Correlating chemical and water purity to the surface metal on silicon wafer during wet cleaning process

Trace metals in hydrogen peroxide and high-purity water, used in wet cleaning of wafers, is correlated to the metallic contamination of the wafer surface since metal contamination adversely impacts IC device yield. Hydrogen peroxide with different level of trace metals, ranging from 100 ppt level to 10 ppb level, is used in the experiment to determine the level of selected metal deposition on the silicon surface. Significant amounts of these trace metallic impurities can be removed by subsequent treatment of the silicon wafer by an acidified solution of water. Contamination of a wafer surface by sodium is also correlated to the level of sodium present in deionized water used in the final rinsing of the wafer. The threshold and mechanism for metal deposition for various metals on wafer surfaces are different. This information is useful in determining purity requirements for process chemicals and improving the wet cleaning process for the next generation of semiconductor devices.