New Protective Groups in Alicyclic Methacrylate Polymers for 193-nm Resists.

Abstract

We used a methacrylate polymer with two acid labile protective groups, mevalonic lactone and 2-methyl-2-adamantanol (Fig. 1), for a 193-nm resist.[1-4] THF resist demonstrated high sensitivity and a high resolution as a single layer resist. In this paper, we investigated polar five protective groups in place of THF lactone group to obtain necessary properties for good lithographic performance. We discuss THF impact of THF polarity and acid cleavability of THF protective groups to make a good match to 2-methyl-2-adamantyl group. Among THF selected protective groups, we found that 3-hydroxy-γ-butyrolactone yielded acceptable lithographic performance.