Comparison of surface morphology and roughness of silicon surfaces etched using pulsed and continuous flow XeF

This work studies the surface morphology and roughness differences of Si surfaces etched by XeF2 under pulsed and continuous flow conditions. During pulsed etch, XeF2 is introduced into the processing chamber in discrete doses. The sample is exposed to the fixed supply of etchant for a set duration. In contrast, during a continuous flow etch, a steady supply of XeF2 gas maintains a stable etchant concentration in the process chamber. Comparable etch rates and etch depths were attained while ensuring that both pulsed and continuous flow etching were conducted under similar chamber pressures and loading. Although the overall root-mean-square (RMS) roughness values for the continuous and pulsed etch were similar, 0.134 and 0.135 μm, respectively, significant differences in the surface morphology were observed. Laser scanning confocal microscopy, SEM imaging, and FIB cross sections of the etched surfaces revealed pronounced differences in the spatial frequency components of the surface textures. Continuous flow etching produced surfaces with sharper features and higher spatial frequency components. These results indicate that the etching methodology influences Si surface characteristics even when etch depths and rates remain constant.