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 c apacitor with 0.5 mu m of TiO2 (oxide layer) has been studied as a fun ction of hydrogen gas concentration and signal frequency. The structur e 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 wi th aluminium back metallization. The G-V response of the fabricated MO S capacitor was studied on exposure to hydrogen in Ar ambient. The fab ricated device is sensitive to hydrogen (1-3%) at room temperature. Th e interface state density (D-it) was determined at the surface potenti al corresponding to the peak in the conductance curve, using a bias sc an conductance method at fixed frequency. It was found that D-it incre ases with an increase in hydrogen gas concentration. Further, it has b een observed that a change in conductance is better at lower frequenci es, which may be due to the balanced communication of interface traps with the valance and conduction bands of silicon substrate. (C) 1998 E lsevier Science Ltd. All rights reserved.