Watermark removal after wafer cleaning is a critical technical step in semiconductor manufacturing, as it directly affects chip yield and performance. Understanding your concerns, we have prepared several solutions that may help.
01
Optimizing Drying Processes on Cleaned Wafers
Spin Drying: Removes moisture from the wafer surface through high-speed spinning, a commonly used drying method.
Nitrogen Purge: Uses dry nitrogen gas to blow across the wafer surface to ensure complete drying.
Isopropanol Vapor Drying: Heats and pressurizes isopropanol to form vapor, which is carried by hot nitrogen gas. The isopropanol molecules can more easily enter the grooves of the device and remove water molecules inside.
02
Chemical Treatment
Rework (Chemical Surface Treatment): For defects caused by watermarks, re-chemical surface treatment can be used to eliminate them. This usually involves specific chemicals to reprocess the wafer and reduce or remove watermarks.
Hot Phosphoric Acid Treatment: Treats the wafer surface with hot phosphoric acid for a period of time, followed by ultrasonic cleaning. This method can help improve watermark issues to some extent.
03
Physical Methods
Ultrasonic Cleaning: In wet cleaning processes, ultrasonic cleaning is an effective method for removing particulates. It uses non-periodic acoustic streaming generated by sound waves propagating through a liquid medium, which acts on the wafer surface to reduce particle adhesion, making them easier to be carried away by the cleaning solution.
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