Investigation of SOS Processes for Fabrication of Radiation Hardened MIS devices and ICs.

摘要

This report covers the first six months work on a program to investigate radiation hardening of MIS devices on SOS material. To date the work has been directed toward understanding radiation-induced leakage mechanisms. Experiments were designed to investigate the effects of radiation-induced trapped charge in the sapphire. Suitable devices were fabricated on SOS material using existing masks for a test structure designated MOS-X. Both n-type and p-type starting material covering a range of doping concentration was used,giving both enhancement and deep depletion mode transistors of both n-and p-channel types. In some cases the sapphire was thinned to 5mils after processing and a back-gate electrode was formed by depositing aluminum on the thinned sapphire substrate. Irradiation of this device only occasionally produced a back channel leakage in the absence of positive drain bias and positive voltage applied across the sapphire using the back gate,indicating the need for an electric field in the sapphire to obtain radiation-induced back channels. Experiments using a positive back-gate bias during irradiation gave a back channel in both n-and p-channel enhancement mode devices,indicating opposite sign of trapped charge for n-and p-type material.