| Laser-Projection-Patterned Etching of GaAs in a Chlorine Atmosphere. (1998) | |||||||||
Abstract | |||||||||
| A pulsed KrF laser and deep UV projection optics were used to perform laser-projection-patterened etching of gallium arsenide. The etching process is shown to result from a purely thermochemical reaction. Local laser surface heating resuts in the desorption of the chlorination products AsCl sub n and GaCl sub n (n=1-3) formed between laser pulses. A thermal model that gives temporal evolution of surface temperatures during a laser pulse was used to calculate activation energy. The influence of etching parameters was investigated as was the effect of the laser irradiation in vacuum, Ar, and Cl2 ambient on the surface morphology. It is shown that the nonlinear dependence of the etch rate on the surface temperature and the heat spread in the semiconductor surface controls the spatial resolution of the etching process. As a result, etched features smaller or larger than the photomask features are achieved depending on the laser energy density. Resolution down to 4 microns with a system having an optical limit of 2 microns was achieved at low fluences. | |||||||||
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