DEPENDENCE OF RADIATION-INDUCED BURIED OXIDE CHARGE ON SILICON-ON-INSULATOR FABRICATION TECHNOLOGY

X-rays have been used to irradiate material fabricated using various S ilicon-on-Insulator (SOI) technologies, including the Bond and Etchbac k 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 nn to 400 mn. The irradiations were do ne under high field (1 MV/cm) bias conditions. For each of these mater ials the net number of occupied traps in the buried oxide and the loca tion of the charge centroid was determined. It was found that the loca tion 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 hav e densities similar tb that of fused silica, the net number of occupie d traps in the BOX saturates at approximately 1.1 x 10(13) cm(-2), and does not depend on the BOX thickness or fabrication technique. Both o f these findings are important in device design, especially for substr ates with thin buried oxides.