Maskless lithography: an approach to SU-8 based sensitive and high-g Z-axis polymer MEMS accelerometer

In this work, Z-axis MEMS accelerometers are investigated with variation in spring topography. The serpentine spring structure demonstrated the optimum sensitivity of MEMS accelerometers due to a large number of beams that reduce the spring constant considerably. The augmented serpentine spring MEMS accelerometers are simulated for SU-8, PolySi, Si3N4, and SiC-based primary structural materials. SU-8 based MEMS accelerometer shows high sensitivity and cost-effective fabrication process suitable for industry. The reliability of the microaccelerometers is investigated by the stress analysis. The computation result of designed accelerometers exhibited a linear response up to +/- 50 g of the input value of acceleration. For the integration with Si-technology, SU-8 microaccelerometer with serpentine spring structure is fabricated using facile maskless lithography based grayscale process technology. The sensitivity is measured by capacitance variation with Z-axis free falls. The frequency response and spring constant of fabricated SU-8 based Z-axis MEMS accelerometer is investigated by Laser Doppler Vibrometer and nanoindentation technique, respectively. The demonstrated SU-8 serpentine spring, highly sensitive, facile and low-cost process technology-based Z-axis accelerometer is suitable for navigation, space, and medical applications.