Negative-working photoresist composition

#The present invention relates to a negative-working photoresist composition or, more particularly, to a chemical-amplification negative-working photoresist composition suitable for use in the photolithographic patterning works in the manufacture of various electronic devices, which has high transparency to the ArF excimer laser beams for pattern-wise exposure and is capable of giving a finely patterned resist layer with high pattern resolution along with little swellability of the resist layer in the developer solution and excellently orthogonal cross sectional profile of the patterned resist layer.

#As is disclosed in Japanese Patent Publication 8-3635 and elsewhere, the basic formulation of a chemical-amplification negative-working photoresist composition is known, which comprises a radiation-sensitive acid-generating agent, an alkali-soluble resin such as novolak resins, polyhydroxy-styrene resins and the like and an amino resin such as melamine resins, urea resins and the like in combination and in which the alkali-soluble resinous ingredient in the exposed areas of the resist layer is rendered alkali-insoluble in the presence of the acid generated from the acid-generating agent. Namely, a crosslinking reaction proceeds between the alkali-soluble resin and the amino resin by interacting with the acid generated by irradiation with actinic rays to form a pattern-wise latent image of the alkali-insolubilized resin which is developed with an alkaline developer solution to dissolve away the resist layer in the unexposed areas leaving a negatively patterned resist layer in the exposed areas.

#The chemical-amplification negative-working photoresist composition of the above described type comprising an acid-generating agent, alkali-soluble resin and amino resin is quite satisfactory for use in the photolithographic process in which the exposure light is the i-line ultraviolet light or KrF excimer laser beam of 248 nm wavelength. As a trend in recent years, however, it is desired to employ an exposure light of a shorter wavelength such as ArF excimer laser beams in order to comply with the requirement for finer and finer patterning in the manufacture of semiconductor devices of higher degrees of integration, for which the photoresist composition of the above described type cannot be quite satisfactory.

#A negative-working photoresist solution was prepared by dissolving 100 parts of the Polymer 1 prepared in Preparation 1 and 3 parts of triphenylsulfonium trifluoromethanesulfonate in 670 parts of propyleneglycol monomethyl ether.

#A semiconductor silicon wafer was coated with this photoresist solution by using a spinner followed by a drying and pre-baking treatment for 90 seconds on a hot plate at 120° C. to form a photoresist layer having a thickness of 0.5 μm. The photoresist layer was pattern-wise exposed to ArF excimer laser beams of 193 nm wavelength on an ArF exposure machine (manufactured by Nikon Co.) followed by a post-exposure baking treatment at 150° C. for 30 minutes and then subjected to a puddle development treatment at 23° C. for 65 seconds with a 2.38% by weight aqueous solution of tetramethylammonium hydroxide followed by rinse for 30 seconds with water and drying.

#The exposure dose with the ArF excimer laser beams was taken as a measure of the photosensitivity of the photoresist composition to find that a patterned resist layer of good quality having a line width of 0.50 μm could be obtained with an exposure dose of 100 mJ/cm2. The patterned resist layer was free from swelling as examined on a scanning electron microscopic photograph for the cross sectional profile of the patterned resist layer.