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Performance Degradations of MISFET-Based Hydrogen Sensors with a Pd-Ta2O5-SiO2-Si Structure During Long-Term Operation

“…The testing n -channel MISFET element based on a Pd–Ta 2 O 5 –SiO 2 –Si structure was fabricated on a single chip (2 × 2 mm 2 ) together with a ( p–n )-junction temperature sensor and heater-resistor by means of conventional n -MOS-technology using laser evaporation Pd-films. Technological processes are presented in detail in [11,17]. Photos of the fragment of the silicon wafer undivided into chips and the separate chip are shown in Figure 1.…”

“…The gas sensors based on MIS-capacitors and field-effect transistors (MISFETs) have been studied by many investigators (e.g., [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]). A great contribution to the developments of gas-sensitive MIS devices has been made by the researchers at Linköping University since their first work in 1975 [2].…”

“…MIS sensors with different gate materials (palladium, platinum and iridium), with dielectric films SiO 2 , Si 3 N 4 –SiO 2 , TiO 2 –SiO 2 and Ta 2 O 5 –SiO 2 have been investigated. The semiconductors Si [2,3,4,5,6,7,8,11,12], GaAs [9] and SiC [14] were used in MIS gas sensors to detect low concentrations of the gases H 2 [2,3,4], NH 3 [5], H 2 S [12] and CO [14]. The studies have shown that performance characteristics of MISFET-based hydrogen sensors depend on technological parameters [6], electrical modes [15], chip temperature [17] and external factors (other gases, irradiation [16]).…”

“…Numerous experiments have demonstrated that with the same technological parameters, MISFETs have the best performance compared to MIS capacitors in IHS-1 and resistors in IHS-2. In addition, the integrated sensors of the second type (IHS-2), containing MISFETs with a Pd–Ta 2 O 5 –SiO 2 –Si-structure, possess the best stability and reproducibility of characteristics [6,11]. Therefore, in recent years we have investigated the characteristics of this MISFET.…”

“…In most of these works, sensor characteristics were studied by measurement of a single or a few (3–5) short-term responses to different hydrogen concentrations. However, previous studies have shown that under long-term hydrogen action, the metrological characteristics of the sensors are subject to change [11]. Performance characteristics (sensitivity, speed, errors and stability) are determined by sensor response parameters, the repeatability of which becomes an important characteristic for long-term operation of gas analytical devices.…”