JP2007301839A - Pattern forming method, imprint mold, and method for producing magnetic recording medum - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern forming method having a high degree of freedom to design the width of a recording track or the like optimally according to the shape of a recording head. <P>SOLUTION: In the pattern forming method, a diblock copolymer film is applied on a substrate, the film is phase-separated, one polymeric component is formed in a form of a cylinder or a lamella, and an imprint is applied to the diblock copolymer film by using an imprint mold having a line pattern to form a first recess crossing the length direction of the cylinder or the lamella. The polymeric component in the form of the cylinder or the lamella is removed by etching to form a second recess. A silicon-containing resist is embedded into the first and second recesses, the diblock copolymer film is etched by using the silicon-containing resist as a mask, and then the substrate is etched. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pattern forming method, an imprint mold manufactured using the pattern forming method, and a method of manufacturing a magnetic recording medium using the imprint mold.

  Since the invention of the magnetic recording apparatus, the recording density has been increasing year by year, and the recording density continues to increase even now.

  However, in magnetic recording, although there are differences depending on the magnetic characteristics of the recording medium, it has been pointed out that due to thermal disturbance, magnetic recording cannot be maintained above a certain recording density. Is believed to be limited.

  In order to avoid this problem, there has been proposed a patterned medium in which a magnetic recording material is divided into dots by a non-recording material in advance and each dot is recorded and reproduced as a single recording cell. In this patterned medium, since the recording cell is isolated by a non-magnetic material, it has high stability against thermal disturbance and high coercive force.

  The patterned medium is considered to be an effective means for realizing a terabit-class recording density. However, in order to achieve such a high recording density, the required cell size becomes 30 to 20 nm, and fine processing exceeding the resolution limit of conventional photolithography is required. Therefore, pattern formation by electron beam drawing has been proposed, but drawing a fine pattern with an electron beam requires a long time, and thus the processed medium becomes very expensive.

  In order to solve such a problem, a method for producing patterned media using phase separation of a diblock copolymer has been proposed (see Non-Patent Document 1 and Patent Document 1). In these production methods, for example, a dot pattern is formed by phase-separating a diblock copolymer of polystyrene and polymethylene methacrylate, and the dot pattern is transferred to a magnetic film to form magnetic dots used as recording cells. In these production methods, a circular dot pattern is formed in a close packed arrangement by phase separation of the diblock copolymer.

In a magnetic recording apparatus equipped with such a patterned medium, there is a risk that writing or reading across two or more recording cells may be performed by the recording head. Therefore, depending on the recording head, the arrangement of magnetic dots, the track width, etc. It is desirable to be able to optimize conditions. However, in the method of forming a dot pattern by phase-separating a diblock copolymer, it is difficult to optimize conditions such as the arrangement of magnetic dots and the track width according to the shape of the recording head.
K. Naito et.al, IEEE Trans. Magn. Vol. 38, pp. 1949. JP 2004-342226 A

  An object of the present invention is to provide a pattern forming method having a high degree of freedom for optimally designing a track width or the like according to the shape of a recording head, for example.

  The pattern forming method according to an aspect of the present invention includes applying a diblock copolymer film on a substrate, phase-separating the diblock copolymer film to form one polymer component in the form of a cylinder or a lamella; Imprint using an imprint mold having a line pattern to form a first recess intersecting the longitudinal direction of the cylinder or lamella; etching a polymer component in the form of the cylinder or lamella To form a second recess; a silicon-containing resist is embedded in the first and second recesses; the diblock copolymer film is etched using the silicon-containing resist as a mask, and then the substrate is etched. It is characterized by doing.

  An imprint mold having a lattice pattern according to another aspect of the present invention includes a substrate processed by the pattern forming method described above.

  According to still another aspect of the present invention, there is provided a method of manufacturing a magnetic recording medium, comprising: forming a magnetic film on a medium substrate; applying a resist on the magnetic film; and having the lattice pattern described above for the resist Imprinting is performed using an imprint mold to form a lattice-shaped concave portion in the resist, and the magnetic film is etched using the resist remaining in a region other than the lattice-shaped concave portion as a mask, and separated by lattice-shaped grooves. A magnetic film pattern is formed.

  According to the pattern forming method of the present invention, the track width and the like can be optimally designed with a high degree of freedom, for example, according to the shape of the recording head.

  Embodiments of the present invention will be described below.

  In the embodiment of the present invention, the substrate material is not particularly limited, and a plastic substrate, a glass substrate, a silicon substrate, and the like are common. A thin film may be formed on the substrate. That is, the substrate may be directly processed by the pattern forming method according to the embodiment of the present invention, or a thin film formed on the substrate may be processed.

  In an embodiment of the present invention, the diblock copolymer film applied on the substrate includes two polymer components having different etching resistances. The composition and molecular weight of the diblock copolymer are not particularly limited as long as the diblock copolymer can be phase-separated into a cylinder or lamellar form. Here, the cylinder expresses a state in which one of the above-mentioned two kinds of polymers has an elongated cylindrical shape in the diblock copolymer film. As an example, it is the PMMA component 15 represented by the cross section in FIG. The lamella represents a state in which the above-mentioned two kinds of polymers are phase-separated in a layered manner, and in the present invention, the case where the phases are separated in the direction perpendicular to the substrate is desirable. As an example, in FIG. 3A, the PMMA component 15 whose cross section has a quadrangular shape instead of a circular shape.

  Examples of the diblock copolymer film include polystyrene-polymethyl methacrylate (PS-PMMA), polystyrene-poly (ethylene-alt-propylene) (PS-PEP), polystyrene-polybutadiene (PS-PBD), polystyrene-polyisoprene ( PS-PI), polystyrene-polyvinyl methyl ether (PS-PVME), polystyrene-polyethylene oxide (PS-PEO), and other known ones. These diblock copolymer films can be phase-separated by annealing.

  In order to align the cylinder or lamella in the desired direction when phase-separating the diblock copolymer film, a guide groove is formed on the substrate in advance, and the diblock copolymer film is applied in the guide groove. Phase separation of membranes (T. Yamaguchi, et al., J. Photopolym. Sci. Technol., 18 (2005) pp. 421), or diblock copolymer membranes while applying shear stress along the membrane surface It is preferable to use a method of separation (DE Angelescu, et al., Adv. Mater., 16 (2004) pp. 1739). In this case, it is desirable that the direction of the guide groove or the tendon stress follows the arm trajectory of the head in the case of the magnetic recording medium which is one of the embodiments of the present invention.

  Next, an imprint mold having a line pattern is prepared. The imprint mold having the line pattern is formed by, for example, electron beam lithography. Imprinting is performed on the diblock copolymer film using an imprint mold having a line pattern to form a first recess that intersects the longitudinal direction of the cylinder or lamella. The angle at which the line pattern and the diblock copolymer intersect in the length direction can be adjusted according to the purpose.

  Next, using the difference in etching resistance between the two polymer components of the diblock copolymer film, the polymer component in the form of a cylinder or a lamella is selectively removed by etching to form a second recess. Examples of the etching method include oxygen etching, but are not particularly limited.

  At this time, as shown in FIG. 7, the depth (A) of the first recess, the film thickness (B) of the ziplock copolymer film, and the depth (C) of the second recess are C ≦ A <B. It is preferable to satisfy the relationship.

  Next, a silicon-containing resist is embedded in the first and second recesses. The silicon-containing resist is a resist having high oxygen etching resistance. Examples of the silicon-containing resist include spin-on glass (SOG) and HSQ (hydrogen silsesquioxane).

  Next, the diblock copolymer film is etched using the silicon-containing resist as a mask, and then the substrate is etched. Thereafter, the silicon-containing resist that has become unnecessary is removed. In this way, a pattern having a grid-like convex portion surrounding the rectangular concave portion can be formed.

  A pattern forming method according to an embodiment of the present invention will be described with reference to FIGS. 1, 2A to 2F, and FIGS. 3A to 3F. 1 is a plan view of the magnetic recording medium of the present invention, FIGS. 2A to 2F are enlarged plan views of a region a in FIG. 1, and FIGS. 3A to 3F are FIGS. It is AA sectional drawing of f). Here, an example will be described in which a carbon film is formed on a substrate, polystyrene-polymethyl methacrylate (PS-PMMA) is used as a diblock copolymer, and a pattern is formed on the carbon film.

  A carbon film 12 is formed on the substrate 11. PS-PMMA is applied as a diblock copolymer film 13 on the carbon film 12, and phase separation is performed by annealing. As a result, a PMMA component 15 in the form of a cylinder is formed in the PS component 14 (FIGS. 2a and 3a).

  An imprint mold 20 having a line pattern is prepared. Imprinting is performed by applying pressure by a pressing device with the diblock copolymer film 13 phase-separated on the substrate 11 and the imprint mold 20 facing each other. In this way, the first recess 16 intersecting the length direction of the cylinder made of the PMMA component 15 of the diblock copolymer film 13 is formed (FIGS. 2b and 3b). The angle formed between the length direction of the cylinder made of the PMMA component 15 and the first recess 16 is set within a range of about 60 ° to 90 ° as shown in FIG. 2b, for example, depending on the shape of the recording head. Can do.

  Oxygen etching is performed to selectively remove the cylinder made of the PMMA component 15 of the diblock copolymer film 13 to form the second recess 17 (FIGS. 2c and 3c).

  SOG 18 is embedded in the first recess 16 and the second recess 17 as a silicon-containing resist having high oxygen etching resistance (FIGS. 2d and 3d).

  Using the SOG 18 as a mask, the diblock copolymer film 13 is etched by oxygen RIE, and the carbon film 12 is further etched (FIGS. 2e and 3e).

Thereafter, the unnecessary SOG 18 is removed by etching with CF ₄ gas. Thus, a lattice-like convex pattern surrounding the rectangular concave portion can be formed on the carbon film 12 on the substrate 11 (FIGS. 2f and 3f).

  The carbon film on the substrate produced by the above method and having a lattice pattern formed thereon can be used as an imprint mold, for example.

  With reference to FIGS. 4A to 4D, a method for manufacturing a magnetic recording medium using an imprint mold having a lattice pattern will be described.

  A magnetic film 32 is formed on the medium substrate 31, and an imprint resist 33 is applied on the magnetic film 32. The resist material is not particularly limited as long as imprinting is possible. A material suitable for imprinting methods such as hot embossing and room temperature imprinting can be selected. Specifically, materials such as organic polymers, SOG, HSQ and the like can be mentioned. An imprint mold 30 having a lattice pattern is set so as to face the resist 33, and imprinting is performed by applying pressure with a pressing device (FIG. 4a). The imprint mold 30 is removed, and lattice-like grooves 34 are formed in the resist 33 (FIG. 4b). After removing the resist residue remaining at the bottom of the groove 34, the magnetic film 32 is etched using the remaining convex resist pattern as a mask (FIG. 4c). Thereafter, the remaining resist pattern is peeled off to manufacture a magnetic recording medium on which recording cells having a desired shape are formed (FIG. 4d). The formed recording cell 35 has a parallelogram shape having different aspect ratios as shown in FIG. 5, for example. The recording cell having such a shape can follow the shape of the recording head.

  As described above, it is difficult to form a rectangular nanopattern simply by utilizing phase separation of a diblock copolymer, but according to the method of the present invention, an optimal pattern can be designed with a high degree of freedom.

  This method is not limited to magnetic recording media, but can be applied to fields that require the formation of fine patterns, such as optical disks and semiconductor devices.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
An example in which a carbon film is processed in accordance with the method shown in FIGS. 2A to 2F and FIGS. 3A to 3F will be described.

  A 20 nm carbon film 12 was formed on a 2.5 inch substrate 11 by sputtering. A toluene solution of polystyrene-poly (ethylene-alt-propylene) (PS-PEP) diblock copolymer was spin-coated on the carbon film 12 to form a diblock copolymer film 13 having a thickness of 30 nm. As shown in FIG. 6, a pad 51 made of polydimethylsiloxane was placed on the diblock copolymer film 13, and a weight plate 52 was placed thereon. By applying a shear stress to the diblock copolymer film 13 through the pad 51 by pulling the weight plate 52 in one direction (indicated by an arrow in the figure) while annealing at 100 ° C. to separate the diblock copolymer. Then, a phase separation membrane in which cylinders made of PEP components were arranged along the direction was obtained.

  Next, an imprint mold 20 made of nickel in which convex lines having a width of 50 nm and a height of 25 nm are formed at a pitch of 200 nm is prepared, and the line of the imprint mold 20 is 90 ° with respect to the length direction of the cylinder of the PEP component. The first concave portion 16 was formed in the diblock copolymer film 13 by performing imprinting by pressing for 60 seconds at a pressure of 2000 bar. Only the cylinder made of the PEP component of the diblock copolymer film 13 was removed by oxygen dry etching to form the second recess 17.

An SOG solution containing 0.3% of a methylsiloxane polymer component was spin-coated and embedded in the first recess 16 and the second recess 17. Oxygen RIE etching was performed using SOG 18 as a mask, the diblock copolymer film 13 was etched, and the carbon film 12 was further etched. Thereafter, the unnecessary SOG 18 was removed by etching with CF ₄ gas. Thus, a lattice-like convex pattern surrounding the concave portion of 25 nm × 150 nm was formed on the carbon film 12 on the substrate 11. This can be used as an imprint mold.

(Example 2)
Another example in which a carbon film is processed according to the methods shown in FIGS. 2 (a) to 2 (f) and FIGS. 3 (a) to 3 (f) will be described.

  A 20 nm carbon film 12 was formed on a 2.5 inch substrate 11 by sputtering. A novolak resist was applied to the carbon film 12 to a thickness of 20 nm, and a nickel mold having a convex portion of 100 nm formed along the arm trajectory of the head of the magnetic recording device at a pitch of 500 nm was pressed at a pressure of 1000 bar. A guide groove with a width of 70 nm was formed on the carbon film.

  A xylene solution of polystyrene-polymethacrylate (PS-PMMA) diblock copolymer is spin coated, the diblock copolymer is embedded in the guide groove, and phase-separated by annealing at 200 ° C. for 10 hours, along the direction of the guide groove. A phase separation membrane in which cylinders made of PMMA components were arranged was obtained.

  Next, a nickel imprint mold 20 in which convex lines having a width of 50 nm and a height of 25 nm are formed concentrically at a pitch of 200 nm is prepared, and imprinting is performed by pressing at a pressure of 2000 bar for 60 seconds to obtain a diblock copolymer film. A first recess 16 was formed in 13. Only the cylinder made of the PMMA component of the diblock copolymer film 13 was removed by oxygen dry etching to form the second recess 17.

An SOG solution containing 0.3% of a methylsiloxane polymer component was spin-coated and embedded in the first recess 16 and the second recess 17. Oxygen RIE etching was performed using SOG 18 as a mask, the diblock copolymer film 13 was etched, and the carbon film 12 was further etched. Thereafter, the unnecessary SOG 18 was removed by etching with CF ₄ gas. Thus, a lattice-like convex pattern surrounding the concave portion of 25 nm × 150 nm was formed on the carbon film 12 on the substrate 11. This can be used as an imprint mold.

(Example 3)
An example in which a magnetic recording medium is manufactured according to the method shown in FIGS.

  A 20 nm magnetic film 32 was formed on the glass substrate 31 and a novolac resist 33 having a thickness of 30 nm was spin-coated on the magnetic film 32. The imprint mold 30 having the lattice pattern prepared in Example 2 was set so as to face the resist 33, and imprinting was performed by applying a pressure of 2000 bar by a press device. The imprint mold 30 was removed, and lattice-like grooves 34 were formed in the resist 33. After removing the resist residue remaining at the bottom of the groove 34, the magnetic film 32 was etched by Ar ion milling using the remaining convex resist pattern as a mask. Thereafter, the remaining resist pattern was peeled off to produce a magnetic recording medium in which 25 nm × 150 nm magnetic cells were formed.

1 is a plan view of a magnetic recording medium to which the present invention is applied. The enlarged plan view of the area | region a of FIG. AA sectional drawing of Fig.2 (a)-(f). Sectional drawing which shows the manufacturing method of the magnetic-recording medium based on embodiment of this invention. FIG. 4 is a perspective view showing a recording cell of a magnetic recording medium manufactured by the method of FIG. 3. FIG. 3 is a diagram showing a method of applying shear stress to the diblock copolymer film in Example 1. Sectional drawing which shows the relationship between the depth (A) of a 1st recessed part, the film thickness (B) of a ziplock copolymer film | membrane, and the depth (C) of a 2nd recessed part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Carbon film, 13 ... Diblock copolymer film, 14 ... PS component, 15 ... PMMA component, 16 ... 1st recessed part, 17 ... 2nd recessed part, 18 ... SOG, 20 ... Imprint mold, DESCRIPTION OF SYMBOLS 30 ... Imprint mold, 31 ... Medium substrate, 32 ... Magnetic film, 33 ... Resist, 34 ... Groove, 35 ... Recording cell, 51 ... Pad, 52 ... Weight plate.

Claims (6)

Applying a diblock copolymer film on a substrate, phase-separating the diblock copolymer film to form one polymer component in the form of a cylinder or lamella,
Imprinting the diblock copolymer film using an imprint mold having a line pattern to form a first recess intersecting the length direction of the cylinder or lamella,
Removing the polymer component in the form of the cylinder or lamella by etching to form a second recess,
A silicon-containing resist is embedded in the first and second recesses;
Etching the diblock copolymer film using the silicon-containing resist as a mask, and then etching the substrate.   A guide groove is formed on the substrate, a diblock copolymer film is applied in the guide groove, the diblock copolymer film is phase-separated, and one polymer component is separated into a cylinder along the length direction of the guide groove or The pattern forming method according to claim 1, wherein the pattern forming method is a lamella.   The diblock copolymer film is phase-separated while applying a shear stress along the film surface, and the one polymer component is in the form of a cylinder or a lamella along the direction of the shear stress. The pattern formation method of description.   The depth (A) of the first recess, the film thickness (B) of the ziplock copolymer film, and the depth (C) of the second recess satisfy the relationship C ≦ A <B. The pattern forming method according to any one of claims 1 to 3.   An imprint mold having a lattice pattern, comprising a substrate processed by the pattern forming method according to claim 1. A magnetic film is formed on a medium substrate,
A resist is applied on the magnetic film,
Imprinting using the imprint mold having the lattice pattern according to claim 5 to the resist, forming a lattice-shaped recess in the resist,
A method of manufacturing a magnetic recording medium, comprising: etching a magnetic film using a resist remaining in a region other than the lattice-shaped recess as a mask to form a magnetic film pattern separated by a lattice-shaped groove.

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