Method for fabricating a magnetic head

A GMR read head for a magnetic head, in which the hard bias layers are fabricated immediately next to the side edges of the free magnetic layer, and such that the midplane of the hard bias layer and the midplane of the free magnetic layer are approximately coplanar. The positioning of the hard bias layer is achieved by depositing a thick hard bias seed layer, followed by an ion milling step is to remove seed layer sidewall deposits. Thereafter, the hard bias layer is deposited on top of the thick seed layer. Alternatively, a first portion of the hard bias seed layer is deposited, followed by an ion milling step to remove sidewall deposits. A thin second portion of the seed layer is next deposited, and the hard bias layer is then deposited.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a read head portion of a magnetic head for a hard disk drive, and more particularly to a giant magnetoresistance (GMR) read head including a free magnetic layer with closely spaced, horizontally aligned hard bias elements in two side regions.

2. Description of the Prior Art

In a commonly used giant magnetoresistance (GMR) read head, a GMR read sensor is located in a central read region, while a hard bias layer and electrical contacts are located in each of two side regions. The GMR read sensor typically includes nonmagnetic seed layers, an antiferromagnetic pinning layer, ferromagnetic pinned layers, a nonmagnetic spacer layer, a ferromagnetic free layer, and a nonmagnetic cap layer. The hard bias layer typically includes a seed layer and a magnetic hard bias layer. The electrical contacts typically comprise highly electrically conducting nonmagnetic layers.

The hard bias layer must exhibit a high coercivity and thus provide a magnetic biasing field for stabilizing the free magnetic layer. This stabilization is the most effective when the midplane of the hard bias layer is located at the same horizontal level as the midplane of the free magnetic layer. In the prior art head fabrication process, however, the hard bias layer is typically deposited on an Al2O3bottom gap layer in the side regions, and thus the midplane of the hard bias layer is typically located at a horizontal level significantly lower than the midplane of the free magnetic layer. As a result, it is difficult to stabilize the free magnetic layer. In an effort to raise the hard bias layer, a thickened seed layer has been deposited beneath it. However, the deposition of such a thickened seed layer results in thick sidewall deposition upon the central sensor layers, thus creating an unwanted separation between the side edges of the free magnetic layer and the hard bias elements. Minimizing this separation is important to improve magnetic head performance.

There is therefore a need for a head fabrication process in which the hard bias elements are fabricated as close as possible to the free magnetic layer, and wherein the midplane of the hard bias layer can be located at the same horizontal level as the midplane of the free magnetic layer, so that the most effective stabilization of the free magnetic layer can be obtained.

SUMMARY OF THE INVENTION

The present invention is an improved GMR read head for a hard disk drive, in which the hard bias layers are fabricated next to the side edges of the free magnetic layer, such that the midplane of the hard bias layer and the midplane of the free magnetic layer are approximately coplanar. The positioning of the hard bias layer is achieved by depositing a thick hard bias seed layer, where an ion milling step is next conducted after the deposition of the thick seed layer to remove seed layer sidewall deposits from the side edges of the free magnetic layer. Thereafter, the hard bias layer is deposited on top of the thick seed layer immediately next to the side edges of the free magnetic layer. Improved free layer magnetic stabilization results from the improved positioning of the hard bias layer.

In an alternative embodiment, the thick hard bias seed layer is deposited, followed by the ion milling step to remove hard bias seed layer deposits from the sidewalls of the free magnetic layer. Thereafter, a thin second portion of the seed layer is deposited to provide a fresh crystallographic seed layer for the nucleation of the hard bias layer. Thereafter, the hard bias layer is deposited upon the thin second seed layer portion. The hard bias layer is positioned such that its midplane is coplanar with the midplane of the free magnetic layer, however there is a thin sidewall deposition of the second seed layer material that separates the hard bias layer from the side edges of the free magnetic layer. The thin sidewall deposition material can be optimized to improve the performance of the magnetic head.

It is an advantage of the magnetic head of the present invention that a head fabrication process has been developed to improve the free magnetic layer stabilization.

It is another advantage of the magnetic head of the present invention that a head fabrication process has been developed, where the midplane of the hard bias layer can be located at the same horizontal level as the midplane of the free magnetic layer.

It is a further advantage of the magnetic head of the present invention that a head fabrication process has been developed, where ion milling is applied to remove unwanted sidewall deposition portions of the hard bias seed layer, such that the hard bias layer is fabricated next to the side edges of the free magnetic layer.

It is an advantage of the hard disk drive of the present invention that it includes a magnetic head fabricated to improve the free magnetic layer stabilization.

It is another advantage of the hard disk drive of the present invention that it includes a magnetic head, in which the midplane of the hard bias layer is located at the same horizontal level as the midplane of the free magnetic layer.

These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.

DETAILED DESCRIPTION OF THE FIRST EMBODIMENT

FIG. 1is a top plan view that depicts significant components of a hard disk drive10. The hard disk drive includes an air bearing slider that includes a magnetic head20generally comprising an Al2O3—TiC substrate, the GMR read head of the present invention, and a write head. The hard disk drive10also includes a hard disk12on which a magnetic medium is deposited. The hard disk is rotatably mounted upon a motorized spindle14. An actuator arm16is pivotally mounted within the hard disk drive10with the magnetic heads20disposed upon a distal end22of the actuator arm16. A typical hard disk drive10may include a plurality of hard disks12that are rotatably mounted upon the motorized spindle14and a plurality of actuator arms16having magnetic heads20mounted upon the distal ends22of the actuator arms16. As is well known to those skilled in the art, when the hard disk drive10is operated, the hard disk12rotates upon the motorized spindle14and the air bearing slider flies above the surface of the rotating hard disk12.

FIG. 2is a side cross-sectional view depicting a prior art magnetic head during the fabrication process of the GMR read head portion, as is known in the prior art, andFIG. 3is a side cross-sectional view depicting the GMR read head ofFIG. 2after completing its fabrication process as is known in the prior art. This prior art fabrication process is improved upon in the present invention, andFIGS. 2 and 3therefore serve as a suitable starting point for the description of this invention.

A wafer40used in the fabrication process typically comprises an Al2O3—TiC ceramic substrate40coated with an Al2O3film (not shown). In the fabrication process, as is depicted inFIG. 2, a bottom magnetic shield layer (S1)42, typically formed of an approximately 1 μm thick Ni—Fe film, is deposited on the wafer40. A bottom gap insulation layer (G1)46, typically formed of an approximately 10.6 nm thick Al2O3film, is deposited on the S1layer42. Thereafter, an antiferromagnetic pinning layer54, typically comprised of an approximately 15 nm thick Pt—Mn, is then deposited on the G1insulation layer. Thereafter, pinned magnetic layers58, typically comprising an approximately 1.6 nm thick Co—Fe film, a 0.8 nm thick Ru film and a 1.8 nm thick Co—Fe film, are deposited on the antiferromagnetic layer54. A spacer layer62, typically formed of an approximately 2.0 nm Cu or Cu—O film, is deposited on the pinned layers58. Thereafter, a free magnetic layer66, typically formed of an approximately 2 nm Co—Fe film, is deposited on the spacer layer62. A cap layer70, typically comprised of an approximately 4 nm thick Ta film, is then deposited on the free magnetic layer66.

After the layer depositions, bilayer photoresists, comprising a lower photoresist80and an upper photoresist84, are then applied and exposed in a photolithographic tool to mask the GMR read sensor in the central read region88for defining a sensor width. The layers in unmasked side regions96are removed by ion milling until the G1layer46is exposed. The hard bias element structure102, typically comprising an approximately 3 nm thick Cr seed layer103and a 30 nm thick Co—Pt—Cr layer104, is then deposited onto the unmasked side regions96. Thereafter, the electrical contacts106, typically comprising an approximately 80 nm thick Rh film and a 5 nm thick Ta film, are also deposited also onto the unmasked side regions96. With further reference toFIG. 3, the bilayer photoresists are then lifted off. Subsequently, the GMR read sensor is patterned for defining a sensor height, connected with a recessed electrical conductor (typically comprising a 3 nm thick Ta film, a 80 nm thick Cu film and a 3 nm thick Ta film), covered by a top gap insulation layer (G2)110typically formed of an approximately 20 nm thick Al2O3film, and a second magnetic shield layer (S2)114.

After the completion of this fabrication process of the GMR read head, the fabrication process of the write head is conducted using well known fabrication steps. After the completion of the fabrication processes of the GMR read and write magnetic heads, the heads are lapped along the alignment mark until designed sensor height and throat height are attained.

It is difficult for this prior art GMR read head to fully stabilize the free magnetic layer66, due to the shadowing effects of the bilayer photoresists during the severe ion milling applied to the GMR read sensor in the unmasked side regions96. The ion milling creates a trench down to the G1layer46in the unmasked side regions, and thus the midplane120of the hard bias layer104deposited on the G1layer46within the trench is located far below the midplane124of the free magnetic layer66. As a result, the desired hard bias layer thicknesses cannot be attained at the free magnetic layer side edges. Particularly, the Cr seed layer of the hard bias structure102is not thick enough to raise the level of the hard bias layer104such that the midplane120of the hard bias layer104would be at the same horizontal level as the midplane124of the free magnetic layer66. While a thicker seed layer will bring the midplane120of the hard bias layer up to the midplane124of the free magnetic layer, it will also increase the amount of the deposited seed layer material on the sensor sidewalls130. It has been determined that the thickness of the seed layer deposited on the shallow sensor sidewalls is typically approximately 50% of the seed layer material thickness deposited upon the wafer surface. Therefore, if a seed layer were deposited to a thickness of approximately 30 nm, it would result in a sidewall deposit of approximately 15 nm which will act as an unwanted spacer between the hard bias layer104and the side edges130of the free magnetic layer66, thereby degrading the performance of the GMR sensor because the magnetic biasing effect of the hard bias layer decreases nearly exponentially with the separation distance between the hard bias layer and the free magnetic layer.

The present invention includes fabrication steps to solve these issues, andFIGS. 4–6are side cross-sectional views, similar toFIG. 2, depicting a magnetic head150of the present invention during the fabrication process of the GMR read head, andFIG. 7is a side cross-sectional view depicting the magnetic head150of the present invention after completion of the GMR read head fabrication steps. It is to be understood that the magnetic head of the present invention includes identical components with those depicted and described hereabove, and such identical components are identically numbered for ease of comprehension.

In the fabrication process, as is depicted inFIG. 4, an S1layer42and a G1layer46, typically formed of a 1 μm Ni—Fe film and 10.6 nm thick Al2O3film, respectively, are sequentially deposited on a wafer. Thereafter, a GMR read sensor, typically comprising Pt—Mn(15)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.8)/Cu—O(2.0)/Co—Fe(1.5)/Ni—Fe(1.5) /Ta(4) films (thickness in nm), is then deposited on the G1layer46. A photoresist80is then applied and exposed in a photolithographic tool to mask the GMR read sensor in a read region88for defining a sensor width. This step may require the use of known reactive ion etch (RIE) processing to define various photoresist materials. The read sensor layers in the unmasked side regions96are removed by ion milling until the G1layer46is exposed, and the hard bias element structure of the present invention is then deposited onto the unmasked side regions96. As depicted inFIG. 4, a thick seed layer154typically comprised of Cr or CrMo of approximately 30 to 40 nm and preferably about 35 nm is first deposited, and this results in a steep sidewall deposition158of approximately 8 to 10 nm. Following the deposition of the seed layer154, as depicted inFIG. 5, a further ion milling step160is conducted at an angle of approximately 70° from normal to the wafer surface. As a result of the seed layer ion milling step160, the unwanted sidewall deposition of seed layer material158is removed, and approximately 6 to 10 nm of the deposited seed layer thickness154is likewise removed. The remaining seed layer has an ion milled upper surface162, and the thickness of the remaining seed layer is approximately 5 to 40 nm with a typical thickness of 25 to 30 nm.

Thereafter, as depicted inFIG. 6, the hard bias layer164is deposited, which may consist of an approximately 5 to 30 nm with a typical thickness of 15–20 nm thick Co—Pt—Cr layer. Thereafter, the electrical contacts168, typically comprising Rh(80)/Ta(5) films, are deposited across the wafer and onto the hard bias layer164in the unmasked side regions96. As is next seen inFIG. 7, the photoresist80along with material deposited upon it is removed, such as by using a chemical mechanical polishing step. Subsequently, the GMR read sensor is patterned for defining a sensor height, connected with a recessed conductor (preferably comprising a Ta(3)/Cu(80)/Ta(3) films), covered by a top gap G2layer178typically formed of an approximately 20 nm thick Al2O3film, and a top shield layer (S2)184typically formed of an approximately 1 μm thick Ni—Fe film is then deposited on the wafer. After photolithographic patterning of the S2layer into desired shapes and completing the fabrication process of the GMR read head, the fabrication process of the write head starts. After the completion of the fabrication processes of the GMR read and write heads, magnetic heads150are lapped along the alignment mark until designed sensor height and throat height are attained, and the magnetic head150of the present invention is completed.

As can be seen inFIG. 7, a first significant feature of the present invention is that the hard bias layer164is fabricated directly against the side edges130of the free magnetic layer66because the ion milling step162removed the sidewall deposits158of the seed layer154. Additionally, the thick seed layer154raises the height of the hard bias layer164, such that the midplane194of the hard bias layer164is generally horizontally aligned with the midplane124of the free magnetic layer66. As a result, the GMR sensor of the magnetic head of the present invention has a stabilized free magnetic layer66which results in improved magnetic head performance characteristics. As will be understood by those skilled in the art, where the nature and/or thicknesses of the various sensor layers varies in differing magnetic heads, such that the height of the midplane124of the free magnetic layer above the G1layer likewise varies, the thickness of the seed layer154should also be varied, such that the midplane194of the hard bias layer will be approximately coplanar (that is within 10 to 15 nm) with the midplane124of the free magnetic layer66.

A concern that arises with the magnetic head150depicted inFIG. 7, is whether the ion milling of the surface162of the seed layer154will detrimentally affect its function as a seed layer in the nucleation the desired epitaxial growth of the Co—Pt—Cr hard bias layer, and an alternative embodiment of the present invention is next described with the aid ofFIGS. 8–11.

FIGS. 8–10are side cross-sectional views, similar toFIGS. 4–6, depicting a magnetic head250of the present invention during the fabrication process of the GMR read head, andFIG. 11is a side cross-sectional view depicting the magnetic head250of the present invention after completion of the GMR read head fabrication steps. It is to be understood that the magnetic head of the present invention includes identical components with those depicted and described hereabove, and such identical components are identically numbered for ease of comprehension.

In the fabrication process, as is depicted inFIG. 8, an S1layer42and a G1layer46, typically formed of a 1 μm Ni—Fe film and 10.6 nm thick Al2O3film, respectively, are sequentially deposited on a wafer. Thereafter, a GMR read sensor214, typically comprising Pt—Mn(15)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.8)/Cu—O(2.0)/Co—Fe(1.5) /Ni—Fe(1.5)/ 4) films (thickness in nm), is then deposited on G1layer46. Bilayer photoresists, comprising a lower photoresist80and an upper photoresist84, are then applied and exposed in a photolithographic tool to mask the GMR read sensor in a read region88for defining a sensor width. The read sensor layers in the unmasked side regions96are removed by ion milling until the G1layer46is exposed, and the hard bias element structure of the present invention is then deposited onto the unmasked side regions96. As depicted inFIG. 8, a relatively thick first portion of a seed layer254, typically comprised of Cr or CrMo of approximately 25 to 30 nm is first deposited, and this results in a sidewall deposition258of approximately 6 to 8 nm. By way of comparison, the seed layer254is not as thick as the seed layer154of magnetic head150. Following the deposition of the first seed layer portion254, as depicted inFIG. 9, a further ion milling step262is conducted at an angle of approximately 70° from normal to the wafer surface. As a result of the seed layer ion milling step262, the unwanted sidewall deposition of seed layer material258is removed, and approximately 4 to 6 nm of the seed layer thickness254is likewise removed.

As is next depicted inFIG. 10, a thin second portion264of the seed layer is next deposited upon the ion milled surface266of the first seed layer portion254after the ion milling step262. The second seed layer portion264is as thin as is practical to provide a fresh seed layer crystalline orientation upon the milled surface266of the first seed layer portion254. It is desirable that the thickness of the second seed layer264be only as thick as is minimally necessary for this purpose, such that the additional sidewall deposition268, which will have a thickness of approximately 20 to 25% of the second seed layer thickness be held to a minimum. A typical thickness for the second seed layer264will be approximately 4 to 10 nm, such that the thickness of the sidewall deposition268will be only approximately 2 nm. In comparing the magnetic head embodiments150and250ofFIGS. 6 and 10, it can be seen that the total thickness of the hard bias seed layer is approximately equal, however the seed layer structure of magnetic head250is formed with a fresh (not ion milled) crystallographic surface of the second seed layer portion264, although it also includes a thin sidewall seed layer deposition268.

Thereafter, as depicted inFIG. 10, the hard bias layer272is deposited upon the second seed layer264, and it may consist of an approximately 20 nm thick Co—Pt—Cr layer. Thereafter, the electrical contacts280, typically comprising Rh(80)/Ta(3) films, are deposited onto the hard bias layer272in the unmasked side regions96. As is next seen inFIG. 11, the bilayer photoresists are then lifted off. Subsequently, the GMR read sensor is patterned for defining a sensor height, connected with a recessed conductor (typically comprising a Ta(3)/Cu(80)/Ta(3) films), covered by a top gap G2layer284typically formed of an approximately 20 nm thick Al2O3film, and a top shield layer (S2)288typically formed of an approximately 1 μm thick Ni—Fe film is then deposited on the wafer. After photolithographic patterning of the S2layer into desired shapes and completing the fabrication process of the GMR read head, the fabrication process of the write head starts. After the completion of the fabrication processes of the GMR read and write heads, magnetic heads250are lapped along the alignment mark until designed sensor height and throat height are attained, and the magnetic head250of the present invention is completed.

As can be seen inFIG. 11, a significant feature of the magnetic head250of the present invention is that the thick seed layer, composed of the first seed layer portion254and the second seed layer portion264, raises the height of the hard bias layer272, such that the midplane294of the hard bias layer272is generally horizontally aligned with the midplane124of the free magnetic layer66. As a result, the GMR sensor of the magnetic head250of the present invention has a stabilized free magnetic layer66which results in improved magnetic head performance characteristics.

While the present invention has been shown and described with regard to certain preferred embodiments, it will be understood that those skilled in the art will no doubt develop certain alterations and modifications thereto which nevertheless include the true spirit and scope of the invention. It is therefore intended that the following claims cover all such alterations and modifications.