Perpendicular magnetic recording (PMR) writer with tunable pole protrusion (TPP) designs for 2 terabytes/platter (TB/P) and beyond

A perpendicular magnetic recording (PMR) writer is disclosed wherein an insulation layer is formed between a top yoke (TY) and an uppermost (PP3) trailing shield to electrically isolate the main pole (MP) from a trailing loop for magnetic flux return. One or both of a first non-magnetic (NM) metal layer and a second NM metal layer are formed between the MP tip and a hot seed layer and side shields, respectively, to form an electrical path that is in parallel to that of a dynamic fly height (DFH) heater circuit. MP tip protrusion is enhanced and writability is improved especially for track widths <40 nm, and is tunable by the volume of the first and second NM layer, and the composition of the NM metals. Existing writer pad layouts may be employed and there is no additional cost to PMR backend processes.

RELATED PATENT APPLICATION

This application is related to U.S. Pat. No. 10,643,640; which is assigned to a common assignee and herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a PMR write head configured to have a one turn coil (1+1T) design with tunable pole protrusion wherein the MP tip is electrically connected to one or both of the trailing shield hot seed (HS) layer and side shields (SS) in a path parallel to the dynamic fly height (DFH) writer heater while a MP back portion is electrically isolated from the trailing and leading flux return loops so that MP protrusion can achieve a range of 0.5-0.8 micron even for a MP track width (PWA) of less than 40 nm, and provide better writability.

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 typically has a main pole layer with a small surface area (pole tip) at an ABS, and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through the 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 (MP) through two pathways including a trailing (top) loop and a leading (bottom) loop. The trailing loop is comprised a trailing shield structure with a front side at the ABS, an uppermost trailing (PP3) shield that arches over the driving coil and connects with a top yoke (TY). The TY adjoins a top surface of the MP above a back gap connection (BGC). The trailing loop is also known as the top driving loop and delivers magnetic flux to the MP tip to write positive and negative field into magnetic media. The leading loop has a leading shield with a side at the ABS and in some schemes is connected to a return path (RTP) having a front side recessed from the ABS. The RTP extends back to the BGC and enables magnetic flux in the leading loop pathway to return from the leading shield at the ABS and through the BGC to the MP for faster saturation speed, better adjacent track interference (ATI) and enhanced wide area track erasure (WATE) potential.

Dual write shield (DWS) designs that feature complete leading and trailing loops were invented for adjacent track erasure (ATE) improvement by reducing stray field in side shields and in the leading shield and trailing shields. Accordingly, a PMR head has a great advantage over LMR in providing higher write field, better read back signal, and potentially much higher areal density. With the growing demand for cloud storage and cloud-based network computing, high and ultra high data rate recording becomes important for high-end disk drive applications.

To achieve areal density in a HDD beyond 2 TB/P for conventional PMR in near line applications, OD high data rate (HDR) performance up to 3.4 gigabytes per second (Gbps) or 1.7 gigahertz (GHz) is essential and critical. A one turn coil design (1+1T) has demonstrated better HDR performance than a two turn coil design (1+1+2T or 2+2T) because of less electrical inductance and more compact magnetic loop with shorter yoke length (YL). Magneto-motive force (MMF) of a one turn coil design is half that of a 2+2T design. Under direct current (DC) or low frequency alternating current (AC) applications, a one turn coil writer requires two times the current of a two turn coil writer to drive a head to the same magnetic field level. However, under high frequency for HDR applications, the 1+1T design has demonstrated an advantage in reaching the same magnetic field level with 1.2-1.5 times the current of a two turn coil design for 1.75 TBPP application with a data rate up to 3.1 Gbps (1.55 GHz). Thus, the 1+1T design, which can operate at less than 1.5× the Iw(0-peak) current of 1+1+2T or 2+2T designs offers less driving to the write shield and better WATE capability that is critical for near line applications.

For 2 terabytes/platter (TB/P) and beyond, write erase width (EW) needs to be <50 nm to achieve 480-500 k tracks per inch (TPI) capability. At such narrow EW, MP tip width (PWA) is likely <40 nm considering a magnetic write bubble fringing of around 10 nm or more. Thus, there is a challenge for a MP with PWA <40 nm to maintain enough writability and down-track gradient to satisfy kilo flux changes per inch (kFCI) and area density capability (ADC) requirements.FIG. 4depicts the trend in MP tip protrusion (PTR) vs. PWA. The MP PWA sweet spot is estimated to be 0.5-0.8 micron from existing products with good writing quality without MP wearing reliability issues. Accordingly, there is a need to design a write head with a PWA <40 nm that is capable of achieving a PTR in the range of 0.5-0.8 micron.

SUMMARY

One objective of the present disclosure is to provide a PMR writer with a 1+1T coil layout that is capable of achieving a MP tip protrusion in the range of 0.5-0.8 micron even for a PWA <40 nm.

Another objective of the present disclosure is to provide a PMR writer according to the first objective without changing the existing pad layout in current PMR heads, and that is transparent to existing PMR backend and HDD processes and may be implemented without modification of existing hardware and software.

A third objective of the present disclosure is to provide a method of fabricating a PMR writer that satisfies the first two objectives.

These objectives are achieved by configuring a PMR writer preferably having a 1+1T coil design wherein the trailing (top) loop for magnetic flux return to the MP has an ultimate double yoke (uDY) design or an Easy Planar (ePL) scheme. The leading (bottom) flux return loop has a so-called recessed DWS (rDWS) BGC or non-DWS (nDWS) structure.

A key feature is that an electrical path is introduced through the MP tip in a path parallel to the DFH writer heater without changing the existing writer pad layout. When the DFH writer heater is turned on, a branch of current flows through the MP tip to heat the MP tip region. As a result of local heating, MP tip protrusion is enhanced and writability is improved. Writer shields are electrically connected to the DFH ground (−) pad. The MP tip is electrically connected to one or both of the trailing shield HS layer and side shields (SS). A MP back portion is electrically connected to a built-in series resistor (Rs) that is electrically connected to the DFH (+) pad. The nominal resistance of Rs is specifically designed to satisfy both DFH heater power and MP tip protrusion requirements.

The tunable PTR aspect arises from the volume and location as well as the metal selected for the one or more non-magnetic (NM) metal layers used to make the electrical connection between the MP tip and shield structure since the aforementioned tuning parameters affect MP tip resistance (R_tip) and heating. In a first embodiment, a first NM metal layer has a width proximate to the PWA (no more than PWA+2×SG (side gap) width when the SG is not NM metal layer) and is formed between the MP trailing side and HS layer at the ABS, or alternatively is recessed behind the ABS. In another embodiment, the first embodiment is modified to also include a second NM metal layer in a side gap between each MP side and SS at the ABS. In other embodiments, the first NM metal layer has a width essentially equal to that of the HS layer and fills the entire WG, or is formed only in the side gaps. There is an additional embodiment where the first NM metal layer is formed in the entire WG at the ABS and the second NM metal layer is in the side gaps at the ABS.

The present disclosure also encompasses a method for fabricating the PMR writer according to embodiments described previously. In an example where the PMR writer has a uDY nDWS scheme, the fabrication follows the sequence described in related U.S. Pat. No. 10,643,640 except the additional steps of forming a photoresist mask over the write shield (WS) and driving coil, and then depositing an insulation layer on the top yoke are performed prior to plating the PP3 shield on the WS and above the top yoke.

DETAILED DESCRIPTION

The present disclosure relates to a PMR writer with a tunable MP tip protrusion where an electrical connection is made between the MP tip and one or both of the trailing shield HS layer and side shields, and where the writer shields are electrically connected to a DFH ground (−) pad. A MP back portion is electrically isolated from the leading and trailing loops for flux return to the MP, but is electrically connected to a built-in series resistor that is electrically connected to the DFH (+) pad. The writer scheme is especially effective in enhancing MP protrusion for a MP PWA <40 nm, and improving writability. 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 device. Dimensions of writer components are expressed as a width in the y-axis direction, height in the x-axis direction, and thickness in the z-axis direction. The term “front side” is defined as the side of a layer that faces the ABS or is at the ABS while a “backside” is a side facing away from the ABS. Although the exemplary embodiments relate to a 1+1T coil design, the MP TPP scheme disclosed herein may also be employed with other coil designs including well known 1+1+2T and 2+2T layouts.

Referring toFIG. 1, a HGA100includes a magnetic recording head101comprised 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 head101in 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 head101is incorporated are depicted. The head stack assembly250is a member to which a plurality of HGAs (HGA100-1and second HGA100-2are at outer positions while HGA100-3and HGA100-4are at inner positions) is 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 heads101correspond 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. 5, magnetic recording head101comprises a combined read-write head. The down-track cross-sectional view is taken along a center plane (44-44inFIG. 16) formed orthogonal to the ABS30-30, and that bisects MP14. The read head is formed on a substrate81that may be comprised of AITiC (alumina+TiC) with an overlying insulation layer82that is made of a dielectric material such as alumina. The substrate is typically part of a slider formed in an array of sliders on a wafer. After the combined read head/write head is fabricated, the wafer is sliced to form rows of sliders. Each row is typically lapped to afford an ABS before dicing to fabricate individual sliders that are used in a magnetic recording device. A bottom shield84is formed on insulation layer82.

A magnetoresistive (MR) element also known as MR sensor86is formed on bottom shield84at the ABS30-30and typically includes a plurality of layers (not shown) including a tunnel barrier formed between a pinned layer and a free layer where the free layer has a magnetization (not shown) that rotates in the presence of an applied magnetic field to a position that is parallel or antiparallel to the pinned layer magnetization. Insulation layer85adjoins the backside of the MR sensor, and insulation layer83contacts the backsides of the bottom shield and top shield87. The top shield is formed on the MR sensor. An insulation layer88and a second top shield (S2B) layer9are sequentially formed on the top magnetic shield. Note that the S2B layer9may serve as a flux return path (RTP) in the write head portion of the combined read/write head. Thus, the portion of the combined read/write head structure formed below layer9inFIG. 5is typically considered as the read head. In other embodiments (not shown), the read head may have a dual reader design with two MR sensors, or a multiple reader design with multiple MR sensors.

The present disclosure anticipates that various configurations of a write head may be employed with the read head portion. In the exemplary embodiment, magnetic flux70in MP14is generated with flowing a current through bucking coil60a-cand driving coil61a-cwhere front portions60aand61aare below and above the MP, respectively, center portions60cand61care connected by interconnect51, and back portions60band61bare connected to writer pads (not shown). Magnetic flux70exits the MP at pole tip14pat the ABS30-30and is used to write a plurality of bits on magnetic media140. Magnetic flux70breturns to the MP through a trailing loop comprised of a trailing shield structure including HS layer17, WS18, and uppermost trailing (PP3) shield26, and top yoke18x. There is also a leading loop with a recessed DWS (rDWS) BGC layout for magnetic flux70areturn to the MP where LSC32and RTP9are recessed from the ABS30-30. The rDWS BGC design features leading shield (LS)11, leading shield connector (LSC)33, S2 connector (S2C)32, return path (RTP)9, lower back gap (LBG)52, and back gap connection (BGC)53. In another embodiment (not shown), only the LS is retained in the leading return loop in a so-called non-dual write shield (nDWS) scheme where the LSC, S2C, RTP, LBG, and BGC are omitted to enhance magnetic flux in the trailing loop. The magnetic core may also comprise a bottom yoke35below the MP.

Dielectric layers10,13,21,37-39, and47-48are employed as insulation layers around magnetic and electrical components. A protection layer27covers the PP3 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.

Typically, a dynamic fly height (DFH) heater (not shown) is formed in one or more insulation (dielectric) layers in each of the read head and write head to control the extent of thermal expansion (protrusion) at the ABS and toward a magnetic medium during a read process and write process, respectively. Read gap (RG) and write gap (WG) protrusion may be tuned by the placement of the DFH heaters, and by the choice of metal or alloy selected for the DFH heaters since each DFH heater is comprised of a resistor material with a particular thermal and mechanical response to a given electrical input.

Referring toFIG. 6, an enlargement of a write head portion of a combined read-write head is shown according to a scheme practiced by the inventors, and is a down-track cross-sectional view taken along center plane44-44inFIG. 16, for example. A uDY rDWS BGC base writer design is shown where the trailing loop has an ultimate double yoke (uDY) scheme, and the leading loop has a rDWS BGC layout. Bucking coil front portion60ahas front side60fthat is recessed from the ABS30-30, backside60kfacing LBG52, and is formed in insulation layer37and above RTP top surface9t. RTP9is formed on bottommost insulation layer19. Leading shield (LS)11contacts a top surface of LS connector (LSC)33at the ABS. Insulation layer38adjoins a backside of the LSC and extends to a BGC front side. The leading loop for flux return70acontinues from the LS and LSC through S2C32and the RTP before passing upward through the lower back gap (LBG)52and BGC53. The BGC contacts a bottom surface of MP14behind tapered bottom yoke (tBY)35. Insulation layer39extends from the LS backside to the BGC front side, and contacts a top surface of insulation layer38. The tBY35is formed within insulation layer39, and between the LS and BGC.

The trailing loop comprises HS layer17, WS18with front side18fat the ABS30-30, PP3 TS26that has front side26fat the ABS, and TY36with top surface36tadjoining the PP3 TS behind driving coil (DC)61aso that magnetic flux70bfrom magnetic medium140is able to return to MP14. DC61ais formed above insulation layer21and is surrounded on the sides and top and bottom surfaces with insulation layer25. PP3 TS top surface26tarches (dome shape) over DC front portion61a. Protection layer27covers the PP3 TS and is made of an insulating material such as alumina. Note that the TY has a thickness t, and height d between a front side36f1and backside36ewhere the front side is directly below the inner corner90of the PP3 TS where the PP3 TS contacts plane45-45.

The uDY aspect of the trailing loop is related to the feature where the TY is comprised of a TY extension36xhaving a front side36f2that is recessed a distance TYd of 0.8 to 1.3 microns from ABS30-30, and a backside that interfaces with TY front side36f1. Yoke length (YL) is defined as the distance between the ABS and TY front side36f1. The TY extension has a thickness t of 0.3-0.8 microns, which is equal to that of TY36. The PP3 TS has a middle portion26cwith a dome shaped top surface26tformed above driving coil front portion61a. A front portion26aof the PP3 TS is formed on WS18and has an inner side26ethat forms an apex angle θ, preferably from 60 degrees to 80 degrees, with respect to plane45-45that comprises TY top surface36tand is orthogonal to the ABS. A back portion26bof the PP3 TS adjoins a top surface of TY36. The PP3 TS apex angle is believed to enhance flux concentration at WS18and provides improved high data rate performance. A key feature is that TYd is less than YL. Driving coil front portion61ais entirely above plane45-45and TY extension36x, and within insulation layer25.

Leading shield11, LSB33, S2C32, LBG52, BGC53, and RTP9are generally made of NiFe, CoFe, CoFeN, CoFeNi or the like with a saturation magnetization (Ms) value of 4 kiloGauss (kG) to 16 kG. WS18, PP3 TS26a-26c, TY36, and TY extension36xare typically made of NiFe, CoFe, CoFeNi, or CoFeN having a Ms 10 kG to 19 kG while HS layer17and MP14have a Ms from 19 kG to 24 kG. In this scheme, the tBY35contacts a bottom surface of MP14below the TY extension. Although the PP3 TS26a-chas a front side26fat the ABS, the front side may be recessed from the ABS30-30in other embodiments (not shown).

FIG. 7depicts a writer with a uDY trailing loop and a nDWS layout for the leading loop according to another writer scheme practiced by the inventors wherein the leading loop terminates at leading shield11. The nDWS approach is beneficial in providing a better return field at the MP trailing edge thereby improving field gradient, BER, and ADC compared with the rDWS BGC layout but at the expense of a worse nearby ATE.

Referring toFIG. 8, another writer scheme is depicted that is known to the inventors and features an ePL trailing loop and a rDWS LBG leading loop. In this case, the LBG/BGC stack in the rDWS BGC layout described previously is replaced with LBG52that extends upward from RTP9to a back portion of MP14. With the ePL scheme, the PP3 TS26in the trailing loop is modified to have a flat top surface26t, and front side26fis recessed from the ABS30-30. However, in other embodiments (not shown) the PP3 TS front side may be at the ABS to satisfy thermo-magnetic requirements because of a larger metal area at the ABS. Moreover, an exposed PP3 TS front side at the ABS means fewer process steps and is preferred when wide adjacent track erasure (WATE) from the PP3 TS, and PP3 TS to WS18interface is manageable.

Referring toFIG. 9, an ePL nDWS base writer structure known to the inventors is shown wherein the ePL design fromFIG. 8is retained, but the LSC33, S2C32, RTP9, and LBG52are removed so that the leading loop terminates at LS11. This scheme has the same advantage as the nDWS base structure inFIG. 7in terms of a better return field at the MP trailing edge compared with the ePL rDWS LBG writer structure, but at the expense of a worse nearby ATE.

All of the writer structures shown inFIGS. 6-9depict a single PMR writer. However, the present disclosure also anticipates a selectable dual PMR writer (SDW) or selectable triple PMR writer (STW) wherein only the better or best performing writer is selected for a write process. When two or more PMR writers (not shown) are formed on a slider, each writer may be fully separated from an adjacent writer with a separate PP3 TS26a-26c, HS layer17, WS18, LS11, LSB33, S2C32, RTP9, LBG52, and BGC53as well as having a separate MP14, tBY35, TY extension36x, and TY36. In another embodiment (not shown), the two or more writers may share a PP3 TS, HS layer, WS, LS, LSB, S2C, and RTP, but have separate LBG, BGC, tBY, TY extension, TY, and MP. In yet another embodiment, all magnetic components in the leading and trailing loops are shared except for the tBY, MP, TY extension, and TY.

FIG. 10shows an equivalent circuit of a PMR writer with tunable MP protrusion according to an embodiment of the present disclosure. Note that writer components except for the writer pads are omitted to more clearly show that circuit121comprising the MP tip runs parallel to the DFH heater circuit120where the latter has a total resistance (Rs+R_lead+R_tip) and the former has resistance R_DFH. A MP back portion is electrically connected to a built-in series resistor with resistance Rs, which is electrically connected to DFH (+) pad63. R_lead accounts for the lead resistance contribution other than Rs and R_tip. Writer shields including the WS, SS, and LS are electrically connected to the DFH ground (−) pad64. The MP tip is electrically connected to one or both of HS layer17and SS12through a NM metal layer as explained later with regard toFIGS. 16-20. MP tip resistance (R_tip) is tuned by adjusting the volume of NM metal in contact with the MP tip, as well as the NM metal composition. A key feature is that the tunable MP protrusion design of the present disclosure may be incorporated in a PMR writer without changing the existing pad layout in current products.

Referring toFIG. 11, HGA100is depicted and features suspension103, an overlying dielectric layer104, and slider102formed thereon. A combined read/write head101comprised of a PMR writer of the present disclosure adjoins a top side of the slider facing away from the suspension. The suspension is supported using an actuator arm that is driven by an actuation motor to sweep the suspension and slider across the surface of a recording disk as described previously with regard toFIG. 1. A plurality of writer pads including DFH pads63,64are employed to control a current to the bucking coil, driving coil, and DFH writer heater while reader pads control current to the reader sensors, and DFH reader heater. Connections between the pads and the PMR writer components are within the slider and not visible from this view. The same fabrication scheme used to build a single writer may be employed to fabricate SDW or STW structures of the present disclosure so that no additional product cost is incurred.

In order to form a current path through the MP tip, one or two insulation layers are added to existing writer structures to give the embodiments illustrated inFIGS. 12-15. According to a first embodiment of the present disclosure depicted inFIG. 12, the uDY rDWS BGC base writer inFIG. 6is modified by including a first insulation layer92behind the tBY35, and between BGC53and a back portion of MP14to electrically isolate the MP back portion from the leading loop. Moreover, a second insulation layer93is formed behind PP3 TS inner corner90and between the top yoke36and PP3 TS back portion26bto electrically isolate the MP back portion from the trailing loop. Both of the first and second insulation layers have a thickness of 10 nm to 300 nm with a nominal value around 100 nm and are made of one or more layers of metal oxide including but not limited to AlOx, SiOx, TaOx, and TiOx, and other metal oxides used in the art.

A second embodiment of the present disclosure is shown inFIG. 13and is a modification of the uDY nDWS base writer structure inFIG. 7where insulation layer93described previously is formed on TY36at plane45-45and behind PP3 TS inner corner90. Thus, the insulation layer separates the PP3 TS back portion26bfrom the TY and electrically isolates the MP back portion from the trailing loop.

According to a third embodiment of the present disclosure depicted inFIG. 14, the ePL rDWS LBG base writer inFIG. 8is modified to include first insulation layer92between LBG52and a back portion of MP14to electrically isolate the MP back portion from the leading loop. Furthermore, second insulation layer93is formed on TY36and adjoins a bottom surface of PP3 TS26behind driving coil front portion61aso that the MP back portion is electrically isolated from the trailing loop. Depending on the thickness of the insulation layers, some magnetic flux70aand70bin the leading loop and trailing loop, respectively, may leak into the MP.

Referring toFIG. 15, a fourth embodiment of the present disclosure is shown where the ePL nDWS base writer inFIG. 9is modified to insert insulation layer93on TY36and adjoining a bottom surface of PP3 TS26. As a result, a back portion of MP14is electrically isolated from the trailing loop.

FIGS. 16-20illustrate various embodiments of the present disclosure from an ABS view of the MP tip and surrounding shield structure. It should be understood that each of the embodiments inFIGS. 16-20may be incorporated in any of the writer schemes described previously with regard toFIGS. 12-15. In particular, R_tip, and therefore MP tip protrusion, is tuned in the various embodiments based on the volume of NM metal contacting the MP tip, and the NM metal composition. R_tip is expected to have the least dependency on MP PWA and MP dimensions when the conducting path width in the WG is narrower than PWA and independent of PWA. As R_tip increases, MP protrusion is enhanced.

Referring toFIG. 16, one embodiment of an electrical connection between MP tip14pand the surrounding shield structure is depicted. First NM metal layer55is formed in the WG, has thickness t1of 15 nm to 22 nm, and extends from the ABS to a height of 20 nm to 60 nm. The first NM metal layer preferably has a width no more than PWA+2s where s is the SG width, and makes a contact between HS17and MP tip14pwithout touching side shield12when SG15is not a NM metal layer. The first NM metal layer is a single layer or multilayer comprised of one or more of Ru, NiCr, Ta, Cu, W, Ti, or other conductive materials used in the art. Center plane44-44bisects the MP trailing side14t1and MP leading side14b1. MP side14sadjoins a side gap15on each side of the center plane. Leading gap13is between the MP leading side and LS11. HS layer17has a width w that is bisected by the center plane, and contacts a top surface of first NM metal layer55and a top surface of WG16on each side of the first NM metal layer. Note that WG side16sis self-aligned to HS layer side17son each side of the center plane. Plane41-41comprises the MP trailing side at the ABS, and forms the interface between WG16and side shields (SS)12, and between write shield (WS)18and each SS. The WS contacts WG sides16sas well as HS layer top surface17tand sides17s. Thus, the MP tip has an electrical connection to the HS layer while the MP back portion is electrically insulated from the trailing loop.

InFIG. 17, a second embodiment of an electrical connection between MP tip14pand the surrounding shield structure is illustrated. The first NM metal layer in the WG of the first embodiment is removed so that WG16has width w and separates MP trailing side14t1from HS layer17. However, a second NM metal layer54is formed in the leading gap, and in each side gap between SS inner side12sand MP side14sso that the MP tip is electrically connected to a top surface11tof LS11, and each SS12, respectively. The second NM metal layer may be a single layer or multilayer and is comprised of one or more materials mentioned previously with respect to the first NM layer. Second NM metal layer width in the SG is typically from 20 nm to 60 nm. One advantage of the second embodiment is to enhance MP protrusion with less HS layer protrusion to avoid reliability issues from excessive HS layer protrusion (wear).

According to a third embodiment of an electrical connection between MP tip14pand the surrounding shield structure shown inFIG. 18, the first embodiment where first NM metal layer55is formed in the WG between MP trailing side14t1and HS layer17is modified to include the second NM metal layer54in the side gaps and leading gap as described previously in the second embodiment.

Referring toFIG. 19, a fourth embodiment of an electrical connection between MP tip14pand the surrounding shields is shown where the third embodiment is modified to widen the first NM metal layer55to have width w so that first NM metal layer side55son each side of center plane44-44is self-aligned (coplanar) with HS layer side17s.

A fifth embodiment of the present disclosure that relates to an electrical connection between MP tip14pand surrounding shields is depicted inFIG. 20. In particular, the first embodiment inFIG. 16is modified to widen the first NM metal layer55to have width w so that first NM metal layer side55son each side of center plane44-44is coplanar with HS layer side17s. R_tip for the third embodiment inFIG. 18is expected to be lower than that of the first two embodiments while R_tip for the fourth embodiment is expected to be the lowest of all assuming the composition for NM metal layers54,55, and the width and height of the NM metal layers are constant in each embodiment.

FIG. 21illustrates a top-down view of any of the second through fourth embodiments (FIGS. 17-19) where all PMR writer layers above MP14and side shields12are removed to clearly reveal second NM metal layer54on each side of center plane44-44. The second NM metal layer adjoins each MP tip side14sfrom the ABS30-30to a throat height (TH) of about 50 nm to 120 nm, has a width of 20 nm to 60 nm, and then slopes away from the center plane with increasing separation from the center plane as the second NM metal layer height from the ABS increases. Each MP tip side connects with curved MP side14c, which in turn connects with MP flared side14fat height h from the ABS. Insulation layer46separates each MP flared side from the second NM metal layer.

Referring toFIG. 22, a down-track cross-sectional view at center plane44-44is shown for any of the first embodiment (FIG. 16) and third through fifth embodiments (FIGS. 18-20) where first NM metal layer55is formed in the WG between MP trailing side14t1and HS layer17. According to one embodiment, the first NM metal layer has a front side55fat the ABS30-30and extends to a backside55eat a height of 20 nm to 60 nm and proximate to HS layer tip height eTHd. LS11has backside11ewhile HS layer and WS18have backsides17eand18e, respectively, that are typically substantially greater than eTHd. Note that eTHd is relatively small compared with other device dimensions mentioned earlier such as width w, and heights TYd and YL, and is therefore sensitive to lapping control, which means that R_tip may have substantial device to device variation.

As depicted inFIG. 23, the present disclosure also anticipates that first NM layer55may be in the WG but front side55fis recessed 50 nm to 100 nm from the ABS30-30. In this embodiment, there is more reproducibility in providing the desired first NM metal layer width and height (volume) and a desired R_tip resistance value than when front side is exposed at the ABS and is subject to variations in the lapping process.

Tables 1-2 show experimental results of PMR heads built according to an embodiment of the present disclosure where the writer has an ABS view according to the first embodiment inFIG. 16, and a down-track cross-sectional view as shown inFIG. 22where the first NM metal layer55is at the ABS30-30. Results are shown with bias off (voltage across MP tip region=V_tip=0) and with bias on where V_tip=100 mV. Two pads (not shown) are added to form an electric circuit from the writer shields to the MP, and apply direct current (DC) current near the MP tip. Special preamp and suspension are required to accommodate the pad layout change and the additional bias application in spin stand testing and HDD application. With bias on, erase width (EW) is increased by an average of about 1 nm, and ADC improvement from kFCI is found to be ˜0.5% if all samples are included with a wide range of EW from 37 nm to 70 nm (average EW=52 nm) as in Table 1. ADC improvement is ˜1% for narrow EW from 38 nm to 48 nm (average EW=44) in Table 2.

For all heads, overwrite (OW2), low frequency write-ability quantified by 15T overwrite 2T, shows no change while bit error rate (BER) and center track bit error rate after squeeze (SqBER) are improved by 0.05 and 0.03 decade, respectively between bias on and bias off. For the aforementioned narrow EW heads, OW2 gain is about 0.5 dB at bias on while writer heater touchdown (TD) spacing is significantly reduced by ˜0.1 nm. Meanwhile, IwPTP shows a consistent 0.07 nm increase suggesting more writer protrusion near MP region with current passing through the MP tip at bias on. Experimental results support that passing a current through the MP tip region will improve MP protrusion, and also improve ADC, especially for narrow EW and heads with a narrow PWA of less than 50 nm. Subsequently, we found that the existing PMR pad layout may be employed so that the existing PMR preamp and suspension are applied transparently without any additional cost to the backend process and HDD applications.

TABLE 3Practical examples of tunable MP protrusion designCaseR_DFH80OhmP_DFH60mWV_DFH2.19Volt#1R_tip15OhmP_tip0.33mWV_tip0.07VoltR_lead15OhmP_lead0.33mWV_lead0.07VoltRs439OhmPs9.57mWVs2.05VoltR_total68OhmP_total70.22mWV_total2.19VoltCaseR_DFH80OhmP_DFH60mWV_DFH2.19Volt#2R_tip15OhmP_tip0.67mWV_tip0.10VoltR_lead15OhmP_lead0.67mWV_lead0.10VoltRs299OhmPs13.27mWVs1.99VoltR_total64OhmP_total74.61mWV_total2.19VoltCaseR_DFH80OhmP_DFH60mWV_DFH2.19Volt#3R_tip10OhmP_tip0.49mWV_tip0.07VoltR_lead15OhmP_lead0.74mWV_lead0.11VoltRs288OhmPs14.11mWVs2.02VoltR_total64OhmP_total75.34mWV_total2.19VoltCaseR_DFH95OhmP_DFH60mWV_DFH2.39Volt#4R_tip15OhmP_tip0.33mWV_tip0.07VoltR_lead15OhmP_lead0.33mWV_lead0.07VoltRs482OhmPs10.49mWVs2.25VoltR_total80OhmP_total71.14mWV_total2.39VoltCaseR_DFH80OhmP_DFH60mWV_DFH2.191Volt#5R_tip14OhmP_tip0.31mWV_tip0.066VoltR_lead15OhmP_lead0.33mWV_lead0.070VoltRs439OhmPs9.62mWVs2.055VoltR_total68OhmP_total70.26mWV_total2.191VoltCaseR_DFH80OhmP_DFH60mWV_DFH2.191Volt#6R_tip16OhmP_tip0.35mWV_tip0.075VoltR_lead15OhmP_lead0.33mWV_lead0.070VoltRs439OhmPs9.54mWVs2.046VoltR_total68OhmP_total70.21mWV_total2.191Volt

Table 3 provides a few practical examples to illustrate the TPP design concept of the present disclosure. Assumptions are that a typical writer DFH heater at operation has power consumption P_DFH˜60 mW and the R_lead is ˜15 ohm. Case #1 has R_DFH=80 ohm and R_tip=15 ohm. If V_tip needs to be controlled at about 70 mV, the series resistance Rs˜439 ohm is required. Power consumption at the MP tip (P_tip) is ˜0.33 mW. If V_tip needs to be controlled around 100 mV, as shown in Case #2, Rs ˜299 ohm is required and P_tip is about doubled at 0.67 mW. Case #3 assumes the R_tip is ˜10 ohm. To reach the same V_tip of 70 mV, Rs may be designed at 288 ohm and P_tip can reach 0.49 mW. If R_total is forced to be 80 ohm as shown in Case #4, R_DFH and Rs may be set at 95 ohm and 482 ohm, respectively. Assuming Case #1 is the nominal case and Rs is built at 439 ohm in the wafer, R_tip is 14 ohm in Case #5 and 16 ohm in Case #6. With the variation of R_tip, V_tip and P_tip vary change accordingly. Higher P_tip has higher power consumption at MP tip and higher MP tip protrusion.

A key sequence in the fabrication process of a PMR writer having a tunable MP protrusion (TPP) design and a uDY layout in the trailing loop according to the present disclosure is depicted inFIGS. 24-26. It should be understood that a similar fabrication method was described in related U.S. Pat. No. 10,643,640. In particular, the current process sequence starts atFIG. 24(alsoFIG. 24in the related patent) where insulation layer25is patterned over driving coil front portion61aand uncovers WS top surface18tat the ABS30-30, and TY top surface36tat plane45-45.

Referring toFIG. 25, a photoresist mask58with backside58eis formed on insulation layers21,25, and on WS18. Opening59behind the photoresist mask backside exposes TY top surface36t. Next, second insulation layer93is deposited on the TY top surface and behind photoresist mask backside58e.

FIG. 26shows a down-track cross-sectional view after the photoresist mask is removed by a conventional method, and the PP3 TS26a-26cis plated on WS18and on TY36and insulation layer21at plane45-45, and also on second insulation layer93behind insulation layer25. Thereafter, a conventional series of steps may be employed to complete the PMR writer as depicted inFIG. 13. Those skilled in the art will appreciate that a similar sequence of steps may be used to form second insulation layer93on TY top surface36tin an ePL trailing loop scheme before the PP3 TS is plated to yield the PMR writer inFIG. 15, for example.