Fabrication of Non‐Underetched Convex Corners in Anisotropic Etching of (100)‐Silicon in Aqueous  KOH  with Respect to Novel Micromechanic Elements

Abstract

The planes occurring at convex corners during anisotropic etching of (100)-silicon in aqueousKOH were identified as {411}-planes, with the help of a specially developed measuring technique. The etching rate of these planes in relation to the rate of the {100}-planes declines with increasing potassium hydroxide concentration. In contrast, the temperature dependence of this etch rate ratio is negligible in the relevant range between 60~ and 100~ Based on these results, special structures suited for the compensation of the undercutting in the case of very narrow contours were developed. With the help of these structures it is feasible to realize, for instance, bent V-grooves or structures with a very low ratio between lateral expansion and etching depth, e.g., a discrete pyramid-trunk with minimum dimensions on the wafer surface. This offers access to completely new applications, among others spiral channels with double-sided anisotropic etching for micro-

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

“…proof mass for accelerometer, mesa structures, chip isolation grooves, bent V-grooves, etc. as shown in Figure 10 [1,2, 39,57,70,92,95,118,120]. Thus, the undercutting is unwanted for the fabrication of these types of microstructures and it is highly anticipated to eliminate this problem by some means.…”

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

“…proof mass for accelerometer, mesa structures, chip isolation grooves, bent V-grooves, etc. as shown in Figure 10 [1,2,39,57,70,92,95,118,120]. Thus, the undercutting is unwanted for the fabrication of these types of microstructures and it is highly anticipated to eliminate this problem by some means.…”

“…In general, these facets in the case of {100} surface are typically {311}, {211}, {331}, {411}, {212}, {772}, etc. are {311}, {772} and {411}, respectively [83,84,92]. Hence, there is some disagreement in the literature about the exact orientation of planes that emerge at the convex corners during etching process.…”

“…triangle, square, <110> −beam) provides sharp edge convex corner. In continuation of the efforts to fabricate sharp convex corner, a simple <100> oriented beam is proposed as presented in Figure 30 [92,100,103,105,108,109,120,122,125].…”

“…Various designs have been reported to fabricate the bent V-grooves. Mayer et al proposed a design in which <100> oriented beam is fanned out into narrow <110> strips at both sides and its free end is connected to the external mask (or frame) by a narrow beam just to eliminate the convex corners as presented in Figure 37 [92]. In this case, the etching of compensation structure starts only from the convex corners at the free end of the <110> narrow beams.…”