component, which have a boiling point within a range from 70 to 180° C. and preferably from 80 to 160° C. A fluorine-based inert liquid having a boiling point within the above-men› tioned range is advantageous in that the removal of the immersion medium after the exposure can be conducted by a simple method. 

[0996] As a fluorine-based inert liquid, a perfluoroalkyl compound in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms is particularly desir› able. Examples of these perfluoroalkyl compounds include perfluoroalkylether compounds and perfluoroalkylamine compounds. 

[0997] Specifically, one example of a suitable perfluoro› alkylether compound is perfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and an example of a suitable perfluo› roalkylamine compound is perfluorotributylamine (boiling point 174° C.). 

[0998] As the immersion medium, water is preferable in terms of cost, safety, environment and versatility. 

[0999] The PEB treatment is conducted at a bake tempera› ture which changes (increases or decreases) the solubility of the first resist film in an alkali developing solution. 

[1000] Specifically, for example, when the first resist film is composed of a chemically amplified resist composition, by conducting PEB treatment after exposure, diffusion of acid generated from the acid-generator component within the resist film and change (increase or decrease) in solubility of the resist film in an alkali developing solution by the action of the acid proceed. 

[1001] More specifically, the first resist film is selectively exposed through a photomask having a defined pattern, and then, post exposure bake (PEB) is conducted at a temperature of 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds. 

[1002] After the PEB treatment, alkali developing is con› ducted to form a first resist pattern. 

[1003] The alkali developing can be conducted by a con› ventional method, for example, using a tetramethylammo› nium hydroxide (TMAH) solution having a concentration of 0.1 to 10% by weight. By the alkali development, the exposed portions of the first resist film are removed, thereby forming a first resist pattern. 

[1004] After the alkali developing, a rinse treatment using water or the like can be conducted. 

[1005] Further, after the alkali developing, post bake treat› ment may be conducted. Post bake (which is performed in order to remove water content after the alkali developing and rinsing) is generally conducted at about 100° C. preferably for 30 to 90 seconds. 

[1006] [Film Forming Step (2)] 

[1007] Next, the resist composition of the present invention is applied to the substrate having a first resist pattern formed thereon, to thereby form a second resist film. For example, when the first resist pattern is a line and space pattern (here› after, referred to as "LS pattern"), the second resist film can be formed in the same manner as in the first resist film by a conventional method to fill the space portions formed between the plurality of LS patterns. 

[1008] The film thickness of the second resist film is at least as thick as the first resist pattern and is preferably thicker. In other words, when the substrate is viewed from the second resist film side, it is preferable that the substrate surface be flat. 

[1009] [Patterning Step (2)] 

[1010] Next, the second resist film is subjected to selective exposure, followed by alkali development to form a resist pattern. 

[1011] Specifically, for example, the second resist film is selectively exposed through a photomask at portions different from where the plurality of resist patterns have been formed, followed by PEB treatment and alkali developing, thereby forming a resist pattern. 

[1012] Accordingly, the exposed portions of the second resist film when the resist composition of the present inven› tion is a positive type and the unexposed portions of the second resist film when the resist composition of the present invention is a negative type are removed, and between a plurality of resist patterns formed previously, a plurality of resist patterns is newly formed in the LS pattern. As a result, a resist pattern is formed on the substrate which is composed of a plurality of resist patterns formed in the previous step, and a plurality of resist patterns newly formed on the second resist film. 

[1013] In the present invention, when a first resist pattern is formed on a substrate, any region within the substrate which does not completely overlap with a region where the first resist pattern is formed is referred to as "region other than the region where the first resist pattern is formed". In other words, the expression includes a region which does not overlap at all with the region where the first resist pattern is formed, and also includes a region which only partially overlaps with the region where the first resist pattern is formed. 

[1014] In the present invention, when forming a resist pat› tern so as to ultimately form a line and space pattern, it is preferable that the region where the first resist pattern is formed and the region exposed selectively in the patterning step (2) do not overlap at all.As a result, a resist pattern can be formed with a pitch smaller than that of the first resist pattern formed in the patterning step (1 ). 

[1015] The selective exposure of the second film can be conducted, for example, by slightly shifting the exposing position of the photomask used in the patterning step (1). Alternatively, at this time, a photomask different from that used in the patterning step (1) may be used. 

[1016] The position of the resist pattern formed from the second resist film may be completely non-overlapping the position of first resist pattern, or partially overlapping the first resist pattern. However, it is preferable that the position of the resist pattern formed from the second resist film be com› pletely non-overlapping the position of first resist pattern. As a result, a resist pattern can be formed with a pitch smaller than that of the first resist pattern formed in the patterning step (1 ). 

[1017] For example, a line and space pattern may be formed in the patterning step (1) using a photomask for forming a line and space pattern, in which a plurality of lines are arranged with a constant pitch; and then a line pattern may be formed in intermediate regions between the adjacent line patterns formed in the patterning step (1) by changing the position of the photomask in the patterning step (2). Accordingly, a line and space pattern ( dense pattern) can be newly formed which has a pitch smaller than that of the previously formed line and space resist pattern (isolated pattern). 

[1018] The "isolated pattern" is preferably a line and space pattern in which the space width is large so that the ratio of the line width to the space width (i.e., line width:space width) is 1 :at least 2. 

