Investigation of MIS gas sensitive structures with Pd and Pd/Cu metal layers

Room temperature gas sensitivity of Metal-Insulator-Silicon (MIS) structures with Pd and Pd/Cu composite metal layers have been compared. SiO2 and SiO2-Si3N4 dielectric films were used as insulator. The metal films were obtained by magnetron deposition in At plasma. Detailed investigations of surface morphology and chemical composition of the layers by SEM and AES depth profiling have been performed too. A. shift of the flat band voltage (Delta V-fb), obtained from the measurements of capacitance voltage characteristics was used as a response of a MIS structure on the supplying of gas pulses. Such gases as hydrogen, humidity, and air (oxygen) were tested by the sensors. The kinetics of the responses was studied experimentally and compared with the results of a computer simulation. To investigate the resistance of the MIS structures to electrode layer aging, they were subjected to an accelerated artificial aging by annealing in air at 100-250 degrees C during 0.3-3 h. It was found that MIS sensors with Pd/Cu composite layer demonstrate higher sensitivity to hydrogen and higher resistance to aging than similar structures with Pd layer only. As a rule they also demonstrate quicker responses to the gas pulses. A model for explanation of the experimental results is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.