Innovative Design of a Compensation Structure for Anisotropic Etching of Adjacent Convex Corners

Abstract

While deeply etching silicon to form various microstructures with bosses or crossing splitting grooves with a V-shaped or trapezoidal cross section, the etching solution will undercut convex corners. The major problem associated with compensation structure design is the large spatial requirement around the convex corners. This paper proposes a compensation pattern to compensate the undercutting of adjacent convex corners of crossing splitting grooves. Four square masks are set at the convex corners of each chip. The twelve convex corners of four square masks are connected by six <110> oriented clamped-clamped beams. In the first stage of etching, the etching solution undercuts <110> oriented clamped-clamped beams from both sides instead of from both ends. The lateral undercutting rate of the narrow clamped-clamped beams is only 9.6% of the etching rate of the (100) plane in 80°C 25% TMAH solution. This greatly reducing the size of compensation pattern between four adjacent convex corners. Square masks are used to protect the convex corners of each chip from being etched during maskless etching the silicon wedges under clamped-clamped beams. This convex corner compensation pattern reduces the width of splitting grooves and improves the yield.