Microhotplates

Device Layout

The microhotplate is a multi-layer structure which has three functional layers: a polysilicon heater, a metal (for example Al or W) thermometer/heat distribution plate, and sensing film electrical contacts. These layers are separated by insulating layers of SiO₂. For the device shown below, there are 10 electrical lines leading onto the suspended structure: two for the heater, four for a van der Pauw measurement on the metal plate, and four for the sensing contacts.

Typical Characteristics

Temperature Range

20 °C to 500 °C for devices with aluminum
20 °C to >800 °C for tungsten metallized devices
Power consumption
50 mW for 500 °C fixed temperature operation. Power is approximately linear with temperature.
Thermal time constant
about 1 ms for both turn on and turn-off.
Size
50 -200 µm

The Images below show a four element array of tungsten-metallized microhotplates in an SEM view, and a four element array of tungsten microheaters, with one element heated to over 1000 °C, hot enough to glow.

References

Suehle, J., Cavicchi, R.E., Gaitan, M., and Semancik, S., "Tin oxide gas sensor using micro-hotplate by CMOS technology and in-situ processing," IEEE-Electron Device Letters, 14, 118-120 (1993).

Cavicchi, R.E., Suehle, J.S., Chaparala, P., Kreider, K.G., Gaitan, M. and Semancik, S., "Microhotplate Gas Sensor," Proc. of the 1994 Solid State Sensor and Actuator Workshop (Hilton Head, S.C.), 53-56 (1994).

Gaitan, M. , Suehle, J. S., Cavicchi, R. E., Semancik, S. "Micro-Hotplate Devices and Methods for Their Fabrication," U.S. Patent 5,464,966 (1994) .

Home -- Personnel -- Facilities -- Mission -- Technology Transfer -- References -- Postdoc Opportunities -- Links -- Table of Contents