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-r_Si = 600 exp(-3900/T)

$$ - r_{Si} = 600{\text{ exp( - 3900/T) C}}_{{\text{K}}_{\text{2}} {\text{Cr}}_{\text{2}} {\text{O}}_{\text{7}} } ^{05} {\text{ C}}_{{\text{HF}}} ^3 $$

C_hk ³ at HF concentrations greater than 8 M.