| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuA |
| Session: | Fundamentals of Plasma-Surface Interactions I |
| Presenter: | K. Koyama, Tohoku University, Japan |
| Authors: | 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 photoresists, namely chemically amplified photoresists, have been used in recent 193-nm lithography processes. However, ArF photoresists have serious problems during plasma etching processes, such as line-edge roughness (LER). LER can be classified with pattern-size roughness, called “low-frequency LER,” and molecular-level-size roughness, called “high-frequency LER”. Especially, high-frequency LER is more serious problem for wiring in ULSI devices of less than 32 nm. In order to overcome these issues, it is essential to understand the relationship between irradiation species from plasma (ions, electrons, radicals, and ultraviolet/vacuum-ultraviolet (UV/VUV) photons) and molecular level reactions on the ArF photoresist surface.
In this study, we investigated the effects of UV/VUV radiation, ion bombardment and gas species on ArF photoresists by using our developed neutral-beam process. Samples were etched by Ar- or Cl2-neutral beam and Ar- or Cl-ion and UV/VUV photon. The surface roughness of the films was measured by SPM. A comparison of neutral beam irradiation with ion and UV/VUV photon irradiation showed that surface roughness of ArF photoresist increased after ion and UV/VUV-photon irradiation for both gasses. Especially, in the case of chlorine gas, significant surface roughness is observed by adding UV/VUV photon. To investigate the effects of irradiation species on the ArF photoresist polymer structure, we analyzed the chemical bonding states in ArF photoresist polymers by using FTIR. FTIR measurement showed that the lactone and ester units in the base polymers were vulnerable to physical bombardment, chemical reactions, and UV/VUV photon irradiation. The vulnerability results in changes in base-polymer structure that could account for the differences in the etching rates and surface roughness of ArF photoresist films. Our results demonstrated that UV/VUV photon irradiation plays an important role for generation of molecular level line-edge roughness.