Particle reduction in high temperature sulfuric acid using PTFE membrane filter and low pulsation bellows pump

Abstract

In order to reduce particles in the chemicals used for the semiconductor wafer cleaning processes, it is important to remove generated particles by filtration technology as well as to reduce particle generation from each part of the cleaning tool. We applied a newly developed bellows pump with low pulsation to 90 °C sulfuric acid, and evaluated the effect of the pulsation on the particle level downstream of the pump and particle removal efficiency of 5 nm-rated PTFE membrane filters in the chemical. Pressure pulsation behavior was compared between a conventional bellows pump and the low pulsation pump, and it was confirmed that the low pulsation pump effectively reduced the peak-to-peak value of pressure fluctuation. In addition, the particle level downstream of the pump drastically decreased for the low pulsation pump compared to the conventional pump. On the other hand, the results of particle challenge tests indicated that the filters' particle removal efficiency was unchanged regardless of the pump used. As a result, the particle level downstream of the filter when using the low pulsation pump became lower compared to that using the conventional pump. In conclusion, the low pulsation pump and the 5 nm-rated PTFE membrane filter are a good combination to effectively reduce particles in 90 °C sulfuric acid.