Antistatic protection in wafer drying process by spin-drying

As part of an effort to produce a static-free wafer spin-dryer the authors developed an ionizer for use with spin-dryers and evaluated its charge removing and particle rejecting effects. Particle generation due to sputtering of the discharge electrodes themselves was prevented. The protection of the discharge electrodes with quartz glass completely prevents particle generation by ion and electron sputters, and the concentration of ozone generated is reduced to less than 1/10 of the usual level. This ionizer is excellent in its charge-removing performance taking only about 1 s to reduce the wafer potential from ±5 kV to ±0.1 kV. The residual potential due to the imbalance of ion polarity is extremely low, only 10 V at the maximum. The ionizer´s charge removing effect to prevent particle deposition was also evaluated, and almost complete success is reported in preventing the statically induced deposition of particles to wafers while they are being dried by a spin-dryer