| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuA |
| Session: | Fundamentals of Plasma-Surface Interactions I |
| Presenter: | R.L. Bruce, University of Maryland |
| Authors: | F. Weilnboeck, University of Maryland R.L. Bruce, University of Maryland G.S. Oehrlein, University of Maryland M. Li, Dow Electronic Materials D. Wang, Dow Electronic Materials D.B. Graves, University of California, Berkeley D.G. Nest, University of California, Berkeley T.-Y. Chung, University of California, Berkeley E.A. Hudson, Lam Research Corp. |
| Correspondent: | Click to Email |
Plasma processes used for pattern transfer of nanometer structures can lead to severe material modification and roughness development of photoresist (PR) materials. We studied the temporal evolution of blanket and patterned films of fully formulated 193nm PR in Ar and Ar/C4F8 plasma discharges. The contribution of the optical radiation component to the overall material modification seen after direct plasma exposure was investigated by applying a filter approach which protects the PR against ion bombardment and neutral deposition. Different filter materials allow testing the influence of emission spectra and wavelength ranges of the plasma radiation from visible to vacuum ultraviolet (VUV) light. Material modifications were characterized by ellipsometry, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy and scanning electron microscopy. In-situ ellipsometry, employing a setup which enables separation of the optical radiation component and other plasma components, enabled to investigate in real time PR degradation effects during plasma processing. The depth dependence of PR degradation was obtained by optical multilayer ellipsometric simulations of the data.
For the plasma discharge chemistries examined, the material modifications depended strongly on PR molecular structure, exposure radiation wavelength range and plasma chemistry. Material degradation was increased for increasing photon energy, and lead to substantial oxygen loss at the PR surface and in the PR bulk. The material modification depth showed a significant dependence on the emission spectrum of the plasma discharge. The amount of oxygen lost in the material bulk was found to directly correlate with a reduction in PR film thickness. Results indicate that compared to the pure Ar discharge (main emission at 104 and 106nm) material bulk modifications are significantly higher for Ar/C4F8 discharges (main emission above 130nm [1]) leading to PR film thickness reduction of up to 20nm. Whereas ion bombardment modified the PR to a depth of ~ 1nm for our conditions during the first few seconds of plasma exposure and then saturated, plasma radiation modified the PR near-surface region to a depth of several tens of nm over a period of tens of seconds.
[1] Woodworth, J.R., et al., Absolute intensities of the vacuum ultraviolet spectra in oxide etch
plasma processing discharges, JVST A, 2001, 19(1)