As the feature size of ultralarge scale integrated circuits shrinks, the thickness of gate oxide decreases and its control becomes important. We have investigated the effect of Al contamination on the oxidation kinetics and the dielectric breakdown for ultrathin oxides. The presence of as little as 1011 - 1013 atom/cm2 of Al at silicon wafer surfaces accelerates the growth rate of thin (<30 angstrom) oxides. The increase in the oxidation rate in the presence of Al results from the decrease in activation energy for the surface reaction constant. It is suggested that the enhanced surface reactivity is due to the spontaneous oxidation and autocatalytic effect of Al. We conclude that retardation of the oxidation rate for thick oxides is due to the decrease in diffusion of oxygen through the Al-residing oxide, since Al mainly exists in the top layer of the oxide. Dielectric breakdown characteristics were performed on metal-oxide-semiconductor capacitors as a function of Al concentration in NH4OH/H2O2/H2O prediffusion clean solution. Dielectric breakdown fields of the ultrathin oxides were large in spite of Al contamination, and we could not observe any significant differences among the Al-contaminated wafers.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry