Bubble monitor for semiconductor manufacturing

摘要

Apparatus for monitoring the hydrogen peroxide concentration in a sulfuric acid bath used to remove photoresist from semiconductor wafers uses the amount of bubbles in the fluid mixture to signal the addition of hydrogen peroxide. The bubbles are directly related to the hydrogen peroxide in sulfuric acid mixture. The bubbles are sensed by a light source and photoelectric sensor connected to a threshold adjustment control which controls a metering solenoid valve to add hydrogen peroxide from a reservoir to the bath when the bubbles decrease.