Fabrication of morphological defect-free vertical electrodes using a (1 1 0) silicon-on-patterned-insulator process for micromachined capacitive inclinometers

This paper presents a novel fabrication method of scalloping-free and footing-free vertical electrodes for micromachined capacitive inclinometers with a high sensing resolution. The proposed fabrication method is based on additional crystalline wet etching of a (1 1 0) silicon that is bonded to a silicon substrate with a patterned insulator layer. The sensing electrodes, which are aligned to the (1 1 1) plane, have very smooth sidewalls because the morphological defects formed by the silicon deep reactive ion etching (DRIE) process are drastically reduced in the crystalline wet etching. The fabricated capacitive inclinometer with smooth sensing electrodes was evaluated in terms of capacitance change and resolution. The capacitance of the fabricated inclinometer is changed from −0.246 to 0.258 pF for the inclination angle (−90° to 90°). The temporal deviation of the capacitance is as small as 0.2 fF, which leads to a high resolution of 0.1° or less for ±45°.