Monolithic multiple axis accelerometer design in standard CMOS

Using a single maskless postprocessing step we have developed an accelerometer in a standard commercial CMOS process capable of a sensitive axis parallel or perpendicular to the die surface. Our postprocess is realized using xenon difluoride (XeF2) as a bulk etchant. The combination of this etchant and the standard CMOS process allows realization of cantilevers with piezoresistive sensors in all spacial coordinates from a widely-accessible source and at a minimal cost. Fabrication of accelerometers for all three axes and associated electronics on a single piece of silicon reduces the cost of three-dimensional acceleration detection while increasing sensor reliability.