Pressure sensors on silicon-on-insulator wafers

The goal of this project is to develop a vibration sensor for monitoring aircraft vibration in order to flag early structural failures. To precisely evaluate vibration, a pressure sensor is needed because the resonant frequency of a vibration sensor is related to the air pressure affecting it. This dissertation research is focused on determining a technique for improving the quality of pressure sensors. We also investigate their use in biomedical applications.; There are many types of pressure sensors. The piezoresistive type of pressure sensor is the easiest one to integrate with other processes and is also cost efficient. In the past, primarily wet etch has been used to fabricate this type of sensor. However, this technique produces a large back opening even when fabricating only a single device. A new technique using dry etch on silicon-on-insulator wafers is being proposed as a better technique which can reduce the size of back openings and the thickness of the diaphragm. The new technique can heighten device sensitivity and increase the number of pressure sensors that can be fabricated on a small area. This allows the collection of multiple readings from an array of pressure sensors, which will enhance the accuracy and stability of vibration assessments.; We successfully fabricated pressure sensors on bulk silicon wafers when this thesis was written. They were tested both in vacuum chamber for a negative pressure test and on a force station for a positive pressure test. The results show a good linearity over a testing pressure range of 0 to 25 in Hg with respect to 1 atm, which meets the requirements of aircraft structural-health monitoring systems. In future, perhaps the project can be developed further.