# Patent

## Title
Straight top main pole for PMR bevel writer

## Abstract

A magnetic recording head includes a write pole comprising a throat region. The throat region includes a lower portion having a substantially trapezoidal cross-section, and an upper portion having a substantially rectangular cross-section. In a beveled region of the write pole, the substantially rectangular cross-section of the upper portion decreases in height towards an air bearing surface of the magnetic recording head.

## Background
FIELD OF THE INVENTION
The present invention generally relates to hard drives and, in particular, relates to damascene straight top main poles for perpendicular magnetic recording (PMR) bevel writers.
BACKGROUND OF THE INVENTION
Hard disk drives include one or more rigid disks, which are coated with a magnetic recording medium in which data can be stored. Hard disk drives further include read and write heads for interacting with the data in the magnetic recording medium. The write head includes an inductive element for generating a magnetic field that aligns the magnetic moments of domains in the magnetic recording medium to represent bits of data.
Magnetic recording techniques include both longitudinal and perpendicular recording. Perpendicular magnetic recording (“PMR”) is a form of magnetic recording in which the magnetic moments representing bits of data are oriented perpendicularly to the surface of the magnetic recording medium, as opposed to longitudinally along a track thereof. PMR enjoys a number of advantages over longitudinal recording, such as significantly higher areal density recording capability.
Some PMR write poles are provided with a bevel near the air bearing surface, which allows the majority of the write pole to have a large thickness while providing a desirable thin pole tip. Unfortunately, in manufacturing trapezoidal write poles with beveled tips, various write pole parameters, such as track width, may be undesirably affected.
SUMMARY OF THE INVENTION
Various embodiments of the present invention solve the foregoing problem by providing a write pole with a bevel that does not affect the track width of the pole. The pole has a cross sectional shape defined by a lower trapezoidal region, and an upper rectangular region, in which upper region the beveled surface intersects the air bearing surface of the pole. This configuration allows for small variations in the position of the beveled surface without any variation in the track width of the write pole.
According to one embodiment of the subject disclosure, a magnetic recording head includes a write pole comprising a throat region. The throat region includes a lower portion having a substantially trapezoidal cross-section, and an upper portion having a substantially rectangular cross-section. In a beveled region of the write pole, the substantially rectangular cross-section of the upper portion decreases in height towards an air bearing surface of the magnetic recording head.
According to another embodiment of the subject disclosure, a method of forming a magnetic recording head comprises the step of forming a damascene trench comprising a lower region having a substantially trapezoidal cross-section and an upper region having a substantially rectangular cross-section. The method further comprises providing a magnetic material within the damascene trench.
It is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1A is a perspective view of a beveled write pole in accordance with one aspect of the subject disclosure;
FIG. 1B is a frontal view of a beveled write pole in accordance with one aspect of the subject disclosure;
FIGS. 2A to 2H illustrate sequential steps in a method of forming a magnetic recording head in accordance with one aspect of the subject disclosure;
FIGS. 3A and 3B are cross-sectional views of a beveled write pole in accordance with one aspect of the subject disclosure;
FIGS. 4A and 4B are cross-sectional views of a beveled write pole in accordance with one aspect of the subject disclosure; and
FIG. 5 is a flow chart illustrating a method of forming a magnetic recording head in accordance with one aspect of the subject disclosure.



DETAILED DESCRIPTION OF THE INVENTION
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present invention. It will be apparent, however, to one ordinarily skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the present invention.
FIG. 1A is a perspective view of a throat region 100 of a beveled write pole (i.e., main pole) in accordance with one aspect of the subject disclosure. Throat region 100 includes an upper region 101 with a substantially rectangular cross section (e.g., defined by substantially parallel side walls, a trailing edge, and an interface with the lower region). Throat region 100 further includes a lower region 102 with a substantially trapezoidal cross section (e.g., defined by angled side walls, a leading edge, and an interface with upper region 101). The substantially trapezoidal cross-section of lower region 102 is substantially constant along a nose length of the throat region, as is illustrated in exemplary FIG. 1A. Near an air bearing surface 104 of the write pole, throat region 100 includes a substantially planar bevel 103 that intersects air bearing surface 104 within upper region 101. Bevel 103 defines an upper surface of upper region 101 of the throat region 100. The beveled region extends from air bearing surface 104 partway along a nose length of throat region 100. Throat region 100 of the write pole is illustrated from the air bearing surface view in FIG. 1B, in accordance with one aspect of the subject disclosure. As can be seen with reference to FIG. 1B, beveled surface 103 intersects air bearing surface 104 within upper region 101 of the write pole.
A write pole with the foregoing configuration enjoys a number of benefits when compared with other write pole designs. For example, by providing an upper region with substantially parallel side walls, variation in the position of bevel 103 will not impact the track width of the write pole (e.g., as the track width is substantially constant within upper region 101). Bevel 103 may intersect air bearing surface anywhere within upper region 101, or even at an interface between upper region 101 and lower region 102, without negatively affecting the track width of the write pole. As beveled surfaces such as bevel 103 are notoriously difficult to manufacture to the precise tolerances required to reliably maintain a desired track width in write poles with trapezoidal cross-sectional shapes, the foregoing configuration can improve the yield and manufacturing simplicity of hard disk drives incorporating such write poles.
For example, a method of forming a magnetic recording head comprising such a beveled write pole is illustrated in FIGS. 2A to 2H. In FIG. 2A, an RIE stop layer 201 of ruthenium (Ru), nickel-iron (NiFe), chromium (Cr), or the like is overlaid with a substrate 202 of alumina (Al2O3), on which is disposed a sacrificial material 203 such as photoresist. In FIG. 2B, the photoresist has been covered over with an RIE mask layer 204 of Ru, Cr, NiFe or the like, over which is disposed a second substrate layer 205 of alumina. A CMP stop layer 206 of Ru, tantalum (Ta), Cr, rhodium (Rh) or the like is disposed over second substrate 205, except in regions in which second substrate layer 205 protrudes upwards (e.g., over and around sacrificial material 203). In FIG. 2C, a chemical-mechanical polishing (CMP) step has removed the uppermost regions of second substrate 205 and part of RIE mask layer 204. An ion milling operation is then performed, exposing sacrificial material 203 (and removing CMP stop layer 206 and additional portions of second substrate 205). Sacrificial material 203 may then be removed, either by reactive ion etching (RIE) or by a photo strip process (e.g., if sacrificial material 203 is photoresist), leaving the structure illustrated in FIG. 2D.
Turning to FIG. 2E, an RIE step forms a damascene trench in first substrate 202 with a substantially trapezoidal cross section. This RIE step may be the same step used to remove sacrificial material 203, or may be a separate step, configured to provide the trapezoidal trench with desired dimensions and/or side wall angles. Turning to FIG. 2F, a plating seed layer/CMP stop layer 207 of Ru, Cr, Rh or the like is deposited over the trench region, and a magnetic material 208 such as CoNiFe, CoFe, NiFe, or the like, is electroplated into the trench, as is shown in FIG. 2G. Another CMP step removes the portion of magnetic material 208 protruding above second substrate 205 and the uppermost portion of CMP stop layer 207, as shown in FIG. 2H. The magnetic material left in the trench forms a write pole, having a lower region with a substantially trapezoidal cross section and an upper region with a substantially rectangular cross section.
In accordance with one aspect of the subject disclosure, the structure illustrated in FIGS. 2A to 2H may be further processed to form a beveled region near an air bearing surface, as is illustrated in FIGS. 3A and 3B. With reference to exemplary FIGS. 3A and 3B, a beveled main pole 303 is illustrated in cross section, both along axis A-A (FIG. 3A) and at the air bearing surface (FIG. 3B). The head structure comprises an RIE stop layer 301, a side gap layer (e.g., a plating seed layer) 302 and the magnetic material of the main pole 303. The head structure may further comprise side shields 305, and additional layers such as RIE mask layer 306 and second substrate layer 307. By disposing a mask layer 304 over the main pole 303, while leaving uncovered a region near the air bearing surface (ABS), an ion beam etching step may be performed to form a substantially planar bevel 308 that intersects air bearing surface in a region of main pole 303 with substantially parallel side walls.
By providing an upper region of main pole 303 with substantially parallel side walls, variation in the position of bevel 308 will not impact the track width of the write pole (e.g., as the track width is substantially constant within the upper region). Bevel 308 may intersect the air bearing surface anywhere within the upper region, or even at an interface between the upper region and the lower region, without negatively affecting the track width of the write pole.
In accordance with one aspect of the subject disclosure, the structure illustrated in FIGS. 3A and 3B may be further processed to provide a trailing shield thereon, conform with the beveled surface thereof, as is illustrated in FIGS. 4A and 4B. With reference to exemplary FIGS. 4A and 4B, a beveled main pole 403 with a trailing shield 409 is illustrated in cross section, both along axis B-B (FIG. 4A) and at the air bearing surface (FIG. 4B). The head structure comprises an RIE stop layer 401, a side gap layer (e.g., a plating seed layer) 402 and the magnetic material of the main pole 403. The head structure may further comprise side shields 405, and additional layers such as RIE mask layer 406, second substrate layer 407, and a beveling mask layer 404. The head structure may further comprise a write gap layer 408 of Al2O3, Ru, Rh, or the like disposed over main pole 403 and a conformal trailing shield 409 of NiFe, CoNiFe or the like disposed over write gap layer 408, near the air bearing surface (ABS) of the head.
FIG. 5 is a flow chart illustrating a method of forming a magnetic recording head in accordance with one aspect of the subject disclosure. The method begins with steps 501 to 505, in which is formed a damascene trench comprising a lower region having a substantially trapezoidal cross-section and an upper region having a substantially rectangular cross-section. In particular, in step 501, a first substrate (e.g., of alumina) is provided. In step 502, a sacrificial material (e.g., photoresist) is provided over the first substrate, the sacrificial material having a substantially rectangular cross-sectional shape. In step 503, as second substrate (e.g., alumina) is provided over the first substrate and surrounding the sacrificial material. In step 504, the sacrificial material is removed (e.g., via RIE, wet etching, photo stripping, or the like). In step 505, the lower substrate exposed by removing the sacrificial material is subjected to a reactive ion etching, to form a damascene trench therein with a substantially trapezoidal cross-sectional shape. In step 506, a magnetic material is provided (e.g., via electroplating) within the trench formed in steps 501 to 505. In step 507, a portion of the magnetic material in the upper region (with the substantially rectangular cross-section) may be removed (e.g., via ion beam etching) to form a beveled surface near an air bearing surface of the magnetic recording head. In step 508, a trailing shield may be disposed over the magnetic material in the upper region (with the substantially rectangular cross-section) near an air bearing surface of the magnetic recording head.
The description of the invention is provided to enable any person skilled in the art to practice the various embodiments described herein. While the present invention has been particularly described with reference to the various figures and embodiments, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the invention.
There may be many other ways to implement the invention. Various functions and elements described herein may be partitioned differently from those shown without departing from the spirit and scope of the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein may be applied to other embodiments. Thus, many changes and modifications may be made to the invention, by one having ordinary skill in the art, without departing from the spirit and scope of the invention.
A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” The term “some” refers to one or more. Underlined and/or italicized headings and subheadings are used for convenience only, do not limit the invention, and are not referred to in connection with the interpretation of the description of the invention. All structural and functional equivalents to the elements of the various embodiments of the invention described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the invention. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description.

## Claims

1. A magnetic recording head having a write pole, the write pole comprising:
a throat region extending to an air bearing surface of the magnetic recording head, the throat region comprising:
a lower portion having a substantially trapezoidal cross-section at the air bearing surface; and
an upper portion having a rectangular cross-section at the air bearing surface,

wherein, in a beveled region of the write pole, the rectangular cross-section of the upper portion decreases in height towards the air bearing surface.

2. The magnetic recording head of claim 1, wherein the substantially trapezoidal cross-section of the lower portion is substantially constant along a nose length of the throat region.

3. The magnetic recording head of claim 1, wherein the beveled region extends from the air bearing surface of the magnetic recording head partway along a nose length of the throat region.

4. The magnetic recording head of claim 1, wherein the beveled region comprises a substantially planar bevel defining an upper surface of the upper portion of the throat region.

5. The magnetic recording head of claim 4, wherein the substantially planar bevel intersects the air bearing surface of the magnetic recording head within the upper portion of the throat region.

6. The magnetic recording head of claim 1, wherein the upper section comprises substantially parallel side walls.

7. The magnetic recording head of claim 1, further comprising:
a trailing shield disposed over the throat region of the write pole adjacent the air bearing surface.

8. The magnetic recording head of claim 7, wherein the trailing shield has a lower surface conformal with a bevel of an upper surface of the upper portion of the throat region.

9. The magnetic recording head of claim 1, further comprising:
first and second side shields on opposing sides of the throat region adjacent the air bearing surface.

10. The magnetic recording head of claim 1, wherein a width of the rectangular cross-section is about equal to a maximum width of the substantially trapezoidal cross-section of the lower portion and substantially constant along a nose length of the throat region.

11. The magnetic recording head of claim 10, wherein the upper portion consists of a rectangular block shape having the beveled region.

12. The magnetic recording head of claim 11:
wherein the beveled region comprises a substantially planar bevel that intersects the air bearing surface within the upper portion of the throat region, and
wherein the beveled region extends from the air bearing surface of the magnetic recording head partway along a nose length of the throat region.

13. The magnetic recording head of claim 12, wherein the substantially trapezoidal cross-section of the lower portion is substantially constant along a nose length of the throat region.

14. The magnetic recording head of claim 13, wherein the upper section comprises substantially parallel side walls.

15. The magnetic recording head of claim 14, further comprising a trailing shield disposed over the throat region of the write pole adjacent the air bearing surface.

16. The magnetic recording head of claim 15, wherein the trailing shield has a lower surface conformal with a bevel of an upper surface of the upper portion of the throat region.

17. The magnetic recording head of claim 16, further comprising first and second side shields on opposing sides of the throat region adjacent the air bearing surface.