A Planar Thin-Film Peltier Cooler for the Thermal Management of a Dew-Point Sensor System

The development of new application fields of microelectromechanical systems (MEMS) devices often implies a high degree of complexity and the integration of several functionalities within these devices. In this paper, thermoelectric planar thin-film microcoolers become more and more important due to their cooling and temperature stabilization ability, respectively, in MEMS devices. This paper reports on the investigation of the design, manufacturing, and characterization of a membrane-integrated thin-film thermoelectric cooling arrangement for active temperature control and precise local cooling of the sensitive region in a thin-film dew-point sensor. The sensor concept is based on the combination of a thermal sensor heater and a planar thin-film Peltier cooler, which are all arranged on a freestanding and thermally insulated membrane. To obtain a high performance concerning the maximum temperature decrease of the active-cooled membrane, a highly efficient thermoelectric materials combination of Sb and Bi_0.87Sb_0.13 was used for the fabrication of the in-plane Peltier configuration. For the first sensor setup, a temperature decrease of 10.6 K was achieved under atmospheric conditions at 293 K. In combination with an externally assembled two-stage Peltier cooler dew-point, temperature measurements down to 213 K (-60 °C) were performed in a climatic exposure test cabinet.