Double-Pulsed Laser Annealing Technologies and Related Applications

Abstract

New applications of the double-pulsed laser annealing (DPLA) technologies were opened up in the coming-generation high-performance devices: insulated gate bipolar transistors (IGBTs) and low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs). The DPLA system was equipped with two solid-state lasers of a green wavelength as pulse laser sources. The line-beam irradiation was done in the same way as conventional excimer laser annealing (ELA) by making a sample stage scan at a constant speed while emitting the double-pulsed laser at 1kHz. The IGBTs demand deep PN junction in high electrical activation, while the LTPS-TFTs do high quality silicon thin films like a single crystal. The low-thermal budget annealing process enabled only the B- and P-implant layers within a depth of about 2mum to be activated without heating the whole wafer. The PN junction consisting of a B-implant layer and a P-implant layer reached more than 80% in activation ratios to adjust a delay time between double laser pulses. The advanced lateral crystal growth (ALCG) process enabled Si grains to be laterally and sequentially grown. The n-channel TFTs (L/W: 5mum/5mum) made of the ALCG-Si thin films reached a level of 600cm2/Vs in average mobility when the drain current flowed along the lateral-growth direction