Etch rate dependence on crystal orientation of lithium niobate

This paper presents the etch rate of lithium niobate (LiNbO₃) as a function of crystal orientation. Etching is a fundamental technology needed for the fabrication of new sensors, actuators, and other new devices. In this study, LiNbO₃ spheres 30 mm in diameter were etched in hydrofluoric acid and a mixture of hydrofluoric and nitric acids at different temperatures and different times. The measured data of the etched sphere shape were processed and plotted, giving etch rate diagrams over the entire spheres. Based on the etch rate data obtained, the Wulff-Jaccodine method was used to predict the etched shape of 128°Y-cut and 155°Y-cut LiNbO₃. The predicted etching profiles were compared with those obtained by experiments. A least-square polynomial fit for the data was also developed and was found to be useful in removing some of the variation in the measurements.