JP4137718B2 - Near-field optical head and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a near-field optical head and a manufacturing method thereof.
[0002]
[Prior art]
The near-field optical element is currently used or studied as a near-field optical head of an information recording / reproducing apparatus or a probe for optical observation of a sample or the like.
[0003]
On the other hand, information recording / reproducing apparatuses using light have evolved toward a larger capacity and a smaller size, and accordingly, a higher recording capacity is required. As a countermeasure, for example, a device using a blue-violet semiconductor laser has been developed. However, these techniques can only improve the current recording density by several times due to the problem of the diffraction limit of light. On the other hand, an information recording / reproducing method using near-field light is expected as a technique for handling optical information in a minute region exceeding the diffraction limit of light.
[0004]
This technique uses near-field light generated in the vicinity of an optical minute aperture or minute projection having a size equal to or smaller than the wavelength of light formed in a near-field light head that is a near-field light element. As a method for reproducing optical information, the recording medium surface is irradiated with near-field light generated from a microscopic aperture or a microprotrusion, and the recording medium surface on which the optical constants such as microscopic unevenness and refractive index on which information is recorded is changed. A method (illumination mode) in which scattered light converted by the above interaction is detected by a separately provided light receiving element is possible. Also, near-field light localized on the recording medium can be used. As a method of reproducing optical information, a method of converting near-field light localized on a minute mark on a recording medium into scattered light by interacting with a minute aperture or minute protrusion by irradiating the surface of the recording medium with light ( (Collection mode) is possible. As a result, it is possible to handle optical information in a region that is equal to or less than the wavelength of light, which is a limit in conventional optical systems. Optical information is recorded by irradiating the surface of the recording medium with near-field light generated from a minute aperture, changing the shape of a minute area on the medium (heat mode recording), or refraction or transmission of the minute area. This is done by changing the rate (photon mode recording). By using a near-field optical head having an optical minute aperture or minute protrusion exceeding the diffraction limit of light, higher density than that of a conventional information recording / reproducing apparatus is achieved.
[0005]
In general, the configuration of a recording / reproducing apparatus using near-field light is almost the same as that of a magnetic disk device, except that a near-field light head is used instead of a magnetic head. A near-field optical head with optical micro-apertures and micro-protrusions attached to the tip of the suspension arm is levitated to a certain height using the flying head technology using air bearings, and an arbitrary data mark on the disk is accessed. To do. In order to make the near-field optical head follow the disk that rotates at high speed, it has a flexure function that stabilizes the posture in response to the waviness of the disk (see, for example, Patent Document 1).
[0006]
In the near-field optical head having such a configuration, as a method for supplying light to the optical minute aperture and minute protrusion, a method of directly connecting the optical fiber to the head from above (see, for example, Patent Document 2), or the head A method of directly irradiating the head with a laser provided above (for example, see Patent Document 3) has been adopted.
[0007]
However, in the former method, since the optical fiber structure is connected between the head and the arm, this hinders the free movement of the head, making it difficult to control the posture of the head with respect to the movement of the disk. Since the configuration of the head is large, it is difficult to keep the distance between the disk and the opening constant. As a result, the output signal-to-noise ratio from the optical information drawn on the disk is reduced, making it difficult to read and write signals. Further, since the fiber protrudes above the head, the apparatus itself becomes large, and it is difficult to reduce the size and thickness.
[0008]
Also in the latter method, in which the head is irradiated directly with a laser placed above the head, it has a structure that moves in accordance with the movement of the head in order to synchronize the incident light in response to the high-speed movement of the head. It was very difficult to provide a separate body. Further, by separately providing such a structure, the apparatus itself becomes large, and it is difficult to reduce the size of the reproducing / recording apparatus.
OLE_LINK1 OLE_LINK1 To solve the above problems, connect an optical fiber or optical waveguide to the side of the head, and reflect the light from the optical fiber or optical waveguide propagating in the horizontal direction to the media surface to open the propagation direction. A method has been devised in which a minute beam spot is made incident on an optical minute aperture using a light reflecting layer directed in the direction and a lens that condenses light directed in the opening direction (see, for example, Patent Document 4).
[0009]
FIG. 4 shows a cross-sectional view of the configuration of the near-field optical head according to the conventional method.
[0010]
The probe substrate 1001 has a protrusion 1003 on its lower surface. The protrusion 1003 is covered with a light shielding film 1004, and an optical minute opening 1002 is formed at the tip of the protrusion 1003. Further, an ABS (air bearing surface) 1005 is formed on the lower surface of the probe substrate 1001, and the ABS 1005 constitutes substantially the same plane as the optical minute aperture 1002. A lens 1006 is formed on the upper surface of the probe substrate 1001. As the lens 1006, a Fresnel zone plate formed by processing the surface of the probe substrate 1001 can be used. The probe substrate 1001 is made of a dielectric, particularly SiO ₂ material such as quartz or glass. In this case, isotropic etching is performed with a mixed solution of hydrofluoric acid and ammonium fluoride using the patterned resist as an etching mask. Thus, the protrusion 1003 can be formed. Further, Al or Au can be used as the material of the light-shielding film 1004, and the thickness thereof is about several nm to several hundred nm. OLE_LINK2, and sputtering or vacuum evaporation can be used for film formation. The formation of the OLE_LINK2 optical micro-aperture 1002 is achieved by a method using a focused ion beam (FIB) (see, for example, Patent Document 5), or by pressing a hard flat plate against the light shielding film 1004 on the top of the protrusion 1003. A method of plastic deformation (for example, see Patent Document 6) can be used.
[0011]
The mirror substrate 1007 has a V-groove 1009 on its lower surface. Only one end of the V-groove 1009 cuts out a part of the side surface 1011 of the mirror substrate 1007. The optical fiber 1010 penetrates from the side surface 1011 of the mirror substrate 1007 and is fixed to the V groove 1009. The light emitted from the end of the fiber 1010 reaches the mirror surface 1008 formed on the other end surface of the V-groove 1009. Since the mirror surface 1008 is provided to be inclined with respect to the mirror substrate 1007, the light reflected from the mirror surface 1008 is emitted below the mirror substrate 1007. The probe substrate 1001 and the mirror substrate 1007 are bonded so that the light reflected from the mirror surface 1008 is condensed by the lens 1006 onto the optical minute aperture 1002. If single crystal silicon is used as the material of the mirror substrate 1007, the V-groove 1009 can be formed by crystal anisotropic etching using KOH (potassium hydroxide) or TMAH (tetramethylammonium hydroxide). The mirror surface 1008 can be formed by depositing Au or Al on the surface formed by the crystal anisotropic etching, and vacuum deposition or sputtering can be used for film formation.
[0012]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-34981 (page 4, FIG. 1)
[0013]
[Patent Document 2]
Japanese Unexamined Patent Publication No. 2000-149291 (page 3, FIG. 1)
[0014]
[Patent Document 3]
JP 2000-21005 (pages 8-9, FIG. 8)
[0015]
[Patent Document 4]
International Patent Publication No. WO00 / 28536 (pages 73-80, FIG. 8)
[0016]
[Patent Document 5]
Japanese Patent Laid-Open No. 11-265520 (page 6-7, FIG. 10)
[0017]
[Patent Document 6]
Japanese Examined Patent Publication No. 5-21201 (page 3-4, FIG. 5)
[0018]
[Problems to be solved by the invention]
The above method is extremely effective for reducing the size and thickness of the near-field optical head, but it cannot always be said to be excellent in mass productivity. Since the optical fiber 1010 has a structure sandwiched between the probe substrate 1001 and the mirror substrate 1007, the optical fiber 1010 and the mirror substrate 1007 must be bonded first, and then the probe substrate 1001 and the mirror substrate 1007 must be bonded. Don't be. The joining of the probe substrate 1001 and the mirror substrate 1007 has to be performed for each near-field optical head in spite of high-precision positioning work, and is complicated and unsuitable for mass production.
[0019]
[Means for Solving the Problems]
According to a first aspect of the present invention for solving the above-described problems, a near-field optical head having an optical fiber and a mirror substrate including a mirror surface that changes the direction of light from the optical fiber supports the optical fiber. A first groove is provided on the upper surface of the mirror substrate, and is disposed on an extension line of the first groove, and a second groove connected at an end of the first groove is provided on the lower surface of the mirror substrate. The near-field optical head has a mirror surface formed in the second groove so as to face the end of the first groove.
[0020]
According to a second aspect of the present invention, in the first aspect, the near-field optical head is characterized in that the first groove is a V-groove.
[0021]
According to a third aspect of the present invention, in the first or second aspect, at least one of the first groove penetrating the lower surface of the mirror substrate or the second groove penetrating the upper surface of the mirror substrate. The near-field optical head is characterized by comprising:
[0022]
A fourth aspect of the present invention is the near-field optical head according to any one of the first to third aspects, wherein the mirror surface is inclined with respect to the mirror substrate.
[0023]
A fifth aspect of the present invention is a near-field optical head according to any one of the first to fourth aspects, wherein the material of the mirror substrate is single crystal silicon.
[0024]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the probe substrate includes an optical minute opening or a minute protrusion, and the probe substrate receives light whose direction is changed on the mirror surface. The near-field optical head is bonded to a mirror substrate so as to be incident on an optical minute aperture or minute protrusion.
[0025]
According to a seventh aspect of the present invention, in the near-field optical head shown in the sixth aspect, a plurality of first grooves, second grooves, and first wafers each having a mirror surface are produced. A second wafer having optical micro-openings or micro-protrusions, and dividing the first wafer and the second wafer after bonding, thereby cutting out a plurality of integrated mirror substrates and probe substrates, In the method of manufacturing a near-field optical head, the optical fiber is fixed to each of the first grooves.
[0026]
According to an eighth aspect of the present invention, in the seventh aspect, an alignment mark is provided on each of the first wafer and the second wafer, and the alignment between the first wafer and the second wafer is performed using the alignment mark. In the method of manufacturing a near-field optical head, the first wafer and the second wafer are bonded together after performing the above.
[0027]
In the present invention, the optical fiber can be fixed in the first groove on the mirror substrate after the probe substrate and the mirror substrate are bonded. Therefore, since only the probe substrate and the mirror substrate can be moved and positioned, easy assembly becomes possible. Further, instead of bonding the probe substrate and the mirror substrate, the first wafer including a plurality of probe substrates and the second wafer including a plurality of mirror substrates can be bonded. The alignment can be greatly reduced, and the near-field optical head can be mass-produced at low cost.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing the structure of a near-field optical head according to Embodiment 1 of the present invention.
[0029]
The probe substrate 101 has a protrusion 103 on its lower surface. The protrusion 103 is covered with a light shielding film 104, and an optical minute opening 102 is formed at the tip of the protrusion 103. Further, an ABS (air bearing surface) 105 is formed on the lower surface of the probe substrate 101, and the ABS 105 forms substantially the same plane as the optical minute aperture 102. A lens 106 is formed on the upper surface of the probe substrate 101. As the lens 106, a Fresnel zone plate formed by processing the surface of the probe substrate 101 can be used. The probe substrate 101 is made of a dielectric, particularly SiO ₂ material such as quartz or glass. In this case, isotropic etching is performed with a mixed solution of hydrofluoric acid and ammonium fluoride using the patterned resist as an etching mask. Thus, the protrusion 103 can be formed. Further, Al or Au can be used as the material of the light-shielding film 104, and the thickness thereof is about several nanometers to several hundred nanometers. For film formation, a sputtering method or a vacuum evaporation method can be used. For forming the optical minute aperture 102, a method using a focused ion beam (FIB) or a method of plastically deforming the light shielding film 104 by pressing a hard flat plate against the light shielding film 104 on the top of the protrusion 103 can be used.
[0030]
The mirror substrate 107 has a V groove 109 on the upper surface of the mirror substrate 107 and a mirror groove 111 on the lower surface of the mirror substrate 107. The V groove 109 and the mirror groove 111 are connected (described later). The optical fiber 110 penetrates from the side surface of the mirror substrate 107 and is fixed to the V groove 109. The light emitted from the end of the optical fiber 110 reaches the mirror surface 108 formed on the end surface of the mirror groove 111. Since the mirror surface 108 is inclined with respect to the mirror substrate 107, the light reflected from the mirror surface 108 is emitted below the mirror substrate 107. The probe substrate 101 and the mirror substrate 107 are bonded so that the light reflected from the mirror surface 108 is condensed by the lens 106 onto the optical minute aperture 102.
[0031]
The structure of the mirror substrate 107 is the most important point of the present invention, and will be described in detail with reference to FIG. 2A is a three-dimensional view showing the structure of the mirror substrate 107, and FIG. 2B is a side view and a front view showing the structure of the substrate 107. FIG.
[0032]
A V-groove 109 formed on the upper surface of the mirror substrate 107 extends from one side surface of the mirror substrate 107 and has a V-groove end 202. If single crystal silicon is used as the material of the mirror substrate 107, the V groove 109 can be formed by crystal anisotropic etching using KOH (potassium hydroxide) or TMAH (tetramethylammonium hydroxide). The optical fiber 110 is fixed to the mirror substrate 107 in contact with two lateral slopes of the V-shaped groove 109 by two lines 112 respectively. The mirror groove 111 formed on the lower surface of the mirror substrate 107 has a shape obtained by cutting the mirror substrate 107 into a quadrangular pyramid shape. The mirror groove 111 may penetrate to the upper surface of the mirror substrate 107. If single crystal silicon is used as the material of the mirror substrate 107, the mirror groove 111 can be formed by crystal anisotropic etching using KOH or TMAH as well as the V groove 109. The mirror groove 111 is disposed on an extension line of the V groove 109 extending from one side surface of the mirror substrate 107, and the V groove 109 and the mirror groove 111 are connected at the V groove end portion 202. Therefore, the V groove 109 and the mirror groove 111 form one space in the mirror substrate 107. One inclined surface of the mirror groove 111 facing the V groove end portion 202 where the V groove 109 and the mirror groove 111 are connected has a structure that reflects light, and is called a mirror surface 108. The mirror surface 108 can be formed by depositing Au or Al on a surface formed by crystal anisotropic etching, and vacuum deposition or sputtering can be used for film formation.
[0033]
Light emitted from the optical fiber 110 propagates through the space formed by the V groove 109 and the mirror groove 111 and reaches the mirror surface 108. Since the mirror surface 108 is inclined with respect to the mirror substrate 107, the light reaching the mirror surface 108 is reflected to become outgoing light 201 below the mirror substrate 107.
[0034]
According to the present embodiment, the optical fiber 110 can be fixed to the V groove 109 on the mirror substrate 107 after the probe substrate 101 and the mirror substrate 107 are joined. Unlike the conventional method, it is not necessary to bond the mirror substrate and the probe substrate after fixing the optical fiber to the mirror substrate. Therefore, since only the probe substrate 101 and the mirror substrate 107 can be moved and positioned, easy assembly is possible.
[0035]
(Embodiment 2)
FIG. 3 is a cross-sectional view showing a method for manufacturing a near-field optical head according to Embodiment 2 of the present invention.
[0036]
The configuration of the near-field optical head in the present embodiment is the same as the configuration of the near-field optical head shown in the first embodiment.
[0037]
3A, a plurality of sets of the protrusion 103, the light-shielding film 104, the optical minute opening 102, the ABS 105, and the lens 106 shown in Embodiment Mode 1 are formed at predetermined positions on the first wafer 301. FIG. 6 is a view after a plurality of sets of V-groove 109, mirror groove 111, and mirror surface 108 shown in Embodiment 1 are formed at predetermined positions on wafer 302. The projection 103, the light shielding film 104, the optical minute aperture 102, the ABS 105, the lens 106, the V groove 109, the mirror groove 111, and the mirror surface 108 on the first wafer 301 and the second wafer 302 apply semiconductor manufacturing technology. Since it can be manufactured using photolithography, a plurality of layers can be formed at the same time.
[0038]
Next, as shown in FIG. 3B, the first wafer 301 and the second wafer 302 are bonded. At the time of bonding, the positions of the first wafer 301 and the second wafer 302 are adjusted, and the optical minute aperture 102, the lens 106, the V groove 109, and the mirror surface 108 form the structure shown in the first embodiment. Like that. An alignment mark may be provided on each of the first wafer 301 and the second wafer 302, and the positions of the first wafer 301 and the second wafer 302 may be adjusted using these marks as marks. As a bonding method, a method using an adhesive or a method not using an adhesive such as anodic bonding can be used.
[0039]
Next, as shown in FIG. 3C, when the first wafer 301 and the second wafer 302 are divided while being bonded, a plurality of probe substrates 101 and mirror substrates 107 shown in the first embodiment are formed. .
[0040]
Next, as shown in FIG. 3D, when the optical fibers 110 are fixed to the V grooves 109 on the mirror substrate 107, a near-field optical head is completed.
[0041]
According to the present embodiment, instead of bonding the probe substrate 101 and the mirror substrate 107, the bonding of the first wafer 301 including a plurality of probe substrates 101 and the second wafer 302 including a plurality of mirror substrates 107 is possible. Therefore, highly accurate alignment at the time of joining can be greatly reduced, and the near-field optical head can be mass-produced at a low cost.
[0042]
【The invention's effect】
As described above, according to the present invention, the optical fiber can be fixed to the V groove on the mirror substrate after the probe substrate and the mirror substrate are bonded. Unlike the conventional method, it is not necessary to bond the mirror substrate and the probe substrate after fixing the optical fiber to the mirror substrate. Therefore, since only the probe substrate and the mirror substrate can be moved and positioned, easy assembly becomes possible.
[0043]
Further, by using the V-groove for fixing the optical fiber, it is possible to easily fix the optical fiber accurately.
[0044]
Further, when the V groove or the mirror groove penetrates the substrate, a space formed by the V groove and the mirror groove is increased, and the degree of freedom of the relative position between the mirror surface and the optical fiber is improved. , The light from the optical fiber can be reflected and the propagation direction can be directed to the direction of the optical minute aperture or minute protrusion.
[0045]
Further, by using single crystal silicon for the mirror substrate, the V-groove and the mirror groove can be easily formed by crystal anisotropic etching.
[0046]
Further, according to the present invention, instead of bonding the probe substrate and the mirror substrate, the first wafer including a plurality of probe substrates and the second wafer including a plurality of mirror substrates can be bonded. High-precision alignment at the time of joining can be greatly reduced, and the near-field optical head can be mass-produced at low cost.
[0047]
In addition, by providing alignment marks on the first wafer and the second wafer, highly accurate alignment at the time of bonding is facilitated.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a near-field optical head according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a structure of a mirror substrate 107 according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a manufacturing method of a near-field optical head according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a configuration of a conventional near-field optical head.
[Explanation of symbols]
101 Probe substrate 102 Optical minute aperture 103 Protrusion 104 Light shielding film 105 ABS
106 Lens 107 Mirror substrate 108 Mirror surface 109 V-groove 110 Optical fiber 111 Mirror groove 112 Two lines 201 Emission light 202 V-groove end 301 First wafer 302 Second wafer 1001 Probe substrate 1002 Optical micro-aperture 1003 Protrusion 1004 Light-shielding film 1005 ABS
1006 Lens 1007 Mirror substrate 1008 Mirror surface 1009 V groove 1010 Optical fiber 1011 Side surface of mirror substrate 1007

Claims (8)

A near-field optical head having an optical fiber and a mirror substrate including a mirror surface that changes the direction of light from the optical fiber,
A first groove for supporting the optical fiber on the upper surface of the mirror substrate;
A second groove disposed on an extension line of the first groove and connected at an end of the first groove on the lower surface of the mirror substrate;
A near-field optical head in which the mirror surface is formed in the second groove so as to face the end of the first groove. The near-field optical head according to claim 1, wherein the first groove is a V-groove. 3. The device according to claim 1, wherein at least one of the first groove penetrates the lower surface of the mirror substrate or the second groove penetrates the upper surface of the mirror substrate. Near-field optical head. The near-field optical head according to claim 1, wherein the mirror surface is inclined with respect to the mirror substrate. 5. The near-field optical head according to claim 1, wherein a material of the mirror substrate is single crystal silicon. The near-field optical head according to any one of claims 1 to 5,
Having a probe substrate including optical micro-apertures or micro-protrusions;
The near-field optical head, wherein the probe substrate is bonded to the mirror substrate so that light whose direction is changed on the mirror surface enters the optical minute aperture or the minute protrusion. It is a manufacturing method of the near-field optical head according to claim 6,
A first wafer having a plurality of the first grooves, the second grooves, and the mirror surface is produced,
A second wafer having a plurality of the optical micro openings or micro projections;
By dividing the first wafer and the second wafer after bonding, a plurality of the integrated mirror substrate and probe substrate are cut out, and the optical fiber is fixed to the first groove of each of the mirror substrate and the probe substrate. A method of manufacturing a near-field optical head. An alignment mark is provided on each of the first wafer and the second wafer, and the first wafer and the second wafer are aligned using the alignment mark, and then the first wafer is aligned. The method of manufacturing a near-field optical head according to claim 7, wherein the second wafer is bonded to the second wafer.

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