Effect of magnesium in KOH solution on anisotropic wet etching of silicon

Etching characteristics of Si in KOH solution containing Mg are investigated. Etch rate of silicon slightly decreases by the Mg on the order of 10 ppm in 32 wt.% KOH, while the etched surface roughness does not change in contrast to Cu as an impurity. The surface roughening caused by the ppb-level of Cu in KOH solution can be fully recovered by adding Mg on the order of 10 ppm in the solution.