CMOS compatible nanoscale thermal conductivity detector for gas sensing applications

•Development of silicon-based CMOS-compatible thermal conductivity detectors.•Promising limit of detection of 60 ppm (pentane/helium) achieved for this kind of sensors.•Improvement of the limit of detection by more than one order of magnitude compared to referenced work.

We present a nanofabricated Thermal Conductivity Detector (nano-TCD), designed to be monolithically integrated with a CMOS technology compatible NEMS, in order to widen its analyte spectrum in the low molecular weight volatile organic compounds range. The nano-TCD uses arrays of silicon nano-wires, with 220 nm × 250 nm cross sections and 2 μm suspension gap over the silicon bulk. In order to filter out the 1/f flicker noise produced by the silicon nanowires, we used a signal modulation technique based on the 3ω method, thanks to the fast response time of the nano-TCD. Experimental results demonstrate detection of pentane and butane with a limit of detection of 60 ppm and 70 ppm respectively (mole fraction).