Electrostatic chuck assemblies for high temperature processing

Abstract

An electrostatic chuck assembly includes a positioning plate and a cooling plate. The positioning plate includes an electrically insulated upper positioning plate plate, the upper positioning plate plate includes one or more heating elements and one or more electrodes for electrostatically fixing a substrate, and the positioning plate further includes a lower positioning plate plate, the lower positioning plate plate is joined to the upper positioning plate plate by metal bonding, and the lower positioning plate plate includes a plurality of features, the plurality of features are distributed on the bottom side of the lower positioning plate plate at a plurality of different distances from the center of the lower positioning plate plate, wherein each of the plurality of features accommodates one of a plurality of fasteners. The cooling plate is coupled to the positioning plate by the plurality of fasteners, wherein each of the plurality of fasteners applies a substantially equal fastening force to couple the cooling plate to the positioning plate.

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 9, 2015, application number "201580041355.8", and invention name "Electrostatic chuck assembly for high temperature processing". Technical Field

[0002] Some embodiments of the present invention are generally directed to substrate support assemblies (also referred to as electrostatic chuck assemblies) that can be used for high temperature processing. Background Art

[0003] Electrostatic chucks are widely used to hold substrates, such as semiconductor wafers, during substrate processing in processing chambers for various applications such as physical vapor deposition, etching, or chemical vapor deposition. Electrostatic chucks generally include one or more electrodes embedded in a single chuck body that includes a dielectric or semiconductive ceramic material across which an electrostatic clamping field is generated.

[0004] Electrostatic chucks provide several advantages over mechanical clamping devices and vacuum chucks. For example, electrostatic chucks reduce stress-induced cracking caused by mechanical clamping, allow larger areas of the substrate to be exposed for processing (little or no edge exclusion), and can be used in low pressure or high vacuum environments. In addition, electrostatic chucks can more uniformly hold the substrate to the clamping surface to allow for greater control of the substrate temperature. Various processes used in the manufacture of integrated circuits may require high temperatures and / or wide temperature ranges for substrate processing. However, electrostatic chucks in etching processes generally operate at a temperature range of up to about 120°C. At temperatures above about 120°C, many components of electrostatic chucks will begin to fail due to various problems, such as de-clamping of the AlO electrostatic chuck, plasma corrosion from corrosive chemicals, reliability of bonding, etc. Summary of the invention

[0005] Some embodiments of the invention described herein encompass an electrostatic chuck assembly comprising a puck having an upper puck plate and a lower puck plate that are electrically insulated, the upper puck plate comprising one or more heating elements and one or more electrodes for electrostatically securing a substrate, and the lower puck plate being joined to the upper puck plate by metal bonding. The lower puck plate comprises a plurality of features distributed on a bottom side of the lower puck plate at different distances from a center of the lower puck plate, wherein each feature accommodates a fastener. The electrostatic chuck assembly further comprises a cooling plate coupled to the puck by fasteners. The fasteners each apply approximately equal fastening forces to couple the cooling plate to the puck.

[0006] Some embodiments of the invention described herein encompass an electrostatic puck comprising an upper puck plate of AlN or Al2O3 having one or more heating elements and one or more electrodes for electrostatically fixing a substrate. The electrostatic puck further comprises a lower puck plate joined to the upper puck plate by metal bonding. The lower puck plate comprises one of: a) molybdenum, b) a porous body of SiC infiltrated with an AlSi alloy, or c) a ceramic, such as AlN or Al2O3. The lower puck plate further comprises a plurality of features distributed on a bottom side of the lower puck plate at different distances from a center of the lower puck plate, wherein each feature accommodates a fastener.

[0007] Some embodiments of the invention described herein encompass a method of manufacturing an electrostatic chuck assembly. The method includes the steps of forming a plurality of features in a lower positioning plate. The method further includes the steps of joining the lower positioning plate to an upper positioning plate using metal bonding to form a positioning plate, the upper positioning plate including one or more heating elements and one or more electrodes for electrostatically fixing a substrate. The method further includes the steps of setting at least one of a perfluoropolymer (PFP) gasket or a PFP O-ring to a top side of at least a portion of a cooling plate. The method further includes the steps of inserting one of a plurality of fasteners into each of a plurality of features formed in the lower positioning plate. The method further includes the steps of coupling the cooling plate to the positioning plate by tightening the plurality of fasteners. The plurality of fasteners may be tightened approximately equally to apply approximately equal tightening forces to couple the cooling plate to the positioning plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like reference numerals refer to like elements. It should be noted that different references to "an" or "an" embodiment in the present disclosure do not necessarily refer to the same embodiment, and such references refer to at least one.

[0009] Figure 1 depicts a cross-sectional side view of one embodiment of a processing chamber;

[0010] Figure 2 depicts an exploded view of one embodiment of a substrate support assembly;

[0011] Figure 3 depicts a cross-sectional top view of one embodiment of an electrostatic chuck assembly;

[0012] Figure 4 depicts a cross-sectional side view of one embodiment of an electrostatic chuck assembly;

[0013] Figure 5 A cross-sectional side view of another embodiment of an electrostatic chuck assembly is shown; and

[0014] Figure 6 One embodiment of a process for manufacturing an electrostatic chuck assembly is illustrated. DETAILED DESCRIPTION

[0015] Embodiments of the present invention provide a substrate support assembly and an electrostatic chuck assembly including a positioning disk, wherein the positioning disk is coupled to a cooling plate by a collection of fasteners. A plurality of fasteners are used to secure the positioning disk to the cooling plate. A plurality of fasteners are located at different distances from the center of the positioning disk. In one embodiment, a first group of fasteners are disposed at a first radius from the center of the positioning disk, and a second group of fasteners are disposed at a second radius from the center of the positioning disk. A plurality of fasteners may be distributed approximately evenly across the top side or surface of the cooling plate to evenly distribute the fastening force to couple the positioning disk to the cooling plate. All fasteners may be tightened equally to ensure that the fastening force applied by each fastener is approximately the same. This may promote uniform heat transfer characteristics between the positioning disk and the cooling plate on the positioning disk.

[0016] In one embodiment, an electrostatic chuck assembly includes a positioning plate having an electrically insulated upper positioning plate plate, the upper positioning plate plate being joined to a lower positioning plate plate by a metal joint. The metal joint may be an aluminum joint, an AlSi alloy joint, or other metal joint. The upper positioning plate plate includes one or more heating elements and one or more electrodes for electrostatically fixing a substrate. The lower positioning plate plate includes a plurality of features, the plurality of features being distributed on the bottom side of the lower positioning plate plate at different distances from the center of the lower positioning plate plate. Each feature accommodates one of a plurality of fasteners. The electrostatic chuck assembly further includes a cooling plate, the cooling plate being coupled to the positioning plate by fasteners. The cooling plate may include a base portion (referred to as a cooling base) and a spring-loaded internal heat sink, the heat sink being connected to the base portion by a plurality of springs, wherein the plurality of springs apply a force to press the internal heat sink against the positioning plate. The fasteners each apply approximately equal fastening forces to couple the cooling plate to the positioning plate (e.g., coupling the base portion of the cooling plate to the positioning plate). This approximately equal fastening force may promote uniform heat transfer between the cooling plate and the positioning plate. Additionally, a spring-loaded internal heat sink promotes even heat transfer between the cooling plate and puck.

[0017] Figure 11 is a cross-sectional view of one embodiment of a semiconductor processing chamber 100 having an electrostatic chuck assembly 150 disposed therein. The electrostatic chuck assembly 150 includes an electrostatic puck (puck 166) having an upper puck plate that is coupled to a lower puck plate, as will be discussed in more detail below. The puck 166 is coupled to a cooling plate by a plurality of fasteners, as will be discussed in more detail below. The processing chamber 100 includes a chamber body 102 and a lid 104 that enclose an interior volume 106. The chamber body 102 may be made of aluminum, stainless steel, or other suitable material. The chamber body 102 generally includes a sidewall 108 and a bottom 110. An external liner 116 may be disposed adjacent to the sidewall 108 to protect the chamber body 102. The external liner 116 may be fabricated and / or coated with a material that is resistant to corrosion by plasma or halogen-containing gases. In one embodiment, the outer liner 116 is made of aluminum oxide. In another embodiment, the outer liner 116 is made of yttrium oxide, a yttrium alloy, or an oxide thereof, or is coated with yttrium oxide, a yttrium alloy, or an oxide thereof.

[0018] An exhaust port 126 may be defined in the chamber body 102 and may couple the interior volume 106 to a pump system 128. The pump system 128 may include one or more pumps and throttle valves for evacuating and regulating the pressure of the interior volume 106 of the processing chamber 100.

[0019] The lid 104 can be supported on the sidewall 108 of the chamber body 102. The lid 104 can be opened to allow access to the interior volume 106 of the processing chamber 100, and can provide a seal to the processing chamber 100 when the lid 104 is closed. A gas panel 158 can be coupled to the processing chamber 100 to provide processing and / or cleaning gases to the interior volume 106 through a gas distribution assembly 130, which is part of the lid 104. Examples of processing gases that can be used for processing in the processing chamber include halogen-containing gases such as C2F6, SF6, SiCl4, HBr, NF3, CF4, CHF3, CH2F3, Cl2, and SiF4, as well as other gases such as O2 or N2O. Examples of carrier gases include N2, He, Ar, and other gases that are inert to the processing gas (e.g., non-reactive gases). The gas distribution assembly 130 may have a plurality of holes 132 on the downstream surface of the gas distribution assembly 130 to direct the gas flow to the surface of the substrate 144. Additionally, or alternatively, the gas distribution assembly 130 may have a central hole at which the gas is fed through a ceramic gas nozzle. The gas distribution assembly 130 may be made of and / or coated with a ceramic material, such as silicon carbide, yttrium oxide, etc., to provide corrosion resistance to halogen-containing chemicals to prevent the gas distribution assembly 130 from corroding.

[0020] The substrate support assembly 148 is disposed in the interior volume 106 of the processing chamber 100 below the gas distribution assembly 130. The substrate support assembly 148 holds the substrate 144 during processing. The inner liner 118 may be coated on the periphery of the substrate support assembly 148. The inner liner 118 may be a material that is resistant to halogen-containing gases, such as those discussed with respect to the outer liner 116. In one embodiment, the inner liner 118 may be made of the same material as the outer liner 116.

[0021] In one embodiment, the substrate support assembly 148 includes a mounting plate 162 supporting a base 152 and an electrostatic chuck assembly 150. In one embodiment, the electrostatic chuck assembly 150 further includes a thermally conductive base, referred to herein as a cooling plate 164, which is coupled to an electrostatic positioning plate (hereinafter referred to as positioning plate 166) via a plurality of fasteners. The electrostatic chuck assembly 150 described in the embodiment can be used for Johnsen-Rahbek and / or Coulombic electrostatic clamping.

[0022] In one embodiment, the protective ring 146 is disposed on a portion of the positioning disk 166 at the outer periphery of the positioning disk 166. In one embodiment, the positioning disk 166 is coated with the protective layer 136. Alternatively, the positioning disk 166 may not be coated with the protective layer 136. The protective layer 136 may be a ceramic, such as Y2O3 (yttrium oxide or yttrium oxide), Y4Al2O9 (YAM), Al2O3 (aluminum oxide), Y3Al5O 12 (YAG), YAlO3 (YAP), quartz, SiC (silicon carbide), Si3N4 (silicon nitride) Sialon ceramics (Sialon), AlN (aluminum nitride), AlON (aluminum oxynitride), TiO2 (titanium dioxide), ZrO2 (zirconium oxide), TiC (titanium carbide), ZrC (zirconium carbide), TiN (titanium nitride), TiCN (titanium carbon nitride), Y2O3 stabilized ZrO2 (YSZ), etc. The protective layer can also be a ceramic composite, such as Y3Al5O distributed in an Al2O3 matrix. 12 , Y2O3-ZrO2 solid solution, or SiC-Si3N4 solid solution. The protective layer can also be a ceramic composition including a solid solution containing yttrium oxide (also known as yttrium oxide and Y2O3). For example, the protective layer can be a ceramic composition including a compound Y4Al2O9 (YAM) and a solid solution Y2-xZr xO3 (Y2O3-ZrO2 solid solution). Note that pure yttrium oxide and solid solutions containing yttrium oxide can be doped with one or more of the following: ZrO2, Al2O3, SiO2, B2O3, Er2O3, Nd2O3, Nb2O5, CeO2, Sm2O3, Yb2O3, or other oxides. Also note that pure aluminum nitride and aluminum nitride doped with one or more of the following: ZrO2, Al2O3, SiO2, B2O3, Er2O3, Nd2O3, Nb2O5, CeO2, Sm2O3, Yb2O3, or other oxides can be used. Alternatively, the protective layer can be sapphire or MgAlON.

[0023] The positioning plate 166 includes an upper positioning plate (not shown) and a lower positioning plate (not shown), which are joined by metal bonding. The upper positioning plate can be a dielectric or electrically insulating material (for example, having a strength greater than 10 14 ohm-meter resistivity) and can be used for semiconductor processing at temperatures of 180°C and higher. In one embodiment, the upper positioning plate includes a material that can be used at about 20°C to about 500°C. In one embodiment, the upper positioning plate is AlN. The AlN upper positioning plate can be undoped or can be doped. For example, AlN can be doped with samarium oxide (Sm2O3), cerium oxide (CeO2), titanium dioxide (TiO2), or a transition metal oxide. In one embodiment, the upper positioning plate is Al2O3. The Al2O3 upper positioning plate can be undoped or can be doped. For example, Al2O3 can be doped with titanium dioxide (TiO2) or a transition metal oxide.

[0024] The lower puck plate may have a thermal expansion coefficient that matches that of the upper puck plate. In one embodiment, the lower puck plate is a porous body of SiC infiltrated with an AlSi alloy (referred to as AlSiSiC). The lower puck plate may alternatively be AlN or Al2O3. In one embodiment, the lower puck plate is undoped AlN or undoped Al2O3. In one embodiment, the lower puck plate comprises the same material as the upper puck plate. AlSiSiC materials, AlN or Al2O3 may be used, for example, in a reactive etching environment or in an inert environment.

[0025] In one embodiment, the lower positioning plate is molybdenum. For example, if the positioning plate 166 is to be used in an inert environment, molybdenum can be used. Examples of inert environments include environments where inert gases (e.g., Ar, O2, N, etc.) flow. For example, if the positioning plate 166 is to clamp a substrate for metal deposition, molybdenum can be used. Molybdenum can also be used for lower positioning plate plates that are to be used in corrosive environments (e.g., etching applications). In such an embodiment, after the lower positioning plate is joined to the upper positioning plate, the exposed surface of the lower positioning plate can be coated with a plasma etch-resistant coating. The plasma etch-resistant coating can be performed via a plasma spray process. The plasma etch-resistant coating can cover, for example, the sidewalls of the lower positioning plate and the exposed horizontal steps of the lower positioning plate. In one embodiment, the plasma etch-resistant coating is Al2O3. Alternatively, the plasma etch-resistant coating can be Y2O3 or an oxide containing Y2O3. Alternatively, the plasma etch-resistant coating can be any material described with respect to the protective layer 136.

[0026] The mounting plate 162 is coupled to the bottom 110 of the chamber body 102 and includes passages for routing supplies (e.g., fluids, power lines, sensor leads, etc.) to the cooling plate 164 and the puck 166. The cooling plate 164 and / or the puck 166 may include one or more optional embedded heating elements 176, optional embedded thermal isolators 174, and / or optional conduits 168, 170 to control the lateral temperature profile of the substrate support assembly 148. In one embodiment, a thermal gasket 138 is disposed on at least a portion of the cooling plate 164.

[0027] The conduits 168, 170 may be fluidly coupled to a fluid source 172 that circulates a temperature regulating fluid through the conduits 168, 170. In one embodiment, an embedded thermal isolator 174 may be disposed between the conduits 168, 170. The embedded heating element 176 is regulated by a heater power supply 178. The conduits 168, 170 and the embedded heating element 176 may be used to control the temperature of the puck 166, thereby heating and / or cooling the puck 166 and the substrate (e.g., wafer) being processed. In one embodiment, the puck 166 includes two separate heating zones that may be maintained at different temperatures. In another embodiment, the puck 166 includes four different heating zones that may be maintained at different temperatures. The temperature of the electrostatic puck 166 and the thermally conductive base 164 may be monitored using a plurality of temperature sensors 190, 192, which may be monitored using a controller 195.

[0028] The puck 166 may further include a plurality of gas passages, such as grooves, mesas, and other surface features that may be formed in the upper surface of the puck 166. The gas passages may be fluidly coupled to a source of heat transfer (or backside) gas, such as He, via holes drilled in the puck 166. In operation, the backside gas may be provided to the gas passages at a controlled pressure to enhance heat transfer between the puck 166 and the substrate 144.

[0029] In one embodiment, the puck 166 includes at least one chucking electrode 180 controlled by a chucking power supply 182. The chucking electrode 180 (also referred to as a chucking electrode) may be further coupled to one or more RF power supplies 184, 186 via a matching circuit 188 to maintain a plasma formed from process and / or other gases within the processing chamber 100. The one or more RF power supplies 184, 186 may generally generate an RF signal having a frequency of about 50 kHz to about 3 GHz and a power of up to about 10,000 watts. In one embodiment, the RF signal is applied to the metal pedestal, an alternating current (AC) is applied to the heater, and a direct current (DC) is applied to the chucking electrode 180.

[0030] Figure 2 An exploded view of one embodiment of a substrate support assembly 148 is depicted. The substrate support assembly 148 depicts an exploded view of an electrostatic chuck assembly 150, which includes a positioning plate 166 and a base 152. The electrostatic chuck assembly 150 includes a positioning plate 166 and a cooling plate 164 attached to the positioning plate 166. As shown, an O-ring 240 may be cured to the cooling plate 164 along the perimeter of the top side of the cooling plate 164. Alternatively, the O-ring may be disposed on the top side of the cooling plate 164 instead of being cured to the top side of the cooling plate 164. The embodiments discussed herein relate to O-rings and gaskets cured to at least a portion of the cooling plate 164. However, it should be understood that the O-rings and / or gaskets may alternatively be cured to the lower positioning plate plate. Alternatively, the O-rings and / or gaskets may not be cured to any surface. In one embodiment, the O-ring 240 is a perfluoropolymer (PFP) O-ring. Alternatively, other types of high temperature O-rings may be used. In one embodiment, a thermally insulating high temperature O-ring is used. O-ring 240 may be a stepped O-ring having a first step of a first thickness and a second step of a second thickness. This may promote uniform tightening of the fastener by causing a dramatic increase in the amount of force used to tighten the fastener after a set amount of compression of the PFP O-ring 240.

[0031] Additional O-rings (not shown) may also be vulcanized to the top side of the cooling plate 164 around the hole 280 in the center of the cooling plate 164 through which the cable travels. Other smaller O-rings may also be vulcanized to the cooling plate 164 around other openings, around lift pins, etc. Alternatively, a gasket (e.g., a PFP gasket) may be vulcanized to the top side of the cooling plate 164. An example of a PFP that may be used for the gasket or O-ring 240 is Dupont TM ECCtreme TM DuPont TM of With Daikin DUPRA TM The O-ring 240 or gasket provides a vacuum seal between the interior volume within the electrostatic chuck assembly 150 and the interior volume of the chamber. The interior volume within the electrostatic chuck assembly 150 includes open space within the base 152 for routing conduits and wiring.

[0032] The cooling plate 164 further includes a plurality of features 242 through which fasteners are inserted. If washers are used, the washers may have cutouts at each feature 242. The fasteners extend through each feature 242 and attach to an additional portion of the fastener (or additional fastener) that is inserted into an additional feature formed in the puck 166. For example, a bolt may extend through a feature 242 in the cooling plate 164 and thread into a nut disposed in a feature of the puck 166. Each feature 242 in the cooling plate 164 may be aligned relative to a similar feature (not shown) in the lower puck plate 232 of the puck 166.

[0033] The positioning disk 166 has a disk-like shape with an annular periphery that can substantially match the shape and size of the substrate 144 positioned thereon. The upper surface of the positioning disk 166 can have an outer ring 216, a plurality of bosses 206, 210, and channels 208, 212 between the bosses 210. The positioning disk 166 includes an upper positioning disk plate 230 that is joined to a lower positioning disk plate 232 by metal bonding. In one embodiment, the upper positioning disk plate 230 can be made of an electrically insulating ceramic material. Suitable examples of ceramic materials include aluminum nitride (AlN), aluminum oxide (Al2O3), etc.

[0034] In one embodiment, the material for the lower puck plate 232 can be appropriately selected so that the coefficient of thermal expansion (CTE) of the lower puck plate 232 material substantially matches the CTE of the electrically insulating upper puck plate 230 material to minimize CTE mismatch and avoid thermomechanical stresses that could damage the puck 166 during thermal cycling. In one embodiment, the lower puck plate 232 is molybdenum. In one embodiment, the lower puck plate is alumina. In one embodiment, the lower puck plate is AlN.

[0035] In one embodiment, a conductive metal matrix composite (MMC) material is used for the lower positioning plate 232. The MMC material includes a metal matrix and a reinforcement material, which is embedded and dispersed throughout the matrix. The metal matrix may include a single metal or two or more metals or metal alloys. The metals that may be used include (but are not limited to) aluminum (Al), magnesium (Mg), titanium (Ti), cobalt (Co), cobalt nickel alloy (CoNi), nickel (Ni), chromium (Cr), gold (Au), silver (Ag) or various combinations thereof. The reinforcement material may be selected to provide the desired structural strength of the MMC, and the reinforcement material may also be selected to provide the desired values ​​of other properties of the MMC, such as, for example, thermal conductivity and CTE. Examples of reinforcement materials that may be used include silicon (Si), carbon (C), or silicon carbide (SiC), but other materials may also be used. The MMC material used for the lower positioning plate 232 is preferably selected to provide the desired conductivity and substantially match the CTE of the upper positioning plate 230 material within the operating temperature range of the electrostatic chuck assembly 150. In one embodiment, the temperature range may be about 20 degrees Celsius to about 500 degrees Celsius. In one embodiment, CTE matching is based on selecting the MMC material such that the MMC material includes at least one material that is also used in the material of the upper puck plate 230. In one embodiment, the upper puck plate 230 includes AlN. In one embodiment, the MMC material includes a SiC porous body infiltrated with an AlSi alloy.

[0036] The constituent materials and percentages of the MMC can be selected to provide an engineered material that meets desired design goals. For example, by appropriately selecting the MCC material to closely match the CTE of the lower puck plate 232 and the upper puck plate 230, the thermomechanical stress at the interface between the lower puck plate 232 and the upper puck plate 230 is reduced.

[0037] The lower puck plate 232 may include a plurality of features (not shown) for receiving fasteners. The features may be generally evenly distributed across the surface of the lower puck plate 232 and may include a first set of features at a first distance from the center of the lower puck plate 232 and a second set of features at a second distance from the center of the lower puck plate 232.

[0038] The cooling plate 164 attached below the positioning disk 166 may have a disk-shaped main portion 224 and an annular flange extending outwardly from the main portion 224 and positioned on the base 152. In one embodiment, the cooling plate 164 may be made of a metal, such as aluminum or stainless steel or other suitable material. Alternatively, the cooling plate 164 may be made of a synthetic ceramic, such as aluminum silicon alloy or molybdenum infiltrated with SiC, to match the thermal expansion coefficient of the positioning disk 166. The cooling plate 164 should provide good strength and durability as well as heat transfer characteristics. Figure 3 A cross-sectional top view of one embodiment of the positioning disk 166 is depicted. As shown, the positioning disk 166 has a radius R3, which can be substantially similar to the radius of the substrate or wafer supported by the positioning disk 166. The positioning disk 166 further includes a plurality of features 305. The features can match similar features in the cooling plate to which the positioning disk 166 is to be mounted. Each feature 305 accommodates a fastener. For example, a bolt (e.g., a stainless steel bolt, a galvanized steel bolt, etc.) can be placed into each feature so that the head of the bolt is inside an opening large enough to accommodate the head and the shaft of the bolt extends out of the bottom side of the positioning disk 166. The bolt can be fastened to a nut that is placed in a corresponding feature in the cooling plate. Alternatively, the feature 305 can be sized to accommodate a nut and can include a hole that can receive the shaft of the bolt accommodated by the corresponding feature in the cooling plate. In another example, a spiral insert (e.g., ) or other threaded inserts (e.g., crimp-on inserts, molded-in inserts, captive nuts, etc.) can be inserted into one or more features to add threaded holes thereto. Bolts placed inside the cooling plate and protruding from the cooling plate can then be screwed into the threaded inserts to secure the cooling plate to the positioning plate. Alternatively, the threaded inserts can be used in the cooling plate.

[0039] The size of feature 305 may be slightly larger than the size of the fastener to accommodate the larger coefficient of thermal expansion of the fastener. In one embodiment, the size of the fastener is designed so that when the fastener is heated to 500 or 600 degrees Celsius, the fastener will not exert a force on the feature.

[0040] As shown, multiple groups of features 305 may be included in the puck 166. Each group of features 305 may be evenly spaced at a particular radius or distance from the center of the puck 166. For example, as shown, a first group of features 305 are located at radius R1, and a second group of features 305 are located at radius R2. Additional groups of features may also be located at additional radii.

[0041] In one embodiment, the features are arranged to produce a uniform load on the positioning disk 166. In one embodiment, the features are arranged so that a bolt is located approximately every 30-70 square centimeters (e.g., every 50 square centimeters). In one embodiment, three groups of features are used for a 12-inch positioning disk 166. The first group of features may be located approximately 4 inches from the center of the positioning disk 166 and include approximately 4 features. The second group of features may be located approximately 6 inches from the center of the positioning disk 166 and include approximately 6 features. The third group of features may be located approximately 8 inches from the center of the positioning disk 166 and include approximately 8 features. In one embodiment, the positioning disk 166 includes approximately 8-24 features, arranged in groups at 2-3 different radii, wherein each feature accommodates a fastener.

[0042] Figure 4 A cross-sectional side view of one embodiment of an electrostatic chuck assembly 150 is depicted. The electrostatic chuck assembly 150 includes a puck 166 comprised of an upper puck plate 230 and a lower puck plate 232 that are bonded together by metal bonding 450. In one embodiment, diffusion bonding is used as the method of metal bonding, although other bonding methods may be used. In one embodiment, the upper puck plate 230 and the lower puck plate 232 include a material containing aluminum (e.g., AlN or Al2O3). The metal bonding 450 may include an "intermediate layer" of aluminum foil that is placed in the bonding area between the upper puck plate 230 and the lower puck plate 232. Pressure and heat may be applied to form diffusion bonds between the aluminum foil and the upper puck plate 230 and between the aluminum foil and the lower puck plate 232. In another embodiment, the diffusion bond may be formed using other interlayer materials selected based on the materials used for the upper puck plate 230 and the lower puck plate 232. In another embodiment, the upper puck plate 230 may be bonded directly to the lower puck plate 232 using direct diffusion bonding (where no interlayer is used to form the bond).

[0043] The plasma resistant and high temperature O-ring 445 may be made of a perfluoropolymer (PFP). The O-ring 445 may be PFP with an inorganic additive, such as SiC. The O-ring is replaceable. When the O-ring 445 deteriorates, the O-ring may be removed and a new O-ring may be extended beyond the upper positioning disk plate 230 and placed at the perimeter of the positioning disk 166 at the interface between the upper positioning disk plate 230 and the lower positioning disk plate 232. The O-ring 445 may protect the metal joint 450 from erosion by the plasma.

[0044] The upper puck plate 230 includes a boss 210, a channel 212, and an outer ring 216. The upper puck plate 230 includes a chucking electrode 180 and one or more heating elements 176. The chucking electrode 180 is coupled to a chucking power supply 182, and to an RF plasma power supply 184 and an RF bias power supply 186 via a matching circuit 188. The upper puck plate 230 and the lower puck plate 232 may additionally include gas delivery holes (not shown) through which a gas supply 440 pumps a backside gas, such as He.

[0045] The upper puck plate 230 may have a thickness of about 3-25 mm. In one embodiment, the upper puck plate 230 has a thickness of about 3 mm. The clamping electrode 180 may be located about 1 mm from the upper surface of the upper puck plate 230, and the heating element 176 may be located about 1 mm below the clamping electrode 180. The heating element 176 may be a screen printed heating element having a thickness of about 10-200 microns. Alternatively, the heating element may be a resistive coil having a thickness of about 1-3 mm using the upper puck plate 230. In such an embodiment, the upper puck plate 230 may have a minimum thickness of about 5 mm. In one embodiment, the lower puck plate 232 has a thickness of about 8-25 mm. The heating element 176 is electrically connected to a heater power supply 178 for heating the upper puck plate 230. The upper puck plate 230 may include an electrically insulating material, such as AlN. The lower puck plate 232 and the upper puck plate 232 may be made of the same material. In one embodiment, the lower puck plate 232 is made of a different material than the material used for the upper puck plate 230. In one embodiment, the lower puck plate 232 comprises a metal matrix composite material. In one aspect, the metal matrix composite material comprises aluminum and silicon. In one embodiment, the metal matrix composite material is a porous body of SiC infiltrated with an AlSi alloy.

[0046] The lower puck plate 232 is coupled to and in thermal communication with the cooling plate 164, which has one or more conduits 170 (also referred to herein as cooling channels) in fluid communication with a fluid source 172. The cooling plate 164 is coupled to the puck 166 by a plurality of fasteners 405. The fasteners 405 may be threaded fasteners, such as nut and bolt pairs. As shown, the lower puck plate 232 includes a plurality of features 430 for receiving the fasteners 405. The cooling plate 164 also includes a plurality of features 432 for receiving the fasteners 405. In one embodiment, the features are bolt holes having counter bores. As shown, the features 430 are through features extending through the lower puck plate 232. Alternatively, the features 430 may not be through features. In one embodiment, the features 430 are slots for receiving a T-bolt head or a rectangular nut, which may be inserted into the slot and then rotated 90 degrees. In one embodiment, the fastener includes a washer, graphite (grafoil), aluminum foil, other load distributing materials to evenly distribute the force from the head of the fastener to the feature. In one embodiment (as shown), a PFP O-ring 410 is vulcanized to (or otherwise disposed on) the cooling plate at the perimeter of the cooling plate 164. Alternatively, the PFP O-ring 410 can be vulcanized to the bottom side of the lower cooling plate 232. The fastener 405 can be tightened to compress the PFP O-ring 410. The fasteners 405 can all be tightened using approximately the same force so that the spacing 415 between the positioning disk 166 and the cooling plate 164 is approximately the same (uniform) across the interface between the positioning disk 166 and the cooling plate 164. This ensures that the heat transfer characteristics between the cooling plate 164 and the positioning disk 166 are uniform. In one embodiment, the spacing 415 is approximately 2-10 mils. For example, if a PFP O-ring 410 is used without a grafoil layer, the spacing may be 2-10 mils. If a grafoil layer is used with the PFP O-ring 410, the spacing may be approximately 10-40 mils. A larger spacing may reduce heat transfer and cause the interface between the puck 166 and the cooling plate 164 to act as a thermal choke. In one embodiment, a conductive gas may be flowed into the spacing 415 to improve heat transfer between the puck 166 and the cooling plate 164.

[0047] The spacing 415 minimizes the contact area between the puck 166 and the cooling plate 164. Additionally, by maintaining a thermal choke between the puck 166 and the cooling plate 164, the puck 166 can be maintained at a much greater temperature than the cooling plate 164. For example, in some embodiments, the puck 166 can be heated to a temperature of 180-300 degrees Celsius while the cooling plate 164 can be maintained at a temperature of less than about 120 degrees Celsius. The puck 166 and cooling plate 164 can freely expand or contract independently during thermal cycling.

[0048] The gap 415 can act as a thermal choke by limiting the heat conduction path from the heated puck 166 to the cooled cooling plate 164. In a vacuum environment, heat transfer can be primarily a radiative process unless a conductive medium is provided. Because the puck 166 can be disposed in a vacuum environment during substrate processing, heat generated by the heating element 176 can be transferred across the gap 415 less efficiently. Therefore, by adjusting the gap and / or other factors that affect heat transfer, the heat flux from the puck 166 to the cooling plate 164 can be controlled. In order to provide efficient heating of the substrate, it is desirable to limit the amount of heat conducted away from the upper puck plate 230.

[0049] In one embodiment (not shown), a layer of graphite (grafoil) is disposed between the positioning disk 166 and the cooling plate 164, within the perimeter of the PFP O-ring 410. The graphite (grafoil) may have a thickness of approximately 10-40 mils. The fastener 405 may be tightened to compress the graphite (grafoil) layer and the PFP O-ring 410. The graphite (grafoil) may be thermally conductive and may improve heat transfer between the positioning disk 166 and the cooling plate 164.

[0050] In one embodiment (not shown), the cooling plate 164 includes a base portion to which the PFP O-ring 410 can be vulcanized. The cooling plate 164 can additionally include a spring-loaded internal heat sink connected to the base portion by one or more springs. The spring applies a force to press the internal heat sink against the positioning disk 166. The surface of the heat sink can have a predetermined roughness and / or surface features (e.g., a boss) to control the heat transfer characteristics between the positioning disk 166 and the heat sink. In addition, the material of the heat sink can affect the heat transfer characteristics. For example, an aluminum heat sink will transfer heat better than a stainless steel heat sink. In one embodiment, the heat sink includes a graphite (grafoil) layer on the upper surface of the heat sink.

[0051] Figure 5 A cross-sectional side view of another embodiment of an electrostatic chuck assembly 505 is shown. In one embodiment, the electrostatic chuck assembly 505 corresponds to Figure 1 to Figure 2 The electrostatic chuck assembly 505 includes an electrostatic positioning plate 510, which is composed of an upper positioning plate plate 515 and a lower positioning plate plate 520. In one embodiment, the electrostatic positioning plate 510 corresponds to Figure 3The upper positioning disk plate 515 is bonded to the lower positioning disk plate 520 by metal bonding 550. In one embodiment, diffusion bonding is used as a method of metal bonding. However, other bonding methods may also be used to produce metal bonding. The upper positioning disk plate 515 includes an electrically insulating (dielectric) ceramic, such as AlN or Al2O3. The upper positioning disk plate 515 includes a clamping electrode 527 and one or more heating elements 529. The clamping electrode 527 can be coupled to a clamping power supply (not shown) and coupled to an RF plasma power supply (not shown) and an RF bias power supply (not shown) via a matching circuit (not shown). The heating element 529 is electrically connected to a heater power supply (not shown) for heating the upper positioning disk plate 515.

[0052] The upper puck plate 515 may have a thickness of about 3-10 mm. In one embodiment, the upper puck plate 515 has a thickness of about 3-5 mm. The clamping electrode 527 may be located about 0.3 to 1 mm from the upper surface of the upper puck plate 515, and the heating element 529 may be located about 2 mm below the clamping electrode 527. The heating element 529 may be a screen printed heating element having a thickness of about 10-200 microns. Alternatively, the heating element 529 may be a resistive coil having a thickness of about 1-3 mm using the upper puck plate 515. In such an embodiment, the upper puck plate 515 may have a minimum thickness of about 5 mm.

[0053] The lower puck plate 520 includes a material having a coefficient of thermal expansion (CTE) similar to or matching that of the upper puck plate 515. The material for the lower puck plate 520 may be appropriately selected so that the CTE of the lower puck plate 520 material substantially matches the CTE of the electrically insulating upper puck plate 515 material to minimize the CTE mismatch and avoid thermomechanical stresses that may damage the electrostatic chuck assembly 505 during thermal cycling. Thus, if the upper puck plate 515 is AlN, the lower puck plate 520 may also be AlN. Similarly, if the upper puck plate is Al2O3, the lower puck plate 520 may also be Al2O3. Other materials may also be used for the lower puck plate 520, such as molybdenum or a conductive metal matrix composite (MMC), such as AlSiSiC.

[0054] In one embodiment, the lower positioning disc plate 520 has a thickness of approximately 8-25 mm. In a further embodiment, the lower positioning disc plate 520 has a thickness of approximately 8-20 mm. In a further embodiment, the lower positioning disc plate 520 has a thickness of approximately 12 mm.

[0055] In one embodiment, the lower puck plate 520 has a rough outer wall coated with a plasma resistant ceramic coating (not shown). The plasma resistant ceramic coating may correspond to any of the plasma resistant ceramic coatings discussed with respect to the protective layer 136.

[0056] The metal bond 550 may include an "intermediate layer" of aluminum foil that is placed in the bonding area between the upper puck plate 515 and the lower puck plate 520. Pressure and heat may be applied to form diffusion bonds between the aluminum foil and the upper puck plate 515 and between the aluminum foil and the lower puck plate 520. In other embodiments, diffusion bonds may be formed using other intermediary layer materials that are selected based on the materials used for the upper puck plate 515 and the lower puck plate 520. In one embodiment, the metal bond 550 has a thickness of 0.2-0.3 mm. In one embodiment, the upper puck plate 515 may be directly bonded to the lower puck plate 520 using direct diffusion bonding (where no intermediary layer is used to form the bond).

[0057] The upper puck plate 515 may have a larger diameter than the lower puck plate 520. In one embodiment, the upper puck plate 515 and the lower puck plate 520 each have a diameter of approximately 300 mm.

[0058] The edge of the cooling plate 594 may have a diameter similar to the diameter of the upper puck plate 515. A plasma resistant and high temperature O-ring 545 may be disposed between the upper puck plate 515 and the base portion 595 of the cooling plate 594. This O-ring 545 may provide a vacuum seal between the interior of the electrostatic chuck assembly 505 and the processing chamber. The O-ring 545 may be made of a perfluoropolymer (PFP). In one embodiment, the O-ring 545 is PFP with an inorganic additive, such as SiC. The O-ring 545 is replaceable. When the O-ring 545 degrades, the O-ring may be removed and a new O-ring may be extended beyond the upper puck plate 515 and placed at the perimeter of the upper puck plate 515 at the interface between the upper puck plate 515 and the cooling plate 594. The O-ring 545 may protect the metal joint 550 from erosion by the plasma.

[0059] The cooling plate 594 includes a base portion (also referred to as a cooling base) 595 and a heat sink (e.g., an internal heat sink) 536. The heat sink 536 may be coupled to the base portion 595 by one or more springs 570, which operate to press the heat sink 536 against the lower positioning disk plate 520. In one embodiment, the spring 570 is a coil spring. The spring 570 applies a force to press the heat sink 536 against the electrostatic positioning disk 510. The heat sink 536 may have one or more conduits 535 (also referred to herein as cooling channels) in fluid communication with a fluid source (not shown). The surface of the heat sink 536 may have a predetermined roughness and / or surface features (e.g., bosses), which may affect the heat transfer characteristics between the electrostatic positioning disk 510 and the heat sink 536. In addition, the material of the heat sink 536 may affect the heat transfer characteristics. For example, an aluminum heat sink 536 transfers heat better than a stainless steel heat sink 536. In one embodiment, the mounting plate 540 is disposed below the cooling plate 594 and is coupled to the cooling plate 594 .

[0060] The lower puck plate 520 may include a plurality of features 524 for receiving fasteners 526. The cooling plate 594 may also include a plurality of features 528 for receiving fasteners 526. Alternatively, or in addition, the mounting plate 540 may include a plurality of features for receiving fasteners. The features 528 may be vertically aligned with the features 524. The features 524, 528 may be through features extending through the lower puck plate 520 and the cooling plate 594. Alternatively, the features 524, 528 may not be through features. In one embodiment, the features 524, 528 are bolt holes with counter bores. In one embodiment, the features 524, 528 are slots that receive T-bolt heads or rectangular nuts that can be inserted into the slots and then rotated 90 degrees. In one embodiment, the cooling plate 594 is coupled to the electrostatic puck 510 by a plurality of fasteners 526 inserted into the features 524, 528. Fastener 526 may be stainless steel, galvanized steel, molybdenum, or other metal. Fastener 526 may be a threaded fastener, such as a nut and bolt pair. In one embodiment, fastener 526 includes washers, grafoil, aluminum foil, other load spreading materials to evenly distribute the force from the head of the fastener to the feature. In one embodiment, a spiral insert (e.g., ) or other threaded inserts (e.g., crimp-on inserts, molded-in inserts, captive nuts, etc.) can be inserted into feature 524 to add a threaded hole thereto. Bolts placed inside cooling plate 594 (e.g., inside feature 524 in base portion 595 of cooling plate 594) and protruding from cooling plate 594 can then be threaded into the threaded inserts to secure the cooling plate to the positioning plate. Alternatively, threaded inserts can be used in the cooling plate.

[0061] In one embodiment, a captive nut, molded insert, crimped insert, or other threaded insert is positioned within feature 524. In a further embodiment, at least a portion of the threaded insert is welded with a copper-zinc alloy prior to insertion into feature 524. Alternatively, a metal foil may be placed between the threaded insert and the surface of feature 524. A metal bonding (e.g., diffusion bonding) process may then be performed to secure the threaded insert to feature 524. This may provide increased durability for the increased forces applied during assembly.

[0062] The heat sink 536 and / or the base portion 595 of the cooling plate 594 can absorb heat from the electrostatic puck 510. In one embodiment (as shown), a low thermal conductivity gasket 525 is disposed on the heat sink 536. The low thermal conductivity gasket 525 can be, for example, a PFP gasket vulcanized to the heat sink 536 (or otherwise disposed on the heat sink 536). In one embodiment, the low thermal conductivity gasket has a thermal conductivity of about 0.2 Watts per meter Kelvin (W / (m·K)) or less. The fastener 526 can be tightened with approximately the same force, and the spring 570 can press the heat sink 536 against the lower puck plate 520 to uniformly compress the low thermal conductivity gasket 525. The low thermal conductivity gasket 525 can reduce heat transfer and act as a thermal choke.

[0063] In one embodiment, a graphite (grafoil) layer (not shown) is disposed on the low thermal conductivity gasket 525. The graphite (grafoil) may have a thickness of approximately 10-40 mils. The fastener 526 and / or spring 570 may compress the graphite (grafoil) layer and the low thermal conductivity gasket 525. The graphite (grafoil) layer may be thermally conductive and may improve lateral heat transfer across the heat sink 536.

[0064] By maintaining a thermal choke between the electrostatic puck 510 and the cooling plate 594, the electrostatic puck 510 can be maintained at a much greater temperature than the cooling plate 594. For example, in some embodiments, the electrostatic puck 510 can be heated to a temperature of 200-300 degrees Celsius while the cooling plate 594 can be maintained at a temperature below about 120 degrees Celsius. In one embodiment, the electrostatic puck 510 can be heated to a temperature of up to about 250°C while maintaining the cooling plate 594 at a temperature of about 60°C or less. Thus, in embodiments, a temperature differential of up to 190°C can be maintained between the electrostatic puck 510 and the cooling plate 594. The electrostatic puck 510 and the cooling plate 594 can freely expand or contract independently during thermal cycling.

[0065] In some embodiments, it may be desirable to provide an RF signal through the electrostatic puck 510 and to the supported substrate during processing. In one embodiment, to facilitate such RF signal transmission through the electrostatic puck 510, a conductive gasket (referred to as an RF gasket 590) is disposed on the base portion 595 of the cooling plate 594. The RF gasket may have a conductivity of 10 -3 The RF gasket 590 can be on the order of ohm-meters or better and can maintain spring action at temperatures up to about 300 degrees Celsius. In one embodiment, the RF gasket is Inconel (a nickel alloy containing chromium and iron) coated in gold, copper, or silver. The RF gasket 590 can electrically connect the base portion 595 of the cooling plate 594 to the lower puck plate 520.

[0066] In embodiments where the lower puck plate 520 has low conductivity (e.g., if the lower puck plate 520 is AlN or Al2O3), a hole may be drilled in the lower puck plate 520 where the lower puck plate 520 will contact the RF gasket. The hole may then be filled with a highly conductive material, such as a metal (e.g., having a 10 -3 ohm-meter or better). For example, the hole may be filled with aluminum, tungsten, copper, nickel, molybdenum, silver, gold, etc. Thus, a conductive path 522 may be formed in the lower positioning plate 520 to electrically connect the RF signal to the metal joint 550. In one embodiment, a conductive pad is formed at the surface of the lower positioning plate 520 around the conductive path 522. This ensures good electrical contact to the metal joint 550 and the RF gasket 590. In one embodiment, a shallow groove is drilled in the lower positioning plate 520 on the center of the hole formed for the conductive path 522. The shallow groove may also be filled with metal or other conductive materials. In the illustrated example, the RF gasket 590 and the conductive path 522 are on the outside of the heat sink 536 (e.g., at a farther distance from the center of the electrostatic chuck assembly 505 than the heat sink 536). Alternatively, the RF gasket 590 and the conductive path 522 may be formed near the center of the electrostatic chuck assembly 505.

[0067] In one embodiment, the conductive path between the metal joint 550 and the RF gasket 590 is formed by coating the outer wall of the lower positioning plate 520 with a metal layer. The metal layer can be aluminum, copper, gold, silver, alloys thereof, or other metals. The top and bottom of the lower positioning plate 520 can also be coated with a metal layer near the outer wall to ensure good electrical contact. In this embodiment, the RF gasket 590 can be positioned near the outer wall of the lower positioning plate 520.

[0068] In another embodiment, the conductive path between the metal joint 550 and the RF gasket 590 is formed by coating the walls of the central hole in the lower positioning plate 520 with a metal layer. The metal layer can be aluminum, copper, gold, silver, alloys thereof, or other metals. The top and bottom of the lower positioning plate 520 can also be coated with a metal layer near the outer wall to ensure good electrical contact. In this embodiment, the RF gasket 590 can be positioned near the center of the lower positioning plate 520.

[0069] In one embodiment, a thermal spacer 585 is disposed on a base portion 595 of the cooling plate 594 (e.g., adjacent to the RF gasket 590). The thermal spacer 585 can be used to ensure that the base portion 594 of the cooling plate 595 will not contact the lower puck plate 520. In one embodiment, an O-ring 580 is disposed adjacent to the thermal spacer 585. In one embodiment, the O-ring 580 can be a PFPO ring. The O-ring 580 can be used to facilitate a vacuum seal.

[0070] In one embodiment, one or more gas holes 532, 542 are drilled into the cooling plate 594, the lower puck plate 520, and the upper puck plate 515. The gas holes 532, 542 can be used to deliver a backside gas (e.g., helium) to the backside of the clamped substrate. In one embodiment, the upper puck plate 515 includes a gas hole 532 that terminates at a porous plug 534. The gas hole 532 can be a through hole drilled with a larger diameter counterbore to allow the porous plug 534 to be inserted into the larger diameter hole. The porous plug 534 can be a porous ceramic, such as AlN or Al2O3. The porous plug 534 can prevent arcing and / or can prevent plasma from being generated within the electrostatic puck 505. The porous plug can have a porosity of anywhere between about 30% to about 60%. In one embodiment, the heat sink 536 includes a hole, and the base portion 595 of the cooling plate 594 includes a protrusion 544 that extends through the hole in the heat sink 536. The hole 542 can be drilled into the protrusion 544 (e.g., into the center of the protrusion 544). In one embodiment, an O-ring 538 is disposed on top of the protrusion 544. The fastener 526 can compress the O-ring 538 when tightened. The O-ring 538 can be the same type of O-ring as the O-ring 545 and / or the O-ring 580.

[0071] Figure 6An embodiment of a process 600 for manufacturing an electrostatic chuck assembly is illustrated. At block 605 of process 600, features are formed in a lower puck plate. The lower puck plate may be an AlSiSiC plate, an AlN plate, an Al2O3 plate, or a molybdenum plate. The features formed in the lower puck plate may include features for accommodating fasteners. Additionally, one or more gas holes may be drilled into the lower puck plate. Additionally, one or more other holes may be drilled into the lower puck plate and filled with metal rods or other conductive materials to provide a conductive path for RF signals. In one embodiment, shallow holes are drilled at both ends of one or more other holes in the lower puck plate and filled with metal or other conductive materials. The upper puck plate may also be processed to form one or more gas delivery holes. In one embodiment, the gas delivery holes in the upper puck plate are counterbored, and the counterbores are filled with porous plugs.

[0072] At block 610, the lower puck plate is metal bonded to the upper puck plate to form a puck. The upper puck plate may be an electrically insulating material (dielectric) with embedded heating elements and clamping electrodes. In one embodiment, the metal bond is formed by placing a metal foil of Al or AlSi alloy between the upper and lower puck plates. In one embodiment, the metal foil may be approximately 50 microns thick. Pressure and heat may be applied to form a diffusion bond between the metal foil, the upper puck plate, and the lower puck plate.

[0073] In one embodiment, a threaded insert is placed into a feature formed in the lower positioning disk plate before the upper positioning disk plate is joined to the lower positioning disk plate. In one embodiment, the threaded insert is welded with a copper-zinc alloy. In another embodiment, a metal foil is placed into the feature before the threaded insert is placed into the feature. During the process of metal joining, the threaded insert can be joined to the lower positioning disk plate by metal joining. At box 615, a PFP gasket or O-ring is disposed on the top side of the cooling plate. In one embodiment, the PFP gasket or O-ring is vulcanized to the top side of the cooling plate. The cooling plate can be, for example, an aluminum or aluminum alloy cooling plate having a plurality of channels to flow a cooling fluid. The cooling plate can also have features formed therein. The features in the cooling plate and the features in the lower positioning disk plate can each accommodate fasteners (e.g., bolts and / or nuts). In one embodiment, the cooling plate includes a base portion and a heat sink. The PFP gasket can be disposed on the heat sink, and in some embodiments, the features can be formed in the base portion. In one embodiment, a grafoil layer is formed on the PFP gasket.

[0074] At block 620, fasteners are inserted into features in the lower puck plate and / or the cooling plate. In one embodiment, the fasteners (or at least a portion of the fasteners) are inserted into the lower puck plate prior to joining the lower puck plate to the upper puck plate. In such an embodiment, the fasteners may be permanently embedded in the puck. At block 625, the puck is coupled to the cooling plate by tightening the fasteners (e.g., by threading a bolt protruding from a feature in the lower puck plate into a nut located in a feature in the cooling plate).

[0075] The foregoing description proposes many specific details, such as examples of specific systems, components, methods, etc., to provide a good understanding of several embodiments of the present invention. However, it will be apparent to those skilled in the art that at least some embodiments of the present invention can be implemented without these specific details. In other examples, well-known components or methods are not described in detail or presented in a simple block diagram format to avoid unnecessarily obscuring the present invention. Therefore, the specific details proposed are only exemplary. Specific implementations can vary from these exemplary details and are still understood to be within the scope of the present invention.

[0076] References throughout this specification to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrase "in an embodiment" or "in an embodiment" appearing in various places throughout this specification need not all refer to the same embodiment. In addition, the term "or" is intended to refer to an inclusive "or" rather than an exclusive "or". When the term "about" or "approximately" is used herein, it is intended to refer to an accuracy of ±10% of the nominal value represented.

[0077] Although the operations of the methods herein are illustrated and described in a particular order, the order of the operations of each method may be changed so that certain operations may be performed in a reverse order, or so that certain operations may be performed at least partially simultaneously with other operations. In another embodiment, instructions or sub-operations of different operations may be performed in an intermittent and / or alternating manner. In one embodiment, multiple metal bonding operations are performed as a single step.

[0078] It should be understood that the above description is intended to be exemplary, not restrictive. After reading and understanding the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the present invention should be determined with reference to the appended claims and the full range of equivalents given by the claims.

Claims

1. An electrostatic positioning plate, comprising: an electrically insulating upper puck plate comprising a ceramic material, one or more heating elements, and one or more electrodes for electrostatically securing the substrate; as well as a lower puck plate joined to the upper puck plate, the lower puck plate comprising a plurality of features distributed on the lower puck plate at a plurality of different distances from a center of the lower puck plate, the lower puck plate comprising the ceramic material; and At least one of the following: a) a plurality of threaded inserts embedded within the lower puck plate, wherein each of the plurality of threaded inserts is disposed within a feature of the plurality of features, and wherein each of the plurality of threaded inserts receives one of a first plurality of threaded fasteners, or b) a second plurality of threaded fasteners at least partially embedded within the lower puck plate, wherein a head of each threaded fastener of the second plurality of threaded fasteners is disposed within a feature of the plurality of features; wherein the plurality of fasteners comprises a plurality of holes in a bottom surface of the lower puck plate, wherein each hole of the plurality of holes a) provides access to one or more of the plurality of threaded inserts or b) causes a shaft portion of one of the second plurality of threaded inserts to protrude from the bottom surface, wherein the upper puck plate lacks the plurality of features.

2. The electrostatic puck of claim 1, wherein at least one of the following is true: a) the plurality of threaded inserts comprises a plurality of molybdenum threaded inserts or b) the second plurality of threaded fasteners comprises a plurality of molybdenum threaded fasteners.

3. The electrostatic puck of claim 1, further comprising a load spreading material for each of the plurality of fasteners, wherein the load spreading material is configured to evenly distribute force on each of the plurality of features.

4. The electrostatic puck of claim 3, wherein the load spreading material comprises at least one of a gasket, graphite, or aluminum foil.

5. The electrostatic puck of claim 1, wherein the plurality of holes are a plurality of bolt holes and the plurality of features include counterbores for the plurality of bolt holes, wherein at least one of the plurality of threaded inserts or heads of the second plurality of threaded fasteners are disposed within the counterbores.

6. The electrostatic puck of claim 1, wherein at least one of the plurality of threaded inserts or the second plurality of threaded fasteners is joined to surfaces of the plurality of features by metallic bonding.

7. The electrostatic puck of claim 1, wherein the upper puck plate is bonded to the lower puck plate by diffusion bonding.

8. The electrostatic puck of claim 1, wherein the ceramic material comprises Al2O3 or AlN.

9. The electrostatic puck of claim 1, wherein the upper puck plate is joined to the lower puck plate by metal bonding.

10. The electrostatic puck of claim 9, further comprising: additional holes in the lower positioning plate; as well as A metal layer on the walls of the additional holes, wherein the metal layer provides a conductive path for a radio frequency (RF) signal.

11. The electrostatic puck of claim 10, wherein the additional hole is a central hole of the electrostatic puck.

12. The electrostatic puck of claim 10, wherein the metal layer comprises aluminum, copper, gold, silver, or an alloy of any one of aluminum, copper, gold, and silver.

13. The electrostatic puck of claim 1, wherein the plurality of threaded inserts comprises a plurality of captive nuts, press-fit inserts, or molded inserts.

14. The electrostatic puck of claim 1, wherein the plurality of features are slightly oversized compared to the plurality of threaded inserts to accommodate a greater coefficient of thermal expansion of the plurality of threaded inserts compared to the ceramic material.

15. The electrostatic puck of claim 1, wherein the plurality of threaded inserts are sized such that when the plurality of threaded inserts are heated to 500 degrees Celsius, the plurality of threaded inserts do not exert a force on the plurality of features.

16. The electrostatic puck of claim 1, wherein the plurality of features are arranged to produce a uniform load on the electrostatic puck by the first plurality of threaded fasteners or the second plurality of threaded fasteners when attached to the plurality of threaded inserts.

17. The electrostatic puck of claim 1, wherein the upper puck plate and the lower puck plate each have a thickness of 8-25 mm, and wherein the upper puck plate includes one or more heating elements and one or more electrodes for electrostatically securing a substrate.

18. The electrostatic puck of claim 1, wherein the plurality of threaded inserts comprises a plurality of helical inserts.

19. The electrostatic puck of claim 1, wherein the plurality of threaded inserts comprises a plurality of metallic threaded inserts.

20. The electrostatic puck of claim 1, wherein said lower puck plate is not engageable with said upper puck plate via said plurality of features.

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