Hydrogenated n-Channel Low Temperature Polycrystalline Silicon TFTs as Ultraviolet Dosimeters

Hong Cheng,Xinnan Lin,Juncheng Xiao

doi:10.1109/jeds.2021.3085193

Abstract

N-channel thin film transistors (TFTs) fabricated with hydrogenated low temperature polycrystalline silicon (LTPS) were exposed to ultraviolet (UV) radiation to a cumulative dose up to 16 J/cm 2 . The effect of radiation on the electrical characteristics of the devices was monitored after the irradiation steps and in a prolonged period after irradiation. The main monitoring parameter was the threshold voltage ( V th ) which was found to have exponentially linear dependence on irradiation dose. This, together with obtained low fading, suggests that hydrogenated n-channel low temperature polycrystalline silicon TFTs have potential as UV radiation dosimeters. In addition, the physical mechanisms of the UV induced electrical degradation were analyzed in terms of the radiation generated traps at poly-Si grain boundary and poly-Si and gate oxide insulator (poly-Si/SiO 2 ) interface.

Highlights

The metal oxide semiconductor field effect transistor (MOSFET) was established in the late 1970s as an important device for radiation detection in space applications [1] and later as a personal and medical dosimeter [2]–[4]
The published articles analyzed electrical degradation of thin film transistors (TFTs) without exploring TFT devices as UV radiation dosimeters. We investigate this idea by irradiating hydrogenated n-channel low temperature polycrystalline silicon (LTPS)-TFTs with UV light to a cumulative dose of 16 J/cm2
The main monitoring parameter in MOSFET dosimeters is usually the shift of threshold voltage ( Vth) which has been studied in this paper

Summary

INTRODUCTION

The metal oxide semiconductor field effect transistor (MOSFET) was established in the late 1970s as an important device for radiation detection in space applications [1] and later as a personal and medical dosimeter [2]–[4]. The application of MOSFET dosimeter is based on converting the threshold voltage shift ( Vth), induced by radiation, into the radiation dose (D). The primary monitoring parameter was the threshold voltage (Vth), other parameters including field effect mobility (μeff) and subthreshold swing (SS) were systematically studied as a function of UV radiation doses. In order to evaluate the ability of retaining information about the absorbed dose, the fading of hydrogenated n-channel LTPS-TFT after UV irradiation was analyzed in this study

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

CONCLUSION