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The goal or this work has been to study candidate fluorocarbon materials that might serve as platforms from which to design 157nm resists. A specific goal of the work has been to identify transparent candidate materials that might provide a polymer backbone and acceptable etch resistance. Several model compounds were synthesized and their vacuum UV spectra were measured in the gas phase.Substituted norbornane (bicyclo[2.2.1]heptane) was of significant interest in this regard because we had used this structure successfully in the design systems for 193nm exposure. Surprisingly, 2-monofluoronorbornane is unstable and undergoes spontaneous dehydrohalogenation upon exposure to glass in vacuo. However, 2,2-substitution with fluorine and with other electron withdrawing groups such as trifluoromethyl and even carbonyl groups gives norbornyl derivatives with greatly improved transparency at 157nm. These observations led to the design a variety of novel norbornenes that can be polymerized by metal catalyzed addition polymerization to give etch resistant polymer platforms with greatly improved transparency at 157nm and led to the study of acrylic co-polymers derived from 2-(trifluoromethyl)acrylic acid.

Directed Self-Assembly (DSA) of block copolymers is considered to be a potential lithographic solution to achieve higher feature densities than can be obtained by current lithographic techniques. However, it is still not well-established how amenable DSA of block copolymers is to an industrial fabrication environment in terms of defectivity and processing conditions. Beyond production-related challenges, precise manipulation of the geometrical and chemical properties over the substrate is essential to achieve high pattern fidelity upon the self-assembly process. Using our chemo-epitaxy DSA approach offers control over the surface properties of the slightly preferential brush material as well as those of the guiding structures. This allows for a detailed assessment of the critical material parameters for defect reduction. The precise control of environment afforded by industrial equipment allows for the selective analysis of material and process related boundary conditions and assessment of their effect on defect generation.In this study, the previously reported implementation of our feature multiplication process was used to investigate the origin of defects in terms of the geometry of the initial pre-patterns. Additionally, programmed defects were used to investigate the ability of the BCP to heal defects in the resist patterns and will aid to assess the capture capability of the inspection tool. Finally, the set-up of the infrastructure that will allow the study the generation of defects due to the interaction of the BCP with the boundary conditions has been accomplished at imec.

Many semiconductor device manufacturers plan to make products with 157 nm lithography beginning in 2004. There is, at this time, no functional photoresist suitable for 157 nm exposure. Developing resist materials for 157 nm lithography is particularly challenging since water, oxygen, and even polyethylene are strongly absorbing at this wavelength. A modular approach to the design of a single layer resist for 157 nm has been undertaken. In this approach, the resist has been conceptually segmented into four functional modules: an acidic group, an acid labile protecting group, an etch resistant moiety, and a polymer backbone. Each of these modules has an assigned function and each must be transparent at 157 nm. Progress has been made toward finding candidate structures for each of these modules. We have demonstrated that acidic bistrifluoromethylcarbinols are very transparent at 157 nm and function efficiently in chemically amplified resists with both high and low activation energy protecting groups. Judicious incorporation of fluorine in acrylates and alicyclics has provided etch resistant polymers with greatly improved transparency at 157 nm. In particular, esters of poly͑␣-trifluromethylacrylic acid͒ are far more transparent than their protio analogs. The Diels-Alder adducts derived from reaction of these and other fluorinated alkenes with cyclopentadiene offer a route to a wide range of alicyclic monomers that show great promise as transparent, etch resistant platforms for the design of 157 nm resists. Polymers of this sort with absorbance below 2 per micrometer are reported.

The selective deposition of polymer thin films can be achieved via spin coating by manipulating interfacial interactions. While this “spin dewetting” approach sometimes generates spatial localization on topographic and chemical patterns, the connection between material selection, process parameters, and resulting film characteristics remains poorly understood. Here, we demonstrate that accurate control over these parameters allows incomplete trichlorosilane self-assembled monolayers (SAMs) to induce spin dewetting on both homogeneous (SiO2) and heterogeneous (Cu/SiO2 or TiN/SiO2) surfaces. Glassy polymers undergo a sharp transition from uniform wetting to complete dewetting depending on spin speed, solution concentration, polymer molecular weight, and SAM chemistry. Under optimal conditions, spin dewetting on line–space patterns results in the selective deposition of polymer over regions not functionalized with SAM. The insights described herein clarify the importance of different variables involved in spin dewetting and provide access to a versatile strategy for patterning polymeric thin films.

Finding materials that offer the all ofthe characteristics required ofphotoresist matrix resin polymers while trying to maintain a high level oftransparency at 157 nm is a daunting challenge. To simplify this task, we have broken the design of these polymers down into subunits, each of which is responsible for a required function in the final material. In addition, we have begun collecting gas-phase VUV spectra of these potential subunits to measure their individual absorbance contributions. Progress on developing materials for each ofthese subunits are presented along with plans for future studies.

Top surface imaging systems based on vapor phase silylation have been investigated for use at a variety of wavelengths. This approach to generating high aspect ratio, high resolution images held great promise particularly for 193 nm and EUV lithography applications. Several 193 nm top surface imaging ͑TSI͒ systems have been described that produce very high resolution ͑low k factor͒ images with wide process latitude. However, because of the line edge roughness associated with the final images, TSI systems have fallen from favor. In fact, TSI does not appear in the strategy or plan for any imaging technology at this time. Most of the 193 nm TSI systems that have been studied are based on poly͑p-hydroxystyrene͒ resins. These polymers have an unfortunate combination of properties that limit their utility in this application. These limiting properties include ͑1͒ high optical density, ͑2͒ poor silylation contrast, and ͑3͒ low glass transition temperature of the silylated material. These shortcomings are related to inherent polymer characteristics and are responsible for the pronounced line edge roughness in the poly͑p-hydroxystyrene͒ systems. We have synthesized certain alicyclic polymers that have higher transparency and higher glass transition temperatures. Using these polymers, we have demonstrated the ability to print high resolution features with very smooth sidewalls. This article describes the synthesis and characterization of the polymers, their application to top surface imaging at 193 nm, and the analysis that was used to tailor the processing and the polymer's physical properties to achieve optimum imaging.

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