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Question Hi, I have a ultrosonic wafer cleaning system that I just bought. The wafers are in a wafer boat and placed in the system. They are then submerged in DI water and the sonics are applied. Once the tank is drained a blower is turned on and the wafers are dried. I would think the blower could generate thousand of volts of charge on these wafers. I'm wondering if a human then picking up the boat will cause a issue. I'm against putting a Ionizer over the system because it will blow particles back on to the wafers. What are your thoughts?
Answer Per ADV1.0-2003 Glossary “Electrostatic discharge (ESD) The rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field. Note: Usually, the charge flows through a spark between two bodies at different electrostatic potentials as they approach one another.” Since the wafer/boat and the human are at different voltages, it is predictable that an ESD event will occur. If there is a charge on the wafer/boat, and the human is grounded, basically at zero potential, then they certainly will be “two bodies at different electrostatic potentials”. Regarding “blowing particles back on the wafers”, the charge on the wafer will cause ElectroStatic Attraction (ESA) and will tend to attract opposite charged particles. Ionizers neutralize charges and can be particularly effective in ElectroStatic Discharge (ESD) control removing ElectroStatic charges from insulators which cannot be grounded or isolated conductors that are not grounded.In addition, Ionizers deal effectively with ElectroStatic Attraction where charged particles cling to products causing contamination problems. Many companies use Ion Viper Ionizers where the ionized air flow can be directed where it is needed and remove particles by neutralizing the charge and blowing the particle off.
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