Evaluation of immersion lithography processes for 55-nm node logic devices

We have investigated relationship between immersion topcoats and water, and between topcoats and ArF resist films for the use in ArF immersion lithography from the stand point of the work of adhesion characteristics. We evaluated surface free energy of topcoat films and resist films each from the contact angle measurement. From values of measured free energy, we obtained work of adhesion between topcoats and water, and between topcoats and resist films. In addition, we calculated an interfacial free energy between topcoats and resist films, which is related to the interface stability. As a result of evaluation of the interfacial free energy of four different kinds of topcoats, the topcoat which has lower surface free energy was found to have lower work of adhesion between topcoat and water, and lower interfacial free energy between a topcoat and a resist. These results indicate that the topcoat which has lower surface free energy has more less interaction between water and topcoat and stabile interface between a topcoat and a resist film.