THE EFFECT OF SUBSTRATES ON THE PERFORMANCE AND HOT-CARRIER RELIABILITY OF N-CHANNEL THIN-FILM TRANSISTORS

We have examined the impact of substrates on the performance and respo nse to hot-carrier stress of polycrystalline silicon n-channel thin fi lm transistors. Non-barrier coated Coming Code 1737 glass, fused silic a and oxidized Si were used as substrates for transistors made in poly crystalline Si films deposited by low-pressure chemical vapour deposit ion. It is established that the substrate type strongly influences the transistor's transfer characteristics: transistors on fused silica ar e found to be superior in performance and hot-carrier reliability to t ransistors on 1737 glass or oxidized Si substrates. It is argued that the transistor's characteristics are determined by grain geometries an d impurities in polycrystalline Si which are functions of the impurity content of the substrate and the properties of its interface with cry stalline Si.