Abstract

Atomic Force Microscopy (AFM) probes with embedded stress sensors have demonstrated the ability to address key issues such as simplicity, reliability, and responsiveness to parallel scanning techniques and therefore are promising devices for AFM applications. Even though there are some other candidates for integration as sensor parts with the mechanical structure of the device (e.g. MOS transistors), piezoresistive materials are still among the most attractive sensors used in cantilever-based devices. Standard CMOS fabrication process is a suitable technology, which allows integration of sensor, mechanical parts and electronic signal conditioning/processing circuits on the same chip. In this thesis we present design and optimization of an AFM probe with integrated polysilicon piezoresistive sensor, based on MEMS techniques. Design goal is to optimize a combination of sensitivity and signal-to-noise (S/N) ratio to achieve the minimum lower detection limit, while maintaining the other important factors such as eigenfrequencies, in an acceptable range. Standard CMOS 0.35om technology is considered as the target fabrication process as well as a multistage masked post-CMOS micro-machining process to release the structure. A sophisticated geometry of the cantilever and the sensor, along with the optimized length of sensor branches in terms of S/N ratio is achieved.