Correlation between Flying Droplet Characteristics and Surface Potential of SiO2 Wafers during Two-Fluid Spray Cleaning

Two-fluid spray cleaning is effective at removing fine particles and residual films in semiconductor processes [1]; however, the high resistivity of the ultrapure water used in two-fluid spray cleaning can lead to electrostatic discharge (ESD) [2]. This study investigated the correlation between the flight characteristics of sprayed droplets, i.e., their velocity, size, and charge, and the surface potential induced on SiO 2 wafers. The amount of charge carried by the sprayed droplets was measured using a Faraday cage, and the surface potential distribution on the wafer was measured using a surface potential measurement system. The results demonstrated that while the flying droplets from the two-fluid spray were positively charged, the SiO 2 wafer surface exhibited a negative potential. This phenomenon is assumed to be caused by triboelectric charging due to the impact of the droplets on the SiO 2 surface and interfacial charge transfer effects. This findings of this study provide guidance to reduce the risk of ESD by elucidating the correlation between the droplet dynamics and the wafer charging behavior.