Methods and apparatus for gas-assisted thermal transfer with a semiconductor wafer

A method for gas-assisted thermal transfer with a semicondutor wafer during processing in a vacuum chamber comprising:

• positioning said wafer on a platen in a processing position with the front surface of the wafer exposed to said vacuum chamber;
• introducing a gas at a prescribed pressure into a thermal transfer region between the rear surface of said wafer and said platen;
• providing structure defining an intermediate region adjacent said wafer and isolated from the external environment;
• restricting the flow of gas between said thermal transfer region and said intermediate region;
• restricting the flow of gas between said intermediate region and said vacuum chamber;
• and
• vacuum pumping said intermediate region so as to maintain the pressure therein below said prescribed pressure during processing.

Apparatus for gas-assisted thermal transfer with a semicondutor wafer during processing in a vacuum chamber comprising:

• a platen for supporting said wafer in a processing position with its front surface exposed to said vacuum chamber, said platen including a curved surface adapted for providing intimate contact with said wafer and means for introduction of a thermal transfer gas at a prescribed pressure into the microscopic voids between said wafer and said platen;
• clamping means adapted for contacting said wafer around the periphery of its front surface and clamping said wafer against said curved surface;
• a housing which, in combination with said clamping means defines an intermediate region adjacent said platen and isolated from the external environment, said thermal transfer gas being restricted from flowing into said intermediate region by the intimate contact between said wafer and said curved surface and being restricted from flowing from said intermediate region into said vacuum chamber by said clamping means;
• and
• vacuum pumping means coupled to said intermediate region and operative to maintain the pressure therein below said prescribed pressure of said thermal transfer gas, whereby differential pumping of said thermal transfer gas is provided.