US 2019/0219920 Al  60  Jul.  18,  2019  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  [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  [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.  [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.  [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.  [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).  [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.  [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).  [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.  [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.  glass. Suitable materials for the wmng pattern include  copper, aluminum, nickel, and gold. 