Method for making coplanar write head pole tips

A method and apparatus for providing a write head having well-defined, precise write head pole tips. A coplanar write head pole tip processing method provides a thin-film magnetic write head pole tip layer and defines first and second pole tips from the pole tip layer. When the pole tips are provided on a write head, a write gap can be defined using ion milling, E-beam lithography, FAB or can be deposited. The write head pole tips can be used in conjunction with read heads by merging a read head with a write head or a read head can be bonded to a write head in a piggybacked fashion.

FIELD OF THE INVENTION

This invention relates in general to magnetic recording systems, and more particularly to a method and apparatus for providing a write head having well-defined, precise write head pole tips.

DESCRIPTION OF RELATED ART

Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modem personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.

As disk drive technology progresses, more data is compressed into smaller areas. Increasing data density is dependent upon read/write heads fabricated with smaller geometries capable of magnetizing or sensing the magnetization of correspondingly smaller areas on the magnetic disk. The advance in magnetic head technology has led to heads fabricated using processes similar to those used in the manufacture of semiconductor devices.

A typical disk drive is comprised of a magnetic recording medium in the form of a disk for storing information, and a magnetic read/write head for reading or writing information on the disk. The disk rotates on a spindle controlled by a drive motor and the magnetic read/write head is attached to a slider supported above the disk by an actuator arm. When the disk rotates at high speed a cushion of moving air is formed lifting the air bearing surface (ABS) of the magnetic read/write head above the surface of the disk.

The read portion of the head is typically formed using a magnetoresistive (MR) element. This element is a layered structure with one or more layers of material exhibiting the magnetoresistive effect. The resistance of a magnetoresistive element changes when the element is in the presence of a magnetic field. Data bits are stored on the disk as small, magnetized region on the disk. As the disk passes by beneath the surface of the magnetoresistive material in the read head, the resistance of the material changes and this change is sensed by the disk drive control circuitry.

The write portion of a read/write head is typically fabricated using a coil embedded in an insulator between a top and bottom magnetic layer. The magnetic layers are arranged as a magnetic circuit, with pole tips forming a magnetic gap at the air bearing surface of the head. When a data bit is to be written to the disk, the disk drive circuitry sends current through the coil creating a magnetic flux. The magnetic layers provide a path for the flux and a magnetic field generated at the pole tips magnetizes a small portion of the magnetic disk, thereby storing a data bit on the disk.

A thin film write head comprises two pole pieces, a top pole piece P1and a bottom pole piece P2. A write head generally has two regions, denoted a pole tip region and a back region. The pole pieces are formed from thin magnetic material films and converge in the pole tip region at a magnetic recording gap, known as the zero throat level, and in the back region at a back gap. The zero throat level delineates the pole tip region and back region. A write head also has two pole tips, P1T and P2T, associated with and extensions of P1and P2respectively. The pole tips, which are relatively defined in their shape and size in contrast to the pole pieces, are separated by a thin layer of insulation material such as alumina, referred to as a gap. As a magnetic disk is spinning beneath a write head, the P2pole tip trails the P1pole tip and is therefore the last to induce flux on the disk. Thus, the P2T dimension predominantly defines the write track width of the write head, and is generally considered an important feature. The write track width, P2B, is especially important because it limits the areal density of a magnetic disk. A narrower track width translates to greater tracks per inch (TP1) written on the disk, which in turn translates to greater areal density.

Processes for fabricating the write portion of a read/write head typically include steps that define the width of pole tips to a large degree of inaccuracy, resulting in large yield losses. This problem will be worse for the next generation of write heads since the sigma on the P2width (P2B) does not scale with width itself. Sigma values, or the standard deviation of the transducer elements, represent greater precision in manufacturing. Additionally, the processes used limit the capability of head design because P1and P2poles are not symmetric, limiting the control of the PIP saturation. Furthermore, higher notch depth limits the maximum height of P2. Slight differences between the P1notch and P2B cause excessive erase bands. Moreover, flare control is not well-defined due to shape variations of photo-resist along the plated direction.

It can be seen that there is a need for a method and apparatus for providing a write head having well-defined, precise write head pole tips.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for providing a write head having well-defined, precise write head pole tips.

The present invention solves the above-described problems by defining first and second pole tips from a pole tip layer. When the pole tips are provided on a write head, a write gap can be defined using ion milling, E-beam lithography, FAB or can be deposited. The write head pole tips can be used in conjunction with read heads by merging a read head with a write head or a read head can be bonded to a write head in a piggybacked fashion.

A method in accordance with an embodiment of the present invention includes forming a thin-film magnetic write head pole tip layer, the write head pole tip layer having a thickness defining a track width and defining a first pole tip and a second pole tip from the pole tip layer.

In another embodiment of the present invention, a method for making a coplanar magnetic write head is provided. This method includes magnetically coupling a thin-film magnetic write head pole tip layer to a yoke, the write head pole tip layer having a thickness defining a track width, defining a first and second pole tip from the pole tip layer and defining a write gap between the first and second pole tip formed from the pole tip layer.

In another embodiment of the present invention, another method for making a coplanar magnetic write head is provided. This method includes forming a yoke for a write head, depositing a pole tip layer on the yoke, the pole tip layer having a thickness defining a track width, defining a first and second pole tip and a write gap between the first and second pole tip from the pole tip layer and forming a read head having a read gap, wherein the forming the read head further comprises forming the read head with the read gap perpendicular to the fist and second pole tips.

In another embodiment of the present invention, another method for making a coplanar magnetic write head is provided. This method includes providing on a planar wafer surface a plurality of write heads including a coil and a yoke having an end disposed at a side of the write head, slicing the planar wafer surface perpendicular to an air bearing surface exposing the yoke of each of the plurality of write heads, forming a pole tip layer along the side of the wafer surface having the exposed yokes, the pole tip layer having a thickness defining a track width, defining from the pole tip layer a first and second pole tip for each of the plurality of write heads and defining a write gap between each of the first and second pole tips for each of the plurality of write heads.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and apparatus for providing a write head having well-defined, precise write head pole tips. According to an embodiment of the present invention, first and second pole tips are defined from a pole tip layer. When the pole tips are provided on a write head, a write gap can be defined using ion milling or E-beam lithography.

FIG. 1illustrates a storage system30according to the present invention. InFIG. 1, a transducer40is under control of an actuator48. The actuator48controls the position of the transducer40. The transducer40writes and reads data on magnetic media34rotated by a spindle32. A transducer40is mounted on a slider42that is supported by a suspension44and actuator arm46. The suspension44and actuator arm46positions the slider42so that the magnetic head40is in a transducing relationship with a surface of the magnetic disk34.

FIG. 2illustrates one particular embodiment of a storage system30according to the present invention. InFIG. 2, a hard disk drive30is shown. The drive30includes a spindle32that supports and rotates magnetic disks34. A motor36, mounted on a frame54in a housing55, which is controlled by a motor controller38, rotates the spindle32. A combined read and write magnetic head is mounted on a slider42that is supported by a suspension44and actuator arm46. Processing circuitry50exchanges signals, representing such information, with the head, provides motor drive signals for rotating the magnetic disks34, and provides control signals for moving the slider to various tracks. The plurality of disks34, sliders42and suspensions44may be employed in a large capacity direct access storage device (DASD).

When the motor36rotates the disks34the slider42is supported on a thin cushion of air (air bearing) between the surface of the disk34and the air bearing surface (ABS)48. The magnetic head may then be employed for writing information to multiple circular tracks on the surface of the disk34, as well as for reading information therefrom.

FIG. 3illustrates a storage system300. InFIG. 3, a transducer310is under control of an actuator320. The actuator320controls the position of the transducer310. The transducer310writes and reads data on magnetic media330. The read/write signals are passed to a data channel340. A signal processor system350controls the actuator320and processes the signals of the data channel340. In addition, a media translator360is controlled by the signal processor system350to cause the magnetic media330to move relative to the transducer310. Nevertheless, the present invention is not meant to be limited to a particular type of storage system300or to the type of media330used in the storage system300.

FIG. 4is an isometric illustration of a suspension system400for supporting a slider42having a magnetic head mounted thereto. InFIG. 4first and second solder connections104and116connect leads from the sensor40to leads122and128on the suspension44and third and fourth solder connections106and118connect the coil to leads123and129on the suspension44. However, the particular locations of connections may vary depending on head design.

FIGS. 5-7illustrate a magnetic head according to the prior art.FIGS. 5 and 6are side cross-sectional elevation view of a magnetic head540and an ABS view of the magnetic head540, respectively. The magnetic head540includes a write head portion570and a read head portion572. The read head portion572includes a sensor574.FIG. 6is an ABS view of the magnetic head ofFIG. 5. The sensor574is sandwiched between first and second gap layers576and578, and the gap layers are sandwiched between first and second shield layers580and582. In a piggyback head as shown inFIG. 5, the second shield layer (S2)582and the first pole piece (P1)592are separate layers. The first and second shield layers580and582protect the MR sensor element574from adjacent magnetic fields. More conventionally, the second shield582also functions as the first pole (P1)592of the write element, giving rise to the term “merged MR head.”

In response to external magnetic fields, the resistance of the sensor574changes. A sense current is conducted through the sensor causes these resistance changes to be manifested as voltage changes. These voltage changes are then processed as readback signals by the signal processing system350shown inFIG. 3.

The write head portion of the magnetic head includes a coil layer584sandwiched between first and second insulation layers586and588. A third insulation layer590may be employed for planarizing the head to eliminate ripples in the second insulation layer caused by the coil layer584. The first, second and third insulation layers are referred to in the art as an “insulation stack.” The coil layer584and the first, second and third insulation layers586,588and590are sandwiched between first and second pole piece layers592and594. The first and second pole piece layers592and594are magnetically coupled at a back gap596and have first and second pole tips598and501which are separated by a write gap layer502at the ABS. The first pole piece layer592is separated from the second shield layer582by an insulation layer503.

FIG. 7illustrates a view of the connect leads520,522coupled to the coil584for the write pole piece594. As shown inFIGS. 4-7, first and second solder connections404and406connect leads from the sensor574to leads412and414on the suspension444, and third and fourth solder connections416and418connect leads520and522from the coil584(seeFIG. 7) to leads424and426on the suspension.

However, as described above, processes for fabricating the write pole portions of a read/write head typically involve a large degree of inaccuracy. This problem worsens because the tolerances for the write poles do not scale with reducing pole tip width for higher density recording. Additionally, the write poles are not symmetric and therefore limit the control of the pole tip saturation. Still other disadvantages for prior write head designs were described above.

According to an embodiment of the present invention, as will be described herein below, pole tip width is determined by the thickness of the pole tip layer, which utilizes vacuum deposition techniques that can be well-controlled. Furthermore, as the pole tip width is getting smaller with new generations of hard disk drives, the thickness control scales with the pole tip width. This is due to the fact the vacuum-deposited film uniformity is proportional to the deposited thickness. Furthermore, according to an embodiment of the present invention, the pole tips can be made symmetric, which allows for better control of the erase bands and pole tip over-saturation. Moreover, pole tip shape can be controlled with high precision using well-established techniques such as optical lithography or e-beam lithography in conjunction with ion milling, or focused ion beam. This allows for precise control of the magnetic flux delivered at the disk surface and control of pole tip saturation.

According to an embodiment of the present invention, there are two main approaches for providing a write head having well-defined, precise write head pole tips. However, there may be various embodiments evolving from the two main approaches. The pole tips need to be perpendicular to the plane of the read gap of the sensor. In the first approach the pole tip plane is parallel to the wafer and the read gap of the sensor is rotated perpendicular to the wafer plane. In the second approach, the read head is deposited in-plane of the wafer (similar to prior art), but the pole tips are rotated 90 degrees out of plane.

FIGS. 8a-dillustrate a method800for making coplanar magnetic write head pole tips according to an embodiment of the present invention. InFIG. 8a, a first magnetic write head pole or yoke810is fabricated on a substrate such as a planar wafer surface having a thin-film deposited thereto. The first magnetic write head pole810is electroplated.

InFIG. 8b, the coplanar pole tips830,840are formed by vacuum-depositing magnetic film CoFe, for example, for a pole tip layer adjacent to and magnetically coupled to a yoke and defining pole tips from the pole tip layer. Coplanar pole tips830,840are defined using photolithography. The pole tip gap835may be formed using ion milling, E-beam lithography, or focused ion beam (FIB), for example.

InFIG. 8c, the coil855is defined. InFIG. 8d, the second write pole or yoke850is then formed and electroplated to complete a magnetic circuit for the write head800. The write head track width is defined by the thickness of the defined pole tips PT1830and PT2840. In an alternative embodiment, the process for fabricating write head800is the same as above except that the pole tips PT1830and PT2840can be deposited first and then yoke810can be deposited and magnetically coupled to PT1830. The layers of the write head in either embodiment can be deposited on a planar wafer surface.

FIG. 9aillustrates fabrication of a read head900that can be used in combination with a write head according to an embodiment of the present invention, including the embodiment described inFIGS. 8a-d. To make a functional read and write head using the above described write head, shields970,990of a read head have to form a gap with the plane parallel to the write head write gap835shown inFIGS. 8b-d. In this embodiment, forming a read gap in a plane parallel to the write gap is achieved by rotating the read shields970,990. As a result, conventional shields S1and S2are not deposited. Rather, the sensor film980is deposited using conventional track definition techniques. The defined width of the sensor film980is set to a desired read gap. Ion milling is used to define the sensor, where the milling depth should be at least 0.2 um. Permalloy deposition forms both shield S1970and S2990rather than hard bias deposition. The permalloy layer, NiFe, forms S1970and S2990shields and can be used as electrical leads for the sensor. Additionally, a slight magnetic biasing can be applied to the shields to insure magnetic stability of the sensor. This is done by depositing hard bias on the outer edges of shield1and shield2. The magnetic flux from the bias layer magnetizes the shields and is transmitted to the sensor free layer.FIG. 10shows the removal of the photoresist, depositing of a fill material such as alumina, and formation of pole tips1092,1094.

Other embodiments of read heads can be implemented to make a functional read and write head in accordance with the present invention including a CPP configuration, MTJ or GMR (not shown). In this configuration conformal shields define the read gap. The MTJ or GMR sensor is then deposited and patterned followed by depositing the isolation layer and CMP-aided lift off exposes the top contact. The upper shield is subsequently deposited. The read head and write head are bonded together to form the read/write head.

FIGS. 11a-fillustrates another method for fabricating a read/write head in accordance with embodiments of the invention. The read head is fabricated with read gap co-planar with the wafer. Write head1100is fabricated using methods that include forming a yoke1110and a coil1120on a planar wafer surface,FIGS. 11aand11b. The planar wafer surface, shown in a blown-out view inFIG. 11a, holds multiple write heads. The wafer is processed using an alumina overcoat at connection pads for read and write heads. Note that pole tips have not been defined. After the wafer is finished, it is sliced in the direction perpendicular to the ABS surface so as to expose the legs of yoke1110, seeFIGS. 11b-c. The write heads are sliced into rows of sliders sliders, seeFIG. 11c. In this embodiment, the head1100is located towards the edge of a slider1111, seeFIG. 11c, and the yoke1110is stretched so as to be exposed on the side after slider slicing. A group of the sliced rows are arranged together,FIG. 11d, and planarized using polishing tools. A magnetic CoFe film of the thickness equal to the desired P2B is deposited at this new surface of the joined planarized sliced slider and patterned using lithography to form pole tips PT11130and PT21140and ion milled to define write gap1135as shown inFIG. 11e, for example. Other processes for defining the write gap1135include E-beam lithography, focused ion beam, forming a bottom isolation layer to a desired gap thickness and vacuum depositing a write gap or forming a gap layer. Alignment marks can be defined during wafer build for the above photo step. The process described above can be used for a single slider,FIG. 11e, or can be used in fabricating multiple sliders in a row,FIG. 11c, or multiple sliders in a row glued together,FIG. 11d.

Embodiments of the present invention allow for tight P2B distribution and mean control, symmetric poles P1and P2to improve transition curvature, reduce erase bands, and avoid pole saturation. Defining write head geometries lithographically allows for more precision for components such as P2T, flare angle and throat height. P1A and P2B are identical. Furthermore, a better choice of magnetic materials such as vacuum-deposited materials having better magnetic and corrosion properties is available.

Embodiments of the invention can be applied to longitudinal recording heads and to perpendicular recording heads. The methods taught in the present application have many advantages in making advanced perpendicular recording heads with complex structures. For example, shield-pole can optimize field gradient and orientation, and detached pole tips can eliminate pole tip remnants.

In all embodiments of the instant application, the most critical step is defining the write track width. Because this invention allows one to use thin films, and the write track width can be defined solely by film thickness, the pole tip width can be well defined using photolithography and ion milling. Alternatively, E-beam lithography can be used, or, a FIB can be used to slice the write gap in the deposited film. Additionally, the following process can be used: the PT2(CoFe) is defined using deposition/photolithography/ion milling with the bottom isolation layer of the same thickness of gap; then the gap is vacuum deposited, following by deposition of PT1(CoFe); finally, PT1layer is chemically mechanically polished with the gap layer serving as the stopping layer.