PNNL

Abstract

Hydrogen bubbles trapped around lithographically formed etch pits on silicon single crystal surfaces were used to guide the formation of patterned regions of porous silicon. Optical lithography and wet (electro) chemical etching were utilized in a series of steps to form the etched surface and guide this growth. It was observed that the pits were surrounded by round regions of porous Si suggesting that hydrogen bubbles defined the areas of porous silicon formation. Consistent with earlier results where porosity seemed to form primarily at the bubble edges, a lower overall etch rate was observed near the bubble center. This is consistent with a variable rate of bubble expansion as etching occurred and an ability of the hydrogen to mask or slow the reaction in the bubble center. Contrary to our initial expectations, the surface profile suggested that the region away from the bubbles was also etched, but very uniformly.