Improvement of Piezoresistive Microcantilever Beams for Gas Detection and Sensing

Past work associated with this project has focused on both symmetric and asymmetric base arrangement piezoresistive microcantilever beams used for gas detection. Symmetric piezoresistive microcantilever beams have been shown to detect the presence of surrounding gas through changes in the resonance behavior of the beam; however, the device sensitivity was relatively low, leading to challenges due to noise and clear identification of resonance changes. An asymmetric base arrangement has been shown to improve the sensitivity of the device dramatically by changing the nature of the stress state in the piezoresistive base. The current work is focused on both improved fabrication methods for the asymmetric piezoresistive microcantilever beams and their resonance behavior in vacuum. The new fabrication method employs new equipment and photoresistors to speed the process. Furthermore, the critical step in beam writing is upgraded to whole wafer writing rather than each individual diced component. This eliminates at least two time-consuming steps and has shown promising results. The new process is being applied to several different types of SOI wafers to assess the importance of resistivity and device/insulation layer thickness on device outcomes. Future studies using these new devices will focus on detection and sensing with gases with suitable modeling and validation to demonstrate their efficacy for general use.