JP4231924B2 - Micro processing equipment for transparent materials - Google Patents

Description

  The present invention relates to a processing apparatus for performing microfabrication on a transparent material using a laser, in particular, a microfabrication apparatus for a transparent material capable of performing laser processing using a fluid material having a large light absorption rate, and a transparent material. Diffraction optics for visible to ultraviolet to vacuum ultraviolet light used as diffraction gratings, polarizing plates, reflectors, antireflection plates, prism arrays, hologram optical elements, photonic crystal elements, etc. by processing three-dimensional surface microstructures The present invention relates to an optical element manufacturing method for manufacturing an element, an optical communication element, an optical waveguide substrate, and a liquid crystal alignment substrate. More specifically, a transparent material is contacted with a fluid substance that absorbs a large amount of light, and laser light is scanned while irradiating laser light with a specific beam shape from the surface side of the transparent material through a specified photomask. Thus, the present invention relates to an optical element manufacturing method characterized by processing a predetermined three-dimensional surface microstructure in a transparent material.

  In a photolithography process that plays a key role in the semiconductor integrated circuit manufacturing process, since the processing resolution is proportional to the wavelength of the light source used, higher resolution and higher integration are being promoted by shortening the wavelength of the light source. Also, in a short wavelength optical processing process other than photolithography, the processing resolution can be improved by shortening the wavelength of the light source. For this reason, the importance of optical elements that can be used to control light having a shorter wavelength, such as near ultraviolet, deep ultraviolet, and vacuum ultraviolet, is increasing. In particular, it is produced by processing a three-dimensional surface microstructure such as a groove array, a curved structure of the groove array, or a two-dimensional array structure on a transparent material, and applying a dielectric film or a metal film by a known method as necessary. The diffractive optical element has functions such as a diffraction grating, a polarizing plate, a reflection plate, an antireflection plate, a prism array, a hologram optical element, and a photonic crystal element, and replaces the functions of a plurality of conventional optical components with one piece. It can play an important role in miniaturization, simplification, and high functionality of the optical system. From this point of view, optical elements using fluoride crystals such as quartz glass and sapphire that can be used to control visible light to deep ultraviolet light and calcium fluoride that can be used to control vacuum ultraviolet light, especially diffraction Optical elements are gaining importance.

  The V-groove and the V-groove array can be used as an optical communication element such as an optical fiber positioning substrate. By using a transparent material such as quartz glass that transmits ultraviolet light, it is easy to bond and fix the optical fiber with ultraviolet light curable resin. Has the advantage of being able to

  Further, the groove structure, the groove array structure, and the curved structure of the groove and the groove array can be used as an optical waveguide substrate and a liquid crystal alignment substrate.

  For the above reasons, a simple, high-quality, high-efficiency method for fabricating optical elements by processing three-dimensional fine shapes on the surface of a wide range of transparent materials from quartz glass, sapphire, etc. to fluoride crystals is desired. Yes.

  However, it is difficult for a transparent material with a low light absorption rate to be finely processed directly on the material surface by laser ablation or laser melting. Further, since the transparent material recited in claim 14 is hard and brittle, the machining speed such as grinding is very low, and cracks and chips are likely to occur, so that the machining efficiency is low. Furthermore, it is more difficult to perform precise fine processing of complicated three-dimensional surface shapes.

  Therefore, as shown in Japanese Patent No. 3012926 (Patent Document 1), for a transparent material that is difficult to be processed by direct laser irradiation, a fluid material having a large light absorption rate is brought into contact with the back surface of the transparent material, and the fluid material A microfabrication method using laser absorption has been proposed.

  Further, as a mechanism for holding the transparent material in the apparatus, as shown in FIG. 5, the front side of the transparent material 1 is brought into contact with the holding plate 3a of the holder 3 through the O-ring 2, and the O-ring is placed on the back surface of the transparent material 1. 4, the opening 6 a of the cell 6 containing the fluid substance 5 having a large light absorption rate is held in contact. In the example shown in FIG. 5, the holder plate 7 is attached to the holding plate 3 a with bolts 8 from the back surface of the cell 6. That is, the transparent material 1 is pressed from the back via the O-ring 4 and the cell 6. Patent Document 1 discloses a technique for performing laser processing by bringing a fluid substance 5 into contact with the back surface of the transparent material 1.

On the other hand, the following method is known as a three-dimensional fine surface processing method by direct irradiation of laser light to a material that absorbs laser light.
(1) A method of processing a predetermined three-dimensional shape by three-dimensionally scanning a point-condensed laser beam and performing ablation processing. [For example, Unexamined-Japanese-Patent No. 2000-317665 (patent document 2)]
(2) A method of preparing a predetermined three-dimensional shape by preparing another type of photomask, performing ablation processing by laser irradiation step by step, and replacing the photomask at each step. [For example, JP 09-308942 A (Patent Document 3), JP 10-16215 A (Patent Document 4)]
(3) A method of processing a predetermined three-dimensional shape by using a liquid crystal panel that can freely control the two-dimensional transmission shape of light as a photomask and changing the beam shape of the laser light while advancing laser processing. [For example, JP 09-15867 (Patent Document 5), JP 2001-212687 (Patent Document 6), JP 2001-212798 (Patent Document 7), JP 2002-292488 ( Patent Document 8)]
(4) A method of processing a predetermined three-dimensional shape by controlling a two-dimensional distribution of transmitted laser light intensity using a gray photomask that continuously changes the amount of transmitted light. [For example, JP 07-58434 A (Patent Document 9), JP 08-224686 A (Patent Document 10), JP 2003-15275 A (Patent Document 11)]
(5) A method of processing a three-dimensional shape by changing the reduction ratio by moving the condenser lens in the irradiation direction while ablating by irradiating a laser beam having a predetermined beam shape through the photomask. [Japanese Patent Laid-Open No. 08-221729 (Patent Document 12)]
(6) A method of processing a three-dimensional surface shape such as a lamp structure by scanning a laser beam having a beam shape transmitted through a photomask on a workpiece in one direction perpendicular to the laser irradiation direction. [Zimmer et al .: Appl. Surf. Sci. Vol. 96-98, p. 425 (1996) (Non-Patent Document 1)]

  However, in the method of paragraph 0009 (1), since the entire processing region is scanned and three-dimensional processing is performed, time efficiency is improved except when the laser repetition frequency is high and the laser intensity is very high. There is a problem of being bad. In the method of paragraph 0009 (2), there is a problem that it is necessary to frequently replace the photomask, which is complicated and time-efficient, and is likely to have a stepped processing section. In the method of paragraph 0009 (3), there is a problem that the wavelength of the laser beam that can be used is limited to that which can be transmitted through the liquid crystal panel. The method of paragraph (0009) (4) has a problem that it is very difficult to produce a gray photomask, particularly a gray photomask that can withstand a high laser intensity with a short wavelength laser. In the method of paragraph 0009 (5), it is necessary to consider the change in processing efficiency due to the change in laser intensity accompanying the change in the reduction ratio, and there is a problem that it is difficult to control the processing shape. Although the method of paragraph 0009 (6) is simple, Zimmer et al. Does not mention its use.

An example of three-dimensional surface processing on quartz glass using the method of Patent Document 1 and the methods of paragraphs 0009 (4) and (6) has been reported.
(1) Processing of Fresnel lens and random phase plate Using a gray photomask, the two-dimensional distribution of laser light intensity is controlled, a fluid substance is brought into contact with the back surface of the quartz glass, and laser light is emitted from the surface side of the quartz glass. To process the Fresnel lens and the random phase plate. [Kopitkovas et al .: Microelectron. Eng. Vol. 67-68, p. 438 (2003) (non-patent document 2). ]
(2) Processing of cylindrical concave lens structure Cylindrical concave lens structure is obtained by scanning the laser light in one direction perpendicular to the laser irradiation direction while irradiating the flowable material from the surface of quartz glass with laser light that has passed through the photomask. processed. [Boehme et al .: Appl. Surf. Sci. Vol. 186, p. 276 (2002) (non-patent document 3). ]

  However, in the method of paragraph 0011 (1), it is difficult to design and manufacture a gray photomask for obtaining a predetermined laser light intensity distribution. Specifically, it is necessary to repeat a complicated process of resist coating, lithography patterning, ion beam etching, and resist stripping a plurality of times, which is very troublesome. At this time, if the number of steps is reduced, the amount of transmitted light changes stepwise and lacks smoothness, which affects the processing quality. In the method of paragraph (0011) (2), Boehme reports only the cylindrical concave lens structure on the quartz glass surface, and does not mention anything about its use.

Japanese Patent No. 3012926 JP 2000-317665 A JP 09-308942 A Japanese Patent Laid-Open No. 10-16215 JP 09-15867 A JP 2001-212687 A JP 2001-212798 A JP 2002-292488 A Japanese Patent Application Laid-Open No. 07-58434 Japanese Patent Application Laid-Open No. 08-224686 JP 2003-15275 A Japanese Patent Application Laid-Open No. 08-221729 Zimmer et al .: Appl. Surf. Sci. Vol. 96-98, p. 425 (1996) Kopitkovas et al .: Microelectron. Eng. Vol. 67-68, p. 438 (2002) Boehme et al .: Appl. Surf. Sci. Vol. 186, p. 276 (2002)

  In the fine processing method of the transparent material described in the paragraph 0008, since the processing site to be laser processed is the back surface of the transparent substrate and is covered with the cell containing the fluid substance, it cannot be directly observed. Therefore, it has been difficult to accurately measure the focal position of the laser beam used for processing. In addition, as shown in FIG. 6, there is no member that directly regulates the back surface of the transparent material 1, and thus the position of the back surface of the transparent material to be finely processed is slightly shifted, which adversely affects the fine processing. Existed.

  The present invention has been proposed in view of the above circumstances, and a microfabrication of a transparent material capable of holding the back surface of a transparent substrate covered with a cell containing a fluid substance at a laser beam condensing position with high reproducibility. An object is to provide an apparatus.

  In addition, by processing a three-dimensional surface microstructure in a transparent material using the above microfabrication apparatus, a diffraction grating, a polarizing plate, a reflector, an antireflection plate, a prism array, a hologram optical element, a photonic crystal element, etc. An object of the present invention is to easily and efficiently produce optical elements such as a diffractive optical element for visible to ultraviolet to vacuum ultraviolet light, an optical communication element, an optical waveguide substrate, and a liquid crystal alignment substrate. Specific three-dimensional surface microstructures include V-groove and V-groove array, sawtooth groove and sawtooth groove array, U-groove and U-groove array, rectangular groove and rectangular groove array, curved structure of the groove and groove array, pyramid shape Assume that a two-dimensional array of structures, a two-dimensional array of lenticular structures, and a rectangular two-dimensional array are used.

In order to achieve the above object, according to the invention described in claim 1, a fluid material having a high absorptance with respect to the laser wavelength is brought into contact with the back surface of the transparent material, and laser light is irradiated from the front to A transparent material micromachining apparatus that performs micromachining on the back surface, a reference plate that directly regulates the position of the back surface of the transparent material, and a first holder plate that includes an O-ring holding recess on the front surface side of the transparent material; The transparent material is inserted into the O-ring holding recess of the first holder plate to prevent back surface position blurring and minute deformation, and the transparent material is interposed between the reference plate and the first holder plate via the O-ring. a plurality of fasteners for clamping by pressure operation at equal torque, the a cell with an opening on one side to accommodate a flowable substance, O phosphorus for preventing fluid material leakage an opening of the cell A second holder plate for pressing the first holder plate against the back surface of the transparent material independently of the pressing operation of the first holder plate and sealing the inside of the cell; and the first holder plate and the second holder plate A holder fixed on the XYZ stage using a plurality of reference pins, and the second holder plate presses and fixes the opening of the cell against the back surface of the transparent material through an O-ring. in, between the first holder plate which holds the O-ring and said reference plate by said fixture is characterized in that the transparent material to allow vertical clamping.

In the first aspect of the present invention, a transparent material in which a fluid material having a high absorptance with respect to the laser wavelength is brought into contact with the back surface of the transparent material, and laser processing is applied from the front to finely process the back surface of the transparent material. A reference plate that directly regulates the position of the back surface of the transparent material, a first holder plate having an O-ring holding recess on the front surface side of the transparent material, and an O of the first holder plate An O-ring to be inserted into the ring-holding recess, a plurality of fixtures for pressing and clamping the transparent material with equal torque through the O-ring between the reference plate and the first holder plate; and the fluid substance And a cell having an opening, and the opening of the cell is pressed against the back surface of the transparent material via an O-ring independently of the pressing operation of the first holder plate. A second holder plate for sealing the inside Le, the first securing the holder plate and a second holder plate, and a holder fixed using a plurality of reference pins on the XYZ stage, the by the second holder plate The transparent material is fixed between the reference plate and the first holder plate holding the O-ring by the fixture in a state where the opening of the cell is pressed and fixed to the back surface of the transparent material via the O-ring. since pinching the can to hold the transparent material in the correct position, it is possible to surface treatment of various shapes with high accuracy. In addition, since the transparent material can be retained with good reproducibility due to the presence of the reference plate, it is possible to finely process the back surface of the transparent material having various shapes.

The transparent material and the front Symbol reference plate, since it is clamped to the holding plate, the transparent material to be machined can be held in the correct position, be subjected to fine processing on the back surface of the good reproducibility transparent material it can.

Moreover, flowable material that is in contact with the back surface of the front Symbol transparent material, because the transparent material is held independently, a transparent material to be machined is not affected by the holding state of the flowable material. Therefore, fine laser processing can be realized by holding the transparent material at an accurate position with high reproducibility.

It is an object of the present invention to provide a microfabrication apparatus for a transparent material capable of holding the back surface of a transparent substrate covered with a cell containing a fluid substance at a laser beam focusing position with good reproducibility. Visible to ultraviolet to vacuum such as diffraction gratings, polarizing plates, reflectors, antireflection plates, prism arrays, hologram optical elements, photonic crystal elements, etc. by processing a three-dimensional surface microstructure into a transparent material using an apparatus High absorption with respect to laser wavelength on the back surface of transparent material for the purpose of producing optical elements such as diffractive optical elements for ultraviolet light, optical communication elements, optical waveguide substrates, liquid crystal alignment substrates, etc. simply, with high quality and high efficiency. A transparent material micromachining apparatus that makes a fluid material having a rate contact with each other and irradiates laser light from the front surface to perform micromachining on the back surface of the transparent material, and directly controls the position of the back surface of the transparent material. A reference plate, a first holder plate having an O-ring retaining recess on a surface side of said transparent material, and the O-ring that fits the O-ring holding recess of the first holder plate, the said reference plate first (1) A plurality of fixtures for pressing and holding the transparent material with equal torque through an O-ring between holder plates, a cell containing the flowable substance and having an opening, and an opening of the cell A second holder plate that presses against the back surface of the transparent material via an O-ring independently of the pressing operation of the first holder plate to seal the inside of the cell; the first holder plate and the second holder; And a holder for fixing the plate on the XYZ stage using a plurality of reference pins, and the second holder plate allows the opening of the cell to pass through an O-ring. The transparent material is sandwiched between the reference plate and the first holder plate holding the O-ring by the fixture in a state where the transparent material is pressed and fixed to the back surface of the transparent material. This is a material microfabrication apparatus.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing a schematic configuration of a transparent material micromachining apparatus according to the present invention, and FIG. 2 is a front view of the transparent material micromachining apparatus according to the present invention. Here, the microfabrication apparatus 10 for transparent material according to the present invention makes a fluid material 12 having a high absorptance with respect to the laser wavelength contact the back surface of the transparent material 11 and irradiates the laser beam L from the front to be transparent. The back surface of the material 11 is finely processed, and a reference plate 13 that directly regulates the back surface position of the transparent material 11 is provided.

  The reference plate 13 presses and holds the transparent material 11 from the back surface, and includes a window portion 13b for bringing the reference surface 13a and the cell 14 containing the fluid substance 12 into contact with each other. The first holder plate 21 is attached.

  The first holder plate 21 has a recess 21 a on the surface that holds the transparent material 11, and the O-ring 17 is disposed in the recess 21 a, and compensates for variations in the thickness of the transparent material 11. Moreover, the 1st holder plate 21 has the opening part 21b for receiving a laser beam in the front.

  The holder 16 has an opening 16a for receiving laser light on the front surface, and a bolt hole 18 for inserting the fixing bolt 15 is formed. The holder 16 configured as described above is fixed to the XYZ stage by a clamp mechanism (not shown).

  The cell 14 has an opening 14a that contacts the back surface of the transparent material 11, and an O-ring 22 is disposed around the opening 14a. The cell 14 contains a fluid substance 12 having a high absorption rate with respect to the laser wavelength. The flowable substance 12 may be any substance having a high absorptance at the laser wavelength used. For example, pyrene in acetone, benzyl in acetone, pyrene in tetrahydrofuran, rhodamine 6G in ethanol, phthalocyanine in ethanol, etc. Organic compounds containing aromatic rings, liquid compounds such as toluene, benzene, and carbon tetrachloride, pyranine aqueous solutions, naphthalene derivative aqueous solutions, organic compounds, organic dyes, inorganic pigments, or fine particles of carbon, etc. A solution or the like can be used. Furthermore, a fluid material made by mixing two or more of the above-listed materials can also be used. These substances need to have a high absorptance with respect to the laser wavelength used, for example, 10% or more at a depth of 0.1 mm from the interface between the fluid substance and the transparent material to the inside of the fluid substance. It is desirable to have an absorption rate. More desirably, it has an absorptance of 50% or more at a depth of 0.1 mm. If the absorption rate is not sufficiently high, the surface processing of the transparent material cannot be sufficiently refined and refined.

  A cylindrical opening 14b extending upward is formed at the upper end of the cell 14, and absorbs bubbles and volume fluctuations generated when the fluid substance 12 is irradiated with laser light. A holder plate 19 is attached to the reference plate 13 with bolts 20 from the back of the cell 14. The holder plate 19 is formed with an opening window 19a substantially at the center so that the state during processing can be observed. In this way, the reference plate 13, the transparent material 11, the first holder plate 21 and the cell 14 are integrally assembled with the fixing bolts, and finally assembled to the holder 16, so that laser processing with good reproducibility can be achieved. It becomes possible.

  Next, a procedure for using the transparent material microfabrication apparatus 10 configured as described above will be described. First, the transparent material 11 to be processed is sandwiched between the reference plate 13 and the first holder plate 21 and fixed with screws by four fixing bolts 15 with a constant tightening torque (about 12 cNm in the current mechanism). At this time, it is easier to omit the reference plate 13 and sandwich the transparent material 11 and the cell 14 together with the holder 16 and the holder plate 19. However, this does not guarantee the position of the back surface of the transparent material 11 at all, and every time the substrate is held, a positional shift of several tens of microns occurs in the laser focusing direction, and fine processing of the transparent material with good reproducibility cannot be performed. .

  For this reason, in the present invention, the reference plate 13 is provided, which is used as a reference for positioning the back surface of the transparent material 11. In addition, if bolting is performed without managing the tightening torque at a constant level, position deviation occurs on the order of over 10 microns due to the deflection of the reference plate 13, and fine processing with good reproducibility cannot be achieved. For this reason, management of the tightening torque when bolting is essential. The same applies to bolting at other locations. Further, the variation in the substrate thickness is compensated by the O-ring 17 for a cushion between the first holder plate 21 and the substrate surface which is a transparent material. If the transparent material 11 is sandwiched between the reference plate 13 and the first holder plate 21 without using the O-ring 17, a gap may remain and the position of the back surface of the substrate may be blurred, or the transparent material 11 may be the reference plate 13 and the first plate. When the pressure is received from the holder plate 21, the surface is slightly deformed or damaged. For this reason, in the present invention, the use of the cushion O-ring 17 is essential.

  Further, the transparent material 11 and the cell 14 are brought into contact with each other through the sealing O-ring 22, sandwiched by the holder plate 19, fixed with bolts with a constant tightening torque, and then a fluid substance is injected into the cell 14. The holder plate 19 is bolted and fixed to the reference plate 13 under a constant tightening torque. Next, the holder 16 is placed on the upper surface of the XYZ stage (not shown) and positioned with four reference pins. Without the reference pin, the position reproducibility when the holder 16 is attached to and detached from the upper surface of the XYZ stage cannot be maintained at all, and as a result, the precision and reproducibility of fine processing cannot be maintained. For this reason, it is desirable to use a reference pin.

  Further, the holder 16 is fixed to the upper surface of the XYZ stage with a low load (about 10 N in the current mechanism) by moving the clamp up and down with a clamp lever. It is necessary to fix the holder 16 to the upper surface of the XYZ stage. However, if screws or bolts are used to fix the holder 16, torque is applied to the XYZ stage by the fixing operation, causing the stage to move slightly, and the substrate to be processed As a result, the precision and reproducibility of micromachining cannot be maintained. For this reason, a soft and strict fixing method is required, which is realized by this method using a clamp mechanism.

  As described in detail below, the specific micromachining procedure holds the processing substrate (transparent material 11) to be processed on the stage by the XYZ stage and the workpiece holding mechanism. Next, the excimer laser beam is adjusted, and the workpiece is irradiated with the beam. The intensity of the laser beam is adjusted by an attenuator (attenuator). Further, the laser light intensity distribution is made uniform by a homogenizer. The laser light is passed through a photomask having a predetermined shape, and the projection lens projects the laser light on the back surface of the processed substrate and the fluid substance, thereby performing etching processing of the predetermined shape. Specific examples of processing, types and concentrations of fluid substances, types and wavelengths of lasers, laser intensity, and examples of shapes projected and processed by a photomask are as shown in Table 1.

  With the configuration described above, the back surface of the transparent material 11 is regulated by the reference plate 13, thereby preventing misalignment and enabling fine processing with good reproducibility. Further, it is possible to quickly cope with a change in the shape of the substrate to be processed by modifying the small reference plate 13 and the first holder plate 21.

  FIG. 3 is a side view showing a second embodiment of the present invention. In the present embodiment, the transparent material 11 is held between the reference plate 13 and the holder 16. The holder 16 has an opening 16a for receiving laser light on the front surface, and a bolt hole 18 for inserting the fixing bolt 15 is formed. The holder 16 has a holding recess 16b on the surface for holding the transparent material 11, and an O-ring 17a is disposed in the holding recess 16b to compensate for variations in the thickness of the transparent material 11. The holder 16 configured as described above is fixed to the XYZ stage by a clamp mechanism (not shown).

  When configured as described above, since the first holder plate is not required, the number of parts can be reduced. Moreover, since the back surface of the transparent material 11 is directly defined by the reference plate 13, fine laser processing with good reproducibility is possible.

  FIG. 4 is a side view showing a third embodiment of the present invention. In the present embodiment, in the transparent material microfabrication apparatus 30, a reference plate 32 that regulates the back surface of the transparent material 11 is formed on the holder 31. The holder plate 33 is fixed to the front side of the transparent material 11 with bolts 34. On the front side of the reference plate 32, a contact surface 32a serving as a reference on the back side of the transparent material 11 is formed. Since the contact surface 32a is flat and formed integrally with the holder 31, the position adjustment with the XYZ stage can be performed accurately. Further, a recess 33a for holding the transparent material 11 is formed on the back surface of the holder plate 33, and an O-ring 35 is disposed to compensate for thickness variations.

  The cell 14 has an opening 14a that contacts the back surface of the transparent material 11, and an O-ring 19 is disposed around the opening 14a. In addition, a cylindrical opening 14b extending upward is formed at the upper end of the cell 14 in the same manner as in the first embodiment, and absorbs the volume fluctuation when the fluid substance 12 is irradiated with laser light. Yes. Further, the holder plate 19 is attached to the reference plate 32 with bolts 20 from the back surface of the cell 14. The holder plate 19 is formed with an opening window 19a in the approximate center so that the state during processing can be observed.

  In such a configuration, the reference plate 32 that regulates the position of the back surface of the transparent material 11 is integrally formed with the holder 31, so that the position of the back surface of the transparent material 11 can be determined more accurately and reproduced. Can be finely processed.

  The present invention is not limited to these embodiments, and various design changes can be made according to the technical scope of the present invention.

  Furthermore, in order to achieve three-dimensional surface micromachining, the above-mentioned micromachining apparatus is used to transmit a laser beam having a specific beam shape through a predetermined photomask, and then scan the laser beam to make it transparent. Control the number of laser pulses and laser intensity irradiated to each processing position of the material. The method of Patent Document 1 has a feature that the processing depth per laser pulse increases linearly with respect to the laser intensity, and the processing depth is proportional to the number of irradiation pulses. For this reason, the processing depth can be easily controlled by the laser intensity and the number of irradiation laser pulses. Therefore, the processing depth at each processing position is arbitrarily controlled to process a complicated three-dimensional surface microstructure. In addition, by scanning with laser light, it is possible to process a region larger than the laser beam size on the workpiece. The photomask to be used may be a normal photomask that controls only light transmission and light shielding, and it is not necessary to dare to use a gray photomask that is difficult to manufacture.

  To make a saw-tooth groove, a transparent material with a light-absorbing fluid is in contact with the back surface of the transparent material. However, the laser beam is scanned in the direction perpendicular to the vertex of the right triangle projected on the transparent material / fluid substance interface in a plane perpendicular to the irradiation direction (FIG. 7). When the state of laser irradiation is viewed from the back side of the transparent material, it is as shown in FIG. 8A, and when scanning a laser beam having a right triangle shape in the direction of the arrow, points A, B, C, The number of laser pulses applied to D and E is proportional to the length of line segments a, b, c, d, and e, respectively. As described in paragraph 0064, since the processing depth is proportional to the number of irradiation laser pulses, the processing depths at points A, B, C, D, and E are proportional to the line segments a, b, c, d, and e, respectively. To do. That is, as shown in FIG. 8B, the cross-sectional shape on the line segment XY is a saw-tooth groove shape with the point Y as the deepest portion. The width of the saw blade coincides with the base of the right triangle, and the depth of the saw blade groove can be controlled by the height of the right triangle, the laser intensity, the scanning speed, the type and concentration of the flowable substance.

  For processing the saw blade groove array, a laser beam having a beam shape in which right triangles are arranged in a line is scanned by a photomask.

  In addition, since the said process will be achieved if the irradiation position of the laser beam with respect to a transparent material moves relatively, (1) A laser beam is scanned, (2) A workpiece is moved with respect to a laser beam, Either is fine.

  Similarly, for the V-groove processing, a laser beam having an isosceles triangular beam shape is scanned. For U-groove processing, a laser beam having a beam shape of one of a circle, an ellipse, a semicircle, and a semi-ellipse is scanned with a photomask. For rectangular groove processing, a laser beam having a rectangular beam shape is scanned.

  Further, for processing the V-groove array, the U-groove array, and the rectangular groove array, a laser beam having a beam shape in which the above shapes are arranged in a row is scanned by a photomask.

  For processing the curved structure of the groove and the groove array, the laser beam having the beam shape described in the paragraphs 0065 to 0069 is scanned so as to draw an arc in a plane perpendicular to the irradiation direction. However, in the processing of the curved structure of the saw blade groove, for example, the groove structure is not smoothly connected even if the arc is drawn only by scanning with the laser beam. During scanning, either the photomask or the workpiece is rotated synchronously, and the vertex direction of the projected right triangle beam shape is always matched with the scanning direction of the laser beam. As a result, the saw blade groove is machined smoothly in an arc. The same applies to the curved structure of other grooves and groove arrays.

  For processing the two-dimensional array of pyramid structures, after the V-groove array is produced, the photomask or workpiece is rotated by 90 ° and the V-groove array processing is performed again. As a result, the V-groove processing is superimposed in the direction orthogonal to the first V-groove processing, and as a result, a pyramid-like structure two-dimensional array shape is formed.

Similarly, U-groove array processing is performed for the processing of the two-dimensional array of lenticular structures, and rectangular groove array processing is performed for the processing of the rectangular two-dimensional array twice so as to be orthogonal. When the interval between the rectangular grooves is constant, a square two-dimensional array is formed by processing twice, and when the interval between the rectangular grooves is not constant, a rectangular two-dimensional array is formed by processing twice. It is also possible to intentionally introduce disturbance into the length of the short side.

  In the three-dimensional surface micromachining according to the present invention, it can be machined by one-step laser processing, and is simple and highly efficient. Furthermore, because of its low laser intensity, large area batch processing is possible through mask projection, and the pattern accuracy can be 1 micrometer or less. In addition, since the etching rate can be controlled and the chemical composition of the etched surface is not changed, the method can be miniaturized, refined, and improved in quality. Furthermore, it is possible to manufacture an optical element having a predetermined three-dimensional surface microstructure by a simple method of scanning laser light that has passed through a photomask.

  In addition, as an optical element produced by applying a dielectric film or a metal film to a three-dimensional microstructure surface produced according to the present invention by a known method as necessary, a diffraction grating, a polarizing plate, a reflector, Examples include diffractive optical elements for visible to ultraviolet to vacuum ultraviolet light, such as antireflection plates, prism arrays, hologram optical elements, and photonic crystal elements, fiber positioning substrates, optical waveguide substrates, and liquid crystal alignment substrates.

Hereinafter, the three-dimensional surface micromachining of the transparent material will be described in more detail by experimental examples.
Experimental example 1
A V-groove was made in a quartz glass substrate. Toluene is used as the flowable material, and the quartz substrate and the flowable material container are in contact with each other and fixed to the electric stage. Using a photomask that transmits a laser beam pattern of right isosceles triangles, KrF excimer laser light is fused with quartz glass. While irradiating the substrate / fluid substance interface, the quartz glass substrate was moved on the electric stage, and the laser beam was scanned. The width of the V-groove matches the base of an isosceles triangle of 100 micrometers, and the groove depth is 20 micrometers, 40 micrometers, and 50 micrometers with good controllability by changing the laser intensity and the moving speed of the laser beam. I was able to change it. Moreover, it has confirmed that the process slope and the bottom were also processed by the predetermined shape. FIG. 9 shows the three-dimensional shape observation result of the processed V groove.

Experimental example 2
A U-groove was processed in a quartz substrate. Using an acetone solution of pyrene as the fluid substance, the quartz substrate and the fluid substance container are in contact with each other and fixed to the electric stage, and a KrF excimer laser beam is applied to the quartz substrate using a photomask that transmits a circular laser beam. / The laser beam was scanned by moving the quartz substrate perpendicular to the laser irradiation direction by an electric stage while irradiating the fluid substance interface. The width of the U groove was 18 microns and the depth of the groove was 9 microns.

FIG. 1 is an explanatory diagram showing a schematic configuration of a transparent material micromachining apparatus according to the present invention. FIG. 2 is a front view of the transparent material microfabrication apparatus. FIG. 3 is a side view showing a second embodiment of the present invention. FIG. 4 is a side view showing a third embodiment of the present invention. FIG. 5 is a side view showing an example of a conventional fine processing apparatus. FIG. 6 is a side view showing an example of a positional shift of a transparent material in a conventional fine processing apparatus. FIG. 7 is an explanatory diagram showing an outline of saw blade groove processing. FIG. 8A is an explanatory diagram viewed from the back side of the transparent material in which the laser beam is scanned while irradiating a laser beam having a right triangular beam shape. FIG. 8B is a schematic view of a saw blade groove to be produced. FIG. 9 shows the observation result of the three-dimensional shape of the V-groove produced on the quartz glass surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transparent material fine processing apparatus 11 Transparent material 12 Flowable substance 13 Reference plate 13a Reference surface 13b Window part 14 Cell 14a Opening part 14b Cylindrical opening part 15 Fixing bolt 16 Holder 16a Opening part 16b Holding recessed part 17 O-ring 18 Bolt hole 19 Second Holder Plate 19a Opening Window 20 Bolt 21 First Holder Plate 21a Recess 21b Opening 22 O-ring 30 Transparent Material Micro-Processing Device 31 Holder 32 Reference Plate 32a Abutting Surface 33 Holder Plate 34 Bolt 35 O-ring 40 Laser Light DESCRIPTION OF SYMBOLS 41 Photomask 42 Condensing lens 43 Right-angled triangular beam 44 Transparent material 45 Fluid substance container 46 Transparent material back surface / fluid substance contact area 47 Laser light scanning direction 48 Saw blade groove processed on the transparent material back surface 49 Za light scan direction

Claims (1)

The back surface of the transparent material (11) is brought into contact with a fluid substance (12) having a high absorption rate with respect to the laser wavelength, and laser light (L) is irradiated from the front surface to finely process the back surface of the transparent material (11). A fine processing apparatus (10) for transparent material to be applied,
A reference plate (13) for directly regulating the back surface position of the transparent material (11) ;
A first holder plate (21) having an O-ring holding recess (21a) on the surface side of the transparent material (11) ;
An O-ring (17) for preventing back-side position blur and preventing micro-deformation, which is fitted into the O-ring holding recess (21a) of the first holder plate (21) ;
A plurality of fixtures (15) for pressing and clamping the transparent material (11) with equal torque via an O-ring (17 ) between the reference plate (13) and the first holder plate (21) ;
A cell (14) containing the flowable substance (12 ) and provided with an opening (14a) on one side;
The pressing operation of the first holder plate (21) through the opening (14a ) of the cell (14) with respect to the back surface of the transparent material (11) through an O-ring (22) for preventing leakage of a fluid substance A second holder plate (19) that presses independently of and seals the inside of the cell (14) ;
A holder (16) for fixing the first holder plate (21) and the second holder plate (19) and fixing them on the XYZ stage using a plurality of reference pins;
In the state where the opening of the cell (14) is pressed and fixed to the back surface of the transparent material (11) via the O-ring (22) by the second holder plate (19) , the fixture (15) between the first holder plate holding the said reference plate (13) and said O-ring (17) (21), fine processing of a transparent material, characterized in that said transparent material (11) made it possible vertical clamping apparatus.