Effects of Capping Layer on Grain Growth with µ-Czochralski Process during Excimer Laser Crystallization

Abstract

The effects of a SiO2 capping layer (CL) on the excimer laser crystallization of amorphous silicon (α-Si) films are investigated during the growth of location-controlled Si grains with a µ-Czochralski (grain filter) process by experiments and numerical simulations. The CL thinner than 400 nm for a 250-nm-thick α-Si precursor serves as a heat reservoir and increases the average grain size to 9 µm, while the CL thicker than 400 nm serves as a heat sink and decreases the average grain size. During laser irradiation, the CL stores heat owing to heat conduction. The CL returns a fraction of the heat into a molten pool after the laser irradiation, which results in a moderate temperature gradient of the layers beneath the molten pool. The grains grown from the molten pool increase in size owing to the long solidification duration, as a result of a slow heat extraction rate from the molten pool. While the CL thicker than 400 nm stores more heat during laser irradiation and returns only a small fraction of the heat after the laser irradiation, the grain size decreases.