The wet-etching behaviors of the SiO₂ layer in LiNbO₃-on-insulator structure

The wet -etching behaviors of the SiO(2 )layer in LiNbO3-on-insulator structure were studied by the concentration of 3.6 % HF acid at different times. Drill etching occurs on the upper surface of the SiO2 layer at a rate of 0.4278 gm/min. The transverse etching rate of the SiO2 layer is 0.3321 gm/min, which is slightly less than the drill etching rate. So a triangular etched region is formed in the HF etched SiO2 layer at an angle of about 30. Moreover, the etching morphology and rate are the same on both sides of the strip. We also studied the etching rate of micro - and nano -structures with HF acid is about 0.22 gm/min. We numerically calculated the comparison of mode sizes between partially removed SiO2 layer and non removed SiO2 layer strip waveguides.