Takaaki Niinomi

Design of acid labile protecting groups in chemically amplified resists

The relation between the characters of the protecting groups and lithographic performance in chemically amplified resist was investigated by computational techniques. The stability of de-blocking reaction was estimated by means of molecular orbital calculation (MO). Their calculated results showed that electron withdrawing group increases the activation energy of de-blocking reaction. And the resists which contain these protecting groups were evaluated with acidic top-coating. Though the stability of de-blocking reaction correlated with the sensitivity of the resist, it was not necessarily effective to acidity of top-coating. Furthermore, we investigated the effect of the bulkiness and hydrophobicity of protecting groups to resist performance. As the bulkiness of the protecting group increased, the top shape of lines became better. However, without top coating, too bulky protecting group formed T-top shapes. These results show that the bulkiness of the protecting groups has relation to formation of the insoluble layer. The stabilization energy in the interaction of protecting groups with hydroxyl group of phenol ((Delta) H) was calculated by means of MO calculation. The highest value of (Delta) H between carbonate group and OH group is larger than that between acetal group and OH group by 1 kcal/mol. This result suggests that the interaction between carbonate group and OH of phenol contribute to the ability of dissolution inhibition.