Abstract:
The method of forming a plated pattern is capable of securely narrowing and miniaturizing a resist pattern, which has been hydrophilic-treated, without widening and deforming the resist pattern. The method comprises the steps of: covering a surface of a plating seed layer with resist; exposing and developing the resist so as to form a resist pattern having a concave part; executing a hydrophilic treatment of the resist pattern; piling a metal in the concave part of the resist pattern by plating; removing the resist pattern; and removing an exposed part of the plating seed layer. The plating seed layer is a volatile metal layer made of a metal, which is oxidized during the hydrophilic treatment, and an oxide of the metal constituting the volatile metal layer has volatility.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method of forming a plated pattern and a method of manufacturing a thin film magnetic head, more precisely relates to a method of forming a plated pattern, which can be applied to form a part of a thin film magnetic head and cable patterns of a circuit board, and a method of manufacturing a thin film magnetic head, which employs said method.  
         [0002]     These days, surface recording density of magnetic recording media have been highly increased, and high performance thin film magnetic heads are required. Thus, a recording gap and an end of a recording magnetic pole must be made narrow and precisely formed.  
         [0003]     For example, a vertical magnetic recording head has a main magnetic pole, which faces a surface of a recording medium to record data therein, and a return yoke. Seen from an air bearing surface (ABS), an end face of the main magnetic pole on a reproducing element side is made narrow; that on a return yoke side is made wide. Namely, the main magnetic pole is formed into an inverted trapezoid. The main magnetic pole is formed by the steps of: forming a magnetic film, which will act as the main magnetic pole; and etching the magnetic film to form into a desired shape of the main magnetic pole by a dry process. Further, the main magnetic pole may be formed by plating.  
         [0004]     In the dry process for shaping the magnetic film, focused ion beam (FIB) etching or ion milling is used. However, the FIB etching is unsuitable for mass production, and the ion milling is unsuitable for precisely shaping the magnetic pole.  
         [0005]     On the other hand, in the process using the plating, a shape and a size of the main magnetic pole depend on resist patterns. Therefore, the shape of the main magnetic pole can be precisely controlled by precisely forming the resist patterns (see Japanese Patent Gazette No. 2004-95006).  
         [0006]     In the case of forming the main magnetic pole by plating, firstly resist is exposed and developed to form prescribed resist patterns, then a hydrophilic treatment is executed before plating. By the hydrophilic treatment, repelling a plating solution by the resist patterns can be prevented, and liquidity of the plating solution can be improved so that the plating solution can fully enter fine grooves.  
         [0007]     For example, an O 2 -plasma treatment, an ultraviolet (UV) treatment, etc. may be employed as the hydrophilic treatment. However, if the hydrophilic treatment, e.g., O 2 -plasma treatment, is applied to the resist patterns, a surface of the resist is volatilized, so that widths of the resist patterns are made wider than initial widths thereof. Namely, narrowing the resist patterns must be limited. In the vertical magnetic recording head, the shape of the end face of the main magnetic pole seen from the ABS must be formed into the inverted trapezoid. However, by the hydrophilic treatment, a width of a bottom section of a concave part of each resist pattern is wider than a width of an opening section thereof, so that a sectional shape of a groove section of each resist pattern is not formed into the inverted trapezoid.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been invented to solve the problems of the conventional technology.  
         [0009]     An object of the present invention is to provide a method of forming a plated pattern, which is capable of securely narrowing and miniaturizing a resist pattern, which has been hydrophilic-treated, without widening and deforming the resist pattern when, for example, a main magnetic pole of a vertical magnetic recording head is manufactured.  
         [0010]     Another object is to provide a method of manufacturing a thin film magnetic head, which employs the method of forming the plated pattern.  
         [0011]     To achieve the objects, the present invention has following methods.  
         [0012]     Namely, the method of forming a plated pattern comprises the steps of: covering a surface of a plating seed layer with resist; exposing and developing the resist so as to form a resist pattern having a concave part, which has a prescribed pattern and in which the plating seed layer is exposed as an inner bottom face; executing a hydrophilic treatment of the resist pattern; piling a metal in the concave part of the resist pattern by plating; removing the resist pattern; and removing an exposed part of the plating seed layer, and the plating seed layer is a volatile metal layer made of a metal, which is oxidized during the hydrophilic treatment, and an oxide of the metal constituting the volatile metal layer has volatility.  
         [0013]     In the method, the metal constituting the volatile metal layer may be ruthenium.  
         [0014]     Next, in the method of manufacturing a thin film magnetic head, a part of the thin film magnetic head is formed by the steps of: covering a surface of a plating seed layer with resist; exposing and developing the resist so as to form a resist pattern having a concave part, which has a prescribed pattern and in which the plating seed layer is exposed as an inner bottom face; executing a hydrophilic treatment of the resist pattern; forming a magnetic film in the concave part of the resist pattern by plating; removing the resist pattern; and removing an exposed part of the plating seed layer, and the plating seed layer is a volatile metal layer made of a metal, which is oxidized during the hydrophilic treatment, and an oxide of the metal constituting the volatile metal layer has volatility.  
         [0015]     In the method, the part of the thin film magnetic head may be a main magnetic pole of a vertical magnetic recording head.  
         [0016]     In the method, the part of the thin film magnetic head may be an end magnetic pole of an upper magnetic pole of a horizontal magnetic recording head.  
         [0017]     In the method, thickness of the volatile metal layer may be equal to a distance between the end magnetic pole of the upper magnetic pole and an end magnetic pole of a lower magnetic pole.  
         [0018]     Further, in the method, the metal constituting the volatile metal layer may be ruthenium.  
         [0019]     In the method of forming the plated pattern, the volatile metal layer is used as the plating seed layer. Therefore, widening the concave part of the resist pattern and deformation of the resist pattern can be prevented in spite of hydrophilic-treating the resist pattern, so that the precise and fine plated pattern can be formed.  
         [0020]     The method of the present invention can be suitably applied to a process of forming a part of a thin film magnetic head, e.g., a main magnetic pole, so that the part of the thin film magnetic head can be precisely formed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:  
         [0022]      FIG. 1  is a sectional view of a thin film magnetic head, which is manufactured by the method of the present invention;  
         [0023]      FIGS. 2A-2F  are explanation view showing steps of manufacturing the thin film magnetic head;  
         [0024]      FIG. 3  is a sectional view showing a main magnetic pole and a trailing shield;  
         [0025]      FIG. 4  is a sectional view of another thin film magnetic head, which is manufactured by the method of the present invention;  
         [0026]      FIG. 5  is an end view showing end magnetic poles of a lower magnetic pole and an upper magnetic pole;  
         [0027]      FIGS. 6A-6C  are explanation views showing steps of forming the end magnetic poles;  
         [0028]      FIGS. 7A-7D  are explanation views showing steps of manufacturing a multilayered circuit board, wherein the method of the present invention is used. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0029]     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0030]     In the present embodiment, the forming method of the present invention is applied to a method of forming a part of a thin film magnetic head.  
         [0031]      FIG. 1  is a sectional view of a thin film magnetic head for vertical magnetic recording, which is manufactured by the forming method of the present invention.  
         [0032]     The thin film magnetic head includes a recording head, which is constituted by a main magnetic pole  10 , a trailing shield  13 , and a return yoke  14 , a coil  16 , and a reproducing head, which is constituted by a magnetic resistance (MR) element  20 , an upper shield  22  and a lower shield  24 .  
         [0033]     An insulating layer  26 , which is made of alumina, is provided between the upper shield  22  and the lower shield  24 . Further, insulating layers, which are made of alumina, etc., are provided between the main magnetic pole  10  and the coil  16 , between the coil  16  and the return yoke  14 , and between the MR element  20 , the upper shield  22  and the lower shield  24 .  
         [0034]     The characteristic point of the thin film magnetic head of the present embodiment is a base layer  11  of the main magnetic pole  10 , which is a volatile metal layer.  
         [0035]     In the thin film magnetic head, the shield layers  22  and  24 , the MR element  20 , the main magnetic pole  10 , the coil  16  and the return yoke  14  are layered an a substrate, which is made of Al 2 O 3 -Tic, in that order and formed into a prescribed pattern.  
         [0036]     As described above, in the thin film magnetic head for vertical magnetic recording, an end face of the main magnetic pole  10  on a reproducing element side is made narrow; that on the return yoke  14  side is made wide. Namely, the main magnetic pole  10  is formed into an inverted trapezoid. The volatile metal layer  11  is adhered to a bottom part of the main magnetic pole  10 .  
         [0037]      FIGS. 2A-2F  are explanation view showing steps of manufacturing the main magnetic pole  10  of the thin film magnetic head. The views show a part “A” of  FIG. 1  seen from the end face.  
         [0038]     In  FIG. 2A , an adhesive layer  12  is formed on a surface of the insulating layer  26 , then the volatile metal layer  11  is formed on the adhesive layer  12 . The adhesive layer  12  adheres the volatile metal layer  11  on the insulating layer  26 . The adhesive layer  12  is formed by spattering or evaporating, for example, Ti, Ta, Cr, Nb, etc.  
         [0039]     In the present embodiment, the volatile metal layer  11  is made of ruthenium (Ru). The volatile metal layer  11  is formed by spattering or evaporating Ru. The volatile metal layer  11  acts as a plating seed layer, and its thickness, e.g., 500 angstrom, is adjusted to gain a prescribed electric resistance. The volatile metal layer  11  may be a single layer. Further, a multilayered structure including the volatile layer  11  may be employed. In the present embodiment, the volatile metal layer  11  is formed by spattering or evaporating Ru on a substrate (a work piece), which is made of Al 2 O 3 -Tic. Namely, a surface of the work piece is covered with the Ru.  
         [0040]     In  FIG. 2B , a resist pattern  30  is formed on a surface of the volatile metal layer  11 . The surface of the work piece is coated with resist, and the resist is exposed and developed so as to pattern the main magnetic pole  10 . A concave part  30   a , whose shape is an inverted trapezoid, is formed in a front end section of the main magnetic pole  10 . The volatile metal layer  11  made of Ru is exposed as an inner bottom face of the concave part  30   a.    
         [0041]     After forming the resist pattern  30 , a hydrophilic treatment is applied to the resist. In  FIG. 2C , the hydrophilic treatment, e.g., O 2 -plasma treatment, is applied to the resist.  
         [0042]     By applying the O 2 -plasma treatment to the resist, a surface of the resist pattern  30  is changed from a hydrophobic surface to a hydrophilic surface. Further, Ru of the volatile metal layer  11 , which is exposed in the concave part  30   a , is oxidized, so that RuO 4  is produced. The RuO 4  volatilizes and deposits on inner faces of the concave part  30   a  as volatiles  11   a.    
         [0043]     The oxides (RuO 4 ) of the volatile metal layer  11  have volatility, and the RuO 4 , which is formed during the hydrophilic treatment, deposits on the inner faces of the concave part  30   a.    
         [0044]     As described above, the volatiles  11   a  deposit on the inner faces of the concave part  30   a  of the resist pattern, so that patterns of the concave part  30   a , etc. are not deformed even if the hydrophilic treatment is applied to the resist pattern. Conventionally, the resist is volatilized by applying the hydrophilic treatment to the resist pattern, so that a width of the concave part or a groove of the resist pattern  30  is widen. In the present embodiment, the function of widening the concave part, which is caused by volatilizing the volatile metal layer  11 , can be restrained.  
         [0045]     After applying the hydrophilic treatment to the resist pattern  30 , electrolytic plating is executed so as to form a magnetic film (high saturation magnetic flux density film)  32  in the concave part  30   a . At that time, the volatile metal layer  11  is used as an electric feed layer for electrolytic plating. In  FIG. 2D , the magnetic film  32  is formed by electrolytic plating.  
         [0046]     Note that, after the hydrophilic treatment, the surface of the volatile metal layer  11  may be activated by dilute acid as a pretreatment of the plating. The magnetic film  32  may be formed in the concave part  30   a  by not only electrolytic plating but also electroless plating. In the electrolytic plating, an electric current may be selected from a direct current, a pulse current, etc.  
         [0047]     A material of the magnetic film  32  may be selected from FeCo, FeCo α(α=Pd, Pt, Rh, Mo, Zr), CoNiFe, NiFe, NiFe α(α=Pd, Pt, Rh, Mo, Zr), etc. according to desired characteristics of the part of the thin film magnetic head.  
         [0048]     In  FIG. 2E , the resist pattern  30  is removed after forming the magnetic film  32 . The resist pattern  30  can be chemically dissolved and removed. When the resist pattern  30  is removed, the volatiles (RuO 4 ) deposited on the inner faces of the concave part  30   a  can be removed together with the resist pattern  30 . Note that, even if the volatiles are left on side faces of the magnetic film  32 , the volatiles are nonmagnetic. Therefore, the volatiles do not badly influence characteristics of the magnetic head.  
         [0049]     After removing the resist pattern  30 , a part of the volatile metal layer  11  and a part of the adhesive layer  12 , which are exposed in the surface of the insulating layer  26 , are removed by ion milling. In  FIG. 2F , the useless parts of the volatile metal layer  11  and the adhesive layer  12  are removed, so that the main magnetic pole  10  is formed on the insulating layer  26 . The volatile metal layer  11  and the adhesive layer  12  are partially covered with the magnetic film  32 . On the other hand, the volatile metal layer  11  and the adhesive layer  12  are very thin layers, so that the exposed parts of the layers  11  and  12  can be easily selectively removed by ion milling. The volatile metal layer  11  left on the lower side of the main magnetic pole  10  does not badly influence characteristics of the magnetic head.  
         [0050]     In the above described method of forming the main magnetic pole  10 , widening the concave part  30   a  of the resist pattern  30  and deforming a shape of an end face of the concave part  30   a , which has been formed into the inverted trapezoid, can be prevented when the hydrophilic treatment is applied to the resist pattern  30  formed on the surface of the volatile metal layer  11 . Therefore, the main magnetic pole  10  can be formed into a designed shape.  
         [0051]     The volatile metal layer  11  is made of a metal, which is oxidized during the hydrophilic treatment of the resist pattern  30 . In the present embodiment, the volatile metal layer  11  is made of Ru, but it may be made of other volatile metals.  
         [0052]     In the present embodiment, the O 2 -plasma treatment is employed as the hydrophilic treatment, other treatments, e.g., inductively coupled plasma (ICP) treatment, ultra violet (UV) treatment, ozone water treatment, may be employed. In any hydrophilic treatments, the volatile metal layer  11  is formed as the plating seed layer so as to prevent deformations of a pattern defined by the resist pattern.  
         [0053]     In the above described embodiment, the method of forming the plated pattern is applied to form the main magnetic pole  10  of the vertical recording head. Further, the method can be applied to form other parts of the thin film magnetic head.  
         [0054]     For example, the trailing shield  13 , which faces the main magnetic pole  10  (see  FIG. 1 ), may be formed by the above described method.  
         [0055]      FIG. 3  shows the main magnetic pole  10  and the trailing shield  13  seen from the ABS. The trailing shield  13  faces the main magnetic pole  10 . In case of forming the trailing shield  13  by plating too, the volatile metal layer  11  is formed as the plating seed layer and the resist pattern is formed on the surface of the volatile metal layer  11  as well as the method of forming the main magnetic pole  10 . Therefore, the deformation of the resist pattern can be prevented during the hydrophilic treatment of the resist pattern, and the trailing shield  13  can be formed into the designed shape by plating.  
         [0056]     Further, the forming method of the present invention can be employed to manufacture a horizontal magnetic recording head shown in  FIG. 4 . In the thin film magnetic head, the volatile metal layer  11  is formed in a gap section between an end magnetic pole  40   a  of a lower magnetic pole  40  and an end magnetic pole  42   a  of an upper magnetic pole  42 .  
         [0057]     In  FIG. 5 , the end magnetic poles  40   a  and  42   a  are seen from an ABS. The volatile metal layer  11  is sandwiched between the end magnetic pole  40   a  and the end magnetic pole  42   a , and the volatile metal layer  11  acts as a write-gap. Since the volatile metal layer  11  is made of a nonmagnetic material, the volatile metal layer  11  can act as the write-gap, without problems, between the end magnetic poles  40   a  and s 42   a.    
         [0058]      FIGS. 6A-6C  are explanation views showing steps of forming the end magnetic poles  40   a  and  42   a  shown in  FIG. 5 .  
         [0059]     In  FIG. 6A , the lower magnetic pole  40  and the end magnetic pole  40   a  are formed on a lower magnetic pole  22   a . Then, the volatile metal layer  11 , whose thickness is equal to a width of the write-gap, is formed by, for example, spattering. Further, a resist pattern  50  is formed on the surface of the volatile metal layer  11 . The resist pattern  50  is exposed and developed to form a concave part  50   a , which corresponds to a shape of the end magnetic pole  42   a.    
         [0060]     After forming the resist pattern  50 , the hydrophilic treatment, e.g., O 2 -plasma treatment, is applied thereto. In  FIG. 5B , electrolytic plating is executed so as to form the end magnetic pole  42   a . At that time, the volatile metal layer  11  is used as the electric feed layer for electrolytic plating. For example, the end magnetic pole  42   a  is formed by plating with FeCo.  
         [0061]     After forming the end magnetic pole  42   a  by plating, the resist pattern  50  is removed after forming the magnetic film  32 . Further, the volatile metal layer  11  left on an insulating layer  52  is removed by ion milling. In  FIG. 6C , the volatile metal layer  11  other than a part covered with the end magnetic pole  42   a  is removed from the insulating layer  52 .  
         [0062]     In the state shown in  FIG. 6C , the upper magnetic pole  42  is formed into a prescribed pattern by, for example, plating, so that the horizontal magnetic recording head shown in  FIG. 4  is produced.  
         [0063]     In the method of producing the horizontal magnetic recording head too, the volatile metal layer  11  is formed as a base layer of the resist pattern  50 , so that widening and deforming the resist pattern  50  can be prevented in spite of hydrophilic-treating the resist pattern  50 . Therefore, the end magnetic pole  42   a , which should have fine patterns, can be precisely formed.  
         [0064]     Further, when other parts of the horizontal magnetic recording head, e.g., the end magnetic pole  40   a , is formed by plating, the volatile metal layer may be previously formed as a base layer of a resist pattern for forming the end magnetic pole  40   a.    
         [0065]     In the above described embodiments, the plated pattern forming method of the present invention is employed to produce the thin film magnetic heads.  
         [0066]     The forming method of the present invention is not limited to the production of the thin film magnetic heads. As shown in  FIGS. 7A-7D , the method can be employed to produce a multilayered circuit board.  
         [0067]     In  FIG. 7A , an insulating layer  74 , e.g., polyimide film, is formed on a surface of a base layer  70 , on which cable patterns  72  are formed. Via holes  74   a  are bored in the insulating layer  74  by laser means, etc., and the volatile metal layer  11  is formed as the plating seed layer.  
         [0068]     In  FIG. 7B , the surface of the volatile metal layer  11  is coated with resist. The resist is exposed and developed to form resist patterns  76 . The resist patterns  76  are patterned so as to expose parts corresponding to cable patterns to be formed on the insulating layer  74 .  
         [0069]     The pretreatment of plating and the hydrophilic treatment are applied to the resist patterns  76 , then electrolytic plating is executed so as to form electric conductive layers  78  in pattern grooves (concave parts)  76   a  of the resist patterns  76 . At that time, the volatile metal layer  11  is used as the electric feed layer for the electrolytic plating.  
         [0070]     In  FIG. 7C , the electric conductive layers  78  are fully formed in the pattern grooves  76   a . The electric conductive layers  78  are, for example, copper films having prescribed thickness, and they are formed by electrolytic copper plating or electroless copper plating.  
         [0071]     Then, the resist patterns  76  are removed, and parts of the volatile metal layer (plating seed layer)  11 , which are not covered with the electric conductive layers  78 , are removed, so that cable patterns  80  are formed on the surface of the insulating layer  74  (see  FIG. 7D ). Since the volatile metal layer  11  is much thinner than the electric conductive layers  78 , only the exposed parts of the volatile metal layer  11  can be easily and selectively removed by chemical etching or ion milling.  
         [0072]     The cable patterns  80  having prescribed patterns are formed on the surface of the insulating layer  74 , and the upper cable patterns  80  and the lower cable patterns  72  are electrically connected by vias  80   a , so that the multilayered circuit board can be produced.  
         [0073]     In the present method of producing the multilayered circuit board too, the volatile metal layer  11  acts as the plating seed layer so that widening the pattern grooves  76   a , etc. of the resist patterns  76  and deformation of the resist patterns  76  can be prevented in spite of hydrophilic-treating the resist patterns. Therefore, the precise cable patterns  80  can be formed.  
         [0074]     By employing the forming method of the present invention, the deformation of the resist patterns can be restrained so that cable patterns can be formed correctly. By applying the hydrophilic treatment to resist, liquidity of a plating solution can be improved so that the plating solution can be fully supplied into fine patterns. Therefore, a highly reliable circuit board, which has very fine and precise cable patterns, can be produced without wire disconnection and short circuit, which are caused by deformation of resist patterns.  
         [0075]     The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.