Ceramic components containing beryllium aluminate

Abstract

A beryllium aluminate component may include a beryllium aluminate ceramic comprising 90 wt% or more beryllium aluminate. The ceramic may be characterized by one or more of: a thermal conductivity from 17 W / m·K to 175 W / m·K at room temperature; a bulk resistivity greater than 1 x 1015 ohm-cm at room temperature and / or greater than 1 x 109 ohm-cm at 700 ºC and / or greater than 1 x 1010 ohm-cm at 600 ºC; a coefficient of thermal expansion from 7.4 to 9.0 µm / (m·K) at room temperature; a near bioequivalence to human body tissue (Zeff) from 7.2 to 11.3; and a density of from 3.4 to 3.9 g / cc. The beryllium aluminate components may be used in pedestal assemblies, wafer pedestals, wafer chucks, integral resistance heaters, and / or components thereof, as well as for optically stimulated luminescence, thermoluminescence, radioluminescence, or dosimetry systems thereof. Processes for preparing the beryllium aluminate ceramic components are also disclosed.

Description

Atty. Ref. No.: B17302-MTRN (00654699)CERAMIC COMPONENTS CONTAINING BERYLLIUM ALUMINATECROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to and filing benefit of U.S. Provisional Patent Application No. 63 / 726,773, filed on December 02, 2024, which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to ceramic components for high temperature applications including semiconductor processing that can be used to process a wafer. The disclosure relates to pedestal assemblies, wafer pedestals, wafer chucks (e.g., electrostatic chuck (ESC) pedestals), integral resistance heaters, and / or components thereof, comprising a ceramic of beryllium aluminate. The present disclosure also relates to ceramic components of beryllium aluminate suitable as a luminescent material for optically stimulated luminescence (OSL), thermoluminescence dosimetry (TLD), and / or radioluminescence systems.BACKGROUND

[0003] In many high temperature wafer processing applications, the wafer is treated, e.g., etched, coated, cleaned, and / or has its surface energy activated in a high temperature processing chamber. To perform the treatment, process gases are introduced into the process chambers and then energized to achieve a plasma state. The energizing may be done by applying an RF voltage to an electrode, e.g., a cathode, and electrically grounding an anode to form a capacitive field in the process chamber The wafer is then treated by the plasma generated within the process chamber to etch or deposit material thereon.

[0004] During this treatment process, the wafer may be supported by a pedestal in the process chamber. Ceramic pedestals have several advantages including suitability for high temperature processing and sufficient corrosion resistance. However, ceramic pedestals - due to thermal matching considerations to reduce stresses - are limited to certain types of materials. Problems associated with ceramic pedestal assemblies include that any metal layers or patterns joined or embedded into the ceramic are likely to fail due to the generation of cracks at the interface or within the ceramic bodies, including micro-fractures, or delamination at higher temperatures.

[0005] Some known plasma processes are often performed at somewhat high temperatures and in highly erosive gases. For example, processes for etching copper or platinum are conducted at temperatures of from 250°C to 600°C, compared to temperatures of 100°C toAtty. Ref. No.: B17302-MTRN (00654699)200°C for etching aluminum. These temperatures and erosive gases thermally degrade the materials used to fabricate the chucks. Conventional ceramic pedestals and / or integral resistance heater assemblies have employed various oxides, nitrides, and alloys, e.g., aluminum nitride, aluminum oxide, silicon dioxide, silicon carbide, silicon nitride, sapphire, zirconia, or graphite or anodized metals, as the main component. In some cases, these requirements can be met by conventional ceramic materials, e.g., aluminum oxide or aluminum nitride.

[0006] As technology advances however, higher wafer treatment operating conditions (temperatures), e.g., temperatures above 650 °C, above 750 °C, or above 800 °C, are desired. Unfortunately, conventional ceramic pedestal and / or integral resistance heater materials have been found to suffer from structural problems, e.g., decomposition, thermal and / or mechanical degradation, powdering, and delamination, at these higher temperatures. In some cases, high temperature requirements can be met by certain ceramic materials, e.g., beryllium oxide. While beryllium oxide can be used in place of conventional ceramics, it is costly to fabricate and also requires special care for safety in handling. Often the application properties requirements do not justify the higher expense, e.g., the thermal conductivity is higher than even necessary for high temperature wafer processing applications using beryllium oxide pedestal assembly components alone. Disadvantageously, conventional ceramic pedestals have been found at elevated operating temperatures, e.g., at 650 °C, 700 °C, 750 °C, 800 °C, or 850 °C, to have an electrical resistivity that is decreased below the point of reliable electrostatic (Johnsen-Rahbek) chucking due to static discharge.

[0007] In addition, conventional ceramic pedestals, integral resistance heater, and / or components thereof have been found to demonstrate inconsistent temperature uniformity (e.g., across the pedestal plate surface) during operation - perhaps due to the inherent properties of aluminum nitride, silicon dioxide, or graphite. This in turn, leads to problematic inconsistencies in the treatment applied to the semiconductor wafer. Attempts have been made to improve temperature uniformity in conventional pedestal plates and / or integral resistance heaters. But these attempts include much more complex heating configurations and control mechanisms, e.g., an increased number of heating zones and thermocouples, which add cost and uncertainty to the formation process.

[0008] Conventional pedestals and / or integral resistance heaters also suffer from problems relating to micro-fractures, surface powdering, (thermal) decomposition, and reduced effusivity at elevated temperatures. In addition to mechanical stress on the various components, several treatment processes benefit from consistent temperature control and inAtty. Ref. No.: B17302-MTRN (00654699) particular temperature uniformity across the pedestal surface that supports the wafer. Various attempts to provide consistent temperature control suffer from complex heating configuration and increased control mechanisms. This further adds costs without adequately providing a desired temperature control.

[0009] Further, many conventional pedestals and / or integral resistance heaters employ layered structures that rely upon an adhesive-type bonding, e.g., using a braze material, or lamination via diffusion bonding to secure the metallic conductor within multiple (ceramic) layers. Such laminate structures, however, repeatedly suffer from structural problems and delamination that often a result from the stresses of the high temperature operations.

[0010] Also, it may be desirable to rapidly cool the wafer in order to maintain the wafer in a narrow range of temperatures or to clean the pedestal, the integral resistance heater, the wafer, or the chamber. However, temperature fluctuations occur in high power plasmas due to variations in the coupling of RF energy and plasma ion densities across the wafer. These temperature fluctuations can cause rapid increases or decreases in the temperature of the wafer, which require stabilization. Thus, it is desirable to have a pedestal assembly that requires little or no cooling during cleaning, e.g., one that can be cleaned at operating temperatures and / or with little or no cleaning cycle time, which advantageously improves process efficiency (by reducing / eliminating downtime).

[0011] Even in view of the conventional pedestal assembly and / or integral resistance heater technology, the need exists for components having improved performance, e.g., reduced decomposition, reduced thermal, micro-fracture reduction, and / or mechanical degradation, improved temperature uniformity, especially at higher temperatures, e.g., above 650 °C, while demonstrating no internal or inter-layer delamination.

[0012] In addition, different materials have been used for luminescence dosimetry (and for making luminescence dosimetry elements). These include Na2SC>4, MgSC>4, Y2O3, AI2O3, CaF2, SrF2 and BaF2, doped materials, such as CaSC>4:Tm, CaF2:Mn, AhC C, LiF:Cu, Mg, Pr, as well as many other materials. Beryllium oxide (BeO) has been used as a thermoluminescence material in ionizing radiation badges for worker protection in the medical and nuclear industries, research, military, universities, national labs, and for HAZMAT handling. OSL is optically stimulated luminescence, where a certain wavelength causes the material to emit photons depending on radiation exposure (fluence). TL is thermoluminescence, where certain elevated temperatures causes the material to emit photons depending on radiation exposure (fluence). The optically stimulated luminescence of beryllium oxide (BeO), e.g., Thermalox® 995 from Materion Ceramics (Tucson, AZ, US),Atty. Ref. No.: B17302-MTRN (00654699) has been used for optically stimulated luminescence (OSL) dosimetry. Beryllium oxide displays strong thermoluminescence (TL) together with tissue-equivalent properties which underline its application as a TL dosimeter.

[0013] There is a need for an improvement of beryllium-containing ceramic components in the thermoluminescence dosimetry (TLD), optically stimulated luminescence (OSL), and radioluminescence fields.SUMMARY

[0014] In general, the disclosure relates to ceramic components made of beryllium aluminate. Such components may include wafer pedestals, wafer chucks (e.g., electrostatic chuck pedestals), integral resistance heaters, and / or components thereof, as well as beryllium aluminate ceramic components as luminescent material (e.g., substrates, chicklets, or chips) for optically stimulated luminescence, thermoluminescence dosimetry, and / or radioluminescence systems, e.g., a pedestal assembly. In a wafer pedestal, preferably the shaft or the base plate or both comprise beryllium aluminate. In particular, it was found that the phase(s) present in the beryllium aluminate ceramic components contributed to the pedestal assemblies and / or luminescent materials herein satisfying long felt needs. Beryllium aluminate provides pedestal assemblies with desirable thermal and mechanical properties for semiconductor fabrication. In particular, beryllium aluminate maintains reliable electrostatic chucking at elevated temperatures due to its higher electrical resistivity even at high operating temperatures. The base plate and / or shaft according to embodiments herein are made of a ceramic comprising beryllium aluminate. The use of such a ceramic allows for the base plate and / or shaft to match thermal properties, such as coefficient of thermal expansion, thus minimizing sources of stress and streamlining manufacturing of compatible components. Beryllium aluminate provides luminescent materials with the required quantum properties.

[0015] In one aspect, there is provided a beryllium aluminate ceramic including 90 wt% or more beryllium aluminate; wherein the beryllium aluminate ceramic is characterized by one or more of: a thermal conductivity from 17 W / m K to 175 W / m K at room temperature; a bulk resistivity greater than 1 x 1015ohm-cm at room temperature and / or greater than 1 x 109ohm-cm at 700 °C and / or greater than 1 x 1010ohm-cm at 600 °C; a coefficient of thermal expansion from 7.4 to 9.0 pm / (m K) at room temperature; a near bioequivalence to human body tissue (Zeft) from 7.2 to 11.3; and a density of from 3.4 to 3.9 g / cc.

[0016] In another aspect, described herein is a beryllium aluminate ceramic for optically stimulated luminescence (OSL), thermoluminescence dosimetry (TLD), and / orAtty. Ref. No.: B17302-MTRN (00654699) radioluminescence systems, wherein the beryllium aluminate ceramic includes: 90 wt% or more beryllium aluminate; and at most 10 wt% total of: beryllia and / or alumina; and / or a dopant selected from chromia, magnesia, silica, and combinations thereof; and / or a sintering aid selected from iron oxide, zirconia, lanthana, fluorine, and combinations thereof.

[0017] In other aspects, there is provided a pedestal assembly for semiconductor processing, the pedestal assembly including a base plate having a top surface and a bottom surface and a shaft joined to the bottom surface, the shaft having an interior conduit, and the shaft and the base plate each of a beryllium aluminate ceramic comprising: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, silica, iron oxide, zirconia, lanthana, and / or fluorine; and balance beryllium aluminate.

[0018] In other aspects, there is provided a pedestal assembly for semiconductor processing, the pedestal assembly including a base plate having a top surface and a bottom surface and a shaft joined to the bottom surface, the shaft having an interior conduit, and the shaft and the base plate each of a beryllium aluminate ceramic consisting of: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, and / or fluorine; and balance beryllium aluminate.

[0019] In yet other aspects, the techniques described herein relate to a process for making a beryllium aluminate ceramic component including: mixing alumina and beryllia in the presence of alumina grinding media to form a ceramic composition; processing the ceramic composition to form a beryllium aluminate component including 90.0 wt% or more beryllium aluminate. The process may include additive manufacturing and / or hot pressing to form the beryllium aluminate ceramic components.BRIEF DESCRIPTION OF THE FIGURES

[0020] FIG. 1 illustrates a side, exploded view of a pedestal assembly in accordance with one embodiment of the invention.

[0021] FIG. 2 illustrates a cross-sectional view of a pedestal shaft as in FIG. 1.

[0022] FIG. 3 illustrates a perspective view of a pedestal assembly as in FIG. 1.

[0023] FIG. 4 illustrates a side, exploded view of a wafer pedestal in accordance with another embodiment of the invention.

[0024] FIG. 5 illustrates a cross-sectional view of a wafer pedestal as in FIG. 4.

[0025] FIG. 6 illustrates a perspective view of a wafer pedestal as in FIG. 4.Atty. Ref. No.: B17302-MTRN (00654699)

[0026] FIG. 7 shows a dosimetry chicklet including beryllium aluminate in a square shape for insertion into a dosimetry card and holder in accordance with one embodiment of the invention.

[0027] FIG. 8 shows a dosimetry chicklet including beryllium aluminate in a round shape in accordance with another embodiment of the invention.

[0028] FIG. 9 is a plot showing Refractive Index vs. Band Gap for various materials including beryllium aluminate in embodiments of the invention.

[0029] FIG. 10 illustrates a band gap region for alumina at ground state.

[0030] FIG. 11 illustrates a band gap region for beryllium aluminate at ground state demonstrating a larger band gap region than for alumina of FIG. 10.

[0031] FIG. 12 illustrates a band gap region for beryllium aluminate at an excited state (ionizing radiation).

[0032] FIG. 13 illustrates a band gap region for beryllium aluminate at a stimulated state (photon).DETAILED DESCRIPTION

[0033] The present disclosure may be understood more readily by reference to the following detailed description of desired embodiments and the examples included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.

[0034] A ceramic comprising beryllium aluminate provides a component and / or pedestal assembly (or in pedestal base plate and shaft components) that demonstrate a synergistic combination of at least two or more of the following properties: high temperature performance, high electrical resistivity, high thermal conductivity, and excellent coefficient of thermal expansion (CTE) match. In one embodiment, the ceramic comprising beryllium aluminate may provide a synergistic combination of high temperature performance, high electrical resistivity, high thermal conductivity, and excellent coefficient of thermal expansion (CTE) match. The phase(s) present (e.g., beryllium aluminate), grain boundaries and grain size, provides for the combination of high temperature performance, high thermal conductivity, and because the ceramic may be used for multiple components, e.g., base plate, shaft, and others an excellent coefficient of thermal expansion (CTE) match is realized. The disclosed ceramic comprising beryllium aluminate also leads to a component having optimal (smaller) quantities of magnesium oxide, silicon dioxide, and / or magnesium trisilicate, which contributes to high bulk resistivity. It has been found that the components comprisingAtty. Ref. No.: B17302-MTRN (00654699) beryllium aluminate, and the effects thereof on microstructure, unexpectedly provides for a component that demonstrates a low corrosion loss and a high bulk resistivity.

[0035] A ceramic comprising beryllium aluminate is also useful for luminescence, which requires quantum properties (a material with a band gap such as an insulator or semiconductor, and not a metallic). Without being bound by theory, when exposed to ionizing radiation, free electrons are promoted toward the conduction band, and then migrate and become captured in the traps of the band gap area. The electrons remain trapped in the beryllium aluminate until heated to above 100 °C and / or when exposed to light, e.g., 455nm from a blue light emitting diode (LED). This excites and stimulates electrons to escape the traps and, when charge carriers fall into a recombination center at a lower energy level, a photon is released from a luminescence center. This photon is measured by a filtered detector in a dosimetry material or equipment, and the signal is digitally processed using software to determine the radiation exposure of the material, for example, in a personal dosimetry radiation badge for medical workers or industry in the nuclear field.

[0036] The disclosed ceramic comprising beryllium aluminate can be used for pedestal assemblies, wafer pedestals, wafer chucks, and / or integral resistance heaters. A wafer pedestal is used to heat a wafer directly and may be part of a pedestal assembly. A wafer pedestal may include an electrostatic chuck (ESC) or a vacuum chuck for positioning the wafer on the heater. A wafer chuck includes an electrostatic chuck and holds a wafer in place during semiconductor processing. An integral resistance heater includes a means of electrical resistance embedded in, for example, a wafer pedestal. A pedestal assembly, which supports and heats the wafer, includes a wafer pedestal and may further include sensors to control heating.

[0037] Ceramic components and / or pedestal assemblies are often used to support and hold in place semiconductor wafers during treatment, e.g., chemical vapor deposition, etching, etc. Previous ceramic components and / or pedestals have employed various oxides, nitrides, and alloys, e.g., aluminum nitride, aluminum oxide, silicon dioxide, or graphite, as the main component. Although such ceramic materials are capable of being used with treatment methods at temperatures below 650 °C or below 600 °C, such ceramic materials are unable to satisfy increasing demands. As technology advances, higher wafer treatment operating temperatures, are desired e.g., temperatures above 650 °C or even above 800 °C. Conventional ceramic pedestal materials have been found to suffer from structural problems, e g., decomposition, thermal and / or mechanical degradation, and delamination at these higher temperatures. In addition, conventional pedestal materials are known to have insufficient bulkAtty. Ref. No.: B17302-MTRN (00654699) resistivity. The beryllium aluminate ceramic described herein can be used as one or more components in a wafer pedestal (also may be referred to as wafer heater or ESC wafer chuck) and / or an integral resistance heater as well as one or more components in the pedestal assemblies described herein.

[0038] Further, conventional ceramic pedestals have been found to demonstrate inconsistent temperature uniformity across the pedestal plate surface, which leads to problematic inconsistencies in the treatment applied to the semiconductor wafer. In addition, many conventional layered pedestal configurations have been found to suffer from structural problems and delamination that often result from the stresses of the high temperature operations.

[0039] In one embodiment, beryllium aluminate components may be prepared from beryllium oxide and aluminum oxide, e.g., in powder form, to form beryllium aluminate components, e.g., pedestal base plate and shaft components comprising beryllium aluminate, for pedestal assemblies. These pedestal components and assemblies satisfy requirements for thermal conductivity (e.g., 17 to 175 W / m K) while providing a coefficient of thermal expansion (e.g., from 7.4 to 9.0 pm / (m K) at room temperature) that matches well with metal layer(s) formed within the assembly (e.g., metal layers containing niobium or platinum).

[0040] Beryllium aluminate includes compounds of formula: BexAlyOz, where x equals from 1 to 3; y equals from 1 to 6; and z equals from 4 to 10. Beryllium aluminate includes phases present in the BeO-AhCh binary phase diagram such as BeAhO^ BeAleOio, and BesAhOe. In some embodiments, the beryllium aluminate is selected from the group consisting of BeAhC , BeAEOio, BesAhOe, and combinations thereof. In certain embodiments, the beryllium aluminate is BeAhC as major phase (e.g., greater than 50 wt% of the beryllium aluminate ceramic is BeAhC ). The beryllium aluminate is characterized by a chrysoberyl crystal structure.

[0041] In certain embodiments, beryllium aluminate is beryllium aluminate (BeAhC ), which has a crystal structure closely related to the spinel structure of many aluminates in terms of chemical composition. The structural arrangement is similar to that of spinel MgAhCh. In some instances, beryllium aluminate may be characterized as “spinel-type”.

[0042] BeAhCh is more closely related to olivine structure or “olivine-type” while possessing similarity with the spinel -type. The crystal structure of beryllium aluminate is in the orthorhombic crystal system and includes the crystallographic isomorphism with olivine-type structures space group Pnma. Chrysoberyl, a beryllium aluminate gemstone, is characterized as alexandrite crystal system. Alexandrite results from small scale replacement of aluminumAtty. Ref. No.: B17302-MTRN (00654699) by chromium ions in the crystal structure. These may include Cr+3-doping to synthetically produce high-quality single crystals, e.g., for lasers. In other applications, chrysoberyl exhibits mechanical and dynamical stability and it is identified as a large gap insulator with a direct band gap of around 8.3 eV. The ceramic comprising beryllium aluminate herein contains no chromium and thus, the structure is believed to be only similar to alexandrite.

[0043] Thus, the beryllium aluminate may be characterized as have a crystal structure that is spinel, spinel-type, olivine, olivine-type, alexandrite, and / or orthorhombic.

[0044] A stoichiometric mixture of high-purity beryllia (BeO) and alumina (AI2O3) powder may be used to form components comprising beryllium aluminate. In one embodiment, a stoichiometric mixture of beryllia and alumina is used to make a base plate and / or a shaft that result in a single phase of beryllium aluminate. In one embodiment, small amounts (e.g., 5 wt% or less) of free beryllia and / or free alumina may be present in the base plate and / or shaft (or other pedestal assembly or semiconductor processing component).

[0045] In one embodiment, the disclosed ceramic, BeAhC , in combination with particular processing parameters described herein unexpectedly leads to a higher bulk resistivity in combination with other material properties.

[0046] Further, the pedestal assembly components comprising BeAhC have been found to provide for a low dielectric constant, which leads to lower capacitance, which in turn improves unchucking time delays to release the silicon wafer. The disclosed BeAhC also have been found to demonstrate improved corrosion resistance, improved thermal effusivity, improved thermal diffusivity, improved thermal conductivity, improved specific heat, and lower thermal hysteresis, all of which contribute to the performance synergies disclosed herein.

[0047] Conventional ceramic pedestals, e.g., those formed with aluminum nitride, aluminum oxide, silicon dioxide, silicon carbide, silicon nitride, sapphire, zirconia, anodized metals, or graphite as the main components, have been unable to achieve high temperature performance. Nor have they been able to achieve acceptable clamping pressure at these temperatures - clamping pressure has been found to be depleted / lessened, especially at high temperatures.

[0048] A pedestal assembly is disclosed herein. Either the base plate or the shaft components, or both, of the pedestal assembly may comprise beryllium aluminate. In some cases, both the base plate and the shaft comprise beryllium aluminate. FIG. 1 illustrates a side, exploded view of a pedestal assembly 100 according to the processes described herein. Base plate 110 receives conductors 150 from within pedestal shaft 190; pass throughs 156 receive conductors 150. Base plate 110 may include holes 145 for alignment with holes 155 and 165Atty. Ref. No.: B17302-MTRN (00654699) for assembly alignment and wafer lift pins (not shown) through the various components of wafer support subassembly 101 including heating element metal layer 120 (having void space in pattern) on substrate 115 (having alignment holes 175) and bias RF electrode 125 (having holes 155). Connector 105, which can be biased to either a cathode or anode, passes through the pedestal shaft, the shaft being an interior conduit for all electrical connections in / out of pedestal assembly 100. Connector 105 is a conductive terminal post that is attached to RF electrode 125 to provide the electrical contact in order to bias the electrostatic clamping force; connector 105 may also be included at or near the center of the aligned assembly. Power supply connection conductors 150 are for connecting to a power supply (not shown). Disposed adjacent to substrate 115, optionally with bias RF electrode 125 or other component between, may be a wafer contact support 140 having an outer surface for holding a wafer atop assembly 100. Heating element metal layer 120 on substrate 115 is deposited on the underside surface of substrate 115 so that it does not electrically short out on RF electrode 125. In some embodiments, the base plate 110, shaft 190, substrate 115, and wafer contact support 140 are each a ceramic component comprising beryllium aluminate.

[0049] FIG. 3 illustrates a perspective view of a pedestal assembly 100 as in FIG. 1. The wafer support subassembly 101 is rotatable to be positioned prior to operation about pedestal shaft 190 (having a center axis) and is connected via power supply connection to a power supply (not shown). The shaft is elongated along an axis perpendicular to the bottom surface of the base plate. In one embodiment, at least two conductors (e.g., conductors 150 as in FIG. 1) may extend through the base plate and connects to the heating element. These conductors are joined to the base plate with either solder, or braze, or tack weld, mechanical screw threads, or by crimping. At least one power source can be connected to the heater conductor for controlling the heating element according to Ohm's law, and its Volts Alternating Current (VAC) equivalent form P(t)=l(t)V(t).

[0050] The pedestal assembly may include at least the shaft and the base plate comprise beryllium aluminate. Further, any of the additional ceramic components of the pedestal assembly, e.g., a substrate and / or a wafer contact support, or a dielectric spacer, may comprise beryllium aluminate. Beryllium aluminate components for the base plate and shaft components (and optionally the other components discussed herein) provides for or contributes to the performance features discussed herein, such as high temperature performance, high thermal conductivity, high bulk resistivity (especially at elevated temperatures, e.g., 800 °C), and / or a close match of coefficient of thermal expansion with the other pedestal components. In embodiments discussed herein, the base plate and shaft may beAtty. Ref. No.: B17302-MTRN (00654699) made of the same ceramic and each have microstructures demonstrating that the primary phase present is beryllium aluminate.

[0051] FIGS. 1-3 illustrate a pedestal shaft 190, however, other types of pedestals may be used in the assemblies herein, e.g., Johnsen-Rahbek ESC wafer chucking pedestal. In other cases, the disclosed pedestal assembly includes a coulombic ESC wafer chucking pedestal. In yet other cases, the disclosed pedestal assembly is a partial Johnsen-Rahbek / partial coulombic ESC wafer chucking pedestal.

[0052] The disclosure also relates to a base plate (110) and shaft (190). The base plate and the shaft may each comprise beryllium aluminate. Due to the ceramic, beryllium aluminate, and optionally the processing thereof, the base plate and / or shaft demonstrate the superior performance characteristics and microstructure disclosed herein. In particular, the microstructure of the base plate and / or shaft has average grain boundaries greater than or equal to 0.1 micron, as discussed herein. In some instances, the base plate has few if any discrete (laminated) layers, e.g., the base plate may have three or less discrete layers, or two discrete layers. In some cases, the base plate has no discrete layers, which beneficially eliminates conventional problems of delamination and deterioration. In one embodiment, the base plate is a single integral ceramic that is dense and has a thickness, tno, as prepared by sintering or other thermomechanical processes disclosed herein. Thickness, tno, of the base plate may range from 3 mm to 25 mm. The shaft includes a circumferential wall 195 and a through hole 205 for conductors. The circumferential wall (as seen in FIG. 2) has a thickness, tw. Wall thickness, tw, may range from 1 mm to 13 mm.

[0053] A wafer pedestal is disclosed demonstrating a monolith ceramic component of beryllium aluminate as in FIG. 4. FIG. 4 illustrates a side, exploded view of a wafer pedestal 300 according to the processes described herein. The wafer pedestal 300 includes a monolith ceramic component 305 that includes heated platen 310, conduit shaft 390, and flange 395 as a single, solid piece. Also shown in FIG. 4 are components separate from monolith ceramic component 305: wafer ‘W’, dielectric layer 315, electrostatic chuck (ESC) electrode 325, heating element 320, and terminal post 350 connected to ESC 325, which can be biased to either a cathode or anode similarly as for connector 105 of FIG. 1 (e.g., in a range from 400VDC to 1000VDC biased positively or negatively). Monolith ceramic component 305 is made of beryllium aluminate as described herein. Wafer ‘W’ may be a silicon wafer. Dielectric layer 315 is a dielectric material and can also be beryllium aluminate as disclosed herein. Suitable metals used for heating element 320 and terminal post 350 include, for example, Nb, Pt, and the like.Atty. Ref. No.: B17302-MTRN (00654699)

[0054] FIG. 5 illustrates a cross-sectional view of a wafer pedestal as in FIG. 4 having monolith ceramic component 305. Monolith ceramic component 305 of the beryllium aluminate disclosed herein is machinable to accommodate terminal post 350 or other hardware as needed according to the application. FIG. 6 illustrates a perspective view of wafer pedestal 300 as in FIG. 4 and FIG. 5 having monolith ceramic component 305.

[0055] In addition to the one or more ceramic components (or monolith ceramic components) for semiconductor processing as described above (e.g., for pedestal assemblies, wafer pedestals, wafer chucks, and / or integral resistance heaters), the beryllium aluminate ceramic described herein can also be for components (e.g., substrates, chicklets, or chips) for optically stimulated luminescence (OSL), thermoluminescence dosimetry (TLD), and / or radioluminescence systems due to beryllium aluminate’s ability to release energy (usually in the form of a photon) when stimulated by light or heat. A dosimeter chip, made of berylliumaluminate, absorbs ionizing radiation near bioequivalence to human body tissue. Common thermoluminescent materials include lithium fluoride (LiF), calcium fluoride (CaF?), and aluminum oxide (AI2O3) doped with various elements to enhance their properties.

[0056] Beryllium aluminate (+ ions of Cr, Mg, Si) components herein exhibit a near bioequivalence to human body tissue (Zeff) that no other material offers. The effective atomic number (Zeff) for biological tissue equivalence can vary depending on the specific type of tissue and the energy range of interest. For soft biological tissues, the Zeff is typically around 7.42. For OSL and TL dosimeters, materials with a low Zeff (typically less than 16) are chosen to ensure that their response to radiation is similar to that of human tissue. Conventional TL materials include aluminum oxide (AI2O3) with a Zeff of about 11.3 and magnesium aluminate spinel (MgALCL) with a Zeff of about 11.2. The beryllium aluminate components herein demonstrate an even lower Zeff at less than about 11.

[0057] Beryllium aluminate components described herein may be made from single crystals, polycrystals, pressed powders, thin layers deposited on substrates, small particles embedded in glass or in polymers, and the like. Ceramics used for thermoluminescent materials can vary in size and shape depending on their specific application. Typically, these ceramics are processed into powders, pellets, chips, substrates, disks, or thin films. Particle size (dso) of the powder may range from about 80 pm to about 140 pm.

[0058] In some cases the beryllium aluminate ceramic is exposed (not encased) during the TL measurement. In other cases each element is placed within a tiny plastic bag, which is part of the personal badge, so that the heating and the luminescence measurements can be carried out without removing the beryllium aluminate ceramic from the plastic bag. The TLDAtty. Ref. No.: B17302-MTRN (00654699) components of beryllium aluminate ceramic may have different geometrical shapes, e.g., plates, discs, rods, pellets, fibers, etc.

[0059] FIG. 7 illustrates a dosimetry “chip” (or “chickief ’) 400 that is beryllium aluminate according to the disclosure herein that is in a square or rectangular shape (or plate) and having a thickness. Detector card 450 includes receptacles 455 allowing space for receiving two dosimetry chips 400. The shape of chips 400 can be variable and are complementary to receptacles 455. Detector shell 460 may be hollow and includes opening 465 for (slidingly) receiving detector card 450. As an example, shown in FIG. 7, the dosimetry chips 400 are 4.7 mm square x 0.5 mm. FIG. 8 shows a beryllium aluminate dosimetry chip 500 in an alternative round shape, also having a thickness. As an example, shown in FIG. 8, the dosimetry chips 500 are 5.6 mm round x 0.5 mm thick. The shape and size and number of the beryllium aluminate dosimetry chips is non-limiting; the beryllium aluminate dosimetry chip can be made in any shape suitable for being received into a detector card 450 and detector shell 460, e.g., a dosimetry badge holder.

[0060] FIG. 9 is a plot showing refractive index vs. band gap for various materials including beryllium aluminate as disclosed herein. Inventors found surprisingly an inverse relationship between band gap and refractive index as shown in plot 600 of FIG. 9: beryllium aluminate (chrysoberyl) with a band gap of 8.3 has a refractive index of 1.75; and, by comparison, alumina (AI2O3) with a band gap of 5.97 has a refractive index of 1.77. The higher band gap of beryllium aluminate is believed to highlight its usefulness as a material for wafer pedestal dielectric for heating, ESC chucking and de-chucking, and luminophore properties in dosimetry. It is theorized that the larger band gap allows greater opportunity for defects between the valence band and conduction band than comparative materials. Ionizing energy excites and promotes valence electrons to the conduction band and then stores them in traps and recombination centers in the band gap (F center vacancies). Thus, larger band gaps allow for more storage of ionizing energy. TL and OSL release the electrons from the band gap which decay to the valence band and emit a photon. Although beryllium aluminate has a lower band gap then BeO (having a band gap of 10.6 has a refractive index of 1.718), the beryllium aluminate likely has a greater number of defects as it is not as resistant to ionizing radiation.

[0061] A comparative illustration in FIG. 10 shows a band gap region for alumina at ground state. FIG. 11 illustrates a band gap region for beryllium aluminate at ground state demonstrating a larger band gap region than for alumina of FIG. 10, thus beryllium aluminate is effective at trapping more electrons than alumina. FIG. 12 illustrates a band gap region forAtty. Ref. No.: B17302-MTRN (00654699) beryllium aluminate at an excited state (ionizing radiation). FIG. 13 illustrates a band gap region for beryllium aluminate at a stimulated state (photon).

[0062] For purposes herein, the beryllium aluminate ceramic will be described below as suitable for any of pedestal assemblies, wafer pedestals, wafer chucks, and / or integral resistance heaters, optically stimulated luminescence dosimetry systems, thermoluminescence dosimetry systems, and radioluminescence dosimetry system unless otherwise specified.

[0063] The beryllium aluminate ceramic may comprise, as the ceramic, beryllium aluminate. The beryllium aluminate may be present in an amount ranging from 75 wt% to 100 wt%, e.g., from 80 wt% to 100 wt%, from 85 wt% to 100 wt%, from 90 wt% to 100 wt%, or from 92 wt% to 99.8 wt%. In terms of lower limits, the base plate may comprise greater than or equal to 75 wt% beryllium aluminate, e.g., greater than 80 wt%, greater than 85 wt%, greater than 90 wt%, greater than 92 wt%, greater than 95 wt%, greater than 98 wt%, or greater than 99 wt% beryllium aluminate.

[0064] Depending on the processing conditions the beryllium aluminate ceramic may comprise minor amounts of alumina and / or beryllia, which may be present as unreacted or having otherwise not converted to beryllium aluminate during processing (e.g., calcining). This may be due to an excess of either alumina or beryllia during processing (e.g., mixing). An excess of either alumina or beryllia may be considered “hyper” beryllia and / or “hyper” alumina, which has not reacted to form beryllium aluminate. In this instance the beryllium aluminate ceramic may be considered a composite of beryllium aluminate with alumina and / or beryllia. Although it is preferred to have low amounts of these starting materials present after processing, the ceramic maintains its properties with minor amounts of either alumina or beryllia present. In one embodiment, the beryllium aluminate ceramic may comprise from 90.0 wt% to 100 wt% beryllium aluminate and at most 10 wt% total of beryllia and / or alumina. In another embodiment, the beryllium aluminate ceramic comprises from 92.0 wt% to 100 wt% beryllium aluminate, 0 to 8.0 wt% of alumina and / or beryllia. In yet another embodiment, the beryllium aluminate ceramic comprises from 98.0 wt% to 100 wt% beryllium aluminate, 0 to 2.0 wt% alumina and / or beryllia. For example, the beryllium aluminate ceramic may include at most 10 wt% total of beryllia and / or alumina; at most 8 wt% total of beryllia and / or alumina; or at most 5 wt% total of beryllia and / or alumina.

[0065] The beryllium aluminate ceramic comprising 90 wt% or more beryllium aluminate may be characterized by one or more of: a thermal conductivity from 17 W / m K to 175 W / m K at room temperature;Atty. Ref. No.: B17302-MTRN (00654699) a bulk resistivity greater than 1 x IO15ohm-cm at room temperature and / or greater than 1 x 109ohm-cm at 700 °C and / or greater than 1 x IO10ohm-cm at 600 °C; a coefficient of thermal expansion from 7.4 to 9.0 pm / (m K) at room temperature; a near bioequivalence to human body tissue (Zeff) from 7.2 to 11.3; and a density of from 3.4 to 3.9 g / cc.

[0066] During processing a (slightly greater than) stoichiometric amount of alumina may be used to control the amount of alumina in the beryllium aluminate ceramic that does not form beryllium aluminate so that alumina is present in an amount less than or equal to 10.0 wt% alumina, e.g., less than 5.0 wt%, less than 4.0 wt%, less than 3.0 wt%, less than 2.0 wt%, less than 1.0 wt%, less than 0.5 wt%, or less than 0.1 wt%. In one embodiment, it is found that the amount of alumina is less than the amount of beryllia. Having alumina in greater amounts may contribute to decreased performance and / or lead to cracking. The alumina which does not form beryllium aluminate may be present in an amount ranging from 0 to 10.0 wt%, e.g., from 0.1 to 5.0 wt%, from 0.1 to 4.0 wt%, from 0.1 to 3.0 wt%, or from 0.1 to 2.0 wt%. In a similar manner, a stoichiometric amount of beryllia may be used such that the beryllia that does not form beryllium aluminate may be less than or equal to 10.0 wt% beryllia, e.g., less than 5.0 wt%, less than 4.0 wt%, less than 3.0 wt%, less than 2.0 wt%, less than 1.0 wt%, less than 0.5 wt%, or less than 0.1 wt%. In one embodiment, it is found that the amount of beryllia is less than the amount of alumina. Beryllia when present in the ceramic may range from 0 to 10.0 wt%, e.g., from 0.1 to 5.0 wt%, from 0.1 to 4.0 wt%, from 0.1 to 3.0 wt%, or from 0.1 to 2.0 wt%. While a bounded range is indicated, it should be understood that the lower limit is not particular limited by the embodiments described herein. In some embodiments, the beryllium aluminate ceramic may contain no alumina and / or beryllia.

[0067] Preferably, the beryllium aluminate ceramic herein comprises at most 10 wt% total of beryllia and / or alumina, or at most 8 wt% total of beryllia and / or alumina, or at most 5 wt% total of beryllia and / or alumina.

[0068] Preferably, the beryllium aluminate ceramic herein comprises at most 10 wt% total of beryllia and / or alumina and additives, e.g., sintering aids. A sintering aid may be chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, fluorine, and combinations thereof. While the sintering aid may include, for example, oxides, in terms of content, the beryllium aluminate ceramic may contain at most 0.9 wt% total sintering aid in terms of the metallic portion only. The at most 0.9 wt% sintering aid and the at most 10 wt% total of beryllia and / or alumina should not exceed 10 wt% total, therefore, the beryllium aluminate ceramic comprises 90 wt% or more beryllium aluminate.Atty. Ref. No.: B17302-MTRN (00654699)

[0069] In one embodiment, the beryllium aluminate ceramic consists of at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total of a sintering aid chosen from: lithia, magnesia, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balance beryllium aluminate.

[0070] The phases present in the ceramic, including beryllium aluminate, alumina, and beryllia may be determined by x-ray diffraction or other analytical techniques known in the art.

[0071] The ceramic used for the base plate and / or shaft may comprise, as other minor or trace component s), magnesium oxide, silicon dioxide, or magnesium trisilicate, which may be used during processing as sintering aids. Preferably, the ceramic does not comprise these minor or trace component(s). However, depending on the processing the ceramic may comprise from 0 wt% to 5 wt% magnesium oxide, e.g., from greater than 0 wt% to 5 wt%, from 0.001 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.05 wt% to 3 wt%, or from 0.1 wt% to 1 wt%. For example, the base plate and / or shaft may comprise from 0 wt% to 5 wt% silicon dioxide, e.g., from greater than 0 wt% to 5 wt%, from 0.001 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.05 wt% to 3 wt%, or from 0.1 wt% to 1 wt%. For example, the base plate and / or shaft may comprise from 0 wt% to 5 wt% magnesium trisilicate, e.g., from greater than 0 wt% to 5 wt%, from 0.001 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.05 wt% to 3 wt%, or from 0.1 wt% to 1 wt%.

[0072] Preferably, the ceramic is of high purity, in other words, the ceramic is greater than or equal to 95 wt% beryllium aluminate, e.g., greater than 96 wt%, greater than 97 wt%, greater than 98 wt%, greater than 99 wt%, greater than 99.5 wt%, greater than 99.8 wt%, or greater than 99.9 wt%. Trace impurities of Mg, Si, S, Ti, Fe, Y, Zr, and / or La, as discussed below, may be present.

[0073] In preparing the ceramic as mentioned above, a ceramic composition that includes an oxide mixture of beryllia and alumina is prepared, which may be in powder form and then thermally and / or thermomechanically processed (e.g., calcined and / or consolidating) to form the base plate and / or shaft (or other pedestal assembly component). Stoichiometric and non- stoichiometric mixtures of beryllia and alumina are contemplated suitable for base plate and / or shaft (or other pedestal assembly component) herein, as discussed below.

[0074] In terms of mole percent, for stoichiometric (or near-stoichiometric) mixtures, the ceramic composition (before calcining to convert the oxides, alumina and beryllia, to beryllium aluminate) may comprise a ratio of AhC BeO of about 1 : 1, or about 50 mol% alumina and 50 mol% beryllia. In some embodiments, the ceramic composition mayAtty. Ref. No.: B17302-MTRN (00654699) comprise from 75 mol% to 85 mol% alumina, e.g., from 76 mol% to 84 mol% alumina, from 77 mol% to 83 mol% alumina, or from 78 mol% to 82 mol% alumina. In one embodiment, the ceramic composition comprises about 80.3 mol% alumina. The ceramic composition may comprise from 15 mol% to 25 mol% beryllia, e.g., from 17 mol% to 23 mol% beryllia, from 18 mol% to 22 mol% beryllia, or from 19 mol% to 21 mol% beryllia. In one embodiment, the ceramic composition comprises about 19.2 mol% beryllia.

[0075] For the stoichiometric (or near-stoichiometric) mixtures, the ceramic composition may comprise 19.7 wt% BeO and 80.3 wt% AI2O3 (a 1 : 1 molar ratio). Upon sintering the composition, synthetic chrysoberyl (BeAhC ) belonging to the spinel group AB2X4. The base plate and / or shaft (or other pedestal assembly component) can have an excess (non- stoichiometric) amount of either beryllia or alumina. In certain embodiments, the ceramic composition may comprise from 0.1 wt% to 50wt% hyper BeO, or 01.wt% to 50wt% hyper AI2O3. Outside of the stoichiometric 1 : 1 molar ratio, an excess (non-stoichiometric) amount of either beryllia or alumina, a (minor) formation of chrysoberyl can be formed upon sintering.

[0076] In certain embodiments, the ceramic composition may include, in the low amounts detailed above as it relates to the ceramic, optional sintering aids such as yttrium oxide, magnesium oxide, silicon dioxide, or magnesium trisilicate.

[0077] Other components may also be present, for example, aluminum (different from the aforementioned alumina), lanthanum, magnesium (other than the aforementioned magnesium oxide or magnesium trisilicate), silicon (other than the aforementioned silicon dioxide and magnesium trisilicate), sulfur, titanium, iron, zirconium, and / or yttria or combinations thereof including oxides, alloys, composites, or allotropes, or combinations thereof. These ranges and limits are applicable to these additional components: 0 wt% to 5 wt% additional components, e.g., from greater than 0 wt% to 5 wt%, from 0.001 wt% to 5 wt%, 0.01 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.01 wt% to 3 wt%, 0.05 wt% to 3 wt%, or from 0.1 wt% to 1 wt%. These may include the presence of unavoidable impurities.

[0078] Preferably, the ceramic composition used for the ceramic for the base plate and / or shaft (or other pedestal assembly component) herein does not comprise non-oxide ceramics (nitrides, borides, carbides), e.g., AIN. However, small amounts are possible in some cases. For example, the ceramic composition may comprise from 0 wt% to 5 wt% non-oxide ceramics, e.g., from greater than 0 wt% to 5 wt%, from 0.001 wt% to 5 wt%, 0.01 wt% to 4 wt%, 0.05 wt% to 3 wt%, or from 0.1 wt% to 1 wt%.Atty. Ref. No.: B17302-MTRN (00654699)

[0079] Upon thermal and / or thermomechanical processing, in one embodiment, the ceramic composition yields a ceramic for a base plate and / or shaft (or other pedestal assembly component) comprising beryllium aluminate and having properties as follows. The ceramic may have a density of 3.15 g / cc or more. In certain embodiments, the density may range from 3.15 to 3.9 g / cc or from 3.5 to 3.9 g / cc. The ceramic may have a thermal conductivity ranging from 17 W / m K to about 175 W / m K. The ceramic may have a CTE of from 8.0 to 9.0 pm / (m K), a bulk resistivity greater than 1 x 1015ohm-cm at room temperature, and a bulk resistivity greater than 1 x 109ohm-cm at 800 °C. The ceramic may be characterized by a microstructure demonstrating an average grain size of about 30 pm or less.

[0080] In some embodiments, the disclosed pedestal assemblies (or the base plates, shafts, substrates, wafer contact supports, or other components thereof) made of the ceramic as detailed above each demonstrate a coefficient of thermal expansion (CTE) in the range of from 6.4 to 9.0 pm / (m K) at room temperature (RT), e.g., from 7.0 to 9.0 pm / (m K) at RT, 7.4 to 9.0 pm / (m K) at RT, or 8.0 to 9.0 pm / (m K) at RT. In one embodiment, the CTE of the ceramic is from 8 to 9 pm / (m K) at RT. The pedestal assemblies herein may synergistically combine with heating elements comprising niobium, where the coefficient of thermal expansion (CTE) of niobium is 7.3 pm / (m K) at room temperature (RT).

[0081] In one embodiment, the ceramic comprising beryllium aluminate may be polycrystalline. In some embodiments, the ceramic provides for a base plate and / or shaft (or other pedestal assembly component) having an average grain size that may range from 1 to 200 microns, e.g., e.g., range from 5 to 200 microns, range from 5 to 180 microns, range from 5 to 100 microns range from 5 to 60 microns, from 10 to 50 microns, from 10 to 30 microns, or from 12 to 18 microns. This grain size may beneficially prevent heat transfer, thus contributing to, or enhancing high temperature performance - the transfer of heat from the plate to the opposite end of the shaft is limited, which allows the base plate and the adjacent end of the shaft to remain hot while the opposing end of the shaft (away from the base plate) remains cool.

[0082] Preferably, as mentioned above, the ceramic comprising beryllium aluminate has a high purity. In terms of microstructure, the ceramic may comprise a primary phase (first phase) and a secondary phase (second phase), where the primary phase is beryllium aluminate. A secondary phase in the ceramic (i.e., shaft and / or base plate or other component) may affect the performance properties thereof, e.g., thermal conductivity, (theoretical) density, and the ability to scatter phonons, among others. Generally, the secondary phase will be a relatively small portion of the overall microstructure of the shaft and / or the base plate. InAtty. Ref. No.: B17302-MTRN (00654699) some cases, the shaft will contain more secondary phase than the base plate, e.g., at least 5% more, at least 10% more, at least, 25% more, or at least 50% more, which contributes to improved performance of the assembly.

[0083] In some embodiments, the shaft comprises from 0.001 wt% to 50 wt% second phase, e.g., from 0.01 wt% to 25 wt%, from 0.01 wt% to 10 wt%, from 0.05 wt% to 10 wt%, 0.1 wt% to 10 wt%, from 0.1 wt% to 5 wt%, from 0.5 wt% to 5 wt%, or from 0.5 wt% to 3 wt%. In terms of upper limits, the shaft may comprise less than or equal to 50 wt% second phase, e.g., less than 25 wt%, less than 10 wt%, less than 5 wt%, less than 3 wt% or less than 2 wt%. In terms of lower limits, the shaft may comprise greater than or equal to 0.001 wt% second phase, e.g., greater than 0.01 wt%, greater than 0.05 wt%, greater than 0.1 wt%, greater than 0.5 wt%, or greater than 1 wt%. The weight percentages are based on the total weight of the shaft.

[0084] In some embodiments, the base plate comprises from 0.05 wt% to 10 wt% second phase, e.g., from 0.05 wt% to 5 wt%, from 0.1 wt% to 5 wt%, from 0.1 wt% to 3 wt, or from 0.1 wt% to 1 wt%. In terms of upper limits, the base plate may comprise less than or equal to 10 wt% second phase, e.g., less than 5 wt%, less than 3 wt%, less than 2 wt%, or less than 1 wt%. In terms of lower limits, the shaft may comprise greater than or equal to 0.05 wt% second phase, e.g., greater than 0.1 wt%, greater than 0.2 wt%, greater than 0.5 wt%, greater than 0.7 wt%, or greater than 1 wt%. The weight percentages are based on the total weight of the base plate.

[0085] In some cases, where beryllium aluminate is the primary phase, the second phase may comprise an oxide or oxides selected from alumina, beryllia, magnesia, silica, yttria, titania, lithia, lanthana, or mixtures thereof. The second phase may comprise a silicate such as or magnesium trisilicate.

[0086] It has been discovered that the particular ceramic composition optionally in conjunction with the processing thereof provides for a specific microstructure of the ceramic that is particularly beneficial for high temperature performance. In some instances, the amounts of magnesium oxide, silicon dioxide, and / or magnesium trisilicate unexpectedly increases grain boundaries and / or decreases grain size, which creates a more thermally restrictive barrier between the grains, e.g., establishes a barrier choke between the grains. This may improve microstructure for high temperature performance.

[0087] In some cases, the shaft comprises a “stub” portion (thermal choke portion). The stub portion may, in some cases, be a ring or washer. The stub portion may be employed to moderate shaft temperature. The coefficient of thermal expansion of the stub may be similarAtty. Ref. No.: B17302-MTRN (00654699) to the remainder of the shaft, e.g., within 25%, within 20%, within 15%, within 10%, within 5%, within 3% or within 1%.

[0088] By utilizing pedestal assemblies (or the base plates, shafts, substrates, wafer contact supports, or other components thereof) as described herein, problems with CTE mismatch are avoided. In addition, the base plate and / or shaft (substrates, wafer contact supports, or other components thereof) has been found to demonstrate synergistic combinations of performance features. For example, the base plate may demonstrate superior performance in terms of one or more of the following:• Temperature uniformity• Bulk resistivity• Corrosion loss• Dielectric constant.

[0089] The numerical ranges and limits for these performance characteristics are described in detail below.

[0090] In some embodiments, the base plate and / or shaft (substrates, wafer contact supports, or other components thereof) has a consistent coefficient of thermal expansion (CTE) from top-to-bottom, e.g., the CTE does not vary from top-to-bottom. For example, the coefficient of thermal may varies from top-to-bottom by less than or equal to 25%, e.g., less than 20%, less than 15%, less than 10%, less than 7%, less than 5%, less than 3%, or less than 1%.

[0091] In one embodiment, the pedestal assembly, e.g., the base plate and / or shaft, demonstrates low (if any) cycle cleaning time. During operation, it may be necessary to clean the pedestal, the wafer substrate, and / or the chamber, cleaning / removing built-up overspray. Conventionally, pedestal assemblies require a cooling step, e.g., at least an hour to get to 300 °C, to get to a temperature suitable for cleaning, and then an additional heating step, e.g., at least another hour to return to temperature. And the wafer must stabilize with these temperature changes. Because of the ceramic composition of the disclosed pedestal shaft / base plate, cooling (or the subsequent re-heating) is not required - cleaning can take place at operating temperature, and the cycle cleaning time is minimized (if not eliminated) and the wafer does not have to stabilize (as much). In some embodiments, the cycle cleaning time of the pedestal / base plate is less than or equal to 2 hours, e.g., less than 1.5 hours, less than 1 hour, less than 45 minutes, less than 30 minutes, less than 20 minutes, less than 10 minutes, or less than 5 minutes.Atty. Ref. No.: B17302-MTRN (00654699)

[0092] In some cases, the disclosure further relates to a process for cleaning a contaminated pedestal assembly / wafer / chamber. The process comprises the steps of providing to a chamber the pedestal assembly and a wafer with the wafer disposed atop the pedestal assembly and heating the wafer to an operating temperature of at least 400 °C, at least 450 °C, at least 500 °C, at least 550 °C, at least 600 °C, at least 650 °C, or at least 700 °C. Once at production temperature (and if contaminated) the process comprises the steps of cooling the wafer by less than or equal to 150 °C, e.g., less than 100 °C, less than 50 °C, less than 25 °C, or less than 10 °C, to a cooled temperature and cleaning the plate at the cooled temperature. In some embodiments, the process further comprises the step of re-heating the wafer to an operating temperature of at least 400 °C, at least 450 °C, at least 500 °C, at least 550 °C, at least 600 °C, at least 650 °C, or at least 700 °C. Importantly, a cleaning cycle time from the cooling step to the reheating step is shorter than conventional methods, e.g., less than or equal to 2 hours, e.g., less than 1.5 hours, less than 1 hour, less than 45 minutes, less than 30 minutes, less than 20 minutes, less than 10 minutes, or less than 5 minutes. Beneficially, because of the ceramic composition of the disclosed pedestal / base plate, cooling (or the subsequent re-heating) is not required or is minimized - cleaning can take place at operating temperature (or only slightly below, and the cycle cleaning time is minimized (if not eliminated) and the wafer does not have to stabilize (as much).

[0093] The disclosed base plate may be larger in size than some conventional base plates, while still demonstrating the superior performance characteristics mentioned herein. Conventionally, manufacturers have struggled with producing larger base plates that demonstrate suitable characteristics. As is known in the art, as the size of a base plate increases, so do the difficulties of maintaining performance and producing the base plate. Some reasons include the higher CTE of conventional pedestal materials, which detrimentally leads to cracking problems, and size limits of conventional commercial machines. In some embodiments, the minimum transverse measurement across the base plate is at least 100 mm, e.g., at least 125 mm, at least 150 mm, at least 175 mm, at least 200 mm, at least 225 mm, at least 250 mm, at least 300 mm, at least 400 mm, at least 500 mm, at least 750 mm, or at least 1000 mm.

[0094] The base plate, in some embodiments, has a flatness with a camber of less than or equal to 50 microns across a distance of 300 mm, e.g., less than 40 microns, less than 30 microns, less than 25 microns, less than 15 microns, less than 10 microns, or less than 5 microns.Atty. Ref. No.: B17302-MTRN (00654699)

[0095] In some cases, the base plate further comprises a mesa (stand-off). A mesa is used to elevate the wafer. In some embodiments, the mesa(s) protrude upwardly from the top surface of the base plate. The mesa(s) may have an average height ranging from 1 micron to 50 microns, e.g., from 1.5 microns to 40 microns, from 2 microns to 30 microns, from 2 microns to 20 microns, from 2.5 microns to 18 microns, or from 5 microns to 15 microns. In terms of lower limits, the mesa(s) may have an average height greater than 1 micron, e.g., greater than 1.5 microns, greater than 2 microns, greater than 2.5 microns, greater than 3 microns, or greater than 5 microns. In terms of upper limits, the mesa(s) may have an average height less than or equal to 50 microns, e.g., less than 40 microns, less than 30 microns, less than 20 microns, less than 18 microns, or greater than 15 microns.

[0096] In some cases, the base plate further comprises a heating element encapsulated therein. In some instances, the heating element is a coiled or crimped heating element. The combination of the BeO composition and / or the crimped or coiled heating element unexpectedly provides improved temperature uniformity (see discussion below), as compared to conventional base plates that employ non-BeO ceramics and / or other types of heating elements. In one embodiment, the heating element is a metal layer. The metal layer may be in a pattern. The metal layer may comprise from 10% to 100 % by weight of niobium.

[0097] The base plate may further comprise other hardware, e.g., antennae. These features are discussed in more detail below. In some cases, the antennae and / or to heating element comprise niobium and / or platinum and / or titanium. Niobium and / or platinum and / or titanium may be employed with the ceramic composition to provide for unexpected performance in terms of synergies in coefficients of thermal expansion, as well as corrosion resistance properties and electrical resistance. In some cases, these metals, when employed as hardware, have a thermal compatibility factor that are synergistically perform well with the base plate and / or shaft herein comprising beryllium aluminate. The thermal compatibility factor may prevent stress induced failures, and in particular those caused due to temperature cycling.

[0098] Thermal conductivity: In some embodiments, the ceramic for the base plate and / or shaft has a thermal conductivity ranging from 15 to 400 W / m K, when measured at room temperature, e.g., 30 W / m K to 400 W / m K, e.g., 40 W / m K to 400 W / m K, 85 W / m K to 400 W / m K, 125 W / m K to 400 W / m K, from 145 W / m K to 350 W / m K, from 175 W / m K to 325 W / m K, from 200 W / m K to 300 W / m K, or 30 W / m K to 175 W / m K, or 17 W / m K to 175 W / m K. In terms of upper limits, the base plate may have a thermal conductivity less than or equal to 400 W / m K at room temperature, e.g., less than 375 W / m K, less than 350Atty. Ref. No.: B17302-MTRN (00654699)W / m K, less than 300 W / m K, less than 275 W / m K, less than 255 W / m K, or less than 250 W / m K.

[0099] The ceramic for the base plate and / or shaft may have a thermal conductivity ranging from 17 to 105 W / m K, when measured at 800 °C, e.g., from 35 to 95 W / m K, from 45 to 85 W / m K, or from 55 to 75 W / m K. Generally the thermal conductivity will vary by 5% or less as measured from top to bottom or from the center to the edge of each component due to the uniformity of the ceramic composition and the uniform distribution of phases present. The thermal conductivity (or any other property herein) may vary 5% or less, when measured at room temperature or at 800 °C or independent of measuring temperature.

[0100] Bulk resistivity: In some cases, a bulk resistivity of the ceramic, at room temperature, ranges from 1 x 105to 1 x 1016ohm-cm, e.g., from 1 x 106to 1 x 1016, from 1 x 107to 5 x 1015, from 1 x 108to 1 x 1015, or from 1 x 109to 1 x 1015. In one embodiment, the ceramic has a bulk resistivity of greater than or equal to 1 x 1016ohm-cm at room temperature. In some embodiments, the ceramic for the base plate and / or shaft demonstrates a bulk resistivity greater than or equal to 1 x 109ohm-cm or more at 800 °C.

[0101] Purity: A purity, in some embodiments, ranges from 99.0% to 99.9%, e.g., from 99.1% to 99.9%, from 99.4% to 99.8%.

[0102] Theoretical density: In some cases, a theoretical density may range from 90% to 100%, e.g., from 91% to 100%, from 92% to 100%, from 93% to 99%, from 95% to 99%, or from 97% to 99%. In terms of lower limits, the base plate and / or shaft has a theoretical density greater than or equal to 90%, e.g., greater than 91%, greater than 92%, greater than 93%, greater than 95%, or greater than 97%. In terms of upper limits, the base plate and / or shaft has a theoretical density less than or equal to 100%, e.g., less than 99.5%, less than 99%, less than 98.7%, or less than 98%. The theoretical density of the base plate and the shaft may be the same (as they are of the same composition and demonstrate the same phases present). Theoretical density of the pedestal components is an important feature. In some cases, the theoretical density (and / or porosity) affects or contributes to the thermal conductivity.

[0103] Grain size: In some cases, an average grain size may range from 1 to 200 microns, e.g., e.g., range from 5 to 200 microns, range from 5 to 180 microns, range from 5 to 100 microns range from 5 to 60 microns, from 10 to 50 microns, from 10 to 30 microns, or from 12 to 18 microns.

[0104] Grain boundary: In some cases, a general grain boundary may range from amorphous to 10 microns, e.g., from 1 to 9 microns, from 2 to 8 microns, or from 3 to 7 microns.Atty. Ref. No.: B17302-MTRN (00654699)

[0105] Specific heat: In some embodiments, the base plate and / or shaft may have a specific heat ranging from 0.7 to 1.19 J / gK, when measured at room temperature, e.g., from 0.9 to 1.19 J / gK, from 0.95 to 1.15 J / gK, or from 1.0 to 1.1 J / gK. The base plate may have a specific heat ranging from 1.0 to 2.06 J / gK when measured at 800 °C, e.g., from 1.8 to 2.06 J / gK from 1.85 to 2.03 J / gK, or from 1.87 to 1.97 J / gK.

[0106] Thermal diffusivity: In some embodiments, the ceramic for base plate and / or shaft may have a thermal diffusivity ranging from diffusivity ranging from 75 to 115 mm2 / sec, when measured at room temperature, e.g., from 90 to 115 mm2 / sec, from 95 to 110 mm2 / sec, or from 97 to 108 mm2 / sec. The base plate and / or shaft may have a thermal diffusivity ranging from 5 to 21 mm2 / sec, when measured at 800 °C, e.g., from 7 to 19 mm2 / sec, from 9 to 17 mm2 / sec, or from 10 to 15mm2 / sec.

[0107] Effusivity: In some embodiments, the ceramic for base plate and / or shaft may have a effusivity ranging from 22.0 to 30.02 S0 5W / I< / km2, when measured at room temperature, e.g., 24.0 to 30.02 S0 5W / K / km2, from 25.0 to 29.0 S0 5W / K / km2, or from 26.0 to 28.0 S0 5W / K / km2. The base plate may have a effusivity ranging from 11.0 to 16.4 S0 5W / K / km2, when measured at 800 °C, e.g., from 12.0 to 15.0 S0 5W / K / km2, from 12.5 to 14.5 S0 5W / I< / km2or from 13.0 to 14.0 S0 5W / I< / km2.

[0108] Average CTE: In some embodiments, the base plate and / or shaft may have an average CTE ranging from 6.4 to 9.0 pm / (m K) at room temperature (RT), e.g., from 7 to 9 pm / (m K) at RT, 7.5 to 8 pm / (m K) at RT, or 8 to 9 pm / (m K) at RT.

[0109] Porosity has been found to beneficially reduce microfractures from spreading. In some embodiments, the base plate and / or the shaft has a porosity ranging from 0.1% to 10%, e.g., from 0.5% to 8%, from 1% to 7%, from 1% to 5%, or from 2% to 4%. In terms of upper limits, the base plate and / or the shaft may have a porosity less than or equal to 10%, e.g., less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. In terms of lower limits, the base plate and / or the shaft may have a porosity greater than or equal to 1%, e.g., greater than 2%, greater than 3%, greater than 4%, greater than 5%, greater than 6%, greater than 7%, greater than 8%, or greater than 9%.

[0110] The first (or second) composition advantageously contributes to uniform temperature performance across the base plate, especially at higher temperatures. Such temperature uniformity has not been achieved using conventional ceramics. In some embodiments, the base plate demonstrates a temperature variance of less than or equal to 3%, e.g., less than 2.5%, less than 2%, less than 1%, or less than 0.5%, when heated to a temperature over 700Atty. Ref. No.: B17302-MTRN (00654699)°C, e.g., over 750 °C, over 800 °C, or 850 °C. The temperatures may be measured as is known in the art, e.g., via thermocouples, IR, or TCR devices on the top surface of the plate.[OHl] The ceramic used for base plate and / or shaft (substrates, wafer contact supports, or other components thereof), in some cases, may demonstrate a corrosion loss of less than 0.016 wt%, e.g., less than 0.015 wt% after 200 cycles, less than 0.013 wt%, less than 0.012, less than 0.010 wt%, less than .008 wt%, or less than 0.005 wt%. Corrosion loss may be tested by measuring the weight of a sample before and after cycling the sample in accordance with a test protocol, e.g., 200 cycles (5.5 hours) in NF3 at 400 °C and 4 cycles (12 hours) in C1F at 300 °C.

[0112] The ceramic used for base plate and / or shaft (substrates, wafer contact supports, or other components thereof), in some cases, may demonstrate a decomposition change of less than or equal to 1 wt%, e.g., less than 0.1 wt%, or less than 0.005 wt% at temperatures of 1600 °C or more. Decomposition may be defined as break down into its precursor component (in some cases disassociation), e.g., a chemical change. It has been found that the disclosed base plate advantageously has an improved softening point and decomposition point. In some embodiments, the base plate has a softening point greater than or equal to 1600 °C, e.g., greater than 1700 °C, greater than 1750 °C, greater than 1800 °C, greater than 1850 °C, greater than 1900 °C, or greater than 2000 °C. In some embodiments, the base plate and / or shaft (substrates, wafer contact supports, or other components thereof), has a melting point greater than or equal to 2200 °C (in nitrogen gas), e.g., greater than 2325 °C, greater than 2350 °C, greater than 2400 °C, greater than 2450 °C. Unlike conventional base plates, the disclosed base plate is capable of providing the aforementioned clamping pressure at these temperatures. Conventional base plates, e.g., aluminum nitride base plates, decompose at temperatures significantly less than 1600 °C and will melt at much lower temperatures that are significantly less than 2200 °C.

[0113] In some embodiments, the ceramic used for base plate and / or shaft (substrates, wafer contact supports, or other components thereof) has a dielectric constant less than or equal to 20, e.g., less than 17, less than 15, less than 12, less than 10, less than 8, or less than 7.

[0114] In some instances, the ceramic used for base plate and / or shaft (substrates, wafer contact supports, or other components thereof) has a surface hardness of at least 50 Rockwell, as measured on a 45N scale, e.g., least 50 Rockwell, at least 52 Rockwell, at least 55 Rockwell, at least 57 Rockwell, at least 60 Rockwell, at least 65 Rockwell, or at least 70 Rockwell.Atty. Ref. No.: B17302-MTRN (00654699)

[0115] In some embodiments, the ceramic used for base plate and / or shaft (substrates, wafer contact supports, or other components thereof) has a coefficient of thermal expansion ranging from 5 to 15 throughout the base plate, e.g., from 6 to 13, from 6.5 to 12, from 7 to 9.5, from 7.5 to 9, or from 7 to 9. In terms of upper limits, the base plate and / or shaft (substrates, wafer contact supports, or other components thereof) may have a coefficient of thermal expansion of greater than or equal to 5, e.g., greater than 6, greater than 6.5, greater than 7, or greater than 7.5. In terms of upper limits, the base plate and / or shaft (substrates, wafer contact supports, or other components thereof) may have a coefficient of thermal expansion of less than or equal to 15, e.g., less than 13, less than 12, less than 9.5, or less than 9. The coefficient of thermal expansion varies from top-to-bottom by less than or equal to 25%, e.g., less than 10%, less than 5%, less than 3%, or less than 1%.

[0116] The disclosed base plate and shaft may be used in conjunction with one another. In the alternative, these components may be used in combination with other components known in the art. For example, the disclosed base plate may be used with an aluminum shaft or the disclosed shaft may be employed with an aluminum base plate.

[0117] In some embodiments, a pedestal assembly comprises the disclosed shaft and a base plate comprising two or more (laminated) layers and / or a co-fired ceramic material. The layers may be bonded to one another with a braze material. In addition to the shaft and the base plate, these assemblies may further comprise additional hardware, e.g., heating elements, antennae, etc.

[0118] The disclosure also relates to a process for making a base plate, a shaft, a substrate, a wafer contact support, or other component. These components may be produced from two or more raw powders including BeO and AI2O3. The powders are mixed into a ceramic composition as described herein and may be used to form a precursor plate, which is then thermally or thermomechanically processed to yield the base plate. Similarly, the other components are made from the ceramic composition.

[0119] In one embodiment, the process comprises the steps of mixing alumina and beryllia to form a ceramic composition and processing the ceramic composition to form a beryllium aluminate component comprising 90.0 wt% or more beryllium aluminate. Mixing the alumina and beryllia starting materials includes targeting 90.0 wt% or more beryllium aluminate for the composition after calcining and / or sintering. Mixing alumina and beryllia may be in the presence of alumina grinding media to form the ceramic composition. In some embodiments, mixing includes starting from 76 wt% to 84 wt% alumina and from 16 wt% to 24 wt% beryllia to form the ceramic composition. Mixing may include additional components such asAtty. Ref. No.: B17302-MTRN (00654699) a sintering aid and / or a doping agent: chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine. Mixing may include milling. Calcining may also include milling to break up aggregate before further processing. Calcining may be at a temperature of from about 1375 °C to 1575 °C in air for a time of from about 4 to about 12 hours or from about 1425 °C to 1525 °C in air for a time of from about 6 to about 10 hours. In some embodiments, calcining is at 1475 °C for 8 hours in air.

[0120] The ceramic composition after calcining may be a powder comprising beryllium aluminate. The ceramic composition may be a powder having beryllium aluminate present in an amount ranging from 75 wt% to 100 wt%, e.g., from 80 wt% to 100 wt%, from 85 wt% to 100 wt%, from 90 wt% to 100 wt%, or from 92 wt% to 99.8 wt%. In terms of lower limits, the ceramic composition (beryllium aluminate powder) may comprise greater than or equal to 75 wt% beryllium aluminate, e.g., greater than 80 wt%, greater than 85 wt%, greater than 90 wt%, greater than 92 wt%, greater than 95 wt%, greater than 98 wt%, or greater than 99 wt% beryllium aluminate.

[0121] The ceramic composition powder (beryllium aluminate powder) may be characterized as having an average particle size (dso), which is defined as the particle diameter at which a cumulative percentage of 50% (by volume) of the total number of particles are attained. In other words, 50% of the particles have a diameter above the average particle size, and 50% of the particles have a diameter below the average particle size. The beryllium aluminate ceramic composition, e.g., beryllium aluminate powder after calcining and optional milling, has an average particle size dso of from about 60 pm to about 160 pm or from about 80 pm to about 140 pm. The average particle size of the beryllium aluminate powder may range from 60 pm to 160 pm, e.g., 70 pm to 150 pm, from 75 pm to 145 pm, or from 80 pm to 140 pm. In terms of lower limits, the average particle size of the beryllium aluminate powder may be greater than 60 pm, e.g., greater than 70 pm, greater than 75 pm, or greater 80 pm. In terms of upper limits, the average particle size of the beryllium aluminate powder may be less than 160 pm, e.g., less than 150 pm, less than 145 pm, or less than 140 pm. The beryllium aluminate powder composition can be characterized by a dio less than 10 pm (where 10% of the population of all particles are under about 10 pm) and a d9o less than 250 pm (where 90% of the population of all particles are under about 250 pm).

[0122] The process may comprise forming a precursor comprising the ceramic composition to make a component for a TL / RL dosimetry system, an integral resistance heater, and / or a pedestal assembly. The process may further comprise forming one or more additional component precursor(s) comprising the ceramic composition.Atty. Ref. No.: B17302-MTRN (00654699)

[0123] The forming may be achieved by distributing the powder composition in a mold. Importantly, in some cases, once the precursor is formed, it may be co-mingled, e.g., vibrated (optionally under controlled conditions), to allow the powders to partially co-mingle or knit, which may provide uniformity after firing. In some cases, insufficient co-mingling or no comingling at all will result in a layered base plate or shaft, which may not achieve all of the benefits mentioned herein. Mingling promotes for a homogeneous mixture of the ceramic composition being achieved. In one embodiment, mixing comprises from 92 wt% to 96 wt% alumina and from 4 wt% to 8 wt% beryllia to form the ceramic composition.

[0124] Precursors herein are “green”, which are unfired or unsintered. The component precursor(s) may optionally include a binder (added during mixing) that is burned off during subsequent heat treatment(s). Whether or not an optional binder is included during mixing, the green component precursor(s) may optionally be subjected to a heat treatment at an intermediate burn-off temperature (prior to heating at higher temperatures to sinter the ceramic to 95% to 100% theoretical density).

[0125] Temperatures for sintering the component precursor(s) are from at least 50% of the composition melting point and up to, but not exceeding, the temperature at which crystal phase transformation occurs, e.g., from 1100 °C to 2000 °C. For heating to the sintering temperature, ramp rates should not exceed 600 °C / minute. The component precursor(s) are held at sintering temperatures until the rate of shrinkage becomes non-linear or less than 17 ppm / minute. Cooling rates follow Euler’s rate of decay.

[0126] The process includes processing the ceramic composition (and / or additional component) including heating the ceramic composition to form a beryllium aluminate powder and forming a component precursor of the beryllium aluminate powder, and further processing the component precursor to 90% to 100% theoretical density to form a beryllium aluminate ceramic component. Upon heating, the ceramic sinters to form the dense ceramic components. Heating also transforms the ceramic composition (starting as alumina and beryllia) to form a ceramic comprising beryllium aluminate. The process may further include, prior to assembling, forming at least one additional plate precursor comprising the ceramic composition and heating the at least one additional plate precursor to 90% to 100% theoretical density. Certain embodiments include forming a wafer holder precursor comprising the ceramic composition and heating the wafer holder precursor to 90% to 100% theoretical density. The beryllium aluminate component includes from 0 to 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balanceAtty. Ref. No.: B17302-MTRN (00654699) beryllium aluminate. Preferably, the beryllium aluminate component at most 10 wt% of phases other than beryllium aluminate, e.g., 0 to 10 wt% total of beryllia and / or alumina and / or at most 0.9 wt% total of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine.

[0127] The process may comprise the steps of cold forming prior to heating / sintering the base plate precursor to form the base plate. Further processing includes cold pressing and / or sintering. Processing the ceramic composition may include forming a component precursor of the ceramic composition and further processing the component precursor to 90% to 100% theoretical density to form a beryllium aluminate ceramic component. In other embodiments, further processing includes additive manufacturing and / or hot pressing. The component precursor(s) may be similarly formed by cold forming following by heating / sintering to form the additional components.

[0128] Other processing techniques suitable to forming beryllium aluminate include: (i) pressing, e.g., cold pressing and sintering or hot pressing or hot isostatic pressing; (ii) mixing with a resin (or binder) additive manufacture components. Beryllium aluminate components can be further sintered and / or machined as needed.

[0129] Cold pressing (uniaxial, extrusion, or isostatic) beryllium aluminate solid compacts may be at a pressure of about 10,000 psi to about 40,000 psi. The compacts may then be sintered in air (or inert or nitriding or reducing atmospheres) at a temperature of from about 1000 °C to about 1900 °C.

[0130] Alternatively, hot isostatic pressing of the beryllium aluminate inside a sealed container (to hold the beryllium aluminate powder) may be at a pressure of about 10,000 psi to about 30,000 psi at a temperature of from about 900 °C to about 1400 °C. A pre-sintered beryllium aluminate ceramic compact with closed surface porosity may be free hot isostatic pressed, at a pressure of about 10,000 psi to about 30,000 psi at a temperature of up to 2000 °C.

[0131] Alternatively, uniaxial hot pressing (vacuum or partial pressure of argon) may be at a pressure of about 800 psi to about 4000 psi at a temperature of from about 900 °C to about 2000 °C. This could include a hot press with a passive resistive heater, induction heater, or a direct current spark plasma heating of the container (die or crucible) that holds the loose powder or pre-compacted powder during simultaneous heating and force, or force before heating, or heating before force.

[0132] The beryllium aluminate ceramic components made by additive manufacturing may be formed to a beryllium aluminate component that is a shape, a geometry, an article, aAtty. Ref. No.: B17302-MTRN (00654699) spacer, am insulator, a tube, a rod, a bar, a billet, a plate, a tile, a platen, a disk, a washer, a segment, a round, a cylinder, a cube, or combinations thereof. Beryllium aluminate ceramic components as described in FIGs. 1-3 can be made by additive manufacturing. In addition, beryllium aluminate components made by additive manufacturing may include multiple components (as) as a single piece to reduce the overall number of components and material waste, e.g., a heated platen / conduit shaft / flange as shown in FIGs. 4-6. Beryllium aluminate ceramic components that are dosimetry chicklets are shown in FIGs. 7-8. Beryllium oxide, aluminum oxide, and crystal forming additives are mixed, milled, and calcined to produce a beryllium aluminate (chrysoberyl) seed crystal precursor powder. Suitable crystal forming additives include yttrium (Y), magnesium (Mg), silicon (Si), and aluminum (Al).

[0133] The precursor powder is mixed with sintering aids, a temporary binder, and optionally a vehicle (liquid portion) to produce an additive manufacturable (3D printable) material. Suitable vehicles include polar aqueous solvents such as water, alcohols, acetates, glycols, esters, petroleum based products, or combinations thereof. A CAD model may be used to render a solid object, which is then printed.

[0134] Binder is removed during subsequent heating, and the additive manufactured body is consolidated, sintered, and machined as needed using conventional techniques. Binder includes organic binders and resins such as acrylates, PVA, or cellulose, or long chain urethane polymers. The wafer pedestal may include niobium and platinum hardware installed in the beryllium aluminate ceramic component as heating element(s) and / or as an electrostatic chucking (ESC) electrode for positioning a wafer on the pedestal for processing. The pedestal is supported in an inverted position and DC power is applied to the ESC electrode. A silicon wafer may then be clamped to the inverted pedestal and AC power is applied to the heating elements. The temperature and voltage at the ESC electrode is recorded at multiple points where the mass of the silicon wafer exceeds the clamping force of the ESC. The clamping force is measured using pressure forced to the backside of the wafer, and also using force applied to a rod that passes through the conduit, and also using weights attached to the inverted wafer.

[0135] Optional dopants included in the additive manufacturing of beryllium aluminate components as described above can improve a luminophore (e.g., by forming intentional defect sites or “F-center oxygen vacancy”). Suitable dopants include carbon or metallic (positively charged) ions selected from: lithium, boron, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, titanium, chromium, manganese,Atty. Ref. No.: B17302-MTRN (00654699) iron, copper, zinc, germanium, strontium, yttrium, zirconium, cadmium, indium, lanthanum, cerium, samarium, europium, terbium, dysprosium, erbium, thulium, or combinations thereof.

[0136] The beryllium aluminate ceramic components made by additive manufacturing techniques as described above can provide a more anisotropic grain microstructure as compared with sintering, which provide a generally isotropic. Porosity is also influenced by process technique and beryllium aluminate ceramic components made by additive manufacturing may have more porosity than for components made by sintering or hot pressing.

[0137] The process further includes joining the shaft to a bottom surface of the base plate to form the pedestal assembly. Forming the pedestal assembly may include placing a heating element in at least one of the regions and / or crimping of terminals. In one embodiment, the process further comprises applying a metal layer in a pattern on a top surface of the base plate (to form the heating element), wherein the pattern of the metal layer comprises from 10 wt% to 100 wt% niobium.

[0138] After heating to form the shaft and / or the base plate, the shaft and the base plate may each comprise the ceramic comprising from 50 wt% to 100 wt% beryllium aluminate. In one embodiment, the ceramic components made according to the above process comprises from 90.0 wt% to 100 wt% beryllium aluminate, 5.0 wt% or less alumina, and 5.0 wt% or less beryllia.

[0139] Some embodiments relate to a process for making a pedestal assembly. The process comprises the steps of providing the disclosed base plate and the disclosed shaft, and connecting the shaft to the base plate.

[0140] Other embodiments relate to where the beryllium aluminate ceramic is a component in a thermally conductive electrically insulated heater, wherein the beryllium aluminate ceramic component is adjacent to a resistive element.

[0141] Other embodiments related to ceramic components of beryllium aluminate as a luminescent material for optically stimulated luminescence (OSL), thermoluminescence dosimetry (TLD), and / or radioluminescence systems. In one embodiment, the beryllium aluminate ceramic is for a luminescent dosimetry system, wherein the beryllium aluminate ceramic includes:90 wt% or more beryllium aluminate; and at most 10 wt% total of: beryllia and / or alumina; and / or a dopant selected from chromia, magnesia, yttria, silica, and combinations thereof; and / or a sintering aid selected from iron oxide, zirconia, lanthana, fluorine, and combinations thereof.Atty. Ref. No.: B17302-MTRN (00654699)

[0142] The beryllium aluminate ceramic has a near bioequivalence to human body tissue (Zeff) ranging from 7.2 to 11.3, e.g., the beryllium aluminate ceramic has a Zeff of from about 8 to about 11, or about 9 to about 11, or about 10 to about 11. In particular embodiments, the Zeff is from 10 to 11. The Zeff may be about 10.5.

[0143] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0144] The singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0145] As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of’ and “consisting essentially of’. The terms “comprise(s)”, “include(s)”, “having”, “has”, “can”, “contain(s)”, and variants thereof, as used herein, are intended to be open-ended transitional phrases that require the presence of the named ingredients / steps and permit the presence of other ingredients / steps. However, such description should be construed as also describing compositions or methods as “consisting of’ and “consisting essentially of’ the enumerated ingredients / steps, which allows the presence of only the named ingredients / steps, along with any impurities that might result therefrom, and excludes other ingredients / steps.

[0146] Numerical values in the specification and claims of this application, as they relate to ceramic components or ceramic compositions, reflect average values for a composition. The numerical values disclosed herein should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0147] All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of “from 1 pm to 200 pm” is inclusive of the endpoints, 1 pm and 200 pm, and all the intermediate values). The endpoints of the ranges and any valuesAtty. Ref. No.: B17302-MTRN (00654699) disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and / or values.

[0148] As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 8 to about 9” also discloses the range “from 8 to 9”, e.g., as in a coefficient of thermal expansion (CTE) in the range of from 8 to 9 pm / (m K) at room temperature. The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1.

[0149] For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 92 to 96, e.g., as a weight percent, the numbers 93, 94, and 95 are contemplated in addition to 92 and 96, and for the range 8.0-9.0, the number 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, and 8.0 are explicitly contemplated.

[0150] As used herein, “greater than” and “less than” limits may also include the number associated therewith. Stated another way, “greater than” and “less than” may be interpreted as “greater than or equal to” and “less than or equal to.” It is contemplated that this language may be subsequently modified in the claims to include “or equal to.” For example, “less than 5” may be interpreted as, and subsequently modified in the claims as “less than or equal to 5.”

[0151] Some of the components and steps disclosed herein may be considered optional. In some cases, the disclosed compositions, processes, etc. may expressly exclude one or more of the aforementioned components or steps in this description, e.g., via claim language. This is contemplated herein by the inventors. For example, claim language may be modified to recite that the disclosed compositions, processes, streams, etc., do not utilize or comprise one or more of the aforementioned components or steps, e.g., tin (or any other of the aforementioned additives). Such negative limitations are contemplated, and this text serves as support for negative limitations for components, steps, and / or features.EXAMPLESAtty. Ref. No.: B17302-MTRN (00654699)

[0152] Example 1. Raw materials of beryllia and alumina were weighed to target a composition of 20 wt% beryllia and 80 wt% alumina. The powders were mixed in a grinding media jar using alumina grinding media. An estimate of how much of the alumina from the grinding media would contribute to the mixture was made so that the amount of alumina powder was slightly under that of 80 wt%. The powder mixture in water was jar milled for approximately 16 hours. After milling, the water was evaporated off using a hot plate to form a dried mixture. For larger scale operations, the milled mixture would have been spray dried. The dried mixture was then crushed to reduce any agglomeration formed and then calcined at a temperature of 1475 °C for 8 hours in air to convert to beryllium aluminate.

[0153] The calcined beryllium aluminate was analyzed to evaluate if the conversion to beryllium aluminate was complete. The conversion was complete as no free beryllia was detected meaning that 0 wt% beryllia or about 1 wt% or less beryllia was present (due to detection limit of the XRD technique). Excess alumina was detected (due at least in part to contribution from the alumina grinding media).

[0154] Table 1 shows the X-Ray Diffraction (XRD) results of the analyzed beryllium aluminate powder of Example 1 showing the major phase beryllium aluminate (92.7 wt%) and the minor phase alumina (7.3 wt%).

[0155] The beryllium aluminate powder of Example 1 was crushed to reduce any agglomerates that formed during calcining. The powder was sintered (e.g., at 1000 °C to 1700 °C with a hold of from 3 to 8 hours in air or inert or nitriding or reducing atmospheres) as needed. The beryllium aluminate powder has an average particle size dso of 87.38 pm, where dio (10% of the particle population) are under 10.26 pm and d9o (90% of the particle population) are under 238.47 pm. The beryllium aluminate powder has an mean particle size of 109.77 pm.

[0156] Sintering the powder prior to forming components may be optional.

[0157] The beryllium aluminate powder of Example 1 was used to form ceramic components by (i) pressing, e.g., cold pressing and sintering or hot pressing or hot isostatic pressing as in FIGs. 1-3; (ii) mixing with a resin (or binder) additive manufacture components as in FIGs. 4-6. These exemplified beryllium ceramic components are suitable for sintering and / or machining as needed.Atty. Ref. No.: B17302-MTRN (00654699)

[0158] The process pressures and temperatures for cold pressing (uniaxial, extrusion, or isostatic) beryllium aluminate solid components are 10,000 psi - 40,000 psi, then sintered in air or inert or nitriding or reducing atmospheres at 1000 °C - 1900 °C.

[0159] The process pressures and temperatures for hot isostatic pressing inside a sealed container to hold the powder are 10,000 psi - 30,000 psi at 900 °C - 1400 °C. A pre-sintered object with closed surface porosity can be free hot isostatic pressed without a can, at these same pressures but up to 2000 °C.

[0160] The process pressures and temperatures for uniaxial hot pressing (vacuum or partial pressure of argon) are 800 psi - 4000 psi at 900 °C - 2000 °C. This could include a hot press with a passive resistive heater, induction heater, or a direct current spark plasma heating of the container (die or crucible) that holds the loose powder or pre-compacted powder during simultaneous heating and force, or force before heating, or heating before force.

[0161] Example 2. A beryllium aluminate pedestal was made of beryllium aluminate powder to form a ceramic component using additive manufacturing techniques and consolidated by sintering. XRD data for the beryllium aluminate powder is shown in Table. 2.

[0162]

[0163] Supplemental XRD analysis showed no minor phases present besides BeO.

[0164] A wafer pedestal as in FIG. 4, which includes an electrostatic chucking (ESC) electrode and heating elements, is used to hold and position a wafer, e.g., a silicon wafer, at elevated temperatures for wafer processing. Beryllium oxide and aluminum oxide powders (similarly as in Example 1) were mixed along with crystal forming additives. The mixture was milled and the milled mixture was then calcined at a temperature of 1475 °C for 8 hours in air to convert to a chrysoberyl (beryllium aluminate) seed crystal precursor powder. The powder was then mixed with 9000 ppm of Y, Mg, and / or Si metallic portion content (from oxide Y2O3, MgO, and / or SiCh sintering aids, 1 wt% to 10 wt% urethane based acrylate temporary binder, and a resin based vehicle to produce a 3D printable material. A CAD model was used to render the solid object, which was then printed using a Tethon Bison™ to produce a 3D printable material at 80% inorganic powder solids. The binder was removed by heating to 150 °C held for 1 hour followed by 540 °C held for 1 hour, and the body was consolidated by sintering at 1650 °C in air held for 8 hours. The beryllium aluminate waferAtty. Ref. No.: B17302-MTRN (00654699) pedestal was then machined to make true mating contact surfaces, e.g., surfaces that are planar and parallel. Niobium and / or platinum hardware was installed to produce heating elements and an ESC electrode as in Figures 4-6. In an inverted position, 500 VDC power was applied to the ESC electrode and a silicon wafer was clamped to the inverted pedestal. 60 to 145 VAC power was then applied to the heating elements. At 650 °C the clamping force was measured at 11 torr using pressure forced to the backside of the wafer.

[0165] Example 3. A beryllium-aluminate pedestal was made of beryllium-aluminate powder to form a ceramic component using additive manufacturing techniques as in Example 2, except that a vehicle was omitted prior to additive manufacturing and the component was consolidated using dry uniaxial pressing equipment (125 ton hydraulic). The beryllium- aluminate pedestal was then machined, and hardware and an ESC electrode were installed as for Example 2.

[0166] Example 4. A beryllium-aluminate luminescent material dosimeter chip was made of beryllium-aluminate powder to form a ceramic component using additive manufacturing techniques. Beryllium oxide and aluminum oxide powders and crystal forming additives were mixed, milled, and calcined as for Example 2, to produce a chrysoberyl seed crystal precursor powder. The powder was then mixed with sintering aids, dopants, temporary binder, and vehicle to produce 3D printable material. A CAD model was used to render the solid object, which was then printed using a Tethon Bison™ to produce a 3D printable material at 80% inorganic powder solids. The binder was removed, and the body was consolidated by sintering at 1650 °C in air held for 8 hours. The chip was further processed, machined square flat and parallel, for suitable testing. The Zetr determined according to the equation below.Zeff=2 9V.516 x (8)294+ .065 X (4)294+ .419 X (13)2 94= 11

[0167] Example 5. A beryllium-aluminate luminescent material dosimeter chip was made of beryllium-aluminate powder to form a ceramic component using additive manufacturing techniques as in Example 4, except that a vehicle was omitted prior to additive manufacturing and the component was consolidated using dry uniaxial pressing equipment (6 ton mechanical).Embodiments

[0168] The following embodiments, among others, are disclosed.

[0169] Embodiment 1. A beryllium aluminate ceramic comprising 90 wt% or more beryllium aluminate; wherein the beryllium aluminate ceramic is characterized by one or more of aAtty. Ref. No.: B17302-MTRN (00654699) thermal conductivity from 17 W / m K to 175 W / m K at room temperature; a bulk resistivity greater than 1 x 1015 ohm-cm at room temperature and / or greater than 1 x 109 ohm-cm at 700 °C and / or greater than 1 x 1010 ohm-cm at 600 °C; a coefficient of thermal expansion from 7.4 to 9.0 pm / (m K) at room temperature; a near bioequivalence to human body tissue (Zeir) from 7.2 to 11.3; and a density of from 3.4 to 3.9 g / cc.

[0170] Embodiment 2. The beryllium aluminate ceramic of embodiment 1 comprising at most 10 wt% total of beryllia and / or alumina; at most 8 wt% total of beryllia and / or alumina; or at most 5 wt% total of beryllia and / or alumina.

[0171] Embodiment 3. The beryllium aluminate ceramic of embodiment 1 or embodiment 2 comprising at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine.

[0172] Embodiment 4. The beryllium aluminate ceramic of embodiment 1, consisting of: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balance beryllium aluminate.

[0173] Embodiment 5. The beryllium aluminate ceramic of any of embodiments 1-4, wherein the beryllium aluminate ceramic is of formula BexAlyOz, where x equals from 1 to 3; y equals from 1 to 6; and z equals from 4 to 10.

[0174] Embodiment 6. The beryllium aluminate ceramic of any of embodiments 1-5, wherein the beryllium aluminate ceramic is selected from the group consisting of BeAhC , BeAEOio, BesAhOe, and combinations thereof.

[0175] Embodiment 7. The beryllium aluminate ceramic of any of embodiments 1-6, wherein the beryllium aluminate ceramic is BeAhC as major phase.

[0176] Embodiment 8. The beryllium aluminate ceramic of embodiment 7, wherein the beryllium aluminate ceramic is characterized by a chrysoberyl crystal structure.

[0177] Embodiment 9. The beryllium aluminate ceramic of any of embodiments 1-8, wherein the beryllium aluminate ceramic has a microstructure characterized by an average grain size less than 200 microns.

[0178] Embodiment 10. The beryllium aluminate ceramic of any of embodiments 1-9, wherein the beryllium aluminate ceramic is polycrystalline.

[0179] Embodiment 11. The beryllium aluminate ceramic of any of embodiments 1-10, wherein the beryllium aluminate ceramic is a component in a thermally conductive electrically insulated heater, wherein the component is adjacent to a resistive element.Atty. Ref. No.: B17302-MTRN (00654699)

[0180] Embodiment 12. A beryllium aluminate ceramic for optically stimulated luminescence, thermoluminescence, radioluminescence , or dosimetry systems thereof, wherein the beryllium aluminate ceramic includes: 90 wt% or more beryllium aluminate; and at most 10 wt% total of: beryllia and / or alumina; and / or a dopant selected from chromia, magnesia, yttria, silica, and combinations thereof; and / or a sintering aid selected from iron oxide, zirconia, lanthana, fluorine, and combinations thereof.

[0181] Embodiment 13. The beryllium aluminate ceramic of embodiment 12 having a near bioequivalence to human body tissue (Zeff) is from 7.2 to 11.3; preferably from 10 to 11.

[0182] Embodiment 14. The beryllium aluminate ceramic of embodiment 12 or embodiment 13, wherein the beryllium aluminate ceramic is characterized by a chrysoberyl crystal structure.

[0183] Embodiment 15. The beryllium aluminate ceramic of any of embodiments 12-14 having a microstructure characterized by an average grain size less than 200 microns.

[0184] Embodiment 16. The beryllium aluminate ceramic of any of embodiments 12-15, wherein the beryllium aluminate ceramic is polycrystalline.

[0185] Embodiment 17. The beryllium aluminate ceramic of embodiment 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a base plate having a top surface and a bottom surface, the base plate comprising the beryllium aluminate ceramic; and a shaft joined to the bottom surface and having an interior conduit, wherein the shaft is elongated along an axis perpendicular to the bottom surface.

[0186] Embodiment 18. The beryllium aluminate ceramic of embodiment 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a shaft comprising the beryllium aluminate ceramic and having an interior conduit; and a base plate having a top surface and a bottom surface, wherein the shaft is elongated along an axis perpendicular to the bottom surface, the shaft joined to the bottom surface.

[0187] Embodiment 19. The beryllium aluminate ceramic of embodiment 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a base plate having a top surface and a bottom surface, the base plate comprising the beryllium aluminate ceramic; and a shaft comprising the beryllium aluminate ceramic and joined to the bottom surface, wherein the shaft has an interior conduit and is elongated along an axis perpendicular to the bottom surface.Atty. Ref. No.: B17302-MTRN (00654699)

[0188] Embodiment 20. A pedestal assembly for semiconductor processing, the pedestal assembly comprising a base plate having a top surface and a bottom surface and a shaft joined to the bottom surface, the shaft having an interior conduit, and the shaft and the base plate each of a beryllium aluminate ceramic consisting of: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, and / or fluorine; and balance beryllium aluminate.

[0189] Embodiment 21. The pedestal assembly of embodiment 20, further comprising a metal layer in a pattern disposed between the top surface of the base plate and a substrate comprising the beryllium aluminate ceramic, wherein the pattern of the metal layer comprises from 10 wt% to 100 wt% niobium.

[0190] Embodiment 22. The pedestal assembly of embodiment 20 or embodiment 21, further comprising a wafer contact support comprising the beryllium aluminate ceramic, wherein an electrode is disposed between the substrate and the wafer contact support.

[0191] Embodiment 23. A process for making a beryllium aluminate ceramic component comprising: mixing alumina and beryllia in the presence of alumina grinding media to form a ceramic composition; processing the ceramic composition to form the beryllium aluminate ceramic component comprising 90.0 wt% or more beryllium aluminate.

[0192] Embodiment 24. The process of embodiment 23, wherein mixing comprises from 76 wt% to 84 wt% alumina and from 16 wt% to 24 wt% beryllia to form the ceramic composition.

[0193] Embodiment 25. The process of embodiment 23 or embodiment 24, wherein the beryllium aluminate ceramic component comprises: 0 to 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balance beryllium aluminate.

[0194] Embodiment 26. The process of any of embodiments 23-25, wherein processing the ceramic composition includes heating the ceramic composition to form a beryllium aluminate powder, forming a component precursor of the beryllium aluminate powder, and further processing the component precursor to 90% to 100% theoretical density to form the beryllium aluminate ceramic component.

[0195] Embodiment 27. The process of any of embodiments 23-26, wherein further processing includes cold pressing and sintering.Atty. Ref. No.: B17302-MTRN (00654699)

[0196] Embodiment 28. The process of any of embodiments 23-27, wherein processing the ceramic composition includes forming a component precursor of the ceramic composition and further processing the component precursor to 90% to 100% theoretical density to form the beryllium aluminate ceramic component.

[0197] Embodiment 29. The process of any of embodiments 23-28, wherein further processing includes additive manufacturing and / or hot pressing.

[0198] Embodiment 30. The process of embodiment 23, wherein processing the ceramic composition to form the beryllium aluminate ceramic component includes additive manufacturing and / or hot pressing.

[0199] Embodiment 31. The process of embodiment 30, wherein further processing includes additive manufacturing to form the beryllium aluminate ceramic component into a shape, a geometry, an article, a spacer, am insulator, a tube, a rod, a bar, a billet, a plate, a tile, a platen, a disk, a washer, a segment, a round, a cylinder, a cube, or combinations thereof.

[0200] While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those of skill in the art. In view of the foregoing discussion, relevant knowledge in the art and references discussed above in connection with the Background and Detailed Description, the disclosures of which are all incorporated herein by reference. In addition, it should be understood that aspects of the invention and portions of various embodiments and various features recited below and / or in the appended claims may be combined or interchanged either in whole or in part. In the foregoing descriptions of the various embodiments, those embodiments which refer to another embodiment may be appropriately combined with other embodiments as will be appreciated by one of skill in the art. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only and is not intended to limit.

Claims

Atty. Ref. No.: B17302-MTRN (00654699)We Claim:

1. A beryllium aluminate ceramic comprising 90 wt% or more beryllium aluminate; wherein the beryllium aluminate ceramic is characterized by one or more of: a thermal conductivity from 17 W / m K to 175 W / m K at room temperature; a bulk resistivity greater than 1 x 1015ohm-cm at room temperature and / or greater than 1 x 109ohm-cm at 700 °C and / or greater than 1 x IO10ohm-cm at 600 °C; a coefficient of thermal expansion from 7.4 to 9.0 pm / (m K) at room temperature; a near bioequivalence to human body tissue (Zeff) from 7.2 to 11.3; and a density of from 3.4 to 3.9 g / cc.

2. The beryllium aluminate ceramic of claim 1 comprising at most 10 wt% total of beryllia and / or alumina; at most 8 wt% total of beryllia and / or alumina; or at most 5 wt% total of beryllia and / or alumina.

3. The beryllium aluminate ceramic of claim 1 or claim 2 comprising at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine.

4. The beryllium aluminate ceramic of claim 1, consisting of: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balance beryllium aluminate.

5. The beryllium aluminate ceramic of any of claims 1-4, wherein the beryllium aluminate ceramic is of formula BexAlyOz, where x equals from 1 to 3; y equals from 1 to 6; and z equals from 4 to 10.

6. The beryllium aluminate ceramic of any of claims 1-5, wherein the beryllium aluminate ceramic is selected from the group consisting of BeAhC , BeAkOio, BesAhOe, and combinations thereof.Atty. Ref. No.: B17302-MTRN (00654699)7. The beryllium aluminate ceramic of any of claims 1-6, wherein the beryllium aluminate ceramic is BeAhC as major phase.

8. The beryllium aluminate ceramic of claim 7, wherein the beryllium aluminate ceramic is characterized by a chrysoberyl crystal structure.

9. The beryllium aluminate ceramic of any of claims 1-8, wherein the beryllium aluminate ceramic has a microstructure characterized by an average grain size less than 200 microns.

10. The beryllium aluminate ceramic of any of claims 1-9, wherein the beryllium aluminate ceramic is polycrystalline.

11. The beryllium aluminate ceramic of any of claims 1-10, wherein the beryllium aluminate ceramic is a component in a thermally conductive electrically insulated heater, wherein the component is adjacent to a resistive element.

12. A beryllium aluminate ceramic for optically stimulated luminescence, thermoluminescence, radioluminescence, or dosimetry systems thereof, wherein the beryllium aluminate ceramic includes:90 wt% or more beryllium aluminate; and at most 10 wt% total of: beryllia and / or alumina; and / or a dopant selected from chromia, magnesia, yttria, silica, and combinations thereof; and / or a sintering aid selected from iron oxide, zirconia, lanthana, fluorine, and combinations thereof.

13. The beryllium aluminate ceramic of claim 12 having a near bioequivalence to human body tissue (Zeff) is from 7.2 to 11.3; preferably from 10 to 11.

14. The beryllium aluminate ceramic of claim 12 or claim 13, wherein the beryllium aluminate ceramic is characterized by a chrysoberyl crystal structure.

15. The beryllium aluminate ceramic of any of claims 12-14 having a microstructure characterized by an average grain size less than 200 microns.Atty. Ref. No.: B17302-MTRN (00654699)16. The beryllium aluminate ceramic of any of claims 12-15, wherein the beryllium aluminate ceramic is polycrystalline.

17. The beryllium aluminate ceramic of claim 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a base plate having a top surface and a bottom surface, the base plate comprising the beryllium aluminate ceramic; and a shaft joined to the bottom surface and having an interior conduit, wherein the shaft is elongated along an axis perpendicular to the bottom surface.

18. The beryllium aluminate ceramic of claim 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a shaft comprising the beryllium aluminate ceramic and having an interior conduit; and a base plate having a top surface and a bottom surface, wherein the shaft is elongated along an axis perpendicular to the bottom surface, the shaft joined to the bottom surface.

19. The beryllium aluminate ceramic of claim 1, wherein the beryllium aluminate ceramic is a component for semiconductor processing, the component comprising: a base plate having a top surface and a bottom surface, the base plate comprising the beryllium aluminate ceramic; and a shaft comprising the beryllium aluminate ceramic and joined to the bottom surface, wherein the shaft has an interior conduit and is elongated along an axis perpendicular to the bottom surface.

20. A pedestal assembly for semiconductor processing, the pedestal assembly comprising a base plate having a top surface and a bottom surface and a shaft joined to the bottom surface, the shaft having an interior conduit, and the shaft and the base plate each of a beryllium aluminate ceramic comprising: at most 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, and / or fluorine; and balance beryllium aluminate.Atty. Ref. No.: B17302-MTRN (00654699)21. The pedestal assembly of claim 20, further comprising a metal layer in a pattern disposed between the top surface of the base plate and a substrate comprising the beryllium aluminate ceramic, wherein the pattern of the metal layer comprises from 10 wt% to 100 wt% niobium.

22. The pedestal assembly of claim 21, further comprising a wafer contact support comprising the beryllium aluminate ceramic, wherein an electrode is disposed between the substrate and the wafer contact support.

23. A process for making a beryllium aluminate ceramic component comprising: mixing alumina and beryllia in a presence of alumina grinding media to form a ceramic composition; processing the ceramic composition to form the beryllium aluminate ceramic component comprising 90.0 wt% or more beryllium aluminate.

24. The process of claim 23, wherein mixing comprises from 76 wt% to 84 wt% alumina and from 16 wt% to 24 wt% beryllia to form the ceramic composition.

25. The process of claim 23, wherein the beryllium aluminate ceramic component comprises:0 to 10 wt% total of beryllia and / or alumina; at most 0.9 wt% total metallic portion of a sintering aid chosen from: lithia, magnesia, yttria, silica, iron oxide, zirconia, lanthana, chromia, and / or fluorine; and balance beryllium aluminate.

26. The process of claim 23, wherein processing the ceramic composition includes heating the ceramic composition to form a beryllium aluminate powder, forming a component precursor of the beryllium aluminate powder, and further processing the component precursor to 90% to 100% theoretical density to form the beryllium aluminate ceramic component.

27. The process of claim 26, wherein further processing includes cold pressing and sintering.Atty. Ref. No.: B17302-MTRN (00654699)28. The process of claim 23, wherein processing the ceramic composition includes forming a component precursor of the ceramic composition and further processing the component precursor to 90% to 100% theoretical density to form the beryllium aluminate ceramic component.

29. The process of claim 28, wherein further processing includes additive manufacturing and / or hot pressing.

30. The process of claim 23, wherein processing the ceramic composition to form the beryllium aluminate ceramic component includes additive manufacturing and / or hot pressing.

31. The process of claim 30, wherein further processing includes additive manufacturing to form the beryllium aluminate ceramic component into a shape, a geometry, an article, a spacer, am insulator, a tube, a rod, a bar, a billet, a plate, a tile, a platen, a disk, a washer, a segment, a round, a cylinder, a cube, or combinations thereof.