Control of Mask Erosion and Correction of Structure Profile in an Adapted Process of Deep Reactive Ion Etching of Silicon

The paper presents a new approach to optimizing the cyclic procedure of deep reactive ion etching (DRIE) of silicon. The etching parameters were adjusted based on direct measurements of the rates of deposition and etching processes in a cycle on the surface of oxidized silicon using a laser interferometer. A high-quality etching profile with minimal erosion of the SiO₂ mask (maximum process selectivity) was achieved by adapting the three-stage DRIE process according to the measured duration of polymer removal at the bottom of the grooves in silicon. It has been shown that the profile shape can be corrected by changing the DRIE parameters during the etching process. As a result of optimization, a recipe was obtained for etching grooves 30 µm wide to a depth of 350 µm with a wall angle of 0.36° at a process rate and selectivity of 3.4 µm/min and ~400, respectively. The adapted recipe was successfully applied in the manufacturing technology of the sensitive element of a micromechanical gyroscope.