Plasma etching of proton-exchanged lithium niobate

Plasma etching of lithium niobate with fluorine gases is limited by the redeposition LiF. This results in a low etch rate and nonvertically etched walls. Etching of proton-exchanged lithium niobate can prevent the LiF deposition to a large extent because of the greatly reduced lithium concentration in lithium niobate. We performed different inductively coupled plasma etching processes using SF6 or CHF3∕Ar on proton-exchanged lithium niobate. Negligible underetching and nearly vertically etched walls on proton-exchanged lithium niobate samples were obtained by CHF3∕Ar gas at chamber pressure of 6mTorr and 130V dc bias.