We have investigated the surface morphology of polysilicon films, prepared by low pressure chemical vapor deposition, with scanning tunnel microscope (STM) under very dilute HF solution. Imaging under HF solution eliminates ambiguities in the STM topographs caused by the presence of oxide. The average grain sizes determined from STM topographs were consistent with transmission electron microscopy and scanning electron microscopy studies. The root mean square surface roughness measured from STM topographs was found to increase with the polysilicon film thickness while the sheet resistance was found to decrease with the film thickness. The surface topography of the film was found to have a fractal structure with a surface fractal dimension of 2.35.
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Carrejo et al. (1991) studied this question.