| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS2-FrM |
| Session: | Plasma Surface Interactions II |
| Presenter: | Makoto Sekine, Nagoya University, Japan |
| Authors: | Y. Zhang, Nagoya University, Japan M. Sekine, Nagoya University, Japan K. Ishikawa, Nagoya University, Japan K. Takeda, Nagoya University, Japan H. Kondo, Nagoya University, Japan M. Hori, Nagoya University, Japan |
| Correspondent: | Click to Email |
For highly precise patterning technologies in device fabrication, it is required to suppress roughness formations on photoresist (PR) polymers during plasma etching processes. The HBr plasma treatment called ‘plasma cure’ was proposed to reduce the roughness formation [1]. In the previous studies, by using a beam irradiation system, we reported the PR roughness formation in fluorocarbon plasma [2], and the effect on roughness suppression by HBr plasma cure [3]. In this report, we have extensively investigated the roughness formation mechanism on the PR for ArF photolithography by some surface analyses and power spectral density (PSD) of the roughness.
The photoresist roughness observed by the atomic force microscope (AFM) is characterized by two dimensional (2D) PSDs and the frequency distribution for a digitized height profile [4]. Average slope and roll-off frequency of PSD are characterized by frequency components, the high-frequency roughness [5]. We treated the roughness data for six samples: (a) initial (pristine), (b) after Ar plasma beam irradiation (Ar), (c) after Ar plasma beam irradiation followed by HBr plasma cure (Ar→HBr), (d) after HBr plasma cure (HBr), (e) after HBr followed by Ar plasma beam irradiation (HBr→Ar), and (f) after HBr followed by H2 plasma beam and Ar plasma beam irradiation (HBr→H2→Ar).
The PSD slopes were changed by each process. The Ar plasma beam irradiation affected higher-frequency roughness, i.e. fine roughness induced on the PR surface. Thus the ion bombardments affected the local fine roughness. In particular for (e), Ar irradiation after HBr cure, the higher-frequency roughness could be reduced. This indicates that the HBr cure possibly hardened the PR surface by crosslinking polymeric chains, and the behavior was observed apparently on the decrease of roll-off frequency. On the other hand, the HBr cure after Ar irradiation, (c), increased lower frequency components of roughness compared with just Ar plasma beam irradiation, (b). We speculated that the Ar-plasma beam formed a crust layer on the PR surface with unrelieved stress and HBr cure may soften the bulk PR to relieve the stress and cause agglomeration of polymers at the size over 10 nm.
References
[1] A. Ando et al., Thin Solid Films 515, 4928 (2007).
[2] T. Takeuchi et al., J. Phys. D: Appl. Phys. 46, 102001 (2013).
[3] Y. Zhang et al., 74th Japan Society of Applied Physics Meeting, 17a-C2-7 (2013).
[4] diNanoScope Software 7.0 User Guide. Veeco Instruments Inc., pp. 163 (2006).
[5] B. N. J. Persson et al., J. Phys.: Condens. Matter, 17 R58 (2005).