Current conduction in thermally grown thin SiO2 films

The I-V characteristics of thin SiO₂ films with thicknesses ranging from 35 to 250 Å were studied using conventional Al-gate MOS capacitors prepared on <100> p-type substrate as the test vehicle. Several measurement techniques including constant voltage, constant current, and voltage pulse were used. Consistent results have been obtained. time-dependent currents were observed in the low field region, i.e. less than 8 MV/cm for oxides thicker than 50 Å due to displacement currents and charge trapping. The slope of the Fowler-Nordheim plot is sensitive to the way the oxide field is estimated. For thicker oxides (greater than 100 Å), the slope may have a value between 240~300 MV/cm depending on the estimated oxide field. For thinner oxides, the slope is smaller due to the enhancement in the direct tunneling effect