Bottom-Gate TFTs with Channel Layer Grown by Pulsed PECVD Technique

Abstract

ABSTRACTIn this paper, we report on nc-Si:H thin films deposited by the pulsed PECVD technique at a temperature of 150C and TFTs made using this material. RF power and silane flow rate were varied in order to study the effect of different levels of crystallinity on the film. Electrical conductivity, Hall mobility, optical transmittance, and Raman backscattering were measured on films of two different thicknesses. From the Raman data we see that the 50 nm films with hydrogen dilution are mostly amorphous, indicating the presence of a thick incubation layer. The values obtained for the conductivity, mobility, and optical gap varied depending on the processing conditions and these results are discussed. Bottom-gate TFTs were fabricated using a pulsed PECVD channel layer and a SiN gate dielectric. The TFTs' extracted parameters are msat μsat ≤ 0.38 cm2=(V s), Vt,sat ≥7:3 V, Ion/off >106, and S < 1 V/decade. The TFT performance and material properties are presented and discussed.