Magnetic head having multilayer heater for thermally assisted write head and method of fabrication thereof

[0001] This application is a continuation-in-part of patent application Ser. No. 10/631,396, filed Jul. 30, 2003 now U.S. Pat. No. 6,956,716, entitled Magnetic Head Having Multilayer Heater for Thermally Assisted Write Head and Method of Fabrication Thereof.

[0002] 1. Field of the Invention

[0003] The present invention relates generally to magnetic heads that are utilized with thin film hard disk data storage devices, and more particularly to the design and fabrication of a magnetic head having a storage media heating device formed within the magnetic heads.

[0004] 2. Description of the Prior Art

[0005] As is well known to those skilled in the art, standard magnetic heads include write head elements that include two magnetic poles, commonly termed the P1 and P2 poles. During a data recording procedure, the passage of magnetic flux between the two poles creates a magnetic field which influences a thin film layer of magnetic media on a hard disk that is located proximate the magnetic head, such that the changing magnetic flux creates data bits within the magnetic media.

[0006] The continual quest for higher data recording densities of the magnetic media demands smaller bit cells, in which the volume of recording material (grains) in the cells is decreased and/or the coercivity (Hc) is increased. When the bit cell size is sufficiently reduced, the problem of the superparamagnetic limit will provide a physical limit of the magnetic recording areal density. A present method to delay the onset of this limit in storage media is the use of a thermally assisted recording head in which a heating device is disposed within the magnetic head. Heat from the heating device is directed to the storage media, and it temporarily reduces the localized coercivity of the media, such that the magnetic head is able to record data bits within the magnetic media. Once the media returns to ambient temperature, the very high coercivity of the media provides the bit latency necessary for the recorded data.

[0007] A problem in creating such heating devices within magnetic heads is that the materials forming the heating device can diffuse into adjacent magnetic head components, and/or can have poor adhesive characteristics which cause delamination with adjacent head components. There is therefore a need to prevent such heating devices from creating unwanted diffusion and delamination problems subsequent to their fabrication.

[0008] A magnetic head of the present invention includes a media heating device that is fabricated within the magnetic head structure following the fabrication of the read head component of the magnetic head. The media heating device serves to heat the magnetic media immediately prior to the passage of the magnetic media beneath the write pole tip of the magnetic head. Heating the media lowers its localized coercivity, and facilitates the writing of data to the media by the write head of the magnetic head.

[0009] The improved media heating device of the present invention may be fabricated with diffusion barrier layers and/or adhesion layers beneath the heating device layers, between heating device layers and/or above the heating device layers. Where diffusion barrier layers are utilized, they prevent the diffusion of the metal materials that comprise the heating device layers from diffusing into layers that are disposed below and/or above the heating device, and a diffusion barrier layer may also be deposited between layers of the heating device to prevent diffusion between those layers as well. Where an adhesion layer is deposited below, between and/or above the heating device layers it promotes adhesion of the heating device to the magnetic head layers adjacent to the heating device, to prevent delamination of the layers of the magnetic head. Following the fabrication of the media heating device with the diffusion barrier and/or adhesion layers, further head components, such as write head induction coils and magnetic poles are fabricated to complete the fabrication of the magnetic head.

[0010] In a preferred embodiment, the heating device includes an electrically resistive heating element, and diffusion barrier and/or adhesion layers are fabricated beneath/within and above the heating element. The heating element is typically comprised of NiCr, CrV or NiFe, and the diffusion barrier layer may be comprised of tantalum, tantalum nitride, other tantalum alloys, titanium, rhodium and ruthenium, and the adhesion layer may be comprised of tantalum, tantalum nitride, tantalum oxide, other tantalum alloys, titanium, nickel iron, chromium, platinum alloys, nickel alloys, and aluminum oxide. Where a diffusion barrier layer or adhesion layer is disposed within the heating device it is preferably composed of an electrically conductive material.

[0011] Where the media heating device includes an electrically resistive heating element, electrical leads are fabricated to conduct heater current to and from the resistive heating element. The electrical leads preferably overlay the heating element in an overlay area of at least approximately 1 μm² to provide good electrical current conduction to the heating element. Additionally, where the heating device includes the resistive heating element, electrical insulation layers are fabricated below and above the heating device to insulate magnetic head components from the heating device electrical current. In a preferred embodiment, the thickness of the electrical insulation layers is preferably from approximately 2 to approximately 4 times the thickness of the resistive heating element to assure insulation at the stepped edges of the heating device.

[0012] In yet another embodiment of the present invention the heating device may be fabricated upon the slider substrate, prior to the fabrication of magnetic head components. In this configuration, the heating device fabrication steps are conducted prior to the magnetic head component fabrication steps, and therefore do not interfere with the well established process steps for fabricating the read head components and/or write head components of the magnetic head.

[0013] It is an advantage of the magnetic head of the present invention that it includes an improved media heating device to facilitate the writing of data to a magnetic disk.

[0014] It is another advantage of the magnetic head of the present invention that it includes one or more diffusion barrier layers that are fabricated above and/or below the media heating device to prevent diffusion of the media heating device material into adjacent magnetic head components.

[0015] It is a further advantage of the magnetic head of the present invention that it includes one or more adhesion layers that are fabricated above and/or below the media heating device to promote adhesion of the media heating device material with adjacent magnetic head components.

[0016] It is yet another advantage of the magnetic head of the present invention that it includes an electrical heating device having electrical leads that overlay a resistive heating element with sufficient overlay area that resistive electrical heating at the electrical connection between the leads and the resistive heating element is minimized.

[0017] It is yet a further advantage of the magnetic head of the present invention that it includes an improved electrical heating device having electrical insulation layers of sufficient thickness to prevent electrical shorts between the heating device electrical leads and other components of the magnetic head.

[0018] It is still another advantage of the magnetic head of the present invention that it includes a heating device that is fabricated upon a substrate surface prior to the fabrication of magnetic head components, such that the fabrication steps for the heating device do not interfere with the fabrication steps for the magnetic head components.

[0019] It is an advantage of the hard disk drive of the present invention that it includes a magnetic head that includes an improved media heating device to facilitate the writing of data to a magnetic disk.

[0020] It is another advantage of the hard disk drive of the present invention that it includes a magnetic head that includes one or more diffusion barrier layers that are fabricated above and/or below a media heating device to prevent diffusion of the media heating device material into adjacent magnetic head components.

[0021] It is a further advantage of the hard disk drive of the present invention that it includes a magnetic head that includes one or more adhesion layers that are fabricated above and/or below a media heating device to promote adhesion of the media heating device material with adjacent magnetic head components.

[0022] These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reviewing the following detailed description which makes reference to the several figures of the drawings.

[0031] Efforts to increase areal data storage density of hard disk drives have lead to improvements in the structure and function of the write head elements of magnetic heads. A simplified top plan view of a typical hard disk drive 10 which is suitable to include the magnetic head of the present invention is presented in FIG. 1. As depicted therein, at least one hard disk 14 is rotatably mounted upon a motorized spindle 18. A slider 22, having a magnetic head 26 formed thereon, is mounted upon an actuator arm 30 to fly above the surface of each rotating hard disk 14, as is well known to those skilled in the art. The present invention includes improved features and manufacturing methods for such magnetic heads 26, and to better described the present invention a prior art magnetic head is next described.

[0032] As will be understood by those skilled in the art, FIG. 2 is a side cross sectional view depicting portions of a prior art magnetic head 38. The magnetic head 38 includes a first magnetic shield layer (S1) 40 that is formed upon a surface 44 of the slider body material 22. A read head sensor element 52 is disposed within insulating layers 56 and 57, and a second magnetic shield layer (S2) 58 is formed upon the upper insulation layer 57. An insulation layer 59 is then deposited upon the S2 shield 58, and a first magnetic pole (P1) 60 is fabricated upon the insulation layer 59.

[0033] Following the fabrication of the P1 pole layer 60, a P1 pole pedestal 64 may be fabricated upon the P1 pole layer 60, and a first induction coil layer 68 is fabricated above the P1 pole layer 60 within the layer that includes the P1 pole pedestal 64. Thereafter, a write gap layer 72 is deposited, followed by the fabrication of a P2 magnetic pole tip 76. A second induction coil layer 80 may be fabricated above the layer containing the P2 pole tip 76. A yoke portion 84 of the second magnetic pole is next fabricated in magnetic connection with the P2 pole tip 76, and through back gap elements 88 and 89 to the P1 pole layer 60. The head is subsequently encapsulated in alumina 90, and it is finally processed such that an air bearing surface (ABS) 92 is created. It is to be understood that this description omits many detailed fabrication steps that are well known to those skilled in the art, and which are not deemed necessary to describe herein in order to provide a full understanding of the present invention.

[0034] As has been indicated hereabove, the present invention is a magnetic head including a heating device that provides thermal assistance in recording data bits to high coercivity magnetic media. As will be understood from the following detailed description, the magnetic head of the present invention includes an improvement in the resistive heating device fabrication process, where the heating device can be disposed at different locations within the head. For ease of description, this application describes in detail a heating device that is fabricated beneath the P1 pole pedestal 64 and above the P1 pole layer 60; however it is not to be limited to that location. Also, the location and fabrication of other head elements, such as the induction coils, may be varied, and the present invention is not to be limited to the number or location of elements such as the induction coil. The fabrication of a heating device within a magnetic head 26 of the present invention is next described.

[0035] FIG. 3 depicts a fabricated read head portion of the magnetic head 26. As with the prior art head depicted in FIG. 2, it includes a first magnetic shield layer 40, a read head sensor element 52 and a second magnetic shield layer 58. It is therefore to be understood that the magnetic head of the present invention makes no significant changes in the fabrication of the read head portion of the magnetic head. Additionally, as is well known to those skilled in the art, in an alternative magnetic head design the S2 shield 58 also serves as a first magnetic pole, in which case the insulation layer 59 is not fabricated. This alternative magnetic head design is termed a merged magnetic head, and the heating device of the present invention can be fabricated above the shield/pole 58 of a merged magnetic head in the same manner as it is fabricated in the piggyback magnetic head design that is described in detail herein.

[0036] As depicted in FIG. 3, following the fabrication of the P1 pole layer 60, a chemical mechanical polishing (CMP) step is preferably undertaken to obtain a smooth surface 104 upon which to fabricate further structures of the magnetic head. An insulation layer 108, that is preferably comprised of alumina or SiO₂, is next deposited upon the surface 104 of the P1 layer 60. The insulation layer 108 provides electrical insulation of the heating device described herebelow from the P1 pole layer 60.

[0037] The heating device 112 is next fabricated on top of the insulation layer 108, and FIG. 4 is a top plan view of such a heating device. As is depicted in FIG. 4, the heating device 112 may be fabricated using well known photolithographic techniques in which heating device components including an electrically resistive heater element layer 116 and electrical leads 120 of the heating device 112 are fabricated. A detailed description of the fabrication of such a heating device is provided in U.S. patent application Ser. No. 10/791,186, filed Mar. 1, 2004, entitled: Magnetic Head Having Thermally Assisted Recording Device, and Method of Fabrication Thereof, the disclosure of which is incorporated herein as though set forth in full. Basically, the heating device 112 includes a central electrically resistive heating element portion 122 of the heating element layer 116 that is located between the inner ends 126 of the electrical leads 120, and fabricated beneath the location in which the write head pole tip will subsequently be fabricated. It is desirable though not necessary that the active central heating element portion 122 be approximately as wide as the track width of the pole tip because it is generally undesirable to heat portions of the magnetic media disposed on data tracks that are adjacent to the track that is being written upon. It is also desirable, though not necessary, that the heating device 112 be fabricated slightly away from the air bearing surface (ABS) 92 of the head, to limit corrosion of the heating device and to avoid possible electrical discharge from the heating device 112 to the media disk during a writing operation.

[0038] A close up cross-sectional view of the heating element and lead ends is provided in the cross sectional view of FIG. 5 which is taken in the direction of lines 5—5 of FIG. 4. As is seen in FIGS. 4 and 5, the heating element layer 116 may be fabricated first, followed by the electrical leads 120 that are deposited on top of the heating element layer 116.

[0039] In a method for creating a heating device 112 of the present invention, a heating device underlayer 130 is first deposited, full film, across the surface of the wafer upon the insulation layer 108. The underlayer 130 may include an adhesion layer 134, a diffusion barrier layer 138, both layers, or a single layer that acts as both a diffusion barrier and an adhesion layer. A diffusion barrier layer is particularly desirable where the insulation layer 108 is comprised of SiO₂ in that the metallic material that will comprise the heater element layer 116 and/or the electrical lead layers 120 of the heating device may otherwise diffuse into the SiO₂ insulation layer 108 and adversely affect its insulative properties. Additionally, an adhesion layer is desirable where the metallic materials that comprise the heater element layer 116 and/or lead layers 120 of the heating device may adhere poorly to the insulation layer 108. Suitable diffusion barrier layer materials are tantalum, tantalum nitride, other tantalum alloys, titanium, rhodium and ruthenium, and suitable adhesion layer materials are tantalum, tantalum nitride, tantalum oxide, other tantalum alloys, titanium, nickel iron, chromium, platinum alloys, nickel alloys and aluminum oxide. It can therefore be seen that materials that will act as both diffusion barriers and adhesion layers are tantalum, tantalum nitride, other tantalum alloys and titanium. A diffusion barrier layer will typically have a thickness in the range of 1–5 nm, and an adhesion layer will typically have a thickness range of 1–5 nm.

[0040] Following the deposition of the underlayer 130, the thin film heating element layer 116 is deposited across the wafer surface. Following the deposition of the heating element layer 116, a mid-layer 144 that may include a diffusion barrier layer 148 and/or an adhesion layer 152 may be deposited upon the heater element layer 116. The mid-layer 144 will be disposed primarily between the heater element layer 116 and the electrical lead layers 120, to act as a diffusion barrier between the heater element layer 116 and the electrical leads 120, and/or to promote adhesion between the heater element layer 116 and the electrical leads 120 that are subsequently deposited. The mid-layer 144 must be comprised of an electrically conductive material to permit electrical current to pass from the leads 120 through the heating element portion 122.

[0041] As is depicted in FIG. 5, the central portion 122 of the heating element layer 116 (with mid-layer 144 deposited thereon) is next protected by a mask 160 during the fabrication of the electrical leads 120. The mask 160 is shaped such that outer end portions 162 of the heater element layer 116 (see FIG. 4) and corresponding portions of a mid-layer 144 that may be deposited thereon, are exposed, such that the electrical lead material can be deposited thereon. Electrical lead material is next deposited full film across the surface of the wafer upon the mid-layer 144. The electrical lead material may typically include rhodium, copper, or other commonly used electrical lead materials. It is important that the area of overlaying contact 162 between the electrical lead 120 and the heater element layer 116 (and any mid-layer 144) be sufficiently large such that unwanted ohmic heating not occur at the interface between the leads 120 and the heater element layer 116. That is, it is desirable that heating occur throughout the central portion 122 of the heater element layer 116 and not at the overlaying end areas 162. In the preferred embodiment, the interconnecting end areas 162 should have a contact area of at least approximately 1 μm².

[0042] Following the deposition of the electrical lead material, an over-layer 166 that may include a diffusion barrier layer 170 and/or an adhesion layer 174, is deposited full film across the surface of the wafer upon the electrical lead layer 120. The over-layer 166 serves to prevent diffusion of the electrical lead material into subsequently fabricated components and/or to provide enhanced adhesion of subsequently fabricated components to the electrical lead material.

[0043] Thereafter, the mask 160 is removed and, as shown in FIG. 6, a mask 180 in the shape of the footprint of the electrical leads (the footprint being shown in the top view of FIG. 4) is formed upon the over-layer 166 and upon the mid-layer 144 in the central portion 122 of the heating device 112. FIG. 6 is a side cross-sectional view of the heating device 112, taken long lines 6—6 of FIG. 4 that depicts the removal of the field material and the protection of the heating device 112 by the mask 180. An ion milling or sputter etching step is next conducted in which the over-layer 166, electrical lead material 120, mid-layer 144, heating element material 116 and the under-layer 130, in the field 184 that are unprotected by the mask 180 are removed.

[0044] Thereafter, as depicted in FIG. 7, the mask 180 is removed, exposing the surface of the mid-layer 144 in the center of the heating device 112 and the over-layer 166 above the electrical leads 120. An electrical insulation layer 190, preferably composed of alumina or SiO₂, is next deposited full film across the surface of the wafer. The thickness of the insulation layers 108 and 190, and particularly layer 190 must be sufficient to provide a good insulative coating to prevent electrical shorts. Referring to FIG. 3, it can be seen that the thickness of the heating device 112, including the heater element layer 116, the electrical leads 120 and the underlayer 130, mid-layer 144 and over-layer 166, can create a significant step which must be successfully covered by the insulation layer 190 particularly at the step edges to avoid electrical shorts. With regard to the lower insulation layer 108, it must be deposited with sufficient thickness such that the remaining thickness of the insulation layer 108 following the material removal step (described hereabove with reference to FIG. 6) be sufficient to provide adequate electrical insulation without the occurrence of electrical shorts. It is therefore desirable that the lower and upper electrical insulation layers 108 and 190 respectively be at least as thick as the heater element layer 116, where the thickness of the electrical lead layer 120 is approximately equal to the thickness of the heater element layer 1116, as has been described hereabove. Therefore, it is generally desirable that the thickness of the lower and upper electrical insulation layers 108 and 190 be from approximately 0.1 microns to approximately 1.0 microns and generally from 2 to 4 times the thickness of the heater element 116.

[0045] Where the electrical insulation layer 190 or 108 is comprised of a Al₂O₃, it is important that the composition of aluminum and oxygen be uniform and consistent to provide good electrical insulation properties. A preferred method for depositing the alumina insulation layer is by atomic layer deposition (ALD), although for a relatively thick insulation layer the ALD deposition process can be overly time consuming. A second preferred insulation layer fabrication method is the use of an ion beam deposition method. Another technique is through the use of a sputter deposition tool that utilizes a high density oxide plasma and an aluminum oxide target. Another method which will produce acceptable results is a sputter deposition tool with an aluminum oxide target that utilizes a typical argon and oxygen plasma. Generally, however, where the Al₂O₃ insulation layer is fabricated utilizing a sputter deposition tool utilizing an argon plus oxygen plasma and an aluminum target, unfavorable insulation layer results may occur, as an uneven composition of AlO_X may be created with unwanted concentrations of electrically conductive Al that produce unwanted electrical shorts.

[0046] Alternate uses of the adhesion and diffusion barriers with the use of a heating element in a head may be where an optical heating element is incorporated into the head. It is commonly known that an optical component such as a laser can be used to heat the media to facilitate writing media with large coercivity. To implement this type of heating, various optical elements would be used in or on the head. The elements such as waveguides, lenses, and coupling devices may advantageously use these aforementioned adhesion and diffusion layers adjacent to these said optical elements. These elements may be heated with photons or their optical properties may be sensitive to contamination from adjacent materials; hence, there is a need to include these layers with such optical elements.

[0047] As is next depicted in FIG. 8, further magnetic head components including an induction coil 68 and a second magnetic pole 84 are subsequently fabricated to complete the manufacture of the magnetic head 26. The steps for fabricating such additional components are essentially identical to those undertaken in the fabrication of those components of the prior art head depicted in FIG. 2, and the components are identically numbered for ease of comprehension. It is to be further understood that it is also possible to place the heating element at different locations in the head, for example, in the write gap 72, where only the method of fabrication may change.

[0048] Another location for the heating element is upon the substrate disk, prior to the fabrication of the read head and write head components of the magnetic head, as is next described with the aid of FIG. 9. As depicted therein, the device 200 includes similar features and structures of the prior art magnetic head depicted in FIG. 2, and such similar structures are identically numbered for ease of comprehension. Basically, in the embodiment 200, the heating element of the present invention is fabricated upon the substrate, prior to the fabrication of the magnetic head components. Particularly, as depicted in FIG. 9, an electrical insulation layer 208 is deposited upon the top surface 44 of a substrate base 22. As is well known in the prior art, the substrate base 22 may have an additional layer, typically termed an underlayer, deposited thereon. Where such an underlayer exists, the electrical insulation layer 208 may be deposited upon the underlayer, or the underlayer may serve as the insulation layer 208 if it is of sufficient thickness.

[0049] Thereafter, a heating element 212 is fabricated upon the insulation layer 208. The heating element 212 is similar in all respects to the heating element 112 described hereabove. That is, it may include an under-layer 130, a heater element layer 116, a mid-layer 144, electrical lead layers 120 and an over-layer 166, all of which are not separately shown in FIG. 9, but are described in detail hereabove. Thereafter, an upper electrical insulation layer 216 is deposited upon the heating element 212. It is to be understood that the lower electrical insulation layer 208, the heating element 212 and the upper electrical insulation layer 216 may be identical in all respects to the lower insulation layer 108, the heating element 112 and the upper electrical insulation layer 190 described in detail hereabove. Following the deposition of the upper electrical insulation layer 216, a CMP process may be undertaken to obtain a flat smooth upper surface 220 upon the electrical insulation layer 216. Thereafter, the magnetic head components, including the read head structures and the write head structures may be fabricated, as is described hereabove.

[0050] A significant feature of the embodiment 200 is that the heating element is fabricated prior to the fabrication of the delicate components that comprise the magnetic head. Where the heater element 212 is first fabricated, the well understood fabrication steps of a typical magnetic head are more easily accomplished, as compared to the embodiments depicted in FIGS. 3–8, wherein the heater element fabrication steps are interspersed within the prior art steps for fabricating the read head components and the write head components. Thus there is an advantage to the manufacturability of the embodiment 200 in that the fabrication steps of the heating element 212 are accomplished before the well known fabrication steps for the typical prior art magnetic head.

[0051] It is therefore to be understood that the significant features of the present invention are the fabrication of the diffusion barrier layer and/or adhesion layer below, between and/or above the heating element and lead layers of the media heating device, that serve as diffusion barriers and/or adhesion layers for the heating device and for magnetic head components that are fabricated below or above the heating device. The diffusion barrier layers serve to primarily prevent the diffusion of the metallic materials that comprise the heating device into the magnetic head layers that are deposited adjacent to the heating device. The adhesion layers serve to promote the adhesion of the metallic heater device layers with the magnetic head layers that are deposited beneath and above the heating device. The diffusion barrier and adhesion layers of the present invention therefore serve to create an improved, more reliable magnetic head in which the contamination of layers adjacent to the heating device and the delamination of the magnetic head proximate the heating device are inhibited.

[0052] While the present invention has been shown and described with regard to certain preferred embodiments, it is to be understood that modifications in form and detail will no doubt be developed by those skilled in the art upon reviewing this disclosure. It is therefore intended that the following claims cover all such alterations and modifications that nevertheless include the true spirit and scope of the inventive features of the present invention. Further, Applicant's intent is to encompass the equivalents of all claim elements, and no amendment to any claim in the present application should be construed as a disclaimer of any interest in or right to an equivalent of any element or feature of the amended claim.