and Process Control for

Lower Line Edge/Width roughness, high resolution, and superior EUVimaging quality, have been achieved using a novel class of chemically amplified resists. 25nm 1:1 line:space features in addition to sub-25nm overexposed lines have been patterned using standard coating and exposure procedures. Examining 1μm x 0.5μm windows of top-down SEM images revealed very promising LER and LWR values of 2.7nm and 4.3nm respectively, for 25nm features. This is the first chemically amplified resist to resolve 25nm 1:1 features indicating that diffusion blur can be overcome using the correct resist design approach. Such a high performance was retained even at film thickness as low as 30nm. The main factor that influenced its performance was the postexposure bake temperature; Relatively small variation affected dramatically the final resolution. The trade-off of the high resolution was the system’s high-activation energy however, current investigation into faster versions exhibiting similar resolution will be highlighted. The EUV exposures were performed using Interference Lithography (EUVIL) at the Swiss Light Source. This paper will focus on the lithographic optimization of these resists for EUV lithography 6517-45, Session 10 Patterning performance of new molecular resist in EUV lithography H. Oizumi, Y. Tanaka, T. Kumise, I. Nishiyama, Association of SuperAdvanced Electronics Technologies (Japan) At present, the development of high-quality EUV resists is the most critical issue in EUV lithography (EUVL) [1]. Considering resist materials, conventional polymeric chemically amplified (CA) resists have reached their performance limit [2]: The resolution is limited by acid diffusion, and the LER is too large due to the large molecules and compositional nonuniformity. A promising solution is molecular resists. A large number of them have been investigated in the search for a suitable one; but most have been found to exhibit the fatal problem of severe pattern collapse. We reported the EUV patterning performance of a chemically amplified positive-tone resist based on a low-molecular-weight partially-protected polyphenol, namely, 4,4'-methylenebis [2-[di(2,5-dimehtyl-4hydroxyphenyl)methyl]phenol (25X-MBSA-P) [3]. It exhibits a high contrast, a resolution of 30 nm at an exposure dose of 10 mJ/cm2, and a low LER of 6 nm (3σ) at an inspection length of 2000 nm. Unfortunately, it suffers from severe pattern collapse in dense fine-pitch patterns [3]. In this work, we designed and synthesized a new partially-protected polyphenol for which the position of the protected hydroxyl group in 25XMBSA-P has no dispersion, and evaluated its EUV patterning performance. Imaging experiments were carried out with a highnumerical-aperture (NA=0.3), small-field EUV exposure tool (HINA) using coherent illumination (σ = 0.0) [4]. The illumination system consists of two flat mirrors, and also a spherical mirror that focuses the image of the EUV light source on a point at the pupil of the projection optics. The advantage of this system is that the image contrast is higher than that obtainable with partially coherent illumination. The light source was synchrotron radiation (SR) on the SBL-1 beamline of Super-ALIS at NTT [5]. An EUV mask with an 80-nm-thick TaGeN absorber and a 10-nmthick-Cr buffer layer was fabricated to replicate dense sub-30-nm patterns [6]. This advanced CA polyphenol molecular resist does not exhibit serious pattern collapse. Moreover, it provides a resolution of less than 30 nm at an exposure dose of 12 mJ/cm2, a high aspect ratio of 2, and a low LER of 5 nm (3σ) at an inspection length of 2000 nm. This performance is equal to that of the best CA polymeric resist currently available. The authors would like to thank Dai Nippon Printing Co., Ltd. for fabricating the masks, and Tokyo Ohka Kogyo Co., Ltd. for preparing the resists. The authors are also grateful to Mr. Murakami, Mr. T. Oshino, and Mr. K. Mashima of Nikon Corporation for useful discussions; the HINA set-3 optics were developed and provided by Nikon. This work was supported by NEDO. [1]. K. Kemp, presented at the 4th International EUV Symposium, 7-9 November, 2005, San Diego. [2]. W. Hinsberg et al., Proc. SPIE 5039 (2003) 1. [3]. H. Oizumi, et al., Microelectron. Eng. 83 (2006) 1107. [4]. H. Oizumi et al., Proc. SPIE Vol. 5751 (2005) 102. [5]. T. Hosokawa et al., Rev. Sci. Instrum. 60 (1989)1783. [6]. Y. Tanaka et. al., Proc. Vol. SPIE 5567 (2004) 1377.