ABSTRACT
Our study aims to fabricate a hydrogen sensor based on thermal stability analysis of Ta2O5 film, and to determine the effect of Pd electrodes on the hydrogen sensor at high temperatures. First, in order to ensure high-temperature stability of silicon carbide (SiC)-based hydrogen sensors, the thermal stability of Ta2O5 dielectric thin film at temperatures above 900 °C was studied. The sensor structure consisted of a metal-insulator-semiconductor (MIS) and a tantalum oxide (Ta2O5) dielectric film was formed by rapid thermal oxidation (RTO). The Ta2O5 film was assessed through SEM, TEM, SIMS, and dielectric breakdown strength to observe thermal stability. Secondly, hydrogen sensors using a SiC substrate were fabricated, with the process considering thermal stability. The response characteristics for hydrogen were evaluated using three types of sensors with different Pd electrode patterns. The patterns of the Pd electrode were designed as squares or grid shapes, and were characterized by 100%, 75%, and 50% area ratios of Pd electrodes covering the Ta2O5 layer. The results showed that the sensor with a 100% area ratio of the Pd electrode had better sensitivity and linear response characteristics compared to sensors with a 50% area ratio of the Pd electrode.
ABSTRACT
We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures.
