Experimental verification of buried-oxide with over-8 MV/cm breakdown fields in low-dose SIMOX wafers

Low-dose SIMOX wafers have attractive features as the material for advanced commercial CMOS LSIs, such as lower cost, and lower threading dislocation density (~10² cm^-2) than high-dose SIMOX. However, the low-dose SIMOX wafers prepared by the Internal-Thermal-OXidation (ITOX) process, still exhibited lower breakdown fields (E_BDs) for the buried-oxide (~5.5 MV/cm), when compared to the intrinsic E_BD of the thermal-oxide (>8 MV/cm) at Si surface in most cases. It has been pointed out that the E_BD degradation of Buried-OXide (BOX) is caused by the presence of Si islands in the BOX. We report here that BOX E_BDs for the low-dose SIMOX is upgraded from the level of the previous case to that of thermal oxide (>8 MV/cm) by the reduction of Si islands and becomes more practical to larger unit-device-size area (7.85×10^-3cm²)