Radiation Damage of Amorphous and Microcrystalline Silicon Image Sensor Structure

Abstract

AbstractThe paper reports radiation damage experiments which influence properties of image sensors using pin photodiodes and thin film transistors. The effect of 60Co radiation at about 1.2MeV on the noise and drain-source current characteristics of hydrogenated amorphous and nanocrystalline silicon film transistor was examined as a function of the γ dose and hydrogen content of the films.An unmeasurable effect upon the noise characteristics of the TFT was observed. The predominant drain-source current with increasing dose was in the form of various shifts of the transfer characteristics toward negative gate voltage and decrease of the transfer characteristic subthreshold slope from 5at% to 26at% of hydrogen content in the films. These, in turn, resulted in a large increase in leakage current for gate voltages at the periods the TFTs were not conducting. The radiation damage of the pin diode has much less influence on operation of array than the damage of the TFT.Annealing for 3h at 180°C restored TFT threshold voltage properties, particularly in the case of amorphous films with greater contents of hydrogen.