JPH07134203A - Exposure device - Google Patents

Abstract

PURPOSE:To provide an exposure device in which a high contrast exposure is obtained without an ND filter, the width of a refractive section, that is related to the exposure, is made wider and precise and uniform concentric circular periodical grating patterns are exposed. CONSTITUTION:Laser beam emitted from a laser light source 1 is controlled in its generation by a shutter 2 and its light quantity is stepwise adjusted by a variable attenuator 3. The laser beam is circularly polarized through a 1/4 wavelength plate 4, converted into a convergent light by a beam enlarging lens 5, converged into a circular slit of a spatial filter 6, passed through it and converted to a beam radius- expanded plane wave by a collimating lens 7. The plane wave is made vertically incident on an incident plant 9P of an interference lens 9, refracted at a light-emitting surface 9S as shown by luminous fluxes 12a, 12b, 12A and 12B and made incident on a photosensitive film 11. The luminous fluxes 12a and 12A and 12b and 12B are located at diagonal positions on the same circumference with respect to a center axis 9L, respectively. Thus, the fluxes 12a and 12B which is located in the inner peripheral side and the fluxes 12A and 12b which is located in the inner peripheral side are interfered with each other on the film 11 and as a whole they form concentric interference fringes centered around the axis 9L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for exposing a concentric circular grating pattern.

[0002]

2. Description of the Related Art In recent years, research and development of new optical elements having a planar structure such as a grating lens, a Fresnel lens, a concentric circular grating coupler and a concentric circular concentrating grating coupler have been actively conducted, and concentric circular lenses for producing these optical elements have been developed. Exposure method of periodic grating pattern,
Research and development of exposure equipment is also active. In particular, the grating required for the grating lens, the Fresnel lens, and the concentric-circle focusing grating coupler has a narrower pitch toward the outer circumference.

An example of the above-mentioned conventional grating pattern exposure apparatus will be described below with reference to Japanese Patent Application Laid-Open No. 3-47878 with reference to the drawings. FIG. 3 is a sectional view showing the arrangement of the exposure apparatus in this conventional example. In FIG. 3, 1 is a laser light source, 2 is a shutter, 3 is a variable attenuator, 4 is a quarter wavelength plate, 5 is a beam expanding lens, 6 is a spatial filter, 7 is a collimation lens, 8 is an ND filter, and 9 is interference. A lens, 10 is a sample substrate, 11 is a photosensitive film formed on the sample substrate 10, and 12 is an optical axis of laser light.

The ND filter 8 is a filter having different transmittances with a circle centered on the optical axis as a boundary, and the axis of symmetry (center axis) is an interference lens 9 by an XY axis stage (not shown).
Is adjusted so as to match the central axis 9L. The interference lens 9 has a rotationally symmetric shape with respect to the central axis 9L, the entrance surface 9P is a flat surface, the exit surface 9S is a conical surface, and a concave surface on the inner peripheral side of the convex surface. Further, the interference lens 9 is formed on an XY-axis stage and an XY-axis tilting stage (not shown), and the central axis 9L is formed by these stages.
Is adjusted to match the optical axis 12 of the laser light from. The sample substrate 10 is configured on an XYZ axis stage and an XY axis tilt stage (not shown), the substrate surface is orthogonal to the central axis 9L, and the sample substrate 10 is central axis 9L, that is, an arrow.
Can be moved along 13.

The operation of the conventional exposure apparatus configured as described above will be described.

In FIG. 3, the shutter 2 controls the passage of the laser light of the wavelength λ emitted from the laser light source 1, and the variable attenuator 3 adjusts the light amount stepwise. Further, the light is converted into circularly polarized light by passing through the quarter-wave plate 4, converted into focused light by the beam expansion lens 5, condensed into the circular slit of the spatial filter 6, passed through this, and collimated by the collimation lens 7. It is converted into a plane wave with an expanded beam diameter.

A part of this plane wave is attenuated through the ND filter 8, is vertically incident on the incident surface 9P of the interference lens 9, and the exit surface 9S is refracted like light beams 12a, 12b, 12A, 12B to form a photosensitive film 11. Incident on.

The insertion of the quarter-wave plate 4 is intended to maintain the rotational symmetry of light as a vector wave, that is, the rotational symmetry of interference fringes by making the light circularly polarized, and refract it as it is as linearly polarized light. As a result, (1) the amount of refracted light depends on the azimuth relationship between the vibrating surface of light and the normal to the refracting surface, and the intensity depending on the refraction position (declination) occurs. This has the effect of avoiding problems such as interference on the surface depending on the vibration plane direction of light.

The light beams 12a and 12A and the light beams 12b and 12B are located diagonally on the same circle with respect to the central axis 9L, and the light beam 12a on the photosensitive film 11 is the light beam 12B on the inner circumference side and the light beam 1
2A interferes with the light flux 12b on the inner peripheral side of this and forms a concentric interference fringe centered on the central axis 9L as a whole. If the exposure pattern is developed, a concentric periodic grating pattern is obtained.

FIG. 4A is a diagram showing the principle of periodic pattern formation, and FIG. 4B is a sectional view showing the grating after development. As shown in FIG. 4 (a), the photosensitive film 11 has θ _A and θ _B
The interference fringes generated by the two light beams 12a and 12B incident at the angle of are (Equation 1) in the direction including the incident surface (radial direction) on this surface.
Has a period Λ of.

[0011]

## EQU1 ## Λ / λ = 1 / (sin θ _A + sin θ _B ) After developing the photosensitive film 11, a concentric grating 14 as shown in FIG. 4B is obtained.

FIG. 5 is a ray tracing diagram of refracted light in the exposure apparatus in the conventional example. The refracting surface is convex outside the point P and concave inside. Therefore, a light beam refracting on the outer peripheral side of the point P
12a and 12A become converging light, and a light beam 1 refracting on the inner circumference side 1
2b and 12B become divergent light. Therefore, the photosensitive film 11
Then, since the incident angles of the light beams 12a, 12A and 12b, 12B increase toward the outer circumference, the grating period Λ becomes smaller toward the outer circumference from (Equation 1). That is, due to the interference of the refracted waves on the convex surface and the concave surface, it is possible to fabricate the grating 14 that has a narrower pitch toward the outer periphery, which is required in a diffraction element such as a grating lens or a concentric circular focusing grating coupler.

[0013]

The above-mentioned conventional exposure apparatus has the following problems.

That is, as is apparent from FIG. 5, the photosensitive film 11
Since the light intensity of the light flux at is proportional to the cross-sectional area of each light flux before refraction, if the light intensity before refraction is uniform (without the ND filter 8), two light fluxes (12a, 12a, The light intensity between 12B) is greatly different, which causes a decrease in contrast. Therefore, by inserting the ND filter 8 that attenuates the amount of transmitted light at a position corresponding to the outer peripheral side of the point P,
It is necessary to make the light intensities between the light beams uniform and improve the contrast. Such an ND filter 8 is manufactured by depositing a metal thin film 8a on the filter portion as shown in FIG. 5, but pinholes are likely to occur in the metal thin film, which causes speckles and has a good grating pattern. Making it difficult.

Since the light beam 12B refracting the concave surface is divergent, the width of the concave portion is narrower than the width of the exposed portion. For example, if the width of the exposed portion is about 1 mm, the width of the concave portion is 100 to 200 microns, and scratches and slight shape errors in this area affect the pitch modulation characteristics (relationship of pitch to radius) of the grating. It has a great impact. That is,
The machining accuracy of the concave portion of the interference lens 9 is quite severe.

In view of the above problems, the present invention can realize a high-contrast exposure without using an ND filter, expose a concentric periodic pattern having a wide width of a refraction portion involved in the exposure, and good accuracy and uniformity. The purpose is to provide a device.

[0017]

In order to solve the above problems and to achieve the object, the present invention provides a refraction body which transmits and refracts laser light emitted from a laser light source, and is substantially orthogonal to the optical axis of the laser light. It consists of a photosensitive film formed on a flat plate, and the refracting surface of the refracting body is a rotating surface with the optical axis as an axis.The light beams refracting each diagonal generatrix of the refracting surface intersect and interfere near the optical axis. Form concentric periodic bright and dark stripes on the optical axis plane,
The bright and dark fringes expose the photosensitive film, and the refraction surface includes two convex surfaces (or concave surface and convex surface), and the outer peripheral convex surface.
Light and dark fringes are obtained by interference between the light flux A after refracting (or concave surface) and passing through the optical axis and the light flux B before refracting through the optical axis and refracting the convex surface on the inner circumferential side at the diagonal position, The light flux A is a divergent light and the light flux B is a focused light on the interference surface.

[0018]

According to the present invention, the light beams refracting each diagonal generatrix of the refracting surface intersect and interfere in the vicinity of the optical axis to form concentric periodic light and dark fringes on the optical axis normal plane. The photosensitive film is exposed. Since the light flux A passes through the optical axis and becomes divergent light on the interference surface, the incident angle with respect to the interference surface becomes larger toward the outer circumference. Since the bundle B of the focused light is incident on the interference surface before passing through the optical axis, the incident angle also becomes larger toward the outer circumference. Therefore, the pitch of the interference fringes is effectively narrowed as the moving radius increases.

[0019]

1 is a sectional view showing the arrangement of an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the same members as those in the conventional example are designated by the same reference numerals for description. An embodiment of the present invention has the same structure as the conventional example except that the generatrix shape of the interference lens 9 is different and the ND filter 8 is not provided. The interference lens 9 has a rotationally symmetric shape with respect to the central axis 9L, the incident surface 9P is a flat surface, and the outgoing surface 9S is a rotational surface close to a conical surface. The interference lens 9 is formed on an XY-axis stage and an XY-axis tilting stage (not shown), and these stages adjust the central axis 9L to coincide with the optical axis 12 of the laser light from the laser light source 1. The sample substrate 10 is configured on an XYZ axis stage and an XY axis tilting stage (not shown), and the substrate surface is orthogonal to the central axis 9L and the sample substrate 10 can be moved along the central axis 9L, that is, the arrow 13.

The operation of the exposure apparatus configured as described above will be described below.

In FIG. 1, the passage of the laser light emitted from the laser light source 1 is controlled by the shutter 2.
The variable attenuator 3 adjusts the light amount stepwise.
Further, the light is converted into circularly polarized light by passing through the quarter-wave plate 4 and converted into focused light by the beam expansion lens 5, condensed into the circular slit of the spatial filter 6, passed through this, and collimated by the collimation lens 7 to obtain a beam diameter. Is converted into a magnified plane wave of.

This plane wave is vertically incident on the incident surface 9P of the interference lens 9 and is refracted on the exit surface 9S like light beams 12a, 12b, 12A and 12B and is incident on the photosensitive film 11. Luminous flux 12a and 12A
And 12b and 12B are at diagonal positions on the same circumference with respect to the central axis 9L, and the light beam 12a on the photosensitive film 11 is the light beam 12B on the inner peripheral side and the light beam 12A is on the inner peripheral side. The light beams 12b interfere with each other to form concentric interference fringes centered on the central axis 9L. When this exposure pattern is developed, a concentric periodic grating pattern is obtained.

FIG. 2 is a ray tracing diagram of refracted light of the exposure apparatus in one embodiment of the present invention. The refracting surface is convex outside the point P and convex inside. Light flux refracting the outer periphery of point P
12a and 12A are converging light, but the photosensitive film 1 passes through the converging point.
Above 1, it is a divergent light. Light flux 12b refracting the inner peripheral side,
12B is a converging light, which reaches the photosensitive film 11 as the converging light. The generatrix of the refracting surface is bent at the point P, and the angle formed by the tangent to the generatrix and the central axis 9L is smaller outside the point P. Therefore, the light fluxes 12a and 12A can intersect the central axis 9L before the photosensitive film 11 because the light fluxes 12a and 12A are close to total reflection and have a large refraction angle on the outer peripheral side of the point P. On the other hand, the refraction angle is small on the inner peripheral side of the point P, and the light beams 12b and 12B have the central axis 9
Reach the photosensitive film 11 before intersecting L. At this time, the photosensitive film 11
Then, since the incident angles of the light beams 12a, 12A and 12b, 12B increase toward the outer circumference, the period Λ of the grating 14 (see FIG. 4B) decreases from (Equation 1) toward the outer circumference. That is, according to the present embodiment, a grating having a narrower pitch toward the outer circumference, which is required for a diffraction element such as a grating lens or a concentric circular focusing grating coupler, can be manufactured.

The light intensity of each light beam on the photosensitive film 11 is proportional to the cross-sectional area of the light beam before refraction. As can be seen in FIG. 2, two light fluxes
There is no big difference in the cross-sectional area before refraction of (12a, 12B). Therefore, even if the ND filter 8 is not provided, there is no large difference in the light intensity between the two light fluxes (12a, 12B) on the photosensitive film 11, and the contrast of interference is high. This is because the focused light is used for the light beam 12B, and thus the cross-sectional area of the light beam before refraction can be increased as compared with the conventional example. Also, since the width of the refraction part is wide, scratches and shape errors in this area cause pitch modulation characteristics of the grating.
The effect on (relationship of pitch to radius) is small.

In the above embodiment, the convex refractive surface is provided outside the point P, but it may be a concave surface. At this time, point P
The light beams 12a and 12A refracting on the outer peripheral side are divergent light and reach the photosensitive film 11 as divergent light. Similar to the above embodiment, if the light beams 12a and 12A intersect the central axis 9L before the photosensitive film 11, the incident angles of the light beams 12a and 12A on the photosensitive film 11 become larger toward the outer circumference. Therefore, from (Equation 1), the grating period Λ can be made smaller toward the outer periphery,
The same effect as the above embodiment can be obtained.

Further, in the above embodiment, the light beams 12a and 12A were able to intersect the central axis 9L before the photosensitive film 11,
Although the generatrix is bent at the point P to increase the refraction angle on the outer peripheral side, this bending may be discontinuous as long as the refraction angle on the outer peripheral side can be increased.

[0027]

As described above, the exposure apparatus of the present invention can realize high-contrast exposure without using an ND filter, and since the width of the refraction portion involved in the exposure is wide, the exposure apparatus is excellent in accuracy and uniformity. The concentric periodic grating pattern can be exposed.

[Brief description of drawings]

FIG. 1 is a sectional view showing the arrangement of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a ray tracing diagram of refracted light of the exposure apparatus in the embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of an exposure apparatus in a conventional example.

4A is a diagram showing a principle of forming a periodic pattern and FIG. 4B is a sectional view showing a grating after development.

FIG. 5 is a ray tracing diagram of refracted light of an exposure apparatus in a conventional example.

[Explanation of symbols]

1 ... Laser light source, 2 ... Shutter, 3 ... Variable attenuator, 4 ... 1/4 wavelength plate, 5 ... Beam expansion lens, 6 ... Spatial filter, 7 ... Collimation lens, 9 ... Interference lens, 10 ... Sample substrate, 11 ... Photosensitive film, 12A, 12B, 12a, 12b ... Luminous flux.

Continued Front Page (72) Inventor Kiyoko Oshima, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A refraction body that transmits and refracts laser light emitted from a laser light source, and a photosensitive film formed on a flat plate that is substantially orthogonal to the optical axis of the laser light. A rotating surface having an optical axis as an axis, and light beams refracting each diagonal generatrix of the refracting surface intersect and interfere in the vicinity of the optical axis to form concentric periodic bright and dark fringes on the optical axis normal plane. In the exposure apparatus in which bright and dark fringes expose the photosensitive film, the refracting surface includes two convex surfaces, the light flux A after refracting the convex surface on the outer peripheral side and passing through the optical axis, and the inner peripheral side at a diagonal position. The exposure apparatus is characterized in that the light and dark fringes are obtained by interference with a light beam B before refracting the convex surface and passing through the optical axis, and the light beam A is divergent light and the light beam B is focused light on the interference surface. 2. A refracting body that transmits and refracts laser light emitted from a laser light source, and a photosensitive film formed on a flat plate that is substantially orthogonal to the optical axis of the laser light. A rotating surface having an optical axis as an axis, and light beams refracting each diagonal generatrix of the refracting surface intersect and interfere in the vicinity of the optical axis to form concentric periodic bright and dark fringes on the optical axis normal plane. In an exposure apparatus in which bright and dark fringes expose the photosensitive film, the refracting surface includes a concave surface and a convex surface, and the light flux A after refracting the concave surface on the outer peripheral side and passing through the optical axis and the inner peripheral side at a diagonal position. The exposure apparatus is characterized in that the light and dark fringes are obtained by interference with a light beam B before refracting the convex surface and passing through the optical axis, and the light beam A is divergent light and the light beam B is focused light on the interference surface. 3. The exposure apparatus according to claim 1, wherein there is a bending point or a discontinuity point on the bus bar between the convex surface on the outer peripheral side and the convex surface on the inner peripheral side. 4. The exposure apparatus according to claim 2, wherein a bending point or a discontinuity point is present on the bus bar between the concave surface on the outer peripheral side and the convex surface on the inner peripheral side. 5. A refraction angle of light refracting the convex surface on the outer peripheral side is larger than a refraction angle of light refracting the convex surface on the inner peripheral side within a plane including a rotation axis and a generatrix of the refracting surface. The exposure apparatus according to claim 1, wherein: 6. A refraction angle of light refracting the concave surface on the outer peripheral side is larger than a refraction angle of light refracting the convex surface on the inner peripheral side in a plane including a rotation axis and a generatrix of the refracting surface. The exposure apparatus according to claim 2, wherein: