Abstract

This thesis is devoted to the design, analysis and characterization of the thermal sensor based on Complementary Metal-Oxide-Semiconductor, (CMOS) compatible microhotplate (MHP). The MHP contains a split electric heater and temperature sensor, has a small area of 0.02mm2 and operates at low overheating temperature. These features of the sensing element which are not typical for traditional thermal sensors have been selected to compromise restrictions imposed by the CMOS fabrication process and materials available for the building of functional elements.
The operating mode of the sensor, signal processing algorithms and the layout of the MHP were analyzed and adjusted such that to provide a stable and low noise operation even with potentially unstable poly-Si as the material used for the heater and temperature sensor. It was experimentally demonstrated that the proposed approach allows to detect extremely small variations of CO2 and O2 concentration in air. The sensor tested as a vacuum gauge demonstrated good sensitivity down to 1mTorr.
The developed MHP due to its small size and true compatibility with CMOS fabrication process has good potential for volume production and can be used in applications where miniature and inexpensive sensors are needed. Freeze drying technology widely used in the pharmaceutic industry is suggested to be one of the possible applications for the developed sensor. It was demonstrated that the network of the developed thermal sensors can be used to monitor water sublimation during primary drying stage that may have an important practical value for the improvement of the quality and efficiency of the freeze drying process.