Support Pin with Dome Shaped Upper Surface

Abstract

A chuck, which may hold a substrate during stress measurements, includes a number of pins that support the substrate. Each support pin has a dome shaped upper surface that contacts a bottom surface of a substrate when supporting the substrate. The dome shaped upper surface minimizes contact with the substrate as well as assists in maintaining the same contact location with the substrate regardless of substrate shape. The dome shaped upper surface may be formed of a layer of soft material having a high coefficient of static friction to hold the substrate stationary with respect to the pins when the chuck is accelerated moved during or between stress measurements. Additionally, the layer of soft material may be a thin layer that covers a hard internal dome to reduce creep.

1 . An apparatus comprising:
 a chuck having a plurality of support pins for supporting a substrate, the support pins having a dome shaped upper surface that contacts a bottom surface of a substrate when supporting the substrate.   
   
   
       2 . The apparatus of  claim 1 , wherein the dome shaped upper surface has a radius of curvature between 0.125 inches to 0.5 inches. 
   
   
       3 . The apparatus of  claim 1 , wherein the support pins have a body formed from a first material, and the dome shaped upper surface is formed from a layer of a second material, the second material being softer than the first material. 
   
   
       4 . The apparatus of  claim 3 , wherein the second material is softer than the substrate to be held by the plurality of support pins. 
   
   
       5 . The apparatus of  claim 3 , wherein the layer of a second material has a hardness of 20 shore A to 50 shore A. 
   
   
       6 . The apparatus of  claim 3 , wherein the layer of a second material has a coefficient of static friction that is greater than 3. 
   
   
       7 . The apparatus of  claim 6 , the apparatus further comprising a stage coupled to the chuck, the stage is configured to move the chuck. 
   
   
       8 . The apparatus of  claim 3 , wherein the second material comprises silicone. 
   
   
       9 . The apparatus of  claim 3 , wherein the layer of a second material overlies an internal dome that is on a top surface of the body of each support pin, wherein the layer of a second material is softer than the internal dome. 
   
   
       10 . The apparatus of  claim 9 , wherein the internal dome is integrally formed with the body of each support pin. 
   
   
       11 . The apparatus of  claim 9 , wherein the layer of a second material is approximately 0.25 mm to 2 mm thick. 
   
   
       12 . An apparatus for supporting a substrate, the apparatus comprising:
 a chuck having a plurality of support pins for supporting a substrate, each support pin has a layer of material that forms a dome shaped upper surface that contacts a bottom surface of a substrate when supporting the substrate, wherein the layer of material that forms the dome shaped upper surface is softer than a remainder of the support pin; and   a movable stage coupled to the chuck to move the chuck while a substrate is supported by the plurality of support pins.   
   
   
       13 . The apparatus of  claim 12 , wherein the layer of a material that forms the dome shaped upper surface is softer than the substrate to be held by the plurality of support pins. 
   
   
       14 . The apparatus of  claim 12 , wherein the dome shaped upper surface has a radius of curvature between 0.125 inches to 0.5 inches. 
   
   
       15 . The apparatus of  claim 12 , wherein the layer of a material that forms the dome shaped upper surface has a coefficient of static friction that is greater than 3. 
   
   
       16 . The apparatus of  claim 12 , wherein the layer of material that forms the dome shaped upper surface comprises silicone. 
   
   
       17 . The apparatus of  claim 12 , wherein the layer of material that forms the dome shaped upper surface has a hardness of 20 shore A to 50 shore A. 
   
   
       18 . The apparatus of  claim 12 , wherein each support pin comprises an internal dome covered by the layer of material that forms the dome shaped upper surface, wherein the layer of material that forms the dome shaped upper surface is softer than the internal dome. 
   
   
       19 . The apparatus of  claim 18 , wherein the internal dome is integrally formed with a body of each support pin. 
   
   
       20 . The apparatus of  claim 18 , wherein the layer of material that forms the dome shaped upper surface is approximately 0.25 mm to 2 mm thick. 
   
   
       21 . An apparatus for supporting a substrate during stress measurements, the apparatus comprising:
 a chuck having a plurality of support pins for supporting a substrate, each support pin comprising a body with an integrally formed dome at a top of the body, and a layer of material that covers the integrally formed dome to produce a dome shaped upper surface that contacts a bottom surface of a substrate when supporting the substrate, wherein the layer of material that forms the dome shaped upper surface is softer than the integrally formed dome; and   a movable stage coupled to the chuck to move the chuck while a substrate is supported by the plurality of support pins.   
   
   
       22 . The apparatus of  claim 21 , wherein the dome shaped upper surface has a radius of curvature between 0.125 inches to 0.5 inches.