Fast wet anisotropic etching of Si{100} and {110} with a smooth surface in ultra-high temperature KOH solutions

We report the etching characteristics of Si {100} and {110} at ultra-high temperature ranges near the boiling point of KOH solutions. The etching rates of Si {100} and {110} at near the boiling point were 5-9 times and 4-20 times higher than those at 80 deg C in the KOH concentrations of more than 32 wt%, respectively. At 145 deg C in 50 wt% KOH, we can get a Si{100} smooth surface with a high etching rate of 9.7 /spl mu/m/min and at 135 deg C in 45-47 wt%KOH, we can get a Si{110} smooth surface with a ultra-high etching rate of 20 /spl mu/m/min. Arrhenius plots of the etching rates were nearly linear from 80 deg C to near the boiling point. It is considered that the activation process in the higher temperature is the same as that in the lower temperature.