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

Abstract

Plasma enhanced chemical vapor deposited (PECVD) silicon nitride (SiN x) is the dominate gate dielectric material for the amorphous silicon (a-Si:H) 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 SiN x gate dielectric material properties to TFT devices and the large area PECVD SiN x processes. The first subject includes: the bulk film characteristics, a-Si:H TFT performance related to the SiN x/a-Si:H interface properties, such as morphology and band gaps, the dual SiN x gate dielectric structure, and the influence of a-Si:H deposition processes to transistor performance. The second subject is concentrated on the large area PECVD SiN x processes which include uniformity, film characteristics, etc. At the end, a unified relationship between the TFT's threshold voltage and the SiN x refractive index is presented. In the conclusion, relationships among SiN x process, material, and TFT device characteristics are summarized.