Evaluation of 193 nm Photoresist Material at Advanced Immersion Nodes

Abstract

As 193 nm immersion lithography under single exposure moves toward the limit of 38 nm half pitch, more and more understanding has been achieved in the illumination. With the availability of same exposure tool and illumination condition, the key to the successful development of the photolithographic process will weigh toward good choice of and good process condition for the photoresist. Though different approaches exist for the evaluation of photoresists among major industrial players, the key understanding of the resist material has converged to some conservation quantity, which related to spatial resolution, line edge roughness, and resist sensitivity (RLS). Such quantity seems to be related to the formulation of modern chemically amplified photoresist. Although it is well-known that usual 193 nm photoresists needs a top coating for exposure tools that need water immersion since the water will interact with the acid that is created by photo-chemical reactions and caused patterning failure, recently, topcoat-less photo resist process was developed for immersion lithography with a small amount of additives blended into the conventional resist material. The availability of such resist has simplified the resist process and saved process cost, but may make the resist material more complicated. We have explored a number of normal immersion and topcoat-less immersion photoresists in the limit of 193 nm immersion lithography. We will present our data in the study of RLS and the resist profile.