US patent 7521335, Yamanaka, Hideo, "Method and apparatus for producing ultra-thin semiconductor chip and method and apparatus for producing ultra-thin back-illuminated solid-state image pickup device", issued 2009-04-21, assigned to Sony Corporation
US patent 4266334, Edwards, Thomas W. & Pennypacker, Ronald S., "Manufacture of thinned substrate imagers", issued 1981-05-12, assigned to RCA Corporation