Continued Development of R.F. Sputtered a-Si:H Thin-Film Transistors Towards an All-Sputtered Device

Abstract

AbstractPrototype thin film transistors have previously been fabricated by r.f. magnetron sputtering of a-Si:H on to CVD Si02 using a crystalline silicon gate. These devices exhibited an on/off current ratio of four orders of magnitude for gate voltages as low as 10 volts. This demonstrated the suitability of the sputtered layer for liquid crystal display applications.The use of a crystalline substrate negates the advantages of using a thin film,such as large area capability and low cost, so we have turned our attention to the provision of a sputtered dielectric. Several candidate materials have been considered, including Si02, Si3N4, Ta205, AIN and Ti02. We present the characteristics of our first all-sputtered transistor utilising an Si02 gate,and assess the dielectric properties and potential of other materials, with emphasis on the silicon oxynitride system.