New shapes in (100) Si using KOH and EDP etches

Abstract

Wet chemical etching in EDP, pure KOH and KOH with isopropyl alcohol (KOH/IPA) are known to etch different crystal planes with different etch rates. It is shown in this work that etching in EDP or KOH/IPA reverses the etch-rate ratios of (100) and (110) planes, as compared to etching in pure KOH. This can be used to reveal other relatively slow etching planes, other than (111), to be used in new structures. V-grooves, retro-reflector ridges and mesa structures were fabricated bounded by (110) planes with 45 degrees angles to the (100) surface. Also, by using a corner-compensated mask aligned in the (100) direction and etched in pure aqueous KOH, free-standing cubic studs bounded by (100) planes were fabricated.