Planar Microstructures in Surface Micromachining Process Using RF Sputtered ZnO as Sacrificial Layer

In this work, we report fabrication of completely planar microstructures for MEMS using RF sputtered ZnO as a new sacrificial material in surface micromachining process. The microstructures fabricated by conventional surface micromachined process have two bends at the anchor point. These have been eliminated using a new modified process, which results in completely planar microstructures. For this purpose, trench formation and chemical mechanical planarization (CMP) techniques have been integrated with surface micromachining process. Issues related with the selection of the appropriate sacrificial/structural layer materials, the deposition process and the sacrificial layer etching are addressed. The deposition of sacrificial layer was carried out on 2-inch silicon wafers in a RF (13.56 MHz) sputtering system using a 4-inch ZnO target. The silicon dioxide, used as structural layer material, was also deposited in the same sputtering system at 5 mTorr pressure and 300 watt RF power. A two-mask process is used for fabricating planar microstructures in surface micromachining technique.