Analysis of Etch Profiles on C-Plane Wafers in Wet Etching of Sapphire Based on Undercutting Rate Distributions in Mixture of H2SO4 and H3PO4 at 236 °C

Abstract

In this paper, the formation and evolution of etch profiles with different mask shapes and sizes on C-plane wafers of sapphire are analyzed based on undercutting rate distributions of characteristic planes. The effect of concentrations of etchants on etch profiles is further analyzed. Firstly, etch rate distributions under different experimental conditions (236 °C, H2SO4:H3PO4 = 3:1 and 6:1) are obtained by wet etching experiments of sapphire hemispheres. Undercutting rate distributions of characteristic planes on C-plane wafers under different experimental conditions are obtained by the maximum positive curvature (MPC) recognition method. Then, the effect of different mask shapes and sizes on the formation and evolution of etch profiles of complex cavities and islands on C-plane wafers are analyzed based on the undercutting rate distribution under the experimental condition (236 °C, H2SO4:H3PO4 = 3:1). Finally, characteristic differences of etch profiles on C-plane wafers at different concentrations are explained based on undercutting rate distributions of characteristic planes at the corresponding concentrations (236 °C, H2SO4:H3PO4 = 3:1 and 6:1). These provide a basis for the study of the anisotropic wet etching mechanism of sapphire.