| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS1-WeA |
| Session: | Plasma Surface Interactions (Fundamentals & Applications) II |
| Presenter: | C.H. Huang, Tohoku University, Japan |
| Authors: | C.H. Huang, Tohoku University, Japan M. Tomura, Tohoku University, Japan Y. Yoshida, Tohoku University, Japan T. Ono, Tohoku University, Japan S. Yamasaki, National Institute of Advanced Industrial Science and Technology (AIST), Japan S. Samukawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
Miniaturization of microcantilever realized increasing resonant frequency and achieving high resolution in image sensing devices such as scanning probe microscopy. Thin film deposition and etching are widely used in micro fabrication process. Therefore, it is indispensible to use plasma process. However, the plasma process usually generates defects in the micro structure due to the high-energy ion bombardment, charge build-up and UV photon radiation from the plasma, which might degrade the mechanical characteristics of the micro elements, such as microcantilever, and result in MEMS malfunction.
In this study, a Si microcantilever was adopted to investigate the influence of plasma irradiation to mechanical characteristic. The Si microcantilever was fabricated with silicon on insulator wafer. After the fabrication, the microcantilevers were irradiated by inductively coupled plasma and neutral beam (NB) with argon gas at room temperature. The influences of the plasma and NB irradiations on Si microcantilevers were evaluated with Q factor and resonant frequency (f) using laser Doppler vibrometer before and after irradiation. After plasma irradiation, Q factor ratio [Q factor after irradiation/Q factor before irradiation] and f ratio [f factor after irradiation/f factor before irradiation] drastically decreased. The Q factor ratio didn’t depend on the irradiation time and the f ratio decreased as the plasma irradiation time increased. On the other hand, the Q factor ratio and f ratio only slightly decreased after Ar NB irradiation, which indicates that NB process have great potential for MEMS application. To understand the degradation mechanism of Si microcantilever, defect (E’ center) density on microcantilever surface was measured by electron spin resonance. The defect density increased when plasma irradiation time increased. The Young’s modulus (E) of microcantilever calculated from f suddenly decreased and became plateau when E’ center was over a threshold defect density. The Q ratio decreased when the microcantilever thickness decreased. It is because the ratio of defect depth to microcantilever thickness being higher. Given these results, plasma irradiation degrades the E resulting in the variation of the f. D egradation of Q factor is determined by the ratio of defect depth to microcantilever thickness.