The planarization, that is leveling, of 1–4 μm thick liquid epoxy films over 25–200 μm wide isolated trenches on a silicon substrate during spin coating is determined by photochemically hardening the film and measuring the film profiles over the trenches with a profilometer. The profiles are quantitatively described by a simple lubrication theory that takes advantage of the thinness of the film compared to the feature width, the narrowness of the feature width compared with the distance of the feature from the substrate center, and the rapidity of change in the film profile compared to the overall rate of centrifugally driven film thinning. For a fixed ratio of film thickness to trench depth hf/d, the experimental data fall on a single curve when planarization is plotted against a dimensionless parameter Ω2≡ρω2w3r0/γhf, where ρ is the density of the liquid film, ω is the substrate angular velocity, w is the trench width, r0 is the radial position of the trench, and γ is the film surface tension. For a fixed value of Ω2, planarization improves with decreasing hf/d ratios. Theoretical planarization versus Ω2 curves agree reasonably well with the experimental data. Data for a positive photoresist film form a similar curve to that formed by the epoxy data, but at lower planarization values because of spinning solvent evaporation that causes film shrinkage and degradation of planarization. The effects of evaporation can be accounted for by dividing the spin-coating process into two stages. In the first the film remains fluid and the profile equilibrates with the overall film thickness. In the second the film is immobile and thins only by evaporation.

The leveling of 100–500-μm-wide, 1-μm-deep isolated holes and trenches on a silicon substrate by 1–3-μm-thick silicone oil films was observed by measuring film thickness changes at the centers of the features using a noncontact, interferometric technique. The dependence of the leveling time t on feature width w, film viscosity η, and the initial film thickness h0 was investigated and compared to theoretical predictions. Experimental data were obtained for various values of w, η, and h0. Except when the film thickness was about 1 μm, the data for each different type of geometry fell on a single curve when the degree of leveling or planarization was plotted against T≡tγh30/ηw4 where γ is the surface tension of the film. At the same value of T, the degree of planarization of isolated holes was about twice that of isolated trenches. The planarization versus T curves should apply to all Newtonian liquids and may be used to predict the degree of planarization that will be achieved at specified leveling times by materials having specified values of η, h0, and γ. Thus, the curves may be useful in selecting planarizing materials for semiconductor fabrication steps that require substrate topography leveling. Simulations of the leveling process based on capillarity-driven flow were performed and agreed well with the experimental data. The simulations predicted some interesting and unexpected behavior that was observed experimentally. At short times the planarization became worse before improving at longer times and bumps appeared in the film profiles that apparently were a first step in minimizing surface energy. Such simulations may prove to be useful in predicting the difficulty of planarizing various types of topographic geometries and in designing ‘‘dummy topography’’ that will make them easier to planarize.

The results of a study of topographic substrate planarization with films applied by a spin-coating process are reported. It is shown that spin coating produces conformal film profiles over topographic gaps on the substrate that are wider than about 50 ~tm and that leveling of these gaps can only occur after spinning ceases if the film is able to flow over large distances. A comparison of the maj or forces acting on the film leads to the conclusion that the flow is driven primarily by capillarity when the width of the gap is less than 5000 ~m. A theory is developed that relates the time required to level the gaps to their width and to the thickness and viscosity of the film. The results of experiments performed to test the theory are presented and discussed. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 142.58.129.109 Downloaded on 2015-03-16 to IP Vol. 134,No. 8

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In this paper we describe the synthesis, properties and lithographic behavior of a new class of chemically amplified, positive-tone, aromatic methacrylate resists incorporating the tetrahydropyranyl protecting group bound to base-solubilizing carboxylic acid moieties. Copolymers containing equimolar amounts of benzyl methacrylate and tetrahydropyranyl methacrylate were prepared by free-radical and group-transfer polymerization (GTP). Photogenerated sulfonic acids formed from covalent ester or ionic salt precursors were used t o remove the acid-labile tetrahydropyranyl (THP) group by heating after exposure. The resulting copolymers of benzyl methacrylate (BMA) and methacrylic acid (MAA) are extremely soluble in aqueous base solutions when the MAA concentration exceeds 35 mol %, thus affording positive tone patterns. This class of resins has low absorbance at 248 nm needed for patterning 21-pm-thick films. The moderate THP group concentration and its relatively small size minimize shrinkage during thermal and plasma processing. The nearly monodisperse polymers formed by GTP offer the advantages of better molecular weight control and the opportunity to study the effect of molecular weight distribution on this class of resists. We have studied these copolymer resists and find them to have high sensitivity (<30 mJ/cm2) when formulated with aromatic sulfonate or trifluoromethyl sulfonate sensitizers. Contrast is greater than 2, and submicrometer patterns in 1-rm-thick films are resolved. Resolution is significantly influenced by the sensitizer, postexposure heating, and development conditions. Resolution presently is limited by resist adhesion which remains to be optimized. Plasma etching resistance to conditions used to etch Al is 1.8 times less than for hard-baked HPR-206 photoresist but can be improved to a value of 1.5 by postexposure thermolysis. Improvements are needed before this type of chemically-amplified resist is able to meet all deep-UV lithographic requirements. 0 (1) Ito, H.; Willson, C. G. (4) Pol, V.; Bennewitz, J. H.; Esher, G. C.; Feldman, M.; Firtion, V. A.; Jewell, T. E.; Wilcomb, B. E.; Clemens, Heap, S. M. A.; Ueno, T.; Toriumi, M.; Nonogaki, S.