Anisotropic etching of {100} and {110} planes in (100) silicon

Anisotropic etching of (100) silicon using KOH with 45° alignment to the primary ⟨110⟩ wafer flat was investigated. It was shown that in KOH solution with isopropyl alcohol added, high KOH concentration and temperature caused the selection of {100} instead of {110} walls, allowing reliable fabrication of {100} walls with improved surface smoothness due to the isopropyl alcohol. TMAOH solutions with methanol and isopropyl alcohol were also found to produce both types of wall, with excellent surface smoothness for the {110} walls. A new maskless etching technique was developed for corner compensation of structures bounded by {110} walls.