be suppressed. In addition, partial dissolution of pattern boundary portions may also be suppressed. Furthermore, by virtue of the acid dissociable group containing a polar group, the affinity for an alkali developing solution may be improved. Therefore, in an alkali developing process, by virtue of the solubility in an alkali developing solution being improved, developing may be proceeded more uniformly and more smoothly. 

[0537] Due to such effects as described above, in the formation of a resist pattern using the resist composition of the present embodiment, various lithography properties such as critical dimension uniformity (CDU) and circularity may be improved, and a resist pattern having a good shape may be formed. 

[0538] (Second Aspect: Method of Forming Resist Pat› tern) 

[0539] The method of forming a resist pattern according to the present embodiment includes: forming a resist film on a substrate using a resist composition of the first aspect; conducting exposure of the resist film; and developing the resist film to form a resist pattern. 

[0540] The method for forming a resist pattern according to the present embodiment may be performed, for example, as follows. 

[0541] Firstly, a resist composition of the present embodi› ment is applied to a substrate using a spinner or the like, and a bake treatment (post applied bake (PAB)) is conducted at a temperature of 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film. 

[0542] Following selective exposure of the thus formed resist film, either by exposure through a mask having a predetermined pattern formed thereon (mask pattern) using an exposure apparatus such as anArF exposure apparatus, an electron beam lithography apparatus or an EUV exposure apparatus, or by patterning via direct irradiation with an electron beam without using a mask pattern, baking treat› ment (post exposure baking (PEB)) is conducted under temperature conditions of 80 to 150° C. for 40 to 120 seconds, and preferably 60 to 90 seconds. 

[0543] Next, the resist film is subjected to a developing treatment. The developing treatment is conducted using an alkali developing solution in the case of an alkali developing process, and a developing solution containing an organic solvent ( organic developing solution) in the case of a solvent developing process. 

[0544] After the developing treatment, it is preferable to conduct a rinse treatment. The rinse treatment is preferably conducted using pure water in the case of an alkali devel› oping process, and a rinse solution containing an organic solvent in the case of a solvent developing process. 

[0545] In the case of a solvent developing process, after the developing treatment or the rinsing, the developing solution or the rinse liquid remaining on the pattern can be removed by a treatment using a supercritical fluid. 

[0546] After the developing treatment or the rinse treat› ment, drying is conducted. If desired, bake treatment (post bake) can be conducted following the developing. 

[0547] In this manner, a resist pattern can be formed. 

[0548] The substrate is not specifically limited and a conventionally known substrate can be used. For example, substrates for electronic components, and such substrates having wiring patterns formed thereon can be used. Specific examples of the material of the substrate include metals such as silicon wafer, copper, chromium, iron and aluminum; and 

glass. Suitable materials for the wmng pattern include copper, aluminum, nickel, and gold. 

[0549] Further, as the substrate, any one of the above› mentioned substrates provided with an inorganic and/or organic film on the surface thereof may be used. As the inorganic film, an inorganic antireflection film (inorganic BARC) can be used. As the organic film, an organic anti› reflection film ( organic BARC) and an organic film such as a lower-layer organic film used in a multilayer resist method can be used. 

[0550] Here, a "multilayer resist method" is method in which at least one layer of an organic film (lower-layer organic film) and at least one layer of a resist film (upper resist film) are provided on a substrate, and a resist pattern formed on the upper resist film is used as a mask to conduct patterning of the lower-layer organic film. This method is considered as being capable of forming a pattern with a high aspect ratio. More specifically, in the multilayer resist method, a desired thickness can be ensured by the lower› layer organic film, and as a result, the thickness of the resist film can be reduced, and an extremely fine pattern with a high aspect ratio can be formed. 

[0551] The multilayer resist method is broadly classified into a method in which a double-layer structure consisting of an upper-layer resist film and a lower-layer organic film is formed ( double-layer resist method), and a method in which a multilayer structure having at least three layers consisting of an upper-layer resist film, a lower-layer organic film and at least one intermediate layer (thin metal film or the like) provided between the upper-layer resist film and the lower› layer organic film (triple-layer resist method). 

[0552] The wavelength to be used for exposure is not particularly limited and the exposure can be conducted using radiation such as ArF excimer laser, KrF excimer laser, F $_{2 }$ excimer laser, extreme ultraviolet rays (EUV), vacuum ultraviolet rays (VlN), electron beam (EB), X-rays, and soft X-rays. The resist composition of the present invention is effective to KrF excimer laser, ArF excimer laser, EB and EUV, and particularly effective to ArF excimer laser, EB and EUV. 

[0553] The exposure of the resist film can be either a general exposure ( dry exposure) conducted in air or an inert gas such as nitrogen, or immersion exposure (immersion lithography). 

[0554] In immersion lithography, the region between the resist film and the lens at the lowermost point of the exposure apparatus is pre-filled with a solvent (immersion medium) that has a larger refractive index than the refractive index of air, and the exposure (immersion exposure) 1s conducted in this state. 

[0555] The immersion medium preferably exhibits a refractive index larger than the refractive index of air but smaller than the refractive index of the resist film to be exposed. The refractive index of the immersion medium is not particularly limited as long as it satisfies the above› mentioned requirements. 

[0556] Examples of this immersion medium which exhib› its a refractive index that is larger than the refractive index of air but smaller than the refractive index of the resist film include water, fluorine-based inert liquids, silicon-based solvents and hydrocarbon-based solvents. 

[0557] Specific examples of the fluorine-based inert liq› uids include liquids containing a fluorine-based compound such as C$_{3}$HC1$_{2}$F$_{5}$ , C$_{4}$F$_{9}$OCH$_{3}$ , C$_{4}$ F$_{9}$OC$_{2}$H$_{5 }$ or C$_{5}$ H$_{3}$ F$_{7 }$ as 

