Perpendicular magnetic recording (PMR) write head with patterned high moment trailing shield

A perpendicular magnetic recording writer is disclosed wherein a first trailing shield (HMTS) layer has a down-track (DT) thickness d in portions thereof proximate to a center plane that bisects the main pole tip trailing side to enable enhanced trailing shield return field at track center thereby improving bits per inch (BPI) capability. Meanwhile, at off track center positions, that in some embodiments are from 25 nm to 500 nm from the center plane, the HMTS layer has a DT thickness d1, where d1>d, and a smaller dielectric gap between the HMTS layer and the main pole thereby protecting side shield return field and adjacent track interference (ATI) performance. A method of forming the HMTS layer on a write gap is provided and includes patterning the HMTS layer in a back portion to form openings that are filled with the smaller dielectric gap and HTMS layer thickness d1.

RELATED PATENT APPLICATION

This application is related to the following: U.S. Patent application 2017/0133044; assigned to a common assignee and herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a high moment trailing shield (HMTS) formed on a write gap wherein a back portion thereof that is recessed from the ABS has a smaller down-track (DT) thickness and greater dielectric gap to the main pole in regions proximate to a center plane formed at the center track position, and a greater DT thickness and smaller dielectric gap at certain off track center regions to enable better overwrite (OW) performance and improved bits per inch (BPI) capability while maintaining, and in some cases, enhancing tracks per inch (TPI) capability and adjacent track interference (ATI) for both conventional and shingle magnetic recording applications.

BACKGROUND

Perpendicular magnetic recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head (writer) typically has a main pole layer with a small surface area at an air bearing surface (ABS), and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through a main pole tip and enters a magnetic medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole through two pathways including a trailing loop and a leading loop where both involve a shield structure. The trailing loop comprises a trailing shield structure at the ABS with a HMTS having a magnetization saturation value from 16 kiloGauss (kG) to 24 (kG), and a second trailing shield formed on a top surface and sides of the HMTS. The leading loop includes a leading shield with a front side at the ABS and that is connected to a return path proximate to the ABS. The return path extends to the back gap connection and enables magnetic flux in the leading loop pathway to return from the leading shield through the back gap connection to the main pole layer.

For both conventional (CMR) and shingle (SMR) magnetic recording, continuous improvement in storage area density is required for a PMR writer. A write head that can deliver or pack higher bits per inch (BPI) and higher tracks per inch (TPI) is essential to the area density improvement. An all wrapped around (AWA) shield design for a PMR write head is desired where the trailing shield is responsible for improving down track field gradient and BPI while side shields and a leading shield enhance the cross track field gradient and TPI as well as improve adjacent track erasure (ATE) also known as ATI.

In today's PMR writer designs, the HMTS formed on the write gap plays a key role in improving BPI. In particular, the HMTS attracts more main pole (MP) field to return from the soft underlayer (SUL) and thus enhance the field gradient in the down-track direction. The spacing (gap) between the HMTS and MP also controls the flux shunting of MP field and helps protect TPI and ATI. In the prior art, the HMTS is patterned only in a perpendicular direction that is orthogonal to the ABS so that there is no variation in down-track (DT) thickness as a function of cross-track position. Accordingly, further improvement in PMR writer performance is limited in terms of the tradeoff between enhancing TS return field, and improving side shield (SS) return field and ATI. Therefore, a new trailing shield design is needed to optimize the tradeoff between DT performance and cross-track (CT) performance for a PMR writer in hard disk drive (HDD).

SUMMARY

One objective of the present disclosure is to provide a HMTS layer for a PMR writer that enables an improvement in BPI and OW without compromising TPI and ATI.

Another objective of the present disclosure is to provide a method of forming the improved HMTS layer of the first objective that is readily implemented in a manufacturing environment.

According to a first embodiment, these objectives are achieved with a PMR writer that has an all wrap around (AWA) shield structure wherein a leading shield, side shields, and trailing shield structure surround a main pole (MP) at the ABS, and adjoin a lead gap, side gap, and write gap, respectively. The trailing shield structure comprises a HMTS layer having a front portion formed on the write gap at the ABS, and a second trailing shield (TS) formed on a top surface and sides of the HMTS layer and write gap. The HMTS layer also has a middle portion behind a front side of the second TS that extends from a backside of the HMTS front portion at a first height (h1) to a front side of a HMTS back portion that is a second height (h2) from the ABS where h2>h1. The HMTS back portion and second TS both have a backend at a third height (h3) where h3>h2. The top surface of the HMTS back portion is aligned orthogonal to the ABS between h2and h3.

The HMTS back portion has a first down-track (DT) thickness d in unpatterned regions having a first bottom surface that is a first gap distance (g) from the MP top surface. The HMTS back portion also has patterned regions with a DT thickness d1, where d1>d, and a second bottom surface that is a second gap distance (g1) from the MP top surface where g>g1. Both of the first and second bottom surfaces are aligned parallel to the MP top surface, and are orthogonal to the ABS. Furthermore, first and second gaps between the HMTS back portion and MP top surface are filled with a dielectric layer.

From a top-down view along a second plane that comprises the second bottom surface of the HMTS back portion and is orthogonal to the ABS, a key feature according to a first embodiment is that the HMTS back portion has variable DT thickness as a function of cross-track position. At a center plane that is orthogonal to the ABS at the center track position, and between third and fourth planes that are equidistant from the center plane and separated by cross-track width w, DT thickness d and gap g are maintained throughout the entire HMTS back portion behind a first plane at pattern height h. Thus, there is a first inner HMTS side formed at each of the third and fourth planes between the first plane and HMTS backend. At cross-track positions behind the first plane and at a width>w/2 from the center plane where w is from 120 nm to 300 nm, the HMTS back portion has a DT thickness d1in patterned regions as explained later.

In front of the first plane and behind a backside of the HMTS front or middle portion, there are two second inner HMTS sides that have greater cross-track separation as distance decreases from the ABS. Within a trapezoidal shape formed by a first side of width w at the first plane, the backside of the HMTS front or middle portion of width m, where m>w, and the second inner HMTS sides, the HMTS back portion has DT thickness d. The HMTS back portion has DT thickness d1at other (patterned) regions in front of the first plane. Each second inner HMTS side intersects the first plane and forms an angle θ with respect to the third plane or fourth plane.

According to a second embodiment that is a modification of the first embodiment, the trapezoid shape in front of the first plane having a HMTS DT thickness d, and patterned regions outside the trapezoid are retained, but the patterned region behind the first plane is expanded such that all of the HMTS back portion between the first plane and backend has DT thickness d1. In the first and second embodiments, θ varies from +10 degrees to +90 degrees.

In a third embodiment that represents a modification of the second embodiment, the size of the patterned region in front of the first plane is expanded meaning that the trapezoid area is reduced. The second inner HMTS sides now have smaller separation with decreasing distance from the ABS such that the width v of a second side of the trapezoid at a backside of the HMTS front or middle portion is less than w of the first side at the first plane. Each second inner HMTS side forms an angle β from 0 to −90 degrees with respect to the third or fourth plane. Again, the HMTS back portion has a constant DT thickness d1behind the first plane, and in regions in front of the first plane that are outside the trapezoid shape.

In all embodiments, the HMTS back portion is patterned such that DT thickness varies from d to d1as a function of cross-track width, at least in front of the first plane. Accordingly, the larger gap g in the HMTS back portion proximate to the center track position (where HMTS DT thickness is d) guarantees a substantial TS return field at track center where transition sharpness is most influential in enhancing writing quality. Meanwhile, at certain off track center regions, excessive MP field will be shunted immediately by the greater DT thickness d1in the HMTS back portion thereby protecting the side shield (SS) return field and ATI.

A fabrication method to form a patterned HMTS layer according to an embodiment of the present disclosure is also provided. A conformal thickness thickness d is formed in HMTS front and middle portions, and in unpatterned HTMS back regions. Subsequently, the HMTS back portion is patterned, and openings are filled with dielectric gap g1and overlying HMTS thickness d1.

DETAILED DESCRIPTION

The present disclosure relates to a trailing shield design in a PMR writer wherein a HMTS layer formed on a write gap is patterned in a back portion thereof so that a HMTS down-track (DT) thickness is either a first thickness d or a second thickness d1(d1>d) depending on the cross-track position from a center plane. The exemplary embodiment depicts a PMR writer having a so-called rDWS BGC base writer structure and an AWA shield design. However, the present disclosure also anticipates that other base writer schemes as well as different shield designs including but not limited to a partial side shield may be used while still providing the advantages of the patterned HMTS designs disclosed herein. In the drawings, the y-axis is a cross-track direction, the z-axis is a down-track direction, and the x-axis is in a direction orthogonal to the ABS and towards a back end of the PMR writer. Thickness refers to a down-track distance, width is a cross-track distance, and height is a distance from the ABS in the x-axis direction.

The term “behind” refers to an x-axis position of one structural feature with respect to another. For example, component B formed behind component or plane A means that B is a greater height from the ABS than A. A “front side” of a layer is a side facing the ABS, and a backside or backend faces away from the ABS. The terms “above” and “below” when referring to a down-track position of a layer with respect to a plane means that a layer above the plane is a greater DT distance from the MP top surface than a layer below the plane.

Referring toFIG. 1, a HGA100includes a magnetic recording head1comprised of a slider and a PMR writer structure formed thereon, and a suspension103that elastically supports the magnetic recording head. The suspension has a plate spring-like load beam222formed with stainless steel, a flexure104provided at one end portion of the load beam, and a base plate224provided at the other end portion of the load beam. The slider portion of the magnetic recording head is joined to the flexure, which gives an appropriate degree of freedom to the magnetic recording head. A gimbal part (not shown) for maintaining a posture of the magnetic recording head at a steady level is provided in a portion of the flexure to which the slider is mounted.

HGA100is mounted on an arm230formed in the head arm assembly103. The arm moves the magnetic recording head1in the cross-track direction y of the magnetic recording medium140. One end of the arm is mounted on base plate224. A coil231that is a portion of a voice coil motor is mounted on the other end of the arm. A bearing part233is provided in the intermediate portion of arm230. The arm is rotatably supported using a shaft234mounted to the bearing part233. The arm230and the voice coil motor that drives the arm configure an actuator.

Next, a side view of a head stack assembly (FIG. 2) and a plan view of a magnetic recording apparatus (FIG. 3) wherein the magnetic recording head1is incorporated are depicted. The head stack assembly250is a member to which a first HGA100-1and second HGA100-2are mounted to arms230-1,230-2, respectively, on carriage251. A HGA is mounted on each arm at intervals so as to be aligned in the perpendicular direction (orthogonal to magnetic medium140). The coil portion (231inFIG. 1) of the voice coil motor is mounted at the opposite side of each arm in carriage251. The voice coil motor has a permanent magnet263arranged at an opposite position across the coil231.

With reference toFIG. 3, the head stack assembly250is incorporated in a magnetic recording apparatus260. The magnetic recording apparatus has a plurality of magnetic media140mounted to spindle motor261. For every magnetic recording medium, there are two magnetic recording heads arranged opposite one another across the magnetic recording medium. The head stack assembly and actuator except for the magnetic recording heads1correspond to a positioning device, and support the magnetic recording heads, and position the magnetic recording heads relative to the magnetic recording medium. The magnetic recording heads are moved in a cross-track of the magnetic recording medium by the actuator. The magnetic recording head records information into the magnetic recording media with a PMR writer element (not shown) and reproduces the information recorded in the magnetic recording media by a magnetoresistive (MR) sensor element (not shown).

Referring toFIG. 4, a PMR writer according to one embodiment of the present disclosure depicted in a down-track cross-sectional view from a plane50-50(FIG. 5) that is orthogonal to ABS30-30and bisects the main pole tip14p. The combined read/write head is formed on a substrate80that may be comprised of AlTiC (alumina+TiC). Those skilled in the art will recognize that layers2-8represent the read head portion of the recording device while overlying layers represent the write head portion. The substrate is typically part of a slider (not shown) formed in an array of sliders on a wafer. After the combined read/write head is completed, the wafer is sliced to form rows of sliders. Each row is typically lapped to afford an ABS before dicing to fabricate individual sliders for a HDD.

The present disclosure anticipates that one or more dynamic fly height (DFH) heater elements (not shown) may be formed in one or more insulation layers in the PMR writer structure to control the extent of thermal expansion (protrusion) along the ABS30-30and toward a magnetic medium140during a read or write process. Read gap (RG) and write gap (WG) protrusion may be tuned by the placement of the one or more DFH heater elements, and by the choice of metal or alloy selected for the DFH heater elements since each DFH heater resistor material has a particular thermal and mechanical response to a given electrical input. The DFH heater in the writer is often positioned in one or more of the dielectric layers38,39, and44behind interconnect61, and between bucking coil60band driving coil60dto yield the desired gamma ratio.

A first insulation layer2that may be comprised of alumina or another dielectric material is disposed on substrate80. There is a second insulation layer3formed on the first insulation layer and behind the read head layers4-8. Above layer2is the S1 shield4that is comprised of NiFe or CoFeNi or the like, and extends from the ABS toward a back end of the read head. A magnetoresistive element (sensor)6is formed between the S1 shield4and S2A shield7at the ABS30-30and typically includes a plurality of layers (not shown) in which two ferromagnetic layers are separated by a non-magnetic layer. The magnetic moment direction in one of the ferromagnetic layers is fixed and provides a reference direction, and the moment direction in the other ferromagnetic layer may be rotated by the magnetic field from the media. Resistance across gap layer5changes as the moment in the second ferromagnetic layer rotates. A “0” or “1” magnetic state can be defined depending on whether the two ferromagnetic layers are magnetically aligned in the same direction or in an antiparallel fashion. The non-magnetic layer in the sensor6may be an insulator such as MgO in a tunneling magnetoresistive (TMR) sensor. Insulation layer8is the uppermost layer in the read head although in some embodiments, the return path (RTP)9also serves as the S2B shield in the read head while magnetic layer7is the S2A shield.

The present disclosure anticipates that various configurations of a write head (PMR writer) may be employed with the read head portion. In the exemplary embodiment, the base writer structure has a so-called rDWS BGC design where DWS refers to a double write shield wherein a trailing loop comprised of a trailing shield structure, and a leading loop comprised of a leading shield allow magnetic flux70band70a, respectively, to return to the main pole layer14. BGC indicates a back gap connection62in the leading loop comprised of the leading shield11, leading shield connector (LSC)33, S2C connector32, RTP9, and the BGC. Magnetic flux70in main pole layer14is generated by flowing a current through bucking coil60band driving coil60dthat are below and above the main pole layer, respectively, and are connected by interconnect61. Magnetic flux70exits the main pole layer at pole tip14pat the ABS30-30and is used to write a plurality of bits on magnetic media140. Magnetic flux70breturns to the main pole through a trailing loop comprised of first trailing shield17also known as the HMTS layer, second trailing shield (TS)18, PP3 shield26, and top yoke18x. The magnetic core may also comprise a bottom yoke35below the main pole layer. Dielectric layers10,11,13,19,22,37-39,44, and45are employed as insulation layers around magnetic and electrical components. A protection layer27covers the PP3 trailing shield and is made of an insulating material such as alumina. Above the protection layer and recessed a certain distance u from the ABS30-30is an optional cover layer29that is preferably comprised of a low coefficient of thermal expansion (CTE) material such as SiC. Overcoat layer28is formed as the uppermost layer in the write head.

HMTS layer17has a bottom surface formed on a write gap (not shown) at the ABS and adjoins a non-magnetic (dielectric) layer41. The second TS layer18also extends from the ABS to dielectric layer41, and like the HMTS layer, may be made of CoFeN, CoFeNi, NiFe, or CoFe. The HMTS layer has a magnetization saturation (Ms) value from 16 kG to 24 kG. Second TS layer18, top yoke18xand the PP3 trailing shield26are typically made of 16 kG to 19 kG materials. Top yoke18xhas a backside at point A that touches the inner corner of the PP3 trailing shield.

Referring toFIG. 5, an ABS view is depicted of a portion of the write head including main pole layer14with main pole tip14pthat has track width TW, a trailing side14t1bisected by center plane50-50, and is surrounded by an AWA shield structure. The HMTS layer has a HMTS front portion17aformed on write gap16. Preferably, each side17sof the HMTS front portion is coplanar with a side16sof the write gap. Second TS layer18is formed on the HMTS layer and adjoins sides16s,17s, and has a bottom surface18bthat adjoins side shields12at plane46-46. Top (trailing) side14t1also intersects the ABS at plane46-46. Leading shield11has a top surface11tthat contacts the side shields and lead gap13. Side gaps15separate sides14sof the main pole tip from the side shields. Plane51-51is a plane that is off track center, and is parallel to plane50-50. Plane40-40is orthogonal to the ABS, intersects a HMTS middle portion (not shown) and comprises a bottom surface of a HMTS back portion as explained later with regard to embodiments of the present disclosure. In other embodiments, the bottom surface of the HMTS back portion may be at plane48-48that intersects the HMTS front portion.

In related application 2017/0133044, we disclosed a conformal HMTS design that has a down-track cross-sectional view with an essentially constant DT thickness as a function of cross-track position. In other words, HMTS front portion17ainFIG. 5, middle portion17b, and back portion17care shown with the down-track cross-sectional view inFIG. 6that features DT thickness d throughout the HMTS front portion, middle portion, and back portion. Moreover, the view inFIG. 6applies to the center track position (plane50-50inFIG. 5), and to all off track center positions that intersect the HMTS layer including plane51-51inFIG. 5. The front portion extends from the ABS30-30to height h1, the middle portion extends from a backside of the front portion to height h2, and the back portion has top surface17tand extends from a backside of the middle portion to height h3at backend17e. Main pole14is shown with a tapered leading side14b1that connects with MP bottom surface14b2, and also has a tapered trailing side14t1that connects with MP top surface14t2, which is orthogonal to the ABS and parallel to bottom surface17dof the HMTS back portion. Dielectric layer41has a DT thickness g between the HMTS back portion and MP top surface at all cross-track locations that are between sides17sof the HMTS front portion inFIG. 5.

In related application 2017/0133044, we also disclosed a patterned HMTS design as depicted inFIG. 7where the conformal HMTS design is modified to have a second DT thickness d1(d1>d) in the HMTS back portion17cat a height greater than pattern height h, and while maintaining DT thickness d in the HTMS layer up to height h. The second DT thickness is achieved by forming a pattern comprised of an opening in the HMTS back portion between an ABS facing side17fat plane43-43and the HMTS backend17e, and that extends to the MP top surface14t2, and then filling the opening by depositing dielectric material to thickness g1, followed by depositing HMTS back portion17cwith thickness d1up to top surface17t. As a result, there is a first gap of DT thickness g in the dielectric layer between the HMTS back portion and main pole top surface14t1up to height h at plane43-43, and a second gap of DT thickness g1(g1<g) between height h and the HMTS backend17eat height h3. In this HMTS design hereinafter referred to as the process of record (POR) design, a key feature is a constant DT thickness (d or d1) as a function of cross-track position along plane43-43or at any plane parallel thereto that intersects the HMTS back portion. Thus, the down-track cross-sectional view illustrated inFIG. 7is found at center plane50-50and at all off track center planes that intersect the HMTS such as plane51-51inFIG. 5.

A top-down view from plane40-40inFIG. 5of the process of record (POR) design for a patterned HMTS layer is provided inFIG. 8. Note that the pattern height between the ABS30-30and plane43-43is a constant h as a function of cross-track position along the y-axis direction, which means the HMTS back portion17chas constant thickness d1behind pattern height h, and constant thickness d in front of plane43-43. HMTS front portion17ais not visible below second TS layer18from this viewpoint, and HMTS middle portion17bhas a backside17r. Dielectric layer41fills the gap between backside17rand a front side17fof HMTS back portion at plane43-43. A side41sof the dielectric layer is coplanar with side17sof the HMTS back portion. Although this design improves the TS return field (BPI), there is a tradeoff with less desirable SS return field (TPI) and ATI. Therefore, we were motivated to modify the HMTS POR design to allow variable DT thickness with cross-track position so that BPI may be enhanced without a loss in TPI and ATI for an overall improvement in ADC according to various embodiments of the present disclosure.

To realize a gain in BPI without compromising TPI and ATI, all embodiments disclosed herein feature a patterned HMTS layer wherein a down-track cross-sectional view at center plane50-50is different from that at plane51-51(FIGS. 9, 11-12), or at plane53-53(FIG. 15) that are off track center. In a first embodiment, the down-track cross-sectional view at center plane50-50is represented byFIG. 6, which is different from the down-track cross-sectional view at plane51-51inFIG. 13. In second and third embodiments, the down-track cross-sectional view at center plane50-50is represented byFIG. 7. In all embodiments, HMTS DT thickness is either d or d1as a function of cross-track position. Moreover, dielectric layer41has DT thickness g from 50 nm to 300 nm below HTMS back portions with thickness d, and a smaller DT thickness g1from 10 nm to 200 nm below patterned HMTS back portions with thickness d1.

Referring toFIG. 9, a first embodiment of a patterned HMTS layer in a PMR writer according to the present disclosure is depicted in a top-down view at plane40-40inFIG. 5. In particular, the POR design inFIG. 8is modified to include a patterned region in the previously described unpatterned HMTS back portion in front of plane43-43. Secondly, the HMTS back portion behind plane43-43now has an unpatterned region of width w and DT thickness d between plane52-52and plane54-54that are equidistant from center plane50-50. Thus, the patterned region of HMTS back portion17cbehind plane43-43has inner sides17i1formed on plane52-52and plane54-54. The HMTS back portion has a DT thickness d1between an inner side17i1and outer side17s. The pattern height h is from 100 nm to 500 nm, and width w is from 50 nm to 1 micron.

In front of plane43-43, the HMTS back portion has DT thickness d1in regions between inner side17i2and outer side17son each side of the center plane50-50. Each inner side1712has a first end at plane43-43and a second (front) end at a backside17rof the HMTS middle portion, and forms an angle θ with plane52-52or plane54-54where θ is from 10 degrees to 90 degrees. The HMTS back portion has DT thickness d within the trapezoid shape formed by plane43-43, inner sides17i2, and backside17rthat has a width m>w. Accordingly, as height within the trapezoid shape decreases from h to h2proximate to the intersection of plane51-51and side17i2, and eventually decreases to less than h2at middle portion backside17r, the cross-track width where the HMTS back portion has DT thickness d increases to a maximum value m between points17vwhere backside17rintersects outer sides17sof the HMTS layer. Second TS layer18adjoins outer sides17s.

At the center plane50-50, and at cross-track positions between plane52-52and plane54-54, the down-track cross-sectional view is found inFIG. 6where the HMTS layers17a-17chave a conformal DT thickness d. However, at plane51-51that intersects side17i2proximate to a midpoint thereof, the down-track cross-sectional view is shown inFIG. 13where an ABS facing side17fof the HMTS back portion17cis at height h2and thereby leaves only a small gap filled with dielectric layer41between plane40-40and HMTS middle portion17b. DT thickness is d1between front side17fand backend17e. At plane55-55that includes point17vwhere HMTS inner side17i2intersects an outer HMTS side17son each side of the center plane, the down-track cross-sectional view is represented inFIG. 14where the entire height between HMTS middle portion17band backend17eis comprised of HMTS material with thickness d1. Accordingly, DT thickness is d1within the patterned regions of HMTS back portion17cinFIG. 9, and is d in unpatterned regions of the HMTS back portion described above. From this view, dielectric layer41fills gaps above plane40-40and below the HMTS back portion having thickness d.

Referring toFIG. 10, the present disclosure also encompasses an embodiment where the bottom surface17nof the patterned HMTS back portion is a minimum gap distance g1from MP top surface14t2. As a result, the bottom surface is formed on plane48-48that intersects the HMTS front portion at the ABS30-30, rather than on plane40-40which intersects the HMTS middle portion at the ABS in the previous embodiment. Furthermore, there is a plurality of other embodiments (not shown) where the bottom surface17nof the HMTS back portion may be formed at a plane between plane40-40and plane48-48inFIG. 5.

InFIG. 11, a top-down view of the alternative embodiment inFIG. 10is illustrated. Note that there is no longer a second TS shield layer18between the ABS30-30and the trapezoid shape comprising backside17r. Instead, HMTS front portion17a(at plane48-48) fills the area between HMTS sides17s, backside17r, and the ABS. It should be understood that in the second and third embodiments shown inFIG. 12andFIG. 15, respectively, an alternative embodiment may be employed where the HMTS bottom surface17nis “lowered” from plane40-40to plane48-48to increase d1and reduce g1to a value proximate to 10 nm.

Referring toFIG. 12, a second embodiment of a patterned HMTS layer according to the present disclosure is shown from a top-down view at plane40-40inFIG. 5. The HMTS pattern inFIG. 9is modified with the removal of the unpatterned region behind plane43-43so that the entire HMTS back portion17cat a height>h has only the DT thickness d1. In front of plane43-43, the HMTS back portion retains the trapezoidal shape with a DT thickness d. Moreover, the patterned regions of HMTS back portion outside of the trapezoid shaped pattern have DT thickness d1. In both of the first and second embodiments, the benefit of forming a HMTS DT thickness d and gap g between the HMTS back portion and MP top surface proximate to the center plane is that BPI is enhanced without compromising TPI and ATI. Because of thinner DT thickness d, a larger TS return field is guaranteed proximate to the center plane at track center where transition sharpness matters most for writing quality. Meanwhile, greater DT thickness d1is maintained in regions of the HMTS back portion outside the thinner DT regions to effectively shunt excessive MP fields and thereby protect SS return field (TPI) and ATI.

In the second embodiment, the down-track cross-sectional view at center plane50-50is illustrated inFIG. 7. The down-track cross-sectional view at plane51-51is provided byFIG. 13, and plane40-40intersects middle portion17bbetween height h1and height h2. However, as indicated earlier, the bottom surface17nin patterned regions of the HMTS back portion may be lowered to plane48-48in some embodiments.

Referring toFIG. 15, a third embodiment of a patterned HMTS layer is depicted in a top-down view at plane40-40inFIG. 5. Note that the trapezoid shape with DT thickness d in the HMTS back portion17cin front of plane43-43in the second embodiment is further reduced in area. In particular, the trapezoid shape is inverted so that the first side17fat plane43-43has a width w greater than a width v at the second side (backside17r). Inner sides17i3that connect the first and second sides in the trapezoid are formed at angle β with respect to plane52-52or plane54-54(not shown), and are a cross-track width<w/2 from center plane50-50. Here, angle β has a minimum value of 0 degrees where side17i3overlays (not shown) on plane52-52, but is less than −90 degrees because at −90 degrees, sides17i3will overlay on front side17fand the trapezoid shape will no longer exist. Since the size of the unpatterned area proximate to the center plane is directly related to the BPI improvement, we believe the first embodiment offers the highest performance advantage (largest unpatterned area with DT thickness d) while the third embodiment provides the least advantage in view of the smallest unpatterned area. The down-track cross-sectional view at center plane50-50is shown inFIG. 7. The down-track cross-sectional view at plane53-53that intersects side17i3proximate to a midpoint thereof at height h2is depicted inFIG. 13. The HMTS back portion has DT thickness d1outside the trapezoid shape.

Referring toFIGS. 16-18, we have demonstrated the advantages of the patterned HMTS layer according to the first embodiment in an experiment using a finite element method (FEM) simulation to compare magnetic performance with that of the POR scheme described previously where DT thickness is uniform as a function of cross-track position. In this simulation, pattern height h is 200 nm, g1is 200 nm, and g is 80 nm in the down-track cross-sectional view according toFIG. 7. Furthermore, the simulation relates to the top-down view of the first embodiment inFIG. 9where the unpatterned region behind plane43-43at height h has cross-track width w, and the unpatterned region in front of the pattern height has a trapezoid shape formed by angle θ at an intersection of an inner side17i2with plane52-52or plane54-54. For this experiment, angle θ is assigned a value of 30 degrees in one example, and 45 degrees in a second example. In both examples, the pattern width w was varied from 120 nm to 300 nm. The POR example is represented by the top-down view inFIG. 8, and with the down-track cross-sectional view inFIG. 7at center track and at all off center track positions.

The plot of Hy field vs. EWAC inFIG. 16indicates the first embodiment at both θ angles provides higher Hy at the same EWAC condition compared with the POR design. Also, at the same Hy field, the patterned HMTS layer of the first embodiment enables the PMR writer to have a more negative TS return field (FIG. 17) and a more negative SS return field (FIG. 18) than the POR scheme. Accordingly, BPI is enhanced and TPI and ATI are maintained, and in some cases improved, compared with the POR scheme. With further tuning and optimization, a net gain in overall ADC is expected from the patterned HMTS layer disclosed herein.

The present disclosure also encompasses a method of fabricating the patterned HMTS layer disclosed herein. The fabrication sequence begins withFIG. 19where a PMR writer that is partially formed with a conventional series of steps is depicted from an ABS view. At this point, the main pole with MP pole tip14pand trailing side14t1is formed, and the main pole is surrounded on the sides by side gaps15that adjoin inner sides12sof the side shield12, and on the leading side with lead gap13that contacts a top surface11tof leading shield11. There is a top surface of each side shield at plane46-46.

In the exemplary embodiment shown inFIG. 20, trailing side14t1is tapered so that the main pole14has increasing DT thickness with increasing height from plane30-30that will become the eventual ABS after a backend lapping process. The tapered trailing side connects with MP top surface14t2at corner14nat height a. Dielectric layer41is deposited on the main pole layer with a chemical vapor deposition (CVD) or plasma enhanced CVD method, for example. A first photoresist layer90is coated on the dielectric layer and patterned with a photolithography process to yield opening81and a front side90son the photoresist layer proximate to height a. Thereafter, an angled ion beam etch (IBE) may be employed to removed unprotected portions of the dielectric layer and form sloped side41fthat faces the ABS, and thereby expose a portion of trailing side14t1proximate to the ABS.

Referring toFIG. 21, the write gap16is deposited on the exposed portion of main pole trailing side14t1, and photoresist layer90is removed by a conventional method. Typically, write gap material is also deposited on sloped side41f. However, to simplify the drawing, the resulting dielectric layer below plane49-49, and from the back side of write gap16at h1up to height a is shown as dielectric layer41. Thereafter, a second photoresist layer91is coated on the write gap and dielectric layer41, and is patterned with a conventional method to yield opening82, and a front side91fon the photoresist layer at height h3.

InFIG. 22, the HMTS layer comprised of front portion17a, middle portion17b, and back portion17cis conformally deposited in opening82with a physical vapor deposition (PVD) process, for example, to give a HMTS thickness d from plane30-30to front side91f. Dielectric layer41has a DT thickness g on MP top surface14t2. The second photoresist layer is removed. Next, a third photoresist layer92is coated on HMTS layer, and is then patterned with a photolithography method to form sides92sas depicted in a view from plane30-30inFIG. 23.

As shown inFIG. 23, photoresist layer92has sides92sthat are separated by a cross-track width b after the patterning step. Uncovered portions of the HMTS layer including front portion17aare removed with an etch process that may involve IBE or reactive ion etch (RIE) conditions. The etch continues through the write gap16and stops on side shields12to provide an outer HMTS side17sand write gap side16sthat are coplanar with a photoresist layer side92son each side of center plane50-50.

InFIG. 24, the third photoresist layer is removed and a fourth photoresist layer93is coated on the HMTS layer17a-17c, and is patterned to give an opening83between plane43-43and a front side93fat height h3. Opening83is designed to uncover regions of the HMTS back portion17cthat will have a greater DT thickness d1after additional process steps are completed. The front part93pof the photoresist pattern covers regions of the HMTS back portion that will have the lesser DT thickness d in the final device, and covers the HMTS front and middle portions. Subsequently, an etch process is employed to expand the opening83downward through exposed regions of the back portion17cand underlying dielectric layer41and stops on the MP top surface14t2.

Referring toFIG. 25, a top-down view of the intermediate structure inFIG. 24is shown after dielectric layer41with thickness g1, and HMTS layer17cwith thickness d1(FIG. 26) are sequentially deposited in opening83where a back portion of the opening is behind plane43-43, and front portions of the opening are between inner side17i2and outer side17son either side of the trapezoidal shape, according to the second embodiment described previously. Accordingly, the HMTS back portion17cthat was deposited in opening83has a front side17fbetween plane52-52and plane54-54, and is formed between plane43-43at height h and backend17eat height h3. Furthermore, the HMTS deposition fills the region between inner side17i2and side17son each side of center plane50-50.

Referring toFIG. 26, photoresist layer93is removed to provide the intermediate PMR writer structure wherein the HMTS back portion17chas top surface17t, DT thickness d1between bottom surface17nand top surface17c, and a backend17e. In summary, the thinner HMTS back portion with DT thickness d in front of plane43-43is formed with a difference series of process steps than the thicker HMTS back portion behind plane43-43, and in the regions between an inner side17i2and outer side17sshown inFIG. 25. According to one embodiment, the dielectric material filling gap g1is made of the same material as in dielectric layer41.

Thereafter, the remaining layers in the write head including the second TS layer18, top yoke18x, PP3 trailing shield26, and driving coils60dare fabricated by methods well known to those skilled in the art and are not shown herein. Finally, a lapping process is performed to form an ABS at plane30-30.