118  US 9,069,246 B2  117  erably distilled water. Pure water obtained by further filtering  the distilled water through an ion exchange filter or the like  may be also used.  The electrical resistance of water is preferably 18.3 MQcm  or more, and TOC (total organic carbon) is preferably 20 ppb  or less. Also, the water is preferably subjected to a deaeration  treatment.  The lithography performance can be enhanced by elevating  the refractive index of the immersion liquid. From such a  standpoint, an additive for elevating the refractive index may  be added to water, or heavy water (D$_{2}$ 0)  may be used in place  of water.  The alkali developer includes, for example, an alkaline  aqueous solution containing inorganic alkalis such as sodium  In the development step, an alkali developer is usually  used.  The development step is described below.  The topcoat is preferably free of intermixing with the film  and further with the immersion liquid. From this standpoint,  when the immersion liquid is water, the solvent used for the  topcoat is preferably a medium that is sparingly soluble in the  solvent used for the composition of the present invention and  is water-insoluble. On the other hand, when the immersion  liquid is an organic solvent, the topcoat may be either water› soluble or water-insoluble.  An organic antireflection film, ARC29A (produced by Nis› san Chemical Industries, Ltd.), was coated on a silicon wafer  and baked at 205°  C. for 60 seconds to form an antireflection  film having a thickness of 78 nm, and the positive resist  composition prepared was coated thereon and baked at 130°  C. for 60 seconds to form a resist film having a thickness of  120 nm. The obtained resist film was exposed through a 6%  halftone mask having a 1: 1 line-and-space pattern with a line  width of 75 nm by using an ArF excimer laser scanner  (PAS5500/1100, manufactured by ASML, NA: 0.75). There- <Evaluation of Resist>  The components shown in Table 2 below were dissolved in  the solvent to prepare a solution having a solid content con› centration of 4.0 mass %, and the obtained solution was  filtered through a polytetrafluoroethylene filter having a pore  size of 0.03 µm to prepare a positive resist solution. The  positive resist compositions (resist solutions) prepared were  evaluated by the following method and the results are shown  in Table 2.  <Preparation of Resist>  Examples IA to 19A and Comparative Examples IA  and2A  Example A  The present invention is described in greater detail below,  but the present invention is not limited thereto.  EXAMPLES  The electronic device of the present invention is suitably  mounted on electric and electronic equipment (home elec› tronic device, OA •media-related  device, optical device com› munication device, etc.).  The present invention also includes an electronic device  manufacturing method involving the above-described pattern  forming method of the present invention, and an electronic  device manufactured by this manufacturing method.  Details of the process when fabricating an imprint mold by  using the composition of the present invention may be refer  to, for example, Japanese Patent 4,109,085, JP-A-2008- 162101, and "Yoshihiko Hirai (compiler), Nanoimprint no  Kiso to Gijutsu Kaihatsu•Oyo  Tenkai-Nanoimprint no Kiban  Gijutsu to Saishin no Gijutsu Tenkai (Basic and Technology  Expansion•Application  Development of Nanoimprint-Sub› strate Technology of Nanoimprint and Latest Technology  Expansion), Frontier Shuppan".  The concentration of the alkali developer is usually from  0.1 to 20 mass%. The pH of the alkali developer is usually  from 10.0 to 15.0.  In the alkali developer, alcohols and/or a surfactant may be  added each in an appropriate amount.  hydroxide, potassium hydroxide, sodium carbonate, sodium  silicate, sodium metasilicate and aqueous annnonia, primary  amines such as ethylamine and n-propylamine, secondary  amines such as diethylamine and di-n-butylamine, tertiary  amines such as triethylamine and methyldiethylamine, alco› hol amines such as dimethylethanolamine and triethanola› mine, quaternary ammonium salts such as tetramethylammo› nium hydroxide and tetraethylammonium hydroxide, or  cyclic amines such as pyrrole and piperidine.  On removing the topcoat, a developer may be used, or a  release agent may be separately used. The release agent is  preferably a solvent less permeating the resist film. From the  standpoint that the removing step can be performed simulta› neously with the film development step, the topcoat is pref- erably removable with an alkali developer and for the removal  with an alkali developer, the topcoat is preferably acidic, but  in view of non-intermixing with the film, the topcoat may be  neutral or alkaline.  With no difference in the refractive index between the  topcoat and the immersion liquid, the resolution is enhanced.  In the case of using water as the immersion liquid at the  exposure with an ArF excimer laser (wavelength: 193 nm),  the topcoat for ArF immersion exposure preferably has a  refractive index close to the refractive index of the immersion  liquid. From the standpoint of making the refractive index  close to that of the immersion liquid, the topcoat preferably  contains a fluorine atom. Also, in view of transparency and  refractive index, the topcoat is preferably a thin film.  In view of transparency to light of 193 nm, the topcoat is  preferably a polymer not abundantly containing an aromatic 25  moiety. Specifically, this polymer includes a hydrocarbon  polymer, an acrylic acid ester polymer, a polymethacrylic  acid, a polyacrylic acid, a polyvinyl ether, a silicon-contain› ing polymer, a fluorine-containing polymer, and the like. The  above-described hydrophobic resin (HR) is suitable also as  the topcoat. From the standpoint that elution of impurities  into the immersion liquid from the topcoat leads to contami› nation of the optical lens, the amount of residual monomer  components of the polymer contained in the topcoat is pref› erably smaller.  In order to prevent the film from contacting directly with  the immersion liquid, an immersion liquid sparingly soluble  15  film (hereinafter, sometimes referred to as "topcoat") may be  provided between the film formed of the composition of the  present invention and the immersion liquid. The functions  required of the topcoat are suitability for coating on the resist  upper layer part, transparency to radiation particularly of 193 20  nm, and difficult solubility in the immersion liquid. It is  preferred that the topcoat does not intermix with the resist and  can be uniformly coated on the resist upper layer. 