High-pressure H2O post-annealing for improving reliability of LTPS and a-IGZO thin-film transistors within a coplanar structure

Abstract

Improving reliability of low-temperature polycrystalline silicon (LTPS) and amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs), components of low-temperature polycrystalline silicon and oxide (LTPO), is crucial for fabricating high-performance and high-stability LTPS and oxide semiconductor-based electronics and display products. However, improving the reliability of these TFTs simultaneously in a uniform and effective manner within a coplanar structure is challenging. In this work, high-pressure H2O post-annealing (H2O HPPA) as a post-treatment for LTPS and a-IGZO TFTs within a coplanar structure are proposed to improve the uniformity and stability of the electrical characteristics simultaneously. It was demonstrated that oxygen and hydrogen in the HPPA-passivated defect state at the channel/gate dielectric layer interfaces and bulk gate dielectric layers of LTPS and a-IGZO TFTs considerably improve the uniformity and stability of the electrical performance and morphologies of the interfaces. Thus, the distribution of electrical characteristics (mobility, threshold voltage, and subthreshold swing) in LTPS and a-IGZO TFTs was reduced by more than 2-fold, and the trap charge densities at their interfaces and bulk gate dielectric layers were reduced by approximately 1.6-fold. Furthermore, the threshold voltage shift was decreased in both LTPS and a-IGZO-TFTs fabricated with H2O HPPA under negative and positive bias temperature stresses, respectively. The proposed H2O HPPA method can effectively facilitate the industry-level application of LTPS and oxide semiconductor-based electronics and display electronics.