Watermark and pattern collapse are easily affected by wetting properties of wafer surfaces and pattern size. Also, these issues are strongly dependent on types of dryer, IPA vapor or liquid dryer. Using the IPA liquid dryer, watermark can easily controlled regardless of wafer types and wetting properties. However, in the case of IPA vapor dryer watermark is easily affected by wetting properties of wafer surface. Generally, HF treated Si surface, hydrophobic, can be easily prevented from watermark generation using a conventional IPA vapor dryer. However, while using IPA vapor dryer, watermark is easily generated on even hydrophilic surface, such as thermally grown oxide and SiON. To overcome watermark generation during HF last cleaning, we modified conventional IPA vapor nozzle and changed a drying condition with a slow rotation while drying process.
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