WO2010090190A1 - Laser exposure device - Google Patents

Abstract

The device is provided with a first fly eye lens (2) to enlarge the cross-sectional shape of a laser beam, a first light path difference adjustment member (3) that is provided on the laser beam incident side of the first fly eye lens (2) and creates phase differences in the laser beam that enters each condenser lens (2a) of the first fly eye lens (2), a condenser lens (4) for transforming the laser beam exiting the light path difference adjustment member (3) into parallel light, a second fly eye lens (6) to produce uniform light intensity distribution by the laser beam in a photomask illumination area, and a second light path difference adjustment member (7) that is provided on the laser beam incident side of the second fly eye lens (6) and creates phase differences in the laser beam that enters each condenser lenses (6a) of the second fly eye lens (6). As a result, interference patterns in the laser beam created by the first fly eye lens are averaged out, and uneven lighting by the laser beam is reduced.

Description

Laser exposure equipment

The present invention relates to a laser exposure apparatus including a fly-eye lens in which a plurality of condensing lenses are arranged in a plane substantially orthogonal to the optical axis of laser light, and more specifically, interference fringes of laser light generated by the fly-eye lens. And a laser exposure apparatus that enables uniform exposure by reducing illuminance unevenness of laser light.

A conventional laser exposure apparatus includes a beam expander that expands the diameter of the laser beam and a fly that equalizes the intensity distribution of the laser beam with the expanded diameter in order to uniformly irradiate the object with the laser beam. Optical integrators such as eye lenses are used. Furthermore, an optical path difference adjusting member is provided between the beam expander and the fly-eye lens in order to reduce interference fringes caused by interference of the light transmitted through the fly-eye lens due to the coherency of the laser light. There are some (see, for example, Patent Document 1).

JP 2004-12757 A

However, in such a conventional laser exposure apparatus, the optical path difference adjusting member is provided only between the beam expander and the fly-eye lens, so that the interference fringes due to the transmitted light of the fly-eye lens are completely removed. However, it is difficult to form a fine pattern due to uneven illuminance on the object to be exposed due to slightly remaining interference fringes.

Accordingly, the present invention addresses such problems, averages the interference fringes of the laser light produced by the fly-eye lens, and reduces the unevenness of the illuminance of the laser light to enable uniform exposure. The purpose is to provide.

In order to achieve the above object, a laser exposure apparatus according to the present invention includes a laser light source that emits laser light and a plurality of lenses arranged in a plane substantially orthogonal to the optical axis of the laser light, and temporarily emits emitted light. A first fly-eye lens that diverges radially after condensing and expands a cross-sectional shape of the laser light; and a first fly-eye lens disposed on the laser light incident side of the first fly-eye lens. First phase difference generating means for generating a phase difference in the laser light respectively incident on each of the condenser lenses, and a condenser for emitting the first fly-eye lens and converting the laser light having an enlarged cross-sectional shape into parallel light A second fly-eye that has a lens and a plurality of lenses arranged side by side in a plane substantially orthogonal to the optical axis of the condenser lens, and uniformizes the light intensity distribution in the illumination area of the photomask by the laser light. And a second phase difference occurrence that causes a phase difference in the laser light that is disposed on the laser light incident side of the second fly-eye lens and is incident on each condenser lens of the second fly-eye lens. Means.

With such a configuration, laser light is radiated from the laser light source, and incident on the first phase difference generating means disposed on the laser light incident side of the first fly-eye lens without expanding the beam diameter, The first phase difference generating means generates a phase difference between the laser beams respectively incident on the plurality of condensing lenses arranged in a plane substantially orthogonal to the optical axis of the first fly-eye lens. The coherency of the laser light emitted from the fly-eye lens is reduced, the light emitted from each condenser lens is once condensed by the first fly-eye lens, and then diverged radially to expand the cross-sectional shape of the laser light. The laser light whose cross-sectional shape is enlarged by the lens is converted into parallel light, and the second fly-eye lens is arranged on the optical axis of the second fly-eye lens by the second phase difference generating means arranged on the laser light incident side of the second fly-eye lens. Nearly orthogonal plane A phase difference is caused in the laser light respectively incident on the plurality of condensing lenses arranged side by side to reduce the coherency of the laser light emitted from the second fly-eye lens again, and the second fly-eye lens reduces the light intensity. The photomask is irradiated with a uniform distribution.

In addition, a transparent parallel plane rotating plate that is inclined with respect to the optical axis and rotates about the optical axis is provided on the laser beam incident side of the condenser lens. As a result, a laser which is provided on the laser beam incident side of the condenser lens and is rotated around the optical axis of the transparent parallel plane rotating plate arranged to be inclined with respect to the optical axis and incident on the second fly-eye lens. The incident angle of light is changed.

According to the laser exposure apparatus of the first aspect of the present invention, the first and second phase difference generating means are used for the plurality of laser beams respectively incident on the condensing lenses of the first and second raiai lenses. Since the phase difference is generated and the coherency of the laser light emitted from the first and second fly-eye lenses is reduced, interference fringes generated in the illumination area can be reduced as compared with the prior art. Further, as compared with the case where one fly-eye lens is used, the intensity distribution of the laser light can be made more uniform, and the illuminance unevenness can be further reduced. Therefore, the photomask can be uniformly illuminated to enable uniform exposure, and a fine pattern can be easily exposed on the object to be exposed. In addition, since the first fly-eye lens has both a laser beam homogenizing function and a beam diameter expanding function, it is not necessary to provide a separate beam expander, and the number of parts can be reduced.

Further, according to the invention of claim 2, the incident angle of the laser beam incident on the second fly-eye lens can be changed during exposure. Therefore, the illumination area on the photomask by the laser light emitted from each condensing lens of the second fly-eye lens can be finely moved in accordance with the rotation of the parallel plane rotating plate, and is generated in the illumination area on the photomask. The interference fringes of the laser light can be averaged and made inconspicuous. Thereby, the illumination intensity nonuniformity of a laser beam can be reduced further, and a to-be-exposed body can be exposed more uniformly.

It is a front view which shows 1st Embodiment of the laser exposure apparatus by this invention. It is explanatory drawing which shows the relationship between the position of the parallel plane rotating plate of the said laser exposure apparatus, the incident angle of the laser beam which injects into a 2nd fly eye lens, and the change of the illumination area on a photomask. It is a front view which shows 2nd Embodiment of the laser exposure apparatus by this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front view showing a first embodiment of a laser exposure apparatus according to the present invention. This laser exposure apparatus exposes an object to be exposed by irradiating a laser beam through a photomask, and includes a laser light source 1, a first fly-eye lens 2, a first optical path difference adjusting member 3, A first condenser lens 4, a parallel plane rotating plate 5, a second fly's eye lens 6, a second optical path difference adjusting member 7, and a second condenser lens 8 are provided.

The laser light source 1 is an ultraviolet pulse laser oscillator, and an excimer laser or a YAG laser can be used.

A first fly-eye lens 2 is provided in front of the laser light source 1 in the radiation direction of the laser light. The first fly-eye lens 2 once functions to condense the laser light emitted from the laser light source 1 and then diverge it radially to expand the cross-sectional shape of the laser light. The light intensity distribution in the incident side surface of the second fly's eye lens 6 is made uniform, and a plurality of condensing lenses 2a are arranged in a plane substantially orthogonal to the optical axis of the laser beam, for example, 3 vertical × 3 horizontal. They are arranged in a matrix.

A first optical path difference adjusting member 3 is provided on the laser light incident side of the first fly-eye lens 2. The first optical path difference adjusting member 3 reduces the coherency of the laser light emitted from the first fly-eye lens 2 and emits a plurality of laser lights emitted from the respective condensing lenses 2 a of the first fly-eye lens 2. Is to suppress interference on the incident side surface of the second fly-eye lens 6, and a phase difference is applied to a plurality of laser beams respectively incident on the condenser lenses 2 a of the first fly-eye lens 2. This is the first phase difference generating means to be generated.

Specifically, the first optical path difference adjusting member 3 is different in length in the axial direction parallel to the optical axis and has a refractive index of 1 corresponding to each condenser lens 2a of the first fly-eye lens 2. A larger rod-shaped transparent member 3a, such as quartz glass or transparent glass, is provided, and the optical path lengths of a plurality of laser beams respectively incident on the condenser lenses 2a of the first fly-eye lens 2 are provided. It plays a function of changing.

A first condenser lens 4 is provided on the downstream side of the first fly-eye lens 2 in the traveling direction of the laser light. The first condenser lens 4 is a plano-convex lens in which the radial laser beam emitted from the first fly-eye lens 2 is converted into parallel light, and the light incident side is flat. The first fly-eye lens 2 is arranged so as to substantially match the rear focal position.

A parallel plane rotating plate 5 is provided on the optical path between the first fly-eye lens 2 and the first condenser lens 4. The plane-parallel rotating plate 5 is for changing the incident angle of laser light incident on a second fly's eye lens 6 described later, and is provided with a transparent, for example, glass disc tilted with respect to the optical axis. This rotates around the optical axis. Thereby, the illumination area of the laser light on the photomask 9 is finely moved, and the interference fringes of the laser light generated by the second fly-eye lens 6 generated on the photomask 9 are averaged to be inconspicuous. Further, the illuminance unevenness of the laser light emitted from the first fly-eye lens 3 through the first optical path difference adjusting member 3 is reduced.

FIG. 2 is an explanatory diagram showing the relationship between the position of the plane-parallel rotating plate 5, the incident angle of the laser light incident on the second fly-eye lens 6, and changes in the illumination area on the photomask 9. When the plane-parallel rotating plate 5 rotates around the optical axis, the plane-parallel rotating plate 5 reciprocates as indicated by arrows in the front view of FIG. In this case, when the parallel plane rotating plate 5 is located at the position indicated by the solid line in FIG. 5A, the laser light is refracted by the parallel plane rotating plate 5 as indicated by the solid line, and the laser beam is refracted at a constant incident angle. The light enters the condenser lens 6 a of the second fly-eye lens 6.

On the other hand, when the plane-parallel rotating plate 5 rotates and reaches the position indicated by the broken line in FIG. 2A, the laser light is refracted by the plane-parallel rotating plate 5 as indicated by the broken line, which is different from the above. The light enters the condenser lens 6a at an incident angle. As a result, the illumination area 10 on the photomask 9 illuminated by the laser beam emitted from the second fly-eye lens 6 moves from the area indicated by the solid line to the area indicated by the broken line in FIG. As described above, by rotating the plane-parallel rotating plate 5 and changing the incident angle of the laser light incident on the second fly-eye lens 6, the intensity unevenness of the laser light emitted from the first fly-eye lens 2 is reduced. While averaging, the illumination area 10 on the photomask 9 is finely moved, and the light and dark pattern of the interference fringes and the illuminance unevenness generated on the photomask 9 due to the interference of the plurality of laser beams emitted from the second fly-eye lens 6 Can be averaged and made inconspicuous.

A second fly-eye lens 6 is provided on the downstream side of the first condenser lens 4 in the traveling direction of the laser light. The second fly-eye lens 6 makes the light intensity distribution in the illumination area 10 of the photomask 9 uniform, and a plurality of condensing lenses in a plane substantially perpendicular to the optical axis of the first condenser lens 4. 6a is arranged in a matrix of, for example, 12 vertical x 4 horizontal, and is a double fly-eye lens in which two identical fly-eye lenses are combined.

A second optical path difference adjusting member 7 is provided on the laser beam incident side of the second fly-eye lens 6. The second optical path difference adjusting member 7 reduces the coherency of the laser light emitted from the second fly-eye lens 6 and emits a plurality of laser lights emitted from the respective condenser lenses 6 a of the second fly-eye lens 6. Is a second phase difference that causes a phase difference in a plurality of laser beams respectively incident on the condenser lenses 6a of the second fly-eye lens 6. It is a means of occurrence.

Specifically, the second optical path difference adjusting member 7 has different lengths in the axial direction parallel to the optical axis, corresponding to the four columns of condensing lenses 6a of the second fly-eye lens 6, respectively. A plate-shaped transparent member 7a having a refractive index larger than 1 such as quartz glass or transparent glass is formed by superimposing them in the horizontal direction and vertically incident on each condenser lens 6a of the second fly-eye lens 6. It functions to change the optical optical path length between columns adjacent to each other in the horizontal direction of the laser beams in the columns.

A second condenser lens 8 is provided on the downstream side of the second fly-eye lens 6 in the traveling direction of the laser light. The second condenser lens 8 is used to convert the laser light emitted from the second fly-eye lens 6 into parallel light so as to enter the photomask 9 vertically, and the two light incident sides are flat. It is configured by combining plano-convex lenses, and is arranged such that its front focal position substantially matches the rear focal position of the second fly-eye lens 6. In FIG. 1, reference numerals 11, 12, and 13 denote planar reflection mirrors that bend the optical path.

Next, the operation of the thus configured laser exposure apparatus will be described.
The laser light emitted from the laser light source 1 is reflected by the two reflecting mirrors 11 and 12 and enters the first optical path difference adjusting member 3. The first optical path difference adjusting member 3 corresponds to each condenser lens 2 a of the first fly-eye lens 2, and has a plurality of refractive indexes greater than 1, each having a different axial length parallel to the optical axis. Therefore, the plurality of laser beams emitted from the plurality of transparent members 3a of the first optical path difference adjusting member 3 are out of phase with each other.

The plurality of laser beams emitted from the plurality of transparent members 3 a of the first optical path difference adjusting member 3 are respectively incident on the corresponding condensing lenses 2 a of the first fly-eye lens 2. The plurality of laser beams emitted from the respective condensing lenses 2a of the first fly-eye lens 2 are condensed at the rear focal points of the respective condensing lenses 3a and then radiate radially. In this case, the laser beams incident on the condenser lenses 2a of the first fly-eye lens 2 are out of phase with each other, so that the coherency of the laser beams emitted from the first fly-eye lens 2 is reduced. . Accordingly, on the second fly-eye lens 6 illuminated by the plurality of laser beams emitted from the respective condensing lenses 2a, the interference of the respective laser beams is suppressed, the generation of interference fringes is suppressed, and the second fly-eye lens is suppressed. The lens 6 is illuminated substantially uniformly.

The radial laser beam emitted from the first fly-eye lens 3 is collimated by the first condenser lens 4 and then enters the second fly-eye lens 6 through the second optical path difference adjusting member 7. . At this time, the laser beam incident side of the first condenser lens 4 is provided with a parallel plane rotating plate 5 in which a transparent disk made of, for example, glass is inclined with respect to the optical axis, and this is centered on the optical axis. Since it is rotating, the position of the chief ray of the laser beam that is refracted by the parallel plane rotating plate 5 and emitted therefrom is incident on the first condenser lens 4 as shown in FIG. 2A. It changes in the radial direction of the lens 4. As a result, the incident angle of the laser light incident on the second fly-eye lens 6 changes as shown in FIG. At the same time, the illuminance unevenness of the laser light incident on the second fly's eye lens 6 is averaged.

On the other hand, the laser light emitted from the first condenser lens 4 has a second optical path difference formed by combining a plurality of transparent members 7a each having a different axial length parallel to the optical axis and a refractive index larger than 1. In the adjustment member 7, the second fly-eye lens 6 is illuminated by being divided into a plurality of laser beams. At this time, since the optical optical path length of each laser beam passing through each transparent member 7a of the second optical path difference adjusting member 7 is different, between each laser beam emitting the second optical path difference adjusting member 7, There is a phase difference. Therefore, the coherency of the laser light emitted from the second fly-eye lens 6 is reduced, and the interference of each laser light emitted from the condenser lens 6a of the second fly-eye lens 6 and applied to the photomask 9 is suppressed. Will be.

The laser light emitted from each condenser lens 6a of the second fly's eye lens 6 is once condensed at the focal point of each condenser lens 6a, and then radiates and enters the plane reflecting mirror 13. The laser light is reflected by the plane reflection mirror 13, is then made parallel light by the second condenser lens 8, and enters the photomask 9 substantially perpendicularly to illuminate the photomask 9 uniformly.

Here, in the first embodiment, the second optical path difference adjusting member 7 is configured by superimposing plate-like transparent members 7a having different lengths in the optical axis direction and long in the vertical direction in the horizontal direction. The laser light having the same phase is incident on the condensing lenses 6a arranged in the vertical direction of the fly-eye lens 6 of No. 2, and the phase of the condensing lenses 6a arranged in the horizontal direction is made incident on the condensing lenses 6a arranged in the horizontal direction. Since different laser beams are incident, the in-phase laser beams emitted from the condenser lenses 6 a arranged in the vertical direction of the second fly-eye lens 6 are incident on the illumination region 10 on the photomask 9. There is a possibility that interference fringes due to the above occur slightly. However, in the first embodiment, the parallel plane rotating plate 5 is provided on the incident side of the first condenser lens 4 and is rotated about its optical axis. The incident angle of the laser light incident on the eye lens 6 changes. Therefore, as shown in FIG. 2B, the illumination area 10 by the laser light on the photomask 9 is finely moved, the light and dark patterns of the interference fringes are averaged and become inconspicuous, and the illuminance unevenness of the laser light is averaged. , Uniform exposure can be performed.

FIG. 3 is a front view showing a second embodiment of the laser exposure apparatus according to the present invention. The second embodiment is different from the first embodiment in that a collimation mirror 14 is arranged at the position of the plane reflection mirror 13 in place of the second condenser lens 8. In this case, the front focal position of the collimation mirror 14 is substantially matched with the rear focal position of the second fly-eye lens 6. As a result, the laser light emitted from the second fly-eye lens 6 can be converted into parallel light and incident perpendicularly on the photomask 9.

In the first and second embodiments, the second optical path difference adjusting member 7 corresponds to each of the four columns of condensing lenses 6a of the second fly-eye lens 6 and is parallel to the optical axis. Although the case where the plate-like transparent members 7a having different lengths in the axial direction are formed by superimposing them in the lateral direction has been described, the present invention is not limited to this, and each of the second fly-eye lenses 6 is collected. It may be formed by combining rod-shaped transparent members having different lengths in the axial direction parallel to the optical axis corresponding to the optical lens 6a. In this case, since the phases of the laser beams emitted from the condenser lenses 6a of the second fly-eye lens 6 are all different, the possibility that the laser beams interfere with each other on the photomask 9 is reduced.

In the above embodiment, the case where the phase difference generating means is an optical path difference adjusting member has been described. However, the present invention is not limited to this, and a phase plate provided corresponding to each condenser lens of the fly-eye lens. There may be.

DESCRIPTION OF SYMBOLS 1 ... Laser light source 2 ... 1st fly eye lens (fly eye lens)
2a ... Condensing lens of the first fly-eye lens 3 ... First optical path difference adjusting member (first phase difference generating means)
3a: Transparent member of first optical path difference adjusting member 4 ... First condenser lens 5 ... Parallel plane rotating plate 6 ... Second fly-eye lens 6a ... Condensing lens of second fly-eye lens 7 ... Second Optical path difference adjusting member (second phase difference generating means)
7a: Transparent member of second optical path difference adjusting member 8 ... Second condenser lens 9 ... Photomask 10 ... Illumination area on photomask

Claims (2)

A laser light source that emits laser light;
A first fly-eye lens in which a plurality of lenses are arranged side by side in a plane substantially orthogonal to the optical axis of the laser light, and after converging the emitted light, the first fly-eye lens expands the cross-sectional shape of the laser light by diverging radially; ,
First phase difference generating means that is arranged on the laser beam incident side of the first fly-eye lens and that causes a phase difference in the laser light incident on each condenser lens of the first fly-eye lens;
A condenser lens that emits the first fly-eye lens and converts the laser light having an enlarged cross-sectional shape into parallel light;
A second fly-eye lens in which a plurality of lenses are arranged side by side in a plane substantially orthogonal to the optical axis of the condenser lens, and the light intensity distribution in the illumination area of the photomask by the laser light is made uniform;
Second phase difference generating means disposed on the laser beam incidence side of the second fly's eye lens and causing a phase difference in the laser light respectively incident on each condenser lens of the second fly's eye lens;
A laser exposure apparatus comprising: 2. A laser exposure apparatus according to claim 1, wherein a transparent parallel plane rotating plate is provided on the laser beam incident side of the condenser lens so as to be inclined with respect to the optical axis and to rotate about the optical axis. .

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