Feasibility study of RF sputtered ZnO film for surface micromachining

In the present studies, we have investigated the feasibility of using RF sputtered zinc oxide (ZnO) films as sacrificial layer in surface micromachining process. For this application, it is required that there should be a gradual slope in the ZnO platform after etching. This gives better step coverage during structural material deposition and patterning. ZnO is a very sensitive material and is susceptible to degradation by acids, bases and even water. These films may easily be damaged or degraded in the micromachining process for fabricating microstructures. In this work, we focus on techniques to (i) deposit ZnO films with good characteristics for use in microelectromechanical systems (MEMS) technology and (ii) protect these films against degradation in subsequent processing steps. The films were prepared on Si substrate using RF diode sputtering in argon atmosphere. Characterization of these films includes X-ray diffraction, IR and optical transmission spectra measurements, electron microscopy, ellipsometry and etching behavior.