due of the carboxylic acid onium salt preferably does not contain an aromatic group and a carbon-carbon double bond. As a particularly preferred anion part, a linear, branched, monocyclic or polycyclic cyclic alkylcarboxylate anion hav› ing 1 to 30 carbon atoms is preferred. An anion of a carboxylic acid in which some or all of alkyl groups are substituted with fluorine is more preferred. An oxygen atom may be included in an alkyl chain. Accordingly, transpar› ency with respect to light of 220 nm or less is secured, and thus sensitivity and resolving power are improved, such that density dependence and exposure margins are improved. 

[0342] The radiation-sensitive or actinic ray-sensitive resin composition of the invention may not contain the carboxylic acid onium salt. However, in a case where the radiation-sensitive or actinic ray-sensitive resin composition contains the carboxylic acid onium salt, the content of the carboxylic acid onium salt is preferably 0.5 to 20 mass %, more preferably 0.7 to 15 mass%, and even more preferably 1.0 to 10 mass % based on the total solid content of the radiation-sensitive or actinic ray-sensitive resin composi› tion. 

[0343] [Solvent] 

[0344] The radiation-sensitive or act1mc ray-sensitive resin composition usually contains a solvent. 

[0345] Examples of the solvent that can be used in the preparation of the radiation-sensitive or actinic ray-sensitive resin composition include organic solvents such as an alky› lene glycol monoalkyl ether carboxylate, an alkylene glycol monoalkyl ether, an alkyl lactate ester, an alkyl alkoxypro› pionate, a cyclic lactone (preferably having 4 to 10 carbon atoms), a monoketone compound (preferably having 4 to 10 carbon atoms) that may have a ring, an alkylene carbonate, an alkyl alkoxyacetate, and an alkyl pyruvate. 

[0346] Specific examples of these solvents include the examples described in paragraphs <0441> to <0455> of US2008/0187860A. 

[0347] In the invention, a mixed solvent obtained by mixing a solvent containing a hydroxyl group in the struc› ture and a solvent containing no hydroxyl group may be used as an organic solvent. 

[0348] As the solvent containing a hydroxyl group and the solvent containing no hydroxyl group, the compounds exemplified in the above description can be appropriately selected. As the solvent containing a hydroxyl group, an alkylene glycol monoalkyl ether, an alkyl lactate, and the like are preferred, and a propylene glycol monomethyl ether (PGME, also referred to as l-methoxy-2-propanol) and an ethyl lactate are more preferred. In addition, as the solvent containing no hydroxyl group, an alkylene glycol monoalkyl ether acetate, an alkyl alkoxy propionate, a monoketone compound that may have a ring, a cyclic lactone, an alkyl acetate, and the like are preferred. Among these, a propylene glycol monomethyl ether acetate (PGMEA, also referred to as l-methoxy-2-acetoxypropane), an ethyl ethoxy propi› onate, a 2-heptanone, a y-butyrolactone, a cyclohexanone, and a butyl acetate are particularly preferred, and a propyl› ene glycol monomethyl ether acetate, an ethyl ethoxy pro› pionate, and a 2-heptanone are most preferred. 

[0349] The mixing ratio (mass) between the solvent con› taining a hydroxyl group and the solvent containing no hydroxyl group is 1/99 to 99/1, preferably 10/90 to 90/10, and more preferably 20/80 to 60/40. A mixed solvent con› taining the solvent containing no hydroxyl group in a proportion of 50 mass % or greater is particularly preferred from the viewpoint of uniform coating. 

[0350] The solvent preferably contains a propylene glycol monomethyl ether acetate, and is preferably a single solvent 

of a propylene glycol monomethyl ether acetate or a mixed solvent of two or more kinds containing a propylene glycol monomethyl ether acetate. 

[0351] The solid content concentration of the radiation› sensitive or actinic ray-sensitive resin composition of the invention is preferably 1 to 40 mass %, more preferably 1 to 30 mass %, and even more preferably 3 to 20 mass %. 

[0352] The invention relates to a resist film formed of the radiation-sensitive or actinic ray-sensitive resin composition of the invention, and such a film is formed by, for example, coating a support such as a substrate with the composition of the invention. The thickness ofthis film is preferably 0.02 to 0.1 µm. As a method for coating on the substrate, an appropriate coating method such as spin coating, roll coat› ing, flow coating, dip coating, spray coating, and doctor coating is used to coat the substrate, and spin coating is preferred. In addition, the rotation speed thereof is prefer› ably 1,000 to 3,000 rpm. As the coating film, a thin film is formed by performing prebaking at 60° C. to 150° C. for 1 to 20 minutes, and preferably at 80° C. to 120° C. for 1 to 10 minutes. 

[0353] As a material constituting a substrate to be pro› cessed and the outermost layer thereof, for example, a silicon wafer can be used, in the case of a semiconductor wafer, and examples of the material that becomes the outermost layer include Si, SiO$_{2}$ , SiN, SiON, TiN, WSi, BPSG, SOG, and an organic antireflection film. 

[0354] The invention also relates to a mask blank on which the resist film obtained as described above is coated. In order to obtain such a mask blank having the resist film, as a transparent substrate to be used in a case where a pattern is formed on a photo mask blank for producing a photo mask, a transparent substrate such as quartz or calcium fluoride can be exemplified. Generally, a necessary func› tional film such as a light shielding film an antireflection film, and further a phase shift film, and additionally, an etching stopper film and an etching mask film are laminated on the substrate. As a material of the functional film, a film containing a transition metal such as silicon, chromium, molybdenum, zirconium, tantalum, tungsten, titanium, and niobium is laminated. In addition, as a material used in the outermost layer, a silicon compound material that contains, as a main constituent material, a material containing silicon or a material containing oxygen and/or nitrogen in silicon, or contains, as a main constituent material, a material contain› ing a transition metal in the above material, and a transition metal compound material that contains, as a main constitu› ent material, a material containing one or more selected from transition metals, particularly, chromium, molybdenum, zir› conium, tantalum, tungsten, titanium, and niobium, or a material containing one or more selected from oxygen, nitrogen, and carbon in the above material are exemplified. 

[0355] The light shielding film may be a single layer, but a multilayer structure in which a plurality of materials is coated in an overlapped manner is more preferred. In a case of the multilayer structure, a thickness of the film per one layer is not particularly limited, but is preferably 5 to 100 nm, and more preferably 10 to 80 nm. The total thickness of the light shielding film is not particularly limited, but is preferably 5 to 200 nm, and more preferably 10 to 150 nm. 

[0356] Generally, in a case where a pattern is formed of the composition of the invention on a photo mask blank that contains, in the outermost layer thereof, a material contain› ing oxygen or nitrogen in chromium among the above materials, a so-called undercut shape in which a constricted shape is formed near the substrate is easily formed. How- 

