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. 

## (1) Film Formation 

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. 

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. 

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. 

## DESCRIPTION OF EMBODIMENTS 

## (2) Exposure 

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. 

## (3) Baking 

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. 

## (4) Development 

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, 

