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 electro-chemical 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 the structures and show that the process is it suitable for use in MEMS sensor applications. Using this process a 30mbar full-scale differential pressure sensor has been demonstrated. The process allows for increased sensor performance, with reduced die size. Details of the pressure sensor design and characterization are presented, showing a device with 20mV/V full-scale output with linearity less than 0.4% (terminal base nonlinearity).