159  US 9,063,416 B2  160  2.42 – 0.10  3.55 – 0.10  0  HO  II  ~OH  3.74 – 0.11  0  HO~OH  4.39 – 0.10  4.39  –  0.10  4.86  –  0.20  -continued  <<Method of Forming a Resist Pattern>>  The method of forming a resist pattern according to the  present invention includes: forming a resist film on a substrate  using a resist composition of the present invention; conduct› ing exposure of the resist film; and developing the resist film  to form a resist pattern.  The method for forming a resist pattern according to the  present invention can be performed, for example, as follows.  Firstly, a resist composition of the present invention is  applied to a substrate using a spinner or the like, and a bake  treatment (post applied bake (PAB)) is conducted at a tem› perature of80 to 150°  C. for 40 to 120 seconds, preferably 60  to 90 seconds, to form a resist film.  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, a KrF 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  treatment (post exposure baking (PEB)) is conducted under  temperature conditions of80 to 150°  C. for 40 to 120 seconds,  and preferably 60 to 90 seconds.  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 pro› cess, whereas the developing treatment is conducted using a  developing solution containing an organic solvent ( organic  developing solution) in the case of a solvent developing pro› cess.  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 developing process,  whereas the rinse treatment is preferably conducted using a  rinse solution containing an organic solvent in the case of a  solvent developing process.  In the case of a solvent developing process, after the <level- oping 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.  After the developing treatment or the rinse treatment, dry› ing is conducted. If desired, bake treatment (post bake) can be  conducted following the developing. In this manner, a resist  pattern can be obtained.  Specific examples of the fluorine-based inert liquids  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 the main  component, which have a boiling point within a range from 70  Examples of this immersion medium which exhibits 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.  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 at it satisfies the above-mentioned require› ments.  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) is conducted in  this state.  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 (liquid immersion lithog› raphy).  The wavelength to be used for exposure is not particularly  limited and the exposure can be conducted using radiations  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.  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) pro› vided between the upper-layer resist film and the lower-layer  organic film (triple-layer resist method).  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 thick› ness 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.  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 antireflection film ( organic  BARC) and an organic film such as a lower-layer organic film  used in a multilayer resist method can be used.  The substrate is not specifically limited and a convention› ally 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 wiring pattern include copper, aluminum,  nickel, and gold. 