Design and fabrication of high-temperature micro-hotplates for drop-coatedgas sensors

This paper reports on the optimisation of micromachined hotplates for gas-s ensing applications designed to stand high-temperature coating processes an d modes of operation. Different thin film materials, geometry and dimension s have been investigated regarding their power consumption, temperature dis tribution over the sensing area and robustness when annealed at high temper ature. In comparison with oxide films, the micro-hotplates made of nitride were the most robust. They withstood annealing temperatures of up to 700 de grees C and a pulsed temperature mode of operation. Their robustness allowe d the sensing area to be heated up to a high temperature (550-700 degrees C ). These micro-hotplates are therefore suitable for the annealing "on-chip" of the: gas-sensitive materials deposited in a drop-coating procedure. Sen sors coated with a Pd-doped tin oxide drop and annealed using the integrate d heater have been tested under different concentrations of CO and CH4 in a ir. (C) 2000 Elsevier Science S.A. All rights reserved.