Single crystalline silicon thin film transistors fabricated on Corning 7059

Abstract

Direct-view active matrix liquid crystal displays (AMLCDs) are now fabricated in very large volumes using amorphous silicon (a-Si:H) technology. For this purpose, high temperature polysilicon technology is currently used in Japan, with the active matrix fabricated on a quartz substrate. However, quartz substrates of display quality are rather expensive and low temperature polysilicon technology on glass substrates using laser annealing has been introduced as one possible alternative. Recently the transfer of single-crystalline Si layers on glass has been reported. In this case, circuits are fabricated on SOI substrates obtained by a zone melting recrystallisation process and transfered on the glass after completion of almost all the processing steps. This technique is of interest, as high temperature processing steps and fine design rules can be utilized. The main drawback of the technique is that the transfer operation is the final step. We propose an alternative and new technique based on the transfer before processing of a single crystalline Si layer on glass. Processing is subsequently performed at low temperature, using technological steps developed for the fabrication of low temperature polysilicon devices. A SIMOX substrate is thermally oxydized and then bonded at 450/spl deg/C to the glass substrate (Corning 7059 or 1737). The silicon substrate and the thin buried oxide are then removed by a combination of mechanical and chemical etching.