Electrostatic chuck assembly for high temperature processes

Abstract

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

What is claimed is: 
     
         1 . An electrostatic chuck assembly comprising:
 a puck comprising:
 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 electrically insulative upper puck plate by a metal bond, the lower puck plate comprising a plurality of features distributed over the lower puck plate at a plurality of different distances from a center of the lower puck plate, wherein each of the plurality of features accommodates one of a plurality of fasteners; 
   a cooling plate coupled to the lower puck plate by the plurality of fasteners; and   at least one of a gasket or an o-ring disposed on a top side of at least a portion of the cooling plate, wherein the plurality of fasteners each apply an approximately equal fastening force to couple the cooling plate to the puck, to compress at least one of the o-ring or the gasket, and to maintain an approximately equal separation between the cooling plate and the lower puck plate and facilitate a uniform heat transfer between the cooling plate and the lower puck plate.   
     
     
         2 . The electrostatic chuck assembly of  claim 1 , wherein the gasket is a perfluoropolymer (PFP) gasket, and wherein the PFP gasket acts as a thermal choke between the cooling plate and the puck. 
     
     
         3 . The electrostatic chuck assembly of  claim 1 , further comprising:
 a flexible graphite layer on the gasket.   
     
     
         4 . The electrostatic chuck assembly of  claim 1 , wherein the cooling plate comprises:
 a base portion; and   a spring loaded heat sink connected to the base portion by a plurality of springs, wherein the plurality of springs apply a force to press the spring loaded heat sink against the lower puck plate.   
     
     
         5 . The electrostatic chuck assembly of  claim 1 , wherein the plurality of fasteners comprise a plurality threaded fasteners and the plurality of features comprise a plurality of openings for receiving the plurality of threaded fasteners. 
     
     
         6 . The electrostatic chuck assembly of  claim 1 , further comprising:
 an interface between the puck and the cooling plate, wherein the interface acts as a thermal choke that is configured to maintain a temperature difference between the cooling plate and the substrate of up to approximately 190° C.   
     
     
         7 . The electrostatic chuck assembly of  claim 1 , wherein the electrically insulative upper puck plate comprises AlN and the lower puck plate comprises one of a) Molybdenum or b) a SiC porous body infiltrated with an AlSi alloy. 
     
     
         8 . The electrostatic chuck assembly of  claim 1 , wherein the electrically insulative upper puck plate comprises Al 2 O 3  and the lower puck plate comprises Al 2 O 3 . 
     
     
         9 . The electrostatic chuck assembly of  claim 1 , wherein the electrically insulative upper puck plate comprises AlN and the lower puck plate comprises AlN. 
     
     
         10 . The electrostatic chuck assembly of  claim 1 , wherein the o-ring is disposed around a perimeter of the puck at an interface between the electrically insulative upper puck plate and a base portion of the cooling plate. 
     
     
         11 . The electrostatic chuck assembly of  claim 1 , further comprising:
 an electrically conductive path between a top of the lower puck plate and a bottom of the lower puck plate.   
     
     
         12 . The electrostatic chuck assembly of  claim 11 , wherein the electrically conductive path comprises a hole filled with an electrically conductive material. 
     
     
         13 . An electrostatic chuck assembly, comprising:
 a puck comprising:
 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 electrically insulative upper puck plate by a metal bond, the lower puck plate comprising a plurality of features distributed over the lower puck plate at a plurality of different distances from a center of the lower puck plate, wherein each of the plurality of features accommodates one of a plurality of fasteners; and 
 an electrically conductive path between a top of the lower puck plate and a bottom of the lower puck plate; 
   a cooling plate coupled to the lower puck plate by the plurality of fasteners, wherein the plurality of fasteners each apply an approximately equal fastening force to couple the cooling plate to the puck; and   an electrically conductive gasket between the lower puck plate and the cooling plate, wherein the electrically conductive gasket contacts the electrically conductive path.   
     
     
         14 . A method comprising:
 forming a plurality of features in a lower puck plate, wherein the plurality of features are distributed over the lower puck plate at a plurality of different distances from a center of the lower puck plate, wherein each of the plurality of features accommodates one of a plurality of fasteners;   bonding the lower puck plate to an electrically insulative upper puck plate with a metal bond to form a puck, the electrically insulative upper puck plate comprising one or more heating elements and one or more electrodes to electrostatically secure a substrate;   disposing at least one of a gasket or an o-ring to a top side of at least a portion of a cooling plate;   inserting one of the plurality of fasteners into each of the plurality of features formed in the lower puck plate; and   coupling the cooling plate to the puck by tightening the plurality of fasteners, wherein the plurality of fasteners are tightened approximately equally to apply an approximately equal fastening force to couple the cooling plate to the puck, to compress at least one of the o-ring or the gasket, and to maintain an approximately equal separation between the cooling plate and the lower puck plate and facilitate a uniform heat transfer between the cooling plate and the lower puck plate.   
     
     
         15 . The method of  claim 14 , further comprising:
 disposing a flexible graphite layer on the gasket.   
     
     
         16 . The method of  claim 14 , further comprising:
 forming an electrically conductive path between a top of the lower puck plate and a bottom of the lower puck plate.   
     
     
         17 . The electrostatic chuck assembly of  claim 13 , further comprising:
 at least one of a gasket or an o-ring disposed on a top side of at least a portion of the cooling plate.   
     
     
         18 . The electrostatic chuck assembly of  claim 17 , wherein the gasket acts as a thermal choke between the cooling plate and the puck. 
     
     
         19 . The electrostatic chuck assembly of  claim 18 , further comprising:
 a flexible graphite layer on the gasket.   
     
     
         20 . The electrostatic chuck assembly of  claim 13 , wherein the cooling plate comprises:
 a base portion; and   a spring loaded heat sink connected to the base portion by a plurality of springs, wherein the plurality of springs apply a force to press the spring loaded heat sink against the lower puck plate.   
     
     
       21. An electrostatic chuck assembly comprising:
 a puck comprising:
 an upper puck plate comprising a ceramic material, the upper puck plate comprising one or more heating elements and one or more electrodes to secure a substrate; 
 a lower puck plate bonded to the upper puck plate, the lower puck plate comprising a plurality of features distributed over 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, wherein the upper puck plate lacks the plurality of features and the plurality of features of the lower puck plate are not accessible via the upper puck plate; and 
 at least one of:
 c) a plurality of threaded inserts embedded within the lower puck plate, wherein each threaded insert 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 accommodates one of a first plurality of threaded fasteners, or 
 d) 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 features comprise 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 of the plurality of threaded inserts or b) enables a shaft of one of the second plurality of threaded fasteners to protrude from the bottom surface; and 
   at least one of a gasket or an o-ring configured to be disposed on a top side of at least a portion of a cooling plate, wherein the first plurality of threaded fasteners or the second plurality of threaded fasteners each are to apply an approximately equal fastening force to couple the cooling plate to the puck, to compress at least one of the o-ring or the gasket, and to maintain an approximately equal separation between the cooling plate and the lower puck plate and facilitate a uniform heat transfer between the cooling plate and the lower puck plate.    
     
     
       22. The electrostatic chuck assembly of  claim 21 , wherein at least one of a) the plurality of threaded inserts comprise a plurality of molybdenum threaded inserts or b) the second plurality of threaded fasteners comprise a plurality of molybdenum threaded fasteners.  
     
     
       23. The electrostatic chuck assembly of  claim 21 , further comprising a load spreading material in each of the plurality of features, wherein the load spreading material is configured to distribute forces evenly over each feature of the plurality of features.  
     
     
       24. The electrostatic chuck assembly of  claim 23 , wherein the load spreading material comprises at least one of a washer, grafoil, or aluminum foil.  
     
     
       25. The electrostatic chuck assembly of  claim 21 , wherein the ceramic material comprises Al 2 O 3  or AlN.  
     
     
       26. The electrostatic chuck assembly of  claim 21 , wherein the plurality of holes are a plurality of bolt holes and the plurality of features comprise counter bores 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 counter bores.  
     
     
       27. The electrostatic chuck assembly of  claim 21 , wherein at least one of the plurality of threaded inserts or the second plurality of threaded fasteners are bonded to surfaces of the plurality of features by a metal bond.  
     
     
       28. The electrostatic chuck assembly of  claim 21 , wherein the upper puck plate is an electrically insulative upper puck plate that is bonded to the lower puck plate by a metal bond.  
     
     
       29. The electrostatic chuck assembly of  claim 28 , further comprising:
 an additional hole in the lower puck plate; and   a metal layer on a wall of the additional hole, wherein the metal layer provides an electrically conductive path for a radio frequency (RF) signal.    
     
     
       30. The electrostatic chuck assembly of  claim 29 , wherein the additional hole is a center hole of the puck.  
     
     
       31. The electrostatic chuck assembly of  claim 29 , wherein the metal layer comprises aluminum, copper, gold, silver, or an alloy of any of aluminum, copper, gold, or silver.  
     
     
       32. The electrostatic chuck assembly of  claim 21 , wherein the upper puck plate is an electrically insulative upper puck plate that is bonded to the lower puck plate by a diffusion bond.  
     
     
       33. The electrostatic chuck assembly of  claim 21 , wherein the plurality of threaded inserts comprises a plurality of captive nuts, press fit inserts, or mold-in inserts.  
     
     
       34. The electrostatic chuck assembly of  claim 21 , wherein the plurality of features are oversized as compared to the plurality of threaded inserts to accommodate a greater coefficient of thermal expansion of the plurality of threaded inserts as compared to the ceramic material.  
     
     
       35. The electrostatic chuck assembly of  claim 34 , wherein the plurality of threaded inserts are sized such that the plurality of threaded inserts do not exert a force on the plurality of features when the plurality of threaded inserts are heated to 500 degrees Celsius.  
     
     
       36. The electrostatic chuck assembly of  claim 21 , wherein the plurality of features are arranged to create a uniform load on the puck by the first plurality of threaded fasteners or the second plurality of threaded fasteners when attached to the plurality of threaded inserts, the plurality of features comprising a first set of features disposed along a first circle at a first distance from the center and a second set of features disposed along a second circle at a second distance from the center, wherein the second circle is concentric with the first circle.  
     
     
       37. The electrostatic chuck assembly of  claim 21 , wherein the upper puck plate and the lower puck plate each have a thickness of 8-25 mm.  
     
     
       38. The electrostatic chuck assembly of  claim 21 , wherein the plurality of threaded inserts comprises a plurality of helical inserts.  
     
     
       39. The electrostatic chuck assembly of  claim 21 , wherein the plurality of threaded inserts comprise a plurality of metal threaded inserts.