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We present secondaly ion mass spectrometry (SIMS) study results on interfaces of LiNbO3 based optoeleclronic devices, which have been performed in order to examine the cause of device failures. The devices are widely used in current high-speed optica1 fiber communication systems. and such investigation from a materials-viewpoint is' important to improve the device quality. Especially. the device long-term stability is strongly affected by alkali-contaminants diffused into the SiO2 buffer layer of device, and here we confirmed that an adoption of common Si3N4 passivation is effective in preventing the process-induced contamination without any influence to device performance.

The fabrication process of an Al thin-film optical polarizer on LiNbO 3 waveguides after CF 4 plasma dry etching of a previously deposited SiO 2 buffer layer was investigated. The problem in this process is a precipitation of compounds containing C, O, F, and Li on the etched LiNbO 3 surface and a chemical deterioration of the Al caused by a reaction with these precipitates. Most notably, the growth of amorphous phase in addition to the crystalline Al metal grains and a partial oxidization of Al were found at the interface using transmission electron microscopy and x-ray photoelectron spectroscopy.

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