Cost-effective cleaning and high-quality thin gate oxides

Some recent findings in the area of wafer cleaning and thin oxide properties are presented in this paper. Results are shown for a practical implementation of a simplified cleaning concept that combines excellent performance in terms of metal and particle removal with low chemical and DI-water consumption. The effect of organic contamination on ultrathin gate-oxide integrity is illustrated, and the feasibility of using ozonated DI water as an organic removal step is discussed. Metal outplating from HF and HF/HCl solutions is investigated. Also, the final rinsing step is critically evaluated. It is demonstrated that Si surface roughness without the presence of metal contaminants does not degrade gate-oxide integrity. Finally, some critical remarks on the reliability measurements for ultrathin gate oxides are given; it is shown that erroneous conclusions can be drawn from constant-current charge-to-breakdown measurements.