Integrated resistance heater containing niobium and method for fabricating the same

Abstract

A method for forming an integrated resistance heater. The method includes the steps of: applying a metal layer in a pattern onto a beryllium oxide ceramic body, wherein the pattern of the metal layer is connected to a conductor; forming a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so that the substrate is aligned with the ceramic body, wherein the substrate includes ceramic; and forming a heating element by heating the pre-assembly to a bonding temperature of 800°C to 1900°C to bond the substrate to the ceramic body, wherein the pattern maintains integrity when forming the heating element. The metal layer contains 10% to 100% by weight of niobium.

Description

Technical Field

[0001] Claim of Priority

[0001] This application claims the priority of U.S. Provisional Patent Application No. 63 / 491,584, filed on Mar. 22, 2023, the entire content and disclosure of which are incorporated herein by reference.

[0002] 【0,002】This disclosure relates to pedestals for semiconductor processing, particularly pedestals that can be used to heat wafers. In one embodiment, a method is provided for fabricating an integrated resistive heater that functions as a heater and uses a niobium-containing metal layer that can bond a ceramic body.

Background Art

[0003]

[0003] In many high-temperature wafer or thin-film processing applications, the wafer is processed, such as etched, coated, cleaned, etc., and / or the surface energy is activated in a high-temperature processing chamber. To perform the process, a reactive process gas is introduced into the process chamber, and then energy is supplied to achieve a plasma state. The energy supply can be performed by applying an RF voltage to an electrode, such as a cathode, and electrically grounding the anode to form a capacitive electric field in the process chamber. Then the wafer is processed by the plasma generated in the process chamber to etch or deposit material thereon.

[0004]

[0004] During this processing process, the wafer can be supported by a pedestal in the process chamber. Ceramic pedestals have several advantages, including compatibility with high-temperature processing and sufficient corrosion resistance. However, ceramic pedestals are limited to certain types of materials due to considerations of thermal integrity to reduce stress. Problems associated with ceramic heaters include that any metal layer or pattern bonded or embedded in the ceramic is likely to break down due to the generation of cracks, including micro-damage at the interface or within the ceramic body, or delamination at higher temperatures.

[0005]

[0005] In addition to mechanical stress on the base, several processing processes benefit from consistent temperature control, particularly temperature uniformity across the base surface supporting the wafer. Various attempts to provide consistent temperature control complicate the heating configuration and increase the number of control mechanisms. This further increases costs without adequately providing the desired temperature control.

[0006]

[0006] U.S. Patent Application Publication No. 2022 / 0289631 describes a base plate having a top and a bottom, comprising a beryllium oxide composition containing at least 95 wt% beryllium oxide and optionally fluorine / fluoride ions. The base plate may further comprise a heating element optionally containing niobium and / or platinum, and optionally a coiled and / or crimped heating element and / or antenna.

[0007]

[0007] U.S. Patent Application Publication No. 2017 / 0295612 discloses an integrated resistance heater. The heater comprises a beryllium oxide (BeO) ceramic body having a first surface and a second surface. A heating element is formed from a metal foil or metallized paint and printed on the upper or second surface of the beryllium oxide ceramic body. The heating element may be formed from a refractory metallized layer, such as molybdenum or tungsten, and bonded to either the first or second surface of the beryllium oxide ceramic body.

[0008]

[0008] In light of current base technology, there is a need for an improved base having an integrated resistance heater that exhibits improved performance, particularly at higher operating temperatures exceeding 650°C, such as reduced decomposition, reduced thermal stress, reduced micro-fracture, and / or mechanical degradation, improved temperature uniformity, and / or superior clamping pressure, while not showing intralayer, interlayer, or interfacial delamination. [Overview of the project]

[0009]

[0009] This disclosure relates to an electric resistance heater integrated on or within a ceramic body containing beryllium oxide (BeO), and a method for fabricating the same. The integrated resistance heater has specific applications in the field of semiconductor manufacturing and operation, which will be described with specific references. However, it should be understood that this disclosure is also suitable for other similar applications.

[0010]

[0010] In one embodiment, the present disclosure relates to a method for forming an integral resistance heater, comprising: applying a metal layer in a pattern on a planar surface of a ceramic body, the pattern of the metal layer being connected to a conductor, the metal layer containing 10% to 100% by weight of niobium, and the ceramic body containing beryllium oxide; forming a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so that the substrate is positioned in line with the beryllium oxide ceramic body, the substrate containing ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the ceramic body, the pattern maintaining integrity when forming the heating element.

[0011]

[0011] In one embodiment, the present disclosure relates to a method for forming an integrated resistance heater, comprising the steps of: applying a metal layer in a pattern on a surface of a ceramic body having recesses, wherein the pattern of the metal layer is connected to a conductor, the metal layer contains 10% to 100% by weight of niobium, and the ceramic body contains beryllium oxide; forming a pre-assembly by bringing a first surface of the substrate into contact with the metal layer so as to position the substrate in contact with a surface of the ceramic body that does not have recesses, wherein the substrate contains ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0012]

[0012] In one embodiment, the present disclosure relates to a method for forming an integrated resistance heater, comprising: applying a metal layer in a pattern onto the surface of a beryllium oxide ceramic body, wherein the pattern of the metal layer is connected to a conductor, and the metal layer contains 10% to 100% by weight of niobium; forming a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so as to position the substrate aligned with the beryllium oxide ceramic body, wherein the substrate contains ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the beryllium oxide ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0013]

[0013] The method may further include the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa during, before, or after heating. The surface of the beryllium oxide ceramic body may be planar. Alternatively, the surface of the beryllium oxide ceramic body may have depressions, forming channels that include patterns and void spaces around the patterns. The channels may further include beryllium oxide powder to fill the void spaces before heating the pre-assembly. Before heating the pre-assembly, the beryllium oxide ceramic body may be a compact (green compact) with a theoretical density of 56% to 64%, or the beryllium oxide ceramic body may be sintered to more than 90% of the theoretical density. The ceramic of the substrate may be beryllium oxide or aluminum oxide. Before heating the pre-assembly, the substrate may be one of beryllium oxide powder, beryllium oxide compact with a theoretical density of 56% to 64%, and beryllium oxide sintered body with a theoretical density of more than 90%. The surface of the beryllium oxide ceramic body may be a planar surface, and the planar surface faces the first surface of the substrate. The metal layer may contain 35% to 100% by weight of niobium. The metal layer may further contain platinum, titanium, tantalum, beryllium, alloys thereof, sublayers thereof, or combinations thereof. The time required for the step of heating the pre-assembly to the bonding temperature may be 1 second to 7200 seconds. The pattern may be a coil, helix, maze, unicursal labyrinth, circle, concentric ring, orthogonal, oblique, parallel, or vertical geometric structure. An integrated resistance heater may be fabricated according to this method.

[0014]

[0014] These, and other, non-limiting features, will be described in more detail below.

[0015] A further understanding of the nature and advantages of the technology described herein can be achieved by referring to the remainder of this specification and the drawings. [Brief explanation of the drawing]

[0015] [Figure 1]

[0016] It is a top view of a pattern on a planar surface of a ceramic body according to an embodiment of the present specification. [Figure 2]

[0017] It is a cross-sectional view of the ceramic body according to FIG. 1. [Figure 3]

[0018] It is a cross-sectional view of an alternative embodiment having a ceramic body as shown in FIG. 1, in which the pattern has a recess partially in the ceramic body. [Figure 4]

[0019] It is a cross-sectional view of an alternative embodiment having a ceramic body as shown in FIG. 1, in which the pattern has a recess. [Figure 5]

[0020] It is a cross-sectional view of an assembly as shown in FIG. 2, further including a substrate according to an embodiment of the present specification. [Figure 6]

[0021] It is a cross-sectional view of an assembly as shown in FIG. 3, further including a substrate according to an embodiment of the present specification. [Figure 7]

[0022] It is a cross-sectional view of an assembly as shown in FIG. 4, further including a substrate according to an embodiment of the present specification. [Figure 8]

[0023] It is a cross-sectional view of an assembly having a metal layer pattern on a substrate surface that reflects a metal layer pattern on a ceramic body surface according to an embodiment of the present specification. [Figure 9]

[0024] It is a cross-sectional view of an assembly similar to FIG. 5 immediately after heating according to an embodiment of the present specification. [Figure 10]

[0025] It is a top view of a heating element in a channel disposed on a planar surface of a ceramic body according to an embodiment of the present specification. [Figure 11]

[0026] It is a side exploded view of an integrated resistance heater according to an exemplary method. [Figure 12]

[0027] It is a perspective view of an integrated resistance heater as shown in FIG. 11.

Mode for Carrying Out the Invention

[0016] Introduction

[0028] In one embodiment, a base is provided that includes a heating element positioned between two ceramic bodies. The heating element may be an integrated resistance heater. The ceramic bodies may be bonded together.

[0017]

[0029] Previously, integrated resistance heaters presented problems due to their susceptibility to mechanical cracking. This was attributed to thermal expansion mismatch and / or thermal stress between the ceramic and metal components, such as metal heating elements. Specifically, multiple layers of ceramic, including beryllium oxide (BeO) ceramic bodies pre-laminated together (e.g., using thin film vapor, metal foil, coiled wire, thick film, or plating), where the metal (e.g., nickel, molybdenum, or other metals with thermal expansion mismatch) is deposited on the BeO surface and diffusely bonded, would produce unmanageable, cracked laminates due to thermal stress.

[0018]

[0030] Therefore, the embodiments disclosed herein satisfy the demand for integrated resistance heaters. Here, the inventors have developed a method for forming an integrated resistance heater by applying a niobium-containing metal layer to bond multiple ceramic components. In one embodiment, the method includes the step of applying a niobium-containing metal layer to bond BeO ceramic bodies. This method produces an integrated resistance heater that is resistant to cracking or fracture even at higher temperatures. The niobium-containing metal layer can function as a heater element and also serves to bond the ceramic bodies. Therefore, no additional bonding material or brazing is required, which improves process efficiency while reducing costs.

[0019]

[0031] In various embodiments of this specification, a method for forming an integrated resistance heater is disclosed, in which a niobium-containing bonded metal layer directly contacts and bonds to a beryllium oxide (BeO) ceramic body, forming a heating element. The beryllium oxide ceramic body described herein is both electrically insulating and highly thermally conductive.

[0020]

[0032] While not bound by theory, the method of this disclosure is envisioned to involve a bonding temperature that allows for bonding between the components of an integrated resistance heater, while simultaneously forming a niobium-containing bonding metal layer heating element while maintaining the integrity of the heating element's shape. Maintaining the integrity of the heating element's shape is useful for providing consistent temperature control. Therefore, the subsequent integrated resistance heater can operate at high temperatures of 600°C to 800°C or higher due to the extremely fire-resistant niobium-containing bonding metal layer.

[0021] term

[0033] For clarity, certain terms are used in the following description, but these terms are intended to refer only to specific structures of embodiments selected for illustrative purposes in the drawings and are not intended to define or limit the scope of this disclosure. In the drawings and the following description, similar numerical designations should be understood to refer to components of similar function.

[0022]

[0034] Unless otherwise explicitly stated in the context, the singular forms "a," "an," and "the" include plural referents.

[0035] As used herein and in the claims, the term “comprising” may include embodiments of “consisting of” and “essentially consisting of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain,” and their variations are intended, as used herein, to be non-restrictive transitional phrases, terms, or words that require the presence of a specified component / component / step and permit the presence of other components / components / steps. However, such descriptions should also be considered to describe a composition, article, or method as “consisting of” and “essentially consisting of” the enumerated components / components / steps, which permits the presence of only the specified component / component / step, along with any impurities that may arise therefrom, and excludes other components / components / steps.

[0023]

[0036] It should be understood that the numerical values ​​in the specification and claims of this application include numerical values ​​that are the same when rounded to the same number of significant figures, and numerical values ​​that differ from the specified values ​​by less than the experimental error of the type of conventional measurement technique described herein for determining the values.

[0024]

[0037] All ranges disclosed herein include the enumerated endpoints and are independently combinable; for example, the range "10% by weight to 100% by weight" includes the endpoints from 10% by weight to 100% by weight, and all intermediate values.

[0025]

[0038] In the methods described herein, the steps refer to temperature, which, unless otherwise specified, refers to the temperature reached by the referenced material and not the temperature at which the heat source (e.g., furnace, oven) is set. The term “room temperature” refers to the range of 20°C to 25°C (68°F to 77°F).

[0026]

[0039] The term "approximately" can be used to include any number that can vary without changing the fundamental function of its value. When used with a range, "approximately" also discloses a range defined by the absolute values ​​of two endpoints; for example, "approximately 2 to approximately 4" also discloses the range "2 to 4". The term "approximately" can refer to plus 10% or minus 10% of the given number.

[0027] How to form an integrated resistance heater

[0040] This disclosure relates to a method for forming an integrated resistance heater having the above-mentioned advantages, such as being crack-free and having the integrity of the heating element. This method is shown in Figures 1 to 12.

[0028]

[0041] The method includes the steps of applying a metal layer in a certain pattern onto the surface of a ceramic body (as shown in Figures 1-4), bringing a first surface of a substrate into contact with the metal layer (as shown in Figures 5-8), and forming an integrated resistance heater having a heating element that bonds the substrate to the ceramic body by heating to a bonding temperature of 800°C to 1900°C (as shown in Figure 9) (as shown in Figures 10-12).

[0029]

[0042] Importantly, the metal layer contains 10% to 100% by weight of niobium, and the ceramic body contains beryllium oxide. Having at least 10% by weight of niobium has been found to provide a heating element with a coefficient of thermal expansion (CTE) closely matched to that of the beryllium oxide ceramic body. Furthermore, niobium has a high thermomechanical compatibility factor (TCF), which is an approximate measure of metal compatibility in sealing with ceramics. For example, niobium has a TCF of 88 in an alumina seal at 780°C, compared to 33 for platinum, 20 for copper, and less than 10 for titanium, Kovar, nickel, molybdenum, stainless steel, and tungsten, respectively. Thus, thermal stress can be minimized or eliminated to prevent cracking after formation. Furthermore, niobium has been found to provide suitable resistance heating that can offer excellent temperature consistency. In one embodiment, the method further includes ensuring that the pattern formed with the niobium metal layer maintains integrity when forming the heating element. For the purposes of this disclosure, "maintaining integrity" means a heating element that is undamaged or free from any discontinuities, such as short circuits. Niobium metal heaters can liquefy and bond ceramic bodies, and liquefaction presents a challenge to integrity. To prevent liquefaction from distorting integrity, the embodiments disclosed herein operate under certain parameters to maintain integrity.

[0030]

[0043] The method may further include the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa, e.g., 75 kPa to 210,000 kPa, 100 kPa to 150,000 kPa, 150 kPa to 138,000 kPa, or 150 kPa to 100,000 kPa during, before, or after heating. The compression is found to further bond the ceramic body with the heating element and to be able to maintain and / or minimize a desired distance between the substrate and the ceramic body, i.e., the distance between the ceramic body and the substrate is controllable.

[0031]

[0044] Accordingly, in one embodiment, a method for forming an integrated resistance heater is provided, which includes the step of applying a metal layer in a pattern onto a planar surface of a ceramic body. In one embodiment, the pattern of the metal layer may be connected to a conductor, for example, a through-conductor that passes through the ceramic body to control resistance heating. In one embodiment, another ceramic body or substrate may be positioned in alignment with the ceramic body and in contact with the metal layer to form a pre-assembly. After the pre-assembly is assembled, the pre-assembly is heated to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the ceramic body. Various embodiments of this method are further described below.

[0032]

[0045] As described above and illustrated in Figure 1, the method includes the step of forming an assembly 100 by applying a metal layer 120 in a pattern 130 onto a planar surface 112 of a ceramic body 110. A conductor (550 as shown in Figure 11) is connected to the ceramic body 110 through a hole 150 or (556 as shown in Figure 11). The metal layer 120 can be applied onto the planar surface 112 of the ceramic body, as shown in Figure 2, a cross-sectional view drawn along line A as in Figure 1. The ceramic body 110 includes another planar surface 114 opposite to the planar surface 112 of the ceramic body 110. In the ceramic body / heating element assembly 100A of Figure 2, the metal layer 120 has a thickness t before heating t1. Thus, the method can form a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so that the substrate is positioned in contact with a surface of the ceramic body that does not have recesses. In one example, the metal layer 120 is a niobium metal foil.

[0033]

[0046] In another embodiment, the ceramic body 110 may have a recess R for receiving the metal layer 120. Therefore, the method can form a pre-assembly by bringing the first surface of the substrate into contact with the metal layer so that the substrate is positioned in contact with the surface of the ceramic body having the recess, as shown, for example, in Figures 3 and 4. The recessed portion may be formed when the ceramic body is manufactured by a mold during sintering, or during post-processing machining after the ceramic body has been formed. The recessed portion may also be referred to herein as a channel. The metal layer 120 has a recess depth d recess This can be applied to recesses R in a ceramic body 110 having a recess. The recess depths d1 shown in Figure 3 and d2 shown in Figure 4 are shown relative to a planar surface 112. In an example like Figure 3, the recess depth d1 is less than the thickness t1 of the metal layer, and therefore the metal layer protrudes from the planar surface 112 in the ceramic body / heating element assembly 100B. In some cases (as in Figure 4), the recess depth d2 is equal to or approximately equal to the thickness t1 of the metal layer, as in the ceramic body / heating element assembly 100C. rThis range may be 0.1 microns to 1999 microns, for example, 0.1 microns to 1500 microns, 1 micron to 1000 microns, 1 micron to 500 microns, or 10 to 250 microns.

[0034]

[0047] In certain embodiments, the recess R forms a patterned channel for receiving niobium or a niobium-containing coil, and the coil is positioned within the recess. In some embodiments, the recess containing the coil may be further filled with beryllium oxide powder to fill the void space and / or to coat the coil. In some embodiments, the beryllium oxide powder may completely coat the coil to form a substrate during subsequent heat treatment for co-sintering within the heater assembly.

[0035]

[0048] As mentioned, the method includes the step of applying a metal layer in a certain pattern onto a planar surface of the ceramic body 110, which may have recesses as described above. The metal layer may be applied by physical vapor deposition, chemical vapor deposition, atomic deposition, wet thick-film deposition, dry powder deposition, or a combination thereof. The choice of application method may depend on the shape and size of the BeO ceramic body. The metal layer may form a thick film that bonds the BeO ceramic body to the substrate, and may also form a heating element on the surface of the BeO ceramic body. The desired thickness of the applied metal layer depends on the resistance required to generate heat from the current provided by the power source, and other factors. Niobium content may also contribute to the electrical resistance. In some embodiments, the thickness of the applied metal layer may range from 0.1 microns to 2000 microns, e.g., 1 micron to 1000 microns, 1 micron to 100 microns, or 5 microns to 50 microns, but may be reduced or increased by multiple applications of the metal layer as needed to achieve the desired electrical resistance required to obey Joule's first law of heat.

[0036]

[0049] In one embodiment, the metal layer may be applied as a pre-formed wire, coil (or coiled wire), foil, sheet, plate, mesh, or a combination thereof. The pre-formed metal layer is preferably in the shape of a desired pattern and has the same thickness as described above.

[0037]

[0050] Suitable patterns for a metal layer on a planar surface of a ceramic body can vary and are generally useful for providing a consistent temperature. In one embodiment, the pattern can provide uniform heating across the surface. In embodiments herein, the pattern may be a coil, spiral, maze, one-stroke labyrinth, circle, concentric ring, orthogonal pattern, oblique pattern, parallel line pattern, or vertical geometric pattern. The patterns described herein are suitable for BeO ceramic bodies as heaters.

[0038]

[0051] The intrinsic volume resistivity of niobium, along with the diameter and length of the metal layer pattern, contributes to providing a pattern with a cross-sectional area adjusted for the Ohm's law correction required for the Joule resistance heating element. Regardless of the pattern, the pattern is connected to a conductor to control resistance heating. In one embodiment, the metal layer pattern is connected to a conductor extending through a ceramic body. The conductor may extend through an opening in the ceramic body (e.g., connected by a hole 150 as in Figure 1). The conductor (e.g., conductor 550 connected by a hole 556 as in Figure 11) may be a lead wire or a similar electrical connection.

[0039]

[0052] The metal layer 120 used in the method contains at least 10 wt% niobium. Pure niobium is intended, but the method may also use alloys or mixtures of niobium. Niobium has a coefficient of thermal expansion that closely matches that of ceramic bodies, particularly BeO ceramic bodies. The coefficient of thermal expansion (CTE) of niobium is 7.3 μm / (m·K) at room temperature (RT), while the CTE of beryllium oxide ceramic body, for example, is 7.4 to 9.0 μm / (m·K) at RT. In one embodiment, the method may use a beryllium oxide ceramic body having a CTE of 7.4 to 8.0 μm / (m·K) at RT.

[0040]

[0053] Niobium may be of high purity. For example, niobium may have a purity of 2N (99%), for example, 3N (99.9%) or 4N (99.99%) or higher. In some embodiments, niobium has a purity of 3N. In some cases, niobium has a purity of 3N or higher. The purity of niobium is important because it affects the intrinsic volume resistivity. The cross-sectional area of ​​the metal layer pattern is adjusted according to the purity to obtain the desired resistance. Surface oxides may be desirable for adhesion to the ceramic body surface, but they may also be undesirable. This is because the oxide layer forms ionic bonds with the metal layer and covalent bonds with the beryllium oxide ceramic body.

[0041]

[0054] The metal layer contains at least 10 wt% (wt%) of niobium based on the total weight of the metal layer. In some embodiments, the metal layer contains 10 wt% to 100 wt% of niobium. For example, the metal layer may contain 10 wt% to 100 wt% of niobium, e.g., 15 wt% to 100 wt%, 20 wt% to 100 wt%, 25 wt% to 99.99 wt%, 30 wt% to 99.9 wt%, or 35 wt% to 99 wt% of niobium. With respect to the lower limit, the metal layer may contain more than 10 wt% of niobium, e.g., more than 15 wt%, more than 20 wt%, more than 25 wt%, more than 30 wt%, or more than 35 wt%. Regarding the upper limit, the metal layer may contain less than 100 wt% niobium, for example, less than 99.99 wt%, less than 99.9 wt%, less than 99 wt%, less than 95 wt%, less than 90 wt%, less than 85 wt%, less than 80 wt%, less than 75 wt%, less than 70 wt%, or less than 65 wt% niobium. In some embodiments, the metal layer is 100 wt% niobium based on the total amount of the metal layer before heating.

[0042]

[0055] The metal layer may contain up to 90% by weight of metals other than niobium, in the form of mixtures or alloys. In other words, in addition to niobium as described above, the metal layer may further contain platinum, titanium, tantalum, beryllium, alloys thereof, or combinations thereof. These metals may be referred to herein as “metals other than niobium.”

[0043]

[0056] In some embodiments, the metal layer includes 0 wt% to 90 wt% of a non-niobium metal, such as platinum, titanium, tantalum, beryllium, their alloys, or combinations thereof. For example, the metal layer may include 0 wt% to 90 wt% of a non-niobium metal, such as 0 wt% to 85 wt% of a non-niobium metal, 10 wt% to 75 wt% of a non-niobium metal, or 25 wt% to 50 wt% of a non-niobium metal. With respect to the lower limit, the metal layer may include more than 0 wt% of a non-niobium metal, such as more than 5 wt%, more than 10 wt%, more than 15 wt%, more than 20 wt%, or more than 25 wt% of a non-niobium metal. With respect to the upper limit, the metal layer may include less than 90 wt% of a non-niobium metal, such as less than 85 wt%, less than 75 wt%, or less than 50 wt% of a non-niobium metal. In some embodiments, a metal other than niobium is included in an amount of 35 wt% of the total weight of the metal layer before heating.

[0044]

[0057] In some embodiments, the metal layer comprises a niobium alloy containing 89 wt% niobium, 10 wt% hafnium, and 1 wt% titanium; for example, the metal layer may also comprise a C103 alloy. In other embodiments, the metal layer comprises a niobium alloy conforming to standard ASTM-B392, such as niobium RO4210, which may contain the elements C, N, O, H, Zr, Ta, Fe, S, W, Ni, Mo, Hf, Ti, and Al in addition to Nb. Other, not limited, examples of niobium alloys conforming to the standard include niobium R04200, Nb-1% zirconium R04251, and Nb-1% zirconium R04261. In addition to niobium, these alloys conforming to the standard may contain the elements C, N, O, H, Zr, Ta, Fe, S, W, Ni, Mo, Hf, Ti, B, Al, Be, and Cr.

[0045]

[0058] In some embodiments, the metal layer further comprises a coating layer containing gold, copper, nickel, silver, palladium, indium, molybdenum, tungsten, titanium, or a combination thereof. The coating layer may be continuous or discontinuous. The coating may be applied to the metal layer (or preform) before positioning / applying the metal layer to the ceramic body.

[0046]

[0059] In other embodiments, the metal layer and / or the planar surface of the ceramic body on which the metal layer is placed may be treated to improve bonding. The metal layer in contact with the planar surface of the ceramic body, for example, a niobium-containing metal layer, may be treated to include an oxide or suboxide layer at the metal layer / ceramic body interface. This layer can assist in covalent and / or ionic bonding. In another example, to improve bonding, a first niobium-containing metal layer may be in contact with a second niobium-containing metal layer. Treatment of the metal layer may include removal of an oxide layer, pretreatment affecting the surface finish, or coating with another metal such as nickel. In another example, to create a planar surface of the ceramic body for application of the metal layer, the ceramic body may be pretreated or coated with titanium, titanium oxide, or a combination thereof. In some embodiments, the metal layer further provides bonding or improved bonding to a beryllium oxide body, a beryllium oxide substrate, or both, thereby pretreated or coated so that the foil, printed metal layer, or coil provides self-brazing upon heating.

[0047]

[0060] Other bonding techniques may be introduced to directly bond the beryllium oxide body and the beryllium oxide substrate to each other, by (1) using molten sealing glass at the interface between the BeO body and the BeO substrate (these are then cooled to form an airtight seal), and / or (2) using eutectic brazing, which is molten between the BeO body and the BeO substrate and then cooled. The glass or brazing material used has a melting point at least 100°C higher than the operating temperature of the heater, and typically in the range of 200°C to 700°C higher than the operating temperature of the heater.

[0048]

[0061] The method, which includes the step of applying a metal layer as described above, further includes the fact that the ceramic body is a beryllium oxide (BeO) ceramic body. The ceramic body 110, as shown in Figures 1-7, is beryllium oxide. The planar surface 112 of the BeO ceramic body, as shown in Figure 2, is opposite to the surface 114 of the ceramic body 110.

[0049]

[0062] BeO ceramic materials used herein may have the following properties (in addition to the CTE described above) that make beryllium oxide ceramic materials sufficiently suitable for integrated resistance heaters: a high melting point of 2514 to 2626°C, a thermal conductivity of 209 to 330 W / (m·K), a dielectric constant of 6.1 to 7.5 at 1 MHz, and a bulk resistivity greater than 1e15 Ω / cm at RT. Depending on the grade, BeO may alternatively have a lower melting point, e.g., as low as 800°C, or a lower thermal conductivity, e.g., as low as 150 W / (m·K). The grade of beryllium oxide affects the chemistry / purity, grain structure, and density.

[0050]

[0063] The BeO ceramic body used herein may be a high-density sintered body. The BeO ceramic body preferably has a density greater than 90% of the theoretical density, which is about 3.008 g / cm³, and a microstructure free from pores, voids, or other defects. With respect to the lower limit, the BeO ceramic body may have a density greater than 90%, greater than 91%, greater than 92%, greater than 93%, or greater than 94% of the theoretical density.

[0051]

[0064] The BeO ceramic body used herein may alternatively include a compact, which is then further processed for sintering with one or more other assembly components, such as a BeO substrate and / or a metal layer. The BeO compact can be formed by cold compression or cold hydrostatic compression, etc., to form a compacted body having a density lower than the final density of the BeO ceramic body after sintering to the density described in the paragraph above. The BeO compact preferably has a density greater than 50% of the theoretical density. With respect to the lower limit, the BeO compact may have a density greater than 50%, greater than 53%, or greater than 56% of the theoretical density. With respect to the upper limit, the BeO compact may have a density less than 70%, less than 67%, or less than 64% of the theoretical density. In certain embodiments, the BeO compact has a density in the range of 56% to 64% of the theoretical density. Advantageously, the BeO compact, which may contain a binder, is machineable to achieve changes in shape, to flatten, to round, and / or to create depressions or channels in the BeO body. The BeO compact is then further processed to a sufficient density to form a one-piece resistance heater as part of an assembly. Exemplary, but not limited to, means of further processing as described herein include hot compression and hot hydrostatic compression to form a high-density sintered body.

[0052]

[0065] The BeO ceramic materials used herein are of high purity. In some embodiments, the BeO ceramic materials have a purity of more than 90%, and for example, with respect to a lower limit, the BeO ceramic materials may have a purity of more than 95%, more than 96%, more than 97%, more than 98%, more than 99%, more than 99.5%, or more than 99.9%. In some cases, dopants (or impurities) are added to modify properties such as thermal, physical, mechanical, chemical, neutron, dosimetric, electromagnetic, and / or dielectric properties.

[0053]

[0066] The BeO ceramic body according to the embodiments herein may contain dopants. Suitable dopants include aluminum, magnesium, silicon, boron, fluorine, lithium, calcium, titanium, iron, yttrium, zirconium, lanthanum, or combinations thereof. In some embodiments, the BeO ceramic body contains dopants ranging from 1 ppm to 100,000 ppm. For example, the BeO ceramic body may contain dopants ranging from 1 ppm to 100,000 ppm, e.g., 10 ppm to 10,000 ppm, or 100 ppm to 1,000 ppm. With respect to the lower limit, the BeO ceramic body may contain dopants greater than 1 ppm, e.g., greater than 10 ppm, or greater than 100 ppm. With respect to the upper limit, the BeO ceramic body may contain dopants less than 100,000 ppm, e.g., less than 10,000 ppm, or less than 1,000 ppm.

[0054]

[0067] The ceramic body described above may be any preferred shape; for example, the BeO ceramic body may be in the shape of a square plate, rectangular plate, platen, or disc. The BeO ceramic body may have a maximum dimension l1, for example, the diameter in the case of a disc shape, or the length in the case of a square or rectangular plate, in the size range of 25 mm to 500 mm. In certain embodiments, the diameter or length of the BeO ceramic body may be in the size range of 25 mm to 300 mm. The BeO ceramic body may have a thickness w1 in the range of 1 mm to 400 mm. In certain embodiments, the thickness of the BeO ceramic body may be in the range of 2 mm to 25 mm.

[0055]

[0068] The method described herein includes the step of aligning and positioning a second ceramic body or substrate with the ceramic body. In one embodiment, the method includes the step of bringing a first surface of the substrate into contact with a metal layer so as to position the substrate in alignment with the beryllium oxide ceramic body, thereby forming a pre-assembly 200A as shown in Figure 5, where the planar surface 112 of the ceramic body 110 faces the first surface 117 of the substrate 115. The pre-assembly 200A has a gap S1 between the ceramic body and the substrate, which may be equal to the thickness t1 of the metal layer in Figure 2.

[0056]

[0069] The ceramic body 110 may be aligned with the substrate 115 along a central axis C perpendicular to the planar surface 112 of the ceramic body 110. Alternatively, the body 110 and the substrate 115 may be aligned by positioning them through holes, pins, or other means.

[0057]

[0070] Similarly, as shown in Figures 6-7, the planar surface 112 of the ceramic body 110 faces the first surface 117 of the substrate 115 of the pre-assemblies 200B and 200C, respectively. However, the gaps S2 and S3 between the respective ceramic bodies and substrates may differ from S1 due to differences in recess depth and / or metal layer thickness.

[0058]

[0071] The maximum distance between the planar surface 112 of the ceramic body 110 and the first surface 117 of the substrate 115 is equal to the thickness t of the metal layer as described above, or up to approximately 2000 microns as shown in Figure 5, in which case the distance S1 is equal to t1. In some cases, the distance may be less than 0.1 microns, or there may be no distance between the ceramic body and the substrate, for example as shown in Figure 7, in which case S3 is zero, and surfaces 112 and 117 are in contact with the metal layer and with each other. Embodiments shown in Figures 5-7 show that the metal layer is applied to a single planar surface of the ceramic body 110, which is then directly bonded to the opposing planar surface 117 of the substrate, for example, a beryllium oxide substrate. In other words, the planar surface 117 of the substrate does not include the metal layer. Other embodiments shown below include cases in which the planar surface of the substrate, for example, a beryllium oxide substrate, may include a metal layer that reflects a pattern applied to the planar surface of the ceramic body opposite the planar surface of the substrate.

[0059]

[0072] The substrate may be a polycrystalline ceramic, a single-crystal ceramic, or a combination thereof. The substrate may be aluminum nitride, aluminum oxide, beryllium oxide, beryllium aluminate, zirconia, lead zirconate titanate (PZT), or a combination thereof. In some embodiments, the substrate is beryllium oxide, as with the ceramic bodies described above.

[0060]

[0073] The substrates used herein are also high-density sintered bodies. The substrates preferably have a density greater than 99% of the theoretical density and a microstructure free from pores, voids, or other defects. With respect to the lower limit, the substrates may have densities greater than 90%, 92%, 95%, 97%, 98%, 99%, 99.5%, or 99.9% of the theoretical density.

[0061]

[0074] Substrates used herein may alternatively be formed first as untreated bodies, which are then further processed for co-sintering with one or more other assembly components, such as BeO bodies and metal layers. BeO substrates may be formed by cold compression or cold hydrostatic compression, etc., to form compacts having a density lower than the final density of the BeO substrate after sintering to the densities described in the paragraph above. Untreated BeO substrates preferably have a density greater than 50% of the theoretical density. With respect to the lower limit, untreated BeO substrates may have a density greater than 50%, greater than 53%, or greater than 56% of the theoretical density. With respect to the upper limit, untreated BeO substrates may have a density less than 70%, less than 67%, or less than 64% of the theoretical density.

[0062]

[0075] In other embodiments, the substrate may be formed from BeO powder. The BeO powder may be free (unconsolidated), consolidated, cold compressed, or cold hydrostatic compressed. It has been found that the BeO powder can be used to form a substrate after being further processed to full density, simultaneously with further processing (e.g., hot compression) using the BeO body and a metal layer to form an integrated resistance heater. For hot compression, uniaxial compression is preferred over hydrostatic compression.

[0063]

[0076] BeO powder may be used to coat a metal layer on a planar surface of a BeO ceramic body. BeO powder may be used to coat a metal layer on a recessed surface of a BeO ceramic body. BeO powder may be used to fill any void spaces in a pattern on a recessed surface (channel) of a BeO body (which may be a high-density body or compacted powder as described above) to which a metal layer or coil is applied. Advantageously, the BeO powder filler acts as a thermal conductor, which ensures that the niobium metal layer makes better contact with the BeO body and / or substrate. By filling recessed surfaces with BeO powder, a monolithic heater can be formed after further processing, e.g., hot compression, to form a high-density integrated resistance heater.

[0064]

[0077] Substrates used in this specification may be of high purity. In some embodiments, ceramic substrates have a purity of more than 90%, and for example, with respect to a lower limit, ceramic substrates may have a purity of more than 95%, more than 96%, more than 97%, more than 98%, more than 99%, more than 99.5%, or more than 99.9%.

[0065]

[0078] The substrate described above may have any preferred shape, for example, a shape similar to that of the BeO ceramic body. For example, the substrate may be in the shape of a square plate, a rectangular plate, a platen, or a disk. The substrate may have a maximum dimension l2, for example, the diameter in the case of a disk-shaped body, or the length in the case of a square or rectangular plate body, in a size range of about 25 mm to 500 mm. In certain embodiments, the diameter or length of the substrate may be in a size range of 25 mm to 300 mm. The substrate may have a thickness w2 of 1 mm to 400 mm. In certain embodiments, the thickness of the substrate may be in the range of 2 mm to 25 mm.

[0066]

[0079] In some other embodiments, the method further includes the step of applying another metal layer, as described above, onto the surface of the substrate before aligning the substrate with the BeO ceramic body. Thus, patterns are applied to mutually facing surfaces of both the ceramic body and the substrate, and the patterns reflect each other. As shown in the cross-sectional view of the pre-assembly 300 in Figure 8, the metal layer pattern 325 may be applied to the surface 317 of the substrate 315 in the same manner as described above, and in the same pattern as the pattern of the metal layer 320 applied to the planar surface 312 of the ceramic body 310. For example, the pre-assembly 300 includes a beryllium oxide ceramic body 310 having a metal layer 320 that reflects the metal layer 325 applied to the surface 317 of the substrate 315. After the metal layers 320 and 325 are bonded, the outer surface of the substrate 315 opposite to the surface 317 may further include a bias RF electrode, a wafer contact plate, and a wafer (not shown).

[0067]

[0080] As described above, metal layers can be applied by physical vapor deposition, chemical vapor deposition, atomic deposition, wet thick-film deposition, dry powder deposition, or a combination thereof.

[0081] According to the method described herein, the pre-assembly (as shown in Figures 5-8) is then heated.

[0068]

[0082] The method further includes the step of heating a pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element for bonding the substrate to the ceramic body. The temperature for heating may be interdependent with the niobium-containing metal layer content, relating to whether the metal layer is pure niobium or an alloy thereof. The bonding temperature for heating in the method herein may be in the range of 800°C to 1900°C, for example, 800°C to 1600°C, 900°C to 1200°C, 900°C to 1100°C, 950°C to 1050°C, or 975°C to 1025°C. Operating below 1900°C prevents the pattern of the metal layer from losing its integrity. Operating above 800°C is useful for bonding the ceramic body and the substrate. In some embodiments, the bonding temperature is about 1000°C.

[0069]

[0083] The bonding temperature can vary, i.e., it may be lower, in which case pressure is also applied via hot compression in addition to heating. In certain embodiments, hot compression is preferred to provide good bonding of the metal layer to the ceramic body and substrate. In embodiments where the BeO ceramic body and / or BeO substrate are untreated before bonding, hot compression is preferred when using BeO free powder, such as that described herein.

[0070]

[0084] The bonding temperature can also depend on the grade of BeO. Certain grades of BeO offer lower bonding temperatures and may work with more economical low-temperature hot compression equipment. However, higher bonding temperatures, such as at least 950°C, are preferable for improved physical, thermal, and mechanical properties, resulting in a longer heater life.

[0071]

[0085] In embodiments of this specification, heating is performed in a non-oxidizing environment. A non-oxidizing environment may include a vacuum, a non-oxidizing gas such as nitrogen or argon, or a reducing gas such as hydrogen. A non-oxidizing environment helps preserve the integrity of the pattern.

[0072]

[0086] In embodiments of this specification, heating is performed for a duration of 1 second to 7200 seconds, or 120 minutes. The time may be interdependent with the temperature for heating. In some embodiments, heating is performed for a duration of 1 second to 120 minutes, 1 minute to 90 minutes, or 30 minutes to 60 minutes.

[0073]

[0087] As described above, the bonding temperature may be 10°C to 50°C lower than the melting temperature of the metal layer. In some embodiments, the bonding temperature may be 800°C to 1900°C, for example, 900°C to 1800°C, 950°C to 1500°C, or 1000°C to 1200°C. Depending on the composition of the metal layer, the bonding temperature may be higher than, equal to, or lower than the liquidus temperature. The liquidus temperature of a pure metal may be equal to its melting temperature. For a metal layer essentially consisting of 100% niobium, the liquidus temperature is 2477°C. For example, in an embodiment where the metal layer is 100% niobium, the bonding temperature is lower than the liquidus temperature. In some embodiments, the bonding temperature is below the liquidus temperature of the metal layer. In certain examples, the bonding temperature may be 950°C or 1000°C.

[0074]

[0088] In other embodiments in which the metal layer includes niobium and a metal other than niobium as described above, the bonding temperature is above the eutectic temperature of the metal layer, or the bonding temperature is below the eutectic temperature of the metal layer. In the case of a metal layer containing niobium and another metal other than niobium (as described above), the eutectic temperature may be lower than at least one of the liquidus temperature of pure niobium and / or the liquidus temperature of the metal other than niobium.

[0075]

[0089] Importantly, the pattern of the formed heating element retains its integrity during the formation of the heating element. In other words, after heating, the thickness of the metal layer and the gap between the ceramic body and the substrate are maintained. Heating of assembly 1000 250 is shown in Figure 9 (referring again to a preliminary assembly as shown in Figure 5), and this heating ensures that the gap is S after heating. 1h The interval (S1 in Figure 5) can be affected in this way. The change in the interval is ΔS, or [(S1-S 1h ) / S1] * It can be 100%, minimal, and does not form a path that could lead to a short circuit. The ΔS of the integrated resistance heater described herein may be less than 10%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. In this way, the integrity of the metal layer is maintained.

[0076]

[0090] While not bound by theory, the methods described herein include a step of providing a short period of time at a temperature such that the metal layer is semi-fluid, for example, the liquidus temperature or eutectic temperature or slightly below, in order to limit the time that the metal layer is completely fluid.

[0077]

[0091] The average distance between the substrate and the ceramic body after heating is between 0.1 microns and 2000 microns, for example, between 1 micron and 1000 microns, between 1 micron and 750 microns, between 5 microns and 500 microns, or between 10 microns and 200 microns.

[0078]

[0092] The integrity of the maintained metal layer can also be seen in the fact that the pattern shape does not change to a noticeable degree. In some embodiments, the contact angle between the metal layer and the substrate is smaller than the minimum thickness of the layer. Ideally, the contact angle between the metal layer and the substrate is fixed in the range of 90 to 101 degrees in order to maintain the integrity of the metal layer.

[0079]

[0093] The method may optionally include cold compression or cold hydrostatic compression to form a compact for a BeO ceramic body or substrate or both. This includes preparing free BeO powder with an optional binder in a mold, sealing it for watertightness, and subjecting the mold containing the BeO powder to hydrostatic pressure at room temperature to provide a machinable compact. The contact pressure may be in the range of 6,900 kPa to 276,000 kPa. In some embodiments, the contact pressure is 138,000 kPa (138 MPa).

[0080]

[0094] The method may optionally include the step of sintering the BeO ceramic body or the substrate separately or both. Sintering for forming the high-density BeO ceramic body and / or substrate may be carried out in a refractory lining furnace at a temperature of about 1400°C to 1900°C, or in the range of 1500°C to 1600°C, or about 1550°C. The sintering process in the furnace may be carried out without pressure and in an oxidizing environment.

[0081]

[0095] In one embodiment, the method may optionally include a step of compressing the pre-assembly, for example, by hot compression. Pressure may be applied under contact pressure during, before, or after heating. The applied pressure assists in the coupling integrity of the resulting heating element to one or both of the ceramic body and the substrate. The contact pressure may be in the range of 60 kPa to 215,000 kPa. In some embodiments, the contact pressure is about 1000 psi (6895 kPa). Heating may be carried out in a non-oxidizing environment or in a vacuum. In an exemplary embodiment, heating is carried out under a vacuum, for example, under a partial pressure of argon less than 500 mtorr, at a contact pressure of 1000 psi for 30 minutes at a temperature of 1000 °C. Exemplary means of compression as provided herein include hot compression and hot hydrostatic compression.

[0082]

[0096] The pressure should not be so great as to deform the metal layer and / or reduce the gap between the ceramic body and the substrate to a desired amount.

[0097] Hot compression may be performed after any of the steps described above to form the assembly. In a particular embodiment, the BeO ceramic body is first formed by cold compression alone or in combination with sintering, and then hot-compressed as a component in the assembly. Furthermore, the substrate may be formed alone or in combination with cold compression and / or sintering using free BeO powder, and then hot-compressed as a component in the assembly. In a particular embodiment, the assembly may be hot-compressed uniaxially between graphite punches at a pressure of 5302 kPa for 1 hour at 950°C to form a high-density BeO integrated resistance heater.

[0083] Integrated resistance heater

[0098] The top view of assembly 501 shown in Figure 10 (viewed from the metal layer 520) illustrates a partial view of an integrated resistance heater 500 as shown in Figures 11 and 12. The method herein may include the step of forming assembly 500 by inserting a niobium (or niobium-containing) metal coil 520 from a planar surface 512 of a ceramic body 510 into a pattern of channels 530 having recesses. A conductor (550 as shown in Figure 11) is connected to the ceramic body 510 through a hole 556. The metal coil 520 may alternatively be a foil or metal layer 120 (as shown in Figure 1) applied to the planar surface of the ceramic body (or on the surface 530 having recesses forming channels as shown in Figure 10). The channels 530 may be filled with free BeO powder before the coil is bonded to the BeO ceramic body 510 (and substrate 515 as shown in Figure 11) by hot compression to form a monolithic assembly 500.

[0084]

[0099] Figure 11 shows a side exploded view of an integrated resistance heater 500 according to the method described herein, having an assembly 501 and a metal coil 520 (as shown in Figure 10). A ceramic body 510 receives a conductor 550 from within a base shaft 590. The ceramic body 510 may include a hole 556 for receiving the conductor 550 and for assembly alignment through various components of the assembly 501, including the niobium-containing metal coil 520 on its top surface 512. The conductor 550 may also be referred to as a conductive rod or terminal. A substrate 515 and an RF electrode 525 are also shown. A connector 505 passes through the base shaft, which is a conduit for all electrical connections to and from the integrated resistance heater 500. The connector 505 is a conductor that is attached to the RF electrode 525 to bias an electrostatic clamping force and provides a ground-plane electrical contact, and the connector 505 may also be included at or near the center of the aligned assembly and extends through the base 590. The power connection conductor 550 is for connecting a power supply (not shown). Optionally, a wafer contact support 540 having an outer surface for holding the wafer on the heater 500 may be positioned adjacent to the substrate 515, together with the bias RF electrode 525 or other components in between. The metal coil 520 may be deposited on the lower surface of the substrate 515 so as not to electrically short-circuit the RF electrode 525.

[0085]

[0100] Figure 12 shows a perspective view of the integrated resistance heater 500 of Figures 10 and 11. The assembly 501 is rotatable so as to be positioned before movement around a base shaft 590 (having a central axis) and is connected to a power supply (not shown) via a power supply connection. A thermocouple 560 may also be located within the base. In one embodiment, at least two conductors (e.g., conductors 550 as in Figures 10 and 11) may extend through a BeO ceramic body and be connected to a heating element, e.g., a coil 520 as in Figures 10 and 11. These conductors are joined to the BeO ceramic body by soldering, brazing, tack welding, mechanical threading, or crimping. At least one power supply may be connected to the heater conductor to control the heating element according to Ohm's law and its AC voltage (VAC) equivalent form P(t)=l(t)V(t).

[0086]

[0101] The method may include the step of forming a base having an integrated resistance heater as shown in Figure 12. The method for forming the integrated resistance heater may include the step of applying a metal layer in a pattern onto the surface of a beryllium oxide ceramic body. The pattern of the metal layer is connected to at least one conductor, and the metal layer may contain 10% to 100% by weight of niobium. The metal layer may be pure niobium metal foil or wire, for example, 100% niobium.

[0087]

[0102] The method may include cases where the beryllium oxide ceramic body is a compact with a theoretical density of 56% to 64%. The compact can be formed by filling an elastomer mold with free beryllium oxide powder (optionally containing a binder that is subsequently burned so that no binder is present in the final integrated resistance heater). The beryllium oxide powder in the mold is sealed and subjected to hydrostatic pressure at room temperature, for example, via cold hydrostatic compression. The beryllium oxide compact can be machined so that the surface of the beryllium oxide ceramic body is planar or has recesses. The surface with recesses forms channels containing patterns and void spaces around the patterns. For a planar surface of the beryllium oxide ceramic body, a metal layer in the form of foil may be preferred, while for a recessed surface of the beryllium oxide ceramic body, a metal layer in the form of coils is preferred.

[0088]

[0103] The method may include firing a beryllium oxide compact in a refractory-lined firing furnace (at a high temperature, e.g., 1500°C or 1550°C, without pressure) to form a beryllium oxide ceramic body with a density exceeding 90% of the theoretical density (high-density sintered beryllium oxide ceramic body). The holding time at 1500°C to 1550°C, e.g., residence time, is between 1 hour and 50 hours. This depends on the required activation energy according to the material mass, cross-sectional area, chemistry, firing furnace operation, and desired material properties (physical properties such as particle size and density, mechanical properties such as strength, and thermal properties such as thermal conductivity). To fire the beryllium oxide compact alone (or the substrate alone), ambient air can be used for firing in the firing furnace as described above. For example, moisture (water vapor) can be removed by passing ambient air over a bed of drying medium. In other embodiments, when the beryllium oxide compact is co-fired with a niobium metal layer, a non-oxidizing environment such as argon is preferred to prevent oxidation. In other embodiments, a hydrogen, nitrogen, or mixed (hydrogen and nitrogen) process gas atmosphere may be used. In other embodiments, the process may omit the calcination / sintering intermediate step and densify in the subsequent heating step.

[0089]

[0104] The method may include the step of forming a preassembly by bringing a first surface of the substrate into contact with a metal layer so that the substrate is aligned and positioned with the beryllium oxide ceramic body, the substrate comprising ceramic. The substrate may also be a compact (e.g., formed by cold isostatic compression) (optionally fired to form a high-density sintered substrate), similar to the beryllium oxide ceramic body which can be further processed as a compact or a high-density sintered body. Another option is that the substrate is formed of a free powder (e.g., beryllium oxide or aluminum oxide powder) which can be densified in a subsequent heating step. When the substrate is formed of BeO powder, the first surface of the substrate is considered to be a beryllium oxide powder particle that is in contact with both the metal layer and the beryllium oxide ceramic body. Thus, the preassembly may include a metal layer and one or both or both of the beryllium oxide ceramic body and the substrate may be either a compact or a high-density sintered body. Furthermore, the substrate of the preassembly may alternatively be free beryllium oxide (or aluminum oxide) powder. Furthermore, the pre-assembly may further contain free beryllium oxide (or aluminum oxide) powder between the beryllium oxide ceramic body and the substrate, for example, at the interface with a metal layer of a pattern, and / or in any void space within or around the pattern, for example, filling channels in the recessed surfaces of the beryllium oxide ceramic body.

[0090]

[0105] The method may then include the step of heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the beryllium oxide ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0091]

[0106] The method described herein provides a crack-free assembly. This is due to the closely matched thermal expansion coefficients between the niobium metal layer, the beryllium oxide ceramic body, and the substrate. By matching the physical, thermal, and mechanical properties of the niobium metal layer with those of both the beryllium oxide ceramic body and the substrate, the integrated resistance heater fabricated herein achieves a long lifespan even at high operating temperatures without failure due to cracking.

[0092]

[0107] In some embodiments, any or some of the steps or components disclosed herein may be considered optional. In some cases, any or some of the items described herein may be explicitly excluded, for example, by the language of the claims. For example, the language of the claims may be modified to state that the metal layer does not contain or excludes a particular metal or alloy. [Examples]

[0093] Example 1

[0108] A niobium heating element was fabricated and tested. A niobium heating element was fabricated from 0.762 mm Nb wire (grade ASTM-B-392 RO4210) in a length of 7.239 m (285 inches), and a coil was made by winding it around a 2.3 mm diameter mandrel. The niobium coil was stretched to 3.9 m. Metal terminals were machined to include a dome (or mushroom cap) shaped apex and a small diameter 0.81 mm hole passing through them. Each end of the coiled wire was inserted into the through-hole of the terminal and crimped for high electrical contact. The niobium coil was placed in a machined channel of 380 mm OD × 13 mm thick aluminum oxide ceramic body for testing. The channel was filled with Resbond® 907GF, a high-temperature refractory sealant. The niobium heating element / aluminum oxide assembly was placed in an insulated chamber. A temperature measuring instrument was placed on the surface of the heater. An alternating current was supplied to the exposed terminals for the duration until the heater reached the desired set temperature of 300°C.

[0094] Example 2

[0109] A beryllium oxide ceramic body was fabricated and tested. An elastomer mold was filled with 9 kg of free BeO powder and a binder, and then sealed for watertightness. The mold containing the BeO powder was subjected to hydrostatic compression at 138 MPa at room temperature to compact the powder into a solid. The "untreated" solid BeO body, meaning unfired, was removed from the mold and machined using a polycrystalline diamond (PCD) tool to obtain a flat and parallel bottom and opposing top surface. A 6 mm wide concave channel was also machined into the top surface as a pattern for holding a heating element (after subsequent heat treatment). The machined BeO body was fired at 1550°C in a refractory lining firing furnace. The fired part was mechanically polished to 380 mm OD × 10 mm thickness (between the opposite top and bottom surfaces). A coiled Nb wire, as in Example 1, was placed in the channel. The assembly was passively heated to 800°C in an insulated chamber containing a nitrogen atmosphere.

[0095] Example 3

[0110] A heater assembly having a BeO body and a BeO substrate for active heating / testing with a metal heating element was fabricated. To form the beryllium oxide body, 1.8 kg of free BeO powder containing a binder was filled into an elastomer mold and then sealed for watertightness. The mold containing the BeO was subjected to hydrostatic compression at 138 MPa at room temperature to compact the powder into a solid. The solid BeO body was removed from the mold and machined flat and parallel using a PCD tool. Then, a 6 mm wide channel for holding the heating element was machined into one side, as in Example 2. The solid BeO body was sintered by firing at 1550°C in a refractory lining firing furnace. The fired part was machined to 230 mm OD × 10 mm thick to have a 200 mm concave pocket for holding a metal foil heating element with terminals. Another BeO body (e.g., substrate) machined to include through holes was separately fired and bonded into the concave pocket on top of the foil heating element. The heater assembly was installed inside the insulated chamber.

[0096]

[0111] A temperature measuring device was positioned on the surface of the heater. Alternating current was supplied to the exposed terminals for a period of time until the heater reached the desired set temperature. The assembly was heated to 400°C in ambient air.

[0097] Example 4

[0112] A fully hot-compressed BeO heater assembly containing a niobium heating element was fabricated. 4.5 kg of BeO powder was packed into a graphite die. The niobium coil heating element from Example 1, with terminals attached, was placed on the powder bed. An additional 4.5 kg of BeO powder was added to coat the heating element. The powder was compacted between graphite punches at 1000°C for 2 hours at a pressure of 6894 kPa to form a solid, high-density BeO heater assembly. The outer diameter and thickness of the assembly were mechanically polished for roundness and flatness. Ultrasonics was used to locate the terminals beneath the surface, and machining exposed the niobium for power connection.

[0098] Example 5

[0113] Beryllium oxide heater assemblies, comprising a BeO ceramic body, a BeO substrate, and a niobium heating element between them, were fabricated, actively heated, and tested.

[0099]

[0114] A BeO ceramic body was fabricated as in Example 2. 9 kg of free BeO powder and a binder were packed into an elastomer mold, which was then sealed for watertightness. The mold containing the BeO powder was subjected to hydrostatic compression at 138 MPa at room temperature to compact the powder into a solid. The solid (untreated) BeO body was removed from the mold and machined using a PCD tool to obtain a flat and parallel bottom surface and opposing top surface. A 6 mm wide concave channel was also machined into the top surface as a pattern for holding the heating element. The machined BeO body was fired at 1550°C in a refractory lining firing furnace. The fired part was mechanically polished to 380 mm OD × 10 mm thickness (between the opposite top and bottom surfaces).

[0100]

[0115] A coiled niobium wire, as shown in Example 1, was placed in a channel with a through-hole to form a ceramic body / niobium coil heating element assembly. Terminal connections were crimped to each end of a 7.2m long 20-gauge pure niobium wire. The wire was coiled with a 5mm pitch and a 3mm coil diameter to form a 4m long heating element. The Nb heating element was placed in a channel of a BeO plate (disk) with a circumference of 381mm x thickness of 28mm, and the terminal connections were passed through the through-hole to the opposite side.

[0101]

[0116] Next, the assembly was placed in a free BeO powder bed, the heating element was coated with beryllium oxide powder, and the empty spaces around the channel and niobium coil were filled. The BeO substrate (fabricated as in Example 3) was placed on top of the coil and BeO powder. The assembly containing the BeO powder was compacted between graphite punches by hot compression at a pressure of 5302 kPa at 950°C for 1 hour to form a solid, high-density BeO heater assembly. The outer diameter and thickness of the heater were mechanically polished using a PCD tool to obtain a flat and parallel bottom and opposing top surface, and to round the sides of the heater connecting the opposing bottom and opposing top surfaces (bottom surface of the BeO ceramic body and top surface of the BeO substrate).

[0102]

[0117] Ultrasound was used to locate the terminals beneath the top surface of the substrate, and niobium was exposed for power connection by machining. A BeO heater was placed inside an insulated chamber. A temperature measuring instrument was placed on the upper surface of the substrate. AC current was supplied to the exposed terminals for a period of time until the heater reached the desired set temperature.

[0103]

[0118] The heater reached the target temperature of 800°C in 350 minutes and was held at 164VAC and 26 amps for 21 minutes. The test data for the heater in Example 5 are shown in Table 1 below.

[0104] [Table 1-1]

[0105] [Table 1-2]

[0106] [Table 1-3]

[0119] As shown in Table 1, the heaters, such as the one in Example 5 that was tested, functioned well without failure at an operating temperature of 800°C. The heaters were inspected before and after testing and were found not to show any crack formation during heating, temperature holding, or cooling.

[0107] Example 6

[0120] Beryllium oxide heater assemblies, comprising a BeO ceramic body, a BeO substrate, and a niobium heating element between them, were fabricated, actively heated, and tested.

[0108]

[0121] The BeO ceramic body was prepared in the same manner as in Examples 2 and 5, except that the BeO ceramic body was not fired in a refractory firing furnace before hot compression. 9 kg of free BeO powder and a binder were packed into an elastomer mold, which was then sealed for watertightness. The mold containing the BeO powder was subjected to hydrostatic compression at 138 MPa at room temperature to compact the powder into a solid. The solid BeO (untreated) body was removed from the mold and machined using a PCD tool to obtain a flat and parallel bottom surface and opposing top surface. A 6 mm wide concave channel was also machined into the top surface as a pattern for holding the heating element. Next, a coiled niobium wire, as in Example 1, was placed on the machined BeO body and set in the concave channel to form an untreated / unfired BeO solid / niobium coil heating element assembly.

[0109]

[0122] Next, the assembly was placed in a free BeO powder bed, and the niobium coil was coated with beryllium oxide powder, filling the channels and the empty spaces around the niobium coil. The BeO powder coating the niobium coil was applied to a thickness such that it would form the BeO substrate after hot compression. The assembly containing the BeO powder was compacted between graphite punches via hot compression at 950°C for 1 hour at a pressure of 5302 kPa to form a solid, high-density BeO heater assembly. The outer diameter and thickness of the heater were mechanically polished using a PCD tool to obtain a flat and parallel bottom and opposing top surface, and to round the sides of the heater connecting the opposing bottom and opposing top surfaces (the bottom surface of the BeO ceramic body and the top surface of the BeO substrate).

[0110]

[0123] Ultrasound was used to locate the terminals beneath the top surface of the substrate, and niobium was exposed for power connection by machining. A BeO heater was placed inside an insulated chamber. A temperature measuring instrument was placed on the upper surface of the substrate. AC current was supplied to the exposed terminals for a period of time until the heater reached the desired set temperature.

[0111] Embodiment

[0124] The following embodiments are intended. All combinations of features and embodiments are intended.

[0112]

[0125] Embodiment 1. A method for forming an integrated resistance heater, comprising the steps of: applying a metal layer in a pattern onto a planar surface of a ceramic body, wherein the pattern of the metal layer is connected to a conductor, the metal layer contains 10% to 100% by weight of niobium, and the ceramic body contains beryllium oxide; forming a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so as to align the substrate with the ceramic body, wherein the substrate contains ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0113]

[0126] Embodiment 2. The method according to Embodiment 1, further comprising the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa during, before, or after heating.

[0114]

[0127] Embodiment 3. The method according to Embodiment 1 or Embodiment 2, wherein the planar surface of the ceramic body faces the first surface of the substrate.

[0128] Embodiment 4. The method according to any one of Embodiments 1 to 3, wherein the metal layer contains 35% to 100% by weight of niobium.

[0115]

[0129] Embodiment 5. The method according to any one of Embodiments 1 to 4, wherein the metal layer further comprises platinum, titanium, tantalum, beryllium, alloys thereof, sublayers thereof, or combinations thereof.

[0116]

[0130] Embodiment 6. The method according to any one of Embodiments 1 to 5, wherein the ceramic of the substrate is polycrystalline, monocrystalline, or a combination thereof.

[0131] Embodiment 7. The method according to any one of Embodiments 1 to 6, wherein the ceramic of the substrate is aluminum nitride, aluminum oxide, beryllium oxide, zirconia, lead zirconate titanate (PZT), or a combination thereof.

[0117]

[0132] Embodiment 8. The method according to any one of Embodiments 1 to 7, wherein the time required for the step of heating the pre-assembly to the bonding temperature is 1 second to 7200 seconds.

[0133] Embodiment 9. The method according to any one of Embodiments 1 to 8, wherein the step of heating the pre-assembly to the bonding temperature is performed in a non-oxidizing environment.

[0118]

[0134] Embodiment 10. The method according to any one of Embodiments 1 to 9, wherein the contact angle between the metal layer and the substrate is 90 degrees to 101 degrees.

[0135] Embodiment 11. The method according to any one of Embodiments 1 to 10, wherein the average distance between the substrate and the ceramic body is 0.1 microns to 2000 microns.

[0119]

[0136] Embodiment 12. The method according to any one of Embodiments 1 to 11, wherein the pattern is a coil, spiral, maze, one-stroke maze, circle, concentric ring, orthogonal, oblique, parallel, or perpendicular geometric structure.

[0120]

[0137] Embodiment 13. The method according to any one of Embodiments 1 to 12, wherein the metal layer is applied by physical vapor deposition, chemical vapor deposition, atomic deposition, wet thick film deposition, dry powder deposition, or a combination thereof.

[0121]

[0138] Embodiment 14. The method according to any one of Embodiments 1 to 13, wherein the metal layer is a preformed wire, foil, sheet, plate, mesh, or a combination thereof.

[0139] Embodiment 15. The method according to any one of Embodiments 1 to 14, further comprising a coating layer in which the metal layer comprises gold, copper, nickel, silver, palladium, indium, molybdenum, tungsten, titanium, or a combination thereof.

[0122]

[0140] Embodiment 16. An integrated resistance heater manufactured according to the method described in Embodiment 1.

[0141] Embodiment 17. A method for forming an integrated resistance heater, comprising the steps of: applying a metal layer in a pattern onto a surface of a ceramic body having recesses, wherein the pattern of the metal layer is connected to a conductor, the metal layer contains 10% to 100% by weight of niobium, and the ceramic body contains beryllium oxide; forming a pre-assembly by bringing a first surface of the substrate into contact with the metal layer so that the substrate is positioned in contact with a surface of the ceramic body that does not have recesses, wherein the substrate contains ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0123]

[0142] Embodiment 18. The method according to Embodiment 17, further comprising the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa during, before, or after heating.

[0124]

[0143] Embodiment 19. The method according to Embodiment 17 or Embodiment 18, wherein the metal layer contains 35% to 100% by weight of niobium.

[0144] Embodiment 20. The method according to any one of Embodiments 17 to 19, wherein the metal layer further comprises platinum, titanium, tantalum, beryllium, alloys thereof, sublayers thereof, or combinations thereof.

[0125]

[0145] Embodiment 21. The method according to any one of Embodiments 17 to 20, wherein the ceramic of the substrate is polycrystalline, monocrystalline, or a combination thereof.

[0146] Embodiment 22. The method according to any one of Embodiments 17 to 21, wherein the ceramic of the substrate is aluminum nitride, aluminum oxide, beryllium oxide, zirconia, lead zirconate titanate (PZT), or a combination thereof.

[0126]

[0147] Embodiment 23. The method according to any one of Embodiments 17 to 22, wherein the time required for the step of heating the pre-assembly to the bonding temperature is 1 second to 7200 seconds.

[0148] Embodiment 24. The method according to any one of Embodiments 17 to 23, wherein the step of heating the pre-assembly to the bonding temperature is performed in a non-oxidizing environment.

[0127]

[0149] Embodiment 25. The method according to any one of Embodiments 17 to 24, wherein the contact angle between the metal layer and the substrate is 90 to 101 degrees.

[0150] Embodiment 26. The method according to any one of Embodiments 17 to 25, wherein the pattern is a coil, spiral, maze, one-stroke maze, circle, concentric ring, orthogonal, oblique, parallel, or perpendicular geometric structure.

[0128]

[0151] Embodiment 27. The method according to any one of Embodiments 17 to 26, wherein the metal layer is applied by physical vapor deposition, chemical vapor deposition, atomic deposition, wet thick film deposition, dry powder deposition, or a combination thereof.

[0129]

[0152] Embodiment 28. The method according to any one of Embodiments 17 to 27, wherein the metal layer is a preformed wire, foil, sheet, plate, mesh, or a combination thereof.

[0153] Embodiment 29. The method according to any one of Embodiments 17 to 28, further comprising a coating layer in which the metal layer comprises gold, copper, nickel, silver, palladium, indium, molybdenum, tungsten, titanium, or a combination thereof.

[0130]

[0154] Embodiment 30. An integrated resistance heater manufactured according to the method described in Embodiment 17.

[0155] Embodiment 31. A method for forming an integrated resistance heater, comprising the steps of: applying a metal layer in a pattern onto the surface of a beryllium oxide ceramic body, wherein the pattern of the metal layer is connected to a conductor, and the metal layer contains 10% to 100% by weight of niobium; forming a pre-assembly by bringing a first surface of a substrate into contact with the metal layer so as to position the substrate aligned with the beryllium oxide ceramic body, wherein the substrate contains ceramic; and heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element that bonds the substrate to the beryllium oxide ceramic body, wherein the pattern maintains integrity when forming the heating element.

[0131]

[0156] Embodiment 32. The method according to Embodiment 31, further comprising the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa during, before, or after heating.

[0132]

[0157] Embodiment 33. The method according to Embodiment 31 or Embodiment 32, wherein the surface of the beryllium oxide ceramic body is planar or the surface of the beryllium oxide ceramic body is recessed.

[0133]

[0158] Embodiment 34. The method according to any one of Embodiments 31 to 33, wherein the surface of the beryllium oxide ceramic body has recesses that form channels including a pattern and void spaces around the pattern.

[0134]

[0159] Embodiment 35. The method according to any one of Embodiments 31 to 34, wherein the channel further comprises beryllium oxide powder for filling the void space before heating the pre-assembly.

[0160] Embodiment 36. The method according to any one of Embodiments 31 to 35, wherein the beryllium oxide ceramic body before heating the pre-assembly is a compacted powder with a theoretical density of 56% to 64%.

[0135]

[0161] Embodiment 37. The method according to any one of Embodiments 31 to 36, wherein the beryllium oxide ceramic body before heating the pre-assembly is sintered to more than 90% of its theoretical density.

[0162] Embodiment 38. The method according to any one of Embodiments 31 to 37, wherein the ceramic of the substrate is beryllium oxide or aluminum oxide.

[0136]

[0163] Embodiment 39. The method according to any one of Embodiments 31 to 38, wherein the ceramic of the substrate is beryllium oxide, and before heating the preassembly, the substrate is one of beryllium oxide powder, beryllium oxide compacts with a theoretical density of 56% to 64%, and beryllium oxide sintered bodies with a theoretical density of over 90%.

[0137]

[0164] Embodiment 40. The method according to any one of Embodiments 31 to 39, wherein the surface of the beryllium oxide ceramic body is a planar surface, and the planar surface faces the first surface of the substrate.

[0138]

[0165] Embodiment 41. The method according to any one of Embodiments 31 to 40, wherein the metal layer contains 35% to 100% by weight of niobium.

[0166] Embodiment 42. The method according to any one of Embodiments 31 to 41, wherein the metal layer further comprises platinum, titanium, tantalum, beryllium, alloys thereof, sublayers thereof, or combinations thereof.

[0139]

[0167] Embodiment 43. The method according to any one of Embodiments 31 to 42, wherein the time required for the step of heating the pre-assembly to the bonding temperature is 1 second to 7200 seconds.

[0168] Embodiment 44. The method according to any one of Embodiments 31 to 43, wherein the pattern is a coil, spiral, maze, one-stroke maze, circle, concentric ring, orthogonal, oblique, parallel, or perpendicular geometric structure.

[0140]

[0169] Embodiment 45. An integrated resistance heater manufactured according to the method described in any one of Embodiments 31 to 44.

[0141]

[0170] While the present invention has been described in detail, modifications to the spirit and scope of the invention will be readily apparent to those skilled in the art. In light of the above discussion, relevant knowledge in the art, and the references discussed above in relation to the background art and modes for carrying out the invention, all such disclosures are incorporated herein by reference. Furthermore, it should be understood that some aspects of the invention, and some of the various embodiments and features enumerated in the following and / or appended claims, are combined or interchangeable, either in whole or in part. In the above description of various embodiments, embodiments that refer to other embodiments may be combined with other embodiments as appropriate, as will be understood to those skilled in the art. Furthermore, those skilled in the art will understand that the above description is for illustrative purposes only and not intended to be limiting.

Claims

1. A method for forming an integrated resistance heater, A step of applying a metal layer in a certain pattern onto the surface of a beryllium oxide ceramic body, wherein the pattern of the metal layer is connected to a conductor, and the metal layer contains 10% to 100% by weight of niobium; A step of forming a pre-assembly by bringing the first surface of the substrate into contact with the metal layer so that the substrate is aligned with the beryllium oxide ceramic body, wherein the substrate includes ceramic; The steps include: heating the pre-assembly to a bonding temperature of 800°C to 1900°C to form a heating element for bonding the substrate to the beryllium oxide ceramic body, wherein the pattern maintains integrity when forming the heating element; A method that includes this.

2. The method according to claim 1, further comprising the step of compressing the pre-assembly with a contact pressure of 60 kPa to 215,000 kPa during, before, or after heating.

3. The method according to claim 1 or 2, wherein the surface of the beryllium oxide ceramic body is planar, or the surface of the beryllium oxide ceramic body has a recess.

4. The method according to claim 3, wherein the surface of the beryllium oxide ceramic body has a recess that forms a channel including the pattern and a void space around the pattern.

5. The method according to claim 4, wherein the channel further comprises beryllium oxide powder for filling the void space before heating the pre-assembly.

6. The method according to any one of claims 1 to 5, wherein the beryllium oxide ceramic body before heating the pre-assembly is a compacted powder with a theoretical density of 56% to 64%.

7. The method according to any one of claims 1 to 5, wherein the beryllium oxide ceramic body is sintered to more than 90% of its theoretical density before heating the pre-assembly.

8. The method according to any one of claims 1 to 7, wherein the ceramic of the substrate is beryllium oxide or aluminum oxide.

9. The ceramic of the substrate is beryllium oxide, and before heating the pre-assembly, the substrate is Beryllium oxide powder, Beryllium oxide compacts with a theoretical density of 56% to 64%, and Beryllium oxide sintered body with over 90% theoretical density The method according to claim 8, which is one of the methods.

10. The method according to claim 3, wherein the surface of the beryllium oxide ceramic body is a planar surface, and the planar surface faces the first surface of the substrate.

11. The method according to claim 1, wherein the metal layer contains 35% to 100% by weight of niobium.

12. The method according to claim 1, wherein the metal layer further comprises platinum, titanium, tantalum, beryllium, alloys thereof, sublayers thereof, or combinations thereof.

13. The method according to claim 1, wherein the time required for the step of heating the pre-assembled body to the bonding temperature is 1 second to 7200 seconds.

14. The method according to claim 1, wherein the pattern is a coil, a spiral, a maze, a one-stroke maze, a circle, concentric rings, orthogonal, oblique, parallel, or perpendicular geometric structure.

15. An integrated resistance heater manufactured according to the method described in claim 1.

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