JP2017161942A - Interference exposure equipment and interference exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interference exposure equipment and an interference exposure method, which can obtain a uniform interference pattern in an exposure substrate by preventing stray light from influencing.SOLUTION: Provided with light shielding opening parts 18A and 18B having an opening part shielding a periphery of a light bundle emitted from special filters 17A and 17B, and an exposure mask 19 that is adjacently arranged on an exposure substrate and masks a periphery of an interference exposure region formed by light bundle emitted from the opening part. Since in addition to reduction of unnecessary stray light to the interference exposure region by the light shielding opening plates 18A and 18B, an influence of diffraction fluctuation of an exposure region periphery by an opening edge of the light shielding opening plates 18A and 18B is removed by the exposure mask 19, a uniform interference pattern may be obtained on the exposure substrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an interference exposure apparatus and an interference exposure method for synthesizing two light beams on an exposure substrate and forming a periodic pattern by the interference fringes.

  In recent years, an optical element using a fine concavo-convex structure having a period smaller than the wavelength of light, a so-called sub-wavelength structure, has attracted attention. When the fine concavo-convex structure is smaller than the wavelength of light used, the transmittance and reflectance have polarization dependency.

  As means for producing such a fine concavo-convex structure, there are exposure by an electron beam, projection exposure by a stepper, interference exposure method using interference of a plurality of light beams, and the like.

  In the exposure with an electron beam, an arbitrary fine pattern can be formed by scanning the condensed electron beam on a substrate coated with an electron beam photoresist. However, since this method physically scans and draws an electron beam, it takes a very long time for exposure and is difficult to apply to large area exposure.

  In the exposure by the stepper, a fine pattern is transferred to the photoresist by performing reduced projection exposure through a mask on which a desired pattern is formed. The shape can be an arbitrary pattern, and there is an advantage that processing in a large area and mass productivity are rich. However, in the case of forming a fine pattern, it is inevitable that the apparatus becomes complicated and large in size, such as a restriction due to the diffraction limit of the optical system and a device for improving the optical system.

  Although the interference exposure is limited only to a lattice pattern, it has a feature that a large area exposure is possible with a relatively simple optical system. Since the sub-wavelength structure as an optical element is sufficient by repeating a simple pattern, the interference exposure method is one of the optimum applications.

  FIG. 24 is a diagram showing an optical system of a conventional general interference exposure apparatus. FIG. 24 shows an optical system called a Mach-Zehnder type, which includes a laser light source 111, a beam expander 112 that expands the laser beam diameter in parallel, a polarization beam splitter (PBS) 113, and a PBS 13. Spatial filters 117A and 117B having a wave plate 114, reflectors 115A and 115B, objective lenses 116A and 116B, and pinholes having substantially the same diameter as the focused beam spot diameter. With. This interference exposure apparatus, for example, splits light (s-polarized light) having a wavelength of 266 nm using a YAG quadruple wave solid-state laser into two optical paths with PBS 113, and then makes the light incident on the exposure substrate 120 from two directions. Perform interference exposure.

  The contrast (black / white ratio) of interference fringes generated when a plurality of light beams are combined depends on the coherency (coherence) of the light beams. There are two types of coherency, which are determined by the monochromaticity (purity) of the wavelength of light contained in the light beam (longitudinal (time) coherency) and that determined by fluctuations in the phase of the light beam (lateral (space) coherency). For example, when the vertical coherency is insufficient, the interference fringe contrast decreases if the optical path length difference between the two light beams increases. When the horizontal coherency is insufficient, the interference pattern does not form a beautiful stripe pattern and approaches a random speckle pattern.

  In order to form stable and high-quality interference fringes as an exposure apparatus, it is necessary to sufficiently maintain such coherency. In general, a laser with high wavelength monochromaticity is selected as the light source, and a plurality of higher-order modes generated in the internal resonator of the laser need to be sufficiently suppressed in order to secure lateral coherency. In addition, when passing through an optical component such as a lens, the phase plane of the reflected light or the light passing through the surface accuracy will be disturbed, and the above (lateral coherency) will be reduced. It is necessary to remove the phase disturbance.

  Thus, in interference exposure, high coherency of the light source is a necessary condition, but since coherency is high, instability due to unnecessary interference components in exposure increases. Among unnecessary interference components, a large one becomes “stray light” which is a scattering component or a reflection component generated away from the original optical path. Since the phenomenon of interference is added not by intensity but by amplitude, the influence of stray light is amplified. For example, stray light having an intensity ratio of 1% causes a 10% change in interference fringe intensity.

  As for the “stray light”, for example, Patent Document 1 discloses the “stray light” due to scattering at the end face of the substrate. In this case, it is described that scattered stray light is reduced by setting the chamfer angle of the substrate end face to a desired angle with respect to the incident light flux. Patent Document 2 discloses reflected stray light from the back surface of the substrate. In this case, it is described that reflection stray light is reduced by forming an antireflection film for the exposure wavelength on the back surface. Moreover, although it is not an influence with respect to a stray light, in patent document 3, the example which applies a mask or a shielding shutter to two-beam interference exposure as a method of restrict | limiting an exposure area | region is disclosed.

  However, the techniques of Patent Documents 1 to 3 cannot prevent the influence of stray light when the light emitted from the spatial filter hits the surface of the vibration isolation table near the exposure substrate, the exposure jig, the screw, or the like.

JP 2010-60621 A JP 2010-60587 A JP-A-9-184909

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an interference exposure apparatus and an interference exposure method capable of preventing the influence of stray light and obtaining uniform interference fringes on an exposure substrate.

  As a result of intensive studies, the inventor shields the peripheral edge of the light beam emitted from the spatial filter with a light-shielding aperture plate, reduces stray light so that light strikes an area used for exposure, and further reduces the light-shield aperture plate. It has been found that a uniform interference fringe can be obtained on the exposure substrate by masking the diffraction fluctuation of the interference fringe intensity caused by the opening end (ridge line portion) with an exposure mask, and the present invention has been achieved.

  That is, the interference exposure apparatus according to the present invention includes a light-shielding aperture plate having an opening that shields the peripheral edge of the light beam emitted from the spatial filter, and an adjacently disposed on the exposure substrate, and the light beam emitted from the opening portion. And an exposure mask that masks the periphery of the interference exposure region to be formed.

  In the interference exposure method according to the present invention, the periphery of the light beam emitted from the spatial filter is shielded by the light-shielding aperture plate having the aperture, and is emitted from the aperture by the exposure mask arranged adjacent to the exposure substrate. The periphery of the interference exposure area formed by the emitted light beam is masked.

  An exposure jig according to the present invention includes a first holding member having a frame portion having the same shape as the edge portion of the exposure substrate, and a second holding member having an opening having the same shape as the exposure substrate. The thickness of the peripheral edge portion of the opening of the second holding member is 0.5 mm or less.

  According to the present invention, unnecessary stray light to the interference exposure area is reduced by the light shielding aperture plate, and the influence of diffraction fluctuations at the periphery of the exposure area due to the opening end of the light shielding aperture plate is removed by the exposure mask. Interference fringes can be obtained.

It is a figure which shows a Mach-Zehnder type optical system. It is a figure which shows a Lloyd Mirror type | mold optical system. It is a figure for demonstrating the diffraction fluctuation produced by the opening end (ridgeline part) of a light-shielding aperture plate. It is a figure which shows an exposure board | substrate surface. It is a figure which shows the light intensity distribution of a X direction. It is a figure which shows the experimental example of Fresnel diffraction in the optical system of a Lloyd Mirror type | mold interference exposure apparatus. It is a photograph which shows the Fresnel diffraction fringe by the opening edge of a light-shielding aperture plate. It is an enlarged photograph which shows the Fresnel diffraction fringe by the opening edge of a light-shielding aperture plate. It is a figure which shows the example which has arrange | positioned the light-shielding aperture plate near the exposure board | substrate side. It is a figure which shows the example which has arrange | positioned the light-shielding aperture plate near the spatial filter side. It is a graph which shows the influence of a stray light with respect to the light intensity distribution on an exposure board | substrate at the time of adding 4% of stray light by intensity ratio. It is a graph which shows the change of the maximum intensity | strength of an interference fringe with respect to the intensity | strength of a stray light / interference light. It is a figure which shows the experiment example when the distance z of an exposure board | substrate and a light-shielding opening is 800 mm. It is a graph which shows the calculation result of a diffraction integral value. It is a figure which shows the structural example of a Mach-Zehnder type optical system. It is sectional drawing which shows an example of the exposure jig | tool in this Embodiment. It is sectional drawing which shows the chamfering process of the conventional mask ridgeline part. It is a top view which shows an exposure jig. It is sectional drawing which shows an exposure jig. It is a schematic diagram which shows a lattice board | substrate. It is an enlarged photograph in the position A on a lattice board | substrate. It is an enlarged photograph in position B on a lattice substrate. It is an enlarged photograph in the position C on a lattice board | substrate. It is a figure which shows the conventional Mach-Zehnder type optical system.

Hereinafter, embodiments of the present invention (hereinafter also referred to as the present embodiment) will be described in detail in the following order with reference to the drawings.
1. Interferometric exposure system (Figs. 1 and 2)
2. Effect of diffraction fluctuations (Figs. 3-8)
3. Reduction of stray light by light shielding aperture plate (FIGS. 9 to 15)
4). Reduction of interference fluctuation by exposure jig (Figs. 16 and 17)
5. 5. Interference exposure method Example (FIGS. 18 to 23)

<1. Interference exposure system>
FIG. 1 is a diagram showing a Mach-Zehnder type optical system in the present embodiment. This interference exposure apparatus is installed in one optical path divided into two by a laser light source 11, a beam expander 12 that expands the laser beam diameter in parallel, a polarization beam splitter (PBS) 13, and the PBS 13. From the wavelength plate 14, the reflecting plates 15A and 15B, the objective lenses 16A and 16B, the spatial filters 17A and 17B having pinholes having substantially the same diameter as the focused beam spot diameter, and the spatial filters 17A and 17B. Light shielding aperture plates 18A and 18B having openings that shield the periphery of the emitted light beam, and an exposure mask 19 that is disposed close to the exposure substrate 20 and masks the periphery of the interference exposure region formed by the light beam emitted from the opening. Is provided.

  As the laser light source 11, for example, a YAG fourth harmonic (266 nm) solid-state laser is used. The laser light from the laser light source 11 has its beam diameter converted by the beam expander 12 and divided into two by the PBS 13. In one branch optical path, a wave plate 14 is installed in order to cause the two split light beams to interfere with each other, and the polarization direction is rotated by 90 degrees to align the polarization.

  The optical path 1 and the optical path 2 divided by the PBS 13 are reflected so as to interfere with each other by the reflecting plates 15A and 15B, and are collected by the objective lenses 16A and 16B. The condensed beam passes through the spatial filters 17A and 17B, and noise and distortion of the laser light wavefront are removed.

  The light fluxes emitted from the spatial filters 17A and 17B are shielded at the periphery by the openings of the light shielding aperture plates 18A and 18B. The openings of the light-shielding aperture plates 18A and 18B are processed so that light strikes an area used for exposure, and light beams emitted from the openings are synthesized on the exposure substrate 20 to form diffraction fringes (interference fringes). ) Is formed to form interference exposure.

  FIG. 2 is a diagram showing the Lloyd Mirror type optical system in the present embodiment. This interference exposure apparatus includes a laser light source 21, a shutter 22, an objective lens 23, a spatial filter 24 having a pinhole having substantially the same diameter as the focused beam spot diameter, and a peripheral edge of a light beam emitted from the spatial filter 24. A light-shielding aperture plate 25 having an aperture that shields light, a mirror 26 that reflects a part of the light beam emitted from the aperture on the exposure substrate 27, and an exposure substrate 28 that is disposed in close proximity and directly emitted from the aperture. An exposure mask 27 that masks the periphery of the interference exposure region formed by the light beam and the outgoing light beam reflected from the mirror 26 is provided.

  As the laser light source 21, for example, a YAG quadruple wave (266 nm) solid-state laser is used as in the Mach-Zehnder type. The laser light that has passed through the shutter 22 is collected by the objective lens 23. The condensed beam passes through the spatial filter 24, and noise and distortion of the laser light wavefront are removed.

  The light beam emitted from the spatial filter 24 is shielded at its periphery by the opening of the light shielding aperture plate 25. The opening portion of the light shielding aperture plate 25 is processed so that the light strikes the exposure substrate 28 and the mirror 26 disposed adjacent to the exposure substrate 28 at a right angle, and the light is emitted from the opening portion. The light beams are synthesized on the exposure substrate 28 to form diffraction fringes (interference fringes), and interference exposure is performed.

  As in the above-described Mach-Zehnder type and Lloyd Mirror type interference exposure apparatuses, the periphery of the luminous flux emitted from the spatial filters 17A, 17B, and 24 is shielded by the light-shielding aperture plates 18A, 18B, and 25, and used for exposure. The stray light can be reduced by allowing the light to strike. Further, the interference fringes of the interference fringe intensity generated by the opening ends (ridge line portions) of the light shielding aperture plates 18A, 18B, and 25 are masked by the exposure masks 19 and 27, thereby obtaining uniform interference fringes on the exposure substrates 20 and 28. Can do.

<2. Effect of diffraction fluctuations>
Next, with reference to FIGS. 3 to 8, the influence of diffraction fluctuations caused by the opening end (ridge line portion) of the light shielding aperture plate will be described. As shown in FIG. 3, when the outgoing light beam is shielded by the light shielding aperture plate 30, an interference exposure region 301 and a light shielding region 302 are formed, and a fresnel diffraction fringe 303 as shown in FIG. Arise. FIG. 5 is a diagram showing a light intensity distribution in the X direction in the interference exposure region. The diffraction fluctuation of the light intensity distribution greatly affects the interference fluctuation of the interference fringe intensity.

  FIG. 6 is a diagram showing an experimental example of Fresnel diffraction in the optical system of the Lloyd Mirror type interference exposure apparatus. The same components as those in the optical system shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted here.

  When exposure is performed without the exposure mask 27, Fresnel diffraction fringes a due to the opening edge of the light shielding aperture plate 25 are observed on the exposure substrate 28 as shown in FIGS. This diffraction region is about 3 mm wide from the edge visually.

  Further, the aperture size of the light shielding aperture plate 25 is preferably narrowed to suppress stray light, but it is preferable to increase the aperture size in consideration of the influence of diffraction. Specifically, the opening size of the light shielding aperture plate 25 is preferably larger by 3 mm or more outside the exposure area determined by the exposure mask 27.

The diffraction phenomenon due to a general one-dimensional knife edge is as follows: λ is the wavelength of light, z is the distance from the light shielding aperture plate to the exposure substrate surface, x is the coordinate when the aperture boundary of the exposure surface is 0, and θ is light shielding. When the angle formed by the aperture plate and the exposure substrate surface, S (ω), C (ω) is each sine cosine Fresnel integral,
It is represented by the following formula (1).

  From the equation (1), it is possible to reduce the region where diffraction fluctuation occurs by reducing the distance z from the light shielding aperture plate to the exposure substrate surface, that is, by bringing the light shielding aperture plate 30 closer to the exposure substrate.

  In the present embodiment, the light shielding aperture plate 30 is arranged on the side of the spatial filter in order to reduce unnecessary stray light that is incident on the exposure substrate from the light source between the light shielding aperture plate 30 and the spatial filter. To do. That is, the distance z from the light shielding aperture plate to the exposure substrate surface is increased, and the influence of diffraction fluctuations is increased by the opening end (ridge line portion) of the light shielding aperture plate 30, but in this embodiment, the interference fringe intensity due to diffraction fluctuations is increased. The interference fluctuation region is masked with an exposure mask. Thereby, uniform interference fringes can be obtained on the exposure substrate.

  Further, the distance z shown in the equation (1) also corresponds to the distance between the opening ridge line portion of the exposure mask and the exposure substrate (thickness of the exposure mask). Therefore, in this embodiment, the distance between the opening ridge line portion of the exposure mask and the exposure substrate is reduced. Thereby, the influence which a diffraction fluctuation produces can be made small.

<3. Reduction of stray light by light shielding aperture plate>
Next, a method for reducing stray light between the spatial filter and the light shielding aperture plate using the light shielding aperture plate will be described. The scattering source (stray light) between the spatial filter and the light-shielding aperture plate is, for example, a protection that is a base of an optical system when exposure is performed with the exposure optical axis being horizontal and the exposure substrate standing vertically to the ground. There are a shaking table surface, a cover surface installed so as to cover the optical path in order to suppress air fluctuation in the optical path.

  FIG. 9 is a diagram showing an example in which the light shielding aperture plate is arranged close to the exposure substrate side. In this case, although the diffraction fluctuation region a is reduced, the probability that the stray light b from the vibration isolation table surface 34 or the stray light c from the light shielding aperture plate 32 is incident on the exposure substrate 33 is increased.

  On the other hand, FIG. 10 is a diagram showing an example in which the light shielding aperture plate is arranged close to the spatial filter side. In this case, although the diffraction fluctuation region a becomes large, the probability that the stray light b from the vibration isolation table surface 34 or the stray light c from the light shielding aperture plate 33 enters the exposure substrate 33 is low.

  FIG. 11 is a graph showing the influence of stray light on the light intensity distribution on the exposure substrate when stray light having an intensity ratio of 4% is added. FIG. 12 is a graph showing a change in the maximum intensity of interference fringes with respect to the intensity of stray light / interference light.

  When stray light with an intensity ratio of 4% is added in this way, an intensity variation of ± 20% at maximum occurs. Further, the line width undulates depending on the incident direction of stray light. In order to make the line width distribution less than 3 nm (5 seconds in terms of exposure time), the stray light intensity ratio needs to be less than 0.4%.

  That is, the light shielding aperture plate 32 is disposed at an optimum position between the spatial filter 31 and the exposure substrate 33 so that stray light with an intensity ratio of less than 0.4% is obtained. Specifically, it is arranged on the spatial filter 31 side from the middle between the spatial filter 31 and the exposure substrate 33.

  FIG. 13 is a diagram showing an experimental example when the distance z between the exposure substrate and the light shielding opening is 800 mm. The wavelength λ was 266 mm, and the inclination of the exposure substrate with respect to the light beam (optical axis) was 64 degrees. The distance L between the exposure substrate and the spatial filter is determined by the relationship with the light intensity distribution on the exposure substrate surface. For example, when L = 1400 mm, the distance z between the exposure substrate and the light-shielding opening is 800 mm. The distance between the spatial filter and the exposure substrate is 600 mm.

  FIG. 14 is a graph showing the calculation result of the diffraction integral value under the above-described conditions. When x is 3 mm or more, the vibration width (= diffraction fluctuation) of the diffraction integral is 10% or less, and when x = 10 mm or more, it is 5% or less. Therefore, by masking the region where the vibration width of the diffraction integration in the interference exposure region exceeds 10% with the exposure mask, that is, by masking the inner side of the periphery of the interference exposure region by 3 mm or more, the entire exposure substrate has a small interference fluctuation. Interference fringes can be formed.

  FIG. 15 is a diagram illustrating a configuration example of a Mach-Zehnder type optical system. In addition, the same code | symbol is attached | subjected to the structure same as the optical system shown in FIG. 1, and description is abbreviate | omitted here.

  The configuration example of this interference exposure apparatus has two stages: an exposure mask 19 disposed adjacent to the exposure substrate 20 and light shielding aperture plates 18A and 18B disposed on the spatial filters 17A and 17B side of the exposure mask 19. The light shielding configuration is as follows. Thereby, both unnecessary stray light components due to light irradiation outside the exposure area and Fresnel diffraction due to the opening end (ridge line portion) can be suppressed at the same time.

  The exposure area b determined by the exposure mask 19 is preferably smaller by 3 mm or more inside than the exposure area a determined by the light shielding aperture plates 18A and 18B. The magnitude of Fresnel diffraction due to the opening edge decreases as the distance from the periphery of the exposure area increases, and the intensity fluctuation at a position 3 mm or more away from the periphery is ± 3% or less. For this reason, the influence of Fresnel diffraction can be sufficiently suppressed by being 3 mm or more smaller than the exposure area a.

<4. Reduction of interference fluctuation by exposure jig>
Next, a method for reducing interference fluctuations by using an exposure mask disposed adjacent to the exposure substrate will be described. The exposure mask functions as an exposure jig for fixing the exposure substrate so that the exposure substrate does not move, in addition to preventing scattered light generated when the exposure light beam strikes the side surface of the exposure substrate.

  FIG. 16 is a cross-sectional view showing an example of an exposure jig in the present embodiment. The exposure jig 40 includes a first holding member 41 having a frame portion 41 a having the same shape as the edge portion of the exposure substrate 43, and a second holding member 42 having an opening having substantially the same shape as the exposure substrate 43. The exposure substrate 43 is sandwiched between the first holding member 41 and the second holding member 42.

  The first holding member 41 can accommodate the exposure substrate 43 by placing at least both end portions of the exposure substrate 43 by a frame portion 41 a that is dug in substantially the same thickness as the exposure substrate 43. The second holding member 42 fixes at least both end portions of the exposure substrate 43 by the opening peripheral edge portion 42a.

  Thus, by covering a part or all of the periphery of the exposure substrate 43 where the influence of the interference fluctuation is large by the exposure jig 40, uniform interference fringes can be formed on the entire surface of the exposure substrate 43.

  Further, the distance between the opening ridge line of the second holding member 42 and the surface of the exposure substrate 43, that is, the thickness of the opening peripheral edge 42a is preferably 0.5 mm or less. When the thickness of the opening peripheral portion 42a is 0.5 mm or less, the diffraction from the opening of the second holding member can reduce the influence on the interference fringes in the exposure area.

  The distance between the opening ridge line of the second holding member 42 and the surface of the exposure substrate 43 (thickness of the opening peripheral edge 42a) corresponds to z in the equation (1). The influence of can be reduced. When the distance z is 1 mm or less, the diffraction fluctuation due to the opening peripheral edge portion 42a can be within 2 mm inside the exposure mask. However, in the case of the oblique incidence direction due to two-beam interference, shadowing due to the oblique incidence is caused. Therefore, the diffraction fluctuation region is shifted to the inside of the exposure mask. For this reason, the distance z between the opening ridge line of the second holding member 42 and the surface of the exposure substrate 43 is preferably 0.5 mm or less.

  By the way, as shown in FIG. 17, when the chamfer 44a is given to the opening peripheral part 42a of the 2nd holding member 44, if the area of this part is large, in addition to essential diffraction, the scattered light by the chamfer 44a will be added. Therefore, the diffraction fluctuation region is enlarged. For this reason, as shown in FIG. 16, it is preferable that the opening peripheral part of the 2nd holding member 42 is chamfered small in the range below 0.2 mm from the surface.

  Thus, by setting the thickness of the opening peripheral portion 42a to 0.5 mm or less, diffraction fluctuations generated by the opening peripheral portion 42a can be reduced, and uniform interference fringes can be formed over the entire exposure area. Furthermore, by making the chamfering of the mask ridge line portion a 0.2 mm or less from the surface, the total amount of scattered stray light generated at the edge portion can be reduced, and interference fringe fluctuations caused by this stray light component in the exposure area can be reduced. it can.

<5. Interference exposure method>
Next, an interference exposure method using the above-described interference exposure apparatus will be described. As the original plate, a substrate transparent to the light used, for example, made of quartz or quartz is used. Further, a metal such as Al or Ta or a semiconductor may be formed on the original plate depending on the optical element.

  First, a resist layer is formed on the main surface (one main surface) of the substrate to produce an exposed substrate. The resist layer is made of a photoresist material (photosensitive organic material) corresponding to an exposure light source generally used in photolithography, and can be etched together with the substrate by a reactive gas, an ion beam, or the like. The resist layer is formed after the formation of the antireflection film or simultaneously with the formation of the antireflection film.

  Next, interference exposure is performed on the resist layer of the exposure substrate to form a photosensitive layer in which the resist layer is exposed to a predetermined pattern. In both the optical systems shown in FIGS. 1 and 2, interference fringes are formed on the exposure substrate by two-beam interference, and the resist layer can be exposed. For example, when a diffraction grating having a pitch of 150 nm is formed using laser light having a wavelength of 266 nm, the incident angle θ of the laser light with respect to the exposure substrate is set to 64 °. Further, after performing interference exposure, heating (PEB: Post Exposure Bake) is performed.

  Next, the photosensitive layer is developed. The development conditions are, for example, alkali development for 30 seconds and fixing with pure water washing for 30 seconds. This removes, for example, the exposed portion of the photosensitive layer and leaves the unexposed portion (or the unexposed portion is removed and the exposed portion remains), and diffraction. The patterning layer is patterned into a lattice-shaped uneven shape.

Next, the patterning layer and the substrate are etched. Etching may be a method that allows the patterning layer and the substrate to be sequentially removed from the surface layer. For example, RIE (reactive ion etching) using a fluorine-based gas such as CF ₄ , Ar gas, or a mixed gas thereof may be used. It is good to process by ion beam etching. At this time, since the patterning layer serves as a mask pattern of the substrate, the uneven shape of the diffraction grating pattern can be formed on the substrate.

<6. Example>
Hereinafter, the present invention will be specifically described with reference to examples. Here, as an example, a sub-wavelength fine grating was fabricated by a two-beam interference exposure method. The present invention is not limited to these examples.

  As a light source used for the interference exposure apparatus, a far ultraviolet CW laser having a wavelength of 266 nm based on the fourth harmonic of Nd: YAG was used. The wavelength monochromaticity was 0.1 fm, the coherent length was 3 m, and the vertical coherency was good. M2 (em square) indicating the state of the emitted light of the laser was 1.1, and the emitted beam with a diameter of 0.8 mm was almost single mode and had good lateral coherency.

  As the optical system, a Mach-Zehnder type interference exposure apparatus was used. The relationship between the incident angle and the period p (pitch) of the fine grating is expressed by the following equation (2).

  In order to have a function as a sub-wavelength grating, a period of half or less of the light wavelength to be used (400 to 700 nm for visible light) is required. For this reason, in this example, the pitch p of 148 nm was obtained by setting the incident angle to 64 degrees. In each branch, the distance between the spatial filter and the light shielding aperture plate was 600 mm, and the distance from the light shielding aperture plate to the exposure substrate was 800 mm. The irradiation area limited by the light-shielding aperture plate is wide enough to cover the entire surface of the exposure substrate and sufficiently narrow to prevent extra scattered light from the stage and other optical components.

  As an original plate of the exposure substrate, glass having a size of 20 mm × 20 mm and a thickness of 0.7 mm was used. First, Al was formed to a thickness of 50 nm by DC sputtering, and then an antireflection film (BARC) and a chemically amplified photosensitive resist were applied by spin coating at 30 nm and 230 nm, respectively, to obtain an exposed substrate. Two-beam interference exposure was performed on the exposure substrate thus prepared.

  FIG. 18 is a top view showing the exposure jig, and FIG. 19 is a cross-sectional view showing the exposure jig. The exposure substrate 51 is arranged in an exposure jig as shown in FIGS. 18 and 19, and a part of the substrate end is not irradiated with light. The distance z between the opening ridge line of the exposure jig 50 and the surface of the exposure substrate 51 was set to 0.5 mm. Further, the peripheral edge of the opening of the exposure jig 50 was chamfered 0.2 mm from the surface.

  The exposure time is determined by the photosensitive sensitivity of the resist and the irradiation intensity of the substrate surface, and is about 40 sec in this example. A chemically amplified resist for KrF was used as the resist, and the reaction was completed through PEB (Post Exposure Bake) treatment after exposure. In the post-exposure PEB (Post Exposure Bake) treatment, heat treatment was performed at 110 degrees for 90 seconds. Thereafter, development with an alkali solution and drying were obtained to form a fine lattice pattern of a resist. The cross-sectional shape was 190 nm in height, 60 nm in width, and the period of the grating was 148 nm.

  Finally, using this resist pattern as a mask, Al was dry etched using chlorine gas to form a lattice-like Al pattern. The Al cross section had a height of 50 nm, a width of 60 nm, and a lattice period of 148 mm.

  About the produced lattice board | substrate, position A, B, C from the board | substrate end shown in FIG. 20 was observed with the microscope. The magnification of the microscope was about 1000 times. As a result, each fine grid is not visible, and on the contrary, a macro-grid distribution such as diffraction is slightly amplified and can be observed. Note that the position D is a substrate pressing portion by the exposure jig.

  FIGS. 21 to 23 are enlarged photographs showing a position A near 1 mm from the substrate end, a position B near 2 mm from the substrate end, and a position C near 10 mm from the substrate end. It was observed that near the position B, the diffraction fluctuation seen at the position A was reduced, and further reduced at the position C near 10 mm from the edge of the substrate. It can be seen that the diffraction fluctuation levels observed at the positions B and C have no problem in the actual transmission characteristics, and the configuration of the light beam interference exposure according to the present embodiment can sufficiently reduce the influence of stray light and the influence of the diffraction fluctuation. It was.

  As described above, by using the light shielding aperture plate having the aperture and the exposure mask, it is possible to maximize the effective area of the substrate and form an interference fringe pattern with less influence of stray light and diffraction.

  DESCRIPTION OF SYMBOLS 11 Laser light source, 12 Beam expander, 13 Polarizing beam splitter, 14 Wavelength plate, 15A, 15B Reflector, 16A, 16B Objective lens, 17A, 17B Spatial filter, 18A, 18B Shading aperture plate, 19 Exposure mask, 20 Exposure Substrate, 21 Laser light source, 22 Shutter, 23 Objective lens, 24 Spatial filter, 25 Light-shielding aperture plate, 26 Mirror, 27 Exposure mask, 28 Exposure substrate, 30 Light-shielding aperture plate, 31 Spatial filter, 32 Light-shielding aperture plate, 33 Exposure substrate, 34 vibration isolator, 40 exposure jig, 41 exposure substrate, 42 exposure jig, 50 exposure jig, 51 exposure substrate

That is, the present invention is an interference exposure apparatus that reflects a part of an outgoing light beam and forms an interference exposure region by the reflected outgoing light beam and the direct outgoing light beam, and the peripheral edge of the light beam emitted from the spatial filter is A light-shielding aperture plate having an aperture to be shielded, and an exposure mask that is arranged adjacent to the exposure substrate and masks the periphery of an interference exposure area formed by a light beam emitted from the aperture.

The present invention also provides an interference exposure apparatus that divides an emitted light beam into two and polarizes one of the light beams to form an interference exposure region, and has an opening that shields the periphery of the light beam emitted from the spatial filter. A light-shielding aperture plate and an exposure mask that is arranged adjacent to the exposure substrate and masks the periphery of an interference exposure region formed by a light beam emitted from the aperture.

In the interference exposure method according to the present invention, the periphery of the light beam emitted from the spatial filter is shielded by the light-shielding aperture plate having the aperture, and is emitted from the aperture by the exposure mask arranged adjacent to the exposure substrate. The periphery of the interference exposure area formed by the emitted light beam is masked.

Claims (10)

A light-shielding aperture plate having an aperture that shields the periphery of the luminous flux emitted from the spatial filter;
An interference exposure apparatus comprising: an exposure mask which is arranged adjacently on an exposure substrate and masks a periphery of an interference exposure region formed by a light beam emitted from the opening.   The interference exposure apparatus according to claim 1, wherein the exposure mask masks an area where a vibration fluctuation width of diffraction fluctuation in the interference exposure area exceeds 10%.   The interference exposure apparatus according to claim 1, wherein the exposure mask masks an inner side of a periphery of the interference exposure region by 3 mm or more.   The interference exposure apparatus according to any one of claims 1 to 3, wherein a distance from a surface of the exposure mask to an exposure substrate is 0.5 mm or less.   The interference exposure apparatus according to claim 4, wherein a ridge line portion is chamfered within a range of 0.2 mm or less from the surface of the exposure mask.   The exposure mask includes a first holding member having a frame portion having the same shape as an edge portion of the exposure substrate, and a second holding member having an opening having the same shape as the exposure substrate, and the second holding member. The interference exposure apparatus according to any one of claims 1 to 3, wherein the thickness of the peripheral edge of the opening is 0.5 mm or less.   The interference exposure apparatus according to claim 6, wherein an opening peripheral edge portion of the second holding member is chamfered within a range of 0.2 mm or less from the surface. The light shielding aperture plate having an opening shields the periphery of the light beam emitted from the spatial filter,
An interference exposure method for masking a peripheral edge of an interference exposure region formed by a light beam emitted from the opening by an exposure mask arranged adjacently on an exposure substrate. A first holding member having a frame portion having the same shape as the edge portion of the exposure substrate, and a second holding member having an opening having the same shape as the exposure substrate,
An exposure jig wherein the thickness of the peripheral edge of the opening of the second holding member is 0.5 mm or less.   The exposure jig according to claim 9, wherein the peripheral edge of the opening of the second holding member is chamfered within a range of 0.2 mm or less from the surface.

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