Patent Publication Number: US-2009239103-A1

Title: Polymer thin-film, process for producing patterned substrate, matter with pattern transferred, and patterning medium for magnetic recording

Description:
TECHNICAL FIELD 
     The present invention relates to a polymer thin film having a microphase separated structure in which cylindrical microdomains are oriented along the penetration direction through the film. Further, the invention relates to a method of producing a patterned substrate having on the surface thereof a regular array pattern of this microphase separated structure. Still further, the invention relates to a pattern carrier for transfer of the regular array pattern onto an object (a transfer object) and relates to a patterned medium for magnetic recording produced using this pattern carrier. 
     BACKGROUND ART 
     In recent years, with miniaturization and high performance of electronic devices, energy storage devices, sensors and the like, necessity of forming a regular array pattern, which is fine in a size of nanometers to hundred nanometers, on a substrate has been risen. Therefore, it is required to establish a process capable of producing a structure with such a fine pattern in high precision and low cost. 
     As a processing method of such a fine pattern, a top-down method represented by lithography, that is, a method providing a shape by finely engraving a bulk material is generally used. A representative example is photolithography used for fine processing of semiconductors, such as producing LSIs. 
     However, as the degree of fineness of a fine pattern rises, applying such a top-down method increases difficulty both in the device and process. Particularly, when the processing dimensions of a fine pattern are as fine as several dozen nanometers, it is necessary to use an electron beam or deep UV rays for patterning, which requires a huge investment for equipment. Further, when it is difficult to form a fine pattern applying a mask, it is forced to apply a direct drawing method, where the problem of a significant drop in processing through put cannot be avoided. 
     In such a situation, attention is paid to a process applying the phenomenon of self assembly of a structure of a substance, in other words, self assembly phenomenon. Particularly, a process applying the self assembly phenomenon of block copolymers, so-called microphase separation, is an excellent process in that the process is capable of forming a fine regular structure having various shapes in a size ranging from several dozen nanometers to several hundred nanometers by a simple coating process. 
     Herein, when polymer segments of different kinds of block copolymers do not mix with each other (incompatible), a fine structure having a specific regularity is self assembled by phase separation (microphase separation) of these polymer segments. 
     As an example of forming a fine regular structure, using such a self assembly phenomenon, there is known a technology for forming a structure, such as holes, or lines and spaces, on a substrate, using as an etching mask a block copolymer thin film composed of a combination of polystyrene and polybutadiene, polystyrene and polyisoprene, polystyrene and polymethylmethacrylate, or the like (for example, refer to the later described Non-patent Document 1 and Non-patent Document 2). 
     Incidentally, by the microphase separation phenomenon of block copolymers, it is possible to obtain a polymer thin film having a structure with a regular array of spherical or cylindrical microdomains in a continuous phase. 
     When using such a microphase separated structure as a pattern carrier, such as an etching mask, it is desirable that cylindrical microdomains are regularly arranged such as to be oriented along the direction (penetration direction through a film) perpendicular to a substrate. 
     It is because, in a structure where cylindrical microdomains are perpendicular to the substrate, the aspect ratio (the ratio of the domain size along the direction perpendicular to the substrate, to the domain size along the direction parallel to the substrate) of an obtained structure can be adjusted more freely, compared with a structure where spherical microdomains are regularly arrayed on the surface of a substrate. 
     On the other hand, when using a microphase separated structure having spherical microdomains as a pattern carrier, such as an etching mask, the maximum aspect ratio of an obtained structure is 1, and accordingly, the aspect ratio is smaller and lacks the degree of freedom for adjustment, compared with the case of cylindrical microdomains perpendicular to a substrate. 
     However, in a cylindrical microdomain structure formed by the microphase separation phenomenon of block copolymers, cylindrical microdomains are often oriented parallel to the surface of the film. 
     Conventional methods for orienting cylindrical microdomains, which tend to be oriented parallel to the surface of a film, along the direction (penetration direction through the film) perpendicular to a substrate includes the followings. 
     In a first conventional method, an extremely high electric field is applied to a film of block copolymers in the penetration direction through the film so as to orient cylindrical microdomains along the direction of the electric field, thereby obtaining a structure in which the cylindrical microdomains are perpendicular to the surface of the film (for example, refer to Non-patent document 3). 
     In a second conventional method, the surface of a substrate is chemically modified so as to make respective segments of block copolymers have the same affinity, thereby obtaining a structure in which the cylindrical microdomains are perpendicular to the surface of the substrate (for example, refer to Non-patent document 4). 
     Non-patent Document 1: Science 276 (1997)1401 
     Non-patent Document 2: Polymer 44 (2003) 6725 
     Non-patent Document 3: Macromolecules 24 (1991) 6546 
     Non-patent Document 4: Macromolecules 32 (1999) 5299 
     However, in the above described first conventional method, in order to apply a high electric field to the film of block copolymers, a special process or equipment has been necessary, such as the necessity of applying a voltage to the film between an extremely narrow gap formed by a tight contact of an electrode with the surface of the film. 
     Further, in the above described second conventional method, it has not been easy, in general, to make the respective segments of block copolymers on the surface of a substrate have the same affinity. 
     As a problem due to these points, it has been impractical to make cylindrical microdomains perpendicular to the surface of a film, employing these conventional methods. 
     As has been described above, although a method of obtaining a regular structure as fine as in the range from several dozen nanometers to several hundred nanometers applying the microphase separation phenomenon of block copolymers is simple and low in cost, it has been difficult to orient cylindrical microdomains along the penetration direction through a film. 
     DISCLOSURE OF THE INVENTION 
     Addressing problems as described above, the invention provides a polymer thin film having a regular array pattern with cylindrical microdomains oriented along the penetration direction through the film, using the microphase separation phenomenon of block copolymers. Further, the invention provides a method of producing a patterned substrate having this regular array pattern on the surface. Still further, the invention provides a pattern carrier, such as an etching mask, capable of providing a fine and regular array pattern having a large aspect ratio onto the surface of an object (a transfer object, namely an object to which a pattern is transferred), and a patterned medium for magnetic recording. 
     To solve the above described problems, in an aspect of the invention, there is provided a polymer thin film, including: 
     a continuous phase primarily composed of polymers of a first monomer; and 
     cylindrical microdomains each of which is primarily composed of a polymer of a second monomer, the cylindrical microdomains being distributed in the continuous phase and oriented along a penetration direction through the film, 
     wherein the polymer thin film contains block copolymers which include at least respective first segments formed by polymerization of the first monomer and respective second segments formed by polymerization of the second monomer, and polymers compatible with the first segments. 
     In this aspect of the invention, cylindrical microdomains, which tend to be oriented parallel to a film, are oriented along the penetration direction through the film due to the action of polymers. 
     According to the invention, using the microphase separation phenomenon of block copolymers, it is possible to provide a polymer thin film having a regular array pattern with cylindrical microdomains oriented along the penetration direction through a film. It is also possible to provide a method of producing a patterned substrate having this regular array pattern on the surface. Further, it is possible to provide a pattern carrier, such as an etching mask, capable of providing a fine and regular array pattern with a large aspect ratio on the surface of an object (the transfer object), and a patterned medium for magnetic recording capable of improving the recording density. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       In  FIG. 1 , (a) is a perspective cross-sectional view of a polymer thin film in accordance with an embodiment of the invention, and (b) is a top view of the film; 
       In  FIG. 2 , (a) is a conceptual view of a block copolymer being an element constituting a polymer thin film in accordance with the embodiment, (b) is a conceptual view of a polymer, (c) is an enlarged top view of unit structures of the polymer thin film, and (d) is a cross-sectional view taken along line P-P of the unit structures shown in (c); 
       In  FIG. 3 , (a) to (d) are conceptual views of types of block copolymers; 
       In  FIG. 4 , (a) to (d) are views illustrating changes, of the microphase separated structure of a polymer thin film, which can occur when the volume ratios of the first monomer and the second monomer are changed, and (e) to (g) are views of surface images observed by an atomic force microscope, corresponding to (b) to (d); 
         FIG. 5  illustrates a process, showing a method of producing a patterned substrate with a polymer thin film in accordance with an embodiment of the invention; 
         FIG. 6  illustrates a process, showing a method of producing a patterned substrate with a polymer thin film in accordance with an embodiment of the invention; 
         FIG. 7  illustrates a process, showing a method of producing a patterned substrate with a polymer thin film in accordance with an embodiment of the invention; 
         FIG. 8  is a table of observation results showing changes in microphase separated structures which occurred when the containing ratio of polymers was changed, wherein PS was adopted for the first segment and PMMA was adopted for the second segment; 
         FIG. 9  is a table of observation results showing changes in microphase separated structures which occurred when the containing ratio of polymers was changed, wherein PMMA was adopted for the first segment and PS was adopted for the second segment; 
         FIG. 10  is a table of observation results showing changes of a microphase separated structure which occurred when the containing ratio of polymers was changed, wherein PMMA was adopted for the first segment, PS was adopted for the second segment, and PVME was adopted for the polymers; 
       In  FIG. 11 , (a) and (b) are tables showing composition and conditions of plating solutions for producing patterned substrates by plating; 
       In  FIG. 12 , (a) is a schematic view of a stamper, and (b) is an enlarged view of the central portion thereof; and 
         FIG. 13  is a schematic view of a nanoprinting apparatus. 
     
    
    
     DESCRIPTION OF REFERENCE SYMBOLS 
       10  continuous phase
   11  first monomer
   12  first segment
   13  polymer
   20  cylindrical microdomain
   21  second monomer
   22  second segment
   23  third monomer
   24  third segment
   25 ,  83  fine pore
   26  cylindrical structure
   30  polymer thin film
   31  ( 31   a,    31   b,    31   c  and  31   d ) block copolymer
   35  porous polymer thin film (pattern carrier)
   40  and  41  substrate (transfer object)
   50  transfer object
   61  and  62  patterned substrate (pattern carrier)
   63  patterned substrate (patterned medium for magnetic recording)
 
     Best Mode for Carrying Out the Invention 
     (Regarding a Polymer Thin Film) 
     Embodiments in accordance with the invention will be described below, referring to the drawings. 
     As shown in (a) of  FIG. 1 , a polymer thin film  30  in the present embodiment has a microphase separated structure which includes a continuous phase  10  and cylindrical microdomains  20 , and is disposed on a surface of a substrate  40 . 
     The microdomains  20  are distributed in the continuous phase  10  and are oriented along the direction (penetration direction through the film) perpendicular to the substrate  40 , namely direction z in (a) of  FIG. 1 . As shown in (b) of  FIG. 1 , the cylindrical microdomains  20  form a regular array pattern having hexagonal close-packed structures on the horizontal plane (X-Y plane in the figure) of the polymer thin film  30 . 
     Next, referring to  FIG. 2 , views of units constituting the polymer thin film  30  are schematically enlarged, and the microphase separated structure of the polymer thin film  30  will be described in more details. 
     As a primary component, the polymer thin film  30  contains a mixture of block copolymers  31  as shown in (a) of  FIG. 2  and polymers  13  as shown in (b) of  FIG. 2 . 
     Each block copolymer  31  includes a first segment  12  formed by polymerization of a first monomer  11  and a second segment  22  formed by polymerization of a second monomer  21 . 
     Herein, the degree of polymerization of the second segments  22  in the block copolymers  31  is preferably less than the degree of polymerization of the first segments  12 . 
     By adjusting the degrees of polymerization in such a manner, the binding portions between the respective first segments  12  and second segments  22  have a circular shape as shown in (c) of  FIG. 2 , and block copolymers  31  can be easily arrayed in such a way. 
     With the bonding portions between the respective first segments  12  and second segments  22  being boundaries, the region of the continuous phase  10  with a primary component of polymers of the first monomer  11  and regions of the cylindrical microdomains  20  with a primary component of a polymer of the second monomer  21  are formed. 
     The block copolymers  31  may be synthesized by any appropriate method. However, in order to improve the regularity of the microphase separated structure, it is appropriate to employ a synthesizing method by which the distribution of molecular weight becomes as small as possible, for example, a living polymerization method. 
     In the present embodiment, as an example of block copolymers  31 , an A-B type diblock copolymers formed by bonding between the respective one ends of the first segments  12  and the second segments  22 , as shown in (a) of  FIG. 2 , is illustrated. However, a block copolymer used in the present embodiment may be an A-B-A type triblock copolymer  31   a , as shown in (a) of  FIG. 3 . Further, it is also possible to employ an A-B-C type block copolymer  31   b  which are composed of more than two polymer segments including a third segment  24  formed by polymerization of a third monomer  23 , as shown in (b) of  FIG. 3 . Still further, besides block copolymers of serially bonded segments as described above, star type block copolymers  31   c  or  31   d  each of which is formed by bonding between segments at a point, as shown in (c) and (d) of  FIG. 3 , may be employed. 
     Yet further, block copolymers  31  applied in the invention are not limited to those shown in  FIG. 3 , and the third segment may be bonded with the end, of the first segment, on the side opposite to the second segment. Still further, in (a) of  FIG. 3 , the location of the first segments  12  and  12 ′ and the location of the second segment  22  may be replaced with each other. 
     Coming back to  FIG. 2 , a polymer formed by polymerization of the first monomer  11  is shown in  FIG. 2  ( b ) as an example of polymers  13 . However, polymers  13  are not limited to polymers of the first monomer  11  as described above, and any kind of polymers which is compatible with the first segments  12 , of the block copolymers  31 , forming the continuous phase  10  can be properly employed. 
     Concretely, polymer molecules applicable to the polymers  13  will be described as examples. Herein, when the first segments  12  are polystyrene, besides that polystyrene is applicable to the polymers  13 , it is also possible to employ polymer molecules which are compatible with the first segments  12  (polystyrene), such as polyphenyleneether, polymethyl vinyl ether, polydimethylsiloxane, poly-(-methylstyrene, nitrocellulose and the like. 
     Further, when the first segments  12  are polymethylmethacrylate, besides that polymethylmethacrylate is applicable to the polymers  13 , it is also possible to employ polymer molecules which are compatible with the first segments  12  (polymethylmethacrylate), such as styrene-acrylonitrile copolymer, acrylonitrile butadiene copolymer, vinylidenefluoride-trifluoroethylene copolymer, vinylidenefluoride-tetrafluoroethylene copolymer, vinylidenefluoride-hexafluoroaceton copolymer, vinylphenol/styrene copolymer, vinylidene chloride/ acrylonitrile copolymer, vinylidenefluoride homopolymer and the like. 
     Herein, the above described polymer molecules may become incompatible, depending on the molecular weight, concentration, and also composition in a case of copolymers. Further, they may become incompatible, depending on the temperature, and accordingly, they are preferably in a compatible state even at a temperature during heat processing. 
     The degree of polymerization of the polymers  13  is preferably less than that of the first segments of the block copolymers  31 . 
     The contained amount of the polymers  13  is preferably adjusted as follows in relation with the block copolymers  31 . 
     That is, representing the volume ratio of the sum of the volume of the first segments  12  and the volume of the polymers  13  in the polymer thin film  30  by φ%, and the maximum φ% capable of forming cylindrical microdomains  20  by φ max %, it is preferable to satisfy the following Formula (1). This Formula (1) will be explained later in detail, referring to  FIGS. 4 ,  8 ,  9  and  10 . 
       φmax−7≦φ≦φmax   (1) 
     In such a manner, adjusting the degree of polymerization and contained amount of the polymers  13  has an effect of orienting most of the cylindrical microdomains  20  along the direction (penetration direction through the film) perpendicular to the substrate  40 , as shown in (d) of  FIG. 2 . It is understood that this is because, as shown in (c) of  FIG. 2 , each of the contained polymers  13  is distributed at the portion of the center of gravity of the respective unit array of cylindrical microdomains  20 , and thereby, as shown in (d) of  FIG. 2 , cylindrical microdomains  20  having started growing from the surface of the substrate  40  grow perpendicular to the surface without lying. 
     The array of the polymers  13  or the block copolymers  31 , shown in (c) and (d) of  FIG. 2 , shows the concept and should be interpreted not to limit the scope of right of the invention. Further, the monomers shown by circle marks in  FIGS. 2 and 3  are conceptually shown for understanding of the outline of the block copolymers  31  and the polymers  13 , and it should not be understood that actual polymer chains are structured in such a manner. Especially, regarding the degree of polymerization of the polymer chains, these figures should not be interpreted to limit the scope of right of the invention. 
     Now, the above described Formula (1) will be explained, referring to  FIG. 4 . 
     Herein, (a) to (d) of  FIG. 4  are views showing the microphase separated structures which are formed when the volume ratio of polymers of the first monomer  11  (refer to (a) and (b) of  FIG. 2 ) and the volume ratio of polymers of the second monomer  21 , both constituting the polymer thin films  30   a,    30   b,    30   c  and  30 , are changed. 
     A microphase separated structure, shown in (a) of  FIG. 4 , can be formed when the volume ratio of the first segments  12  and the volume ratio of the second segments  22  both forming the block copolymers  31 , as shown in (a) of  FIG. 2 , are substantially equal. 
     In other words, the polymer thin film  30   a  in (a) of  FIG. 4  has a structure formed by alternate arrays of plate shaped polymer phases  10   a  and  20   a  with respective primary components of the first segment  12  and the second segment  22 . 
     A microphase separated structure, shown in (b) of  FIG. 4 , is for a case where polymers  13  already introduced as a conventional art is not contained, and can be formed when the volume ratio of the first segments  12  is larger than in the case of (a) of  FIG. 4 . A result of observation of a surface by a later described atomic force microscope is shown in (e) of  FIG. 4 . 
     In other words, the polymer thin film  30   b  in (b) of  FIG. 4  has a structure in which cylindrical microdomains  20   b  are distributed in a continuous phase  10   b  of the first segments  12 . The difference of these cylindrical microdomains  20   b  from cylindrical microdomains  20  (refer to (d) of  FIG. 4 ) in the present embodiment is that the cylindrical microdomains  20   b  are lying with respect to a substrate  40 , in other words, parallel to the substrate  40 . 
     This is because, in the polymer thin film  30   b,  the cylindrical microdomains  20   b  tend to be arrayed in such a manner that segments with a higher affinity with the substrate  40  contact the substrate  40  while segments with a higher affinity with the free surface (the surface opposite to the substrate  40 ) contact the free surface. 
     A microphase separated structure shown in (c) of  FIG. 4  can be formed when the volume ratio of the first segment  12  is larger than in the case of (b) of  FIG. 4 . A result of observation of a surface by the later described atomic force microscope is shown in (f) of  FIG. 4 . 
     In other words, the polymer thin film  30   c  in (c) of  FIG. 4  has a structure in which spherical microdomains  20   c  are distributed in a continuous phase  10   c  of the first segment  12 . 
     In such a manner, as shown in (b) and (c) of  FIG. 4 , when the volume ratio φ % of the first monomer  11  is continuously increased, the volume ratio has a threshold at which the polymer thin film  30   b  is switched to the polymer thin film  30   c.  For Formula (1), this threshold is defined to be the maximum volume ratio φmax capable of forming cylindrical microdomains  20 . 
     Diagram (d) of  FIG. 4  is a schematic view showing a polymer thin film  30  (corresponding to (a) of  FIG. 1 ) in the present embodiment, for comparison with the cases of the other diagrams (a) to (c) of  FIG. 4 . A result of observing a surface by the later described atomic force microscope is shown in (g) of  FIG. 4 . 
     The microphase separated structure in the present embodiment, shown in (d) of  FIG. 4 , is added with polymers  13  (refer to (b) of  FIG. 2 ) so as to satisfy above described Formula ( 1 ), and thereby, a structure in which the cylindrical microdomains  20   b,  which were lying as shown in (b) of  FIG. 4 , are oriented along the direction perpendicular to the substrate  40  (penetration direction through the film). 
     As described above, the form of a microphase separated structure of a polymer thin film  30  greatly changes with the ratio between the first segments  12 , second segments  22  and polymers  13  which constitute the polymer thin film  30 . 
     A substrate  40  is preferably a Si wafer, while allowing appropriate selection of other materials, such as glass, ITO and resin, suitable for a purpose. 
     A polymer thin film  30  formed on a flat substrate  40  with a large surface, as shown in  FIG. 5 , may have a grain structure formed with a number of regions having different array regularities of cylindrical microdomains  20 . Also in the grain, there may be a case where the array of cylindrical microdomains  20  has point defects and line defects. Accordingly, there may be cases where such a polymer thin film  30  can not be applied as it is, to purposes which require a high regularity over a large area, such as processing of a later described patterned medium for magnetic recording. 
     As shown in  FIG. 7 , the surface of a substrate  41  may not be flat and formed with recessions  42  and guides  43 . By processing the surface of the substrate  41  in such a manner, creation of a particle field which disturbs the regularity of the regular array pattern of cylindrical microdomains  20  in a continuous phase  10  is prevented in the polymer thin film  30  formed in a recession  42 . 
     Photolithography is an example of a method of forming such recessions  42  and guides  43  on the surface of a substrate  41 . Through creation of a microphase separated structure in the spaces of the recessions  42 , the space being enclosed or constrained by the guides  43 , a polymer thin film  30  can be formed on the substrate  41 , wherein creation of defects, grains, particle field and the like are inhibited. 
     (Method of Producing Patterned Substrate) 
     An embodiment of a method of producing a polymer thin film and a patterned substrate will be described below, referring to  FIG. 5 . 
     First, a mixture (hereinafter, also referred to as a polymer mixture) of block copolymers  31  (refer to  FIG. 2 ) and polymers  13  are solved in a solvent so as to prepare a solution of the polymer mixture. Then, this solution is coated on the surface of a substrate  40 , shown in (a) of  FIG. 5 , by a spin-coat method, dip-coat method, solvent-cast method or the like. The solvent used here is preferably one in which both the block copolymers  31  and the polymers  13  constituting the polymer mixture are soluble. 
     In this process, in order to make the thickness of the coated film  38 , shown in (b) of  FIG. 5 , become a predetermined value, it is necessary to adjust the concentration of the polymer mixture, rotation speed or time in the spin-coat method, or the lifting speed in the dip-coat method. 
     Then, having the solvent vaporize from the solution of the polymer mixture, the coated film  38  is fixed to the surface of the substrate  40 . Herein, the thickness of the coated film  38  may be arbitrarily adjusted depending on a purpose. However, in general, the degree of orientation of perpendicular cylindrical microdomains  20  tends to drop as the thickness of the polymer thin film  30 , shown in (c) of  FIG. 5 , increases. Therefore, the thickness of the polymer thin film  30  is preferably smaller than or equal to ten times the diameter of the cylindrical microdomains  20 . 
     Next, the coated film  38  fixed on the substrate  40  is subjected to heating, and, as shown in (c) of  FIG. 5 , a microphase separated structure with a separation between a continuous phase  10  and cylindrical microdomains  20  being oriented along the direction perpendicular to the substrate  40  is created. 
     When the coated film  38  fixed in the stage (b) of  FIG. 5  is left as it is, the microphase separation in the coated film  38  does not develop sufficiently, and the coated film  38  often has a nonequilibrium structure where a low regularity is present. Accordingly, through heating, the microphase separation sufficiently develops and the structure changes into one having a high regularity and being more equilibrium. 
     In order to prevent oxidization of the polymer mixture, this heat processing is preferably performed in an atmosphere of vacuum, nitrogen or argon and to a temperature higher or equal to the glass transition temperature of the polymer mixture. 
     In such a manner, a polymer thin film  30  having a regular array pattern of a microphase separated structure is formed on a substrate  40 , and a patterned substrate  61  is produced. Herein, the cross-sectional area of and the disposition interval between cylindrical microdomains  20  constituting the regular array pattern can be properly adjusted by changing the molecular weight and composition of the block copolymers  31  in the polymer mixture, the molecular weight of the polymers  13 , and the respective volume ratios of the both. 
     Next, from the microphase separated structure of the polymer thin film  30 , shown in (c) of  FIG. 5 , the polymer phase of the cylindrical microdomains  20  is selectively removed, and as shown in (d) of FIG.  5 , a porous polymer thin film  35  formed with a regular array pattern of plural fine holes  25  is obtained. Though not shown, it is also possible to obtain a polymer thin film formed with a regular array pattern of plural cylindrical structures (cylindrical microdomains  20 ) by selectively removing the polymer phase of the continuous phase  10 . In such a manner, a porous polymer thin film  35  formed with a regular array pattern of plural fine pores  25  or cylindrical structures is formed on the substrate  40 , and thus a patterned substrate  62  is produced. 
     Further, though not describing in details, with reference to (d) of  FIG. 5 , by peeling off the remaining polymer phase (the porous polymer thin film  35  of the continuous phase  10  in the figure) from the surface of the substrate  40 , it is also possible to produce a porous polymer thin film  35  alone as a patterned substrate. 
     As shown in (d) of  FIG. 5 , as a method of selectively removing one of the polymer phase of the continuous phase  10  and the polymer phase of the cylindrical microdomains  20  constituting the polymer thin film  30 , a method is used in which the difference in the etching rate between the polymer phases is utilized, applying a reactive ion etching (RIE) or another etching method. 
     To carry out this method, it is necessary to properly select a combination of the first monomer  11  and the second monomer  21  constituting a block copolymer  31 , shown in (a) of  FIG. 2 . 
     For example, in the case of block copolymers  31  with a combination of the first monomer  11  and the second monomer  21  which are polystyrene and polybutadiene, development processing is possible so as to leave only the polymer phase of the polystyrene segments by ozonization. 
     Further, in the case of block copolymers  31  with a combination of the first monomer  11  and the second monomer  21  which are polystyrene and polymethylmethacrylate, polystyrene has a higher etching resistance than polymethylmethacrylate against RIE which uses oxygen or CF4 as etchant. Accordingly, applying etching by RIE enables it to obtain a porous polymer thin film  35  for which only the polymer phase of polymethylmethacrylate is selectively removed. 
     Block copolymers  31  capable of forming a polymer thin film  30  for which only one of two polymer phases can be selectively removed as described above includes, for example, polybutadiene-polydimethylsiloxane, polybutadiene-4-vinylpyridine, polybutadiene-methylmethacrylate, polybutadiene-poly-t-butyl methacrylate, polybutadiene-t-butyl acrylate, poly-t-butyl methacrylate-poly-4-vinylpyridine, polyethylene-polymethylmethacrylate, poly-t-butyl methacrylate-poly-2-vinylpyridine, polyethylene-poly-2-vinylpyridine, polyethylene-poly-4-vinylpyridine, polyisoprene-poly-2-vinylpyridine, polymethylmethacrylate-polystyrene, poly-t-butyl methacrylate-polystyrene, poly-t-butyl methacrylate-polystyrene, polymethylacrylate-polystyrene, polybutadiene-polystyrene, polyisoprene-polystyrene, polystyrene poly-2-vinylpyridine, polystyrene poly-4-vinylpyridine, polystyrene poly dimethylsiloxane, polystyrene poly-N, N-dimethylacrylamide, polybutadiene- sodium polyacrylate, polybutadiene-polyethylene oxide, poly-t-butyl methacrylate-polyethylene oxide, polystyrene polyacrylate, polystyrene polymethacrylate, or the like. 
     Further, by doping either polymer phase of the continuous phase  10  or cylindrical microdomains  20  with metal atoms or the like, it is also possible to improve the selectivity for etching. For example, when the combination of the first monomer  11  and the second monomer  21  is a block copolymer  31  of polystyrene and polybutadiene, the polymer phase of polybutadiene is easier to be doped with osmium compared with the polymer phase of polystyrene. Utilizing this effect, etching resistance of the domains of polybutadiene can be improved. 
     On the other hand, the polymer phase of either the continuous phase  10  or the cylindrical microdomains  20  is doped with metal atoms, and accordingly, the polymer thin film  30  is also expected to serve as a membrane reactor that causes catalyst reaction of an introduced material at the boundary. Further, with regard to timing of doping, metal atoms may be doped before generating phase separation into the continuous phase  10  and the cylindrical microdomains  20 , and may be doped after generating phase separation. 
     Next, using the remaining and other polymer phase (porous polymer thin film  35 ) as a mask, the continuous phase  10  in the case of (d) of  FIG. 5  for example, the substrate  40  is subjected to etching by RIE or a plasma etching method. Then, as shown in (e) of  FIG. 5 , a patterned substrate  63  is formed onto which surface a regular array pattern in a micro separated structure has been transferred through fine pores  25 . Then, when the porous polymer thin film  35  remaining on the surface of the patterned substrate  63  is removed by RIE or a solvent, as shown in (f) of  FIG. 5 , the patterned substrate  63  is obtained with fine pores  25  formed on the surface thereof, the fine pores  25  having a regular array pattern corresponding to the cylindrical microdomains  20 . 
     Next, referring to  FIG. 6 , another embodiment related to a method of producing a patterned substrate will be described. 
     Herein, the process from (a) to (d) of  FIG. 6  is the same as that from (a) to (d) of  FIG. 5 , and accordingly description of it is omitted. 
     Utilizing the patterned substrate  62 , shown in (d) of  FIG. 6 , as a pattern carrier, the remaining and other part being the polymer phase (the continuous phase  10 ) is, as shown in (e) of  FIG. 6 , made tightly contact a transfer object  50 , namely an object to which a pattern is transferred, and thus the regular array pattern of the microphase separated structure is transferred to the surface of the transfer object  50 . Thereafter, as shown in (f) of  FIG. 6 , the transfer object  50  is peeled off from the patterned substrate  62 , and thus a replica  64  (patterned substrate) with the regular array pattern transferred from the porous polymer thin film  35  is obtained. 
     Herein, the material of the replica  64  can be selected from metals including nickel, platinum and gold, from inorganic materials including glass and titania, or from other materials, depending on the purpose. If the replica  64  is made of metal, the transfer object  50  can be made tightly contact with the surface of the patterned substrate  62  by spattering, evaporation, plating, or a combination of them. 
     Further, if the replica  64  is made of an inorganic material, the transfer object  50  can be made into tight contact by spattering, a CVD method as well as a sol-gel process. Herein, plating and the sol-gel method are preferable methods capable of accurately transferring a fine regular array pattern in a size of several dozen nanometers of a microphase separated structure, and lowering the cost by a non-vacuum process. 
     By the above described method of producing a patterned substrate, a patterned substrate can be produced which has a fine regular array pattern with a large aspect ratio on the surface thereof. 
     (Pattern Carrier and Patterned Medium for Magnetic Recording) 
     Since a patterned substrate obtained by the above described producing method has on the surface thereof a regular array pattern which is fine and large in aspect ratio, it is applicable to various purposes. 
     For example, by making the surface of the produced patterned substrate tightly and repeatedly contact with a transfer object by a nanoimprinting method or the like, it can be used for a purpose of mass production of replicas of pattern carriers having the same regular array patterns on the surfaces thereof. 
     Methods of transferring a fine regular array pattern of the surface of a pattern carrier to a transfer object by nanoimprinting method will be described below. 
     The first one is a method of transferring a regular array pattern by direct imprinting of a pattern carrier  63  produced as shown in (f) of  FIG. 5  to a transfer object (not shown), which is called a thermal imprint method. This method is applied to a case where the transfer object is made of a material allowing direct imprinting. For example, in a case of a transfer object of a thermoplastic resin represented by polystyrene, after heating the thermoplastic resin up to or higher than the glass transition temperature, the pattern carrier  63  is pressed to tightly contact with the transfer object, then cooled down to or lower than the glass transition temperature, thereafter the pattern carrier  63  is peeled off from the surface of the transfer object, thereby obtaining a replica. 
     As the second method, in a case where the pattern carrier  63  is made of a phototransmitting material, such as glass, a photo-curable resin is employed as the transfer object (not shown), and this method is called a photo-imprint method. This photocurable resin is made tightly contact with the pattern carrier  63  and then irradiated with light, thereby the photocurable resin is cured, then the pattern carrier  63  is peeled off, and the photo-curable resin (the transfer object) after curing is used as a replica. 
     Further, in a case of employing a substrate of glass or the like as a transfer object (not shown) in such a photo-imprint method, it is also possible to have the pattern carrier  63  and the substrate as the transfer object in tight contact with each other, irradiate light at the nip therebetween, and, after having the photo-curable resin cured, the pattern carrier  63  is peeled off, then the photo-cured resin having a relief on the surface thereof is used as a mask for etching by plasma, ion beams or the like, and thereby the regular array pattern is transferred onto the substrate. 
     Pattern carriers applicable in the first and second methods described above may be the patterned substrate  63 , shown in (f) of  FIG. 5 , as well as the patterned substrate  62 , shown in (d) of  FIG. 5 , and the pattern  64  prepared, as shown in (f) of  FIG. 6 . When executing a thermal imprint method using the patterned substrate  62  prepared, as shown in  FIG. 5 , as the pattern carrier, it is necessary to employ a material with a softening temperature higher than that of the thermoplastic resin for the transfer object (not shown), for the porous polymer thin film  35 . 
     Now, a patterned medium for magnetic recording will be described. 
     Prior to describing the present embodiment, a magnetic recording media will be described. 
     For a magnetic recording media, it is always required to improve the density of recording data. Therefore, dots on a recording medium, each of which being a basic unit for recording data, are made minute, and the interval between dots is narrowed for high density. 
     In order to construct a recording medium with a recording density of 1 terabit /inch 2 , it is understood that the periodic cycle of the array pattern of dots needs to be approximately 25 nanometers. 
     If the density of dots is made higher, there may be a problem that magnetism applied for switching a dot ON/OFF affects adjacent dots. 
     Therefore, in order to eliminate affects by magnetism leaking from adjacent dots, a method is considered which forms an array pattern by physically dividing regions of dots on a magnetic recording medium. 
     That is, for the patterned medium for magnetic recording described here, a regular array pattern of a patterned substrate produced in accordance with the invention is used, and thereby formed is an array pattern of dots of such a magnetic recording medium. Description will be continued, referring to  FIG. 5 . 
     A material, such as glass or aluminum, is used for a substrate  40  for this patterned medium for magnetic recording. Then, as described above, the surface of the substrate  40  is processed, according to (a) to (f) of  FIG. 5 , to obtain a patterned medium  63  for magnetic recording, thereafter a magnetic recording layer is formed on the surface of the patterned medium  63  by spattering or the like, and thus a magnetic recording medium is produced. 
     On the other hand, it is also possible to process a patterned medium for magnetic recording, by a nano-imprint method, such as photo-imprinting or thermal-imprinting, using a patterned substrate  62 ,  63  or  64 , shown in (d) of  FIG. 5 , (f) of  FIG. 5  or (f) of  FIG. 6 , as the pattern carrier. 
     Specifically, a substrate of a patterned medium for magnetic recording before forming a regular array pattern is coated with a thermoplastic resin or photo-curable resin to form a film, and the regular array pattern in a relief is transferred to the coated film. The coated film to which the regular array pattern with relief is transferred is used as a mask for etching by plasma, ion beams or the like, and thus the relief of the regular array pattern is formed on the substrate. This method is more preferable in terms of cost and productivity. 
     In the above, a polymer thin film  30  has been described mostly with regard to a purpose of producing the patterned substrates  61 ,  62 ,  63  or  64  to which the regular array pattern on the surface of the polymer thin film  30  is transferred. However, a polymer thin film  30  is used without being limited to such a purpose, and for example, there is also a purpose of producing a porous polymer thin film  35  to be used alone as a filter. 
     Further, a regular array pattern having hexagonal close-packed structures has been illustrated in the above description. However, without being limited thereto, a regular array pattern may have a square array. Still further, the scope of protection of a polymer thin film in accordance with the invention is not limited to a case of having a regular array pattern, and includes a case of having an irregular array pattern. 
     EMBODIMENT 1  
     In the present embodiment, in accordance with the process shown in (a) to (c) of  FIG. 5 , an example will be described where a polymer thin film  30  having a structure with cylindrical microdomains  20  of polymethylmethacrylate (PMMA) arrayed in a continuous phase  10  of polystyrene (PS) is formed on a substrate  40 . An example will be illustrated, where, in accordance with the process shown in (c) and (d) of  FIG. 5 , the cylindrical microdomains  20  of PMMA in the polymer thin film  30  are decomposed and removed, and a porous polymer thin film  35  is formed on the surface of a substrate  40 . 
     Herein, block copolymers  31  (hereinafter, referred to as PS-b-PMMA) with PS as the first segments  12  (refer o (a) of  FIG. 2 ) and PMMA as the second segments  22  (hereinafter, referred to as PMMA segments), and polymers  13  (refer to (b) of  FIG. 2 ) (hereinafter, referred to as homo-PS) of PS were mixed to prepare a polymer mixture. 
     The prepared polymer mixture was dissolved in a solvent of toluene, and polymer mixture solution with a concentration of 1.0 weight % was prepared. This polymer mixture solution was dropped on the surface of the substrate  40  for spin coating, and thus a coated film  38  was formed on the surface of the substrate  40 , as shown in (b) of FIG.  5 . Herein, the rotation speed of a spin coater was adjusted so as to make the thickness of the coated film  38  be 100 nm. 
     Herein, a Si wafer was employed for the substrate  40 . Before using the substrate  40  for experiment, the surface of the substrate  40  was sufficiently cleaned by immersing the substrate  40  in a mixed solution (piranha solution) of concentrated sulfuric acid and hydrogen peroxide solution in a ratio of 3:1 at 60° C. for ten minutes. 
     The polymer mixture of PS-b-PMMA and homo-PS used here will be described in detail below. First, the number average molecular weight Mn of the respective segments constituting PS-b-PMMA were 46,000 for PS segments and 21,000 for PMMA segments. The molecular amount distribution Mw/Mn as the whole PS-b-PMMA was 1.09. Mn was 7,500 and Mw/Mn was 1.09 for homo-PS. 
     These samples will be referred to respectively as PS(46 k)-b-PMMA(21 k) and PS(7 k) in the following. 
     Next, PS(46 k)-b-PMMA(21 k) and PS(7 k) were mixed with each other, and a series of polymer mixtures with different ratios (φ PS  (%)) of the sum of the PS segments and homo-PS to the entire polymer mixture were prepared. Herein, φ PS  of PS(46 k)-b-PMMA(21 k) alone was 69%. By adding PS(7 k) to PS(46 k)-b-PMMA(21 k), φ PS  was adjusted with steps of 1% from 69% to 85% as shown in the left column of  FIG. 8 . 
     Then, the surface of the coated film  38  formed on the surface of the substrate  40  was observed by an atomic force microscope (Veeco Instrument Japan made model D-500). As a result, it proved that the surface of the coated film  38  was uniform and the surface of the substrate  40  was coated with a uniform thickness. A part of the coated film  38  was peeled off by a sharp blade, and the step between the portion where the coated film  38  is present and the peeled portion was measured by the atomic force microscope. As a result, the thickness of the coated film  38  proved to be 100 nm. 
     Next, the substrate  40  formed with the coated film  38  was subjected to heat processing in a vacuum atmosphere at 230° C. for four hours to create a microphase separated structure in the polymer thin film  30  (refer to (c) of  FIG. 5 ). A part of the obtained substrate  40  was cut off, and the microphase separated structure in the polymer thin film  30  was observed by the atomic force microscope. 
     Observation by the atomic force microscope was carried out by forming a relief derived from a microphase separated structure on the surface of the polymer thin film  30  by the following method. That is, the surface of the polymer thin film  30  was subjected to ashing by irradiating UV-light for six minutes, and the PMMA phase was removed by approximately 5 nm, and thus a relief derived from the microphase separated structure was produced on the polymer thin film  30 . 
     Schematic views of observation results with respective values of φ PS  are shown in the left part of  FIG. 8 . Diagrams (e), (f) and (g) of  FIG. 4  show representative observed images by the atomic force microscope. 
     Diagram (e) of  FIG. 4  shows an observed image of a sample with φ PS  of 72%. In the most part of the image, cylindrical recessed shapes in a diameter of approximately 20 nm are lying with respect to the film surface. These recessed shapes were formed by etching the PMMA phase by UV, and it proved that the microdomains  20   b  (refer to (b) of  FIG. 4 ) of PMMA are lying in the continuous phase  10   b  of PS with respect to the film surface. 
     Diagram (g) of  FIG. 4  shows an observed image of a sample with a φ PS  of 80%. A structure in which cylindrical recessed shapes with a diameter of approximately 20 nm are regularly arrayed in the film surface is observed. Herein, the cylindrical recessions are arrayed substantially in a hexagonal close packed structure, with the distance between the centers thereof was approximately 40 nm. These recessed shapes were formed by etching the PMMA phase by UV, and it proved that the cylindrical microdomains  20  (refer to (d) of  FIG. 4 ) of PMMA are present perpendicular to the film surface in the continuous phase  10 . 
     Diagram (f) of  FIG. 4  is an observed image of a sample with φ PS  of 84%, in which no clear structure is observed. It is understood that no clear structure is observed because the microphase separated structure turned, with the increase in φ PS , into a structure where spherical microdomains  20   c  (refer to (c) of  FIG. 4 ) are distributed. 
     Illustrations about the above are shown in the table in  FIG. 8 . Changing φ PS  (%) continuously as such, it proved that a structure, where cylindrical microdomains  20   b  of PMMA are lying with respect to the film surface, is formed in a region of φ PS  from 69% to 75%, a structure where cylindrical microdomains  20  of PMMA are perpendicular to the film surface is formed in a region of φ PS  from 76% to 83%, and a structure where spherical microdomains  20   c  of PMMA are distributed in the film surface is formed in a region of φ PS  from 84% to 85%. 
     Next, based on the above described results, taking samples of φ PS  of 76% to 83% which form a structure where cylindrical microdomains  20  of PMMA are perpendicular to the film surface (oriented along the penetration direction through the film), the PMMA phase was removed by RIE, as shown in (d) of  FIG. 5 , and thus a porous polymer thin film  35  were obtained. Herein, the oxygen gas pressure was set to 1 Pa and the output was set to 20 W. The time for etching was set to 90 seconds. The surface shapes of the produced porous thin films  35  were observed using a scan type electronic microscope. 
     A representative result is shown in the right part of  FIG. 8 . This diagram shows a result using a sample with φ PS  80%. It was confirmed that the porous polymer thin film  35  is formed with cylindrical fine pores  25  oriented along the penetration direction through the film. Herein, the diameters of the fine pores  25  are approximately 20 nm, and the state was observed where the fine pores  25  are arrayed substantially in a hexagonal close-packed structure. The distance between the centers of adjacent fine pores  25  was approximately 40 nm. The depth of the fine pores  25  was approximately 80 nm. Herein, a part of the porous polymer thin film  35  was peeled off by the thickness thereof from the surface of the substrate  40  by a sharp blade, and the step between the surface of the substrate  40  and the surface of the porous polymer thin film  35  was measured by the atomic force microscope, resulting in a value of 80 nm. 
     The above described result proved that the fine pores  25  penetrate from the surface of the porous polymer thin film  35  to the surface of the substrate  40 . Further, the aspect ratio of the obtained fine pores  25  was 4, realizing a large value which cannot be obtained by spherical microdomain structures. It is understood that the film thickness of the polymer thin film  30  decreased from 100 nm, which was prior to performing RIE, to 80 nm because the PS continuous phase  10  was also etched a little, along with the PMMA phase through performing RIE. 
     A series of samples of φ PS  of 76% to 83% were evaluated likewise, and similar results were obtained. It was confirmed that a porous polymer thin film  35  was formed with cylindrical fine pores  25  oriented along the penetration direction through a film. 
     As shown in  FIG. 8 , using a sample of a substrate on which surface a film of a sample prepared by mixing PS(46 k)-b-PMMA(21 k) with PS(7 k) was formed, a microphase separated structure was created. It was confirmed that when fps is 83% or lower, a cylindrical microphase separated structure is formed, and in a range from 76% to 83%, cylindrical microdomains are oriented perpendicular to the polymer thin film and the surface of the substrate. 
     COMPARATIVE EXAMPLE 
     In the sample prepared by mixing PS(46 k)-b-PMMA(21 k) and PS(7 k) to make φ PS  be 81% in such a manner, the cylindrical microdomains  20  were oriented perpendicular to the surface of the substrate  40 , as shown in  FIG. 8 . Herein, the following test was carried out to confirm the effect of adding homo PS. 
     First, a sample of PS-b-PMMA alone was prepared with φ PS  as 81%, and verified the effect of adding homo PS. For the sample, PS-b-PMMA was used of which Mn of PS segments is 89,000, Mn of PMMA segments is 21,000, and molecular weight distribution Mw/Mn is 1.07. 
     Hereinafter, this sample will be referred to as PS(89 k)-b-PMMA(21 k) for abbreviation. PS(89 k)-b-PMMA(21 k) alone has φ PS  of 81%, namely without mixing with homo PS. 
     By the same method as preparing the above described mixture system of PS(46 k)-b-PMMA(21 k) and PS(7 k), a film of PS(89 k) b-PMMA(21 k) was formed on the surface of a substrate  40  and a microphase separated structure was created by heat processing. The obtained polymer thin film was irradiated with UV and observed by the atomic force microscope, which proved that cylindrical microdomains  20   b  with a diameter of approximately 21 nm were oriented, as shown in (b) and (e) of  FIG. 4 , in a state of lying with respect to the surface of the film at an interval of approximately 40 nm. 
     Next, discussion was made on a case where a sample in which PS-b-PMMA alone has a φ PS  of 85% was prepared and the Ups was adjusted to 81% by adding homo PMMA. For the sample, PS-b-PMMA was employed in which Mn of PS segments was 85,000, Mn of PMMA segments was 15,000, and molecular weight distribution Mw/Mn was 1.08. Hereinafter, this sample will be referred to as PS(85 k)-b-PMMA(15 k) for abbreviation. 
     PS(85 k)-b-PMMA(15 k) alone has Ups of 85%, and forms spherical microdomains  20   c.  By mixing this sample with homo PMMA with Mn of 5,000 and molecular weight distribution Mw/Mn of 1.10, a polymer mixture was prepared of which fps was adjusted to 81%. 
     By the same method as preparing the above described mixture system of PS(46 k)-b-PMMA(21 k) and PS(7 k), a film of PS(85 k)-b-PMMA(15 k) and PMMA (5 k) was formed on the surface of a substrate  40  and a microphase separated structure was created by heat processing. The obtained polymer thin film was irradiated with UV and then observed by the atomic force microscope, which proved that cylindrical microdomains  20   b  with a diameter of approximately 20 nm were oriented in a state of lying with respect to the surface of the film at an interval of approximately 42 nm. 
     From the above results, it proved that, a microphase separated structure, in which cylindrical microdomains  20  of PMMA are oriented perpendicular to the substrate  40  in a continuous phase  10  of PS, can be formed by mixing PS-b-PMMA with polymer (PS) of the same monomer as PS segments forming the continuous phase such that the above described Formula (1) is satisfied. 
     EMBODIMENT 2 
     An embodiment will be described below, where, by the same method as in Embodiment 1, a polymer thin film was formed which has a structure in which cylindrical microdomains  20  of polystyrene (PS) are arrayed in a continuous phase  10  of polymethylmethacrylate (PMMA) in a state where the cylindrical microdomains  20  are oriented perpendicular to a substrate  40 . 
     A polymer mixture of diblock copolymers (PS-b-PMMA), composed of PS segments and PMMA segments, and homo PMMA was used for discussion. 
     The polymer mixture used for discussion will be described below in detail. The number average molecular weight Mn of each segment constituting PS-b-PMMA is 20,000 for PS segments and 50,000 for PMMA segments. The molecular weight distribution Mw/Mn as the entire PS-b-PMMA was 1.09. Mn of homo PMMA was 6,500 and Mw/Mn thereof was 1.07. Hereinafter, these samples will be referred to as PS(20 k)-b-PMMA(50 k) and PMMA(6 k). 
     A series of polymer mixtures were prepared by mixing PS(20 k)-b-PMMA(50 k) and PMMA(6 k) such that the respective ratios (volume ratio: φ PMMA  (%)) of the sum of the volumes of the PMMA segments and homo PMMA to the entire polymer mixture are different from each other. Although PS(20 k)-b-PMMA(50 k) alone has φ PMMA  of 71%, φ PMMA  was adjusted with steps of 1% from 71% to 87% by adding PMMA(6 k) to PS(20 k)-b-PMMA(50 k). Obtained results are shown in the left part of  FIG. 9 . 
     A microphase separated structure was created by forming on the surface of a substrate a film of a sample prepared by mixing PS(20 k)-b-PMMA(50 k) and PMMA(6 k) in such a manner. The obtained film was irradiated with UV and then observed by the atomic force microscope, which confirmed that a cylindrical microphase separated structure was formed with φ PMMA  lower than or equal to 85%, and cylindrical microdomains  20  were oriented perpendicular to the surface of the substrate in a region from 78% to 85%. 
     Further, a representative observation result after RIE processing is shown in the right part of  FIG. 9 .  FIG. 9  shows a result of a case of using a sample with φ PMMA  of 82%. It was confirmed that cylindrical structures  26  perpendicular to the surface of the substrate  40  were formed on the surface of the substrate  40 . 
     Herein, the diameter of the cylindrical structures  26  were approximately 20 nm, and a state was observed where they were arrayed substantially in a hexagonal close-packed structure. The distance between the centers of adjacent cylindrical structures  26  was approximately 40 nm. Further, the height of the cylindrical structures  26  was approximately 70 nm. From the above results, it proved that the aspect ratio of the obtained cylindrical structures  26  was 3.5. 
     From the above results, it was verified that a microphase separated structure can be formed in which cylindrical microdomains  20  of PS in the continuous phase  10  of PMMA are oriented perpendicular to the substrate  40 , by mixing PS-b-PMMA with polymers (PMMA) of the same monomer as the PMMA segments forming the continuous phase such as to satisfy Formula (1). 
     EMBODIMENT 3  
     An embodiment will be described below, where, by the same method as in Embodiment 1, a polymer thin film is formed, on a substrate  40 , which has a structure in which cylindrical microdomains  20  of polymethylmethacrylate (PMMA) are arrayed in a continuous phase  10  of polystyrene (PS). 
     A polymer mixture of diblock copolymers (PS-b-PMMA) composed of PS segments and PMMA segments, and polymers  13  composed of polymethyl vinyl ether (PMVE) compatible with PS segments, was used. 
     The polymer mixture of PS-b-PMMA and PMVE used here will be described below in detail. First, the number average molecular weight Mn of each segment constituting Ps-b-PMMA was 46,000 for PS segments and 21,000 for PMMA segments. The molecular weight distribution Mw/Mn as the entire PS-b-PMMA was 1.09. Further, Mn of PMVE was 8,700 and Mw/Mn was 1.05. Hereinafter, these samples will be referred to as PS(46 k)-b-PMMA(21 k) and PMVE(9 k). 
     A series of polymer mixtures were prepared by mixing PS(46 k)-b-PMMA(21 k) and PMVE(9 k) such that the respective ratios (φ PS+PMVE  (%) ) of the sum of the volumes of the PS segments and PMVE to the entire polymer mixture are different from each other. Although PS(46 k)-b-PMMA(21 k) alone has φ PS+PMVE  of 69%, φ PS+PMVE  was adjusted with steps of 1% from 69% to 88% by adding PMVE(9 k) to PS(46 k)-b-PMMA(21 k), as shown in the left column of  FIG. 10 . Obtained results are shown in the left part of  FIG. 10 . 
     A microphase separated structure was created by forming on the surface of a substrate a film of a sample prepared by mixing PS(46 k)-b-PMMA(21 k) and PMVE(9 k). The obtained film was irradiated with UV and then observed by the atomic force microscope, which confirmed that there arises a structure in which cylindrical microdomains are lying with respect to the surface of the film with φ PS+PMVE  in a range from 69% to 76%, a structure in which cylindrical microdomains of PMMA are perpendicular to the surface of the film with φ PS+PMVE  in a range from 77% to 84%, and a structure in which spherical microdomains of PMMA are distributed on the surface of the film with φ PS+PMVE  in a range from 85% to 88%. 
     Herein, the diameter of the cylindrical structures was approximately 21 nm, and a state was observed where they were arrayed substantially in a hexagonal close-packed structure. The distance between the centers of adjacent cylindrical structures was approximately 43 nm. Further, the height of the cylindrical structures was approximately 70 nm. From the above results, it proved that the aspect ratio of the obtained cylindrical structures was 3.5. 
     From the above results, it was verified that a microphase separated structure can be formed in which cylindrical microdomains  20  of PMMA in the continuous phase  10  of PS are oriented perpendicular to the substrate  40 , by mixing PS-b-PMMA with polymers (PMVE) compatible with the PS segments forming the continuous phase such as to satisfy Formula (1). 
     EMBODIMENT 4 
     In the present embodiment, an example will be described where a recessed structure is formed on the surface of a substrate by a top-down method. By forming a microphase separated structure in the recessed structure, namely, in a constrained space, cylindrical microdomain structures are arrayed in a state where extremely few defects, grains, particle fields and the like are present. In the following, according to the process shown in (a) to (d) of  FIG. 7 , such a microphase separated structure is formed, and thereafter a patterned substrate having a regular array pattern on the entire surface of a substrate  41  is formed. 
     First, as shown in (a) of  FIG. 7 , a substrate  41  provided with recessions  42  on the surface thereof is prepared. Herein, the width (L) of the recessions  42  is 350 nm, the depth (d) is 80 nm, and the distance (t) between adjacent recessions  42  is 50 nm. The recessions  42  are arranged in parallel on the surface of the substrate  41 . The recessions  42  are processed by the following method. That is, a thin film of SiO 2  with a thickness of 80 nm is laminated on a silicon substrate having a flat surface by plasma CVD, and then an ordinary photolithography process is used, wherein the SIO 2  thin film is etched by dry etching so as to process the recessions  42 . 
     Next, the obtained substrate  41  is immersed in a mixed solution (piranha solution) with a ratio between concentrated sulfuric acid and hydrogen peroxide solution of 3:1 at 60° C. for ten minutes so that the surface thereof is sufficiently cleaned. 
     According to the method same as in Embodiment 1, a film of a polymer mixed system is formed inside a recession  42  obtained by the above described method, and thus a coated film  38  is obtained. Herein, the polymer mixed system is prepared by adding PS(7 k) to PS(46 k)-b-PMMA(21 k) so that φ PS  is adjusted to 80%. 
     Then, as shown in (b) and (c) of  FIG. 7 , according to the same process as in Embodiment 1, a microphase separated structure is formed in which cylindrical microdomains  20  of PMMA are arrayed in a continuous phase  10  of PS in a polymer thin film  30 , and further, the cylindrical microdomains  20  of PMMA are decomposed by oxygen RIE so as to form fine pores  25  inside the recessions  42 . 
     Observation of the surface of the obtained substrate  41  by the scan type electronic microscope proved that cylindrical fine pores  25  are formed through a porous polymer thin film  35  along the penetration direction through the film. Herein, the diameter of the cylindrical pores was approximately 20 nm, and a state was observed where the cylindrical pores were arrayed in a hexagonal close-packed structure. The distance between the centers of adjacent fine pores  25  was approximately 40 nm. The depth of the fine pores was approximately 60 nm. Further, it was confirmed that these fine pores  25  were arrayed along the side walls of the respective recessions  42 , in a hexagonal close-packed structure. Still further, the region of 10 micron square was observed with a lower magnification of the electronic microscope, and no particle field or the like that distorts the array of the fine pores  25  was observed. Yet further, the directions of orientation of the fine pores  25  in the recessions  42  were all the same. 
     The above described results proved that, by forming a structure including recessions  42  on the surface of a substrate  41  by a top-down method and forming a micro separated structure inside the structures, namely, constrained spaces, cylindrical microdomains  20  can be arrayed in a state where extremely few defects, grains, particle fields and the like are present. 
     EMBODIMENT 5  
     Referring to  FIG. 6 , a method, by plating with a nickel film, of producing a replica  64  of the porous polymer thin film  35  having cylindrical fine pores  25  prepared by the method described in Embodiment 1 will be described below. First, according to the process shown in (a) to (d) of  FIG. 6 , a porous polymer thin film  35  with fine pores  25  was produced, using the same sample and same method as in Embodiment 1. Herein, PS(46 k)-b-PMMA(21 k) added with PS(7 k) was used with φ PS  adjusted to 80%. 
     Then, the surface of the porous polymer thin film  35  was subjected to electroless nickel plating. Further, electric nickel plating was performed with the electroless nickel plating layer as a power supply layer, and thus a nickel thin film with a thickness of 20 μm was formed as a transfer object  50  on the surface of a patterned substrate  62  (refer to (e) of  FIG. 6 ). 
     The following method was applied for the electroless nickel plating. First, a substrate  40  having a porous polymer thin film  35  (hereinafter, referred to merely as a substrate  40 ) was immersed in cleaning solution (Securiganth 902 made by ATOTECH Japan) for promoting addition of catalyst for electroless plating, at 30° C. for five minutes. Then, the substrate was sufficiently cleaned with pure water and immersed in pre-dip solution (Neoganth B made by ATOTECH Japan) at a room temperature for one minute in order to prevent contamination of the catalyst solution. Thereafter, the substrate  40  was immersed in a catalyst solution (Neoganth 834 made by ATOTECH Japan) at 40° C. for five minutes. The catalyst used here is a solution with palladium complex molecules dissolved in it. After adding the catalyst, the substrate was immersed in a pure water to be cleaned, and was activated with the added palladium as a core, using Neoganth W solution made by ATOTECH Japan. 
     Finally, by cleaning with pure water, the substrate  40  provided with a catalyst layer for electroless plating precipitation was obtained. Then, the substrate  40  subjected to addition of catalyst was immersed in an electroless nickel plating solution for 30 seconds, and thus a nickel plated film was precipitated on the entire surface of the porous polymer film  35  on the substrate  40 . The composition of the electroless nickel plating solution and the plating conditions used here are shown in (a) of  FIG. 11 . The pH of the plating solution was adjusted using an ammonia solution. 
     Electric nickel plating was carried out by the following procedure. That is, making a lead by a conductive tape from the periphery of the nickel plated film precipitated covering the entire surface of the porous polymer thin film  35  by electroless nickel plating, and having a nickel plate serve as the return electrode, electric nickel plating was performed by the use of sulfamic acid Ni plating solution made by Nihon Kagaku Sangyo-sha. The composition of the plating solution and the plating conditions are shown in (b) of  FIG. 11 . 
     Finally, the nickel thin film  50  obtained by the above described method was peeled off from the porous polymer thin film  35 , and thus a replica  64  having fine pore structures was obtained ((f) of  FIG. 6 ). The surface structure of the replica  64  of the obtained nickel film was observed by a scan type electronic microscope (S-4800 made by Hitachi High-Technologies Corporation), and it was proved that fine cylindrical structures  26  with a diameter of 20 nm and height of 80 nm were present with the distance between the centers of adjacent cylindrical structures  26  of 40 nm on the entire surface of the nickel film in such a manner that the cylindrical structures are arrayed in a hexagonal close-packed structure in a substantially regular state without defects, grains, or particle fields. 
     EMBODIMENT 6 
     As Embodiment 6, an example of processing a substrate  40  by dry etching will be described below, wherein, as a mask, used is a porous polymer thin film  35  with cylindrical fine pores  25  produced by the method described in Embodiment 1 through the process shown in  FIG. 5 . First, according to the process shown in (a) to (d) of  FIG. 5 , a porous polymer thin film  35  having fine cylindrical pores  25  was prepared by the use of the same sample and same method as in Embodiment 1. Herein, φ PS  was made 80%. For the substrate  40 , a SiO 2  thin film with a thickness of 100 nm was laminated by plasma CVD on the surface of a silicon substrate. 
     Herein, it was confirmed that the porous polymer thin film  35  was formed with cylindrical fine pores  25  along the penetration direction through the film. The diameter of the cylindrical pores was approximately 20 nm, and a state was observed where the cylindrical pores were oriented substantially in a hexagonal close-packed structure. The distance between centers of adjacent fine pores  25  was approximately 40 nm. The depth of the fine pores  25  was approximately 80 nm. Further, it was confirmed that the fine pores  25  penetrate from the surface of the porous polymer thin film  35  to the surface of the substrate  40 . 
     Next, the SiO 2  thin film on the surface of the substrate  40  was subjected to dry etching by C 2 F 6  gas with the fine pores  25  as a mask. As the etching conditions, the output power was set to 150 W, the gas pressures was set to 1 Pa, and the etching time was set to 60 seconds. After etching the SiO 2  layer, the porous polymer thin film  35  remaining on the surface of the substrate was removed by oxygen plasma processing (30 W, 1 Pa and 120 seconds), and thus a patterned substrate  63  formed with fine pores  25  was produced, as shown in (f) of  FIG. 5 . 
     Herein, the obtained patterned substrate  63  was observed by the scan type electronic microscope. The diameter of the fine pores  25  was 20 nm, and a state was observed where hexagonal closed-pack structures forming triangle lattices were substantially regularly arrayed with the distance between the centers of adjacent fine pores  25  of 40 nm. Further, the patterned substrate  63  was processed by convergent ion beams, and the cross-sectional structure of the substrate was observed by the scan electronic microscope, which proved that the depth of the fine pores  25  was 50 nm without variation. 
     EMBODIMENT 7 
     In the present embodiment, an example will be described where a nickel film having on the surface thereof a regular array pattern, produced by a process equivalent to the method disclosed by Embodiment 4, was used as a stamper for a nano-imprint method. 
     First, a nickel stamper  81  produced for experiment is schematically shown in (a) of  FIG. 12 . The outer diameter of the nickel stamper  81  is 4 inch φ and 25 μm thick. In a 2.5 cm square area  82  in the central part of the stamper  81 , fine pores  83  with a diameter of 20 nm and a height of 80 nm are regularly arrayed to form hexagonal close-packed structures. An enlarged view of the 2.5 cm square area in the central part is shown in (b) of  FIG. 12 . The nickel stamper  81  was produced by the same method as in Embodiment 5. 
       FIG. 13  is a schematic view of a prototype nao-priniting device  90  by the use of the stamper  81 . 
     The procedure will be described below. First, a peeling agent for easy release in resin forming was coated on the surface of the stamper  81 . A polydimethylsiloxane group peeling agent was employed as the peeling agent. 
     Next, a process of forming of resin by the use of the stamper  81  coated with the peeling agent will be described. First, a polystyrene resin  92  (Polystyrene 679 made by A &amp; M) was spin coated with a thickness of 600 nm on a Si substrate  91  (4 inch φ and 0.5 mm thick) . The stamper  81  coated with the peeling agent was fitted with positioning, and thereafter set above a stage  98 . 
     The stage  98  has a structure capable of moving horizontally and vertically to an arbitrary position by a driving section  93  connected to the stage  98  through a support  99 . 
     The nano-printing device  90  has a vacuum chamber  97 , and the stage  98  is provided with a heating mechanism. The pressure inside this vacuum chamber  97  was reduced to 0.1 Torr or lower and the vacuum chamber  97  was heated to 250° C. Then, the stamper  81  held by a support  96  driven up and down was pressed at 12 MPa against the polystyrene resin  92  for 10 minutes. Then, the vacuum chamber was left until the temperature dropped to 100° C. or lower, and then released to the atmosphere. A peeling tool was adhesively fixed at the back side of the stamper  81  at the room temperature, and the stamper  81  was lifted in the vertical direction at a speed of 0.1 mm/s. Thus, the shape of the stamper surface was transferred to the surface of the polystyrene resin. 
     Next, using the stamper  81  coated with the same peeling agent, the above described resin forming process was repeated 100 times so as to obtain one hundred pieces of formed resin products to which the shape of the stamper surface was transferred. The surface of the central part of each of the obtained formed resin products was observed by the atomic force microscope, and for all the formed polystyrene resin products, a state was observed where cylindrical fine pores form hexagonal close-packed structures arrayed substantially regularly with almost no defects. The diameter of the fine pores was 20 nm and the distance between the centers of adjacent pores was 40 nm. From the above, it was confirmed that it is possible to transfer the surface shape of the stamper accurately to the surface of a polystyrene resin. 
     EMBODIMENT 6  
     A method of producing a patterned medium for magnetic recording in accordance with the invention will be described below. This method includes a process of producing a patterned substrate by self assembly of block copolymers, a process of producing a replica of the patterned substrate by nickel plating, a process of forming a fine pattern on the surface of a glass substrate for a patterned medium for magnetic recording, with the nickel plated replica as a stamper (pattern carrier), and a process of forming a magnetic film on the surface of the patterned medium, having been produced, for magnetic recording. 
     First, the process of producing a patterned substrate of a polymer thin film by self assembly of block copolymers will be described. 
     First, a SiO 2  layer with a thickness of 80 nm was formed by a CVD method on a surface of a silicon substrate with a thickness of 2.5 inches. Then, applying an ordinary photo-lithography process, the SiO 2  layer was etched so as to form concentric grooves with a depth of 80 nm and width of 200 nm at an interval of 1000 nm. Next, according to the process described in Embodiment 2, a patterned substrate with fine convex shapes of PS which are regularly arrayed was produced. Herein, used was a sample of which φ PMMA  was adjusted to 80% by adding PMMA(6 k) to PS(20 k)-b-PMMA(50 k). 
     The surface of the obtained patterned substrate was observed by the atomic force microscope. A microscopic state was observed where fine cylindrical structures of PS with a diameter of 20 nm and a height of 70 nm were regularly arrayed with almost no defects on the surface of the patterned substrate and form triangle lattices with a hexagonal close-packed structure with a distance of 30 nm between the centers of adjacent cylindrical structures. Further, when macroscopic observation was made with a lower magnification of the atomic force microscope, it was proved that the regular structure formed by the fine cylindrical structures of PS were arrayed concentrically with a center at the center of the patterned substrate, with almost no defects. 
     Next, according to the method described in Embodiment 5, the surface of the patterned substrate on which the fine cylindrical structures of PS were regularly arrayed was subjected to nickel plating, and produced was a stamper for nanoimprint of nickel film with a thickness of 25 μm having a replica shape which was formed by reverse transfer of the surface structure. The surface of the obtained stamper was observed by the scan type electronic microscope, and it was confirmed that fine cylindrical pores with a diameter of 20 nm were regularly formed on the surface of the nickel film. 
     On the surface of a glass substrate with a diameter of 2.5 inches in a torus-shape with a hole of a diameter of 0.5 inch at the center thereof, a Pd foundation layer with a thickness of approximately 30 nm and a film of CoCrPt layer with a thickness of approximately 30 nm were formed, and thus a magnetic layer was produced. Then, a PS layer with a thickness of 50 nm was formed on the surface of the magnetic layer by a spin coat method. The molecular weight Mn of the PS used here was 5,000. The PS thin film on the surface of the magnetic layer was subjected to nanoimprint by the same method as that described in Embodiment 7, using a stamper obtained by the above described method. When the PS thin film on the surface of the obtained magnetic layer was observed by the atomic force microscope, it was confirmed that fine cylindrical structures with a diameter of 20 nm were formed regularly in the PS thin film. Herein, the shapes and positions of the fine cylindrical structures were the reverse transfer of the shapes and positions of the fine pores on the surface of the stamper. Further, the cross-sections of the fine convex shapes were measured in detail by the atomic force microscope, and the height of the fine convex shapes was 50 nm. 
     Next, the magnetic layer was etched by Ar ion milling, using the fine cylindrical structures of PS produced on the surface of the magnetic layer as a mask. Through this process, all of the PS thin film was lost. The surface of the obtained glass substrate was observed in detail by the atomic force microscope, and a microscopic state was observed where fine convexes of a magnetic layer with a diameter of 20 nm and a height of 30 nm form triangle lattices with a hexagonal close-packed structure with a distance of 30 nm between the centers of adjacent convex magnetic layers on the surface of the substrate. The fine convexes were regularly arrayed with almost no defects. Further, macroscopic observation was made with a lower magnification ratio of the atomic force microscope, and it was proved that the regular structures formed by the fine convexes of the magnetic layer were arrayed concentrically with a center at the center of the substrate with almost no defects. 
     Finally, a SiO 2  layer with a thickness of 30 nm was formed on the entire surface of the obtained substrate, and the obtained surface was made flat by CMP grinding. Thereafter, a carbon layer was formed on the entire surface of the obtained substrate by a CVD method to form a protection film, and thus a patterned substrate for magnetic recording was obtained.