Metal body formed with a magnesium fluoride region

Abstract

A metal body made of a magnesium-containing metal and having a magnesium fluoride surface passivation region formed at a surface of the body is described, as well as a method of forming a magnesium fluoride surface passivation region at a surface of a metal body, and the use of said body.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of and priority to U.S. Provisional Application No. 62 / 954,798, filed December 30, 2019, which is incorporated by reference in its entirety for all purposes. TECHNICAL FIELD

[0003] The present disclosure relates to metal bodies made of magnesium-containing metals, having formed at the surface thereof a magnesium fluoride surface passivation region; uses of those metal bodies; and methods of forming a magnesium fluoride surface passivation region at the surface of a metal body. BACKGROUND

[0004] Semiconductor and microelectronic device processing methods require various processing steps involving highly reactive processing materials, such as plasmas. Example processes using reactive processing materials include plasma etching steps, plasma deposition steps, and plasma cleaning steps. These processes are performed inside a processing chamber that contains a workpiece and the reactive processing material. The processing chamber also includes various structures and components (also referred to as “processing chamber components”) that define the processing chamber and items needed for the processing chamber to operate. These can include chamber walls, flow conduits (e.g., flow lines, flow heads, tubing, pipes, etc.), fasteners, trays, supports, and other structures to support a workpiece or to deliver or contain the reactive processing material with respect to the processing chamber.

[0005] When used as part of a processing chamber, the processing chamber components should be resistant to the reactive processing materials that will be used within the processing chamber. The processing chamber components should not degrade or be damaged by contact with the processing materials, especially in a manner that will produce debris or particulates that can be incorporated into the process being performed and can contaminate the workpiece being processed.

[0006] Processing chamber components in semiconductor processing equipment used to manufacture semiconductor and microelectronic devices are often made from solid materials (“substrates” or “bases”), such as metals (e.g., stainless steel, aluminum alloys that can optionally be anodized, tungsten), mineral or ceramic materials, etc. The substrates are often coated with a protective layer that is more resistant to the reactive processing materials than the substrate material. In the past, such protective thin film coatings or layers have often been placed on the substrates by various applicable methods, often by processes of anodization (e.g., to produce anodized aluminum), spray coating, or physical vapor deposition (PVD). SUMMARY

[0007] The following disclosure relates to metal bodies made from magnesium-containing metals having a magnesium fluoride surface passivation region formed at a surface of the metal body. The disclosure also relates to methods of forming a magnesium fluoride surface passivation region at a surface of a metal body; articles and structures including a metal body having a magnesium fluoride surface passivation region at a surface, and methods of using the articles and structures.

[0008] The method involves forming a magnesium fluoride region within a metal body through a chemical reaction between a fluorine source and magnesium present in a magnesium-containing metal of the metal body. The metal body can be made from any metal containing at least a small amount of magnesium. Examples include aluminum alloys, magnesium alloys, stainless steel, stainless magnesium, and alloys of other metals such as vanadium, chromium, zinc, titanium, and nickel.

[0009] The method differs from previous methods of depositing a separately produced layer or coating of protective material onto a surface of a metal body. In particular, the method is not performed by placing a coating or layer containing an exogenous protective material onto the surface, such as by a deposition method, such as by a chemical vapor deposition method, a physical vapor deposition method, an atomic layer deposition method, or any similar method or modification of any of these methods. Rather, the method forms a magnesium fluoride layer from magnesium originally present within the metal substrate (i.e., endogenous magnesium) and fluorine provided separately (i.e., exogenous fluorine).

[0010] Additionally, the method does not involve the use or formation of a plasma as part of the method of forming magnesium fluoride at a surface of a metal body. The methods as described herein involve forming magnesium fluoride by exposing a surface of a metal body to a molecular fluorine vapor source at an elevated temperature. These non-plasma methods are capable of producing highly conformal magnesium fluoride surface passivation regions having uniform thickness over all exposed surfaces of a metal body, including features (e.g., pores, channels, internal gas cells, metal films) having high aspect ratios. Example metal bodies can include high aspect ratio features having an aspect ratio of at least 20: 1, 50: 1, 100: 1, 200: 1, or even 500: 1.

[0011] The magnesium fluoride surface passivation region provides chemical inertness and resistance to chemical degradation. Metal bodies having a magnesium fluoride surface passivation region at a surface can be suitable for any application for which a chemically inert surface is suitable or desired. Examples include protective surfaces for pieces of manufacturing equipment, such as coatings for components of semiconductor processing tools. Semiconductor processing tool components are often made from aluminum (e.g., aluminum 6061). For such uses, the surface of the aluminum requires a protective surface treatment, which can typically be performed by anodization, application of a protective spray coating, or deposition of a protective coating by physical vapor deposition, atomic layer deposition, chemical vapor deposition, etc. Examples include oxides such as aluminum oxide, yttrium oxide, zirconium oxide, etc. Exemplary coatings include fluorides such as AlF3or YF3, which can be more stable and can provide relatively strong resistance to etching and corrosion. But fluorides are more difficult to form.

[0012] Described herein are methods effective to form a magnesium fluoride surface passivation region at a metal surface, as well as metal bodies including a magnesium fluoride surface passivation region, and articles, devices, and methods involving the metal bodies. The magnesium fluoride surface passivation region can be present in the form of a continuous or discontinuous layer within the metal body at a surface of the metal body.

[0013] In one aspect, the present disclosure relates to an aluminum alloy body having a surface and a magnesium fluoride surface passivation region at the surface. The aluminum alloy includes at least 93 wt.% aluminum; magnesium; and at least 0.5 wt.% of a non-magnesium impurity.

[0014] In another aspect, the present disclosure relates to a metal body including a magnesium-containing metal alloy region and a magnesium fluoride surface passivation region at a surface. The magnesium-containing metal alloy contains less than 95 wt.% aluminum.

[0015] In yet another aspect, the present disclosure relates to a method of forming a magnesium fluoride surface passivation region at a surface of a magnesium-containing metal substrate. The method includes exposing the surface to molecular fluorine source vapor at an elevated temperature to form a continuous or discontinuous region of magnesium fluoride at the surface of the magnesium-containing metal substrate. BRIEF DESCRIPTION OF DRAWINGS

[0016] The present disclosure can be more completely understood in consideration of the following description in connection with the accompanying drawings.

[0017] Figure 1 is a schematic illustration of a magnesium fluoride surface passivation region formed at a surface of a metal body according to various embodiments of the present disclosure.

[0018] Figure 2A is a FIB-SEM image of a cross-section of a metal test coupon manufactured according to embodiments of the present disclosure.

[0019] Figure 2B is a FIB-SEM image of a cross-section of a metal test coupon manufactured according to embodiments of the present disclosure. Figure 2A is a FIB-SEM top-down image of a cross-section of a metal test coupon manufactured according to embodiments of the present disclosure.

[0020] Figure 3 is an X-ray photoelectron spectroscopy (XPS) depth profile of the composition of a metal test coupon manufactured according to embodiments of the present disclosure.

[0021] Figure 4 is an X-ray diffraction (XRD) spectrum of a metal test coupon manufactured according to embodiments of the present disclosure.

[0022] Figure 5is a plot showing the thickness of a magnesium fluoride surface passivation region formed at a surface of a metal test coupon as a function of etching time.

[0023] While the disclosure is susceptible to various modifications and alternative forms, specific details thereof have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the intention is not to limit the aspects of the disclosure to the particular illustrative embodiments described. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. DETAILED DESCRIPTION

[0024] The following description relates to a metal body made of a magnesium-containing metal and having a magnesium fluoride surface passivation region formed at a surface of the body; to methods of forming a magnesium fluoride surface passivation region at a surface of a metal body; to articles, devices, and apparatuses, such as processing chamber components of semiconductor manufacturing apparatuses, including a metal body having a magnesium fluoride surface passivation region at a surface; and to related methods of use.

[0025] Figure 1 is a schematic illustration of a metal body 2 having a magnesium fluoride surface passivation region 4 formed at a surface of the metal body 2 as described herein according to various embodiments. According to various embodiments, the magnesium fluoride surface passivation region 4 is formed at a surface of a metal body 2 made of a magnesium-containing metal, thereby passivating the surface of the metal body 2. As used herein, a magnesium-containing metal is defined as any metal or metal alloy containing an amount of magnesium. The magnesium fluoride surface passivation region 4 is formed at the surface of the metal body 2 by exposing the surface to a molecular fluorine source at an elevated temperature in a manner that causes the fluorine in the molecular fluorine source to react with the magnesium present in the metal of the metal body 2 to form the magnesium fluoride surface passivation region 4. Thus, the metal body 2 includes the magnesium fluoride surface passivation region 4 formed at the surface of the metal body 2, a bulk region 8 composed of the magnesium-containing metal, and a transition region 6 between the surface passivation region and the bulk region. The transition region 6 has a ratio of magnesium fluoride to magnesium-containing metal that gradually increases in a direction from the bulk region 8 to the magnesium fluoride surface passivation region 4.

[0026] Advantageously, the magnesium fluoride surface passivation region as described can be formed at (including beneath) the surface of the metal body from magnesium originally present in the metal of the metal body, as compared to other conventional methods of adding a chemically resistant coating material to the surface of a solid body. During the reaction, magnesium contained within the magnesium-containing metal body can travel along the metal grain boundaries to the surface to form the magnesium fluoride passivation region at the surface of the metal body. The magnesium fluoride passivation region is not a coating or layer applied to the surface as a composition or material added to the surface by coating or another deposition technique (e.g., by chemical vapor deposition, physical vapor deposition, atomic layer deposition, etc.). Rather, the magnesium fluoride that becomes part of the magnesium fluoride surface passivation region at the surface is a reaction product of fluorine from a molecular fluorine source exposed to the surface of the metal body reacting with magnesium that was originally present in the magnesium-containing metal. The magnesium fluoride surface passivation region can be a continuous region covering the entire surface of the metal body from which it is formed, or the magnesium fluoride surface passivation region can be a discontinuous region covering only a portion of the metal body from which it is formed. The magnesium fluoride surface passivation region formed at the surface of the metal body passivates the surface of the metal body.

[0027] Additionally, the magnesium fluoride surface passivation region according to the present disclosure is distinct from reaction products that are chemically formed at the surface of a process chamber assembly during use of the process chamber assembly, or in a "seasoning" step prior to use, including such layers that can include magnesium fluoride. Certain uses of semiconductor processing equipment involve exposing process chamber assemblies that are operably mounted within the processing tool and perform functions of the tool to reactive process materials, such as fluorine in the form of a plasma, during use of the processing tool. Fluorine of the plasma can contact the process chamber assembly during use of the tool, possibly forming magnesium fluoride at the surface.

[0028] The methods of the present disclosure to form magnesium fluoride surface passivation regions on process chamber components or other metal bodies are distinguished from prior types of "in-use" formation. As one distinction, the methods described in the present disclosure are not performed within a semiconductor processing tool during use of the tool, where the process chamber component is an installed operational component of the processing tool. The methods described in the present disclosure form magnesium fluoride surface passivation regions on process chamber components that are not operatively installed in a processing tool during use, but are contained and supported in a different type of process chamber adapted to perform the steps of forming magnesium fluoride on the surface of the process chamber component. In addition, the methods of forming magnesium fluoride surface passivation regions described in the present disclosure do not use plasma as a source of fluorine, but instead use molecular fluorine as a source of fluorine, and can be performed under different times, pressures, and temperature conditions, such as in the presence of non-plasma materials (e.g., air) as well as molecular fluorine source vapor. Further, certain structural and compositional differences can also exist between process chamber components having magnesium fluoride surface passivation regions formed during use of a semiconductor processing tool and metal bodies prepared to include magnesium fluoride surface passivation regions by the methods of the present disclosure.

[0029] Magnesium-containing metals on which magnesium fluoride surface passivation regions are formed can be referred to herein as "metal bodies" or "substrates." Forming a magnesium fluoride surface passivation region at a "surface" of a metal body means that magnesium fluoride is formed at the exposed metal surface of the body as well as below the surface. It is understood that the exposed metal composition includes magnesium, and the exposed metal surface can also include metal oxide compounds formed by exposing the surface to oxygen. The type and amount of metal oxide compounds can be consistent with a naturally oxidized surface of the metal alloy. The preferential oxidation at the surface can be of a type and extent that will not interfere with the desired formation of magnesium fluoride at the surface by the processes as described. Preferably, any oxidation present at the surface is formed naturally and not by an intentional chemical oxidation process, such as by anodization or otherwise chemically or electrochemically treating the surface to intentionally form metal oxides at the surface.

[0030] A suitable method of forming a magnesium fluoride surface passivation region as described herein includes exposing a surface of a magnesium-containing metal body to a molecular fluorine source vapor at a temperature such that fluorine in the molecular fluorine source vapor reacts with magnesium originally present in the metal of the metal body to form magnesium fluoride at (including beneath) the surface. As used herein, a "molecular fluorine source vapor" is a non-plasma (i.e., molecular) chemical molecule in gaseous (gas) form that is not considered to be a plasma. A "plasma" is a non-solid gaseous composition that contains a high density of ionic fragments derived from one or more plasma precursor compounds that are intentionally exposed to energy (e.g., from a radio frequency power source) for the purpose of dissociating the plasma precursor compounds into ions for use in processing a workpiece. In contrast to a plasma, a suitable or preferred molecular fluorine source vapor can contain less than 10E-6 atomic % of ionized material, e.g., less than 10E-6 atomic % of ionic species.

[0031] The molecular fluorine source vapor can be provided to a processing chamber for forming a magnesium fluoride surface passivation region by any method or from any useful and effective source or location. In a preferred method, the molecular fluorine source vapor can be generated in situ, meaning during a process of forming a magnesium fluoride surface passivation region on a surface of a magnesium-containing metal body, and within a processing chamber for forming a magnesium fluoride surface passivation region on the surface. The molecular fluorine source vapor can be generated in situ from a non-gaseous fluorine source by heating the non-gaseous fluorine source such that molecules of the non-gaseous fluorine source become gaseous (i.e., molecular vapor). The non-gaseous fluorine source can be a liquid or solid fluorine-containing substance, and the heating step generates the molecules in gaseous form without causing significant degradation or ionization of the molecules of the liquid or solid fluorine source. In some embodiments, the molecules in gaseous form can be at least 99.9999 atomic % of the molecules, i.e., non-chemically altered molecules of the liquid or solid fluorine-containing substance; can contain less than 10E-6 atomic % of ionized or degraded material, e.g., less than 10E-6 atomic % of ionic species.

[0032] The heating step of generating the molecular fluorine source vapor is distinct from a plasma generation step used in various semiconductor processing steps. Generally, a plasma generation step involves applying one or more forms of energy to a plasma source that is typically a gaseous chemical substance to ionize and chemically degrade molecules of the plasma source to generate ionic fragments of the molecules. The energy can be thermal energy (high temperature), electromagnetic radiation such as RF (radiation generated by a radio frequency power source), or a combination of these.

[0033] As a specific comparison, the heating step of the present disclosure to generate molecular fluorine source vapor is different from a step to generate a fluorine-containing plasma for a semiconductor processing tool to plasma etch, plasma clean, "season" a process chamber of a semiconductor processing tool. An example of a plasma generation step that is different from the heating step described in the present disclosure is described in U.S. Patent No. 5,756,222, which describes a fluorine-containing plasma generated in a reaction chamber designed for a plasma etching or plasma cleaning process. The plasma is prepared by exposing a fluorine precursor to RF power.

[0034] The present method for forming a magnesium fluoride surface passivation region at a surface of a magnesium-containing metal body can be performed in a process chamber at an elevated temperature as follows: positioning the metal body in a process chamber in a removable, temporary non-operational manner; dispensing a molecular fluorine source vapor into the process chamber, or generating a molecular fluorine source vapor in the process chamber by heating a non-gaseous fluorine source such that molecules of the non-gaseous fluorine source become gaseous, i.e., vapor, in the process chamber; and elevating the temperature of the process chamber, the metal body, the molecular fluorine source vapor, or a combination thereof, such that fluorine in the molecular fluorine source vapor reacts with magnesium present at the surface of the metal body to form a magnesium fluoride surface passivation region at the surface of the metal body.

[0035] During the step of forming a magnesium fluoride surface passivation region, the process chamber can contain process materials including the molecular fluorine source vapor, the optionally present non-gaseous fluorine source, and one or more magnesium-containing metal bodies, each having a surface at which a magnesium fluoride surface passivation region is to be formed. The interior space and atmosphere of the chamber need not be evacuated or under reduced pressure, and can contain an amount of atmospheric air. Elimination of air or oxygen, or introduction of an inert gas (flush gas, e.g., N2) into the process chamber for the formation step is not required. The process chamber need not contain and can exclude any other additional gaseous or liquid process materials other than air and the molecular fluorine source vapor, e.g., can exclude other gaseous materials (e.g., inert gases) or gaseous co-reactants that can sometimes be used in the gaseous atmosphere for other semiconductor processing steps.

[0036] The process chamber is not part of a semiconductor processing tool, and need not contain and preferably does not contain any other workpiece that is additionally processed, e.g., a semiconductor device or precursor thereof. The process chamber also need not and does not involve the use of components for generating a plasma, e.g., a radio frequency power source or components for applying an electrical potential (voltage) to a component or workpiece.

[0037] Suitable processing chambers may preferably include: temperature controllers for controlling the temperature within the chamber; components for controlling the composition and purity of the environment within the chamber, such as pressure controllers, filters, etc.; components for temporarily containing and supporting one or more metal bodies to continuously form a magnesium fluoride surface passivation region on the body for a period of time within the chamber; and components for controlling the composition of the atmosphere within the processing chamber, including supplying and controlling the amount and concentration of a molecular fluorine source within the processing chamber. Suitable processing chambers do not require and can exclude components for generating plasma, such as radio frequency power supplies.

[0038] According to certain embodiments, the molecular fluorine source vapor can be a gaseous fluorinated or perfluorinated organic compound, such as a fluorinated or perfluorinated alkane or olefin, either of which can be straight-chain or branched-chain. Examples particularly include CF4, C2F4, C3F6, C4F8, CHF3, C2H2F2, C2F6, HF, and CH3F, each in molecular form, meaning substantially nonionic and untreated (by adding energy other than heat) to degrade or form plasma.

[0039] According to other embodiments, the molecular fluorine source vapor can be a gaseous fluorinated polymer that has not been processed using energy to form plasma. The gaseous fluorinated polymer can be obtained, for example, from a non-gaseous (e.g., liquid or solid) fluorinated polymer by heating a non-gaseous fluorinated polymer in the presence of a magnesium-containing metal body on which magnesium fluoride needs to be formed, for example, in a processing chamber.

[0040] The fluorinated polymer can be any fluorinated polymer that is effective according to the method described for forming a magnesium fluoride surface passivation region on the surface of a magnesium-containing metal body. Examples of suitable fluorinated polymers include homopolymers and copolymers comprising polyfluoroolefin monomers and optionally nonfluorinated comonomers. The polymer may be fluorinated (i.e., partially fluorinated), perfluorinated, or may include nonfluorinated halogen atoms, such as chlorine. The molecular fluorine source may be liquid or solid at room temperature but will become gaseous at the temperature of the processing chamber used according to the method described.

[0041] Non-limiting examples of specific fluoropolymers include: polymerized perfluoroalkyl ethylene having a C1-C2 configuration. 10 Perfluoroalkyl; polytetrafluoroethylene (PTFE); tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA); tetrafluoroethylene / hexafluoropropylene copolymer (FEP); tetrafluoroethylene / perfluoro(alkyl vinyl ether) / hexafluoropropylene copolymer; polyhexafluoropropylene; ethylene / tetrafluoroethylene copolymer (ETFE); polytrifluoroethylene; polyvinylidene fluoride (PVDF); polyvinyl fluoride (PVF); polychlorotrifluoroethylene (PCTFE); ethylene / chlorotrifluoroethylene copolymer (ECTFE); or combinations thereof.

[0042] The step of forming a magnesium fluoride surface passivation region as described can be performed at any temperature effective to cause fluorine from the fluorine source vapor to react with magnesium at the surface of the magnesium-containing metal body. Relatively high elevated temperatures are generally useful or preferred, with temperature ranges including temperatures that can be at least as high as, or higher than, example or typical temperatures used in some types of semiconductor processing steps, such as deposition steps, plasma etching steps, and plasma cleaning steps. Example temperatures can be at least 200, 250, 300, or 350 degrees Celsius, or higher, such as temperatures in the range of 350 to 500, such as 375 or 400 to 425 or 450 degrees Celsius.

[0043] The processing chamber can be operated at any useful pressure, with example pressures being about atmospheric pressure (760 Torr), such as 100 to 1500 Torr, such as 250 or 500 to 1000 or 1250 Torr. The atmosphere within the processing chamber for forming magnesium fluoride on the metal body can include a portion that is air, as well as molecular fluorine source vapor.

[0044] The amount of time for forming a magnesium fluoride surface passivation region at the surface of the metal body by the method as described can be based on factors such as temperature, type and amount (concentration) of molecular fluorine source vapor in the processing chamber, type of magnesium-containing metal, and desired thickness of the magnesium fluoride passivation region. Useful example amounts of time can range from 1 hour to 15 hours, such as 2 hours to 13 hours or 3 hours to 12 hours. A useful amount of time can be a period of time that results in a magnesium fluoride passivation region of a useful or preferred thickness. The thickness will increase over time as the metal body is continuously exposed to the molecular fluorine source vapor, but after a certain amount of time, such as after 12 hours, the thickness of the magnesium fluoride passivation region no longer continues to increase.

[0045] As used herein, the term "region" describing a magnesium fluoride formed at a surface of a metal body refers to a portion of the metal body at or below the surface of the metal body, and which optionally contains a specified minimum concentration of magnesium fluoride. The region can be a discontinuous or continuous region. The concentration of magnesium fluoride in the magnesium fluoride passivation region can be relatively high, such as at least 50%, 70%, 90%, or 90%, and generally will be higher or highest at the surface, and can gradually decrease with increasing distance from the surface. Forming a magnesium fluoride passivation region at and below the surface of the metal body can advantageously eliminate certain difficulties involved with forming or placing a protective coating on top of the surface, such as: substrate surface cleanliness, substrate surface conditioning (prior to coating), coefficients of thermal expansion (CTE) of the coating material and the substrate, adhesion of the coating to the surface, interface modification, etc., as compared to forming on top of the surface.

[0046] The magnesium fluoride passivation region can be formed to any suitable or desired thickness below the surface of the metal body. The depth (thickness) of the magnesium fluoride formed below the surface can be influenced by factors such as the time and temperature of formation, the type of molecular fluorine source, and the chemical composition of the metal body (e.g., its magnesium content). Suitable or preferred thicknesses of the magnesium fluoride passivation region can range from 1 to 200 nanometers, such as 5 to 150 nanometers or 25 to 130 nanometers, as measured by the presence of a magnesium fluoride concentration of at least 10%, 20%, 40%, 50% at a specified depth below the surface, for example.

[0047] The thickness of the magnesium fluoride passivation region based on the magnesium fluoride concentration measured at a specified depth (thickness) can be measured by known techniques; thickness can be measured or estimated by using SEM (scanning electron microscope) cross-sections; XPS (x-ray photoelectron spectroscopy) depth profiling; and EDAX (energy dispersive x-ray microanalysis) techniques.

[0048] During formation of the magnesium fluoride passivation region, magnesium within the bulk metal region of the metal body travels along the metal grain boundaries toward the surface of the metal body. This results in a metal body having three regions including a magnesium fluoride surface passivation region, a bulk region composed of a magnesium-containing metal or metal alloy (e.g., an aluminum alloy), and a transition region between the magnesium fluoride surface passivation region and the bulk region. According to various embodiments, the transition region has a gradually increasing ratio of magnesium fluoride to magnesium-containing metal in a direction from the bulk region to the magnesium fluoride surface passivation region. In some cases, the measurement of the thickness of the magnesium surface passivation region can begin at a point within the transition region where the ratio of magnesium fluoride to magnesium-containing metal in the metal body is approximately 50:50.

[0049] The magnesium fluoride passivation region effectively serves as a chemical resistant layer of a process chamber component or other article or device that can desirably include a chemically resistant surface. Suitable magnesium fluoride passivation regions exhibit a beneficial degree of resistance to process materials used in a process chamber of a semiconductor processing tool, including (but not limited to) acids and plasmas, especially over extended periods of exposure. Among other uses, the magnesium fluoride passivation region can protect a surface from oxidation of a metal alloy in a use atmosphere, which can include a biological environment (e.g., a surface for a medical implant) or an ambient air atmosphere.

[0050] In the context of semiconductor processing tools, a "resistant" coating is one that, during use, particularly during long-term use over a period of weeks or months, experiences a commercially useful small amount of degradation or chemical change after exposure to process materials such as acids, bases, gas plasma, or other reactive chemical materials in the processing chambers of the semiconductor processing tool, including preferably an amount that is consistent with or reduced relative to other protective coatings used previously (e.g., relative to a previous coating used in the processing chamber of the semiconductor processing tool), example coatings include yttrium oxide or aluminum oxide coatings applied by physical vapor deposition (PVD) or atomic layer deposition (ALD) and aluminum oxide layers formed by anodization. The preferred magnesium fluoride surface passivation regions of the present disclosure can have a beneficially long useful lifetime as a protective coating in the processing chambers of semiconductor processing tools, most preferably significantly greater than the useful lifetime of the mentioned previous protective coatings. Degradation or lack of degradation of the magnesium fluoride surface passivation regions as described herein can be measured using any of a variety of techniques commonly used in protective coating technology, including visual means such as optical or scanning electron microscopy in which cracked regions, cracks, or other defects are examined.

[0051] The magnesium fluoride surface passivation regions as described herein can be used with other product structures and types other than processing components of semiconductor processing tools, such as medical devices or implants, airplane or other vehicle parts or other structural or functional devices, items, or structures that have a surface that is preferably inert in the relevant use environment, e.g., that does not degrade or oxidize or otherwise react with or in the environment over time.

[0052] The applicable magnesium fluoride surface passivation regions described herein can also be temperature resistant during use over an extended period of time, including at high temperatures (e.g., in the range of 350 to 500 degrees Celsius) in semiconductor processing tools. More generally, the applicable or preferred magnesium fluoride surface passivation regions can have a resistance to thermal degradation over an extended period of time at temperatures up to or exceeding 200, 300, 400, 450, or 500 degrees Celsius. Relative to other types of protective coatings deposited on the surface of a metal body, the magnesium fluoride surface passivation regions of the present disclosure exhibit an improved resistance to high temperatures by exhibiting reduced cracking, blistering, or delamination, etc. due to CTE-induced thermal stress and / or other mechanisms when exposed to high temperatures (e.g., 200, 300, 400, 450, or 500 degrees Celsius) for an extended period of time.

[0053] Magnesium-containing metals internally formed with magnesium fluoride surface passivation regions as described herein can contain any amount of magnesium that will allow magnesium fluoride (MgF2) to form on the surface of the metal body when treated by methods as described. Suitable magnesium concentrations in the magnesium-containing metal can be as low as 0.01 wt% or possibly lower, with a maximum concentration of substantially 100% magnesium. Example ranges can be 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, or 5 wt% to or exceeding 80 wt%, 90 wt%, 95 wt%, or 99 wt% magnesium, based on the total weight of the metal body.

[0054] Examples of suitable magnesium-containing metal alloys include general and specific types known and suitable for use in commercial and industrial devices and structures. These include pure magnesium, magnesium alloys containing relatively high amounts of magnesium (e.g., greater than 50 wt%), and various other metal alloys containing lower amounts of magnesium (e.g., less than 50%, 40%, 30%, 20%, or 10% magnesium as elemental magnesium). A short list of examples includes stainless steels, aluminum alloys, vanadium alloys, magnesium alloys (e.g., "stainless magnesium"), other types of iron alloys, nickel alloys, chromium alloys, zinc alloys, and the like.

[0055] Iron alloys (e.g., steel or stainless steel) that also contain at least a small amount of magnesium can be used as the metal body. Steel alloys, such as stainless steel, can contain a mixture of chromium (16.5 wt% to 18.5 wt%), nickel (10.5 wt% to 13.5 wt%), molybdenum (2.0 wt% to 2.5 wt%), magnesium (e.g., at least 0.01 wt%, 0.1 wt%, or 1 wt%), carbon, and the remainder iron, each in elemental form.

[0056] Suitable alloys of nickel, vanadium, chromium, aluminum, magnesium, zinc, titanium, or other metals can include at least 40 wt%, 50 wt%, 60 wt%, 70 wt%, or 80 wt% of a single such base metal, with known blends of additional metals and with magnesium in an amount of at least 0.01 wt%, 0.1 wt%, or 1 wt%, each in elemental form.

[0057] Suitable magnesium alloys can contain up to or exceeding 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or 99 wt% magnesium. Particular types of suitable magnesium alloys are sometimes referred to as "stainless magnesium" and contain a dominant amount (e.g., at least 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or 99 wt%) of a combination of magnesium with lithium, or a combination of magnesium with aluminum. The magnesium is preferably not in the form of magnesium oxide. Preferred alloys can contain no more than an insignificant amount of magnesium oxide (MgO), such as less than 1 wt%, 0.5 wt%, 0.1 wt%, or 0.05 wt% magnesium oxide.

[0058] Alloys suitable for use in metal bodies also include aluminum alloys, which can include alloys containing up to or more than 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 93 wt%, or 95 wt% aluminum, an amount of magnesium, and non-magnesium elements (e.g., one or a mixture of silicon, iron, copper, chromium, zinc, titanium, manganese, or other metals).

[0059] An example of an aluminum alloy, one that is used with a process chamber component of a semiconductor processing tool, is aluminum 6061, which can be considered to be an aluminum alloy containing components in amounts such as at least 96 wt%, 97 wt%, 97.5 wt% aluminum, with the remainder being magnesium (e.g., 0.5 wt% or 0.8 wt%, up to 1.2 wt%), silicon (e.g., 0.4 wt% to 0.8 wt%), iron (0.0 wt% to 0.7 wt%), copper (e.g., 0.15 wt% to 0.4 wt%), chromium (e.g., 0.04 wt% to 0.35 wt%), zinc (e.g., 0.0 wt% to 0.25 wt%), titanium (e.g., 0.0 wt% to 0.25 wt%), and manganese (e.g., 0.0 wt% to 0.15 wt%). More particularly, an example of an aluminum alloy referred to as aluminum 6061 can contain about 98 wt% aluminum, about 0.60 wt% silicon, about 0.28 wt% copper, about 1.0 wt% magnesium, and about 0.2 wt% chromium.

[0060] In aluminum alloys such as aluminum 6061 and similar aluminum alloys (e.g., other 6000 series aluminum alloys), the amount of metal components other than aluminum and other than magnesium can be any amount, such as those amounts described herein. Such non-magnesium components of an aluminum alloy can be referred to as "non-magnesium impurities," or as "mobile impurities," and include metal species other than aluminum or magnesium that are readily diffusible in an aluminum matrix. Such mobile impurities include metals, transition metals, semiconductors, and elements that can form semiconducting compounds such as gallium, antimony, tellurium, arsenic, and polonium; for example, a mixture of silicon, iron, copper, chromium, zinc, titanium, manganese, or other metals. The methods of the present disclosure are effective for forming a suitable magnesium fluoride surface passivation region at a surface of an aluminum alloy body even when the aluminum alloy contains a total amount of such impurities that is considered to be relatively high for aluminum 6061, such as even when the concentration of non-magnesium impurities or "mobile impurities" is greater than 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, or 5.0 wt% of the aluminum alloy.

[0061] The metal body as described having a magnesium fluoride surface passivation region can typically include on the surface an amount of one or more metal oxides formed by the metal surface contacting atmospheric oxygen. The oxide layer need not be present and can preferably be minimized. A sufficiently thin or dispersed oxide layer will not unduly hinder or prevent the formation of magnesium fluoride at the underlying metal alloy surface by exposure to a fluorine source. The metal oxides, especially for aluminum alloys such as aluminum 6061 or another 6000 series aluminum alloy, are preferably of the type that have not been artificially placed at the surface, such as by anodizing the surface.

[0062] The example thickness of the naturally occurring metal oxide will depend on various factors, such as the particular conditions present during oxide formation and the type and particular composition of the alloy. For a general metal alloy, and especially for an aluminum alloy such as aluminum 6061 or another 6000 series aluminum alloy, the thickness of the metal oxide at the surface can be as low as 5 Angstroms, 10 Angstroms, or 100 Angstroms or 500 Angstroms, up to 1000 Angstroms. Higher thicknesses are also possible, such as in the nanometer range, such as up to 3 nanometers, 5 nanometers, or 10 nanometers or even higher.

[0063] The naturally occurring metal oxide will be present in a lower amount and have a thickness less than a layer of metal oxide artificially created at the alloy surface, such as by anodizing. For aluminum, an aluminum oxide layer formed by anodizing an aluminum surface, such as an aluminum surface of aluminum 6061 or another 6000 series aluminum alloy, can be in the range of greater than 5 microns or 10 microns.

[0064] The metal body as described having a magnesium fluoride surface passivation region can be suitable as part of any structure, device, article, or apparatus that includes a surface desirably inert, chemically resistant, or otherwise stable in a use environment. The metal body can be part of a processing or manufacturing apparatus, a storage container or storage apparatus, a medical device such as a medical (biological) implant, a vehicle such as an airplane, etc.

[0065] In particular uses, the metal body as described having a magnesium fluoride surface passivation region can be suitable for use or operation in a manufacturing or processing apparatus that is used in a liquid or gaseous environment containing reactive chemical materials. One example of this type of apparatus is a semiconductor processing tool.

[0066] Without limiting the scope of the disclosure, semiconductor processing tools typically include processing chambers that operate under vacuum, within which semiconductor substrates are processed. Processing chambers are operated under high vacuum to contain and allow processing of semiconductor substrates by exposing the substrates to highly pure processing materials (e.g., plasma, ions, or molecular compounds in gas or vapor form) that are to be applied to the semiconductor substrates. The processing chambers must contain components and surfaces suitable for transporting, holding, securing, supporting, or moving the substrates into, out of, and within the processing chambers. The processing chambers must also contain structural systems that are effective to contain, deliver, generate, or remove processing materials (e.g., plasma, ions, gaseous deposition materials, etc.) relative to the processing chambers. Examples of these different types of processing chamber components include sidewalls or liners that define the interior surfaces of the processing chambers, as well as flow nozzles (showerheads), shrouds, trays, supports, nozzles, valves, tubing, stages for handling or holding substrates, wafer handling clamps, ceramic wafer carriers, wafer holders, pedestals, spindles, chucks, rings, baffles, and various types of fasteners (screws, nuts, bolts, clamps, rivets, etc.). Any of these or other types of processing chamber components can be fabricated in the form of a metal body, with a magnesium fluoride surface passivation region formed at a surface thereof, as described herein.

[0067] Metal bodies suitable for use as processing chamber components or otherwise can have any shape or any form of surface, such as flat and planar surfaces (for liners or sidewalls), or can additionally or alternatively have physical shapes or forms including openings, orifices, channels, tunnels, threaded screws, threaded nuts, porous membranes, filters, three-dimensional networks, holes, etc., including such features that are considered to have high aspect ratios. The method of forming a magnesium fluoride surface passivation region as described herein by exposing a surface of a metal body to a molecular fluorine source at high temperature can be effective to provide a uniform and high-quality magnesium fluoride surface passivation region on such surfaces, including on components having structures with aspect ratios of at least 20: 1, 50: 1, 100: 1, 200: 1, or even 500: 1.

[0068] Metal bodies having magnesium fluoride surface passivation regions as described can be suitable for use as processing chamber components of any type of semiconductor processing tool, and for semiconductor processing tools operated at any temperature and other processing conditions.

[0069] Although the present disclosure often relates to the use of magnesium fluoride surface passivation regions on metal bodies of processing chamber components for semiconductor manufacturing processes (e.g., ion implantation, deposition steps) with semiconductor processing tools, the metal bodies with magnesium fluoride surface passivation regions as described are not limited to these items and applications. Examples of other uses of the solid bodies as described include uses in other environments, such as in high vacuum environments, biological environments, or ambient (e.g., air) environments, to improve the inertness and chemical resistance of the surface of the metal body.

[0070] Example

[0071] Example 1

[0072] A magnesium fluoride surface passivation region was formed at the surface of an aluminum alloy (6061 Al) test coupon by exposing the test coupon to fluorine-containing gas vapor at 400 degrees Celsius for approximately four hours. The test coupon was then evaluated using focused ion beam scanning electron microscopy (FIB SEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The test coupon was also evaluated for its resistance to reactive ion etching (RIE-F) and its resistance to concentrated nitric acid (HNO3).

[0073] Figure 2A is a FIB-SEM image of a cross-section of the metal test coupon. Visible in the cross-section is the conductive coating 10 necessary for FIB-SEM analysis. Present beneath the conductive coating 10 is a surface passivation region 12 of magnesium fluoride formed at the surface of the metal test coupon. The thickness of the surface passivation region 12 within the metal test coupon is approximately 100 nm. Also visible are magnesium fluoride decorated grain boundaries 14 and bulk regions 16 comprising the aluminum alloy (6061 Al).

[0074] Figure 2B is a top-down image taken by FIB-SEM of a cross-section of the metal test coupon. Visible in the top-down image are microcrystals with sizes in the range of about 50 to 100 nm.

[0075] The metal test coupon was also evaluated using X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). The spectrum produced by XPS is shown in Figure 3 . As shown in Figure 3It is visible in the spectrum that there is an extremely thin layer containing surface-bound extraneous carbon and oxygen that is etched away in less than 10 seconds. The next 80 nm is MgF2 with less than 15 atomic % Al. As the surface is etched deeper, the mixture of MgF2 and Al becomes richer in Al, reaching about 50 atomic % at a depth of 200 nm. As the surface is etched even deeper, the Al content increases and the ratio of F:Mg remains close to 2:1, which indicates that MgF2 is the primary state of Mg.

[0076] The XRD spectrum is shown in Figure 4 The XRD spectrum shows aluminum and magnesium fluoride markers, which are consistent with the FIB-SEM and XPS analysis, revealing that the magnesium fluoride in the surface passivation layer is polycrystalline and has a crystal structure consistent with humite (MgF2), powder diffraction file 072-2231.

[0077] The test coupons were subjected to reactive ion etching (RIE-F). The thickness of the magnesium fluoride surface passivation region was plotted as a function of etching time to produce a graph shown in Figure 5 The data indicates that the etching rate of the magnesium fluoride surface passivation region formed at the surface of the 6061 aluminum test coupons is less than 1 pm / hour, and specifically about 0.06 pm / hour.

[0078] Example 2

[0079] Test coupons of 6061 Al were provided with different treatments to protect the surface. Each test coupon was then immersed in a concentrated HNO3 solution and the metal content of the solution was analyzed by ICP-MS. The metal content of the different test coupons subjected to acid soaking is shown in Table 1.

[0080] Table 1

[0081]

[0082] The data in Table 1 shows that test coupons including a magnesium fluoride surface passivation region leach metals at lower levels than comparable test coupons anodized by either of the two methods or the untreated test coupons. In particular, the test data reveals that, in addition to expected aluminum (Al) leaching, untreated 6061 Al test coupons leach high levels of copper (Cu), lead (Pb), and magnesium (Mg). Type II anodization improves the leaching of magnesium (Mg), but adds other undesirable impurities, such as bismuth (Bi), chromium (Cr), iron (Fe), lead (Pb), manganese (Mn), titanium (Ti), vanadium (V), and zinc (Zn). Anodization with oxalic acid produces a cleaner surface than Type II, but still adds new impurities that are not present in the base metal. The magnesium fluoride surface passivation region effectively reduces aluminum as well as nearly eliminates all magnesium, copper, and lead.

[0083] Thus, those skilled in the art will readily appreciate that other embodiments can be made and used other than those described herein without departing from the scope of the disclosure as claimed. The disclosure's numerous aspects are described with reference to particular embodiments. However, it will be understood that the disclosure is not limited to these particular embodiments. The specific details of the particular embodiments can be eliminated in the art without departing from the scope of the disclosure as claimed. The scope of the disclosure is expressly set forth in the appended claims.

Claims

1. A method for forming a magnesium fluoride surface passivation region on the surface of a metal body, the method comprising: adding a solid fluorinated polymer and a magnesium-containing metal body to a processing chamber; heating the solid fluorinated polymer to generate a molecular fluorine source vapor; and exposing the magnesium-containing metal body to the molecular fluorine source vapor at a temperature of at least 200 degrees Celsius for a period of time ranging from 1 to 15 hours, wherein fluoride from the molecular fluorine source vapor reacts with magnesium in the magnesium-containing metal body to form the magnesium fluoride surface passivation region of a desired thickness on the surface of the metal body, wherein the surface of the metal body has a high aspect ratio feature ranging from 20:1 to 500:1, and wherein the surface passivation region conforms to the high aspect ratio feature.

2. A method for forming a magnesium fluoride surface passivation region on the surface of a metal body, the method comprising: adding a solid fluorinated polymer and a magnesium-containing metal body to a processing chamber; heating the solid fluorinated polymer to generate a molecular fluorine source vapor; and exposing the magnesium-containing metal body to the molecular fluorine source vapor at a temperature of at least 200 degrees Celsius for a period of 1 to 15 hours, wherein fluoride from the molecular fluorine source vapor reacts with magnesium in the magnesium-containing metal body to form the magnesium fluoride surface passivation region of a desired thickness on the surface of the metal body, wherein the surface of the metal body has a high aspect ratio characteristic in the range of 20:1 to 500:1, wherein the surface passivation region conforms to the high aspect ratio characteristic, and wherein the desired thickness of the magnesium fluoride surface passivation region is in the range of 1 to 200 nm.

3. The method according to claim 1 or 2, wherein the magnesium-containing metal body is any one of an opening, a channel, a threaded screw, a threaded nut, or a filter.

4. The method according to claim 1 or 2, wherein the magnesium-containing metal body is an orifice.

5. The method according to claim 1 or 2, wherein the magnesium-containing metal body is a tunnel.

6. The method according to claim 1 or 2, wherein the solid fluorinated polymer comprises: having C1-C 10 Polymers of perfluoroalkyl groups: perfluoroalkyl ethylene; polytetrafluoroethylene (PTFE); tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA); tetrafluoroethylene / hexafluoropropylene copolymer (FEP); tetrafluoroethylene / perfluoro(alkyl vinyl ether) / hexafluoropropylene copolymer; polyhexafluoropropylene; ethylene / tetrafluoroethylene copolymer (ETFE); polytrifluoroethylene; polyvinylidene fluoride (PVDF); polyvinyl fluoride (PVF); polychlorotrifluoroethylene (PCTFE); ethylene / chlorotrifluoroethylene copolymer (ECTFE); or combinations thereof.

7. The method according to claim 1 or 2, wherein the molecular fluorine source vapor comprises CF4, C2F4, C3F6, C4F8, CHF3, C2H2F2, C2F6, HF, CH3F or a combination thereof.

8. The method according to claim 1 or 2, wherein the surface of the metal body is exposed to the molecular fluorine source vapor at a temperature of at least 350 degrees Celsius.

9. The method according to claim 1 or 2, comprising exposing the surface to the molecular fluorine source vapor for a period of time ranging from 3 hours to 12 hours.

10. The method according to claim 1 or 2, wherein the magnesium-containing metal body comprises an aluminum alloy.

11. The method according to claim 1 or 2, wherein the magnesium-containing metal body is a three-dimensional network.

12. The method according to claim 1 or 2, wherein the magnesium-containing metal body is a porous membrane.

13. The method of claim 1 or 2, wherein the magnesium-containing metal body is a processing chamber assembly.

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