Magnetic recording head with a side shield structure for controlling side reading of thin film read sensor

Side shield structures magnetically shielding a read sensor to block side reading of tracks on a magnetic media. The read heads include bottom and top magnetic shield layers, a read sensor or magnetically sensitive element between the bottom and top magnetic shield layers, and a side shield assembly formed of magnetically shielding material positioned between the bottom and top magnetic shield layers and adjacent at least a portion of the read sensor. In current-in-plane embodiments, the side shield assembly includes a pair of side shields of magnetically shielding material adjacent a lower portion of the read sensor formed on a lower read gap. In current-perpendicular-to-plane embodiments, the side shield assembly includes a pair of side shields extending from the bottom magnetic shield adjacent lower sides of the read sensor and/or a pair of side shields extending from the top magnetic shield adjacent upper sides of the read sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of magnetic read/write heads and magnetic data storage, and more particularly, to a shield structure for a shielding a read sensor in the lateral or cross-track direction to reduce side reading.

2. Relevant Background

Data is stored on magnetic media by writing on the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular area on the magnetic media. The state of the magnetic moment is later read, using a read head, to retrieve the stored information. Data density is determined by the amount of data stored on an area of magnetic media and depends on how much area must be allocated to each bit. Data on magnetic media is often stored in a line or track. Magnetic media often have multiple tracks. In the case of disks, the tracks are nested annular rings with more bits per track and more tracks per disk increasing data density. Data density or areal density, therefore, is determined by both the bit length and by the width of the bit. To decrease bit size, head size is decreased by fabricating thin film read and write heads.

Ongoing, important goals of researchers in magnetic recording technology include producing disk drive read heads that achieve strong signals, providing accurate readback of those signals, minimizing noise interference, and providing very high areal density while controlling manufacturing costs. Unfortunately, some of these goals directly conflict with one another. For example, to achieve ever-higher areal densities, track widths on a disk become smaller necessitating that the components used to read and write data also become smaller, which makes manufacturing more difficult and expensive.

High density recording, such as over 100 Gbit/in2, requires a highly sensitive read head. At higher densities, resistance changes in the head originating from the giant magnetoresistive (GMR) effect are reduced based on the progressively smaller dimensions of the length of the read head. The GMR effect (as well as the MR effect) is the measure of changes in electrical resistance of magnetically soft material, with the GMR effect found specifically in thin film materials systems. In current-in-plane (CIP) read heads, electrical current flows between contacts parallel to the disk or media surface through a GMR element or a read sensor with changes in resistance detected by voltage changes (i.e., readback voltage or output signal). More sensitive read heads have current flows through the films or GMR elements perpendicular (CPP) to the long axis of the structure and normal to the disk or media surface. The sensitivity of the CPP read heads has recently been further enhanced by building CPP read head structures that utilize tunneling magnetoresistance (TMR) concepts in which electrons “tunnel” through very thin insulators based on the magnetization of layers above and below the insulator.

One problem associated with using CIP and CPP read heads is directly related to reduced track widths and head size. Side reading occurs when a read sensor receives noise or stray signals from tracks adjacent the track being read by the read sensor and has become a bigger problem as the tracks have been placed closer together. Traditional head design that uses a permanent magnet abutted junction is typically adequate for larger track widths but as the track widths decrease the magnitude of the output signal or readback voltage weakens while at the same time the unwanted signals from adjacent data tracks yields more and more severe interference. The increased side reading of the read sensor results in degraded read data integrity. Achieving a high recording density requires a narrow head track width while maintaining the readback voltage output. Presently, the magnetic read width decreases have not scaled linearly with reductions to very narrow track widths (such more than 50,000 tracks per inch (TPI)). For example, recent studies have shown an almost 30 percent reduction in physical read width from 0.16 micrometers to 0.11 micrometers while magnetic widths have only changed by a small fraction of this amount. Prior efforts to shield the read sensor, such as in the track direction, have not been entirely successful and have even caused a sharpening of the readback voltage waveform (as measured by PW50 which is a pulse width measurement made at a 50 percent voltage level of the readback pulse), while the goal is to reduce the pulse width measurement to provide a read head able to read narrow pulses having a minimum interaction with each other.

Hence, there remains a need for a read head capable of effectively reading narrower track widths or having a narrower read back width (MRW). Such a read head preferably would provide improved control over noise from adjacent tracks including effects of side reading and would produce reduced PW50 measurements and would be suitable for manufacture using existing technologies including existing lithography processes.

SUMMARY OF THE INVENTION

The present invention addresses the above problems by providing side shield assemblies or structures for providing magnetic shielding of a read sensor to at least partially block side reading of tracks on a magnetic media adjacent the track currently under the read sensor. Briefly, the read heads of the invention include bottom and top magnetic shield layers, a read sensor or magnetically sensitive element between the bottom and top magnetic shield layers, and a side shield assembly formed of magnetically shielding material positioned between the bottom and top magnetic shield layers and adjacent at least a portion of the read sensor.

In current-in-plane (CIP) embodiments, the read head includes bottom and top read gap layers formed between the read sensor and the bottom and top magnetic shield layers. The read head further includes a pair of electrical contacts between the read gap layers and contacting first and second sides of the read sensor for conducting electricity through the read sensor and typically, a pair of magnetic bias elements between the read gap layers adjacent the first and second sides of the read sensor formed of hard magnetic material. The side shield assembly includes a first layer of magnetically shielding material deposited on the bottom read gap layer adjacent the first side of the read sensor and a second layer of magnetically shielding material deposited on the bottom read gap layer adjacent the second side of the read sensor.

In current-perpendicular-to-plane (CPP) embodiments, the side shield assembly typically includes a first side shield and a second side shield extending a distance, e.g., a shielding distance, from the bottom magnetic shield layer. The first and second side shields are often formed integrally with the bottom magnetic shield layer of the same soft magnetic alloy and are spaced apart to provide a gap for receiving the read sensor between the side shields. The read head further includes a bottom electrical contact layer deposited over the side shields and the bottom shield layer, a pair of read gap elements adjacent the sides of the read sensor over the bottom electrical contact layer, and a top electrical contact layer formed over the read gap elements and the read sensor. In some embodiments, additional side shielding is provided by third and fourth side shield elements that extend toward the first and second side shields from the top magnetic shield layer and adjacent the sides of the read sensor (or in some cases, the third and fourth side shields are provided without the first and second side shields). A pair of magnetic bias elements may be provided adjacent the sides of the read sensor and sandwiched between the bottom electrical contact layer and the read gap elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed toward shield structure designs for reducing side reading in magnetic recording heads, toward read heads including side shielding assemblies, toward methods of making a side-shielded read head, and toward merged read/write heads and storage systems that incorporate the side shield designs. The read heads of the present invention include a magnetic shield structure or assembly that surrounds a read sensor in the lateral or cross-track direction. The inclusion of the side shield structures significantly reduces side reading by the read sensor which allows narrower read back width or the width of the read sensor (MRw) and reduces the readback pulse waveform as measured by PW50.

Significantly, the side shield structures of the present invention can be used with a variety of read head configurations (which can then be included with merged read/write heads) and is not limited to a specific read head design or read sensor type. In the following description, for example, side shield structures are described for use with current-in-plane (CIP) GMR read heads as well as with current-perpendicular-to-plane (CPP) GMR read heads (and more particularly, for CPP GMR read heads with tunnel magnetoresistive (TMR) structures and CPP GMR read heads with longitudinal hard bias). A number of side shield structures or assemblies are described for CPP GMR read heads and others will become apparent to those skilled in the arts once these embodiments are understood. Additionally, the read sensor used in each of the examples is the same, i.e., a bottom type spin valve GMR read element, but the read sensor utilized may be different and is not considered limiting of the invention. For example, read elements that are more complex with more or different material layers may readily be used with the side shield structures of the present invention. The important aspect is that the side shield structures are included in the read head to improve control over side reading of the selected read sensor, not the specific configuration of the read sensor or the materials included in the read sensor.

FIG. 1shows a typical disk type magnetic data storage and retrieval apparatus100in which embodiments of the writer of the invention may be incorporated. The read head with side shield assembly of the present invention is located within a merged read/write head assembly120that rides above a magnetic storage media110, depicted inFIG. 1as a rotatable hard disk type storage media. The hard disk110is coupled to a motor140via a spindle150to provide rotation of the disk110relative to the head assembly120. An actuating device130may be used to position the head assembly120above the surface of the media110to read and write data in the form of magnetic bits from and to the media110. Of course, the data storage and retrieval apparatus100typically has several hard disks110and several corresponding head assemblies120, not shown here for ease of description. The writer portion of the read/write head assembly120is not limiting to the invention and its configuration may vary significantly to practice the invention as long as the writer portion is combined with a side-shielded read head or reader portion as described below. Further, in some cases, a read head may be provided without a writer and the apparatus100would simply substitute such a read head constructed according to the invention for the read/write head assembly120.

FIG. 2illustrates a conventional design (i.e., a design without a side-shield structure of the invention) for a CIP GMR read head200. The head200is shown in cross section as seen from the air bearing surface between the head200and a recording medium. As shown, the read head200includes a bottom (or first) magnetic shield layer204formed of a soft magnetic alloy, such as a NiFe alloy, a CoZrNb alloy, CoNiFe alloy, and the like, which is generally formed on a ceramic substrate (not shown), such as alumina. A bottom (or first) read gap layer or film208as an insulating layer is deposited over the bottom shield layer204and is typically formed of alumina, aluminum nitride, or materials with similar insulating properties. A read sensor220is built on the read gap film208, and although a number of GMR and MR sensor element configurations can be used in the invention, is shown to include a four layer element. The four layers may provide a spin valve sensor220and include a pinning layer222(such as an anti-ferromagnet such as PdPtMn), a pinned layer224(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer226(such as a copper layer), and a free layer228(such as a magnetic film of NiFe, CoFe, CoFeB, or the like).

A top (or second) read gap layer or film250of soft magnetic material is deposited over the read sensor220and is typically formed of the same material chosen for the bottom read gap layer208, i.e., alumina, alumina nitride, and the like. A top (or second) magnetic shield layer260is formed over the top read gap250with a soft magnetic alloy the same or similar to that of the bottom magnetic shield layer204. Sandwiching the read sensor220are layers of non-magnetic underlayer material210,212upon which is deposited domain control hard magnets230,232, such as CoCrPt films to create a hard bias and stabilize the domain structure in the free layer222. Finally, a pair of electrical leads or contacts240,242are placed on the bias layers230,232and electrically connected to the sensor element220to allow current to pass through the sensor and changes in resistance to be detected. The side read gap or effective side gap is shown by arrow270. The side gap270in the conventional read head200is generally the distance between the first and second (or bottom and top) magnetic shields204,260, and it is through this gap270(typically, on both sides of the head200) that side reading from adjacent tracks on a magnetic media occurs and interferes with effective reading of the track under the read sensor220.

To reduce side reading, a CIP read head300of the invention shown inFIG. 3is provided with a side shielding structure that reduces the effective read gap (as shown by arrow370) such that noise from side reading of adjacent tracks is significantly reduced. According to the invention, the effective side gap370is a reduced portion of the space between the down track magnetic shields304,360and is measured form a pair of intermediate or side shields310,312that replace a portion of the non-magnetic underlayers210,212of the conventional read head200.

As shown, the read head300includes bottom and top magnetic shield layers304,360with adjacent bottom and top read gap layers308,350. A read sensor320is provided between the read gap layers308,350and may take a form similar to that of read sensor220having a pinning layer322(such as an anti-ferromagnet such as PdPtMn), a pinned layer324(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer326(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer328(such as a magnetic film of NiFe, CoFe, CoFeB, or the like). Again, it should be noted that the configuration of the read sensor320may vary to practice the invention as side shielding according to the invention may be provided for nearly any magnetic read element design with beneficial effects.

The side shield structure or assembly of read head300includes first and second side shields310,312formed on the bottom (or first) read gap layer308adjacent to the read sensor320. The side shields310,312are fabricated of soft magnetic material, often of the same material used for bottom and top shields304,360but this is not necessary, such as a soft magnetic alloy, e.g., a NiFe alloy, a CoZrNb alloy, CoNiFe alloy, and the like. The thickness of this layer may vary and is typically selected to be as large as practical to maximize side shielding while being compatible with the formation of the hard bias or magnet layers330,332and electrical leads or contacts340,342. For example, the side shields310,312may be deposited at a thickness of previously used but not replaced non-magnetic underlayers (such as layers210,212of head200). Also, side spacers311,313formed of a non-magnetic, metallic material are typically included adjacent the read sensor320to isolate the side shields310,312from the pinning layer322or more generally, from the read sensor320. The thickness of the side spacers311,313may be about that of the side shields310,312(as shown) or may be that of the side shields310,312combined with the hard bias layers330,332.

Further, to facilitate fabrication, the side shields310,312may be formed on the planar first read gap layer308to have a similar or the same thickness as the first layer of the read element320(e.g., the pinning layer322in the element320shown inFIG. 3) and further, to be coplanar with the top surface of this first layer. Alternatively, the side shields310,312may be fabricated independently of the read sensor320(or be formed to coplanar with different ones of the layers of the element320to provide a desired shield thickness) to provide a desired side shield thickness adjacent the sides of the read sensor320. In this case, the shields310,312are planar devices arranged normal to the ABS with a thickness providing the shielding of the read sensor320from adjacent tracks.

FIG. 4illustrates a conventionally designed CPP read head400with a TMR structure or CPP GMR structure. As with CIP head200, the CPP read head400includes a bottom (or first) shield layer404and a top shield layer408fabricated of a material, such as a soft magnetic alloy, e.g., a NiFe alloy, a CoZrNb alloy, and the like, for providing magnetic shielding inline with a track being read by the head400. A read sensor420is sandwiched between the shields404,408with electrical contact or lead layers410,412provided on each shield404,408to direct electricity through the sensor (i.e., perpendicular to the plane of the sensor layers). The read sensor or element420is again shown to be a four-layer element having a pinning layer422(such as an anti-ferromagnet such as PdPtMn), a pinned layer424(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer426(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer428(such as a magnetic film of NiFe, CoFe, CoFeB, or the like). Adjacent the read sensor420is a pair of read gap elements or layers414,418fabricated of an electrically insulating material such as alumina, alumina nitride, or other dielectric material and defining a read gap on each side of the read sensor420. In the head400, this read gap or effective side gap is basically the distance between the two shields404,408that provide a space or path for side reading of tracks adjacent the track underneath the read sensor420.

FIGS. 5-8illustrate a number of embodiments of CPP read heads in which side shielding structures are provided to reduce the size of the effective side gaps while still including adequate read gap materials. Referring first toFIG. 5, a CPP read head500is provides that includes a bottom and a top shield504,508, a pair of electrical contact or lead layers510,512, and a read sensor520including a pinning layer522(such as an anti-ferromagnet such as PdPtMn), a pinned layer524(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer526(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer528(such as a magnetic film of NiFe, CoFe, CoFeB, or the like). Read gap elements514,518are provided but, significantly, the effect side gap defined in part by these elements514,518is reduced compared with the convention head400because of the addition of side shield elements505,506(or bottom shielding extensions) adjacent a bottom portion of the read sensor520.

As shown, the side shield elements505,506are formed as an integral part of the bottom shield504and typically are formed of the same magnetically insulating material, such as a soft magnetic alloy, e.g., a NiFe alloy, a CoZrNb alloy, CoNiFe alloy, and the like, to provide shielding from noise from tracks adjacent to the track currently being read. In other embodiments (not shown), the side shield elements505,506are formed of a differing material that is deposited on the bottom shield504after its top surface is planarized but prior to depositing the electrical lead layer510. The thickness of the side shield elements determine the amount of shielding provided and is shown to be about the thickness of the pinning layer522of the read sensor520although this is not a limitation as the thickness may be greater as long as proper insulation of the leads510,512is maintained or may be less and still achieve an amount of useful reduction in side reading by the read sensor520.

FIG. 6illustrates another CPP read head600similar to that ofFIG. 5but providing upper and lower side shield elements to further reduce the size of the effective read gaps and/or to provide shielding from side reading at the upper and the lower ends of the read sensor (i.e., portions adjacent the first and second magnetic shields). The head600includes bottom and top magnetic shields604,607; bottom and top leads610,612; a read sensor620with a pinning layer622(such as an anti-ferromagnet such as PdPtMn), a pinned624(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer626(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer628(such as a magnetic film of NiFe, CoFe, CoFeB, or the like); and read gap elements614,618that define the effective side gaps adjacent the read sensor620.

Side shielding is provided by the inclusion of bottom side shields605,606(or bottom shield extensions) positioned adjacent a lower portion of the read sensor620and the inclusion of top side shields608,609(or top shield extensions) positioned adjacent an upper portion of the read sensor620. Again, the side shields605,606,608, and609are typically formed from the same material as used for the shield layers604,607or another material useful for providing magnetic shielding. The thicknesses of the side shields605,606,608,609may vary while providing adequate thickness of the read gap elements614,618such as by having the thicknesses be equal, having the bottom side shields605,606have thicknesses greater than the top side shields608,609, of having the top side shields608,609being thicker than the bottom side shields605,606. Preferably, the top side shields608,609and the lead612is spaced apart, such as at an angle as shown, from the side of the read sensor620such that a portion of the read gap elements614,618abuts the sides of the read sensor620.

FIG. 7illustrates yet another embodiment of a CPP read head700in which side shielding is provided solely by upper side shields or extensions from the top (or second shield layer). The head700includes bottom and top (or first and second) magnetic shield layers704,707, electrical contacts710,712, read gap elements714,718defining read gaps or side gaps and a read sensor720sandwiched between the contacts710,712and including a pinning layer722(such as an anti-ferromagnet such as PdPtMn), a pinned layer724(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer726(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer728(such as a magnetic film of NiFe, CoFe, CoFeB, or the like). The side shield assembly of head700includes side shields708and709which may be formed separately from the shield707or formed as extensions of the shield707(such as by depositing in the same process on lead layer712) and is formed of a magnetic shielding material, such as a soft magnetic alloy, e.g., a NiFe alloy, a CoZrNb alloy, CoNiFe alloy, and the like. Again, the upper or top contact layer712is spaced apart (such as at an angle or bevel as shown) from the sides of the read sensor720so that the adjacent side shields708,709is also spaced apart from the read sensor720. The thickness of the side shields708,709(as measured normal to the shield layer707) is preferably thick as practical to provide maximum side shielding while allowing a desired read gap insulative layer714,718thickness. In a four element read sensor720as shown, the thickness may be about equal to or greater than the top three layers of the read sensor720(i.e., the pinned layer724, the interlayer726, and the free layer728). Of course, the thickness may be less and still provide some beneficial shielding from side reading.

In some cases, a hard bias layer may be provided within a CPP read head, andFIG. 8illustrates one embodiment of a CPP read head800using side shielding and including a hard bias. As shown, the head800includes bottom and top magnetic shield layers704,708and electrical contacts710,712connected to a read sensor720. The read sensor720includes a pinning layer722(such as an anti-ferromagnet such as PdPtMn), a pinned layer724(such as a magnetic film of NiFe, CoFe, CoFeB, or the like), an interlayer726(such as a copper layer for CPP GMR embodiments and alumina oxide for TMR embodiments), and a free layer728(such as a magnetic film of NiFe, CoFe, CoFeB, or the like). A pair of hard magnetic or bias elements714and718are built on the bottom contact710and abut the sides of the lower portion of the read sensor720. Read gap elements740,746are positioned on top of the bias elements714,718and abut the top portion of the read sensor720. Generally, it is preferable to include side spacers715,719formed of a non-magnetic, metallic material (such as alumina) adjacent the read sensor720to isolate the sensor720from the read gap elements740,746and the hard bias layers740,746.

The effective side gap is defined in part by the thickness of the bias elements714,718and the thickness of the read gap elements740,746. Side shielding is provided by the inclusion of bottom side shield elements705and706which may be formed integral with the bottom shield704or deposited on the bottom shield704. The side shield elements705,706are formed of a magnetically shielding material such as a soft magnetic alloy, e.g., a NiFe alloy, a CoZrNb alloy, CoNiFe alloy, and the like. The side shield elements705,706typically contact the lead layer710that abuts the lower portion of the read sensor720to provide a thickness of shielding (e.g., about the thickness of the pinning layer722or less (as shown)).

While only a read head is shown in FIGS.3and5-8, it will be understood by those skilled in the art that the read heads of the invention can readily be incorporated within a merged read/write head (such as head120of FIG.1). In such merged heads, a writer is built upon the top shield of read sensor which acts as the first pole (e.g., P1) of the writer. The specific configuration of the writer is not important to the side shielding features of the invention used for the described read sensors and can be any of a number of writer configurations well known in the art or yet to be created.

The CIP read head300is fabricated generally by providing in conventional fashion the bottom shield layer304and the bottom read gap layer308. The spin valve read sensor320layers are then sequentially deposited (such as with vacuum deposition) and then a bi-layer photoresist liftoff pattern or mushroom is produced over the deposited stack layers. Ion beam etching or other removal techniques are used to remove deposited stack layer material except for under the photoresist pattern or mask. Material deposition continues with the non-magnetic metallic side spacers311,313and the side shields310,312followed by the hard bias material for layers332,330, and contacts340,342. Material lift-off is then performed on the head300followed by the formation of the top read gap layer350and magnetic shield360using conventional processing techniques.

Fabrication of the head500ofFIG. 5includes forming a bottom shield504with conventional techniques and then depositing material for bottom side shields505,506. A bi-layer photoresist pattern is formed followed by etching to form a gap for read sensor520and then lift-off of the photoresist material from the shields505,506. The bottom lead510is then deposited and then the read sensor502stack is formed as discussed with reference toFIG. 3including a second bi-layer photoresist pattern formation and etching. The read gap elements514,518are then deposited and the photoresist is lifted off. The top electrode512and the top shield are then formed using conventional deposition and processing techniques.

Fabrication of the head600ofFIG. 6proceeds similar to the head500except that after the read gap elements614,618are deposited and lift off occurs, the top electrode612is deposited followed by another photoresist patterning step. The top side shields608,609are then deposited and then lift off is completed. The top shield607is then deposited over the top side shields608,609and the top electrode612. The head700ofFIG. 7is formed in a manner similar to that of the head600with the omission of the steps required to build the bottom side shields605,606. The head800ofFIG. 8is formed in a manner similar to the head500ofFIG. 5with the added steps of depositing or forming of the side spacers715,719prior to the deposition of the read gap elements714,718and the depositing of the hard bias layers740,746over the read gap elements714,718.

Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed. For example, the specific materials and thicknesses of the layers described above can be varied significantly to practice the invention as will be readily appreciated by those skilled in the art.