Minimizing Wafer Surface Charging for Single-Wafer Wet Cleaning for 10 nm and beyond

Wafer charging has become an issue since single-wafer wet clean has been introduced and multiple aspects could be potential root causes. In chemistry and DIW process factors, typical process parameters; flow rate and time were re-evaluated. As an alternative solution, dilute NH4OH could reduce the wafer surface charging. Hardware parts were also investigated and wafer holding chuck-pin material was revealed to become a risk of discharging failure at edge of wafer. Ionizer has been known to discharge wafer surface; however, it is not enough to remove pre-existing charge from post DIW rinsed wafer. Soft X-ray is challenged to remove pre-existing charge and obtained initial positive result.