JP5391670B2 - Manufacturing method of fine structure - Google Patents

Description

  The present invention relates to a technique for manufacturing an element (for example, an optical element) having a fine structure.

  2. Description of the Related Art A diffractive optical element that gives a diffractive action to incident light by an uneven structure provided on the surface is known. The applicant of the present application considered adding a function for preventing reflection of incident light to such a diffractive optical element by forming a convex portion that is even smaller than the above-described concavo-convex structure. ing. In addition, the applicant of the present application may add a polarization separation function to the diffractive optical element by forming a stripe-shaped convex portion (wire grid) that is finer than the concavo-convex part of the diffractive optical element. Are considering. As described above, when a diffractive optical element in which a concavo-convex structure for a diffractive function and a minute convex part for an antireflection function or a polarization separation function are superimposed is realized, the application range is greatly expanded.

  In many cases, a photolithographic technique using a photosensitive film is employed to form the minute projections that bear the antireflection function or the polarization separation function. In this case, a photosensitive film is provided to cover the concavo-convex structure on the substrate, and a fine pattern mask is formed by exposing and developing the photosensitive film. Then, by performing etching using this mask, minute convex portions are formed. However, when a photosensitive film is formed by employing a conventionally well-known method (for example, spin coating or spray coating), the surface of the photosensitive film is often not flat due to the influence of the concavo-convex structure below. This is considered to be due to the fact that the material solution of the photosensitive film accumulates in the concave portion of the concave-convex structure. For this reason, it has been difficult to satisfactorily form a microstructure having a concavo-convex structure and a minute convex portion superimposed thereon. Such a problem is not limited to the manufacturing of the diffractive optical element, but is common to the manufacturing of a fine structure having a similar structure. Further, the same technical problem may be caused not only when a further minute convex portion is formed on the concavo-convex structure intended for some function but also when a minute convex portion is simply formed on a substrate having low flatness. .

  In addition, as a prior art document relevant to this application, the Japanese translations of PCT publication No. 2002-520777 (patent document 1) is mentioned, for example. However, although this patent document 1 discloses an example of a microstructure having a minute convex portion superimposed on the concavo-convex structure, there is no sufficient disclosure or suggestion about the manufacturing method thereof, and the technical problem described above. Has not yet been resolved.

Japanese translation of PCT publication No. 2002-520777

  A specific aspect of the present invention has an object to provide a manufacturing technique that can satisfactorily manufacture a fine structure in which a minute convex portion is formed on a surface having low flatness.

The manufacturing method of the fine structure according to the first aspect of the present invention includes a substrate having a plurality of projections on at least one surface, and a plurality of projections smaller than each of the plurality of projections provided on one surface of the substrate. A microstructure having a microprojection, comprising: (a) forming a photosensitive film on the plurality of convex portions provided on the substrate; and (b) over the photosensitive film. (C) disposing the transparent substrate opposite to the substrate with the liquid sandwiched therebetween, (d) generating interference light using a laser beam, and transmitting the interference light to the transparent substrate and the substrate Irradiating the photosensitive film through a liquid; (e) developing the photosensitive film after removing the liquid and the transparent substrate; and (f) masking the photosensitive film pattern formed in (e). Etching the substrate, using as Wherein, in the (c), using a parallel plate having a diffraction grating, wherein the diffraction grating parallel plate is provided face disposed on the liquid so that the opposite side with respect to the liquid, In (d), the interference light is generated by causing a single laser beam to enter the diffraction grating, and the refractive index of the liquid in (b) is greater than 1 and equal to the refractive index of the photosensitive film. Or a lower value.

In (d) in the manufacturing method of the first aspect described above, interference light can be generated by crossing a plurality of laser beams. In (c), a transparent substrate provided with a diffraction grating may be used, and in (d), interference light may be generated by causing a single laser beam to enter the diffraction grating.

  Moreover, in (c) in the manufacturing method of the 1st aspect mentioned above, the light shielding layer which has an opening part in a parallel plate can be formed. At this time, in (c), a plurality of openings are formed, and in (d), a shielding plate that individually exposes the openings is arranged on the parallel plate to irradiate the plurality of regions with interference light. it can. In (c), a single opening may be formed, and in (d), the parallel plate may be moved to irradiate a plurality of regions with interference light.

The method for manufacturing a microstructure according to the second aspect of the present invention includes a substrate having a plurality of projections on at least one surface, and a plurality of projections smaller than each of the plurality of projections provided on one surface of the substrate. A microstructure having a microprojection, comprising: (a) forming a photosensitive film on the plurality of convex portions provided on the substrate; and (b) over the photosensitive film. (C) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the water-soluble film, and (d) developing the photosensitive film. (E) etching the substrate using the photosensitive film pattern formed in (d) as a mask, and in (b), the laser beam incident side of the water-soluble film A parallel plate with a diffraction grating is disposed on the In c), the diffraction grating to generate the interference light by diffracting the laser beam in the singular, the refractive index of the water-soluble film in the (b) is equal to the refractive index of greater than 1 the photoresist Or a lower value.

Moreover, in (c) in the manufacturing method of the second aspect described above, interference light can be generated by crossing a plurality of laser beams.

In the manufacturing method according to the present invention, a liquid having a higher refractive index than air or a water-soluble film equivalent to air is disposed on the photosensitive film, and laser interference exposure is performed in this state. By placing a liquid or water-soluble film, the photosensitive film is in contact with the photosensitive film as compared with the case where interference light is directly incident on the photosensitive film (that is, when exposure is performed in the state where the air and the photosensitive film are in contact). The refractive index difference from the medium (liquid and transparent substrate ) becomes small. Thereby, the diffraction of the interference light due to the unevenness of the surface of the photosensitive film is suppressed, and the disturbance of the intensity distribution of the interference light in the photosensitive film can be avoided. Therefore, according to the manufacturing method according to the present invention, it is possible to realize good exposure even on a surface with low flatness, and to manufacture a fine microstructure.

  In the above (d) in the manufacturing method of the second aspect, the photosensitive film can be developed after removing the water-soluble film. Further, the photosensitive film can be developed without removing the water-soluble film. That is, it is not essential to remove the water-soluble film before developing the photosensitive film. When development is performed with the water-soluble film provided, a pattern is formed on the photosensitive film, and the water-soluble film can be dissolved at the same time.

  Preferably, the method further includes forming the plurality of convex portions on the one surface side of the substrate prior to (a). Here, the “plurality of convex portions” is, for example, for exhibiting a diffraction function for incident light. Thereby, after forming some convex part, in the case of forming a convex part finer than these convex parts, favorable exposure can be realized.

  Preferably, the method further includes removing the photoresist pattern after the substrate is etched. If the photosensitive film pattern is left, this step need not be performed. If the photosensitive film pattern is finally unnecessary, it can be removed.

The transparent substrate preferably has an antireflection film on a surface on which the plurality of laser beams are incident. Thereby, the reflected light generated at the interface between the air layer and the transparent substrate is suppressed, and the exposure unevenness can be further reduced.

The manufacturing method of the fine structure according to the third aspect of the present invention includes a substrate having a plurality of convex portions on at least one surface, and a plurality of smaller than each of the plurality of convex portions provided on one surface of the substrate. A microstructure comprising: a microprojection; (a) forming a metal film on the plurality of convex portions provided on the substrate; (b) on the metal film (C) forming a first antireflection film on the first antireflection film, (c) forming a photosensitive film on the first antireflection film, (d) disposing a liquid on the photosensitive film, (e) (B) generating interference light using a laser beam, and irradiating the photosensitive film with the interference light through the transparent substrate and the liquid; (G) developing the photosensitive film after draining the liquid and the transparent substrate; It uses the photoresist pattern formed by (h) the (g) as a mask, etching the metal film and the first antireflection film comprises, in said (e), a diffraction grating The parallel plate is disposed on the liquid so that the surface on which the diffraction grating is provided is opposite to the liquid, and in (f), the single laser beam The interference light is generated by making the light incident on the diffraction grating, and the refractive index of the liquid in (d) is greater than 1 and equal to or lower than the refractive index of the photosensitive film. And

In (f) in the manufacturing method of the third aspect described above, interference light can be generated by crossing a plurality of laser beams. In (e), a transparent substrate provided with a diffraction grating may be used, and in (f), interference light may be generated by causing a single laser beam to enter the diffraction grating.

Moreover, in (e) in the manufacturing method of the 3rd aspect mentioned above, the light shielding layer which has an opening part in a transparent substrate can be formed. At this time, in (e), a plurality of openings are formed, and in (f), a shielding plate that individually exposes the openings is arranged on the transparent substrate , and the interference light is irradiated to a plurality of regions. Can do. In (e), a single opening may be formed, and in (f), the transparent substrate may be moved to irradiate a plurality of regions with interference light.

The manufacturing method of the fine structure according to the fourth aspect of the present invention includes a substrate having a plurality of convex portions on at least one surface, and a plurality of smaller than each of the plurality of convex portions provided on one surface of the substrate. A microstructure comprising: a microprojection; (a) forming a metal film on the plurality of convex portions provided on the substrate; (b) on the metal film (C) forming a photosensitive film on the first antireflection film, (d) forming a water-soluble film on the photosensitive film, e) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the water-soluble film; (f) developing the photosensitive film; (g) (f) The metal film and the first antireflection film are formed using the photosensitive film pattern formed by the above as a mask. Etching the film, wherein the said (b), the said parallel flat plate having a diffraction grating on the incident side of the laser beam of the water-soluble film disposed, in the (c), by the diffraction grating singular The interference light is generated by diffracting the laser beam, and the refractive index of the water-soluble film in (d) is greater than 1 and equal to or lower than the refractive index of the photosensitive film. Features.

  Further, in (e) in the manufacturing method of the fourth aspect described above, interference light can be generated by crossing a plurality of laser beams.

  In the manufacturing method according to the present invention, a liquid having a higher refractive index than air or a water-soluble film equivalent to air is disposed on the photosensitive film, and laser interference exposure is performed in this state. By placing a liquid or water-soluble film, the photosensitive film is in contact with the photosensitive film as compared with the case where interference light is directly incident on the photosensitive film (that is, when exposure is performed in the state where the air and the photosensitive film are in contact). The refractive index difference from the medium (liquid and parallel plate) is reduced. Thereby, the diffraction of the interference light due to the unevenness of the surface of the photosensitive film is suppressed, and the disturbance of the intensity distribution of the interference light in the photosensitive film can be avoided. Therefore, according to the manufacturing method according to the present invention, it is possible to realize good exposure even on a surface with low flatness, and to manufacture a fine microstructure.

  In the above (f) in the manufacturing method of the fourth aspect, the photosensitive film can be developed after removing the water-soluble film. Further, the photosensitive film can be developed without removing the water-soluble film. That is, it is not essential to remove the water-soluble film before developing the photosensitive film. When development is performed with the water-soluble film provided, a pattern is formed on the photosensitive film, and the water-soluble film can be dissolved at the same time.

  Preferably, the method further includes forming the plurality of convex portions on the one surface side of the substrate prior to (a). Here, the “plurality of convex portions” is, for example, for exhibiting a diffraction function for incident light. Thereby, after forming some convex part, in the case of forming a convex part finer than these convex parts, favorable exposure can be realized.

  Preferably, the method further includes removing the photosensitive film pattern after the metal film and the first antireflection film are etched. If the photosensitive film pattern is left, this step need not be performed. If the photosensitive film pattern is finally unnecessary, it can be removed.

  Preferably, the method further includes removing the first antireflection film after the photosensitive film pattern is removed. If the first antireflection film is finally unnecessary, it can be removed.

  Note that this step is not necessary when the first antireflection film is left. Thereby, the process can be simplified.

The transparent substrate preferably has a second antireflection film on a surface on which the plurality of laser beams are incident. Thereby, the reflected light generated at the interface between the air layer and the transparent substrate is suppressed, and the exposure unevenness can be further reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the dimensions and ratios of the constituent elements are appropriately changed from the actual ones in order to make the constituent elements large enough to be recognized on the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a cross-sectional structure of a diffractive optical element which is an example of a fine structure according to the first embodiment. A diffractive optical element (optical element) 1 according to this embodiment shown in FIG. 1 includes a substrate 2, a diffractive structure part 3, and a grid part (non-diffractive structure part) 4.

  The substrate 2 is a substrate that is transparent to the wavelength of incident light. As the substrate 2, for example, a substrate made of an inorganic material such as a glass substrate (quartz glass substrate) is used. The thickness of the substrate 2 is, for example, about 1.2 mm. A diffractive structure 3 is provided on one surface side of the substrate 2. The other surface of the substrate 2 is a plane as shown in the figure.

  The diffractive structure 3 is provided on one side of the substrate 2. The diffractive structure portion 3 includes a plurality of concave portions 3a and convex portions 3b arranged alternately. In addition, in the figure, the code | symbol is attached | subjected about each one recessed part 3a and the convex part 3b for convenience. As shown in the figure, the diffractive structure part 3 composed of the concave part 3a and the convex part 3b has a rectangular cross section. The shape may have a slight taper. In the present embodiment, the diffractive structure 3 is formed by processing one side of the substrate 2. That is, the substrate 2 and the diffractive structure 3 are integrally formed.

  The grid part 4 is provided on one surface of the substrate 2 and along the upper surface of the diffraction structure part 3. The grid part 4 of the present embodiment is formed integrally with the substrate 2 and the diffraction structure part 3 described above. The grid portion 4 includes a plurality of minute convex portions 4a having a size smaller than each of the plurality of convex portions 3b in the diffraction structure portion 3 described above. Each minute projection 4a is made of a dielectric material. In this embodiment, the constituent material of each minute convex part 4a is quartz glass.

  FIG. 2 is a schematic perspective view showing a part of the grid portion 4 in an enlarged manner. Each minute convex part 4a of the grid part 4 is a stripe-shaped structure extending in one direction (the Y direction shown in the figure), for example, as shown in FIG. These minute convex portions 4a are periodically arranged, for example, along the X direction. Further, each minute convex portion 4a is not limited to the one-dimensional grid as shown in FIG. 2A, and is, for example, one arranged in a matrix (two-dimensional grid) as shown in FIG. 2B. May be. In this case, the interval between the minute convex portions 4a may be constant or may not be constant. In FIG. 2B, a conical shape is shown as an example of the minute convex portion 4a, but the shape of the minute convex portion 4a is not limited to this. The shape of the minute convex portion 4a may be any shape such as a hemispherical shape, a pyramid shape, or a column shape.

  FIG. 3 is a schematic perspective view showing a part of the diffractive structure 3 in an enlarged manner. As shown in FIG. 3A, the diffractive structure portion 3 has a plurality of concave portions 3a and convex portions 3b extending in one direction (the Y direction shown in the drawing). These concave portions 3a and convex portions 3b have a stripe shape as shown in the figure, and are periodically arranged along the X direction. In addition, each recessed part 3a and the convex part 3b are not limited to the one-dimensional arrangement | sequence (one-dimensional grid) as shown to FIG. 3 (A), For example, as shown to FIG. The part 3b may be a two-dimensional array (two-dimensional grid).

  FIG. 4 is a schematic perspective view showing the diffractive structure portion 3 and the grid portion 4 partially enlarged. Based on this figure, the suitable aspect of the arrangement | positioning relationship between the diffraction structure part 3 and the grid part 4 in case each minute convex part 4a of the grid part 4 is a one-dimensional grid is demonstrated. The mutual arrangement relationship between the diffractive structure portion 3 and the grid portion 4 can be, for example, as shown in FIG. Specifically, in the example shown in FIG. 4A, each concave portion 3a and each convex portion 3b of the diffractive structure portion 3 extend along the Y direction shown in the drawing, and these concave portions 3a and convex portions are formed. The parts 3b are alternately arranged along the X direction. Similarly, each minute convex part 4a of the grid part 4 extends along the Y direction shown in the figure, and these minute convex parts 4a are alternately arranged along the X direction. That is, the extending direction of each concave part 3a and each convex part 3b and the extending direction of the minute convex part 4a are parallel.

  Further, the mutual arrangement relationship between the diffractive structure portion 3 and the grid portion 4 is such that the extending directions of the concave portions 3a and the convex portions 3b and the minute convex portions are shown in FIGS. 4B and 4C. It is also preferable that the extending direction of the portion 4a intersects at a certain angle. Specifically, in the example shown in FIG. 4B, each concave portion 3a and each convex portion 3b of the diffractive structure portion 3 extend along the Y direction shown in the drawing, and these concave portions 3a and convex portions are formed. The parts 3b are alternately arranged along the X direction. On the other hand, each minute convex part 4a of the grid part 4 extends along a direction intersecting at an angle of approximately 45 ° with respect to the Y direction shown in the figure, and these minute convex parts 4a They are alternately arranged along the direction orthogonal to the intersecting direction.

  In the example shown in FIG. 4C, each concave portion 3a and each convex portion 3b of the diffractive structure portion 3 extend along the Y direction shown in the drawing, and these concave portions 3a and convex portions 3b are in the X direction. Are arranged alternately. On the other hand, each of the minute convex portions 4a of the grid portion 4 extends along a direction intersecting at an angle of about 90 ° with respect to the Y direction shown in the drawing (that is, the X direction). The convex portions 4a are alternately arranged along a direction orthogonal to the intersecting direction (that is, the Y direction). In this way, by making the concave portions 3a and the convex portions 3b intersect with the micro convex portions 4a, it becomes easier to form the micro convex portions 4a in the vicinity of the step between the concave portions 3a and the convex portions 3b. Become. What is necessary is just to set suitably the intersection angle of the extending direction of each recessed part 3a and each convex part 3b, and the extending direction of each micro convex part 4a. The crossing angles of 45 ° and 90 ° as an example above are preferable because they are often used in optical systems in general.

FIG. 5 is a schematic cross-sectional view showing a part of the diffraction structure portion 3 and the grid portion 4 in an enlarged manner. For convenience of explanation, hatching is omitted. Based on this FIG. 5, the structure of the diffraction structure part 3 and the grid part 4 is demonstrated still in detail. As shown in the figure, the mutual interval (period of the concavo-convex structure) of the convex portions 3b of the diffractive structure section 3 is δ (nm), and the mutual interval (grid period) of the minute convex portions 4a of the grid section 4 is d (nm). The wavelength of incident light is λ (nm). In the diffractive optical element 1 of the present embodiment, there is a relationship of the following expression (1) between the wavelength λ of the incident light and the diffractive structure and the grid structure.
d <λ and λ <δ (1)
Considering the case where the diffractive optical element 1 is used for visible light, the above-mentioned δ and d can be determined to be, for example, d = 300 nm and δ = 5.0 μm, respectively. That is, the grid period d may be a value that is about half of the wavelength λ of incident light or smaller. The period δ of the concavo-convex structure may be about several to 10 times the wavelength λ of incident light. By satisfying these relationships, it is possible to realize a minute convex portion 4a having a smaller size than the convex portion 3b.

Moreover, the period d and the depth h of the grid part 4 can be defined as the following formula (2), for example, in relation to the wavelength λ of the incident light.
d = 0.550λ, h = 0.207λ (2)
If the grid portion 4 is formed under such conditions, the reflected light can be made substantially zero by the grid portion 4. For example, when λ = 532 nm, d = 293 nm and h = 110 nm.

On the other hand, a suitable condition for the depth g of the concavo-convex structure of the diffractive structure 3 (the step between the concave portion 3a and the convex portion 3b) can be determined by the following equation (3).
g = λ / 2 (n−1) (3)
However, the refractive index of the material of the diffractive structure 3 is n. Equation (3) means that there is an appropriate depth for the wavelength λ. For example, when λ = 532 nm and n = 1.46, g = 578 nm.

The diffractive optical element 1 of the present embodiment has the above-described configuration. Next, a method for manufacturing the diffractive optical element 1 will be described.
6 and 7 are schematic process diagrams showing an example of a method for manufacturing a diffractive optical element (fine structure). A part of the cross section of the diffractive optical element 1 is shown enlarged.

First, the diffractive structure part 3 which consists of the recessed part 3a and the convex part 3b is formed in one surface of the board | substrate 2 (FIG. 6 (A)). This step can be realized using, for example, a well-known photolithography technique and etching technique. Specifically, a photosensitive film (resist film or the like; not shown) is formed on one surface of the substrate 2, and this photosensitive film is used using an exposure mask having an exposure pattern corresponding to each concave portion 3a and convex portion 3b. Is exposed and developed. Thereafter, dry etching or wet etching is performed using the developed photosensitive film as an etching mask. Thereby, a predetermined uneven shape is formed on one surface of the substrate 2 corresponding to the pattern of the exposure mask. Here, the board | substrate 2 is a quartz glass board | substrate as mentioned above, for example, The plate | board thickness is 1.2 mm, for example. Further, the step between the concave portion 3a and the convex portion 3b (that is, the depth of the diffractive structure portion 3) is, for example, 578 nm as described above. This depth g is controlled by the etching time or the like.

  Next, a photosensitive film 9 covering the diffractive structure 3 is formed on one surface of the substrate 2 (FIG. 6B). The photosensitive film 9 is, for example, a negative or positive resist film. The photosensitive film 9 can be formed using, for example, a spin coating method. The film thickness of the photosensitive film 9 may be set as appropriate, but it is desirable to cover at least all the regions overlapping the concave portions 3a and the convex portions 3b and to make the film surface substantially flat. However, due to the influence of the concave portion 3a and the convex portion 3b on the lower side of the photosensitive film 9, the surface of the photosensitive film 9 may have low flatness as illustrated.

  Next, a high refractive index liquid (liquid film) 10 covering the photosensitive film 9 is formed, and a transparent parallel plate (substrate) 11 is disposed opposite to the substrate 2 with the liquid 10 interposed therebetween (FIG. 6B). )). By being sandwiched between the parallel plate 11 and the substrate 2, the liquid 10 is held on the photosensitive film 9 as shown in the figure. It is desirable that at least the surface of the parallel plate 11 in contact with the liquid 10 has high flatness (for example, several nm level). The parallel plate 11 is made of, for example, a quartz glass substrate. Further, as shown in the figure, the parallel plate 11 preferably has an antireflection film 13 on the surface on which a plurality of laser beams to be described later are incident. The antireflection film 13 is, for example, a dielectric multilayer film.

  Here, the liquid 10 having a refractive index larger than 1 (that is, larger than the refractive index of air) and a value equal to (or substantially equal to) or lower than the refractive index of the photosensitive film 9 is used. As the liquid 10, for example, a high refractive index liquid used in immersion lithography at the time of manufacturing a semiconductor device can be used. In this case, the refractive index of the liquid 10 is about 1.53, for example. The refractive index of the photosensitive film 9 is, for example, about 1.70, and the refractive index of the parallel plate 11 is, for example, about 1.50. The refractive index of the liquid 10 is preferably as close as possible to the refractive index of the photosensitive film 9. In addition, each illustrated refractive index is a value in the wavelength (266 nm) of the laser mentioned later.

  Next, laser interference exposure is performed on the photosensitive film 9 formed on one surface of the substrate 2 through the liquid 10 and the parallel plate 11 (FIG. 6C). As a light source used for laser interference exposure, for example, a continuous wave DUV (Deep Ultra Violet) laser having a wavelength of 266 nm may be mentioned. The laser beam output from this laser is appropriately branched into two laser beams L1 and L2, and crossed at a predetermined angle as shown. Thereby, light (interference light) including interference fringes composed of periodic brightness and darkness is generated. The pitch of the interference fringes (brightness / darkness cycle) is determined by the crossing angle. By appropriately setting the crossing angle, the pitch of the interference fringes can be set to 293 nm. By irradiating the photosensitive film 9 with such interference light, a latent image pattern corresponding to the pitch of the interference fringes is formed on the photosensitive film 9. When the antireflection film 13 is provided on the parallel plate 11 as described above, the reflected light generated at the interface between the air layer and the parallel plate 11 is suppressed, and the exposure unevenness can be further reduced. . Depending on the accuracy required for the diffractive optical element 1 as a fine structure, a certain amount of exposure unevenness may be allowed, and the balance of the refractive indexes of the parallel plate 11, the liquid 10, and the photosensitive film 9 may be considered. Depending on the case, the reflected light at the interface between the air layer and the parallel plate 11 may be suppressed to an extent that there is no practical problem. For this reason, it is not essential to provide the antireflection film 13 on the parallel plate 11.

  Next, the photosensitive film 9 on which the latent image pattern is formed using the interference light is developed (FIG. 6D). As a result, a photosensitive film pattern 9a having a period corresponding to the pitch of the interference fringes is formed as shown. For example, when the pitch of the interference fringes is 293 nm, the period of the photosensitive film pattern 9a is also approximately 293 nm.

  Next, etching (for example, dry etching) is performed using the photosensitive film pattern 9a as a mask (FIG. 7A). As a result, the pattern of the photosensitive film pattern 9a is transferred to the substrate 2 as shown. Thereafter, the photosensitive film pattern 9a is removed (FIG. 7B). Thereby, the grid part 4 (namely, each minute convex part 4a) is formed on one surface of the board | substrate 2 along the surface of each recessed part 3a and the convex part 3b of the diffraction structure part 3 like illustration.

  6 and 7 show the method for manufacturing the diffractive optical element including the grid portion 4 of the one-dimensional grid. However, when the laser interference exposure shown in FIG. By performing exposure twice while changing the relative position of one surface of the substrate 2 by 90 degrees, a diffractive optical element including the grid portion 4 of a two-dimensional grid can be manufactured. Specifically, a two-dimensional lattice-like latent image pattern can be formed on the photosensitive film 9 by performing laser interference exposure twice by changing the relative position between the interference light and one surface of the substrate 2. By performing etching using such a latent image pattern, the grid portion 4 of a two-dimensional grid can be formed.

Next, a modified embodiment of the manufacturing method described above will be described. In the manufacturing method described above, interference light is generated by crossing a plurality of laser beams. However, by using a diffraction grating, it is possible to generate interference light using a single laser beam.
FIG. 8 is a schematic process diagram showing an example of a method for manufacturing a diffractive optical element (fine structure) according to this modified example corresponding to FIG. 6 in the manufacturing method described above.

Similar to the manufacturing method described above, first, the diffractive structure portion 3 including the concave portions 3a and the convex portions 3b is formed on one surface of the substrate 2 (FIG. 8A), and then the diffractive structure is formed on one surface of the substrate 2. A photosensitive film 9 covering the portion 3 is formed (FIG. 8B).
Next, similarly to the above-described manufacturing method, a high refractive index liquid (liquid film) 10 covering the photosensitive film 9 is formed, and the parallel plate (substrate) 11 is disposed opposite to the substrate 2 with the liquid 10 interposed therebetween. (FIG. 8B). Here, in this modification, a diffraction grating 14 described later is formed on the surface of the parallel plate 11 on the side on which the laser beam is incident.

  Next, laser interference exposure is performed on the photosensitive film 9 formed on one surface of the substrate 2 through the liquid 10 and the parallel plate 11 (FIG. 8C). As a light source used for laser interference exposure, the same manufacturing method as described above is used, and one laser beam L1 output from this laser is incident on the diffraction grating 14 at a predetermined angle. Thereby, light (interference light) including interference fringes composed of periodic brightness and darkness is generated. By irradiating the photosensitive film 9 with such interference light, a latent image pattern corresponding to the pitch of the interference fringes is formed on the photosensitive film 9 as in the above-described manufacturing method.

Next, similar to the manufacturing method described above, the photosensitive film 9 on which the latent image pattern is formed is developed using interference light (FIG. 8D). As a result, a photosensitive film pattern 9a having a period corresponding to the pitch of the interference fringes is formed as shown.
Next, similarly to the manufacturing method described above, etching is performed using the photosensitive film pattern 9a as a mask, and the photosensitive film pattern 9a is removed (see FIG. 7). Thereby, the grid part 4 (namely, each minute convex part 4a) is formed on one surface of the board | substrate 2 along the surface of each recessed part 3a and the convex part 3b of the diffraction structure part 3 like the manufacturing method mentioned above. The

FIG. 9 is an enlarged view of the diffraction grating 14.
The method of forming the convex portions 14a of the diffraction grating 14 includes, for example, forming a photosensitive film (resist film or the like; not shown) on one surface of a quartz parallel plate 11, and having an exposure pattern corresponding to each convex portion 14a. The photosensitive film is exposed and developed using an exposure mask. Thereafter, dry etching or wet etching is performed using the developed photosensitive film as an etching mask. Thereby, a predetermined uneven shape is formed on one surface of the parallel plate 11 corresponding to the pattern of the exposure mask.

As shown in the figure, the incident angle of the laser beam is θ _i , the diffraction order is m, the wavelength of the incident light is λ, and the mutual interval (period of the concavo-convex structure) of the convex portions 14a of the diffraction grating 14 is d1 (nm). . In the diffraction grating 14 of this modified embodiment, there is a relationship of the following equation (4) between the incident angle and wavelength λ of the incident light and the diffraction structure.
sin θ _i = mλ / (2d1) (4)

For example, when a laser beam having a wavelength λ = 266 nm is incident on the diffraction grating 14 having a mutual interval d1 = 140 nm and a width W = 70 nm and exposure is performed using 0th-order and −1st-order diffracted light, the diffraction order m = −. If 1, the incident angle θ _i = 71.8 °. At this time, the diffraction angle θ ₀ = 71.8 ° of the _0th order diffracted light and the diffraction angle θ ₋₁ = 71.8 ° of the −1st order diffracted light are obtained. The pitch (interval of light and dark) of the interference fringes formed by and is 140 nm. That is, an interference pattern similar to the interference pattern obtained by crossing two laser beams is formed.

The intensities of the 0th order and −1st order diffracted light can be adjusted by the depth D of the diffraction grating.
FIG. 10 shows the relationship between the diffraction efficiency of the diffracted light and the depth D of the diffraction grating 14 with the vertical axis representing the diffraction efficiency of the 0th order and −1st order diffracted light and the horizontal axis representing the depth D of the diffraction grating 14. It is a graph.
As shown in FIG. 10, it can be seen that by using the diffraction grating 14 having a depth D = about 150 nm, the intensities of the 0th-order and −1st-order diffracted light become substantially equal. Therefore, by setting the depth D of the diffraction grating 14 to about 150 nm, interference fringes with high contrast can be obtained.

FIG. 11 is a perspective view schematically showing a region in which the substrate 2 is irradiated with the laser beam.
The substrate 2 has a size of about 40 cm × about 50 cm, for example, and a plurality of liquid crystal panels are formed from the substrate 2. The intensity distribution of the laser beam has a normal distribution on the substrate 2. For this reason, as shown in FIG. 11, when the central portion of the substrate 2 is irradiated with a laser beam, a region R1 in which the intensity of the laser beam is relatively uniform and a region R2 in which the intensity variation is large are generated. Therefore, although interference fringes with high contrast can be obtained in the region R1, the contrast of the interference fringes is lowered in the region R2, and the intended latent image pattern of the photosensitive film 9 cannot be obtained. Therefore, it is necessary to shield the laser beam in the region R2 and irradiate only the region R1 with the laser beam.

FIG. 12A is a cross-sectional view showing a wider region of the parallel plate 11 by reducing the scale of FIG. 8B showing a state in which the parallel plate 11 is disposed opposite to the substrate 2 with the liquid 10 interposed therebetween. .
As shown in FIG. 12 (A), a light shielding layer 15 is formed on the surface of the parallel plate 11 on the liquid 10 side by using a light shielding material such as a metal film. The light shielding layer 15 is formed with an opening 15a corresponding to the size of one liquid crystal panel. The opening 15a is formed by patterning the light shielding layer 15 by a photolithography method, an etching method, or the like. The opening 15a is formed to be smaller than the region R1 shown in FIG.
When the dimension of the parallel plate 11 is equal to or less than the dimension of the substrate 2, it is preferable to form a plurality of openings 15a. Moreover, when the dimension of the parallel plate 11 is sufficiently larger than the dimension of the substrate 2, the opening 15a may be single.

FIG. 12B is an exploded perspective view showing a state in which a plurality of openings 15a are formed in the parallel plate 11 shown in FIG.
As shown in FIG. 12B, a shielding plate 16 that exposes one of the openings 15a is disposed on the incident side of the parallel plate 11 on the laser beam. As shown in FIG. 8C, when the parallel plate 11 provided with the diffraction grating 14 is irradiated with the laser beam L1, the opening 15a exposed from the shielding plate 16 is exposed as shown in FIG. In addition, the region R1 where the intensity of the laser beam shown in FIG. 11 is uniform is overlapped. As a result, the laser beam in the region R <b> 2 where the intensity variation is large can be shielded by the light shielding layer 15 and the shielding plate 16, thereby obtaining an interference fringe with high contrast. Therefore, the latent image pattern of the photosensitive film 9 can be formed uniformly.

  Next, the shielding plate 16 is rotated, or another opening 15a is exposed using another shielding plate, and the laser beam L1 is irradiated in the same manner. Thus, the latent image pattern of the photosensitive film 9 can be uniformly formed in the formation region of the plurality of liquid crystal panels on the substrate 2 by sequentially exposing the individual openings 15a and irradiating the laser beam L1.

FIG. 12C is an exploded perspective view showing a state in which a single opening 15a is formed in the parallel plate 11 shown in FIG.
As shown in FIG. 12C, the parallel plate 11 is formed sufficiently large with respect to the substrate 2. That is, the parallel plate 11 is covered with the light shielding layer 15 formed on the parallel plate 11 except for the portion exposed by the opening 15a in a state where the opening 15a is moved to the periphery of the substrate 2. It is formed as follows.

  Therefore, the parallel plate 11 and the substrate 2 are moved relative to each other to sequentially expose a plurality of liquid crystal panel formation regions in the opening 15a, and the laser R so that the region R1 having uniform laser beam intensity shown in FIG. The beam L1 can be irradiated. Thereby, the laser beam in the region R <b> 2 where the intensity variation is large can be shielded by the light shielding layer 15, and interference fringes with high contrast can be obtained. Therefore, the latent image pattern of the photosensitive film 9 can be uniformly formed in the formation region of the plurality of liquid crystal panels on the substrate 2.

  Next, another modified example of the manufacturing method described above will be described. In the manufacturing method described above, the parallel plate 11 is used to hold the liquid 10 having a high refractive index. However, by using a water-soluble film having a high refractive index instead of the liquid 10, the use of the parallel plate 11 can be used. It can be omitted.

  FIG. 13 is a schematic process diagram showing a method of manufacturing a diffractive optical element (fine structure) according to a modified example. Note that only the differences from the manufacturing method shown in FIGS. 6 and 7 are shown, and the common parts are not shown.

  First, in the same manner as described above, the diffractive structure portion 3 including the concave portion 3a and the convex portion 3b is formed on one surface of the substrate 2 (see FIG. 6A), and the photosensitive film 9 covering the diffractive structure portion 3 is formed. (See FIG. 6B).

  Thereafter, a water-soluble film 12 is formed on the photosensitive film 9 (FIG. 13A). The water-soluble film 12 is formed by, for example, a spin coating method. By appropriately adjusting the viscosity or the like of the water-soluble film 12, a step on the surface of the photosensitive film 9 can be relaxed by the water-soluble film 12. As such a water-soluble film, for example, an antireflection film for coating on the surface of a photoresist, referred to as TSP series of Tokyo Ohka Kogyo Co., Ltd. can be used. When using the water-soluble film | membrane 12, it is not necessary to use the parallel plate 11 like the said embodiment. As the water-soluble film 12, a film having a refractive index larger than 1 and a value equal to or lower than the refractive index of the photosensitive film 9 is used. For example, the refractive index of the water-soluble film 12 is about 1.40 to 1.50. The refractive index of the water-soluble film 12 is preferably as close as possible to the refractive index of the photosensitive film 9.

Next, laser interference exposure is performed on the photosensitive film 9 formed on one surface of the substrate 2 through the above-described water-soluble film 12 (FIG. 13B). Various conditions for laser interference exposure are as described above. As described above, the laser interference exposure may be performed twice.
Further, as shown by a virtual line (two-dot chain line) in FIG . 13B, a parallel plate 11 having the diffraction grating 14 shown in FIGS . 8 to 12 is arranged on the laser beam incident side of the water-soluble film 12. Then, laser interference exposure may be performed using either the laser beam L1 or L2.

  Next, the photosensitive film 9 is developed (see FIG. 6D). At this time, the water-soluble film 12 can also be easily removed because of its water solubility. Specifically, the water-soluble film 12 may be removed prior to exposure of the photosensitive film 9, or the photosensitive film 9 can be developed without removing the water-soluble film 12. That is, it is not essential to remove the water-soluble film 12 before the development of the photosensitive film 9. When development is performed with the water-soluble film 12 provided, a pattern is formed on the photosensitive film 9 and the water-soluble film 12 can be dissolved at the same time. Etching is performed using the obtained photosensitive film pattern 9a as a mask (see FIG. 7A), and the pattern of the photosensitive film pattern 9a is transferred to the substrate 2. Thereafter, the photosensitive film pattern 9a is removed (see FIG. 7B). Thereby, the grid part 4 (namely, each micro convex part 4a) is formed on one surface of the board | substrate 2 along the surface of each recessed part 3a of the diffraction structure part 3, and the convex part 3b.

  As described above, in the manufacturing method of the first embodiment, a liquid having a higher refractive index than air or a water-soluble film equivalent to air is disposed on the photosensitive film, and laser interference exposure is performed in this state. Do. By placing a liquid or water-soluble film, the photosensitive film is in contact with the photosensitive film as compared with the case where interference light is directly incident on the photosensitive film (that is, when exposure is performed in the state where the air and the photosensitive film are in contact). The refractive index difference from the medium (liquid and parallel plate) is reduced. Thereby, the diffraction of the interference light due to the unevenness of the surface of the photosensitive film is suppressed, and the disturbance of the intensity distribution of the interference light in the photosensitive film can be avoided. Therefore, according to the manufacturing method according to the present embodiment, it is possible to realize good exposure even on a surface with low flatness and to manufacture a fine microstructure.

  The diffractive optical element manufactured by the manufacturing method according to the present embodiment described above has a grid structure (subwavelength structure) superimposed on the surface of a diffractive structure formed on the surface of a glass substrate. It is used for applications such as branching a beam into a plurality of beams and beam shaping such as changing the energy distribution. Due to the antireflection function exhibited by the subwavelength structure, it is possible to reduce the reflection loss of incident light and achieve high light utilization efficiency. Such a diffractive optical element is particularly suitable when using light in the ultraviolet or infrared region, for which there is no suitable antireflection film material at present.

  In the first embodiment, the diffractive optical element is shown as an example of the fine structure. However, the scope of the present invention is not limited to this, and can be applied when manufacturing various fine structures. It is. Further, although quartz glass has been described as an example of the substrate 2, a semiconductor substrate (for example, a silicon substrate) or a metal substrate (for example, a nickel substrate) can also be used as the substrate 2. A fine structure formed on a semiconductor substrate or a metal substrate can also be used as a mold.

(Second Embodiment)
FIG. 14 shows a cross-sectional structure of a diffractive optical element which is an example of a fine structure according to the second embodiment.
It is a schematic diagram. A diffractive optical element (optical element) 31 of this embodiment shown in FIG. 14 includes a substrate 32, a diffractive structure part 33, and a grid part (non-diffractive structure part) 34. Among these configurations, the substrate 32 and the diffractive structure section 33 are common to the substrate 2 and the diffractive structure section 3 in the first embodiment described above, and detailed description thereof will be omitted. The diffractive optical element 31 in the present embodiment is different from the diffractive optical element 1 in the first embodiment in that the grid portion 34 includes a plurality of minute convex portions 34a made of metal.

The grid part 34 is provided on one surface of the substrate 32 and along the upper surface of the diffraction structure part 33. Grid unit 34 of this embodiment includes a plurality of minute projections 3 4a is smaller than each of the plurality of convex portions 3b of the diffractive structure 3 described above. Each fine convex portions 3 4a is composed of a metallic material. In the present embodiment, the constituent material of the fine convex portions 3 4a is aluminum, for example. Each fine convex portions 3 4a of the grid portion 34, similar to that shown in FIG. 2 (A) in the first embodiment described above, the structure of a stripe shape extending in one direction (shown in the Y-direction) It is. These minute projections 3 4a is, for example, periodically arranged along the X direction. Such a grid portion 34 has a polarization separation function. That is, the diffractive optical element 31 of this embodiment has both a diffraction function by the diffraction structure portion 33 and a polarization separation function by the grid portion 34.

FIG. 15 is a schematic perspective view showing the diffractive structure portion 33 and the grid portion 34 partially enlarged. For a preferred embodiment of the arrangement relation between the fine convex portions 3 4a and the diffraction structure portion 3 3 of the grid 34 is one-dimensional grid is the same as the first embodiment described above. That is, the mutual arrangement relationship between the diffractive structure portion 33 and the grid portion 34 can be, for example, as shown in FIG. Specifically, in the example shown in FIG. 15A, each concave portion 33a and each convex portion 33b of the diffractive structure portion 33 extend along the Y direction shown in the drawing, and these concave portions 33a and convex portions are formed. The portions 33b are alternately arranged along the X direction. Similarly, each minute convex part 34a of the grid part 34 extends along the Y direction shown in the drawing, and these minute convex parts 34a are alternately arranged along the X direction. That is, the extending direction of each concave portion 33a and each convex portion 33b is parallel to the extending direction of the minute convex portion 34a.

  Further, the mutual arrangement relationship between the diffractive structure portion 33 and the grid portion 34 is such that the extending direction of each concave portion 33a and each convex portion 33b and each minute convexity are shown in FIG. 15 (B) and FIG. 15 (C). It is also preferable that the extending direction of the portion 34a intersects at a certain angle. Specifically, in the example shown in FIG. 15B, each concave portion 33a and each convex portion 33b of the diffractive structure portion 33 extend along the Y direction shown in the drawing, and these concave portions 33a and convex portions are formed. The portions 33b are alternately arranged along the X direction. On the other hand, each minute convex portion 34a of the grid portion 34 extends along a direction intersecting at an angle of approximately 45 ° with respect to the Y direction shown in the figure, and these minute convex portions 34a They are alternately arranged along the direction orthogonal to the intersecting direction.

  In the example shown in FIG. 15C, each concave portion 33a and each convex portion 33b of the diffractive structure portion 33 extend along the Y direction shown in the drawing, and these concave portions 33a and convex portions 33b are in the X direction. Are arranged alternately. On the other hand, each minute convex part 34a of the grid part 34 extends along a direction (that is, the X direction) intersecting at an angle of about 90 ° with respect to the Y direction shown in the drawing, and these minute protrusions 34a. The convex portions 34a are alternately arranged along a direction orthogonal to the intersecting direction (that is, the Y direction). In this way, by forming the concave portions 33a and the convex portions 33b and the minute convex portions 34a to cross each other, it becomes easier to form the minute convex portions 34a in the vicinity of the step between the concave portions 33a and the convex portions 33b. Become. What is necessary is just to set suitably the crossing angle of the extending direction of each recessed part 33a and each convex part 33b, and the extending direction of each minute convex part 34a. The crossing angles of 45 ° and 90 ° as an example above are preferable because they are often used in optical systems in general.

The diffractive optical element 31 of the present embodiment has the above-described configuration. Next, a method for manufacturing the diffractive optical element 31 will be described.
16 and 17 are schematic process diagrams showing an example of a method for manufacturing a diffractive optical element (fine structure). A part of the cross section of the diffractive optical element 31 is enlarged. Note that description of matters common to the first embodiment is omitted.

  First, the diffractive structure 33 including the concave portion 33a and the convex portion 33b is formed on one surface of the substrate 32 (FIG. 16A). This step can be realized using, for example, a well-known photolithography technique and etching technique. Next, a metal film 43 covering the diffractive structure portion 33 is formed, and an antireflection film (first antireflection film) 44 covering the metal film 43 is further formed (FIG. 16A). As described above, for example, an aluminum film having a thickness of about 120 nm is suitable for the metal film 43, and the metal film 43 is formed using a physical vapor deposition method such as a sputtering method. As the antireflection film 44, for example, a SnO2 film having a thickness of about 90 nm is suitable. A SiON film can also be used as the antireflection film 44.

  Next, a photosensitive film 39 that covers the metal film 43 and the antireflection film 44 on the diffraction structure 33 is formed on one surface of the substrate 2 (FIG. 16B). The details of this step are the same as in the case of the first embodiment described above.

  Next, a high refractive index liquid (liquid film) 40 is disposed on the photosensitive film 39, and a transparent parallel plate 41 is disposed opposite to the substrate 32 with the liquid 40 interposed therebetween (FIG. 16C). . The details of this step are the same as in the case of the first embodiment described above. That is, as shown in the figure, the parallel plate 41 preferably has an antireflection film (second antireflection film) 45 on the surface on which a plurality of laser beams described later are incident. The antireflection film 45 here is, for example, a dielectric multilayer film.

Next, laser interference exposure is performed on the photosensitive film 39 formed on one surface of the substrate 32 through the liquid 40 and the parallel plate 41 (FIG. 16D). The details of this step are the same as in the case of the first embodiment described above. Through this step, a latent image pattern corresponding to the pitch of the interference fringes is formed on the photosensitive film 39. When the antireflection film 45 is provided on the parallel plate 41 as described above, reflected light generated at the interface between the air layer and the parallel plate 41 is suppressed, and uneven exposure can be further reduced. . Depending on the accuracy required for the diffractive optical element 31 as a fine structure, a certain amount of exposure unevenness may be allowed, and the balance of the refractive indexes of the parallel plate 41, the liquid 40, and the photosensitive film 39 may be considered. Depending on the case, the reflected light at the interface between the air layer and the parallel plate 41 may be suppressed to a practically acceptable level. For this reason, it is not essential to provide the antireflection film 45 on the parallel plate 41.

  Next, the photosensitive film 39 on which the latent image pattern is formed using the interference light is developed (FIG. 17A). As a result, a photosensitive film pattern 39a having a period corresponding to the pitch of the interference fringes is formed as shown.

  Next, etching (for example, dry etching) is performed using the photosensitive film pattern 39a as a mask (FIG. 17B). Thereby, the pattern of the photosensitive film pattern 39 a is transferred to the antireflection film 44 and the metal film 43 as shown in the figure. Thereafter, the photosensitive film pattern 39a is removed (FIG. 17B). As a result, as shown in the drawing, the grid portions 34 (that is, the minute convex portions 34a) are formed on one surface of the substrate 32 along the surfaces of the concave portions 33a and the convex portions 33b of the diffraction structure portion 33. The film pattern 44a obtained by transferring the pattern of the photosensitive film pattern 39a to the antireflection film 44 is removed as necessary (see FIG. 17C) or left as it is.

Next, a modified embodiment of the manufacturing method described above will be described.
First, similarly to the above-described manufacturing method, the diffractive structure portion 33 including the concave portion 33a and the convex portion 33b is formed on one surface of the substrate 32, the metal film 43 covering the diffractive structure portion 33 is formed, and the metal film 43 is further formed. A covering antireflection film (first antireflection film) 44 is formed (FIG. 18A).
Next, similarly to the manufacturing method described above, a photosensitive film 39 covering the metal film 43 and the antireflection film 44 on the diffraction structure portion 33 is formed (FIG. 18B).

  Next, a liquid (liquid film) 40 having a high refractive index is disposed on the photosensitive film 39, and a transparent parallel plate 41 is disposed opposite to the substrate 32 with the liquid 40 interposed therebetween (FIG. 18C). . Here, in this modified example, a diffraction grating 46 similar to that of the modified example of the first embodiment is formed on the surface of the parallel plate 41 on the side on which the laser beam is incident.

Next, the photosensitive film 39 formed on one surface of the substrate 3 2, a laser interference exposure through a liquid 10, and parallel flat plate 11 described above is carried out (FIG. 18 (D)). As a light source used for laser interference exposure, the same manufacturing method as described above is used, and one laser beam L1 output from this laser is incident on the diffraction grating 46 at a predetermined angle. Thereby, light (interference light) including interference fringes composed of periodic brightness and darkness is generated. By irradiating the photosensitive film 39 with such interference light, a latent image pattern corresponding to the pitch of the interference fringes is formed on the photosensitive film 39 as in the above-described manufacturing method.

  Next, as in the manufacturing method described above, the photosensitive film 39 is developed, and etching is performed using the photosensitive film pattern 39a as a mask to remove the photosensitive film pattern 39a (see FIG. 17). As a result, as shown in the drawing, the grid portions 34 (that is, the minute convex portions 34a) are formed on one surface of the substrate 32 along the surfaces of the concave portions 33a and the convex portions 33b of the diffraction structure portion 33.

  Next, another modified example of the manufacturing method described above will be described. In the manufacturing method described above, the liquid 40 having a high refractive index is held using the parallel plate 41. However, the use of the parallel plate 41 may be omitted by using a water-soluble film instead of the liquid 40. It becomes possible.

  FIG. 19 is a schematic process diagram showing a method of manufacturing a diffractive optical element (fine structure) according to a modified example. It should be noted that only the differences from the manufacturing method shown in FIGS. 16 and 17 are shown, and the common parts are not shown.

First, in the same manner as described above, the diffractive structure 3 3 consisting of the recess 33a and the convex portion 33b on one surface of the substrate 32, the metal film 43 and the antireflection film 44 is formed (see FIG. 16 (A)) The antireflection film 44 Is formed (see FIG. 16B).

Thereafter, a water-soluble film 42 is formed on the photosensitive film 39 (FIG. 19A). The details of the water-soluble film 42 are the same as those of the water-soluble film 12 in the modified example of the first embodiment described above.

Next, laser interference exposure is performed on the photosensitive film 39 formed on one surface of the substrate 32 through the above-described water-soluble film 42 (FIG. 19B). Various conditions for laser interference exposure are as described above.
Further, as shown by a virtual line (two-dot chain line) in FIG. 19B, a parallel plate 41 provided with the diffraction grating 46 shown in FIG. 18 is disposed on the laser beam incident side of the water-soluble film 42, and L1 Alternatively, laser interference exposure may be performed using either one of the laser beams L2.

  Next, the photosensitive film 39 is developed (see FIG. 17A). At this time, the water-soluble film 42 can be easily removed because of its water-solubility. Specifically, the water-soluble film 42 may be removed prior to the exposure of the photosensitive film 39, or the photosensitive film 39 can be developed without removing the water-soluble film 42. That is, it is not essential to remove the water-soluble film 42 before the development of the photosensitive film 39. When development is performed with the water-soluble film 42 provided, a pattern is formed on the photosensitive film 39, and the water-soluble film 42 can be dissolved simultaneously. Etching is performed using the obtained photosensitive film pattern 39a as a mask (see FIG. 17B), and the pattern of the photosensitive film pattern 39a is transferred to the metal film 43 and the antireflection film 44. Thereafter, the photosensitive film pattern 39a is removed (see FIG. 17B). Thereby, the grid part 34 (namely, each micro convex part 34a) is formed on one surface of the board | substrate 32 along the surface of each recessed part 33a of the diffraction structure part 33, and the convex part 33b.

  Thus, also in the manufacturing method of the second embodiment, a liquid having a higher refractive index than air or a water-soluble film equivalent to air is disposed on the photosensitive film, and laser interference exposure is performed in this state. Do. By placing a liquid or water-soluble film, the photosensitive film is in contact with the photosensitive film as compared with the case where interference light is directly incident on the photosensitive film (that is, when exposure is performed in the state where the air and the photosensitive film are in contact). The refractive index difference from the medium (liquid and parallel plate) is reduced. Thereby, the diffraction of the interference light due to the unevenness of the surface of the photosensitive film is suppressed, and the disturbance of the intensity distribution of the interference light in the photosensitive film can be avoided. Therefore, according to the manufacturing method according to the present embodiment, it is possible to realize good exposure even on a surface with low flatness and to manufacture a fine microstructure.

  The diffractive optical element manufactured by the manufacturing method according to the above embodiment has a one-dimensional grid structure (subwavelength structure) made of a metal film superimposed on the surface of a diffractive structure formed on the surface of a glass substrate. For example, it is used for a purpose of diffusing an incident laser beam or a shape of a beam such as changing an energy distribution. Due to the polarization separation function exhibited by the sub-wavelength structure, only one polarization component of incident light can be diffusely reflected with high light utilization efficiency. A diffractive optical element having such a polarization separation function is preferably used, for example, as a component constituting a display unit of a portable device such as a mobile phone or as a component constituting a light modulation unit of a liquid crystal projector.

  In the second embodiment, a diffractive optical element is shown as an example of a fine structure. However, the scope of application of the present invention is not limited to this, and can be applied when manufacturing various fine structures. It is.

(Modified embodiment)
Below, the deformation | transformation implementation aspect about each embodiment mentioned above is demonstrated.

  In each of the above-described embodiments, the diffractive structure is formed by performing processing such as etching on the one surface side of the substrate. However, other manufacturing methods may be employed. Specifically, a polymer (polymer resin) film that is transparent to the light wavelength to be used is formed on one surface of the substrate, and then photomask exposure and wet etching are performed on the polymer film. It is also possible to form a diffractive optical element similar to the above. An example of the structure of an optical element formed by this method is shown in FIG. A diffractive optical element 201 shown in FIG. 20 corresponds to the first embodiment described above, and a diffractive structure 203 and a grid 204 formed on one surface side of a substrate 202 such as glass using a polymer film. Is arranged. The diffractive structure part 203 includes a concave part 203a and a convex part 203b, and a grid part 204 composed of a plurality of minute convex parts 204a is arranged along the surfaces of the concave part 203a and the convex part 203b. Although not described and illustrated, the same applies to the second embodiment.

  In addition to the above, mold forming is possible, and a substrate having a diffractive structure is integrally formed using high refractive index glass (n = 2.0) that is transparent to the light wavelength used. Also good. In this case, since the refractive index is high, the depth g of the diffractive structure portion can be further reduced, which is preferable in forming the grid portion. Alternatively, the diffraction structure can be formed by forming another film (for example, an inorganic film such as SiO2) on the substrate and selectively etching the film. An example of the structure of an optical element formed by this method is shown in FIG. An optical element 301 shown in FIG. 21 corresponds to the first embodiment described above, and a diffractive structure portion 303 formed using a film such as SiO 2 is disposed on one surface side of a substrate 302 such as glass. ing. The diffractive structure portion 303 includes a concave portion 303a and a convex portion 303b, and a grid portion 304 including a plurality of minute convex portions 304a is disposed along the surfaces of the concave portion 303a and the convex portion 303b. Although not described and illustrated, the same applies to the second embodiment.

  The uneven structure on the one surface side of the substrate is not the one that exhibits some function like the diffractive structure part in the above embodiment, but the substrate is originally uneven, such as when the surface flatness of the substrate is low. The present invention can be applied even if it has a structure.

It is a schematic diagram which shows the cross-section of the optical element which concerns on 1st Embodiment. It is the typical perspective view which expanded and showed a part of grid part. It is the typical perspective view which expanded and showed a part of diffraction structure part. It is a model perspective view which expands and shows a diffraction structure part and a grid part partially. It is the schematic cross section which expanded and showed a diffraction structure part and a part of grid part. It is a schematic cross section which shows the manufacturing method of a diffractive optical element (fine structure). It is a schematic cross section which shows the manufacturing method of a diffractive optical element (fine structure). It is a schematic cross section which shows the manufacturing method of the diffractive optical element (fine structure) which concerns on a modified example. It is an enlarged view of a parallel plate. It is a graph which shows the relationship between the diffraction efficiency of diffracted light, and the depth of a diffraction grating. It is the perspective view which represented typically the area | region where a laser beam is irradiated to a board | substrate. (A) is a figure which shows the manufacturing method of the diffractive optical element (fine structure) which concerns on a modification, (A) is a schematic cross section, (B) and (C) are typical perspective views. It is a schematic process drawing which shows the manufacturing method of the diffractive optical element which concerns on a modified example. It is a schematic diagram which shows the cross-section of the optical element which concerns on 2nd Embodiment. It is a model perspective view which expands and shows a diffraction structure part and a grid part partially. It is a schematic cross section which shows the manufacturing method of a diffractive optical element (fine structure). It is a schematic cross section which shows the manufacturing method of a diffractive optical element (fine structure). It is a schematic process drawing which shows the manufacturing method of the diffractive optical element which concerns on a modified example. It is a schematic process drawing which shows the manufacturing method of the diffractive optical element which concerns on a modified example. It is a schematic diagram which shows the cross-section of the diffractive optical element of other embodiment. It is a schematic diagram which shows the cross-section of the diffractive optical element of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diffractive optical element (micro structure), 2 ... Board | substrate, 3 ... Diffraction structure part, 3a ... Concave part, 3b ... Convex part, 4 ... Grid part, 4a ... Micro convex part, 9 ... Photosensitive film, 9a ... Photosensitive film Pattern: 10 ... Liquid, 11 ... Parallel plate, 12 ... Water-soluble film, 13 ... Antireflection film, 14 ... Diffraction grating, 15 ... Light shielding layer, 15a ... Opening, 16 ... Shielding plate

Claims (17)

A manufacturing method of a fine structure comprising: a substrate having a plurality of convex portions on at least one surface; and a plurality of micro convex portions provided on one surface of the substrate and smaller than each of the plurality of convex portions,
(A) forming a photosensitive film on the plurality of convex portions provided on the substrate;
(B) disposing a liquid on the photosensitive film;
(C) placing a transparent substrate opposite to the substrate across the liquid;
(D) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the transparent substrate and the liquid;
(E) developing the photosensitive film after draining the liquid and the transparent substrate;
(F) etching the substrate using the photoresist pattern formed in (e) as a mask;
Including
In (c), using a parallel plate provided with a diffraction grating, the parallel plate is disposed on the liquid so that the surface on which the diffraction grating is provided is opposite to the liquid,
In (d), the interference light is generated by causing a single laser beam to enter the diffraction grating,
The refractive index of the liquid in (b) is a value larger than 1 and equal to or lower than the refractive index of the photosensitive film,
A manufacturing method of a fine structure. The method for manufacturing a microstructure according to claim 1 , wherein in (c), a light shielding layer having an opening is formed in the transparent substrate. In (c), a plurality of the openings are formed,
3. The method for manufacturing a microstructure according to claim 2 , wherein in (d), a shielding plate that individually exposes the openings is arranged on the transparent substrate, and the interference light is irradiated to a plurality of regions. . In (c), a single opening is formed,
The method for manufacturing a microstructure according to claim 2 , wherein in (d), the transparent substrate is moved to irradiate a plurality of regions with the interference light. A manufacturing method of a fine structure comprising: a substrate having a plurality of convex portions on at least one surface; and a plurality of micro convex portions provided on one surface of the substrate and smaller than each of the plurality of convex portions,
(A) forming a photosensitive film on the plurality of convex portions provided on the substrate;
(B) forming a water-soluble film on the photosensitive film;
(C) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the water-soluble film;
(D) developing the photosensitive film;
(E) etching the substrate using the photoresist pattern formed in (d) as a mask;
Including
In (b), a parallel plate provided with a diffraction grating is disposed on the incident side of the laser beam of the water-soluble film,
In (c), the interference light is generated by diffracting a single laser beam by the diffraction grating,
The refractive index of the water-soluble film in (b) is greater than 1 and equal to or lower than the refractive index of the photosensitive film.
A manufacturing method of a fine structure. 6. The method of manufacturing a microstructure according to claim 5 , wherein (d) develops the photosensitive film after removing the water-soluble film. The method for manufacturing a microstructure according to claim 1, 5, or 6 , further comprising forming the plurality of convex portions on one surface side of the substrate prior to the step (a). After the substrate has been etched, the removing the photoresist pattern further includes a method for manufacturing a microstructure according to claim 1 or 5 or 6. A manufacturing method of a fine structure comprising: a substrate having a plurality of convex portions on at least one surface; and a plurality of micro convex portions provided on one surface of the substrate and smaller than each of the plurality of convex portions,
(A) forming a metal film on the plurality of convex portions provided on the substrate;
(B) forming a first antireflection film on the metal film;
(C) forming a photosensitive film on the first antireflection film;
(D) disposing a liquid on the photosensitive film;
(E) placing the transparent substrate opposite to the substrate with the liquid interposed therebetween;
(F) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the transparent substrate and the liquid;
(G) developing the photosensitive film after removing the liquid and the transparent substrate;
(H) etching the metal film and the first antireflection film using the photoresist pattern formed in (g) as a mask;
Including
In (e), using a parallel plate provided with a diffraction grating, the parallel plate is disposed on the liquid so that the surface on which the diffraction grating is provided is opposite to the liquid,
In (f), the interference light is generated by causing a single laser beam to enter the diffraction grating,
The refractive index of the liquid in (d) is a value greater than 1 and equal to or lower than the refractive index of the photosensitive film.
A manufacturing method of a fine structure. The method for manufacturing a microstructure according to claim 9 , wherein in (e), a light shielding layer having an opening is formed in the transparent substrate. In (e), a plurality of the openings are formed,
Wherein in (f), said openings successively arranged a shielding plate exposing individually illuminating said interference light into a plurality of regions on the transparent substrate, producing a fine structure according to claim 1 0 Method. In (e), a single opening is formed,
In the (f), the transparent substrate is moved to irradiate the interference light into a plurality of regions, method for manufacturing a microstructure according to claim 1 0. A manufacturing method of a fine structure comprising: a substrate having a plurality of convex portions on at least one surface; and a plurality of micro convex portions provided on one surface of the substrate and smaller than each of the plurality of convex portions,
(A) forming a metal film on the plurality of convex portions provided on the substrate;
(B) forming a first antireflection film on the metal film;
(C) forming a photosensitive film on the first antireflection film;
(D) forming a water-soluble film on the photosensitive film;
(E) generating interference light using a laser beam and irradiating the photosensitive film with the interference light through the water-soluble film;
(F) developing the photosensitive film;
(G) etching the metal film and the first antireflection film using the photoresist pattern formed in (f) as a mask;
Including
In (b), a parallel plate provided with a diffraction grating is disposed on the incident side of the laser beam of the water-soluble film,
In (c), the interference light is generated by diffracting a single laser beam by the diffraction grating,
The refractive index of the water-soluble film in (d) is greater than 1 and equal to or lower than the refractive index of the photosensitive film.
A manufacturing method of a fine structure. Wherein (f), the developed photoresist after discharge said water-soluble film, method for manufacturing a microstructure according to claim 1 3. The prior (a), the forming the plurality of protrusions on one surface of said substrate, further comprising a method for manufacturing a microstructure according to claim 9 or 1 3. After the metal film and the first anti-reflection film has been etched, the photoresist pattern to remove, further comprising a method for manufacturing a microstructure according to claim 9 or 1 3. The method of manufacturing a microstructure according to claim 16 , further comprising removing the first antireflection film after the photosensitive film pattern is removed.

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