Suppression of hydrogen deterioration

Abstract

The present disclosure provides techniques for the inhibition of hydrogen degradation. In some embodiments, a method for reducing the amount or rate of hydrogen degradation of a material includes (a) exposing the material to gaseous hydrogen peroxide, (b) forming a hydroxyl layer on the surface of the material in a chamber, and (c) exposing the material to hydrogen during a controlled process or application after forming the hydroxyl layer.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 009,915, filed April 14, 2020, and entitled "Active Suppression of Hydrogen Embrittlement," the contents of which are incorporated by reference in their entirety herein. [Background technology]

[0002] In semiconductor device manufacturing, the demand for faster, smaller and more energy efficient logic devices, and higher density, higher speed, and higher reliability of advanced memory devices poses numerous challenges. To address these challenges, new metal materials, 3D architectures, and increasing high aspect ratio (HAR) structures are being used, which places additional demands on photolithography, film deposition, and film etching methods.

[0003] Various process gases may be used in microelectronics manufacturing and processing. Additionally, various chemicals may be used in other environments requiring high purity gases, such as controlled processes and applications, including, but not limited to, microelectronic applications, wafer patterning, atomic layer deposition, chemical vapor deposition, etching and selective etching, wafer cleaning, wafer bonding, photoresist stripping, silicon oxidation, surface passivation, photolithography mask cleaning, flat panel displays, industrial parts cleaning, pharmaceutical manufacturing, nanomaterials manufacturing, power generation and control devices, fuel cells, power transmission devices, and other applications where process control and purity are important considerations. These processes and applications require the delivery of specific amounts of specific process gases under controlled operating conditions, such as temperature, pressure, flow rates, and various plasma conditions.

[0004] However, processes of high energy light intensity, high temperature, and high energy plasma are known to generate hydrogen radicals, i.e. excited hydrogen species, which over time cause hydrogen embrittlement of metals and metal oxides. Hydrogen embrittlement, especially from atomic hydrogen, causes premature failure of metal and metal oxide surface coatings, which leads to degradation of desired mechanical and physical properties. This is especially true in the semiconductor industry with respect to any stainless steel or metal oxide covered surfaces. Stainless steel and other metals are commonly used in the construction of process chambers, internal chamber parts, sensors, susceptors, heaters, mirrors, showerheads, and robots. These materials may or may not be covered with metal oxides for corrosion resistance, anti-reflective coatings, or to ensure process inertness. As a result of hydrogen embrittlement, these manufacturing processes must be stopped occasionally or frequently to allow maintenance and / or replacement of metal components that deteriorate over time and cause production delays, contamination of the process or process chambers, reduced manufacturing throughput, and loss of profits over time.

[0005] Currently, exposure to water and oxygen in ambient air can lead to stabilized surfaces that provide some protection against hydrogen-induced embrittlement of metal surfaces. However, water and oxygen can lead to uneven surface coatings and, in some instances, can damage metallic materials by penetrating deeply into the material (subsurface oxidation). These subsurface oxides can detrimentally alter the physical and mechanical properties of metal surfaces exposed to atomic hydrogen. Summary of the Invention

[0006] The present disclosure provides techniques for the inhibition of hydrogen degradation. In some embodiments, a method for reducing the amount or rate of hydrogen degradation of a material includes (a) exposing the material to gaseous hydrogen peroxide, (b) forming a hydroxyl layer on the surface of the material in a chamber, and (c) exposing the material to hydrogen during a controlled process or application after forming the hydroxyl layer. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a graph showing results after 12 hours of H2 plasma, where the oxygen 1s peak is shifted to lower binding energy, according to some embodiments. [Diagram 2] FIG. 2 is a graphical representation showing results after 12 hours of H2 plasma, where the metal oxide 3d peak is shifted to lower binding energy, according to some embodiments. [Diagram 3] FIG. 3 is a pictorial diagram showing images from an atomic force microscope (AFM) of a film before and after H 2 plasma, according to some embodiments. [Figure 4] FIG. 4 is a graphical diagram showing results after a 50 ms pulse of substantially anhydrous hydrogen peroxide (HO) into a vacuum chamber followed by a 10 second wait before a 10 minute H plasma, in accordance with some embodiments, where no shift in the oxygen peak was observed. [Diagram 5] FIG. 5 is a graph illustrating a smaller shift compared to FIG. 2, according to some embodiments. [Figure 6] FIG. 6 is a pictorial representation of AFM images showing reduction in film surface roughness after 12 hours of H 2 plasma with administration of substantially anhydrous H 2 O 2 , according to some embodiments. [Figure 7] FIG. 7 is a pictorial diagram showing comparative AFM images side-by-side of particles (white spots) with approximately 10-fold reduction in particle numbers after 12 hours of H2 plasma, in accordance with some embodiments. [Figure 8] FIG. 8 is a pictorial diagram showing images from an atomic force microscope (AFM) of a film before and after H2 plasma, according to some embodiments. [Figure 9] FIG. 9 is a pictorial representation of AFM images showing reduction in film surface roughness after 12 hours of H2 plasma with administration of substantially anhydrous H2O2, according to some embodiments. [Figure 10]FIG. 10 is a pictorial diagram showing side-by-side AFM images of comparisons of particles (white specks) with reduced particle counts after 12 hours of H2 plasma, in accordance with some embodiments. [Figure 11] FIG. 11 is a flow chart of a method for mitigating hydrogen degradation of a material, according to some embodiments. [Figure 12] FIG. 12 is a flowchart of a method for mitigating hydrogen degradation of a material, according to some embodiments. [Figure 13] FIG. 13 illustrates a simplified diagram of one example of a system for reducing hydrogen degradation of a material, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present disclosure generally relates to the degradation of metals, and more specifically, to the use of hydroxyl groups to reduce the amount of hydrogen degradation of materials resulting from exposure to hydrogen. In some embodiments, a material (e.g., a metal and / or metal oxide film) is exposed to hydrogen peroxide (e.g., in a gas mixture with or without water vapor), which forms a hydroxyl layer on the material that reduces the amount of hydrogen degradation of the material when the material is exposed to hydrogen (e.g., hydrogen gas, hydrogen atoms, hydrogen ions, hydrogen radicals, or hydrogen plasma). In some cases, the administration of hydrogen peroxide can be used to treat materials (e.g., that are part of an article or device) used in processes that expose the material (e.g., a metal or metal oxide-covered surface) to hydrogen, ultraviolet light (UV light), infrared radiation, a reducing atmosphere, high temperature, or a combination thereof to prevent hydrogen degradation of the material. In some cases, the material is exposed to hydrogen during a controlled process or application.

[0009] Conventional solutions typically focus on material selection or surface coating to prevent hydrogen degradation (e.g., due to hydrogen and hydrogen plasma used to generate a reducing atmosphere). Hydrogen peroxide creates an oxidizing environment and would typically be considered incompatible with hydrogen process chemistry. Furthermore, the ability to deliver controlled and consistent concentrations of active hydroxyl species (e.g., hydrogen peroxide in a gas mixture) is challenging. Systems and methods for delivering hydrogen peroxide are further described in U.S. Patent Nos. 8,282,708, 9,545,585, and 10,363,497, U.S. Patent Publication Nos. US20200291517A1 and US20200393086A1, and International Publication Nos. WO2016 / 164380 and WO2017 / 027581, each of which is incorporated herein by reference in its entirety. This disclosure describes techniques for the inhibition of hydrogen degradation (e.g., hydrogen embrittlement) at the surface, subsurface, and within the bulk of a material. In some cases, hydrogen peroxide is provided using the systems and methods described in the patents and patent publications listed above.

[0010] Before describing the compositions and methods of the present invention, it is to be understood that the invention is not limited to the particular compositions, methods, and experimental conditions described, as such compositions, methods, and conditions may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, as the scope of the present invention will be limited only by the appended claims.

[0011] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise. Thus, a reference to a "method" includes one or more methods and / or steps of the type described herein that will be apparent to a person of ordinary skill in the art upon reading this disclosure and so forth.

[0012] As used in this specification and the appended claims, the term "about" refers to a variation of + / - 5%. For example, about 100°C refers to a temperature from 95°C to 105°C.

[0013] As used herein, the term "controlled process or application" refers to a process or application where process control and / or purity are important considerations. Examples of controlled processes and applications include, but are not limited to, microelectronic applications, photolithography, wafer patterning, atomic layer deposition, chemical vapor deposition, selective etching, wafer cleaning, wafer bonding, photoresist stripping, silicon oxidation, surface passivation, photolithography mask cleaning, exposure to UV light, sterilization of surfaces contaminated with bacteria, viruses, and other biological agents, industrial parts cleaning, pharmaceutical manufacturing, hydrogenation reactions, nanomaterials manufacturing, power generation and control devices, fuel cells, power transmission devices, and any process where a metal or metal oxide surface is exposed to hydrogen or hydrogen radicals.

[0014] As used herein, the term "administration" refers to the introduction of a species into an environment. For example, administering hydrogen peroxide gas to a metal or metal oxide surface with a 50 ms pulse length refers to introducing hydrogen peroxide gas into an environment (e.g., a vacuum chamber) containing the metal or metal oxide for a duration of 50 ms.

[0015] As used herein, the term "hydrogen degradation" refers to the degradation of a material exposed to hydrogen (e.g., H2, hydrogen atoms, hydrogen ions, hydrogen radicals, or hydrogen plasma). "Hydrogen degradation" may include hydrogen embrittlement, cracking, surface degradation of the material, blistering of the material, delamination of a layer from another layer or from the bulk of the material, and / or the formation of particles on or from the material.

[0016] As used herein, the term "Langmuir" refers to a unit of exposure (or dose) to a surface. It can be derived by multiplying the pressure of the gas by the time of exposure (e.g., 1 Langmuir is 10 Langmuir for 1 second). -6 Torr exposure).

[0017] In some embodiments, the hydroxyl layer is formed on the material by exposing the material to hydrogen peroxide. In some cases, the hydrogen peroxide is substantially anhydrous. In practice, it is difficult to remove all of the water from hydrogen peroxide, and in some cases, substantially anhydrous hydrogen peroxide includes less than 10% by weight, less than 1% by weight, less than 0.1% by weight, less than 0.01% by weight, or less than 0.001% by weight. In some cases, hydrogen peroxide with a low water content is included in a hydrogen peroxide source that provides hydrogen peroxide to the material, and the hydrogen peroxide will be mixed with water (e.g., from the environment in the process equipment) before interacting with the material (e.g., forming a hydroxyl layer on the surface). In some cases, the hydrogen peroxide in the source or the hydrogen peroxide that interacts with the material is part of a gas mixture that may include other species such as water. In some cases, the hydrogen peroxide in the source or the hydrogen peroxide that interacts with the material is mixed with water, and the water content in the mixture (or mixed gas) is less than 10% by weight, less than 2%, less than 0.5%, less than 0.1%, less than 0.01%, less than 0.001%, or 10 ppm to 99% by weight, or 100 ppm to 75% by weight, or 100 ppm to 35% by weight, or 0.001% to 99% by weight, or 1% to 99% by weight, or 30% to 99% by weight, or 30% to 75% by weight. In some cases, the hydrogen peroxide in the source or the hydrogen peroxide that interacts with the material is mixed with a carrier gas, such as nitrogen, argon, air, or hydrogen. Hydrogen peroxide and mixtures thereof are also further described in U.S. Pat. Nos. 8,282,708, 9,545,585, and 10,363,497, U.S. Patent Publication Nos. US20200291517A1 and US20200393086A1, and International Publication Nos. WO2016 / 164380 and WO2017 / 027581, each of which is incorporated herein in its entirety.

[0018] In some embodiments, when exposed to hydrogen, a hydroxyl layer is formed on the material that reduces the amount of hydrogen degradation of the material. For example, the material may be any metal substrate or metal oxide film formed on a substrate (e.g., used in a fabrication process) that may be exposed to hydrogen gas or hydrogen radicals and thus undergo hydrogen degradation. The material may be a material on which a process is being performed (e.g., a silicon wafer, or a multi-layer stack of metal oxides and / or semiconductors), or the material may be a material that is part of a piece of processing equipment that performs a process involving hydrogen (e.g., the stainless steel wall of a process chamber, or the oxide-covered inner surface of a metal pipe). Thus, the systems and methods of the present invention can be used to protect materials being processed or materials of processing equipment from hydrogen degradation.

[0019] The material deposited to reduce the amount of hydrogen degradation when the hydroxyl layer is exposed to hydrogen may be a bulk material, a material with a bulk and a coating on the bulk, or a material with multiple layers of coatings forming a multi-layer structure (either on the bulk material or free-standing). The geometry of the material is not limited, and the material may have a flat surface, a curved surface, a mesa, a groove, a hole, or other geometric shape. Some examples of materials are metals, metal oxides, semiconductors, semiconductors covered with metals or metal oxides, distributed Bragg reflectors (DBRs), and anti-reflective coatings (ARCs). In some cases, these materials may be part of a semiconductor device (e.g., a processor), an optoelectronic device (e.g., a laser or LED), or other type of device. In some cases, these materials may be part of processing equipment, such as the interior surface of a vacuum chamber.

[0020] Hydrogen degradation (e.g., hydrogen embrittlement) of metals such as stainless steel, stainless steel alloys, titanium alloys, or aluminum alloys, and hydrogen degradation (e.g., blistering, cracking, or peeling) of coatings such as metal oxides of Si, Al, Ti, In, Zr, Hf, Ta, Ga, Cd, Yi, Nb, lanthanides, and combinations thereof exposed to energetic H2 gas, atomic hydrogen, hydrogen ions, and hydrogen radicals are typical causes of failure in process chambers, vacuum systems, and metal parts subjected to temperature or stress. Some examples of systems having components where hydrogen degradation (e.g., hydrogen embrittlement) may occur are systems commonly used in semiconductor manufacturing processes, as well as systems in the medical, pharmaceutical, and chemical industries. A hydroxyl layer can be formed on any of the above-mentioned materials to reduce the amount or rate of hydrogen degradation using the methods and systems described herein.

[0021] In some cases, after repeated or extended exposure to hydrogen, materials (e.g., components of a system or substrates being processed) may develop cracks and blisters on the nanoscale (e.g., smaller than 1 micron, or smaller than 100 nm, or smaller than 10 nm, or about 1 nm to about 10 nm, or about 1 nm to about 20 nm, or about 1 nm to about 100 nm, or about 1 nm to about 500 nanometers in size). These particles may be detrimental to manufacturing processes. For example, in semiconductor wafer processing, plasma processes may generate particles that are detrimental to thin film performance and ultimately lead to reduced device performance.

[0022] Previous work in the art has attempted to delay hydrogen embrittlement by using thin oxide layers, such as black oxide. However, as hydrogen diffuses through the thin oxide film and / or into the metal substrate, it can later collect at molecular interfaces or grain boundaries to form molecular hydrogen and then hydrogen bubbles that can lead to cracks and blisters. It is noteworthy that the passage of hydrogen through the coating depends not only on its diffusivity, but also on the ability of the adsorbed hydrogen to recombine into molecular form and escape as bubbles before it can enter the coating. The amount or rate of hydrogen ingress can be reduced by the presence of cadmium in the coating, since cadmium increases the rate of this recombination (Bhadeshia HK "Prevention of Hydrogen Embrittlement in Steels" ISIJ International 56 (2016) 24-36).

[0023] The present inventors have shown that hydrogen peroxide rapidly decomposes into two hydroxyl groups on reduced metal surfaces.

[0024] The density of hydroxyl groups in hydrogen peroxide is much higher than that of water, and hydrogen peroxide typically chemisorbs, not physisorbs, like water (Kaufman-Osborn, et al., Surface Science 630 (2014) 273-279, and Edmonds, et al. Surface Science 660 (2017) 31-38, both of which are incorporated herein by reference).

[0025] TIFF0007671779000001.tif8170 shows that water can liberate hydrogen ions and hydroxylate metal (e.g., iron) surfaces. In the absence of a hydroxylated surface, as described herein, atomic hydrogen would lead to increased hydrogen degradation of the metal. The effects of degradation due to atomic hydrogen can be reduced by adding hydrogen peroxide to the process and forming a hydroxyl layer on the metal. In such a situation, the hydroxyl layer provided on the surface of the metal or metal oxide will react with atomic hydrogen to form water (according to the reverse reaction of equation (1) above). The water formed in this (reverse) reaction will then be removed in the gas phase by vacuum or purge gas.

[0026] The present disclosure relates to surface functionalization of materials (e.g., metals and metal oxides) with hydrogen peroxide to reduce the amount or rate of degradation (e.g., embrittlement) caused by hydrogen (e.g., hydrogen gas, hydrogen atoms, hydrogen ions, hydrogen radicals, or hydrogen plasma) or to prevent degradation (e.g., embrittlement). In some cases, the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement) of the metal is reduced when hydrogen peroxide gas is used to form a monolayer coating on a metal surface or a thin metal oxide film. Without being limited by theory, it is believed that the hydroxyl layer can prevent hydrogen (e.g., atomic hydrogen) from penetrating the surface (or reduce the rate of hydrogen penetration into the surface), thereby preventing (or reducing the rate of) degradation (e.g., embrittlement, flaking, particle formation, or blistering) of the underlying material.

[0027] By administering hydrogen peroxide gas to a material (e.g., a metal or metal oxide) surface that is exposed to hydrogen (e.g., atomic hydrogen), the oxide on the surface of the material can be protected from reduction reactions by reacting the hydroxyl groups on the surface with hydrogen (according to the reverse reaction of equation (1)) before it can react with and / or diffuse into the material. Thus, the surface oxide can be maintained to prevent (or limit) hydrogen (e.g., atomic hydrogen) from penetrating below the surface. In this manner, hydrogen degradation (e.g., hydrogen embrittlement) of the material (e.g., a metal or metal oxide) can be delayed or prevented. In some cases, a monolayer of hydroxyl groups on the surface is sufficient to reduce the susceptibility of the material (e.g., a metal or metal oxide) to hydrogen degradation (e.g., hydrogen embrittlement). In some cases, the monolayer of hydrogen peroxide is dense and continuous. In some cases, the hydroxyl monolayer is regenerated by continuous administration of hydrogen peroxide to replenish the depleted hydroxyl monolayer and prevent (or limit) reduction of the material (e.g., a metal oxide surface).

[0028] In some cases, the material includes a transparent or conductive oxide, and additional oxide grown on the surface (e.g., to form a protective coating on the transparent or conductive oxide) can degrade the properties of the transparent or conductive oxide. For example, in the case of a DBR mirror or an anti-reflective coating (ARC), the thickness of the layer is important to the optical properties, and additional oxide growth on the surface can degrade the optical properties of the DBR or ARC. In some cases, the oxide (e.g., to protect the metal surface) is kept to a minimum thickness on the surface of the material, and a layer of hydroxyl groups is formed on the surface of the material ready to react with any atomic hydrogen that collides with the surface. In other words, the use of hydrogen peroxide to form a layer of hydroxyl groups on the surface of the material allows the protective oxide layer on the surface of the material to be thinner than would be possible without forming a layer of hydroxyl groups on the surface. In some cases, the use of hydrogen peroxide to form a layer of hydroxyl groups on the surface of the material can protect the material from hydrogen degradation, and thus a protective oxide layer on the surface of the material is not required to reduce the amount or rate of hydrogen degradation.

[0029] In certain cases, the presence of water may cause subsurface oxidation of the material, which may be detrimental to the integrity of the material properties of the material. Due to Raoult's Law, water in a typical hydrogen peroxide solution will preferentially evaporate, thereby increasing the concentration of gaseous hydrogen peroxide evaporating from the solution over time (e.g., this may be undesirable for process control and may pose health and safety risks). Thus, in various embodiments, the systems and methods of the present invention provide surface treatment with hydrogen peroxide that has a low water content (e.g., substantially anhydrous hydrogen peroxide) to avoid the detrimental effects of the presence of water, where high concentrations of water should be avoided (e.g., due to safety hazards or processes and / or materials that are sensitive to water). The use of low water content, anhydrous, or substantially anhydrous hydrogen peroxide formulations allows for safe treatment with hydrogen peroxide with minimal water content, thereby allowing for consistent and continuous dosing of hydrogen peroxide (e.g., during a controlled process). In some cases, low water content, anhydrous, or substantially anhydrous hydrogen peroxide may be provided from a non-aqueous liquid source, such as those described in U.S. Pat. No. 9,545,585, which is incorporated herein by reference in its entirety.

[0030] In various embodiments, a monolayer of hydroxyl groups (or a layer of hydroxyl groups thinner or thicker than a monolayer) is added to a material (e.g., a metal surface or a metal oxide thin film) to protect against hydrogen degradation (e.g., embrittlement or blistering) caused by exposure of the surface to hydrogen (e.g., molecular hydrogen H2, atomic hydrogen H·, or hydrogen plasma H·*). As used herein, H· denotes a free hydrogen atom that is a radical (i.e., contains a reactive unpaired electron) and H·* denotes atomic hydrogen in a higher excited state (e.g., in a plasma).

[0031] If the initial material (e.g., surface oxide) is not reinfused by exposure to hydroxyl radicals, then hydrogen (e.g., atomic hydrogen) can reduce the material (e.g., surface oxide) to a substoichiometric metal oxide or metal. Removal of oxygen from the metal oxide may impair the physical and mechanical properties of the metal. Furthermore, it is well established that exposure of exposed metal surfaces to molecular or atomic hydrogen can cause embrittlement, leading to mechanical failure. In some cases, atomic hydrogen can permeate through the surface below the thin film and then recombine either at grain boundaries or elsewhere below the surface of the thin film, causing cracking, delamination, and / or blistering due to compositional changes and induced intrinsic stresses. Metal oxides are sometimes used as protective coatings on metals, but they themselves can degrade over time when exposed to molecular hydrogen or hydrogen radicals. Thus, regenerable surface functionalization with hydrogen peroxide, according to embodiments of the present disclosure, is a sustainable method for protecting materials that undergo long-term exposure and / or exposure under extreme conditions such as hydrogen gas, hydrogen plasma, reducing atmospheres, and / or high temperatures.

[0032] In some embodiments, during the process of generating hydrogen (e.g., hydrogen radicals), the surface of the material may be periodically regenerated by exposure to hydrogen peroxide gas to replenish surface hydroxyl groups that react with (and are depleted by) incoming hydrogen (e.g., hydrogen atoms or atomic hydrogen). Thus, the hydroxyl groups act as a sacrificial atomic layer coating that reacts with hydrogen species to produce water and / or oxygen. This is advantageous over traditional protective methods (e.g., using oxide coatings) because the protective hydroxyl layers described herein can be replenished in situ (e.g., without removing material from the processing chamber), whereas traditional protective methods cannot be easily regenerated. For example, an oxide coating would be grown or deposited on a substrate (e.g., using an oxidation oven, or a sputter coating process) to protect the substrate from hydrogen embrittlement in the process chamber. To replenish the oxide coating in such a situation, the substrate would have to be removed from the process chamber, the old film would have to be removed without damaging the substrate, and a new oxide coating would have to be grown or deposited (e.g., using an oxidation oven or a sputter coating process). In contrast, the hydroxyl layer could be used to protect materials in a process chamber by dosing the material with hydrogen peroxide while it is in the chamber (e.g., prior to exposure to hydrogen). To replenish the oxide coating in this situation, the substrate would be dosed with additional hydrogen peroxide (e.g., between or during periods of hydrogen exposure). This can be done without removing the material from the process chamber. Thus, the systems and methods of the present invention allow for protecting materials from hydrogen degradation (e.g., hydrogen embrittlement) for longer durations of hydrogen exposure and / or at lower cost and / or more efficiently (e.g., with less processing downtime) than conventional protection methods.

[0033] In some cases, reducing species (e.g., hydrogen, hydrazine, ammonia, carbon monoxide, or hydrogen sulfide) can cause degradation of material properties. For example, reducing species can reduce surface oxides to substoichiometric metal oxides or metals, degrading the properties of the metal oxides or metals. In some cases, a hydroxyl layer formed from hydrogen peroxide can inhibit material degradation caused by reducing species. Without being bound by theory, in some cases, the hydroxyl layer can react with reducing species to form by-products that are not harmful (or less harmful than) the material.

[0034] One example of a metal oxide that may undergo hydrogen degradation is hafnium oxide (HfO2). Hafnium oxide may be reduced to a substoichiometric oxide by hydrogen exposure. A layer of hydroxyl groups on the surface of hafnium oxide may reduce the amount or rate of hydrogen degradation. Another example of a metal oxide that may undergo hydrogen degradation is titanium dioxide (e.g., TiO2). Titanium dioxide is transparent and may be reduced to a substoichiometric oxide by hydrogen exposure, which may cause the substoichiometric titanium oxide to become less transparent (e.g., some forms of reduced titanium oxide are black). A layer of hydroxyl groups on the surface of titanium dioxide may reduce the amount of hydrogen degradation, thereby maintaining the optical transparency of the material.

[0035] Exposure of a material (e.g., a metal and / or metal oxide film) to hydrogen peroxide (or substantially anhydrous hydrogen peroxide) can reduce the amount or rate of hydrogen degradation (e.g., surface degradation or embrittlement) when substantially exposed to hydrogen (e.g., hydrogen radicals) over time. Accordingly, systems and methods for reducing hydrogen degradation (e.g., hydrogen embrittlement) are described herein. In some cases, a method for reducing the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement) includes forming a hydroxyl layer on a material involved in a controlled process or application by exposing the material to hydrogen peroxide (e.g., hydrogen peroxide gas) prior to, during, or at an intermittent period during the controlled process or application. The method can provide a protective hydroxyl group functionalized surface on the material that reduces the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement) of the material.

[0036] The following examples are intended to illustrate the invention rather than limit it.

[0037] Example 1 A control study was performed to demonstrate film degradation due to exposure to atomic hydrogen. In this study, a thin metal oxide film was exposed to H2 plasma at 160 mTorr pressure and 100 watts at room temperature for 12 hours without H2O2. Figures 1 and 2 show X-ray photoelectron spectroscopy (XPS) results showing the oxygen 1s peak (in Figure 1) and zirconium 3d peak (in Figure 2) before and after hydrogen plasma exposure. As shown in Figures 1 and 2, both the oxygen 1s peak and the metal oxide 3d peak shifted to lower binding energies indicating film degradation. Figure 3 is a pictorial representation showing atomic force microscope (AFM) images of the film before and after H2 plasma exposure. The AFM results showed that the metal oxide film became rougher after hydrogen exposure, with the root mean square (RMS) roughness increasing by about 3.1 Angstroms (about a four-fold increase). Figure 3 shows that there was a significant increase in the density of particles (e.g., from about 3 nm to about 5 nm in size) after H2 plasma exposure. Therefore, it was concluded that in this example, the H2 plasma damaged the metal oxide surface of the film.

[0038] Example 2 In this example, an experimental study was conducted to demonstrate a reduction in the amount of degradation of metal oxide films due to atomic hydrogen exposure using hydrogen peroxide. In this experimental study, substantially anhydrous H2O2 was administered into a vacuum chamber at a pressure of about 2 mTorr or 100 Langmuir. The administration was performed with a 50 ms pulse length, and a 10 second wait time was used after the pulse before turning the H2 plasma back on for 10 minutes at a pressure of about 2 mTorr. This cycle of administration of H2O2 followed by hydrogen exposure was repeated for 12 hours. Figures 4 and 5 show X-ray photoelectron spectroscopy (XPS) results showing the oxygen 1s peak (in Figure 4) and the zirconium 3d peak (in Figure 5) before and after hydrogen plasma exposure. As shown in Figures 4 and 5, no shift in the oxygen peak (Figure 4) was observed, and a smaller shift in the metal peak (Figure 5) was observed, compared to the shift in the metal 3d peak observed in Example 1 (e.g., shown in Figure 2). These results indicate that the metal oxide layer did not degrade significantly during exposure to H2O2. FIG. 6 is a pictorial representation showing AFM images of the film before and after H2 plasma exposure. FIG. 6 shows that after 12 hours of H2 plasma with H2O2 dosing cycles, the metal oxide film became rougher, but the amount of roughening was reduced compared to the amount of roughening of the film in Example 1. The RMS roughness of the film in Example 2 increased from 1.1 Å to 3.0 Å. Thus, although some roughening of the film was observed, the increase in RMS roughness after H2 plasma was smaller when hydrogen peroxide was dosed (i.e., the increase in RMS roughness was 3.1 Å when H2O2 was not dosed compared to an increase of 1.9 Å when H2O2 was dosed).

[0039] Furthermore, the particles are an indication of degradation (e.g., embrittlement) of the film as it spalls off from below the surface. Figure 7 is a pictorial representation of AFM images of the film after H2 plasma exposure in Example 1 compared to the film after H2 plasma exposure in Example 2. Figure 7 shows that the number of small (e.g., about 3 nm to about 5 nm in size) particles (white spots in Figure 7) was reduced by about 10 times as a dose of H2O2 was injected into the chamber.

[0040] Experimental Example 3 A second control study was performed to demonstrate film degradation due to exposure to atomic hydrogen. In this study, a thin metal oxide film was formed on a Si substrate and then exposed to H2 plasma at 160 mTorr pressure and 100 watts at room temperature for 12 hours without being treated with H2O2. The XPS data showed no Si peaks before hydrogen exposure, but Si substrate peaks were observed after 12 hours of hydrogen exposure. Since XPS is very sensitive to surfaces, this indicates that the film was degraded (e.g., thinned or holes formed) during exposure. In this control, no changes in the Zr 3d peak or O 1s peak due to hydrogen exposure were observed.

[0041] FIG. 8 is a pictorial diagram showing AFM images of the film before and after H2 plasma exposure. The AFM results showed that the metal oxide film became rougher after hydrogen exposure, with the root mean square (RMS) roughness increasing from 1.3 Å to 22.2 Å (about a 16-fold increase). FIG. 8 shows that many small particles (e.g., 3 nm to 5 nm in height) and some large particles (e.g., about 20 nm in height) were formed after H2 plasma exposure. Therefore, it was concluded that the H2 plasma damaged the metal oxide surface of the film in this example.

[0042] Example 4 In this example, a second experimental study was conducted to demonstrate a reduction in the amount of degradation of metal oxide films due to atomic hydrogen exposure using hydrogen peroxide. In this second experimental study, substantially anhydrous H2O2 was continuously dosed into a vacuum chamber at a pressure of about 8 mTorr to about 10 mTorr while the metal oxide film was exposed to a H2 plasma at room temperature for 12 hours at a pressure of 160 mTorr and 100 watts. In this case, the XPS data showed no Si peaks after hydrogen exposure and there was no significant thinning or holes in the film. The XPS data also showed that there was no change in the Zr 3d peak after hydrogen exposure. The XPS data also showed that there was no change in the major O 1s peak, but a shoulder on the O 1s peak was observed after hydrogen exposure.

[0043] FIG. 9 is a pictorial representation showing AFM images of the film of this example before and after H2 plasma exposure. The AFM results showed that only the metal oxide film became slightly rougher after hydrogen exposure, with the root mean square (RMS) roughness increasing from 1.2 Å to 2.2 Å (about a two-fold increase). FIG. 9 shows that some small particles (e.g., about 3 nm to 5 nm in height) were formed after H2 plasma exposure, but no large particles (e.g., about 20 nm in height) were observed. Thus, the continuously dosed hydrogen peroxide effectively reduced the amount of degradation of the metal oxide film during hydrogen exposure.

[0044] FIG. 10 is a pictorial diagram showing AFM images of the film before hydrogen exposure, the film after H2 plasma exposure in Example 4 ("Post H2 plasma with H2O2"), and the film after H2 plasma exposure in Example 3 ("Post H2 plasma without H2O2"). FIG. 10 shows that there was significantly less change in RMS roughness when hydrogen peroxide was used to reduce the amount of hydrogen degradation of the metal oxide film. FIG. 10 also shows that the use of hydrogen peroxide reduced the amount of small particles (e.g., about 3 nm to 5 nm in height) and large particles (e.g., about 20 nm in height) formed during hydrogen exposure.

[0045] Exemplary Methods FIG. 11 is a flow chart of a method 1100 for reducing hydrogen degradation of a material. In step 1110, a hydroxyl layer is formed on a material in a chamber (e.g., a vacuum chamber). As described herein, the hydroxyl layer can be formed using, for example, gaseous hydrogen peroxide or substantially anhydrous hydrogen peroxide. In some cases, hydrogen peroxide is used to form a hydroxyl layer on a material in a controlled process, and the reaction by-products (e.g., water from hydrogen peroxide reacting with hydrogen) are not harmful (or do not significantly affect) the controlled process. In step 1120, the material is exposed to hydrogen (e.g., hydrogen gas, hydrogen plasma, atomic hydrogen, hydrogen ions, and / or hydrogen radicals). The hydroxyl layer formed in step 1110 reduces the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement, spalling, blistering, and / or particle formation).

[0046] FIG. 12 is a flow chart of a method 1200 for reducing the amount or rate of hydrogen degradation of a material. In step 1210, the material is exposed to hydrogen peroxide gas. In some cases, as described herein, the gaseous hydrogen peroxide may have less than 10% water by weight or may be substantially anhydrous. In some cases, the gaseous hydrogen peroxide may also be provided as part of a mixed gas stream including hydrogen peroxide gas and water vapor (e.g., hydrogen peroxide concentration of 100 ppm to 99% by weight). In step 1220, a hydroxyl layer is formed on the material in a chamber (e.g., a vacuum chamber) (similar to step 1110 of method 1100). In step 1230, the material is exposed to hydrogen (e.g., hydrogen gas, hydrogen plasma, atomic hydrogen, hydrogen ions, and / or hydrogen radicals). The hydroxyl layer formed in step 1220 reduces the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement, delamination, blistering, and / or particle formation) of the material caused by exposure to hydrogen in step 1230.

[0047] In various embodiments, forming the hydroxyl layer (e.g., step 1110 of method 1100 or step 1220 of method 1200) includes exposing the material to gaseous hydrogen peroxide, such as substantially anhydrous hydrogen peroxide gas, or a mixture of gaseous hydrogen peroxide and water. In some embodiments, the mixed gas stream includes 10 ppm to 5% hydrogen peroxide gas by weight, or 100 ppm to 99% hydrogen peroxide gas by weight. In some embodiments, the mixed gas stream may include 100 ppm to 75% hydrogen peroxide by weight, or 20% to 40% hydrogen peroxide by weight mixed with 80% to 60% water by weight (e.g., 70% water and 30% hydrogen peroxide gas by weight). In various embodiments, forming the hydroxyl layer is performed at a temperature between about 0° C. and about 500° C. In some embodiments, the hydrogen peroxide gas is provided at a pressure (or partial pressure) between about 1 mTorr and about 1000 Torr. In some embodiments, hydrogen peroxide gas, or a mixture of gaseous hydrogen peroxide and water, can be drawn directly into the chamber by a pressure differential or vacuum, hi some embodiments, hydrogen peroxide gas, or a mixture of gaseous hydrogen peroxide and water, can be carried to the chamber in a carrier gas, including clean, dry air, nitrogen, argon, hydrogen, oxygen, or other inert gases.

[0048] In various embodiments, the step of exposing the material to hydrogen peroxide (e.g., step 1110 of method 1100, or steps 1210 and 1220 of method 1200) is repeated to replenish the hydroxyl layer formed on the material. In various embodiments, the step of replenishing the hydroxyl layer is performed at a temperature between about 0° C. and about 500° C. The forming and exposing steps may be repeated multiple times (or may be performed sequentially) during a controlled process or application.

[0049] In various embodiments, gaseous hydrogen peroxide is provided (e.g., in step 1210 of method 1200) into a sealed chamber (e.g., a vacuum chamber) at a pressure (or partial pressure) of about 2 mTorr to about 76 Torr. In some embodiments, gaseous hydrogen peroxide is provided at a pressure of about 1 mTorr to about 100 Torr. In some embodiments, hydrogen peroxide is administered in a pulse length of about 2 milliseconds to about 1 minute, or about 50 milliseconds. In some embodiments, hydrogen peroxide is administered in a pulse length of about 50 milliseconds to about 1 second. In some embodiments, hydrogen peroxide is administered in a pulse length of about 2 seconds to about 1 hour. In various embodiments, hydrogen peroxide is administered in a pulse length of about 1 hour to about 12 hours. In various embodiments, hydrogen peroxide is administered continuously into the chamber (e.g., during the exposure to hydrogen in step 1120 of method 1100 or step 1230 of method 1200).

[0050] In various embodiments, the material (e.g., in method 1100 or 1200) is selected from the group consisting of metals such as stainless steel, stainless steel alloys, titanium alloys, aluminum alloys, silicon, or metals covered with metal oxides such as stainless steel alloys covered with metal oxides. Metal oxides forming coatings on the materials described herein may include oxides of Si, Al, Ti, In, Zr, Hf, Ta, Ga, Cd, Yt, Nb, lanthanides, and combinations thereof. In various embodiments, the material (in method 1100 or 1200) is a bulk material, a material with a bulk and a coating on the bulk, or a material with a coating of multiple layers forming a multilayer structure (either on a bulk material or free-standing). In some embodiments, the chamber (in step 1110 of method 1200 or in step 1220 of method 1200) is selected from the group consisting of a vacuum chamber, an atomic layer deposition reactor chamber, an etching or selective etching reactor chamber, a surface cleaning reactor chamber, and a photolithography process chamber.

[0051] In various embodiments, the material is exposed to hydrogen during a controlled process or application (e.g., step 1120 of method 1100 or step 1230 of method 1200). Examples of controlled processes and applications in which the material may be exposed to hydrogen include, but are not limited to, microelectronic applications, photolithography, wafer patterning, atomic layer deposition, chemical vapor deposition, etching and selective etching, wafer cleaning, wafer bonding, photoresist stripping, silicon oxidation, surface passivation, photolithography mask cleaning, exposure to UV light, sterilization of surfaces contaminated with bacteria, viruses, and other biological agents, industrial parts cleaning, pharmaceutical manufacturing, hydrogenation reactions, nanomaterials manufacturing, power generation and control devices, fuel cells, power transmission devices, and any process in which a metal or metal oxide surface is exposed to hydrogen or hydrogen radicals.

[0052] In some cases, hydrogen degradation can be measured by an XPS oxygen and / or metal peak shift of the material caused by exposure to hydrogen (e.g., in step 1120 of method 1100 or in step 1230 of method 1200), by a change in AFM RMS roughness of the material, and / or by an increase in particle count from the material.

[0053] For example, in some cases, a first oxygen peak in a first XPS spectrum of a material measured before step 1110 of Method 1100 or before step 1210 of Method 1200 is substantially the same as a second oxygen peak in a second XPS spectrum of the material measured after step 1120 of Method 1100 or after step 1230 of Method 1200.

[0054] In another example, in some cases, a first shift of a first pair of metal peaks of a first pair of XPS spectra of a material measured before step 1110 and after step 1120 of method 1100 is less than a second shift of a second pair of metal peaks of a second pair of XPS spectra of the reference material that would be measured before step 1120 and after step 1120 of method 1100 if the reference material did not undergo step 1110 before undergoing step 1120 of method 1100.

[0055] In another example, in some cases, a first shift of a first pair of metal peaks of a first pair of XPS spectrum of a material measured before step 1210 and after step 1230 of method 1200 is less than a second shift of a second pair of metal peaks of a second pair of XPS spectrum of the reference material that would be measured before step 1230 and after step 1230 of method 1200 if the reference material did not undergo steps 1210 and 1220 before undergoing step 1230 of method 1200.

[0056] In another example, in some cases, a first change in the root mean square (RMS) roughness of the material measured using an AFM before step 1110 and after step 1120 of method 1100 is less than a second change in the surface roughness of the reference material that would be measured using an AFM before step 1120 and after step 1120 of method 1100 if the reference material did not undergo step 1110 before undergoing step 1120 of method 1100.

[0057] In another example, in some cases, a first change in the root mean square (RMS) roughness of the material measured using an AFM before step 1210 and after step 1230 of method 1200 is less than a second change in the surface roughness of the reference material that would be measured using an AFM before step 1230 and after step 1230 of method 1200 if the reference material did not undergo steps 1210 and 1220 before undergoing step 1230 of method 1200.

[0058] Exemplary System FIG. 13 shows a simplified schematic diagram of one example of a system 1300 for reducing the amount or rate of hydrogen degradation (e.g., hydrogen embrittlement, spalling, blistering, and / or particle formation) of a material. The system 1300 includes a chamber 1310 having a material 1320 inside the chamber, an inlet 1330 to the chamber for dosing hydrogen peroxide, and an outlet 1340 to the chamber for removing species from the chamber. Some examples of the chamber 1310 are a vacuum chamber, an atomic layer deposition reactor chamber, an etch or selective etch reactor chamber, a surface cleaning reactor chamber, and a photolithography process chamber. The material 1320 may be an article being processed by the system 1300 or may be a component of the system 1300 in different embodiments. Hydrogen peroxide (e.g., gaseous hydrogen peroxide, substantially anhydrous hydrogen peroxide, or a mixed gas stream including hydrogen peroxide) may be introduced into the chamber through the inlet 1330. In some cases, by-products (e.g., water) may be removed from the chamber 1310 using the outlet 1340. Material 1320 can be exposed to hydrogen (not shown) inside chamber 1310. System 1300 can be used to perform the methods described herein (e.g., method 1100 and method 1200). System 1300 can be used for any of the controlled processes or applications described herein.

[0059] In some cases, hydrogen peroxide source 1350 is coupled to inlet 1330 via conduit 1360 to provide hydrogen peroxide to chamber 1310. In some cases, hydrogen peroxide gas can be delivered from an ampoule in source 1350. In some cases, conduit 1360 includes appropriate valving and gas controls (not shown). The ampoule may contain hydrogen peroxide in solution or on a sorbent. In other cases, hydrogen peroxide source 1350 may be a hydrogen peroxide delivery system that includes a vapor generation system that replenishes its source of hydrogen peroxide to allow for intermittent or continuous operation. Systems including a source for providing hydrogen peroxide are further described in U.S. Pat. Nos. 8,282,708, 9,545,585, and 10,363,497, U.S. Patent Publication Nos. US20200291517A1 and US20200393086A1, and International Publication Nos. WO2016 / 164380 and WO2017 / 027581, each of which is incorporated by reference in its entirety herein.

[0060] Reference has been made in detail to the disclosed embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided as an explanation of the technology, not as a limitation of the technology. Indeed, while the specification has been described in detail with respect to certain embodiments of the invention, it will be understood that those skilled in the art, upon gaining an understanding of the foregoing, may readily conceive modifications, variations, and equivalents to these embodiments. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield yet a further embodiment. It is therefore intended that the subject matter of the invention encompass all such modifications and variations within the scope of the appended claims and their equivalents. These and other modifications and variations to the invention may be implemented by those skilled in the art without departing from the scope of the invention, which is more particularly set forth in the appended claims. Moreover, those skilled in the art will appreciate that the foregoing description is for illustrative purposes only, and is not intended to limit the invention.

[0061] Although the invention has been described with reference to the above examples, it will be understood that modifications and variations are encompassed within the spirit and scope of the invention. Accordingly, the invention is limited only by the scope of the following claims.

Claims

1. 1. A method for reducing the amount or rate of hydrogen degradation of a material, comprising: (a) exposing the material to gaseous hydrogen peroxide; (b) forming a hydroxyl layer on a surface of the material in a chamber; (c) exposing the material to hydrogen during a controlled process after forming the hydroxyl layer; The method comprising:

2. The method of claim 1 , wherein the exposing the material to hydrogen comprises exposing the material to hydrogen molecules, hydrogen radicals, hydrogen ions, or a hydrogen plasma.

3. 2. The method of claim 1 , wherein a first amount of hydrogen degradation of the material caused by step (c) is less than a second amount of hydrogen degradation of the material that would be caused by step (c) if the material had not undergone step (a) or step (b) prior to undergoing step (c).

4. 10. The method of claim 1, wherein the gaseous hydrogen peroxide contains less than 95% water by weight.

5. 10. The method of claim 1, wherein the gaseous hydrogen peroxide is provided in a mixed gas stream comprising the gaseous hydrogen peroxide and water vapor.

6. The method of claim 5, wherein the mixed gas stream comprises from 100 ppm to 75% of the gaseous hydrogen peroxide.

7. 10. The method of claim 1, wherein the gaseous hydrogen peroxide is provided in a mixed gas stream comprising the gaseous hydrogen peroxide and a carrier gas.

8. The method of claim 7 , wherein the carrier gas comprises hydrogen, nitrogen, argon, air, or a combination thereof.

9. 10. The method of claim 1, further comprising replenishing the hydroxyl layer formed on the material by repeating steps (a) and (b).

10. 10. The method of claim 9, wherein during said exposing said material to gaseous hydrogen peroxide, said gaseous hydrogen peroxide is administered in a pulse length of between 2 milliseconds and 12 hours.

11. 2. The method of claim 1, wherein the material is selected from the group consisting of a metal, a metal oxide, stainless steel, a stainless steel alloy, a titanium alloy, an aluminum alloy, silicon, a material having multiple layers including a metal oxide layer, a metal coated with a metal oxide, a distributed Bragg reflector, and an anti-reflective coating.

12. 10. The method of claim 1, wherein the chamber is selected from the group consisting of an atomic layer deposition reactor chamber, a chemical vapor deposition reaction chamber, an etch reactor chamber, a selective etch reactor chamber, a surface cleaning reactor chamber, and a photolithography process chamber.

13. 2. The method of claim 1 , wherein a first oxygen peak in a first X-ray photoelectron spectroscopy (XPS) spectrum of the material measured before step (a) is the same as a second oxygen peak in a second XPS spectrum of the material measured after step (c).

14. 2. The method of claim 1 , wherein a first shift of a first pair of metal peaks of a first pair of X-ray photoelectron spectroscopy (XPS) spectrum of the material measured before step (a) and after step (c) is less than a second shift of a second pair of metal peaks of a second pair of XPS spectrum of the reference material measured before step (c) and after step (c) when the reference material did not undergo steps (a) or (b) before undergoing step (c).

15. 2. The method of claim 1, wherein a first change in root mean square (RMS) roughness of the material measured using an atomic force microscope (AFM) before step (a) and after step (c) is less than a second change in surface roughness of the reference material measured using an AFM before step (c) and after step (c) when the reference material did not undergo step (a) or step (b) before undergoing step (c).

Images