Modeling and characterization of sacrificial polysilicon etching using vapor-phase xenon difluoride

Xenon Difluoride is an isotropic dry etch which is increasingly being used to release structures made of polysilicon. By using a vapor-phase XeF/sub 2/ pulse etching system we have investigated the effects of aperture size and thickness of polysilicon films versus etch rates. Decreasing the aperture size resulted in reduced etch rates. For a 100 /spl mu/m wide structure the etch rates varied from 1.38 /spl mu/m/min (1.25 /spl mu/m thick polysilicon) down to 0.41 /spl mu/m/min (0.1 /spl mu/m thick polysilicon). Rate constants are obtained for a modified, aperture-dependent Deal-Grove model from the experimental data.