Abstract:
A thin-film magnetic head includes an ABS and a three-layer pole tip structure located between the ABS and a position at a predetermined height from the ABS. The structure consists of a first pole, a recording gap layer and a second pole. The recording gap layer is made of a material having a etching rate equal to or higher than that of a material for making the first and second poles.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a thin-film magnetic head provided with at least an inductive recording transducer element and to a method of manufacturing the head. 
     DESCRIPTION OF THE RELATED ART 
     FIG. 1 is a cross-sectional view perpendicular to the plane of the air bearing surface (ABS), illustrating an example of a conventional composite type thin-film magnetic head with an inductive recording head part and a magnetoresistive (MR) reproducing head part. 
     In the figure, the reference numeral  10  denotes a lower shield layer of the MR reproducing head part,  11  denotes an upper shield layer of the MR head part, which also acts as a lower pole of an inductive recording head part,  12  denotes a MR layer provided through an insulating layer  13  between the lower shield layer  10  and the upper shield layer  11 ,  14  denotes a recording gap layer of the recording head part,  15  denotes an upper pole,  16  denotes a lower insulating layer deposited on the recording gap layer  14 ,  18  denotes a coil conductor formed on the lower insulating layer  16 , and  17  denote an upper insulating layer deposited so as to cover the coil conductor  18 . The upper pole  15  is magnetically connected with the lower pole (upper shield layer)  11  at its rear portion so as to constitute a magnetic yoke together with the lower pole  11 . 
     As apparent from the figure, since the recording gap layer  14  of the conventional thin-film magnetic head is formed even under the coil conductor for generating a recording magnetic field, it is necessary to use materials having a high thermal conductivity. Thus, as the material of the recording gap layer  14 , aluminum oxide (Al 2 O 3 ) with comparatively high thermal conductivity has typically been used. 
     Recently, demand for higher recording density has made a recording track width narrower, and therefore a submicron width of the pole of the recording head part has been needed. To cope with such narrower pole width, a thin-film magnetic head is formed in a manner that only the recording pole portion is separated from other portions. That is, a three-layer pole structure with a lower pole tip element, a recording gap layer and an upper pole tip element is formed at only a pole tip region located between the ABS and a position at a predetermined height from the ABS in the recording head part, and an upper yoke and a lower yoke are magnetically connected to the top surface and the bottom surface of this pole tip structure, respectively. 
     FIGS. 2 and 3 illustrate an example of a conventional composite type thin-film magnetic head having such a three-layer pole tip structure. FIG. 2 is a cross-sectional view perpendicular to the plane of the ABS, and FIG. 3 is a schematic ABS view. In these figures, the reference numeral  20  denotes a lower shield layer of the MR reproducing head part,  21  denotes an upper shield layer of the MR head part, which also acts as a lower auxiliary pole of an inductive recording head part,  22  denotes a MR layer provided through an insulating layer  23  between the lower shield layer  20  and the upper shield layer  21 ,  24  denotes a lower pole tip element of the inductive recording head part,  25  denotes an upper pole tip element,  26  denotes a recording gap layer formed between the lower pole tip element  24  and the upper pole tip element  25 ,  27  denotes a lower insulating layer deposited on the upper shield layer  21  and around a three-layer pole structure consisting of the lower pole tip element  24 , the recording gap layer  26  and the upper pole tip element  25 ,  28  denotes a coil conductor formed on the lower insulating layer  27 ,  29  denotes an upper insulating layer deposited so as to cover the coil conductor  28 , and  30  denotes an upper auxiliary pole formed on the upper insulating layer  29  and deposited to contact with the upper pole tip element  25 . The upper auxiliary pole  30  is magnetically connected with the lower auxiliary pole (upper shield layer)  21  at its rear portion so as to constitute a magnetic yoke together with the lower auxiliary pole  21 . 
     In manufacturing the above-mentioned thin-film magnetic head in which only the recording pole portion is separated from other portions, when three-layer pole structure consisting of the lower pole tip element  24 , the recording gap layer  26  and the upper pole tip element  25  is formed by a dry etching process such as ion milling, conventional use of Al 2 O 3  as a material of the recording gap layer causes its shape control to become difficult. That is, since Al 2 O 3  has a lower etching rate than that of magnetic materials used for the lower and upper pole tip elements  24  and  25  of the three-layer pole structure, shape control, such as formation of the side surface of the three-layer pole structure to make perpendicular to the top surface of the upper shield layer  21  is very difficult. In other words, when the three-layer pole structure is patterned by a dry etching process, the side surface of the Al 2 O 3  gap layer  26  is not easily etched due to the lower etching rate of Al 2 O 3  than that of the magnetic material of the upper pole  25 . Thus, the side surfaces of the patterned recording gap layer  26  incline with respect to that of the upper pole layer as shown in FIG.  3 . In addition, the side surfaces of the lower pole layer  24  below the recording gap layer  26  also incline as well as the recording gap layer  26 , thereby generating problems such as increase of recording track width and side fringing. 
     In order to enhance the etching rate of Al 2 O 3 , use of a reactive ion etching (RIE) may be considered. However, when the three-layer pole structure mentioned above is etched, not only etching gas must be changed for every layer, but also an etching device should be formed so as to correspond to the etching gas for Al 2 O 3  such as chlorine series. Additionally, a countermeasure for corrosion should be also considered. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a thin-film magnetic head and a method of manufacturing the same, whereby a little side fringing and stable recording properties can be realized even in a narrower track. 
     According to the present invention, a thin-film magnetic head includes an ABS and a three-layer pole tip structure located between the ABS and a position at a predetermined height from the ABS. The structure consists of a first pole, a recording gap layer and a second pole. The recording gap layer is made of a material having a etching rate equal to or higher than that of a material for making the first and second poles. 
     According to the present invention, furthermore, a thin-film magnetic head has a MR reproducing head part, an inductive recording head part multilayered with the reproducing head part, and an ABS. The recording head part includes a three-layer pole tip structure located between the ABS and a position at a predetermined height from the ABS. The structure consists of a first pole, a recording gap layer and a second pole. The recording gap layer is made of a material having a etching rate equal to or higher than that of a material for making the first and second poles. 
     Also, according to the present invention, a method of manufacturing a thin-film magnetic head includes a step of sequentially depositing a first magnetic layer, a non-magnetic layer and a second magnetic layer, and a step of forming a three-layer pole tip structure located between an ABS and a position at a predetermined height from the ABS by dry etching the first magnetic layer, the non-magnetic layer and the second magnetic layer. The non-magnetic layer is made of a material having an etching rate equal to or higher than that of a material for making the first and second magnetic layers. 
     The first and second pole tip elements may correspond to a lower pole tip element and an upper pole tip element, respectively, or correspond to an upper pole tip element and a lower pole tip element respectively, depending upon the layered order of each layer in the manufacturing processes of the thin-film magnetic head. 
     Since the recording gap layer of the conventional thin-film magnetic head is extended to an area below the coil conductor for producing recording magnetic field, it is necessary to use materials having high thermal conductivity. However, in a pole separation type recording head in which a pole tip elements are separated from a yoke portion of the recording head part, the recording gap layer does not extend to the area below the coil. Thus, various materials can be selected for making the recording gap layer without being limited to those having high thermal conductivities. 
     Therefore, when a three-layer pole tip structure is formed by a dry etching process such as ion milling, a recording gap layer material having an etching rate equal to or higher than that of a magnetic material for making poles is used. As a result, the shape of the three-layer pole tip structure can be easily controlled. Thus, a thin-film magnetic head can be provided by a method of easily controlling the shape of the pole tip structure without selecting the dry etching process such as ion milling, while maintaining the thermal conduction level in the coil to a conventional level. 
     It is preferred that the material for making the recording gap layer is one selected from a group of SiO 2 , Ta 2 O 5 , SiC, and AlN. 
     It is also preferred that the material for making the first and second poles is nitride containing Fe. 
     It is further preferred that the material for making the recording gap layer is Ta 2 O 5 , and that the material for making the first and second poles is NiFe. 
    
    
     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 
     FIG. 1 is a cross-sectional view of the already described example of the conventional composite type thin-film magnetic head, perpendicular to the plane of the ABS; 
     FIG. 2 is a cross-sectional view of the already described another example of the conventional composite type thin-film magnetic head having the three-layer pole structure, perpendicular to the plane of the ABS; 
     FIG. 3 is a schematic ABS view of the example shown in FIG. 2; 
     FIG. 4 is a schematic ABS view of a preferred embodiment of a composite type thin-film magnetic head having an inductive recording head part and a MR reproducing head part according to the present invention; 
     FIG. 5 is a cross-sectional view of the magnetic head of FIG. 4, perpendicular to the plane of the ABS; and 
     FIGS. 6 to  12  are schematic illustrations of a sequence of processes in the manufacturing method of the thin-film magnetic head according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 4 and 5 illustrate a preferred embodiment of a composite type thin-film magnetic head having an inductive recording head part and a MR reproducing head part according to the present invention. FIG. 4 is a schematic ABS view, and FIG. 5 is a cross-sectional view perpendicular to the plane of the ABS. 
     In these figures, the reference numeral  40  denotes a lower shield layer for the MR reproducing head part,  41  denotes an upper shield layer,  42  denotes a MR layer formed between the lower shield layer  40  and the upper shield layer  41  through an insulating layer  43 ,  44  denotes a lower pole tip element of the inductive recording head part,  45  denotes an upper pole tip element,  46  denotes a recording gap layer formed between the lower pole tip element  44  and the upper pole tip element  45 , and  47  denotes a lower insulating layer deposited on the upper shield layer  41  and around a three-layer pole structure consisting of the lower pole tip element  44 , the recording gap layer  46  and the upper pole tip element  45 . Furthermore, in the figures, the reference numeral  48  denotes a coil conductor formed on the lower insulating layer  47 ,  49  denotes an upper insulating layer deposited so as to cover the coil conductor  48 , and  50  denotes an upper auxiliary pole. The upper shield layer  41  contacts to the lower pole tip element  44  to act as a lower auxiliary pole. The upper auxiliary pole  50  is magnetically connected with the lower auxiliary pole (upper shield layer)  41  at its rear portion so as to constitute a magnetic yoke together with the lower auxiliary pole  41 . 
     The recording gap layer  46  is made of a material having an etching rate equal to or higher than that of the material of the lower and upper pole tip elements  44  and  45 . In this embodiment, as the magnetic material for the lower and upper pole tip elements  44  and  45 , nitride of Fe series such as FeN, FeZrN or FeBN, or a magnetic material having substantially the same etching rate as the nitride of Fe series is used. As the material of the recording gap layer  46 , AlN, Ta 2 O 5 , SiO 2 , SiC or an insulating material having substantially the same etching rate as that of the aforementioned materials. However, when NiFe having a comparatively high etching rate is used as the magnetic material for the lower and upper pole tip elements  44  and  45 , it is necessary to use an insulating material such as Ta 2 O 5  having a higher etching rate than that of NiFe for the recording gap layer  46 . In stead of using an insulating material for the recording gap layer  46 , a conductive non-magnetic material such as NiP can be used. 
     Table 1 indicates magnetic materials which can be used for the lower and upper pole tip elements  44  and  45  with their ion etching rates, and insulating materials which can be used for the recording gap layer  46  with their ion etching rates. In this Table, Al 2 O 3  and its ion etching rate, which has been conventionally used, is indicated as a comparative example. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 MATERIAL 
                 USED FOR 
                 ETCHING RATE (nm/min) 
               
               
                   
               
             
             
               
                 NiFe 
                 MAGNETIC POLE 
                 50 
               
               
                 FeZrN 
                 MAGNETIC POLE 
                 27 
               
               
                 Al 2 O 3   
                 RECORDING GAP 
                 8.5 
               
               
                 SiO 2   
                 RECORDING GAP 
                 33 
               
               
                 Ta 2 O 3   
                 RECORDING GAP 
                 60 
               
               
                 SiC 
                 RECORDING GAP 
                 35 
               
               
                 AlN 
                 RECORDING GAP 
                 30 
               
               
                   
               
             
          
         
       
     
     In the conventional head, Al 2 O 3  is used for the gap layer of the three-layer pole structure. Thus, when the three-layer pole structure is patterned by a dry etching process such as ion milling other than RIE, the side surface of the Al 2 O 3  gap layer is not easily etched due to the lower etching rate of Al 2 O 3  than that of the magnetic material of the poles. Thus, the side surfaces of the patterned recording gap layer incline with respect to that of the upper pole layer as shown in FIG.  3 . In addition, the side surfaces of the lower pole layer below the recording gap layer also incline as well as the recording gap layer, thereby generating problems such as increase of recording track width and side fringing. 
     However, according to this embodiment, since the recording gap layer  46  is made of a material having milling rate equal to or higher than that of the magnetic material for the pole layers  44  and  45 , the etching can be executed as well as a single material layer is etched. Thus, the patterning control of the shape of particularly the side surface of the three-layer pole structure is facilitated, thereby preventing the occurrence of increase of the recording track width and side fringing. 
     It should be noted that, in the embodiment, since the recording head part is constructed as a pole separation type in which the recording gap layer  46  is not expanded into the area below the coil  48 , materials other than Al 2 O 3  can be used for the recording gap layer  46 . That is, in such head, material having high thermal conductivities does not need for the recording gap layer. 
     FIGS. 6 to  12  are schematic ABS views illustrating processes of a method of manufacturing a thin-film magnetic head according to the present invention. The magnetic head manufactured by the following steps is a composite type thin-film magnetic head having an inductive recording head part and a MR reproducing head part. 
     First, on a substrate (wafer) (not shown) is formed the MR reproducing head part consisting of the lower shield layer  40 , the MR layer  42 , the insulating layer  43 , and the upper shield layer  41 . As the upper shield layer  41 , about 3.5 μm thick NiFe (82 wt % Ni-18 w t % Fe) is deposited and patterned by the photolithography technique, or formed by electroplating. After that, Al 2 O 3  insulating layer  51  is deposited on the entire surface by sputtering as shown in FIG.  6 . Preferably, the thickness of the insulating layer  51  is such that the top of the upper shield  41  is fully buried therein. In the this embodiment the insulating layer has a thickness of about 8.5 μm. 
     After that the insulating layer  51  is polished by a chemical-mechanical polishing (CMP) process to expose the top surface of the upper shield layer  41 , as shown in FIG.  7 . This CMP in this embodiment is carried out by using oxide abrasion grains with each diameter of about 0.02 to 0.3 μm and alkaline slurry using KOH as additives. As a polishing pad, a synthetic fiber type such as urethane is used. 
     After completion of the CMP, on the upper shield layer  41  and the insulating layer  51 , a magnetic layer  52  for the lower pole tip element  44  of the inductive recording head part, an insulating layer for the recording gap layer  46  and a magnetic layer  54  for the upper pole tip element  45  are sequentially deposited to obtain a three-layer structure, as shown in FIG.  8 . 
     In this embodiment, as the lower pole tip element  44 , the layer  52  made of a high Bs material such as FeZrN is deposited by sputtering to have a thickness of about 0.5 μm. As the recording gap layer  46 , the insulating layer  53  made of insulating material such as SiO 2  is deposited by sputtering to have a thickness of about 0.3 μm. As the upper pole tip element  45 , the magnetic layer  54  made of a high Bs material such as FeZrN is deposited by sputtering to have a thickness of about 0.7 μm. 
     These three layers constituting the pole tip structure can be deposited in the same chamber. For the high Bs material layers  52  and  54  made of FeZrN, a reactive DC magnetron sputtering wherein an alloy target of 88.2 at % Fe-11.8 at % Zr is sputtered under a mixed gas of Ar+N 2  is executed to add nitrogen to the FeZr layer. In this case, the total pressure is 0.2 Pa, and the partial pressure of nitrogen is of 10%. Also, the applied power is 1.4 kW, and the layer formation speed is 15 nm/min. For the insulating layer  53 , RF magnetron sputtering wherein a SiO 2  target is sputtered under Ar, Ar+O 2 , O 2  gas is executed. In this case, the total pressure is 1.0 Pa, the applied power is 1.0 kW, and the layer formation speed is 4 nm/min. 
     Then, as shown in FIG. 8, a resist frame  55  having an opening corresponding to a portion of a mask ( 56  shown in FIG. 9) to be formed is formed on the magnetic layer  54  for the upper pole tip element  45 . The opening has a width of about 0.3 to 2.0 μm. In this embodiment, as the resist frame  55 , a novolak type resist layer having a thickness of about 2 to 5 μm is deposited and then patterned by a photolithography technique. 
     The mask  56  is then formed by electroless plating. It is desirable that before electroless plating, the wafer is immersed in 4.5% HCl solution for 1.5 min to obtain wetting properties of the plating surface. 
     The plated mask  56  is a metal compound composed of a base material of nickel (Ni) metal and cobalt (Co) metal, and additives of 3B group element such as boron (B) and 5B group element such as phosphorus (P). The thickness of the mask  56  is about 1.0 to 3.0 μm. 
     The resist frame  55  is then removed with acetone remover thereby obtaining a structure shown in FIG.  9 . 
     Then, the three layers  54 ,  53  and  52  are etched by ion milling using the mask  56 . The ion milling conditions are, for example, an accelerating voltage of 500 mV and an accelerating current of 400 mA. By this ion milling, the magnetic layer  52 , insulating layer  53  and magnetic layer  54  except for an area below the mask  56  are removed to form the lower pole tip element  44 , recording gap layer  46  and upper pole tip element  45 . 
     Then, the mask  56  is removed by using organic solvent such as acetone to provide a patterned three-layer pole tip structure consisting of the FeZrN lower pole tip element  44 , the SiO 2  recording gap layer  46  and the FeZrN upper pole tip element  45 , as shown in FIG.  10 . 
     Then, as shown in FIG. 11, an insulating layer  57  consisting of an insulating material such as Al 2 O 3  or SiO 2  is deposited by sputtering. The thickness of the insulating layer  57  is determined to a value such that the top of the three-layer pole structure formed by ion milling is fully buried in this layer  57 , for example about 0.5 to 15 μm. In this embodiment this thickness of the insulating layer  57  is about 2.5 μm. 
     After depositing the insulating layer  57 , this layer  57  is polished by a CMP process to expose the upper pole tip element  45 , as shown in FIG.  12 . The CMP in this embodiment is carried out using oxide abrasion grains such as Al 2 O 3  or SiO 2 , having each diameter of about 0.02 to 0.3 μm and alkaline slurry using KOH as additives. As a polishing pad, a synthetic fiber type such as urethane is used. 
     Then, on the lower insulating layer  47  is formed the coil conductor  48  on which the upper insulating layer  49  is deposited. This upper insulating layer  49  is formed by depositing a novolak type photoresist and by patterning using a photolithography technique. A resist frame is then formed by a photolithography technique and the upper auxiliary pole  50  is formed by electroplating process. The upper auxiliary pole  50  is magnetically connected to the upper shield layer  41  at the rear portion so as to form a yoke. By the above-mentioned processes, the thin-film magnetic head having the cross-sectional view of FIG. 5 can be obtained. 
     In stead of the mask  56 , only the patterned upper pole tip element  45  is formed by plating, and then the three-layer pole structure can be formed by ion milling by using the upper pole tip element  45  as a mask. 
     In the above-mentioned embodiment, after forming the MR reproducing head part on the substrate, the inductive recording head part is formed. However, it is apparent that after forming the inductive recording head part on the substrate, the MR reproducing head part may be formed. In the latter case, the above-mentioned lower shield layer, the lower pole tip element, the lower auxiliary pole and the lower insulating layer will be substituted for an upper shield, an upper pole tip element, an upper auxiliary pole and an upper insulating layer, respectively. 
     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.