Electrostatic chuck assembly for high temperature processes

This patent application is areissue application of U.S. Pat. No. 10,872,800, issued Dec. 22, 2020, which is acontinuation of U.S. patent application Ser. No. 14/878,955, filed Oct. 8, 2015, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/065,503, filed Oct. 17, 2014,bothallof which are incorporated by reference herein.More than one reissue application has been filed for the reissue of U.S. Pat. No. 10,872,800. The reissue applications are application Ser. Nos. 17/973,417 (the present application) and 17/973,425, both of which broadening reissues of U.S. Pat. No. 10,872,800.

Some embodiments of the present invention relate, in general, to a substrate support assembly (also referred to as an electrostatic chuck assembly) that is usable for high temperature processes.

Electrostatic chucks are widely used to hold substrates, such as semiconductor wafers, during substrate processing in processing chambers used for various applications, such as physical vapor deposition, etching, or chemical vapor deposition. Electrostatic chucks typically include one or more electrodes embedded within a unitary chuck body which includes a dielectric or semi-conductive ceramic material across which an electrostatic clamping field can be generated.

Electrostatic chucks offer several advantages over mechanical clamping devices and vacuum chucks. For example, electrostatic chucks reduce stress-induced cracks 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. Additionally, the electrostatic chuck can hold the substrate more uniformly to a chucking surface to allow a greater degree of control over substrate temperature.

Various processes used in the fabrication of integrated circuits may call for high temperatures and/or wide temperature ranges for substrate processing. However, electrostatic chucks in etch processes typically operate in a temperature range of up to about 120° C. At temperatures above about 120° C., the components of many electrostatic chucks will begin to fail due to various issues such as de-chucking in AlO electrostatic chucks, plasma erosion from corrosive chemistry, bond reliability, and so on.

Some embodiments of the present invention described herein cover an electrostatic chuck assembly that includes a puck with an electrically insulative upper puck plate comprising one or more heating elements and one or more electrodes to electrostatically secure a substrate and a lower puck plate bonded to the upper puck plate by a metal bond. The lower puck plate includes multiple features distributed over a bottom side of the lower puck plate at different distances from a center of the lower puck plate, wherein each of the features accommodates a fastener. The electrostatic chuck assembly further includes a cooling plate coupled to the puck by the fasteners. The fasteners each apply an approximately equal fastening force to couple the cooling plate to the puck.

Some embodiments of the present invention described herein cover an electrostatic puck that includes an AlN or AlOupper puck plate with one or more heating elements and one or more electrodes to electrostatically secure a substrate. The electrostatic puck further includes a lower puck plate bonded to the upper puck plate by a metal bond. The lower puck plate is composed of one of a) Molybdenum, b) a SiC porous body infiltrated with an AlSi alloy, or c) a ceramic such as AlN or AlO. The lower puck plate further includes multiple features distributed over a bottom side of the lower puck plate at different distances from a center of the lower puck plate, wherein each of the features accommodates a fastener.

Some embodiments of the present invention described herein cover a method of manufacturing an electrostatic chuck assembly. The method includes forming a plurality of features in a lower puck plate. The method further includes bonding the lower puck plate to an upper puck plate with a metal bond to form a puck, the upper puck plate comprising one or more heating elements and one or more electrodes to electrostatically secure a substrate. The method further includes disposing 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 inserting one of a plurality of fasteners into each of the plurality of features formed in the lower puck plate. The method further includes coupling the cooling plate to the puck by tightening the plurality of fasteners. The plurality of fasteners may be tightened approximately equally to apply an approximately equal fastening force to couple the cooling plate to the puck.

Embodiments of the present invention provide a substrate support assembly and an electrostatic chuck assembly including a puck that is coupled to a cooling plate by a collection of fasteners. Multiple fasteners are used to secure the puck to the cooling plate. The multiple fasteners are located at different distances from a center of the puck. In one embodiment, a first set of fasteners are disposed at a first radius from the center of the puck and a second set of fasteners are disposed at a second radius from the center of the puck. The multiple fasteners may be approximately uniformly distributed across a top side or surface of the cooling plate to evenly distribute a fastening force to couple the puck to the cooling plate. The fasteners may all be tightened an equal amount to ensure that the fastening forces applied by each fastener is about the same. This facilitates uniform heat transfer properties between the puck and the cooling plate over the puck.

In one embodiment, an electrostatic chuck assembly includes a puck having an electrically insulative upper puck plate bonded to a lower puck plate by a metal bond. The metal bond may be an aluminum bond, an AlSi alloy bond, or other metal bond. The upper puck plate includes one or more heating elements and one or more electrodes to electrostatically secure a substrate. The lower puck plate includes multiple features distributed over a bottom side of the lower puck plate at different distances from a center of the lower puck plate. Each of the features accommodates one of a plurality of fasteners. The electrostatic chuck assembly further includes a cooling plate coupled to the puck by the fasteners. The cooling plate may include a base portion (referred to as a cooling base) and a spring loaded inner heat sink connected to the base portion by a plurality of springs, wherein the plurality of springs apply a force to press the inner heat sink against the puck. The fasteners each apply an approximately equal fastening force to couple the cooling plate to the puck (e.g., to couple the base portion of the cooling plate to the puck). This approximately equal fastening force may facilitate uniform heat transfer between the cooling plate and the puck. Additionally, the spring loaded inner heat sink may also facilitate uniform heat transfer between the cooling plate and the puck.

is a sectional view of one embodiment of a semiconductor processing chamberhaving an electrostatic chuck assemblydisposed therein. The electrostatic chuck assemblyincludes an electrostatic puck (puck) having an upper puck plate bonded to a lower puck plate, as will be discussed in greater detail below. The puckis coupled to a cooling plate by multiple fasteners, as discussed in greater detail below.

The processing chamberincludes a chamber bodyand a lidthat enclose an interior volume. The chamber bodymay be fabricated from aluminum, stainless steel or other suitable material. The chamber bodygenerally includes sidewallsand a bottom. An outer linermay be disposed adjacent the sidewallsto protect the chamber body. The outer linermay be fabricated and/or coated with a plasma or halogen-containing gas resistant material. In one embodiment, the outer lineris fabricated from aluminum oxide. In another embodiment, the outer lineris fabricated from or coated with yttria, yttrium alloy or an oxide thereof.

An exhaust portmay be defined in the chamber body, and may couple the interior volumeto a pump system. The pump systemmay include one or more pumps and throttle valves utilized to evacuate and regulate the pressure of the interior volumeof the processing chamber.

The lidmay be supported on the sidewallof the chamber body. The lidmay be opened to allow access to the interior volumeof the processing chamber, and may provide a seal for the processing chamberwhile closed. A gas panelmay be coupled to the processing chamberto provide process and/or cleaning gases to the interior volumethrough a gas distribution assemblythat is part of the lid. Examples of processing gases may be used to process in the processing chamber including halogen-containing gas, such as CF, SF, SiCl, HBr, NF, CF, CHF, CHF, Cland SiF, among others, and other gases such as O, or NO. Examples of carrier gases include N, He, Ar, and other gases inert to process gases (e.g., non-reactive gases). The gas distribution assemblymay have multiple apertureson the downstream surface of the gas distribution assemblyto direct the gas flow to the surface of the substrate. Additionally, or alternatively, the gas distribution assemblycan have a center hole where gases are fed through a ceramic gas nozzle. The gas distribution assemblymay be fabricated and/or coated by a ceramic material, such as silicon carbide, Yttrium oxide, etc. to provide resistance to halogen-containing chemistries to prevent the gas distribution assemblyfrom corrosion.

A substrate support assemblyis disposed in the interior volumeof the processing chamberbelow the gas distribution assembly. The substrate support assemblyholds a substrateduring processing. An inner linermay be coated on the periphery of the substrate support assembly. The inner linermay be a halogen-containing gas resist material such as those discussed with reference to the outer liner. In one embodiment, the inner linermay be fabricated from the same materials of the outer liner.

In one embodiment, the substrate support assemblyincludes a mounting platesupporting a pedestal, and electrostatic chuck assembly. In one embodiment, the electrostatic chuck assemblyfurther includes a thermally conductive base referred to herein as a cooling platecoupled to an electrostatic puck (referred to hereinafter as a puck) by multiple fasteners. The electrostatic chuck assemblydescribed in embodiments may be used for Johnsen-Rahbek and/or Coulombic electrostatic chucking.

In one embodiment, a protective ringis disposed over a portion of the puckat an outer perimeter of the puck. In one embodiment, the puckis coated with a protective layer. Alternatively, the puckmay not be coated by a protective layer. The protective layermay be a ceramic such as YO(yttria or yttrium oxide), YAlO(YAM), AlO(alumina), YAlO(YAG), YAlO3 (YAP), Quartz, SiC (silicon carbide), SiN(silicon nitride) Sialon, AlN (aluminum nitride), AlON (aluminum oxynitride), TiO(titania), ZrO(zirconia), TiC (titanium carbide), ZrC (zirconium carbide), TiN (titanium nitride), TiCN (titanium carbon nitride), YOstabilized ZrO(YSZ), and so on. The protective layer may also be a ceramic composite such as YAlOdistributed in AlOmatrix, YO—ZrOsolid solution or a SiC—SiNsolid solution. The protective layer may also be a ceramic composite that includes a yttrium oxide (also known as yttria and YO) containing solid solution. For example, the protective layer may be a ceramic composite that is composed of a compound YAlO(YAM) and a solid solution Y-xZrO(YO—ZrOsolid solution). Note that pure yttrium oxide as well as yttrium oxide containing solid solutions may be doped with one or more of ZrO, AlO, SiO, BO, ErO, NdO, NbO, CeO, SmO, YbO, or other oxides. Also note that pure Aluminum Nitride as well as doped Aluminum Nitride with one or more of ZrO, AlO, SiO, BO, ErO, NdO, NbO, CeO, SmO, YbO, or other oxides may be used. Alternatively, the protective layer may be sapphire or MgAlON.

The puckincludes an upper puck plate (not shown) and a lower puck plate (not shown) bonded by a metal bond. The upper puck plate may be a dielectric or electrically insulative material (e.g., having an electrical resistivity of greater than 10Ohm·meter) that is usable for semiconductor processes at temperatures of 180° C. and above. In one embodiment, the upper puck plate is composed of materials usable from about 20° C. to about 500° C. In one embodiment, the upper puck plate is AlN. The AlN upper puck plate may be undoped or may be doped. For example, the AlN may be doped with Samarium oxide (SmO), Cerium oxide (CeO), Titanium dioxide (TiO), or a transition metal oxide. In one embodiment, the upper puck plate is AlO. The AlOupper puck plate may be undoped or may be doped. For example, the AlOmay be doped with Titanium dioxide (TiO) or a transition metal oxide.

The lower puck plate may have a coefficient of thermal expansion that is matched to a coefficient of thermal expansion of the upper puck plate. In one embodiment, the lower puck plate is a SiC porous body that is infiltrated with an AlSi alloy (referred to as AlSiSiC). The lower puck plate may alternatively be AlN or AlO. In one embodiment, the lower puck plate is undoped AlN or undoped AlO. In one embodiment, the lower puck plate is composed of the same material as the upper puck plate. The AlSiSiC material, AlN or AlOmay be used, for example, in reactive etch environments or in inert environments.

In one embodiment, the lower puck plate is Molybdenum. Molybdenum may be used, for example, if the puckis to be used in an inert environment. Examples of inert environments include environments in which inert gases such as Ar, O2, N, etc. are flowed. Molybdenum may be used, for example, if the puckis to chuck a substrate for metal deposition. Molybdenum may also be used for the lower puck plate for applications in a corrosive environment (e.g., etch applications). In such an embodiment, exposed surfaces of the lower puck plate may be coated with a plasma resistant coating after the lower puck plate is bonded to the upper puck plate. The plasma coating may be performed via a plasma spray process. The plasma resistant coating may cover, for example, sidewalls of the lower puck plate and an exposed horizontal step of the lower puck plate. In one embodiment, the plasma resistant coating is AlO. Alternatively, the plasma resistant coating may be YOor a YOcontaining oxide. Alternatively, the plasma resistant coating may be any of the materials described with reference to protective layer.

The mounting plateis coupled to the bottomof the chamber bodyand includes passages for routing utilities (e.g., fluids, power lines, sensor leads, etc.) to the cooling plateand the puck. The cooling plateand/or puckmay include one or more optional embedded heating elements, optional embedded thermal isolatorsand/or optional conduits,to control a lateral temperature profile of the substrate support assembly. In one embodiment, a thermal gasketis disposed on at least a portion of the cooling plate.

The conduits,may be fluidly coupled to a fluid sourcethat circulates a temperature regulating fluid through the conduits,. The embedded thermal isolatorsmay be disposed between the conduits,in one embodiment. The embedded heating elementsare regulated by a heater power source. The conduits,and embedded heating elementsmay be utilized to control the temperature of the puck, thereby heating and/or cooling the puckand a substrate (e.g., a wafer) being processed. In one embodiment, the puckincludes two separate heating zones that can maintain distinct temperatures. In another embodiment, the puckincludes four different heating zones that can maintain distinct temperatures. The temperature of the electrostatic puckand the thermally conductive basemay be monitored using multiple temperature sensors,, which may be monitored using a controller.

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

In one embodiment, the puckincludes at least one clamping electrodecontrolled by a chucking power source. The clamping electrode(also referred to as a chucking electrode) may further be coupled to one or more RF power sources,through a matching circuitfor maintaining a plasma formed from process and/or other gases within the processing chamber. The one or more RF power sources,are generally capable of producing an RF signal having a frequency from about 50 kHz to about 3 GHz and a power of up to about 10,000 Watts. In one embodiment, an RF signal is applied to the metal base, an alternating current (AC) is applied to the heater and a direct current (DC) is applied to the clamping electrode.

depicts an exploded view of one embodiment of the substrate support assembly. The substrate support assemblydepicts an exploded view of the electrostatic chuck assemblyincluding the puckand the pedestal. The electrostatic chuck assemblyincludes the puck, as well as the cooling plateattached to the puck. As shown, an o-ringmay be vulcanized to the cooling platealong a perimeter of a top side of the cooling plate. Alternatively, the o-ring may be disposed on the top side of the cooling platewithout being vulcanized thereto. Embodiments are discussed herein with reference to o-rings and gaskets that are vulcanized to at least a portion of the cooling plate. However, it should be understood that the o-rings and/or gaskets may alternatively be vulcanized to the lower puck plate. Alternatively, the o-rings and/or gaskets may not be vulcanized to any surface. In one embodiment, the o-ringis a perfluoropolymer (PFP) o-ring. Alternatively, other types of high temperature o-rings may be used. In one embodiment, thermally insulating high temperature o-rings are used. The o-ringmay be a stepped o-ring having a first step at a first thickness and a second step at a second thickness. This may facilitate uniform tightening of fasteners by causing the amount of force used to tighten the fasteners to increase dramatically after a set amount of compression of the PFP o-ring.

Additional o-rings (not shown) may also be vulcanized to the top side of the cooling plate around a holeat a center of the cooling platethrough which cables are run. Other smaller o-rings may also be vulcanized to the cooling platearound other openings, around lift pins, and so forth. Alternatively, a gasket (e.g., a PFP gasket) may be vulcanized to the top side of the cooling plate. Examples of PFPs usable for the gasket or o-ringare Dupont's™ ECCtreme™, Dupont's KALREZ® and Daikin's® DUPRA™. The o-ringor gasket provide a vacuum seal between a chamber interior volume and interior volumes within the electrostatic chuck assembly. The interior volumes within the electrostatic chuck assemblyinclude open spaces within the pedestalfor routing conduits and wiring.

The cooling plateadditionally includes numerous featuresthrough which fasteners are inserted. If a gasket is used, the gasket may have cutouts at each of the features. Fasteners extend through each of the featuresand attach to additional portions of the fasteners (or additional fasteners) that are inserted into additional features formed in the puck. For example, a bolt may extend through a featurein the cooling plateand be screwed into a nut disposed in a feature of the puck. Each featurein the cooling platemay line up to a similar feature (not shown) in a lower puck plateof puck.

The puckhas a disc-like shape having an annular periphery that may substantially match the shape and size of a substrate positioned thereon. An upper surface of the puckmay have an outer ring, multiple mesas,and channels,between the mesas. The puckincludes an upper puck platebonded to the lower puck plateby a metal bond. In one embodiment, the upper puck platemay be fabricated by an electrically insulative ceramic material. Suitable examples of the ceramic materials include aluminum nitride (AlN), alumina (AlO), and the like.

In one embodiment, the material used for the lower puck platemay be suitably chosen so that a coefficient of thermal expansion (CTE) for the lower puck platematerial substantially matches the CTE of the electrically insulative upper puck platematerial in order to minimize CTE mismatch and avoid thermo-mechanical stresses which may damage the puckduring thermal cycling. In one embodiment, the lower puck plateis Molybdenum. In one embodiment, the lower puck plate is alumina. In one embodiment, the lower puck plate is AlN.

In one embodiment, an electrically conductive metal matrix composite (MMC) material is used for the lower puck plate. The MMC material includes a metal matrix and a reinforcing 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. Metals which 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 reinforcing material may be selected to provide the desired structural strength for the MMC, and may also be selected to provide desired values for other properties of the MMC, such as thermal conductivity and CTE, for example. Examples of reinforcing materials which may be used include silicon (Si), carbon (C), or silicon carbide (SiC), but other materials may also be used.

The MMC material for the lower puck plateis preferably chosen to provide the desired electrical conductivity and to substantially match the CTE of the upper puck platematerial over the operating temperature range for the electrostatic chuck assembly. In one embodiment, the temperature may range from about 20° Celsius to about 500° Celsius. In one embodiment, matching the CTEs is based on selecting the MMC material so that the MMC material includes at least one material which is also used in the upper puck platematerial. In one embodiment, the upper puck plateincludes AlN. In one embodiment, the MMC material includes a SiC porous body that is infiltrated with an AlSi alloy.

The constituent materials and composition percentages of the MMC may be selected to provide an engineered material which meets desirable design objectives. For example, by suitably selecting the MCC material to closely match the CTEs of the lower puck plateand upper puck plate, the thermo-mechanical stresses at an interface between the lower puck plateand the upper puck plateare reduced.

The lower puck platemay include numerous features (not shown) for receiving fasteners. The features may be approximately evenly distributed across a surface of the lower puck plate, and may include a first set of features at a first distance from a center of the lower puck plateand a second set of features at a second distance from the center of the lower puck plate.

The cooling plateattached below the puckmay have a disc-like main portionand an annular flange extending outwardly from the main portionand positioned on the pedestal. In one embodiment, the cooling platemay be fabricated by a metal, such as aluminum or stainless steel or other suitable materials. Alternatively, the cooling platemay be fabricated by a composite ceramic, such as an aluminum-silicon alloy infiltrated SiC or Molybdenum to match a thermal expansion coefficient of the puck. The cooling plateshould provide good strength and durability as well as heat transfer properties.

depicts a sectional top view of one embodiment of a puck. As shown, the puckhas a radius R, which may be substantially similar to a radius of substrates or wafers that are to be supported by the puck. The puckadditionally includes multiple features. The features may match similar features in a cooling plate to which the puckis mounted. Each featureaccommodates a fastener. For example, a bolt (e.g., a stainless steel bolt, galvanized steel bolt, etc.) may be placed into each feature such that a head of the bolt is inside of an opening large enough to accommodate the head and a shaft of the bolt extends out of a bottom side of the puck. The bolt may be tightened onto a nut that is placed in a corresponding feature in the cooling plate. Alternatively, featuresmay be sized to accommodate a nut, and may include a hole that can receive a shaft of a bolt that is accommodated by a corresponding feature in the cooling plate. In another example, a helical insert (e.g., a Heli-Coil®) or other threaded insert (e.g., a press fit insert, a mold-in insert, a captive nut, etc.) may be inserted into one or more of the features to add a threaded hole thereto. A bolt placed inside of the cooling plate and protruding from the cooling plate may then be threaded into the threaded insert to secure the cooling plate to the puck. Alternatively, threaded inserts may be used in the cooling plate.

The featuresmay be slightly oversized as compared to a size of the fasteners to accommodate a greater coefficient of thermal expansion of the fasteners. In one embodiment, the fasteners are sized such that the fasteners will not exert a force on the features when the fasteners are heated to 500 or 600 degrees Celsius.

As shown, multiple sets of featuresmay be included in the puck. Each set of featuresmay be evenly spaced at a particular radius or distance from a center of the puck. For example, as shown a first set of featuresis located at a radius R and a second set of featuresis located at a radius R. Additional sets of features may also be located at additional radii.

In one embodiment, the features are arranged to create a uniform load on the puck. In one embodiment, the features are arranged such that a bolt is located approximately every 30-70 square centimeters (e.g., every 50 square centimeters). In one embodiment, three sets of features are used for a 12 inch puck. A first set of features may be located about 4 inches from a center of the puckand includes about 4 features. A second set of features may be located about 6 inches from a center of the puckand includes about 6 features. A third set of features may be located about 8 inches from a center of the puckand includes about 8 features. In one embodiment, the puckincludes about 8-24 features arranged in sets at 2-3 different radii, where each feature accommodates a fastener.

depicts a sectional side view of one embodiment of an electrostatic chuck assembly. The electrostatic chuck assemblyincludes a puckmade up of an upper puck plate, and a lower puck platethat are bonded together by a metal bond. In one embodiment, diffusion bonding is used as the method of metal bonding, but other bonding methods may also be used. In one embodiment, the upper puck plateand the lower puck platecomprise materials which include aluminum (e.g., AlN or AlO). Metal bondmay include an “interlayer” of aluminum foil which is placed in a bonding region between the upper puck plateand the lower puck plate. Pressure and heat may be applied to form a diffusion bond between the aluminum foil and the upper puck plateand between the aluminum foil and lower puck plate. In another embodiment, the diffusion bond may be formed using other interlayer materials which are selected based upon the materials used for upper puck plateand lower puck plate. In another embodiment, the upper puck platemay be directly bonded to the lower puck plateusing direct diffusion bonding in which no interlayer is used to form the bond.

A plasma resistant and high temperature o-ringmay be made of a perfluoropolymer (PFP). The o-ringmay be a PFP with inorganic additives such as SiC. The o-ring may be replaceable. When the o-ringdegrades it may be removed and a new o-ring may be stretched over the upper puck plateand placed at a perimeter of the puckat an interface between the upper puck plateand the lower puck plate. The o-ringmay protect the metal bondfrom erosion by plasma.

The upper puck plateincludes mesas, channelsand an outer ring. The upper puck plateincludes clamping electrodesand one or more heating elements. The clamping electrodesare coupled to a chucking power source, and to a RF plasma power supplyand an RF bias power supplyvia a matching circuit. The upper puck plateand lower puck platemay additionally include gas delivery holes (not shown) through which a gas supplypumps a backside gas such as He.

The upper puck platemay have a thickness of about 3-25 mm. In one embodiment, the upper puck platehas a thickness of about 3 mm. The clamping electrodesmay be located about 1 mm from an upper surface of the upper puck plate, and the heating elementsmay be located about 1 mm under the clamping electrodes. The heating elementsmay be screen printed heating elements having a thickness of about 10-200 microns. Alternatively, the heating elements may be resistive coils that use about 1-3 mm of thickness of the upper puck plate. In such an embodiment, the upper puck platemay have a minimum thickness of about 5 mm. In one embodiment, the lower puck platehas a thickness of about 8-25 mm.

The heating elementsare electrically connected to a heater power sourcefor heating the upper puck plate. The upper puck platemay include electrically insulative materials such as AlN. The lower puck plateand upper puck platemay be made of the same materials. In one embodiment, the lower puck plateis made of materials which are different from the materials used for the upper puck plate. In one embodiment, the lower puck plateis composed of a metal matrix composite material. In one aspect, the metal matrix composite material includes aluminum and silicon. In one embodiment, the metal matrix composite is a SiC porous body infiltrated with an AlSi alloy.

The lower puck plateis coupled to and in thermal communication with a cooling platehaving one or more conduits(also referred to herein as cooling channels) in fluid communication with fluid source. The cooling plateis coupled to the puckby multiple fasteners. The fastenersmay be threaded fasteners such as nut and bolt pairs. As shown, the lower puck plateincludes multiple featuresfor accommodating the fasteners. The cooling platelikewise includes multiple featuresfor accommodating the fasteners. In one embodiment, the features are bolt holes with counter bores. As shown, the featuresare through features that extend through the lower puck plate. Alternatively, the featuresmay not be through features. In one embodiment, the featuresare slots that accommodate a t-shaped bolt head or rectangular nut that may be inserted into the slot and then rotated 90 degrees. In one embodiment, the fasteners include washers, GRAFOIL®, aluminum foil, or other load spreading materials to distribute forces from a head of the fastener evenly over a feature.

In one embodiment (as shown), a PEP o-ringis vulcanized to (or otherwise disposed on) the cooling plate at a perimeter of the cooling plate. Alternatively, the PFP o-ringmay be vulcanized to the bottom side of the lower cooling plate. The fastenersmay be tightened to compress the PFP o-ring. The fastenersmay all be tightened with approximately the same force to cause a separationbetween the puckand the cooling plateto be approximately the same (uniform) throughout the interface between the puckand the cooling plate. This may ensure that the heat transfer properties between the cooling plateand the puckare uniform. In one embodiment, the separationis about 2-10 mils. The separation may be 2-10 mils, for example, if the PFP o-ringis used without a GRAFOIL® layer. If a GRAFOIL® layer is used along with the PFP o-ring, then the separation may be about 10-40 mils. Larger separation may decrease heat transfer, and cause the interface between the puckand the cooling plateto act as a thermal choke. In one embodiment, a conductive gas may be flowed into the separationto improve heat transfer between the puckand the cooling plate.

The separationminimizes the contact area between the puckand the cooling plate. Additionally, by maintaining a thermal choke between the puckand the cooling plate, the puckmay be maintained at much greater temperatures than the cooling plate. For example, in some embodiments the puckmay be heated to temperatures of 180-300 degrees Celsius, while the cooling platemay maintain a temperature of below about 120 degrees Celsius. The puckand the cooling plateare free to expand or contract independently during thermal cycling.

The separationmay function as a thermal choke by restricting the heat conduction path from the heated puckto the cooled cooling plate. In a vacuum environment, heat transfer may be primarily a radiative process unless a conduction medium is provided. Since the puckmay be disposed in a vacuum environment during substrate processing, heat generated by heating elementsmay be transferred more inefficiently across the separation. Therefore, by adjusting the separation and/or other factors that affect heat transfer, the heat flux flowing from the puckto the cooling platemay be controlled. To provide efficient heating of the substrate, it is desirable to limit the amount of heat conducted away from the upper puck plate.

In one embodiment (not shown), a graphite foil (referred to as GRAFOIL®) layer is disposed between the puckand the cooling platewithin a perimeter of the PFP o-ring. The GRAFOIL® may have a thickness of about 10-40 mil. The fastenersmay be tightened to compress the GRAFOIL® layer as well as the PFP o-ring. The GRAFOIL® may be thermally conductive, and may improve a heat transfer between the puckand the cooling plate.

In one embodiment (not shown), the cooling plateincludes a base portion to which the PFP o-ringmay be vulcanized. The cooling platemay additionally include a spring loaded inner heat sink connected to the base portion by one or more springs. The springs apply a force to press the inner heat sink against the puck. A surface of the heat sink may have a predetermined roughness and/or surface features (e.g., mesas) that control heat transfer properties between the puckand the heat sink. Additionally, the material of the heat sink may affect the heat transfer properties. For example, an aluminum heat sink will transfer heat better than a stainless steel heat sink. In one embodiment, the heat sink includes a GRAFOIL® layer on an upper surface of the heat sink.

depicts a sectional side view of another embodiment of an electrostatic chuck assembly. In one embodiment, electrostatic chuck assemblycorresponds to electrostatic chuck assemblyof. The electrostatic chuck assemblyincludes an electrostatic puckmade up of an upper puck plateand a lower puck plate. In one embodiment, electrostatic puckcorresponds to puckof. In one embodiment, the upper puck plateis bonded to the lower puck plateby a metal bond. In one embodiment, diffusion bonding is used as the method of metal bonding. However, other bonding methods may also be used to produce the metal bond.