AVS 46th International Symposium
    Thin Films Division Monday Sessions
       Session TF+VM-MoA

Paper TF+VM-MoA8
Surface Acoustic Wave Propagation Properties of Nitrogenated Diamond-like Carbon Films

Monday, October 25, 1999, 4:20 pm, Room 620

Session: Advances in Hard and Superhard Coatings II
Presenter: J.Y. Kim, Seoul National University, Korea
Authors: J.Y. Kim, Seoul National University, Korea
H.J. Chung, Seoul National University, Korea
H.J. Kim, Seoul National University, Korea
H.M. Cho, Korea Electronics Technology Institute
H.K. Yang, Korea Electronics Technology Institute
J.C. Park, Korea Electronics Technology Institute
Correspondent: Click to Email
Surface acoustic wave (SAW) devices have become more important as mobile telecommunication systems need high-frequency, low-loss, and down-sized components. Higher-frequency SAW devices can be more easily realized by developing new high-SAW-velocity materials. The ZnO/diamond/Si multilayer structure is one of the most promising material components for GHz-band SAW filters because of its high SAW velocity above 10,000 m/sec. Recently, DLC films are also considered to have a potential for this application, since their physical properties, such as hardness and elastic modulus, are comparable with those of diamond. However, the residual stress during deposition is an obstacle to this application, because the film having high residual stress could not sustain during the full fabrication process of SAW devices. Recently, there have been many reports of the nitrogenated DLC films, which is mainly driven by the possibility of realizing the superhard @beta@-C@sub3@N@sub4@ phase. Some researchers reported the residual stress reduction by nitrogen incorporation without any other significant change in film mechanical properties. In this study, nitrogenated (a-C:N) films were deposited by reactive sputtering method. The a-C:N film properties were investigated using Raman spectroscopy, FT-IR, AES, and x-ray reflectivity (GIXR). To investigate the SAW propagation characteristics of the a-C:N films, SAW filters were fabricated using interdigital transducer electrodes between the ZnO layer and a-C:N/Si(100), which were used to excite surface acoustic waves. SAW velocities were calculated from the frequency-response measurements of SAW filters. A generalized SAW mode with velocities between 5,000 m/s and 7,000 m/s were observed as well as a high velocity Pseudo-SAW mode with 14,000 m/s. We also calculated the film elastic constants from SAW propagation velocities in the layered structure.