Seong-Hyok Kim

[110] silicon etching for high aspect ratio comb structures

The characteristics of [110] silicon anisotropic bulk etching for fabrication of comb structure are studied with varied temperature and concentration of aqueous KOH solution The etch rates of [110] and (111) planes increase with increasing temperature but decrease with increasing concentration. The maximum etch rate ratio is above 150 at 45 exact wt.% and 60/spl deg/C of aqueous KOH solution. Surface roughness varies greatly with concentration, and the minimum roughness is observed in an aqueous KOH solution of 41 exact wt.%. The mechanism of beam reduction is also studied and modelled simply. Considering the etching characteristics, comb structure have been fabricated which are 8 /spl mu/m wide, 150 /spl mu/m high and separated by 7 /spl mu/m gaps, using a comb mask pattern 10 /spl mu/m wide with 5 /spl mu/m gaps in 41 exact wt.% aqueous KOH solution at 65/spl deg/C.

A high-aspect-ratio comb actuator using UV-LIGA surface micromachining and (110) silicon bulk micromachining

A novel micromachining process based on the UV-LIGA process and (110) silicon anisotropic etching to fabricate a high-aspect-ratio comb actuator was developed. The comb electrodes were fabricated by (110) silicon anisotropic etching and the spring structures were fabricated using a UV-LIGA micromachining process. The (110) silicon comb structure was designed considering the etch-rate-ratio between the (110) and (111) planes and the lateral etch rate of a line-type structure. The fabricated structure was 400 μm thick and 18 μm wide comb electrodes separated by 7 μm and the height–gap ratio was approximately 57. In addition, the number, width, height and length of the spring structures were designed considering resonant frequency of the comb actuator and frequency-matching between the sensing and driving mode for gyroscope application. The electroplated gold springs on both sides of the seismic mass were 15 μm wide, 14 μm thick and 500 μm long. The fabricated comb actuator had a resonant frequency at 1430 Hz, which was calculated to be 1441 Hz. The proposed fabrication process can be applied to fabricating a high-aspect-ratio comb actuator for large displacement actuators and precision sensors. Moreover, this combined process enables the fabrication of a more complex structure, which cannot be fabricated by surface or bulk micromachining alone.

A Bulk-Micromachined Single Crystal Silicon Gyroscope Operating at Atmospheric Pressure

A novel bulk-micromachined gyroscope operating at atmospheric pressure is designed, fabricated and tested. It is fabricated by a simple single-mask process and has high-aspect ratio comb fingers for driving and sensing electrodes. It also has a large gap between the substrate and the structure for high Q value. Since the proposed gyroscope has a large driven displacement and a large mechanical sensitivity, it has good performances such as sensitivity of 116.8mV/° /s, the noise equivalent level of smaller than 0.05° and wide dynamic range of ±189° with non-linearity of smaller than 0.3% at atmospheric pressure.

A surface-bulk micromachined electromagnetic gyroscope operating at atmospheric pressure

This paper reports an electrostatically driven and electromagnetically sensed planar vibratory gyroscope. The fabrication process is based on a surface-bulk combined micromachining, and the fabricated gyroscope can be operated at atmospheric pressure with good output characteristics.

Modeling of the comb actuator deformed by microloading effect in deep reactive ion etching

The comb actuator deformed by microloading effect in DRIE process generally has í«Lí» shape comb electrodes. Therefore, the actuator shows nonlinear differential driving characteristics. A simple modeling is suggested and simulated to explain the driving characteristics. For modeling convenience, the damaged comb electrode is assumed to be a simple í«Lí» shape. According to the modeling, the resonant frequency is estimated to increase as the bias voltage increases. The static displacement curve shows í«Sí» shape.