Native Oxide Growth and Organic Impurity Removal on Si Surface with Ozone‐Injected Ultrapure Water

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Abstract
To manufacture ULSI devices with high performance and reliability in large volume, further integration and miniaturization are being promoted. The key issue in realizing what we call “Noise‐Free Manufacturing” is to keep the wafer surface ultraclean all the time. To realize the ultraclean wafer, organic impurities adsorbed on the wafer surface must be removed first before other wafer cleaning procedures. This is because native oxide and metallic impurities on the wafer cannot be removed completely in the presence of residual organic impurities on the surface. The conventional wet cleaning process is designed to have the cleaning performed at the first stage to remove organic impurities on the wafer. Because the solution in this cleaning must be heated to about 130°C, the chemical composition of the solution cannot be maintained at a constant level. This means that the cleaning is not perfectly controlled. The cleaning has another serious problem: the cleaning step produces a large volume of chemical waste that must be treated properly. We have developed a cleaning technology using ozone‐injected ultrapure water. Ozone concentration in the water is 1–2 ppm. This process is capable of effectively removing organic contaminants from the wafer surface in a short time at room temperature. Processing waste from this process is simple. Chemical composition of the ozone‐injected ultrapure water can be controlled easily.
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