# Patent

## Title
Process for making PMR writer with constant side wall angle

## Abstract

A process for manufacturing a writer main pole for a perpendicular magnetic recording system is provided. The writer pole may have a constant sidewall angle from the ABS to yoke and may be formed out of an insulating material and a magnetic material. The sidewall angle of the yoke region may be adjusted during manufacture. The ABS region may correspond to the magnetic material and the yoke region may correspond to the insulating material. The insulating material may comprise Alumina. The magnetic material may comprise a NiFe alloy.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to provisional U.S. Patent Application Ser. No. 61/828,267, filed on May 29, 2013, which is hereby incorporated by reference in its entirety.


TECHNICAL FIELD
This invention relates to the field of perpendicular magnetic recording (PMR) technology and more specifically, to the manufacture of PMR write heads.
BACKGROUND
PMR systems have been developed to meet the growing demand for improved magnetic disk drive data rate and capacity. With the ever increasing need for higher recording areal densities (over 920 GB/in2) and track densities (over 500K tracks per inch), improved processes for manufacturing PMR writers with wrap around shields (WAS) continue to be developed.
Damascene processes may be used to build up structures for use in a PMR writer head, as opposed to methods which rely upon material removal to form such structures. As applied to the formation of PMR writing heads, the damascene process involves forming trapezoidal trenches in a material, and then depositing (e.g., electroplating) a magnetic pole material into the trenches to form write poles. The PMR writer pole is the trapezoidal formation of the magnetic material deposited in the trapezoidal trench etched in a surrounding material.
An important consideration during the manufacture of PMR writers is the sidewall angle of the structure, which affects both on track performance and neighboring track impact from the head skew angle. In current magnetic disk drives, the head generally has a skew angle relative to the track direction when the head operates at inner and outer radii of the recording medium surface. This skew may cause magnetic fields from the writer pole surface to erase data in neighboring tracks. A high sidewall angle for a writer pole at an air bearing surface (ABS) prevents this skew impact on neighboring tracks. However, a high sidewall angle may also cause on track reverse overwrite loss. Optimization of the sidewall angle is thus needed to achieve acceptable on track performance while avoiding skew impact in neighboring tracks.
Existing processes for manufacturing PMR writer poles, however, generally produce a varying sidewall angle from the pole's yoke to its air-bearing surface (ABS). FIG. 1 illustrates this variation for four PMR writer main poles manufactured using existing processes. The sidewall angle continuously increases from the ABS through the yoke region. This sidewall angle increase from the ABS to the yoke results in an increase in on track reverse overwrite loss without any corresponding benefit to skew impact.
For example, existing Alumina (Al2O3) based damascene reactive ion etching (“RIE”) processes produce an inconsistent sidewall angle from the ABS 120 through the yoke region 110 due to the RIE loading effect. Under the RIE loading effect, the yoke region etches at a faster rate than the ABS region (assuming the same etching chemistry and selectivity in both regions) because the yoke region has a larger surface area. The faster etching process in the yoke region results in a larger sidewall angle in the yoke region in contrast to the ABS region.



BRIEF DESCRIPTION OF THE DRAWINGS
The present application is illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which:
FIG. 1 shows sidewall angle plotted against the distance from ABS for four PMR writer main poles manufactured using existing processes.
FIG. 2 is a flowchart describing a process used for manufacturing a PMR writer main pole.
FIGS. 3-11 are diagrams illustrating an exemplary embodiment of a PMR writer main pole during fabrication in accordance with the process of FIG. 2.



DETAILED DESCRIPTION
In the following description, numerous specific details are set forth, such as examples of specific layer compositions and properties, to provide a thorough understanding of various embodiment of the preside sent invention. 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 invention. In other instances, well known components or methods have not been described in detail to avoid unnecessarily obscuring various embodiments of the present invention.
The terms “over,” “under,” “between,” and “on” as used herein refer to a relative position of one media layer with respect to other layers. As such, for example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. By contrast, a first layer “on” a second layer is in contact with that second layer. Additionally, the relative position of one layer with respect to other layers is provided assuming operations are performed relative to a substrate without consideration of the absolute orientation of the substrate.
FIGS. 2-11 illustrate an exemplary damascene process 200 for fabricating a PMR writer main pole. Implementations of the process allow for an approximately constant (i.e. range of 2 degrees) sidewall angle from the ABS of the pole to the yoke. This in turn improves on track write field performance in the writer main pole while not affecting skew impact on neighboring tracks.
FIGS. 3-11 illustrate side, cross-sectional, and top views of the PMR pole after various process operations and will be described in conjunction with FIG. 2, which details the process operations themselves.
For simplicity, some process operations may be omitted. The PMR writer pole being fabricated may be part of a merged head that also includes a read head (not shown) and resides on a slider (not shown) in a disk drive. The process 200 also may commence after formation of other portions of the PMR writer pole.
At operation 202, a substrate 305 is provided with a bottom layer 320′ and an intermediate layer of magnetically insulating material 310 and magnetic material 320 deposited over the substrate. The intermediate layer may be planarized (i.e. both materials are same height) and has a thickness of 0.6 to 1.5 microns. In the illustrated embodiment, bottom layer 320′ comprises magnetic material 320. For ease of reference, bottom layer 320′ is given the same label as magnetic material 320 in subsequent FIGS. 4-11. However, this labeling only indicates that bottom layer 320′ comprises the same material as magnetic material 320 and does not mean that any of the operations of process 200 act on bottom layer 320′. Moreover, in other embodiments bottom layer 320′ may comprise a different material than magnetic material 320.
As further described in exemplary embodiments below, the insulating material 310 and magnetic material 320 may be etched to form a yoke and ABS region of a PMR main pole as indicated by dotted pattern 325 in FIG. 3 (provided for illustration only and not present on substrate 305 at this operation). The yoke region corresponds to the pole's yoke and may be etched out of the insulating material 310. The ABS region corresponds to the region from the ABS (i.e. pole tip) to the start of the yoke region (i.e. neck area of pole) and may be etched out of the magnetic material 320.
The separation boundary between the yoke region and ABS region of the PMR pole (not yet etched) may be defined as the separation boundary between insulating material 310 and magnetic material 320 at dotted line 322 as shown in the top view of FIG. 3. Accordingly, the distance from the ABS to the separation boundary is the distance that the yoke region is from or behind the ABS. In some embodiments, the yoke region (separation boundary) may be 20 to 250 nm behind the ABS. In the embodiment illustrated by process 200, the yoke region is 50 to 150 nm behind the ABS.
The separation boundary 322 may be defined during an initial process (not shown) used to create the structure provided in FIG. 3. In the illustrated embodiment, the separation boundary 322 is defined by shield or shield pattern 321, which comprises magnetic material 320. Shield pattern 321 may have been created during photolithography, RIE, and plating processes (preceding operation 202) used to form magnetic material 320 in the intermediate layer of substrate 305, where the intermediate layer comprised only insulating material 310 prior to these processes. During the photolithography process, the placement of a photoresist mask with pattern 321 relative to the substrate may define the placement of the separation boundary. Accordingly, the substrate provided at operation 202 may have a predefined separation boundary 322 between insulating material 310 and magnetic material 320.
In the illustrated embodiment, insulating material 310 comprises Alumina (Al2O3) and magnetic material 320 comprises a Nickel-Iron (NiFe) alloy. In other embodiments, the insulating material 310 may comprise Silicon Dioxide (SiOx). The magnetic material 320 and insulating material 310 may be provided such that they have similar etching rates, for example, an etch selectivity range of 1 to 1.1 between the two materials.
At operation 204, hard mask 330 and hard mask 340 are deposited on the substrate. As illustrated by FIG. 4, hard mask 330 is deposited on the intermediate layer. Hard mask 330 may be deposited over some or all of the intermediate layer. In the illustrated embodiment, hard mask 330 is deposited over all of the intermediate layer and has a thickness between 50 and 100 nm. As further described in exemplary embodiments below, hard mask 330 may be used as an etching mask for adjusting a sidewall angle corresponding to a yoke region etched out of the insulating material.
A second hard mask 340 is then deposited on hard mask 330. Hard mask 340 may be deposited over some or all of the first hard mask 330. In the illustrated embodiment, hard mask 340 is deposited over all of hard mask 330 and has a thickness between 100 and 200 nm. As further described in exemplary embodiments below, hard mask 330 may be used as an etching mask for etching a PMR main pole yoke and ABS region in insulating material 310 and magnetic material 320.
In the illustrated embodiment, hard mask 330 comprises Nickel-Chrome (NiCr) and hard mask 340 comprises Tantalum (Ta). In other embodiments, hard mask 330 may comprise Nickel-Iron-Chrome (NiFeCr). Further, in other embodiments hard mask 340 may comprise Titanium (Ti).
Operations 206-214 illustrate an exemplary process for forming a PMR main pole yoke and ABS region in hard mask 340 using lithography and etching processes. This process may prepare hard mask 340 as a hard mask for etching a PMR pole opening in insulating material 310 and magnetic material 320.
At Operation 206 a lithography process is used to form a resist pattern layer 350 over the hard mask 340. Lithographic techniques for forming the resist pattern layer 350 can include any technique such as photolithography. The resist pattern layer 350 may cover some of hard mask layer 340. In the illustrated embodiment, the resist pattern layer 350 has a writer main pole photo pattern (VP3 photo pattern), which comprises a yoke and ABS region as described above.
A hard mask layer 360 is deposited over the resist pattern layer 350 and the hard mask layer 340 at operation 208. Hard mask layer 360 may be deposited over some or all of the resist pattern layer 350 and over all or some of the hard mask layer 340 not covered by the resist pattern. In the illustrated example, hard mask layer 360 is deposited over all of the resist pattern layer 350 and over all of hard mask layer 340 not covered by the resist pattern 350. Hard mask layer 360 may comprise Chromium (Cr) or Ruthenium (Ru), or any other material that has a high etching selectivity with respect to the material being patterned.
At operation 210, hard mask layer 360 is side milled to prepare for a lift-off of resist pattern layer 350. As illustrated in FIG. 5, side milling removes hard mask layer 360 on lateral sides 355 of the resist pattern layer 350. The operation exposes some portions (e.g. lateral sides) of the resist pattern layer 350 so that an etchant can access the layer during an etching operation.
At operation 212 the resist layer 350 and hard mask layer 360 are lifted off to transfer the ABS region and yoke region pattern from the resist pattern layer 350 to hard mask layer 360. This forms a corresponding ABS region and yoke region opening in layer 360. Thus, a hard mask layer 360A has been formed. Hard mask layer 340 is then etched using hard mask layer 360A as a hard mask (operation 214). In this exemplary process an RIE is performed. The RIE may be performed with a CO—NH3 etch chemistry or an etch chemistry that includes Cl, for example Cl2O2. The RIE transfers the yoke and ABS region openings from hard mask layer 360A to hard mask layer 340. Thus, a hard mask layer 340A has been formed from hard mask 360A. This is illustrated by aperture 361 and the top view in FIG. 6.
A PMR pole opening may then be formed in insulating material 310 and magnetic material 320. At operation 216, hard mask layer 330, and the intermediate layer (insulating material 310 and magnetic 320) are etched using hard mask layer 340A as a hard mask. In this exemplary process a RIE is performed. The RIE may be performed with a CO—NH3 etch chemistry or an etch chemistry that includes Cl, for example Cl2O2. As illustrated in FIG. 7, the RIE forms a hard mask layer 330A, an insulating material 310A, and a magnetic material 320A. Magnetic material 320A may have a trench opening 362 corresponding to the ABS region of the formed pole opening. Insulating material 310A may have a trench opening 363 corresponding to the yoke region of the formed pole opening.
The sidewall angle corresponding to insulating material's 310A formed trench opening (yoke region) may be larger than the sidewall angle corresponding to magnetic material's 320A formed trench opening (ABS region). For example, the yoke region may have a sidewall angle between 13 and 17 degrees and the ABS region may have a sidewall angle between 11 and 13 degrees. The sidewall angle in each region may be continuous or variable. Moreover, the sidewall angle may continuously increase from the ABS (beginning of ABS region) to the end of the yoke region. The difference in side wall angles between the two regions after etching may be caused by the yoke region having a larger surface area than the ABS region. The difference may also be caused by the differing etching rates between insulating material 310A and magnetic material 320A.
An operation may then be performed to adjust the sidewall angle in the yoke region corresponding to insulating material 310A such that it is within a desired range of the sidewall angle in the ABS region (e.g. within 4 degrees, 2 degrees, or 1 degree). At operation 218, insulating material 310A is etched using hard mask layer 330A as a hard mask. Thus, an insulating material 310B has been formed. In this exemplary process a RIE is performed. The RIE may be performed with a CO—NH3 etch chemistry or an etch chemistry that includes Cl, for example Cl2O2. As illustrated in FIG. 8, operation 218 may remove the remainder of mask 340A and may adjust trench 363 such that the sidewall angle in the yoke region is closer to the sidewall angle in the ABS region. Thus, a trench 363A has been formed with a new sidewall angle.
The RIE may be performed such that the sidewall angle from the ABS to the end of the yoke region is now approximately constant (i.e. varies less than 2 degrees). In one exemplary embodiment, the sidewall angle from the ABS to the end of the yoke region stays within the range of 11.5 to 12.5 degrees after operation 218. As discussed above, this exemplary operation may improve on track reverse overwrite loss in a manufactured PMR writer main pole by lowering the sidewall angle in the yoke region. Thus, a desired PMR main pole opening has been formed.
Next, a PMR main pole may be formed. At operation 220, a non-magnetic gap layer 370 may be deposited on the intermediate layer (insulating material 310B and magnetic material 320A) using an atomic layer deposition (“ALD”) process. Layer 370 may serve as a seed layer for a PMR main pole plating. The structure after operation 220 is illustrated in FIG. 9. In an alternative embodiment, the non-magnetic gap layer 370 may be deposited using a chemical vapor deposition (“CVD”) process. In this exemplary embodiment, layer 370 comprises Ruthenium (“Ru”). In other embodiments, the layer may comprise any material having sufficient conductivity and capable of serving as a seed layer for the upper magnetic materials (i.e. the PMR main pole layer).
As discussed above, the non-magnetic gap layer 370 serves a seed layer for a PMR pole layer. At operation 222, magnetic plating material is deposited over the seed layer 370 to form PMR pole layer 380. As illustrated in FIG. 10, plating material 380 (the PMR pole layer) fills trenches 362 and 363A of insulating material 310B and magnetic material 320A. Moreover, plating material 380 is deposited outside the trenches at lateral sides on seed layer 370. Pole layer 380 may be plated with a hard magnetic material. In the illustrated embodiment, Cobalt-Iron (CoFe) is used to the plate the PMR pole layer 380. In other embodiments Cobalt-Nickel-Iron (CoNiFe) may be used. In yet other embodiments, multiple layers may be used to plate the PMR pole layer.
At operation 224, a chemical mechanical planarization (“CMP”) may be performed to adjust the height of pole layer 380. Thus, a pole layer 380A has been formed. In the illustrated embodiment, the pole height is adjusted using CMP such that the plating material is the same height as trenches 362 and 363A. In an alternative embodiment, an ion beam etch (IBE) may be performed to adjust the pole layer height.
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.

## Claims

1. A method, comprising:
forming over a substrate a layer comprising insulating material and magnetic material, wherein the insulating material and magnetic material are planar at a top surface of the layer;
depositing a first hard mask and a second hard mask over the top surface of the layer;
forming an air-bearing surface (ABS) region in the magnetic material with a first sidewall angle;
forming a yoke region in the insulating material with a second sidewall angle; and
decreasing the second sidewall angle by performing a reactive ion etch (RIE) on the insulating material using the first hard mask.

2. The method of claim 1 wherein the ABS region and yoke region are formed using the second hard mask.

3. The method of claim 2, wherein forming the ABS region and the yoke region comprises:
forming a resist pattern over a portion of the second hard mask;
depositing a third hard mask over the resist pattern;
removing a portion of the third hard mask deposited over the resist pattern to form a patterned third hard mask;
performing a RIE on the second hard mask using the third hard mask; and
performing a RIE on the first hard mask, insulating material, and magnetic material using the second hard mask.

4. The method of claim 3 wherein the third hard mask comprises at least one of chromium (Cr) or ruthenium (Ru).

5. The method of claim 3 wherein the resist pattern is a writer main pole photo pattern.

6. The method of claim 2, wherein the magnetic material comprises nickel-iron (NiFe).

7. The method of claim 2, wherein the insulating material comprises alumina (Al2O3).

8. The method of claim 7, wherein the second sidewall angle is decreased to within 2 degrees of the first sidewall angle.

9. The method of claim 8 wherein the first and second sidewall angles are between 11 and 13 degrees.

10. The method of claim 2 wherein the first hard mask comprises nickel chromium (NiCr).

11. The method of claim 2 wherein the second hard mask comprises tantalum (Ta).

12. The method of claim 2 wherein the yoke region is 20 to 250 nm behind the ABS.