Quartz has many remarkable characteristics such as piezoelectricity nature, high frequency, and thermal stability. It has been widely used as the main materials for oscillators, resonators, and surface acoustic wave filters. In recent years, quartz has been used in micro-sensors and MEMS applications, such as quartz SAW micro-sensors for biological analysis, and quartz microbalance for gas detection. To make quartz micro-sensors, it usually requires etching processes. Comparing dry and wet etching techniques of quartz, the cost of dry etching has more preferable profile control but is much more expensive than the wet etching. It is very attractive to make complex structures using wet etching. In this thesis, we develop wet etching technique to fabricate micro-pillars and micro-needles which have potential usages in increasing sensitivity of micro-sensors and surface modification.
To fabricate the structures, chromium and gold thin film is evaporated on the quartz substrate and patterned as etching masks. The sample is then etched in ammonium fluoride solution of saturated concentration at 55℃. Due to the anisotropic etching property, micro-pillars can be formed. The etched profiles are observed using SEM to establish etching rate in the X direction, Y direction, and the shape and angle of the base structure.
Using the experimental data, the etching criteria and equations can be established that provide ways for the predictions of the grows of high-density micro-pillars. The experimental etching profiles of micro-pillars consist with the prediction. This research is helpful for developing novel MEMS devices.