The effect of hydrogen-induced interface traps on a titanium dioxide-based palladium gate MO capacitor (Pd-MOSC): a conductance study

The conductance versus gate voltage response of a palladium-gate MOS capacitor with 0.5 mu m of TiO2 (oxide layer) has been studied as a function of hydrogen gas concentration and signal frequency. The structure of the device was completed by evaporating titanium dioxide over p < 111 > -type silicon wafer (cleaned as per standard silicon technology) having a resistivity of 3-5 Ohm cm and subsequent palladium front with aluminium back metallization. The G-V response of the fabricated MOS capacitor was studied on exposure to hydrogen in Ar ambient. The fabricated device is sensitive to hydrogen (1-3%) at room temperature. The interface state density (D-it) was determined at the surface potential corresponding to the peak in the conductance curve, using a bias scan conductance method at fixed frequency. It was found that D-it increases with an increase in hydrogen gas concentration. Further, it has been observed that a change in conductance is better at lower frequencies, which may be due to the balanced communication of interface traps with the valance and conduction bands of silicon substrate. (C) 1998 Elsevier Science Ltd. All rights reserved.