Abstract:
At least one strippable film on a surface of a thin film to be patterned is formed, then the at least one strippable film and the thin film to be patterned is patterned by using FIB, and thereafter the at least one strippable film is removed.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method of patterning a thin film by using focused ion beam (FIB), to a method of manufacturing a thin-film device, and to a method of manufacturing a thin-film magnetic head.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    [0002]FIGS. 1 a  to  1   c  illustrate processes of a conventional method of directly patterning a thin film by using FIB.  
           [0003]    First, on a substrate  10  shown in FIG. 1 a , a thin film  11  to be patterned is deposited by for example sputtering as shown in FIG. 1 b . Then, as shown in FIG. 1 c , unnecessary portions of the thin film  11  are removed by directly radiating FIB to the film  11  and thus a patterned thin film  11 ′ is obtained.  
           [0004]    This method using FIB has allowed patterning without using a mask, and may pave the way for a minute patterning. However, the conventional patterning method using FIB has the following problems.  
           [0005]    Since the FIB directly radiated to a thin film to be patterned is not a beam completely focused to its center but is a beam spreading in the Gaussian distribution, upper parts of the thin film such as upper edges of each pattern are needlessly etched to some extent. Thus, it is difficult to improve the patterning precision.  
           [0006]    Since according to the conventional patterning method using FIB, a beam of ions such as charged Ga is directly radiated to a thin film to be patterned, the radiated thin film will be charged by the ions and therefore may be broken by the electrostatic discharge.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore an object of the present invention to provide a thin-film patterning method, a method of manufacturing a thin-film device and a method of manufacturing a thin-film magnetic head, whereby a patterning resolution or a patterning precision can be more improved.  
           [0008]    Another object of the present invention is to provide a thin-film patterning method, a method of manufacturing a thin-film device and a method of manufacturing a thin-film magnetic head, whereby a thin film to be patterned can be prevented from being damaged due to electric charge applied by FIB.  
           [0009]    According to the present invention, a thin film patterning method includes a step of forming at least one strippable film on a surface of a thin film to be patterned, a step of patterning the at least one strippable film and the thin film to be patterned by using FIB, and a step of removing the at least one strippable film. In a method of manufacturing a thin-film device and in a method of manufacturing a thin-film magnetic head, at least a part of a thin-film pattern is fabricated by using this thin-film patterning method.  
           [0010]    The FIB etching is performed after forming the strippable film on the thin film to be patterned. Thus, even if the FIB is not completely focused but spread, only upper edges of the pattern of the strippable film which is removed after the patterning are etched but upper edges of the thin film to be patterned are not needlessly etched. As a result, it is possible to greatly increase resolution of patterning and to extremely improve the patterning precision.  
           [0011]    According to the present invention, also, a method of patterning a thin film includes a step of forming at least one strippable film, a step of patterning the at least one strippable film by using FIB, a step of forming a thin film to be patterned by using the patterned at least one strippable film, and a step of removing the patterned at least one strippable film. In a method of manufacturing a thin-film device and in a method of manufacturing a thin-film magnetic head, at least a part of a thin-film pattern is fabricated by using this thin-film patterning method.  
           [0012]    Since the mask pattern used in a lift off process is etched by using FIB, the lower limitation of patterning, which is about 0.2 μm in width according to the conventional optical patterning method, can be further improved. In addition, since the FIB etching is performed through the strippable film, even if the FIB is not completely focused but spread, only upper edges of the pattern of the strippable film which is removed after the patterning are etched but lower edges of the strippable film, which are important as the mask pattern, are not needlessly etched. As a result, it is possible to greatly increase resolution of patterning and to extremely improve the patterning precision.  
           [0013]    According to the present invention, further, a method of patterning a thin film includes a step of forming at least one strippable film on a surface of a first thin film to be patterned, a step of patterning the at least one strippable film and the first thin film to be patterned by using FIB, a step of forming a second thin film to be patterned using the patterned at least one strippable film and the patterned first thin film to be patterned as a mask, and a step of removing the patterned at least one strippable film. In a method of manufacturing a thin-film device and in a method of manufacturing a thin-film magnetic head, at least a part of a thin-film pattern is fabricated by using this thin-film patterning method.  
           [0014]    Since the first thin film etched by using FIB is used as the mask pattern in a lift off process, the lower limitation of patterning, which is about 0.2 μm in width according to the conventional optical patterning method, can be further improved. In addition, since the FIB etching is performed after forming the strippable film on the first thin film to be patterned, even if the FIB is not completely focused but spread, only upper edges of the pattern of the strippable film which is removed after the patterning are etched but upper edges of the first thin film are not needlessly etched. Therefore, it is possible not only to greatly improve the patterning precision of the first thin film but also to greatly increase resolution of mask patterning because lower edges of the strippable film, which are important as the mask pattern for forming the second thin film, are not needlessly etched. As a result, the patterning precision of the first and second thin films and can be greatly improved.  
           [0015]    It is preferred that the at least one strippable film is an insulating organic film or a conductive organic film.  
           [0016]    It is also preferred that the at least one strippable film has a two-layers structure of an insulating organic film and a conductive film such as a metallic material film or a conductive organic film, formed on the insulating organic film. Thus, electric charge due to the FIB will escape to the conductive film. Therefore, the thin film to be patterned will never be charged resulting that a breakdown of the thin film due to electrostatic discharge can be effectively prevented.  
           [0017]    Preferably, the conductive film is a grounded film. If the conductive film is grounded, more reliable prevention of the breakdown due to electrostatic discharge can be expected.  
           [0018]    Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIGS. 1 a  to  1   c , already described, show sectional views illustrating processes of a conventional method of directly patterning a thin film by using FIB;  
         [0020]    [0020]FIGS. 2 a  to  2   f  show sectional views illustrating processes of a thin-film patterning in a preferred embodiment according to the present invention;  
         [0021]    [0021]FIGS. 3 a  to  3   f  show sectional views illustrating processes of a thin-film patterning in another embodiment according to the present invention;  
         [0022]    [0022]FIGS. 4 a  to  4   g  show sectional views illustrating processes of a thin-film patterning in a further embodiment according to the present invention;  
         [0023]    [0023]FIGS. 5 a  to  5   g  show sectional views illustrating processes of a thin-film patterning in a still further embodiment according to the present invention; and  
         [0024]    [0024]FIGS. 6 a  to  6   h  show sectional views illustrating processes of a thin-film patterning in a further embodiment according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    [0025]FIGS. 2 a  to  2   f  illustrate processes of a thin-film patterning in a preferred embodiment according to the present invention. In this embodiment, a thin film to be patterned is directly patterned by using FIB. The thin film to be patterned may be any film applicable in a thin-film device. In a thin-film magnetic head, the thin film to be patterned may be a thin film of a magnetic pole, or a thin film or a multi-layered film of a magnetoresistive effect (MR) element for example.  
         [0026]    As shown in FIG. 2 a , first, a substrate or an under layer  20  on which a thin film to be patterned will be formed is prepared. On this substrate or under layer  20 , the thin film to be patterned  21  is deposited by sputtering for example as shown in FIG. 2 b.    
         [0027]    Then, as shown in FIG. 2 c , an insulating organic film  22  as a strippable film is coated on the thin film  21 , and, as shown in FIG. 2 d , a conductive film  23  is formed on the film  22  by sputtering or coating.  
         [0028]    Thereafter, as shown in FIG. 2 e , unnecessary portions are etched and removed by using FIB, so that a patterned conductive film  23 ′, a patterned insulating organic film  22 ′ and a patterned thin film  21 ′ are obtained.  
         [0029]    Then, the patterned insulating organic film  22 ′ is melted by an organic solvent to remove this melted film  22 ′ and also the patterned conductive film  23 ′ on the film  22 ′. As a result, as shown in FIG. 2 f , only the patterned thin film  21 ′ is remained.  
         [0030]    The strippable film is not limited to the aforementioned insulating organic film. Any film is applicable as the strippable film if it can be formed as a thin film by coating for example and melted by an organic solvent. For example, a conductive organic film which will be mentioned later is applicable.  
         [0031]    As for the insulating organic film  22 , an organic resin film material such as resist film material may be used. More specifically, the resist film material may be negative resist materials such as polyglycidyl methacrylate, polymer of glycidyl methacrylate and ethyl acrylate, chloromethylation polystyrene, polyvinylphenol and azide compound, and novolak resin with cross linking agent and acid generating agent, or positive resist materials such as polymethyl methacrylate, poly(butene-1-sulfone), novolak resin with solubilizing inhibitor of for example PMPS (poly(2-methylpentene-1-sulfone), poly(2,2,2-trifluoroethyl-2-chloroacrylate), copolymer of α-methyl styrene and α-chloro acrylic acid, and novolak resin with quinonediazide.  
         [0032]    As for the conductive film  23 , any kind of metallic film material may be used. Instead of the metallic film material, carbon film material or conductive organic film material may be used. More specifically, the conductive organic film material may be poly(isothianaphthenedil sulfonate), TCNQ chain polymer, poly(3-thienylalkanesulfonic acid compound), or ammoniate of polyaniline sulfonate.  
         [0033]    According to this embodiment, the FIB etching is performed after depositing two layers of the insulating organic film  22  that is the strippable film and the conductive film  23  on the thin film to be patterned  21 . Thus, even if the FIB is not completely focused but spread, only upper edges of the pattern of the insulating organic layer  22  which is removed after the patterning are etched but upper edges of the thin film to be patterned  21  are not needlessly etched. As a result, it is possible to greatly increase resolution of patterning and to extremely improve the patterning precision.  
         [0034]    In addition, according to the embodiment, since the conductive film  23  with a larger area is formed on the insulating organic film  23 , electric charge due to the FIB will escape to the conductive film  23 . Therefore, the thin film to be patterned  21  will never be charged resulting that a breakdown of the thin film  21  due to electrostatic discharge can be effectively prevented. If the conductive film  23  is grounded, more reliable prevention of the breakdown due to electrostatic discharge can be expected.  
         [0035]    In the aforementioned embodiment of FIGS. 2 a  to  2   f , the two layers of the insulating organic film  22  and the conductive film  23  are deposited on the thin film to be patterned  21  and then the patterning using FIB is performed. However, in modification, an additional film may be deposited on the two layer and then the patterning using FIB will be performed. Furthermore, in another modification, only a single strippable film such as an insulating organic film or a conductive film may be deposited on a thin film to be patterned and then the patterning using FIB will be performed. In the former case depositing only the insulating organic film, no prevention of the breakdown due to electrostatic discharge can be obtained.  
         [0036]    [0036]FIGS. 3 a  to  3   f  illustrate processes of a thin-film patterning in another embodiment according to the present invention. In this embodiment, a mask used in a lift-off method is patterned by using FIB. A thin film to be patterned may be any film applicable in a thin-film device. In a thin-film magnetic head, the thin film to be patterned may be a thin film of a longitudinal bias film or lead conductor films of a MR element for example.  
         [0037]    As shown in FIG. 3 a , first, a substrate or an under layer  30  on which a thin film to be patterned will be formed is prepared. On this substrate or under layer  30 , an insulating organic film  32  as a strippable film is coated as shown in FIG. 3 b , and then, as shown in FIG. 3 c  a conductive film  33  is formed on the film  32  by sputtering or coating.  
         [0038]    Thereafter, as shown in FIG. 3 d , unnecessary portions are etched and removed by using FIB, so that a patterned conductive film  33 ′ and a patterned insulating organic film  32 ′ are obtained.  
         [0039]    Then, as shown in FIG. 3 e , the thin film to be patterned  34  is deposited by sputtering for example, using the patterned conductive film  33 ′ and the patterned insulating organic film  32 ′ as a mask pattern.  
         [0040]    Then, as well as done in the general lift-off method, the mask pattern is removed by an organic solvent. Namely, the patterned insulating organic film  32 ′ is melted by the organic solvent to remove this melted film  32 ′ and also the patterned conductive film  33 ′. As a result, as shown in FIG. 3 f , only a patterned thin film  34 ′ is remained.  
         [0041]    The strippable film is not limited to the aforementioned insulating organic film. Any film is applicable as the strippable film if it can be formed as a thin film by coating for example and melted by an organic solvent. For example, a conductive organic film which will be mentioned later is applicable.  
         [0042]    As for the insulating organic film  32 , an organic resin film material such as resist film material may be used. More specifically, the resist film material may be negative resist materials such as polyglycidyl methacrylalte, polymer of glycidyl methacrylate and ethyl acrylate, chloromethylation polystyrene, polyvinylphenol and azide compound, and novolak resin with cross linking agent and acid generating agent, or positive resist materials such as polymethyl methacrylate, poly(butene-1-sulfone), novolak resin with solubilizing inhibitor of for example PMPS (poly(2-methylpentene-1-sulfone), poly(2,2,2-trifluoroethyl-2-chloroacrylate), copolymer of α-methyl styrene and α-chloro acrylic acid, and novolak resin with quinonediazide.  
         [0043]    As for the conductive film  33 , any kind of metallic film material may be used. Instead of the metallic film material, carbon film material or conductive organic film material may be used. More specifically, the conductive organic film material may be poly(isothianaphthenedil sulfonate), TCNQ chain polymer, poly(3-thienylalkanesulfonic acid compound), or ammoniate of polyaniline sulfonate.  
         [0044]    According to this embodiment, the FIB etching is performed after depositing two layers of the insulating organic film  32  that is the strippable film and the conductive film  33  on the substrate  30 . Thus, even if the FIB is not completely focused but spread, only upper edges of the pattern of the insulating organic layer  32  which is removed after the patterning are etched but lower edges of the insulating organic film  32 , which are important as the mask pattern, are not needlessly etched. As a result, it is; possible to greatly increase resolution of patterning and to extremely improve the patterning precision.  
         [0045]    In addition, according to the embodiment, since the conductive film  33  with a larger area is formed on the insulating organic film  33 , electric charge due to the FIB will escape to the conductive film  33 . Therefore, the substrate  30  will never be charged resulting that a breakdown of other films on the substrate  30  due to electrostatic discharge can be effectively prevented. If the conductive film  33  is grounded, more reliable prevention of the breakdown due to electrostatic discharge can be effected.  
         [0046]    In the aforementioned embodiment of FIGS. 3 a  to  3   f , the two layers of the insulating organic film  32  and the conductive film  33  are deposited on the substrate  30  and then the patterning using FIB is performed. However, in modification, an additional film may be deposited on the two layer and then the patterning using FIB will be performed. Furthermore, in another modification, only a single strippable film such as an insulating organic film or a conductive film may be deposited on the substrate and then the patterning using FIB will be performed. In the former case depositing only the insulating organic film, no prevention of the breakdown due to electrostatic discharge can be obtained.  
         [0047]    [0047]FIGS. 4 a  to  4   g  illustrate processes of a thin-film patterning in a further embodiment according to the present invention. In this embodiment, a mask used in a lift-off method is patterned by using FIB. A thin film to be patterned may be any film applicable in a thin-film device. In a thin-film magnetic head, the thin film to be patterned may be a thin film of a longitudinal bias film or lead conductor films of a MR element for example.  
         [0048]    As shown in FIG. 4 a , first, a substrate or an under layer  40  on which a thin film to be patterned will be formed is prepared. On this substrate or under layer  40 , an insulating organic film  42  as a strippable film is coated as shown in FIG. 4 b , and then, as shown in FIG. 4 c  a conductive film  43  is formed on the film  42  by sputtering or coating.  
         [0049]    Thereafter, as shown in FIGS. 4 d  and  4   e , unnecessary portions are etched and removed by using FIB. Especially, in this embodiment, during the FIB etching, the substrate  40  is inclined with respect to the beam so that a section of a patterned conductive film  43 ′ and a patterned insulating organic film  42 ′ has a reversed taper shape or a reversed trapezoidal shape.  
         [0050]    Then, as shown in FIG. 4 f , a thin film to be patterned  44  is deposited by sputtering for example by using the patterned conductive film  43 ′ and the patterned insulating organic film  42 ′ as a mask pattern.  
         [0051]    Then, as well as done in the general lift-off method, the mask pattern is removed by an organic solvent. Namely, the patterned insulating organic film  42 ′ is melted by the organic solvent to remove this melted film  42 ′ and also the patterned conductive film  43 ′. As a result, as shown in FIG. 4 g , only a patterned thin film  44 ′ is remained.  
         [0052]    Applicable material for the films, advantages and modifications in this embodiment are the same as those in the embodiment of FIGS. 3 a  to  3   f.    
         [0053]    [0053]FIGS. 5 a  to  5   g  illustrate processes of a thin-film patterning in a still further embodiment according to the present invention. In this embodiment, a method for directly patterning a thin film to be patterned by using FIB is used in conjunction with a lift off method. The thin film to be patterned may be any film applicable in a thin-film device. In a thin-film magnetic head, the thin film to be patterned may be a thin film of a longitudinal bias film or lead conductor films of a MR element for example.  
         [0054]    As shown in FIG. 5 a , first, a substrate or an under layer  50  on which a thin film to be patterned will be formed is prepared. On this substrate or under layer  50 , a first thin film to be patterned  51  is deposited by sputtering for example as shown in FIG. 5 b.    
         [0055]    Then, as shown in FIG. 5 c , an insulating organic film  52  as a strippable film is coated on the first thin film  51 , and then, as shown in FIG. 5 d  a conductive film  53  is formed on the film  52  by sputtering or coating.  
         [0056]    Thereafter, as shown in FIG. 5 e , unnecessary portions are etched and removed by using FIB, so that a patterned conductive film  53 ′, a patterned insulating organic film  52 ′, and a patterned first thin film  51 ′ are obtained.  
         [0057]    Then, as shown in FIG. 5 f , a second thin film to be patterned  54  is deposited by sputtering for example by using the patterned conductive film  53 ′, the patterned insulating organic film  52 ′ and the patterned first thin film  51 ′ as a mask pattern.  
         [0058]    Then, as well as done in the general lift-off method, the mask pattern is removed by an organic solvent. Namely, the patterned insulating organic film  52 ′ is melted by the organic solvent to remove this melted film  52 ′ and also the patterned conductive film  53 ′. As a result, as shown in FIG. 5 g , only the patterned first thin film  51 ′ and a patterned thin film  54 ′ is remained.  
         [0059]    The strippable film is not limited to the aforementioned insulating organic film. Any film is applicable as the strippable film if it can be formed as a thin film by coating for example and melted by an organic solvent. For example, a conductive organic film which will be mentioned later is applicable.  
         [0060]    As for the insulating organic film  52 , an organic resin film material such as resist film material may be used. More specifically, the resist film material may be negative resist materials such as polyglycidyl methacrylate, polymer of glycidyl methacrylate and ethyl acrylate, chloromethylation polystyrene, polyvinylphenol and azide compound, and novolak resin with cross linking agent and acid generating agent, or positive resist materials such as polymethyl methacrylate, poly(butene-1-sulfone), novolak resin with solubilizing inhibitor of for example PMPS (poly(2-methylpentene-1-sulfone), poly(2,2,2-trifluoroethyl-2-chloroacrylate), copolymer of α-methyl styrene and α-chloro acrylic acid, and novolak resin with quinonediazide.  
         [0061]    As for the conductive film  53 , any kind of metallic film material may be used. Instead of the metallic film material, carbon film material or conductive organic film material may be used. More specifically, the conductive organic film material may be poly(isothianaphthenedil sulfonate), TCNQ chain polymer, poly(3-thienylalkanesulfonic acid compound), or ammoniate of polyaniline sulfonate.  
         [0062]    According to this embodiment, the FIB etching is performed after depositing two layers of the insulating organic film  52  that is the strippable film and the conductive film  53  on the first thin film to be patterned  51 . Thus, even if the FIB is not completely focused but spread, only upper edges of the pattern of the insulating organic layer  52  which is removed after the patterning are etched but upper edges of the first thin film to be patterned  51  are not needlessly etched. Therefore, it is possible not only to greatly improve the patterning precision of the first thin film  51  but also to greatly increase resolution of mask patterning because lower edges of the insulating organic film  52 , which are important as the mask pattern, are not needlessly etched. As a result, the patterning precision of the first and second thin films  51  and  54  can be greatly improved.  
         [0063]    In addition, according to the embodiment, since the conductive film  53  with a larger area is formed on the insulating organic film  53 , electric charge due to the FIB will escape to the conductive film  53 . Therefore, the first thin film to be patterned  51  will never be charged resulting that a breakdown of the first thin film  51  due to electrostatic discharge can be effectively prevented. If the conductive film  53  is grounded, more reliable prevention of the breakdown due to electrostatic discharge can be expected.  
         [0064]    In the aforementioned embodiment of FIGS. 5 a  to  5   g , the two layers of the insulating organic film  52  and the conductive film  53  are deposited on the first thin film to be patterned  51  and then the patterning using FIB is performed. However, in modification, an additional film may be deposited on the two layer and then the patterning using FIB will be performed. Furthermore, in another modification, only a single strippable film such as an insulating organic film or a conductive film may be deposited on a first thin film to be patterned and then the patterning using FIB will be performed. In the former case depositing only the insulating organic film, no prevention of the breakdown due to electrostatic discharge can be obtained.  
         [0065]    [0065]FIGS. 6 a  to  6   h  illustrate processes of a thin-film patterning in a further embodiment according to the present invention. In this embodiment, a method for directly patterning a thin film to be patterned by using FIB is used in conjunction with a lift off method. The thin film to be patterned may be any film applicable in a thin-film device. In a thin-film magnetic head, the thin film to be patterned may be a thin film of a longitudinal bias film or lead conductor films of a MR element for example.  
         [0066]    As shown in FIG. 6 a , first, a substrate or an under layer  60  on which a thin film to be patterned will be formed is prepared. On this substrate or under layer  60 , a first thin film to be patterned  61  is deposited by sputtering for example as shown in FIG. 6 b.    
         [0067]    Then, as shown in FIG. 6 c , an insulating organic film  62  as a strippable film is coated on the first thin film  61 , and then, as shown in FIG. 6 d  a conductive film  63  is formed on the film  62  by sputtering or coating.  
         [0068]    Thereafter, as shown in FIGS. 6 e  and  6   f , unnecessary portions are etched and removed by using FIB. Especially, in this embodiment, during the FIB etching, the substrate  60  is inclined with respect to the beam so that a section of a patterned conductive film  63 ′, a patterned insulating organic film  62 ′ and a patterned first thin film  61 ′ has a reversed taper shape or a reversed trapezoidal shape.  
         [0069]    Then, as shown in FIG. 6 g , a second thin film to be patterned  64  is deposited by sputtering for example by using the patterned conductive film  63 ′, the patterned insulating organic film  62 ′ and the patterned first thin film  61 ′ as a mask pattern.  
         [0070]    Then, as well as done in the general lift-off method, the mask pattern is removed by an organic solvent. Namely, the patterned insulating organic film  62 ′ is melted by the organic solvent to remove this melted film  52 ′ and also the patterned conductive film  63 ′. As a result, as shown in FIG. 6 h , only the patterned first thin film  61 ′ and a patterned thin film  64 ′ is remained.  
         [0071]    Applicable material for the films, advantages and modifications in this embodiment are the same as those in the embodiment of FIGS. 5 a  to  5   g.    
         [0072]    Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.