RESUMO
A novel technology for the precise fabrication of quartz resonators for MEMS applications is introduced. This approach is based on the laser-induced chemical etching of quartz. The main processing steps include femtosecond UV laser treatment of a Cr-Au-coated Z-cut alpha quartz wafer, followed by wet etching. The laser-patterned Cr-Au coating serves as an etch mask and is used to form electrodes for piezoelectric actuation. This fabrication approach does not alter the quartz's crystalline structure or its piezo-electric properties. The formation of defects, which is common in laser micromachined quartz, is prevented by optimized process parameters and by controlling the temporal behavior of the laser-matter interactions. The process does not involve any lithography and allows for high geometric design flexibility. Several configurations of piezoelectrically actuated beam-type resonators were fabricated using relatively mild wet etching conditions, and their functionality was experimentally demonstrated. The devices are distinguished from prior efforts by the reduced surface roughness and improved wall profiles of the fabricated quartz structures.
RESUMO
A 170µW readout IC for a capacitive MEMS acceleration sensor was implemented in a 1.5V 0.13µm CMOS for high-end medical motion sensing applications. The accelerometer achieves a 45µg/vHz noise floor and a dynamic range larger than 87dB for a 400Hz bandwidth. Power reduction is achieved by introducing reset and common-mode feedback circuit techniques based on a non-unity-gain feedback configuration.
