Abstract
A magnetic write head has a plated coil with narrow pitch and is suitable for writing at high frequencies on magnetic media with high coercivity. The narrow pitch is obtained without such disadvantages as overplating that has adversely affected prior art attempts to produce such narrow pitches. The process that produces the magnetic write head is characterized by an RIE plasma etch using O.sub.2/N.sub.2 to etch plating trenches into a baked layer of photoresist with the ratio of gases being 5/45 sccm so that a dilute O.sub.2 concentration does not create unwanted side etching of the plating trenches. In addition, a Cu seed layer is coated with an insulating layer of Al.sub.2O.sub.3 which redeposits on the trench sidewalls to inhibit redeposition of any Cu from the seed layer and prevent outward growth of the plated Cu that would result in overplating.
Claims
1. A magnetic write head comprising: an underlayer; a plated conducting coil formed on that underlayer, wherein that plated conducting coil has a pitch that is approximately 0.6 and shows no evidence of overplating.
2. The write head of claim 1 wherein said plated conducting coil is formed of Cu.
3. The write head of claim 1 wherein said plated coil is a spirally wound coil formed in a horizontal plane.
4. The write head of claim 1 further including a magnetic pole structure capable of being energized by said plated coil wherein said narrow pitch of said plated coil allows said pole structure to be characterized by a short flux path and results in high frequency writing.
5. The write head of claim 4 further including a TAMR (thermal assisted magnetic writing) apparatus capable of reducing the coercivity of a magnetic recording medium whereby said high frequency writing is effectively applied.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic representation of an initial step in a prior art photolithographic process to plate Cu coils within a patterned photoresist.
[0037] FIG. 2 is a schematic representation showing the coils produced using the prior art process of FIG. 1.
[0038] FIG. 3 is a schematic representation of the initial formation leading to a conventional, prior art coil plating process using an RIE etching of a photoresist pattern.
[0039] FIG. 4 is a schematic representation of the next step of the prior art process initiated in FIG. 3.
[0040] FIG. 5 is a schematic representation of yet a further step in the prior art process shown in FIG. 4.
[0041] FIG. 6 is a schematic representation of the final step in the prior art process begun in FIG. 3.
[0042] FIG. 7 is a schematic diagram showing the problem of overplating that results from application of the prior art process in FIGS. 3-6.
[0043] FIG. 8 is a schematic illustration showing in greater detail the causes of the overplating shown in FIG. 7 with particular attention shown to the role of redeposition of the seed layer on the sidewalls.
[0044] FIG. 9 is a schematic illustration showing the illustration of FIG. 8 with the trenches now Filled with the plated material and the presence of overplating.
[0045] FIG. 10 is a schematic illustration analogous to that of FIG. 8 but with the presence of redeposited insulator protection on the sidewalls such as would result using the presently claimed method of this disclosure.
[0046] FIG. 11 is a schematic diagram showing the effects of the additional protection in FIG. 10 on the actual plated coil.
[0047] FIG. 12 is an illustration drawn from a microphotograph of a plated coil, taken from above, showing the appearance of overplating as might result from the effects of FIG. 9.
[0048] FIG. 13 is an illustration analogous to that in FIG. 12 showing the coil's appearance when the overplating is absent, as would be the result when using the presently claimed process.
[0049] FIG. 14 is a schematic illustration of the first step in a process-flow that implements the presently claimed process.
[0050] FIG. 15 is a schematic illustration of the second step in that process-flow.
[0051] FIG. 16 is a schematic illustration of the third step in that process-flow.
[0052] FIG. 17 is a schematic illustration of the fourth step in that process-flow.
[0053] FIG. 18 is a schematic illustration of the fifth and final step in that process-flow, leading to a plated coil such as shown in FIG. 13.
DETAILED DESCRIPTION
[0054] We describe a process for fabricating a magnetic write head having a plated coil with a narrow pitch that is suitable for high frequency recording on magnetic media having high coercivity. We also describe the write head that is fabricated using that process. Such a write head is particularly appropriate for use in a TAMR scheme for recording on magnetic media having high coercivity.
[0055] Referring now to FIG. 14 there is shown schematically the first step in the present process-flow that will produce the narrow pitch plated write coil. The illustration shows, in vertically ascending order, an underlayer 10, preferably formed of Al.sub.2O.sub.3. On the underlayer there is formed a Cu seed layer 20 of thickness between approximately 500 and 1000 A. On the Cu seed layer is formed an insulating stopper layer 25, which in this example is a layer of between approximately 50 A and 400 A of Al.sub.2O.sub.3 whose purpose is both to protect the Cu seed layer from a subsequent RIE etching process through a photoresist layer that will next be formed on the stopper layer, and also to provide sidewall protection from the effects of redeposition of Cu from the plated Cu coils.
[0056] On the stopper layer 25 is then formed a layer of photoresistive material (i.e., photoresist) 30 to a thickness of between 2 and 3.5. This photoresist layer is baked at approximately 180 C. The baking process has two purposes. First, it insures that the photoresist layer is not removed by a wet etch process that is used to remove the Al.sub.2O.sub.3 stopper layer 25 before coil plating. A bake temperature below approximately 150 C. is insufficient to produce a photoresist layer that will not also be removed by the wet etch. The second purpose of the bake is to provide self-planarization. The bake produces a flat upper surface of the photoresist. In our discussion of FIG. 3, above, we noted that a series of baking processes sequentially reduced surface height variations of the photoresist so that a subsequent hard mask layer (described below) could be advantageously formed on a smooth surface.
[0057] Finally, a hard mask layer 40 is formed by the deposition of approximately 1000 A of Al.sub.2O.sub.3 on the now planarized photoresist layer 30. This hard mask layer, which will itself be patterned by a photoresist layer in the following figure, will then be used to pattern layer 30 by a RIE.
[0058] Referring next to schematic FIG. 15 there is shown the results of a photoresist patterning 50 of the hard mask layer 40 that is formed by the deposition of approximately 1000 A of Al.sub.2O.sub.3 after the 180 C. bake. The patterning is done by the formation of a photoresist mask 50 on the Al.sub.2O.sub.3 and then patterning the photoresist mask while it is on the hard mask layer. In conventional photoresistive mask patterning, the thickness of the photoresist is between approximately 2 and 3.5, because the thickness of the resist must be greater than the thickness of the plated coil; but in this process, the layer of resist 50 is only approximately 0.5 because it is used for hard-mask patterning. This much thinner photoresist thickness is advantageous for the present photo process. The thinner resist is easier to use in making a narrow pattern.
[0059] Referring now to schematic FIG. 16, the photoresist pattern is used in conjunction with a Cl.sub.2/BCl.sub.3 plasma RIE to etch (wavy arrow 60) through the Al.sub.2O.sub.3 hard mask layer 40. Then the photoresist layer 30 beneath the hard mask layer is etched with an O.sub.2 based plasma RIE, in which a gas mixture O.sub.2/N.sub.2 is fed at the rate of 5/45 sccm, with the O.sub.2 component being dilute to avoid side etching of the trench sidewalls formed by the surfaces of the photoresist 30. During this process, the stop layer 25 partially re-deposits (see arrows 100 in FIG. 10) on the photoresist sidewalls that form the trenches for the coil plating process that follows. Note that redeposition of the stop layer of Al.sub.2O.sub.3, which is an insulator, on trench sidewalls will not adversely affect the subsequent plating process because it does not act as a seed layer for the plating material. However, if there is redeposition of Cu (or whatever conductor is being used for plating the coils) on trench sidewalls, the Cu will play the role of a seed layer there and plated Cu will grow out from the sidewalls as well as up from the bottom of the trench. Sidewall outgrowth will result in overplating and must be avoided. Any redeposition of Al.sub.2O.sub.3 on the resist sidewalls, moreover, can be removed by a wet etch process immediately prior to the plating of the Cu.
[0060] Referring now to schematic FIG. 17, there is shown that the remaining Al.sub.2O.sub.3 stopper layer 25 has been removed from the seed layer 20 by wet etching and the Cu 70 is plated on the resulting exposed portions of the seed layer 20. This wet etching can also remove unwanted redepositions of the Al.sub.2O.sub.3 along the trench sidewalls.
[0061] Referring finally to schematic FIG. 18, there is shown only the plated coils 70 remaining after a wet etch to remove the remaining Al.sub.2O.sub.3 stopper layer (40 in FIG. 17), followed by a resist strip of the trench walls (30 in FIG. 17), followed then by a wet etch to remove the remaining stopper layer (25 in FIG. 17) beneath the trench walls and, finally, an ion-milling operation to remove remnants of the Cu seed layer (20 in FIG. 17) beneath the stopper layer (25 in FIG. 17). The resulting coil structure has a narrow 0.6 pitch, which is the sum of the width of the coil piece and the space between adjacent pieces.
[0062] As is understood by a person skilled in the art, the present description is illustrative of the present disclosure rather than limiting of the present disclosure. Revisions and modifications may be made to methods, materials, structures and dimensions employed in forming and providing a magnetic write head having a plated coil of narrow pitch and, therefore, being suitable for high frequency recording on high coercivity magnetic media, while still forming and providing such a device and its method of formation in accord with the spirit and scope of the present disclosure as defined by the appended claims.
