JP4135150B2 - Optical information recording / reproducing apparatus - Google Patents

Description

The present invention relates to an optical information recording and reproducing apparatus using an optical information recording medium capable of recording and reproducing data in very high density and high speed.

  In recent years, the multimedia era, in which various types of information such as audio and video moving image files and text files are combined, has been developing at a remarkable pace. Recording and storage media for capacity information has become essential.

  If bidirectional communication such as High-Definition video and VOD (Video-On-Demand), which are expected to become more popular in the future, will be realized, the required information recording medium and storage medium The capacity of will increase further.

  Under such circumstances, many recording and reproducing methods have been proposed at present. One of such data recording and reproducing methods is a method of recording and reproducing on a recording medium using light.

The following method is known as a typical example of a recording method using light.
(A) A method of irradiating a specific polymer material with predetermined light to locally change its molecular structure, thereby changing the refractive index of the portion.

(B) A method in which an amorphous alloy thin film generally composed of a rare earth metal and a transition metal is irradiated with light in a predetermined magnetic field and locally heated above the Curie point or the compensation point, thereby changing the magnetization direction of the portion.

(C) by heating the substance to the melting point or higher by laser light irradiation and then rapidly cooling to form an amorphous phase, or by gradually cooling from a temperature above the crystallization transition point to form a crystalline phase, A method of reversibly changing the structure between crystal and amorphous.

  Since these methods irradiate the recording medium with the laser beam condensed by the lens optical system, the spot diameter of the laser beam is an important parameter for determining the size of the recording mark. That is, the smaller the laser beam spot size, the more information can be recorded on the optical recording medium, and the higher the recording density.

  For this purpose, the wavelength of the laser beam is shortened and the numerical aperture (NA) of the objective lens of the optical pickup is increased. However, the spot size 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 at most about the wavelength of the laser beam.

  For example, if a blue semiconductor laser (-400 nm) is used as a DVD light source instead of a red semiconductor laser (-660 nm) that is currently used as a DVD light source in order to shorten the wavelength of the laser light, the unit area of the DVD The amount of information that can be recorded per hit can be improved by about 2.5 times the amount of information on the recording medium when a red semiconductor laser is used.

  However, in such a method, the spot diameter of light is limited by the diffraction limit of light, and there is a limit to improving the recording density of the recording medium.

  In view of these problems, near-field optics, volume holograms, and photochemical halls are technologies based on principles that are completely different from conventional technologies when processing terabyte (TB) -class information. Ultra-high density recording methods such as burning (photo-chemical hole burning) and three-dimensional optical recording have been proposed.

  However, the volume hologram and the photochemical hole burning have a drawback that it is difficult to put into practical use because there are significant restrictions on the usage environment of the recording medium.

  In general, from the light diffraction theory, the size (major axis) of the light focusing spot is determined by the wavelength of the light source and the numerical aperture, and the upper limit of the recording density of the recording medium is determined by the degree of reduction of the size of the light focusing spot. The

  Furthermore, the light diffraction phenomenon has a property that the beam becomes wider as the size of the light beam is reduced by using a lens, which is expressed as θ˜λ / d. In the equation, θ represents the diffraction angle, d represents the beam diameter, and λ represents the wavelength of light.

  Therefore, as the beam diameter d is reduced using a lens, the diffraction angle θ increases, and the beam diameter (size) cannot be reduced below a predetermined value.

  The limit of the recording density of the optical recording medium is determined by the light diffraction theory approximately expressed as d to 1.22λ / NA. 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 (diameter) of the focused beam, and the recording surface density of the recording medium is the spot density. The minimum size of information that can be recorded and reproduced per bit is approximately the wavelength of light due to the diffraction phenomenon due to the wave nature of light.

Therefore, in such a conventional technique, a 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 used. The recording density obtained by this method is expected to be limited to 20-30 Gbit / in ² . That is, in the conventional system, since light is used as an electromagnetic wave, when the recording density is improved, there is a problem that a restriction due to a diffraction limit cannot be avoided.

  In order to overcome such a diffraction limit, a method of using light (near-field light) existing in the near-field in the near-field region (distance below the light wavelength from the surface of the substance) as a light source for the recording medium has been proposed. ing.

  This is based on the principle that “near-field light generated from an aperture smaller than the wavelength of light is not emitted in principle”. Information is recorded on and reproduced from the recording medium by causing the near-field light to interact with a material to be a recording medium located near the opening. Thereby, there is a possibility that the diffraction limit as described above can be overcome and the recording density of the conventional optical recording can be dramatically improved.

  In a conventional recording / reproducing apparatus (recording / reproducing apparatus) for recording data on an optical disk or reproducing data recorded on an optical disk, the laser beam spot diameter is the center of the track in order to accurately scan the laser beam on the track of the optical disk. It is detected whether it is not off.

  Detection of whether or not the track is off the center is performed by irradiating a tracking mark on the optical disc with a laser beam and detecting a signal based on the reflected light.

  The fact that the laser beam deviates from the track center is called tracking error. A tracking error is detected by a tracking signal. For example, a rewritable recording medium using a phase change material or the like for the recording layer employs a pregroove method as a tracking method. In this method, a groove (pre-groove) for guiding the laser head is formed on the substrate in advance, and the center of the groove is irradiated with the laser beam using diffraction of light generated at the end of the groove. This is a method of applying servo.

  A positional deviation signal (track error signal) between the laser beam and the guide groove (pre-groove) is detected by a push-pull method or the like. That is, a far-field pattern of light reflected from a medium (far-field pattern; a field pattern at a position away from the medium) is detected by a two-divided photodetector having two light receiving areas, and the two light receiving areas are detected. The positional deviation between the guide groove (pre-groove) and the laser beam is detected from the difference in the detected photocurrent.

  The depth of the guide groove (pre-groove) is set to a value in the vicinity of (wavelength / 8) where the tracking error signal (push-pull signal) is the largest. The amplitude of the push-pull signal becomes maximum when the depth of the guide groove is (wavelength / 8), and an amplitude of 1/2 or more of this maximum value is obtained in the range of (wavelength / 20) to (wavelength / 5). (See Patent Document 4 described later).

  However, when near field light is applied not only to data recording on an optical disk but also to various fields, light generated from an aperture having a size equal to or smaller than the wavelength, that is, near field light is used. In this case, the distribution of the near-field light is localized only in the range of the opening diameter, and the near-field light interacts only with the material located near the opening. Since information is recorded and reproduced on a recording medium based on this principle, a conventional tracking method using light diffraction cannot be used.

  In addition, in order to record and reproduce information at high speed, a planar array type probe has been conventionally proposed (Japanese Patent Laid-Open No. 11-191238 (Patent Document 1)). In this method, microscopic openings are formed in an array on the same substrate by anisotropic etching of a silicon substrate.

  In this case, there are a large number of probes in one element (planar array type probe) provided on the same substrate, and therefore 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 a large number of probes arranged in a grid pattern, and each probe arranged on the two-dimensional plane passes through a different point on the recording medium.

  Further, in these planar array type probes, a minute opening is produced by digging a Si substrate by anisotropic etching. In this case, the part where the laser beam passes through the probe is a cavity. However, when more efficient light output (that is, for faster optical writing and reading) is required, It was necessary to fill with a material having a high refractive index and a high confinement effect.

  In response to this problem, a near-field optical probe in which a truncated cone-shaped protrusion made of a high refractive index material is formed on a transparent substrate, and a truncated cone-shaped protrusion made of a high refractive index material are formed by dry etching. A method for manufacturing a near-field optical probe has been proposed (Japanese Patent Laid-Open No. 2002-340773 (Patent Document 2)). This near-field probe has good dimensional controllability and a high refractive index. It is excellent in reachability of light etc. emitted from.

  In addition, as an optical recording / reproducing medium suitable for a near-field recording method and a method for manufacturing the same, a cross-sectional shape in a direction perpendicular to the guide groove of at least one of the concave or convex portions in the concave and convex constituting the optical groove guide groove 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, and an improved tracking method, and a rectangular unevenness A method of manufacturing an optical recording / reproducing medium in which the rectangular irregularities are deformed by heat treatment has been proposed (Japanese Patent Laid-Open No. 2000-322772 (Patent Document 3)).

  Furthermore, for processed products using photosensitive materials that form recesses or projections depending on the intensity of the irradiated light, the surface of the photosensitive material can be processed with fine light using a controlled intensity of light. An optical recording composed of a photosensitive material that forms a concave or convex portion depending on the optical processing method and the irradiation light intensity, and formed recording bits of two or more different shapes by irradiation light with controlled intensity A medium has been proposed (Japanese Patent Laid-Open No. 2003-39400 (Patent Document 4)).

JP-A-11-191238 JP 2002-340773 A JP 2000-322772 A JP 2003-39400 A

Therefore, an object of the present invention is to further improve the above-described conventional technique, and when recording / reproducing using near-field light, it is possible to accurately track a minute guide groove, and to record / reproduce with high density, high efficiency and stability. to provide an optical information recording and reproducing apparatus (claim 8) for recording and reproducing optical information on an optical information recording medium, also capable of recording and reproducing information with strong reliable wear surface can is there.

In order to achieve the above object, the present invention has the following means.
a) The invention according to claim 1 has a concave-convex tracking guide groove on the surface, and at least one of the concave portion or the convex portion constituting the concave-convex shape is asymmetric in a direction perpendicular to the guide groove. An optical information recording / reproducing apparatus for recording / reproducing optical information on / from an optical information recording medium having a side cross-sectional shape, wherein the movement direction of the probe is determined by detecting a variation in near-field light reflected from the optical information recording medium. The probe is tracked to a desired position of the optical information recording medium by detecting and feeding back a signal indicating the moving direction .

b) The invention according to claim 2 is the variation of the near-field light reflected from the optical information recording medium with respect to the optical information recording medium in which one side of the cross-sectional shape of the asymmetric side is linear. And detecting the moving direction of the probe by detecting the signal and tracking the probe to a desired position of the optical information recording medium by feeding back a signal indicating the moving direction. The direction of movement of the probe by detecting the fluctuation of the near-field light reflected from the optical information recording medium with respect to the optical information recording medium in which one side of the cross-sectional shape of the asymmetric side is curved And the probe is tracked to a desired position of the optical information recording medium by feeding back a signal indicating the moving direction .

c) fourth aspect of the present invention, the probe, on a quartz board forming a silicon nitride film, characterized by including a planar probe having a projection made of a high refractive index material, according to claim 5, wherein The present invention is characterized in that the planar probe and the optical information recording medium are in a non-contact state, and the distance between the planar probe and the optical information recording medium is held in a region that is less than or equal to the light source wavelength used. Yes.

d) According to a sixth aspect of the invention, the light on the surface portion of the laser light incident surface of the planar probe relative to the exit surface of the objective lens for condensing the plane probe, anti-reflective coating film is formed It is characterized by that.

e ) The invention according to claim 7 is characterized in that the antireflective coating film is composed of three or more dielectric films, and the invention according to claim 8 is the thickness of the antireflective coating layer. Is characterized by being 100 nm or more.

The present invention has the following effects. The effects of each claim will be described below.
a) According to the invention described in claims 1 to 3 , at least one of the concave portion or the convex portion constituting the concavo-convex shape is a cross-sectional shape of an asymmetric side surface in a direction orthogonal to the guide groove (one side surface is linear or because one side was made to have a curved (quadratic curve)), it is possible accurately tracked small guide groove, is possible to record and reproduce fine recording mark density, high efficiency and stable it can.

b ) According to the inventions of claims 4 and 5, a flat probe provided with a protrusion made of a high refractive index material is provided on a quartz substrate substrate on which a silicon nitride film is formed, and the flat probe and the optical recording medium are not Since the distance between the flat probe and the optical recording medium is held in a region that is less than or equal to the wavelength of the light source used, it can be accurately tracked in a minute guide groove, and minute recording marks can be recorded at high density and high density. Recording and reproduction can be performed efficiently and stably.

c ) According to the invention of claim 6 , since the non-reflective coating film is formed on the surface portion of the laser light incident surface of the planar probe, the laser beam can be coupled to the planar probe with high efficiency and stability. Furthermore, it is possible to accurately track the minute guide groove, and information can be recorded and reproduced on the recording medium with high efficiency and stability.

d ) According to the invention of claim 7 , since the antireflective coating film is composed of three or more dielectric films, the laser beam can be coupled to the planar probe more efficiently and stably. Therefore, information can be accurately recorded in and reproduced from a recording medium with high efficiency.

e) According to the invention described in claim 8, since the thickness of the non-reflective coating layer is 100 nm or more, since it has a sufficient mechanical strength and is stable, the laser beam is coupled to the planar probe with high efficiency and stability. Therefore, it is possible to accurately track the minute guide groove and to record and reproduce information on the recording medium with high efficiency and stability.

  An optical information recording medium according to the present invention is an optical information recording medium for recording and reproducing by near-field light, and has a concave-convex tracking guide groove on the surface, and in particular, at least a concave portion or a convex portion constituting the concave-convex shape. One has a cross-sectional shape that is asymmetrical in the direction perpendicular to the guide groove, and the width of the flat portion on the top of the convex portion of the cross-sectional shape is 100 nm or less.

Embodiments of an optical information recording medium and an optical information recording / reproducing apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a diagram for explaining a cross-sectional shape in a radial direction (a direction perpendicular to a guide groove, hereinafter referred to as a medium radial direction) of the first embodiment of the optical information recording medium according to the present invention.

As shown in FIG. 1A, the surface of the optical information recording medium according to the present embodiment is formed in a concavo-convex shape. The concavo-convex shape is formed of a concave portion 101, a convex portion 102, and both side surfaces 103 and 104. Information is recorded on a flat portion on the upper surface of the convex portion 102 having an uneven shape. The width of the flat portion is 100 nm or less. Both side surfaces 103 and 104 of the convex portion 102 are formed in an asymmetric shape .

In this embodiment, as shown in FIG. 1B, the side surface 103 is approximately 90 degrees, the side surface 104 is the origin of the intersection of the upper surface of the convex portion 102 and the side surface 104, and the coordinate axis is as shown in FIG. When xy is set, the slope of the slope is formed to have a relationship of linear equation y = ax (a: constant) . The period of the uneven structure is sufficiently smaller than the wavelength of the light source used in the optical information recording / reproducing apparatus according to the present invention.

  FIG. 8 is a diagram showing a configuration of an optical information recording / reproducing apparatus according to the present invention, and performs recording and reproduction of optical information on an optical information recording medium as shown in FIG.

Next, an optical information recording / reproducing apparatus according to the present invention will be described.
As shown in the figure, the optical information recording medium 89 is irradiated with near-field light from a planar probe 88 having a micro-aperture array having a size sufficiently smaller than the incident wavelength. The minute aperture array is composed of protrusions made of a high refractive index material as will be described with reference to FIG. The optical information recording medium 89 has an uneven structure having a shape as shown in FIG.

  The flat probe 88 is formed in a slider shape, supported by a holder 90, and traversed on a rotating optical information recording medium 89.

  The optical information recording medium 89 has a multilayer structure as will be described later (see FIG. 7), and includes a surface protective layer, a recording layer, and a heat dissipation layer (reflective layer), and a slider portion provided with a planar probe by the surface protective layer. It is configured to withstand wear.

  The light emitted from the semiconductor laser 81 is converted into a parallel light beam by the collimator lens 82 and enters the beam splitter 83. The speed of light that has passed through the beam splitter 83 forms an image of a spot on the flat probe 88 formed on the bottom surface of the slider by the objective lens 86, and generates near-field light from the tip of the flat probe.

  When the planar probe 88 and the optical information recording medium 89 are sufficiently closer than the wavelength of the irradiation light, the generated near-field light is coupled to the optical information recording medium 89 to form a recording mark in the recording layer.

In the case of reproduction, the near-field light component reflected from the optical information recording medium 89 is detected by the flat probe 88 formed on the bottom surface of the slider. The planar probe 88 is stably controlled with a flying distance of about 10 nm .

  The detected near-field light is converted into a parallel light beam by the objective lens 86 through the probe portion, deflected by the beam splitter 83, and a spot is formed on the photodetector 85 by the imaging lens 84. Information recorded on the optical information recording medium 89 can be reproduced by the light intensity on the photodetector 85. An antireflection film 87 is formed on the planar probe 88.

  FIG. 3 is a diagram showing the relationship of the near-field light intensity distribution generated at the probe tip with respect to the distance x from the probe 88 tip.

  The intensity distribution near the aperture of the near-field light can be expressed by Exp [−kz] / z. Here, z is a distance from the opening, and k is a constant. In this embodiment, the opening diameter is 50 nm.

  As shown in FIG. 3, it can be seen that the energy of the near-field light rapidly decreases as the distance from the opening increases. This near-field light is localized at a distance substantially equal to the aperture diameter. When recording and reproducing information using this near-field light, the probe and the recording medium need to be close to each other.

  Here, since the probe can be stably controlled with a flying distance of about 10 nm, in FIG. 1, when the probe moves in the medium radial direction from the substantially flat upper surface of the convex portion 102, it is reflected from the optical information recording medium. The amount of light detected changes. That is, the near-field light reflected from the medium detected when the probe moves in the x-axis positive direction in FIG. 1B is abrupt according to the distance moved because the distance between the optical information recording medium and the probe is increased. Becomes smaller.

  At this time, as shown in FIG. 1, if the slopes of the slopes on both sides of the convex portion of the optical information recording medium are asymmetrical between the positive direction and the negative direction of the x-axis, the probe moves in the positive direction of the x-axis. The fluctuation of the near-field light reflected from the optical information recording medium also becomes asymmetric depending on whether it moves in the negative direction or in the negative direction.

  Therefore, by detecting the state of the fluctuation, it can be determined whether the probe has moved in the positive direction or the negative direction of the x axis, and by feeding back a signal indicating the moving direction, the probe can be moved as much as possible in the x axis. It is possible to control so as not to move in either the positive direction or the negative direction.

  FIG. 4 is a diagram showing the relationship between the deviation with respect to the x-axis at this time and the amount of near-field light reflected from the optical information recording medium. In this way, by controlling the movement of the probe so that the amount of near-field light reflected from the optical information recording medium is constant, it is possible to track to a desired position on the medium.

Next, a second embodiment of the optical information recording medium will be shown.
FIG. 2 is a diagram for explaining a cross-sectional shape in a radial direction (a direction perpendicular to the guide groove, hereinafter referred to as a medium radial direction) of the second embodiment of the optical information recording medium according to the present embodiment.
As shown in FIG. 2, the surface of the recording medium according to the present invention is formed in an uneven shape. The concavo-convex shape is formed of a concave portion 201, a convex portion 202, and both side surfaces 203 and 204. Information is recorded on the upper surface of the concavo-convex convex portion 202. Both side surfaces of the convex portion 202 are asymmetrical, that is, one side surface is vertical and the other side surface is curved .

In this embodiment, as shown in FIG. 1B, the side surface 203 is approximately 90 degrees, the side surface 204 is the origin of the intersection of the upper surface of the convex portion 202 and the side surface 204, as shown in FIG. when setting the coordinate axis, the inclination of the slope quadratic equation y = bx ^2: is formed so as to relationship ^(b constants).

  The period of the uneven structure is sufficiently smaller than the wavelength of the light source used in the optical information recording apparatus of the present invention. Also at this time, the near-field light reflected from the medium detected when the probe moves in the positive direction of the x-axis in FIG. 2B depends on the distance moved because the distance between the optical information recording medium and the probe is large. Suddenly decreases.

  At this time, as shown in FIG. 2, by making the inclination of the side surfaces on both sides of the medium convex portion asymmetric in the positive direction and the negative direction of the x-axis, as described in the embodiment of FIG. The moving direction from the flat upper surface of the convex portion 202 can be determined, and the probe can be tracked to a desired position of the medium.

  FIG. 5 is a diagram showing the relationship between the displacement with respect to the x-axis at this time and the amount of near-field light reflected from the optical information recording medium. In this way, by controlling the movement of the probe so that the amount of near-field light reflected from the optical information recording medium is constant, it is possible to track to a desired position on the medium.

Next, a probe that generates near-field light will be described.
In the present invention, a planar probe array is used as the probe.
FIG. 6 is a diagram showing an example of a method for producing a planar probe in the optical information recording / reproducing apparatus according to the present invention.

As shown in FIG. 6, first, a silicon nitride film 46 is formed as a high refractive index material on a transparent substrate (quartz substrate) 42 (a). The silicon nitride film 46 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 46 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, SiO ₂ is sputtered on quartz glass (about 1 μm from the substrate surface), and then an intrusion layer of N atoms or C atoms is produced. In the case of C atoms, ion implantation is performed on quartz glass by an ion implantation method using CH ₄ as a source gas. In the case of N atoms, SiO ₂ is formed by thermal decomposition CVD using SiH ₄ and N ₂ O as raw materials. Thus, 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 CVD, vacuum deposition, sputtering, or the like, or a thermal diffusion method.

  Also, a substrate called a SOI substrate in which a silicon oxide buffer layer is formed on a silicon single crystal substrate is used, and electrodes are provided on the SOI substrate and the glass substrate, and an appropriate voltage is applied in a temperature atmosphere of about 300 degrees. By applying, a high refractive index material can be formed on a stone substrate by bonding an SOI substrate and a glass substrate.

  As another method, the surfaces of the quartz substrates 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.

Also, the bonded surface of the quartz substrate to be bonded and the SOI is mirror-polished, cleaned with RCA, and irradiated with FAB (Fast Atom Beam) of Ar simultaneously for about 300 seconds in a vacuum chamber of 1 × 10 ⁻⁹ Torr or less, and a pressure of 10 MPa. Can be joined by pressure bonding.

  A columnar resist pattern 43 is formed on the substrate on which the silicon nitride film 46 is formed on the quartz substrate 42 by using a photolithographic technique of a semiconductor process (b). The cylindrical resist pattern 43 is formed in a region where a silicon protrusion is formed.

  Using this resist pattern 43 as a mask, the silicon nitride film 46 is removed by dry etching. By using the quartz substrate 42 as a stopper layer at the time of etching, the near-field optical probe 45 made of a protrusion made of a high refractive index material can be formed on the optically transparent quartz substrate (ce).

  Further, by adjusting the etching time, the silicon nitride film 46 in a region where the resist pattern 43 does not exist on the quartz substrate 42 is left on the substrate, and the near-field optics made of protrusions made of a high refractive index material on the quartz substrate 42. A probe 45 can be formed. Thereafter, a flat probe can be formed by coating the back surface of the substrate 42 with an antireflection film 47 by sputtering or the like (f).

  Here, the shape of the formed silicon nitride protrusion can be changed by changing the dry etching conditions. For the dry etching, a parallel plate type RIE (Reactive Ion Etching) apparatus was used.

Here, various types of silicon nitride protrusions can be formed by changing the gas type, processing pressure, and RF power to optimum conditions. By using the transparent substrate 42 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 transparent substrate .

  After the etching, the resist pattern 43 is subjected to resist ashing using oxygen plasma to remove the resist. A metal film 44 is formed on the surface on which the silicon nitride protrusions are formed by sputtering (e). By depositing the metal film to a depth greater than the penetration depth of light, it is possible to block light other than near-field light generated from the silicon protrusion.

  After the silicon etching, the resist can be removed by performing resist ashing with oxygen plasma on the remaining resist pattern 43. Further, the sidewall protective film and the like attached to the side surfaces of the silicon protrusions can be removed with a BHF solution.

  Examples of the substrate 42 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. Arbitrary methods, such as metal vapor deposition, plating, and electrodeposition, can be employed for forming a metal film suitable as a reflecting member. Examples of the metal include aluminum, gold, and silver, but those having low oxidizability are particularly preferable.

An antireflection film 47 is formed on the upper surface of the planar probe on which laser light is incident. Compared to the case where the antireflection film 47 is not provided, for example, when the antireflection film 47 of MgF ₂ is formed to 140 nm, the reflectance can be reduced from 4% to 1.4%.

As the single-layer antireflection 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 as much as the reflectance is lowered, it becomes possible to detect the signal with high efficiency and high speed .

Also, by changing the antireflection film 47 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 thickness of CeO ₂ made of 96 nm is made as the second dielectric film. When a thin film made of SiO having a thickness of 108 nm is formed as the thin film and the third dielectric film, the reflectance can be made substantially zero .

  FIG. 7 is a diagram showing an example of a cross-sectional shape of an optical information recording medium using a phase change film capable of repeated recording.

In FIG. 7, the material of the substrate 7011 is polycarbonate. A recording thin film having a laminated structure exists on the substrate. Reference numeral 7012 denotes an AlTi thin film as a heat dissipation layer, and the film thickness is 50 nm. Reference numeral 7013 denotes ZnS · SiO ₂ which is a lower dielectric layer, and the film thickness is 20 nm.

Reference numeral 7014 denotes AgInSbTe which is a recording layer, and the film thickness is 15 nm . 7015 is ZnS · SiO ₂ which is an upper dielectric layer, and the film thickness is 10 nm. 7016 is SiN which is a protective layer, and the film thickness is 30 nm . Guide grooves are provided spirally on the substrate surface.

  In such an optical information recording medium, a photoresist is applied with a film thickness of 0.25 μm by spin coating on the surface of a precisely polished glass substrate. Thereafter, the resist is cured by baking at 90 ° C. Next, an electron beam is irradiated onto the photoresist to expose a predetermined portion at a desired pitch in a spiral shape.

  Next, the photoresist is developed using an alkaline solution, and the exposed portion is removed. By the above processing, a rectangular convex pattern of a photoresist having a height of 0.25 μm can be formed on the surface of the glass substrate. After the resist pattern is formed, baking is performed again. Baking temperature shall be 180 degreeC. The baking here is intended to reflow the resist.

  By reflow, the rectangular resist pattern is deformed into a semicircular shape. The radius of curvature of the semicircle is controlled by the resist film thickness and baking conditions. By the above method, a resist pattern is formed on a glass substrate, and used as a master for recording / reproducing media. Thereafter, a nickel thin film is formed to a thickness of, for example, 100 nm by sputtering. Using this conductive film as an electrode, nickel is formed to a predetermined thickness by electrolytic plating. Thereafter, the nickel is peeled from the glass substrate to obtain a stamper.

  Next, a polycarbonate resin is molded using the stamper as a mold for injection molding. By the above method, a polycarbonate substrate having a thickness of 0.6 mm and having an uneven shape on the surface can be formed.

Next, by sputtering, the AlTi thin film that is the reflective layer and the heat dissipation layer (7012) is 50 nm, the ZnS · SiO ₂ thin film that is the lower dielectric layer (7013) is 20 nm, and the AgInSbTe thin film that is the recording layer (7014) is 15 nm. The optical information recording medium 89 can be formed by sequentially depositing a ZnS · SiO ₂ thin film as the upper dielectric layer (7015) of 10 nm and a SiN thin film as the surface protective layer (7016) of 20 nm.

  The exposure shape is controlled by adjusting the exposure threshold value and film thickness of each of the laminated resists and the electron beam exposure conditions.

Diamond-like carbon can also be used as the surface protective film, and in this case, it is possible to use a film forming apparatus such as sputtering, ion beam sputtering, or CVD .

It is a figure for demonstrating the cross-sectional shape of the radial direction of 1st Example of the optical information recording medium based on this invention. It is a figure for demonstrating the cross-sectional shape of the radial direction of 2nd Example of the optical information recording medium based on this invention. It is a figure which shows the relationship of the near field light intensity distribution which has generate | occur | produced in the probe tip with respect to the distance x from a probe tip. It is a figure which shows the relationship between the tracking shift | offset | difference with respect to the x-axis in 1st Example, and the light quantity of the near-field light reflected from the optical information recording medium. It is a figure which shows the relationship between the tracking shift | offset | difference with respect to the x-axis in 2nd Example, and the light quantity of the near-field light reflected from the optical information recording medium. It is a figure which shows one example of the manufacturing method of the planar probe in the optical information recording / reproducing apparatus which concerns on this invention. It is a figure which shows an example of the cross-sectional shape of the optical information recording medium using the phase change film which can be repeatedly recorded. It is a figure which shows one structure of the optical information recording / reproducing apparatus based on this invention.

Explanation of symbols

101, 201: Concave portion 102.202: Convex portion 103, 104, 203, 204: Side surface 42: Substrate (quartz substrate, transparent substrate)
43: resist pattern 44: metal film 45: near-field optical probe 46: silicon nitride film 47: antireflection film (single layer or multilayer)
7011: Substrate (polycarbonate)
7012: Heat dissipation layer (AlTi thin film)
7013: Lower dielectric layer (ZnS · SiO ₂ )
7014: Recording layer (AgInSbTe)
7015: Upper dielectric layer (ZnS · SiO ₂ )
7016: Protective layer (SiN)
81: Semiconductor laser 82: Collimator lens 83: Beam splitter 84: Imaging lens 85: Optical detector 86: Objective lens 87: Antireflection film 88: Planar probe 89: Optical information recording medium 90: Holder

Claims (8)

It has a guide groove for tracking of the uneven shape on the surface, and the unevenness at least one recess or convex shape constituting the optical information recording to have a cross-sectional shape of the asymmetrical sides in the direction orthogonal to the guide groove An optical information recording / reproducing apparatus for recording / reproducing optical information on a medium,
The movement direction of the probe is detected by detecting the fluctuation of the near-field light reflected from the optical information recording medium, and the probe is moved to the desired position of the optical information recording medium by feeding back a signal indicating the movement direction. An optical information recording / reproducing apparatus for tracking . The optical information recording / reproducing apparatus according to claim 1, wherein one side surface of the cross-sectional shape of the asymmetric side surface is linear. 2. The optical information recording / reproducing apparatus according to claim 1, wherein one side surface of the cross-sectional shape of the asymmetric side surface has a quadratic curve shape. The probes on a quartz board forming a silicon nitride film, optical information according to any one of claims 1 to 3, characterized in that it comprises a planar probe having a projection made of a high refractive index material Recording / playback device. The planar probe and the optical information recording medium is a non-contact state, claim 4, characterized in that the distance between the optical information recording medium and the flat probe is held in use the light source wavelength or less of the area The optical information recording / reproducing apparatus described . The light on the surface portion of the laser light incident surface of the planar probe relative to the exit surface of the objective lens for converging light onto the plane probe, to claim 5, characterized in that non-reflection coating film is formed The optical information recording / reproducing apparatus described . The optical information recording / reproducing apparatus according to claim 6, wherein the non-reflective coating film is composed of three or more dielectric films. 8. The optical information recording / reproducing apparatus according to claim 6, wherein the thickness of the non-reflective coating layer is 100 nm or more.

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