Columbia University

Technology Ventures

Refined sequential lateral solidification (SLS) system based on excimer laser and projection beam delivery enables controlled crystallization of thin amorphous silicon films

Technology #ms99-04-26a

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.

High-throughput system allows for SLS production of single-crystal, directionally solidified, and large-grained uniform polycrystalline silicon thin films at low temperatures

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.

Lead Inventor:

James Im, Ph.D.


  • Processing of amorphous silicon thin films into polysilicon thin films
  • Polysilicon patterning


  • Produces polysilicon with long grains whose microstructure may be controlled
  • Improves polysilicon sample quality
  • Semiconductor processing at low temperatures
  • Increases manufacturing throughput

Patent Information:

Patent Issued (US 6,635,554)

Tech Ventures Reference: IR MS99/04/26A

Related Publications: