Thinning of SOI by Numerically Controlled Plasma CVM(Chemical Vaporization Machining)

Development of the NC-PCVM Machine and Trial of Ultra-thin SOI wafer

Abstract

SOI (Silicon on Insulator) wafer is expected as a semiconductor substrate which realizes the high-speed and low-power device for the next generation. In this report, the result of thinning the SOI layer of the SOI wafer by using the numerically controlled plasma CVM (Chemical Vaporization Machining) apparatus is described. In plasma CVM, since the removal volume is proportional to the dwelling time of the plasma, numerical control machining is realized by controlling the scanning speed of the worktable. Scanning speed distribution for obtaining the target film thickness can be decided by, measuring the pre-machining SOI layer thickness distribution and removal rate per unit time, and the thickness distribution of the SOI layer was measured by spectroscopic ellipsometry. The sample is the commercial SOI wafer (6 inch UNIBOND wafer), and SOI layer thickness before thinning is about 200nm. As the result of thinning the SOI layer by the numerically controlled plasma CVM, the order of 10 nm of the SOI layer was achieved.