Carbon dioxide gas purification and analytical measurement for leading edge mask and wafer cleaning

High pressure carbon dioxide provides a very effective alternative for cleaning integrated circuits and masks. This great cleaning ability is due to CO2 having the physical characteristics of both a liquid and a gas: like a gas, it diffuses rapidly, has near zero surface tension, very low viscosity and thus penetrates easily into mask features or deep wafer trenches and vias. As a liquid it can be utilized to clean particles and to solvate other chemicals such as alcohols and fluorinated hydrocarbons. This paper covers the analytical tests and characterizations carried out to assess impurity removal from 3.0 N CO 2 (beverage grade) for its final utilization in mask cleaning applications.