A miniaturized bulk micromachined triaxial accelerometer fabricated using deep reactive etching through a multilevel thickness membrane

We present the design, fabrication and characterization of an application specific triaxial accelerometer for post-surgery heart monitoring. The accelerometer chip is designed as a 2?×?4?×?1.2?mm³ chip with nominal acceleration range of?±4?g and frequencies below 50?Hz. It has been fabricated using a multiproject wafer service with an additional deep reactive ion etching process to obtain controlled etch-through of membranes of 3, 23 and 400?μm thicknesses simultaneously. The novelty of the work presented here is the bulk micromachining technique using both deep reactive dry etching and alkali-based anisotropic wet etching of single crystal (100) silicon wafers used to obtain a space efficient design. Proof of concept is demonstrated with preliminary testing, with an acceleration sensitivity of?~0.04 mv/V/g for out of plane (z axis) acceleration.