Magnetic write head having a first magnetic pole with a self aligned stepped notch

A magnetic write head and method of manufacture thereof that has a first pole structure having a step notched first pole structure. The step notched structure includes a bottom notched portion that is wider than the second notched portion formed thereover. The upper, or narrower, notched portion has a width that is substantially equal to and self aligned with a second pole structure (P2) formed thereover. The invention may also include first and second wing portions formed in the first pole that are recessed from the ABS and that extend laterally from the first notched portions of the first pole. The formation of the winged portions is assisted by an ion mill resistant bump (alumina bump) formed thereover, which acts as a mask during the ion milling operations that are used to form the first and second notches.

FIELD OF THE INVENTION

The present invention relates to magnetic write heads for magnetic data recording, and more particularly to a magnetic write head having a narrow P2 write pole that is self aligned with a P1 write pole having a steep shoulder for reduced flux leakage.

BACKGROUND OF THE INVENTION

The heart of a computer's long term memory 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.

In recent read head designs a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor, has been employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, hereinafter referred to as a spacer layer, sandwiched between first and second ferromagnetic layers, hereinafter referred to as a pinned layer and a free layer. First and second leads are connected to the spin valve sensor for conducting a sense current therethrough. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to the ABS, but is free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer.

The thickness of the spacer layer is chosen to be less than the mean free path of conduction electrons through the sensor. With this arrangement, a portion of the conduction electrons is scattered by the interfaces of the spacer layer with each of the pinned and free layers. When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering is minimal and when the magnetizations of the pinned and free layer are antiparallel, scattering is maximized. Changes in scattering alter the resistance of the spin valve sensor in proportion to cos Θ, where Θ is the angle between the magnetizations of the pinned and free layers. In a read mode the resistance of the spin valve sensor changes proportionally to the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals.

Magnetization of the pinned layer is usually fixed by exchange coupling one of the ferromagnetic layers (AP1) with a layer of antiferromagnetic material such as PtMn. While an antiferromagnetic (AFM) material such as PtMn does not in and of itself have a magnetization, when exchange coupled with a magnetic material, it can strongly pin the magnetization of the ferromagnetic layer.

The magnetic signals are written to the magnetic medium by a write head that includes an electrically conductive write coil that passes between first and second poles. The poles are joined at a back gap region and separated from one another by a write gap in a pole tip region near the ABS. When a current passes through the coil, a resulting magnetic flux in the magnetic yoke generated a fringing magnetic field that extends between the pole tips fringes out to write a magnetic signal onto an adjacent magnetic medium.

The configuration of the magnetic poles in the pole tip region of the write head is very important to the magnetic performance. For example, the pole tips must have sufficient area to avoid choking off the flow of magnetic flux to the pole tip or saturating the pole tips. Also, since the width of the pole tips defines the track width of the write head, at least one of the poles must have a width that is sufficiently narrow to define a desired narrow track width. A smaller track width means that more tracks of data can be written onto a given amount of disk space. The write element should also be constructed to prevent undesired, stray magnetic fields, such as those that can contribute to adjacent track writing. For example, fields that extend laterally from the sides of the pole tips rather than straight from one pole to the other can result in a signal being bleeding to an adjacent track and can interfere with the signal of that adjacent track.

However, constructing a write head to have these desired characteristics has been limited by currently available manufacturing methods. For example, the resolution limitations of currently available photolithographic processes, and the ability to align multiple photolithographically defined mask structures limits the amount to which the track width of the pole tips can be reduced.

Therefore, there is a strong felt need for a write head structure that can define a very narrow track width, with sufficiently strong field strength and with minimal side writing. Such a write head must be constructed by a method that allows proper alignment and symmetry between and within each of the pole tips.

SUMMARY OF THE INVENTION

The present invention provides a write head that produces a strong, narrow write field while preventing side writing. The write head includes a step notched first pole structure having a wider bottom portions that steps to a narrower top portion. The narrower top portion is self aligned with a second pole P2 structure formed opposite a write gap.

The write head may also include first and second winged portions extending laterally from the notches in the first pole. The winged portions can be recessed from the air bearing surface ABS by a desired amount, and act to draw stray side emitting magnetic fields back away from the ABS.

An ion mill resistant layer or bump such as an alumina bump may be formed over the winged portion of the first pole structure to aid in forming the winged structure during the various milling processes used to form the notch.

The first pole structure of the present invention advantageously provides a self aligned pole structure that avoids side writing (adjacent track writing) by moving the base of the notch away from the write gap where it might otherwise attract magnetic fields.

The stair notched structure provides an efficient means for ensuring sufficient magnetic material is available in the notched region to prevent saturation of the pole tips which would otherwise choke of flux and limit the available write field.

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 OF THE PREFERRED EMBODIMENTS

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.

With reference now toFIG. 3, a magnetic write head300according to an embodiment of the invention includes a first magnetic pole (P1)302, and a second magnetic pole304formed over the first pole302. The first and second magnetic poles are constructed of one or more magnetic materials such as CoFe or NiFe. The first and second magnetic poles302,304are magnetically connected to one another by a back gap structure306, which can also be constructed of a magnetic material such as NiFe or CoFe, and are separated from one another at a pole tip region by a, non-magnetic write gap material layer308.

The second pole304includes a pedestal portion (P2)310, and a portion (P3)312that extends from the P2 portion310to the back gap306. The P2 portion310is preferably constructed of a high Bsat material such as Ni50Fe50or CoFe. P3312, and the back gap306can be constructed of CoFe or NiFe. A non-magnetic, electrically conductive write coil314passes between the first and second poles302,304. The coil314is constructed of a non-magnetic, electrically conductive material, such as Cu, and when a current flows through the coil a magnetic field from the coil causes a magnetic flux in the poles302,304, resulting in a fringing field (write field) across the write gap308at the pole tips. The coil314is embedded in one or more layers of insulation316, which can be, for example, alumina (Al2O3).

The first pole has a notched portion318which can be seen more clearly with reference toFIG. 4. As can be seen inFIG. 4, P2310is preferably very narrow. The notched portion318of the first pole has a stepped configuration having a narrow top portion320that has the same width as and is self aligned with the P2 pedestal portion310. The notched portion318of the first pole302has a wider portion322with a step324forming the junction between the narrow portion and the wider portion322.

According to the present invention, the P2 structure310is preferably constructed very narrow to achieve a desired narrow track width. A manufacturing method that will be described herein below, makes this narrow track width possible while also achieving self alignment of the P2 structure310with the first notched portion318of the first pole302. The configuration of the notch318provides the head300with improved magnetic performance.

The step320prevents flux from leaking to the sides and keeps the flux more tightly confined with the write gap308. Such flux leakage at the sides would lead to adjacent track interference. However, a certain amount of magnetic material is needed in the notched portion318of the first pole302to conduct flux to the narrow, vertical notched portion324to avoid magnetic saturation of the tip of the first pole302which would limit magnetic performance by reducing the available write field that the head300is capable of producing. By providing the notched portion318with a stepped structure leading to a wider bottom notched portion, the write head300can provide a narrow track width and avoid side writing while also preventing saturation of the pole302in the pole tip region.

With reference still toFIG. 4, the gap308has a gap thickness G as measured along a track length direction. The height of the narrow notch portion320defines a first notch height NH1that is measured from the gap308to the step324. Preferaby NH1is 0.5 to 2 times the gap thickness G, or about equal to G. NH1. The distance from the gap324to the base of wider notch portion322defines a second notch height NH2(total notch height). NH2can be 1.5 to 3 times NH1. Each step can have a width (SW) as measured from the edge of the narrow portion320to the edge of the wider portion322that is about 0.01-0.03 times the gap thickness.

With reference toFIG. 5, which shows a perspective view of the write head300, it can be seen that the first pole can be formed with laterally extending wing portions. These wing portions are optional, as the above described notch structure318can be used without the wings326. These laterally extending wing portions, which are formed in the first pole structure improve magnetic performance of the write head by further preventing side writing. Should any magnetic field be emitted from the sides of the pole tips320,310during writing, this field will be drawn back toward the wing portions away from the magnetic medium, thereby preventing side writing to the medium.

It should also be pointed out that P2 structure310does not flair out, but remains narrow beyond the location of the laterally extending wing portions326. We have found this configuration to provide optimal magnetic performance in avoiding side writing and providing a strong narrow magnetic field. A layer or bump328, constructed of a material that is resistant to ion milling, is provided over the wing portion326, and is useful in the manufacture of the wing portions326. This will be better understood upon reading the following description of a possible method for constructing a write head according to an embodiment of the invention. The bump328may be constructed of alumina (Al2O3), but could be constructed of some other material, and will hereinafter be referred to as an alumina bump328.

FIGS. 6A-12B, illustrate a method for constructing a write element302according to an embodiment of the invention. With particular reference toFIG. 6A and 6B, a first magnetic layer (first pole)502is formed. An alumina bump504(or other ion mill resistant material) is formed over the first pole layer. The alumina bump504is spaced a distance R from an intended air bearing surface (ABS) plane506. Although the ABS does not actually exist at this point in the manufacturing process, it will later be formed by lapping to remove material to form an ABS plane at a location indicated by dashed line506.

With continued reference toFIGS. 6A and 6B, a layer or non-magnetic, electrically conducive write gap material508is deposited. The write gap508can be constructed of several materials, such as for example alumina. An optional seed layer510may be deposited over the write gap layer508. The seed layer510may be an electrically conductive material such as a metal that can be deposited by sputtering in order to provide an electrically conductive surface on which to perform electroplating. If an electrically conductive material is used for the write gap508(such as in a “metal in gap” design), then the seed layer510may not be necessary. A mask512, such as a photoresist frame can then be formed with an opening configured to define the P2 structure310(FIG. 3-5).

With reference now toFIG. 7, a magnetic material702can be deposited such as by electroplating. The magnetic material702is preferably a high Bsat material such as CoFe or Ni50Fe50, and will form the P2 structure310illustrated inFIGS. 3-5. With reference now toFIG. 8, the photoresist frame512can be removed leaving the magnetic P2 material702. With reference toFIG. 9, a material removal process902such as ion milling can be performed to remove portions of the seed layer510, gap layer508and first pole layer502using the P2 magnetic layer702as a mask to form a first notch904.

With reference toFIG. 10, a layer of non-magnetic material1002such as alumina is conformally deposited. The conformal deposition of the non-magnetic layer can be for example by ion beam sputtering, atomic layer deposition (ALD), RF sputtering, chemical vapor deposition (CVD) or some other technique. The non-magnetic layer1002is preferably deposited to a thickness of about 1-3 times the thickness of the gap material508.

With reference now toFIG. 11, a second material removal process1102such as an Argon notching ion mill is performed to remove horizontally disposed portions of the non-magnetic material1002. The second material removal process is a directional process that preferentially removes horizontally disposed material. In this way, the process1102can remove the non-magnetic material from the top of the P2 layer702and from the surface of the first pole layer502while leaving non-magnetic material1002on the sides of the P2 layer702and on the sides of the first notch904.

With reference now toFIGS. 12A and 12B, a third material removal process1202, such as ion milling is performed to remove portions of the first pole material that are not protected by the remaining ion mill resistant material layer1002and P2702to form a second notch1204. Using the remaining ion mill resistant material as a mask during this third material removal process forms a desired step at the junction between the first notch1206and second notch1204. In this way the first pole502can be formed with a stepped notch structure having a wider base322that steps to the narrower notched upper portion320as described earlier with reference toFIGS. 3-5.FIG. 12Bshows that the first pole material502that is located under the alumina bump504is protected from and not removed by the first, second and third material removal processes902,1002,1102. This masking provided by the alumina bump forms the laterally extending portions326described with reference toFIGS. 3-5.

The above described process forms a desired P2 structure502having a stepped notch structure318described with reference toFIGS. 305. The process also forms the advantageous laterally extending wing portions326. With the first pole502, write gap508and P2 structure310formed, the other structures, such as the write coil314insulation316, and P3312can be constructed by methods that will be familiar to those skilled in the art. These methods may include the photolithographic formation of photoresist frames and plating of electrically conductive material for the coil and magnetic material for the P3 structure312. The back gap306may be formed simultaneously with the P2 structure310or at some other manufacturing stage.

The use of the bump1208, makes it possible to construct the first pole1202to have the laterally extending wings, while the second pole structure1212can be constructed with a narrow width that extends beyond the location of the wings1204. Our modeling has shown that this structure provides improved magnetic performance by minimizing side writing. As the magnetic write field extends across the write gap1210a certain amount of this field may extend out the sides as a side leaking field. The laterally extending wing portions1204draw this side leaking flux back away from the ABS and away from the adjacent magnetic medium, thereby preventing side writing.

The wing portions1204are preferably recessed from the ABS. The wing portions1204can be recessed from the ABS a distance R that is 0.5-5 times the gap G. Our modeling has shown that this configuration, with a first pole having wing portions and a second narrow pole that remains narrow past the location of the wings, provides optimal magnetic performance.

It should be pointed out that while the above step notched pole structure has been described as having a single step, multiple steps could also be employed. It is believed however that as the number of steps increases, the advantage of additional steps diminishes while the cost and complexity of manufacture increases. Therefore, a single step as described above is believed to bet the best embodiment presently contemplated.