Plasma enhanced chemical vapor deposited silicon nitride as a gate dielectric film for amorphous silicon thin film transistors - A critical review

Plasma enhanced chemical vapor deposited (PECVD) silicon nitride (SiNx) is the dominate gate dielectric material for the amorphous silicon (a-Si) thin film transistors (TFTs) today. In this paper, the author critically reviewed several major issues in this field. Two subjects are included in the discussion: effects of SiNx gate dielectric material properties to TFT devices and the large area PECVD SiNx processes. The first subject includes: the bulk film characteristics, a-Si TFTperformance related to the SiNx/a-Si interface properties, such as morphology and band gaps, the dual SiNx gate dielectric structure, and the influence of a-Si deposition processes to transistor performance. The second subject is concentrated on the large area PECVD SiNx processes which include uniformity, film characteristics, etc. At the end, a unified relationship between the TFT's threshold voltage and the SiNx refractive index is presented. In the conclusion, relationships among SiNx process, material, and TFT device characteristics are summarized. © 1998 Elsevier Science Ltd. All rights reserved.