In a general way, non-CARs consist of the matrix resins and photoactive compounds (PACs), and the dissolution properties of the resists are dependent on the amount of PACs. In common, I-line and G-line resists based on novolac and diazonaphthoquinone (DNQ) are typical non-CARs. But most PACs absorb much light in the deep UV, and they are poorly photobleached by deep UV exposure. This strong absorption of PACs prevents the deep UV light from reaching the bottom of the resist film, leading to scum and sloped pattern profiles. Several PACs which contain diazoketo groups have been reported for deep UV lithography. Our goal in this investigation is to find a proper resist that is processable without photoacid generator and induces both photobleaching in the deep UV regions and polarity change upon exposure. We thought diazoketo groups attached to the polymer side chains could give such effects. There is no necessity for the post-exposure bake step that is the cause of acid-diffusion. The diazoketo groups undergo the Wolff rearrangement upon irradiation in the deep UV, affording ketenes that react with water to provide base soluble photoproducts. The polymers were synthesized by radical copolymerization of 2-(2-diazo-3-oxo-butyryloxy)-ethyl methacrylate, 2-hydroxyethyl methacrylate, and γ-butyrolacton-2-yl methacrylate. The single component resist showed 0.7μm line and space patterns using a mercury-xenon lamp in a contact printing mode.
A novel nanomolecular resist based on POSS substituted with diazodiketo-functionalized cholate derivatives was successfully synthesized as a candidate for 193-nm lithography. The diazodiketo group was introduced into the cholate derivatives to provide the solubility change and to eliminate the problems of chemically amplified resists. The decomposition temperature of the resist was found to be 130°C. The initial lithographic studies showed the feasibility of the resist to be used as a candidate for 193-nm lithography.
We synthesized a new type of polymers that have diazoketo groups instead of acid-labile protecting groups. The polymers do not need a photoacid generator for formulation of resists. That is, the new matrix polymers absorb UV light and produce carboxylic groups. Also, there is no necessity for a post-exposure bake step, which is the cause of post-exposure delay effects. New monomer, ethyl 2-diazo-4-methyl-3-oxo-pent-4-enoate was synthesized. This monomer was copolymerized with hydroxystyrene and adamantyl methacrylate. After UV exposure, the polymers became soluble in an aqueous base developer. The polymers showed bleaching effect after UV exposure. Thermal properties of the polymers were measured by TGA and DSC. Characterization of the polymers has been done using other techniques such as FT-IR, NMR, GPC, and UV. The resist patterns of 0.8 μm feature size were resolved using a DUV contact printer and with a tetramethylammonium hydroxide aqueous solution.
We synthesized a new type of norbornene-maleic anhydride copolymer which as diazoketo groups instead of acid labile protecting groups. The matrix polymer does not need a photoacid generator for the lithographic evaluation. And there is no necessity for the post-exposure bake step that is the cause of PED effects. Methyl 5-norbornenyl-3-oxopropionate was prepared by the reaction of acetyl norbornene with dimethyl carbonate in the presence of sodium hydride. And methyl 5-norbornenyl-2-diazo-3-oxopropionate was synthesized from the reaction between methyl 5-norbornenyl-3-oxopropionate and p-carboxybenzenesulfonyl azide. The polymer was prepared by free radical polymerization. Upon exposure to DUV light, diazoketo groups undergo a series of reactions that culminate in the formation of a carboxylic acid. The matrix polymer in the exposed region becomes soluble in the aqueous base developer. The polymer showed bleaching effect after exposure. Thermal stability of the polymer is measured by TGA and DSC. Characterization of the polymer is achieved using other techniques such as FT-IR, NMR, GPC, and UV. The resist patterns of 0.6 μm feature size were resolved using a KrF exposure tool and with a conventional developer, 2.38 wt% TMAH aqueous solution.