Towards wet anisotropic silicon etching of perfect pyramidal pits

Abstract

Wet anisotropic etching of sharp silicon cavities is a critical step in the fabrication of nanopores and scanning probe tips. This paper reports a straightforward method to reliably obtain sharp pyramidal cavities in (1 0 0) oriented silicon wafers from a relatively inaccurate mask fabricated with a conventional laser exposure system. The relative angular orientation of the mask patterns toward the crystallographic planes of silicon improves the sharpness of pyramidal etch pits. A trigonometric relation shows that the rotation of the mask squares up the etch patterns, which results in the sharpening of the pyramidal structures. This noticeable effect could be verified in (1 0 0)-silicon wafers etched in potassium hydroxide (KOH).