A high-performance planar piezoresistive accelerometer

The micromachined piezoresistive accelerometer is now 20 years old. Design variations have been investigated, but commercial devices have generally ma intained a consistent topology with incremental improvements. In this paper , a new approach is introduced to the design and construction of this devic e that offers functional and manufacturing advantages. Piezoresistive accel erometers are described that combine deep reactive ion etching and oblique ion implantation to form self-caging proof masses and flexures with vertica l sidewalls and sidewall piezoresistive strain sensors. These devices defle ct in-plane rather than out-of-plane, which allows one to form multiaxis ac celerometers on one substrate. Performance is comparable to inexpensive com mercial capacitive accelerometers and is limited by 1/f noise. The design, fabrication, and experimental characterization is presented. This new topol ogy provides the foundation for a new category of piezoresistive accelerome ters. [438].