A Modernized Bosch Etching Process for the Formation of Tapered Structures on a Silicon Surface

Abstract A method to form tapered structures via the cyclic plasma-chemical etching of silicon using a spherical photoresist mask is described. The method is based on the possibility of controlling the structure profile by adjusting the silicon and photoresist etching selectivity. In this study, to control the selectivity value, each cycle of the well-known two-stage Bosch silicon etching process is supplemented with a third stage, namely, photoresist etching in oxygen-containing plasma. A model of transformation of the photoresist-mask contour during etching is developed using the experimental results. The parameters of the additional stage are calculated for each silicon etching cycle in terms of model concepts. The result is the formation of tapered structures with a sidewall taper angle close to the target value.