Patent ID: 7059475

Claim:
A wafer cushion, for cushioning semiconductor wafers in a carrier, made of an energy-absorbing material thick enough and with a compressive strength suitable to absorb energy applied to the carrier by a sudden shock caused by dropping the carrier, the cushion comprising an approximately circular shape for disposition in a coin stack wafer carrier pocket dimensioned to accommodate an approximately circular semiconductor wafer, with the wafer cushion being made of closed-cell polyethylene material with a compressive strength of about 5 to about 9 psi at 10% strain and a surface resistivity of less than 5×10 7 ohms per square, less than 1800 ng/g Cl − , 400 ng/g F − /Acetate, 270 ng/g NO 3 − , 350 ng/g SO 4 2− , and 60 ng/g PO 4 3− ions leachable under moderate conditions, and no detectable outgassing organics under stringent conditions, wherein the closed-cell polyethylene has carbon present as part of the structure of the material to inherently provide the surface resistivity in the absence of carbon black.