| Plasma etch based CMOS MEMS technologies have the advantage of monolithic integration of sensors and conditioning electronics, which yields small size, low noise and low cost of the devices. In this thesis work, a new deep reactive-ion-etch (DRIE) based post-CMOS MEMS microfabrication technology was developed, and single-axis and 3-axis integrated accelerometers were fabricated using the new microfabrication technology. Compared to the previous CMOS-MEMS technological approaches, the new microfabrication technology features the capability of monolithic integration for high performance MEMS sensors. The integrated accelerometers demonstrate small size, high sensitivity and high resolution with low power consumption. They can be used in a large spectrum of applications including human activity monitoring, engineering measurement, security, and portable electronics.; Detailed post-CMOS microfabrication processes are presented. Reactive-ion-etch (RIE) and DRIE tools and processes are tuned to satisfy the technological requirements of the device fabrication. Some general design rules are extracted based on the systematic characterization of the etching tools. Special techniques were developed for aluminum wet etch and electrical isolation etch. The thermal issues in the device fabrication were identified and an alternate fabrication process was developed to avoid the device damage due to the overheat in the plasma processes. Wafer-level fabrication processes are also proposed.; Detailed design of 3-axis and single-axis accelerometers is presented. Device performance is predicted based on the calculations and finite-element analysis (FEA) using Coventor, a commercial FEA tool. The Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 mum technology is used for the CMOS fabrication.; With power consumption of 1 mW in each axis, the fabricated 3-axis accelerometer achieves sensitivities of 560 mV/g and 320 mV/g in the lateral and z axes, with noise floors of 12 mug/√Hz and 110 mug/√Hz, respectively. The single-axis accelerometer achieves a sensitivity of 90.1 mV/g with a noise floor of 60.7 mug/√Hz. The non-linearity in all lateral axes is less than 0.35%. |
