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Photoresist Stripping

In wafer fabrication, photoresist is used to transfer a circuit pattern onto the wafer. Once a pattern is transferred, the remaining photoresist must be removed from the wafer before it can move to the next processing step. Plasma stripping systems such as the YES-CV200 Series are effective for removing thick layers of photoresist in the shortest amount of production time.

Another common process involves applying resist via a spin coat that is 10,000 Angstroms thick (for example). The wafer is then soft baked to remove solvents, exposing discrete areas which converts the sensitizer to a mild acid. The wafer is then washed in a basic solution to eat the acidic areas. Then the wafer is baked to set the resist areas so they are strong enough to endure harsh etchants.

During baking, a light film from the bottom of the defined resist areas can spread across areas that were open. This is called scum and is typically about 500 Angstroms thick. This has to be removed using a gentle resist strip, also known as a descum process so that 500 Angstroms of scum can be removed without removing too much from the bulk 10,000 Angstroms of resist.

Plasma cleaning systems such as the YES-G Series are ideally suited for a gentle descum applications.