JP2001291258A - Near field optical head, method for manufacturing near field optical head and optical information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near field optical head which can form a light spot as small as 20 to 50 nm in size and has excellent transmittance for light, to provide a method for manufacturing a near field optical head and to provide a recording and reproducing device which uses that head. SOLUTION: In the near field optical head having a minute aperture 23 on a flat face 22, a noble metal fine particle structure 24 is formed in the minute aperture opening 23 and the top of the noble metal fine particle 24 does not protrude to outside from the flat face 22 of the head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-field optical head capable of performing high-density recording by light, a method of manufacturing a near-field optical head, and an information recording / reproducing apparatus.

[0002]

2. Description of the Related Art In the information-oriented society in recent years, a recording / reproducing method and a recording / reproducing apparatus based on the recording / reproducing method having a remarkably high recording density corresponding to an ever-increasing amount of information are expected. I have.

Techniques for realizing optical recording include a heat mode in which light is used as heat and a photon mode recording in which recording is performed without converting the heat. Heat mode recording is currently in practical use for magneto-optical recording and phase transition recording.

[0004] In order to improve the recording density in heat mode recording, a near-field optical scanning near-field microscope capable of forming a spot smaller than the wavelength of light from a minute opening.
dScanning Optical Microsc
A technology using ope (NSOM) has been proposed. For example, Betzig et al. Reported that the output of an Ar ion laser was obtained by using an NSOM probe made by stretching a fiber.
Irradiate the / Pt multilayer film and try to record / reproduce information magneto-optically to form a recording pattern with a diameter of 60 nm (A
ppl. Phys. Lett. 61, 142 (199
2)). Hosaka et al. Used a NSOM probe to measure the output of a semiconductor laser using a 30 nm-thick Ge ₂ Sb ₂ T
by irradiating e ₅ films were a phase change, thereby realizing a recording pattern having a diameter of 50 nm (Thin Solid Fil
ms 273, 122 (1996); Appl. P
bys. 79, 8082 (1996)).

However, in the method using the fiber NSOM probe described above, the intensity of the near-field light emitted from the minute aperture is extremely small, and high-speed writing and reading cannot be performed. On the other hand, Matsumoto et al. Reported that the light transmission rate was improved by attaching noble metal fine particles to the tip of the fiber probe as shown in FIG. 1, but as an optical head for a recording medium that rotates at a high speed. Cannot be used (T. Matsumoto, T. Ic
Himura, T .; Yatsui, M .; Kour
Ogi, T .; Saiki and M.S. Ohts
u,, inTech. Digest of 5t
h Int. Conf. on Near Field
d Optics and Related Tech
niques (NFO-5), paper PC7
(1998)). Further, the plasmon resonance effect is reduced due to the distance d. Furthermore, because of difficulty in manufacturing, it is very difficult to cope with an opening having a diameter of 20 to 50 nm required for an ultra-high density memory having a recording capacity of 1 terabit per square inch.

[0006] Isshiki et al. Have reported an optical head having a fine opening in a flat part (Fumio Isshiki, Akito Ito,
Kimitoshi Eto and Sumio Hosaka, The 46th Joint Lecture on Applied Physics, Spring 1999, 30P-ZB-15). in this case,
The laser beam can be condensed into the minute opening without using the fiber, but the opening is air, so that the light transmittance from the opening is low.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to
An object of the present invention is to provide a near-field optical head capable of forming a minute light spot of about 50 nm and having excellent light transmittance, a method of manufacturing the near-field optical head, and a recording / reproducing apparatus using the same.

[0008]

According to a first aspect of the present invention, there is provided a near-field optical head having a fine opening in a flat surface, wherein a noble metal fine particle structure is formed in the fine opening. The tip of the noble metal fine particles does not protrude outside the flat surface of the head.

Therefore, as shown in FIG. 2, the noble metal fine particles can efficiently perform plasmon resonance with the light incident on the opening, and the light transmittance is improved. Further, since the flatness can be ensured, it can be used for a flying head or the like in which the medium rotates at high speed. Furthermore, the noble metal particles themselves are smaller than the aperture, and the near-field light concentrates there,
It is possible to obtain a light spot smaller than the aperture diameter.

The noble metal fine particles include gold, silver, platinum and alloys thereof, but gold and silver are preferred. Preferably, the noble metal fine particles are chemically bonded to the minute openings.
As a method of manufacturing a micro aperture of a near-field optical head, an optical fiber is stretched or etched to create a conical probe, a light shielding film such as aluminum is formed in the opening, and then an electron beam or a high-speed ion beam is formed. Irradiation to remove aluminum. Further, it can be formed by forming a light shielding film such as aluminum on a flat portion of a lens such as a solid immersion lens and then irradiating an electron beam or a high-speed ion beam to remove the aluminum. Further, as shown in Japanese Patent Application Laid-Open No. H11-110793, after a Si substrate is anisotropically etched using a semiconductor process, a minute opening is directly formed by irradiating an electron beam or a high-speed ion beam, or a resist is formed. And can be formed using electron beam lithography or X-ray lithography. When a semiconductor process is used, a multi-aperture near-field optical head having a plurality of minute openings in one near-field optical head can be easily manufactured.

A near-field optical head according to a second aspect of the present invention is a near-field optical head having a minute aperture on a flat surface.
The first transparent dielectric is filled in the minute opening, and the refractive index of the transparent dielectric is substantially the same as or larger than the refractive index of the second dielectric that guides light in contact with the transparent dielectric. And the first dielectric does not protrude outside the flat surface of the head.

When the fine aperture is filled with a transparent dielectric material having a high refractive index, the dielectric polarization by the electric field is efficiently transmitted to the tip of the aperture, so that the efficiency of generating near-field light can be increased. . Further, since the structure is such that the dielectric does not protrude outside the flat surface of the head, the flatness of the head can be obtained, and the medium can be rotated at high speed.

A near-field optical head according to a second aspect of the present invention is further characterized in that noble metal fine particles are contained inside the first transparent dielectric. With such a structure, it is possible to further increase the light transmittance using plasmon resonance.

A method for manufacturing a near-field optical head according to a third aspect of the present invention is characterized in that a chemical species having an affinity for noble metal fine particles is provided in a minute opening.

[0015] In this case, the noble metal fine particles can be adsorbed to the opening. The noble metal fine particles and the chemical species preferably form a chemical bond. It is more preferable that the noble metal fine particles have a repulsive force because the interval and the number of the fine particles adsorbed to the opening can be controlled. Examples of combinations having affinity include gold and a thiol group, and silver and a carboxyl group. Further, the noble metal fine particles have a charge in water, and it is preferable that a chemical species having an opposite charge is placed in the opening and a chemical species having the same charge is placed around the opening.

After the transparent fine particles are adsorbed on the opening,
The above structure can be produced by depositing a noble metal.

According to a fourth aspect of the present invention, there is provided the optical information recording / reproducing apparatus according to the present invention, wherein the noble metal fine particle structure is formed in the minute opening, and the tip of the noble metal fine particle does not protrude outside the flat surface of the head, or The opening is filled with a first transparent dielectric, and the refractive index of the transparent dielectric is the same as or larger than the refractive index of a second dielectric that guides light in contact with the transparent dielectric, and The present invention is characterized in that it has a near-field optical head in which the dielectric does not project outside the flat surface of the head and a means for sensing light, a magnetic field or an electric field.

The near-field optical head may be formed on a flying or contact slider such as a magnetic disk drive, or has a means for precisely controlling the vertical distance, such as a probe used in a probe microscope. It may be installed as. Optical information recording media include magnetic recording media, magneto-optical recording media, phase-change recording media, charge recording media, rewritable recording media such as photochromic recording media, write-once recording media such as dye media, perforated and metal dot reflection media. A read-only recording medium such as a mold and a fluorescent medium can be used. These recording media can be used in the form of a disk and rotated, or in combination with a near-field optical head that is two-dimensionally driven in the form of a card. One or more near-field optical heads may be used for one recording medium.

As a means for sensing light, a method utilizing a change in a photodiode or laser oscillation is preferable. As a means for sensing magnetism, a head utilizing the magnetoresistance effect is preferable. As a means for sensing an electric field, a field effect transistor and a single electron transistor are preferable.

Further, these may be combined with a write head for applying a magnetic field or an electric field. The near-field optical head and the writing means or the sensing means may be provided separately, or may be provided integrally with one head.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments.

First Embodiment 30 n of aluminum is used as a light shielding film 32 on a flat part of a solid imagin lens 31 made of heavy flint glass.
m was deposited. Next, after applying an electron beam resist on the aluminum film, a portion corresponding to the minute opening was irradiated with an electron beam using a high-resolution electron microscope. After forming an opening by RIE etching, the resist is removed and one side 30
A solid immersion lens having a square minute aperture 33 of nm square was obtained. Next, the chemical formula is applied to the opening of the solid immersion lens.

Embedded image An ethanol solution of the substance represented by is dropped and immersed for 10 minutes, washed with ethanol, and heated at 80 ° C. for 1 hour, whereby the substance represented by the chemical formula (1) was chemically adsorbed to the opening. A thiol group having an affinity for the fine gold particles was formed on the surface. Then the chemical formula

Embedded image An ethanol solution of the substance represented by is dropped into the opening and immersed for 10 minutes, washed with ethanol, and heated at 50 ° C. for 30 minutes to chemically adsorb the substance represented by the chemical formula (2) on aluminum. Next, it was immersed in a commercially available aqueous dispersion of fine gold particles having a diameter of 20 nm for 30 minutes, and then washed with water. Gold particles are negatively charged in water, and have the chemical formula (2)
Repel with the substance. On the other hand, it was confirmed from the AFM measurement that one of the fine gold particles 34 was selectively adsorbed to the opening due to the reaction with the thiol group.

Next, the solid immersion lens was attached to a slider head 37 to which a magnetic head 35 for writing and a GMR head 36 for reading were attached, and a near-field optical head 38 shown in FIG. 3 was obtained. The tips of the noble metal particles did not protrude outside the flat surface of the head.

Next, an optical information recording / reproducing apparatus 41 shown in FIG. 4 was prepared. As a recording medium, a perpendicular magnetic recording medium disk 42 having a diameter of 2.5 inches, a semiconductor laser 43 having a wavelength of 620 nm and an output of 6 mW and an objective lens 44 for inputting light to the near-field optical head 38 were provided. 45 is a motor for rotating the disk.

The signal was written by the magnetic head 35 while rotating the disk at 4000 rpm and continuously irradiating near-field light. For reproduction, a magnetic signal was read by the GMR head 36. A signal of 500 gigabits per square inch could be read at a CN ratio of 25 dB.

COMPARATIVE EXAMPLE 1 Instead of using the near-field optical head having a fine aperture shown in FIG. 3, the structure is the same as that of the first embodiment except that a near-field optical head having no fine gold particles is used. In this way, a near-field optical head and an optical information recording / reproducing device were produced.

The disk was rotated at 4000 rpm, and signals were written with a magnetic head while continuously irradiating near-field light. For reproduction, a magnetic signal was read by a GMR head. 500 gigabits per square inch is 10
The data could only be read at a dB CN ratio.

Second Embodiment On a flat portion of a solid immersion lens 51 made of glass having a refractive index of 1.80, chromium 40 is used as a light shielding film 52.
It was deposited with a thickness of nm. Next, a high-speed ion beam was irradiated to obtain a solid immersion lens having a minute aperture. Next, after flint glass having a refractive index of 1.85 was melted in the minute openings, the surface was shaved by chemical mechanical polishing to obtain a solid immersion lens in which minute openings 53 having a diameter of 20 nm were filled with flint glass. The solid immersion lens 51, a writing electrode head 54, and a charge reading FET sensor 55
The solid immersion lens is attached to the slider head 56 to which the near-field optical head 57 shown in FIG.
I got

Next, an optical information recording / reproducing apparatus 61 shown in FIG. 6 was prepared. As a recording medium, a charge recording medium disk 62 having a diameter of 2.5 inches shown in FIG.
A semiconductor laser 63 having a wavelength of 620 nm and an output of 6 mW and an objective lens 64 for setting the wavelength at 620 nm were installed. 65 is a motor for rotating the disk. The charge recording medium disk 62 includes an electrode 71 formed on a substrate 70, a photoconductive layer 72, a recording layer 74 in which metal dots 73 for storing electric charges are embedded in an insulator, and a protective film 75.

A signal was written by applying a voltage to the electrode head 54 while continuously irradiating near-field light while rotating the disk at 4000 rpm. In the reproduction, the charge signal was read by the FET sensor head 55. A signal of 600 terabits per square inch could be read at a CN ratio of 20 dB.

Comparative Example 2 Instead of using the near-field optical head shown in FIG. 5, the near-field optical head and the optical information recording were performed in the same manner as in Example 2 except that the fine aperture was not filled with flint glass. A playback device was created.

The disk was rotated at 4000 rpm, and a signal was written by applying a voltage to the electrode head while continuously irradiating near-field light. In the reproduction, the charge signal was read by the FET sensor head, but 600 per inch square.
It was found that a terabit signal could not be read at a CN ratio of 10 dB, and that sufficient recording was not performed.

Third Embodiment A silicon oxide film 82 was prepared by anisotropically etching a Si substrate 81 using a semiconductor process and then oxidizing the surface. 30n of aluminum as a light shielding film 83 on a flat part
m was deposited. Next, after applying an electron beam resist on the aluminum film, a portion corresponding to the minute opening was irradiated with an electron beam using a high-resolution electron microscope. After minute openings were formed by RIE etching, the resist was removed to obtain a Si substrate having 10 × 10 square minute openings 84 of 30 nm square on each side. Next, an ethanol solution of the substance represented by the chemical formula (1) is dropped into the opening and immersed for 10 minutes, washed with ethanol, and heated at 80 ° C. for 1 hour, whereby the substance represented by the chemical formula (1) is placed in the opening. Chemisorbed. A thiol group having an affinity for the fine gold particles was formed on the surface.
Next, an ethanol solution of the substance represented by the chemical formula (2) is dropped into the opening and immersed for 10 minutes.
By heating at 0 degrees for 30 minutes, the substance represented by the chemical formula (2) was chemically adsorbed on the aluminum. Next, after immersing in a commercially available aqueous dispersion of gold fine particles having a diameter of 20 nm for 30 minutes, washing with water, it was confirmed from AFM measurement that one gold fine particle 85 was selectively adsorbed to each opening. Was. Next, after a spherical condenser lens 86 was set in the opening, it was mounted on a slider head 87 to produce a multi-near-field light head 88 shown in FIG.

[0034]

As described above, according to the present invention,
It is possible to provide a near-field optical head capable of forming a minute light spot of 20 to 50 nm and having excellent light transmittance, a method of manufacturing the near-field optical head, and an optical information recording / reproducing apparatus using the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a fiber probe having noble metal fine particles.

FIG. 2 is a diagram illustrating the structure of a near-field optical head according to the present invention.

FIG. 3 is a diagram showing a near-field optical head manufactured in the first embodiment.

FIG. 4 is a diagram showing an optical information recording / reproducing device manufactured in the first embodiment.

FIG. 5 is a diagram showing a near-field optical head manufactured in a second embodiment.

FIG. 6 is a diagram showing an optical information recording / reproducing device manufactured in a second embodiment.

FIG. 7 is a diagram showing a structure of a recording medium used in a second embodiment.

FIG. 8 is a diagram showing a near-field optical head manufactured in a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Optical fiber 12 ... Light shielding film 13 ... Precious metal fine particles 21 ... Near field optical head 22 ... Flat part 23 ... Small aperture 24 ... Precious metal fine particles 25 ... Transparent dielectric 26 ... Condensing lens 31 ... Solid immersion lens 32 ... Light shielding film Reference Signs List 33 minute aperture 34 gold particles 35 magnetic head 36 GMR head 37 slider head 38 near-field optical head 41 optical information recording / reproducing device 42 perpendicular magnetic recording medium disk 43 semiconductor laser 44 objective lens 45 motor, 51 solid immersion lens 52 light shielding film 53 minute aperture 54 electrode head 55 FET sensor 56 slider head 57 near-field optical head 61 optical information recording / reproducing device 62 electric charge recording medium disk 63: semiconductor laser 64: objective lens 65: motor 7 0 ... Substrate 71 ... Electrode 72 ... Photoconductive layer 73 ... Metal dot 74 ... Recording layer 75 ... Protective film, 81 ... Si substrate 82 ... Silicon oxide film 83 ... Light shielding film 84 ... Micro aperture 85 ... Gold fine particles 86 ... Condensation Lens 87: slider head 88: near-field optical head

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Claims (5)

[Claims] 1. A near-field optical head having a minute opening in a flat surface, wherein a noble metal fine particle structure is formed in the minute opening, and a tip of the noble metal fine particle does not protrude outside the flat surface of the head. Characteristic near-field optical head. 2. A near-field optical head having a minute opening in a flat surface, wherein the minute opening is filled with a transparent first dielectric, and the refractive index of the first dielectric is reduced. A near-field optical head, wherein the refractive index of a second dielectric that guides the contacting light is equal to or greater than a refractive index of the second dielectric, and the first dielectric does not project outside the flat surface of the head. 3. The near-field optical head according to claim 2, wherein the noble metal fine particles are contained inside the first dielectric. 4. A method for producing a near-field optical head, comprising placing a chemical species having an affinity for noble metal fine particles in a minute opening. 5. A noble metal fine particle structure is formed in the minute opening, and the tip of the noble metal particle does not protrude outside the flat surface of the head, or the minute opening is filled with a transparent first dielectric, The refractive index of the first dielectric is equal to or greater than the refractive index of a second dielectric that guides light in contact with the dielectric, and the first dielectric is located outside the flat surface of the head. An optical information recording / reproducing apparatus, comprising: a near-field optical head which is not shown in FIG. 1; and means for sensing light, magnetic field or electric field.