6  US 8,637,222 B2  5  DESCRIPTION OF EMBODIMENTS  If desired, a commercially available inorganic or organic  antireflection film may be used. Furthermore, an antireflec› tion film may also be used as an underlying layer of the resist.  The composition is applied on such a substrate as used in  the production of a precision integrated circuit device (for  example, a silicon- or silicon dioxide-coated substrate) by an  appropriate coating method such as spinner and then dried to  form a photosensitive film.  For obtaining a negative chemical-amplification resist  composition film, respective components described later are  dissolved in a solvent, and the solution is filtered through a  filter, if desired, and then applied on a support (substrate). The  filter is preferably a polytetrafluoroethylene-, polyethylene› or nylon-made filter having a pore size of0.1 µm  or less, more  preferably 0.05 µm  or less, still more preferably 0.03 µm  or  less.  19. A crosslinkable negative chemical-amplification resist  composition for organic solvent development, which is used  in the resist pattern forming method described in any one of 1  to 17 above.  20. A resist pattern formed by the resist pattern forming  method described in any one of 1 to 17 above.  The negative chemical-amplification resist composition of  the present invention and a pattern forming method using the  same are described in detail below.  Incidentally, in the present invention, when a group  ( atomic group) is denoted without specifying whether substi› tuted or unsubstituted, the group includes both a group having  no substituent and a group having a substituent. For example,  "an alkyl group" includes not only an alkyl group having no  substituent (unsubstituted alkyl group) but also an alkyl group  having a substituent (substituted alkyl group).  In the present invention, the term "actinic ray" or "radia› tion" indicates, for example, a bright line spectrum of mer› cury lamp, a far ultraviolet ray typified by excimer laser, an  extreme-ultraviolet ray (EUV light), an X-ray or an electron  beam. Also, in the present invention, the "light" means an  actinic ray or radiation.  Furthermore, in the present invention, unless otherwise  indicated, the "exposure" includes not only exposure with a  mercury lamp, a far ultraviolet ray typified by excimer laser,  an X-ray, EUV light or the like but also lithography with a  particle beam such as electron beam and ion beam.  [Pattern Forming Method and Resist Pattern]  The mode of using the negative chemical-amplification  resist composition of the present invention is described  below.  The pattern forming method of the present invention com› prises, in the following order, (1) a step of forming a film by  using a negative chemical-amplification resist composition  capable of undergoing negative conversion by a crosslinking  reaction, (2) a step of exposing the film, and ( 4) a step of  developing the exposed film by using a developer containing  an organic solvent.  The term "negative conversion" as used herein means that  the molecular weight of the resin is increased by a crosslink- ing reaction to insolubilize the resin in a solvent (developer).  Also, the resist pattern of the present invention is formed by  the above-described pattern forming method of the present  invention.  An actinic ray or radiation is irradiated on the formed film  through a predetermined mask. Here, irradiation with an elec› tron beam is generally performed to draw a pattern without a  mask (direct lithography).  The actinic ray or radiation is not particularly limited, but  examples thereof include KrF excimer laser, ArF excimer  laser, EUV light and electron beam, with EUV light and  electron beam being preferred.  The exposed film is preferably baked (heated) before per› forming development.  The heating temperature is preferably from 80 to 150°  C.,  more preferably from 90 to 150°  C., still more preferably  from 100 to 140°  C.  The heating time is preferably from 30 to 300 seconds,  more preferably from 30 to 180 seconds, still more preferably  from 30 to 90 seconds.  The heating may be performed by normal means equipped  with an exposure/developing machine and may also be per› formed using a hot plate or the like.  The reaction of the exposed area is accelerated by the  baking and in turn, the sensitivity or pattern profile is  improved.  In the present invention, development is performed using a  developer containing an organic solvent.  Developer:  The organic solvent used for the developer is preferably an  organic solvent having a vapor pressure at 20°  C. of 5 kPa or  less, more preferably 3 kPa or less, still more preferably 2 kPa  or less. By setting the vapor pressure of the organic solvent to  5 kPa or less, evaporation of the developer on a substrate or in  a development cup is suppressed and the temperature unifor- mity in the wafer plane is enhanced, as a result, the dimen› sional uniformity in the wafer plane is improved.  As for the organic solvent used as the developer, various  organic solvents may be widely used but, for example, at least  one kind of a solvent selected from solvents such as ester› based solvent, ketone-based solvent, alcohol-based solvent,  amide-based solvent, ether-based solvent and hydrocarbon- based solvent may be used. Such a solvent is preferred par› ticularly when the later-described resin (A) containing a  repeating unit represented by formula (1) is used.  Above all, a developer containing at least one kind of a  solvent selected from a ketone-based solvent, an ester-based  solvent, an alcohol-based solvent and an ether-based solvent  is preferred.  Examples of the ester-based solvent include an alkyl car- boxy late-based solvent such as methyl acetate, butyl acetate,  ethyl acetate, isopropyl acetate, amyl acetate, ethyl-3-ethox› ypropionate, propylene glycol diacetate, 3-methoxybutyl  acetate, 3-methyl-3-methoxybutyl acetate, methyl formate,  ethyl formate, butyl formate, propyl formate, ethyl lactate,  butyl lactate and propyl lactate, and an alkylene glycol  monoalkyl ethercarboxylate-based solvent such as propylene  glycol monomethyl ether acetate (PGMEA; another name:  l-methoxy-2-acetoxypropane ), ethylene glycol monoethyl  ether acetate, diethylene glycol monobutyl ether acetate,  diethylene glycol monoethyl ether acetate and propylene gly› col monoethyl ether acetate. Among these, butyl acetate,  amyl acetate, ethyl lactate and propylene glycol monomethyl  ether acetate are preferred.  Examples of the ketone-based solvent include 1-octanone,  2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone,  1-hexanone, 2-hexanone, diisobutyl ketone, cyclopentanone,  cyclohexanone,  methylcyclohexanone,  phenylacetone,  (4) Development  (3) Baking  (2) Exposure  (1) Film Formation 