| This paper presents a process technology to form thin diaphragms with sealed cavities in a lithium niobate (LiNbO3) wafer, which will be used for small and sensitive SAW based pressure sensors. The process technology uses thermal inversion, wet etching with an electroplated Au mask, etch stop at the thermal inversion layer and Au-Au bonding. By the combination of an etch stop and pinhole-free masking, LiNbO3 thin diaphragms with thicknesses of several tens of μm to 10 μm were fabricated in 128° Y cut LiNbO3 wafers. The Au-Au bonding of the LiNbO3 wafer gave hermetic sealing. In addition the etch profiles of the LiNbO3 wafer predicted by Wulff-Jaccodine plots and observed in experiments were compared, and good agreement was confirmed. |