Future Cleaning Role of DI Water

Even with advancements in dry cleaning and other alternative cleaning technologies, wet cleaning will continue to be widely used because of its versatility. High-purity water and wet cleaning processes will remain critical in containment and reduction of defects and associated yield loss. But the question remains — what role will DI water take in future device manufacturing?

One point of view, by Drew Sinha, formerly an applications manager with SCP Global Technologies (Boise, Idaho), was reported in the December 2001 Ultrapure Water journal. The paper states that "high-purity water and its mixture with various solutes will continue to be used for wet cleaning and rinsing process from wafer to semiconductor device manufacturing." The author also predicts growth in dry cleaning technology and single-wafer processing, along with the integration of cleaning steps in cluster tools. "Dry cleaning processes are expected to complement the wet cleaning processes and will further reduce the overall consumption of DI water for wafer cleaning."

The challenge is to meet future production requirements. Today the wafer must be free of particulate impurities, ionic and metallic impurities, organic impurities and native oxide/surface oxygen, and have both a hydrogen terminated and atomically smooth surface. Future requirements must also include high-aspect-ratio trench cleaning, watermark and backside particle prevention, and control of crystal originated particle (COP) defects. The compiled results from SCP suggest that these issues taken separately can be attained. For example, the use of IPA vapor drying technologies following DI water rinsing was shown to eliminate the creation of watermarks. For cleaning deep-trench structures, results showed that adding a surfactant to wet chemistries can improve trench cleanability. SCP points out that wet processing can simultaneously clean both sides of the wafer. Results also show reduction in the ratio of ammonia and DI water can impact the measurable COP generation during the cleaning process.

Because technology advancements promote change to standard cleaning, DI water quality and its requirements change. Are DI water processes combined with alternative technologies the cleaning answer?

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