Gradient write gap for perpendicular magnetic recording writer

The present disclosure provides for a magnetic writer pole for use in a hard drive. The magnetic writer pole comprises a first bevel formed by a non-magnetic layer, the first bevel formed at a first angle and extending to a first throat height. The magnetic writer pole further comprises a second bevel formed by the non-magnetic layer and extending distally from the first bevel at a second angle that is greater than the first angle and extending to a second throat height. The magnetic writer pole further comprises a third bevel formed by the non-magnetic layer and extending distally from the second bevel at a third angle that is greater than the second angle.

DESCRIPTION OF THE RELATED ART

Disk drives typically use heads residing on sliders to read from and write to magnetic media. Read and write transducers residing in the head are flown at a small, controlled spacing above the magnetic medium (disk) during read and write operations. An air bearing forms between the head and the disk due to the disk rotating at high speeds, which provides controlled head to disk spacing. Magnetic fields emanating from the write transducer pole tip switch magnetization of the magnetic medium, i.e., writing to the medium.

FIG. 1illustrates a conventional disk drive10used for data storage. Figures are not drawn to scale and only certain structures are depicted for clarity. A disk media50is attached to a spindle motor and hub20. The spindle motor and hub20rotate the media50in a direction shown by arrow55. A head stack assembly (HSA)60includes a magnetic recording head30on an actuator arm70and positions the actuator arm70by positioning the voice coil motor (VCM)25over a desired data track, shown as a recording track40in this example, to write data onto the media50.

FIG. 1Aillustrates an enlarged view of a section ofFIG. 1including the head30and the track40. A magnetic recording transducer90is fabricated on a slider80. The slider80may be attached to a suspension75and the suspension75may be attached to the actuator arm70as shown inFIG. 2. The slider80may include a read transducer93.

Referring again toFIG. 1A, the slider80is illustrated above the recording track40. The media50and the track40are moving under the slider80in a down-track direction shown by arrow42. The cross-track direction is shown by arrow41.

The magnetic recording transducer90has a leading edge91and a trailing edge92. In this embodiment, the trailing edge92of the recording transducer90is the final portion of the magnetic transducer90that writes onto the recording track40as the media50moves under the slider80in the down-track direction42.

FIG. 2illustrates a side view of the disk drive10shown inFIG. 1. At least one disk media50is mounted onto the spindle motor and hub20. Head Disk Assembly60comprises at least one actuator arm70that carries the suspension75and slider80. The slider80has an air bearing surface (ABS) facing the media50. When the media50is rotating and the actuator arm70is positioned over the media50, the slider80slide above the media50by aerodynamic pressure created between the slider ABS and the surface of media50.

FIG. 3illustrates a perspective view of a main pole tip section300of a perpendicular magnetic recording (PMR) transducer that may be implemented on the slider80ofFIG. 2. The main pole tip section300has a pole tip face310that faces the ABS. The pole tip face310is illustrated in a trapezoidal shape having a trailing edge311, a leading edge312, a first side wall edge313, and a second side wall edge314. The first side wall340extends distally from the first side wall edge313, the second side wall350(not visible, opposite first side wall340) extends distally from the second side wall edge314, the trailing side wall320extends distally from the trailing edge311, and the leading side wall330(not visible, opposite trailing side wall320) extends distally from the leading edge312.

The main pole tip section300is illustrated with a trapezoidal shape at the ABS with the trailing edge311wider than the leading edge312. However, other shapes may also be used. In other embodiments, for example, the side wall edge313and the side wall edge314and the corresponding side wall340and the side wall350may have facets or a curved shape; the leading edge312may be small, or form a point; and a trapezoid shape is not required, and may be a rectangle, or another shape having side walls. Pole surfaces and edges illustrated with straight lines may also be implemented as curved or faceted. One ordinarily skilled in the art will recognize that these shapes, combinations or variations of these shapes, and other shapes may be used.

FIG. 4illustrates a side section view of a PMR read/write head400having a write transducer450and read sensor410, both facing the ABS490. The read sensor410may include a first shield411and a second shield413as well as a sensor412. The write transducer450includes a shield414, a main pole401, an assist pole (or auxiliary pole)401′, a coil440and a coil440′, a leading shield417and a trailing shield420. The main pole401has a trailing bevel401aand a leading bevel401b. A leading nonmagnetic gap layer415separates main pole401from underlying structures, and a trailing nonmagnetic gap layer405separates main pole401from structures above. The trailing nonmagnetic gap layer405is also known as a “write gap.” A non-magnetic spacer406may be included on a portion of the trailing bevel401ato provide magnetic separation between the main pole401and the magnetic structures above. A nonmagnetic spacer layer402is illustrated on the non-beveled section of main pole401; however, this nonmagnetic spacer layer402may be provided above main pole401beginning at any point distal from the ABS490, including on the bevel401a. A trailing seed layer407overlays trailing nonmagnetic gap layer405and spacer406. A leading seed layer416is provided between leading nonmagnetic gap layer415and leading shield417.

Magnetic fields emanating from the write gap switch magnetization of a magnetic medium, i.e., writing to the medium. Among other factors, a smaller and more tightly controlled magnetic writing field will allow more data to be written in the same space, thereby increasing areal density. As such, write gap characteristics play an important role in writer performance.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth to provide a thorough understanding of various embodiments of the present disclosure. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice various embodiments of the present disclosure. In other instances, well known components or methods have not been described in detail to avoid unnecessarily obscuring various embodiments of the present disclosure.

Perpendicular magnetic recording (PMR) writers are commonly used in today's hard drives. Write gap characteristics are an important aspect in high density PMR writers, particularly in PMR writers with linear densities beyond ˜2000 kFCl. With increasing areal densities, write gap thickness continues to scale down and is generally tightly controlled by atomic layer depositions. Writer performance is very sensitive to write gap thickness. Generally, thin write gaps will directly improve signal-to-noise ratio (SNR), but degrade the reverse overwrite (revOW). However, improvements in revOW will generally result in performance losses in wide area track erasure (WATEr), as the improved signal strength will tend to lead to increased leakage into adjacent tracks. A small distance between the main pole and high moment magnetic shield (i.e., a thin write gap) will increase the field gradient at the air bearing surface (ABS), thus improving SNR. However, thin nonmagnetic write gaps also lead to magnetic flux shunting before the flux reaching the ABS, thereby hurting the revOW.

FIG. 5Ashows a PMR writer structure510ahaving a write gap (WG)512that leads into a non-magnetic spacer514. The end of the write gap512opposite the non-magnetic spacer514interacts with an air-bearing surface518. In this formulation, the write gap512has a generally constant width. The write gap512and the non-magnetic spacer514are each composed of non-magnetic material, and together form a non-magnetic layer between the main pole511and the trailing shield513. A second non-magnetic spacer210may also form a part of the non-magnetic layer between the main pole511and the trailing shield513. The trailing shield513may also comprise a magnetic seed layer515. The thin write gap512improves the signal-to-noise ratio of the writer510a. However, the abrupt change in width of the write gap512leading into the non-magnetic spacer514results in magnetic flux shunting before the flux reaches the air-bearing surface518. The presently disclosed gradient write gap addresses these issues.

A PMR writer510bincorporating a gradient write gap (GWG), in accordance with an embodiment of the present disclosure, is presented inFIG. 5B. A gradient write gap portion516is added as part of the write gap512to gradually increase the write gap's width as it moves toward the non-magnetic spacer514. The gradient write gap portion516, like the write gap512, generally comprises non-magnetic material. Examples of such non-magnetic materials may include Ru or Al2O3.

The PMR writer510ainFIG. 5Ahas a first bevel517formed by the write gap512, which leads directly into a second bevel519formed by the non-magnetic spacer514. The newly added gradient write gap portion516inFIG. 5Bcreates a third bevel521that forms an angle that is greater than the angle formed by the first bevel517, and smaller than that formed by the second bevel519. In this way, a gradient is formed from the write gap512to the non-magnetic spacer514.

In the structure depicted inFIG. 5B, the write gap512has a thin opening at the air bearing surface518, which increases the write head's signal-to-noise ratio (SNR). However, the thickness of the gradient write gap gradually increases as it moves away from the ABS518towards the non-magnetic spacer514, thereby reducing flux shunting. In this way, the benefit of an increased SNR is obtained, while simultaneously protecting against the problem of flux shunting by gradually increasing the write gap width. This can greatly improve device performance.

FIGS. 6A and 6Bprovide the same images ofFIGS. 5A and 5B, respectively, with labeling of the relevant bevel angles so as to demonstrate the gradient write gap. InFIG. 6A, the non-magnetic layer between the main pole511and the shield513,515is primarily defined by two bevel angles: (1) a first bevel517proximate the ABS518at a first angle520, and (2) a second bevel519at a second angle522that is greater than the first angle520.

InFIG. 6B, the gradient write gap portion516is added to the write gap512to create a gradient write gap. There is still the first bevel517at a first angle520(i.e., BV1A), a second bevel519at a second angle522(i.e., BV2A), and there is now an intermediate third bevel521at a third angle530(i.e., the gradient write gap angle or GWGA). The gradient write gap angle530creates a more gradual transition from the write gap512into the non-magnetic spacer514, i.e., a gradient. As such, the gradient write gap angle530is greater than the first angle520(BV1A), and less than the second angle522(BV2A). Additionally, inclusion of this additional gradient write gap portion516to create the gradient write gap creates two different throat heights, TH1 and TH2 (as shown inFIGS. 5 and 6). The narrow opening of the write gap512at TH2 increases SNR, while the wider write gap opening516at TH1 minimizes flux shunting.

Table 1 provides data demonstrating the advantages that may be obtained by implementing the presently disclosed gradient write gap. A write head having a constant width write gap (row 1) was compared with a write head having a gradient-write gap, in accordance with an embodiment of the present disclosure (row 2). The data in the table shows that the first angle520(BV1A) was approximately 28 degrees, and the second angle522(BV2A), was approximately 65 degrees, the throat height being about 90 units. In the GWG implementation, an intermediate gradient-write gap angle530(GWGA) of approximately 49 degrees was created. As discussed with respect toFIG. 6, the gradient-write gap implementation results in two different throat heights. The first throat height was about 75 units, and the second throat height was about 30 units. It can be seen in Table 1, that by adding the gradient write gap, revOW increased from 30.9 to 33.3.

In certain embodiments, it may be desirable for the constant write gap width portion of the write gap, i.e., TH2, to be zero units in length. However, in practice, it should also be considered that lapping techniques for magnetic write heads are not perfectly precise, and as such, the constant write gap portion TH2 allows for a certain margin of error in the lapping process without compromising manufacturing sigmas. In any case, it should be understood that both of these situations (inclusion or removal of the constant write gap portion) are within the scope of the present disclosure.

The gradient write gap may be an added feature to current PMR writers. One process proposed to implement gradient write gaps in PMR writers is to utilize the non-magnetic spacer514as a hard mask for its shadowing effects. An ion-beam mill process with proper mill angle and sweep angular range will create the gradient write gap at the junction of the trailing first bevel517and the second bevel519. Examples of methods for forming a gradient write gap will now be discussed in greater detail.

Exemplary method embodiments of the present invention are described below. This method may be broken down into several exemplary components:regular write gap (WG) depositionWG cap layer deposition: to protect the write gap from gradient-write gap (GWG) millingnon-magnetic spacer depositionGWG material deposition: to control GWG thicknessGWG cap layer deposition: for mill endpoint registrationGWG formation by ion mill or any other appropriate method.

These components may be re-arranged in different ways to create multiple methods by which to form an exemplary gradient write gap. To provide examples of how these steps may be re-arranged, three possible methods are discussed in greater detailed here as Process Routes 1, 2, and 3, which are depicted as image flow charts inFIGS. 7,8, and9, respectively.

FIG. 7provides a step-by-step breakdown of a first process route (Process Route 1) to form a gradient write gap. Process Route 1 may be summarized in the following eight steps, which are demonstrated inFIGS. 7(a)-7(f):0. BV1 process (FIG. 7(a))—This is the starting point of the process. An angled surface is formed on the main pole750;1. WG dep—A regular write gap layer752is deposited on the main pole750. One possible method for performing this step is fast ALD (atomic layer deposition). Alternative deposition methods might include physical vapor deposition or sputtering. (FIG. 7(b)). The write gap layer may comprise a non-magnetic material. Examples of such a non-magnetic material may include Al2O3or Ru;2. Ru STP—A write gap stop layer754is deposited on the regular write gap layer752to protect the write gap752from the gradient write gap milling process, which will be discussed in greater detail in step 7. The write gap stop layer754may comprise Ru, Al2O3, Ta, amorphous carbon or similar materials;3. Spacer FALD—A non-magnetic spacer756is deposited on the write gap752and the write gap stop layer754. Much like the write gap layer752, the non-magnetic spacer756may comprise a non-magnetic material such as Ru or Al2O3. In a particular embodiment, the non-magnetic spacer756may comprise a different non-magnetic material from the write gap layer752. For example, if the write gap layer752comprises Ru, then the non-magnetic spacer756may comprise Al2O3, or vice versa. In a particular embodiment, the non-magnetic spacer756may be deposited using fast ALD, or any other appropriate deposition method;4. BV2 RIE—A second stop layer758is formed on the non-magnetic spacer756. The second stop layer758may comprise Ru, Al2O3, Ta, amorphous carbon or similar materials, and may be formed via reactive ion etch (RIE)) (FIG. 7(c));5. GWG dep—A gradient write gap (GWG) layer760is deposited over the write gap752and the non-magnetic spacer756. This may be performed via fast ALD using a non-magnetic material, such as Ru or Al2O3(FIG. 7(d));6. GWG cap—A GWG cap layer762, which may comprise Ru, Al2O3, Ta, amorphous carbon or similar materials, is deposited on the GWG layer760(FIG. 3(d));7. GWG Mill—An ion mill is used to shape the GWG layer760(FIG. 3(e)). It can be seen inFIG. 7(e) that a portion of the GWG layer760directly above the write gap752has been milled away to form a more gradual, sloped shape in the GWG layer760. The re-shaped gradient write gap layer760and the write gap layer752together form a gradient write gap. This step creates a three-bevel surface with each beveled-surface have a progressively increasing angle. A first bevel753is at an angle that is substantially determined by the angle of the regular write gap layer752. A second bevel755is formed by the re-shaped gradient write gap layer760, with the angle of the second bevel755being greater than the angle of the first bevel753. And then a third bevel757extends from the second bevel755, with the angle of the third bevel757substantially approximating the angle of the non-magnetic spacer756, and being greater than the angle of the first and second bevels753,755.

FIG. 7(f) provides an image of an actual gradient write gap that has been formed using the Process 1 steps described above. It can be seen that the regular write gap layer752has a narrow opening on the left, leading to the air-bearing surface (ABS), and the GWG layer760creates a gradual widening of the write gap as it leads into the non-magnetic spacer756.

FIG. 8provides a step-by-step breakdown of a second process route (Process Route 2) that may be used to form a gradient write gap, in accordance with an embodiment of the present disclosure. Process Route 2 may be summarized in the following nine steps, as shown inFIG. 8:0. BV1 process—like Process Route 1, the process starts with a first angled surface being formed on the main pole750;1. WG dep—Again, as in Process Route 1, a regular write gap layer752is deposited on the main pole750. One possible method for performing this step is fast ALD (atomic layer deposition). Alternative deposition methods might include physical vapor deposition or sputtering (FIG. 8(a));2. Ru STP—A write gap stop layer754is deposited on the regular write gap layer752to protect the regular write gap layer752from the GWG milling process in step 7;3. GWG dep—This is where Process Route 2 begins to differ from Process Route 1. In Process Route 1, a non-magnetic spacer756was deposited on the regular write gap layer752, and the gradient write gap layer760was deposited over both the regular write gap layer and the non-magnetic spacer. Here, in Process Route 2, the gradient write gap layer760is deposited over the write gap layer752before deposition of the non-magnetic spacer756. Deposition of the gradient write gap layer760may be performed via fast ALD, or any other appropriate deposition method. The gradient write gap layer760may comprise a non-magnetic material such as Ru or Al2O3(FIG. 8(c));4. GWG cap—A gradient write gap cap layer762, which may comprise Ru, Ta, Al2O3, or similar non-magnetic materials, is deposited on the gradient write gap layer760(FIG. 8(c));5. BV2 FALD—A non-magnetic spacer756(i.e., BV2) is now formed on the regular write gap layer752and the gradient write gap layer760(FIG. 8(d));6. BV2 RIE—A BV2 stop layer758is formed on the non-magnetic spacer756. The BV2 stop layer758may comprise Ru, Ta, Al2O3, or similar non-magnetic materials, and may be formed via reactive ion etch (RIE)) (FIG. 8(d));7. GWG Mill—An ion mill may now be used to shape the GWG layer760(FIG. 8(e)). It can be seen inFIG. 8(e) that a portion of the GWG layer760directly above the write gap752has been milled away to form a more gradual, sloped shape in the GWG layer760. Once again, three contiguous beveled surfaces have been formed that progressively increase in angle: a first bevel753has a first angle approximating the regular write gap layer752, a second bevel755has a second angle that is milled into the gradient write gap layer760and is greater than the first angle, and a third bevel757has a third angle substantially determined by the non-magnetic spacer756, the third angle being greater than the angles of the first and second bevels753,755.8. Ru RIE—A final Ru cap layer764is formed over the re-shaped GWG layer760. The Ru cap layer764may be formed via reactive ion etch using Ru, or another similar non-magnetic material.

FIG. 9provides a step-by-step breakdown for a third process route (Process Route 3) to form a gradient write gap, in accordance with an embodiment of the present disclosure. Process Route 3 may be summarized using the following steps, as shown inFIG. 9:1. Each of the following steps have been performed inFIG. 9(a): BV1 process—like Process Routes 1 and 2, the process starts with a first angled surface formed on the main pole750;Deposit BV3 stop layer—Unlike Process Routes 1 and 2, Process Route 3 includes a BV3 non-magnetic layer770that is deposited on the main pole750;Spacer FALD—A non-magnetic spacer756(i.e., BV2) is formed on the BV3 non-magnetic layer770. The non-magnetic spacer756may comprise a non-magnetic material, as has been discussed previously;BV2 RIE—A BV2 stop layer758is formed on the non-magnetic spacer756. The BV2 stop layer758may comprise Ru, or other non-magnetic material, and may be formed via reactive ion etch (RIE));2. BV3 Mill—The BV3 non-magnetic layer770is re-shaped using an ion mill;3. WG DEP—A regular write gap layer752is deposited over the main pole750, the non-magnetic spacer756, and the BV3 non-magnetic layer770. This may be performed using fast ALD;4. Ru STP—An write stop layer756is deposited on the regular write gap layer752(e.g., Ru or amorphous carbon or similar materials);5. GWG FALD—A gradient write gap layer760is deposited on the regular write gap layer752(e.g., fast ALD and Al2O3, etc);6. Ru CAP—A gradient write gap layer762is deposited on the gradient write gap760(e.g., Ru);7. GWG Mill—The gradient write gap layer760is shaped using an ion mill. This results in the formation of a first bevel753, a second bevel755, and a third bevel757, similar to the end results of Processes 1 and 2 (FIGS. 7-8).8. Ru RIE—A final Ru cap layer764is formed over the re-shaped gradient layer760.

In each of the processes discussed above, the regular write gap layer752, the gradient write gap layer760, and the non-magnetic spacer756together form a non-magnetic layer between the main pole750and a magnetic shield. As has been discussed extensively above, each of the three different process routes (FIGS. 7-9) result in the end goal of a wedge-shaped gradient write gap. The gradient write gap has a narrower write gap opening at the air-bearing surface and a gradual slope into the non-magnetic spacer756. The gradual slope is achieved by shaping the gradient write gap layer760to form a bevel755having an angle that is greater than the angle formed by the regular write gap layer752and smaller than the angle formed by the non-magnetic spacer756.

In the foregoing specification, embodiments of the disclosure have been described with reference to specific exemplary features thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure. The specification and figures are, accordingly, to be regarded in an illustrative rather than a restrictive sense. Although the disclosure has been presented with reference only to the presently preferred embodiments, those of ordinary skill in the art will appreciate that various modifications can be made without departing from this disclosure. Accordingly, this disclosure is defined only by the following claims.