REACTION-KINETICS OF SILICON ETCHING IN HF-K2CR2O7-H2O SOLUTION

The reaction kinetics of silicon etching in HF-K2Cr2O7-H2O solution wa s 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 etch ed surfaces consisted mainly of silicon and showed a relatively smooth and planar morphology. At sufficiently high HF concentration, the etc h rate was increased with increasing K2Cr2O7 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 sl owly because of insufficient hole concentration for etching reaction. The apparent activation energy was about 7.8 kcal/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(HF)3 at HF con centrations greater than 8 M.