| Plasma enhanced chemical vapor deposited (PECVD) silicon oxide (SiO x) is the most commonly used interlayer dielectric (ILD) in MEMS devices and structures. In this thesis, PECVD SiOx is chosen as an example for the systematic study of mechanical behavior and underlying causal mechanisms of amorphous thin films for MEMS applications, which are generally less well understood because of the complex interplay among the deformation mechanisms.; Mechanical behaviors of the PECVD SiOx thin films are probed at (1) different size scales (from wafer level down to micro/nano-scale, and different length-scale within each realm); (2) different temperatures (from room temperature up to 1100°C); and (3) with a combination of different experimental techniques (such as substrate curvature measurements, nanoindentation tests, and a novel "microbridge testing" technique, etc.). A broad range of mechanical analysis is covered, including film stress and related material properties changes, elastic properties, plastic properties (both time-independent and time-dependent), deformation mechanisms (both at room temperature and elevated temperatures). Wherever applicable, materials analysis techniques such as SEM, AFM, FTIR, XRD, and SIMS were employed to strengthen the discussions on the structure-properties relationship and the causal mechanisms of the mechanical responses of the PECVD SiOx. These experiments reveal various interesting and distinctive characteristics of the mechanical responses of the PECVD SiOx thin films, and the microstructural causal mechanisms for each of them are analyzed in depth.; The outcome of this thesis will provide a comprehensive characterization of the mechanical responses of the PECVD SiOx thin films under different thermal conditions, stress levels, size scales, and in both elastic and plastic regions. In addition, both new experimental methodologies and theoretical models for data analysis are resulted, which can be readily applied to a wide variety of thin film materials for various different applications. Last but not least, the physical causal mechanisms for the experimental results are elucidated, which is a significant contribution to the scientific understanding of this type of amorphous thin film materials. These theoretical interpretations will also provide valuable insights to the understanding of similar responses of many other similar amorphous thin film materials for MEMS applications. |
