JP4507928B2 - Holographic grating manufacturing method - Google Patents

Description

  The present invention relates to a grating (diffraction grating) which is a wavelength separation / selection element used in a spectroscope or a duplexer, and more particularly to a holographic grating manufacturing method manufactured using a holographic exposure method. .

As a method of manufacturing a grating (diffraction grating), a mechanical method of mechanically engraving a grating groove on a substrate, and exposure and development of an interference fringe due to two-beam interference on a photoresist film applied on the substrate, the photoresist There is a holographic method in which a pattern is produced on a substrate by etching it. A diffraction grating manufactured by the holographic method is called a holographic grating.
Producing a grating requires many steps and is therefore expensive, and it is inevitable that there will be individual differences in performance. For this reason, a negative grating is produced from one original grating by resin duplication, and a replica grating is produced by duplicating the negative grating again.

FIG. 3 shows an original plate manufacturing process (a, b, c, d, e, f), a negative plate manufacturing process (g, h, i), and a replica plate manufacturing process (j) of a conventional holographic grating manufacturing method. .
(A) of the original production process shows the application of the photoresist film 11, and the optically polished and cleaned optical glass substrate 12 is coated with a holographic exposure-possible photoresist film 11 with a spinner and baked in an oven. Then, a 300 nm thick photoresist film 11 is formed.
(B) shows the formation of a sinusoidal half-wave resist pattern, which is exposed by the holographic exposure apparatus shown in FIG. The holographic exposure apparatus shown in FIG. 4 is a holographic exposure method using a two-beam interference of a He—Cd laser (λ = 441.6 nm) 21, and the laser beam is reflected by a mirror 22 and reflected / transmitted by a beam splitter 23. The light enters and is reflected by 22a and 22b and passes through the spatial filter 24a and the spatial filter 24b, respectively. The transmitted light exposes a 900 / mm latent image of interference fringes on the photoresist film 11 on the workpiece (substrate 12 processed in FIG. 3A) 25, and is then developed, rinsed with pure water, and photoresist. The diffraction grating pattern 11a is manufactured.
At this time, since the intensity distribution of the interference fringes of the two-beam interference is a sine wave, the diffraction pattern of the produced photoresist 11a also has a sine half-wave cross section.
(C) shows ion beam irradiation, and ion beam etching is performed. The etching gas to be used is CF ₄ and the gas pressure is 1.5 × 10 ⁴ Torr, and irradiation is performed perpendicularly to the engraving direction of the pattern of the photoresist 11a and obliquely from above the substrate 12.
(D) shows etching of the substrate 12, ion beam irradiation is continued until the pattern is completely directly engraved on the substrate 12, a sawtooth diffraction grating is manufactured, and (e) a gradient of 7 is applied to the substrate 12. A scored line pattern having a serrated cross section with a pattern pitch of 1.25 μm is formed at 5 °.
(F) shows a reflective coating, the original grating after etching is cleaned, and aluminum Al is coated on the substrate 12 as an optimum material in the operating wavelength range (ultraviolet to visible region) with a vacuum deposition apparatus. The Al film 13 is used as a reflective film. The original production process is completed by the above process.

Next, (g) of the negative plate manufacturing process shows the deposition of the Al film 15 after the release agent 14 is applied. (F) A thin oil film (thickness of about 1 nm) is formed on the original plate (substrate 12 + Al film 13) completed in the process by using, for example, silicone grease as the release agent 14 again with a vacuum deposition apparatus, and then aluminum is vacuum deposited. Then, a thin Al film 15 (thickness: about 0.2 μm) is formed.
(H) shows adhesion of the negative substrate 16 by applying the adhesive 17. The substrate 12 processed in the step (f) is taken out from the vacuum deposition apparatus, and an epoxy resin or the like is used as the adhesive 17 to bond a negative substrate 16 (glass substrate or the like). When the negative substrate 16 is peeled off from the original plate (substrate 12 + Al film 13) after the adhesive 17 is cured, a negative plate (negative substrate 16 + adhesive 17 + Al film 15) is formed with the release agent 14 as a boundary.
(I) shows a negative version. Since the release agent remains on the surface of the peeled negative plate (negative substrate 16 + adhesive 17 + Al film 15), it is removed by washing with a solvent such as Freon. In this way, the original diffraction grating is transferred to the surface to complete the negative plate.

Next, in the replica plate manufacturing step (j), the same as the negative plate manufacturing step, a release agent layer and an Al film 18 are formed on the negative plate, and the replica substrate 20 is bonded by the adhesive 19 and then peeled off. . The groove shape of the negative plate is reversed again and transferred to the replica plate, and as a result, a replica plate having a groove shape equal to that of the original plate is produced (see, for example, Patent Document 1 and Patent Document 2).
JP-A-1-161302 (Page 7, FIGS. 1 to 4) JP 2001-235611 A (Page 6, FIG. 1)

Although the conventional holographic grating manufacturing method is configured as described above, the pattern of the photoresist 11a and the etching speed of the substrate 12 are different, but the ratio of these speeds is stable as set. It is important to obtain the desired sawtooth wave pattern. However, if the type of gas used for etching, the ratio in the case of a mixed gas, the density of the ion beam, the velocity, etc. change, this ratio changes greatly, so that a desired sawtooth wave pattern cannot be produced stably. There is a problem.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a holographic grating manufacturing method capable of stably producing a desired sawtooth wave pattern.

In order to achieve the above object, a holographic grating manufacturing method of the present invention includes a first step of marking a photoresist pattern on a photoresist film provided on an optical glass substrate by a holographic exposure method, and the photoresist. A second step of etching the optical glass substrate with an ion beam perpendicular to the optical glass substrate on which the pattern is formed to form a sinusoidal or sinusoidal engraving pattern; and the ion beam is engraved on the engraving pattern. And a third step of producing a sawtooth pattern by irradiation from a direction perpendicular to the direction and inclined with respect to the normal direction of the substrate.

Furthermore, the holographic grating manufacturing method of the present invention includes a first step of engraving a photoresist pattern on a photoresist film provided on an optical glass substrate by a holographic exposure method, and an optical in which the photoresist pattern is formed. Etching the optical glass substrate with an ion beam perpendicular to the glass substrate to form a sinusoidal or sine half-wave engraved pattern; and an ion beam perpendicular to the engraving direction of the engraving pattern and the substrate The negative holographic grating and / or the replica grating are manufactured through the transfer process using the holographic grating manufactured in the third step of manufacturing the sawtooth pattern by irradiating from the direction inclined with respect to the normal direction of To do.

The holographic grating manufacturing method of the present invention is configured as described above. In the first step, a photoresist material is applied onto an optical glass substrate by a spinner or the like. Then, using a holographic exposure apparatus, a photoresist pattern is engraved by a holographic exposure method using two-beam interference such as a He—Cd laser (λ = 441.6 nm). Next, in a second step, ion beam etching is performed from the direction perpendicular to the substrate using CF ₄ gas or the like, and etching is performed until the photoresist completely disappears, and a sinusoidal half-wave pattern is engraved on the substrate. Then, in a third step, an ion beam is irradiated from a direction perpendicular to the engraving direction and inclined with respect to the normal direction of the substrate using Ar gas or the like to produce a sawtooth pattern. Finally, in order to increase the reflection efficiency, a reflective film is formed by vacuum-depositing Al or the like on the surface, and an original plate is manufactured.
Also, in the negative plate production process, a mold release agent and then an Al film are formed on the original plate, and a glass substrate is adhered with an adhesive (such as an epoxy resin), and after curing, peeled off from the original plate and remains on the surface The mold release agent is washed with a solvent, and the negative plate is transferred and manufactured.
Next, similarly for the replica plate, a release agent and then an Al film are formed on the negative plate, and the glass substrate is bonded with an adhesive (such as an epoxy resin). The remaining mold release agent is washed with a solvent, and a replica plate is transferred and manufactured.

The holographic grating manufacturing method of the present invention is configured as described above. In the prior art, the ratio of the etching rate due to the difference in the material of the photoresist and the substrate is not stabilized as set, and various conditions of ion beam etching In the third step of the production, the material of the pattern part and the material of the substrate manufactured in the second step are the same, and the rate ratio of etching the pattern and the substrate is the same. A desired sawtooth wave pattern can be stably produced by performing ion beam etching from an oblique direction.
In addition, the ratio of the etching rate of the photoresist to the etching rate of the substrate is about 1: 2 in the CF ₄ gas often used in the prior art, but when the sawtooth wave pattern of an angle is to be formed, this ratio is The smaller the value, the larger the incident angle of the ion beam. In the manufacturing method of the present invention, this ratio is always 1: 1, and the incident angle of the ion beam can be made large, and in the production of the concave grating, the ion beam is less likely to be behind the edge of the substrate and is easy to process on the production surface. .

  A holographic grating manufacturing method provided by the present invention includes a first step of forming a sinusoidal photoresist by a holographic exposure method, and a second step of etching with an ion beam perpendicular to the glass substrate on which the photoresist is formed. And the third step of irradiating the ion beam obliquely, etching the same material of the pattern and the substrate, and stably producing a desired sawtooth wave pattern.

One embodiment of the holographic grating manufacturing method of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a manufacturing process of the holographic grating manufacturing method.
In the holographic grating manufacturing method of the present invention, as a first step, (a) a photoresist film 1 is applied on a substrate 2 of optical glass, and (b) a holographic exposure apparatus is used for the applied photoresist film 1. Then, a sinusoidal half-wave photoresist 1a is formed on the substrate 2, and as a second step, (c) the photoresist 1a formed on the substrate 2 is subjected to ion beam etching with CH ₄ gas from the vertical direction (d ) Ion beam etching is performed until the photoresist 1a on the substrate 2 disappears to form a sinusoidal wave-shaped engraving pattern on the substrate 2, and (e) Ar gas ion beam etching is performed on the substrate 2 as a third step. Is irradiated at an angle of 16 ° from the horizontal position, (f) ion beam etching is continued on the substrate 2, and (g) a gradient of 7.5 is applied to the substrate 2. Forming a scored pattern having a sawtooth cross section with a pattern pitch of 1.25 μm, and (h) forming a reflective Al film 3 on the surface of the substrate 2 by vacuum deposition, the first and second steps described above, And the third step.

One embodiment of the negative plate manufacturing method and replica plate manufacturing method of the holographic grating manufacturing method of the present invention will be described with reference to FIG. FIG. 2 shows a process of manufacturing a negative plate and a replica plate from the holographic grating original plate manufactured in the first step, the second step, and the third step.
In the negative plate production process, (i) a release agent 4 such as grease is applied to the holographic grating original plate (original plate produced in the step (h)), an Al film 5 is formed by vacuum deposition, and (j ) Adhesive material 7 such as epoxy resin is applied, and a new negative substrate 6 such as a glass substrate is adhered. (K) The negative substrate 6 having the transfer-formed adhesive material 7 with the Al film 5 is separated from the original. Then, the mold release agent 4 remaining on the surface is washed with a solvent to complete a negative plate.
In the replica plate production process, (l) a release agent such as grease is applied to the negative plate (negative plate produced in the (k) step), an Al film 8 is formed by vacuum deposition, and an epoxy resin or the like is formed thereon. The adhesive 9 is applied, the new replica substrate 10 is adhered, the replica substrate 10 having the transfer molded adhesive 9 with the Al film 8 is released from the negative substrate 6, and the release agent remaining on the surface Wash the with solvent to complete the replica version.

  The difference between the holographic grating manufacturing method of the present invention and the conventional manufacturing method is that the conventional manufacturing method has an inclined sinusoidal half-wave photoresist film 11 photoetched on the substrate 12, as shown in FIG. Irradiating with an ion beam from the direction, etching the photoresist 11a and the substrate 12 of different materials at the same time, until the pattern is completely engraved directly on the substrate 12, and forming a diffraction grating with a sawtooth groove shape To manufacture. On the other hand, in the holographic grating manufacturing method of the present invention, a sine half-wave photoresist 1a is formed on the substrate 2 in the first step, and the ion beam is irradiated from the vertical direction in the second step. Etching is continued until the resist 1a disappears, and a sinusoidal wave-shaped engraving pattern is formed on the substrate 2, and in the third step, an ion beam is irradiated from the direction of 16 ° with respect to the horizontal position of the substrate 2 to form the same material. The etched pattern and the substrate 2 are etched. The pattern and the etching rate ratio of the substrate 2 are the same, and a desired sawtooth wave pattern can be manufactured stably.

Next, each material and manufacturing method of the holographic grating manufacturing method will be described.
As the substrate 2, a substrate 2 made of optical glass is used. The optical glass has a low expansion coefficient due to thermal deformation, and is excellent as a substrate material for a diffraction grating which is an optical element. For example, BK7, BSC2, heat-resistant tempered glass, soda glass, quartz glass and the like can be used favorably. Then, the surface is cleaned by optical polishing and ultrasonic cleaning.
The photoresist film 1 only needs to be capable of holographic exposure. For example, Mp1400 (manufactured by Shifley Co., Ltd.) or OFPR5000 (manufactured by Tokyo Ohka Co., Ltd.) can be used. Then, using a spinner device, a photoresist agent is dropped on the substrate 2 that rotates at high speed to spread the photoresist film 1 to a thickness of about 300 nm.
The holographic exposure is performed by a holographic exposure method using two-beam interference of a He—Cd laser (λ = 441.6 nm) 21 using an exposure apparatus shown in FIG. Photoetching is performed to expose a 900 / mm interference fringe latent image, which is then developed and rinsed with pure water to produce a sine half-wave pattern having a pitch of 1.25 μm and a height of 125 nm of the photoresist 1a.
In the second step, ion beam irradiation is performed using CF ₄ gas or the like from the direction perpendicular to the substrate 2 and etching is performed until the photoresist 1a completely disappears, and the substrate 2 has a sinusoidal half-wave shape with a height of 250 nm. Engrave the pattern.
In the ion beam irradiation in the third step, ion beam etching with Ar gas or the like is performed from a horizontal direction with respect to the substrate 2 in an inclined direction of 16 °. Simultaneously with the etching of the half-sine wave pattern, the same material of the substrate 2 is etched at the same speed, and the substrate 2 is formed with a sawtooth pattern having a tilt angle of 7.5 ° and a pattern pitch of 1.25 μm.
The Al film 3 is formed as a reflective film by depositing an aluminum film by vacuum deposition on the substrate 2 on which the sawtooth pattern is formed. Depending on the wavelength range used, even if no reflective film is deposited, the reflectance is sufficiently high so that it can be used as it is. However, in other wavelength ranges, Au, Pt, or an X-ray multilayer film can be used as necessary. Use with increased reflectance and durability by coating with.
The release agent 4 is used when producing a negative plate and a replica plate. For example, a thin oil film (thickness: about 1 nm) is formed with silicone grease, and the release agent 4 is formed on the original plate or negative plate, transferred, and the negative plate or replica plate is peeled off.
The Al films 5 and 8 are used as reflection films for negative plates or replica plates, and are deposited on the release agent 4 or the release agent 4 at the time of producing the replica plate. Peeled and plays the same role as the Al film 3.
Adhesives 7 and 9 are made of epoxy resin, but other heat-resistant thermosetting resins such as urea resin, melanin resin, and phenol resin may also be used.
When producing a negative plate, after the adhesive 7 is cured, the negative plate is peeled off from the original plate (base material) with the release agent 4 as a boundary, and the release agent 4 is removed by washing with a solvent such as Freon. Make a plate.
When making a replica plate, after the adhesive 9 is cured, the replica plate is peeled off from the negative plate (base material) at the boundary of the release agent, and the release agent is washed and removed with a solvent such as Freon. Is produced.

In the above embodiment, CF ₄ and Ar gas are used as the etching gas. However, the present invention is not limited to this, and any ion beam gas may be used. A mixed gas may also be used.
Further, the photoresist pattern (FIG. 1B) is not limited to a sine half wave shape, but may be a sine wave shape or a slanted one.
Further, the etching in the second step (FIG. 1C) is not limited to being vertical, but may be performed with an angle.
Further, the pattern on the substrate 2 in the second step (FIG. 1D) is not limited to a sine half wave shape, but may be a sine wave shape or a pattern in which they are inclined.

  As an application example of the present invention, it relates to a grating (diffraction grating) which is a wavelength separation / selection element used in a spectroscope or a demultiplexer, and more particularly to a holographic grating manufacturing method manufactured using a holographic exposure method. Is.

It is explanatory drawing which showed the holographic grating manufacturing method of this invention. It is explanatory drawing which showed the replica manufacturing method of the holographic grating of this invention. It is a figure for demonstrating the conventional holographic grating manufacturing method. It is explanatory drawing which showed the structure of the holographic exposure apparatus.

Explanation of symbols

1, 11 Photoresist film 1a, 11a Photoresist 2 Substrate 3, 5, 8, 13, 15, 18 Al film 4, 14 Release agent 6 Negative substrate 7, 9, 17, 19 Adhesive Adhesive 10, 20 Replica Substrate 12 Substrate 16 Negative substrate 21 He-Cd laser 22, 22a, 22b Mirror 23 Beam splitter 24a, 24b Spatial filter 25 Workpiece

Claims (2)

A first step of engraving a photoresist pattern by a holographic exposure method on a photoresist film provided on an optical glass substrate;
A second step of etching the optical glass substrate with an ion beam perpendicular to the optical glass substrate on which the photoresist pattern is formed to form a sinusoidal or sine half-wave marking pattern ;
Holographic grating, characterized in that and a third step of fabricating a sawtooth pattern with an ion beam is irradiated from a direction and inclined with respect to the normal direction of the substrate in the ruling direction perpendicular of the score line pattern Production method. A holographic grating manufacturing method, wherein the holographic grating manufactured by the manufacturing method according to claim 1 is used as a base, and a negative grating and / or a replica grating are manufactured through a transfer process.

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