JP2006164410A - Optical information recording medium, its manufacturing method, and optical information recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium in which optical information of high quality and large capacity can be highly efficiently and stably recorded by using an optical information processing apparatus using a near field effect of light, to provide its manufacturing method and to provide an optical information recording apparatus. <P>SOLUTION: The optical information recording medium has a flat plate-shaped substrate and a finely structured recording layer of a size of a wavelength of recording light or below formed on the substrate. The finely structured recording layer has a laminated structure wherein an optical recording layer 42 recording optical information and a metal layer 41 generating plasmon are sequentially laminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium, a manufacturing method thereof, and an optical information recording apparatus, and more particularly to an optical information recording medium capable of recording information at an ultra-high density using a near-field optical effect.

  In recent years, with the advancement to the multimedia era where various types of information such as audio, video motion picture files and text files are combined, large capacity that can process and store large amount of information quickly There is a need for a recording medium for recording such information. In addition, when bi-directional image communication such as high-definition moving images and VOD (Video-On-Demand), which are expected to become more popular in the future, is realized, the capacity of the information recording medium is reduced. It will be further increased.

  In accordance with such a request, various recording and reproduction methods for recording media widely used at present have been proposed. As one of such information recording and reproducing methods, recording and reproducing on a recording medium using light is possible. There is a way to do it. A typical example of a recording method using light is a method using a local refractive index change by irradiating a specific polymer material with a predetermined light to change its molecular structure, generally a rare earth metal. There is a method of changing the local magnetization direction by irradiating an amorphous alloy thin film made of a transition metal with light in a predetermined magnetic field and locally heating it above a Curie point or a compensation point.

  By the way, in these methods, laser light is condensed by a lens optical system and irradiated onto a recording medium, and the spot diameter of this laser is an important parameter for determining the size of a recording mark. In other words, the smaller the spot size of the laser beam, the more information can be recorded and reproduced on the optical recording medium, and the higher recording density can be achieved. For this purpose, it is only necessary to shorten the wavelength of the laser light and increase the numerical aperture (NA) of the objective lens of the optical pickup. However, the size of the spot of the laser beam that can be reduced by shortening the wavelength of the laser beam and increasing the numerical aperture of the objective lens is about the wavelength of the laser beam. Therefore, in order to shorten the wavelength of the laser beam, when a blue semiconductor laser (up to 400 nm) is used as a DVD light source instead of a red semiconductor laser (up to 660 nm) that is currently used as a DVD light source, The amount of information that can be recorded can be improved by about 2.5 times the amount of information on the recording medium when a red semiconductor laser is used.

  However, according to such a method, the spot diameter of light has a limit in improving the information recording density of the recording medium due to the light diffraction limit. Therefore, in view of the above-described problems, near-field optics or volume holograms are used as techniques based on a completely different principle from the prior art when processing terabyte (TB) information. Ultra-high density recording methods such as photo-chemical hole burning and three-dimensional optical recording have been proposed. However, volume holograms and photochemical hole burning have a drawback that they are difficult to put into practical use because there are significant restrictions on the usage environment of the recording medium.

  In general, based on the light diffraction theory, the size (major axis) of the light focusing spot is determined by the light source wavelength and the numerical aperture, and the upper limit of the information recording density of the recording medium depends on the degree of reduction of the size of the light focusing spot. It is determined. In addition, the light diffraction phenomenon has the property that the beam becomes wider as the size of the light beam is reduced using a lens.

  θ ≒ λ / d (1)

  It becomes. However, (theta) represents a diffraction angle, d represents the diameter (waist) of a beam, and (lambda) represents the wavelength of light. That is, based on diffraction theory, the smaller the beam size using a lens, the larger the diffraction angle, and the beam size cannot be reduced below a predetermined value. Therefore, the limit of the recording density of the optical recording medium is

  d≈1.22λ / NA (2)

  It is determined by the diffraction theory of light expressed approximately. Here, NA represents the numerical aperture of the objective lens. That is, the shorter the wavelength (λ) of the laser beam and the larger the numerical aperture (NA) of the lens, the smaller the size of the focused beam, and the recording surface density of the recording medium is equal to the spot size. Due to the diffraction phenomenon due to the wave nature of light, the minimum size of information that can be recorded and reproduced per bit is about the wavelength of light.

Therefore, in such a conventional technique, the method of shortening the wavelength of light, reducing the size of the focused light spot using a lens having a large numerical aperture, and increasing the recording density is the best. The recording density obtained by this is expected to be limited to 20-30 Cbit / in ² . That is, in the conventional technique, since light is used as an electromagnetic wave, there is a problem in that when the recording density is improved, a restriction due to the diffraction limit is unavoidable.

  Therefore, in order to overcome such a diffraction limit, a method has been proposed in which light existing in the near field in the near field region (distance below the light wavelength from the surface of the substance) is used as a light source for the recording medium. That is, in principle, near-field light generated from an aperture smaller than the wavelength of light is not emitted. By using this near-field light to interact with the material located near the aperture, information can be recorded and reproduced on the recording medium, thereby overcoming the diffraction limit and dramatically increasing the information recording density of conventional optical recording. May be improved.

  In order to record and reproduce information at a high speed, a planar array type probe has been proposed in Patent Document 1 or Patent Document 2, for example. In this planar array type probe, microscopic openings are formed in an array on the same substrate by anisotropically etching the silicon substrate. Therefore, there are many probes in one element, and the sweep speed of the element itself does not need to be so high. The recording medium is arranged so as to rotate with respect to the probes arranged in a matrix, and the probes arranged on the two-dimensional plane pass through different points on the recording medium. In addition, these planar opening probes produce minute openings by digging a Si substrate by anisotropic etching. In this case, the part where the laser beam passes through the probe is a cavity, and when it is necessary to perform more efficient optical output, that is, faster optical writing and reading, this cavity part is confined to light. It was necessary to fill with a highly effective substance having a high refractive index.

  In order to solve this problem, a frustoconical protrusion made of a high refractive index material is formed on a transparent substrate, and in the manufacturing method of the near-field optical probe, a truncated cone shape made of the high refractive index material is used. A near-field optical probe having protrusions formed by dry etching is proposed in Patent Document 3. Since this near-field probe has good dimensional controllability and a high refractive index, it has excellent reachability of light emitted from a minute aperture.

  In addition, as a method of forming a planar aperture probe having a plurality of micro aperture arrays and generating near-field light in the vicinity of the micro apertures for recording / reproducing on an optical recording medium, a photosensitive resin is formed on the substrate. A step of forming a film, a step of forming a latent image of a conical photosensitive resin pattern on a substrate using at least a photomask having a ring-shaped pattern and an exposure means having a diffused light component; A near-field optical probe in which a truncated cone-shaped protrusion is formed on a transparent substrate by developing the latent image of the photosensitive resin pattern and transferring the cone-shaped photosensitive resin pattern to the substrate by dry etching. It is proposed in Patent Documents 4 to 8.

  Furthermore, as an optical recording / reproducing medium suitable for the near-field recording method and a method for manufacturing the same, a cross-sectional shape in a direction perpendicular to the guide groove in at least one of the concave or convex portions in the unevenness forming the guide groove of the light spot, An optical recording / reproducing medium formed so as not to have a side perpendicular to the optical axis of the light spot, an optical recording / reproducing method using the optical recording / reproducing medium with an improved tracking method, and a rectangular unevenness are formed. Patent Document 9 proposes a method for manufacturing an optical recording / reproducing medium in which the rectangular irregularities are deformed by heat treatment.

  In addition, for processed products using photosensitive materials that form recesses or protrusions depending on the intensity of irradiated light, the surface of the photosensitive material can be processed with fine light with a controlled intensity. By a light processing method, a fine concavo-convex shape or a binary or multi-value concavo-convex information recording bit is formed easily and inexpensively by a single photosensitive material and optical system in a fine optical processing or optical recording medium. A method is also proposed in Patent Document 10.

Further, the recording medium is formed by a near-field light radiated from a microscopic aperture of a flat probe having a microscopic structure having a size smaller than the wavelength of light and a microstructural recording layer on the recording medium, and having a microscopic aperture of the wavelength of light or less. Patent Document 11 discloses a method for recording and reproducing information with high efficiency and stability by recording information on an upper fine structure recording layer, increasing the coupling of the near-field light radiated from the probe to the fine structure recording layer. Proposed.
Patent No. 3,023,085 JP-A-11-191238 JP 2002-340773 A JP 2003-317301 A JP 2003-322603 A JP 2004-005905 A JP 2004-039041 A JP 2004-061219 A JP 2000-322772 A Japanese Patent Laid-Open No. 2003-039400 JP 2003-308632 A

  However, in any of the patent documents, a fine structure recording layer having a high refractive index is formed on the fine structure layer. Therefore, when this fine structure recording layer is present, the peak value of the signal intensity is higher than when there is no fine structure recording layer. There was a problem that the signal intensity decreased several times, which was not suitable for practical use.

  The present invention is for solving these problems, and an optical information recording medium capable of recording high-capacity optical information of high quality with high efficiency and stability with an optical information processing apparatus using the near-field effect of light. Another object of the present invention is to provide a method for manufacturing the same and an optical information recording apparatus.

  In order to solve the above problems, the optical information recording medium of the present invention has a flat substrate and a fine structure recording layer formed on the substrate and having a size equal to or smaller than the wavelength of the recording light. The microstructure recording layer is characterized by having a laminated structure in which an optical recording layer for recording optical information and a metal layer for generating plasmons are sequentially laminated. Therefore, it is possible to provide an optical information recording medium capable of recording high-capacity optical information of high quality with high efficiency and stability.

  Further, the microstructure recording layer can record optical information with higher efficiency by laminating a first thermal reaction layer that confines heat generated in the optical recording layer below the optical recording layer.

  Further, the microstructure recording layer is a second layer in which optical information which is bonded to the plasmon generated in the metal layer and enhanced in strength is transferred between the optical recording layer and the metal layer, and the generated heat is transferred to the optical recording layer. By laminating the thermal reaction layer, high-quality and large-capacity optical information can be recorded more stably.

  In addition, since the protective layer is provided on the entire surface of the fine structure recording layer, it is possible to record information with high reliability against wear on the surface.

  Furthermore, the protective layer is preferably formed of diamond-like carbon or SiN.

  Further, the surface of the substrate has irregularities smaller than the wavelength of light. Therefore, it is possible to couple the light from the minute opening provided at the probe tip to the recording medium with higher efficiency, and it is possible to form a good recording mark and reproduce the signal with a high SN ratio.

  Furthermore, another method for manufacturing an optical information recording medium includes a step of implanting ions capable of increasing the refractive index over the entire surface of a glass substrate, forming fine irregularities on the surface with a resist, and retreating the resist. While etching the glass substrate to form a predetermined diffraction grating-like irregularity on the glass substrate surface, and after removing the resist, forming a metal layer and an optical recording layer on the entire surface of the diffraction grating-like irregularity; And a step of forming a microstructure recording layer by performing a lift-off process for removing the resist layer. Therefore, light from a minute aperture provided at the probe tip can be coupled to the optical information recording medium with higher efficiency, and the optical information recording medium can be manufactured stably and inexpensively. Marks can be formed and signals can be reproduced with a high signal-to-noise ratio.

  Another method of manufacturing an optical information recording medium includes a step of forming fine irregularities with a resist on the surface of the glass substrate, and etching the glass substrate while retracting the resist to cause predetermined diffraction on the surface of the glass substrate. Microstructural recording by forming a grid-like irregularity, removing the resist, forming a metal layer and an optical recording layer over the entire surface of the diffraction grating-like irregularity, and performing a lift-off process to remove the resist layer And a step of forming a layer. Therefore, light from a minute aperture provided at the probe tip can be coupled to the optical information recording medium with higher efficiency, and the optical information recording medium can be manufactured stably and inexpensively. Marks can be formed and signals can be reproduced with a high signal-to-noise ratio.

  Furthermore, the manufacturing method of the optical information recording medium as another invention includes forming a cobalt oxide nanoglass thin film on the entire surface of the glass substrate by sputtering, and then forming fine irregularities with a resist on the surface; Etching the glass substrate while retracting the resist to form predetermined irregularities on the surface of the glass substrate; and removing the resist and then forming a metal layer and an optical recording layer on the entire surface of the diffraction grating-like irregularities; And a step of forming a microstructure recording layer by performing a lift-off process for removing the resist layer. Therefore, the light from the minute opening provided at the probe tip can be coupled to the optical information recording medium with higher efficiency, and it is possible to form a good recording mark and reproduce the signal with a high SN ratio.

  Further, by forming a protective layer on the entire surface of the fine structure recording layer, it is possible to manufacture an optical information recording medium that is resistant to surface abrasion and can record information with high reliability.

  Furthermore, an optical information recording apparatus as another invention is characterized in that information is recorded with a probe having a minute aperture of a wavelength equal to or less than the wavelength of light on the microstructure recording layer of the optical information recording medium. Therefore, information can be recorded with high efficiency and stability, high signal intensity can be obtained, and high practicality can be obtained. Here, the opening size of the minute opening of the probe is preferably equal to the size of the fine structure portion in the fine structure recording layer of the optical information recording medium, and a large amount of information can be recorded efficiently and stably.

  The optical information recording medium of the present invention has a flat substrate and a fine structure recording layer formed on the substrate and having a size equal to or smaller than the wavelength of the recording light. The fine structure recording layer is a light for recording optical information. It has a laminated structure in which a recording layer and a metal layer that generates plasmons are laminated in order. Therefore, it is possible to provide an optical information recording medium capable of recording high-capacity optical information of high quality with high efficiency and stability.

  FIG. 1 is a schematic view showing the operation principle of an optical information reproducing apparatus using the optical information recording medium of the present invention. As shown in the figure, the optical information recording medium 12 is irradiated with near-field light from a probe 11 having a minute aperture having a size sufficiently smaller than the wavelength of incident light. On the optical information recording medium 12, a fine structure 13 having, for example, a cylindrical shape having a diameter substantially equal to the size of the minute opening of the probe 11 is formed. Therefore, by irradiating the fine structure 13 with near-field light from the probe 11, it is possible to reproduce information recorded in the fine structure 13 formed in advance on the optical information recording medium 12. Further, by forming a recordable material on the optical information recording medium 12, write-once type or rewritable type information recording is possible.

  FIG. 2 is a schematic sectional view showing the structure of an optical information reproducing apparatus using the optical information recording medium of the present invention. In the figure, the probe 11 shown in FIG. 1 is formed in a protruding shape on the bottom surface of the planar substrate. The probes can be formed in an array, and information from the optical information recording medium can be reproduced from the arrayed probes sequentially or in parallel. The flat probe is formed on the bottom surface of the slider 27, supported by the holder 28, and traversed on the rotating optical information recording medium 30. As described above, the optical information recording medium 30 has the microstructure recording layer 29 having a microstructure having a columnar shape with a size equal to or less than the wavelength, for example, a diameter equal to or less than the wavelength, and as described above, the microstructure recording layer 29. It is possible to record information. Note that the surface of the microstructure recording layer 29 may be provided with a protective layer to be described later and configured to withstand abrasion with a slider portion (not shown). The light emitted from the semiconductor laser 21 is converted into a parallel light beam by the collimator lens 22 and enters the beam splitter 23. The light beam that has passed through the beam splitter 23 forms an image of a spot on the flat probe formed on the bottom surface of the slider 27 by the objective lens 26, and generates near-field light from the tip of the flat probe. The generated near-field light is coupled to the microstructure recording layer 29 formed on the optical information recording medium 30. When reproducing information, the near-field light component reflected from the microstructure recording layer 29 of the optical information recording medium 30 is detected by a flat probe formed on the bottom surface of the slider 27. The detected near-field light is converted into a parallel light beam by the objective lens 26 through the probe, deflected by the beam splitter 23, and a spot is formed on the photodetector 25 by the imaging lens 24. The information recorded on the optical information recording medium 30 can be reproduced by the intensity of light intensity on the photodetector 24.

  Next, FIG. 3 is a schematic sectional view showing another configuration of the optical information reproducing apparatus using the optical information recording medium of the present invention. In the figure, the same reference numerals as those in FIG. 2 denote the same components. As shown in the figure, information can be recorded and reproduced by detecting light transmitted through the substrate. In this case, unlike the optical information reproducing apparatus shown in FIG. 2, the beam splitter 23 is unnecessary, and the near-field light transmitted through the surface of the optical information recording medium 30 is coupled onto the photodetector 25 by the imaging lens 24. Image and detect. Information recorded on the fine-structure recording layer 29 of the optical information recording medium 30 can be reproduced by the light intensity on the photodetector 25.

  The semiconductor laser 21 shown in FIGS. 2 and 3 is preferably linearly polarized light, and a linearly polarized light may be inserted, but a laser diode or the like itself has linearly polarized light. It can be generated in combination with a plate. By arranging a quarter-wave plate and a polarizing beam splitter at the upper part of the plane minute aperture, it is possible to detect the signal light with a higher S / N ratio by rotating the polarization plane of the incident light and the signal light by 90 degrees. . In this case, the return light to the semiconductor laser can be suppressed, the laser oscillation state can be kept good, a good recording mark can be formed, and the reproduction signal can be detected stably. can do.

Next, the structure of the optical information recording medium according to the first embodiment of the present invention will be described.
FIG. 4 is a schematic view showing the fine structure of the optical information recording medium according to the first embodiment of the present invention. In the figure, by forming, for example, a cylindrical microstructure on the surface of the optical recording substrate, it is possible to use near-field light from a probe having a minute aperture with high efficiency. The size of the fine structure in the present embodiment is not more than the wavelength of the light source, for example, the diameter is 30 nm. In the figure, a microstructure protrusion 44 is formed on a substrate, glass or high refractive index glass doped with ions, silicon compound material such as SiO ₂ , SiON, SiN, sulfide material such as ZnS, CaS, BaS, ZnSe , BaSe and other selenide materials, CaF ₂ , BaF ₂ and other fluorine compound materials, ZnS, SiO _{2 and the} like. On top of that, a thermal reaction layer 43, an optical recording layer 42, and a metal layer 41 are laminated. As the thermal reaction layer 43, a silicon compound material such as SiO ₂ , SiON, or SiN, a sulfide material such as ZnS, CaS, or BaS, a selenide material such as ZnSe or BaSe, or a fluorine compound material such as CaF ₂ or BaF ₂ is used. Can be used. The material of the optical recording layer 42 is a semiconductor material such as Si, Ge or GaAs, an intermetallic compound material containing a low melting point metal such as BiTe, BiIn, GaSb, GaP, InP, InSb, InTe, or SnSn, V ₂ O ₅ , Cr ₂ O ₃ , Mn ₃ O ₄ , Fe ₂ O ₃ , Co ₃ O ₄ , oxide materials such as CuO, carbide materials such as C and SiC, nitride materials such as AlN, and binary phase changes such as SbTe Materials, ternary phase change materials such as GeSbTe, InSbTe, BiSbTe, and GaSbTe, and phase change materials such as quaternary materials such as AgInSbTe. As the metal layer 41, it is desirable to use Au, Ag, Al, Cu, Pt or the like that can excite plasmons.

  Since the near-field light coupled from the probe to the microprotrusions has the metal layer 41, plasmons are generated, and therefore can be coupled to the metal microstructure with high efficiency. The near-field light coupled to the metal layer 41 is coupled to the plasmon and enhanced in intensity, and then transferred to the optical recording layer 42 immediately below it. The optical recording layer 42 absorbs the coupled near-field light and generates heat. If the optical recording layer 42 is a phase change material, information can be recorded by, for example, a phase change from a crystalline phase to an amorphous phase or from an amorphous phase to a crystalline phase due to heat generation of the combined near-field light. In the magneto-optical material, it is possible to record information by applying a magnetic field at the time of near-field light irradiation. The thermal reaction layer 43 is formed to confine heat generated in the optical recording layer 42, and the same effect can be obtained even if only the metal layer 41 and the optical recording layer 42 are used.

  FIG. 5 is a schematic view showing the fine structure of an optical information recording medium according to the second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 4 denote the same components. Similarly to the first embodiment, the size of the fine structure in the present embodiment is equal to or smaller than the wavelength of the light source. For example, the diameter is 30 nm. The difference from the first embodiment is that a thermal reaction layer 51 is provided between the metal layer 41 and the optical recording layer 42, and the microstructure protrusions 44, the thermal reaction layer 43, the optical recording layer 42, the thermal recording layer 42 are formed on the substrate. The reaction layer 51 and the metal layer 41 are sequentially laminated. The thermal reaction layers 43 and 51 are made of the same material as that in the first embodiment.

  Since the near-field light in the present embodiment having such a configuration also has the metal layer 41, plasmons are generated, and thus can be coupled to the metal microstructure with high efficiency. The near-field light coupled to the metal layer 41 is coupled to the plasmon and enhanced in intensity, and then transferred to the thermal reaction layer 51 immediately below it, and the heat generated in the thermal reaction layer 51 is transferred to the optical recording layer 42. . If the optical recording layer 42 is a phase change material, information can be recorded by, for example, a phase change from a crystalline phase to an amorphous phase, or from an amorphous phase to a crystalline phase. In the magneto-optical material, it is possible to record information by applying a magnetic field at the time of near-field light irradiation. The thermal reaction layer 43 is formed to confine heat generated in the optical recording layer 42.

  Here, in the optical near field, when the size of the aperture radius provided at the tip of the probe having a minute aperture and the size of the structure of the irradiated medium are substantially the same, the light intensity that is coupled from the tip of the aperture to the medium. Is maximized. Therefore, when a fine structure equivalent to the probe opening radius is formed on the optical information recording / reproducing medium, light can be used with higher efficiency compared to a planar shape having no fine structure. The size is preferably about the same as the probe opening radius, and the spacing between the microstructures is preferably greater than or equal to the size of the microstructures. In this case, the distance between the probe 11 and the optical information recording medium 12 shown in FIG. 1 needs to be sufficiently closer than the wavelength of the incident light. Further, in this case, a planar near-field optical pickup manufactured as shown in FIG. 2 is formed on the floating head 27, so that the distance between the optical information recording medium and the micro-opening of the optical pickup is constant and minute. It is possible to maintain a high density recording by forming a finer recording mark.

  Note that the optical recording layer having a fine structure on the optical information recording medium side may have a structure in which the real part of the refractive index changes at a certain interval or an imaginary part, that is, a structure in which the absorptance changes at a certain interval. Examples of the substrate 30 shown in FIG. 2 include chemically tempered glass such as aluminosilicate glass and quartz glass, and the thickness is usually 0.5 to 1.5 mm, preferably 0.6 to 1.2 mm.

  Next, the fine structure recording layer of the above-described optical information recording medium of the present invention can be manufactured by the following method, for example. FIG. 6 is a process cross-sectional view showing an example of the manufacturing process of the optical information recording medium of the present invention.

  First, as shown in FIG. 5A, for example, ions are implanted into the entire surface of the glass substrate 61 to form a high refractive index layer 62. Then, as shown in FIG. 5B, cylindrical irregularities are formed by a resist pattern 63 on the surface of the high refractive index layer 52. Thereafter, as shown in FIG. 2C, the glass substrate 61 is etched while the resist pattern 63 is retracted to form a fine structure recording layer having predetermined diffraction grating-like irregularities on the surface of the glass substrate 61. Further, as shown in FIG. 4D, a metal film 64, an optical recording layer 65 having a fine structure, and a thermal reaction layer 66 are formed on the entire surface with the resist pattern 63 left. Here, the configuration of the second embodiment shown in FIG. 5 can be formed by forming a thermal reaction layer next to the metal layer 64. By removing the resist pattern 63 in this state, an optical information recording medium having a laminated fine structure can be formed.

  FIG. 7 is a process sectional view showing an example of another manufacturing process of the optical information recording medium of the present invention. First, as shown in FIG. 2A, for example, ions are implanted into the entire surface of the glass substrate 71 to form a high refractive index layer 72. Then, as shown in FIG. 5B, cylindrical irregularities are formed by a resist pattern 73 on the surface of the high refractive index layer 72. Thereafter, as shown in FIG. 2C, the glass substrate 71 is etched while the resist pattern 73 is retracted to form a microstructure recording layer having predetermined diffraction grating-like irregularities on the surface of the glass substrate 71. Further, as shown in FIG. 4D, a metal film 74, an optical recording layer 75 having a fine structure, and a thermal reaction layer 76 are formed on the entire surface with the resist pattern 63 left. Here, by forming a thermal reaction layer next to the metal layer 74, the configuration of the second embodiment shown in FIG. 5 can be formed. Although not shown in the drawing, it is possible to produce an optical information recording medium having a flat surface by polishing the surface to remove the protruding portion.

In addition, after forming the glass substrate 61 and 71 directly and etching the glass substrate itself, without forming the high refractive index layers 52 and 62 shown in FIGS. (E) By performing the steps (b) to (d) in FIG. 7, it is possible to produce an optical information recording medium having a similar fine structure. Examples of the glass substrate 51 include chemically tempered glass such as aluminosilicate glass and quartz glass, and the thickness thereof is usually 0.5 to 1.5 mm, preferably 0.6 to 1.2 mm. Examples of the impurity include sodium, potassium, lithium, magnesium, thallium, and the like, and ions having a high polarizability or ions having a high polarization ability are particularly preferable. As ions having a high polarizability, Tl (thallium) is preferable. Li (lithium) is good as an ion having a large polarization ability. Further, in order to selectively implant ions into the substrate surface, Tl having a large ion radius and a high polarizability is preferable. Examples of the ion implantation include an ion implantation method, an ion exchange method, and an electro float method, and the ion implantation method is particularly preferable. In this case, the refractive index is increased by increasing the ion concentration to be implanted. Therefore, the refractive index of the convex portion can be easily changed by changing the type of ions to be implanted and the amount of implanted dope. In addition, there are various substances introduced to increase the refractive index described above. For example, in the case of the ion exchange method, the mobility in the high-temperature glass must be sufficiently high in order to perform ion exchange efficiently. Monovalent ions are selected based on such conditions as not to be necessary and that the properties are not impaired even if the glass is doped in a large amount. Furthermore, in order to enhance the performance of an optical probe such as an optical fiber probe or a planar probe, ions having an effect of increasing the refractive index as much as possible are desired. Considering this, thallium ions (Tl +) and cesium ions (Cs +) are appropriate. The thallium ion (Tl +) has a non-rare glass type (18 + 2) structure in the outer shell electron arrangement, is easily diffused in high-temperature glass, and can be added to glass in a large amount as a glass stitch modifying ion, and has a large refractive index. Change can be obtained. The metal film 64 in FIG. 6 and the metal film 74 in FIG. 7 can be formed by any method such as metal vapor deposition, plating, or electrodeposition. Examples of the metal include aluminum, gold, silver, and the like, but those having low oxidizability are particularly preferable. In addition to the above, a cobalt oxide nanoglass thin film may be formed. By forming at room temperature Co ₃ O ₄ thin film usually well high-frequency sputtering method to be used, on the glass substrate 71 of glass substrate 61 and 7 of Figure 6, it is possible to form a Co ₃ O ₄ thin film .

  Furthermore, since the outermost surface of the optical information recording medium approaches the near-field flat probe at a distance shorter than the wavelength and runs at a high speed, a protective layer for preventing wear of the optical recording layer having a fine structure is necessary. Since the near-field light oozes from the probe at a wavelength or less as the protective layer, a material that is thin and hardly absorbs light is desirable in order to make the distance to the recording layer as close as possible. In the present invention, for example, diamond-like carbon is used as a material that satisfies the above conditions. This protective film can be formed by a film forming apparatus such as sputtering, ion beam sputtering or CVD. In the present embodiment, diamond-like carbon was produced by CVD as the outermost surface protective film. Also, SiN can be used as the protective layer. This protective layer of SiN can also be formed by a film forming apparatus such as sputtering, ion beam sputtering or CVD.

A planar probe array can also be used as a probe that generates near-field light. Here, an example of a method for producing the planar probe array is shown in FIG. As shown in FIG. 8A, a silicon nitride film 82 is formed on a transparent quartz substrate 81 as a high refractive index material. The silicon nitride film 82 can be formed by a high temperature thermal CVD method in which SiH ₄ and NH ₃ are thermally reacted at a high temperature of 700 to 1100 degrees. The film thickness of the silicon nitride film 82 is desirably 2 μm or more. Here, a silicon nitride film is used as the high refractive index material, but there is no problem with other high refractive index materials. For example, after sputtering about ₂ μm of SiO ₂ on the quartz substrate 81, an intrusion layer of N atoms or C atoms is produced. In the case of C atoms, ions are implanted into the quartz substrate 81 by an ion implantation method using CH ₄ as a source gas. On the other hand, in the case of N atoms, SiO ₂ is formed by thermal decomposition CVD using SiH ₄ and N ₂ O as raw materials. By doing so, a high refractive index layer can be formed. This high refractive index layer can be formed not only by the above method but also by other CVD, vacuum deposition, sputtering, etc. or a thermal diffusion method. In addition, a silicon single crystal substrate called a SIO substrate is used in which a silicon oxide buffer layer is formed, electrodes are provided on the SOI substrate and the quartz substrate 81, and an appropriate voltage is applied in a temperature atmosphere of about 300 degrees. By applying this, the high refractive index material can be formed on the quartz substrate 81 by bonding the SOI substrate and the quartz substrate 81. As another method, the surfaces of the quartz substrate 81 to be bonded can be sufficiently cleaned, the active silicon layers of the SOI substrate can be bonded together, and bonded by heat treatment at 900 ° C. or higher in a nitrogen atmosphere. Further, the bonded surface of the quartz substrate 81 to be bonded and the SOI substrate is mirror-polished and cleaned by RCA, and Ar FAB (Fast Atom Beam) is simultaneously irradiated for about 300 seconds in a vacuum chamber of 1.333 × 10 ³ Pa or less. And can be joined by pressure bonding at a pressure of 10 MPa.

  Next, as shown in FIG. 8B, a cylindrical resist pattern 83 is formed on a substrate in which a silicon nitride film 82 is formed on the quartz substrate 81 by using a photolithographic technique of a semiconductor process. This cylindrical resist pattern 83 is formed in a region where a silicon protrusion is formed. Then, as shown in FIG. 8C, the silicon nitride film 82 is removed by dry etching using the resist pattern 83 as a mask. By using the quartz substrate 81 as a stopper layer at the time of this etching, the near-field optical probe 84 made of a protrusion made of a high refractive index material can be formed on the optically transparent quartz substrate 81. Further, by adjusting the etching time, the silicon nitride film 82 in the region where the resist pattern 83 does not exist on the quartz substrate 81 is left on the quartz substrate 81, and the proximity of the projection made of a high refractive index material on the quartz substrate 81. A field light probe 84 can be formed. Then, as shown in FIG. 8D, the resist pattern 83 is removed by resist ashing using oxygen plasma. Thereafter, as shown in FIG. 8E, an antireflection film 85 is formed on the surfaces of the silicon nitride film 82 and the near-field optical probe 84 by sputtering or the like. By depositing the antireflection film 85 to a depth greater than the penetration depth of light, it is possible to block light other than near-field light generated from the near-field light probe 84. Finally, as shown in FIG. 8F, a planar probe array can be formed by coating the back surface of the quartz substrate 81 with an antireflection film 86 by sputtering or the like.

  Here, the shape of the formed near-field optical probe 84 can be changed by changing the dry etching conditions described above. For the dry etching, a parallel plate type RIE (Reactive Ion Etching) apparatus was used. Here, various types of near-field optical probes 84 can be formed by changing the gas type, processing pressure, and RF power to optimum conditions. By using the quartz substrate 81 as a stopping layer during this etching, a near-field optical probe made of a cylindrical or conical silicon protrusion can be formed on the quartz substrate 81.

Further, as shown in FIG. 8E, an antireflection film 85 is formed on the upper surface on which the laser light of the planar probe is incident. Compared with the case where the antireflection film 85 is not provided, for example, when the antireflection film of MgF ₂ is formed to 140 nm, the reflectance can be reduced from 4% to 1.4%. As the single-layer thin film, SiO, CeF ₃ or the like can be used in addition to MgF ₂ . Therefore, since the near field light can be efficiently generated due to the decrease in the reflectance, the signal can be detected with high efficiency and high speed.

Further, by changing the antireflection film 85 shown in FIG. 8E from a single layer film to a multilayer film, it is possible to obtain a lower reflectance in a wider wavelength region than in the case of a single layer film. For example, a first dielectric film made of MgF _{2 having a} thickness of 140 nm is formed on a planar probe having an aperture sufficiently smaller than the incident wavelength, and the second dielectric film is made of CeO ₂ and has a thickness of 96 nm. When the thin film and the third dielectric film are made of a thin film made of SiO having a thickness of 108 nm, the reflectance can be made almost zero.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

It is the schematic which shows the principle of operation of the optical information recording / reproducing apparatus of this invention. It is a schematic sectional drawing which shows the structure of the optical information reproducing | regenerating apparatus of this invention. It is a schematic sectional drawing which shows another structure of the optical information reproducing | regenerating apparatus of this invention. It is the schematic which shows the fine structure of the optical information recording medium based on the 1st Example of this invention. It is the schematic which shows the fine structure of the optical information recording medium based on the 2nd Example of this invention. It is process sectional drawing which shows an example of the manufacturing process of the optical information recording medium of this invention. It is process sectional drawing which shows an example of another manufacturing process of the optical information recording medium of this invention. It is process sectional drawing which shows an example of the production process of a planar probe array.

Explanation of symbols

41; metal layer, 42; optical recording layer, 43, 51; thermal reaction layer,
44; Microstructural protrusion.

Claims (12)

  A flat substrate and a microstructure recording layer formed on the substrate and having a size equal to or smaller than the wavelength of the recording light, the microstructure recording layer being an optical recording layer for recording optical information, a metal for generating plasmons An optical information recording medium having a laminated structure in which layers are sequentially laminated.   The optical information recording medium according to claim 1, wherein the microstructure recording layer is formed by laminating a first thermal reaction layer for confining heat generated in the optical recording layer below the optical recording layer.   The microstructure recording layer transfers between the optical recording layer and the metal layer optical information that is bonded to plasmons generated in the metal layer and enhanced in intensity, and transfers the generated heat to the optical recording layer. The optical information recording medium according to claim 2, wherein the second thermal reaction layer is laminated.   The optical information recording medium according to claim 1, further comprising a protective layer on the entire surface of the microstructure recording layer.   The optical information recording medium according to claim 4, wherein the protective layer is formed of diamond-like carbon or SiN.   The optical information recording medium according to claim 1, wherein a surface of the substrate has irregularities smaller than a wavelength of light. Implanting ions capable of increasing the refractive index over the entire surface of the glass substrate and forming fine irregularities with a resist on the surface;
Etching the glass substrate while retracting the resist to form irregularities in a predetermined diffraction grating pattern on the glass substrate surface;
After removing the resist, a step of forming a metal layer, an optical recording layer on the entire surface of the diffraction grating-like irregularities,
And a step of forming a microstructure recording layer by performing a lift-off process for removing the resist layer. Forming fine irregularities with a resist on the surface of the glass substrate;
Etching the glass substrate while retracting the resist to form irregularities in a predetermined diffraction grating pattern on the glass substrate surface;
After removing the resist, a step of forming a metal layer, an optical recording layer on the entire surface of the diffraction grating-like irregularities,
And a step of forming a microstructure recording layer by performing a lift-off process for removing the resist layer. Forming a cobalt oxide nanoglass thin film on the entire surface of the glass substrate by sputtering, and then forming fine irregularities on the surface with a resist;
Etching the glass substrate while retracting the resist to form predetermined irregularities on the glass substrate surface;
After removing the resist, a step of forming a metal layer, an optical recording layer on the entire surface of the diffraction grating-like irregularities,
And a step of forming a microstructure recording layer by performing a lift-off process for removing the resist layer.   The method for producing an optical information recording medium according to claim 7, wherein a protective layer is formed on the entire surface of the fine structure recording layer.   An optical information recording apparatus, wherein information is recorded on the fine structure recording layer of the optical information recording medium according to any one of claims 1 to 6 with a probe having a minute aperture having a wavelength equal to or smaller than the wavelength of light. The optical information recording apparatus according to claim 11, wherein an opening size of the minute opening of the probe is equal to a size of a fine structure portion in the fine structure recording layer of the optical information recording medium according to claim 1.

Images