Hydrogen Modulation-Doped Structures to Improve Crystalline Fraction of Polycrystalline Silicon Films Prepared by Excimer Laser Annealing at Low Energy Densities

Abstract

An excimer laser annealing (ELA) of amorphous silicon (a-Si) with a hydrogen modulation-doped layer (ELHMD) was investigated using a-Si films with various H concentrations and H distributions for forming high-quality polycrystalline silicon (poly-Si) films at a low energy irradiation (100 mJ/cm2). Poly-Si films with a high crystalline fraction of 80% are obtained by controlling the H concentration distribution and shot number for ELA. In addition, the film exfoliation caused by a H2 burst can be suppressed, and secondary grain growth can be induced using HMD a-Si films. It is considered that the nucleation is enhanced by the recombination energy of the H atoms around the Si–H2 bond during Si melting and that H desorption affects grain growth and film exfoliation.

Review—Technology Trends of Poly-Si TFTs from the Viewpoints of Crystallization and Device Performance

“…Hydrogen-induced crystallization 22,[36][37][38][39][40][41][42][43] .-Hydrogen atoms/ molecules in an a-Si film might degrade the crystallized film during ELA. Dehydrogenation is usually carried out before the ELA process, because the explosive boil of liquid Si occurs as a result of hydrogen atoms/molecules included in the a-Si film.…”