Single-grain thin-film transistor using Ni-mediated crystallization of amorphous silicon with a silicon nitride cap layer

Amorphous silicon was crystallized by metal-induced crystallization through a cap with a Ni area density of 2×1014 atoms/cm2 on the cap. The crystallized polycrystalline silicon (poly-Si) shows hexagonal-shaped or disk-shaped grains with average grain size of ∼40 μm. The p-type channel thin-film transistor (TFT) on a single-grain poly-Si exhibited a field-effect mobility of 114 cm2/V s, a threshold voltage of −4.7 V and a subthreshold slope of 0.5 V/dec. The gate bias-stressed changes in the TFT performance was found to be greatly reduced compared to the laser-annealed poly-Si TFT. The surface roughness of the poly-Si is 2.35 nm smaller than that of conventional excimer laser-annealed poly-Si (13.1 nm), which appears to be related to better device performance and improved stability.