TWI850444B - Selective and self-limiting tungsten etch process - Google Patents

Abstract

Methods of dep-etch in semiconductor devices (e.g. V-NAND) are described. A metal layer is deposited in a feature. The metal layer is removed by low temperature atomic layer etching by oxidizing the surface of the metal layer and etching the oxide in a layer-by-layer fashion. After removal of the metal layer, the features are filled with a metal.

Description

Selective and self-limiting tungsten etching process

Embodiments of the present disclosure generally relate to methods for filling gaps or features in semiconductor devices. More specifically, embodiments of the present disclosure relate to methods for gap filling in three-dimensional semiconductor devices using tungsten.

As semiconductor device designs and material feature complexity continue to increase, the selective removal of materials has become critical to the continued scaling and improvement of semiconductor devices. Selective atomic layer etching (ALE) has emerged as a precise etching method that exploits self-limiting surface reactions. Selective ALE of metal oxides ( _MOx ) is particularly important for many semiconductor technologies but can be difficult to achieve due to the inherent stability of these oxide materials.

V-NAND (or 3D-NAND) structures are used in flash memory applications. V-NAND devices are vertically stacked NAND structures with a large number of cells arranged in blocks. Back-gate wordline formation is the mainstream process flow in current 3D-NAND manufacturing. Before wordline formation, the substrate is a layered oxide stack supported by memory strings. The interstitial space is filled with tungsten using CVD or ALD. The top/sidewalls of the memory stack are also coated with tungsten. Tungsten is removed from the top/sidewalls of the stack by an etching process (e.g., a reactive ion etching (RIE) process or a radical-based etching process) so that tungsten exists only on the inside of the interstitial space and each tungsten filling is completely separated from the other tungsten fillings. However, due to the loading effect of the etching process, the separation etch usually results in different wordline recesses at the top and at the bottom of the stack. This difference becomes more pronounced as the oxide stack layer increases.

There are challenges in filling tungsten in multi-layer VNAND tungsten fills, especially in buried word lines. Deposition-etch cyclic techniques are being sought to produce better gapfill. However, currently, there is no cyclic deposition-etch process that can produce effective tungsten gapfill.

Therefore, there exists a need for improved methods of etching tungsten, especially in NAND applications.

One or more embodiments of the present disclosure relate to a method of processing a substrate. In one or more embodiments, a processing method includes the steps of: depositing a metal layer in at least one feature on the substrate; oxidizing the metal to a first depth to form a metal oxide layer on the metal layer; and etching the metal oxide layer to selectively remove the metal oxide layer.

Other embodiments of the disclosure relate to methods of processing substrates. In one or more embodiments, a processing method includes the steps of depositing a metal layer on a substrate surface having at least one feature on the substrate surface, at least one feature extending a feature depth from the substrate surface to a bottom surface, at least one feature having a width defined by a first sidewall and a second sidewall, wherein the metal layer is deposited on the substrate surface, the first sidewall of the at least one feature, the second sidewall, and the bottom surface; and performing a processing cycle including the steps of oxidizing a metal to a first depth to form a metal oxide layer on the metal layer; and etching the metal oxide layer to selectively remove the metal oxide layer.

Further embodiments of the present disclosure relate to methods of processing substrates. In one or more embodiments, a method of processing a substrate includes the following steps: forming a film stack on a substrate, the film stack including a plurality of alternating layers of oxide materials and nitride materials, and the film stack having a stack thickness; forming an opening extending from a top to a bottom surface of the film stack surface to a depth, the opening having a width defined by a first sidewall and a second sidewall; optionally forming a film stack on the film stack surface and on the first sidewall, the second ... A barrier layer is formed on two sidewalls and a bottom surface, the barrier layer comprising TiN with a thickness in a range of about 20Å to about 50Å; a metal layer is deposited on the film stack so that the metal layer fills the opening and covers the top of the film stack with the thickness of the metal layer; and the surface of the metal layer is repeatedly oxidized to form a metal oxide layer, and the metal oxide layer is etched from at least one feature until the metal layer is removed, the oxidizing the surface comprising the steps of: exposing to _O2 , and etching the metal oxide layer comprising the steps of: exposing to a halogenide etchant.

Before describing several exemplary embodiments of the present disclosure, it should be understood that the present disclosure is not limited to the details of construction or processing steps set forth in the following description. The present disclosure is capable of other embodiments and can be practiced or carried out in various ways.

As used in this specification and the accompanying claims, the terms "substrate" and "wafer" are used interchangeably to refer to a surface or a portion of a surface on which a process acts. Those skilled in the art will also understand that reference to a substrate may also refer to only a portion of a substrate unless the context clearly indicates otherwise. In addition, reference to depositing on a substrate may refer to both a bare substrate and a substrate on which one or more films or features are deposited or formed.

As used herein, "substrate" refers to any substrate or material surface formed on a substrate on which film processing is performed during a manufacturing process. For example, substrate surfaces on which processing may be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys and other conductive materials, depending on the application. Substrates include, but are not limited to, semiconductor wafers. The substrate may be exposed to a pre-treatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, electron beam cure, and/or bake the substrate surface. In addition to performing film treatment directly on the surface of the substrate itself, in the present disclosure, any film treatment step disclosed may also be performed on an underlying layer formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include such underlying layers as the context indicates. Thus, for example, where a film/layer or portion of a film/layer is already deposited on the substrate surface, the exposed surface of the newly deposited film/layer becomes the substrate surface.

Semiconductor manufacturing processes often involve depositing metals, such as tungsten (W), into features, such as (but not limited to) vias or trenches, to form contacts or interconnects. Metals, such as tungsten (W), are often deposited into features using chemical vapor deposition (CVD), where a substrate having at least one feature to be filled is exposed to a metal-containing precursor and a reducing agent to deposit the metal into the feature. However, as devices shrink, features become smaller and smaller, making filling with CVD more challenging, particularly in advanced logic and memory applications.

One or more embodiments of the disclosure advantageously provide a method of depositing a tungsten film in a gap of a three-dimensional structure. Some embodiments of the disclosure advantageously provide methods of depositing a conformal tungsten oxide film and selectively removing the tungsten oxide. Some embodiments advantageously provide methods of filling lateral features of a V-NAND with a high-quality tungsten film having a uniform thickness from the top to the bottom of the oxide stack. In one or more embodiments, the processing method advantageously does not use plasma. In addition, the processing method of one or more embodiments advantageously selectively removes tungsten at a more controlled rate than other deposition etching techniques.

One or more embodiments of the present disclosure relate to a word line separation method based on highly conformal metal (e.g., tungsten) oxidation and highly selective metal oxide (e.g., tungsten oxide) removal. The method may use high temperature or low temperature processing.

One or more embodiments of the present disclosure relate to a deposition-etch ("dep-etch") cyclic technique to produce better gap fill. The method of one or more embodiments facilitates such a deposition-etch cyclic process. Additionally, in one or more embodiments, the contact resistance of a semiconductor device is improved because the native oxide is removed from the surface of a metal (e.g., tungsten).

Referring to FIG. 1 , a substrate 10 has a stack 12 of layers thereon. The substrate 10 may be any suitable substrate material and is not limited to being the same material as any single layer. For example, in some embodiments, the substrate is an oxide, nitride, or metal layer. The stack 12 has a plurality of oxide layers 14 spaced apart from one another to form gaps 16 between the oxide layers 14 so that each gap forms a word line or a shell for forming a word line. The stack 12 has a top 13 and a side 15.

The stack 12 may have any suitable number of oxide layers 14 or gaps 16. In some embodiments, there are greater than or equal to about 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 gaps 16 formed in the stack 12, and the gaps 16 may be used to form an equal number of word lines. The number of gaps 16 is measured on either side of the memory string 11 connecting all the individual oxide layers 14. In some embodiments, the number of gaps 16 is a multiple of 2. In some embodiments, the number of gaps is equal to ²ⁿ , where n is any positive integer. In some embodiments, the number of gaps 16 is about 96.

As shown in FIG. 2 , metal 20 is deposited on stack 12. Metal 20 fills gap 16 to form word line 19. Metal 20 is formed around stack 12 so that metal 20 covers top 13 and sides 15 of stack 12 with a thickness of metal cap layer 22. Cap layer 22 is the material deposited on the outside of gap 16. The cap layer can have any suitable thickness, depending on the process used to deposit metal 20. In some embodiments, the thickness of cap layer 22 is in the range of about 1 Å to 1000 Å. In some embodiments, the thickness of the capping layer 22 is greater than or equal to about 5Å, 10Å, 15Å, 20Å, 25Å, 30Å, 35Å, 40Å, 45Å, or 50Å.

Metal 20 may be any suitable metal used in wordline applications. In some embodiments, the metal film includes tungsten. In some embodiments, the metal film does not include tungsten. In some embodiments, the metal film consists essentially of tungsten. As used in this regard, the term "consisting essentially of tungsten" means that the composition of the bulk metal film is greater than or equal to about 95%, 98%, or 99% tungsten on an atomic basis. The bulk metal film excludes surface portions of metal 20 that may contact another surface (e.g., an oxide surface) or be open for further processing, because these areas may undergo a small amount of atomic diffusion with adjacent materials or have some surface functional groups (moieties) such as hydride termination.

Metal 20 may be deposited by any suitable technique, including but not limited to chemical vapor deposition (CVD) or atomic layer deposition (ALD). Metal 20 is deposited inside the interstitial space and on the top/side walls of the memory stack.

Referring to FIGS. 3A and 3B , a high temperature oxidation with a low temperature etching process is shown. In FIG. 3A , metal 20 is oxidized to metal oxide 25 to a depth of about the thickness of capping layer 22. Substantially all of capping layer 22 can be oxidized in a single step oxidation process. The oxidation of the capping layer can be affected by, for example, the oxidizing gas flow, the oxidizing gas partial pressure, the wafer temperature, and the processing time to form a highly conformal oxidation of the metal capping layer 22.

The oxidizing gas may be any suitable oxidizing gas that can react with the deposited metal 20. Suitable oxidizing gases include, but are not limited to, O ₂ , O ₃ , H ₂ O, H ₂ O ₂ , NO, NO ₂ or combinations thereof. In some embodiments, the oxidizing gas comprises one or more of O ₂ or O _3. In some embodiments, the oxidizing gas consists essentially of one or more of O ₂ or O _3. When used in this manner, the term "consisting essentially of..." means that the oxidizing component of the oxidizing gas is greater than or equal to about 95%, 98% or 99% of the claimed species. The oxidizing gas may include an inert gas, a diluent gas or a carrier gas. For example, the oxidizing gas may be co-flowed or diluted with one or more of Ar, He or N ₂ .

The metal oxide 25 of some embodiments comprises tungsten oxide (WO _x ). In some embodiments, the metal oxide 25 is a derivative of metal 20, which may or may not include oxygen. Suitable derivatives of the metal film include, but are not limited to, nitrides, borides, carbides, oxynitrides, oxyborides, oxycarbides, carbonitrides, borocarbides, boronitrides, borocarbonitrides, borooxycarbonitrides, oxycarbonitrides, borooxycarbides, and borooxynitrides. Those skilled in the art will appreciate that the deposited metal film may have non-stoichiometric atoms with the metal film. For example, a film designated as WO may have different amounts of tungsten and oxygen. A WO film may be, for example, 90 atomic % tungsten. Using WO to describe a tungsten oxide film means that the film contains tungsten and oxygen atoms and should not be considered to limit the film to a particular composition. In some embodiments, the film consists essentially of the specified atoms. For example, a film consisting essentially of WO means that the film is composed of greater than or equal to about 95%, 98%, or 99% tungsten and oxygen atoms.

In the processes shown in FIGS. 3A and 3B , the oxidation process occurs at an elevated temperature. As used in this regard, the term “elevated temperature” refers to a temperature greater than or equal to 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., or 850° C. In some embodiments, the temperature of the oxidation process is in the range of about 400° C. to about 950° C., or in the range of about 450° C. to about 900° C., or in the range of about 500° C. to about 850° C.

The pressure during the oxidation treatment may be in the range of about 0.1 Torr to about 760 Torr. The treatment time (exposure time) may be in the range of about 0.1 seconds to 12 hours. The temperature during the oxidation treatment may affect the pressure and treatment time.

In some embodiments, the metal 20 of the capping layer 22 is oxidized to form a metal oxide 25 on the top 13 and sides 15 of the stack 12, while leaving the metal 20 in the gap 16 to form the word line 19. In some embodiments, substantially all of the metal 20 in the gap 16 remains after oxidation. When used in this manner, the term "substantially all" means that the metal 20 is oxidized to within ±1Å of the side 15 of the stack 12.

Referring to FIG. 3B , metal oxide 25 formed from capping layer 22 is etched from top 13 and side 15 of stack 12 to leave metal 20 in gap 16 as word line 19. The etching process of some embodiments is a selective etching process that removes metal oxide 25 without substantially affecting metal 20.

In some embodiments, the etchant comprises a metal halide etchant. The etchant of some embodiments consists essentially of a metal halide etchant. When used in this manner, the term "consisting essentially of a metal halide etchant" means that the specified metal halide etchant species constitutes 95%, 98%, or 99% of the total metal halide etchant species (excluding inert gases, diluent gases, or carrier gases). The metal halide etchant may have the same metal species as the metal oxide 25 or a different metal species. In some embodiments, the metal halide etchant comprises the same metal species as the metal oxide 25.

In some embodiments, the metal halide etchant comprises halogen atoms consisting essentially of chlorine. When used in this manner, the term "consisting essentially of chlorine" means that chlorine constitutes greater than or equal to about 95%, 98%, or 99% of the halogen atoms in the metal halide etchant on an atomic basis. In some embodiments, the metal halide etchant comprises halogen atoms consisting essentially of fluorine. When used in this manner, the term "consisting essentially of fluorine" means that fluorine constitutes greater than or equal to about 95%, 98%, or 99% of the halogen atoms in the metal halide etchant on an atomic basis.

In some embodiments, the metal halide etchant comprises one or more of _WF6 , _WCl5 , _WCl6 , or tungsten halides. In some embodiments, the metal halide etchant consists essentially of one or more of _WF6 , _WCl5 , or _WCl6 . When used in this manner, the term "consisting essentially of" means that the claimed species constitutes greater than or equal to about 95%, 98%, or 99% of the metal halide on a molar basis.

The etching temperature of some embodiments is lower than the temperature during oxidation. In some embodiments, the etching temperature is in the range of about 300°C to about 600°C, or in the range of about 400°C to about 500°C. In some embodiments, the etching temperature is less than or equal to about 600°C, 550°C, 500°C, 450°C, 400°C, or 350°C. In some embodiments, the temperature during etching is lower than the temperature during oxidation by greater than or equal to about 50°C, 75°C, 100°C, 125°C, or 150°C. In some embodiments, oxidation and etching both occur at a temperature greater than or equal to about 300°C.

After etching the metal oxide 25, the metal capping layer 22 is removed and the metal 20 remaining in the gap 16 as the word line 19 is substantially flush with the side 15 of the stack 12. When used in this manner, the term "substantially flush" means that the word line 19 in the gap 16 is within ±1Å of the side 15 of the stack 12.

The embodiment shown in Figures 3A and 3B shows a high temperature oxidation-low temperature etching process. The embodiment shown in Figures 4A to 4D shows a low temperature oxidation and etching process. Some differences between the processes include (but are not limited to) lower temperature oxidation and slower capping layer removal.

After the stack 12 has the metal 20 formed with the capping layer 22 (as shown in FIG. 2 ), removal of the capping layer may be performed by an atomic layer etching type process. The atomic layer etching process may include multiple repeated processes that modify the surface to be etched and then evaporate or remove the modified surface, thereby exposing a new surface underneath.

Referring to FIG. 4A , the capping layer 22 is oxidized to form a metal oxide 25 on the surface of the capping layer 22. The oxidation process may use the same reactants and parameters as the embodiment shown in FIG. 3A , with some changes to allow for atomic layer etching (ALE) processing. The oxidation process of some embodiments occurs at a temperature of about 300° C. to about 500° C. In some embodiments, the oxidation occurs at a temperature of less than or equal to about 500° C., 450° C., 400° C., or 350° C. The pressure during the low temperature oxidation process may be in the range of about 0.1 Torr to about 760 Torr. The treatment or exposure time may be in the range of about 0.001 seconds to about 60 seconds. In an atomic layer etching process, each oxidation and etching process is self-limiting in that once a reaction with an active surface site occurs, the process stops. For example, once all active surface sites of metal 20 are exposed to the oxidant and react with the oxidant to form a metal oxide 25 film, further oxidation is not likely to occur. Similarly, once the etchant has removed the oxide film to expose the fresh metal 20 underneath, the etchant has no further oxide to remove.

Referring to FIG. 4B , after forming the metal oxide 25 on the metal 20, the stack 12 is exposed to an etchant. The etchant and etching conditions may be the same as shown and described with respect to FIG. 3B . The metal oxide 25 layer on the metal 20 is thinner than the embodiment shown in FIGS. 3A and 3B , so that the etching process will take less time. In some embodiments, the etchant treatment time is in the range of about 0.1 seconds to about 60 seconds.

In some embodiments, the temperature during the oxidation and etching processes occurs at a temperature less than or equal to about 400° C. The temperature of the etching process shown in FIG. 4B can be the same as the oxidation process of FIG. 4A , so that the substrate containing the stack 12 can be quickly moved from one processing area of the processing chamber to another processing area of the processing chamber to sequentially expose the substrate to the oxidation and etching conditions.

This type of ALE processing may be referred to as spatial ALE, where various reactive gases (e.g., oxidizers and etchants) flow into separate zones of a processing chamber and the substrate moves between zones. The different processing zones are separated by gas curtains that include one or more purge gas flows and/or vacuum flows to prevent the oxidizers and etchants from mixing in the gas phase. ALE processing may also be performed by time-domain processing, where the processing chamber is filled with oxidizer, purged to remove excess oxidizer and reaction products or byproducts, filled with etchant, and then purged to remove excess etchant and reaction products or byproducts. In time-domain processing, the substrate may remain stationary.

4C and 4D show repeated exposure to an oxidant to form metal oxide 25 and an etchant to remove the metal oxide, respectively. Although the process is shown as using two cycles, those skilled in the art will understand that this is only a representation and more than two cycles may be used to remove the capping layer 22 and leave the metal 20 as the word line 19 in the gap 16.

In some embodiments, a barrier layer is formed on the oxide layer 14 prior to depositing the metal 20. The barrier layer can be any suitable barrier material. In some embodiments, the barrier layer comprises titanium nitride. In some embodiments, the barrier layer consists essentially of titanium nitride. When used in this manner, the term "consisting essentially of titanium nitride" means that the composition of the barrier layer is greater than or equal to about 95%, 98%, or 99% titanium and nitrogen atoms on an atomic basis. The thickness of the barrier layer can be any suitable thickness. In some embodiments, the thickness of the barrier layer is in the range of about 20Å to about 50Å.

Figures 5A-5D show partial cross-sectional views of a substrate 100 having a feature 110 and detail an atomic layer etching process according to one or more embodiments of the present disclosure. The figures show a substrate having a single feature for illustrative purposes; however, those skilled in the art will understand that there may be more than one feature. The shape of feature 110 may be any suitable shape, including, but not limited to, a trench and a cylindrical through hole. In this regard, the term "feature" refers to any intentional surface irregularity. Suitable examples of features include, but are not limited to, a trench having a top, two sidewalls, and a bottom, a peak having a top and two sidewalls. Features may have any suitable aspect ratio (the ratio of the depth of the feature to the width of the feature). In some embodiments, the aspect ratio is greater than or equal to approximately 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40:1.

Substrate 100 has a substrate surface 120. At least one feature 110 forms an opening in substrate surface 120. At least one feature 110 extends from substrate surface 120 a feature depth _Df to a bottom surface 112. At least one feature 110 has a first sidewall 114 and a second sidewall 116 defining a width W of at least one feature 110. The open area formed by sidewalls 114, 116 and bottom 112 is also referred to as a gap. In one or more embodiments, width W is uniform along a depth D1 of at least one feature 110. In other embodiments, the width (W) at the top of at least one feature 110 is greater than the width (W) at the bottom surface 112 of at least one feature 110.

In one or more embodiments, substrate 100 is a film stack comprising a plurality of alternating layers of nitride material 104 and oxide material 106 deposited on semiconductor substrate 102.

The semiconductor substrate 102 may be any suitable substrate material. In one or more embodiments, the semiconductor substrate 102 includes a semiconductor material, such as silicon (Si), carbon (C), germanium (Ge), silicon germanium (SiGe), gallium arsenide (GaAs), indium phosphate (InP), indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), copper indium gallium selenide (CIGS), other semiconductor materials or any combination thereof. In one or more embodiments, the semiconductor substrate 102 includes one or more of silicon (Si), germanium (Ge), gallium (Ga), arsenic (As), indium (In), phosphorus (P), copper (Cu) or selenium (Se). Although some examples of materials from which substrate 102 may be formed are described herein, any material that may be used as a basis for constructing passive and active electronic devices (e.g., transistors, memories, capacitors, inductors, resistors, switches, integrated circuits, amplifiers, optoelectronic devices, or any other electronic device) may fall within the spirit and scope of the present disclosure.

In one or more embodiments, at least one feature 110 comprises a memory hole or a wordline slit. Thus, in one or more embodiments, the substrate 100 comprises a memory device or a logic device, such as a NAND, V-NAND, DRAM, or the like.

As used herein, the term "3D NAND" refers to a type of electronic (solid-state) non-volatile computer storage memory in which memory cells are stacked in multiple layers. A 3D NAND memory typically includes a plurality of memory cells, the plurality of memory cells including floating gate transistors. Traditionally, a 3D NAND memory cell includes a plurality of NAND memory structures arranged in three dimensions around a bit line.

As used herein, the term "dynamic random access memory" or "DRAM" refers to a memory cell that stores data bits by storing packets of charge (i.e., binary ones) or no charge (i.e., binary zeros) on a capacitor. The charge is gated on the capacitor via an access transistor and sensed by the voltage perturbation created by turning on the same transistor and seeing the charge packet dumped on the interconnect at the transistor output. Thus, a single DRAM cell consists of one transistor and one capacitor.

5B , a metal layer 124 is deposited in at least one feature 110. In one or more embodiments, the metal layer 124 comprises one or more of tungsten (W), titanium (Ti), tantalum (Ta), nickel (Ni), cobalt (Co), or molybdenum (Mo). In one or more embodiments, the metal layer 124 comprises tungsten (W). In one or more embodiments, the metal layer 124 is deposited with a capping layer 126. In some embodiments, prior to depositing the metal layer 124, a conformal liner 122 is deposited in at least one feature 110. The conformal liner 122 may comprise any suitable material known to those skilled in the art. In one or more embodiments, the conformal liner 122 includes one or more of titanium nitride (TiN) or tantalum nitride (TaN).

Referring to FIG. 5C , after the metal layer 124 having the capping layer 126 (and optionally the conformal liner 122) has been deposited, removal of the capping layer 126 may be performed by an atomic layer etching type process. The atomic layer etching process may include multiple repetitive processes that modify the surface to be etched and then volatilize or remove the modified surface, thereby exposing a new surface underneath.

Referring to FIG. 5C , the capping layer 126 is oxidized to form a metal oxide layer 128 on the surface of the capping layer 126 . In one or more embodiments, the metal layer 124 is oxidized to form the metal oxide layer 128 to a depth of about the thickness of the capping layer 126 . Substantially all of the capping layer 126 may be oxidized in a one-step oxidation process. The oxidation of the capping layer 126 may be affected by, for example, the oxidizing gas flow, the oxidizing gas partial pressure, the wafer temperature, and the processing time to form a highly conformal oxidation of the metal capping layer 126 .

In one or more embodiments, the oxidizing gas is any suitable oxidizing gas that can react with the deposited metal layer 124. Suitable oxidizing gases include, but are not limited to, _O2 , _O3 , _H2O , _H2O2 , NO, _NO2 , or combinations thereof. In some embodiments, the oxidizing gas comprises one or more of _O2 or _O3 . In some embodiments, the oxidizing gas consists essentially of one or more of _O2 or _O3 . When used in this manner, the term "consisting essentially of... _" means that the oxidizing component of the oxidizing gas is greater than or equal to about 95%, 98%, or 99% of the claimed species. The oxidizing gas may include an inert gas, a diluent gas, or a carrier gas. For example, the oxidizing gas may be co-flowed or diluted with one or more of Ar, He, or _N2 .

The metal oxide layer 128 of some embodiments comprises tungsten oxide (WO _x ). In some embodiments, the metal oxide layer 128 is a derivative of the metal layer 124, which may or may not include oxygen. Suitable derivatives of the metal layer 124 include, but are not limited to, nitrides, borides, carbides, oxynitrides, oxyborides, oxycarbides, carbonitrides, borocarbides, boronitrides, borocarbonitrides, borooxycarbonitrides, oxycarbonitrides, borooxycarbides, and borooxynitrides. Those skilled in the art will appreciate that the deposited metal layer 124 may have non-stoichiometric atoms than the metal film. For example, a metal layer 124 designated as WO may have different amounts of tungsten and oxygen. A WO film may be, for example, 90 atomic % tungsten. The use of WO to describe a tungsten oxide film means that the film comprises tungsten and oxygen atoms and should not be construed as limiting the film to a particular composition. In some embodiments, the film consists essentially of the specified atoms. For example, a film consisting essentially of WO means that the film consists of greater than or equal to about 95%, 98%, or 99% tungsten and oxygen atoms.

In the processes shown in Figures 5A to 5D, the oxidation process occurs at a high temperature, so that the oxidation is a thermal oxidation or a rapid thermal oxidation or a spike annealing process. In this regard, the term "high temperature" refers to a temperature greater than or equal to about 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, or 850°C. In some embodiments, the temperature of the oxidation process is in the range of about 400°C to about 950°C, or in the range of about 450°C to about 900°C, or in the range of about 500°C to about 850°C.

In one or more embodiments, the pressure during the oxidation treatment is in the range of about 0.1 Torr to about 760 Torr. The treatment time (exposure time) can be in the range of about 0.1 seconds to 12 hours. The temperature during the oxidation treatment affects the pressure and the treatment time.

In some embodiments, metal layer 124 of cap layer 126 is oxidized to form metal oxide layer 128 on top 130 and side 132 of at least one feature 110 while retaining metal layer 124 in at least one feature 110. In some embodiments, substantially all of metal layer 124 in at least one feature 110 remains after oxidation. When used in this manner, the term "substantially all" means that metal layer 124 is oxidized to within ±1Å of side 132 of at least one feature 110.

Referring to FIG. 5D , the metal oxide layer 128 formed by the capping layer 126 is etched from the top 130 and the side 132 to leave the metal layer 124. The etching process of some embodiments is a selective etching process that removes the metal oxide layer 128 without substantially affecting the metal layer 124.

In some embodiments, the etchant comprises a metal halide etchant. The etchant of some embodiments consists essentially of a metal halide etchant. When used in this manner, the term "consisting essentially of a metal halide etchant" means that the specified metal halide etchant species constitutes 95%, 98%, or 99% of the total metal halide etchant species (excluding inert gases, diluent gases, or carrier gases). The metal halide etchant can have the same metal species as the metal oxide layer 128 or a different metal species. In some embodiments, the metal halide etchant comprises the same metal species as the metal oxide layer 128.

In some embodiments, the metal halide etchant comprises halogen atoms consisting essentially of chlorine. In other embodiments, the metal halide etchant comprises halogen atoms consisting essentially of fluorine. When used in this manner, the term "consisting essentially of fluorine" means that fluorine constitutes greater than or equal to about 95%, 98%, or 99% of the halogen atoms in the metal halide etchant on an atomic basis.

In some embodiments, the metal halide etchant comprises one or more of WF ₆ , WCl ₅ , WCl ₆ , or tungsten halides. In some embodiments, the metal halide etchant consists essentially of one or more of WF ₆ , WCl ₅ , WCl ₆ , or tungsten halides. When used in this manner, the term "consisting essentially of" means that the claimed species constitutes greater than or equal to about 95%, 98%, or 99% of the metal halide on a molar basis.

The etching temperature of some embodiments is lower than the temperature during oxidation. In some embodiments, the etching temperature is in the range of about 100°C to about 600°C, or in the range of about 100°C to about 500°C. In some embodiments, the etching temperature is less than or equal to about 600°C, 550°C, 500°C, 450°C, 400°C, or 350°C. In some embodiments, the temperature during etching is lower than the temperature during oxidation by greater than or equal to about 50°C, 75°C, 100°C, 125°C, or 150°C. In some embodiments, etching occurs at about 300°C. In some embodiments, oxidation and etching both occur at a temperature greater than or equal to about 400°C.

The oxidation process of some embodiments occurs at a temperature of about 300°C to about 500°C. In some embodiments, oxidation occurs at a temperature of less than or equal to about 500°C, 450°C, 400°C, or 350°C. The pressure during the low temperature oxidation process may be in the range of about 0.1 Torr to about 760 Torr. The process or exposure time may be in the range of about 0.001 seconds to about 60 seconds. In atomic layer etching processes, each oxidation and etching process is self-limiting because once reaction with active surface sites occurs, the process stops. For example, once all active surface sites of metal layer 124 are exposed to the oxidant and react with the oxidant to form metal oxide layer 128, further oxidation is not likely to occur. Similarly, once the etchant has removed the metal oxide layer 128 to expose the underlying fresh metal layer 124, the etchant has no further oxide to remove.

Referring to FIG. 5D , after forming the metal oxide layer 128 on the metal layer 124, the substrate 102 is exposed to an etchant. The etchant and etching conditions may be the same as shown and described above. In some embodiments, the etchant treatment time is in the range of about 0.1 seconds to about 60 seconds.

In one or more embodiments, this type of ALE processing may be referred to as spatial ALE, where various reactive gases (e.g., oxidizers and etchants) flow into separate regions of a processing chamber and the substrate moves between the regions. The different processing regions are separated by gas curtains that include one or more purge gas flows and/or vacuum flows to prevent the oxidizers and etchants from mixing in the gas phase. ALE processing may also be performed by time-domain processing, where the processing chamber is filled with an oxidizer, purged to remove excess oxidizer and reaction products or byproducts, filled with an etchant, and then purged to remove excess etchant and reaction products or byproducts. In time-domain processing, the substrate may remain stationary

After etching the metal oxide 128, the process is repeated - oxidizing the metal layer 124 to form the metal oxide layer 128, and then etching it to remove the oxide layer. Although the process is shown as using a single cycle, those skilled in the art will understand that this is only a representation and more than two cycles may be used to remove the metal layer 124. In one or more embodiments, the process is repeated for n processing cycles. In one or more embodiments, n is a number in the range of about 2 to about 2000. In other embodiments, n is a number greater than about 10, greater than about 25, greater than about 50, greater than about 75, or greater than about 100.

As shown in FIG. 5D , processing is performed in a layer-by-layer approach until the metal layer 124 is selectively removed from at least one feature 110. In some embodiments, as shown, the conformal liner 122 remains. In other embodiments not shown, the conformal liner 122 is etched so that it is partially or completely removed from at least one feature. In one or more embodiments, the metal layer 124 is selectively removed so that the dielectric material (e.g., silicon oxide layer 106, silicon nitride layer 104) is not affected.

Throughout the specification, references to "one embodiment", "certain embodiments", "one or more embodiments" or "an embodiment" mean that the particular features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the disclosure. Therefore, phrases such as "in one or more embodiments", "in certain embodiments", "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment of the disclosure. In addition, in one or more embodiments, the particular features, structures, materials or characteristics may be combined in any suitable manner.

Although the present disclosure has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations may be made to the methods and apparatus of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, it is intended that the present disclosure include modifications and variations that come within the scope of the appended claims and their equivalents.

10: Substrate

11: Memory string

12: Stacking

13: Top

14: Oxide layer

15: Side

16: Gap

19: Word line

20: Metal

22: Covering layer

25: Metal oxides

100: Substrate

102: Substrate

104: Nitride material/silicon nitride layer

106: Oxide material/silicon oxide layer

110: Features

112: Bottom surface/bottom

114: First side wall/side wall

116: Second side wall/side wall

120: Substrate surface

122: Conformal lining

124:Metal layer

126: Covering layer

128: Metal oxide layer

Therefore, in order to understand in detail the manner in which the above-mentioned features of the present disclosure are provided, a more detailed description of the present disclosure briefly summarized above may be obtained by reference to the embodiments, some of which are shown in the accompanying drawings. The accompanying drawings show only typical embodiments of the present disclosure and therefore should not be considered limiting, as the present disclosure may admit to other equally effective embodiments.

FIG. 1 shows a stack of oxide layers where word lines will be formed according to one or more embodiments of the present disclosure;

FIG. 2 shows a metal film formed on the stack of oxide layers of FIG. 1;

3A and 3B illustrate high temperature oxidation and etching processes according to one or more embodiments of the present disclosure;

Figures 4A to 4D illustrate low temperature oxidation and etching processes according to one or more embodiments of the present disclosure; and

5A-5D illustrate cross-sectional views of substrate features according to one or more embodiments of the present disclosure.

100: Substrate

102: Substrate

104: Nitride material/silicon nitride layer

106: Oxide material/silicon oxide layer

122: Conformal lining

124:Metal layer

126: Covering layer

128: Metal oxide layer

Claims (18)

A processing method comprises the following steps: depositing a conformal liner in at least one feature on a substrate, wherein the conformal liner comprises one or more of titanium nitride (TiN) or tantalum nitride (TaN); depositing a metal layer on the conformal liner in the at least one feature, the metal layer comprising a metal; oxidizing the metal to a first depth to form a metal oxide layer on the metal layer; and etching the metal oxide layer to selectively remove the metal oxide layer. The method as described in claim 1, wherein the metal comprises one or more of tungsten (W), titanium (Ti), tantalum (Ta), nickel (Ni), cobalt (Co) or molybdenum (Mo). The method as described in claim 2, wherein the metal comprises tungsten (W). The method as described in claim 1, wherein the metal oxide layer comprises tungsten oxide (WO). A method as claimed in claim 1, wherein oxidation of the metal occurs at a temperature greater than or equal to 400°C. The method of claim 1, wherein etching the metal oxide layer occurs at a temperature in a range of about 100°C to about 500°C. The method as described in claim 1, wherein etching the metal oxide layer comprises the following steps: exposing the metal oxide layer to a metal halide etchant. The method of claim 7, wherein the metal halide etchant comprises one or more of WF ₆ , WCl ₅ , WCl ₆ or tungsten halides. A processing method comprises the following steps: depositing a metal layer on a substrate surface, the substrate surface having at least one feature, the at least one feature extending a feature depth from the substrate surface to a bottom surface, the at least one feature having a width defined by a first sidewall and a second sidewall, wherein the metal layer is deposited on the substrate surface, the first sidewall of the at least one feature, the second sidewall and the bottom surface; and performing a processing cycle, comprising the following steps: oxidizing the metal layer to a first depth to form a metal oxide layer on the metal layer; and etching the metal oxide layer to selectively remove the metal oxide layer. The method as described in claim 9, wherein the metal layer comprises tungsten (W) and the metal oxide layer comprises tungsten oxide (WO). The method as described in claim 9 further comprises the step of depositing a conformal liner in the at least one feature before depositing the metal layer, wherein the conformal liner comprises one or more of titanium nitride (TiN) or tantalum nitride (TaN). A method as described in claim 9, wherein oxidation of the metal layer occurs at a temperature greater than or equal to 400°C. The method of claim 9, wherein etching the metal oxide layer occurs at a temperature in a range of about 100°C to about 500°C. The method of claim 9, wherein etching the metal oxide layer comprises the following steps: exposing the metal oxide to a metal halide etchant, wherein the metal halide etchant comprises one or more of WF ₆ , WCl ₅ , WCl ₆ or tungsten halogenide. The method as described in claim 9 further comprises the following steps: repeating the processing loop n times. The method of claim 9, wherein oxidizing the metal layer comprises the step of exposing a surface of the metal layer to oxygen (O ₂ ). A method as described in claim 9, wherein the substrate comprises a plurality of alternating oxide layers and nitride layers. A method for processing a substrate, the method comprising the following steps: forming a film stack on a substrate, the film stack comprising a plurality of alternating layers of oxide material and nitride material, and the film stack having a stacking thickness; forming an opening extending from a top portion of a surface of the film stack to a bottom surface thereof to a depth, the opening having a width defined by a first sidewall and a second sidewall; optionally forming a film stack on the surface of the film stack and on the first sidewall, the second sidewall of the opening; and forming a barrier layer on the bottom surface, the barrier layer comprising TiN having a thickness in a range of about 20Å to about 50Å; depositing a metal layer on the film stack so that the metal layer fills the opening and covers the top of the film stack with a metal layer thickness; and repeatedly oxidizing the surface of the metal layer to form a metal oxide layer, and etching the metal oxide layer from at least one feature until the metal layer is removed, oxidizing the surface comprising the steps of: exposing to _O2 , and etching the metal oxide layer comprising the steps of: exposing to a halogenide etchant.