Laser irradiation apparatus, laser irradiation method, and method for manufacturing a semiconductor device

摘要

A laser irradiation or annealing apparatus and method for semiconductor crystallization uses two lasers for improving the crystallinity and throughput. A beam spot from a first pulsed wave laser and a beam spot from a second continuous wave (CW) is used and controlled to overlap when scanning the substrate. The first laser beam has a wavelength of visible light or a shorter wavelength than that of visible light. Since the first laser beam melts the semiconductor film, the absorption coefficient of the second laser beam to the semiconductor increases drastically and thereby becomes more absorbable. The first pulsed laser can be operated using the second harmonic. The shape of the beam spots of both lasers can be controlled and shaped into elliptical, rectangular or linear forms. The angle of incidence of both lasers to the substrate can be made oblique to hinder interference when the beams are reflected.