Abstract:
A method of making a magnetic head includes imbedding a coil layer in an insulation stack. The coil layer is formed with a filament that extends about a central axis. The central axis is perpendicular to a planar head surface and a coil plane. First and second pole pieces are formed with the insulation stack sandwiched between the first and second pole pieces. A first shield layer having first and second major planar thin film surfaces is joined by a third edge with the first major planar thin film surface of the first shield layer forming a portion of the planar head surface. A magnetoresistive (MR) sensor and first and second gap layers are formed with the MR sensor sandwiched between the first and second gap layers and the first and second gap layers located between the third edge and the first horizontal component and with the MR sensor and the first and second gap layers forming portions of the planar head surface.

Description:
This Divisional Application claims the priority of U.S. patent application Ser. No. 10/688,726, filed Oct. 17, 2003, now U.S. Pat. No. 6,925,702, which was a continuation of application Ser. No. 09/044,268, filed Mar. 19, 1998. now U.S. Pat. No. 6,722,019, which was a divisional of application Ser. No. 08/856,532 filed May 14, 1997, now U.S. Pat. No. 5,768,070. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a horizontal head with combined thin film write and MR (magnetoresistive) read elements at an air bearing surface (ABS) and more particularly to a merged or piggyback horizontal head wherein an MR sensor employs one or two MR stripes, the two MR stripes being uniquely formed for improved common mode rejection. 
     2. Description of the Related Art 
     A typical combined head includes a thin film inductive write element and a magnetoresistive (MR) read element. The thin film inductive write element includes one or more coil layers embedded in an insulation stack, the insulation stack being sandwiched between first and second pole piece layers that extend into a pole tip region. A gap layer forms a write gap between the pole pieces in the pole tip region. The pole pieces are magnetically coupled across a back gap in a back gap region. Between the pole tip region and the back gap region lies a yoke region where the pole piece layers separate from one another to accommodate the insulation stack. The insulation stack typically includes a first insulation layer (I 1 ) on the first pole piece layer, one or more coil layers on the first insulation layer, a second insulation layer (I 2 ) over the coil layer and a third insulation layer (I 3 ) over the second insulation layer. 
     An MR read element includes an MR sensor sandwiched between first and second gap layers which are, in turn, sandwiched between first and second shield layers. In a merged head a single layer serves both as a second shield layer for the read element and as a first pole piece for the write element. In a piggyback MR head the second shield layer and the first pole piece are separate layers. The merged (or piggyback) head is carried on a slider which, in turn, is mounted on a suspension in a magnetic disk drive. The suspension is mounted to an actuator which moves the head over selected tracks on a rotating disk for reading and writing signals thereon. Rotation of the disk creates a cushion of air that serves as an air bearing between the disk and the slider that counterbalances a loading force exerted by the suspension. A surface of the slider facing the disk is called an air bearing surface (ABS). The ABS is typically spaced from the disk in the order of 0.050 μm when the disk is rotating. A combined head (that is, a merged or a piggyback head) may be a “vertical” head or a “horizontal” head. In a vertical head a major plane of the first pole piece layer is generally perpendicular to the ABS, with edges of the first and second pole piece layers exposed at the ABS. In a typical horizontal head horizontal components of the first and second pole piece layers form a portion of the ABS so that edges of these layers are generally perpendicular to the ABS and extend internally into the head without being exposed at the ABS. In a horizontal head an insulation or gap layer separates the edges of the first and second pole piece layers at the ABS. 
     In the vertical head, the MR sensor for the read element is located at the ABS. In the horizontal head the edge of the MR sensor for the read element is typically recessed from the ABS and receives read signals via one of the pole piece layers which serves as a flux guide. Accordingly, the MR sensor, the first and second shields and the first and second pole pieces are all in series. There are several problems with this arrangement. First, it is desirable that the trace of a track being read be narrower than the track as written. This is impossible with the prior art arrangement since the write gap also serves as the read gap. Next, each time a write operation is performed the shields are subjected to a high density of flux, which can render them unstable. As a result of instability, the magnetic domains of shield layers may not return to their initial state, which can change the bias point of the MR sensor and result in inaccurate playback. 
     In both the vertical and horizontal heads it is desirable to increase the signal-to-noise ratio durng readback. This can be accomplished by employing a dual stripe MR sensor wherein each MR stripe conducts an identical sense current. During operation, both sense currents may be conducted to a differential amplifier in order to implement common mode noise rejection. If the read head collides with an asperity on a magnetic disk, noise generated by this collision will be reduced by common mode rejection. However, it is difficult to obtain near absolute common mode rejection because the MR stripes are typically formed in separate process steps. When MR stripes are formed in separate process steps they are not identical, due to slight differences in temperature, pressure, atmosphere and process times. In a dual stripe, vertical MR head, the thin film layers of the read element are sequentially formed by separate process steps. Thus, there is a strong felt need to form the two stripes of an MR element in a single process step so that the two stripes are substantially identical, the better to implement near-absolute common mode rejection of noise. 
     SUMMARY OF THE INVENTION 
     The present invention provides a horizontal combined head which has read and write elements located at the ABS. The read element is embodied in an MR sensor. The write element is embodied in a thin film structure with a write gap. An edge of the MR sensor as well as the write gap are located at the ABS. This is accomplished by insulating the MR sensor from the first pole piece and spacing the MR sensor from the write gap along the plane of the ABS. With this arrangement the track width of the read element may be less than the track width of the write head. 
     The present invention also provides a horizontal combined head including a dual stripe MR sensor, wherein a pair of MR stripes are formed in a single process step. This is accomplished by constructing an elongated pedestal, depositing a layer of MR material on the sides and top of the pedestal, and then milling the MR material from the top of the pedestal, leaving an MR stripe on each side of the pedestal. The two MR stripes are substantially identical, thereby promoting near absolute common mode rejection of noise. 
     An object of the present invention is to provide a horizontal head which has both of its read and write elements located at the ABS. 
     Another object is to provide a dual stripe MR sensor wherein the pair of MR stripes are nearly identical to promote near absolute common mode rejection of noise. 
     A further object is to provide a method of making a horizontal head with combined read and write elements at the ABS. 
     Yet another object is to provide a method of making a dual stripe MR sensor wherein the pair of MR stripes are formed in the same process step. 
     Other objects and many of the advantages of the invention will become apparent upon reading the following description of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a planar view of an exemplary magnetic disk drive; 
         FIG. 2  is an end view of a slider with a magnetic head of the disk drive as seen in plane II—II; 
         FIG. 3  is all elevation view of the magnetic disk drive wherein multiple disks and magnetic heads are employed; 
         FIG. 4  is an isometric illustration of an exemplary suspension system for supporting the slider and magnetic head; 
         FIG. 5  is a partial view of the slider and magnetic head as seen in plane V—V of  FIG. 2 ; 
         FIG. 6  is a view seen in plane VI—VI of  FIG. 5 ; 
         FIGS. 7A–7F  are schematic cross-sectional side views illustrating various process steps employed in constructing the horizontal magnetic head on a substrate or slider; 
         FIGS. 8A–8M  are schematic cross-sectional side views of the MR sensor portion of the horizontal head during various steps of its construction with the exception of  FIGS. 8F and 8H  which are isometric views illustrating steps during the construction; 
         FIG. 9  is a schematic diagram of the conductors for applying currents to the coil layer of the write head and the MR stripe of the single stripe MR sensor embodiment; 
         FIGS. 10A–10M  are schematic cross-sectional side views of a dual MR sensor during various steps of its construction; and 
         FIG. 11  is a schematic diagram illustrating the conductors for applying currents to the write coil of the write gap and the pair of sensors of the dual MR sensor. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views there is illustrated in  FIGS. 1–3  a magnetic disk drive  30 . The drive  30  includes a spindle  32  which supports and rotates a magnetic disk  34 . The spindle  32  is rotated by a motor  36  which in turn is controlled by a motor controller  38 . A horizontal combined magnetic head  40  for reading and recording is mounted on a slider  42  which, in turn, is supported by a suspension  43  and actuator arm  44 . A plurality of disks, sliders and suspensions may be employed in a large capacity direct access storage device (DASD) as shown in  FIG. 3 . The suspension  43  and actuator arm  44  position the slider  42  to place the magnetic head  40  in a transducing relationship with a surface of the magnetic disk  34 . When the disk  34  is rotated by the motor  36  the slider is supported on a thin (typically, 0.05 μm) cushion of air (air bearing) by the air bearing surface (ABS)  46 . The magnetic head  40  may then be employed for writing information to multiple circular tracks on the surface of the disk  44 , as well as for reading information therefrom. Processing circuitry  48  exchanges signals representing such information with the head  40 , provides motor drive signals, and also provides control signals for moving the slider to various tracks. In  FIG. 4  the slider  42  is shown mounted to a head gimbal assembly (HGA)  50  which in turn is mounted to the suspension  43 . 
     The horizontal head  40  is shown embedded in the slider  42  in  FIGS. 5 and 6 . The horizontal head  40  includes one or more oil layers  52  which are embedded in an insulation stack  54 . The insulation stack  54  is surrounded by and sandwiched between first and second pole pieces  56  and  58 , the pole pieces  56  and  58  being separated by an insulative gap layer  60  at the ABS and being connected at a back gap region  62 . Accordingly, when a current is conducted through the coil layers  52  flux will fringe between the first and second pole pieces across the gap  60  to write signals into the magnetic disk  34  ( FIG. 1 ). 
     The first pole piece  56  has a horizontal component  64  and the second pole piece  58  has a horizontal component  66 . The horizontal components  64  and  66  are thin film layers which have major planar surfaces which form a part of the ABS and which have edges  68  and  70  which are substantially perpendicular to the ABS. This structure distinguishes the horizontal head  40  from a vertical head (not shown) which has thin film edges of the first and second pole pieces forming a portion of the ABS and major thin film planar surfaces of the first and second pole pieces extending substantially perpendicular to the ABS. Horizontal and vertical magnetic heads should not be confused with horizontal and vertical recording in the magnetic media. Vertical recording means that the signals in the magnetic media are polarized perpendicular to the surface of the media whereas in horizontal recording the polarization of the signals is parallel to the surface of the media. The first pole piece  56  has a recessed horizontal component  72  which is connected to the horizontal component  64  by a slanted component  74  and the second pole piece  58  has a recessed horizontal component  76  which is connected to the horizontal component  66 . 
     Exposed at the ABS is an MR sensor  80  which is sandwiched between first and second gap layers  82  and  84 . The first and second gap layers  82  and  84  are sandwiched between edge surfaces of first and second shield layers  86  and  88 . Major thin film surfaces of the first and second shield layers  86  and  88  form a portion of the ABS. The horizontal head  40  shown in  FIG. 5  is a merged MR horizontal head since the horizontal component  64  of the first pole piece  56  and the second shield  88  of the MR head are a common layer. Optionally, the common layer can be two separate layers separated by an insulation layer so that the horizontal component  64  of the first pole piece and the second shield  88  are magnetically decoupled. This latter type of head is referred to as a piggyback MR head. 
     A pair of vias, one of which is shown at  90 , extends through the slider  42  and the insulation stack  54  for providing a current I to the coil layers  52  and a pair of vias, one of which is shown at  92 , extends through the slider  42  and the insulation stack  54  for providing a sense current I s  to the MR sensor  80 . The vias  90  and  92  are filled with a conductive material, such as copper, for conducting the currents. The pair of vias, including via  90 , terminate at exposed pads  94  and  96  and the pair of vias, including via  92 , terminate at exposed pads  98  and  100 , as shown in  FIGS. 4 and 5 . Conductors  102  and  104  are connected to the pads  94  and  96  and conductors  106  and  108  are connected to the pads  98  and  100  at first ends thereof and second ends of the conductors (not shown) are connected to the processing circuitry  48  shown in  FIG. 3 . 
     The present invention is distinguished by an insulation layer  110  which is sandwiched between the recessed horizontal component  72  of the first pole piece  56  on one side and the MR sensor  80 , the first and second gap layers  82  and  84  and the first and second shield layers  86  and  88  on the other side. This isolates the operation of the read head portion from the write head portion so that the read head portion can be located at the ABS. This obviates the problem associated with employing one of the pole pieces as a flux guide for the read head which causes instability of the shield layers as well as the problem of coupling the track width of the read head to the write head discussed hereinabove. 
       FIGS. 7A–7F  show various steps in the construction of the horizontal combined head with emphasis on the construction of the write and read elements. In the construction of the horizontal head a substrate  112  is provided which, after construction of multiple heads thereon, is diced into individual sliders  42  with a respective horizontal head  40  carried thereby. A layer of head compatible material, such as silicon dioxide, may be laid on top of the substrate  112 . A layer of Permalloy  116  is then formed on top of the layer  114 , a first insulation layer  118  is formed on top of the Permalloy layer  116 , the first coil layer  52  is formed on top of the first insulation layer  118 , a second insulation layer  122  is formed on top of the first insulation layer  118  and the first coil layer  52 , a third insulation layer  124  is formed on top of the second insulation layer and the first coil layer  120 , the second coil layer  52  is formed on top of the third insulation layer  124  and a fourth insulation layer  128  is formed on top of the third insulation layer  124  and the second coil layer  52 . The Permalloy layer  116  and the coil layers  52  may be formed by employing typical photolithography techniques. The layers  116 ,  118 ,  122 ,  124  and  128  extend laterally throughout a wide expanse of the wafer  112  and may be lapped after each formation. Vertical components  130  and  132  of the first and second pole pieces are formed in vias and joined to the Permalloy layer  116 . Construction of a similar head is shown in a commonly assigned U.S. Pat. No. 5,408,373 which is incorporated by reference herein. 
     Insulation layers  118 ,  122 ,  124  and  128  form the aforementioned insulation stack  54 . On top of the insulation stack  54  there is formed an insulation layer  134 , such as alumina, which extends over the entire wafer  112 . As shown in  FIG. 7B  a resist layer  136  is formed on top of the insulation layer  134  and is patterned to provide an opening so that the insulation layer can be recessed by milling as shown in  FIG. 7B . A resist layer  138  is then provided, as shown in  FIG. 7C , for recessing the insulation stack on the right side and removing the insulation layer on the left side. As shown in  FIG. 7D , a photoresist layer  140  with openings is then provided for the deposition of the recessed horizontal components  72  and the slanted component  74  discussed hereinabove. As shown in  FIG. 7E , a photoresist layer  142  is then formed with an opening so that the aforementioned insulation layer  110  can be formed. 
     The horizontal components  64  and  66  and the gap  60 , shown in  FIG. 7F , may be formed by typical photolithography patterning techniques or by side wall technology. If side wall technology is employed a rectangular box of photoresist (not shown) may be formed on the insulation stack  54  immediately to the left of the region where the gap layer  60  is to be formed. Insulative gap material is then deposited on the top of the photoresist box as well as its sides. Milling is then employed to remove the insulative gap material from the top of the box exposing the photoresist so that the photoresist can be removed by developing thereby leaving a rectangular fence of gap material, one side of the fence being located at  60 . Photoresist is then employed for patterning and forming the horizontal component  66 , after which this photoresist layer can be removed and another photoresist layer is employed after patterning for removing all portions of the insulative gap material except the gap  60 . The horizontal component  64  may then be formed by photoresist patterning or side wall technology. Side wall technology formation of vertical components will become more readily understood by the following description. 
       FIGS. 8A–8L  show the various steps in the construction of the read element portion of the horizontal head, the read element portion being located at the ABS.  FIG. 8A  shows the first step in the construction of the read head after the construction of the horizontal component  64  shown in  FIG. 7F . An insulative gap layer  150  is formed over the entire wafer including side walls, as shown in  FIG. 8A , and then the top portions are removed by any suitable means, such as ion beam milling, leaving the side wall  84  which is the second gap layer of the read head. The formation of the layer  150  may be by plasma vacuum chemical deposition (PVCD) which covers not only top surfaces but also the side walls. This process of covering an entire wafer, including side walls, with a deposition followed by milling of the top surfaces is generally referred to as the aforementioned side wall technology formation of components. It should be understood that these components can be alternatively formed by typical photo-lithography techniques. 
     A layer or layers  152  of MR material is then deposited, as shown in  FIG. 8C , and the top portions are milled away, as shown in  FIG. 8D , to form the MR sensor  80 . It should be understood that the MR sensor  80  may be multiple layers of a soft adjacent layer (SAL), an insulation layer, an MR stripe and a capping layer as desired. A photoresist layer  154  is then formed in the active region of the MR sensor, as shown in  FIGS. 8E and 8F , and hard biasing and lead layer material  156  may be deposited as shown. The photoresist  154  is then removed and photoresist  156  is placed to protect hard bias and lead material which is to be retained, as shown in  FIGS. 8G and 8H , after which the top hard bias and lead material is milled away to leave first and second lead layers  158  and  160 . The photoresist layer  154  is then removed and a layer of gap material  162  is formed as shown in  FIG. 8I . Photoresist  164  is then placed to protect the gap material to be retained and top portions of the gap material are removed by milling, as shown in  FIG. 8J , leaving the first gap  82 . The photoresist  164  is then removed and first shield material layer  166  is formed as shown in  FIG. 8K . Photoresist  168  is then formed and the top of the second shield material layer is then removed by milling as shown in  FIG. 8L . The photoresist layer  168  is then removed leaving the first shield  86 . 
       FIG. 9  is a schematic diagram of the conductors for the write and the read elements of the single stripe MR sensor embodiment of the horizontal head. Conductors  170  and  172  are connected to opposite ends of one or more of the coil layers  52  wherein one of the conductors such as conductor  170  may be grounded and the other conductor  172  may receive a current signal I. Conductors  174  and  176  may be connected to opposite ends of the active region of the single MR stripe of the sensor  80  wherein the conductor  174  may be grounded and the other conductor  176  receives a sense current I s . 
       FIGS. 10A–10M  describe an alternative embodiment for constructing an MR element which has a dual stripe MR sensor which can be substituted for the single stripe MR sensor. In this embodiment the formation of the horizontal component  64 , shown in  FIG. 7F , will be postponed. The first step in the construction of the dual stripe MR sensor embodiment is to place photoresist  200  for appropriately locating the MR sensor and then forming a layer of spacer material  202 . Top portions of the spacer material  202  are then removed by milling and the photoresist  200  is removed leaving a fence of spacer  204  as shown in  FIG. 10B . MR material  206  is then deposited on the top and the sides of the spacer  204  after which the top MR material is removed by milling, as shown in  FIG. 10D , leaving MR stripes  208  and  210 . It should be noted that by this single deposition the MR stripes  208  and  210  will be nearly identical so that they can implement near absolute common mode rejection. 
     Active regions of the MR stripes  208  and  210  are then protected by photoresist layers  212  and  213 , as shown in  FIGS. 10E and 10F . Hard bias and lead material  214  is then formed after which the photoresist layers  212  and  213  are removed. Photo-resist layers  215  and  216  are then placed, as shown in  FIGS. 10G and 10H , for protecting the hard bias and lead material to be retained and all other hard bias and lead material is milled away leaving hard bias and leads  217 ,  218 ,  219  and  220  as shown in  FIG. 10G . Second gap material  221  is then deposited over the entire wafer, as shown in  FIG. 10I . Photoresist layers  222  and  223  are then placed, as shown in  FIG. 10J , for protecting second gap material to be retained and all other gap material is milled away, as shown in  FIG. 10J , leaving gap layers  224  and  225 . Shield material  226  is then deposited, as shown in  FIG. 10K . Photoresist layers  228  and  230  are then formed, as shown in  FIG. 10L , to protect shield material to be retained and all other shield material is removed by milling, as shown in  FIG. 10L . The photoresist layers  228  and  230  are then removed leaving the final MR head structure with a dual stripe and first and second shields  232  and  234 , as shown in  FIG. 10M . The shield  234  can be a common layer with the horizontal component  64  of the first pole piece as shown in  FIG. 5 . The structure encompassed by the numeral  80  would be substituted for the single stripe MR sensor  80 , shown in  FIG. 5 , to provide the second embodiment of the invention employing the dual stripe MR sensor. 
     Conductors for the dual stripe MR sensor are shown in  FIG. 11 . Conductors  236  and  238  may be connected to opposite ends of one or more of the lead layers  52  with the conductor  236  connected to ground and the conductor  238  receiving current I. Conductors  240  and  242  may be connected at first ends to respective ends of the MR stripes  208  and  210  and conductors  244  and  246  may be connected at first ends to opposite ends of the MR stripes  208  and  210 . Second ends of the conductors  240  and  242  may be connected to ground. A second end of the conductor  244  may receive a first sense current I s1  and a second end of the conductor  246  may receive an identical sense current I s2 . The currents may be conducted through the MR sensors  208  and  210  with opposite polarity or they may be conducted therethrough with the same polarity and then processed by a differential amplifier to implement common mode rejection of noise. The second embodiment of the present invention has the advantages of both aspects of the invention, namely location of the MR sensor at the ABS of a horizontal head and employing near identical MR stripes of a dual MR sensor for near absolute common mode rejection of noise. 
     Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.