| Friction, wear and stiction problems have been the important factors affecting the performance and reliability of microelectromechanical systems (MEMS). Surface modification of the microstructure materials has been an effective means of improving friction, reducing wear, restraining stiction and enhancing stability of the microsystems. To solve the surface modification problems of microstructure in MEMS, three subjects including the preparation and characterization of DLC films, the friction behavior of the films under the load condition in MEMS and their applications in solving the stiction problem of polysilicon cantilever beams, were mainly investigated in this dissertation.DLC films were prepared by three methods including unbalance magnetron sputtering (UMS), plasma source ion implantation (PSⅡ) and plasma enhanced chemical vapor deposition (PECVD), and the effects of preparation methods and process conditions on the structure and properties of the DLC films were investigated. The experimental results show that the optimum substrate bias is 50 V and the appropriate distance between the target and substrate is 150mm for UMS process, the optimum pulse voltage is 20kV and the appropriate high voltage pulse frequency is 100Hz for the PSⅡ process, and the optimum substrate bias is 100V for PECVD process. The infrared absorption spectrogram of DLC films prepared by PECVD shows there are a lot of H in the film. The hydrophobe experiments show DLC films by PECVD method have the highest contact angle (about 90°) and the lowest surface energy. Nano-hardness value of DLC films by PSII method is the highest, about 14.6 Gpa. According to the analysis of the structure and performance of DLC films, the growth mechanisms of the film were briefly discussed.The effects of preparation methods and tribology measurement conditions on the tribology performance of the DLC film were investigated by the microtribolotester and the atomic force microscope (AFM), respectively. The experimental results show that the prepared films have low friction coefficient and good wear resistance. When the experiment was carried out with the microtribolotester, the increase of load and sliding cycle number would promote the surface layer graphitization of the DLC film and formation of the graphitized transfer layers on the surface of the friction couples, which redounds to reduce the friction coefficient; When the experiment was carried out with AFM, the corresponding relationship between microfrictionforce and surface topography was found, but there is a little offset between the peak positions. Microwear experiments show there is the non-linear relationship between the wear depth and wear cycle numbers, and the wear resistance performance of the surface layer of DLC films is not as good as the interior. Comparison of the results attained by two methods shows the increase of friction couples' sliding velocity redounds to reduce the friction coefficient when the load is at the mN level, but the sliding velocity hardly affects the friction coefficient when the load is at the nN level.The factors influencing the stiction in MEMS were investigated in detail, and the effect of DLC films for solving the stiction was evaluated by solving the stiction of the polysilicon cantilever beam. The stiction model of the polysilicon cantilever beam was deeply discussed, and the adhesion energy per unit area between the polysilicon cantilever beam and the substrate was analyzed. The results show, when the DLC film presents, the average critical length of the polysilicon cantilever beams that don't adhere to the substrate distinctly increases, the capillary force and the adhesion force between the cantilever and substrate are reduced with the application of DLC films; and the stiction of polysilicon cantilever beams is effectively restrained.These results are expected to be good references to the application of the DLC films for the surface modification of the microstructure materials in MEMS.
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