NEW RIPPLE PATTERNS OBSERVED IN EXCIMER-LASER IRRADIATED SIO2 POLYCRYSTALLINE SILICON SIO2 STRUCTURES

A new ripple formation mechanism is observed in excimer-laser irradiat ed polycrystalline silicon (polysilicon) films on oxidized silicon waf ers. The ripples form for polysilicon films capped with a thin oxide, and for laser fluences that completely melt the buried polysilicon. Th e resulting ripples are unlike those previously reported in that (1) t heir wavelength cannot be predicted by Rayleigh's diffraction conditio n, (2) their wave fronts are arranged in chaotic patterns, rather than parallel lines, and (3) the wave fronts can be manipulated by changin g the polysilicon surface topology. The characteristics of these rippl es are investigated in the context of understanding the underlying phy sics. (C) 1997 American Institute of Physics.