Fabrication of side-by-side sensors for MIMO recording

The embodiments of the present invention relate to a method for forming a magnetic read head having side by side sensors. The method includes depositing a pinned layer, a barrier layer and a free layer over a shield, and removing portions of the pinned layer, barrier layer and free layer to expose portions of the shield. A bias material is deposited over the exposed shield. An opening is formed in the free layer to expose the barrier layer, and an insulative material is deposited into the opening. The resulting side by side sensors each has its own free layer separated by the insulative nonmagnetic material. The side by side sensors share the pinned layer.

BACKGROUND

Embodiments of the present invention generally relate to a magnetic read head for use in a hard disk drive.

2. Description of the Related Art

The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of 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 signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.

The read head typically utilizes a spin valve sensor, also referred to as a magnetoresistive (MR) sensor. The sensor at the ABS typically includes a barrier layer sandwiched between a pinned layer and a free layer. The magnetization of the pinned layer is pinned perpendicular to the ABS and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields.

In order to respond to the demand for even higher density recording in recent years, the effective track width of magnetoresistive sensors has been made narrower, but this has caused the element resistance to increase, the noise to increase, and sensitivity to reduce, and has produced the separate issue that it is difficult to increase the sensitivity. Therefore, there is a need for an improved magnetic head and method of manufacture.

SUMMARY OF THE INVENTION

The embodiments of the present invention relate to a method for forming a magnetic read head with side by side sensors. The method includes depositing a pinned layer, a barrier layer and a free layer over a shield, and removing portions of the pinned layer, barrier layer and free layer to expose portions of the shield. A bias material is deposited over the exposed shield. An opening is formed in the free layer to expose the barrier layer, and an insulative nonmagnetic material is deposited into the opening. The resulting side by side sensors each has its own free layer separated by the insulative nonmagnetic material. The side by side sensors share the pinned layer.

In one embodiment, a magnetic read head for multiple input multiple output recording is disclosed. The magnetic read head includes side by side sensors including a shield, a pinned layer disposed over a first portion of the shield, a barrier layer disposed over the pinned layer, a first free layer disposed over a first portion of the barrier layer, a second free layer disposed over a second portion of the barrier layer, an insulative nonmagnetic material disposed over a third portion of the barrier layer, a first lead layer disposed over the first free layer and a second lead layer disposed over the second free layer.

In another embodiment, a method for forming a magnetic read head for multiple input multiple output recording is disclosed. The method includes depositing a pinned layer over a shield, depositing a barrier layer over the pinned layer, depositing a first free layer over the barrier layer, removing portions of the pinned layer, barrier layer and first free layer to expose portions of the shield, depositing a bias material over the exposed portions of the shield, depositing a hard mask layer over the bias material and the first free layer, forming an opening in the hard mask layer and the first free layer, depositing an insulative nonmagnetic material in the opening, and removing the hard mask layer. A portion of the insulative nonmagnetic material protrudes out of a top surface, and the protruded portion of the insulative nonmagnetic material has a first side and a second side. The method further includes forming a first lead layer on the top surface adjacent the first side and a second lead layer on the top surface adjacent the second side.

In another embodiment, a method for forming a magnetic read head for multiple input multiple output recording is disclosed. The method includes depositing a pinned layer over a shield, depositing a barrier layer over the pinned layer, depositing a first free layer over the barrier layer, removing portions of the pinned layer, barrier layer and first free layer to expose portions of the shield, depositing a bias material over the exposed portions of the shield, depositing a first lead layer over the bias material and the first free layer, forming an opening in the hard mask layer, the first lead layer and the first free layer, depositing an insulative nonmagnetic material in the opening, and removing the hard mask layer and a portion of the insulative nonmagnetic material that protrudes above the first lead layer.

DETAILED DESCRIPTION

The embodiments of the present invention relate to a method for firming a magnetic read head with side by side sensors. The method includes depositing a pinned layer, a barrier layer and a free layer over a shield, and removing portions of the pinned layer, barrier layer and free layer to expose portions of the shield. A bias material is deposited over the exposed shield. An opening is formed in the free layer to expose the barrier layer, and an insulative material is deposited into the opening. The resulting side by side sensors each has its own free layer separated by the insulative nonmagnetic material. The side by side sensors share the pinned layer.

FIG. 1illustrates a top view of an exemplary hard disk drive (HDD)100, according to an embodiment of the invention. As illustrated, HDD100may include one or more magnetic disks110, actuator120, actuator arms130associated with each of the magnetic disks110, and spindle motor140affixed in a chassis150. The one or more magnetic disks110may be arranged vertically as illustrated inFIG. 1. Moreover, the one or more magnetic disks may be coupled with the spindle motor140.

Magnetic disks110may include circular tracks of data on both the top and bottom surfaces of the disk. A magnetic head180mounted on a slider may be positioned on a track. As each disk spins, data may be written on and/or read from the data track. Magnetic head180may be coupled to an actuator arm130as illustrated inFIG. 1. Actuator arm130may be configured to swivel around actuator axis131to place magnetic head180on a particular data track.

FIG. 2is a fragmented, cross-sectional side view through the center of a read/write head200mounted on a slider201and facing magnetic disk202. The read/write head200and magnetic disk202may correspond to the magnetic head180and magnetic disk110, respectively inFIG. 1. In some embodiments, the magnetic disk202may be a “dual-layer” medium that includes a perpendicular magnetic data recording layer (RL)204on a “soft” or relatively low-coercivity magnetically permeable underlayer (PL)206formed on a disk substrate208. The read/write head200includes an ADS, a magnetic write head210and a magnetic read head211, and is mounted such that the ABS is facing the magnetic disk202. InFIG. 2, the disk202moves past the write head210in the direction indicated by the arrow232, so the portion of slider201that supports the read/write head200is often called the slider “trailing” end203.

The magnetic read head211is a magneto-resistive (MR) read head that includes a MR sensing element230located between MR shields S1and S2, which are composed of a highly permeable and magnetically soft material such as permalloy. The distance between S1and S2, which is the sensor thickness, defines the read gap of the read head. The MR sensing element230may be one or more side by side sensors which are described in detail below. The RL204is illustrated with perpendicularly recorded or magnetized regions, with adjacent regions having magnetization directions, as represented by the arrows located in the RL204. The magnetic fields of the adjacent magnetized regions are detectable by the MR sensing element230as the recorded bits.

The write head210includes a magnetic circuit made up of a main pole212and a yoke216. The write head210also includes a thin film coil218shown in the section embedded in non-magnetic material219and wrapped around yoke216. In an alternative embodiment, the yoke216may be omitted, and the coil218may wrap around the main pole212. A write pole220is magnetically connected to the main pole212and has an end226that defines part of the ABS of the magnetic write head210facing the outer surface of disk202.

Write pole220is a flared write pole and includes a flare point222and a pole tip224that includes an end226that defines part of the ABS. The flare may extend the entire height of write pole220(i.e., from the end226of the write pole220to the top of the write pole220), or may only extend from the flare point222, as shown inFIG. 2. In one embodiment the distance between the flare point222and the ABS is between about 30 nm and about 150 nm.

The write pole220includes a tapered surface271which increases a width of the write pole220from a first width W1at the ABS to a second width W2away from the ABS. In one embodiment, the width W1may be between around 60 nm and 200 nm, and the width W2may be between around 120 nm and 350 nm. While the tapered region271is shown with a single straight surface inFIG. 2, in alternative embodiment, the tapered region271may include a plurality of tapered surface with different taper angles with respect to the ABS.

The tapering improves magnetic performance. For example, reducing the width W1at the ABS may concentrate a magnetic field generated by the write pole220over desirable portions of the magnetic disk202. In other words, reducing the width W1of the write pole220at the ABS reduces the probability that tracks adjacent to a desirable track are erroneously altered during writing operations.

While a small width of the write pole220is desired at the ABS, it may be desirable to have a greater width of the write pole220in areas away from the ABS. A larger width W2of the write pole220away from the ABS may desirably increase the magnetic flux to the write pole220, by providing a greater thickness of the write pole220in a direction generally parallel to the ABS. In operation, write current passes through coil218and induces a magnetic field (shown by dashed line228) from the write pole220that passes through the RL204(to magnetize the region of the RL204beneath the write pole220), through the flux return path provided by the PI.206, and back to an upper return pole250. In one embodiment, the greater the magnetic flux of the write pole220, the greater is the probability of accurately writing to desirable regions of the RL204.

FIG. 2further illustrates one embodiment of the upper return pole or magnetic shield250that is separated from write pole220by a nonmagnetic gap layer256. In some embodiments, the magnetic shield250may be a trailing shield wherein substantially all of the shield material is on the trailing end203. Alternatively, in some embodiments, the magnetic shield250may be a wrap-around shield wherein the shield covers the trailing end203and also wraps around the sides of the write pole220. AsFIG. 2is a cross section through the center of the read/write head200, it represents both trailing and wrap-around embodiments.

Near the ABS, the nonmagnetic gap layer256has a reduced thickness and forms a shield gap throat258. The throat gap width is generally defined as the distance between the write pole220and the magnetic shield250at the ABS. The shield250is formed of magnetically permeable material (such as Ni, Co and Fe alloys) and gap layer256is formed of nonmagnetic material (such as Ta, TaO, Ru, Rh, NiCr, SiC or Al2O3). A taper260in the gap material provides a gradual transition from the throat gap width at the ABS to a maximum gap width above the taper260. This gradual transition in width forms a tapered bump in the non-magnetic gap layer that allows for greater magnetic flux density from the write pole220, while avoiding saturation of the shield250.

It should be understood that the taper260may extend either more or less than is shown inFIG. 2. The taper may extend upwards to an end of shield250opposite the ABS (not shown), such that the maximum gap width is at the end of the shield opposite the ABS. The gap layer thickness increases from a first thickness (the throat gap width) at the ABS to greater thicknesses at a first distance from the ABS, to a final thickness at a second distance (greater than the first distance) from the ABS.

FIGS. 3A-3Killustrate the process of making the magnetic read head211according to one of the embodiments.FIG. 3Ais an ABS view of a sensor stack300. The sensor stack300includes a shield302, a seed layer304formed on the shield302, a pinned layer306formed on the seed layer304, a barrier layer308formed on the pinned layer306, a free layer310formed on the barrier layer308and a capping layer312formed on the free layer310. The shield302may be the shield S1and may comprise a ferromagnetic material. Suitable ferromagnetic materials that may be utilized include Ni, Fe, Co, NiFe, NiFeCo, NiCo, CoFe and combinations thereof. The seed layer304may comprise Ta or Ru. The pinned layer306may be a ferromagnetic layer comprising NiFe, CoFe, CoFeB, Co, CoZr, CoHf or CoFeTaB. The pinned layer306may comprise a multilayer structure such as an antiparallel (AP) pinned structure having a first magnetic layer, a second magnetic layer and a nonmagnetic AP coupling layer sandwiched between the two magnetic layers. The first and second magnetic layers may be constructed of several magnetic materials such as, for example NiFe, CoFe, CoFeB, Co, CoZr, CoHf or CoFeTaB. The nonmagnetic layer may comprise Ru.

The barrier layer308may comprise an insulating material such as MgO, TiO2or alumina, or a nonmagnetic material such as Cu, Ag or the like. The free layer310may comprise ferromagnetic materials such as Co, CoFe, CoFeB, NiFe, CoHf or combinations thereof. The capping layer312may comprise a material such as Ru, Ta or a layered structure of these materials. The layers304,306,308,310and312may be deposited by physical vapor deposition (PVD), chemical vapor deposition, ion beam deposition (IBD) or any other suitable deposition method.

FIG. 3Bis a side view of the sensor stack300before the stripe height of the free layer310and the pinned layer306have been defined. Next, as shown inFIG. 3C, a portion of the seed layer304, a portion of the pinned layer306and a portion of the barrier layer308have been removed to expose a portion of the shield302. The removal process may include one or more suitable removal processes, such as reactive ion etching (RIE) and/or ion milling. As a result of the removal process, the stripe height of the pinned layer306is defined, indicated as “D1” inFIG. 3C. A portion of the free layer310and a portion of the capping layer312have been removed to expose a portion of the capping layer308. The removal process may include one or more suitable removal processes, such as RIE and/or ion milling. As a result of the removal process, the stripe height of the free layer310is defined, indicated as “D2” inFIG. 3C. The pinned layer306may have the same stripe height as the free layer310, or may have a greater stripe height than the free layer310, as shown inFIG. 3C. The etching steps that remove the pinned layer306and the seed layer304in order to define “D1” may be performed either before or after the steps enumerated in the following paragraphs that define the track widths of the side-by-side sensors.

FIG. 3Dshows an ABS view of the sensor stack300according to one embodiment. After the stripe heights of the pinned layer306and the free layer310have been defined, portions of the capping layer312, the free layer310, the barrier layer308, the pinned layer306and the seed layer304are removed to expose portions of the shield302. The removal process may include one or more suitable removal processes, such as RIE and/or ion milling. As a result of the removal process, the track width of the combined sensors is defined, indicated as “D3” inFIG. 3D. The combined track width “D3” may be about 100 nm. In some embodiments, the track width “D3” of the combined sensors is defined before the stripe heights of the pinned layer306and the free layer310are defined.

A bias material316is then deposited over the exposed portions of the shield302, as shown inFIG. 3E. The bias material316may be a hard or soil bias comprising a material having a high magnetic moment such as CoFe or NiFe. An insulating layer314may be first deposited on the exposed portions of the shield302and then the bias material316is deposited on the insulating layer314. The insulating layer314may be made of an insulating material such as alumina, silicon nitride, silicon dioxide, tantalum oxide or other suitable materials. Without the insulating layer314, the metal bias layer would short out the device. An optional bias capping layer may be deposited over the bias material316.

Next, a hard mask layer320is deposited over the bias316and the capping layer312, as shown inFIG. 3F. The hard mask layer320may be as thin as possible to minimize shadowing. In one embodiment, the hard mask layer320comprises diamond like carbon (DLC) and is about 10-50 nm thick. An opening322is formed in the hard mask layer320, as shown inFIG. 3G. The opening322may be formed by removing a portion of the hard mask layer320with an RIE to expose a portion of the capping layer312. The opening322may have a width “D4” that is 30 nm or smaller, and may be located above the center portion of the free layer310.

The exposed portion of the capping layer312and the center portion of the free layer310that is disposed below the exposed portion of the capping layer312are removed, forming an opening335as shown inFIG. 3H. The removal process may include ion milling of the capping layer312and the free layer310, or ion milling the capping layer312and then RIE the free layer310using methanol. Because the hard mask layer320is very thin, shadowing is minimized and optimal controlling of this precise milling step is achieved. As a result of the removal process, the center portion of the free layer310has been completely removed, exposing the underlying portion of the barrier layer308and creating two free layers330,340having substantially identical track width “D5”. Each free layer330,340has a capping layer332,342disposed thereon, respectively. The barrier layer308may be resistant to ion milling, creating a generous operating window for the complete separation of the free layers330,340. It may be desirable to not mill through the barrier layer308, so shunting issues may be avoided. In one embodiment, the track width “D5” of the two free layers330,340is about 20 nm to 45 nm. In one embodiment, the track width “D5” of the free layers330,340is greater than the stripe height of the free layers330,340.

Next, an insulative nonmagnetic material345is deposited in the opening335, as shown inFIG. 3I. The insulative nonmagnetic material345may be alumina, TaO, SiN, combinations thereof, or other suitable insulative nonmagnetic materials, and may be deposited by IBD). A top surface350may be planarized by a chemical mechanical polishing (CMP) process.

The hard mask layer320is then removed by any suitable removal process, such as RIE, leaving a portion of the insulative nonmagnetic material345protruding out of a top surface347, as shown inFIG. 3J. Next, leads352,354are deposited on the top surface347and adjacent the protruded portion of the insulative nonmagnetic material345. The leads352,354may be any suitable metal such as Ta, Rh, W, or multilayer structure of suitable metals such as a three layer structure having an Rh layer sandwiched between two Ta layers. In one embodiment, the leads352,354are made of one or more refractory hard metals to avoid smearing during one or more subsequent CMP processes. In another embodiment, the leads352,354, or some portions of them, are made of a soft magnetic material to act as a top shield to the sensors. Different processes may be used to form the leads352,354. In one embodiment, a lead layer is deposited on the top surface347and the insulative nonmagnetic material345, and a chemical mechanical kiss polish may be performed to remove the portion of the lead layer that is deposited on the insulative nonmagnetic material345, leaving the lead layers352,354. In another embodiment, a lead layer is deposited on the top surface347and the insulative nonmagnetic material345, and resists are formed on the portions of the lead layer that would be the lead layers352,354. The portion of the lead layer that is not covered by the resists is removed by an ion milling process, and the resists are then lifted off, leaving the lead layers352,354. In yet another embodiment, a resist is formed on the insulative nonmagnetic material345, and a lead layer is deposited on the top surface347and the resist. The resist and the portion of the lead layer disposed thereon are removed by a lift off process, leaving the lead layers352,354.

FIGS. 3A-3Killustrate a method for forming side by side sensors360,370. The sensors360,370each has its own lead354,352, capping layer342,332and free layer340,330, respectively. The sensors360,370share the barrier layer308and the pinned layer306. The side by side sensors360,370may be used for multiple input multiple output (MIMO) recording which helps decreasing noise and improving sensitivity.FIGS. 4A-4Eillustrate another method for forming the side by side sensors for MIMO recording.

FIG. 4Ashows the sensor stack400that is identical to the sensor stack300described inFIG. 3E. Next, a lead layer402is formed on the bias material316and the capping layer312, and a hard mask layer404is formed on the lead layer402, as shown inFIG. 411. The lead layer402may comprise the same material as the lead layers352,354. In one embodiment, the lead layer402comprises W, which is a RIEable metal. The hard mask layer404may comprise the same material as the hard mask layer320. The lead layer402and the hard mask layer404may be deposited by any suitable deposition method, such as PVD, CVD or IBD. The lead layer402and the hard mask layer404may have a combined thickness of about 10-60 nm, and the lead layer402may have a thickness that is less than 15 nm in order to minimize the distance between the free layers330,340and a top shield disposed over the lead layer402. Although the thickness constraint of the lead layer402may be relaxed if materials are chosen so that the lead layer402provides shielding to the free layers330,340.

Next, as shown inFIG. 4C, an opening420is formed in the hard mask layer404, the lead layer402, the capping layer312and the free layer310, forming two lead layers414,416, two capping layers410,412, and two free layers406,408. The opening420may be formed by one or more removal processes. In one embodiment, an opening is first formed in the hard mask layer404by an RIE process, and then portions of the lead layer402, capping layer312and free layer310are removed by ion milling to expose the underlying portion of the barrier layer308and to form the opening420. In one embodiment, the portion of the lead layer402is removed by RIE, the portion of the capping layer312is removed by ion milling, and the free layer310is removed by RIE. The opening420is formed in the center of the free layer310. The opening420may have a width “D6” of about 30 nm and the free layers406,408each has a width “D7” of about 35 nm.

An insulative nonmagnetic material430is deposited in the opening420, as shown inFIG. 4D. The insulative nonmagnetic material430may comprise the same material as the insulative nonmagnetic material345. The deposition of the insulative nonmagnetic layer430may be any suitable deposition method, such as IBD. A top surface432of the sensor stack400may be planarized by CMP. Next, the hard mask layer404is removed by any suitable removal method, such as RIE, and the portion of the insulative nonmagnetic material430that is protruding above the lead layers414,416is etched back, as shown inFIG. 4E. Again the resulting structure has two side by side sensors440,450, each having its own lead layers414,416, capping layers410,412and free layers406,408, respectively. The two sensors440,450share the barrier layer308and the pinned layer306.

In summary, a method for forming a magnetic read head having side by side sensors is disclosed. The method includes depositing a pinned layer, a barrier layer and a free layer over a shield, and defining a total track width by removing portions of the pinned layer, barrier layer and the free layer, exposing portions of the underlying shield. A bias material is formed over the exposed portions of the shield. A portion of the free layer is replaced with an insulative nonmagnetic material, forming two separate free layers. The side by side sensors each has its own free layer and share the pinned layer.