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Thinned Wafer Stress Relief
Christopher Mielke, BKM Technology Partners
As devices get smaller and capability grows, so does the need for thinner more versatile die. This is evident in cellular technology, notebook computers, smart cards, RFID security devices, power devices, MEMS and memory chips. With the need for higher performance and density, comes the need to thin the substrates on which these devices are made. Once processed the “extra” substrate material is no longer needed it is removed to create smaller Chip Stack Packages, flexible IC’s and to allow for backside metalization which acts as a heat sink for the active devices on the front side. This material is usually ground away using a two step process which leaves the completed wafer thinner, but weaker and more brittle and prone to other problems such as electrical failures, intermittent light creating false flops, fragile die which can not be handled with standard pick and place equipment, warped die which jump out of their packaging during pick and place, brittle/rigid die with no ductility that are prone to breakage, and poor contrast during die marking.
Remote plasma stress relief offers the advantages of increasing the strength of these die, often by a factor of ten. It reduces electrical failures, reduces chipping during singulation, reduces the “pop corn” effect during packaging by reducing warpage, provides a selectable matte or shiny finish, allows for a passivation layer to be applied, reduces backside light transmission and at the same time does not subject the wafer to high temperatures, physical shear forcees or ion bombardment.
Christopher Mielke is a partner in BKM Technology Partners and has been working in the semiconductor industry for 13 years. Chris taught plasma and advanced plasma as well as vacuum and advanced vacuum classes at Intel Corporation. He has also taught at the collegiate level. With a bachelor’s degree in Mechanical engineering from the University of Arizona, Chris also worked as a design engineer for Rockwell International Rocketdyne Division on the Space Shuttle Main Engines.