High-performance polycrystalline silicon TFTs fabricated by high-temperature process with excimer laser annealing

Abstract

Polycrystalline silicon (p-Si) thin film transistors (TFTs) were fabricated using a high temperature process that included solid phase crystallization (SPC) and dry thermal oxidation with excimer laser annealing (ELA). Raman spectroscopy, X-ray diffraction and transmission electron microscopy analyses showed that the ELA process improved the quality of p-Si films markedly. The p-Si TFTs exhibited higher performance than the SPC p-Si TFTs. The field effect mobility for n-type self-aligned TFT was 251cm 2 ·V -1 ·s -1 . The longitudinal junction diffusion length of the p-Si TFTs was shorter than that of the SPC p-Si TFTs. This is favorable for fine design rules. If optimization of amorphous silicon (a-Si) deposition and SPC conditions enables the grains of p-Si films to grow larger than the channel length and the positions of the grain boundaries are controlled, this process will produce great scaling rule merits such as singlegrain Si TFTs. This fabrication process is consistent with the high temperature p-Si TFT development trend towards using large substrates, low temperatures, and fine design rules. High temperature p-Si TFTs are expected to be used in LSI circuits as silicon-on-insulator (SOI) devices in the future.