Adhesion and removal behavior of nanoscale bubble on resist film surface for immersion lithography

Various sizes of concave square patterns are used for microscale bubble adhesion and removal investigation in a water/methanol mixture solution. As decreasing the surface energy of the solution, the micro bubbles are more likely to remove from the square patterns. However, the micro bubble is less likely to remove as decreasing the square size of patterns. The threshold concentration of water/methanol solution for bubble removal can be determined experimentally. Based on the surface energy analysis, the adhesion and removal mechanisms of micro bubble can be explained. The nanoscale bubbles adhered on an ArF excimer resist surface can be observed clearly by using atomic force microscope (AFM). The growth of bubbles on the ArF excimer resist surface can be imaged. By the AFM technique, nanoscale bubble can be divided into some minute bubbles on the ArF resist surface under applying certain force about 5nN. The condensation nature of nanoscale bubbles is discussed.