Magnetic sensor with recessed AFM shape enhanced pinning and soft magnetic bias

A magnetic read sensor having an antiferromagnetic located embedded within a magnetic shield of the sensor so that the antiferromagnetic layer can pin the magnetization of the pinned layer without contributing to read gap thickness. The sensor is configured with a pinned layer having a free layer structure located within an active area of the sensor and a pinned layer that extends beyond the free layer and active area of the sensor. The antiferromagnetic layer can be located outside of the active and exchange coupled with the extended portion of the pinned layer.

FIELD OF THE INVENTION

The present invention relates to magnetic data recording and more particularly to a magnetic read sensor having an antiferromagnetic pinning layer that is embedded within a bottom shield so as to reduce gap spacing and provide increased data density.

BACKGROUND OF THE INVENTION

The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.

The write head includes at least one coil, a write pole and one or more return poles. When a current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the write pole, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic disk, thereby recording a bit of data. The write field, then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.

A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the adjacent magnetic media.

As the need for data density increases there is an ever present need to decrease the gap spacing of the magnetic sensor in order to decrease bit size and thereby increase linear data density. However, the thickness of the sensor layers can only be reduced so much without adversely affecting sensor performance and stability. Therefore, there remains a need for a magnetic sensor design that can provide robust sensor performance while also reducing gap spacing.

SUMMARY OF THE INVENTION

The present invention provides a magnetoresistive sensor that includes first and second magnetic shields a sensor stack sandwiched between the first and second magnetic shields. The sensor stack includes a pinned layer structure a free layer structure and a non-magnetic layer sandwiched between the pinned layer structure and the free layer structure. The free layer structure extends to a first stripe height measured from an air bearing surface and the pinned layer structure extends to a second stripe height measured from the air bearing surface, the second stripe height being greater than the first stripe height. The sensor also includes a layer of anti-ferromagnetic material embedded in the first magnetic shield and exchange coupled with a portion of the pinned layer structure.

Because the antiferromagnetic layer is removed from the active area of the sensor and embedded within the magnetic shield, it does not contribute to read gap, which is measured as the distance between the upper and lower shields at the air bearing surface. This advantageously increases data density while also providing robust magnetic pinning of the pinned layer structure.

The bottom shield can include a shield base layer and a magnetic fill layer in the active sensor area. The layer of antiferromagnetic material can be formed over the bottom shield base layer in an area outside of the base layer. A thin layer of magnetic material can be formed over and exchange coupled with the layer of antiferromagnetic material and the pinned layer structure can extend over and contact the magnetic layer. The magnetic fill layer, located in the active area of the sensor behaves functionally as a part of the bottom shield so that the read gap is the distance between upper edge of the magnetic fill layer and the bottom edge of the upper shield at the air bearing surface.

These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the figures in which like reference numerals indicate like elements throughout.

DETAILED DESCRIPTION

Referring now toFIG. 1, there is shown a disk drive100embodying this invention. As shown inFIG. 1, at least one rotatable magnetic disk112is supported on a spindle114and rotated by a disk drive motor118, all of which are mounted within a housing101. The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk112.

During operation of the disk storage system, the rotation of the magnetic disk112generates an air bearing between the slider113and the disk surface122which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension115and supports slider113off and slightly above the disk surface by a small, substantially constant spacing during normal operation.

With reference toFIG. 2, the orientation of the magnetic head121in a slider113can be seen in more detail.FIG. 2is an ABS view of the slider113, and as can be seen the magnetic head including an inductive write head and a read sensor, is located at a trailing edge of the slider. The above description of a typical magnetic disk storage system and the accompanying illustration ofFIG. 1are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.

FIG. 3shows a schematic view of a magnetic read head300as viewed from the air bearing surface. The read head300includes a sensor stack302that is sandwiched between a leading magnetic shield304and a trailing magnetic shield306. The sensor stack302includes a magnetic pinned layer structure308, a magnetic free layer structure310and a non-magnetic barrier or spacer layer312sandwiched between the free and pinned layer structures308,310. If the sensor302is a tunnel junction (TMR) sensor, then the layer312can be a non-magnetic, electrically insulating barrier layer such as MgO. If the sensor302is a giant magnetoresistive (GMR) sensor, the layer312can be a non-magnetic, electrically conductive material such as AgSn. A capping layer314may be provided at the top of the sensor stack302to protect the under-lying layers during manufacture. A seed layer316may also be provided at the bottom of the sensor stack302to promote a desired grain structure in the other above applied layers of the sensor stack302.

The pinned layer structure308can be an anti-parallel coupled structure that includes first and second magnetic layers318,320that are anti-parallel coupled across a non-magnetic, anti-parallel coupling layer such as Ru322. The free layer310has a magnetization that is biased in a direction that is parallel with the air bearing surface and orthogonal to the directions of magnetization of the pinned layers318,320, but which is free to move in response to an external magnetic field. Biasing of the magnetization of the free layer310can be provided by magnetic bias structures326,328, which can be soft magnetic bias layers or hard magnetic bias layers. If the bias structures326,328are soft magnetic bias structures, they can be formed of a material having a low magnetic coercivity and high saturation magnetization such as CoFe or NiFe. If the layers326,328are hard magnetic bias structures, they can be constructed of a material such as CoPt or CoPtCr. The bias structures326,328are separated from the sensor stack302by non-magnetic, electrically insulating layers330, which can be constructed of one or more layers of material such as alumina (Al2O3), SiN, TaOx, MgO, SiOxNy, or a combination thereof. A bias capping layer332can be provided at the top of each of the magnetic bias structures326,328. These capping layers332can be constructed of a material such as Ta/Ru, Ta/Cr, Ta/Rh, or a combination thereof, which protects the bias structures326,328. The bias structures326,328have a magnetization that is oriented in a desired direction parallel with the ABS as indicated by arrows335.

FIG. 4shows a side cross sectional view of the sensor300. As can be seen inFIG. 4, the free layer310extends to a first stripe height distance SH1as measured from the air bearing surface ABS to the back edge of the free layer310opposite the ABS. The capping layer314also extends to the first stripe height location and the non-magnetic barrier/spacer layer310can extend to this first stripe height distance as well. However, all or a portion of the non-magnetic barrier/spacer layer310can extend beyond the first stripe height distance SH1as shown inFIG. 4.

The pinned layer structure308, however, extends beyond the first stripe height SH1to a second stripe height distance SH2. This extension of the pinned layer structure308improves pinning strength by providing a desired shape enhanced magnetic anisotropy as well as increased pinned layer area. The area behind SH1and behind SH2can be filled with a non-magnetic, electrically insulating fill layer404such as alumina.

The sensor includes a layer of anti-ferromagnetic Material (AFM)402that is embedded within the bottom or leading shield304. The AFM is only located in the region that is beyond the first stripe height SH1so that it is not between the free layer310and the leading shield304. As can be seen inFIG. 4, the sensor300includes a shield fill material304athat can be constructed of a material such as NiFe or CoFe or alloys thereof that are adjusted to provide a desired saturation magnetization. The shield fill layer304afunctions magnetically as a part of the shield304, so that the gap thickness G of the sensor is only the distance between the top of the shield fill layer304aand the leading edge of the trailing magnetic shield306. The layer304acan be NiFe, CoFe or alloys thereof. As can be seen, the AFM layer402does not contribute to the gap thickness so that the total gap thickness G is greatly reduced.

Also as can be seen inFIG. 4, the sensor300includes pinned sub-layer318abetween the AFM402and first magnetic pinned layer318. This layer318acan be constructed of the same material as the layer318and is magnetically connected with the layer318so that it functionally becomes a part of the first pinned layer318. However, this layer318ais strongly exchange coupled with the AFM layer402and carries this exchange coupling through to the rest of layer318to pin the magnetization of the layer318in a first direction perpendicular to the ABS as indicated by arrow406. The anti-parallel coupling between the layer318and layer320pins the magnetization of the second pinned layer320in a second direction that is perpendicular to the ABS and opposite to the first direction as indicated by arrow408. The AFM layer402can be constructed of a material such as IrMn or PtMn, NiMn, PdPtMn, or CrPtMn, and as can be seen, the AFM layer402is effectively embedded within the shield304/304ain a region that is removed from the air bearing surface. In this way, the AFM layer402can provide strong pinning, while also not contributing to gap thickness. This, therefore, provides the desired small gap spacing for improved data density without sacrificing sensor performance or reliability.

FIGS. 5,6and7show a top down view as seen from line5-5ofFIG. 4illustrating several possible configurations of the AFM layer402. With reference toFIG. 5, the AFM layer402can have sides502that are aligned with the sides504of the sensor stack302. This alignment of the sides502,504can be achieved using a self aligned processes that will be described in greater detail herein below.

FIG. 6shows another possible configuration of the AFM layer402. In this configuration the AFM layer402has sides602that extend beyond the sides502of the sensor stack302. InFIG. 6the portion of the extended pinned layer structure308that extends beneath the AFM layer402is shown in dashed line. A process for constructing a sensor having such an AFM configuration will be described herein below.

FIG. 7illustrates yet another configuration wherein the AFM layer has a bent or “U” shape. In this configuration the AFM has side portions702that extend toward or to the air bearing surface ABS. The AFM layer402can be separated from the bias structures326and sensor stack302by an insulation layer704. The construction of a sensor having such an AFM structure402will be described herein below.

FIGS. 8-32show a magnetic sensor in various intermediate stages of manufacture in order to illustrate methods for manufacturing a magnetic sensor with an embedded AFM having various configurations. With particular reference toFIG. 8, a magnetic shield base portion802is formed. This shield can be formed on a substrate (not shown) by electroplating and can be constructed of a magnetic material such as NiFe or CoFe or a combination of these materials. InFIG. 8the location of an intended air bearing surface plane is indicated by the dashed line denoted as ABS.

Then, with reference toFIG. 9a seed layer902is deposited over the shield802. The seed can be constructed of Ta or Ru or a combination both of these materials. Then a layer of antiferromagnetic material (AFM)904is deposited over the seed layer. The AFM layer904is preferably constructed of IrMn but could also be constructed of PtMn or NiMn, PdPtMn, or CrPtMn. The seed layer902allows the ATM layer to grow with a crystal structure that promotes desired antiferromagnetic properties. A layer of magnetic material906is deposited directly onto the AFM layer904. The magnetic material906is a material that will make up a first portion of a first pinned layer (AP1 first portion) as will be seen below. Therefore, the magnetic layer906is constructed of a material having desired pinned layer properties, such as CoFe or some similar material. A capping layer908is then deposited over the magnetic layer906. The capping layer908can be a material such as Ru, Ta, Au, Rh, Cu or Mg or optional no capping but with a thicker layer906. All of the layers902,904,906,908can be deposited in a single deposition tool, such as a sputter deposition tool, in situ, without breaking vacuum.

After all of the layers902,904,906,908have been deposited, a first annealing process is performed to achieve strong magnetic exchange coupling between the magnetic layer906and the AFM layer904and to strongly pin the magnetization of the magnetic layer906in a desired direction perpendicular to the ABS as indicated by arrow910. This annealing process includes heating the structure to a high temperature while applying a magnetic field. The capping layer908protects the underlying layers906,904during this high temperature annealing.

With reference now toFIG. 10, an AFM defining mask structure1002is formed over the layers902,904,906,908. The mask1002can include a photolithographically patterned and developed photoresist and may include other layers as well, such as CMP stop layer such as carbon, one or more hard mask layers, a bottom anti-reflective coating release layer, image transfer layer, etc. A reactive ion etching can be performed to transfer the image of the photoresist mask onto these under-lying layers.

After the mask1002has been formed, an ion milling process can be performed to remove portions of the layers902,904,906,908that are not protected by the mask1002. As can be seen inFIG. 11, the mask1002has a front edge1004that defines a front edge1006of the AFM layer904. The mask1002can be formed to define various AFM shapes. For example,FIG. 12shows a top down view as seen from line12-12ofFIG. 11. InFIG. 12it can be seen that the mask1002can be formed with a rectangular shape having the front edge1004located at a desired distance from the AFM plane. The mask1002could also be constructed as a bent “U” shape as shown inFIG. 32. In this case the mask1002can be constructed to have side portions that extend beyond the ABS plane.

With reference now toFIG. 13, a magnetic material1302such as NiFe, CoFe or alloys thereof is deposited over the shield802and mask1002. This magnetic material is a magnetic fill layer that will effectively become a part of the leading magnetic shield802with the AFM904being embedded therein as will be seen. The material of the layer1302is chosen so as to provide optimal magnetic moment to avoid magnetic saturation. Optionally, and not shown, a glancing milling can be performed to remove side portions of the layer1302before depositing a capping layer1304. Then, the capping layer1304is deposited over the magnetic material1302. The capping layer1304can be constructed of one or more of Ta and/or Ru, and while it can be constructed of the same material as the capping layer908, it is preferably deposited thicker than the layer908for reasons that will become apparent below. The layer1304is deposited at least to the level of the layer908.

After the layers1302,1304have been deposited a mask liftoff process is performed leaving as structure as shown inFIG. 14. Alternatively, a layer of material that is resistant to chemical mechanical polishing can be deposited such as carbon or diamond like carbon, followed by a mask liftoff process and chemical mechanical polishing (CMP). A reactive ion etching can then be performed to remove the remaining CMP stop layer (e.g. carbon or diamond like carbon). These processes can be adjusted so that layer1304has a desired thickness to provide optimal magnetic spacing between the shield802and later the pinned layer structure, as will be seen. A sputter etching or glancing angle milling can be performed to remove any remaining fencing of materials and to adjust the thickness of the layer1304. InFIG. 15it can be seen that, because the layer1304was deposited thicker than the capping layer908(FIG. 14) the capping layer1304remains even though the capping layer908has been removed during the sputter etching, which can be performed in a deposition tool expose layer906before further deposition of sensor layer as discussed below.

After the above processes have been performed, the structure is placed back into a deposition tool for further deposition of sensor layers. With reference toFIG. 16, the remaining sensor layers1602are deposited over the layers1304,906. A second portion of the first pinned layer1604is deposited over the magnetic layer906so that it is in direct contact and “stitched to” the magnetic layer906. As will be recalled, the previously performed annealing process pinned the magnetization of the layer906in a desired direction perpendicular to the ABS. This pinned magnetization carries through the above applied magnetic layer1604so that both layers906and1604have their magnetizations pinned in the same desired direction perpendicular to the ABS plane. A second annealing process is then performed to set the magnetization of the layer1604. The magnetic layer906, which was previously annealed, will, therefore, be annealed twice.

After the layer906is deposited, an anti-parallel coupling layer1606such as Ru is deposited over the layer1604. A second magnetic pinned layer (AP2) such as NiFe or CoFe1608is deposited over the anti-parallel coupling layer1606. A non-magnetic spacer or barrier layer1610is deposited over the second magnetic pinned layer1608. A magnetic free layer1612is deposited over the non-magnetic spacer or barrier layer1610. The magnetic free layer1612can include one or more layers of CoFe, NiFe or other magnetic materials. Finally, a capping layer1614is deposited over the magnetic free layer1612.

With reference now toFIG. 17, a stripe height defining mask1702is formed over the sensor layers1602. The stripe height defining mask1702has a back edge1704that is located a desired distance from the air bearing surface plane (ABS) so as to define a desired sensor stripe height (the stripe height being the length of the sensor as measured from the air bearing surface (ABS)). Again, this mask structure1702can include a photolithographically patterned photoresist and may include other layers such as one or more hard mask layers a CMP stop layer an image transfer layer a bottom anti-reflective coating layer and/or a release layer, all of which are not shown for purposes of clarity. A reactive ion etching can be used to transfer the image of the photolithographically patterned photoresist layer onto one or more of these other mask layers.

An ion milling is then performed to remove portions of the free layer1612that are not protected by the stripe height defining mask1702. While this ion milling may remove the non-magnetic barrier/spacer layer1610it can be terminated before removing the pinned layer1608. Alternatively, the ion milling can be terminated before reaching the barrier/spacer layer1610, and then a treatment with a gas such as N2, O2or O3can be performed to render the remaining portion of the free magnetic layer1612that is not protected by the mask non-magnetic. For this stripe height defining step, the ion milling can stop at the barrier/spacer layer1610, AP2 layer1608, AP1 layer1604, or AFM layer904. If ion milling is stopped at the barrier/spacer1610, AP21608, AP11604, or AFM904the pinned layer structure will not have shape anisotropy. The choice of where to stop ion can be used to strike a balance between shape anisotropy and minimizing etching damage or “knock-on effects”. After the ion milting has been performed, a non-magnetic, electrically insulating fill layer1802is deposited, as shown inFIG. 18. The fill layer1802can be alumina, tantalum oxide, silicon nitride, or a combination of these materials, and is preferably deposited at least to the level of the capping layer1614.

The back edge1704of the mask1702is located such that after the ion milling, the free layer1612has a back edge1804that is located at a desired offset distance (OS) relative to the front edge1006of the AFM layer904. The offset distance (OS) is the difference between the location (as measured from the ABS plane) of the back edge of the free layer1804and front edge of the AFM1006. This offset distance OS is preferably as small as possible while taking into account manufacturing tolerances and variations, such as variations in mask alignment. One way to minimize such variations is to use the same photolithographic tooling for patterning both the AFM defining mask1002(FIG. 10) and the stripe height defining mask1702(FIGS. 17,18).

Then, a mask liftoff and planarization process can be performed, leaving a structure such as shown inFIG. 19. This can include depositing a CMP stop layer such as carbon (not shown), performing a mask liftoff such as a chemical liftoff, performing a chemical mechanical polishing and performing a reactive ion etching (RIE) to remove the remaining CMP stop layer (including the CMP stop layer within the mask structure1702if one was included).FIG. 20shows a top down view of the structure ofFIG. 19. The dashed line denoted904indicates the location of the embedded AFM904beneath the fill layer1802.

With reference toFIG. 21a track-width defining mask2102is formed. The track-width defining mask2102has openings2104and the mask area between these openings2103is configured to define a track-width TW of the sensor. As before, the mask structure can include a photolithographically patterned photoresist layer and may also include other layers as well, such as one or more hard mask layers, an image transfer layer, a bottom anti-reflective coating layer, release layer, CMP stop layer, etc.

After the mask has been formed, an ion milling can be performed to form the sides of the sensor and define the track-width of the sensor. The configuration of the AFM layer can be controlled by the manner in which this ion milling process is performed. If a partial ion milling is performed, the AFM layer can be formed so as to extend from the sides, such as described with reference toFIG. 6. Also, the ion can stop on barrier/spacer layer1610, AP2 layer1608, AP1 layer1604, or at or within AFM layer904. The location at which ion milling stops defines the various sensor designs. For example, if a full ion milling is performed an AFM having sides that are self aligned with the sides of the sensor stack can be formed, such as the sensor described above with reference toFIG. 5. Moreover, a semi-full ion milling can be performed and stopped within the AP1 layer1604to leave AFM layer904intact.

FIGS. 22-26show a process using a partial ion milling, whereasFIGS. 27-29illustrate a full milling process. The decision of whether to use a partial or full ion milling depends on the desired shape of the AFM layer904, for example, whether a rectangular or “U” shape is desired. For a rectangular AFM904, either partial or full ion milling can be performed. For a rectangular AFM904formed by a full ion milling, the ion milling can be extend all of the way through the AFM layer904to give shape anisotropy to AP21608, AP11604in the front end and back end. For a rectangle AFM using partial ion milling, the ion milling can extend through AP21608and AP11604in the front end while stopping at the layer906or the top of AFM904. For a “U” shaped AFM904using full ion milling, etching can extend through the AFM904layer to give shape anisotropy to AP21608, AP11604in the front end and back end. For “U” shape AFM's using partial ion milting, ion milling can be terminated at the harrier/spacer1610or at AP21608to give it shape anisotropy while preserving AP11604and AFM904, or can be terminated at or below AP11604to give AP21608and AP11604a shape anisotropy while preserving AFM904. In short, depending on where etching stops various configuration can be achieved to maximize performance and stability.

FIG. 22shows a cross sectional view of the active sensor area as seen from line22ofFIG. 21,FIG. 23shows a cross sectional view of the extended pinned layer area at the location of the embedded AFM904, as taken from line23-23ofFIG. 21. As shown inFIGS. 22 and 23a partial ion milling is performed to remove material exposed through the openings in the mask2102. The ion milling is terminated before the shield refill1302(FIG. 22) or embedded AFM904(FIG. 23) have been removed. This allows the embedded AFM904to extend beyond the sides of the pinned and free layers.

After this partial ion milling is performed, a thin insulation layer2404such as alumina, Si3N4, Ta2O5, or combinations thereof is deposited by a conformal deposition process such as atomic layer deposition or chemical vapor deposition or ion beam deposition and a magnetic bias layer2402is deposited over the insulation layer2404. A liftoff and planarization process is then performed to remove the mask2102, some of2402layer, and form a flat surface, resulting in a structure as shown inFIGS. 24 and 25, whereFIG. 24shows the active sensor area andFIG. 25shows the extended pinned layer area. As before, the liftoff and planarization can include depositing a CMP stop layer, performing a mask liftoff such as a chemical liftoff, performing a chemical mechanical polishing to form a planar upper surface and performing a quick reactive ion etching to remove the remaining CMP stop layer.

FIGS. 26 and 27show a cross section in the active sensor location and extended pinned layer location for a full ion milling process. As seen inFIG. 26, the ion milling is performed until the shield refill1302has been removed from the area beyond the sides of the sensor. Similarly, as shown inFIG. 27, the ion milling is performed until the AFM layer904is removed as well. This process results in the AFM layer having a width that is self aligned with the sensor stack (similar to the configuration shown inFIG. 5).

With reference now toFIGS. 28 and 29a thin insulation layer2902is deposited by a conformal deposition process such as atomic layer deposition, ion beam deposition, or chemical vapor deposition. Because of the full ion milling, the gap at the side of the sensor stack is deeper than in the partial mill design discussed previously. In order to ensure proper alignment of the bias structure with the free layer1612, a fill layer2904can be deposited. This fill layer2904can be a nonmagnetic, conducting or insulating material such as alumina, NiP, Cr, Ru, Ta, Ta2O5, or combinations thereof and is preferably deposited by a non-conformal deposition process that primarily deposits the material on horizontal surfaces rather than on vertical sides. Then, a magnetic bias layer2906is deposited over the fill layer2904and the thin insulation layer2902. As before, a liftoff and planarization process can be performed to remove the mask2102(FIG. 27), some magnetic bias layer2906and to provide a smooth planar surface. This can include: depositing a CMP stop layer; performing a mask liftoff; performing a mask liftoff; performing a chemical mechanical polishing; and performing a reactive ion etching to remove the CMP stop layer. This results in a structure as shown inFIG. 29.

Then, after either of the above processes has been performed (i.e. full milling or partial milling) another masking process is performed to define the stripe height AFM layer904, and optionally (although not shown) also the width and stripe height of the extended pinned layer1604,1606,1608.FIG. 30is a top down view showing a mask3002formed over the sensor. The mask3002has a back edge3004that defines the back edge of the AFM layer904, and (optionally) the pinned layer structure (e.g. layers1604,1606,1608) bias layer2906. This mask3002also has outer edges that define the outer edges of the bias structure2906. After this mask3002has been formed. An ion milling is performed to remove material not protected by the mask3002. An insulating refill layer (not shown) can be deposited and a liftoff and planarization process can again be performed to remove the mask3002and form a planar upper surface.

It should be pointed out that the above described process, where the stripe height of the free layer is first defined by a first masking and milling process and then the sensor width is later defined by a second masking and milling process results in a sensor wherein the magnetic bias layer extends beyond the back edge of the free layer1612. If design requirements result in a preference for a bias structure that only extends to the same stripe height as the free magnetic layer, the order of operations can be reversed. In this case the track-width would first be defined by a first masking and milling process, and the bias layers would then be deposited. If full ion milling, the magnetic bias layer can consists of a bilayer of lower fill layer2904and upper magnetic bias layer2906as described above. Or, if a partial ion milling is used, the magnetic bias layer can consist only of magnetic bias layer2906. The thickness of the magnetic bias layer can be adjusted so that the second ion milling process defines both the free layer and bias structure materials. Then, later, a second masking and ion milling process can be performed to define both the back edge of the free layer1612and the back edge of the bias structure2906(or2402inFIGS. 24 and 25). In this case the back edge of the bias structure would be self aligned with the back edge of the free layer.

FIG. 31shows a cross sectional view of a plane parallel with the air bearing surface in the active region of the sensor. The bias structure2906(or2402ofFIG. 24) can be a hard magnetic bias structure (constructed of a magnetic material having a high magnetic coercivity) or could be a soft magnetic bias structure (constructed of a material having a low magnetic coercivity). In one embodiment shown inFIG. 31, the bias structure2906is a soft magnetic material such as NiFe, NiFeCr, CoFe or a combination thereof. An upper magnetic shield3108is formed over the sensor. A layer of antiferromagnetic material3104is deposited over the sensor and exchange coupled with a layer of magnetic material3102. The exchange coupling between the AFM layer3104and the magnetic material3102can be used to align the magnetization of the magnetic layer3102in a desired direction parallel with the ABS. The magnetic material3102is magnetically coupled with the soft bias structure2906in such a manner as to set the magnetization of the bias layers2906. A non-magnetic decoupling layer3106can be provided between the AFM layer3104and the upper shield3108to prevent the shield from being magnetically pinned.