변압기 절연유중 용존수소를 감지하기 위해 Pd/Pt 게이트 MISFET 센서를 제조하고 그 특성을 조사하였다. 동일 칩안에 내장형 히터와 온도측정용 다이오드를 제조하고 MISFET의 전압 드리프트를 줄이기 위해 차동형구조로 하였다. 수소유입 드리프트를 줄이기 위해, 양쪽 FET의 게이트 절연층을 실리콘 산화막과 실리콘 질화막의 2중 구조로 하였다. 수소감지막의 블리스터를 줄이기 위해 Pd/Pt 2중 금속층을 증착하였다. 제조된 센서의 변압기 절연유에 대한 수소감지 특성은 40mV/10ppm 감도와 0.14mV/day 안정도를 보였다.
The Pd/Pt gate MISFET type hydrogen sensors, for detecting dissolved hydrogen gas in the transformer oil, were fabricated and their characteristics were investigated. These sensors including diffused resister heater and temperature monitoring diode were fabricated on the same chip by a conventional silicon process technique. The differential pair plays a role in minimizing the intrinsic voltage drift of the MISFET. To avoid the drift of the sensors induced by the hydrogen, the gate insulators of both FETs were constructed with double layers of silicon dioxide and silicon nitride. In order to eliminate the blister formation on the surface of the hydrogen sensing gate metal, Pt and Pd double metal layers were deposited on the gate insulator. The hydrogen response of the Pd/Pt gate MISFET suggests that the proposed sensor can detect the dissolved hydrogen in transformer oil with 40mV/10ppm of sensitivity and 0.14mV/day of stability.
