Piezoresistive characteristic of microcantilever-based biosensor according to doping level of polysilicon resistor

We investigate about the resolution limit for a surface stress sensitive cantilever that microcantilever-based biosensor with piezoresistor has been fabricated using surface micromachining technique. It is an advantage to obtain as high a gauge factor as possible in order to maximize the sensitivity. This piezoresistive characteristic depends on the doping level and the grain size in the material. From this characterization, the best material composition can be found and then used for further optimization. The LPCVD polysilicon is used for piezoresistor and its thickness is 300nm. The polysilicon were implanted with boron of various and adjustable dose concentration and are encapsulated in LPCVD silicon nitride. We evaluate the characteristics of piezoresistive that doping level with boron. The gauge factor decreases by up to 40{\%} when the doping is increased. The results presented that the optimized piezoresistive readout has much better sensitivity than optical readout.