Growth and properties of thin SiO2films by inductively coupled low-temperature plasma anodisation

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Abstract
The increasing trend towards smaller MOS devices for VLSI has led to the need the thinner gate dielectrics grown at lower temperatures. The electrical quality of thin ( approximately 20 nm) films of SiO2 prepared by inductively coupled plasma anodisation at temperatures down to room temperature is investigated. Using MOS capacitors with plasma-grown dielectric, the oxide quality is measured in terms of dielectric breakdown strength, Eb, interface state density, Dit, and the net oxide fixed charge density, Nf, and is shown to be a function of plasma conditions. It is also shown that the DC biasing voltage, rather than the DC biasing current, is a critical parameter on the quality of the SiO2. Thin plasma oxides comparable with high-quality thermally grown oxides are demonstrated having average dielectric breakdown strengths Eba>10 MV cm-1, interface state density at mid-gap Ditm10 cm-2 eV-1 and Nf11 cm-2. Small-geometry MOS transitions fabricated using this technique are also demonstrated with threshold voltages of 0.4 V and n-channel mobilities in excess of 650 cm2 V-1 s-1.