Condensation behavior of nanoscale bubbles on ArF excimer resist surface analyzed by atomic force microscope

By using atomic force microscope (AFM), a nanoscale bubble (NB) formed on a film surface of ArF excimer resist can be imaged clearly in deionized water. The diameter and height of NBs observed are approximately 40 similar to 100nm and 3 similar to 8nm, respectively. By approaching the AFM tip onto the NBs, the repulsive force can be detected but the attractive force on the resist surface. The interaction analysis between the AFM tip and the ArF excimer resist surface is effective in order to identify the NBs and to distinguish from solid particles. These phenomena can be discussed on the basis of Lifshitz theory. The separation procedure of the NB is accomplished with the AFM tip. The applying load at which the NB can be separated into the minute one is approximately 5nN. Therefore, the NB is more likely to adhere to the ArF excimer resist surface than the AFM tip surface. The condensation among the NBs can be realized experimentally by the scanning with the AFM tip. Consequently, the line shape NBs of 200nm similar to 1 mu m width and 5 similar to 15 mu m length can be formed at the scanning edge of the AFM tip. The analysis of NB nature is discussed on the point of the immersion lithography.