A hollow stiffening structure for low-pressure sensors

This paper presents a novel process for producing thin-walled hollow stiffening structures on thin silicon diaphragms using an electrochemical etch-stop process. Examples of structures produced using the method are presented together with focused ion beam (FIB) analysis of critical areas within the structure. These demonstrate the integrity of the structures and show that the process is suitable for use in MEMS sensor applications. Using this process a 30 mbar full-scale differential pressure sensor has been demonstrated, and used to verify the suitability of these hollow structures for use in MEMS sensors. The novel process allows for increased sensor performance, with reduced die size. Details of the pressure sensor design and characterization are presented, showing a device with 18 mV/V full-scale output with linearity <0.4% (terminal base non-linearity).