Method of making an ultra-sharp tip mode converter for a HAMR head

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 61/946,483, filed Feb. 28, 2014, which is incorporated herein by reference in its entirety.

BACKGROUND

For all types of substrates, magnetic recording media has begun to incorporate perpendicular magnetic recording (PMR) technology in an effort to increase magnetic recording areal density. Although magnetic recording areal densities of approximately 1 Tb/in² have been achieved, further increases are unlikely as the physical limits of PMR have nearly been met due to the superparamagnetic effect. Accordingly, Heat-assisted magnetic recording (HAMR) technology has been developed to meet the growing demand for improved magnetic disk drive data capacity.

HAMR media is often made of magnetic materials or compounds with a substantially higher magnetocrystalline anisotropy than that of non-HAMR media. Because HAMR media is made of higher-stability magnetic compounds, HAMR media relies upon the application of heat to achieve changes in magnetic orientation. That is, HAMR media is temporarily heated to reduce its coercivity below that of an applied magnetic write field from a recording head. These materials can store bits in a much smaller area without being limited by the superparamagnetic effect. In this regard, HAMR technology is a promising solution for pushing the magnetic recording areal density of a hard disk to beyond 1 Tbit/in².

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which:

FIG. 1 is a block diagram depicting an example HAMR head;

FIG. 2 is a graph illustrating mode converter (MC) output as a function of MC tip width;

FIG. 3 is a flow chart illustrating example processes performed to manufacture a mode converter having an ultra-sharp tip in accordance with various embodiments;

FIGS. 4A and 4B are respective cross-sectional and top views of a wafer film stack used for manufacturing a mode converter having an ultra-sharp tip in accordance with various embodiments;

FIGS. 5A and 5B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B upon which a first mode converter edge has been defined;

FIGS. 6A and 6B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B, where the first mode converter edge has been transferred to a hard mask layer;

FIGS. 7A and 7B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B, where a second mode converter edge has been defined;

FIGS. 8A and 8B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B, where the second mode converter edge has been transferred to the hard mask layer;

FIGS. 9A and 9B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B, where a temporary mode converter pattern has been formed on the hard mask layer;

FIGS. 10A and 10B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B, where the temporary mode converter pattern has been transferred into a core layer;

FIGS. 11A and 11B are respective cross-sectional and top views of the wafer film stack of FIGS. 4A and 4B where the hard mask and stop layers have been removed and a protective layer has been deposited subsequent to formation of the mode converter; and

FIG. 12 is an example disk drive including a read/write head that can be created in accordance with various embodiments.

DETAILED DESCRIPTION

In a modern magnetic hard disk drive device, each read/write head is a sub-component of a head gimbal assembly (HGA). The read/write head typically includes a slider and a read/write transducer. The read/write transducer typically comprises a magneto-resistive read element (e.g., a so-called giant magneto-resistive read element, or a tunneling magneto-resistive read element) and an inductive write structure comprising a flat coil deposited by photolithography and a yoke structure having pole tips that face a disk media.

In a HAMR head, delivering laser light from a source onto a HAMR media surface through a tapered wave guide (TWG) and a near field transducer (NFT) becomes critical. The NFT allows for the transfer of enough energy to a small region, thereby heating that small region to a temperature, e.g., close to the Curie temperature of the HAMR media, temporarily so as to achieve writability within a short duration. The scalability of the magnetic recording areal density is determined by that of the NFT, and the writability of a recording layer of the HAMR media (with a high coercivity material as previously alluded to) depends on NFT delivery efficiency.

A mode converter (MC) may be used to couple/bend light (e.g., from an external laser diode) into the TWG, and subsequently, to the NFT, where tip width of the MC is also critical for achieving proper/desired optical output. Accordingly, various embodiments are directed to systems and methods for making an ultra-sharp tip MC that can be utilized in a HAMR head to efficiently collect light from a light source and pass it on to the TWG.

FIG. 1 is a diagram depicting an example HAMR head 100. It should be noted that only some components of HAMR head 100 are illustrated and discussed herein, while other components commonly known in the art are omitted for clarity. Utilizing HAMR head 100, light energy generated by a light source, e.g., an external laser diode (not shown), is coupled to TWG 110 via MC 115 located on top of an input area of the tapering region of TWG 110. Grating 120, located on top of an output area of the tapering region of TWG 110 may be utilized to monitor the operation of the external laser diode by monitoring the output of TWG 110. TWG 110 guides and directs the light energy to PMR writer/write pole 125 and a recording medium (not shown). PMR writer 125 can include, at least in part, NFT 130, which may be formed on TWG 110 (e.g., a waveguide core) and chimney 135, which can act as a heatsink and which can be formed on a surface of NFT 130. NFT 130 focuses the light energy received from the TWG 110 into a nano-sized light beam and delivers the beam to the recording media so as to heat up a specific recording region thereof.

As mentioned above, the tip width of an MC, e.g., MC 115, is critical for light coupling efficiency. FIG. 2 is a graph 200 that illustrates MC optical throughput as a function of MC tip width in nanometers (nm). It can be appreciated that after MC tip width increases beyond approximately 300 nm wide, optical throughput via an MC begins to drop dramatically. It should be noted that MC tip widths contemplated in accordance with various embodiments are preferably in the 200 nm (approximately) or sub-200 nm width range, although the methods described herein can be utilized to form an MC having an MC tip of varying/alternative widths. Again, an MC with an ultra-sharp tip would be advantageous in the HAMR context.

Conventionally, critical layers of a read/write head are processed using, e.g., a single-pattern process, where the critical layers are aligned to the read element. However, such a process is insufficient to produce an MC capable of preferred/optimal performance in a HAMR context. Accordingly, various embodiments are directed to systems and methods of manufacturing an ultra-sharp tip MC utilizing a two-pattern transform process, where overlay control (using a first edge, such as a right edge as a reference layer relative to which positioning of a second edge, such as a left edge, is measured) allows for aligning of the right and left edges of a tip portion of the MC to ultimately create the ultra-sharp tip MC.

FIG. 3 is a flow chart illustrating example processes performed in accordance with various embodiments to manufacture an ultra-sharp tip MC. FIGS. 4A-11B illustrate respective cross-sectional and top views of various stages of an MF process film stack during the ultra-sharp tip MC manufacturing process described in connection with the flow chart of FIG. 3.

At operation 300, an MC process film stack is formed. The MC process film stack may include a stop layer, a core material, a buffer layer, a hard mask layer, and a first cladding layer. In accordance with various embodiments, the MC process film stack may be formed by depositing a thin layer of Aluminum Oxide (AlOx) as an MC reactive ion etch (RIE) stop layer. In accordance with one embodiment, this thin layer of AlOx may be approximately 2-3 nm. This can be followed by depositing a layer of Tantalum Pentoxide (Ta₂O₅), the core material, on the AlOx MC RIE stop layer, and subsequently depositing a layer of thin Silicon Dioxide (SiO₂) as the buffer layer. In one embodiment, the Ta₂O₅ layer may be approximately 100-150 nm. The hard mask layer may be deposited on the SiO₂ buffer layer. It should be noted that although some embodiments described herein describe utilizing material layers having a certain thickness, other materials and/or thickness are contemplated in accordance with desired performance characteristics of a resulting MC/TWG.

In accordance with one embodiment, the hard mask layer can be a Chromium (Cr) hard mask layer. It should be noted that the hard mask layer can also be Ruthenium (R) or other metallic hard mask layer. The Cr hard mask layer can be deposited on the (SiO₂) buffer layer using a bi-layer lift-off process, which subsequent to a dry etching process results in an open metal seed window. That is, and whereas conventionally, metal would be deposited, in accordance with various embodiments a lift-off photoresist “mold” is formed to provide an open target layer with no metal on which metal material may subsequently be deposited. Therefore, in contrast to conventional systems and methods, where, e.g., an ion milling process, would normally be performed to produce an open metal seed window, ion milling need not be performed in the process of creating an MC in accordance with various embodiments. The MC process film stack may further include another SiO₂ layer, which as will be described further below, may act as a (first) cladding layer for TWG 110.

As illustrated in the respective cross-sectional and top view of FIGS. 4A and 4B, the MC process film stack 400 may comprise a plurality of layers, including a Cr hard mask layer 405, a SiO₂ buffer layer 410, a Ta₂O₅ core material layer 415, an AlOx MC RIE stop layer 420, and a first SiO₂ cladding layer 425.

At operation 305, a first edge of the MC is defined. In accordance with various embodiments, the first edge of the mode converter to be defined can be either the right edge or the left edge. As illustrated in the respective cross-sectional and top view of FIGS. 5A and 5B, photoresist material 430 defining the first edge (in this example, the right edge 435) can be applied on the Cr hard mask layer 405 of MC process film stack 400. Using a first deep ultraviolet (DUV) photolithography process, the pattern defined by the photoresist material 430 can be exposed and developed.

At operation 310, the first edge is transferred into the hard mask layer. The transferring of the first edge (in this example, right edge 435) can be accomplished by a first hard mask RIE process utilized on the Cr hard mask layer 405. As illustrated in the respective cross-sectional and top view of FIGS. 6A and 6B, RIE can be used to etch off the unwanted areas of CR hard mask layer 405, leaving the pattern defining right edge 435 in the Cr hard mask layer 405. Additionally, and subsequent to etching of Cr hard mask layer 405, photoresist material 430 may be cleaned/stripped away.

At operation 315, and similar to operation 305, a second edge of the MC is defined (in this example, the left edge 445), wherein respective ends of the first and second edges define an MC tip. As previously discussed, the MC tip in accordance with various embodiments, is an ultra-sharp tip having a width, in accordance with one embodiment, in the 200 nm range, and in another embodiment, in the sub-200 nm range. As illustrated in the respective cross-sectional and top view of FIGS. 7A and 7B, photoresist material 440 defining the second edge (in this example, left edge 445) can be applied to MC process film stack 400. Using a second deep ultraviolet (DUV) photolithography process, the pattern defined by photoresist material 440 can be exposed and developed. In other words, a sequential dual photolithograph process can be utilized to achieve the desired ultra-sharp tip in accordance with various embodiments.

As alluded to above, creating an MC with an ultra-sharp tip having a width of approximately 200 nm or less cannot be achieved or is at best, impractical, utilizing a single-pattern process aligned to the reader element of a read/write head. That is, conventional MC formation processes may utilize a reference layer relative to which first and second edges of an MC tip are measured. In contrast, and in accordance with various embodiments, a separate reference layer need not be utilized. Instead, the first edge may be utilized as a reference layer, and measurements associated with formation of the second edge are made relative to that first edge. Accordingly, various embodiments utilize the two-pattern process described herein where the first and second (e.g., right and left) edges are measured and aligned relative to each other using overlay control with the second DUV photolithography process.

At operation 320, the second edge is transferred into the hard mask layer to form a temporary MC pattern on the hard mask layer. The transferring of the second edge (in this example, left edge 445) can be accomplished by a second hard mask RIE process utilized on the remaining portion of Cr hard mask 405 (in which right edge 435 has been defined). As illustrated in the respective cross-sectional and top view of FIGS. 8A and 8B, RIE can be used to etch off the unwanted areas of the remaining area of CR hard mask layer 405 (defining right edge 435), thus leaving/forming a temporary pattern defining the MC with an ultra-sharp tip in Cr hard mask layer 405. Additionally, and subsequent to etching of the remaining area of Cr hard mask layer 405, photoresist material 440 may be removed by, e.g., a dry etching process, such as RIE.

At operation 325, the temporary MC pattern is transferred into the core material to form a final MC having the defined MC tip. In particular, using MC RIE, the temporary MC pattern formed by the remaining area of Cr hard mask layer 405 (temporarily defining the MC with an ultra-sharp tip) can be transferred into the Ta₂O₅ core material layer 415. As illustrated in the respective cross-sectional and top view of FIGS. 9A and 9B, MC RIE can be utilized to etch away the unwanted portions of the SiO₂ buffer layer and the Ta₂O₅ core material layer 415 (i.e., the portions not covered/protected by the remaining area of the Cr hard mask layer 405 temporarily defining the final MC.

At operation 330, the hard mask layer and the buffer layer are removed. As illustrated in the respective cross-sectional and top view of FIGS. 10A and 10B, the temporary MC pattern formed in Cr hard mask layer 405 and the AlOx MC RIE stop layer 420 are removed.

At operation 335, a protective layer is deposited over the final MC. That is, a SiO₂ layer can be deposited on the final MC to protect the final mode converter. This protective SiO₂ layer also acts as a second cladding layer for the Ta₂O₅ core material layer 415. As would be understood by those of ordinary skill in the art, cladding may be used to surround a waveguide core to reflect light back to the waveguide core and prevent light from escaping. The respective cross-sectional and top view of FIGS. 11A and 11B illustrate the final MC having an ultra-sharp tip and a protective/cladding layer of SiO₂.

Various embodiments provide an MC having an ultra-sharp tip for use in a HAMR head. Such an MC allows the HAMR head to efficiently couple light (from an external light source such as an external laser diode) into a TWG, such as an interferometric TWG. It should be noted that although various embodiments have been described in the context of an MC for use in a HAMR head, the MC having an ultra-sharp tip and/or the processes for creating the MC having an ultra-sharp tip are contemplated for use in the context of other structures/purposes, e.g., a probing tip

FIG. 12 is a diagram illustrating an example disk drive 1200 including a read-write the head 1205 that can be created in accordance with some embodiments. Disk drive 1200 may include one or more disks 1210 to store data. The disks 1210 reside on a spindle assembly 1215 that is mounted to drive housing 1220. Data may be stored along tracks in the magnetic recording layer of one of the disks 1210. The reading and writing of data is accomplished with the head 1205 that has both read and write elements. The write element is used to alter the properties of the perpendicular magnetic recording layer of disk 1210. In some embodiments, the head 1205 may comprising a magnetic recording pole fabricated according to an embodiment described herein. Additionally, for some embodiments, the head 1205 may be a HAMR head. In various embodiments, the disk drive 1200 may be a PMR drive, and the head 1205 may be suitable for PMR. A spindle motor (not shown) rotates the spindle assembly 1215 and, thereby, disks 1210 to position the head 1205 at a particular location along a desired disk track. The position of the head 1205 relative to the disks 1210 may be controlled by position control circuitry 1225.

Although described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the application, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments.

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. In 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.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.