1.5.3 Environmental Hardness of Pt-Ti-O gate Si-MISFET Hydrogen Gas Sensors from Siloxane, Humidity, and Radiation

14th International Meeting on Chemical Sensors - IMCS 2012
2012-05-20 - 2012-05-23
Nürnberg/Nuremberg, Germany
1.5 Transistor-based Sensors
T. Usagawa, Y. Kikuchi, A. Nambu, A. Yoneyama, K. Ueda - Central Research Laboratory, Hitachi, Ltd. (Japan), A. Watanabe - Hitachi Research Laboratory, Hitachi, Ltd. (Japan)
136 - 139


Platinum-titanium-oxygen (Pt-Ti-O) gate Si-MISFET hydrogen gas sensors have been found to show large sensing amplitude (delta Vg) of 624.4 mV with sigma delta Vg of 7.27 mV for nine repeated measurements even under nitrogen-diluted 1.0% hydrogen gas, which are nearly the same values of 654.5 mV with sigma delta Vg of 3.77 mV under air-diluted 1.0% hydrogen gas. The Pt-Ti-O sensor devices can work stably as hydrogen sensors up to about 300 °C and also show environmental hardness as follows: When nitrogen-diluted 10ppm HMDS (hexamethyldisiloxane) was exposed to the sensor FETs for 40 minutes at working temperature of 115 °C, the sensing amplitude (delta Vg) little changed within repeating errors before and after HMDS exposures. The variations of delta Vg between relative humidity of 20% and 80% are very small within ±6 % around 50 % under the 40 °C atmosphere. The radiation hardness of developed hydrogen sensor chips from gamma ray (60 Co) and/or X-ray (Synchrotron Radiation) is sufficiently strong enough even at extremely high integral dose such as 1.8 MGy. It comes from the robustness of PN-junction between drain and pwell due to large device dimensions.