer is formed on the sidewalls of alternating oxide and nitride material (ONON). In some embodiments, the protective layer is formed on the sidewalls of alternating oxide and nitride material (ONON) during the 3D NAND fabrication. In some embodiments, the protective layer is formed on the sidewalls of alternating oxide and polysilicon material (OPOP). In some embodiments, the protective layer is formed on the sidewalls of alternating oxide and polysilicon material (OPOP) during the 3D NAND fabrication.

[0079] In some embodiments, the protective material may be removable. The protective material may be removed during or after an etching operation to etch the feature bottom. In some embodiments, where the underlayer is a hydrogen-terminated layer and the metal-containing layer is a tungsten layer, the hydrogen-terminated underlayer and tungsten layer are removable.

[0080] Referring to operation 111 of Figure 3, forming the underlayer involves exposing the substrate to an underlayer precursor. Exposure may be performed thermally in a plasma-free environment or may be performed using plasma, which may be generated in situ or remotely. Underlayer precursors may be hydrogen-containing precursors, halogen-containing precursors, silicon-containing precursors, carbon-containing precursors, boron-containing precursors, and combinations thereof.

[0081] In some embodiments, forming an underlayer involves exposing the substrate to a hydrogen-containing precursor. Examples of hydrogen-containing precursors include, but are not limited to, silane (SiH4), borane (BEE), phosphide, hydrocarbons (CaHb), hydrofluorocarbons(CxHyFz or CHjFk), carbon halides, phosphine (PH3), and combinations thereof. For CaHb, a and b may be integers and in some embodiments, a is an integer greater than or equal to 1 and less than or equal to 3, or between 1 and 3, and b may be greater than or equal to 2, or less than or equal to 4, or between 2 or 4. For CxHyFz, x can be any integer greater than or equal to 1, y can be any integer greater than or equal to 0, and z can be any integer greater than or equal to 1. For CHjFk, j may be an integer greater than or equal to 1 and less than or equal to 4, where j+k = 4.

[0082] In some embodiments, forming an underlayer involves exposing the substrate to a halogen-containing precursor. The halogen-containing precursor may contain fluorine or chlorine. Examples of hydrogen-containing precursors include, but are not limited to, silicon tetrachloride (Si Cl 4), silicon tetrafluoride (SiF4), carbon tetrachloride (CCI4), and hydrofluorocarbons (CxHyFz or CHjFk). In some cases, forming the underlayer with a halogencontaining precursor may further include exposing the substrate to hydrogen gas (H2). In some embodiments, exposing the substrate to hydrogen gas may further include igniting a plasma to generate plasma-activated hydrogen species.

[0083] In some embodiments, forming an underlayer involves exposing the substrate to a silicon-containing precursor. Examples of silicon-containing precursors include but are not limited to, silicon tetrafluoride and silicon tetrachloride, and combinations thereof. In some embodiments, silicon-containing precursors may not contain silane (SiH4).

[0084] In some embodiments, forming an underlayer involves exposing the substrate to a carbon-containing precursor. Examples of carbon-containing precursors include, but are not limited to, hydrocarbons (CxHy), hydrofluorocarbons (CxHyFz), and carbon halides. In some embodiments, carbon-containing precursors may be used in combination with halogencontaining precursors. In another embodiment, carbon-containing precursors are used in conjunction with hydrogen-containing precursors.

[0085] In some embodiments, the underlayer may contain silicon or carbon. In some embodiments, the underlayer may be amorphous, for example, amorphous silicon or amorphous carbon. In some embodiments, the underlayer may be a doped or undoped silicon- or carbon- containing layer. In some embodiments, the underlayer may include other elements, such as boron and / or phosphorus. In some embodiments, boron and / or phosphorus may present as dopants in silicon- or carbon-containing layers.

[0086] In some embodiments, the underlayer includes a composition that enables a higher sticking coefficient for a metal-containing precursor to form a metal-containing material thereon as compared to a multi-layer surface after an etching operation, where the surface is ONON, OPOP, or other material.

[0087] In some embodiments, the thickness of the underlayer is less than about 30%, less than about 20%, less than about 10%, or less than about 5% of the width of the feature opening at or near the feature opening. In some implementations, the thickness of the underlayer is less than about 30 nm, e.g., about 1 A to about 3 nm, about 3 nm to about 4 nm, about 20 nm to about 30 nm, and about 1 to about 30 nm.

[0088] In some embodiments, the underlayer is deposited to a sidewall depth of about the top 50% of the sidewalls, as measured from the dielectric feature opening. For example, for a feature having a sidewall depth of 7 pm, the underlayer may be formed to a depth of about 3 pm to about 4 pm. In another example, for a feature having a sidewall depth of 9 pm, the underlayer may be formed to a depth of about 4 pm to about 5 pm. In yet another example, for a feature having a sidewall depth of 12 pm, the underlayer may be formed to a depth of about 5 pm to about 7 pm.

[0089] In some embodiments, the underlayer formed in operation 111 has a hydrogen- terminated surface. In some embodiments, operation 111 serves to cover the underlying functionality of the sidewall surface, which may be a dielectric surface, and thereby form a surface having different functionality to allow formation of a metal-containing protective material. Hydrogen-terminated surfaces may be advantageous for deposition of a metalcontaining material on the sidewalls of a feature, which may be conformal in some embodiments and may be non-conformal in other embodiments. For example, in an ONON stack, the nitride material may have hydrogen-terminated surfaces while the oxide materials may have little or no hydrogen-terminated surfaces. This can lead to preferential deposition of metal (e.g., tungsten) on silicon nitrides, i.e., hydrogen-terminated surfaces, over silicon oxide. Certain disclosed embodiments result in formation of metal-containing protective material over both oxide and nitride and polysilicon material. The metal layer deposited over silicon oxides and / or silicon nitrides may act as a protective layer in subsequent etching. The lack of a protective layer over silicon oxides may leave the silicon oxide susceptible in subsequent etching. Hence, the forming the hydrogen-terminated underlayer, in turn, facilitates deposition of the metal layer regardless of the underlying substrate.

[0090] In some embodiments, the hydrogen-terminated underlayer may contain Si-H bonds or C-H bonds.

[0091] A hydrogen-terminated underlayer may be formed by any suitable deposition technique, technique, such as atomic layer deposition (ALD), plasma-enhanced atomic layer deposition (PEALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD). In some embodiments, a hydrogen-terminated underlayer may be formedwith or without plasma.

[0092] In some embodiments, a hydrogen-terminated underlayer is formed by exposing the substrate to an underlayer precursor having a hydrogen atom, e.g., CH4.

[0093] In various embodiments, a hydrogen-terminated underlayer is formed by exposing the substrate to an underlayer precursor and a hydrogen gas, or hydrogen-containing plasma. Examples include SiF4 with plasma activated H2, or SiCh with plasma activated H2.

[0094] In some embodiments, a hydrogen-terminated underlayer is formed by exposing the substrate to boron-containing or phosphorus-containing underlayer precursors. Examples of boron-containing precursors include, but are not limited to, BH3, BCI3, and B2H6. Examples of phosphorous-containing precursors include phosphorous tetrafluoride (PF3) and phosphine (PH3).

[0095] In various embodiments, operation 111 may be performed at low to moderate substrate temperatures. For example, the substrate temperature may be less than about 500°C, less than about 300°C, e.g., less than about 100°C, less than about 75°C less than about 50°C, about 20°C to about 100°C, or about 20°C to about 50°C. In some embodiments, operation 111 is performed at higher temperatures when the hydrogen-terminated underlayer is formed without plasma. For example, without plasma, operation 111 may be performed at a temperature less than about 100°C, less than about 200°C, e.g., 100°C to about 200 °C, or less than 300 °C, e.g., 100°C to about 300 °C or about 200°C to about 300°C.

[0096] In some embodiments, operation 111 may be performed at a chamber pressure of about 100 mTorr to about 300 mTorr, e.g., 100 mTorr, 200 mTorr, and 300 mTorr. In some embodiments, pressure may be less than 100 mTorr, e.g., 50 mTorr, or less than 300 mTorr. In some embodiments, pressure may be more than 300 mTorr, e.g., 350 mTorr, 500 mTorr, and 1 Torr. In various embodiments, pressure is less than 1 Torr. For example, forming an underlayer using SiF4 as a precursor may be performed at a chamber pressure may be 100 mTorr, 200 mTorr, or 300 mTorr.

[0097] In various embodiments, operation 111 is performed at higher pressure when the hydrogen-terminated underlayer is formed without plasma. For example, without plasma, operation 111 may be performed at a pressure less than 1 Torr. In another example, with plasma, operation 111 may be performed at pressure between 100 mTorr to 300 mTorr.

[0098] In operation 113, a metal-containing layer is formed on the hydrogen-terminated underlayer. In some embodiments, the tungsten may be deposited over the underlying silicon or carbon layer. In some implementations, molybdenum may be deposited over the silicon or carbon layers.

[0099] Figure 3 depicts a process flow diagram illustrating example operations in a method of forming a protective material on the sidewalls of a feature. The method for forming the protective material 110 begins with operation 111, where an underlayer is formed on the sidewalls of a feature. In various embodiments, the underlayer includes a hydrogen-terminated surface. In operation 113, a metal-containing layer is formed on the underlayer.

[0100] Examples of certain disclosed embodiments may be used for a variety of applications, including but not limited to forming a DRAM architecture including a buried wordline (bWL), and wordline features in a 3D NAND.

[0101] Figure 4A provides an illustrative example of forming a protective material involving the ONON substrate, hydrogen-terminated silicon underlayer, and tungsten hexafluoride precursor. As depicted in Figure 4A, during operation 113, the metal-containing layer (e.g., tungsten) may be formed on the hydrogen-terminated underlayer (e.g., hydrogen-terminated silicon underlayer). The hydrogen-terminated underlayer may be formed on the ONON substrate. In some embodiments, metal halide bonds (e.g., W-F bond, Mo-F bond) in metalcontaining precursor may react with Si-H bond or C-H bond and deposits a metal-containing layer over the underlayer. Figure 4A depicts a process using a tungsten hexafluoride, in such depiction, W-F bond may react with Si-H bond, and depositing tungsten layer over the silicon underlayer.

[0102] The metal-containing layer may contain tungsten, cobalt, molybdenum, tin, titanium, hafnium, zirconium, ruthenium, and combinations thereof. In some embodiments, the metalcontaining layer contains elemental tungsten. In some embodiments, the metal-containing layer contains elemental molybdenum. In some embodiments, the metal-containing layer may incorporate some species from the underlayer, such as but not limited to boron, phosphorous, and arsenic.

[0103] In some embodiments, the thickness of the metal-containing layer is less than about 30%, less than about 20%, less than about 10%, or less than about 5% of the width of the feature opening at or near the feature opening. In some implementations, the thickness of the metalcontaining layer is less than 30 nm, e.g., about 1A to about 3 nm, about 3 nm to about 4 nm, about 20 nm to about 30 nm, and about 1 to about 30 nm.

[0104] In some embodiments, the depth of the metal-containing layer is about 50% of the sidewalls. For example, for a feature having a sidewall depth of about 7 pm, the metalcontaining layer may be about 3 pm to about 4 pm. In another example, a feature having a sidewall depth of about 9 pm, the metal-containing layer may be about 4 pm to about 5 pm. Yet another example is a feature having a sidewall depth of about 12 pm, the metal-containing layermay be about 5 pm to about? pm.

[0105] Returning to FIG. 3, in operation 113, forming the metal-containing layer on the underlayer involves exposing the hydrogen-terminated underlayer to a metal-containing precursor. The metal of the metal-containing layer may be tungsten, molybdenum, tin, or any other metal, or combinations of metals, or metal alloys. The metal-containing layer may be formed by exposing the hydrogen-terminated underlayer with an appropriate metal-containing precursor. For example, in some embodiments, the tungsten-containing layer may be formed by exposing the hydrogen-terminated underlayer to a tungsten-containing precursor, or in some embodiments, the molybdenum-containing layer may be formed by exposing the hydrogen- terminated underlayer to a molybdenum-containing precursor.

[0106] In some embodiments, the metal-containing precursor contains a halogen atom.

[0107] In some embodiments, a metal-containing precursor may be a metal halide, e.g., tungsten halide, molybdenum halide, cobalt halide, tin halide, etc. The metal halide may contain any appropriate metal, including molybdenum, tungsten, cobalt, tin, titanium, hafnium, zirconium, ruthenium, etc., and any halide, including fluorine, chlorine, bromine, and iodine. In various embodiments, any suitable metal-containing precursors may be used to form the metalcontaining layer.

[0108] In some embodiments, the tungsten halide is tungsten hexafluoride (WFe), tungsten hexabromide, tungsten hexachloride, tungsten pentafluoride, tungsten pentachloride, tungsten pentabromide. In some embodiments tungsten halide is tungsten (II) halide, tungsten (III) halide, tungsten (IV) halide.

[0109] In some embodiments, the molybdenum halide is molybdenum chloride, molybdenum fluoride. Examples of molybdenum chloride precursors include, but are not limited to, molybdenum dichloride, molybdenum trichloride, molybdenum tetrachloride, molybdenum pentachloride, and molybdenum hexachloride. Examples of molybdenum fluoride include, but are not limited to, molybdenum difluoride, molybdenum trifluoride, molybdenum tetrafluoride, molybdenum pentafluoride, and molybdenum hexafluoride.

[0110] In some embodiments, the molybdenum halide is a molybdenum oxyhalide. Examples of molybdenum oxyhalide include but are not limited to, molybdenum dichloride dioxide (MOO2CI2), molybdenum tetrachloride oxide (MoOCh), molybdenum tetrafluoride oxide (MoOF4), molybdenum dibromide dioxide (MoChBrc), and the molybdenum iodides MOO2I, and MO4O11I.

[0111] Additional lists of tungsten-containing precursors and molybdenum-containing precursors are provided below and in Figures 6, 7, and 8.

[0112] The metal-containing layer may be formed by any suitable deposition technique, technique, such as atomic layer deposition (ALD), plasma-enhanced atomic layer deposition (PEALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD). In some embodiments, a hydrogen-terminated underlayer may be formed with or without plasma.

[0113] In some embodiments, the metal-containing layer may be deposited with or without plasma. For example, metal halides such as WFe with EE plasma may be used to deposit a metal-containing layer. Any one or more of the above identified metal containing precursors may be used in conjunction with the plasma. For example, in some embodiments, a metal halide may be introduced with a reducing agent while igniting a plasma. In one example, tungsten hexafluoride is introduced to the chamber with hydrogen gas and plasma is ignited within the chamber to react tungsten hexafluoride with hydrogen in a plasma environment to form a tungsten protective material. In some embodiments where plasma may be used for formation of the protective layer, a plasma may be generated by remote means or in-situ. The plasma may be generated using an inductively coupled plasma or a capacitively coupled plasma. For an in-situ example, the substrate may be processed in a chamber having a showerhead and a pedestal, which electrically communicate with a radio frequency (RF) power supply and matching network 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 timing. For example, the RF power supply and the matching network may be operated at any suitable power to form a plasma having a desired composition of radical species. Likewise, the RF power supply may provide RF power of any suitable frequency. In some embodiments, a dual frequency plasma may be used. In some embodiments, the RF power supply may be configured to control high- and low-frequency RF power sources independently of one another. In some embodiments, the RF frequency is non- sinusoidal. In some embodiments, the RF frequency is sinusoidal. 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 60 MHz, or greater than 80 MHz. In some embodiments, a single frequency plasma is used. In various embodiments, forming the underlayer may be performed with a plasma at a power of less than about 2500W. In various embodiments, forming the metal-containing layer may be performed at a plasma power of less than about 1000 W. In some embodiments, the plasma power used for forming the metal-containing layer may be about 50% or less of theplasma power used for forming the underlayer. It will be appreciated that any suitable parameters may be modulated discretely or continuously to provide plasma energy for the surface reactions. In some embodiments, during deposition, a bias may be applied to the pedestal holding the substrate. In some embodiments, the bias may be powered at a voltage of less than about 10% of the voltage used during etching as further described below. In some embodiments the bias may be less than about 1.5 kV or less than about 1 kV.

[0114] In some embodiments, both operations 111 and 113 are performed with plasma. In various embodiments, operation 111 is performed with plasma, and operation 113 is performed in a plasma-free environment. In some embodiments, operation I l l is performed in a plasma- free environment, and operation 113 is performed with plasma.

[0115] In various embodiments, operation 113 may be performed at low to moderate substrate temperatures. For example, the substrate temperature may be less than about 500°C, less than about 300°C, e.g., less than about 100°C, less than about 75°C less than about 50°C, about 20°C to about 100°C, or about 20°C to about 50°C. In some embodiments, operation 113 is performed at higher temperatures when the metal-containing layer is formed without generating a plasma. For example, without plasma, operation 113 may be performed at a temperature less than 100°C, less than 200°C, e.g., about 100°C to about 200°C, or less than about 300°C, e.g., about 100°C to about 300°C or about 200°C to about 300°C.

[0116] In some embodiments, operating pressure for operations 111 and 113 may be the same or different. Non-limiting examples include where both operations 111 and 113 may be performed at about 100°C, about 50°C, or at room temperature. In another non-limiting example, operation 111 may be performed at about 50°C, and operation 113 may be performed at about 100°C.

[0117] In some embodiments, operation 113 may be performed at a pressure of about 5 mTorr to about 100 mTorr, or about 10 mTorr to about 100 mTorr or about 20 mTorr to about 100 mTorr, e.g., about 25 mTorr. In some embodiments, operation 113 may be performed at the pressure of about 100 mTorr to about 300 mTorr, e.g., about 100 mTorr, about 200 mTorr, and about 300 mTorr. In some embodiments, pressure may be less than about 100 mTorr (e.g., about 50 mTorr, or about 25 mTorr), or less than about 50 mTorr, or less than about 300 mTorr. In some embodiments, pressure may be more than about 300 mTorr, e.g., about 350 mTorr, about 500 mTorr, and about 1 Torr. In various embodiments, pressure is less than about 1 Torr. For example, deposition of the metal-containing layer using WFe may be performed at a chamber pressure of about 25 mTorr or of about 50 mTorr. The pressure may be selected depending on the composition of the material deposited and the precursor used.

[0118] In various embodiments, operation 113 is performed at higher pressure when the metalcontaining layer is formed without plasma. For example, without plasma, operation 113 may be performed at a pressure less than about 1 Torr. In another example, with plasma, operation 113 may be performed at a pressure of about 100 mTorr to about 300 mTorr.

[0119] In some embodiments, operating pressure for operations 111 and 113 may be the same or different. Non-limiting examples include where operations 111 and 113 may be performed at about 100 mTorr. In another non-limiting example, operation 111 is performed at about 100 mTorr and operation 113 is performed at 25 mTorr. Other non-limiting examples include, operation 111 performed at about 200 mTorr and operation 113 is performed at 25 mTorr; operation 111 performed at about 300 mTorr and operation 113 is performed at 25 mTorr.

[0120] In some embodiments, operation 113 is performed at a lower pressure than operation 111. For example, operation 113 is performed at 25 mTorr and operation 111 is performed at 300 mTorr.

[0121] In some embodiments, characteristics (coverage, location, depth, penetration, conformality) of the protective layer on the sidewalls of a feature is modulated by the pressures. For example, interplay of the operating pressure in operations 111 and 113 may be used to modulate where the hydrogen-terminated underlayer and metal-containing layer are formed, respectively. In various embodiments, operating pressure of operations 111 and 113 are selected such that protective layer has desired characteristics such as location, depth, uniformity, conformality, and composition.

[0122] After forming the protective layer, in some embodiments, the substrate is etched. Etching may be performed using a halogen-containing gas, a hydrogen-containing gas, or plasmas thereof, or combinations thereof. In some embodiments, during etching, a bias is applied to the pedestal which may be used to assist in directional etching. The bias may be powered to deliver a voltage of about 8 kV to about 16 kV or about 10 kV to about 15kV.

[0123] In various embodiments, the selection of the chamber pressure used during the deposition of the underlayer and during the deposition of the metal -containing layer of the protective material may have a critical effect on the deposition profile of the protective material. Figure 5 shows an example graph of the underlayer deposition pressure on the Y-axis and the metal-containing layer deposition pressure on the X-axis. The shading depicts the relative deposition profile on a substrate having high aspect ratio features. The normalized mask key shows a darker color where distribution of the deposited protective film was only at the tops of the feature, which in some embodiments may not be desirable. The lighter shading and the noshading regions (normalized mask 0.960 and lower) are regions for embodiments where theprotective material deposited into sufficient depths of the sidewalls of the high aspect ratio features, such as at least about 30% or at least about 50% into the depth of the feature.

[0124] Returning to Figure 3, in some embodiments, protective layer may be formed by performing operation 111 with SiF4 precursor at 300 mTorr and performing operation 113 with WFe at 25mTorr. This combination of pressure resulted in tungsten primarily near the feature opening, and tungsten deposited on the sidewall penetrating to about 4 pm depth from the feature opening. This may be due to a larger amount of Si-H present near the feature opening compared to the feature bottom. In some implementation, tungsten deposited at or near the feature opening is thicker than sidewalls and / or towards feature bottom.

[0125] In some embodiments, protective layer may be formed by performing operation 111 with SiF4 precursor at 200 mTorr and performing operation 113 with WFe at 25mTorr. Such operating conditions may be used to deposit tungsten on the sidewalls of the feature, penetrating more than 4 pm depth from the feature opening, e.g., between about 4 pm and 7 pm depth in some implementations.

[0126] In some embodiments, protective layer may be formed by performing operation 111 with SiF4 precursor at 100 mTorr and performing operation 113 with WFe at 25mTorr. Such operating conditions may be used to deposit tungsten on the sidewalls of the feature, penetrating to about 7 pm depth from the feature opening.

[0127] In some embodiments, tungsten or metal-containing layer is deposited at or near the feature bottom, regardless of the SiF4 operating pressure. This may be caused by tungsten precursors diffusing to and collected at or near the feature bottom, leading to tungsten deposition at or near the feature bottom. In some cases, the tungsten deposited at or near the feature bottom may not be uniform or conformal.

[0128] In various embodiments, operation 111 and 113 may be repeated to form a protective layer with a desired thickness.

[0129] Additional details for forming of tungsten-containing layer and molybdenum- containing layer are provided below.

[0130] Figure 4B shows an example of a feature undergoing various operations performed in accordance with certain disclosed embodiments. In 401, a substrate having an ONON stack and a mask formed thereon is provided. The ONON stack is directionally etched to form a via using a hydrogen-containing and fluorine-containing plasma. Etching may result in the bottom of the feature having a width of the feature opening as measured from sidewall to sidewall being smaller than that of the width of the feature opening as measured from sidewall to sidewall at or near the top of the feature. In 403, an underlayer is deposited on the substrate. The underlayerdeposits on the sidewalls at or near the top of the feature and into about 50% of the depth of the feature on the sidewalls as measured from the top of the feature. The bottom of the feature may not have underlayer material deposited thereon. The underlayer material may have a hydrogen- terminated surface. In 405, a metal-containing layer is deposited over the underlayer. In some embodiments, the metal-containing layer may preferentially be deposited on the underlayer material, or growth on the underlayer may be faster than on other regions of the substrate, such as the bottom of the feature. In this example, tungsten is deposited. In 407, etching is performed to widen the bottom of the feature which can be done to reduce the delta between the feature opening width at the top of the feature and at the bottom of the feature, thereby reducing the delta of the critical dimension at the top versus at the bottom of the feature. Etching may be performed using a fluorine-containing and / or hydrogen-containing gas and / or plasma.APPARATUS

[0131] In an exemplary embodiment, FIG. 9 is a schematic view of an etch reactor that may be used in an embodiment. In one or more embodiments, a plasma processing chamber 900 comprises a gas distribution plate 906 providing a gas inlet and an electrostatic chuck (ESC) 908, within an etch chamber 949, enclosed by a chamber wall 952. Within the etch chamber 949, a stack 903 is positioned over the ESC 908. An edge ring 909 surrounds the ESC 908. An ESC temperature controller 950 is connected to a chiller 914. In this embodiment, the chiller 914 provides a coolant to channels 912 in or near the ESC 908. A radio frequency (RF) source 930 provides RF power to a lower electrode, which in this embodiment are the ESC 908. In an exemplary embodiment, 400 kHz and 60 MHz power sources make up the RF source 930. In this embodiment, the upper electrode is grounded. In this embodiment, one generator is provided for each frequency. Other arrangements of RF sources and electrodes may be used in other embodiments. A controller 935 is controllably connected to the RF source 930, an exhaust pump 920, and the etch gas source 910. An example of such an etch chamber is the Flex® etch system manufactured by Lam Research Corporation of Fremont, CA. The process chamber can be a CCP (capacitive coupled plasma) reactor or an ICP (inductive coupled plasma) reactor.

[0132] In some implementations, a controller 935 is part of a system, which may be part of the above-described examples. Such systems can comprise 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 toas the “controller,” which may control various components or subparts of the system or systems. The controller, 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 settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0133] Broadly speaking, the controller 935 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 integrated 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 935 in the form of various individual settings (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.

[0134] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller 935 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 a new 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 settings, which are then communicated to the system from the remote computer. In some examples, the controller 935 receives instructions in the form of data, which specify parameters for each of the processing steps to beperformed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller 935 is configured to interface with or control. Thus as described above, the controller 935 may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller 935 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.

[0135] 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 physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (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 / or manufacturing of semiconductor wafers.

[0136] As noted above, depending on the process step or steps to be performed by the tool, the controller 935 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.PRECURSORSTUNGSTEN DEPOSITION AND PRECURSOR

[0137] Examples of W-containing precursors include tungsten hexacarbonyl (W(CO)e) and tungsten halides such as tungsten hexafluoride (WFe), tungsten hexachloride (WCk), and tungsten pentachloride (WCls). In some embodiments, tungsten oxy-halides including WO2CI2, WOBr4, WOCh, and WOF4 may be used. Organo-metallic precursors such as MDNOW (methylcyclopentadienyl-dicarbonylnitrosyl-tungsten) and EDNOW (ethylcyclopentadienyl- dicarbonylnitrosyl-tungsten) may also be used. PVD of Mo or W can be performed by sputter deposition of the target material.

[0138] In some embodiments, tungsten-containing precursors may contain oxygen. Examplesof such W-containing precursors used herein may be metal oxohalide precursors. Examples of metals that may be deposited include W, Mo, chromium (Cr), vanadium (V), and iridium (Ir). The metal oxohalide precursors include those of the form MxOyHzwhere M is the metal of interest (e.g., W, Mo, Cr, V, or Ir) and H is a halide (e.g., fluorine (Fl), chlorine (Cl), bromine (Br), or iodine (I) and x, y, and z being any number greater than zero that can form a stable molecule. Specific examples of such precursors include: tungsten tetrafluoride oxide (WOF4), tungsten tetrachloride oxide (WOCI4), tungsten dichloride dioxide (WO2CI2), molybdenum tetrafluoride oxide (MoOF4), molybdenum tetrachloride oxide (MoOCh), molybdenum dichloride dioxide (MOO2CI2), molybdenum dibromide dioxide (MoChBrc), molybdenum oxoiodides MOO2I and MO4O11I, chromium dichloride dioxide (CrChCh), iridium dichloride dioxide (IrChCh), and vanadium oxytri chloride (VOCI3). The metal oxohalide precursor may also be a mixed halide precursor that has two or more halogens.MOLYBDENUM DEPOSITION AND PRECURSOR

[0139] In the methods described herein, molybdenum deposition may be performed after operation 111. 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.

[0140] In some embodiments, a Mo precursor is a molybdenum chloride (MoCk) compound, also referred to as a molybdenum chloride precursor or MoCk precursor. Operations 113 may use a molybdenum oxyhalide 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 (M0CI4), molybdenum pentachloride (Mods), 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 MoXz precursors include molybdenum fluoride (MoFe). In some embodiments, a non-fluorine-containing MoXz precursor is used to prevent fluorine etch or incorporation. In some embodiments, a non-brominecontaining and / or a non-iodine-containing MoXz precursor is used to prevent etch or bromine or iodine incorporation.

[0141] In some embodiments, molybdenum oxyhalide precursor may be used. 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 MoOyXz forms a stable compound. Examples of molybdenum oxyhalides include molybdenum dichloride dioxide (MOO2CI2), molybdenum tetrachloride oxide (MoOCh), 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 MoCk precursor, MoOyXz precursor, or a combination thereof.

[0142] In some embodiments, molybdenum precursor may be reacted with a co-reactant. Examples of co-reactants include hydrogen (H2), silane (SiEL), diborane (B2H6), germane (GeEL), ammonia (NH3), and hydrazine (N2H4).

[0143] In some embodiments, molybdenum-precursors may be used with 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, nitrogen-containing gas, such as nitrogen (N2) and other gases, such as Ar and NH3. The plasma species may be inert or react with the molybdenum precursor to form a film.

[0144] Molybdenum-containing layer may be formed 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.

[0145] 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, 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 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 beused to control the rate of reactions. In some embodiments, the temperature and / or pressure may be used to control selectivity.

[0146] In some embodiments, molybdenum fill may involve CVD. In a CVD process, the molybdenum precursor and reactant are in vapor phase together in the deposition chamber. Generally speaking, a CVD process fills a feature faster than an ALD process. In one example, the precursor may be a molybdenum oxychloride, such as MOO2CI2, and is flowed into the chamber with a reactant, such as H2. In this example, the wafer is simultaneously exposed to the precursor and reactant, which react and fill features with Mo.

[0147] In still some other embodiments, a feature may be filled using a pulsed CVD process. The pulsed CVD process continuously flows a reactant into a chamber while pulses of a precursor flow into the chamber. For example, H2 gas may be flowed into the chamber and is continuously flowing into the chamber while the molybdenum-containing precursor is intermittently flowing into the chamber. The temperature of the substrate and pressure in the chamber may be controlled during a CVD operation.

[0148] Molybdenum may be selectively deposited into a feature using the methods described herein. Selective deposition refers to preferential deposition on a first material with respect to a second material. Molybdenum deposition and growth may be easier on a metal material relative to molybdenum deposition and growth on a dielectric material. For example, a feature may have a sidewall surface of SiCh and a TiN plug in a bottom portion of the feature. In selective deposition, molybdenum is deposited into the feature and may grow on the TiN plug but not grow (or grow to a lesser extent) on the SiCh sidewall surfaces.

[0149] Process conditions such as the precursor gas, the reducing agent, process temperature, process pressure, and exposure time may affect the selectivity of the molybdenum film being deposited. Different precursor gases may have different process windows in which molybdenum film may be selectively deposited. 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 200°C to 800°C, e.g., 250°C to 550°C, or 300°C to 500°C. Generally speaking, higher process temperatures and higher process pressures reduce the selectivity of the deposited gas. For example, at higher temperatures, a precursor gas such as M0CI5 may lose its selectivity and deposit molybdenum film on both a metal surface and a dielectric surface within a feature.

[0150] M0CI5 may be reacted with different reactant to deposit a molybdenum film. Described below are examples of deposition of molybdenum film within a feature using a M0CI5precursor and different process controls. In a first example, the M0CI5 precursor is reacted with a hydrogen (H2) reactant using the deposition methods described above. In the description herein, the metal precursors are reacted with hydrogen (H2) as a co-reactant (also referred to as a hydrogen reactant or H2 reactant). However, other reactants may be used instead of hydrogen including other hydrogen-containing reactants such SiH4, B2H6, NH3, as appropriate. While reactants such as B2H6 and / or SiH4 are stronger reducing agents, they can also result in higher resistivity. Thus, in some embodiments, using H2 as described herein is advantageous. Process temperatures for selective deposition of the molybdenum film may be between 200°C to 800°C, e.g., 250°C to 550°C, or 300°C to 500°C. At these temperatures, the molybdenum film is selectively deposited on conductive metal or metal compound surfaces, such as a TiN surface, in a feature relative to dielectric surfaces. The molybdenum film grows from the locations where the conductive surfaces are located in a feature. If the conductive surface is a TiN plug at the bottom of the feature, the molybdenum film may be deposited and grown from the bottom of the feature. In a second example, the molybdenum film may be deposited using the M0CI5 precursor and the H2 reactant, but at higher temperatures, i.e., above 800°C. This process window may have the molybdenum film deposited on both the dielectric and conductive surfaces within the feature. The deposition of the molybdenum film on the dielectric surface may be used to create a barrierless molybdenum layer in the feature.

[0151] In some embodiments, selective deposition is performed using a molybdenum oxyhalide precursor. As described above, the surface treatments described above significantly improve selectivity of Mo deposition from MOO2CI2. As indicated above, examples of MoOyXzprecursors include MOO2CI2, MoOCh, MoOF4, MoChBn, MOO2I, and MO4O11I. The feature may be filled using ALD, plasma enhanced ALD, chemical vapor deposition (CVD), or plasma enhanced CVD. For ALD or CVD, H2 may be the reducing agent. Molybdenum deposits more quickly using a molybdenum oxyhalide precursor than the MoCk precursor used in the surface treatment. For example, a MoOyXz precursor may deposit molybdenum at a deposition rate at least twice as fast as a MoCk precursor for a non-plasma process. Plasma enhanced processes may be used to fill features at lower temperatures and / or increase deposition rates.

[0152] In many embodiments, a molybdenum-containing nucleation layer is deposited by an ALD process. In some embodiments, a Mo nucleation layer is deposited using one or more of a boron-containing reducing agent (e.g., B2H6) or a silicon-containing reducing agent (e.g., SiH4) as a co-reactant. For example, one or more S / Mo cycles or Mo / S cycles may be used to deposit a Mo nucleation layer. In another example, one or more B / Mo cycles or Mo / B cycles may be used to deposit a Mo nucleation layer on which a bulk Mo layer is deposited. B refers to a pulseof diborane or other boron-containing reducing agent and S to a pulse of silane or other silicon- containing reducing agent, such that S / Mo refers to a pulse of silane followed by a pulse of a Mo-containing precursor. B / Mo and S / Mo cycles (or Mo / B and / or Mo / S) may both be used to deposit a Mo nucleation layer, e.g., x(B / Mo) + y(S / Mo), with x and y being integers. Examples of boron-containing reactants include diborane (B2H6), alkyl boranes, alkyl boron, aminoboranes (CH3)2NB (CH2)2, carboranes such as C2BnHn+2, and other boranes. Examples of boranes include BnHn+4, BnHn+6, BnHn+8, BnHm, where n is an integer from 1 to 10, and m is a different integer than m. Examples of silicon-containing reducing agents including silane (SiEU) and other silanes such as disilane (Si2He).

[0153] In some embodiments, deposition of a Mo nucleation layer may involve using a non- oxygen-containing precursor, e.g., molybdenum hexafluoride (MoFe) or molybdenum pentachloride (M0CI5). Oxygen in oxygen-containing precursors may react with a silicon- or boron-containing reducing agent to form MoSixOy or MoBxOy, which are impure, high resistivity films. In some embodiments, oxygen-containing precursors may be used for nucleation layer deposition with oxygen incorporation minimized. Oxygen incorporation can be minimized by high reducing agent flows (e.g., greater than 100: 1 volumetric flow rate of reducing agent to oxygen-containing Mo precursor).

[0154] In some embodiments, H2 may be used as a reducing gas for Mo nucleation layer deposition instead of a boron-containing or silicon-containing reducing gas. Example thicknesses for deposition of a Mo nucleation layer range from 5 A to 30 A. Films at the lower end of this range may not be continuous; however, as long as they can help initiate continuous bulk Mo growth, the thickness may be sufficient.

[0155] In some embodiments, the reducing agent pulses during deposition of a nucleation or bulk Mo layer may be done at lower substrate temperatures than the Mo precursor pulses. For example, or B2H6 or a Sikh (or other boron- or silicon-containing reducing agent) pulse may be performed at a temperature below 300°C, with the Mo pulse at temperatures greater than 300°C.

[0156] In some embodiments, the reducing agent is NH3 or other nitrogen-containing reducing agents such as hydrazine (N2H4). NH3 chemisorption on dielectrics is more favorable than that of H2. In some embodiments, the reducing agent and precursor are selected such that they react without reducing agent dissociation. NH3 reacts with metal oxychlorides and metal chlorides without dissociation. This is in contrast to, for example, ALD from metal oxychlorides that use H2 as a reducing agent; H2 dissociates on the surface to form adsorbed atomic hydrogen, which results in very low concentrations of reactive species and low surface coverage during initial nucleation of metal on the dielectric surface. By using NH3 and metal oxychloride or metalchloride precursors, nucleation delay is reduced or eliminated at deposition temperatures up to hundreds of degrees lower than used by H2 reduction of the same metal precursors.

[0157] In some embodiments, the reducing agent may be a boron-containing or silicon- containing reducing agent such as B2H6 or SiH4. These reducing agents may be used with metal chloride precursors, with metal oxychlorides; however, the B2H6 and SiFL may react with water formed as a byproduct during the ALD process and form solid B2O3 and SiCh. These are insulating and can remain in the film, increasing resistivity. Use of NH3 also has improved adhesion over B2H6 and Sikh ALD processes on certain surfaces including AI2O3. The resulting nucleation layer is generally not a pure elemental film but a metal nitride or metal oxynitride film. In some embodiments, there may be residual chlorine or fluorine from the deposition, particularly if the deposition is performed at low temperatures. In some embodiments, there may be no more than a trace amount of residual chlorine or fluorine. In some embodiments, the nucleation layer is an amorphous layer. Impurities in the film (e.g., oxygen, NH3, chlorine, or other halogens) facilitate the growth of an amorphous microstructure. In some embodiments, the nucleation layer as deposited is an amorphous molybdenum oxynitride layer or an amorphous molybdenum nitride layer. The amorphous character templates large grain growth in the subsequently deposited conductor. The surface energy of nitride or oxynitride relative to an oxide surface is much more favorable than that of a metal on an oxide surface, facilitating formation of a continuous and smooth film on the dielectric. This allows formation of thin, continuous layers. Example thicknesses of the nucleation layer range from 5-30 A as deposited. Depending on the temperature, this may be about 5-50 ALD cycles, for example.

[0158] The low valent molybdenum compounds described herein can advantageously provide high purity molybdenum metal in CVD and ALD deposition. Further, the use of these compounds can be associated with reduced etching of the substrate materials. These advantages are described for illustration purposes and do not limit the use of these compounds solely to molybdenum metal deposition or to deposition on etching-sensitive substrates.Low- VALENT MOLYBDENUM COMPLEXES

[0159] Generally, molybdenum precursors may have from two (M0L2) to six (MoLe) ligands and can include molybdenum in a wide range of oxidation states ranging from 0 to +6. Molybdenum precursors may also be dimolybdenum compounds having 1) two molybdenum atoms singly or multiply bonded to one another; or 2) two molybdenum atoms connected by a linking group such as a bidentate ligand.

[0160] Low valent molybdenum complexes or compounds are those having molybdenum inlow oxidation states 0, +1, +2 or +3. In certain embodiments, the low valent molybdenum complexes may be efficacious precursors as it is easier to reduce Mo(I) to Mo (0) or Mo(II) / (III) to Mo(0) than it is to reduce the more commonly utilized Mo(IV) / (V) halide precursors.

[0161] Low valent molybdenum precursors may offer a less circuitous surface redox process to obtain fully reduced molybdenum metal films with minimal impurities. Without wishing to be bound by a particular theory, this is likely the result of the ease of reduction of low valent molybdenum precursors.MOLYBDENUM ZERO COMPLEXES

[0162] Mo (0) precursors are advantageous because do not require any reduction steps, and are energetically facile, as their use provides a lower energy barrier to Mo film formation upon exposure to a reducing agent. They are especially amenable in multi-step ALD processes where surface-ligand exchange and conversion (reduction) occurs. Molybdenum hexacarbonyl (Mo(CO)e) is an example of a molybdenum complex existing in the oxidation state of zero.

[0163] A general structure for low valent molybdenum precursors having one molybdenum is MoLn(Formula I), and general structures for low valent molybdenum precursors with two molybdenum atoms are M02L11 (Formula II) or LnMo(L’)mMoLn(Formula III). For any of Formulas I-III, each L is independently a monodentate ligand, ambidentate ligand, bidentate ligand or tridentate ligand and n is an integer of 2 to 6. For Formula III, L’ is a linking moiety such as a bidentate ligand; and m is an integer of 1 to 3.MONODENTATE LIGANDS

[0164] Suitable ligands for the low valent molybdenum complexes include monodentate ligands, also referred to as unidentate ligands. A monodentate ligand is one which binds or coordinates to a metal center via one coordination site of the metal only, or via one site of the ligand only. They may include a wide variety of substituents such as hydrogen, halo, hydroxy, alkyl silyl, silylalkyl, alkenyl, alkynyl, allyl, alkoxy, alkenoxy, alkynoxy, thioalkoxy, aliphatic acyl, -CF3, nitro, amino, imino, -N(CI-C3 alkyl)C(O)(Ci-C3 alkyl), -C1-C3 alkylamino, alkenylamino, alkynylamino, di(Ci-C3 alkyl)amino, -C(O)O-(Ci-C3 alkyl), -C(O)NH-(CI-C3 alkyl), -CH=NOH, -P(Ci-C3alkyl)3, -PO3H2, -OPO3H2, -C(O)N(CI-C3alkyl)2, haloalkyl, alkoxycarbonyl, alkoxyalkoxy, carboxaldehyde, carboxamide, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, aroyl, aryloxy, arylamino, biaryl, thioaryl, heterocyclyl, alkylheterocyclyl, heterocyclylalkyl, heterocycloyl, alkylaryl, alkylcarbonyl, CO, =0, =S, =N, =CR, =CR2, -NO, aralkenyl, aralkyl, sulfonyl, sulfonamido, sulfonimido, carbamate, aryloxyalkyl, carboxyl, carboxy, -C(O)NH(benzyl), amido, azido, isocyanato, thiocyanato, isothiocyanato, cyano,isocyano or cyclyl groups where each R is independently an aliphatic such as haloalkyl or aryl such as a haloaryl group.

[0165] In some embodiments, the low valent molybdenum precursors include at least one OR, P(R)3, CNR, allyl or aryl group, where each R is independently an aliphatic, aryl, haloalkyl or haloaryl group.

[0166] In some embodiments, the monodentate ligand can include an oxygen atom. In particular embodiments, one or more ligands can be optionally substituted alkoxy. Non-limiting ligands include, e.g., methoxy, ethoxy, isopropoxy (i-PrO), t-butoxy (t-BuO), and -O=C(CH3)- CH=C(CH3)-O- (acac). Non-limiting molybdenum-containing precursors include, e.g., Mo(CH2F)(t-BuO)3, Mo(CF3)(t-BuO)3, Mo(CH2I)(t-BuO)3, Mo(CI3)(t-BuO)3, Mo(CH2CH2F)(t- BUO)3, Mo(CH2CH2I)(t-BuO)3, Mo(CH2F)2(t-BuO)2, Mo(CF3)2(t-BuO)2, Mo(CH2I)2(t-BuO)2, Mo(CI3)2(t-BuO)2, Mo(CH2CH2F)2(t-BuO)2, Mo(CH2CH2I)2(t-BuO)2, Mo(t-BuO)2, Mo(CH3)(t- BUO)3, Mo(CH2CH3)(t-BuO)3, Mo(CH=CH2)(t-BuO)3, Mo(CH=CHCH3)(t-BuO)3, Mo(CH2- CH=CH2)(t-BuO)3, Mo(C=CH)(t-BuO)3, Mo(C=CCH3)(t-BuO)3, Mo(CH2C=CH)(t-BuO)3, or Mo(acac)2.

[0167] In certain embodiments, the oxygen-containing monodentate ligand may be -OC(CH3)(CF3)2, -OC(CH3)2(CF3), -OC(CH3)3, -OSiRs (such as -OSiPh3), OO (carbonyl ligand) or -OAr (where Ar groups include but are not limited to phenyl, mesitylenyl, 2,6- iPr2CeH3, hexa-z o-propyl-ter-phenyl, and 2,3,5,6-Ph4CeH). In certain embodiments, the oxygen-containing ligand is an ether, epoxide, or ketone. In some cases, the oxygen-containing ligand may be a silyloxy group.

[0168] In certain embodiments, the ligand is a phosphorous-containing ligand. Suitable complexes may be of the formula R3P where R is a halo, aliphatic or aryl group. Examples include secondary or tertiary organophosphines such as P(t-Bu)3, PMes, PPI13, P(OMe)3, P(OEt)3, PCI3 or PF3. In some embodiments, the phosphorus containing ligand is phosphanetriyltris(benzene sulfonic acid). Other phosphorus containing ligands include - CH2P(CH3)3, -P(O)OH, -P(O)(OCH3)2, -P(O)(OCH2CH3)2, and -CH(Si(CH3)3)(P(CH3)3).

[0169] In some embodiments, the ligand is an isocyano functional group, including isonitriles of the formula -C=NR, such as isocyanoalkyl, isocyanohaloalkyl, isocyanoaryl, isocyanohaloaryl. In some embodiments, R is an aliphatic group such as a haloalkyl, or an aryl group such as haloaryl. In certain embodiments, R may be -CH2CF3, -C(F)=CF2, - C(F)=C(F)CF3, -CF2C(F)=CF2, -CH(CF3)2, -CH(CH3)(CF3), or -C(CH3)2(CF3). In certain embodiments, R is a perfluoroalkyl substituent of one to ten carbon atoms such as perfluorinated methyl, ethyl, z-propyl, / / -propyl, / -butyl, .scc-butyl, / / -butyl, cyclopentyl, / / -pentyl, cyclohexyl or / / -hexyl group.

[0170] In some embodiments, the monodentate ligand is one with sp2hybridized character such as an allyl, allenyl, ethenyl, indenyl or cyclopentadienyl group. Two of the same such substituents or two different such substituents may be utilized to form precursors with a sandwich structure. In some embodiments, one such substituent is utilized to form a halfsandwich complex. In certain embodiments, the ligand may be mesitylenyl, tolyl, xylyl, benzyl, anilinyl, N,N-dimethylanilinyl, tetrahydrofuranyl, piperidinyl, pyrrolyl, pyrrolidinyl, pyridinyl, piperidinyl, imidazolyl, or pyrimidinyl.

[0171] In some embodiments, the ligand is an atom which is connected directly to molybdenum via a multiple bond such as a double or triple bond. Examples include =0, =NR, =S, =N, =CR2or =CR, where each R is independently an aliphatic, aryl, haloalkyl or haloaryl group.

[0172] In some embodiments, the molybdenum-containing precursor has at least one optionally substituted haloalkyl group. Non-limiting haloaliphatic group ligands include - CXyHs-y, wherein y is 1, 2, or 3, and wherein each X is, independently, halo (F, Cl, Br, or I); - CXzH2-zCXyH3-y, wherein z is 0, 1, or 2, wherein y is 0, 1, 2, or 3, and wherein each X is, independently, halo (F, Cl, Br, or I), in which at least one of z or y is not 0; or -CEECXyEE-y, wherein y is 1, 2, or 3, and wherein each X is, independently, halo (F, Cl, Br, or I). Yet other non-limiting haloalkyl groups include fluoromethyl (-CH2F), difluoromethyl (-CHF2), trifluoromethyl (-CF3), chloromethyl (-CH2CI), dichloromethyl (-CHCh), trichloromethyl (- CCI3), bromomethyl (-CEEBr), dibromomethyl (-CHBr?), tribromomethyl (-CBn), iodomethyl (- CH2I), diiodomethyl (-CHI2), triiodomethyl (-CI3), bromofluoromethyl (-CHFBr), chlorofluoromethyl (-CHFC1), fluoroiodom ethyl (-CHFI), 2-fluoroethyl (-CH2CH2F), 2- chloroethyl (-CH2CH2CI), 2-bromoethyl (-CEECEEBr), 2-iodoethyl (-CH2CH2I), 2,2- difluoroethyl (-CH2CHF2), 2,2-dichloroethyl (-CH2CHCI2), 2,2-dibromoethyl (-CEkCHBrc), 2,2-diiodoethyl (-CH2CHI2), 2,2-fluoroiodoethyl (-CH2CHFI), and the like. In particular embodiments, the C1-2 haloalkyl includes P-halo-substituted ethyl. Yet other haloaliphatic groups include Ci-4 haloalkyl, C2-4 haloalkenyl, and C2-4 haloalkynyl.

[0173] In other embodiments, the ligand is an optionally substituted alkyl group, optionally substituted alkenyl, or optionally substituted alkynyl. Non-limiting groups include -CnEbn+i, in which n is 1 or 2; -CnEkn-i, in which n is 2, 3, or 4; or -CnH2n-3, in which n is 2, 3, or 4. Yet other non-limiting groups include methyl (-CH3), ethyl (-CH2CH3), vinyl or ethenyl (-CH=CH2), 1- propenyl (-CH=CHCH3), allyl or 2-propenyl (-CH2-CH=CH2), 1-butenyl (-CH=CHCH2CH3), 2- butenyl (-CH2CH=CHCH3), 3-butenyl (e.g. -CH2CH2CH=CH2), ethynyl (-C=CH), 1-propynyl (-C=CCH3), 2-propynyl or propargyl (-CH2C=CH), 1-butynyl (-C=CCH2CH3), 2-butynyl (-CH2C=CCH3), 3-butynyl (-CH2CH2C=CH), 2-methyl-l -propenyl (CH=C(CH3)2, isopropenyl (C(CH3)=CH2, 1 -methylallyl (CH(CH3)CH=CH2and the like.

[0174] In some embodiments, the monodentate ligand may be -CH2P(CH3)3, -CH(Si(CH3)3)(P(CH3)3), -C(O)C3F7, or -CHCHSChCeHs.

[0175] In some embodiments, the monodentate ligand includes a sulfur atom. In particular embodiments, one or more monodentate ligands can be -SO2CF3, -SO2C3N2H3, - CHCHSO2C6H5, -SO2OCH3, or -SO2C6H4CH3.

[0176] In some embodiments, the monodentate ligand includes a nitrogen atom. In particular embodiments, one or more monodentate ligands can be optionally substituted amino or optionally substituted bis(trialkylsilyl)amino. Non-limiting ligands can include, e.g., -NMe2, - NEt2, -NMeEt, -N(t-Bu)-[CHCH3]2-N(t-Bu)- (tbba), -N(SiMe3)2, and -N(SiEt3)2.

[0177] In some embodiments, the optionally substituted amino is -NR'R2, in which each R1and R2is, independently, H or alkyl; or in which R1and R2, taken together with the nitrogen atom to which each are attached, form a heterocyclyl group, as defined herein. In other embodiments, the optionally substituted bis(trialkylsilyl)amino is -N(SiR1R2R3)2, in which each R1, R2, and R3is, independently, alkyl. In yet other embodiments, the optionally substituted trialkylsilyl is -SiRJR2R3, in which each R1, R2, and R3is, independently, alkyl.

[0178] In other embodiments, the low valent molybdenum precursor includes a first ligand that is -NR'R2and a second ligand that is -NR'R2, in which each R1and R2is, independently, H or alkyl. In yet other embodiments, the formula includes a first ligand that is -OR1and a second ligand that is -OR1, in which each R1is, independently, H or alkyl.

[0179] In some embodiments, the monodentate ligand is optionally substituted alkyl. Nonlimiting alkyl groups include, e.g., CnEhn+i, where n is 1, 2, 3, or greater, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, or t-butyl. In various embodiments, the ligand has at least one beta-hydrogen or beta-halogen.

[0180] In some embodiments, at least one monodentate ligand is optionally substituted haloalkyl. Non-limiting haloalkyl groups include, e.g., CnEhn+i-zXz, wherein n is 1, 2, 3, or greater; wherein z is 1 to 2n+l (e.g., 1 to 3, 1 to 5, or 1 to 7); and wherein each X is, independently, halo (F, Cl, Br, or I).

[0181] In some embodiments, at least one monodentate ligand is optionally substituted alkenyl or optionally substituted alkynyl. Non-limiting alkenyl groups include, e.g., CnEhn-i, where n is 2, 3, 4, or greater, such as ethenyl, 1 -propenyl, 2-propenyl, 1-butenyl, 2-butenyl, or 3-butenyl. Non-limiting alkynyl groups include, e.g., CnH2n-3, where n is 2, 3, 4, or greater, such as ethynyl,1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, or 3-butynyl.

[0182] Alkynyl groups are also suitable monodentate ligands in certain embodiments. In some embodiments, the carbon-carbon triple bond is not bound directly to the molybdenum, for example in a formula R1CCCH2MoL3 where R1is a C1-C2 linear or branched alkane such as methyl or ethyl; and L is an amino (dimethylamino, diethylamino, ethylmethylamino, methylpropylamino, aminiocyclopentane, aminocyclohexane) or alkoxy group (methoxy, ethoxy, n-propoxy, isopropoxy, t-butoxy, sec-butoxy, or n-butoxy).

[0183] Alkyne compounds which have a carbon-carbon triple bond directly bonded to the molybdenum atom will hydrolyze in the presence of water similar to, although much slower than, amino and alkoxy groups. Therefore, compounds such as (R1C=C)sMoR2and (R1C=C)4Mo where R1is a simple alkane such as methyl or ethyl, and R2is a C1-C2 hydrocarbon are precursors having monodentate ligands in accordance with certain embodiments. In compound (R1C=C)sMoR2the molybdenum center has three alkynes with the carbon-carbon triple bond bonded to the molybdenum center. Tetra-alkynes such as those shown for (R1C=C)4MO.

[0184] In some embodiments, the monodentate ligand is halo. In particular, the metalcontaining precursor can be a metal halide or organometal halide. Non-limiting metal halides and organometal halides include FCH2M0X3, CF3M0X3, ICH2M0X3, CI3M0X3, CH2FCH2M0X3, CH2ICH2M0X3, M0X2, or M0X4, in which each X is, independently, halo. In other embodiments, the metal-containing precursor is RM0X3, in which R is Ci-4 haloalkyl, C2-4 haloalkenyl, or C2-4 haloalkynyl; and in which each X is, independently, halo. In yet other embodiments, the metal-containing precursor is RM0X3, in which R is C1-2 alkyl, C2-4 alkenyl, or C2-4 alkynyl; and in which each X is, independently, halo.

[0185] In other embodiments, the monodentate ligand is Ci- C3 aliphatic (wherein the C1-C3 aliphatic may be optionally substituted with a ketone, an alkoxy group, an epoxy group) or a - C(O)Ci-C3 alkyl group. Ethers, ketones or epoxide-containing ligands on the low valent molybdenum-containing precursors may be advantageous to assist in crosslinking.

[0186] In some embodiments, the monodentate ligand can include a silicon atom. In some embodiments, the monodentate ligand may be -Si(CH3)3, -Si(C2Hs)3, -CH2Si(CH3)3, - CH(Si(CH3)3)2 or -C(Si(CH3)3)3. In particular embodiments, one or more ligands can be optionally substituted trialkylsilyl or optionally substituted bis(trialkylsilyl)amino. Non-limiting ligands can include, e.g., -SiMes, -SiEt3, -N(SiMe3)2, and -N(SiEt3)2.

[0187] For any formula herein, each monodentate ligand may independently be hydrogen, halo, azido, cyano, akylcarbonyl, isothiocyanato, thiocyanato, optionally substituted alkyl,optionally substituted aryl, optionally substituted amino, optionally substituted bis(trialkylsilyl)amino, optionally substituted trialkylsilyl, or optionally substituted alkoxy (e.g., -OR1, in which R1can be alkyl).

[0188] The present disclosure also encompasses hydrogen as a monodentate ligand. An example of a complex having a hydrogen monodentate ligand is a molybdenum hydride precursor such as Mo(Cp)2H2, where Cp is cyclopentadienyl.

[0189] The monodentate ligand may be an ambidentate ligand, which has two potential donor atoms, but only attaches to a metal via one of the two. In certain embodiments, the ambidentate ligand is NCh', which may bond to a metal through either the nitrogen atom or the oxygen atom.BIDENT ATE LIGANDS

[0190] Suitable ligands for the low valent molybdenum complexes include bidentate ligands. A bidentate ligand (also referred to as a chelating ligand) is one which binds or coordinates to a metal center via two coordination sites of the metal, or via two sites of the ligand. Bidentate ligands are Lewis bases that donate two pairs of electrons to a metal atom. The bidentate ligands may be neutral or anionic. Furthermore, the bidentate ligands may have the same two coordination atoms, or may be unsymmetrical bidentate ligands, where the two coordination atoms are not the same. In some embodiments, the bidentate ligands may be ethylenediamine (en), bipyridyl (bpy), l,2-bis(dimethylphosphino)ethane (dmpe), phenanthroline (phen), 1,2- bis(diphenylphosphino)ethane (dppe), acetate (OAc), oxalate (ox), or acetylacetonate (acac).

[0191] Example structures containing the bidentate ligand include, but are not limited to

[0192] The bidentate ligand may be a linking moiety L’ of the structure -(E)e- where each E independently includes NR, C(R)n, Si(R)n, S, O or P(R)n; each R independently includes hydrogen, aryl, amino or aliphatic; n is 0, 1 or 2 and e is 1, 2, 3, 4 or 5.

[0193] Suitable low valent molybdenum precursors may contain one, two or three bidentate ligands each of which may be the same or different.

[0194] The bidentate ligand may be an amidinate, an amidate, an iminopyrrolidinate, a di azabutadiene, a beta-imino amide, an alpha-imino alkoxide, a beta-diketiminate, a beta-ketoiminate, a beta-diketonate, a pyrazolate, a beta-amino alkoxide, a guanidinidate, a dithiolene, an alpha-iminothiolene, an alpha-dithiolate, or a beta-dithiolate. Other examples of suitable materials include the bidentate ligands described in US 2022 / 0170155 and WO 2021 / 035236, which are incorporated herein by reference in their entireties.TRIDENTATE LIGANDS

[0195] A tridentate ligand is one with three atoms that can function as acceptors in a coordination complex. In certain embodiments, the tridentate ligand three nitrogen, three sulfur, three phosphorus or three oxygen atoms available for chelation. Tridentate ligands include cis, cis- 1 ,3 , 5-triaminocyclohexane, 1 ,4,7-triazacyclononane, 1 ,4, 7, -trimethyl- 1,4,7- triazacyclononane, 1,4,7-trithiacyclononane, Z>A(diphenylphosphinoethyl)phenylphosphine, N,N,N’,N”N”-pentamethyldiethylenetriamine, / / 7.s(4S-isopropyl-2-oxazolinyl)phenylborate, / / 7.s(4,4-dimethyl-2-oxazolinyl)phenyl borate, / mpyrazoly lb orate, 1,4,7-trioxonane, diethylenetriamine, or an iminodiacetate anion. Suitable low valent molybdenum precursors may contain one, two or more tridentate ligands which may be the same or different.

[0196] The low valent molybdenum precursors may have two to six ligands. Each occurrence of L may independently be a monodentate, ambidentate, bidentate or tridentate ligand as described above. Low valent molybdenum precursors having two ligands may be of the formula M0L2. FIG. 6 illustrates example structures for molybdenum precursors having three ligands (Formula XIV), four ligands (Formula V and Formula VI) or five ligands (Formula IX and Formula X) in certain embodiments. For Formulas XIV, VI, IX and X, R4, R6, R7and R15are each independently -CH3, -C2H5, -C3H7, -C4H9, -C5H11, -CF3, -C4F9, -C5F11, -CH2CF3, -CH(CF3)2, -CH(CH3)(CF3), -C(CH3)2(CF3), -C(CF3)3, -Si(CH3)3, -Si(C2H5)3 or - CH2Si(CH3)3. -CH(Si(CH3)3)2, -C(Si(CH3)3)3, -P(CH3)3, -CH2P(CH3)3, -P(O)OH,-P(O)(OCH3)2, -P(O)(OCH2CH3)2, -CH(Si(CH3)3)(P(CH3)3), -SO2CF3, -SO2C3N2H3,-C(O)C3F7, -CHCHSO2C6H5, -SO2OCH3, or -SO2C6H4CH3. For Formula IX, G may be =0, =NR, =S or =CR2, where each R is independently an aliphatic, aryl, haloalkyl or haloaryl group. For Formula X, each R8is independently any of the monodentate, ambidentate or bidentate ligands described above. For Formula V, R1may be aliphatic, R2may be any of the monodentate, ambidentate, bidentate or tridentate ligands described above, and n may be 1, 2, 3, 4 or 5.

[0197] Low valent molybdenum precursors may also have six ligands. Such precursors may have the general formula Mo(X)P(R10)q(XII) where each X independently includes chloro, fluoro, bromo or iodo; each R10independently includes allyl, allenyl, ethenyl, mesitylenyl, tolyl,xylyl, benzyl, cyclopentadienyl, indenyl, anilinyl, N,N-dimethylanilinyl, tetrahydrofuranyl, piperidinyl, pyrrolyl, pyrrolidinyl, pyridinyl, piperidinyl, imidazolyl, pyrimidinyl, -NO, -CO, - P(CHS)3, -P(CH2CH3)3 or -CNR11, where R11includes aliphatic, aryl or heterocyclyl; p is 1 to 4; q is 2 to 5; and p + q = 6.

[0198] Low valent molybdenum precursors having six ligands may also be of the formula the Formula (XIII): Mo(R12)r(R13)s (XIII) where each R12independently includes allyl, allenyl, ethenyl, mesitylenyl, tolyl, xylyl, benzyl, cyclopentadienyl, indenyl, anilinyl, N,N- dimethylanilinyl, tetrahydrofuranyl, piperidinyl, pyrrolyl, pyrrolidinyl, pyridinyl, piperidinyl, imidazolyl, pyrimidinyl, -NO, -CO, -P(CH3)3, -P(CH2CH3)3 or -CNR14, where R14includes aliphatic, aryl or heterocyclyl; each R13independently includes trimethylphosphine, triethylphosphine, tri-z-propyl phosphine, triphenylphosphine, tris(trimethylsilyl)phosphine, tris(2-carboxyethyl)phosphine, tris(dimethylamino)phosphine, tris(o-tolyl)phosphine, tris(4- methoxyphenyl)phosphine or tris(2-furyl)phosphine; r is 1 to 6; s is 0 to 5; and r + s = 6.

[0199] FIG. 7 illustrates example structures for low valent molybdenum precursors having six ligands. Structures 1-9 have one or more CNR ligands which may be isocyanoalkyl, isocyanohaloalkyl, isocyanoaryl, or isocyanohaloaryl groups. In some embodiments, R is an aliphatic group such as a haloalkyl, or an aryl group such as haloaryl. In certain embodiments, R may be-CH2CF3, -CH(CF3)2, -CH(CH3)(CF3), or -C(CH3)2(CF3). In certain embodiments, R is a perfluoroalkyl substituent of one to ten carbon atoms such as perfluorinated methyl, ethyl, i- propyl, / / -propyl, Lbutyl, .scc-butyl, / / -butyl, cyclopentyl, / / -pentyl, cyclohexyl or / / -hexyl group. Structures 10-18 have one or more PMe3ligands.

[0200] Molybdenum complexes can be prepared using a zero valent starting material such as molybdenum hexacarbonyl. Other synthetic routes include reaction of MoC13(THF)3 with the appropriate ligand followed by reduction and reaction of M0X5 (X = Cl, Br, I) with the appropriate ligand followed by reduction.

[0201] The starting material can be treated with a neutral ligand, such as a thioether (dialkylsulfide), to induce redox neutral ligand exchange. The zero valent starting material can also be treated with a ligand precursor, such as bis(diethylthiocarbamoyl)disulfide or bis(trifluoromethyl)-l,2-dithiete, to induce oxidative addition and form the sulfur-containing complexes described herein.

[0202] The reactions may be conducted in a variety of non-protic solvents. For example the reaction may be conducted in an ether solvent, such as tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, methyl-tert-butyl ether, 1,2-dimethoxy ethane, in a hydrocarbon solvent such astoluene, benzene, heptane, hexane, pentane, or in a halocarbon solvent such as chlorobenzene, di chlorobenzene, fluorobenzene, difluorobenzene, dichloromethane, chloroform, etc. The reactions can be conducted in a wide temperature range depending on the boiling point of the solvent and on solubility of the products. In some embodiments, the starting materials, reaction intermediates, and the desired products are unstable toward moisture and oxygen. Accordingly, the reaction process should be conducted using anhydrous and air-free conditions using a protective inert gas, such as nitrogen or argon.DIMOLYBDENUM COMPLEXES

[0203] In another aspect, precursors for deposition of molybdenum-containing films are dimolybdenum compounds containing a direct molybdenum-molybdenum bond (e.g., a multiple molybdenum-molybdenum bond, such as a double bond, or any multiple bond with a bond order of 2-5). The directly bonded dimolybdenum precursors may be of the structure M02L11 (II), where each occurrence of L is independently a monodentate, ambidentate, bidentate or tridentate ligand as described above, and n is 2 to 6. One example precursor is Mo2(O-isopropyl)e. Other example precursors are shown in FIG. 8. In some embodiments, the dimolybdenum precursor has molybdenum atoms directly connected by a double bond (such as structure 19). In some embodiments, the dimolybdenum precursor has molybdenum atoms directly connected by a triple bond (such as structures 20-23). For structures 20 and 21, R may be an aliphatic group such as an alkyl group, a haloalkyl group or a silyl group. For structure 23, L may be any ligand described above, or may be any one of CO, CNR or PMes (where R is aliphatic, aryl or heterocyclyl) and X is halo. Such precursors are particularly useful for deposition of molybdenum metal and high purity molybdenum metal because it may be easier to reduce such compounds to metallic molybdenum than some monoatomic molybdenum compounds.

[0204] Di-molybdenum precursors described herein can be synthesized using dimolybdenum tetraacetate as a starting material by treatment with a ligand salt such as lithium amidate. In one aspect, a container housing any of the precursors described herein in a solid or liquid form is provided. In another aspect a solution of any of these precursors is provided, where the solvent may include, for example, a high boiling point hydrocarbon solvent, such as a higher alkane. In some embodiments a container holding the molybdenum precursor (in solid or liquid form or in solution) is filled with an inert gas, such as nitrogen (N2), or argon (Ar), to prevent contact of the precursor with air, and possible decomposition due to contact with moisture and / or air. In some embodiments the container is adapted for vaporization of the precursor inside the container. For example, the container may include an inlet and an outlet, where the inlet is adapted to beconnected with a source of a carrier gas that can be flowed over or through the precursor thereby assisting in precursor vaporization. The outlet is adapted for removing the carrier gas and the precursor vapor from the container and is configured to be connected to a conduit that can be used to deliver the precursor vapor to the processing chamber. The inlet and the outlet each has a closed position and an open position, and, for example, can include manual valves that can be used to switch from closed to open positions and back. When the container is stored or transported the inlet and the outlet are closed. When the container is fitted to the deposition apparatus for use, the inlet and the outlet valves may be open, and a carrier gas may be flown into the inlet, and out from the outlet carrying the precursor vapor.

[0205] In some embodiments the container has a flow-over design, in which the inlet and the outlet are positioned above the surface of the precursor. For example, in a cylindrical container the inlet and the outlet may be positioned at a similar vertical elevation (e.g., the vertical distance between the inlet and the outlet may be less than about 20% of the cylinder height). In other embodiments the container has a bubbler design, in which the inlet is positioned below the surface of the precursor and the outlet is positioned above the inlet (e.g., above the surface of the precursor). For example, in a cylindrical container the inlet and the outlet may be positioned far from each other in a vertical direction (e.g., the vertical distance between the inlet and the outlet may be more than about 30%, such as more than about 50%, or more than about 80% of the cylinder height.

[0206] A low valent dimolybdenum complex may also contain two molybdenum atoms connected indirectly to each other by a linking moiety. Such precursors may be of the formula LnMo(L’)mMoLn (III) where each L is independently a monodentate ligand, ambidentate ligand, bidentate ligand or tridentate ligand as described above; L’ is a linking moiety; n is 2 to 6; and m is 1 to 3. The linking moiety L’ may be of the structure -(E)e- where each E independently includes C(R)n, NR, Si(R)n, S, O or P(R)n; each R independently includes hydrogen, aryl, amino or aliphatic; n is 0, 1 or 2 and e is 1, 2, 3, 4 or 5.

[0207] In some embodiments, the low valent dimolybdenum complex may contain two molybdenum atoms both directly bonded to each other and also connected indirectly to each by a linking moiety as described above. Returning to FIG. 8, example structures 24 and 25 having both types of connections are shown. For structures 24 and 25, L may be any ligand described above, or preferably CO, CNR or PMes (where R is aliphatic, aryl or heterocyclyl) and X is halo.CONCLUSION

[0208] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein.

Claims

CLAIMSWhat is claimed is:

1. A method of processing a semiconductor substrate, the method comprising: providing a substrate having a feature thereon, the feature having a feature opening and sidewalls; and forming a protective material on the sidewalls, wherein forming the protective material comprises: forming an underlayer on the sidewalls, wherein the underlayer comprises a hydrogen- terminated surface, and forming a metal-containing layer on the underlayer.

2. The method of claim 1, wherein the underlayer comprises silicon.

3. The method of claim 2, wherein the underlayer comprises amorphous silicon.

4. The method of claim 1, wherein the underlayer comprises carbon.

5. The method of claim 4, wherein the underlayer comprises amorphous carbon.

6. The method of claim 1, wherein the underlayer comprises boron.

7. The method of claim 1, wherein the underlayer comprises phosphorous.

8. The method of claim 1, wherein the underlayer is deposited to a thickness of less than about 30% of a width of the feature opening at or near the feature opening.

9. The method of claim 1, wherein forming the underlayer comprises exposing the substrate to an underlayer precursor.

10. The method of claim 9, wherein the underlayer precursor is a hydrogen-containing precursor.

11. The method of claim 10, wherein the hydrogen-containing precursor is selected from the group consisting of boranes, phosphides, hydrocarbons, hydrofluorocarbons, and carbon halides.

12. The method of claim 9, wherein the underlayer precursor is a halogen-containing precursor.

13. The method of claim 12, wherein the halogen-containing precursor comprises fluorine.

14. The method of claim 12, wherein the halogen-containing precursor comprises chlorine.

15. The method of claim 12, wherein forming the underlayer further comprises exposing the substrate to a hydrogen gas.

16. The method of claim 12, wherein forming the underlayer further comprises exposing the substrate to a hydrogen and igniting a plasma.

17. The method of claim 9, wherein the underlayer precursor is a carbon-containing precursor.

18. The method of claim 9, wherein the underlayer precursor is a halogen-containing and carbon-containing precursor.

19. The method of claim 9, wherein the underlayer precursor is a hydrogen-containing and carbon-containing precursor.

20. The method of claim 1, wherein the hydrogen-terminated surface is formed by exposing the substrate to an underlayer precursor having a hydrogen atom.

21. The method of claim 1, wherein the hydrogen-terminated surface is formed by exposing the substrate to an underlayer precursor and a hydrogen gas or hydrogen-containing plasma.

22. The method of claim 9, wherein the underlayer precursor is selected from the group consisting of silicon tetrafluoride, silicon tetrachloride, and carbon tetrachloride.

23. The method of claim 9, wherein the underlayer precursor is a non-silane.

24. The method of claim 1, wherein the metal-containing layer comprises a metal selected from the group consisting of tungsten, cobalt, molybdenum, tin, titanium, hafnium, zirconium, ruthenium, and combinations thereof.

25. The method of claim 1, wherein the metal-containing layer comprises elemental tungsten.

26. The method of claim 1, wherein the metal-containing layer comprises elementalmolybdenum.

27. The method of claim 1, wherein forming the metal-containing layer comprises exposing the hydrogen-terminated surface to a metal-containing precursor.

28. The method of claim 27, wherein the metal-containing precursor comprises a halogen atom.

29. The method of claim 27, wherein the metal-containing precursor is selected from the group consisting of tungsten hexafluoride, tungsten pentafluoride, tungsten hexachloride, tungsten pentachloride, molybdenum dichloride, molybdenum trichloride, molybdenum tetrachloride, molybdenum pentachloride, molybdenum hexafluoride, and molybdenum hexachloride.

30. The method of any of claims 1-29, wherein at least one of the underlayer and the metalcontaining layer are formed by plasma enhanced chemical vapor deposition.

31. The method of any of claims 1-29, further comprising igniting a plasma.

32. The method of claim 31, wherein the plasma is ignited during forming the underlayer.

33. The method of claim 31, wherein the plasma is ignited during forming the metalcontaining layer.

34. The method of claim 32, wherein the underlayer is formed at a pressure of less than about 300 mTorr.

35. The method of claim 32, wherein the underlayer is formed at a temperature of less than about 300°C.

36. The method of claim 33, wherein the metal-containing layer is formed at a pressure of less than about 50 mTorr.

37. The method of claim 33, wherein the metal-containing layer is formed at a temperature of less than about 300°C.

38. The method of claim 31, wherein the plasma is ignited using a dual frequency plasma generator.

39. The method of claim 31, wherein the plasma is ignited during forming the underlayer and the plasma is ignited at a low power maintain a deposition rate that prevents pinch- off of material at or near the feature opening.

40. The method of claim 38, wherein the plasma is ignited during forming the underlayer and the plasma is ignited using a power of less than about 2500 W.

41. The method of claim 38, wherein the plasma is ignited during forming the metalcontaining layer and the plasma is ignited using a power of less than about 1000 W.

42. The method of claim 31, wherein a bias is not applied during igniting of the plasma.

43. The method of claim 31, further comprising applying a bias during igniting of the plasma using a first bias power.

44. The method of claim 43, wherein the first bias power has a voltage of less than about 1 kV.

45. The method of claim 43, further comprising after forming the protective material, etching a bottom of the feature by applying a second bias at a second bias power, wherein the first bias power is less than about 10% of the second bias power.

46. The method of claim 31, wherein the plasma is ignited using an inductively coupled plasma generator.

47. The method of claim 31, wherein the plasma is ignited using an capacitively coupled plasma generator.

48. The method of any of claims 1-29, wherein the protective material is formed in a plasma-free environment.

49. The method of claim 48, wherein the protective material is formed at a temperature of less than about 500°C.

50. The method of any of claims 1-29, wherein the protective material is formed on the sidewalls from the feature opening to a depth of about 50% of a depth of the feature.

51. The method of any of claims 1-29, wherein the sidewalls comprise a surface having one or more materials selected from the group consisting of silicon oxide material, siliconnitride material, polysilicon material, and doped variations thereof.

52. The method of claim 51, wherein the doped variations thereof comprise dopants selected from the group consisting of boron and phosphorous.

53. The method of any of claims 1-29, wherein the protective material is formed on the sidewalls comprising alternating oxide and nitride material during 3D NAND fabrication.

54. The method of any of claims 1-29, after forming the protective material, etching a bottom of the feature to form a feature width at or near the bottom of the feature that is within about 10% of the width of a feature width at or near the feature opening.

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