JPH08314361A - Holography device - Google Patents

Abstract

PURPOSE: To provide a hologram recording device which decreases the noises to be superposed on a hologram at the time of recording on the hologram and a hologram reconstructing device which decreases the noises to be superposed on the hologram at the time of reconstruction of the hologram. CONSTITUTION: This holography recording device is arranged with a mask 3 opposite to the hologram 1 and is constituted to split the light emitted from the same light source to object irradiation light 5 and reference light 6, to irradiate the mask 3 with the object irradiation light 5, to irradiate the hologram 1 with the reference light 6 and to transfer the patterns recorded on the mask 3 to the hologram 1 by the object light 9 emitted from the mask 3 and the reference light 6. A spatial filter 8 is arranged in the optical path of the object irradiation light 5 and the mask 3 is directly irradiated with the divergent light emitted from the spatial filter 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic recording device for recording a two-dimensional image such as an image memory or lithography on a hologram, and a holographic reproduction for reproducing interference fringes recorded on the hologram on a recording member such as a semiconductor wafer. Regarding the device.

[0002]

2. Description of the Related Art Total reflection holography is known as a method for recording and reproducing a two-dimensional image with high resolution. In total reflection holography, a mask with an image to be recorded can be placed near the hologram.
Recording of a two-dimensional image in total reflection holography has conventionally been performed as follows, as shown in FIG. Light emitted from a laser light source (not shown) is split by the half mirror 4 into object irradiation light 5 and reference light 6. The object irradiation light 5 has its noise removed by the spatial filter 8 and has been collimated by the collimator lens 20 and then irradiated onto the mask 3, and the object light 9 from the mask 3 is incident on the hologram 1. Similarly, the reference light 6 split by the half mirror 4 has its noise removed by the spatial filter 11, becomes parallel light by the collimator lens 21, enters the prism 2 supporting the hologram 1, and then the hologram 1 Was incident on. Depending on the arrangement of the optical system, the light emitted from the collimator lens may be reflected by the mirror 22 and applied to the mask 3 or the prism 2. The same applies to the reproduction of interference fringes recorded in total reflection holography, and the reproduction light emitted from the laser light source is
Noise was removed by the spatial filter, and collimated by the collimator lens into parallel light, which was then incident on the hologram through the prism.

[0003]

Although image recording with high resolution can be realized by total reflection holography, there is also a problem that even noise light is recorded and the quality of the image is degraded. That is, among the scattered light generated in the process of guiding the laser light 5, 6 from the laser light source to the hologram 1, the scattered light generated by the optical system arranged in front of the spatial filters 8, 11 is the spatial light.
Although the light is cut by the pinholes 8b and 11b of the filters 8 and 11, the light scattered by the optical system such as the collimator lenses 20 and 21 and the mirror 22 arranged after the spatial filters 8 and 11 is reflected by the hologram 1. However, the interference fringes to be recorded on the hologram 1 are superimposed and recorded as noise.

Also during reproduction, among scattered light generated in the process of guiding the laser light from the laser light source to the hologram, scattered light generated by an optical system in front of the spatial filter is a pinhole of the spatial filter. However, the light scattered by the collimator lens and the mirror after that reaches the hologram, and was recorded as noise superimposed on the image to be reproduced on the wafer. Therefore, it is an object of the present invention to provide a hologram recording device that has less noise superimposed on it when recording on a hologram, and also provides a hologram reproducing device that has less noise superimposed on it when reproducing a hologram. To aim.

[0005]

The present invention has been made in order to achieve the above-mentioned object, that is, a spatial filter is arranged in the optical path of object irradiation light, and a divergence emitted from the spatial filter is emitted. This is a holographic recording device in which a mask is directly irradiated with light or a spatial filter is arranged in the optical path of reference light, and divergent light emitted from the spatial filter is directly incident on a hologram support member. The present invention is also a holographic reproduction device in which a spatial filter is arranged in the optical path of the reproduction light and the divergent light emitted from the spatial filter is directly incident on the hologram support member.

[0006]

In the present invention, there is no scattering source such as a collimator lens or a mirror in the optical system after the spatial filter. Therefore, all the scattered light generated by the optical system is cut by the spatial filter, does not reach the hologram during recording and reproduction, and a good image without noise can be recorded and reproduced. Thus, in recording the image on the mask on the hologram and reproducing the information recorded on the hologram on the wafer, the image recorded on the mask needs to be faithfully reproduced on the wafer. It will be described below that the image recorded on the mask is faithfully reproduced on the wafer even with the configuration of the present invention.

In order to completely form a real image of the image recorded on the hologram, it is necessary to irradiate the hologram with light that is conjugate with the reference light. Therefore, when the reference light is a diverging spherical wave, the reproducing light must be a converging spherical wave, and when the reproducing light is a diverging spherical wave, the reference light must be a converging spherical wave. However, in order to create a convergent spherical wave, it is necessary to insert a lens after the spatial filter, and this lens becomes a new scattering source. As a method of producing convergent light without introducing a new scattering source, there is a method of processing the incident surface or the reflecting surface of the hologram supporting member into a spherical surface.In the case of total reflection holography, the reference light and the reproduction light are combined. It is proved by the imaging theory that there is no problem even if both are divergent spherical waves.

Now, as shown in FIG. 5, an x, y, z orthogonal coordinate system is provided, the hologram plane is at z = 0, and all the light sources O, S _r and S _{c of} the object wave, the reference wave and the reproduction wave are all included. When they are on the same plane (xz plane), the image formation formulas of the sagittal image and the meridional image are as follows: 1 / R _IS = 1 / R _c ± μ / m ² · (1 / R _o −1 / R _r ). (A ₀ ) cos ² α _I / R _IM = cos ² α _c / R _c ± μ / m ² · (cos ² α _o / R _o −cos ² α _r / R _r ) (B ₀ ) Given in. The direction in which an image can be formed is represented by sin α _I = sin α _c ± μ / m · (sin α _o −sin α _r ) ... (C ₀ ). The position of the light source S _r of the reference wave is treated as the origin of divergence of the light wave after being totally reflected by the hologram surface. Here, R is the hologram origin, the light source O of the object wave, that is, the object point on the mask, the light source S _{r of the} reference wave, the light source S _{c of the} reproduction wave,
Alternatively, it is the distance from the light source I of the diffracted wave, that is, the image point on the resist. When z> 0, it is (+), and when z <0, it is (-). α is the light source O, S _r , S _c or I of each wave
Direction and is defined by an acute angle with the z axis, and the sign is (+) counterclockwise. Therefore, -90 ° <α ≦ + 9
It is 0 °. m is the change in magnification of the hologram, and μ is the ratio of the reproduction wavelength to the recording wavelength (λ _c / λ _o ). The subscripts o, r, c and I respectively represent an object wave, a reference wave, a reproduction wave and a diffracted wave, and the subscripts S and M respectively represent a sagittal image and a meridional image.

The sign ± of each expression is + in the case of normal reproduction.
Corresponds to the virtual image, and-corresponds to the real image. In the case of the conjugate reproduction in which the reproduction light is incident in the opposite direction to the reference light, + corresponds to the real image and − corresponds to the virtual image. Since what is being considered here is the reproduction of the conjugate real image, the sign + of each expression is +. Therefore, the formulas (A ₀ ), (B ₀ ), and (C ₀ ) are as follows: 1 / R _IS = 1 / R _c + μ / m ² · (1 / R _o −1 / R _r ) ... (A ₁ ). cos ² α _I / R _IM = cos ² α _c / R _c + μ / m ² · (cos ² α _o / R _o −cos ² α _r / R _r ) ... (B ₁ ) sin α _I = sin α _c + μ / m · (sinα _o −sinα _r ) ... (C ₁ ).

Here, if μ = m = 1 and α _c = α _r (D ₁ ), then α _I = α _o from the formula (C ₁ ). Therefore, the formulas (A ₁ ) and (B ₁ ) are respectively 1 / R _IS = 1 / R _c + 1 / R _o − 1 / R _r ... (A ₂ ) 1 / R _IM = k ² / R _c + 1 / _{R o} -k ² / R _r ‥‥ the (B _2). However, k ≡ cosα _r / cosα _o .

A feature of total internal reflection holography is that the mask can be placed very close to the hologram (for example, 100 μm). In this case, since R _o << R _r and R _o << R _c , the formulas (A ₂ ) and (B ₂ ) are respectively 1 / R _IS = 1 / R _o ... (A ₃ ) 1 / R _IM = 1 / R _o (B ₃ ) That is, R _IS = R _IM = R _o , and it is understood that perfect real image reproduction is realized. Thus, in total internal reflection holography, if the radius of curvature of the reference wave and the reproduction wave is sufficiently larger than the distance between the hologram and the mask, complete real image reproduction is realized even if both the reference wave and the reproduction wave are divergent waves.

Next, in the transformation from the formulas (A ₂ ) and (B ₂ ) to the formulas (A ₃ ) and (B ₃ ), a first-order minute amount (R _o /
Although R _r ), (R _o / R _c ) and the following are ignored, the first minute amount (R _o / R _r ) and (R _o / R _c ) are adopted, and the second minute amount (R _o ). _The equations (A ₂ ) and (B ₂ ) are modified in more detail by ignoring _o / R _r ) ² and (R _o / R _c ) ^{2 and} thereafter. From the formula (A ₂ ), R _IS = R _o / {1- (R _o / R _r −R _o / R _c )} = R _o {1+ (R _o / R _r −R _o / R _c ) + ( R _o / R _r −R _o / R _c ) ² + ...} ≈R _o {1+ (R _o / R _r −R _o / R _c )} (A ₄ ). Similarly, from the formula (B ₂ ), R _IM = R _o / {1-k ² · (R _o / R _r −R _o / R _c )} = R _o {1 + k ² · (R _o / R _r −R ^{_{o / R c) + k 4}} · (R o / R r -R o / R c) 2 + ‥‥} ≒ R o {1 + k 2 · (R o / R r -R o / R c)} ‥‥ ( B ₄ ).

Therefore, the difference ΔR _SM between the image forming positions of the sagittal image and the meridional image is ΔR _SM ≡ | R _IS −R _IM | = (R _o ) ² (1 / R _r −1 / R _c ) · | 1 −k ² | ... (E ₁ ), and assuming that the allowable limit for ΔR _SM is ε, (R _o ) ² (1 / R _r −1 / R _c ) · | 1-k ² | <ε. It would be good if (F) holds. On the other hand, from the position of the mask in the hologram exposure, the movement amount z to the imaging position at the time of hologram reproduction, from the formula _{(A 4), z≡R IS -R} o = (R o) 2 (1 / R r −1 / R _c ) ... (G)

Here, when | 1-k ² | <1 is solved, 0 <k <2 ^1/2, that is, 0 <cosα _r / cosα _o <2 ^1/2 (H). In the total reflection holography, the light source S of the object illumination light
_{Since o} is placed directly above the mask, the reproduction light is obliquely incident so as to be totally reflected on the hologram surface. Therefore, unless the light source of the object illumination light S _o is placed extremely close to the mask, | α _r |> | α _o |, therefore, the formula (H) is normally established, and | 1-k ² | <1. Therefore, the formula (E ₁ ) becomes ΔR _SM <(R _o ) ² (1 / R _r −1 / R _c ) ... (E ₂ ).

For example, if R _o = 100 μm, the permissible limit ε for ΔR _SM is ε = 0.1 μm, and R _r = −R _c ... (D ₂ ), then from equation (E ₂ ), R _r As long as = −R _c > 200 mm, ΔR _SM <ε. Further, at this time, the movement amount z from the position of the mask to the image forming position during reproduction is also z <ε. The conditions (D ₁ ) and (D ₂ ) correspond to irradiating a reproducing wave (divergent wave) having the same radius of curvature as the reference wave (divergent wave) from the opposite direction to the reference wave. That is, when the mask on which the two-dimensional image is recorded is placed at a position of 100 μm from the hologram, the radii of curvature of the reference wave and the reconstructed wave are each 2
It can be seen that when the distance is 00 mm or more, there is no problem even if a diverging wave is used, and there is no problem with defocus. Although the analysis here is based on the paraxial imaging theory regarding thin holograms, there is no problem if it is applied to the case of volume holograms.

[0016]

The present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of a holographic recording device according to the present invention, in which a total reflection hologram 1 is arranged on a prism 2 and a mask on which an image pattern is recorded with a minute gap between the hologram and the hologram 1. 3 are arranged. Laser light generated by a laser light source (not shown) is split by the half mirror 4 into object irradiation light 5 and reference light 6. The object irradiation light 5 transmitted through the half mirror 4 is turned by the mirror 7 in a direction perpendicular to the plane of the mask 3, and then transmitted through a spatial filter 8 including a microscope objective lens 8a and a pinhole 8b. The object irradiation light 5 is condensed at the focal point of the objective lens 8a and transmitted through the pinhole 8b placed at this point, but is generated by the laser light source before the objective lens 8a, the half mirror 4, the mirror 7 and other optical systems. Of the scattered light and the scattered light generated in the objective lens 8a, the component tilted with respect to the optical axis does not form an image at the focal point of the objective lens 8a and therefore cannot pass through the pinhole 8b. In this way, the spatial light 8 cuts noise light. The divergent light object illumination light 5 that has passed through the spatial filter 8 directly enters the mask 3 as divergent light, and the object light 9 that has passed through the mask 3 enters the hologram 1.

Similarly, the reference light 6 reflected by the half mirror 4 is deflected by the mirror 10 in a direction perpendicular to the inclined surface of the prism 2 and then passed through a spatial filter 11 composed of a microscope objective lens 11a and a pinhole 11b. It is transparent. The divergent light reference light 6 that has passed through the spatial filter 11 is directly incident on the slope of the prism 2 as divergent light, and is further incident on the hologram 1 arranged on the prism 2 so as to be totally reflected. The object light 9 and the reference light 6 that have entered the hologram 1 interfere with each other to form interference fringes, and thus an interference fringe pattern corresponding to the image pattern recorded on the mask 3 is recorded on the hologram 1.

This embodiment is constructed as described above,
Although both the object light 9 and the reference light 6 are divergent light, since the mask 3 is arranged extremely close to the hologram 1, the origin of divergence of the light wave of the object light 9, that is, the object The distance from the position of the pinhole 8b for the irradiation light 5 to the hologram 1 can be regarded as infinity. Similarly, the origin of the light wave of the reference light 6, that is, the position of the pinhole 11b for the reference light 6 and the hologram. The distance to 1 can also be considered infinite. That is, compared to the distance between the hologram 1 and the mask 3, both the object light 9 and the reference light 6 can be regarded as parallel light fluxes. Therefore, in the hologram 1, both the object light 9 and the reference light 6 are parallel light fluxes. The same interference fringe pattern as that obtained in the case of is recorded.

Since the object illumination light 5 transmitted through the spatial filter 8 is directly incident on the mask 3, only the noise generated on the surface of the mask 3 is superposed on the object light 9 emitted from the mask 3. . Further, since the reference light 6 transmitted through the spatial filter 11 is directly incident on the prism 2, only the noise generated on the surface of the prism 2 is superimposed on the reference light 6 incident on the hologram 1. Therefore, the noise superimposed on the interference fringe pattern recorded on the hologram 1 is significantly reduced.

The pinholes 8b and 11b of the spatial filter have a pinhole diameter of 8 mm.
It must be adjusted to the spot diameter collected by a and 11a. When the pinholes 8b and 11b having a larger pinhole diameter than the spot diameter are used, scattered light slightly passes through the pinholes 8b and 11b. Conversely, when the pinhole diameter is smaller than the spot diameter, the scattered light is cut, but the object irradiation light 5 or the reference light 6 is diffracted by the pinholes 8b and 11b. Diffraction does not pose a problem if the central portion of the diffracted light is used, so it is desirable to set the pinhole diameters of the pinholes 8b and 11b to be small so that the scattered light can be surely cut. The objective lens 8
When the scattered light at a and 11a becomes a problem, the object irradiation light 5 or the reference light 6 is provided without providing the objective lenses 8a and 11a.
It is also possible to directly irradiate the pinholes 8b and 11b with diffracted light.

Since only the scattered light generated on the surface of the mask 3 is superimposed on the object light 9, the mask 3 having a small surface roughness and antireflection on both the pattern surface and the back surface is provided in order to reduce the scattered light. It is preferable to use
It is important to use the mask 3 in the absence of scattering sources such as dust. On the other hand, the reference light 6 has an incident surface of the prism 2 and
Since only the scattered light at the interface between the hologram 1 and the prism 2 is superposed, the prism 2 having a small surface roughness is used in order to reduce the scattered light, and a scattering source such as scratches or dust is not attached. It is important to use the prism 2 in this state.

The hologram 1 is usually formed by coating a hologram recording material on a flat substrate, and is placed on the prism 2 via an index matching liquid. Therefore, it is preferable to select, as the index matching liquid, a liquid that has small scattering and does not emit fluorescence. When scattering at the interface between the substrate of the hologram 1 and the prism 2 or scattering at the index matching liquid poses a problem,
It is also possible to apply the hologram recording material directly onto the prism 2. Since the reference light 6 is totally reflected on the surface of the hologram recording material, the surface of the recording material is kept as uniform as possible so that scattered light does not occur at the time of reflection, and scratches and dust are prevented from adhering as much as possible. It is essential to do this.

Next, FIG. 2 shows a second embodiment of the holographic recording apparatus according to the present invention. In this embodiment, the prism 2 is used.
A pinhole 11b for the reference light 6 is provided on the surface. With this configuration, it is possible to reduce the generation of scattered light on the incident surface of the prism 2.

Next, FIG. 3 shows a third embodiment of the holographic recording device according to the present invention. In the second embodiment, since the pinhole 11b for the reference light 6 is provided on the surface of the prism 2, the origin of divergence of the light wave of the reference light 6, that is, the reference light, is compared with the distance between the hologram 1 and the mask 3. The distance from the position of the pinhole 11b for the light 6 to the hologram 1 may not be regarded as infinite. Therefore, in this third embodiment,
The prism 2 is formed so that the distance from the incident surface of the reference light 6 to the hologram installation surface is long so that the reference light 6 can be regarded as a parallel light flux.

Next, FIG. 4 shows an embodiment of the holographic reproducing apparatus according to the present invention. A total reflection hologram 1 in which an interference fringe pattern corresponding to an image pattern of a mask is recorded is arranged on a prism 2, and a wafer 12 having a lower surface coated with a resist with a minute gap from the hologram 1.
Is arranged. The reproduction light 13 generated by a laser light source (not shown) is a spatial filter 14 including a microscope objective lens 14a and a pinhole 14b.
After passing through, the light directly enters the inclined surface of the prism 2 as divergent light and further enters the hologram 1 arranged on the prism 2 so as to be totally reflected. A part of the reproduction light 13 incident on the hologram 1 is totally reflected on the surface of the hologram 1 and returns to the inside of the prism 2, while the other part of the reproduction light 13 is diffracted by the interference fringe pattern recorded on the hologram 1. Then, a reproduced image is formed, and a resist is arranged at the position of the reproduced image. In this way, the image pattern corresponding to the interference fringe pattern recorded on the hologram 1 is reproduced on the resist.

The present embodiment is configured as described above,
Although the reproduction light 13 is divergent light, since the wafer 12 is arranged very close to the hologram 1, the divergence origin of the light wave of the reproduction light 13, that is, the pinhole for the reproduction light 5, is compared with this interval. The distance from the position of 14b to the hologram 1 can be regarded as infinity. That is, since the reproduction light 13 can be regarded as a parallel light flux in comparison with the distance between the hologram 1 and the wafer 12, the wafer 12 has the same image pattern as the image pattern obtained when the reproduction light 13 is a parallel light flux. Is played. Since the reproduction light 13 that has passed through the spatial filter 14 is directly incident on the prism 2, only the noise generated on the surface of the prism 2 is superimposed on the reproduction light 13 that is incident on the hologram 1. Therefore, the noise superimposed on the image pattern recorded on the wafer 12 is significantly reduced. In order to prevent the scattering at the prism 2, it is preferable to use a low scattering prism that does not generate scattered light at the incident surface and the reflecting surface.

In the above reproducing apparatus, the spatial filter 14 is arranged apart from the incident surface of the prism 2, but the pinhole 14b of the spatial filter is formed as in the second embodiment of the recording apparatus. ,
It can also be provided on the surface of the prism 2. With this configuration,
It is possible to prevent generation of scattered light on the incident surface of the prism 2. At that time, the prism 2 can be formed in a shape in which the distance from the incident surface of the reproduction light 13 to the hologram installation surface is long, as in the case of the third embodiment in the recording apparatus.

In the above-mentioned reproducing apparatus, the case where the entire surface of the hologram 1 is reproduced at once is described. However, a part of the interference fringe pattern recorded on the hologram 1 is irradiated with a narrowed reproduction beam to cause interference of part of the interference fringe pattern. The image pattern corresponding to the fringe pattern was transferred to the resist, and the reproduction beam was scanned so as to cover the interference fringe pattern in a certain range recorded in the hologram 1 or the entire interference fringe pattern. The interference fringe pattern can be transferred to the resist. According to this beam scanning method, only an image in an arbitrary range can be reproduced. If scanning is performed while changing the incident angle of the beam, it is necessary to satisfy the conditional expression (F) for the difference ΔR _SM between the image formation positions of the sagittal image and the meridional image to be within the allowable limit ε. It will be easier than it is.

In the above description, the spatial filters 8, 11, 14 are the objective lenses 8a, 11a, 1
Although it has been described as being configured by the combination of 4a and the pinholes 8b, 11b, 14b, another configuration may be used.

[0030]

According to the present invention, since there is no scattering source such as a collimator lens or a mirror in the optical system after the spatial filter, all the scattered light generated by the optical system is removed by the spatial filter. . Therefore, the scattered light does not reach the hologram at the time of recording and at the time of reproducing, and it is possible to record and reproduce a high-quality pattern without noise caused by the scattered light.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a holographic recording device according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the same.

FIG. 3 is a block diagram showing a third embodiment of the same.

FIG. 4 is a configuration diagram showing an embodiment of a holographic reproducing device according to the present invention.

FIG. 5 is an explanatory diagram showing the operation of the present invention.

FIG. 6 is a configuration diagram showing a holographic recording device according to a conventional example.

[Explanation of symbols]

1 ... Total reflection hologram 2 ... Prism 3 ... Mask 4 ... Half mirror 5 ... Object irradiation light 6 ... Reference light 7, 10 ... Mirror 8, 11, 14 ... Spatial filter 8a, 11a, 14a ... Microscope objective lens 8b, 11b , 14b ... Pinhole 9 ... Object light 12 ... Wafer 13 ... Reproduction light

Claims (4)

[Claims] 1. A mask is disposed so as to face a hologram, and light emitted from the same light source is divided into object irradiation light and reference light, and the object irradiation light irradiates the mask, and the reference light is used. In a holographic recording device that irradiates the hologram and transfers the pattern recorded on the mask to the hologram by the object light and the reference light emitted from the mask, a spatial filter is arranged in the optical path of the object irradiation light. The holographic recording device is characterized in that the mask is directly irradiated with divergent light emitted from the spatial filter. 2. A mask is arranged so as to face a hologram arranged on a supporting member, light emitted from the same light source is divided into object irradiation light and reference light, and the mask is irradiated by the object irradiation light. Then, irradiating the hologram through the supporting member by the reference light, the object light emitted from the mask and the reference light, in the holographic recording device for transferring the pattern recorded on the mask to the hologram, A holographic recording device, wherein a spatial filter is arranged in the optical path of the reference light, and divergent light emitted from the spatial filter is directly incident on the support member. 3. A hologram is recorded on the hologram by arranging a recording member coated with a resist so as to face the hologram arranged on the supporting member and irradiating the hologram through the supporting member with reproduction light. In a holographic reproducing device for transferring a different pattern to the resist, a spatial filter is arranged in the optical path of the reproducing light, and divergent light emitted from the spatial filter is directly incident on the supporting member. And a holographic playback device. 4. A part of the pattern recorded on the hologram is irradiated with the reproduction light, the pattern of the part is transferred to the resist, and the reproduction light is covered so as to cover the pattern recorded on the hologram. The holographic reproducing device according to claim 3, wherein the pattern recorded on the hologram is transferred to the resist by scanning.