Eur. Phys. J. B 52, 355-359 (2006)
https://doi.org/10.1140/epjb/e2006-00312-9

Influence of high energy electron irradiation on the characteristics of polysilicon thin film transistors

Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria

Corresponding author: ^a val@issp.bas.bg

Received: 14 April 2006
Revised: 10 July 2006
Published online: 2 August 2006

Abstract

The influence of high energy electron (23 MeV) irradiation on the electrical characteristics of p-channel polysilicon thin film transistors (PSTFTs) was studied. The channel 220 nm thick LPCVD (low pressure chemical vapor deposition) deposited polysilicon layer was phosphorus doped by ion implantation. A 45 nm thick, thermally grown, SiO2 layer served as gate dielectric. A self-alignment technology for boron doping of the source and drain regions was used. 200 nm thick polysilicon film was deposited as a gate electrode. The obtained p-channel PSTFTs were irradiated with different high energy electron doses. Leakage currents through the gate oxide and transfer characteristics of the transistors were measured. A software model describing the field enhancement and the non-uniform current distribution at textured polysilicon/oxide interface was developed. In order to assess the irradiation-stimulated changes of gate oxide parameters the gate oxide tunneling conduction and transistor characteristics were studied. At MeV dose of 6×10¹³ el/cm², a negligible degradation of the transistor properties was found. A significant deterioration of the electrical properties of PSTFTs at MeV irradiation dose of 3×10¹⁴ el/cm² was observed.