| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS1-WeA |
| Session: | Plasma Surface Interactions (Fundamentals & Applications) II |
| Presenter: | T. Uesugi, Tohoku University, Japan |
| Authors: | T. Uesugi, Tohoku University, Japan K. Koyama, Tohoku University, Japan B. Jinnai, Tohoku University, Japan S. Maeda, Mitsubishi Rayon Co., Ltd, Japan K. Kato, Mitsubishi Rayon Co., Ltd, Japan A. Yasuda, Mitsubishi Rayon Co., Ltd, Japan H. Momose, Mitsubishi Rayon Co., Ltd, Japan S. Samukawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
ArF excimer laser (193nm) lithography is used in the fabrication of sub-100-nm devices. However, during plasma etching processes, activated species radiated from plasma, such as ions, radicals, and photons, degrade ArF photoresist, resulting in low etching resistance and the formation of line-edge roughness (LER). To solve these issues, it is important to understand the interaction of plasma and ArF photoresist and to clarify deciding factors for the plasma resistance and the formation of LER in ArF photoresist. For this purpose, using our developed neutral beam process, effects of the activated species from plasma are divided into physical bombardment (by ions), chemical reactions (by radicals), and UV radiation. UV radiation drastically increased the etching rates of ArF photoresist films, and, in contrast, chemical reactions enhanced the formation of surface roughness in ArF photoresist. FTIR analysis shows that UV radiation preferentially dissociates C-H bonds in ArF photoresist, rather than C=O bonds, because of these bond dissociation energies; E(C-H, 4.25eV) < E(C=O, 7.71eV). This indicates that the etching rates of ArF photoresist are determined by UV radiation, because UV radiation can break C-H bonds, which are a majority of structures in ArF photoresist. On the other hand, according to the FTIR analysis, c hemical species, such as radicals and ions, are likely to react with C=O bonds, especially C=O bonds in lactone groups of ArF photoresist due to the structural and electronic effects of lactone groups. As a result, the etching rates of ArF photoresist can microscopically vary in different bond structures, leading in the enhancement of surface roughness in ArF photoresist. To reduce the chemical reactivity and the surface roughness, radical trap additives were injected into ArF photoresist. Radical trap additives, which can reduce surface roughness by 30%, are very effective to suppress the roughness formation in ArF photoresist.