Functional Modeling of Wet Etch at Semiconductor Manufacturing
Consider alternative chamber/process architecture
A more radical solution is to redesign the process so the wafer is processed face down toward a shallow liquid bath. This could improve wetting, reduce air trapping, and reduce evaporation. A shallow bath may also allow fast replacement of chemistry and rinse water while keeping the wafer continuously covered by liquid.
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Improve wafer wetting at the beginning of the process
The process should ensure complete replacement of air by liquid. Possible actions include pre-wet steps, lower initial rotation speed, temporary stop of wafer rotation during first dispense, optimized nozzle position, improved dispense profile, and chemical additives that improve wetting.
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Reduce evaporation of chemistry and DI water
Evaporation can be reduced by controlling chamber atmosphere, humidity, pressure, temperature, exhaust rate, and process timing. The goal is to prevent the liquid film from drying too early and leaving residues or particles behind.
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Prevent bubble formation and air trapping
The dispense sequence should avoid trapping air between the liquid and the wafer surface. Liquid should contact the wafer smoothly and continuously, especially in patterned areas and high-aspect-ratio features.
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Control airflow inside the chamber
Airflow should not directly disturb the liquid film on the wafer. Instead of simply increasing airflow, it should be minimized, redirected, or isolated from the wafer surface while still maintaining safe vapor removal.
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