Proposal of Silicon on Insulator Reach through APDs for Soft X-ray Imaging Optimized by TCAD Simulation

We have been developing a soft X-ray imager called as Silicon on Insulator-Reach ThroughAvalanche Photo Diode aiming at application to the surface analysis and spintronics. In order to detect the low energy soft X-rays, the imager employs a full depletion and back-side illumination sensor with a high resistivity floating zone grown Si wafer. Thus, a multiple high-energy implantation and rapid thermal annealing process is newly adopted instead of a conventional process to eliminate slip generation during the high temperature annealing. The process condition optimization was done by using technology computer aided design (TCAD) regarding gain and noise performance. The optimized process conditions are obtained by making a flat boron concentration of multiplication region. The optimized APD has 55 in gain and 0.13 in k-factor which satisfies the sensor requirement for the soft X-ray analysis.