Substrates comprising a diamond layer and a composite layer of diamond and silicon carbide and optionally silicon

Abstract

The multilayer substrate includes a CVD-grown diamond layer on a composite layer. The composite layer includes particles of diamond and silicon carbide, and optionally silicon. The loading level of diamond in the composite layer (by volume) can be ≥5%, ≥20%, ≥40%, or ≥60%. The multilayer substrate can be used as an optical device; a detector for detecting radiation particles or electromagnetic waves; a device for cutting, drilling, machining, grinding, lapping, polishing, coating, bonding, or brazing; a braking device; a sealing strip; a thermal conductor; an electromagnetic wave conductor; a chemically inert device for use in corrosive, strongly oxidizing, or strongly reducing environments at elevated temperatures or under cryogenic conditions; or a device for polishing or planarizing other devices, wafers, or films.

Description

[0001] This patent application is a divisional application of patent application with application number 2015800057708, application date January 21, 2015, and invention name “Substrate comprising a diamond layer and a composite layer of diamond, silicon carbide and optionally silicon”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 61 / 931,227, filed January 24, 2014, which is incorporated herein by reference. Background of the Invention Technical Field

[0005] The present invention is a multilayer substrate comprising a diamond layer and a composite layer comprising particles of diamond and silicon carbide, and optionally silicon particles, and a method of making the multilayer substrate. Background Art

[0007] Diamond is the hardest known material, with a Mohs hardness of 10, making it ideal for applications such as cutting, machining, drilling, and grinding. Diamond is also the most thermally conductive material known, with a thermal conductivity of 2,000 to 2,200 watts per degree Kelvin (K), making it well-suited for thermal management applications under demanding conditions. Diamond also has an extremely low coefficient of friction, making it a versatile material for applications such as brakes.

[0008] Diamond is also an excellent optical material for transmitting microwaves, infrared, visible light, and other ultraviolet electromagnetic waves. Diamond also exhibits high stability when used as a high-throughput nuclear radiation detector. Furthermore, diamond is highly inert in chemical environments involving strong acids, bases, strong oxidizing agents, or strong reducing agents, even at high or low temperatures. Furthermore, diamond has a high refractive index, making it popular and highly valued in the jewelry industry.

[0009] Information about diamond can be found in the following references: (1) “Properties, Growth and Applications of Diamond” edited by MH Nazare and AJ Neves, published by The Institute of Electrical Engineers, 2001; (2) “Diamond Films Handbook” edited by Jes Asmussen and DK Reinhard, published by Marcel Dekker, 2002; and (3) “Diamond Films, Chemical Vapor Deposition for Oriented and Heteroepitaxial Growth” edited by Koji Kobashi, published by Elsevier, 2005.

[0010] Although diamond is one of the most versatile and valuable materials, its availability in nature is extremely limited. Furthermore, diamonds mined from the earth are typically single crystals, which are very limited in size and often too small for industrial applications requiring large sizes. Naturally formed diamonds often contain impurities and crystal defects. Diamond crystals that are relatively large, chemically pure, and relatively perfect with no crystal defects are extremely expensive and often priceless.

[0011] Synthetic diamond is known to be produced industrially in chemical reactors under extremely high pressure and temperature, a process known as high-temperature, high-pressure (HTHP) production. Due to the demanding growth conditions, reactor size is typically limited, and therefore the size of diamonds produced by the HTHP process is also limited, not to mention the high costs associated with the process, equipment, and safety. Diamonds produced by the HTHP process often have a yellow tint due to the introduction of catalyst impurities into the diamond lattice.

[0012] Industrially, single-crystal diamond can also be grown in a reactor using a process known as chemical vapor deposition (CVD), where suitable growth conditions can be achieved using microwave-enhanced plasma, tungsten hot filaments, DC jet plasma, laser-induced plasma, acetylene torches, and the like. It is well known in the art that CVD growth processes can also successfully grow polycrystalline diamond thin films and / or free-standing thick diamond films on various substrates, but obtaining low-stress films or large, crack-free diamonds is challenging. However, CVD processes typically produce diamond flakes significantly larger than the diameter of single-crystal diamonds found in nature or grown using HTHP processes. However, diamond growth rates in CVD processes, or any diamond growth process, are typically slow, ranging from less than 1 micron / hour to no more than approximately 10 to 20 microns / hour. While some claims have been made that single crystals can be grown at higher growth rates, these have numerous drawbacks.

[0013] Growing a thick film of diamond on a substrate to form a composite of a diamond film layer on a substrate layer is challenging because the physical and chemical properties (e.g., thermal conductivity, electrical conductivity, coefficient of thermal expansion, Young's modulus, etc.) between diamond and the substrate on which it is grown are very different, resulting in significant stress. Chemically, the substrate material needs to be capable of carbide formation (i.e., bonding between atoms of the substrate's chemical element and carbon atoms), which can form an interface with a certain affinity for other carbon-bonded materials to adhere, at least by virtue of surface physical interactions (e.g., van der Waals forces), allowing diamond crystals to seed thereon, while also bridging some of the chemical differences between the diamond and the substrate. Silicon, tungsten, molybdenum, silicon carbide, tantalum, niobium, etc. are carbide formers, where the carbon from the carbide provides a certain anchoring mechanism for diamond adhesion. This may be why existing technologies have shown some success in depositing diamond layers on this type of substrate under certain growth conditions. However, the interaction between diamond and substrate is likely to be at best at the level of physical interaction via van der Waals forces, or at a chemical level with some carbon-carbon bonding, not to mention the lattice mismatch between the diamond lattice and the metal carbide lattice, for which the carbon-carbon bonds between the diamond carbon and the substrate carbon will be imperfect, thereby creating stress defects at the interface that lead to failure.

[0014] Regarding physical properties, diamond and substrate materials are also very different. For example, silicon has a thermal conductivity of 149 W / mK, tungsten is 173 W / mK, molybdenum is 138 W / mK, tantalum is 57.5 W / mK, niobium is 53.7 W / mK, etc., while diamond has a thermal conductivity of 2000 to 2200 W / mK. Silicon has a thermal conductivity of 2.7×10 -6 The thermal expansion coefficient of tungsten is 4.6×10-6 / m / mK, molybdenum is 4.8×10 -6 / m / mK, tantalum is 3.6×10 -6 / m / mK, niobium is 4.0×10 -6 / m / mK, etc., while diamond only has 1.0×10 -6 / m / mK thermal expansion coefficient. Silicon has a resistivity of 103Ω-m, and tungsten is 52.8×10 -9 Ω-m, molybdenum is 53.4×10 -9 Ω-m, tantalum is 131×10 -9 Ω-m, niobium is 152×10 -9 Ω-m, etc., while diamond has 10 11 Resistivity in Ω-m. Herein, when used as units to express numerical values, "m" = meter and "K" = degree Kelvin.

[0015] In addition to the inherent limitations imposed by the chemical bond between diamond and the substrate (if any), the significant differences in physical properties between diamond and such substrate materials also pose challenges in growing thick diamond films or layers on these substrate materials without delamination. As one might imagine, diamond films grown by CVD on these substrates can exhibit high stresses before delamination from the substrate, which sometimes occurs during deposition and sometimes after the reaction has ceased. Even if a diamond film survives delamination, the film (most often a thin film) still exhibits high stresses, which is highly unfavorable for various applications because the film can delaminate while standing or when being used for a different purpose.

[0016] Existing techniques exploit the exfoliation behavior of diamond films on substrates to separate the diamond film from the substrate and produce a self-supporting diamond film, but this is difficult. The exfoliation process can involve significant stress. Consequently, thick diamond films can break into numerous small pieces, making it difficult to obtain a crack-free thick diamond film. As the diameter or geometric dimensions of the diamond film or layer increase, maintaining the geometry without cracking becomes even more challenging or impossible, whether for thick or thin diamond films or layers. Sometimes the diamond film partially exfoliates, leaving some substrate areas with unexfoliated diamond, which can hinder the substrate from being reused for the next diamond film growth. Because diamond is the hardest material on Earth, grinding away the residual diamond film from the substrate is difficult, time-consuming, and expensive. Even if the diamond film survives the exfoliation, it (even at a small size) is extremely brittle and difficult to handle, making the practical industrial application of self-supporting diamond films impossible.

[0017] In many practical applications, a unique and complete composite consisting of a diamond layer on a substrate layer, with minimal or less stress between the diamond layer and the substrate layer, no cracking or breaking, or no risk of cracking or breaking during storage or use, is highly desirable. Sometimes, a thin diamond layer supported on an inexpensive substrate is advantageous, exhibiting minimal or less stress, allowing for successful use under the demanding conditions of machining, drilling, cutting, grinding, and the like. Sometimes, a composite consisting of a thick diamond layer on a geometrically larger substrate layer, exhibiting minimal or less stress, no cracking, or minimal cracking, is desirable in applications such as optics, thermal management, friction control, and mechanical applications (e.g., drilling, machining, cutting, grinding, and the like). Summary of the Invention

[0018] Disclosed herein is a multilayer substrate comprising a diamond layer and a composite layer containing diamond particles and silicon carbide particles and optionally silicon particles. The diamond layer in the multilayer substrate has low or minimal stress as confirmed by Raman spectroscopy, and the diamond layer can be a thin diamond layer or a thick diamond layer, which is determined by the requirements of the application and the diamond growth method. In addition to physical interactions (such as van der Waals forces) and possible chemical interactions (if any) between the diamond seed carbon-carbon bonding to the metal carbide of the substrate (there is a large lattice mismatch between the diamond lattice and the metal carbide lattice at the interface between the silicon carbide and the diamond seed), the diamond layer can be formed at the diamond lattice level by sp 3 Carbon-carbon bonds connect to exposed diamond particles in the surface of a composite comprising diamond and silicon carbide, and optionally silicon, and are firmly anchored to the composite layer. Furthermore, the physical properties of the diamond layer and the composite layer have additional advantages, such as Young's modulus, thermal conductivity, and thermal expansion coefficient. These advantages (possibly due to the chemical anchoring mechanism and physical property similarities between the diamond layer and the composite layer) enable the multilayer substrate to be used in applications such as (but not limited to) mechanical applications (drilling, cutting, machining, or milling), thermal management (electronics, lasers, optics, semiconductors, or light-emitting devices), detectors (high-energy radiation particles, ultraviolet light, and probes), optical mirrors (mirrors or lenses), friction control (braking systems), electromagnetic and acoustic wave management (sound conduction), chemical inertness, wear control (e.g., pump seals or underground borehole seals), or in areas where temperature fluctuations may be relatively high and high-pressure control is critical. However, the scope of the present invention is not limited by the explanation provided in this disclosure.

[0019] Also disclosed is a method for manufacturing a multilayer substrate comprising a diamond layer and a composite layer comprising diamond particles, silicon carbide particles, and optionally silicon particles. The method comprises preparing the composite layer comprising diamond particles, silicon carbide particles, and optionally silicon particles. During this process, the composite layer or a preform thereof may be machined, ground, polished, cut, drilled, or otherwise processed. Subsequently, a thin or thick diamond layer is formed or deposited on the composite layer by, but not limited to, chemical vapor deposition.

[0020] Chemical vapor deposition of the diamond layer may include, but is not limited to, microwave plasma chemical vapor deposition, hot filament chemical vapor deposition, DC jet / thermal plasma chemical vapor deposition, combustion spray plasma chemical vapor deposition, laser-assisted chemical vapor deposition, and the like.

[0021] The multilayer substrate can be further processed (e.g., cut, grind, machine, drill, grind, bond, braze, or polish, coat, etc.) for applications such as mechanical applications (drilling, cutting, machining, or grinding, etc.), thermal management (electronics, lasers, optics, semiconductors, or light-emitting devices, etc.), detectors (high-energy radiation particles, ultraviolet light, and probes, etc.), optical mirrors (mirrors or lenses, etc.), friction control (brake systems), electromagnetic and acoustic wave management (sound conduction, etc.), chemical inertness, wear control (e.g., pump seals or underground borehole seals), or fields where temperature fluctuations may be relatively high and high stress control is critical, or large geometric sizes may be required, or rapid heat removal or transport is required, or wear resistance or friction resistance is required, or the excellent properties of diamond are required but solid pieces of diamond are too expensive.

[0022] Various preferred and non-limiting embodiments or aspects of the present invention will now be described and set forth in the following numbered clauses:

[0023] Item 1: A multilayer substrate comprising: a composite layer comprising diamond particles and silicon carbide particles; and a chemical vapor deposition (CVD) grown diamond layer located on the composite layer, wherein the diamond of the diamond layer is grown by CVD on the crystal surfaces of the diamond particles and / or the silicon carbide particles constituting the composite layer.

[0024] Item 2: The multi-layer substrate of Item 1, wherein the diamond layer comprises polycrystalline diamond.

[0025] Item 3: The multilayer substrate of Item 1 or 2, wherein the composite layer further comprises silicon particles.

[0026] Item 4: The multi-layer substrate of any of Items 1 to 3, wherein the diamond layer is one of: undoped; doped with an n-type element or compound; doped with a p-type element or compound; or doped with boron.

[0027] Item 5: The multi-layer substrate of any of Items 1 to 4, wherein the diamond layer is patterned or selectively etched.

[0028] Item 6: The multilayer substrate of any of Items 1 to 5, wherein the diamond particles in the composite layer have a concentration gradient in the composite layer between 0% and 100%.

[0029] Item 7: The multilayer substrate of any of Items 1 to 6, wherein the loading level (by volume) of diamond particles in the composite layer is one of: ≥5%; ≥20%, ≥40%, or ≥60%.

[0030] Item 8: The multilayer substrate of any one of Items 1 to 7, wherein the thickness of the diamond layer is one of: between 10 -9 m to 10 -6 Between meters, between 5×10 -6 m to 20×10 -3 Between 500×10 -6 m to 10×10 -3 Between meters, between 1×10 -6 m to 5×10 -3 Between meters, between 3×10 -6 m to 3×10 -3 Between 50×10 -6 m to 50×10 -2 Between 100×10 -6 m to 10×10 -2 Between 200×10 -6 m to 5×10 -2 meters, or between 500×10 -6 m to 2×10 -2 Between meters.

[0031] Clause 9: The multilayer substrate of any one of clauses 1 to 8, wherein the thickness of the multilayer substrate is one of the following: ≥200×10 -6 m, ≥20×10 -3 m, ≥40×10 -3 m, ≥75×10 -3 m, ≥50×10 -6 m, ≥500×10 -6 m, or ≥1×10 -3 rice.

[0032] Item 10: The multilayer substrate of any one of items 1 to 9, wherein the multilayer substrate has one of the following shapes or a combination of two or more of the following shapes: circular, square, rectangular, polygonal, elliptical, curved, spherical, non-spherical, cylindrical, conical, concave, or convex.

[0033] Item 11: The multi-layer substrate of any of Items 1 to 10, wherein the surface of the diamond layer is grown or polished to desired roughness and flatness values.

[0034] Item 12: A multilayer substrate as described in any of Items 1 to 11, constructed to be used as one of the following: an optical device; a detector for detecting high-energy radiation particles; a detector for detecting electromagnetic waves; a device for cutting, drilling, machining, grinding, lapping, polishing, coating, bonding, or brazing; a braking device; a seal; a thermal conductor; an electromagnetic wave conducting device; a chemically inert device constructed for use in a highly corrosive environment, a strongly oxidizing environment, or a strongly reducing environment at high or low temperatures; or a device for polishing or planarizing semiconductor devices, wafers or films, optical devices, wafers or films, and or electronic devices, wafers or films.

[0035] Item 13: The multi-layer substrate of any of Items 1 to 12, wherein the optical device is a planar optical mirror or a non-planar optical mirror.

[0036] Item 14: The multi-layer substrate of any of Items 1 to 13, wherein the planar optical mirror is a mirror or a lens.

[0037] Item 15: The multilayer substrate of any of Items 1 to 14, wherein the non-planar optical mirror is spherical, aspherical, conical, or cylindrical.

[0038] Clause 16: The multilayer substrate of any of clauses 1 to 15, wherein the optical device comprises an optical coating for managing electromagnetic waves.

[0039] Item 17: A method of forming a multilayer substrate as described in any one of Items 1 to 16, comprising: (a) forming a composite layer comprising diamond and silicon carbide; (b) placing the composite layer on a substrate support of a reactor; and (c) growing a diamond layer on the composite layer placed on the substrate support of the reactor, wherein the diamond of the diamond layer is grown directly on the crystal surfaces of the diamond particles constituting the composite layer.

[0040] Clause 18: The method of any of Clauses 1 to 17, wherein the composite layer further comprises silicon.

[0041] Clause 19: The method of any one of clauses 1 to 18, wherein step (c) comprises growing the diamond layer on the composite layer by chemical vapor deposition.

[0042] Clause 20: The method of any one of clauses 1 to 19, wherein step (a) further comprises machining, grinding, polishing, cutting, or drilling the composite layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is an exemplary multilayer substrate comprising a diamond layer and a composite layer, wherein the composite layer comprises diamond and silicon carbide and optionally silicon;

[0044] Figure 2 To show that it can be used to manufacture Figure 1 A diagram of each step of a multi-layer substrate;

[0045] Figure 3 To be able to be used to deposit a diamond layer on a composite layer to form Figure 1 Schematic diagram of an exemplary microwave plasma chemical vapor deposition (CVD) system for a multi-layer substrate;

[0046] Figure 4A For composite layers (similar to Figure 1 SEM image of the surface of the composite layer before CVD deposition of diamond on the composite layer;

[0047] Figure 4B For Figure 4A SEM image of the diamond layer grown on the composite layer after about 20 hours of CVD deposition of diamond on the composite layer;

[0048] Figure 4C For Figure 4A SEM image of the growth surface of the diamond layer grown on the composite layer after about 117 hours of CVD growth of diamond on the composite layer;

[0049] Figure 5 for Figure 4C UV-Vis-NIR reflectance spectrum of the diamond layer after grinding and polishing;

[0050] Figure 6 is an SEM image of the growth plane at the center of a diamond layer grown by CVD on a composite layer containing 70% diamond (by volume);

[0051] Figures 7A-7E for Figure 6 Raman spectra of 5 different positions of the CVD diamond layer are shown;

[0052] Figure 8is an exemplary Raman spectrum of natural single crystal diamond;

[0053] Figures 9A-9D Raman spectra of a CVD optical diamond window collected from the center and edge of the growth and nucleation sides of the diamond window;

[0054] Figure 10 This is an SEM image of the center of the growth surface of a diamond layer grown by CVD on a tungsten substrate;

[0055] Figures 11A-11C for Figure 10 Raman spectra of three different positions of the CVD diamond layer shown in;

[0056] Figure 12 is an SEM image of the growth plane at the center of a diamond layer grown by CVD on a composite layer containing 40% diamond (by volume);

[0057] Figures 13A-13E For Figure 12 Raman spectra obtained at five different positions of the CVD diamond layer shown in;

[0058] Figures 14A-14E Raman spectra obtained at five different locations on a CVD-grown diamond layer deposited on opposite sides of a composite substrate on which a Figure 12 CVD diamond layer shown;

[0059] Figures 15A-15E Raman spectra at five different locations of a CVD-grown diamond layer grown on a composite layer containing 0% diamond;

[0060] Figure 15F is the reference Raman spectrum of natural single crystal diamond;

[0061] Figure 16 Table of Raman data for natural single crystal diamond (native SCD), a grown free-standing diamond window (04A05901), and diamond layers grown on various substrates including the composite layers disclosed herein, namely, tungsten, a composite layer containing 40% diamond particles, a composite layer containing 70% diamond particles, and a SiC / Si substrate without diamond particles (1A178). DETAILED DESCRIPTION

[0062] Reference Figure 1 , disclosed herein is a multilayer substrate 2 comprising at least a diamond layer 4 and a composite layer 6 comprising diamond and silicon carbide and optionally silicon.

[0063] Regardless of the method of manufacturing the diamond layer 4, the diamond layer 4 comprises polycrystalline (including nanocrystalline, microcrystalline, macrocrystalline, and / or single crystal) diamond. Regardless of the method of preparing the composite layer 6, the composite layer 6 comprises diamond particles and silicon carbide particles and optionally silicon particles.

[0064] Surprisingly, thin or thick diamond layers 4 can be grown or deposited on the composite layer 6 without peeling, cracking, or shattering after diamond deposition. Even more surprisingly, the diamond layer 4 grown or deposited on the composite layer 6 has lower stress, as confirmed by Raman peak shifts, which may explain the unique characteristics of the multilayer substrate 2. However, the scope of the present invention should not be construed as limited by the explanations herein.

[0065] The diamond particles in the composite layer 6 may be exposed or partially exposed on the surface of the composite layer 6. Therefore, the diamond layer 4 formed on the composite layer 6 during, for example, the CVD deposition of diamond grows on the crystal surfaces of the diamond particles and / or silicon carbide particles that are part of the composite layer 6, thereby achieving seamless and inherent CC sp of the diamond lattice. 3 Chemical bonding. Thus, unlike the prior art where diamond crystals are seeded onto a substrate surface comprising metal carbides, the bond between the newly grown diamond layer 4 and the diamond particles in the composite layer 6 is inherently strong and well-anchored.

[0066] It is contemplated that the diamond particles located on the surface of the composite layer 6 may not have exposed diamond lattices for CVD growth of the diamond layer 4. More specifically, during the preparation of the composite layer 6, it is contemplated that silicon may react with the diamond particles of the composite layer 6, thereby forming an interfacial layer of silicon carbide on, for example (but not limited to), the exposed surfaces of the diamond particles of the composite layer 6. If the composite layer 6 is processed (e.g., ground or polished) before CVD deposition of the diamond layer 4 thereon, it is contemplated that the interfacial layer of silicon carbide will not be present on the exposed diamond crystal surfaces of the diamond particles of the composite layer 6, and the diamond layer 4 may grow directly on these exposed diamond crystal surfaces and the silicon carbide particles forming the composite layer 6. On the other hand, if the diamond layer 4 is deposited on an unprocessed composite layer 6 (e.g., on the diamond crystal surfaces of the diamond particles in the composite layer 6 including the silicon carbide interfacial layer), it is contemplated that the diamond layer 4 will grow on the silicon carbide interfacial layer and on the silicon carbide particles forming the composite layer 6. The surface of the prior art substrate comprising metal carbide may have a certain degree of affinity for diamond carbon atoms through physical interactions (e.g., van der Waals forces), thereby providing adhesion for the newly nucleated diamond particles located on the substrate surface, or at most a monolayer of carbon-carbon bonds (one carbon atom from the substrate surface of the metal carbide and one carbon atom from the newly seeded diamond particle), although the bonding is expected to be highly defective due to the mismatch between the diamond lattice and the substrate metal carbide lattice. Therefore, it is advantageous to add any amount of diamond particles to the composite system forming the composite layer 6 comprising diamond and silicon carbide and optionally silicon.

[0067] The diamond loading (by volume) contained in the composite layer 6 is preferably ≥5%, more preferably ≥10%, still more preferably ≥20%, even more preferably ≥30%, highly preferably ≥40%, further preferably ≥50% or more, and most preferably ≥60%.

[0068] The composite layer 6 of the multilayer substrate 2 may have a diamond concentration gradient along a certain geometric dimension, the diamond concentration gradient being as low as 0% diamond to as high as 100% diamond.

[0069] The diamond layer 4 can be undoped, p-type doped, or n-type doped. For different applications, the diamond layer 4 can also be patterned or selectively etched.

[0070] The size of the diamond particles contained in the composite layer 6 may range from a few nanometers to hundreds of micrometers or larger. Such diamond particles may be doped with other chemical elements (eg, boron) to achieve other properties (eg, electrical conductivity) for some unique applications.

[0071] The size of the silicon carbide particles contained in the composite layer 6 may range from a few nanometers to hundreds or thousands of micrometers or more. Sometimes, for economic reasons, such silicon carbide particles may contain other chemical impurities.

[0072] The size of the optional silicon in the composite layer 6 can range from a few nanometers to hundreds of microns or larger. The silicon particles can be crystalline or amorphous. The silicon can be of semiconductor grade purity or industrial grade purity.

[0073] The multilayer substrate 2 can have any thickness and can be a circle of any diameter, a square of any size, a rectangle of any size, or any geometric shape of any size, or an irregular geometric shape. The size, dimensions, and shape can be dictated by the application or by the CVD method used to grow or deposit the diamond layer 4 on the composite layer 6.

[0074] The diamond layer 4 can have any thickness. For thin film or coating applications, the thickness can be as thin as a few nanometers to a few microns. Such thin coatings can be diamond or diamond-like carbon in properties such as optical transparency, reflectivity, smoothness, or flatness. For thick film applications, the thickness can be a few microns to a few millimeters or thicker. Preferably, the thickness of the diamond layer 4 ranges from a few nanometers to 5 millimeters, more preferably from 20 microns to 4 millimeters, still more preferably from 50 microns to 3 millimeters, and most preferably from 100 microns to 3 millimeters. For a newly grown diamond layer 4 or a newly grown diamond layer 4 subsequently subjected to different surface finishing techniques (e.g., conventional polishing processes or electron beam polishing processes, which can be applied to thin film diamond or thick film diamond), desired optical surface finishing parameters (e.g., surface roughness and flatness) can be achieved.

[0075] The composite layer 6 can be of any thickness. For example, the thickness of the composite layer 6 can be on the order of several micrometers, several millimeters, several centimeters, or more, depending on its application.

[0076] Depending on the application and the method and reactor size used for chemical vapor deposition of the diamond layer 4 on the composite layer 6, the diameter or maximum lateral dimension of the multilayer substrate 2 may be several millimeters, tens of millimeters, hundreds of millimeters, or even larger.

[0077] Given the mechanical hardness of the diamond layer 4, the diamond layer 4 is highly desirable for products intended for mechanical applications because, at a given thickness, the diamond layer 4 will have a long lifespan and durability, and the chance of failure, which may be caused by stress in the diamond layer 4, is low. Examples of mechanical applications include (but are not limited to) drilling, cutting, grinding, machining, etc. For less demanding environments, only a thin diamond layer 4 may be required. For more demanding processing conditions, a thicker diamond layer 4 can be grown on the composite layer 6, which can extend the lifespan of the multilayer substrate 2 and make the multilayer substrate 2 perform more consistently under those more demanding conditions.

[0078] The thermal conductivity of the diamond layer 4 grown on the composite layer 6 by CVD can enable the diamond layer 4 to be used in thermal management applications, such as (but not limited to) optical applications, electronic applications (heat sinks), aerospace applications, chemical applications, etc., which is hitherto unknown in the art.

[0079] In addition to the thermal conductivity of the diamond layer 4, when the diamond loading in the composite layer 6 is 70%, the composite layer 6 has a thermal conductivity of 625 W / mK or higher (far superior to the thermal conductivity of copper, which is 401 W / mK). At a diamond loading level of 42%, the composite layer 6 has a thermal conductivity of 450 W / mK, which is still higher than the thermal conductivity of copper (401 W / mK). As the diamond loading in the composite layer 6 increases, the thermal conductivity of the composite layer 6 increases from the thermal conductivity of the prior art product (M-Cubed Technology's SSC-702, a composite of silicon carbide and silicon, which is 170 W / mK) to the thermal conductivity of diamond, i.e., 2000 to 2200 W / mK.

[0080] Using a linear model to calculate thermal conductivity, composite layer 6 exhibits a thermal conductivity of 981 W / mK at a 42% diamond loading and 1,521 W / mK at a 70% diamond loading. These unexpected thermal conductivity properties of the composite layer are evident. The unique combination of diamond layer 4 and composite layer 6 in multilayer substrate 2 enables diamond layer 4 to conduct thermal energy from concentrated, hot, and / or heat-generating areas along the lateral or horizontal direction of diamond layer 4 and dissipate this energy vertically into the bulk of composite layer 6. This allows composite layer 6 to be thicker, less expensive, and easier to manufacture than using a pure diamond layer. This is particularly advantageous for applications such as laser optics, electronics, aerospace, or other applications requiring rapid heat removal. Alternatively, it can be used in applications requiring rapid thermal energy transport.

[0081] The diamond layer 4 may optionally be ground and polished to an optical finish and / or may optionally be covered with one or more optical coatings for controlling electromagnetic waves (e.g., microwaves, infrared light, and visible light) or other types of coatings for different purposes (achieved using grinding, polishing, and coating processes well known in the art). Optical devices manufactured using the multilayer substrate 2 may have planar surfaces or may have non-planar surfaces, such as, but not limited to, spheres, cones, cylinders, or any surface that can be used for optical applications in the prior art. The diamond layer 4 of the multilayer substrate 2 may be polished by post-processing or may be grown to a roughness and flatness value range that meets the requirements of practical applications. Other types of coatings may be applied to the surface of the multilayer substrate 2, such as, for example, to the surface of the diamond layer 4 or to the surface of the composite layer 6.

[0082] The dimensional stability of both the diamond layer 4 and the composite layer 6 provide unexpected advantages when used in environments where the properties of the diamond layer 4 are required and where significant temperature fluctuations are experienced. The thermal expansion coefficient of the composite layer 6 is unexpectedly increased from 2.9×10 -6 / m / mK is reduced to 1.5×10 -6 / m / mK (calculated by linear model, its thermal expansion coefficient is reduced to 2.1×10 -6 / m / m·K), and further decreased to as low as 1.2×10 -6 / m / mK (calculated by linear model, its thermal expansion coefficient is reduced to 1.6×10 -6 / m / mK), wherein the composite layer 6 containing 70% diamond particles is almost a diamond-like material (the thermal expansion coefficient of diamond is 1.0×10 -6 / m / mK). This is highly desirable in applications such as braking systems involving friction, which require the excellent wear resistance of diamond and simultaneously involve significant heat generation and subsequent rapid removal of heat without experiencing extreme temperature rises and which may require excellent dimensional stability of the multilayer substrate 2. However, the scope of the present invention should not be construed as being limited to only these applications.

[0083] Diamond is known to be an excellent detector of high-energy particle radiation. The unique composition of the multilayer substrate 2 is less expensive and easier to manufacture, and since it cannot crack or shatter, it has no size limitations. All of these desirable properties make the multilayer substrate 2 viable and economical for use as a transmission mechanism for high-energy radiation, sound, and many other applications.

[0084] Due to the chemical inertness of diamond, the unique composition of the multilayer substrate 2 can be used in demanding applications involving chemically harsh corrosive environments and even high temperatures.

[0085] Additionally or alternatively, as Figure 1 As shown by the dashed lines in FIG, one or more additional diamond layers 4' may be applied to one, or more, sides, and / or the bottom surface of the composite layer 6, as long as the chemical vapor deposition (CVD) reactor used to grow the diamond layer 4' allows. It is contemplated that the diamond 4' may be bonded to or grown on one or more surfaces of the composite layer 6 by any possible means.

[0086] Due to the unique properties of diamond, the surface of the diamond 4 can be patterned or selectively etched for different applications.

[0087] Due to the unique anchoring mechanism of the diamond layer 4 on the composite layer 6, the multilayer substrate 2 can be used as a polishing or planarization conditioner for chemical mechanical planarization or grinding of semiconductor device wafers or films, optical device wafers or films, and / or electronic components, wafers or films.

[0088] A process for manufacturing a multi-layer substrate 2 including a diamond layer 4 and a composite layer 6.

[0089] Reference Figure 2 And continue to refer to Figure 1 , Figure 2 1 is a diagram of various steps that can be used to manufacture a multilayer substrate 2 comprising at least a diamond layer 4 and a composite layer 6 comprising diamond and silicon carbide and optionally silicon. A more detailed process will be disclosed below.

[0090] The first step is the preparation of a composite layer 6 comprising diamond and silicon carbide, and optionally silicon. Diamond particles are mixed with silicon carbide (SiC) particles or a precursor to silicon carbide (SiC), optionally silicon particles, and optionally carbon, wherein the carbon is in the form of graphite, carbon black, and / or a precursor to carbon. The mixture is then used to form a solid article by casting, extrusion, or isostatic pressing. The solid article is optionally heated to a temperature sufficient to form the carbonaceous material.

[0091] The article is then optionally hot-pressed and sintered, or optionally sintered at high temperature and pressure, or at high temperature at atmospheric or atmospheric pressure, or siliconized at high temperature at pressures above atmospheric or atmospheric pressure, at atmospheric or atmospheric pressure, or under vacuum. During the sintering, hot-pressing, or infiltration process, the diamond particles may partially react with the silicon to form silicon carbide, and added non-diamond carbon (e.g., graphite, carbon black, carbon fibers, and / or carbonaceous materials formed at intermediate temperatures) may also react with the silicon to form silicon carbide. The non-diamond carbon source may not completely react with the silicon, and the silicon may not completely react with the diamond and carbon sources. The resulting composite layer 6 may comprise diamond and silicon carbide; may comprise diamond, silicon carbide, and silicon; may comprise diamond, silicon carbide, and carbon; or may comprise diamond, silicon carbide, silicon, and non-diamond carbon. The composite may be machined or processed by any method into any shape or size during or at the end of the process.

[0092] The composite layer 6 prepared in the first step may be optionally ground, polished, cut, or processed by any other method before the second step (which will be described below, i.e., the step of depositing or bonding the diamond layer 4 onto the prepared composite layer 6). As a second step, the diamond layer 4 may be bonded onto the prepared composite layer 6 to form the multilayer substrate 2. The diamond layer 4 may be deposited onto the surface of the composite layer 6 to form the multilayer substrate 2 by a chemical vapor deposition (CVD) method (such as, but not limited to, microwave plasma, hot wire, DC plasma, combustion flame, radio frequency and / or extremely high frequency plasma, laser, etc., which will be described in detail in the following paragraphs).

[0093] The diamond layer 4 may be bonded or deposited onto one side, both sides, or all sides of the composite layer 6 to form a multi-layer substrate 2 .

[0094] As a third step, the prepared multilayer substrate 2 can then be optionally further processed by different processes, including (but not limited to) cutting, drilling, machining, grinding, polishing, coating, bonding, brazing, etc., so as to be used for different applications, including (but not limited to) mechanical applications (such as (but not limited to) cutting, drilling, machining, or grinding, etc.), optical applications (such as (but not limited to) reflectors, lenses, etc.), thermal management (such as (but not limited to) electronics, semiconductors, lasers, rapid heat removal or rapid heat transport, or thermal management under high or low temperature conditions), chemically inert applications (corrosive environments, such as (but not limited to) strong acids, strong bases, strong oxidizing environments, strong reducing environments, high or low temperature conditions), friction control applications (such as (but not limited to) braking systems requiring appropriate friction and rapid thermal control), electromagnetic or acoustic wave management (such as (but not limited to) acoustic wave conduction), wear-resistant elements (such as (but not limited to) pump seals, underground borehole seals, etc.), detectors (such as (but not limited to) high-energy radioactive particles, ultraviolet light, electrodes, etc.), or any other application that can use the multilayer substrate 2.

[0095] A method of making a composite comprising diamond and silicon carbide, and optionally silicon, for use in the present invention.

[0096] Composite layer 2 can be prepared by the method disclosed in US Pat. No. 8,474,362 (incorporated herein by reference), wherein (1) silicon carbide particles and diamond particles are weighed in predetermined amounts and placed in a container, (2) phenolic resin is then added to the container and the mixture is mixed, (3) the resulting mixture is then extruded or cast into a preform in a mold, (4) the extruded or cast preform is then placed in a furnace and carbonized under an inert atmosphere, and (5) the carbonized preform is then infiltrated with silicon metal under vacuum and high temperature for a desired time. The preform removed from the furnace is composite layer 6.

[0097] Alternatively, the composite layer 6 may be manufactured by the methods disclosed in US Pat. Nos. 4,171,339 and / or 4,353,963 (each incorporated herein by reference), wherein the diamond and silicon carbide composite is formed by isostatically pressing a mixture of diamond, silicon, and a silicon carbide substrate or a silicon-silicon carbide substrate. Alternatively, the composite layer 6 may be manufactured by the methods disclosed in US Pat. Nos. 4,417,906, 4,428,755, and 4,453,951 (each incorporated herein by reference), wherein the diamond-silicon carbide composite is prepared by mixing diamond and carbon black in paraffin wax to form a first dispersion, and mixing carbon fibers and carbon black in paraffin wax to form a second dispersion, followed by compacting the two dispersions together to form a double-layer composite, removing the paraffin wax under vacuum, and then siliconizing at high temperature.

[0098] Furthermore, the composite layer 6 may be manufactured in the manner disclosed in US Pat. No. 4,643,741 (incorporated herein by reference), wherein a composite of diamond and silicon carbide is formed by subjecting a mixture of caustic soda-cleaned diamond particles and silicon to a high temperature and high pressure treatment.

[0099] Alternatively, the composite layer 6 may be manufactured by the method disclosed in US Pat. No. 5,010,043 (incorporated herein by reference), which is similar to the method disclosed in US Pat. No. 4,643,741 except that the step of washing the diamond particles with caustic soda is omitted.

[0100] Still further, the composite layer 6 can be manufactured in the manner disclosed in US 6,939,506 and / or US 7,060,641 (all incorporated herein by reference), wherein a composite of diamond and silicon carbide is prepared by sintering / infiltrating a ball-milled mixture of microcrystalline diamond particles and amorphous silicon powder so that some of the amorphous silicon is partially converted into nanocrystalline silicon at 600°C and into nanocrystalline silicon carbide at a higher temperature.

[0101] Alternatively, the composite layer 6 may be manufactured by the method disclosed in US 7,959,841 (a method for manufacturing a composite of diamond and silicon carbide) or US 8,168,115 (a method for manufacturing a high-strength abrasive compact of a composite of diamond and silicon carbide) (both incorporated herein by reference).

[0102] Alternatively, the composite layer 6 may be manufactured in the manner disclosed in US 2011 / 0283629 (incorporated herein by reference), wherein a high-strength diamond-silicon carbide compact having less than about 2% unreacted silicon and about 1% graphite is produced by mixing a mixture of diamond of different particle sizes and silicon of different particle sizes and then hot pressing the mixture.

[0103] The diamond layer is deposited on a composite layer comprising diamond and silicon carbide and optionally silicon to produce the present invention. Multilayer substrate method.

[0104] The diamond layer 4 can be deposited on the composite layer 6 by chemical vapor deposition in the manner disclosed in any one of US 5,250,149, US 5,628,824, or US 5,523,160 (all incorporated herein by reference), wherein the chemical vapor deposition conditions are: microwave plasma, using methane and hydrogen as reaction gases, vacuum, high temperature, and controlled microwave power.

[0105] The diamond layer 4 can be deposited on the composite layer 6 in the manner disclosed in US Pat. No. 5,015,494 (incorporated herein by reference), wherein a microwave plasma reactor operating at 2.45 GHz is used, and acetylene, ethylene, methanol, ethanol, or methane is used as a carbon source together with hydrogen gas to deposit the diamond film onto the substrate. The patent further discloses that nitrogen and boron containing chemicals can also be introduced into the reaction system together with the carbon and hydrogen containing gases.

[0106] US 4,958,590 (incorporated herein by reference) teaches the deposition of diamond onto a substrate at a growth rate of approximately 6 micrometers per hour using a gas mixture of hydrogen, methane, and carbon dioxide in a 2.45 GHz microwave plasma reactor. US 5,660,894 (incorporated herein by reference) discloses a method for depositing diamond onto a silicon substrate using a microwave plasma and a reaction gas mixture of acetylene and carbon dioxide. US 5,749,966 (incorporated herein by reference) discloses the deposition of polycrystalline, nanocrystalline diamond, and diamond-like carbon by using a microwave plasma and controlling the reaction gas composition (a mixture of hydrogen, methane, oxygen, and argon) at different growth temperatures ranging from 250° C. to 950° C. and a selected bias voltage. US 6,110,541 (incorporated herein by reference) discloses the deposition of diamond films on silicon substrates from a gas mixture containing methane using a microwave plasma, optionally with a negative bias applied during the nucleation phase. US 7,115,241, US 7,452,420, US 7,713,507, US 7,754,180, and US 2010 / 0116197 (all incorporated herein by reference) disclose growing single crystal diamond by chemical vapor deposition using microwave plasma from a gas mixture of nitrogen and methane, wherein the nitrogen concentration ranges from 0.5% to about 5%.

[0107] US5,270,114 (incorporated herein by reference) discloses depositing a diamond layer of approximately 350 microns thick onto a silicon single crystal by microwave plasma chemical vapor deposition (CVD) from a gas mixture of hydrogen and methane in a two-stage process after scraping the surface of the silicon single crystal with diamond powder. The diamond film is then stripped by chemical etching. The patent also discloses using CVD to consolidate and infiltrate porous or irregular surfaces of a substrate, wherein the substrate comprises particles of diamond, silicon carbide, tungsten, tungsten carbide, molybdenum, and silicon. More specifically, the substrate is prepared by chemically removing metal from a polycrystalline diamond compact, wherein the polycrystalline diamond compact is made by: (1) metal-coated diamond particles, and (2) pressing the metal-coated diamond particles together under relatively high pressure and temperature conditions, wherein the metal coating melts, thereby causing the underlying diamond grains to partially grow together. The substrate after the metal is removed by acid etching comprises a porous diamond substrate having CVD diamond deposited therein, which infiltrates the pores and consolidates the porous diamond substrate into a solid diamond sheet, resulting in improved physical properties of the porous diamond substrate. US 6,344,149 (incorporated herein by reference) discloses a similar process in which CVD diamond is used to infiltrate a porous surface created by removing a catalyst from a diamond-metal composite.

[0108] As disclosed in US Pat. Nos. 5,479,874, 5,445,106, 5,437,891, 5,437,728, 5,424,096, 5,391,229, 5,286,524, 4,970,986, and / or 5,523,121 (all incorporated herein by reference), a hot filament reactor may be used to deposit a diamond layer 4 on a composite layer 6 by chemical vapor deposition in order to produce a multilayer substrate 2. In this process, a gas mixture of hydrogen and a hydrocarbon (e.g., methane), sometimes together with some nitrogen, is used as a feedstock and is heated to a suitable dissociation temperature (controlled by a hot filament), at which the hydrogen molecules are converted into hydrogen radicals, and the original hydrocarbon (where methane is used) is converted into various intermediate hydrocarbon radicals, such as CH3, CH2, CH, etc. The substrate is maintained at a temperature that promotes the transition from hydrocarbon radicals to diamond nucleation and growth.

[0109] To manufacture the multilayer substrate 2, the diamond layer 4 may also be deposited by chemical vapor deposition using a method similar to that disclosed in US Pat. No. 5,270,077 (incorporated herein by reference, which discloses a method using a convex substrate of molybdenum to resist stress of a diamond film during and after lift-off).

[0110] The multilayer substrate 2 can also be manufactured in the manner disclosed in US 5,190,823 (incorporated herein by reference), wherein a silane layer is applied to a molybdenum substrate, enabling the thickness of the diamond deposited in a hot filament reactor to be increased from 10 to 20 microns to 100 microns, or even up to 300 microns, without peeling off.

[0111] The multilayer substrate 2 can also be manufactured by the method disclosed in any of the following U.S. patent documents. U.S. Pat. No. 6,414,338 (incorporated herein by reference) discloses a method for depositing diamond on a molybdenum foil as a substrate using a reaction gas mixture of hydrogen and methane by rhenium hot filament plasma. U.S. Pat. No. 6,981,465 (incorporated herein by reference) discloses a method for chemical vapor deposition of diamond onto a silicon substrate using hot filament plasma. U.S. Pat. No. 4,707,384 (incorporated herein by reference) discloses a method for depositing a diamond film onto a transition metal carbide, nitride, nitride carbide, oxycarbide, and boride substrate using a hot filament CVD process. In the latter patent, making the diamond film adhere to the substrate is a challenge, and the patent discloses how to insert an intermediate layer between the diamond film and the substrate to achieve a stronger adhesion of the diamond film to the substrate. This intercalated interlayer is primarily titanium carbide, which has a good affinity for diamond through monolayer bonding (primarily through physical interactions via van der Waals forces). US2005 / 0064097 (incorporated herein by reference) discloses a method for growing a diamond film of several microns on an iron-based substrate by pre-treating with boron to form an iron boride. The diamond film did not delaminate. However, the diamond film had a stress of 2 GPa and a Raman shift of 1332.54 cm for single crystal diamond. -1 to 1335cm -1 , the positive displacement is about 2.5cm -1, which means that there is significant compressive stress on this diamond film. The patent discloses that the stress will be reduced when the diamond thickness is only 80nm to 300nm thick. It is reported that diamond films of about 40-50 microns have a stress of up to 8GPa, as determined by Raman shift, and some of the diamond films have a stress of 1.4GPa. As disclosed in US 5,952,102 (incorporated herein by reference), removing cobalt metal from a tungsten carbide substrate by a hot wire method for mechanical applications allows diamond films with a stress of 500MPa and over 30 microns to adhere better to the tungsten carbide. US 6,042,886 (incorporated herein by reference) discloses that by roughening the surface of the grinding tool, a hot wire CVD diamond film is made to adhere to the surface of the grinding tool, otherwise the diamond will not adhere, most likely because the diamond film has a large amount of stress. In addition, US2005 / 0276979 and US2005 / 0025973 (both incorporated herein by reference) disclose the use of a hot-filament CVD method to deposit an 8 to 200 micron diamond film around diamond grit (10 to 75 microns), wherein the diamond grit is implanted on the surface of a 2-inch diameter silicon carbide and silicon composite; the disclosed products are used for CMP (chemical mechanical planarization) pad conditioning, heat sinks, and wear elements.

[0112] Alternatively, the polycrystalline diamond layer 4 may be deposited on the composite layer 6 by chemical vapor deposition similar to that taught in US Pat. Nos. 5,403,399 and 5,368,897 (both incorporated herein by reference), wherein hydrogen and gaseous carbon are excited under arc discharge jet plasma or DC thermal plasma conditions to deposit diamond onto a silicon substrate. The diamond layer 4 may be deposited on the composite substrate 6 by the method disclosed in US Pat. No. 5,314,652 (incorporated herein by reference), wherein a free-standing diamond film having a thickness of between 200 and 1000 microns is deposited by using DC arc plasma and applying an intermediate layer of titanium nitride, titanium carbide, hafnium nitride, zirconium nitride, aluminum nitride, or aluminum oxide, and separated from a molybdenum substrate. US Pat. No. 5,507,987 (incorporated herein by reference) discloses a method for depositing diamond films using DC jet plasma to obtain free-standing diamond films having a thickness of up to 1270 microns. US 5,792,254 (incorporated herein by reference) discloses the use of DC plasma and a gas mixture of hydrogen and methane to grow diamond films on surface-treated graphite substrates. US 5,897,924 (incorporated herein by reference) discloses the use of microwave plasma to grow diamond on glass substrates. US 7,306,778, US 7,771,823, and US 7,767,184 (all incorporated herein by reference) disclose the use of DC plasma and acetylene as a carbon source to deposit sub-100 nm diamond layers on polycarbonate substrates. US 2010 / 0178730 (incorporated herein by reference) discloses a DC plasma CVD apparatus for depositing an 80 micron diamond film onto a molybdenum substrate. US 7,833,581 (incorporated herein by reference) discloses a method of forming a diamond film to coat a metal substrate (eg, titanium) by increasing the deposition temperature through multiple steps throughout the growth of the diamond film.

[0113] US 5,480,686 and US 5,418,018 (both incorporated herein by reference) disclose forming a polycrystalline diamond layer by deposition on a composite layer using a water-based plasma discharge by chemical vapor deposition. This process involves alcohols and hydrocarbons as carbon sources and water as an oxygen source for reactive oxygen etching of graphite materials.

[0114] US Pat. Nos. 5,433,977, 5,505,158, and 5,665,430 (all incorporated herein by reference) disclose the formation of polycrystalline diamond layers by chemical vapor deposition under combustion flame conditions using a torch generated by high-purity oxygen and acetylene gas. These patents disclose the deposition of diamond films typically 10 microns thick onto composite substrates made of tungsten carbide and cobalt and / or silicon nitride substrates. US Pat. No. 5,491,028 (incorporated herein by reference) discloses a method for depositing diamond films onto WC-Co (tungsten carbide-cobalt) composite surfaces using a combustion flame, with the addition of a high-temperature binder to improve the adhesion of the diamond.

[0115] US 5,902,563 (incorporated herein by reference) discloses that deposition of polycrystalline diamond layers can be performed by chemical vapor deposition, wherein a gas mixture of hydrogen and methane is excited under radio frequency (RF, 3 kHz to 300 GHz) plasma, or very high frequency (VHF, 50 to 300 MHz) plasma conditions to deposit diamond onto silicon and or molybdenum substrates.

[0116] US 5,302,231 (incorporated herein by reference) discloses that polycrystalline diamond layers can be deposited by chemical vapor deposition, where hydrogen is insufficient and other alternative chemicals, such as halocarbon molecules (CCl4, CF4, CBr4, and CI4), are used to replace the typical hydrogen and methane for diamond growth. US 5,071,677 (incorporated herein by reference) discloses a method for depositing diamond onto a substrate at high temperature using a gas mixture capable of supplying carbon, hydrogen, and halogens.

[0117] US 5,154,945 (incorporated herein by reference) discloses that polycrystalline diamond layers can be deposited from a gas mixture of methane and hydrogen, from pure carbon in the form of carbon ash, by chemical vapor deposition using an infrared laser. US 4,948,629 (incorporated herein by reference) discloses that polycrystalline diamond layers can be deposited from organic acids using an ultraviolet laser.

[0118] US 5,474,808 (incorporated herein by reference) discloses that a polycrystalline diamond layer may be deposited directly onto a composite surface that has been seeded by applying diamond particles, optionally mixed with an aqueous or non-aqueous liquid.

[0119] US 2008 / 0256850 (incorporated herein by reference) discloses a method for coating diamond sheets with silicon carbide of varying thicknesses for the purpose of producing oxidation resistance and unique optical characteristics. US 2002 / 0015794 (incorporated herein by reference) discloses a method for coating CVD diamond with a thin layer of carbide / ductile metal film, which is then bonded to a cemented carbide layer (which contains nickel, cobalt, iron, or an alloy containing one or more of these metals). Self-supporting CVD diamond is expensive, and large sheets of CVD diamond are difficult to obtain. This process appears to be uneconomical. However, this treatment may be applicable to the diamond layer surface of the multilayer substrate of the present invention comprising at least a diamond layer and a composite layer, wherein the composite layer comprises diamond and silicon carbide and optionally silicon.

[0120] Characterization methods

[0121] Scanning electron microscopy (SEM) images were collected on a Tescan's Vega scanning electron microscope equipped with an energy dispersive analysis X-ray (EDAX) detector.

[0122] Raman spectra are collected by confocal Raman microscopy. Laser Raman spectroscopy is widely used as a standard for characterizing diamond, single crystal or polycrystal. Laser Raman spectroscopy provides easily distinguishable characteristics of each different form (allotrope) of carbon (such as diamond, graphite, buckyballs, etc.). Combined with photoluminescence (PL) technology, Raman spectroscopy provides a non-destructive way to study various properties of diamond, including phase purity, crystal size and orientation, defect level and structure, impurity type and concentration, and stress and strain of diamond crystals and films. Specifically, at 1332 cm -1 The width of the primary diamond Raman peak (full width at half maximum, FWHM) and the diamond peak and graphite peak (D band at 1350cm -1 The G band is at 1600 cm -1 ) is a direct indicator of diamond quality. In addition, the stress and strain levels in diamond grains and films can be estimated from the diamond Raman peak shift. It is reported that the diamond Raman peak shift rate is about 3.2 cm under hydrostatic pressure. -1 / GPa, and the peak shifts to lower wavenumbers under tensile stress, while the peak shifts to higher wavenumbers under compressive stress. The Raman spectra presented herein were collected using a confocal microscope with a 514 nm excitation laser. More information on the use of Raman spectroscopy to characterize diamond can also be found in references (1) A.M. Zaitsev, Optical Properties of Diamond, 2001, Springer and (2) S. Prawer, R.J. Nemanich, Phil. Trans. R. Soc. Lond. A (2004) 362, 2537-2565.

[0123] Reflectance UV / Vis / NIR spectra were collected by UV / Vis / NIR (ultraviolet / visible / near infrared) spectrometer.

[0124] Density was determined by water immersion according to ASTM C135-86.

[0125] Young's modulus was measured by ultrasonic velocity according to ASTM E494-95.

[0126] The coefficient of thermal expansion (CTE) was determined by dilatometry according to ASTM E 831.

[0127] Thermal conductivity was measured by the laser flash technique according to ASTM E 1461.

[0128] Diamond chemical vapor deposition by microwave plasma.

[0129] Diamond chemical vapor deposition enhanced by microwave plasma is known in the art and has been discussed extensively herein. Figure 3 The schematic diagram of the microwave plasma CVD system used in the deposition of the diamond layer 4 on the composite layer 6 is shown. Specifically, a reaction gas mixture containing hydrogen and methane is flowed into the microwave plasma CVD reactor, and the flow rates of hydrogen and methane are controlled by independent mass flow controllers. The discharged gas flows out of the CVD reactor and usually flows into a vacuum pump. Microwaves are usually generated by a magnetron and are guided into the reactor through a quartz window. Inside the reactor, the microwave energy is converted into plasma and hydrogen molecules are excited into hydrogen radicals, and methane molecules are excited into methyl radicals (CH3), methylene radicals (CH2), methine radicals (CH3), and secondary or tertiary radicals containing two or more carbons. A substrate holder for supporting the substrate is provided at the bottom of the reactor. A composite layer 6 comprising diamond and silicon carbide and optional silicon is provided on the substrate holder.

[0130] When the plasma is turned on, excited radicals containing carbon bombard the surface of the substrate, thereby achieving carbon fixation under the action of the so-called "hit and stick" mechanism. Hydrogen radicals then bombard the fixed surface carbon species (still containing hydrogen atoms) and extract hydrogen atoms from the fixed carbon species, resulting in the formation of surface carbon radicals that are used to form C-C bonds with fewer hydrogen atoms until all hydrogen atoms are extracted. Some pure carbon-carbon bonds may be sp in nature. 3 (which is ideal for the diamond lattice.) Some pure carbon to carbon bonding may be inherently non-ideal sp 2 , because it is essentially graphitic. However, hydrogen radicals are more capable of stripping sp from the diamond lattice than 3 Carbon strips sp from graphite faster 2 carbon.

[0131] It is well known in the art that, in addition to growth temperature, the concentrations of hydrogen and methane in the gas mixture are key parameters for diamond growth if the plasma size is adjusted to sufficiently cover the substrate surface. The microwave power and pressure within the CVD reactor are highly dependent on substrate size. For the purposes of seeding, depositing, and growing high-quality diamond, those skilled in the art should be able to adjust their plasma to the appropriate size to cover substrates of varying sizes by following the procedures and instructions disclosed herein.

[0132] Example 1: Preparation of a composite layer 6 comprising diamond and silicon carbide and optionally silicon, which is used to prepare Make a multi-layer substrate 2.

[0133] The detailed process for making the composite layer 4 comprising diamond and silicon carbide and optionally silicon is disclosed in Examples 4 and 5 below and in US Pat. No. 8,474,362 (incorporated herein by reference). The basic process is (1) a predetermined amount of diamond particles (76 micron diameter, 300 micron diameter, 500 micron diameter) and silicon carbide (54 grit, 240 grit, or 500 grit) are mixed with a binder (phenolic resin) and reagent grade alcohol and then cast into a rubber mold under vibration and periodically remove the liquid from the surface. (2) The mold is then placed in an oven and heated at 140°C for 2 to 3 hours. The oven and the rubber mold containing the contents (called a preform) are then cooled to ambient temperature. The preform is then removed from the rubber mold and placed on a graphite plate, which is then placed in a furnace with an inert atmosphere. The interior of the furnace in which the preform is placed is then maintained at an elevated temperature (e.g., 650° C.) for 2 hours and then cooled to room temperature, thereby carbonizing the preform. The preform is then soaked in phenolic resin and carbonized a second time under similar conditions. (3) The preform is then placed in a graphite boat along with the silicon block, which is then placed in a vacuum sintering furnace. The furnace is evacuated, for example, to a pressure below 0.1 Torr, and the internal temperature of the furnace is raised to approximately 1450° C. and maintained for 1 hour. The internal temperature of the furnace is then lowered to room temperature. As a result, the silicon metal has melted and infiltrated the preform and reacted with carbon, which may be from diamond, graphite, and carbonaceous matter, to form silicon carbide, thereby producing a composite comprising diamond and silicon carbide and optionally silicon (if some excess or unreacted silicon remains).

[0134] An alternative procedure involves omitting the steps of adding alcohol and casting into a rubber mold, and instead performing the steps of extruding a mixture of silicon carbide, diamond, and phenolic resin in a mold to form a preform. The preform is then carbonized at high temperature (e.g., 600°C) in an inert atmosphere, followed by siliconization in a vacuum at 1483°C for a period of time. This alternative procedure produces a fully dense, i.e., porosity-free, composite layer 6. The resulting composite layer 6 contains diamond and silicon carbide, and optionally silicon (if excess or unreacted silicon remains in the composite layer 6).

[0135] Table 1 below shows the physical properties (including density, Young's modulus, coefficient of thermal expansion (CTE), and thermal conductivity) of a composite layer 6 (made according to the above method) comprising diamond and silicon carbide and optionally silicon (if excess or unreacted silicon is present) compared to the physical properties of a standard product of a reaction bonded silicon carbide (RBSC) composite. As can be seen in Table 1, as the diamond content (or loading) increases from 0% to 42% and to 70% (by volume), the density of the composite layer 6 increases from 2.95 g / cm3 to 3.95 g / cm4, respectively. 3 Increased to 3.27g / cm3 And increased to 3.30g / cm 3 At the same time, the Young's modulus increases from 350 GPa to 630 GPa and to 700 GPa, respectively. It is noted that the increase in both density and Young's modulus is not exactly linear with the increase in diamond loading level, which is unexpected. The density of pure diamond is reported to be about 3.52 g / cm 3 , and the Young's modulus of pure diamond is about 1,220 GPa. However, as the diamond loading level in the composite increases, physical properties such as density and Young's modulus become increasingly similar to those of pure diamond.

[0136] Table 1 also shows that as the diamond loading level (by volume) increases from 0% to 42% and to 70%, the coefficient of thermal expansion (CTE) increases from 2.9×10 -6 / m / mK is reduced to 1.5×10 -6 / m / mK, and reduced to 1.2×10 -6 / m / mK, while the thermal expansion coefficient of pure diamond is 1.0×10 -6 / m / mK. Calculations using a linear model predict that the thermal expansion coefficient of a composite containing 42% diamond will only decrease to 2.1×10 -6 / m / mK, and the thermal expansion coefficient of the composite containing 70% diamond is only reduced to 1.6×10 -6 / m / mK, which is very surprising. However, such results further indicate that as the diamond loading level (by volume) increases, the composite layer 6 comprising diamond and silicon carbide and optionally silicon becomes increasingly similar to diamond in terms of diamond physical properties, particularly in terms of thermal expansion coefficient.

[0137] Although increasing the diamond loading level (by volume) increases the thermal conductivity from 170 W / mK for RBSC Std. to 450 W / mK for the composite layer 6 containing 42% diamond, and to 625 W / mK for the composite layer 6 containing 70% diamond (much better than the thermal conductivity of pure copper (401 W / mK)), these thermal conductivities are still far lower than the theoretically predicted thermal conductivity (calculated by the linear model) (981 W / mK for the composite layer 6 containing 42% diamond and 1521 W / mK for the composite layer 6 containing 70% diamond), which is highly unexpected. However, these results still support the conclusion that as the diamond loading level increases, the composite layer 6 containing diamond and silicon carbide, and optionally silicon, becomes increasingly similar in physical properties to pure or natural diamond.

[0138] Table 1. Comparison of density, Young's modulus, coefficient of thermal expansion (CTE), and thermal conductivity of composite layers comprising diamond and silicon carbide, and optionally silicon, with standard reaction bonded silicon carbide (RBSC) composites comprising silicon carbide and silicon.

[0139] nature RBSC Std. RBSC+42% diamond RBSC+70% diamond <![CDATA[Density (g / cm 3 )]]> 2.95 3.27 3.30 Young's modulus (GPa) 350 630 700 CTE, 20-100℃( / K) <![CDATA[2.9×10- 6 ]]> <![CDATA[1.5×10- 6 ]]> <![CDATA[1.2×10- 6 ]]> Thermal conductivity (W / mK) 170 450 625

[0140] Using a process similar to the above-described procedures and processes, multiple sheets of composite layers 6 comprising diamond and silicon carbide, and optionally silicon, having different geometric dimensions were prepared and used as substrates for chemical vapor deposition of diamond layers 4 in a microwave plasma reactor, which will be further described below, and the method of chemical vapor deposition of diamond by microwave plasma discussed previously will be described.

[0141] Example 2: Diamonds are continuously grown on the exposed diamond particles of the composite layer 6 to secure the diamond layer 4. Solidly anchored to the diamond particles in the composite layer 6 comprising diamond and silicon carbide and optionally silicon.

[0142] A composite layer 6 (68 mm in diameter and 12 mm in thickness) containing 40% (by volume) diamond and the balance being silicon carbide and possibly silicon was used as a substrate in a microwave plasma chemical vapor deposition (CVD) reactor. A mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into the microwave plasma CVD reactor. After starting the plasma, the microwave power and reactor pressure were adjusted so that the size of the plasma covered the composite layer 6, and the temperature of the composite layer 6 was controlled at 820°C by cooling the substrate holder supporting the composite layer 6 in the microwave plasma CVD reactor. After chemical vapor deposition of the diamond layer 4 on the composite layer 6 for about 20 hours, the reaction was stopped and the multilayer substrate 2 was removed from the microwave plasma CVD reactor and analyzed by optical microscopy, scanning electron microscopy, and Raman scattering spectroscopy. The results of the Raman spectroscopy study confirmed that the grown diamond film or layer 4 was intact and that the newly grown diamond layer 4 was of high quality with a wavelength of about 1332 cm -1 After about 20 hours of growth, the diamond layer 4 was estimated to have a thickness of about 30 microns.

[0143] Figure 4A FIG. 4 shows an SEM backscattered image of the surface of the composite layer 6 before the composite layer 6 is used for chemical vapor deposition of the diamond layer 4 thereon. Due to the difference in electron density, Figure 4A The diamond particles in the composite layer 6 are shown as dark images, silicon carbide is shown as a gray continuous phase, and silicon is shown as discrete light gray filling the composite pores, which shows that the composite layer 6 containing diamond, silicon carbide, and silicon is highly dense. The diamond particles in the composite layer 6 exposed at the surface of the composite layer 6 have a maximum size between about 10 and 30 microns.

[0144] like Figure 4B As shown in the multi-layer substrate, after growing a diamond layer 4 of about 30 microns onto the surface of the composite layer 6 for about 20 hours, it was surprisingly found that the grown diamond particles grew larger and small diamond crystals grew in the silicon carbide and silicon regions of the composite layer 6.

[0145] Then it will Figure 4B The multilayer substrate was returned to the microwave CVD reactor for an additional 117 hours of diamond deposition under the same gas flow conditions. The multilayer substrate was then removed from the CVD reactor, and the diamond layer 4 was found to be intact, which was surprising, as the thickness of the diamond layer 4 was estimated to be approximately 190 microns. Previously, a diamond layer 4 approximately 190 microns thick would typically be separated from the molybdenum or tungsten substrate. It was further surprising to find that the original diamond crystals were now 100 microns or larger, while the small diamond grains noted between the large diamond grains after 20 hours of growth had grown from a few microns to approximately 20 to 30 microns, as shown in Figure 2. Figure 4C shown.

[0146] Based on the foregoing observations, a multilayer substrate 2 comprising a diamond layer 4 and a composite layer 6 (containing diamond and silicon carbide and optionally silicon) has many advantages. Chemically, the diamond layer 4 continues to grow onto exposed diamond crystals on the surface of the composite layer 6 at the lattice level. It can be imagined that the diamond layer 4 is firmly anchored to the matrix of the composite layer 6. This lattice anchoring can result in the multilayer substrate 2 being inherently strong. This advantage ensures that the multilayer substrate 2 has excellent performance and excellent ability to withstand many physical and chemical challenges (such as mechanical applications involving large amounts of external forces, stresses, and temperature fluctuations). This advantage also enables the growth of a diamond layer 4 of any thickness on the composite layer 6, as long as the CVD reactor allows.

[0147] Example 1 above shows that, from a physical property perspective, as the diamond loading level increases, the composite layer 6 becomes increasingly similar to the diamond layer 4. This similarity in physical properties enables the two different layers of the multilayer substrate 2 to interact better, thereby helping to more effectively withstand external stresses, particularly the thermal expansion coefficients of the diamond layer 4 and the composite layer 6, which results in the advantage of lower thermal stress due to temperature fluctuations.

[0148] As the diamond loading level in the composite increases, the area of ​​physical interaction between the silicon carbide or silicon and the seed diamond particles decreases, and the area of ​​chemical interaction through the diamond lattice increases. It is believed that the interaction due to van der Waals forces may be more effective than that due to chemical bonding (particularly sp in the diamond lattice). 3The interactions generated by C-C bonding are smaller. All of these observations suggest that the multilayer substrate 2 has advantages over the prior art. However, the scope of the present invention is not limited by the description provided herein.

[0149] The multilayer substrate 6 comprising the diamond layer 4 (approximately 190 micrometers thick) and the composite layer 6 containing 40% (by volume) diamond, the balance being silicon carbide and possibly silicon, is ground and polished to a polished finish. Figure 5 As shown, the UV-Vis-NIR reflectance spectrum of the diamond layer 6 was collected from a wavelength of 2500 nm to a wavelength of 300 nm at a reflection angle of 8° (substantially allowing only reflected light to be collected from a single surface). The single surface reflectance in this spectrum is in good agreement with the reflectance index of high-quality diamond corresponding to these wavelengths.

[0150] Example 3: Low stress or reduced stress thick diamond layer 4 chemically anchored to composite layer 6.

[0151] A composite layer 6 (140 mm in diameter and 10 mm in thickness) comprising 70% by volume of diamond particles and the balance being silicon carbide and possibly silicon was used as a substrate for chemical vapor deposition of a diamond layer 4. A mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into a microwave plasma CVD reactor (see Figure 3 ). After initiating the plasma, the microwave power and reactor pressure were adjusted so that the plasma covered the composite layer 6. The substrate temperature was then controlled at 820°C by cooling the substrate holder. After approximately 17 hours of chemical vapor deposition of the diamond layer 4, the reaction was terminated and the multilayer substrate 2 was removed from the microwave CVD reactor. An approximately 30-micron diamond layer 4 was observed to adhere to the composite layer 6. The multilayer substrate 2, with an approximately 30-micron diamond layer 4 on the composite layer 6 comprising approximately 70% diamond, was then returned to the microwave CVD reactor for continued diamond growth, for a total growth time of approximately 130 hours. The diamond microwave chemical vapor deposition reaction was then terminated again, and the multilayer substrate 2 was removed from the microwave CVD reactor. An approximately 200-micron diamond layer 4 adhered to the composite layer 6 comprising 70% diamond. This multilayer substrate 2 was then returned to the microwave reactor for further diamond growth, for a total growth time of approximately 290 hours. After terminating the reaction, the multilayer substrate 2 was removed from the microwave CVD reactor. Surprisingly, approximately 450 microns of diamond layer 4 remained bonded to composite layer 6. Typically, a diamond layer 4 of approximately 450 microns thick on a substrate (e.g., tungsten) with a diameter of 140 mm would be very susceptible to delamination. This multilayer substrate 2, including the diamond layer 4 and the composite layer 6 containing diamond, silicon carbide, and optionally silicon, is defined as substrate 1A175.

[0152] Figure 6An SEM image of the growth surface at the center of a diamond layer 4 (deposited in a microwave CVD reactor for approximately 290 hours) on a 140 mm diameter composite layer 6 (substrate 1A175) containing 70% diamond is shown. The diamond grain size appears to be greater than several hundred microns, with smaller diamond grains still in the process of growth observed.

[0153] Figures 7A-7E The Raman spectra of the diamond layer 4 of substrate 1A175 at five different locations (i.e., center, north edge, east edge, south edge, and west edge) are shown. The diamond characteristic Raman peaks are located at 1332.75 cm -1 、1333.27cm -1 、1333.52cm -1 、1332.45cm -1 、1332.89cm -1 , with an average of 1332.98cm -1 The Raman peak width (full width at half maximum, FWHM) is 3.20 cm -1 、3.40cm -1 、3.82cm -1 、3.43cm -1 , and 4.29cm -1 , with an average of 3.63cm -1 The baselines of these Raman scattering spectra are flat, and sp associated with graphitic carbon are virtually undetectable. 2 The diamond layer 4 of substrate 1A175 is therefore of high quality, even across the entire surface of a multilayer substrate 2 having a diameter of 140 mm. Raman data for natural single-piece diamond (SCD), a self-supporting diamond window (04A05901), and diamond grown on various substrates (including the composite layers disclosed herein) are shown in ( Figure 16 )middle.

[0154] In order to better evaluate the quality of the diamond layer 4 from the multilayer substrate 2, Raman spectra of high quality natural single crystal diamond (natural SCD) were collected and used as a baseline. One of these spectra was plotted in Figure 8 The characteristic Raman peak of this natural single crystal diamond is located at 1332.53 cm -1 The Raman peak width (full width at half maximum, FWHM) is 4.04 cm -1 Moreover, the baseline of the Raman spectrum of this single crystal is very flat, and no sp associated with graphitic carbon can be detected. 2 Characteristics of carbon-carbon bonds. By comparison Figure 8 Raman spectra of the single crystal diamond and the diamond layer 4 of the multilayer substrate 2 (substrate 1A175, Figures 7A-7E) It can be observed that not only the quality of the diamond layer 4 of the multilayer substrate 2 is high, but also the diamond stress of the diamond layer 4 of the multilayer substrate 2 is low, which can be seen from the Raman peak (1332.53 cm) of the single crystal diamond. -1 ) was confirmed, with a shift of +0.22 cm at the center. -1 , the displacement at the north edge is +0.74cm -1 The displacement at the eastern edge is +0.99 cm -1 The displacement at the southern edge is -0.08 cm -1 , and the displacement at the western edge is +0.36cm -1 , with an average of +0.45cm -1 These results indicate that the diamond stress of the diamond layer 4 of the multilayer substrate 2 (substrate 1A175) is exceptionally low when the thickness is approximately 450 microns and the diameter is 140 mm. Generally, the diamond stress of a diamond film increases with increasing thickness and / or diameter (or size) of the diamond film.

[0155] To further illustrate the quality of the multilayer substrate 1A175, consider the Raman spectrum of a free-standing CVD optical diamond window (substrate 04A05901) (both sides of which have been polished and trimmed for optical applications), as shown in Figure 2. Figures 9A-9D As shown, the spectrum was collected from the center and edge, as well as the growth side and the nucleation side. The diamond characteristic Raman peak of the self-supporting CVD diamond window 04A05901 is 1332.67 cm -1 、1332.36cm -1 、1332.53cm -1 , and 1332.61cm -1 , with an average of 1332.54cm -1 ; and compared with the Raman peak of single crystal diamond (1332.53cm -1 ) are separated by a Raman peak shift of +0.14 cm -1 、-0.17cm -1 , 0.00cm -1 , and +0.08cm -1 , with an average of +0.01cm -1 This indicates that high-quality, free-standing diamond is not subject to observable stress. The stress in the diamond film 4 of substrate 1A175 arises from the interaction between the two layers of different materials at the interface, namely the interaction between the diamond layer 4 and the composite layer 6 comprising diamond, silicon carbide, and optionally silicon.

[0156] Reference Figure 10-11CTo further illustrate the quality of the multilayer substrate 2 (substrate 1A175) consisting of the diamond layer 4 and the composite layer 6, a 140 mm tungsten substrate (substrate #124) with a thickness of 10 mm was placed in a microwave plasma CVD reactor (see Figure 3 ). A mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into the microwave plasma CVD reactor. After starting the plasma, the microwave power and reactor pressure were adjusted so that the plasma size could cover the tungsten substrate, and the temperature of the tungsten substrate was controlled at 820°C by cooling. After chemical vapor deposition of the diamond layer on the tungsten substrate for 24 hours, the reaction was stopped and the tungsten substrate with the diamond layer was removed from the microwave CVD reactor. The diamond layer remained adhered to the tungsten substrate, and the thickness of the diamond layer was estimated to be less than 30 microns. Typically, growing a diamond layer on a tungsten substrate for 24 hours or longer will cause the diamond layer or film to peel off from the tungsten substrate.

[0157] Figure 10 : is an SEM image of the growth surface at the center of a diamond layer or film grown on (and adhered to) a tungsten substrate (ie, substrate #124) having a grain size of about 20 microns or less.

[0158] Figures 11A-11C The following table shows three Raman spectra from the center, edge 1, and edge 2 of the grown diamond film after overnight microwave CVD diamond growth on a tungsten substrate. The characteristic Raman peaks of diamond are located at 1335.85 cm -1 、1335.87cm -1 , and 1335.85cm -1 , with an average of 1335.86cm -1 Compared with the Raman peak of single crystal diamond (1332.53cm -1 ) are separated by a Raman peak shift of +3.32 cm -1 、+3.34cm -1 , and +3.32cm -1 , with an average of +3.33cm -1 This level of Raman peak shift from single crystal diamond indicates that even if the diamond layer (e.g. Figure 10 Although the thickness of the diamond film is less than 30 microns (as shown in FIG. 1 ), a considerable stress level still exists between this thin diamond layer and the tungsten substrate. If the diamond film were as thick as the diamond layer 4 of the substrate 1A175 described above (approximately 450 microns), the stress of the diamond film on the tungsten substrate would be very high.

[0159] Example 4: For a multilayer substrate 2, the stress of the diamond layer 4 may be affected by the presence of diamond and silicon carbide and any Effect of diamond loading in composite layer 6 of selected silicon.

[0160] First, a composite layer 6 (140 mm in diameter and 10 mm in thickness) containing 40% diamond loading (by volume) and the balance being silicon carbide and optionally silicon was ground with a polishing slurry. Then, its surface was rubbed with diamond powder and rinsed with isopropyl alcohol. The composite layer 6 was then used as a substrate for chemical vapor deposition of the diamond layer 4 in a microwave plasma CVD reactor. After the composite layer 6 was placed on a substrate holder, a mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into the microwave plasma CVD reactor (see Figure 3 ). After the plasma is initiated, the microwave power and reactor pressure are adjusted so that the plasma size can cover the composite layer 6, and the temperature of the composite layer 6 is controlled at 820°C by cooling the substrate holder. A diamond layer 4 is chemically vapor deposited on the composite layer 6 for approximately 301 hours to form the multilayer substrate 2, after which the reaction is terminated. The multilayer substrate 2 is then removed from the microwave CVD reactor. The CVD diamond layer 4 of the deposited multilayer substrate 2 is observed to have a thickness of approximately 480 microns and is bonded to the composite layer 6 comprising diamond, silicon carbide, and possibly silicon. This multilayer substrate 2 is then defined as substrates 1A to 177B.

[0161] Figure 12 An SEM image of the growth surface at the center of a diamond layer 4 (deposited in a microwave CVD reactor for approximately 301 hours) on a composite layer 6 (substrate 1A177B) with a diameter of 140 mm and containing 40% diamond is shown. Diamond grains larger than several hundred microns are observed, while smaller diamond grains are still in the process of growth.

[0162] Figures 13A-13E The Raman spectra of five different positions (i.e., center, north edge, east edge, south edge, and west edge) of substrate 1A177B are shown. The diamond characteristic Raman peaks are located at 1333.67 cm -1 、1334.35cm -1 、1333.43cm -1 、1333.62cm -1 、1333.58cm -1 , with an average of 1333.73cm -1 The Raman peak width (full width at half maximum, FWHM) is 3.20 cm -1 、5.82cm -1 、3.42cm -1 、3.10cm -1 , and 6.43cm -1 , with an average of 4.39cm -1 (Quality close to Raman peak width or half maximum width FWHM at 4.04cm -1The baselines of these Raman scattering spectra are flat, and virtually no sp ions associated with graphitic carbon are detected. 2 The diamond layer 4 is characterized by carbon-carbon bonding. Therefore, the quality of the diamond layer 4 is very high over the entire surface.

[0163] Comparison of Raman scattering spectra of natural single crystal diamond ( Figure 8 ) and the Raman scattering spectrum of diamond from the diamond layer 4 of the substrate 1A177B ( Figures 13A-13E ), it is noted that not only is the quality of the diamond layer 4 of the multilayer substrate 2 good, but also the stress of the diamond in the diamond layer 4 of the substrate 1A177B is less than that of a thin diamond layer (<30 μm) grown on a tungsten substrate (substrate #124; Figures 11A-11C ), which can be seen from the Raman peak of single crystal diamond (1332.53cm -1 ) was confirmed to have a minimal Raman peak shift of +1.14 cm at the center. -1 , +1.82cm at the northern edge -1 , +0.90cm at the eastern edge -1 , +1.09cm at the southern edge -1 , and +1.05cm at the western edge -1 , with an average of +1.20cm -1 ; while the tungsten substrate (substrate #124; Figures 11A-11C ) on thin diamond films (<30 μm) with a +3.33 cm -1 The average Raman peak shift of the multilayer substrate 2 (substrate 1A177B, with composite layer 6 containing 40% diamond particles) is shown in Table 1. These results show that the diamond stress is still particularly low when the thickness of the diamond layer 4 of the multilayer substrate 2 (substrate 1A177B, with composite layer 6 containing 40% diamond particles) is about 450 microns and the diameter is up to 140 mm. However, with respect to the diamond stress of the diamond layer 4, because the composite layer 6 of substrate 1A175 has 70% diamond and the composite layer 6 of 1A177B has only 40% diamond, in fact, the substrate 1A177B ( Figures 13A-13E ) is not as good as substrate 1A175 ( Figures 7A-7E ). Therefore, these results seem to indicate that a higher diamond loading (by volume) in composite layer 6 is more desirable, possibly because (1) composite layer 6 containing a higher diamond loading is more similar to natural diamond in physical properties, and (2) more diamond particles in composite layer 6 are exposed to form CVD-like sp with diamond layer 4. 3 The surface of the composite layer 6 is lattice-bonded to carbon-carbon diamond, so that the newly formed diamond layer 4 is anchored in the matrix of the composite layer 6 comprising diamond and silicon carbide and optionally silicon by chemical interactions at the lattice level.

[0164] Example 5: For a multi-layer substrate 2, the stress of the diamond layer 4 may be affected by the diamond layer 4 in the multi-layer substrate 2. The thickness of the multilayer substrate 2 includes a diamond layer 4 and a layer containing diamond and silicon carbide and optionally silicon. Composite layer 6.

[0165] The side of the multilayer substrate 1A177B with a diameter of 140 mm and a thickness of 10 mm described in the above embodiment 4 opposite to the diamond layer 4 was placed in a microwave CVD reactor for depositing the diamond layer 4' (at Figure 1 4) was deposited onto the surface of composite layer 6 opposite diamond layer 4. A mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into the microwave plasma CVD reactor. After the plasma was initiated, the microwave power and reactor pressure were adjusted so that the plasma volume covered the surface of composite layer 6 opposite diamond layer 4. The temperature of composite layer 6 was then controlled at 820°C by cooling the substrate holder. Chemical vapor deposition of diamond layer 4' continued for approximately 50.5 hours, after which the CVD reaction was terminated. Substrate 1A177B was removed from the microwave CVD reactor, and the deposited CVD diamond layer 4' was observed to be approximately 80 microns thick and adhered to the side of composite layer 6 opposite diamond layer 4. This multilayer substrate 2 is defined as substrate 1A177A.

[0166] Figures 14A-14E The Raman spectra of the diamond layer 4' of the substrate 1A177A at five different positions (i.e., the center, the north edge, the east edge, the south edge, and the west edge) are shown. The diamond characteristic Raman peaks are located at 1333.93 cm -1 、1332.99cm -1 、1333.40cm -1 、1332.93cm -1 、1332.98cm -1 , with an average of 1333.25cm -1 ; Raman peak width (full width at half maximum, FWHM) is 4.68cm -1 、6.35cm -1 、6.48cm -1 、4.42cm -1 , and 5.31cm -1 , with an average of 5.45cm -1 (Quality is not as good as Raman peak FWHM at 4.04cm -1 The single crystal diamond is excellent, but it is still a good quality CVD diamond). Figures 14A-14E The baseline of the Raman spectrum shown is flat, and virtually no sp associated with graphitic carbon is detected. 2 Characteristics of carbon-carbon bonding. Therefore, the quality of the diamond layer 4' is high, and even the quality of the entire surface of the substrate 1A177A is relatively high.

[0167] By comparing natural single crystal diamond ( Figure 8 ) and the Raman scattering spectrum of the diamond layer 4' of the substrate 1A177A ( Figures 14A-14E ), it is noted that not only is the quality of the diamond of the diamond layer 4' good, but also the stress of the diamond of the diamond layer 4' is much smaller than the stress of the thin diamond layer (<30 microns) grown on the tungsten substrate ( Figures 11A-11C ), which can be obtained by comparing with natural single crystal diamond ( Figure 8 ) of the Raman peak (1332.53cm -1 ) was confirmed to be +1.40 cm at the center. -1 , +0.46cm at the northern edge -1 , +0.87cm at the eastern edge -1 , +0.40cm at the southern edge -1 , and +0.45 cm at the western edge -1 , with an average of +0.72cm -1 , while tungsten substrates (such as Figures 11A-11C The thin diamond film (<30 μm) on the surface of the substrate has a 3.33 cm -1 The results show that the diamond stress of the diamond layer 4' of substrate 1A177A (in this case, the composite layer 6 contains 40% diamond particles) is related to the thickness of the diamond layer 4'. It is observed that as the diamond layer 4' on the composite layer 6 of the multilayer substrate 2 grows thicker, the stress of the diamonds constituting the diamond layer 4' increases, which can be observed by a more positive diamond Raman peak shift, indicating greater compressive stress.

[0168] As Figure 1 As shown, diamond layers 4 and 4' can be deposited or formed on both sides of the composite layer 6. Diamond layers 4 and / or 4' can be applied simultaneously or alternatively to all sides of the composite layer 6 comprising diamond and silicon carbide and optionally silicon. Different applications may require this type of multilayer substrate 2.

[0169] Example 6: On a composite layer 6' consisting of reaction-bonded silicon carbide and possibly silicon without diamond particles High stress diamond layer 4 grown by CVD (control group).

[0170] It is believed that a diamond layer 4 (serving as a control) grown on a composite layer 6' composed of reaction-bonded silicon carbide and possibly silicon (without the addition of diamond particles to the composite layer 6') would have high stress and would exhibit a higher Raman peak shift in Raman spectroscopy studies. Therefore, a control composite layer 6' composed of silicon carbide and possibly silicon (without diamond) was used in a control experiment. In this control experiment, the composite layer 6' was placed on the substrate holder of a microwave plasma CVD reactor. A mixture of 1850 mL / min of hydrogen and 13.7 mL / min of methane was flowed into the microwave plasma CVD reactor. After starting the plasma, the microwave power and reactor pressure were adjusted so that the plasma size covered the control composite layer 6'. The temperature of the composite layer 6' was controlled at 820°C by cooling the substrate holder. After about 112 hours of CVD growth of the diamond layer 4 on the composite layer 6', the CVD reaction was stopped and the composite layer 6' (with the diamond layer 4 thereon) was removed from the microwave plasma CVD reactor and the composite layer 6' was defined as the substrate 1A178 ( Figures 15A-15E The diamond layer 4 of substrate 1A178 was analyzed at five different locations by optical microscopy and Raman scattering spectroscopy, wherein the diamond layer 4 on the composite layer 6 ′ (composed of silicon carbide and possibly silicon without added diamond particles) had a thickness of approximately 180 μm.

[0171] Figures 15A-15E The Raman spectra of five different positions (i.e., center, north edge, east edge, south edge, and west edge) of substrate 1A178 are shown. The diamond characteristic Raman peaks are located at 1335.03 cm -1 、1335.33cm -1 、1334.52cm -1 、1334.56cm -1 、1334.56cm -1 , with an average of 1334.80cm -1 The Raman peak width (full width at half maximum, FWHM) is 4.71 cm -1 、3.64cm -1 、3.71cm -1 、3.84cm -1 , and 4.71cm -1 , with an average of 4.01cm -1 (Mass and Raman peak FWHM at 4.04cm -1 The baselines of these Raman spectra are flat, and virtually no sp ions associated with graphitic carbon are detected. 2 Characteristics of carbon-carbon bonding. Therefore, the quality of the diamond layer 4 of the substrate 1A178 is high and uniform across the entire surface.

[0172] By comparing the Raman spectra of natural single crystal diamond ( Figure 15F ) and the Raman spectrum of diamond of the diamond layer 4 of the substrate 1A178 ( Figures 15A-15E ), wherein all of these Raman spectra were obtained substantially simultaneously, it can be confirmed that the quality of the diamond layer 4 of substrate 1A178 is good, but the diamond stress of the diamond layer 4 of substrate 1A178 is substantially higher than the stress of the diamond of substrates 1A175, 1A177B, and 1A177A (discussed above), which can be seen from the fact that the diamond layer 4 of substrate 1A178 has a larger Raman peak (1331.91 cm -1 ) was confirmed to be +3.12 cm at the center. -1 , +3.42cm at the northern edge -1 , +2.61cm at the eastern edge -1 , +2.65cm at the southern edge -1 , and +2.65cm at the western edge -1 , with an average of +2.89cm -1 , while the Raman peak shifts of substrates 1A175, 1A177B, and diamond layer 4 of 1A177A are smaller: 1A175 is +0.45 cm -1 , 1A177B is +1.20cm -1 , and 1A177A is 0.72cm -1 .

[0173] The observed Raman shift of substrate 1A178 is exciting because it demonstrates that the multilayer substrate 2 comprising a diamond layer 4 and a composite layer 6 composed of diamond, silicon carbide, and optionally silicon is unique, unexpected, and highly valuable for various applications.

[0174] The present invention has been described with reference to the accompanying drawings. Obvious modifications and variations will occur to others upon reading and understanding the foregoing detailed description. It is intended that the present invention be construed as including all such modifications and variations as come within the scope of the appended claims or their equivalents.

Claims

1. A multi-layer substrate comprising: a composite substrate layer comprising diamond particles, silicon carbide particles, and silicon particles, wherein the silicon particles react with the diamond particles to form a silicon carbide interface layer, and unreacted silicon penetrates between the diamond particles and the silicon carbide particles to make the composite substrate layer completely dense and free of pores; and a diamond layer grown on at least one of the diamond particles or silicon carbide particles of the composite substrate layer by chemical vapor deposition, wherein the diamond layer comprises polycrystalline diamond, wherein the diamond lattice of the diamond particles of the composite substrate layer is exposed to the surface of the composite substrate layer, so that the silicon carbide interface layer does not exist on the diamond lattice, and the diamond of the diamond layer is sp 3 carbon-carbon bonds to the diamond lattice, The loading level of the diamond particles in the composite substrate layer is 40% to 70% by volume. 2 . The multi-layer substrate according to claim 1 , wherein the diamond layer is patterned or selectively etched. 3 . The multi-layer substrate according to claim 1 , wherein a concentration gradient of the diamond particles in the composite substrate layer is between 0% and 100%. 4 . The multi-layer substrate of claim 1 , wherein a loading level of the diamond particles in the composite substrate layer is greater than or equal to 60% by volume.

5. The multi-layer substrate according to claim 1, wherein the thickness of the diamond layer is between 10 -9 m to 10 -6 Between meters.

6. The multi-layer substrate according to claim 1, wherein the thickness of the diamond layer is between 3×10 -6 m to 3×10 -3 Between meters.

7. The multi-layer substrate according to claim 1, wherein the thickness of the multi-layer substrate is ≥50×10 -6 rice. The multi-layer substrate according to claim 1 , wherein the multi-layer substrate has a circular shape.

9. The multi-layer substrate according to claim 1, wherein the surface of the diamond layer is grown or polished to a roughness value and a flatness value.

10. The multi-layer substrate according to claim 1, configured for use as an optical device. The multi-layer substrate according to claim 10 , wherein the optical device is a planar optical mirror or a non-planar optical mirror.

12. The multi-layer substrate according to claim 11, wherein the planar optical mirror is a reflective mirror or a lens. The multi-layer substrate according to claim 11 , wherein the non-planar optical mirror is spherical or aspherical. The multi-layer substrate according to claim 11 , wherein the non-planar optical mirror is conical or cylindrical.

15. The multi-layer substrate of claim 10, wherein the optical device comprises an optical coating for managing electromagnetic waves.

16. A method of forming the multi-layer substrate of claim 1, the method comprising: (a) forming a composite substrate layer, which includes grinding or polishing the composite substrate layer; (b) placing the composite substrate layer on a substrate support of a reactor; as well as (c) growing a diamond layer on the composite substrate layer placed on the substrate holder of the reactor by chemical vapor deposition.

17. A multi-layer substrate comprising: A composite substrate layer comprising diamond particles, silicon carbide particles, and silicon particles, wherein the silicon particles react with the diamond particles to form a silicon carbide interface layer, and unreacted silicon penetrates between the diamond particles and the silicon carbide particles to make the composite substrate layer completely dense and free of pores; and a diamond layer grown on at least one of the diamond particles or silicon carbide particles of the composite substrate layer by chemical vapor deposition, wherein the diamond layer comprises polycrystalline diamond, The diamond layer is one of the following: undoped; doped with an n-type element or compound; or doped with a p-type element or compound. wherein the diamond lattice of the diamond particles of the composite substrate layer is exposed to the surface of the composite substrate layer, so that the silicon carbide interface layer does not exist on the diamond lattice, and the diamond of the diamond layer is sp 3 carbon-carbon bonds to the diamond lattice, The loading level of the diamond particles in the composite substrate layer is 40% to 70% by volume. The multi-layer substrate according to claim 17 , wherein the diamond layer is patterned or selectively etched.

19. The multi-layer substrate of claim 17, wherein a concentration gradient of the diamond particles in the composite substrate layer is between 0% and 100%.

20. The multi-layer substrate of claim 17, wherein a loading level of the diamond particles in the composite substrate layer is greater than or equal to 60% by volume.

21. The multi-layer substrate according to claim 17, wherein the thickness of the diamond layer is between 10 -9 m to 10 -6 Between meters.

22. The multi-layer substrate according to claim 17, wherein the thickness of the diamond layer is between 3×10 -6 m to 3×10 -3 Between meters.

23. The multi-layer substrate according to claim 17, wherein the thickness of the multi-layer substrate is ≥50×10 -6 rice. The multi-layer substrate according to claim 17 , wherein the multi-layer substrate has a circular shape.

25. The multi-layer substrate of claim 17, wherein a surface of the diamond layer is grown or polished to a roughness value and a flatness value.

26. The multi-layer substrate of claim 17, configured for use as an optical device. The multi-layer substrate according to claim 26 , wherein the optical device is a planar optical mirror or a non-planar optical mirror.

28. The multi-layer substrate of claim 27, wherein the planar optical mirror is a mirror or a lens. The multi-layer substrate according to claim 27 , wherein the non-planar optical mirror is spherical or aspherical.

30. The multi-layer substrate of claim 27, wherein the non-planar optical mirror is conical or cylindrical.

31. The multi-layer substrate of claim 26, wherein the optical device comprises an optical coating for managing electromagnetic waves.

32. A method of forming the multi-layer substrate of claim 17, the method comprising: (a) forming a composite substrate layer, which includes grinding or polishing the composite substrate layer; (b) placing the composite substrate layer on a substrate support of a reactor; as well as (c) growing a diamond layer on the composite substrate layer placed on the substrate holder of the reactor by chemical vapor deposition.

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