US 2017 /0059990 Al  68  Mar. 2, 2017  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  [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- [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.  [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.  [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.  [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.  [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 %.  of a propylene glycol monomethyl ether acetate or a mixed  solvent of two or more kinds containing a propylene glycol  monomethyl ether acetate. 