EFFECTS OF [110]-ORIENTED CORNER COMPENSATION STRUCTURES ON MEMBRANE QUALITY AND CONVEX CORNER INTEGRITY IN (100)-SILICON USING AQUEOUS KOH

To preserve the shape of convex corners when etching in aqueous KOH, corner compensation structures have to be used. The etching of convex corners is due to the fact that some planes etch faster than others, resulting in a loss of the desired structure. By adding extra structures at these convex corners, these structures will be removed during etching resulting in the desired convex corners. The basic corner compensation structures reported in the literature are oriented along the [100] direction or the [110] direction. This paper shows a step-by-step analysis of the etching of these structures. The results show that the {411} planes are responsible for the undercutting, which implies that a perfect compensation of a convex corner using structures oriented along the [100] direction is not possible. Moreover, it is shown that each compensation structure leaves an imprint on the membrane, which cannot be removed by further etching, as the convex corner would otherwise be etched.