Patent Publication Number: US-2007115595-A1

Title: Cpp-type thin-film magnetic head and manufacturing method thereof

Description:
This application claims the benefit of Japanese Patent Application No. 2005-334865 filed Nov. 18, 2005, which is hereby incorporated by reference.  
     FIELD  
      The present embodiments relate to a CCP-type thin-film magnetic head and a manufacturing method thereof.  
     BACKGROUND  
      A thin-film magnetic head mounted on a hard disk apparatus can be classified as a CIP (Current In the Plane) type in which a sense current flows in a direction parallel to a surface of each layer constituting the thin-film magnetic head element and a CPP (Current Perpendicular to the Plane) type in which the sense current flows in a direction perpendicular to the surface of each layer constituting the thin-film magnetic head element.  
      The CIP-type thin-film magnetic head is generally used as a product. However, since an output thereof is reduced with a reduction in track width, there are various problems in forming an even narrower track. In the CPP-type thin-film magnetic head, when a current density is kept constant, an output thereof is not varied in spite of reducing the track width. Accordingly, the CPP-type thin-film magnetic head, which has an output that does not depend on the track width, has a narrower track than the CIP-type thin-film magnetic head.  
       FIG. 7  is a cross-sectional view showing a structure of a known CPP-type thin-film magnetic head. The CPP-type thin-film magnetic head includes a lower shield layer (bottom electrode layer)  110 , and a thin-film magnetic head element  120  formed on the lower shield layer  110 . A side fill gap layer  140  is formed on the lower shield layer  110  in contact with both sides of the thin-film magnetic head element  120 . A bias layer  141  and a cap layer  142  are stacked on the side fill gap layer  140 . An upper shield layer (top electrode layer)  130  is formed on the thin-film magnetic head element  120  and the cap layer  142 .  
      A GMR (Giant Magnetoresistive) element or a TMR (Tunneling Magnetoresistive) element is used as the thin-film magnetic head element  120 . The side fill gap layer  140  is formed of an insulating material, for example, Al 2 O 3  or SiO 2 . The side fill gap layer  140  is an insulating layer that secures an insulating property of the lower shield layer  110  and the upper shield layer  130 .  
      In the CPP-type thin-film magnetic head, the lower shield layer  110  and the upper shield layer  130  serve as electrode layers. When the sense current flows in a direction perpendicular to the film surface of the thin-film magnetic head element  120  from one side of the lower shield layer  110  and the upper shield layer  130  toward the other side thereof, a leakage flux from a storage medium can be detected by using a magnetoresistive effect of the thin-film magnetic head element  120 .  
      [Patent Document 1] JP-A-2000-182223 (US Pub. No. 2001033462A1)  
      [Patent Document 2] JP-A-2002-353538  
      [Patent Document 3] JP-A-2001-344708  
      [Patent Document 4] JP-A-2001-331908  
      In the CPP-type thin-film magnetic head, due to a element structure, the side fill gap layer  140  can be only reduced by approximately several tens Å. Therefore, a pin hole could be easily generated and an insulation failure might occur between the lower shield layer  110  and the upper shield layer  130  due to the pin hole. When the insulation failure occurs between the lower shield layer  110  and the upper shield layer  130 , the sense current flowing in the thin-film magnetic head element  120  decreases and a reproduction characteristic deteriorates.  
     SUMMARY  
      The present embodiments may obviate one or more of the limitations of the related art. For example, in one embodiment, CPP-type thin-film magnetic head is capable of improving a reproduction characteristic by enhancing an electrical insulating property between an upper shield layer and a lower shield layer. However, the present embodiments are not limited to obviating the limitations of the discussed related art.  
      Generally, an insulating property between an upper shield layer and the lower shield layer is enhanced by interposing a different insulating layer between a lower shield layer and a side fill gap layer and that the thickness of the insulating layer is secured without jumboizing a head by burying the insulating layer on a top surface of the lower shield layer.  
      In one embodiment, a CPP-type thin-film magnetic head includes a thin-film magnetic head element formed between a lower shield layer and an upper shield layer. A side fill gap layer secures the insulating property of the lower shield layer and the upper shield layer. The side fill gap layer is formed from both end faces in a track width direction of the thin-film magnetic head element to the lower shield layer and a current flows in a direction perpendicular to a film surface of the thin-film magnetic head element.  
      In one embodiment, the top surface of the bottom shield layer is formed in a non-flat surface that has a convex portion disposed at a center in the track width direction and a concave portion disposed at both sides in the track width direction of the convex portion, the thin-film magnetic element is formed on the convex portion. A buried gap layer contacts the side fill gap layer formed in the concave portion.  
      In one exemplary embodiment, the buried gap layer is thicker than the side fill gap layer to sufficiently secure the insulating property.  
      In one embodiment, the convex portion of the lower shield layer has an extension region extending outwardly from the both end faces of the thin-film magnetic head element and contacting the side fill gap layer. The size of the extension region in the track width direction is about 1/10 times to 20 times the track width of the thin-film magnetic head element. In this embodiment, a region, which has the lower shield layer and the side fill gap layer directly contacting each other, can be narrowed as much as possible in this range. In this embodiment, the probability that an insulation failure will occur due to a defect of the side fill gap layer is reduced.  
      In one embodiment, the extension region of the lower shield layer has the surface roughness of about 30 Å or less. In this range, for example, the defect such as the pin hole is difficult to occur on the side fill gap layer stacked on the lower shield layer. Therefore, the insulation failure by the defect can be evaded.  
      In one embodiment, the top surface of the convex portion of the lower shield layer and the top surface of the buried gap layer are formed in the concave portion of the lower shield layer and are in the same plane. According to this embodiment, even if the buried gap layer is formed, the flatness of the top surface of the lower shield layer is secured and a bad effect is not given to each layer formed on the convex portion of the lower shield layer and the buried gap layer.  
      In one embodiment, the buried layer is formed of one or more types of insulating materials, for example, SiO2, Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4 , AlN, AlSiO or SiAlON.  
      In another embodiment, a bias layer and a cap layer are sequentially stacked from the side fill gap layer side. The bias layer and the cap layer are interposed between the side fill gap layer and the upper shield layer.  
      According to another embodiment, a method of manufacturing a CPP-type thin-film magnetic head in which a current flows in a direction perpendicular to a film surface of a thin-film magnetic head element is provided. The method comprising the steps of: forming a first liftoff resist which defines the track width of the top surface of the lower shield layer, the first liftoff resist being disposed at the center in the track width direction on the lower shield layer; forming the top surface of the lower shield layer with a non-flat surface having the convex portion covered with the resist and the concave portion disposed at both sides in the track width direction of the convex portion by removing the lower shield layer not covered with the first resist up to a predetermined depth; forming the buried gap layer in the concave portion of the lower shield layer; exposing the convex portion of the lower shield layer by lifting off the first resist; forming a multilayer film constituting the thin-film magnetic head element on the convex portion and the buried gap layer of the lower shield layer; forming a second liftoff resist which defines the track width of the multilayer film; forming the multilayer film covered with the second resist layer with the thin-film magnetic head element by removing the multilayer film not covered with the second resist, and exposing a part of the convex portion and the buried gap layer of the lower shield layer to the removed par; forming the side fill gap layer, bias layer and cap layer on both end faces in the track width direction of the thin-film magnetic head element, and the exposed convex portion and buried gap layer of the lower shield layer; exposing the top surface of the thin-film magnetic head element by lifting off the second resist; and forming the upper shield layer on the thin-film magnetic head element.  
      In one embodiment, the lower shield layer is not covered with the first resist that is sharpened by etching and an inclination angle of the both end faces in the track width direction of the convex portion of the lower shield layer by an etching angle, thereby flattening the top surface of the buried gap layer formed in the concave portion of the lower shield layer.  
      In one embodiment, the lower shield layer is not covered with the first resist and is sharpened in a depth greater than the thickness of the side fill gap layer. Therefore, the buried gap layer has the film thickness so that the top surface of the buried gap layer and the top surface of the lower shield layer can be in the same plane. The thickness of the buried gap layer is sufficiently secured without drastically increasing the head, thereby improving the insulating property between the top shield and the bottom shield.  
      In the lower shield layer, it is practical that the size of the top surface of the lower shield layer in the track width direction is greater than the track width of the thin-film magnetic head element. The both end faces in the track width direction of the convex portion of the lower shield layer are disposed outwardly from the both end faces in the track width direction of the thin-film magnetic head element. For example, the extension region that extends from the both end faces of the thin-film magnetic head element contacting the side fill gap layer is formed, and the size in the track width direction is about 1/10 times to 20 times the size of the thin-film magnetic head element in the track width direction.  
      In one embodiment, since the insulating property of the side fill gap layer are improved by the buried gap layer formed on the top surface of the lower shield layer and a region directly contacted by the lower shield layer and the side fill gap layer decreases, the insulating property between the upper shield layer and the lower shield layer are improved, thereby acquiring the CPP-type thin-film magnetic head capable of improving the reproduction characteristic and the manufacturing method thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       FIG. 1  is a fragmentary cross-sectional view showing a structure of a thin-film magnetic head when viewed from a surface side opposite to a storage medium according to one embodiment.  
       FIG. 2  is a fragmentary cross-sectional view showing a portion of a CPP-type thin-film magnetic head.  
       FIG. 3  is a fragmentary cross-sectional view showing a portion of a CPP-type thin-film magnetic head when viewed from a surface side opposite to a storage medium.  
       FIG. 4  is a fragmentary cross-sectional view showing a portion of a CPP-type thin-film magnetic head when viewed from a surface side opposite to a storage medium.  
       FIG. 5  is a fragmentary cross-sectional view showing a portion of a CPP-type thin-film magnetic head when viewed from a surface side opposite to a storage medium.  
       FIG. 6  is a fragmentary cross-sectional view showing a portion of a CPP-type thin-film magnetic head when viewed from a surface side opposite to a storage medium.  
       FIG. 7  is a fragmentary cross-sectional view showing a CPP-type thin-film magnetic head of the known structure when viewed from a surface side opposite to a storage medium. 
    
    
     DETAILED DESCRIPTION  
      Exemplary embodiments of a thin-film magnetic head will be described with reference to the drawings. In the respective drawings, the X-direction represents a track width direction. The Y-direction represents the height direction (direction of a leakage flux from a storage medium). The Z-direction represents the moving direction of the storage medium moves and the stacking direction of each layer constituting the thin-film magnetic head.  
      In one embodiment, a thin-film magnetic head  1  includes a thin-film magnetic head element  20  between a lower shield layer  10  and an upper shield layer  30 . When a sense current  1  flows in a direction (Z-direction shown in the figure) perpendicular to the surface of each layer constituting the thin-film magnetic head element  20 , the leakage flux from the storage medium is detected by using a magnetoresistive effect of the thin film magnetic head element  20 .  
      As is well known in the art, a giant magnetoresistive element (GMR element) and a tunneling magnetoresistive element (TMR element), both of which exhibit the giant magnetoresistive effect, may be used as the thin-film magnetic head element  20 .  
      The lower shield layer  10  and the upper shield layer  30  have an area even greater than the track width Tw and the height direction size MRh of the thin-film magnetic head element  20 . The lower shield layer  10  and the upper shield layer  30  are composed of a soft magnetic material that exhibits a satisfactory magnetic shielding effect, for example, NiFe. The lower shield layer  10  and the upper shield layer  30  operate as the magnetic shield and a an electrode which feeds a power to the thin-film magnetic head element  20 .  
      A side fill gap layer  40 , a bias layer  41  and a cap layer  42  are disposed between the lower shield layer  10  and the upper shield layer  30  at both regions of the thin-film magnetic head element  20 . The side fill gap layer  40 , the bias layer  41  and the cap layer  42  are stacked sequentially from the lower shield layer  10 . The side fill gap layer  40  is formed of an insulating material, for example, AI 2 O 3  or SiO 2 . The side fill gap layer  40  electrically insulates the lower shield layer  10  and the upper shield layer  30 . The side fill gap layer  40  is formed in a very thin film thickness of about 150 Å or less. The bias layer  41  is formed of a hard magnetic material such as a Co—Pt alloy film or a Co—Cr—Pt alloy film and is disposed in vicinity of both end faces  20   a  in the track width direction of the thin-film magnetic element  20 . The bias layer  41  applies a bias flux to a free magnetic layer. A bias underlying layer (not shown in figure) is formed directly below the bias layer  41  to improve the properties (coercive force and remanence ratio) of the bias layer  41  as not shown in the figure. The cap layer  42  is formed of, for example, Ta.  
      A back fill gap layer (not shown in figure) disposed in the height direction of the thin-film magnetic head element  20  and made of the insulating material, for example, AI 2 O 3  or SiO 2  is formed on the lower shield layer  10 .  
      In one embodiment, the top surface of the lower shield layer  10  is formed in the non-flat surface having a convex portion  10   a  disposed at the center in the track width direction and a concave portion  10   b  disposed at both sides in the track width direction of the convex portion  10   a . The thin-film magnetic head element  20  is formed on the convex portion  10   a  of the lower shield layer  10  and an buried gap layer  50  contacting the side fill gap layer  40  is formed in the concave portion  10   b  of the lower shield layer  10 . The top surface of the buried gap layer  50  and the top surface of the convex portion  10   a  of the lower shield layer  10  are in the same plane (flat surface). For example, the flatness of the top surfaces are higher than the lower shield layer  10  and the buried gap layer  50  are secured.  
      The buried gap layer  50  is formed of one or more types of insulating materials, for example, SiO 2 , A 1   2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4 , AlN, AlSiO or SiAlON. The insulating property of the lower shield layer  10  and the upper shield layer  30  is secured by the buried gap layer  50  and the side fill gap layer  40 . The buried gap layer  50  is thicker than the side fill gap layer  40 , and specifically, has the film thickness 3 times thicker than the side fill gap layer  40 .  
      In one embodiment, the buried gap layer  50  is formed in a film thickness of approximately 500 Å. Since the side fill gap layer  40  is formed in a very thin thickness of 150 Å or less as described above, the defect such as the pin hole may occur, but the insulation failure caused by the defect of the side fill gap layer  40  can be evaded by contacting the buried gap layer  50  of a sufficient thickness to the side fill gap layer  40 .  
      A region in which the side fill gap layer  40  and the lower shield layer  10  are directly contacted to each other, for example, a region in which the insulating property is secured only with the side fill gap layer  40  is narrowed by forming the buried gap layer  50 . The probability that the insulation failure caused by the defect of the side fill gap layer  40  will occur decreases.  
      The convex portion loa of the lower shield layer  10  has the extension region in which the location of the both end faces  10   c  in the track width direction thereof extends outwardly from the location of the both end faces  20   a  in the track width direction of the thin-film magnetic head element  20 . The size Tw 2  in the track width direction of the extension region is 1/10 times to 20 times the track width of the thin-film magnetic head element  20 . For example, it is preferable that the region in which the side fill gap layer  40  and the lower shield layer  10  are directly contacted to each other is not present. It is difficult to align the location of the both end faces of the convex portion  10   a  of the lower shield layer  10  with the location of the both end faces in the track width direction of the thin-film magnetic head element  20  with high precision.  
      In one embodiment, when the size Tw 2  in the track width direction of the extension region of the lower shield layer  10  is about 1/10 times smaller than the track width of the thin-film magnetic head element  20 , the alignment is not accomplished and the location of the both end faces of the lower shield layer  10  may be misaligned inwardly from the both end faces of the thin-film magnetic head element  20 . When the location of the both end faces of the lower shield layer  10  is misaligned inwardly from the location of the both end faces of the thin-film magnetic head element  20 , the effective track width of the thin-film magnetic head element  20  is reduced, thereby deteriorating the reproduction characteristic. When the size Tw 2  in the track width direction of the extension region of the lower shield layer  10  is small, the shielding effect by the lower shield layer  10  is reduced. Therefore, a side reading may occur.  
      Alternatively, the size Tw 2  in the track width direction of the extension region of the lower shield layer  10  is about 20 times greater than the track width of the thin-film magnetic head element  20 , the region in which the lower shield layer  10  is in contact directly with the side fill gap layer  40  is broaden. Therefore, the probability that the insulation failure caused by the defect of the side fill gap layer  40  will occur increases.  
      In one embodiment, the extension region of the lower shield layer  10  in which the size Tw 2  in the track width direction satisfies the range has the surface roughness of about 30 Å or less. In this embodiment, an occurrence of the pin hole on the side fill gap layer  40  stacked on the extension region of the lower shield layer  10  can be suppressed and the insulating property can be secured even if the lower shield layer  10  is in contact directly with the side fill gap layer  40  in the extension region.  
      In another embodiment, a method of manufacturing the CPP-type shown in  FIGS. 1 and 2  according to method will be described with reference to FIGS.  2  to  6 .  
      As shown in  FIG. 2 , a substrate is completely coated with the lower shield layer  10  and a first resist Rl that defines the size Twl in the track width direction of the top surface of the lower shield layer  10  (convex portion  10   a ) is disposed at the center in the track width direction over the lower shield layer  10 . The lower shield layer  10  is formed of the soft magnetic material such as NiFe and in the film thickness of approximately 1 μm by sputtering or plating. The first resist R 1  is the liftoff resist. The size Tw 1  in the track width direction of the top surface of the lower shield layer  10  is greater than the track width Tw of the thin-film magnetic head element to be formed (Tw 1 &gt;Tw).  
      In one embodiment, as shown in  FIG. 2 , the lower shield layer  10  not covered with the first resist R 1  is removed in a predetermined depth. The top surface of the lower shield layer  10  is formed in the non-flat surface having the convex portion  10   a  covered with the first resist R 1  and the concave portion  10   b  disposed at both sides in the track width direction of the convex portion  10   a . In this embodiment, the both end faces  10   c  in the track width direction of the convex portion  10   a  is formed in an inclined surface broadening the size of the lower shield layer  10  in the track width direction as the both end faces  10   c  are directed from the convex portion  10   a  to the concave portion  10   b . The inclination angle of the both end faces  10   c  in the track width direction of the convex portion  10   a  can be controlled by an etching angle (milling angle) and a shape of the concave  19   b  is defined by shapes of the both end faces in the track width direction of the convex portion  10   a . A depth in which the lower shield layer  10  not covered with the first resist R 1  is removed, for example, the depth of the concave portion  10   b  is greater than the depth of the side fill gap layer  40  formed in the subsequent step and preferably, 3 times greater than the thickness of the side fill gap layer  40 .  
      In one embodiment, as shown in  FIG. 3 , when the first resist remains the buried gap layer  50  is formed in the concave portion  10   b  of the lower shield layer  10 . In the buried gap layer  50 , the top surface of the buried gap layer  50  and the top surface of the convex portion  10   a  of the lower shield layer  10  have the film thickness to be in the same plane by using one or more types of insulating materials out of, for example, SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 2 O 5 , WO 3 , Si 3 N 4 , AlN, AlSiO and SiAlON. The shape of the concave portion  10   b  in which the buried gap layer  50 , for example, the inclination angle of the both end faces  10   c  in the track width direction of the convex portion  10   a  of the lower shield layer  10  is controlled as described above, thereby flattening the top surface of the buried gap layer  50 . The thickness of the buried gap layer  50  is substantially the same as the depth of the concave portion  10   b . For example, the thickness of the buried gap layer  50  is greater than the thickness of the side fill gap layer  40  and preferably, 3 times greater than the thickness of the side fill gap layer  40 .  
      In one embodiment, the convex portion  10   a  of the lower shield layer  10  is exposed as shown in  FIG. 4  by lifting off the first resist R 1  after forming the buried gap layer  50 .  
      In one embodiment, as shown in  FIG. 5 , a multilayer film M which exhibits the magnetoresistive effect is formed on the convex portion  10   a  and the buried gap layer  50  of the lower shield layer  10 . A second resist R 2  which defines the track width Tw of the thin-film magnetic head element is formed on the multilayer film M. The second resist R 2  is the liftoff resist. The track width Tw of the thin-film magnetic head element to be formed is smaller than the size Tw 1  in the track width direction of the top surface of the convex portion  10   a  of the lower shield layer  10  (Tw 1 &gt;Tw). The size Tw 1  in the track width direction of the top surface of the lower shield layer  10  is greater than the track width Tw of the thin-film magnetic head element to be formed (Tw 1 &gt;Tw).  
      In one embodiment, as shown in  FIG. 5 , when the second resist R 2  is formed, the multilayer film M not covered with the second resist R 2  is removed by the etching process such as the milling, and the convex portion  10   a  and the buried gap layer  50  are exposed in the lower shield layer  10 . The location of the both end faces in the track width direction of the convex portion  10   a  of the lower shield layer  10  extends from the location of the both end faces in the track width direction of the thin-film magnetic head element  20 . The extension region is exposed in the removed part.  
      In this embodiment, the size of the top surface of the convex portion  10   a  in the track width direction is pre-defined so that the size Tw 2  in the track width direction of the extension region of the convex portion  10   a  is about 1/10 times to 20 times the track width Tw of the thin-film magnetic head element  20 . In this embodiment, the multilayer film (multilayer film covered with the second resist R 2 ) M disposed on the convex portion  10   a  of the lower shield layer  10  becomes the thin-film magnetic head element  20 .  
      In one embodiment, as shown in  FIG. 6 , when the second resist R 2  remains as it is, the side fill gap layer  40 , the bias layer  41  and the cap layer  42  are stacked sequentially from the both end faces  20  in the track width direction of the thin-film magnetic head element  20  to the convex portion  10   a  and the buried gap layer  50  of the exposed lower shield layer  10 . The bias layer  41  is formed of the hard magnetic material, for example, the Co—Pt alloy film or the Co—Cr—Pt alloy film. After the cap layer  42  is formed, the second resist R 2  is lifted off.  
      In one embodiment, a third resist which defines the height of the thin-film magnetic head element  20  is formed on the thin-film magnetic head element  20 . The thin-film magnetic head element  20  not covered with the third resist is removed by the etching process. The back fill gap layer is formed in the removed part. After the back fill gap layer is formed, the third resist is lifted off.  
      In one embodiment, an upper shield layer  30  is formed on the thin-film magnetic head element  20 , the cap layer  42  and the back fill gap layer. The upper shield layer is formed of the soft magnetic material, for example, NiFe and in the film thickness of approximately 1 μm by sputtering or plating.  
      As described above, the present embodiments were applied to a reproducing thin-film magnetic head, but the present embodiments can be also applied to, for example, the recording/reproducing thin-film magnetic head in which a recording inductive head is stacked on the reproducing thin-film magnetic head.  
      Various embodiments described herein can be used alone or in combination with one another. The forgoing detailed description has described only a few of the many possible implementations of the present invention. For this reason, this detailed description is intended by way of illustration, and not by way of limitation. It is only the following claims, including all equivalents that are intended to define the scope of this invention.