3.3 - New Microsystems-Based IR Gas Sensing Technology

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings IRS² 2011
I3 - Gas Analysis
P. Ohlckers - Tucson, Arizona (USA) and Vestfold University College, Borre (Norway), A. Kropachev - Intex, Tucson, Arizona (USA, J. Kunsch - Laser Components GmbH, Olching (Germany)
65 - 70


Combining Bulk Silicon Micromachining (BSM) with Diamond-Like Carbon (DLC) thin film technology can be favourably used to make high performance MEMS devices. We highlight the versatility of BSM combined with the unique features of our proprietary nanoamorphous carbon (NAC) thin film technology to make high performance MEMS devices at favourable cost. A family of high performance infrared emitters has been designed and commercialised, with the most distinctive features being high speed with a modulation depth of more than 100 Hz, broadband IR emission from 1 to 14 micrometer, more than 10% power efficiency, and a lifetime beyond 100,000 hours. These emitters have been commercialised by Intex, and are already in use in system applications like non-dispersive infrared gas sensors.

Recently, two new versions have been launched, one with 30 % higher output for demanding application, and the other with smaller chip size for low cost applications. These advances in emitter design will be discussed.

Intex is also devoloping photoacoustic gas sensors. The photoacoustic principle offers very high sensitivity and selectivity when used for gas trace analysis. Current systems are too expensive for widespread environmental use. Here, the design, modeling, fabrication and characterization of two micromachined silicon microphones with piezoresistive readout designed for low cost photoacoustic gas sensors, are presented. The microphones have been fabricated using a foundry MPW service. One of the microphones has been fabricated using an additional etching step that allows etching through membranes with large variations in thickness. To increase sensitivity and resolution, a design based on a released membrane suspended by four beams was chosen. The microphones have been characterized for frequencies up to 1 kHz and 100 Hz, respectively. Averaged sensitivities are measured to be 30μV/(V × Pa) and 400μV/(V × Pa).