DESING CONSIDERATIONS FOR MONOLITHIC INTEGRATION OF A MICRO HOT PLATE TEMPERATURE CONTROLLER IN A MEMS GAS SENSOR, S. MENDOZA-ACEVEDO, M. A. REYES-BARRANCA, L. M. FLORES-NAVA, A. aVILA-GARCiA, J. L. GONZaLEZ-VIDAL, 2009 6TH INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING, COMPUTING SCIENCE AND AUTOMATIC CONTROL (CCE 2009), TOLUCA, EDO. DE MEXICO, MEXICO, 2009, 262-266.
A control system to regulate the temperature of the micro hotplate in a MEMS gas sensor is presented. The controlelement, called micro hotplate, is comprised of a micro heater and a temperature sensor, both made with polysilicon, located near each other. This material has a Temperature Coefficient of Resistance (TCR) that is the basis for the design of the temperature controller of the gas sensor system. A high temperature between 250 and 400ÂC is needed to produce a chemical reaction between the gas and the sensing film, hence a reliable temperature control for the micro hotplate is desired. Thermal insulation of the circuitry from the heating element, having a monolithic sensor system, and low power consumption, are the main specifications for the system. This is obtained by means of a micro pit realized with MEMS micromachining processes. The analysis of the circuit proposed to fulfill these characteristics is presented, for its future integration with a standard CMOS technology. A trade off is established between the sensor structure parameters and the circuit design.