Chemical-resistant multilayer coating applied by atomic layer deposition.

Abstract

A method for preparing chemically resistant multilayer protective coatings by atomic layer deposition is provided. [Solution] A method for applying a coating to a substrate includes depositing amorphous alumina on the substrate by atomic layer deposition, and depositing yttria having a crystallinity of less than 10% on the substrate by atomic layer deposition, wherein the coating has a Y / Al atomic ratio in the range of 2:1 to 1:2.

Description

[Technical Field]

[0001] Cross-references to related applications This application claims the interests of U.S. Provisional Patent Application No. 62 / 599,865, filed on 18 December 2017 under 35 U.S.C. 119, and the disclosures of this application are incorporated herein by reference in their entirety for all purposes.

[0002] This specification relates to a multilayer coating applied by atomic layer deposition (ALD), a substrate having a multilayer coating on its surface, and a method for preparing a multilayer coating by atomic layer deposition, wherein the coating comprises at least two layers of different deposition materials containing alumina and yttria. [Background technology]

[0003] The fabrication of semiconductors and microelectronic devices requires processes involving highly reactive process materials, such as plasma. These processes involving highly reactive process materials, such as plasma etching, plasma deposition, and plasma cleaning, are carried out inside a process chamber containing the workpiece being manufactured and the highly reactive process materials. The process chamber also includes components (also known as "reactor components") such as chamber walls, flow conduits (e.g., flow lines, showerheads, etc.), fasteners, trays, supports, and other structures that support the workpiece being manufactured or deliver or contain the highly reactive process materials to the process chamber. For use as part of a process chamber, reactor components should be resistant to the highly reactive process materials that will be used within the process chamber. In particular, reactor components should not be degraded or damaged by the process materials in a manner that would generate debris, particulate matter, or trace metallic contaminants that may enter the process being carried out or potentially contaminate the workpiece being manufactured.

[0004] Reactor components used in the process of fabricating semiconductors and microelectronic devices are frequently made from bases or substrates that are metallic or non-metallic materials such as stainless steel, anodized aluminum, or mineral or ceramic materials. Reactor component substrates are typically coated with a thin film coating that enhances resistance to highly reactive process materials. Traditionally, such protective thin film coatings have been typically applied to substrates by various beneficial methods, such as anodizing (e.g., producing anodized aluminum), spray coating, or physical vapor deposition (PVD). [Overview of the project]

[0005] According to this specification, the coating is a multilayer protective coating applied to the substrate surface by atomic layer deposition, and is made of amorphous alumina (Al y O x ) layer and yttria (Y y O x The coatings of the present invention include at least two distinct layers of deposited material, including a layer of ). Compared to conventional protective coatings such as coatings applied by non-ALD methods, for example by PVD, or to equivalent coatings prepared by ALD methods but not prepared or configured in a manner that results in the advantageous properties of the multilayer coatings exemplified herein (for example, including yttria, alumina, or mixtures of yttria and alumina), the coatings of the present invention are advantageous, and may in some cases advantageous, with respect to their physical structure, performance as a protective coating, or both.

[0006] Therefore, atomic layer deposition can be used to apply multilayer coatings onto substrates, and the multilayer coatings have particularly beneficial physical properties, including one or more of the following: beneficial or advantageous levels of chemical resistance, and beneficial or advantageous levels of fracture resistance. For example, a multilayer coating comprising yttria and alumina layers, where the yttria layer is provided at a selected thickness or input ratio, may be extremely effective for use as a protective coating and may exhibit beneficial or improved physical properties or one or more of the performances described herein. Furthermore, coatings applied by atomic layer deposition as described may also have beneficial coating properties such as very uniform coating over surface area, low levels of defects such as pinholes, cracks, fissures, and grain boundaries, and these beneficial or desired properties may be applied to surfaces that are three-dimensional and optionally have high aspect ratios. In contrast to certain other conventional methods for forming protective coatings on substrates (such as protective coatings used in process chambers as described herein), such as anodizing, spray coating, and physical vapor deposition, using atomic layer deposition can achieve coating of equipment components, which can also be beneficial in the semiconductor and microelectronic device manufacturing industries (among other applications).

[0007] Compared to various other methods for producing thin-film coatings, this disclosure discloses that certain special advantages can be achieved in multilayer coatings prepared by ALD technology. For example, the advantageous properties of the described multilayer coatings, achieved by preparing the multilayer coating to include yttria layers of a preferred thickness or input ratio, may include one or more of the following: a nanocrystalline structure (substantially amorphous) with a crystallite size of less than 10 nm; a desirable full width at half maximum (FWHM) of the X-ray diffraction (XRD) peak of the coating greater than 2.5 degrees 2 theta; a high-density coating (compared to conventional protective coatings); low porosity (compared to conventional protective coatings); and a low level of defects such as pinholes, cracking, fissures, or grain boundaries. In addition, coatings formed by atomic layer deposition may also benefit from: excellent harmony of ALD coatings with substrates (e.g., three-dimensional substrates); precise thickness control on a small scale; large-area uniformity of coatings on surfaces; sharp interfaces with vertically stacked layers; effective and uniform application to surfaces containing non-planar structures such as apertures, channels, or fluid channels with high aspect ratios; and multilayer processing, which allows for the preparation of thin-layer coatings of multiple materials.

[0008] In one embodiment, the present invention relates to a chemical-resistant multilayer protective coating prepared by atomic layer deposition, comprising alternating layers of yttria and amorphous alumina.

[0009] In another aspect, the present invention relates to a coated article comprising a chemical-resistant multilayer protective coating applied to a substrate such as a vacuum-stable substrate, which is prepared by atomic layer deposition and comprises alternating layers of yttria and amorphous alumina, for use as a reaction apparatus component in a semiconductor or microelectronic device fabrication system, such as a reaction chamber used for processing plasma.

[0010] In another aspect, the present invention relates to a method of using a coated article comprising a chemically resistant multilayer protective coating coated on a substrate, the coating being prepared by atomic layer deposition and comprising alternating layers of yttria and amorphous alumina. The coated article can be used as a reactor component of a semiconductor or microelectronic device fabrication system, such as a reaction chamber used for processing plasma.

Brief Description of the Drawings

[0011] [Figure 1] A diagram showing X-ray diffraction data of the multilayer coating herein.

Modes for Carrying Out the Invention

[0012] The following is described: a protective coating in the form of a thin multilayer film applied to a substrate surface by atomic layer deposition; a method of applying a thin film coating by atomic layer deposition; a coated article comprising a substrate having a thin film coating applied to a surface(s); and a method of using a coated article in a processing apparatus, such as a component of a process chamber (alternatively referred to as a "reactor" or "reaction chamber").

[0013] Protective coatings applied by atomic layer deposition, as described herein, may be multilayer coatings prepared to include layers of two different deposition materials, including (e.g.) a layer of yttria and a layer of alumina. The coatings are resistant to process materials that will be present in the process chamber during use for known or future-developed processes, particularly acids and plasma (but not limited to these), specific processes which are described herein as examples. The level of chemical resistance achieved by the multilayer coatings described herein may be greatly beneficial or relatively improved compared to the level of resistance achieved by conventional protective coatings. The type of chemical resistance and the level of resistance to various chemical materials may be a result of the type of material of the multilayer coating and the physical properties of the multilayer coating, such as the density of the coating; the crystallinity and crystalline structure of the coating; the porosity of the coating; the reduction in the presence of defects in the multilayer coating; and the properties of the various layers of the multilayer coating (e.g., thickness), particularly the thickness of the yttria layer.

[0014] For example, beneficial chemical resistance of multilayer coatings can be achieved through the combined effect of the alumina and yttria layers of the coating, particularly the yttria layer of a preferred thickness or input ratio as described. Alumina provides effective or very effective resistance to chlorine and bromine-based plasma exposure, as can be demonstrated by exposure to hydrochloric acid. Resistance to other acids, including phosphoric acid, can also be expected. While the alumina layer of the multilayer coatings herein provides a beneficial or very effective level of resistance to these halogens, alumina may not have particularly high resistance to fluorine-based plasma compositions. On the other hand, a yttria layer may be included in the protective coating to provide beneficial or particularly effective resistance to fluorine-based plasmas. Thus, multilayer coatings herein, comprising a combination of alumina and yttria layers, may be beneficial in providing chemical resistance to a variety of acidic materials (based on the presence of the alumina layer), as well as chemical resistance to all halogen-based plasmas, including halogen-based plasmas such as fluorine-based plasmas (based on the presence of the yttria layer).

[0015] Coated articles may include substrates having multilayer coatings applied to the surface of the substrate in a solid, continuous form or a patterned form. Examples of coated articles include items such as any of the various reactor components of a process chamber used to prepare semiconductor materials, microelectronic devices, etc. By exhibiting resistance to process materials such as acids and plasma, multilayer coatings can be used to protect components of a process chamber in the presence of these and other process materials. Preferred protective coatings are made from layers of deposited material that exhibit resistance to process materials and have a low amount of defects such as cracks, fissures, pinholes, and grain boundaries; as a result, the coating exhibits reduced degradation and particulation when exposed to process materials compared to conventional protective coatings.

[0016] As used herein, the term “multilayer,” as in “multilayer coating,” refers to a coating applied to a surface by a series of atomic layer deposition steps, which involve exposing the surface to a series of gaseous precursor materials that will form multiple different alternating “layers” of the deposit material. The “layers” do not have to be a complete or continuous composition across the surface. If the deposition produces separate, incomplete layers, a multilayer coating may be considered a composite coating. Each amount of deposit material (e.g., alumina or yttria) of a coating, alternating on and between different types of deposit material (e.g., yttria or alumina, respectively), is considered a “layer,” regardless of whether complete or incomplete deposition occurs. A “bilayer” film is made from only two different types of deposit material (e.g., alternating layers of alumina and yttria). A “double layer” is made from only two different layers.

[0017] By atomic layer deposition, each "layer" of the multilayer film described is formed from one or more single layers of deposition material derived from a gaseous precursor such as an aluminum-containing precursor (including AlCl3, Al(CH3)3, etc.) in combination with an oxidizing agent (including O2, O3, H2O, NO, NO2, N2O, CO, CO2, etc.). Each gaseous precursor contains a portion that will be deposited onto the substrate surface or onto a pre-deposited ALD layer to form a "single layer" of the deposited portion of the precursor on the surface, for example, at a "reaction site". According to this specification, a series of atomic layer deposition steps are carried out using different precursor materials to form at least two layers of different types of deposition material (e.g., alternating layers). Different precursors (e.g., AlCl3 and H2O) are individually exposed to the surface in a successive ALD step to form a single type of deposition material (e.g., AlCl3, Al(CH3)3, etc.). y O x ) generates a layer.

[0018] Coatings as described are considered to contain and are referred to as containing multiple "layers" due to a multi-step process in which specific amounts of deposit material are laid on the substrate in an alternating repeating sequence. This specification uses the term "multilayer" to refer to coatings produced by multiple deposition steps by ALD, although discret "layers" of different deposit materials in a coating may be challenging to identify using known techniques. In addition, as discussed above, deposition steps may form incomplete layers (e.g., islands of deposit material), and multiple steps may be considered to form a multilayer coating as a composite of incomplete multiple "layers." Discrete layers may also be formed in some multilayer coatings, which may be detectable using a tunneling electron microscope.

[0019] As used herein, the term “single layer” refers to a certain amount of deposited portion of a precursor deposited (e.g., added or reacted) onto the surface of a substrate or onto a conventional ALD layer such that the deposited material saturates reaction sites on the substrate or a conventional ALD layer; a single layer has a thickness of only a few atoms, i.e., a single layer of atoms or molecules, covering the surface by binding to a limited number of reaction sites on the surface to produce a single layer having a thickness of about 2, 3, or 5 atoms or less.

[0020] Furthermore, as used herein, the term “layer” in describing a “layer” of a multilayer coating’s deposited material means a continuous or pulsed single type of deposited material obtained by depositing one or more single layers of precursor deposits onto a surface, i.e., the result of a precursor material being exposed to the surface and reacting with reaction sites on the surface to provide a desired deposited material that is a functional layer of a multilayer protective coating, e.g., a “layer” of alumina or a “layer” of yttria; the “layer” of the deposited material (e.g., yttria or alumina) can be formed from one or more single layers of the deposited material derived from two or more different gaseous precursor materials.

[0021] Preferred multilayer coatings applied by atomic layer deposition exhibit good adaptability to surfaces of various shapes or forms, including three-dimensional shapes with channels, grooves, or openings, such as structures with relatively high aspect ratios, for example, up to 20:1, 50:1, 100:1, 200:1, 500:1 or more.

[0022] Preferred multilayer coatings can also be applied using atomic layer deposition to exhibit a high level of coating thickness uniformity across the coating surface, compared to coatings applied by other methods, such as physical vapor deposition. Preferably, the coating is compositionally uniform, perpendicular to the thickness of the coating and across the entire length / width of the coating.

[0023] Preferred coatings also have a low level of coating defects such as cracks, fissures, pinholes, or grain boundaries, and one or more of these defects may become larger defects during the lifespan of the multilayer coating in the process chamber. Defects such as pinholes, cracks, fissures, and grain boundaries can be identified by visual inspection using optional magnification with an optical microscope or scanning electron microscope, or by other appropriate inspection methods. Certain preferred multilayer coatings described herein may have substantially fewer pinholes (e.g., a 50, 70, 80, or 90 percent reduction in the amount of pinholes) compared to conventional protective coatings applied by other methods, such as physical vapor deposition, as protective coatings useful for equivalent purposes, such as protective coatings for components of process chambers as described. Examples of preferred protective coatings may also be substantially pinhole-free and substantially grain boundary-free, meaning, for example, that the coating has fewer than one pinhole per square centimeter on average and fewer than one grain boundary per square centimeter on average.

[0024] Preferred multilayer coatings described herein exhibit favorable levels of resistance to process materials used in process chambers, including, but not limited to, acids and plasma, during prolonged exposure to process materials used in process chambers. High levels of resistance to process materials may be at least partially attributable to factors including the type (chemical properties) of the depositing material used to prepare the different layers (e.g., yttria, alumina); films with low or no long-range order (amorphous); high-quality films meaning low levels of defects such as pinholes, cracks, fissures, and grain boundaries; and coatings with low porosity and high density.

[0025] A “resistant” coating is one that, when exposed to process materials such as acids or gas plasma in a process chamber during the use of the process chamber, particularly during prolonged use over periods of weeks or months, undergoes a commercially beneficial and low amount of degradation compared to other conventional protective coatings used in process chambers for processing semiconductor or microelectronic device substrates, such as yttria or alumina coatings applied by physical vapor deposition (PVD), for example. Preferred coatings herein may also have, advantageously, a long and beneficial service life as protective coatings in process chambers, most preferably a significantly longer and more beneficial service life than such conventional protective coatings. Whether a protective coating is degraded or not may be determined by using one of the various techniques commonly used in the art of protective coatings, including visual means such as optical or scanning electron microscopy in which areas of cracks, fissures, or other defects are investigated, or by evaluating the strength of the film’s adhesion to the substrate, where higher adhesion indicates less degradation.

[0026] More preferably, the multilayer film of the present specification can have a relatively high density and low porosity relative to conventional protective coatings such as protective coatings of yttria or alumina applied by physical vapor deposition (PVD) for use equivalently (e.g., components of a process chamber). For example, the density of an ALD coating containing yttria and alumina layers as described can be at least 10 or 20 percent higher than that of a coating applied by PVD with an equivalent composition. The porosity of an ALD coating containing yttria and alumina layers as described can be less than that of a coating applied by PVD with an equivalent composition. The alumina layer applied by ALD can have a density in the range of 3.0 to 4.0 g per cubic centimeter and a porosity of less than 0.5 percent.

[0027] A particular presently preferred multilayer coating deposited on a substrate surface by atomic layer deposition can be a bilayer coating comprising alternating layers of only the following two different deposition materials: a first deposition material that is a substantially amorphous oxide such as alumina (Al y O x ); and a second deposition material that is a layer of yttria (Y y O x ). Particularly preferred coatings can include layers of these two deposition materials and can substantially exclude layers made from any other materials. For example, layers of other materials can be less than 1, 0.5, or 0.1 percent based on the total number of layers of the coating. For example, a preferred multilayer coating can include alternating layers of yttria and alumina totaling from 2 to 10,000 layers.

[0028] The multilayer coatings described are applied by atomic layer deposition (ALD), a technique for depositing thin layers (e.g., thin films) of material onto a surface as a coating. This technique is carried out as a series of vapor deposition steps. Each deposition step involves a single gaseous chemical reactant, typically called a precursor, which is supplied to the surface in a manner that deposits or reacts with the material present on the surface. At least a portion of the precursor (i.e., the deposited portion) reacts with the surface material, and the number present on the surface is limited. A certain amount of precursor is supplied to the surface to react with all the reaction sites, and at this point, the deposited material is said to form a single layer.

[0029] One or more gaseous precursors are provided on the surface, individually and sequentially, as the precursor deposition portion, to react with the surface at reaction sites, or otherwise to deposit on it. The deposition process is self-limiting with respect to the amount of precursor that can react with the reaction sites on the surface, and also with respect to the thickness of a single layer, which is the function of factors including the properties of the surface to which the precursor is applied, including the size of the atoms or molecules being deposited and the number of reaction sites. Through repeated and continuous exposure to different precursors in separate deposition steps, thin film coatings created from multiple layers of different deposition materials (each layer being optionally formed by multiple deposition steps and multiple deposited single layers) can grow on the surface, each layer being a deposition material formed by selectively depositing one or more specific precursors. For comparison, other known techniques for depositing thin films or coatings of material onto a surface include chemical vapor deposition (CVD) and physical vapor deposition (PVD), which deposit material onto a surface as a thin film coating in a continuous and steady manner, during which the deposited material forms a film whose thickness continuously increases within the scope of the deposition process.

[0030] In atomic layer deposition (ALD), the gas phase precursor reacts at reaction sites on the surface of the substrate to which the precursor is deposited. The reaction is limited by the presence of reaction sites on the surface, as the gas phase atoms or molecules of the precursor can only react with a finite number of reaction sites on the surface. Once all of these sites are consumed, a "single layer" is formed, and the deposition and growth of the single layer, including the growth of the thickness of the single layer, is complete. The amount of deposited material deposited on the surface (the deposited portion of the precursor) is called a single layer, which has a characteristic thickness of up to 2, 3 to several angstroms and, based on being coated by ALD, has an extremely uniform thickness across the single layer region (assuming a continuous layer is formed).

[0031] The advantages that can be achieved by multilayer protective coatings prepared by atomic layer deposition and applied to the substrates herein include: excellent harmony of the coating with respect to the substrate; precise control of the coating thickness; high uniformity of coating thickness across the coating area; the ability to apply two or more different deposition materials as different layers of the coating; uniformity of composition throughout the vertical direction of the coating; preparation of coatings with extremely low levels of defects such as pinholes, cracks, fissures, and grain boundaries; the ability to prepare coatings with high density and low porosity; and the ability to apply coatings having these physical properties to substrates including non-planar, highly formed, angled structures, or structures including openings, channels, grooves, etc., including structures with high aspect ratios.

[0032] In a first example of atomic layer deposition, a first gaseous precursor material (e.g., AlCl3) is provided to the surface of a substrate in a reaction chamber (also known as a "reaction apparatus"). The atoms or molecules of the first gaseous precursor react at sites on the surface until all sites are consumed, at which point a single layer of the precursor deposition portion is formed on the surface, and the growth of the single layer is complete. The thickness of the single layer is controlled accordingly and is determined by the number of reaction sites available to the atoms or molecules of the precursor, as well as the size of the deposition portion of the precursor atoms or molecules. In a subsequent step, a second precursor (e.g., an oxidizing agent such as water) may be introduced into the reaction chamber and react with the pre-deposited single layer to form a new single layer on the surface of the pre-deposited single layer. As a result of one or more of these types of deposition steps, the deposited material (e.g., AlCl3) is formed. y O x These are formed on the surface. These steps, in a sequence of multiple steps to deposit a series of single layers, trigger a series of reactions on the surface that produce the deposited material, can increase the thickness of the layers of deposited material.

[0033] As requested, between the deposition of two single layers, or between the deposition of different types of precursors to form layers of two different deposition materials, the gas atmosphere of the reaction chamber may be washed (or "purged") to remove any remaining precursor atoms or molecules, for example, using an inert gas.

[0034] The growth (i.e., increase in thickness) of a multilayer protective coating prepared by atomic layer deposition proceeds in a single-layer sequence and a layer-by-layer sequence. Each layer of the deposition material (e.g., alumina or yttria) is formed by arranging one or more single layers on the surface in a manner that forms the deposition material of the layer, each layer optionally containing chemical reactions between precursor substances. To produce each single-atom or single-molecule layer (single layer), the addition of precursors must be uniformly delivered to the substrate surface to achieve saturation of the reaction sites on the substrate surface. Saturation occurs when all available surface bonding sites are filled with new chemical species resulting from the reaction between the precursor and the surface bonding sites. The resulting surface does not create new bonding sites for the precursor being used, but instead forms bonding sites for the next precursor. After saturation, the surface may be exposed to different precursors (to continue forming the desired layer of the deposition material) or treated to create new bonding sites again. As desired, the process chamber can be cleaned to remove any residual precursors. By alternately supplying a first set or sequence of precursor materials beneficial for forming a first type of deposit material (e.g., alumina) to a substrate together with a second set or sequence of precursor materials (different from the first set or sequence) beneficial for forming a second type of deposit material (e.g., yttria), a thin multilayer coating containing alternating layers of two different deposit materials can be produced in alternating cycles with optional cleaning steps between cycles, each layer having a desired or controlled thickness.

[0035] Precursors for use in atomic layer deposition can be selected to provide beneficial and efficient deposition of the desired material (deposit material) or its reactants onto a surface, thereby forming a layer of the deposit material. Generally, the atoms or molecules of the precursor may chemiadsorb onto the surface of the substrate to which the precursor substance is coated, or react with a pre-deposited single layer of the deposit material. The precursor may be in solid, liquid, or gaseous form that can be effectively introduced as vapor into the reaction chamber and the substrate surface. The vapor pressure of the precursor does not need to be excessively high, as long as the gaseous precursor provides sufficient flow of material to saturate the surface. For example, it may be beneficial if the precursor can be provided in gaseous form with a vapor pressure of about 1 torr at a temperature at which the precursor does not decompose. A beneficial precursor should be stable enough not to react with itself and not decompose on the surface or in the gas phase in order to achieve a self-terminating surface reaction.

[0036] Preferably, the multilayer protective coatings described herein may be multilayer (e.g., dilayer coatings or composite coatings) thin films formed by atomic layer deposition of materials that are essentially composed of, or comprise, a first deposit material and a second deposit material. A preferred first deposit material is alumina in a substantially amorphous form, i.e., AlyOx (with y / x in the range of 1.5 / 3 to 2.5 / 3). A preferred second deposit material is yttria, meaning YyOx (with y / x in the range of 1.5 / 3 to 2.5 / 3). A multilayer coating "essentially composed" of layers of two different deposit materials, e.g., layers of yttria and substantially amorphous alumina, refers to a coating that includes layers of only the two different deposit materials and any layers of any other substance not exceeding 1, 0.5, or 0.1 percent based on the total number of layers of the coating; such a coating is also referred to herein as a "dilayer" coating.

[0037] Alumina as a layer in multilayer coatings can provide a high level of resistance to certain process chemicals such as acids, and can be deposited by atomic layer deposition in a substantially amorphous form, i.e., non-crystalline form, where the FWHM of the XRD peak of the coating is broader than 4 degrees 2 theta.

[0038] An example thickness of an amorphous alumina layer may be at least 1 angstrom, and may be thicker than 1 angstrom as desired, for example, in the range of 1 to 50 angstroms. The alumina layer may be substantially amorphous within the thickness range. However, the thickness of the alumina layer may be selected based on other factors, such as providing a multilayer coating with a desired level of resistance to specific process materials to which alumina is particularly resistant, in order to increase the resistance of the multilayer protective coating to acids. A thickness of 100 nm can be prepared.

[0039] The second deposition material of the multilayer protective coating may be yttria. Yttria can preferably be deposited on the substrate such that the yttria layer and the protective coating as a whole provide a relatively high level of resistance to process materials such as acids and plasma, as well as relatively high fracture resistance and a reduction in the presence of grain boundaries and other defects.

[0040] A preferred multilayer coating may include a layer of yttria deposited on alumina to a thickness (of the yttria layer) that will cause the yttria layer to take the form of an alumina layer and maintain it. The amorphous alumina layer provides an amorphous substrate to which the yttria layer may be coated, which will promote the formation of yttria in an amorphous form. By coating the yttria layer on the amorphous alumina layer, the yttria layer tends to become amorphous when coated to an effective thickness, thereby producing a substantially amorphous multilayer coating that exhibits the desired physical properties described, including chemical resistance, fracture resistance, and the absence of grain boundaries and other defects. Therefore, using amorphous alumina as the depositing material for the layers of a multilayer coating may be preferred as a technique to improve the ability to deposit yttria in an amorphous form and to allow for a low level of crystallinity of the entire multilayer coating. For these reasons, the first layer of the multilayer coating, which is coated on the surface of the substrate, may preferably be a depositing material that naturally tends to be highly amorphous, such as alumina.

[0041] Referring to Figure 1, this graph shows data from tests of example alumina-yttria bilayer ALD coatings as described herein, the example coatings having different input ratios (atoms) of yttria:alumina ranging from 10:1 to 1:10. Details regarding the prepared samples are shown in Table 1. TIFF0007869076000001.tif72170

[0042] Therefore, for example, a coating with a target input Y / Al ratio of 1:10 was prepared from 10 ALD deposition cycles using an alumina-producing precursor after 1 ALD deposition cycle using an yttria-producing precursor. The Y / Al ratio is defined as at% Y / (at% Al + at% Y), and thus it is assumed that oxygen is equally distributed between yttria and alumina in the coating. The measured Y / Al ratio was determined by energy-dispersive X-ray spectroscopy (EDAX). Similar measurements were performed using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The results for 1:1 Y / Al samples are shown in Table 2. Differences between measurements reflect the limitations / characteristics of the technique and would be expected by those skilled in the art. TIFF0007869076000002.tif43170

[0043] Therefore, a multilayer coating with a target input Y / Al ratio of 1:1 would likely have a measured Y / Al ratio in the range of approximately 0.35 to 0.6 (approximately 1:2 to 2:1).

[0044] The tests were performed by X-ray diffraction (XRD) using a grazing incidence attachment to simply detect X-rays diffracted from a thin film surface, as is well known in the relevant technical field. The graph shows the counts per second for 2 theta. The test results demonstrate that increasing the thickness of the yttria layer results in sharper peaks. Sharper peaks indicate a higher level of long-range order with larger crystallite sizes. Referring to Figure 1, 10:1 (yttria:alumina) has an FWHM of 2.501 degrees 2θ, indicating that it has a crystallite size of 33 Å. 8:1 has an FWHM of 3.793 degrees 2θ, indicating that it has a crystallite size of 22 Å. The FWHMs of 1:1, 1:3, and 1:10 are wider than 4 degrees 2θ, indicating that the bilayer is amorphous.

[0045] Surprisingly, multilayer ALD coatings of yttria and alumina with a 1:1 input Y / Al ratio (and measured Y / Al ratios of 2:1 to 1:2) have been found to have significantly reduced crystallinity compared to coatings with higher Y / Al ratios. Amorphous multilayer coatings would be preferable in various coating applications. Accordingly, surprisingly, it has been found that yttria layers can be deposited on amorphous alumina layers with a thickness that allows the yttria layer to be substantially amorphous (e.g., less than 10, 5, or 1 percent crystallinity as measured by X-ray diffraction) or extremely low in crystallinity (i.e., amorphous), for example, such that the FWHM of the coating's XRD peak is broader than 2 degrees 2 theta. Relatively thinner yttria layers tend to form crystalline structures compared to relatively thicker yttria layers—that is, as the thickness of the yttria layer increases, the likelihood of yttria crystallizing increases. Therefore, a thin yttria layer is preferred, sufficient to maintain a separate yttria layer and a low level of crystallinity in the entire multilayer coating containing the yttria layer. An example thickness of the yttria layer in a preferred multilayer coating, as described, may be a thickness that makes the yttria substantially amorphous, and a specific range is, for example, 6 to 12 angstroms, typically about 8 to 10 angstroms.

[0046] According to an example protective coating of the present invention, the multilayer coating is substantially amorphous or has very low crystallinity. Preferred multilayer coatings may have a crystal size of less than 10 nm, i.e., the FWHM of the coating's XRD peak is broader than 2 degrees 2 theta.

[0047] The total thickness of multilayer coatings described herein, such as coatings formed from alternating layers of (amorphous) yttria and amorphous alumina, may be any thickness that provides the desired properties described herein, including good resistance to process materials, high uniformity of coating thickness across the coating area, few defects, high density, low porosity, low crystallinity, and high compositional uniformity. Examples of thicknesses useful for using multilayer coatings as protective coatings on process chamber components are at least 10 nanometers (i.e., at least 0.01 microns), for example, at least 100 nanometers (0.1 microns), which is equivalent to a thickness of 2 microns, preferably 1.0 micron or less.

[0048] Yttria (Y) during multi-layer coating y O x ) and alumina (Al y O x The relative amounts of ) can be selected to provide desired features of the protective coating as described herein, such as one or more of the following: desired resistance to process chemicals; desired low level of crystallinity (and grain boundaries) of the multilayer coating; desired high density and low porosity; low level of defects; and other beneficial and preferred features of the multilayer coating as described. Examples of the relative amounts of yttria and alumina in a multilayer coating consisting of, or essentially made from, substantially amorphous alumina and substantially amorphous or amorphous yttria may be in the range of about 1:50 to 50:1, Al y O x :Y y O x The preferred relative quantities are, for example, in the range of 1:15 to 12:1, or for example, 1:15 to 10:1.

[0049] Yttria (Y y O x ) and alumina (Al y O x In line with these examples of relative quantities, yttria (Y y Ox ) layer and alumina (Al y O x The relative thickness of the layers can be selected to provide a desired balance of one or more desired properties and characteristics, such as those described herein: desired resistance to process chemicals; a desired low level of crystallinity (and grain boundaries) of the multilayer coating; a desired high density and low porosity; and other beneficial and preferred features of the multilayer coating as described. Often, all layers of each type of deposited material in the coating are selected to be approximately the same thickness; all alumina layers are approximately the same thickness, and all yttria layers are approximately the same thickness, although the thickness of the yttria layers may differ from that of the alumina layers. The thickness of each deposited material layer can be selected to provide a desired (low) crystallinity of yttria and high resistance to specific process components. Multilayer coatings as described also have any relative thickness, for example, 1:50 to 50:1, including yttria (Y y O x ) and alumina (Al y O x ) may also include layers. This number may be used to describe separate layers of the multilayer coating or to describe the total thickness of all layers of the multilayer coating combined. In certain embodiments, these two layers (Al y O x :Y y O x The relative thicknesses (separate or combined) may be in the range of 1:15 to 12:1, for example, 1:15 to 10:1.

[0050] Also, Yttria (Y y O x ) and alumina (Al y O x These relative amounts of ) and yttria (Y) in multilayer coatings y O x ) and alumina (Al y O xConsistently with the relative thickness of the layers, the multilayer coating may have relative atomic weights of yttrium and aluminum, which is effective in providing the multilayer coating described, preferably including the desired combination of features and characteristics as described. In an example coating, the relative atomic weights of yttrium (as part of the yttria in the yttria layer) and aluminum (as part of the alumina in the alumina layer) (Y(atom):Al(atom)) may be 1:50 to 50:1, for example, 1:10 to 10:1.

[0051] For example, an atomic layer deposition method effective for preparing beneficial or preferred multilayer coatings, such as those described, consisting of alternating layers of amorphous yttria and amorphous alumina deposition materials, can be carried out using any of a variety of beneficial precursors and process conditions that would be effective in providing the desired multilayer coating, as well as using known commercially available ALD apparatus, process conditions, and techniques. An example ALD process can be carried out by a series of steps, including a separate step of depositing a gaseous precursor onto a substrate surface in a reaction chamber to form a single layer of precursor material on the surface. A second single layer of the second precursor may be deposited (e.g., reacted with) the first single layer to form a layer of deposition material. The cycle of coating these two precursors to form the deposition material can be repeated to increase the thickness of the layer of deposition material.

[0052] For example, to form an alumina layer, a first precursor such as AlCl3 can be introduced to the surface to react with the surface and provide aluminum atoms (with bonded chlorine atoms) bound to the surface; a second precursor (e.g., water, ozone, oxygen) can be introduced to the surface to replace chlorine atoms with oxygen atoms, and alumina (AlCl3) can be formed. y O x) can be formed. An alternative example of an aluminum-containing precursor is trimethylaluminum (TMA). Multiple cycles of these two deposition steps can be carried out in an alternating sequence to produce layers of alumina with increasing thickness. Preferably, as the first layer of an alumina-yttria multilayer film, the alumina layer can be deposited first before the yttria layer, and as a result, the amorphous nature of alumina acts to prevent the subsequently coated yttria layer from forming with a crystalline structure. The processing temperature can be selected to allow the alumina to deposit effectively.

[0053] As an example of the process for forming a yttria layer, a yttrium-containing precursor (e.g., Y(thd)3, thd=2,2,6,6-tetramethyl-3,5-heptanedionate) is introduced to the surface (preferably a pre-coated ALD-deposited amorphous material such as amorphous alumina) to react with the surface, providing yttrium atoms (having bonded thd groups) to the surface. A second precursor (e.g., water, ozone, oxygen) is introduced to the surface to replace the thd groups with oxygen atoms, thereby providing yttria (Y y O x ) can be formed. An alternative example of a yttrium-containing precursor is tris(cyclopentadienyl)yttrium(III(YCp3)). Multiple cycles of these two deposition processes can be carried out in an alternating sequence to produce layers of yttria with increasing thickness. The processing temperature can be selected to allow the yttria to be effectively deposited in a substantially amorphous state.

[0054] These separate deposition processes, or a series of processes for forming a layer of a single deposit material such as alumina or yttria, can be carried out in combination with other intermediate processes, such as cleaning the reaction chamber to purge any remaining gaseous precursors.

[0055] The multilayer coatings described herein can be formed on any surface or substrate on which layers or a single layer of material can be effectively coated by atomic layer deposition, and may be beneficial. In certain embodiments, the substrate may be made from a vacuum-stable substrate material and may also be in the form of components of a process chamber used to process substrates, materials, or devices by using one or more different process materials that are highly reactive, corrosive, otherwise actively degradable, or react with other materials, including internal components of a process chamber. In this context, the multilayer protective coatings described herein can be advantageously applied to substrates that are formed to function as components of a process chamber used to process microelectronic devices, semiconductor devices, and the like, by being treated with process materials such as plasma.

[0056] A process chamber is beneficial for containing highly corrosive or highly reactive process materials, which may be in the form of liquids, gases, or plasmas, used, for example, during the process of manufacturing microelectronic or semiconductor devices to etch the material of a microelectronic device substrate or semiconductor device substrate. Specific examples of highly reactive process materials include, among others, bromine plasma, chlorine plasma, and fluorine plasma. The process chamber must include components and surfaces that are beneficial for transporting, holding, fixing, supporting, or moving the substrate into, out of, and within the process chamber without excessive degradation by the process materials that may be present in the process chamber. The process chamber must also include a system of structures that are effective for flowing, delivering, and removing highly reactive process materials (e.g., plasma) into and out of the process chamber. Examples of different types of process chamber components include flow heads (shower heads), 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.).

[0057] The preferred coatings of the present invention may be particularly useful for preparing coated articles that are beneficial in process chambers as process chamber components. This generally includes articles of this type having any shape, but advantageously includes articles having physical shapes or forms such as openings, apertures, channels, tunnels, threaded screws, threaded nuts, porous membranes, filters, three-dimensional network structures, holes, channels, etc., which are considered to have a high aspect ratio. Unlike conventional methods for depositing equivalent coatings, atomic layer deposition of amorphous coatings as described may be effective in providing uniform, high-quality coatings on such structures, including articles having structures with aspect ratios of at least 20:1, 50:1, 100:1, 200:1, or 500:1.

[0058] Chamber components may be made from a material called a substrate, which may preferably be a vacuum-compatible substrate. Generally, examples may include ceramic materials, metals, and metal alloys that are coated with a protective coating and can be used in a process chamber. Examples of ceramic materials that may be beneficial as vacuum-compatible substrates include alumina, silicon carbide, and aluminum nitride. Examples of metals and metal alloys include stainless steel and aluminum. Vacuum-compatible substrates may also be plastics such as quartz, sapphire, silica, fused silica, fused quartz, silicon, anodized aluminum, zirconium oxide, and certain plastics used in the semiconductor industry, such as polyether ether ketone (PEEK) and polyimides.

[0059] In many cases, this specification refers to process chambers and process chamber components (e.g., etching chamber components) as useful substrates for protective coatings as described, but the coatings described are not limited to these items. Various other ceramic, inorganic, metallic, and metallic alloy articles and substrates that would benefit from protective coatings with a high level of resistance to highly reactive chemical materials may also be coated as described herein.

[0060] Accordingly, the present invention relates to the multilayer coatings described; coated articles and devices including substrates coated with the multilayer coatings described (e.g., process chamber components); apparatus and devices such as reaction chambers or other process apparatuses (including, but not limited to, semiconductor processing apparatuses) including one or more components having protective multilayer coatings as described; and processes and methods using reaction chambers or other process apparatuses to process substrates such as semiconductor devices or microelectronic devices by processing the substrate using, for example, plasma, the substrate, including one or more components coated with protective multilayer coatings as described. Examples of such processing include NF3, Cl2, CHF3, CH2F2, SF3 6、 This includes plasma etching using plasma such as that derived from HBr (e.g., dry plasma etching).

Claims

1. A method for applying a coating to a substrate, The method is, Depositing amorphous alumina onto a substrate by atomic layer deposition, and Depositing yttria with a crystallinity of less than 10% onto a substrate by atomic layer deposition. Includes, The method has an input Y / Al ratio in the range of 1:1 to 1:

10. Yttria is a layer with a thickness ranging from 6 to 12 angstroms. A method for applying a coating to a circuit board.

2. The method according to claim 1, wherein the coating has a thickness in the range of 0.01 to 1.0 microns.

3. The method according to claim 1, wherein the coating is a composite coating of yttria and amorphous alumina.

4. The method according to claim 1, wherein the coating does not contain grain boundaries.

5. The method according to claim 1, wherein the coating is free of pinholes.

6. The method according to claim 1, wherein the substrate is a component of a reaction apparatus for a microelectronic device or a semiconductor manufacturing system.

7. The method according to claim 1, wherein the substrate is a vacuum-compatible substrate.

8. The method according to claim 1, wherein the substrate includes the wall surface of a plasma etching chamber, a wafer susceptor, a chuck, a shower head, a liner, a ring, a nozzle, a baffle, a fastener, a wafer support, a wafer transport structure, or a part or component of any of these.

9. The method according to claim 1, wherein the substrate includes three-dimensional features selected from threaded screws, threaded nuts, porous membranes, filters, three-dimensional mesh structures, holes, and channels.

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