A Novel Fabrication for Pressure Sensor with Polymer Material and Its Characteristic Testing

In the current fabrication of pressure sensor, both the sensor cavity and the sensor diaphragm were made of SU-8 which can be readily spun coat on the substrate at desired thickness and patterned by lithography. The thickness of the diaphragm, and the height of the sensor cavities, allowing deformation of diaphragm, can be readily varied from few to hundreds of microns by spin coat different thickness of SU-8 layer. This allows fabrication of cavity with much greater heights and measurement of pressure with much wider range. However, the sensor material used for the pressure sensor is the polysilicon doped with a high concentration of boron, which can readily sense the deformation of a diaphragm. This has precluded the possibility of fabricating the cavities and diaphragm first - which is a low temperature process, and then depositing the polysilicon sensor on the above - which is a high temperature process. Fabrication strategy has to be reversed, i.e., starts with the high temperature process of depositing the doped polysilicon layer and then the low temperature process.