Elimination of square pits on SIMOX wafer by using nitrogen-doped Cz crystal

Recent developments in LSI technology require SOI wafers for realization of higher speed operation and lower power consumption. SIMOX wafers are one of the leading SOI wafer materials, and have been revealing high performance such as excellent SOI layer thickness uniformity, even below the 0.1 μm thickness range which is required for CMOS applications. To realize high device performance, a defect-free SOI surface is desirable, especially for achieving superior gate oxide integrity (GOI). While the GOI on the SIMOX wafers fabricated by the internal thermal oxidation (ITOX) process was reported to be superior to that on the conventional Cz wafers (Kawamura et al, 1996), it was reported that crystal originated particle (COP)-like pits exist on standard SIMOX wafers (Naruoka et al, 1997), although their origin has not been clearly resolved. In this study, we investigated the pits on ITOX-SIMOX wafers fabricated on various starting materials with different COP density. The influence of COPs in the starting materials on the pits on the SIMOX wafers was discussed and the possibility of pit-free SIMOX using nitrogen-doped Cz crystals was illustrated