oxide

Poor gettering of metal impurities is a fundamental problem in integrated MEMS and CMOS processes on thick BSOI wafers. The buried oxide forms a diffusion barrier for most transition metals in silicon preventing the use of standard gettering methods common in conventional bulk silicon active devices [1]. Inadequate metal gettering in CMOS devices is known to lead to oxide breakdown device failures and decrease in gate oxide integrity (GOI) [2]. A new technique based on adding a thin polycrystalline silicon layer between the active layer and buried oxide for solving the aforementioned gettering problem in thick BSOI wafers is presented. Device wafers with prepared LPCVD grown polysilicon films were bonded with oxidized handle wafers using commercially available bonder and annealed for 2 hours at 1100°C to strengthen the bond. The bonded wafer pairs were thinned down to a final active layer thickness by grinding and polishing. SEM image of the cross-section is presented in Fig 1