Which etchant used and whether an etching mask exists: how they make differences on convex-corner undercutting configuration and compensation criteria

摘要

Anisotropic etching of silicon creates different convex-comer undercutting contours in different varieties of etchant. This difference in undercutting configuration is investigated by analyses of the undercutting formation in detail. Based on Wulff-Jaccodine rules and some experimental results, theoretical analyses are given to clarify the reasons of different undercutting configuration caused by different etchant and the rationality of a certain plane occupying the undercutting position for a certain etchant. Furthermore, the investigation is lead to the convex-comer undercutting under maskless etching, i.e. during the etching mask on the structure removed. Experimental results show that the convex-comer undercutting under maskless etching is far different from that of conventional masked etching. The geometrical evolution of the undercutting is studied both experimentally and analytically. The compensation criteria for maskless etching are discovered and the corresponding compensation schemes are provided.