Abstract:
A giant magnetoresistance recording head includes a writer having a top pole, a shared pole, a conductive coil and a write gap region. The top pole includes a first top pole piece and a second top pole piece. The second top pole piece is formed at least in part over the first top pole piece and is recessed from the air bearing surface. The first top pole piece is formed over a top flat surface of the shared pole and is separated from the shared pole by the write gap region. The shared pole has a recess on the top surface. The recess is placed under the top pole and filled with a non-magnetic material. The non-magnetic recess in the shared pole defines the throat height of the writer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of the filing date of U.S. provisional application serial No. 60/212,933 entitled “RECORDING HEAD WITH THROAT HEIGHT DEFINED BY NONMAGNETIC RECESS IN SHARED POLE,” which was filed Jun. 20, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of electronic data storage and retrieval, and in particular to an improved writer in a merged giant magnetoresistance (GMR) read/write head. 
     A GMR read/write head generally consists of two portions, a writer portion for storing magnetically-encoded information on a magnetic disc and a reader portion for retrieving magnetically-encoded information from the disc. The reader portion typically consists of a bottom shield, a top shield, and a giant magnetoresistive (GMR) sensor positioned between the bottom and top shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a free layer of the GMR sensor, which in turn causes a change in electrical resistivity of the GMR sensor. The change in resistivity of the GMR sensor can be detected by passing a current through the GMR sensor and measuring a voltage across the GMR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary. 
     The writer portion typically consists of a top and a bottom pole, which are separated from each other at an air bearing surface of the writer by a gap layer, and which are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. Positioned between the top and bottom poles are one or more layers of conductive coils encapsulated by insulating layers. The writer portion and the reader portion are often arranged in a merged configuration in which a shared pole serves as both the top shield in the reader portion and the bottom pole in the writer portion. 
     To write data to the magnetic media, an electrical current is caused to flow through the conductive coils to thereby induce a magnetic field across the write gap between the top and bottom poles. By reversing the polarity of the current through the coils, the polarity of the data written to the magnetic media is also reversed. Because the top pole is generally the trailing pole of the top and bottom poles, the top pole is used to physically write the data to the magnetic media. Accordingly, it is the top pole that defines the track width of the written data. More specifically, the track width is defined by the width of the top pole near the write gap at the air bearing surface. 
     In magnetic recording, it is desirable to improve the areal density at which information can be recorded and reliably read. This desire has lead to a trend toward shorter bit length along a magnetic recording track and a shrinking track width. Narrow track widths are achieved by use of narrow pole tips at an air bearing surface (ABS) of the head. However, the pole width must be large in the paddle region of the head where the coil passes between the poles. The larger pole width is necessary to gain adequate magnetic flux through the poles by the coil write current. Hence, it is common to taper the pole from the larger width in the paddle region to a narrower width in the pole tip region at the ABS. 
     The length of the bit cell is largely dictated by a length of the write gap. The gap length is defined as the length between opposing pole tips at the ABS along the length of a recorded track. The gap height, commonly referred to as the throat height, is the distance from the ABS to a “zero throat position”, where both of the pole tips converge at the write gap. Typically, the throat height is 1 or 2 micrometers and is defined in part by the position of a zero throat insulator. The zero throat insulator is used not only for zero throat height definition, but also to improve efficiency of the recording head. The thickness of the zero throat insulator is typically about 1-2 micrometers. 
     Prior art configurations have a distinct limitation in that the top pole is typically formed over the zero throat insulator, resulting in the top pole having a “bump” shape. The portion of the top pole adjacent the air bearing surface in prior art configurations is sloped. It is therefore difficult to precisely control the width of the top pole at the air bearing surface, particularly as the width necessarily becomes smaller to allow for greater data storage densities. Since the pole tip is formed on the zero throat insulator, which requires a thick photoresist process with a very high aspect ratio of the resist thickness to the pattern width that is targeted, the top pole tip width is limited to the precision of the photolithography. Moreover, the highly developed topography of the top pole tip at the ABS initiates light distortion on the slope of the zero throat insulator during exposing. Hence, as the track width decreases, it becomes progressively more difficult to produce the pole tips to the precision required. To solve this problem, a two-piece structure of the top pole was proposed in U.S. Pat. No. 5,452,164. 
     The use of a two-piece pole structure facilitates the achievement of a submicron pole tip width at the ABS. The two-piece pole employs a first piece (pole tip) having a very narrow width at the ABS, and a second pole piece connected to the first pole piece and extending to the back region of the head. Thus, the first pole piece defines the narrow track width, and the second pole piece links through the coils and connects to the other (e.g., bottom) pole. The second pole piece of a two-piece pole is made wider at the ABS than the first pole piece due to photolithography limitations. As a result, sharp corners are formed in the second pole piece at the ABS. These corners produce a large fringing magnetic field during recording. The fringing field may adversely affect data recorded on adjacent tracks by erasing or re-writing previously recorded information. 
     In addition, the two-piece pole structure design proposed in U.S. Pat. No. 5,452,164 has a high sensitivity of non-linear transition shift (NLTS) and overwrites (OVW) to the write current due to a poor control of the pole tip saturation at the ABS. An improved structure of the top pole exhibiting better NLTS and OVW characteristics was proposed in U.S. Pat. No. 5,801,910. In the improved structure, the pole tip has a funnel shape with a long saturation zone localized at the ABS. That saturation zone is generated by one or more break points. However, the funnel-shaped top pole tip is normally formed on the zero throat insulator with uncontrolled light distortion. 
     It would be desirable to produce a read/write head that allows for greater tolerance control of the width of the top pole at the air bearing surface, that exhibits good NLTS and OVW characteristics, and that eliminates the fringing field effect found in prior art pole structures. 
     BRIEF SUMMARY OF THE INVENTION 
     A magnetic recording head includes a writer having a top pole, a shared pole, a first conductive coil and a write gap region. The top pole includes a first top pole piece and a second top pole piece. The second top pole piece is formed at least in part over the first top pole piece. The write gap region is positioned between the top pole and the shared pole and under the first conductive coil. The second top pole piece is recessed from the air bearing surface. A recess is formed in the shared pole and filled with a non-magnetic material. The recess defines a throat height of the magnetic recording head. 
     The read/write head of the present invention includes a substantially planar first top pole piece, which allows for greater tolerance control of the width of the top pole at the air bearing surface. The first top pole piece has a funnel-shape with a long saturation zone to suppress sensitivity of the NLTS and OVW characteristics to the write current. By recessing the second top pole piece from the air bearing surface, the fringing field effect found in prior art structures is eliminated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross-sectional view of a prior art merged MR head. 
     FIG. 2 is an ABS view of the prior art head of FIG.  1 . 
     FIG. 3 is a side view of a prior art magnetic write head. 
     FIG. 4 is a top view of the prior art write head of FIG.  3 . 
     FIG. 5 is a side cross-sectional view of a merged GMR read/write head according to a first preferred embodiment of the present invention. 
     FIG. 6 is a top view of the read/write head of FIG.  5 . 
     FIG. 7 is an ABS view of the read/write head of FIG.  5 . 
     FIG. 8 is a side cross-sectional view of a write head according to a second preferred embodiment of the present invention, with a modified recess structure. 
     FIG. 9 is a top view of the write head of FIG.  8 . 
     FIG. 10 is a side cross-sectional view of a write head according to a third preferred embodiment of the present invention, with the notch, write gap and first top pole formed with the same photomask using electroplating. 
     FIG. 11 is an ABS view of the write head of FIG.  10 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a side cross-sectional view of a prior art merged MR head disclosed in U.S. Pat. No. 5,452,164. Head  20  includes top pole P 2 , second insulation layer  12 , conductor layer  22 , first insulation layer I 1 , bottom magnetic layer  24 , bottom pole P 1 , pole tip elements PT 2   a  and PT 2   b , gap layer G and pole tip PT 1 . FIG. 1 also shows pole tip region  26 , the zero throat level, a back region and a back gap (BG) region. As shown in FIG. 1, pole tip elements PT 2   a  and PT 2   b  both extend to the ABS. FIG. 2 shows an ABS view of the head of FIG.  1 . As shown in FIG. 2, the top pole tip element PT 2   a  is made wider at the ABS than the bottom pole tip element PT 2   b  due to photolithography limitations. The wider top pole tip element PT 2   a  causes a large fringing magnetic field to be produced during recording. The fringing field may adversely affect data recorded on adjacent tracks by erasing or re-writing previously recorded information. In addition, the two-piece pole structure proposed in U.S. Pat. No. 5,452,164 has a high sensitivity of non-linear transition shift (NLTS) and overwrites (OVW) to the write current due to a poor control of the pole tip saturation at the ABS. 
     An improved structure of the top pole exhibiting better NLTS and OVW characteristics was proposed in U.S. Pat. No. 5,801,910. FIG.  3  and FIG. 4 show the prior art head disclosed in U.S. Pat. No. 5,801,910. FIG. 3 is a side view of the prior art magnetic write head. FIG. 4 is a top view of the prior art write head of FIG.  3 . Write head  50  includes electrical energization  52 , write coil  54 , top pole piece  60 , gap layer  62 , bottom pole piece  70  and gap  72 . Top pole piece  60  includes side surfaces  64  and  66 , top pole tip  68 , wide portion  82  and convergent portions  84  and  88 . Bottom pole piece  70  includes bottom pole tip  74 . FIG. 4 also shows throat height  58 , pole tip region  94 , track width  104  and saturation zone  106 . The funnel-shaped structure of top pole piece  60  results in the generation of saturation zone  106 , which results in a lower sensitivity of the NLTS and OVW characteristics to the write current. However, the funnel-shaped top pole piece  60  is normally formed on a zero throat insulator with uncontrolled light distortion. 
     FIG. 5 is a cross-sectional view of a merged GMR read/write head according to a preferred embodiment of the present invention. Read/write head  120  is capable of supporting high-speed recording with a submicron track width. Read/write head  120  includes reader portion  121  and writer portion  123 . Reader portion  121  includes substrate  154 , bottom shield  152 , GMR sensor  132 , read gap  150  and shared pole  130 . Read gap  150  includes two insulating layers  156  and  158 . GMR sensor  132  is positioned in read gap  150  between insulating layers  156  and  158 . Read gap  150  isolates GMR sensor  132  from shared pole  130  and bottom shield  152 . 
     Writer portion  123  is a multi-layer structure that includes shared pole  130 , coil  136 , write gap  126 , first top pole  122 , second top pole  134 , back gap closer  144  and insulating layers  138 ,  140  and  142 . Shared pole  130  serves as a top shield for reader  121  and a bottom pole for writer  123 . As a shield, shared pole  130  should have a high permeability, low coercivity and magnetostriction, and a stable domain structure. As the bottom pole of the writer  123 , shared pole  130  should possess high magnetization saturation and low electrical conductivity. To satisfy these requirements, shared pole  130  has a multi-layer structure including bottom magnetic layer  148 , first top magnetic layer  146  and second top magnetic layer  128 . Bottom magnetic layer  148  of shared pole  130  is preferably made of a soft magnetic material such as Ni 79 Fe 21 . Top magnetic layers  146  and  128  are preferably made of a material with a high magnetization saturation, such as Ni 45 Fe 55  or NiCoFe-alloys, exhibiting a saturation induction B s  of up to 2.1 T. The multi-layer structure of shared pole  130  provides high shielding and writing performance, and suppresses writer effect on reader  121 . 
     A recess  124  is formed in shared pole  130 . Recess  124  is preferably filled with a non-magnetic material  125 , such as Al 2 O 3 , although any non-magnetic material including metals may be used in recess  124 . 
     The throat height is defined by the height of the shared pole  130  located between the ABS and the non-magnetic recess  124 . In the writer  123  according to the present invention, the non-magnetic recess  124  in second top layer  128  of shared pole  130  serves as the traditional zero throat insulator defining the zero throat. The top surface of shared pole  130  adjacent to write gap  126  is planarized by polishing. The flat top surface of shared pole  130  and the absence of the traditional zero throat insulator allow a photoresist with a reduced thickness to be used during the formation of first top pole  122 , which considerably improves the resolution of the photo technology. Light distortion is eliminated during exposure of first top pole  122 . Patterns of 0.15-0.2 micrometers wide can be formed without the use of expensive and time consuming ion mill focused ion beam technologies. 
     Write gap  126  is formed over shared pole  130 , and is preferably made of Al 2 O 3 . The top pole of writer  123  has a two-piece structure, including first top pole  122  (pole tip) and second top pole  134 . First top pole  122  has a funnel shape with several break points (see FIG. 6) to provide a long saturation zone to suppress sensitivity of the writer characteristics to the write current. First top pole  122  is preferably made of a high moment material such as Ni 45 Fe 55  or CoNiFe. The thickness of first top pole  122  is preferably about 1.0-2.0 micrometers. Second top pole  134  overlays first top pole  122 . Second top pole  134  contacts shared pole  130  in the back gap region through back gap closer  144 . Second top pole  134  and back gap closer  144  are preferably made of Ni 45 Fe 55  and have a thickness of 1.5-2.5 micrometers. 
     Write head  120  also includes a coil  136  isolated from the rest of the head by insulating layers  138 ,  140  and  142 , each made of a hard baked photoresist. Insulating layer  142  can alternatively be made of Al 2 O 3  or other vacuum deposited insulator. Coil  136  has a two layer structure and is preferably made of Cu. Coil  136  is in a pancake configuration, and encircles back gap closer  144 . 
     FIG. 6 shows a top view of the head of FIG.  5 . The cross-sectional view shown in FIG. 5 is viewed from the perspective of section lines  5 — 5  in FIG.  6 . To provide high efficiency of the write head  123 , the shape of non-magnetic recess  124  in second top magnetic layer  128  of shared pole  130  is made to resemble the projection of second top pole  134 . The magnetic material of top layer  128  of shared pole  130  surrounds recess  124 , which provides effective flux supply to gap area  126  during recording. 
     As shown in FIG. 6, top magnetic layer  128  narrows to the throat height value at the ABS near the center of read/write head  120  and broadens at the edges of read/write head  120 . Thus, top magnetic layer  128  has a variable height along the ABS. 
     First top pole  122  is patterned to a submicron width near the ABS and broadens away from the ABS. The points at which top pole  122  changes in width are referred to as “break points”. Because of the planar structure of first top pole  122 , the size of the various regions of first top pole  122  defined by break points may be precisely controlled. 
     An ABS view of merged GMR head  120  according to the present invention is shown in FIG.  7 . Read/write head  120  in FIG. 7 is viewed from the perspective of a disc looking at the ABS of head  120 . Conductor leads  162 A and  162 B are coupled to GMR sensor  132 . Top layer  128  of shared pole  130  is made separately from layers  146  and  148  by using an additional photomask. Writer portion  123  includes notch  160  formed on a top surface of top magnetic layer  128 . Notch  160  improves the track resolution of writer portion  123 . The width of notch  160  is equal to the width of first top pole  122  in write gap area  126  adjacent the ABS (i.e., writer width or WW). Notch  160  is made by ion mill on a top surface of top layer  128  of shared pole  130 . First top pole  122  serves as a mask during ion mill of notch  160 . 
     A second preferred embodiment of the present invention is shown in FIG.  8  and FIG.  9 . FIG. 8 shows a cross-sectional view of read/write head  163 . FIG. 9 shows a top view of read/write head  163 . The cross-sectional view shown in FIG. 8 is viewed from the perspective of section lines  8 — 8  in FIG.  9 . The reader portion of read/write head  163  is the same as reader  121  of read/write head  120 , and is not shown in FIGS. 8 and 9. Read/write head  163  is substantially the same as read/write head  120  shown in FIGS. 5-7, but has a different structure of shared pole  168 . The shape of non-magnetic recess  164  in shared pole  168  has an ellipse-like shape and is localized in write gap area  126  under first top pole  122  and a sloped region of second top pole  134 . The ellipse-like shape of recess  164  suppresses domain wall formation in gap area  126  due to a uniform distribution of magnetization in top magnetic layer  166  of shared pole  168 , which surrounds recess  164 . The suppression of domain wall formation results in improved magnetic stability of the GMR sensor. As shown in FIG. 9, back gap closer  165  extends beyond second top pole  134 , and is therefore visible in the top view. Like top magnetic layer  128  shown in FIG. 6, top magnetic layer  166  shown in FIG. 9 has a variable height along the ABS. 
     FIG.  10  and FIG. 11 show a third preferred embodiment of a read/write head according to the present invention. FIG. 10 shows a cross-sectional view of read/write head  170 . FIG. 11 shows an ABS view of read/write head  170 . The reader portion of read/write head  170  is the same as reader  121  of read/write head  120 , and is not shown in FIGS. 10 and 11. Read/write head  170  is substantially the same as read/write heads  120  and  163  shown in FIGS. 5-9, but includes a different write gap structure. In read/write head  170 , notch  174  of shared pole  175 , write gap  172  and first top pole  122  are made through the same photomask by electroplating. Notch  174  is preferably made of magnetic material with a high saturation induction, such as Ni 45 Fe 55 , and has a thickness of 0.2-0.4 micrometers. Write gap  172  is preferably 0.1-0.3 micrometers thick and is made of a non-magnetic conductive material such as NiP, NiPd, or a similar material. The process for forming layers  122 ,  172 , and  174  is based on photo technology only, and does not require the ion mill for notch definition. As shown in FIG. 10, write gap  172  ends at insulating layer  142 , rather than extending under insulating layer  142  as in the embodiments shown in FIGS. 5-9. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.