Reaction kinetics of silicon etching in HF-K2Cr2O7-H2O solution

Abstract

The reaction kinetics of silicon etching in HF-K2Cr2O7-H2O solution was studied experimentally. The etch rates were measured with varying HF and K2Cr2O7 concentrations, agitation speed reaction temperature and time. The etch rates of n- and p-Si (100) were both similar. The etchec surfaces consisted mainly of silicon and showed a relatively smooth and planar morphology. At suffi ciently high HF concentration, the etch rate was increased with increasing K2Cr2O7 concentratior 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 concentratior for etching reaction. The apparent activation energy was about 7.8 kcal/g-mole, and the rate equatior for the silicon etching reaction in HF-K2Cr2O7-H2O solution was obtained as-rSi = 600 exp(-3900/T) $$ - r_{Si} = 600{\text{ exp( - 3900/T) C}}_{{\text{K}}_{\text{2}} {\text{Cr}}_{\text{2}} {\text{O}}_{\text{7}} } ^{05} {\text{ C}}_{{\text{HF}}} ^3 $$ Chk3 at HF concentrations greater than 8 M.