The reaction kinetics of silicon etching in HF-K₂Cr₂O₇-H₂O solution was studied experimentally. The etch rates were measured with varying HF and K₂Cr₂O₇-H₂O concentrations, agitation speed, reaction temperature and time. The etch rates of n-and p-Si(100) were both similar. The etched surfaces consisted mainly of silicon and showed a relatively smooth and planar morphology. At sufficiently high HF concentration, the etch rate was increased with increasing K₂Cr₂O₇-H₂O concentration due to the increase of hole formation on the silicon surface. However, at low HF concentration, the etch rate maintains low value and increases very slowly because of insufficient hole concentration for etching reaction. The apparent activation energy was about 7.8kcal/g-mole, and the rate equation for the silicon etching reaction in HF-K₂Cr₂O₇-H₂O solution was obtained as
-r_Si = 600 exp(-3900/T) C_K2Cr2O7^0.5 C_HF³
at HF concentrations greater than 8M.