Sidewall Surface Roughness of Sputtered Silicon II: Model Verification

Abstract

Experiments were carried out to verify sidewall surface roughness models for sputtered silicon. The beam shape was determined by measuring the topograph of craters sputtered by focused ion beam (FIB) on single crystal (100) silicon and then the appropriate beam radius was selected to form a steady state sidewall surface profile. The surface profile was the unsputtered material attached to the sidewall and therefore, the material function did not affect the sidewall surface profile. Sidewall microsurface was generated by FIB sputtering of a single crystal (100) silicon wafer. The surface roughness at the sidewall of the sputtered features was then measured by using atomic force microscopy (AFM). Theoretical surface roughness was calculated for different combinations of beam radius and pixel spacing. These calculated surface roughness values were found to be within ±1 and ±2 nm of the measured surface roughness values with a measurement uncertainty of about ±0.5 and ±1.0 nm for R_a and R_t respectively.