Patent ID: 12211525

DETAILED DESCRIPTION

The present disclosure is a reader comprised of a sensor and that is in a combined read-write head wherein a SHE layer is formed between a free layer (FL) in the sensor and a top shield (S2) so that when a current is applied across the SHE layer in a cross-track direction, and a portion or all of the current flows in a down-track direction through the sensor in a three terminal or two terminal configuration, respectively, spin torque from the SHE layer offsets spin torque from a reference layer on the FL to substantially reduce magnetic noise in the FL thereby reducing the sensor SNR and improving BER. In the drawings, the y-axis is in a cross-track direction, the z-axis is in a down-track direction, and the x-axis is in a direction orthogonal to the ABS and towards a back end of the writer structure. Thickness refers to a down-track distance, width is a cross-track distance, and height is a distance orthogonal to the ABS in the x-axis direction. A magnetization in a transverse direction is orthogonal to the ABS, while a longitudinal direction is the cross-track direction. A back end or backside refers to a side of a layer facing away from the ABS, and a front side is a side of a layer facing the ABS or at the ABS.

Referring toFIG.2, a head gimbal assembly (HGA)100includes 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.3) and a plan view of a magnetic recording apparatus (FIG.4) 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.2) 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.4, 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.5, magnetic recording head1comprises a combined read-write head. The down-track cross-sectional view is taken along a center plane (46-46described later with respect toFIGS.19-21) that is formed orthogonal to the ABS30-30, and that bisects the main pole layer14. The read head (reader) is formed on a substrate81that may be comprised of AlTiC (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 shield (S1)84is 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 reference layer and a free layer where the FL has a magnetization (not shown) that rotates in the presence of a local magnetic field from a magnetic bit to a position that is substantially parallel or antiparallel to the reference layer magnetization as described previously with regard toFIG.1B. Insulation layer85adjoins the backside of the MR sensor, and insulation layer83contacts the backsides of the bottom shield and top shield (S2) 87. The top shield is formed on the MR sensor. An insulation layer88and a top shield (S2B) layer89are sequentially formed on S2. Note that the S2B layer89may 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 layer89inFIG.5is typically considered as the read head (reader). 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 (writer) may be employed with the read head portion. The exemplary embodiment shows magnetic flux70in main pole (MP) layer14is generated with flowing a current (not shown) through bucking coil80band driving coil80dthat are below and above the main pole layer, respectively, and are connected by interconnect51. Magnetic flux70exits the MP layer at MP pole tip14pat the ABS30-30and is used to write a plurality of bits on magnetic medium140. Magnetic flux70breturns to the MP through a trailing loop comprised of trailing shield17, write shield18, PP3shield26, and top yoke18x. There is also a leading return loop for magnetic flux70athat includes leading shield11, leading shield connector (LSC)33, S2connector (S2C)32, return path89, and back gap connection (BGC)62. The magnetic core may also comprise a bottom yoke35below the MP layer. Dielectric layers10,13,36-39, and47-49are employed as insulation layers around magnetic and electrical components. A protection layer27covers the PP3trailing 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 the uppermost layer in the writer.

In related U.S. Pat. No. 10,559,318, we disclosed the use of a SHE layer in a write head between a MP trailing side and the trailing shield. When a current (ISHE) is conducted across the SHE layer during a write process and synchronized with the write current, spin transfer torque is generated on both of the MP trailing side and trailing shield to provide a boost in transition speed and transition sharpness, and improved BER. Now we have discovered that the spin torque generated by flowing a current through a SHE layer may be advantageously employed in reducing magnetic noise within a FL in a reader sensor.

Spin Hall Effect (SHE) is a physics phenomenon discovered in the mid 20thcentury, and is described by M. Dyaknov et al. in Physics Lett. A, Vol. 35, 459 (1971). Similar to a regular Hall Effect where conduction carriers with opposite charges are scattered to opposite directions perpendicular to the current density due to a certain scattering mechanism, SHE causes electrons with opposite spins to be scattered to opposite directions perpendicular to the charge current density as a result of strong spin-orbit coupling in the conducting layer. As shown inFIG.6, electrons pass through a non-magnetic conductor8with strong spin orbit interaction, and electrons e2with spin in the negative x-axis direction are deflected to the +z-axis surface8s2while electrons e1with spin in the positive x-axis direction are deflected to the negative z-axis surface8s1. SHE is quantified by the Spin Hall Angle (SHA) defined as the ratio of the spin current in the direction transverse to the charge current (z-axis inFIG.6) to the charge current (y-axis direction inFIG.6). For many years after SHE was discovered, the absolute value of SHA materials evaluated was typically <0.01, and SHE layers had very limited applications in industry.

During the past 10 years, materials with substantially larger (giant) SHA have been found. B. Gu et al. in Phys. Rev. Lett. 105, 216401 (2010), and L. Liu et al. in Phys. Rev. Lett. 106, 036601 (2011) provided examples of SHA ˜0.07 in a Pt layer, and as large as 0.12 in Au layers with Pt doping. A large but negative SHA of around −0.12 was found in β-Ta, meaning that electrons in the β-Ta layer are spin scattered in the opposite directions compared to what is shown inFIG.6.

Referring toFIG.7A, an ABS view of the reader with MR sensor86inFIG.5is shown according to a first embodiment of the present disclosure where a single SHE layer9made of a positive giant SHA material contacts a top surface5tof FL5in the sensor. The sensor is a stack of layers with sidewalls5s1, and wherein seed layer2, AP2layer3a, AF coupling layer3b, AP1layer3c, non-magnetic layer4, and FL5are sequentially formed on S184. The non-magnetic spacer is a tunnel barrier layer in preferred embodiments, but also may be a metal spacer in other embodiments. The MR sensor also typically comprises one or more additional layers including an AFM layer (not shown) behind the stack pictured inFIG.7A, and described later. FL magnetization5mis longitudinally biased with magnetization7min biasing layers7formed within an insulation layer85athat contacts each sidewall5s1of the MR sensor. An upper portion of insulation layer85aseparates each biasing layer from SHE layer9. Note that the SHE layer has a full width such that each side9s1,9s2is coplanar with a side84sof S1and a side87sof S287. Insulation layer85bis formed on the SHE layer and electrically separates the SHE layer from S2. Insulation layers85a,85bare bottom and top portions, respectively, of insulation layer85shown inFIG.5.

The benefit of the SHE layer9is explained as follows. Conduction electrons in the input current in the SHE layer (hereinafter referred to as Iin) that flows in a positive y-axis direction with current density j2in the input direction at side9s1, and current density j in the output direction at side9s2, and that carry spin downward propagate to FL top surface5t. This spin polarization9psubstantially offsets a similar spin polarization (not shown) that is generated when a portion of the input current j2splits off and flows with current density j1through sensor86to S184and conduction electrons in j1that carry spin upward from AP1layer3cproduce spin torque on FL5. In particular, spin current density represented by the product (j1×P0) where P0is the spin polarization from AP1to the FL is preferably proximate to the spin current density represented by the product (j2×SHA) where SHA is the spin polarization from the SHE layer to the FL. In the ideal case where (j1×P0)=(j2×SHA), or optionally, when (j1×P0) is proximate to (j2×SHA), then spin torque induced magnetic noise within the FL is minimized to essentially zero or reduced substantially and will enable smaller sensor widths w1with a smaller RA product of <0.6 in the tunnel barrier4for optimum performance. Note that when sensor sidewalls5s1are non-vertical, width w1refers to the FL width.

SHE layer thickness t is preferably less than 12 nm since the L. Liu reference mentioned earlier indicates that a SHE assist (spin torque applied to an adjacent magnetic layer, i.e. FL5in the present disclosure) is reduced when the giant SHA material has a thickness >12 nm. Preferably, the absolute value for SHA is >0.05, and more preferably is greater than 0.10 to enable a lower j2current density. In some embodiments, the SHA material is a heavy metal that is one of β-Ta, Hf, Pt, Ir, and W that may be embedded with Au, for example. In other embodiments, a topological insulator (TI) may serve as a SHA material according to a report at phys.org/news/2017-11-significant-breakthrough-topological-insulator-based-devices.html. A TI may be one of Bi2Sb3, Bi2Se3, Bi2Te3, or Sb2Te3, and has an inner portion that is an insulator or a high resistance material while an outer portion comprising the surface thereof has a spin-polarized metal state. Therefore, the TI has an internal magnetic field such as a spin orbit interaction. A pure spin current can be generated in a highly efficient manner due to the strong spin orbit interaction and collapse of the rotational symmetry at the surface.

Seed layer2typically includes one or more metals such as Ta, Ti, Ru, and Mg, an alloy such as NiCr, or a nitride (TiN or TaN) that promote uniform thickness and the desired crystal growth in overlying MR sensor layers. Each of AP2layer3a, AP1layer3c, and FL5may be a single layer or multilayer comprised of one or both of Co and Fe that may be alloyed with one or more of Ni, B, and with one or more non-magnetic elements such as W, Mo, Ta, and Cr. AF coupling layer3bis typically one of Ru, Rh, Ir, or Os and has a thickness that ensures AP2layer3ais AF coupled to AP1layer3c. A non-magnetic spacer4that is a tunnel barrier layer is preferably MgO but may be another metal oxide, metal oxynitride, or metal nitride used in the art. In other embodiments, the non-magnetic spacer is a metal such as Cu. Insulation layers85a,85bmay be one or more of Al2O3, TaOx, SiN, AlN, SiO2, MgO, and NiO. S184and S287typically extend from a front side at the ABS to a backside (not shown) that is 10 microns or more from the ABS, have a magnetization saturation (Ms) value from 5 kiloGauss (kG) to 15 kG, and are generally comprised of CoFe, CoFeNi, CoFeN, or NiFe, or a combination thereof. In some embodiments, each biasing layer7is a junction shield that is comprised of one or more magnetic materials such as CoFe and NiFe. However, the biasing layer may also be a hard magnetic material that is CoCrPt or CoCrPtX where X is B, O or other elements that can assist a perpendicular growth of the HB easy axis, TbFeCo, or a multilayer ferromagnetic/non-magnetic super-lattice structure that is [Co/Pt/Co]nor [Co/Pd/Co]n, for example, where n is a lamination number.

As shown inFIG.7B, the first embodiment also encompasses a MR sensor having the three terminal configuration shown inFIG.7Aexcept where j1flows from S184through sensor86to SHE layer9, and merges with j that flows in the negative y-axis direction from the right side9s2of SHE layer9to give current density j2in the output direction at the left side9s1. In this case, SHE layer spin polarization9pis in the opposite direction shown inFIG.7Abut still opposes spin polarization (not shown) from AP1layer3con FL5because j1is also reversed compared with theFIG.7Aconfiguration. As a result, the same advantageous result of reduced spin torque induced magnetic noise in the FL that enables a reduced SNR, lower tunnel barrier RA, and improved reader performance for a MR sensor width w1<25 nm, is realized as inFIG.7Awhen the product (j1×P0) is proximate or equal to the product (j2×SHA).

Referring toFIG.8A, all aspects of the embodiment inFIG.7Aare retained except the (+) SHE layer is replaced with a negative giant SHA material to give (−) SHE layer9n. Therefore, j2in SHE layer9nis reversed compared withFIG.7Aand flows in the input direction from side9s2and splits into j1that flows through sensor86to S184and j in the output direction to side9s1in order to achieve the same effect where spin torque produced by spin polarization9pfrom j2essentially cancels spin torque caused by spin polarization (not shown) from AP1layer3cthat is generated on FL5. In other words, spin torque induced magnetic noise in the FL is effectively reduced to zero, or substantially decreased, to provide the same benefit mentioned previously for theFIG.7Aconfiguration when (j1×P0) is proximate or equal to (j2×SHA).

FIG.8Bdepicts an alternative configuration for the embodiment inFIG.8Awhere all aspects are retained except the direction is reversed for j, j1, and j2. Thus, j1flows from S184through sensor86to SHE layer9n, and merges with j that flows from side9s1to yield j2that flows to side9s2in SHE layer9n. Then the spin torque from the SHE layer essentially cancels the spin torque from AP1layer3cwhen (j1×P0) equals or is proximate to (j2×SHA) as explained earlier.

In a conventional reader with an RA of 0.5 Ohm-μm2, a voltage of about 140 mV is generally applied across tunnel barrier4. Thus, the resulting current density is j1=2.8×107Amps/cm2. Assuming the stripe height (SH2inFIG.12) is substantially larger than the FL stripe height (SH1inFIG.12), the amount of current that is input from SHE layer side9s1inFIG.7A, for example, and split into the MR sensor current is negligible. Thus, the injected current density j2from side9s1and output current density j at side9s2inFIG.7Aare equal. Spin polarization P0from AP1layer3cto FL5is typically 0.4-0.6, and the SHA for a giant SHE layer9is in the range of 0.1-0.2. Accordingly, j2should be a factor of 3-4 times j1to satisfy the objective of (j1×P0)=(j2×SHA). It follows that the desired j2of around 8-10×107Amps/cm2is applicable in a SHE layer with good reliability. It should be understood that in embodiments where (j1×P0) is proximate to (j2×SHA), a significant decrease in spin torque induced magnetic noise within the FL is still achieved compared with the prior art where there is no SHE layer.

Referring toFIG.9, an enlarged view of SHE layer9and FL5fromFIG.7Aaccording to an alternative embodiment is depicted. If the stripe height of the SHE layer9is equal to that of the FL5, the current ISsplit from j2into the FL and sensor cannot be neglected. Assuming the FL has a width×SH1of 24×24 nm2area for the j1path, the SHE layer has a thickness×SH2of 6×24 nm2for the j2path, the current density from the left lead94into SHE layer side9s1is jinand the current density from side9s2to the right lead95is jout, then total input current Iinto the SHE layer equals the sum of output current split into the sensor (IS) and the output current (Iout) into the right lead where Iout×jin=jout+4xj1because j1has a cross-sectional area in the (x, y) plane that is a factor of 4 higher than the cross-sectional area for j2in the (x, z) plane, and j2=(jin+jout)/2=jin+2xj1, which is still in the applicable regime. Note that Iin=1.25×ISand Iout=0.25×IS. The same result is realized for the alternative embodiments inFIG.7B,FIG.8A, andFIG.8Bwhere SH1is essentially equal to SH2(FIG.25).

InFIG.10A, another embodiment of the present disclosure is illustrated and is a modification of the reader in the first embodiment where the three terminal device becomes a two terminal device. In particular, for a SHE layer9made of a giant positive SHA material, and when the stripe height of the SHE layer is proximate to that of the FL, current through the SHE layer is substantially the same as the current through the MR sensor. In other words, current with current density j2may be input from a first terminal (not shown) and through a lead to SHE layer side9s1, and continues through sensor86with current density j1to S184that serves as a second terminal. A key feature is that a right portion9eof the SHE layer between dashed line9xand right side9s2is either not connected to an output lead as in the first embodiment, or is removed by etching and replaced with an insulation layer (not shown). In addition to the spin torque induced magnetic noise reduction in the FL associated with the three terminal embodiments described earlier, this embodiment has an additional advantage of simplifying the circuit and process steps. Note that the thickness and stripe height of the SHE layer may be adjusted so that product (j1×P0) is proximate or equal to product (j2×SHA) so that spin polarization9pfrom the SHE layer opposes spin polarization (not shown) from AP1layer3con FL5with the overall outcome of substantially reducing or essentially eliminating, respectively, spin torque induced magnetic noise in the FL.

As shown inFIG.10B, the reader configuration inFIG.10Aalso encompasses an embodiment where current with current density j1flows from S184upward through sensor86and to the SHE layer9, and then exits with current density j2through SHE layer side9s1to a lead (not shown). In this case, SHE layer spin polarization9pis in the opposite direction shown inFIG.10Abut still opposes spin polarization from AP1layer3con FL5because the j1pathway through the AP1layer is also reversed compared with theFIG.10Aconfiguration. Therefore, the same advantageous result of reduced spin torque induced magnetic noise in the FL that enables a reduced SNR, lower tunnel barrier RA, and improved reader performance for MR sensor width w1<25 nm, is realized.

Referring toFIG.11A, all aspects of the embodiment inFIG.10Aare retained except the (+) SHE layer is replaced with a negative giant SHA material to give SHE layer9n. Moreover, the left portion9eof the SHE layer between dashed line9xand side9s1is either not connected to an output lead as in the three terminal embodiment, or is removed with an etching process and replaced by an insulation layer (not shown). A key feature is that current with current density j2in SHE layer9nis reversed compared withFIG.10Aand flows from side9s2to a center portion of the SHE layer and then continues with current density j1down through MR sensor86to S184in order to achieve the same effect where spin torque produced by spin polarization9pin the SHE layer essentially cancels spin torque caused by spin polarization from AP1layer3cthat is generated on FL5.

Alternatively inFIG.11B, the reader configuration shown inFIG.11Ais retained except the current pathway is reversed so that current with current density j1proceeds from S184up through sensor86, and then exits SHE layer9nat side9s2with current density j2. Spin polarization9pis in the opposite direction compared with theFIG.11Aembodiment, but spin torque from the SHE layer continues to oppose spin torque from AP1layer3con FL5because the current pathway through the AP1layer is also reversed.

In the two terminal device embodiments, an upper portion of FL5proximate to top surface5tor an upper layer in a multilayer stack for the FL preferably has a higher resistivity than the lower portion of the FL, and preferably a resistivity that is at least ˜5×10−7Ohm·m. If the resistivity in the upper portion of the FL is too low, then the spin torque generated by SHE layer9(or9n) will be concentrated in the FL corner nearer to the spin current injection side, which is side9s1inFIG.10Aand side9s2inFIG.11A, or in the FL corner nearer the spin current exit, which is side9s1inFIG.10Band side9s2inFIG.11B. Magnetic materials with B doping such as CoFeB, CoB, and FeB typically have higher resistivity than non-B containing materials, and are preferred for an upper portion of the FL proximate to the SHE layer since they also do not reduce the TMR ratio. In other embodiments, the upper FL portion may contain a high damping impurity that is one of Re, Tb, or the like that also provides higher resistivity as long as the impurity element does not diffuse into the tunnel barrier4and cause a reduction in the tunneling magnetoresistive (TMR) ratio.

As indicated earlier, the present disclosure anticipates that the MR sensor in any of the previously described reader configurations may have different locations for an AFM layer that is used to pin the AP2layer3aand thus stabilize the direction of magnetization3min AP1layer3c. In conventional reader designs where reader shield to shield spacing (RSS) at the ABS is not a critical concern, then an AFM layer (not shown) may be formed between the seed layer2and AP2layer3ainFIG.1A, for example. However, in more recent designs where reducing RSS is an important requirement, then the AFM layer may be recessed behind one or more other layers in the MR sensor. In related U.S. Pat. No. 9,437,225, we disclosed a MR sensor structure where an AFM layer is formed behind the FL, and in related U.S. Pat. No. 9,799,357, we disclosed a MR sensor wherein the AFM layer is behind an upper portion of S1in order to reduce RSS and pin related noise.

The present disclosure also encompasses reader designs with different stripe heights and positions for SHE layer9(or9n). In the exemplary embodiment shown inFIG.12that is a down-track cross-sectional view of the reader structure in one ofFIGS.7A-8Bor in one ofFIGS.10A-11B, the SHE layer has a front side9fat the ABS30-30, and a backside9bat a stripe height SH2. FL5has stripe height SH1between the ABS and backside5e, and magnetization5min the absence of an external field. AP1layer magnetization3mis AF coupled to AP2layer magnetization3m1. The AFM layer that is typically employed to pin magnetization3m1is not pictured in this drawing since the MR sensor may accommodate various AFM layer positions such as in U.S. Pat. No. 9,799,357, for example. As explained previously, SH2may be greater than SH1in a reader with a three terminal device configuration inFIGS.7A-8B. In other embodiments (FIGS.10A-11B) where SH1is proximate to SH2, the reader may have a two terminal device configuration where current with current density j2flows from one side of the SHE layer in a longitudinal direction to a center portion thereof, and then with current density j1in a down-track direction to S1, or in the reverse pathway mentioned previously.

Referring toFIG.13, an alternative embodiment for the placement of SHE layer9is depicted. A key feature is that front side9fis recessed behind a portion of S2front side87fto reduce RSS. The SHE layer has stripe height SH2, but a backside thereof is at height h1from ABS30-30where h1>SH2. Insulation layer85bcontinues to separate the SHE layer from S287.

In yet another embodiment shown inFIG.14, the SHE layer front side9fmay be maintained at ABS30-30, but S287has a lower portion with a front side87f2that is recessed behind SHE layer backside9bin order to reduce RSS. Meanwhile, an S2upper portion has front side87f1at the ABS. Here, SHE layer stripe height SH2is less than FL stripe height SH1, and less than height h2that is the recessed distance of S2front side87f2from the ABS. FL5has a front side5fat the ABS.

The present disclosure also encompasses a process sequence for fabricating a SHE layer9(or9n) on a top surface5tof FL5according to an embodiment described herein. The particular fabrication sequence that is illustrated relates to a reader with a MR sensor design with an ABS view in one ofFIGS.7A-8B, a down-track cross-sectional view shown inFIG.12, and an AFM layer placement described in related U.S. Pat. No. 9,799,357. However, various combinations of a two terminal or three terminal device with one of multiple alternative AFM layer positions, and one of the SHE layer positions fromFIGS.12-14are anticipated by the present disclosure as appreciated by those skilled in the art.

Referring toFIG.15, a down-track cross-sectional view is shown where a S2bottom portion84awith top surface84tis provided. AFM layer20, ferromagnetic (FM) layer21, AF coupling layer22, and FM layer23are sequentially laid down on the bottom shield. Optionally, FM layer21and the AF coupling layer22may be omitted so that the AFM layer pins a magnetization (not shown) in FM layer23, which in turn is ferromagnetically coupled to AP2layer3a(shown inFIG.17). Thus, the AFM layer is responsible for pinning a magnetization in the AP2layer through a stack comprised of layers21/22/23, or through a single FM layer23.

A first photoresist layer60is coated on FM layer23and is patterned by a conventional photolithography method to form a front side60fthat faces the eventual ABS, which is indicated here by plane30-30. Thereafter, a reactive ion etch (RIE) or ion beam etch (IBE) is performed to remove uncovered portions of underlying layers and stops on top surface84tto leave an opening70between plane30-30and plane44-44that includes front side60f.

Referring toFIG.16, S2top portion84balso known as a bottom shield refill and the seed layer2are sequentially deposited on S2top surface84tto a level that fills essentially all of opening70thereby forming a seed layer top surface2tthat is coplanar with top surface23ton FM layer23. The bottom shield refill is an extension of bottom shield84aso that the bottom and top S2portions may be collectively referred to as S284. A chemical mechanical polish (CMP) process may be performed to form coplanar top surfaces2tand23t.

Referring toFIG.17, AP2layer3a, AF coupling layer3b, AP1layer3c, tunnel barrier4, and FL5are sequentially laid down on seed layer2and FM layer23. The aforementioned sensor layers may be deposited in an Anelva C-7100 thin film sputtering system or the like which typically includes three physical vapor deposition (PVD) chambers each having multiple targets, an oxidation chamber, and a sputter etching chamber. Next, a second photoresist layer61is coated on FL5and is patternwise exposed and developed with a photolithography process to generate a photoresist mask that extends from plane30-30to a backside61bat stripe height SH1from the eventual ABS. Opening71exposes a portion of FL top surface5t. It should be understood that the ABS is not defined until a back end lapping process occurs after all layers in the read head and overlying write head are formed in combined read/write head structure. For the purpose of more clearly describing the process flow in this disclosure, the eventual ABS is illustrated as a reference plane30-30. Thus, all layers contacting plane30-30actually extend to the opposite side of the eventual ABS until the lapping process is performed.

Referring toFIG.18, patterned photoresist layer61is used as an etch mask during a RIE or IBE step that removes portions of the FL5, and tunnel barrier4that are not protected by the etch mask. The etching process stops on a back portion of AP1layer top surface3tbehind FL backside5ewhere a bottom end at tunnel barrier4may be a greater distance from plane30-30than a top end at top surface5t. Note that the FL backside may be essentially vertical in other embodiments depending on FL thickness and the etching conditions. Then, insulation layer85ais deposited with a top surface85tthereon. A planarization step may be performed to form a top surface85tthat is coplanar with FL top surface5t. Insulation layer85ais preferably one or more of Al2O3, TaOx, SiN, AlN, SiO2, MgO, and NiO although other dielectric materials known in the art may be employed.

With regard toFIG.19, a photoresist layer63is coated on FL5and insulation layer85awith backside85e, and is patternwise exposed and developed with a conventional photolithography process to form a photoresist mask having width w1between sides63sthat extend from a front side63fat the plane30-30to backside63e. Portions of FL5are exposed on either side of center plane46-46between a side63sand a far side of the MR sensor structure at FL side5s. Portions of insulation layer85aare exposed between each photoresist mask side63sand a far side85sof the insulation layer, and behind FL backside5e.

FIG.20depicts a view of the partially formed MR sensor structure from plane30-30after exposed portions of the sensor stack between each photoresist mask side63sand FL side5sinFIG.19are removed by an IBE process thereby forming a MR sensor side5s1that extends from FL top surface5tto S1refill top surface84t2on each side of center plane46-46. An opening72is generated on each side of the MR sensor. Insulation layer85ahas a composition that provides a slower etching rate than the sensor stack of layers to prevent etching into AP1layer3cbehind plane44-44inFIG.19.

Referring toFIG.21, the MR sensor structure inFIG.20is depicted after a second portion of insulation layer85aand biasing layer7are deposited on S1top surface84t2and on sidewall5s1to fill the opening72. A planarization process may be used to form top surface511that is coplanar with insulation layer top surface85t. Thus, each biasing layer7extends from the plane30-30to a backside at plane44-44(not shown).

InFIG.22, SHE layer9(or9n) is deposited on FL5and on insulation layer85a. Then, another photoresist is coated on the SHE layer and patterned with a conventional method to yield photoresist mask64that extends a stripe height SH2from plane30-30to a photoresist mask backside64e.

As shown from a top-down view inFIG.23, unprotected portions of the SHE layer are removed with an IBE or RIE step behind photoresist mask backside64e. The photoresist mask has outer sides64s. The etch stops on or within insulation layer85aand thereby forms SHE layer backside9b.

Referring toFIG.24, after photoresist mask64is removed, insulation layer85bwith top surface8511is deposited on SHE layer top surface9tand on insulation layer85a. Thereafter, another photoresist patterning and etch sequence well known to those skilled in the art may be performed to generate a backside on the MR sensor stack of layers at plane45-45.

The present disclosure also encompasses an annealing step after all layers in the MR sensor structure have been deposited. A first annealing process may be performed to set the magnetization direction of the AP1layer3cand AP2layer3aby heating the patterned MR sensor to a temperature range of 200° C. to 350° C. while applying a magnetic field along the x-axis direction. A second annealing process is typically used to set the direction of magnetization7min biasing layers7. If the temperature and/or applied field employed during the anneal of biasing layers7is lower than during annealing of the sensor stack, the first annealing process may be performed before the second annealing process to maintain the AP1and AP2magnetization directions established during the first annealing process.

While the present disclosure has been particularly shown and described with reference to, the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of this disclosure.