| AVS 54th International Symposium | |
| Plasma Science and Technology | Friday Sessions |
| Session PS-FrM |
| Session: | Plasma-Surface Interactions III |
| Presenter: | M. Sumiya, Hitachi High-Technologies Corp., Japan and University of Maryland |
| Authors: | M. Sumiya, Hitachi High-Technologies Corp., Japan and University of Maryland R.L. Bruce, University of Maryland S. Engelmann, University of Maryland F. Weilnboeck, University of Maryland G.S. Oehrlein, University of Maryland |
| Correspondent: | Click to Email |
The degradation of photoresists (PR) during plasma etching is one of the issues for nanoscale-fabrication. Although it has been already reported that surface roughness develops within a few seconds plasma exposure and leads to striations,1 the mechanism of surface roughness formation during the initial stages of plasma exposure is not well understood. In this study we employed a shutter approach2 to achieve rapidly steady-state plasma condition for processing PR surface. The time-evolutions of optical constants and thickness of the modified layer on the PR surface were obtained using 2 layer optical modeling of the ellipsometric data. The change of surface composition was observed by X-ray photoelectron spectroscopy (XPS). Remarkable differences of the etch behavior during the early etch period for different discharge conditions, i.e., ion energy, pressure and stage temperature, were observed. We found that the modified layer is formed within a few seconds and a steady-state modified layer is subsequently seen. It was revealed that these differences of etch behavior for different etch condition at the earlier etch period are due to difference of fluorination degree of the PR surface and having higher etch rate under low fluorination leads to rough surface. We also compared the etch behaviors of 193 nm PR and 248 nm PR materials. Whereas for 193 nm PR etching was observed immediately, for 248 nm PR, fluorocarbon film deposition took place at first until a fluorinated surface developed. The reason for different etch behavior of both PRs is the high oxygen content of 193 nm PR relative to that of 248 nm PR. Oxygen enhanced the etching rate of 193 nm PR during early plasma exposure when the surface roughness is introduced. Additional details on the relationship of the initial surface condition and formation of rough surface for PR materials will be discussed.
1X. Hua et al., J. Vac. Sci. Technol. B24(4)(2006)1850.
2G. S. Oehrlein, et al., J. Vac. Sci. Technol. B24(1)(2006)279.