Abstract: Etching LNOI (lithium niobate on insulator) usually uses amorphous silicon thin film as a mask. When depositing amorphous silicon thin films onto LNOI surfaces by PECVD equipment, blistering often occurs. Such small bubbles are mostly between 5 μm and 60 μm in size, and they can affect the morphology of LNOI etching. It was found that bubbles in amorphous silicon thin films may be caused by surface defects in lithium niobate thin films. The oxygen atoms on the surface of these defects combine with hydrogen in the amorphous silicon film, breaking the Si-H bond and causing an increase in local tensile stress in the film, resulting in foaming of the amorphous silicon film. Through comparative experiments, it was found that depositing a 50 nm silicon dioxide film to isolate defects on the surface of lithium niobate film before depositing amorphous silicon film can solve this process problem. This provides a reference for depositing flat amorphous silicon thin films on LNOI surfaces using PECVD equipment.

Key words: lithium niobate on insulator, PECVD, amorphous silicon thin film, stress, bubble