Yttrium fluoride films and methods of making and using yttrium fluoride films

Abstract

The present invention describes yttrium fluoride compositions, including deposited films, such as coatings, containing yttrium fluoride; methods of making yttrium fluoride compositions and deposited film coatings containing yttrium fluoride; and substrates having deposited film coatings containing yttrium fluoride at their surfaces and methods and apparatuses including the same.

Description

Technical Field

[0001] The present disclosure relates to yttrium fluoride films including protective coatings; methods of making yttrium fluoride films; substrates and surfaces including yttrium fluoride films; and methods of making and using yttrium fluoride films. Background Art

[0002] Semiconductor and microelectronic device manufacturing methods require various processing steps involving highly reactive process materials, such as plasma. Example processes using reactive process materials include plasma etching steps, plasma deposition steps, and plasma cleaning steps. These processes are performed inside a processing chamber containing a workpiece (e.g., a "substrate") and the reactive process materials. The processing chamber also includes various structures and components required for operation (also referred to as "processing chamber components") that define the processing chamber and objects within or associated with the processing chamber. These processing chamber components may include chamber walls, flow conduits (e.g., flow lines, flow heads, tubing, pipes, etc.), fasteners, trays, supports, and other structures and devices used to support the workpiece or deliver or contain reactive process materials with respect to the processing chamber.

[0003] To function as part of a processing chamber, the processing components should be resistant to the reactive process materials that will be used within the processing chamber. The processing chamber components should not degrade or become damaged due to contact with the process materials, particularly in a manner that would generate debris or particulates that could be incorporated into the process being performed and potentially contaminate the workpiece being processed.

[0004] Process chamber components used in semiconductor processing equipment for manufacturing semiconductors and microelectronic devices are typically made of a solid material ("substrate" or "base") such as a metal (e.g., stainless steel, optionally anodized aluminum alloys, tungsten), a mineral, or a ceramic material. The substrate is typically coated with a protective layer that is more resistant to reactive process materials than the substrate material. In the past, such protective thin-film coatings have typically been applied to the substrate by various suitable methods, typically by anodizing (e.g., to produce anodized aluminum), spraying, or deposition methods (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD)). Summary of the Invention

[0005] As described herein, yttrium fluoride ("YF3") can be prepared as part of a deposited yttrium oxide film by converting the yttrium oxide of the deposited film into yttrium fluoride. The resulting yttrium fluoride film can have a relatively high concentration of fluorine and a relatively low concentration of oxygen. Due to the relatively high fluorine content (e.g., compared to fluorinated metal oxides such as YOF), the yttrium fluoride film can be effective as a material for a protective coating.

[0006] Previous and current methods suitable for preparing deposited films as protective coating materials containing relatively high amounts of fluorine (e.g., higher than that of YOF) have been difficult to use due to the complexities of handling fluorine chemicals, such as environmental health and safety regulations, compatibility of processing equipment with highly fluorinated raw materials, abatement and disposal procedures, etc.

[0007] Yttrium fluoride has previously been used for purposes other than as a protective coating material. As one example, yttrium fluoride has been formed into transparent, low-refractive-index films for use as optical coatings. Previously, yttrium fluoride films have been formed using sputtering techniques, which do not allow for uniform and continuous deposition of yttrium fluoride onto three-dimensional surfaces, particularly those with high-aspect-ratio features.

[0008] The yttrium fluoride material described herein differs from previously deposited yttrium fluoride films, such as those formed by sputtering deposition techniques. For example, the yttrium fluoride films of the present disclosure can be formed as a continuous film over three-dimensional surfaces, including surfaces with high-aspect-ratio structures. Because the yttrium fluoride films of the present disclosure are formed by converting yttrium oxide into yttrium fluoride and fluorine annealing the yttrium oxide, the yttrium fluoride films of the present disclosure can also contain a certain amount of oxygen, particularly in the lower portion of the film thickness, and can contain varying concentrations of fluorine, oxygen, or both along the thickness (depth) of the film.

[0009] The methods of the present description are particularly suitable for forming yttrium fluoride by converting yttrium oxide from a deposited yttrium oxide film that has been formed by atomic layer deposition into yttrium fluoride. Similar methods have not been shown to be effective for other (non-yttrium) metal oxide materials or for yttrium oxide or other metal oxide deposited films formed by deposition methods other than atomic layer deposition.

[0010] As used herein, "deposited thin film," "thin film," or "film" refers to a coating of material that has been deposited onto a substrate surface by a deposition process (e.g., by atomic layer deposition), and also refers to modified forms or derivatives of those deposited films, including films that were initially deposited and then subsequently chemically modified by a fluorination step.

[0011] In one aspect, a coated substrate is described herein. The coated substrate includes: a substrate; and an yttrium fluoride film formed on the substrate. The yttrium fluoride film comprises: yttrium, fluorine, oxygen, a surface, a thickness, and an yttrium fluoride portion extending from the surface over a portion of the thickness where the oxygen concentration is less than 20 atomic percent. The fluorine concentration in the yttrium fluoride film varies relative to the thickness.

[0012] In another aspect, a method for preparing yttrium fluoride is described herein. The method comprises depositing an yttrium oxide film onto a surface by atomic layer deposition; and exposing the yttrium oxide film to fluorine and high temperature to convert the yttrium oxide in the yttrium oxide film into yttrium fluoride. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Graph showing X-ray diffraction data of the coating of the present specification.

[0014] Figure 2 Graph showing x-ray diffraction data for yttrium fluoride films as described.

[0015] Figure 3 Examples of methods and specific method steps suitable for forming yttrium fluoride thin films as described are described.

[0016] Figure 4 An example of a substrate having a thin coating of yttrium fluoride at the surface is illustrated. DETAILED DESCRIPTION

[0017] The following description relates to deposited thin films containing yttrium fluoride (sometimes referred to as "yttrium fluoride thin films" or alternatively "yttrium fluoride films"), protective coatings comprising yttrium fluoride thin films, and substrates having a surface and a yttrium fluoride thin film deposited thereon. The substrate surface can be a highly three-dimensional surface, for example, a surface having at least one structure exhibiting a high aspect ratio.

[0018] The present specification also relates to methods for preparing yttrium fluoride thin films and methods of using yttrium fluoride thin films, including yttrium fluoride thin films that serve as protective coatings.

[0019] According to the method described in the present invention, a deposited film containing yttrium fluoride can be formed from the deposited yttrium oxide film by converting at least a portion of the yttrium oxide of the deposited yttrium oxide film into yttrium fluoride. For example, a method may include the step of depositing yttrium oxide as a thin film onto a surface by atomic layer deposition (ALD) technology. Subsequently, at least a portion of the yttrium oxide of the deposited film is converted into yttrium fluoride by a fluorine annealing step. The fluorine annealing step is performed at a relatively high temperature and for a period of time, resulting in a large amount of yttrium oxide being converted into yttrium fluoride (YF3) rather than remaining in the form of yttrium oxide fluoride (YOF).

[0020] Yttrium fluoride is an inorganic material made of yttrium and fluorine, having a chemical composition of YF3 or approximately so. In this specification, the yttrium fluoride film or a portion thereof contains primarily yttrium and fluorine atoms, wherein a large amount of the yttrium and fluorine is in the form of yttrium fluoride or YF3. The yttrium fluoride film may also contain a certain amount of oxygen, and various elemental combinations of yttrium, fluorine, and oxygen, such as yttrium oxyfluoride (YOF). However, the preferred yttrium fluoride film or a portion thereof may contain oxygen in an amount (concentration) less than the amount of oxygen that would be present in a composition that would be referred to as yttrium oxyfluoride (YOF), for example, not more than 20 percent oxygen measured at a particular location along the thickness (depth) of the yttrium fluoride film.

[0021] In general, the yttrium fluoride film contains throughout its thickness essentially only yttrium, fluorine, oxygen, an optional but relatively low amount of carbon ("C") (e.g., up to 4 or 5 atomic percent carbon), and no more than small or trace amounts of other materials. The yttrium fluoride film as described can consist of Y, F, O, and C (e.g., up to 4 or 5 atomic percent carbon), or can consist essentially of Y, F, O, and C, for example, can contain Y, F, O, and C (e.g., no more than 5 or 4 atomic percent carbon) and no more than 1, 0.5, 0.1, 0.05, or 0.01 atomic percent of any material other than Y, F, O, and C.

[0022] The method of forming a thin film of yttrium fluoride as described has been identified as being particularly effective for producing thin films containing high concentrations of yttrium fluoride, particularly for forming thin films onto three-dimensional and high-aspect-ratio surfaces. The method as described does not deposit yttrium fluoride (YF3) itself directly onto the surface. Instead, the method as described forms yttrium fluoride by forming a thin film of yttrium oxide on a substrate by atomic layer deposition; and converting at least a portion of the yttrium oxide of the deposited film into yttrium fluoride by a fluorine annealing step.

[0023] These steps have been shown to be particularly effective for forming films containing a high concentration of yttrium fluoride compared to alternative methods of initially depositing the yttrium oxide film by a different deposition method (e.g., chemical vapor deposition, physical vapor deposition, or variations of these depositions), followed by a fluorine annealing step. The yttrium fluoride film as described can be prepared by converting the deposited yttrium oxide film into yttrium fluoride using a relatively high temperature fluorine annealing step, for example, a fluorine annealing step performed at a temperature of at least 300 degrees Celsius. Comparable fluorine annealing techniques that attempt to convert yttrium oxide into yttrium fluoride at relatively high temperatures are less effective when performed on yttrium oxide that has been deposited by different deposition techniques, such as physical vapor deposition ("PVD") or chemical vapor deposition ("CVD").

[0024] These specific steps have also been determined to be more effective for forming highly fluorinated metal fluoride materials, that is, YF3, compared to methods for forming other types of metal fluorides from other metals by comparable deposition and fluorine annealing steps. The high temperature fluorine annealing step as described is less effective for converting other metal oxides into metal fluorides, even for metal oxides that have been deposited by atomic layer deposition techniques. Specifically, it was found that the fluorine annealing step at a relatively high temperature is less effective for converting metal oxide materials such as zirconium oxide, titanium oxide, or aluminum oxide into fluorinated oxide materials (zirconium fluoride, titanium fluoride, or aluminum fluoride), even if the metal oxide has been deposited by atomic layer deposition techniques.

[0025] In a preferred method, due to the thermal stress experienced by the deposited yttrium oxide film during the relatively high temperature fluorine annealing step, an intermediate layer (e.g., a "buffer layer") may be placed on the substrate surface between the substrate surface and the deposited yttrium oxide film. The intermediate layer (described in more detail below) can effectively allow the deposited yttrium oxide film to be processed through the fluorine annealing step at a relatively high fluorine annealing temperature without causing the deposited yttrium oxide film to crack or otherwise be physically damaged due to the stress generated during the high temperature fluorine annealing step.

[0026] Advantageously, the methods of the present disclosure allow for the preparation of yttrium fluoride thin films using specialized vapor-phase techniques, namely, atomic layer deposition and fluorine annealing techniques. Previous methods for forming yttrium fluoride films relied on sputtering techniques, which were considered "line-of-sight" techniques that were ineffective in uniformly depositing yttrium fluoride onto three-dimensional surfaces or surfaces including high-aspect-ratio structures. According to the methods described herein, deposited thin films containing yttrium fluoride can be efficiently and effectively formed onto three-dimensional surfaces, including surfaces with high-aspect-ratio structures.

[0027] In one aspect, the example deposited films of the present disclosure can be distinguished from previously sputtered yttrium fluoride films by being uniformly deposited over surfaces of substantially three-dimensional structures or structures having high aspect ratios. Alternatively or in addition, the deposited films of the present disclosure can be distinguished from sputtered yttrium fluoride films by containing oxygen in portions of the film, particularly at depths below the film surface. Sputtered yttrium fluoride films will be formed solely of yttrium and fluorine and will not contain more than trace amounts of oxygen.

[0028] In a related sense, the yttrium fluoride thin films of the present description will contain amounts (i.e., concentrations) of fluorine and oxygen that will not be uniform in the thickness (depth) direction, that is, will contain fluorine and oxygen whose concentrations will vary by measurable amounts along the thickness (depth) of the deposited film. Yttrium fluoride films formed by sputtering will not exhibit fluorine or oxygen concentrations that vary substantially along the thickness of the deposited film.

[0029] The film as described can be produced by a method comprising the following steps: forming a deposited yttrium oxide thin film on a substrate surface by atomic layer deposition. Prior to depositing the yttrium oxide thin film, the substrate surface may optionally include an intermediate layer as described elsewhere herein. Yttrium oxide (Y2O3, also referred to as "yttrium oxide") is prepared from yttrium and oxygen and contains yttrium and oxygen in a relative amount (atomic) of approximately 2:3 (yttrium:oxygen). Methods for forming yttrium oxide by atomic layer deposition are known. See, for example, U.S. Patent Publication 2018 / 0202047.

[0030] In an example method, a deposited yttrium oxide thin film can be formed on a substrate by an atomic layer deposition method that deposits yttrium oxide onto a substrate surface maintained at a temperature in a range of 100 degrees Celsius to 350 degrees Celsius, such as a temperature in a range of 140° C. to 200° C. The deposited yttrium oxide thin film can be formed to any suitable thickness, such as a thickness in a range of about 0.01 micrometers (10 nm), up to or greater than 0.25 micrometers (250 nm), 0.5 micrometers (500 nm), 0.75 micrometers (750 nm), or 1 micrometer. After the yttrium oxide thin film is deposited, the deposited yttrium oxide thin film is treated by a fluorine annealing step (a "fluoro-annealing" step) that converts at least a portion of the total amount of yttrium oxide in the deposited film into yttrium fluoride. The fluorine annealing step is performed at a temperature and for a time effective to not only fluorinate the yttrium oxide to form yttrium oxyfluoride (or "yttrium oxide fluoride," YOF), but also at a temperature and for an amount of time sufficient to convert at least a majority of the yttrium oxide of the deposited yttrium oxide film into yttrium fluoride (YF), particularly at the surface portion of the deposited yttrium oxide film. According to an applicable or preferred method, at least the outer surface or "surface portion" of the yttrium oxide thin film (including a portion of the film thickness between the surface and a depth of at least 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 nanometers) is converted to YF3 having a low amount of oxygen or substantially no oxygen, for example, less than 15 atomic percent oxygen, less than 10, less than 5, or less than 3 atomic percent oxygen as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion, and having a large amount of fluorine, for example, at least 45 atomic percent oxygen, at least 50, at least 55, or at least 60 atomic percent fluorine as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion. In some embodiments, the surface portion may have a thickness of at least 10 nanometers, less than 5 atomic percent oxygen as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion, and at least 60 atomic percent fluorine as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion. In some embodiments, the surface portion can have a thickness of at least 50 nanometers, less than 15 atomic percent oxygen as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion, and at least 50 atomic percent fluorine as measured by x-ray photoelectron spectroscopy over the entire thickness of the surface portion.

[0031] Methods for converting yttrium oxide to yttrium oxyfluoride (YOF) by a fluorine annealing step performed at a temperature below 300 degrees Celsius have been previously described. See U.S. Patent Publication 2018 / 0202047. The method described herein now includes the specific feature of a fluorine annealing step performed at a temperature exceeding 300 degrees Celsius, performed in a manner that successfully converts yttrium oxide at least at the surface portion of the deposited yttrium oxide film to contain a high concentration of yttrium fluoride (YF3) with a low amount of oxygen, substantially no oxygen, or a low amount of fluorinated yttrium oxide (YOF) or substantially no fluorinated yttrium oxide (YOF).

[0032] A suitable and preferred fluorine annealing technique comprises the steps of exposing an yttrium oxide surface (e.g., the surface of an yttrium oxide thin film deposited by atomic layer deposition) to a molecular fluorine source vapor at a temperature such that the fluorine of the molecular fluorine source vapor reacts with the yttrium oxide of the deposited yttrium oxide thin film (also referred to as a "yttrium oxide layer") to form yttrium fluoride at or below the surface of the deposited yttrium oxide thin film.

[0033] As used herein, a "molecular fluorine source vapor" is a non-plasma (i.e., molecular) fluorine-containing chemical molecule in vapor (gaseous) form that is not considered a plasma. A "plasma" is a non-solid, gaseous composition containing a high density of ion fragments derived from one or more plasma precursor compounds that have been intentionally exposed to energy (e.g., from a radio frequency power source) for the purpose of decomposing the plasma precursor compounds into ions, with the goal of using the ions for processing a workpiece. In contrast to a plasma, a suitable or preferred molecular fluorine source vapor may contain less than 1×10E-5 atomic percent of ionized material, for example, less than 1×10E-6 atomic percent of ionic species.

[0034] The molecular fluorine source vapor may be provided to the processing chamber for forming the yttrium fluoride thin film by any method or from any suitable and effective source or location. In suitable or preferred methods, the molecular fluorine source vapor may be generated in situ, meaning during the process of forming the yttrium fluoride thin film on the substrate surface and within the processing chamber used to form the yttrium fluoride thin film on the surface. The molecular fluorine source vapor may be generated in situ from a non-gaseous fluorine source by heating the non-gaseous fluorine source so that the molecules of the non-gaseous fluorine source become gaseous (i.e., molecular vapor). The non-gaseous fluorine source may be a liquid or solid fluorine-containing substance, and the heating step produces the molecules in gaseous form without causing significant degradation or ionization of the liquid or solid fluorine source molecules. Suitable or preferred molecules in gaseous form may be at least 99.9999 atomic percent molecules, i.e., chemically unaltered molecules of the liquid or solid fluorine-containing substance. The molecules in gaseous form may contain less than 1×10E-5 atomic percent ionized or degraded material, for example, less than 1×10E-6 atomic percent ionic species.

[0035] The heating step for generating molecular fluorine source vapor is distinct from the step for generating plasmas used in various semiconductor processing steps. Generally, the plasma generation step involves applying one or more forms of energy to a plasma source, typically a gaseous chemical substance, to ionize the plasma source and chemically degrade the molecules of the plasma source to produce 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.

[0036] As a specific comparison, the heating step of the present disclosure for generating molecular fluorine source vapor is distinct from the step of generating a fluorine-containing plasma for use in semiconductor processing tools used for plasma etching, plasma cleaning, or "seasoning" a process chamber of a semiconductor processing tool. An example of a plasma generation step that is distinct from the heating step described herein is described in U.S. Patent No. 5,756,222, which describes a fluorine-containing plasma generated in a reaction chamber designed for plasma etching or plasma cleaning processes. The plasma is prepared by exposing a fluorine precursor to RF power.

[0037] The fluorine annealing step may be performed in a processing chamber at an elevated temperature by the following steps: positioning a substrate in a removable, temporary, non-operational manner within the processing chamber, the substrate having a surface including a deposited yttrium oxide thin film deposited thereon by atomic layer deposition; dispensing molecular fluorine source vapor into the processing chamber or generating molecular fluorine source vapor within the processing chamber by heating a non-gaseous fluorine source such that molecules of the non-gaseous fluorine source become gaseous (i.e., vapor) within the processing chamber; and increasing the temperature of the processing chamber, the substrate, the deposited yttrium oxide thin film, the molecular fluorine source vapor, or a combination thereof such that a reaction between the fluorine of the molecular fluorine source vapor and the yttrium oxide of the deposited yttrium oxide thin film converts at least a portion of the yttrium oxide into yttrium fluoride.

[0038] During the fluorine annealing step, the processing chamber may contain: a processing material comprising a molecular fluorine source vapor, optionally a non-vapor fluorine source; and one or more substrates having a deposited yttrium oxide thin film deposited on the surface by atomic layer deposition techniques. The interior space and atmosphere of the chamber need not be evacuated or under reduced pressure, and may contain a certain amount of atmospheric air. There is no need to eliminate air or oxygen, or introduce an inert gas (a flushing gas, such as N2) into the processing chamber for the fluorine annealing step. The processing chamber need not contain and may not include any other additional gaseous or liquid processing materials other than air and molecular fluorine source vapor, for example, it may not include other gaseous materials (e.g., inert gases) or gaseous co-reactants in the gaseous atmosphere that are sometimes used in other semiconductor processing steps.

[0039] The processing chamber is not part of a semiconductor processing tool and need not, and preferably does not, contain any other workpieces that are otherwise processed, such as semiconductor devices, microelectronic devices, or precursors thereof. The processing chamber also does not require and does not involve the use of means for generating a plasma, such as a radio frequency power source, or means for applying an electrical potential (voltage) to a component or workpiece.

[0040] A suitable processing chamber may preferably include: a temperature control member for controlling the temperature within the chamber; components for controlling the composition and purity of the environment inside the chamber, such as a pressure control member, a filter, etc.; an assembly for temporarily containing and supporting one or more substrates in the chamber for a period suitable for converting the yttrium oxide of the deposited yttrium oxide film into yttrium fluoride, the one or more substrates each having a deposited yttrium oxide film at the surface; and an assembly for controlling the composition of the atmosphere within the processing chamber, including an assembly for supplying and controlling the amount and concentration of a molecular fluorine source within the processing chamber.

[0041] According to certain suitable or preferred example fluorine annealing methods, the molecular fluorine source vapor can be a gaseous fluorinated or perfluorinated organic compound, such as a fluorinated or perfluorinated alkane or olefin, any of which can be linear or branched. Examples include CF4, C2F4, C3F6, C4F8, CHF3, C2H2F2, C2F6, HF, CH3F, and others, each of which is in molecular form, meaning it is essentially non-ionic and has not been treated (by the addition of energy other than heat) to degrade or form a plasma.

[0042] According to other suitable or preferred example methods, the molecular fluorine source vapor can be a gaseous fluorinated polymer that has not been subjected to energy treatment to form a plasma. The gaseous fluorinated polymer can be derived from a non-gaseous fluorinated polymer by heating the non-gaseous (e.g., liquid or solid) fluorinated polymer, for example, in a processing chamber in the presence of a deposited yttrium oxide film that is to be converted to yttrium fluoride by a fluorine annealing step.

[0043] The fluorinated polymer can be any fluorinated polymer that will be effective in forming yttrium fluoride from a deposited yttrium oxide thin film present on a substrate surface according to the method described. Examples of suitable fluorinated polymers include homopolymers and copolymers, including polymerized fluoroolefin monomers and optional non-fluorinated comonomers. The polymer can be fluorinated (i.e., partially fluorinated), perfluorinated, or can include non-fluorine halogen atoms, such as chlorine. The molecular fluorine source can be a liquid or solid at room temperature, but will become a vapor at the temperature of the processing chamber used according to the method described.

[0044] Non-limiting examples of specific fluoropolymers include: polymerized perfluoroalkylethylenes having C1-C 10Perfluoroalkyl; polytetrafluoroethylene (PTFE); tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA); tetrafluoroethylene / hexafluoropropylene copolymer (FEP); tetrafluoroethylene / perfluoro(alkyl vinyl ether) / hexafluoropropylene copolymer (EPA); polyhexafluoropropylene; ethylene / tetrafluoroethylene copolymer (ETFE); polytrifluoroethylene; polyvinylidene fluoride (PVDF); polyvinyl fluoride (PVF); polychlorotrifluoroethylene (PCTFE); ethylene / chlorotrifluoroethylene copolymer (ECTFE); or a combination thereof.

[0045] The fluorine annealing step as described can be performed at any temperature that effectively reacts fluorine from the fluorine source vapor with yttrium oxide of the deposited yttrium oxide film to convert at least a portion of the deposited yttrium oxide film into yttrium fluoride (e.g., at a concentration and depth as described herein). Relatively high temperatures are generally suitable or preferred to cause the fluorine source vapor to react with the yttrium oxide to convert the yttrium oxide into a high concentration of yttrium fluoride (YF3) rather than yttrium oxide fluoride (YOF). Example temperatures for the fluorine annealing step can be at least 300 or 350 degrees Celsius, or higher, such as in the range of from 300 to 500 degrees Celsius, such as from 350 or 400 degrees Celsius to 425 or 450 degrees Celsius, to produce a high concentration of YF3 at the surface portion of the deposited film.

[0046] The processing chamber can be operated at any suitable pressure, with an example pressure being approximately atmospheric pressure (760 Torr), such as 100 Torr to 1500 Torr, such as 250 or 500 Torr to 1000 or 1250 Torr. The atmosphere within the processing chamber for converting yttrium oxide to yttrium fluoride can include air in combination with molecular fluorine source vapor.

[0047] The amount of time used to form yttrium fluoride by the fluorine annealing step can be based on factors such as the temperature of the fluorine annealing step, the type and amount (concentration) of the molecular fluorine source vapor in the processing chamber, the thickness and composition of the deposited yttrium oxide film, and the desired thickness of the yttrium fluoride portion to be formed from the deposited yttrium oxide film. Suitable or preferred example amounts of time can range from 1 hour to 48 hours, such as 2 hours to 24 hours or 3 hours to 12 hours. A suitable period of time for performing the fluorine annealing step can be a period of time that produces an yttrium fluoride portion (of the deposited film) having a suitable or preferred thickness. During the fluorine annealing step, as the deposited yttrium oxide film continues to be exposed to the molecular fluorine source vapor, the thickness will increase over time. After a certain amount of time, such as after 12, 18, or 24 hours, the thickness of the yttrium fluoride portion of the deposited film may no longer substantially increase.

[0048] The deposited film formed by converting the yttrium oxide of the deposited yttrium oxide film into yttrium fluoride as described will have a composition including yttrium, fluorine, oxygen, and possibly a small amount of carbon (e.g., less than 4 or 5 atomic percent carbon). For example, the yttrium fluoride film may contain: yttrium fluoride (YF3), potentially an amount of yttrium oxide fluoride (YOF), and possibly yttrium oxide (Y2O3). These different materials may be present in different portions of the deposited film in amounts (concentrations) that vary in thickness (depth) and based on the thickness position of the deposited material, that is, in varying amounts (that is, in non-uniform amounts or concentrations) relative to the depth (thickness) of the yttrium fluoride film.

[0049] As used herein, the terms "yttrium fluoride thin film" and "yttrium fluoride film" refer to a film or coating produced on a substrate by the following steps: depositing a layer of yttrium oxide material onto a substrate; then converting at least a portion of the deposited yttrium oxide into yttrium fluoride. By these steps, not all of the yttrium oxide of the deposited yttrium oxide film will necessarily be converted into yttrium fluoride. A portion of the film thickness, including the film surface (that is, the "surface portion"), will be converted to yttrium fluoride to a large extent. The middle or lower portion of the film will be converted into yttrium fluoride or yttrium oxyfluoride (YOF) and may contain a higher concentration of oxygen than a location located closer to the surface. Optionally, the lower portion of the film may be converted into yttrium fluoride, may be converted into yttrium oxyfluoride, or may remain in the form of yttrium oxide.

[0050] Because the yttrium fluoride thin film as described is formed by a fluorine annealing step, the deposited film will potentially exhibit a non-uniform concentration, such as a gradient, of one or more of the atomic components (particularly fluorine and oxygen) that make up the film. The fluorine concentration within the yttrium fluoride thin film may decrease along the thickness of the film, such that the surface and outer portions of the film (the "upper portion" or "surface portion") will contain a higher concentration of fluorine than portions at greater depths. For example, in some embodiments, the film may have an upper portion substantially made of yttrium fluoride and a lower portion that is fluorinated yttrium oxide or even non-fluorinated yttrium oxide.

[0051] Different portions of a deposited thin film can be identified and characterized by x-ray photoelectron spectroscopy, or "XPS," techniques based on their varying composition at different locations through the thickness of the film. These quantitative spectroscopic techniques allow for compositional analysis of deposited films or layers of material at and below the surface of the material, across the thickness (depth) of the deposited material. XPS profile analysis can identify the elemental composition of the deposited material at different locations along the thickness of the material.

[0052] Figure 1] is the XPS profile of a deposited yttrium oxide film that was deposited by atomic layer deposition and subsequently treated to convert the yttrium oxide of the deposited yttrium oxide film into yttrium fluoride via a fluorine annealing step, as described. The "upper" portion (or "surface" portion) of the film is considered to include the surface of the film (at a depth equal to zero) and the portion of the film extending below the surface to a specified thickness (or "depth"). As shown, the surface portion of the deposited film tested included a significant amount of yttrium fluoride. The portion of the tested film between the surface (at a depth of zero) and a depth of 50 nanometers and 60 nanometers contained at least 60 atomic percent fluorine and less than 5 atomic percent oxygen, indicating a very high YF3 concentration and a low YOF concentration. As shown, the yttrium fluoride film was formed above an intermediate layer of aluminum oxide (Al2O3), which had been formed on the surface of a silicon (Si) substrate.

[0053] Figure 1 A measured yttrium fluoride film may be considered to have a "portion" that may be referred to as "yttrium fluoride," such as a "yttrium fluoride portion," which includes a surface portion of the film. The yttrium fluoride portion is the portion that includes the surface of the film and extends to a thickness or depth where the composition of the film material is substantially yttrium fluoride (e.g., not substantially yttrium oxide fluoride). As an example, the yttrium fluoride portion may be considered to be the portion of the yttrium fluoride film that extends from the surface to a depth where the oxygen concentration in the film is less than 20 atomic percent oxygen. This thickness may be referred to as "t(20%)." Alternatively, the yttrium fluoride portion may be considered to be the portion that extends from the surface to a depth where the oxygen concentration in the film remains less than 10 atomic percent oxygen. This thickness may be referred to as "t(10%)."

[0054] Based on a maximum oxygen concentration of 20 atomic percent, an example thickness t(20%) of the yttrium fluoride portion as described can be at least 5 or 10 nanometers, for example at least 20 nanometers from the surface of the deposited film, and can have a thickness of up to or greater than 50, 75, 100, 125, 150, or 200 nanometers. In other words, the yttrium fluoride portion having an oxygen content below 20 atomic percent at all thickness locations can extend from the surface to a depth of at least 5 nanometers below the surface and up to or greater than 10, 20, 50, 75, 100, 125, 150, or 200 nanometers.

[0055] Based on a maximum oxygen concentration of 10 atomic percent, an example thickness t(10%) of the yttrium fluoride portion as described can be at least 5, 10, or at least 20 nanometers from the surface of the deposited film, and can have a thickness of up to or greater than 50, 75, or 100 nanometers. In other words, the yttrium fluoride portion having an oxygen content below 10 atomic percent at all thickness locations can extend from the surface to a depth of at least 5 nanometers below the surface and up to or greater than 10, 20, 50, 75, or 100 nanometers.

[0056] like Figure 1 As shown, an example yttrium fluoride film may contain a fluorinated yttrium oxide (YOF) portion, for example, at a lower portion of the film away from the surface and adjacent to a substrate or intermediate layer. Also as shown, this can result in a gradual transition from an intermediate (buffer) metal oxide layer (e.g., alumina, zirconia, titania, etc., and combinations thereof) to YOF and then to YF3, rather than a direct transition from the metal oxide layer to YF3. If the yttrium fluoride film contains a YOF portion, for example, adjacent to a substrate or intermediate layer, the thickness of the YOF portion can be controlled based on the controllable thickness of the initial deposited Y2O3 film and the conditions of the fluorine annealing step (temperature, exposure time, etc.).

[0057] The films of the present invention can also be analyzed by x-ray diffraction to show that the yttrium fluoride portion of the film contains a significant or high concentration of crystalline YF3 compared to other possible stoichiometric combinations of Y, F, and O. X-ray diffraction (XRD) is a known analytical technique for evaluating the atomic and molecular structure of materials, including deposited film materials. For example, x-ray diffraction is suitable for evaluating the structural and stoichiometric characteristics of deposited films of the type described herein, such as those prepared by atomic layer deposition.

[0058] Figure 2 XRD data for an example yttrium fluoride film of this specification is presented. The data shows that the film contains a significant concentration of (poly)crystalline YF3, as indicated by diffraction peaks consistent with the expected YF3 characteristics. To the extent that the film contains some amount of oxygen, the XRD data shows that the film contains a stoichiometric mixture of materials consisting primarily of YF3 and lower amounts of YOF.

[0059] Depending on the applicable or preferred method, deposited film, and coated substrate, the substrate to which the deposited film is applied may include an intermediate layer disposed on the substrate between the substrate and the deposited film as described. As a step in the method as described, a yttrium oxide film may be deposited onto the substrate. The yttrium oxide film is then converted to yttrium fluoride by annealing the yttrium oxide film at an elevated temperature in the presence of fluorine to convert at least a majority of the yttrium oxide into yttrium fluoride. The elevated temperatures used in the fluorine annealing step may cause physical damage, such as cracking, to the deposited yttrium oxide film.

[0060] In a preferred method, to prevent physical damage to the yttrium oxide film that may be caused by thermal stresses that occur during the fluorine annealing step, an intermediate layer (e.g., a "buffer layer") may be placed on the substrate surface between the substrate surface and the yttrium oxide layer. The intermediate layer can effectively allow the yttrium oxide layer to be processed at high temperatures during the fluorine annealing step without causing the yttrium oxide layer to crack due to stresses caused by the high processing temperature of the fluorine annealing step. The intermediate layer can have physical properties, such as a coefficient of thermal expansion, that reduces the severity or impact of thermal stresses experienced by the deposited yttrium oxide film when the deposited yttrium oxide film is processed during the fluorine annealing step, such as at temperatures exceeding 300 degrees Celsius.

[0061] The intermediate layer can be any layer that effectively reduces or prevents the adverse physical effects of the thermal stress experienced by the deposited yttrium oxide film, preferably preventing cracking or other physical damage to the deposited yttrium oxide film during the fluorine annealing step. The composition, thickness, and preparation method of the intermediate layer can be any composition, thickness, and preparation method suitable for preparing an effective intermediate layer. Examples of intermediate layers can be made of ceramic materials, such as metal oxides, such as aluminum oxide, titanium oxide, zirconium oxide, etc. Example thicknesses can be in the range of 25 to 300 nanometers, for example, in the range of 50 to 200 or 250 nanometers. Example intermediate layers can be applied to the substrate surface by any technique that effectively allows the intermediate layer to function as described and prevents physical damage to the deposited yttrium oxide film during the fluorine annealing step. Specific example techniques include chemical vapor deposition, physical vapor deposition, and atomic layer deposition techniques.

[0062] See Figure 3 , illustrating examples of applicable steps of the method as described and depositing thin films as described. According to method 10, a substrate 20 is provided and, in step (i), an intermediate layer 22 is applied to the surface of the substrate 20. In step (ii), an yttrium oxide thin film 24(a) is applied to the surface of the intermediate layer 22. In step (iii), the substrate 20 having the intermediate layer 22 and the deposited yttrium oxide thin film 24(a) is subjected to a fluorine annealing step, which converts at least a portion of the yttrium oxide of the yttrium oxide thin film 24(a) into yttrium fluoride, thereby producing an yttrium fluoride thin film 24(b).

[0063] Figure 4 The substrate 20, the intermediate layer 22, and the yttrium fluoride thin film 24(b) are shown with added details regarding the composition of the yttrium fluoride thin film 24(b). As shown, the yttrium fluoride thin film 24(b) has a thickness (t1) between the lower surface 32 (adjacent to the upper surface of the intermediate layer 22) and the upper surface 30. Thickness t1 is also the thickness of the deposited yttrium oxide thin film 24(a) as deposited onto the intermediate layer 22.

[0064] Transition region 28, represented by a dashed line, indicates a lower boundary of yttrium fluoride portion 34 extending between surface 30 and transition region 28 and has a thickness t2. Yttrium fluoride portion 34 contains a major amount of yttrium fluoride (YF3) and a minor amount of oxygen, as described herein.

[0065] Thickness t2 of yttrium fluoride portion 34 can be defined as described, for example, by defining transition region 28 at a depth (thickness) where the oxygen concentration in the film initially reaches 20 atomic percent below surface 30, or at a depth (thickness) where the oxygen concentration in the film initially reaches 10 atomic percent below surface 30. In some embodiments, the thickness of the yttrium fluoride portion can be in a range of 10 to 200 nanometers, 10 to 175 nanometers, 10 to 150 nanometers, 10 to 125 nanometers, 10 to 100 nanometers, or any range therebetween.

[0066] Figure 3 The oxygen ([O]2) concentration in example yttrium fluoride portion 34 may be 20 (or 10) atomic percent at thickness locations in transition region 28. The oxygen concentration at thickness locations above transition region 28 is less than 20 (or less than 10) and gradually (if not linearly, then regularly or uniformly) decreases to substantially zero ([O]1) at surface 30. The oxygen concentration at thickness locations below transition region 28, between transition region 28 and lower surface 32, is greater than 20 (or greater than 10) atomic percent.

[0067] Yttrium fluoride thin films, including at least a portion containing a high concentration of yttrium fluoride (YF3) and a low concentration of oxygen, as described, can be effective as protective coatings. The protective coatings are chemically resistant to various process materials, particularly (but not exclusively) acids and plasmas that may be present in various types of processing chambers during operation to perform known or future-developed manufacturing processes, some example processes of which are described herein.

[0068] Compared to previously deposited films made of yttrium oxide or fluorinated yttrium oxide, yttrium fluoride has a substantially higher fluorine concentration. Therefore, the chemical resistance achieved by the yttrium fluoride films described herein can be highly suitable or relatively improved compared to the chemical resistance achieved by previous protective materials.

[0069] Suitable and preferred yttrium fluoride films can also be temperature resistant for extended periods of time, including during use in semiconductor processing tools at elevated temperatures (e.g., in the range of 350 to 500 degrees Celsius). More generally, suitable or preferred yttrium fluoride films can resist degradation for extended periods of time at temperatures up to or exceeding 200, 300, 400, 450, or 500 degrees Celsius.

[0070] A device, apparatus, or article comprising a yttrium fluoride thin film as a protective coating may include a substrate comprising a yttrium fluoride thin film formed on a substrate surface, optionally with an intermediate layer disposed between the substrate and the yttrium fluoride thin film. Advantageously, because the yttrium fluoride thin film can be prepared using two specific processing steps, each involving vapor deposition (i.e., atomic layer deposition of yttrium oxide) and fluorine annealing of the deposited yttrium oxide thin film, the resulting yttrium fluoride thin film can be efficiently and uniformly applied to substrate surfaces that are highly three-dimensional and have a high aspect ratio. Suitable yttrium fluoride thin films can be applied to three-dimensional surfaces comprising channels, grooves, or openings, such as structures having relatively high aspect ratios, such as aspect ratios of up to or greater than 10:1, 20:1, 50:1, 100:1, or greater than 100:1. In some embodiments, the three-dimensional features on the substrate are selected from the group consisting of: a threaded screw, a threaded nut, a porous membrane, a filter, a three-dimensional network, pores, and channels.

[0071] Examples of substrates to which a protective yttrium fluoride coating as described can be applied include objects used in the preparation of semiconductor materials, microelectronic devices, and the like, such as various components of a processing chamber ("processing chamber components"). Yttrium fluoride films, while being resistant to process materials such as acids and plasmas, can be used to protect components of a processing chamber in the presence of these and other process materials during operation.

[0072] Preferred protective coatings can be prepared to include a small number of defects, such as cracks, crevices, pinholes, and other physical defects. Defects such as pinholes, crevices, and cracks can be identified by visual inspection, optionally by magnification using an optical microscope or a scanning electron microscope, or by other suitable inspection methods. Preferred coatings can also be applied to exhibit a high degree of coating thickness uniformity across the coating surface, especially when compared to coatings applied by other methods such as physical vapor deposition. For example, high uniformity can refer to a coating having a thickness of less than 2 microns over an area of 1, 5, or 10 square centimeters and a thickness variation of no more than 20, 10, or 5 percent over said area.

[0073] The protective coating as described can be formed on and used with any surface or substrate to which the yttrium fluoride thin film can be effectively applied. In certain embodiments, the substrate can be made of a vacuum-compatible substrate material and can be in the form of a component of a processing chamber, including an internal component of a processing chamber used to process substrates, materials, or devices using one or more different process materials that are highly reactive, corrosive, or otherwise capable of aggressively degrading or reacting with other materials. In this context, the yttrium fluoride thin film as described can be advantageously applied to a substrate, referred to herein as a "vacuum-compatible substrate," that is formed to serve as a component ("processing component") of a processing chamber used to process microelectronic devices, semiconductor devices and equipment, their precursors, and the like by processing process materials, such as plasma.

[0074] Processing chambers are suitable for containing highly corrosive or reactive process materials, which may be in the form of liquids, gases, or plasmas, such as those used to process microelectronic device substrates or semiconductor device substrates during the steps of fabricating microelectronic or semiconductor devices. Specific examples of reactive process materials include bromine plasma, chlorine plasma, and fluorine plasma, such as those derived from NF3, Cl2, CHF3, CH2F2, SF, or HBr.

[0075] The processing chamber must contain components and surfaces suitable for transporting, holding, securing, supporting, or moving a workpiece into, out of, and within the processing chamber without being unduly degraded by process materials that will be present in the processing chamber. The processing chamber must also contain structural systems that effectively flow, deliver, and remove reactive process materials (e.g., plasma) into and from the interior of the processing chamber.

[0076] Examples of processing chamber components include items of any shape, including flat, planar, substantially two-dimensional surfaces, but also those having more complex shapes. Advantageously, the methods and films of the present invention can be used with substrates having a solid shape or form that is three-dimensional, such as forms including openings, pores, channels, tunnels, threaded screws, threaded nuts, porous membranes, filters, three-dimensional networks, pores, channels, extended surfaces, and the like, including such features that are considered to have high aspect ratios. More specific example structures include: flow heads (shower heads), protective shields, trays, supports, nozzles, valves, conduits, stages for handling or holding substrates, wafer handling fixtures, chamber liners, ceramic wafer carriers, wafer holders, susceptors, spindles, chucks, rings, baffles, and various types of fasteners (screws, nuts, bolts, clamps, rivets, etc.).

[0077] The atomic layer deposition technique and fluorine annealing technique as described are vapor deposition techniques that are effective in providing uniform and high quality deposited thin films on such three-dimensional surfaces, including surfaces having an aspect ratio of at least 10:1, 20:1, 50:1, 100:1, or greater than 100:1.

[0078] The substrate of the processing component on which the yttrium fluoride film may be formed can be made of a variety of different solid materials, including materials sometimes referred to as "vacuum compatible" substrate materials. In general, examples may include ceramic materials, metals, and metal alloys that can be coated with a protective coating and used in processing chambers. Examples of ceramic materials that can be suitable for use as vacuum compatible substrates include aluminum oxide, silicon carbide, silicon, silicon oxide, and aluminum nitride. Examples of metals and metal alloys include nickel, nickel alloys, stainless steel, and aluminum. Vacuum compatible substrates can also be quartz, sapphire, silicon dioxide, fused silica, fused quartz, silicon, anodized aluminum, zirconium oxide, glass, and plastics, such as certain plastics used in the semiconductor industry, such as polyetheretherketone (PEEK) and polyimide. In some embodiments, the substrate can be a wall surface of a plasma etch chamber, a wafer pedestal, a chuck, a shower head, a liner, a ring, a nozzle, a baffle, a fastener, a wafer support, a wafer transport structure, or a portion or component of any of these.

[0079] While this description generally refers to process chambers and process chamber components (e.g., etch chamber components) as suitable substrates for protective coatings as described, the yttrium fluoride thin films described are not limited to use with these objects. As described herein, various other ceramic, mineral, metal, and metal alloy objects and substrates that would benefit from a protective coating that is highly resistant to highly reactive chemical materials can also be treated to have yttrium fluoride thin films placed on their surfaces.

Claims

1. A method for preparing yttrium fluoride, the method comprising: Depositing an aluminum oxide layer onto the substrate to form a surface, depositing an yttrium oxide film onto the surface by atomic layer deposition, and The yttrium oxide film is exposed to molecular fluorine source vapor and elevated temperature to convert the yttrium oxide film into yttrium fluoride, wherein the molecular fluorine source vapor is derived by heating a fluorinated polymer, wherein an outer surface of the yttrium oxide film is converted into yttrium fluoride (YF3), wherein the elevated temperature exceeds 300 degrees Celsius, and wherein the method does not include a plasma.

2. The method of claim 1 , wherein exposing the yttrium oxide film to fluorine and a high temperature forms an yttrium fluoride portion of the yttrium oxide film, the yttrium fluoride portion having a thickness between the surface of the yttrium oxide film and a position below the surface of the yttrium oxide film containing 20 atomic percent oxygen.

3. The method of claim 1, wherein the surface comprises an intermediate layer, and the method comprises depositing the yttrium oxide thin film onto the intermediate layer.

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