ESD Prevention Technology for Two-Fluid Pure Water Spray Cleaning with Controlled Electrostatic Charge

In the manufacture of semiconductor chips, the cleaning process is an important process. A two-fluid spray is used in single-wafer cleaning. However, two-fluid spray cleaning has the problem of electrostatic discharge (ESD) on devices on the wafer. In this study, we measured the current generated by two-fluid spraying of pure water using a prototype Faraday cage. We also measured the velocity and size of flying droplets using a shadow doppler particle analyzer (SDPA) to clarify the relationship between the generated current and flying droplet characteristics. As a result, it was confirmed that the current generated during two-fluid spraying shows positive polarity and that the amount of droplet charge increases as the flying droplet velocity increases. To reduce ESD generated during two-fluid spray cleaning, we have confirmed that the amount of electrification of pure water droplets can be controlled by installing an induction charging device immediately after the injection of pure water.