AES and SIMS investigation of diffusion barriers for copper metallization in power-SAW devices
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Barrier layers for Cu-metallization in surface acoustic wave (SAW) devices were investigated by AES and SIMS depth profiles. Two layered systems on LiNbO3 substrate have been analyzed after annealing in air up to 400 °C. The investigated systems were (A) Ta(20 nm)/Cu(150 nm)/Ti(30 nm), deposited by electron beam evaporation, and (B) Ta30Si18N52(50 nm)/Cu(150 nm)/Ta30Si18N52(50 nm) deposited by magnetron sputtering. In system A the Ta layer shows oxidation in air for T≥300 °C. Ti from the buffer layer diffuses into the Cu at about 100 °C, and segregates at the Ta/Cu interface for T≥200 °C. Oxidation of the Ti layer starts at 300 °C. But no remarkable amounts of oxygen could be found in the Cu film. The depth profiles show that the TaSiN layer in system B operates as a more effective barrier for the Cu-SAW technology up to more than 300 °C.
KeywordsCu metallization Diffusion barrier Depth profiling AES SIMS
The authors thank R. Hübner for providing the Cu/TaSiN samples and U. Merkel from the Semiconductor and Microsystems Technology Laboratory of the Dresden University of Technology for support in thin film deposition.
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