WO2011048877A1

WO2011048877A1 - Laser exposure device

Info

Publication number: WO2011048877A1
Application number: PCT/JP2010/065236
Authority: WO
Inventors: 畑中　誠
Original assignee: 株式会社ブイ・テクノロジー
Priority date: 2009-10-22
Filing date: 2010-09-06
Publication date: 2011-04-28
Also published as: TW201128320A; JP2011091177A

Abstract

Disclosed is a laser exposure device provided with: a laser light source (1); a first fly-eye lens (2) which uniformizes the light intensity distribution within a plane orthogonal to a light axis (9), and also after temporarily focusing emitted light, radially diverges the focused light to thereby enlarge the cross-sectional shape of the laser light; a first condenser lens (4) which converts the laser light the cross-sectional shape of which is enlarged into parallel light; a second fly-eye lens (5) which uniformizes the light intensity distribution within an illumination region on a photomask (12) illuminated by the laser light; a diffuser plate (3) which is provided between the first fly-eye lens (2) and the first condenser lens (4) and diffuses the laser light; and a transparent rotation plate (6) which is provided on the laser light emission side of the second fly-eye lens (5), has a surface (6a) inclined with respect to the light axis (9), and rotates around the light axis (9). Consequently, it becomes possible to average interference fringes of the laser light, which are generated by the fly-eye lenses, and reduce the illumination unevenness of the laser light, thereby enabling uniform exposure.

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's eye lens in order to reduce interference fringes caused by interference of the light transmitted through the fly's 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 unit lenses that are arranged in a plane substantially orthogonal to the optical axis of the laser light source. A first fly-eye lens that equalizes the intensity distribution of the light in the orthogonal plane, condenses the emitted light, and then diverges radially to enlarge the cross-sectional shape of the laser light; and the first fly-eye lens A condenser lens that emits laser light whose cross-sectional shape is expanded by emitting an eye lens, and a plurality of unit lenses provided on a downstream side of the condenser lens in the light traveling direction and substantially perpendicular to the optical axis thereof Are arranged, and a second fly-eye lens that equalizes the light intensity distribution in the illumination area on the photomask illuminated by the laser light, and between the first fly-eye lens and the condenser lens A diffusing plate for diffusing the laser beam; and provided on the laser beam emission side of the second fly-eye lens, having a surface inclined with respect to the optical axis, and rotating about the optical axis A transparent rotating plate.

With such a configuration, laser light is emitted from the laser light source, and a plurality of unit lenses are arranged in a plane substantially orthogonal to the optical axis of the laser light source, and the first fly-eye lens is in the plane orthogonal to the optical axis. The light intensity distribution is made uniform, and the emitted light is once condensed, then radially diverged to enlarge the cross-sectional shape of the laser light, and the first fly-eye lens is emitted from the condenser lens to enlarge the cross-sectional shape. The laser beam is converted into parallel light, and is provided on the downstream side in the light traveling direction of the condenser lens. The second fly-eye lens in which a plurality of lenses are arranged in a plane substantially perpendicular to the optical axis The light intensity distribution in the illumination area of the illuminated photomask is made uniform. In this case, the laser beam is diffused by a diffusion plate provided between the first fly-eye lens and the condenser lens, and the interference fringes of the laser beam generated on the second fly-eye lens are averaged, and the second A transparent rotating plate provided on the laser beam emission side of the fly-eye lens and having a surface inclined with respect to the optical axis is rotated about the optical axis to finely move the illumination area on the photomask by the laser beam. Further uniformize the interference fringes of the laser beam.

The plurality of unit lenses of the first fly-eye lens are arranged at a pitch that can sufficiently disperse the energy of the laser light so that the laser light condensed by each unit lens does not turn air into plasma. . Thereby, the energy of the laser beam is sufficiently dispersed by each unit lens of the first fly-eye lens, and even if the laser beam is collected by each unit lens, the air is prevented from being turned into plasma.

Furthermore, the diffusion plate is a ground glass plate in which fine uneven patterns are randomly formed on the surface. Thereby, the diffusion angle of the laser beam is controlled to a predetermined value with a ground glass plate on which fine uneven patterns are randomly formed on the surface.

In the second fly-eye lens, a pair of lens arrays in which a plurality of unit lenses are arranged in a plane are opposed to each other, and a principal ray of diffused light that is diffused and incident by the diffuser plate is used as an optical axis. It is configured to inject in parallel. As a result, the principal ray of the diffused light that is diffused by the diffuser plate and incident by the second fly-eye lens in which a pair of lens arrays in which a plurality of unit lenses are arranged in a plane are opposed to each other is made parallel to the optical axis. Eject.

The rotating plate is adapted to rotate at least once from the start to the end of the multiple exposure when one exposure is a multiple exposure by a plurality of shots of the laser beam. As a result, when one exposure is a multiple exposure using a plurality of shots of laser light, the rotating plate is rotated at least one time from the start to the end of the multiple exposure to reduce the unevenness of the laser light on the photomask. To reduce.

Further, the condenser plate further includes another condenser lens that converts the laser light applied to the photomask into parallel light on the downstream side in the light traveling direction of the rotating plate, and is close to the exit side face of the other condenser lens. A transparent protective plate for preventing foreign matter from adhering to the surface is detachably provided. As a result, the laser beam applied to the photomask by another condenser lens provided on the downstream side of the light traveling direction of the rotating plate is converted into parallel light, and is detachably provided close to the exit side surface of the other condenser lens. A transparent protective plate prevents foreign matter from adhering to the surface of another condenser lens.

According to the laser exposure apparatus of the first aspect, the interference fringes of the laser light generated by the fly-eye lens can be averaged, and the illuminance unevenness of the laser light can be reduced to uniformly illuminate the photomask. Therefore, uniform exposure can be performed and a fine pattern can be easily exposed on the object to be exposed. Further, since the first fly-eye lens has both the function of uniformizing the intensity distribution of the laser light and the function of expanding the beam diameter, it is not necessary to provide a separate beam expander, and the number of parts can be reduced. .

According to the second aspect of the present invention, the energy of the laser beam is sufficiently dispersed by each unit lens of the first fly-eye lens, and even if the laser beam is condensed by each unit lens, the air is turned into plasma. The light utilization efficiency can be improved. Therefore, since it is not necessary to make the vicinity of the condensing point of the laser beam by the first fly-eye lens in a vacuum atmosphere in order to prevent air from being turned into plasma, the configuration of the apparatus can be simplified. Furthermore, since the arrangement pitch of the unit lenses of the first fly-eye lens is approximately one order of magnitude smaller than the arrangement pitch of the unit lenses of the fly-eye lens that is generally used, the laser emitted from the laser light source Even if the light profile is non-uniform, it can be made uniform by the first fly-eye lens. Thereby, the illuminance distribution on the photomask can be made more uniform.

Further, according to the invention of claim 3, the diffusion angle of the laser light diffused by the diffusion plate can be controlled to a predetermined value. Therefore, it is possible to average the interference fringes caused by the light emitted from each unit lens of the first fly-eye lens while suppressing the diffusion angle of the laser light to a predetermined value.

According to the fourth aspect of the present invention, the laser light diffused by the diffusion plate can be squeezed by the second fly-eye lens and irradiated onto the photomask, and the utilization efficiency of the laser light can be improved. .

Further, according to the invention of claim 5, it is possible to uniformly illuminate the entire irradiation region on the photomask by moving the interference fringe for each shot of the laser beam.

Furthermore, according to the invention of claim 6, for example, it is possible to prevent the mist of the photosensitive material from adhering to the surface of another condenser lens and fogging the lens. In this case, since the protective plate is detachably provided, the protective plate can be easily removed and cleaned. Therefore, if the protective plate is periodically cleaned, the exposure can always be performed under certain conditions, and the exposure can be stabilized.

It is a front view which shows embodiment of the laser exposure apparatus by this invention. It is a principal part expanded sectional view which shows the structure of the 2nd fly eye lens used for the said laser exposure apparatus. It is explanatory drawing which shows the shape of the rotating plate used for the said laser exposure apparatus, and its function. It is explanatory drawing which shows the profile of a laser beam, (a) shows an example of the profile of the laser beam radiated | emitted from the laser light source, (b) shows the example of the profile homogenized with the 1st fly eye lens. Is.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front view showing an 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. The laser light source 1, the first fly-eye lens 2, the diffusion plate 3, and the first condenser lens 4, a second fly-eye lens 5, a rotating plate 6, a second condenser lens 7, and a protective plate 8.

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 makes the light intensity distribution in a plane orthogonal to the optical axis 9 of the laser light source 1 uniform, condenses the laser light once, and then diverges radially to cross-section the laser light. It functions as a beam expander that expands the shape. For example, a plurality of minute unit lenses (condensing lenses) with a pitch of about 100 μm to about 300 μm, for example, in a plane substantially perpendicular to the optical axis 9 of the laser beam. × 100 are arranged in a matrix.

A diffusion plate 3 is provided on the downstream side of the first fly-eye lens 2 in the traveling direction of the laser light. This diffusing plate 3 averages interference fringes generated by diffusing the laser light and emitting each unit lens of the first fly-eye lens 2 to interfere on the second fly-eye lens 5 described later. It is a ground glass-like plate in which fine irregular patterns of about 5 μm are randomly formed on the surface. Thereby, the diffusion angle of the laser beam can be controlled to about 1 °, for example. In addition, the disposition position of the diffusion plate 3 can be arbitrarily selected between the back focal position of the first fly-eye lens 2 and the first condenser lens 4 described later.

A first condenser lens 4 is provided on the downstream side of the diffusion plate 3 in the traveling direction of the laser light. The first condenser lens 4 is a plano-convex lens that emits the first fly-eye lens 2 and converts the laser light radially diffused by the diffusion plate 3 into parallel light, and has a flat light incident side. Thus, the front focal position is substantially matched with the rear focal position of the first fly-eye lens 2.

A second fly-eye lens 5 is provided on the downstream side of the first condenser lens 4 in the traveling direction of the laser light. The second fly's eye lens 5 includes a plurality of unit lenses (condensing lenses) arranged in a matrix at a pitch of, for example, several mm in a plane substantially orthogonal to the optical axis 9 of the first condenser lens 4. The light intensity distribution in the illumination area of the photomask 12 illuminated with light is made uniform, a pair of lens arrays in which a plurality of unit lenses are arranged in a plane are arranged facing each other, and diffused by the diffusion plate 3 Thus, the principal ray of the diffused light incident thereon is emitted in parallel with the optical axis 9.

Specifically, as shown in FIG. 2, the second fly-eye lens 5 includes a first lens array 10 disposed on the upstream side in the light traveling direction and a second lens array 11 disposed on the downstream side. The optical axes of the

unit lenses

10a and 11a corresponding to each other in the

lens arrays

10 and 11 are made to coincide with each other. In this case, the front focal position of the unit lens 11 a of the second lens array 11 matches the approximate vertex position of the curved surface of the unit lens 10 a of the first fly-eye lens 2. As a result, the principal ray of the diffused light (laser light 13) diffused by the diffusing plate 3 and incident on the first lens array 10 can be emitted parallel to the optical axis 9 by the second lens array 11. Therefore, the laser beam 13 diffused by the diffusion plate 3 can be squeezed by the second fly-eye lens 5 to irradiate the photomask 12, and the utilization efficiency of the laser beam 13 can be improved.

When the first and

second lens arrays

10 and 11 are the same, the back focal position of the first lens array 10 is a substantially vertex position of the curved surface of the unit lens 11a of the second lens array 11. Therefore, the second lens array 11 may be damaged by the laser light 13 collected by the first lens array 10. Accordingly, the unit lens 10 a of the first lens array 10 has a longer focal length than the unit lens 11 a of the second lens array 11 so that the laser beam 13 is not condensed on the second lens array 11. Alternatively, a short one may be selected.

A rotating plate 6 is provided on the downstream side of the second fly-eye lens 5 in the traveling direction of the laser beam 13. The rotating plate 6 finely moves the illumination region 14 (see FIG. 3B) of the laser beam 13 on the photomask 12, and the laser beam 13 emitted from the plurality of unit lenses 11a of the second fly-eye lens 5 is emitted. An interference fringe generated by interference is averaged to make it inconspicuous, and is made of a transparent quartz plate having a surface 6a inclined with respect to the optical axis 9 and rotating around the optical axis 9. is there.

Specifically, as shown in FIG. 3A, the light emitting side surface 6a is a so-called wedge substrate formed with an inclination of about 1 ° with respect to a surface orthogonal to the optical axis 9. As a result, the laser beam 13 incident on the rotating plate 6 is refracted and emitted by the inclined surface 6a on the emission side, and the illumination area of the laser beam 13 on the photomask 12 (shown with diagonal lines shown in FIG. 5B). The center of the region 14 is shifted laterally from the center O of the irradiation region 15 (the region surrounded by the broken line shown in FIG. 5B). Therefore, when the rotating plate 6 is rotated around the optical axis 9 in this state, the illumination area 14 of the laser beam 13 is within the area surrounded by the broken line shown in FIG. Are moved so as to make a circular motion, and the entire region of the irradiation region 15 is illuminated by the laser beam 13. A broken line indicated by an arrow in FIG. 5B is a locus drawn by the center of the illumination area 14 while the rotating plate 6 is rotated once.

At this time, the rotation of the rotating plate 6 is controlled so as to rotate at least once from the start to the end of the multiple exposure when the single exposure is a multiple exposure by a plurality of shots of the laser beam 13. Thereby, the irradiation region 15 on the photomask 12 is illuminated with the laser beam 13 without excess or deficiency.

A second condenser lens 7 is provided on the downstream side of the rotating plate 6 in the traveling direction of the laser beam 13. The second condenser lens 7 is for converting the laser beam 13 emitted from the second fly-eye lens 5 into parallel light and allowing it to enter the photomask 12 vertically, and two plano-convex lenses 7a and 7b. The front focal position of the second fly-eye lens 5 is substantially matched with the rear focal position of the second fly-eye lens 5.

A protective plate 8 is detachably provided in the vicinity of the exit side surface of the second condenser lens 7. The protective plate 8 is a transparent quartz substrate for preventing foreign matters such as mist of a photosensitive material from adhering to the surface of the second condenser lens 7 and causing the lens to become fogged. In FIG. 1,

reference numerals

16, 17, and 18 denote planar reflecting mirrors that bend the optical path.

Next, the operation of the thus configured laser exposure apparatus will be described.
The laser beam 13 emitted from the laser light source 1 is reflected by the two

plane reflecting mirrors

16 and 17 and enters the first fly-eye lens 2. The plurality of laser beams 13 emitted from the plurality of minute unit lenses of the first fly-eye lens 2 are condensed at the rear focal points of the respective unit lenses, and then radiate radially.

In this case, since the unit lenses of the first fly-eye lens 2 are arranged in a matrix at a minute pitch of about 100 μm to about 300 μm, the profile of the laser light 13 emitted from the laser light source 1 is, for example, FIG. Even if it is non-uniform as shown in (a), it is mixed when exiting the first fly-eye lens 2 and is made substantially uniform as shown in FIG. Furthermore, since the energy of the laser beam 13 is dispersed by a large number of minute unit lenses, air is not turned into plasma even if the laser beam 13 is collected by the unit lens. Therefore, there is no possibility that the plasmaized air will diffusely reflect the laser beam 13 and reduce the luminance of the laser beam 13 irradiated to the photomask 12.

The laser beam 13 emitted from the first fly-eye lens 2 and diverging radially is incident on the diffusion plate 3 formed of a ground glass plate having a fine uneven pattern of about 5 μm randomly formed on the surface. In this diffusing plate 3, the incident laser beam 13 is diffused with the diffusion angle controlled to about 1 °. Thereby, each unit lens of the first fly-eye lens 2 is emitted, and the interference fringes of the laser beam 13 that interferes on the incident-side surface of the second fly-eye lens 5 are averaged. Further, since the diffusion angle of the laser beam 13 is controlled to about 1 °, excessive divergence of the laser beam 13 is suppressed, and almost all of the laser beam 13 emitted from the laser light source 1 is used for illumination of the photomask 12. It can be used effectively.

The radial laser beam 13 emitted from the diffusion plate 3 is collimated by the first condenser lens 4 and then enters the second fly-eye lens 5. In the second fly-eye lens 5, the diffused light (laser light 13) diffused by the diffuser 3 and incident on the unit lens 10a of the first lens array 10 has its principal ray as shown in FIG. The unit lens 11 a corresponding to the second lens array 11 is made parallel to the optical axis 9. Thereby, the diffused light diffused by the diffusion plate 3 is narrowed down by the second fly-eye lens 5 and is effectively used for illumination of the photomask 12.

The laser beam 13 emitted from the second fly-eye lens 5 is incident on the rotating plate 6 and is refracted by the exit-side surface 6a provided to be inclined with respect to the optical axis 9 as shown in FIG. After that, the light is collimated by the second condenser lens 7 and is incident on the photomask 12 substantially perpendicularly. As a result, the center of the illumination region 14 of the laser beam 13 on the photomask 12 is shifted laterally from the center O of the irradiation region 15 of the photomask 12 as shown in FIG. At this time, since the rotating plate 6 rotates about the optical axis 9, the illumination area 14 of the laser light 13 moves so as to make a circular motion about the center O of the irradiation area 15. Thereby, the entire region of the irradiation region 15 is illuminated by the laser beam 13.

Note that the rotation of the rotating plate 6 is controlled so that it rotates at least once from the start to the end of the multiple exposure when the single exposure is a multiple exposure with a plurality of shots of the laser beam 13. The irradiation area 15 on the photomask 12 is illuminated by the laser beam 13 without excess or deficiency.

In this way, interference fringes generated on the photomask 12 due to the interference of the laser beams 13 emitted from the plurality of unit lenses 11a of the second fly-eye lens 5 can be averaged and made inconspicuous. Therefore, the entire irradiation region 15 on the photomask 12 can be uniformly illuminated with the laser beam 13, and a fine pattern of the photomask 12 can be accurately exposed on the object to be exposed.

In the above embodiment, the case where the laser light 13 emitted from the second fly-eye lens 5 is converted into parallel light by the second condenser lens 7 has been described. However, the present invention is not limited to this, and the second embodiment Instead of the condenser lens 7, a collimation mirror may be arranged at the position of the plane reflection mirror 18. In this case, the front focal position of the collimation mirror may be substantially matched with the rear focal position of the second fly-eye lens 5.

DESCRIPTION OF SYMBOLS 1 ... Laser light source 2 ... 1st fly eye lens 3 ... Diffusing plate 4 ... 1st condenser lens (condenser lens)
5 ... Second fly-eye lens 6 ... Rotating plate 6a ... Surface inclined with respect to optical axis of rotating plate 7 ... Second condenser lens (another condenser lens)
DESCRIPTION OF SYMBOLS 8 ... Protection board 9 ... Optical axis 10 ... 1st lens array 10a ... Unit lens of 1st lens array 11 ... 2nd lens array 11a ... Unit lens of 2nd lens array 12 ... Photomask 13 ... Laser beam

Claims

A laser light source that emits laser light;
A plurality of unit lenses are arranged in a plane substantially orthogonal to the optical axis of the laser light source, uniformizing the light intensity distribution in the plane orthogonal to the optical axis, and condensing the emitted light once, then radially A first fly-eye lens that diverges into a laser beam and expands the cross-sectional shape of the laser light
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 light intensity distribution in an illumination area on a photomask that is provided downstream of the condenser lens in the light traveling direction and in which a plurality of unit lenses are arranged in a plane substantially orthogonal to the optical axis and is illuminated by laser light A second fly-eye lens that equalizes
A diffusion plate that is provided between the first fly-eye lens and the condenser lens and diffuses laser light;
A transparent rotating plate provided on the laser beam emission side of the second fly-eye lens, having a surface inclined with respect to the optical axis, and rotating about the optical axis;
A laser exposure apparatus comprising:
The plurality of unit lenses of the first fly-eye lens are arranged at a pitch capable of sufficiently dispersing the energy of the laser light so that the laser light collected by each unit lens does not turn the air into plasma. 2. The laser exposure apparatus according to claim 1, wherein:
2. The laser exposure apparatus according to claim 1, wherein the diffusion plate is a ground glass plate having a fine uneven pattern randomly formed on a surface thereof.
In the second fly-eye lens, a pair of lens arrays in which a plurality of unit lenses are arranged in a plane are arranged to face each other, and a principal ray of diffused light that is diffused and incident by the diffusion plate is made parallel to the optical axis. The laser exposure apparatus according to claim 1, wherein the laser exposure apparatus is configured to emit light.
The rotating plate is configured to rotate at least once from the start to the end of the multiple exposure when one exposure is a multiple exposure by a plurality of shots of the laser light. Item 2. A laser exposure apparatus according to Item 1.
There is further provided another condenser lens that converts the laser light applied to the photomask to parallel light downstream of the rotating plate in the light traveling direction, and a foreign substance is placed on the surface in the vicinity of the surface on the emission side of the other condenser lens. The laser exposure apparatus according to any one of claims 1 to 5, wherein a transparent protective plate for preventing the attachment of said film is detachably provided.