Fabrication Challenges for Realization of Wet Etching Based Comb Type Capacitive Microaccelerometer Structure

Abstract

The current paper presents fabrication of wet etching based comb-type microaccelerometer structure consisting of 47 interdigitated fingers attached to a large proof mass, which is suspended by two narrow torsional beams. Silicon (, p-type) was oxidized and the microaccelerometer structure was patterned by photolithography. Desired device thickness was achieved by combination of wet anisotropic etching of 15μm depth and formation of 12 μm thick p++ etch stop layer. Pits of 15 μm were formed in Pyrex glass and metallic lines with bonding pads were formed by UHV Ti-Au metallization and pattern plating (Au). Patterned glass and silicon wafers were aligned and anodically bonded; whereas, the metallic lines and the microaccelerometer anchors are eutectically bonded. Finally, the suspended comb-type device structure consisting of two torsional beams of 5μm width and interdigitated comb fingers of 10μm width is achieved by Dissolve Wafer Process (DWP). The paper highlights the fabrication challenges faced during the realization of the comb-type structure.

Keywords

• Comb-type accelerometer
• Capacitive sensing
• Wet etching
• Dissolve Wafer Process (DWP)