N-well based CMOS calorimetric chemical sensors

New micromachined calorimetric chemical sensors based on an n-well island structure have been designed, fabricated in industrial CMOS technology, and tested. The suspended island structure is covered with a polymer and changes its temperature upon absorption or desorption of analyte. The temperature change is recorded by integrated polysilicon/aluminum thermopiles. A polysilicon or metal heating resistor covers the n-well structure which allows a more accurate calibration compared to our previous design . The system provides a physical sensitivity of 34 and 26.5 mV//spl mu/W for the square and rectangular shaped membrane devices, respectively. Sensitivity and performance of the calorimetric chemical microsystem are shown by measurements for different volatile organic compounds. The system has a sensitivity of 0.045 and 0.049 mV/ppm to ethanol and 0.209 and 0.229 mV/ppm to toluene for the square and rectangular membrane devices, respectively.