In the production process of semiconductor devices, such as IC and LSI, fine processing by lithography using a photoresist composition is carried out. Associated with the high integration of integrated circuits in recent years, formation of a super fine pattern in submicron region and quarter micron region has been demanded. According thereto, the exposure wavelength tends to become shorter from g-line to i-line, and further KrF excimer laser light. In these days, furthermore, lithography using an electron beam, X-ray and EUV light has been developed in addition to that using excimer laser light.
The lithography using an electron beam or EUV light is recognized as a pattern forming technique of the next generation or the generation after the next, and such a positive resist is demanded that has high sensitivity and high resolution. In particular, the high sensitivity is a significantly important demand for reducing the wafer processing time, but in the case where a positive resist for an electron beam or EUV light is pursued in sensitivity, not only the resolution is deteriorated, but also the line edge roughness is deteriorated. Therefore, there is a strong demand for development of a resist satisfying both of the factors simultaneously. The line edge roughness used herein means such a phenomenon that the edge between the resist pattern and the interface of a substrate is irregularly fluctuated in the direction perpendicular to the line direction due to the characteristics of the resist, whereby the edge of the pattern is fluctuated as viewed from the above. The fluctuation of the edge is transferred in the etching process using the resist as a mask, and thus the electric characteristics of the device are deteriorated to lower the yield thereof. In particular, improvement of the line edge roughness in the super fine region of 0.25 μm or less becomes an important problem. High sensitivity, high resolution, good pattern shape and good line edge roughness are in trade-off relationship, and it is an important problem to satisfy them simultaneously.
It is also an important problem that high sensitivity, high resolution, good pattern shape and good edge line roughness are simultaneously satisfied in the lithography using KrF excimer laser light, and solutions for the problems are demanded.
A chemically amplified resist utilizing an acid catalytic reaction has been mainly used as a resist suitable for a lithography process using KrF excimer laser light, an electron beam or EUV light, and such a chemically amplified resist composition is effectively used as a positive resist that contains as main components a phenolic polymer that is insoluble or slightly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by an action of an acid (hereinafter, abbreviated as a phenolic acid decomposable resin), and an acid generator.
As the positive resist, such a resist composition has been known that contains a phenolic acid decomposable resin obtained by copolymerizing an acid decomposable acrylate monomer, and a compound capable of generating sulfonic acid upon irradiation of actinic ray or radiation (hereinafter, abbreviated as a sulfonic acid generator). Examples of the aforementioned resist composition include positive resist compositions disclosed in Patent Documents 1 to 5.
However, it is the current situation that no combination thereof simultaneously satisfies high sensitivity, high resolution, good pattern shape and good line edge roughness in the super fine region.    Patent Document 1: U.S. Pat. No. 5,561,194    Patent Document 2: JP-A-2001-166474 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)    Patent Document 3: JP-A-2001-166478    Patent Document 4: JP-A-2003-107708    Patent Document 5: JP-A-2001-194792
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