Manufacturing method of patterned medium

The present invention relates to a method of forming a fine pattern on a magnetic recording layer of a patterned medium using nanoimprint lithography.

With the recent miniaturization of processing patterns in semiconductor devices, from KrF laser lithography to ArF laser lithography, F₂Technologies such as laser lithography, extreme ultraviolet exposure (EUVL), electron beam (EB) lithography, and X-ray lithography have been developed, and fine pattern formation of about 30 nm has been realized. However, as the pattern to be processed becomes finer, the equipment required for processing becomes more expensive. On the other hand, nanoimprint lithography capable of producing a fine resist pattern at low cost has been proposed (Non-Patent Document 1).

Optical nanoimprint lithography is a technology that applies a photo-curing resin on a substrate, presses a translucent mold onto the photo-curing resin, cures the resin by irradiating it with ultraviolet light, and transfers the mold pattern to the resin. is there. Since it is only necessary to use ultraviolet light irradiation to cure the pattern, it is possible to perform high-throughput and high-precision processing as compared with thermal nanoimprint lithography in which heat is used to cure the resin. In recent years, optical nanoimprint lithography has been studied for application not only to semiconductor device processes but also to manufacturing processes of discrete track media for magnetic recording.

<nplcit num="1"><text>Appl. Phys. Lett. 67, 3114 (1995)</text></nplcit>

<p> In order to realize high-density recording, it is necessary to reduce the spacing between the magnetic head and the magnetic recording layer as much as possible to read information from fine recording bits, and the characteristics and shape of the surface of the magnetic recording layer are the performance of magnetic recording. Has a great effect on.</p><p> An important issue in forming patterned media using optical nanoimprint lithography technology is to suppress damage to the magnetic recording layer and to completely remove processing residues.</p>

<p> Reactive ion etching is effective as a method for removing the optical nanoimprint resist, but the residue cannot be completely removed and particles are generated. Therefore, it is desirable to wash off the optical nanoimprint resist with a solution. A strong acid is required to dissolve the optical nanoimprint resist, and if a strong acid is used, the magnetic recording layer will corrode during the process. Therefore, as a method of preventing corrosion, it is conceivable to wash off the optical nanoimprint resist with a solution by lift-off together with the release layer. Here, when a metal such as aluminum is used for the peeling layer, it is necessary to perform peeling using an acidic or alkaline aqueous solution. At this time, deterioration of the characteristics of the magnetic recording layer is observed.</p><p> Therefore, in the present invention, when the pattern shape formed on the optical nanoimprint resist is transferred to the magnetic recording layer to produce a patterned media, a release layer made of a polymer material soluble in an organic solvent is formed under the optical nanoimprint resist. Is formed. Then, the pattern shape formed on the optical nanoimprint resist is transferred to the magnetic recording layer or the mask layer made of an inorganic material formed on the magnetic recording layer, and then the release layer is peeled off using an organic solvent. As the material of the release layer, for example, a polymer material made of polystyrene or polyimide or an imprint resist such as PMMA (polymethyl methacrylate resin) can be used.</p><p> According to the present invention, the release layer and the optical nanoimprint resist remaining on the release layer can be peeled off and washed away using an organic solvent, so that the magnetic recording layer is not corroded and the characteristics of the magnetic recording layer are deteriorated. The pattern can be transferred to the magnetic recording layer without any problem. In addition, a clean media surface without residues or particles can be obtained.</p>

<p> According to the present invention, it is possible to transfer a pattern to the magnetic recording layer without corroding the magnetic recording layer and without deteriorating the characteristics of the magnetic recording layer.</p>

Hereinafter, specific means for producing the magnetic recording medium of the present invention will be described with reference to Examples.

FIG. 1 is a process sectional view illustrating an example of a patterned media manufacturing method according to the present invention.

First, as shown in FIG. 1A, the base layer 12, the soft magnetic layer 13, the magnetic recording layer 15, and the mask layer 16 are laminated on the substrate 11. A release layer 18 is formed on the release layer 18 by using a spin coating method. Next, an optical nanoimprint resist layer 47 made of a photocurable resin is applied onto the release layer 18. The substrate 11 is made of glass, alumina, Si or the like. As the base layer 12, Ru was formed to have a film thickness of 16 nm. As the soft magnetic layer 13, an amorphous alloy of Co composed of Fe, Co, Ta, and Zr was formed to have a film thickness of 30 nm. The magnetic recording layer 15 is, for example, a Co, Cr, Pt-based alloy and SiO.₂It is composed of a granular perpendicular recording medium made of a non-magnetic material such as. The mask layer 16 contains C and the like, and after forming a pattern on the magnetic recording layer, RIE and O₂It can be removed by ashing.

The release layer 18 is made of a polymer material such as polystyrene or polyimide that can be cured at a temperature that does not deteriorate the magnetic properties of the magnetic recording layer 15 or lower, or an imprint resist such as PMMA (polymethyl methacrylate resin). Can be listed as a candidate. In the case of a polymer material or an imprint resist, it may be formed by molding using a spin coating method, an inkjet method, or a thermal imprint method. The release layer 18 is formed to have a film thickness of 10 nm or more so that it can be lifted off.

Next, the imprint mold 24 is pressed against the optical nanoimprint resist layer 47, and in that state, ultraviolet rays are irradiated to cure the optical nanoimprint resist layer 47, and the pattern structure of the imprint mold 24 is copied to the optical nanoimprint resist layer. As a result, as shown in FIG. 1 (b), the concave portion 22 and the convex portion 23 are formed in the optical nanoimprint resist layer. For the optical nanoimprint resist, for example, PAK-01 manufactured by Toyo Gosei Co., Ltd. can be used. Then, the imprint mold 24 is separated from the optical nanoimprint resist 23 on which the pattern is formed.

Next, the optical nanoimprint resist in the recess 22 of the pattern is removed as shown in FIG. 1 (c) by using dry etching such as RIE (reactive ion etching) with oxygen or the like. Subsequently, the structure of the optical nanoimprint resist 23 is transferred to the release layer 18 as shown in FIG. 1 (d) by using a dry etching process such as RIE.

If the release layer 18 is a polymer material, O in RIE₂, CO₂An inert gas such as Ar may be used in combination with a gas containing oxygen such as Ar for the purpose of forming a resist linearly. When the imprint resist is used for the release layer 18, the material is PMMA or the like, and RIE is performed with a gas containing oxygen.

After that, as shown in FIG. 1 (e), the pattern shape is transferred to the mask layer 16 by using the release layer 18 as a mask and dry etching such as RIE. Next, as shown in FIG. 1 (f), the release layer 18 is lifted off and removed. At this time, when the release layer 18 is a polymer material made of polyimide or the like, the release agent used for lift-off is NMP (N-methylpyrrolidone) or the like. When an imprint resist such as polystyrene or PMMA is used for the release layer 18, the liquid used for lift-off is an organic solvent such as acetone.

The lift-off method may be ultrasonic cleaning, high-pressure jet lift-off, or the like. Further, if there is a residue such as burrs after lift-off, it may be removed by using an ice scrub method or another scrub method in which dry ice or the like is sprayed on the substrate surface. According to this embodiment, the peeling layer and the optical nanoimprint resist remaining on the peeling layer can be peeled off and washed away using an organic solvent, so that the magnetic recording layer is not corroded and the characteristics of the magnetic recording layer are deteriorated. The pattern can be transferred to the magnetic recording layer without causing the pattern to be transferred. In addition, a clean media surface without residues or particles can be obtained.

After lift-off, as shown in FIG. 1 (g), the mask layer 16 is used as a mask, and the pattern is transferred to the magnetic recording layer 15 by using ion beam etching, magnetic material RIE, or the like. Next, the mask layer 16 is removed as shown in FIG. 1 (h) by RIE or ashing with oxygen or the like.

After this, the packed bed 19 is formed as shown in FIG. 1 (i). SiO for the material of the packing layer 19₂An oxide film such as, or a non-magnetic metal is used. SOG (Spin-On-Glass) or the like that can be cured at a temperature that does not deteriorate the magnetic recording characteristics or lower may be used.

Next, as shown in FIG. 1 (j), the surface irregularities of the filler 19 are flattened by using Dora etching, chemical mechanical polishing (CMP), gas cluster ion beam (GCIB), etc., and the magnetic recording layer 15 Match the outermost surface with the surface. At this time, the surface of the filler 19 may be recessed by several nm from the surface of the magnetic recording layer 15. After this, as shown in FIG. 1 (k), the protective layer 20 and the lubricating layer 21 made of carbon are formed to complete the patterned media.

By forming a release layer made of a polymer material under the optical nanoimprint resist layer, the following advantages can also be obtained. As shown in FIG. 2A, when there is a hard layer 17 such as metal on the magnetic recording layer 15 and defects such as foreign matter 33 are present on the surface of the magnetic recording layer 15, the imprint mold uses an optical nanoimprint resist layer. It cannot be pressed uniformly, and the optical nanoimprint resist is not applied around the defect, and the defect of the pattern shape spreads. It may also cause defects in the imprint mold. Since the polymer material used for the release layer of the present invention is generally soft, it has the effect of suppressing the influence of foreign matter caught during the imprinting process. As shown in FIG. 2B, foreign matter 33 smaller than the thickness of the release layer 18 is absorbed in the release layer 18, which is useful for reducing defects on the media and reducing the risk of mold damage.

FIG. 3 is a process cross-sectional view illustrating another example of the patterned media manufacturing method according to the present invention.

In the same manner as in Example 1, the substrate 11 to the magnetic recording layer 15 are laminated. Next, a release layer 18 and an optical nanoimprint resist layer 47 are prepared on the upper layer of the magnetic recording layer 15 as shown in FIG. 3 (a). Since there is no mask layer as compared with Example 1, the steps of forming the mask layer and the steps of removing the mask layer can be reduced.

As shown in FIGS. 3 (b) to 3 (d), the pattern formation of the optical nanoimprint resist layer is performed in the same manner as in Example 1. The pattern is transferred to the magnetic recording layer 15 as shown in FIG. 3 (e) by using ion beam etching or the magnetic material RIE. After that, the release layer 18 is lifted off in the same manner as in Example 1.

In this pattern forming method, when the magnetic recording layer 15 is dry-etched, reattachments adhere to the side walls of the release layer 18 and the optical nanoimprint layer 23, but when the release layer is removed, the reattachments can also be removed together with the release layer. Therefore, there is no problem that the reattached matter remains on the surface of the patterned media.

FIG. 4 is a process cross-sectional view illustrating another example of the patterned media manufacturing method according to the present invention.

In the same manner as in Example 1, the substrate 11 to the magnetic recording layer 15 are laminated. Next, as shown in FIG. 4A, a release layer 18 is formed, and a mask layer 16 is formed on the release layer 18. The stacking order of the release layer 18 and the mask layer 16 is reversed from that of the first embodiment. Then, as shown in FIGS. 4 (b) to 4 (c), a pattern of the optical nanoimprint resist layer is formed in the same manner as in Example 1.

Next, using the formed optical nanoimprint resist 23 as a mask, as shown in FIG. 4D, the pattern is transferred to the mask layer 16 by dry etching such as RIE. Next, using the remaining optical nanoimprint resist 23 and the mask layer 16 as masks, the pattern is transferred to the release layer 18 by dry etching such as RIE. At this time, if the mask layer 16 retains its shape during the time when the release layer 18 is etched, the optical nanoimprint resist 23 does not have to remain. Next, as shown in FIG. 4 (f), the pattern is transferred to the magnetic recording layer 15 by using ion beam etching or the magnetic material RIE with the mask layer 16 and the release layer 18 as masks. After that, the release layer 18 is lifted off in the same manner as in Example 1.

In this pattern forming method, when the magnetic recording layer 15 is dry-etched, the mask layer 16 and the optical nanoimprint layer 23 remain on the upper layer of the release layer 18, and the reattachments are the release layer 18, the mask layer 16, and light. Although it is attached to the side wall of the nanoimprint layer 23, there is no problem that the reattached matter remains on the surface of the patterned media because the reattached matter can be removed together with the peeling layer when the peeling layer is removed.

<figref num="1">FIG. 5 is a process sectional view illustrating an example of a method for producing a patterned media according to the present invention.</figref><figref num="2">The conceptual diagram about the defect generation mechanism of the prior art and the optical nanoimprint resist of this invention.</figref><figref num="3">FIG. 5 is a process sectional view illustrating another example of the patterned media manufacturing method according to the present invention.</figref><figref num="4">FIG. 5 is a process sectional view illustrating another example of the patterned media manufacturing method according to the present invention.</figref>

Code description

11 board 12 Underlayer 13 Soft magnetic layer 15 Magnetic recording layer 16 Mask layer 17 metal layer 18 Peeling layer 19 Filled layer 20 protective layer 21 Lubricating layer 23 Optical nanoimprint resist 24 Imprint mold 33 Foreign matter 47 Optical nanoimprint resist layer