AVS 47th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL+MS-ThM

Paper DI+EL+MS-ThM10
Studies on Electrical Properties of Ultrathin Oxides of Silicon Grown by Wet Oxidation at Low Water Vapor Pressure

Thursday, October 5, 2000, 11:20 am, Room 312

Session: Ultrathin Dielectrics and Interfaces
Presenter: V.K. Bhat, Indian Institute of Technology, India
Authors: V.K. Bhat, Indian Institute of Technology, India
K.N. Bhat, Indian Institute of Technology, India
A. Subrahmanyam, Indian Institute of Technology, India
Correspondent: Click to Email
The rapid downscaling of the device dimension has increased the interest in the ultrathin (< 5 nm) oxides of silicon. Ultrathin oxides with thickness uniformity and good electrical properties are required for the silicon submicron devices. In general, the dry oxidation is being followed to grow these ultarthin oxides. Wet oxidation is not considered for the growth of ultrathin oxides of silicon because of the following reasons: i) high growth rate associated with the conventional wet oxidation at 1 atm. water vapor pressure and ii) large density of electron trapping centres present in the wet oxide. In the present study we report the results on the electrical properties of ultrathin oxides of silicon grown by wet oxidation at low (0.04 atm.) water vapor pressure. Ultrathin oxide of silicon is grown at 900°C on n-type single crystal silicon, single side polished, (100) oriented and having 1-10 @ohm@ cm resistivity (procured from M/s Wacker GmbH, Germany). The grown ultrathin oxides are characterized for their electrical properties by fabricating MOS tunnel diodes (aluminum is thermally evaported with a metal mask on to the ultrathin oxide). The capacitance-voltage (C-V), conductance-voltage (G-V) and current-voltage (I-V) charcteristics of the MOS tunnel diodes are studied. The interafce state density (D@sub it@) and the density of the fixed oxide charge (Q@sub f@) are being calculated. The grown ultrathin oxide thickness is estimated from the measured C-V characteristics and are in the range 2.5-5.0 nm. The oxide growth rate is found to be linear. The charge trapping characteristics of the ultrathin oxides are studied by using consatnt current stress (CCS) technique. The decrease in the gate voltage is observed with the stress time. This observation may be attributed to the positive charge trapping in the oxide during the CCS. The charge trapping is found to be oxide thickness dependent and it decreases with the decrase in the oxide thickness.