Dependence of radiation induced buried oxide charge on silicon-on-insulator fabrication technology

X-rays have been used to irradiate material fabricated using various Silicon-on-Insulator (SOI) technologies, including the Bond and Etchback SOI (BESOI) process and several different Separation-by-Implantation-of-Oxygen (SIMOX) processes. The thickness of the buried oxide (BOX) in these samples ranged from 80 nm to 400 nm. The irradiations were done under high field (1 MV/cm) bias conditions. For each of these materials the net number of occupied traps in the buried oxide and the location of the charge centroid was determined. It was found that the location of the charge centroid depends on the density of the BOX, and on the radiation dose. It was also found that for buried oxides which have densities similar to that of fused silica, the net number of occupied traps in the BOX saturates at approximately 1.1×10¹³ cm^-2, and does not depend on the BOX thickness or fabrication technique. Both of these findings are important in device design, especially for substrates with thin buried oxides