High Resolution Resists for Next Generation Lithography: The Nanocomposite Approach
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High Resolution Resists for Next Generation Lithography: The Nanocomposite Approach
Kenneth E. Gonsalves, Hengpeng Wu, Yongqi Hu, and Lhadi Merhari* Polymer Program at the Institute of Materials Science & Department of Chemistry University of Connecticut, Storrs, CT 06268, USA, [email protected] *CERAMEC R&D, F-87000, Limoges, France, [email protected] ABSTRACT The SIA roadmap predicts mass production of sub-100 nm resolution circuits by 2006. This not only imposes major constraints on next generation lithographic tools but also requires that new resists capable of accommodating such a high resolution be synthesized and developed concurrently. Except for ion beam lithography, DUV, X-ray, and in particular electron beam lithography suffer significantly from proximity effects, leading to severe degradation of resolution in classical resists. We report a new class of resists based on organic/inorganic nanocomposites having a structure that reduces the proximity effects. Synthetic routes are described for a ZEP520/nano-SiO2 resist where 47nm wide lines have been written with a 40 nm diameter, 20 keV electron beam at no sensitivity cost. Other resist systems based on polyhedral oligosilsesquioxane copolymerized with MMA, TBMA, MMA and a proprietary PAG are also presented. These nanocomposite resists suitable for DUV and electron beam lithography show enhancement in both contrast and RIE resistance in oxygen. Tentative mechanisms responsible for proximity effect reduction are also discussed.
INTRODUCTION Within the next decade the microelectronic industry will require a lithographic process capable of mass-producing integrated circuits with sub-70 nm critical dimensions (CD) [1]. This formidable challenge is unlikely to be achieved by evolutionary steps. Extreme UV, X-ray, electron beam and ion beam lithography therefore have become more promising candidates for next generation nanofabrication, as it is widely accepted that the shorter the radiation wavelength the finer the theoretical resolution. Although it is uncertain which exposing tools will prevail, it is imperative to design and synthesize new resist materials to meet the specific requirements for individual exposing tools. Over the past decades, many different kinds of resist materials have been investigated [2, 3]. Among these, two types of resists have received special attention: chain-scission resists developed primarily for e-beam lithography, and chemically amplified (CA) resists designed for both photo and e-beam lithographies. Although significant progress has been achieved in the design and preparation of new resists, much remains to be accomplished. A few critical issues, frequently encountered in designing new resists, are addressed here:
½ Proximity effect for e-beam resists: among all the lithographic technologies for sub-100 nm patterning, electron beam lithography (EBL) is considered one of the mainstreams for next generation lithography (NGL) as it is probably the most versatile technique benefiting from D6.5.1
major R&D knowledge a
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