Method of manufacturing an amorphous-silicon thin film transistor

Abstract

A structure of an amorphous-silicon thin film transistor array comprises a substrate, a gate electrode, a gate insulating layer, an amorphous-silicon active layer, an n+ amorphous-silicon layer and a metal layer. The metal layer defines a source electrode and a drain electrode. The structure simplifies the photolithography process by using a less number of masks to manufacture thin film transistors. It also reduces the occurrence of open circuits in the first metal (MI) layer or short circuits between the MI layer and the second metal (MII) layer caused by the photoresist residue or particle contamination. The manufacturing method combines a conventional back-channel-etched (BCE) reduced mask process and a two-step exposure technology. The two-step exposure technology uses two photoresist pattern masks. One is a pattern mask for complete exposure with higher light intensity and the other is a pattern mask for incomplete exposure with lower light intensity. The photoresist pattern with incomplete exposure is then etched by an O plasma etching process. The amorphous-silicon layer and the metal layer has the characteristic of an island metal masking structure that protects the active layer from plasma damage in plasma etching process.