Novel fabrication of a pressure sensor with polymer material and evaluation of its performance

Fabrication of a micro, essentially polymer pressure sensor is presented. Both the sensor cavity and the sensor diaphragm were made of SU-8 which can be readily spun coated on the substrate at the desired thickness and patterned by lithography. The thickness of the diaphragm and the height of the sensor cavities, allowing deformation of the diaphragm, can be readily varied from a few to hundreds of microns by spin coating different thickness of the SU-8 layer. This allows fabrication of a cavity with much greater height and measurement of pressure with a much wider range. However, the sensor material, which can readily sense deformation of the diaphragm, is a piezoresistive film. This has precluded the possibility of fabricating the cavity and diaphragm first, which is a low temperature process, and then depositing the piezoresistive sensor on the above, which is a high temperature process. The fabrication strategy has to be reversed, i.e., starts with the high temperature process of depositing the sensor layer and then the low temperature process. The fabrication process is simple. The fabricated sensor has been evaluated and has a higher sensitivity than that of the polysilicon sensor, has rapid response, and is thermally stable. The sensor is reliable and can be widely applied or integrated in the microfluidic system or biochip where pressure information is required.