Maskless convex corner compensation technique on a (1 0 0) silicon substrate in a 25 wt% TMAH water solution

A maskless convex corner compensation technique in a 25 wt% TMAH water solution at the temperature of 80 °C is presented and analyzed. The maskless convex corner compensation technique is defined as a combination of masked and maskless anisotropic etching with convex corner compensation in the form of a 〈1 0 0〉 oriented beam. This technique enables the fabrication of three-level micromachined silicon structures with compensated convex corner at the bottom of the etched structure. All the planes that appear during the etching of (1 0 0) silicon in the 25 wt% TMAH water solution at the temperature of 80 °C are determined. Analytical relations have been found to explain the etching of all exposed planes and to calculate their etch rates. Analytical relations are determined and empirically verified in order to obtain regular shapes of the three-level silicon mesa structures. A boss for a low-pressure piezoresistive sensor has been fabricated as an example of the maskless convex corner compensation technique. (paper)