High throughput laser techniques to process amorphous silicon into single or polycrystalline silicon are highly desired for high-speed circuitry applications. This technology uses the sequential lateral solidification (SLS) process, an excimer laser projection-based scheme, to controllably crystallize amorphous silicon thin films into polycrystalline silicon thin films with long grains. The technique consists of generating a sequence of excimer laser pulses that are modulated to a predetermined fluence. Upon irradiating an amorphous silicon thin film sample, the homogenized laser pulses are masked so that the patterned beams may then pattern the sample as desired. Translating the sample with respect to the patterned beams may be used to produce polysilicon with long grained, directionally-controlled crystals.
This refined SLS technique presents several advantages over conventional excimer laser annealing systems. Two-dimensional projection of mask features onto the sample film and the use of an ultra-precise sample translator allow for a high level of control. An energy density modulator is used to rapidly and periodically change the incident energy density of the beam to block stray beamlets and to planarize the surface morphology. The system does not require vacuum atmosphere or preheating of the substrate, improving throughput. By systematically manipulating and controlling the locations, shapes, and extent of the melting induced by the incident laser pulses, the system produces uniform large-grained and grain boundary location-controlled polycrystalline thin film semiconductors using the SLS process.
Patent Issued (US 6,635,554)
Tech Ventures Reference: IR MS99/04/26A