CN102308364A - Laser exposure device - Google Patents

Abstract

The invention provides a laser exposure device, which comprises: a first fly-eye lens (2), which enlarges the cross-sectional shape of laser light; a first optical path difference adjustment member (3), which is arranged on the first fly-eye lens (2) The incident side of the laser light and make the laser light respectively incident on each condenser lens (2a) of the first fly's eye lens (2) produce phase difference; The laser light is converted into parallel light; the second fly-eye lens (6), which uniformizes the light intensity distribution in the illumination area of the photomask brought by the laser light; the second optical path difference adjustment member (7), which is configured in On the incident side of the laser beam of the second fly's eye lens (6), phase differences are generated in the laser beams respectively incident on the condenser lenses (6a) of the second fly's eye lens (6). Thereby, the interference fringes of the laser light generated by the fly-eye lens are averaged, and the unevenness of the illuminance of the laser light is reduced.

Description

Laser exposure device

technical field

The present invention relates to a laser exposure apparatus including a fly-eye lens in which a plurality of condenser lenses are arranged in parallel in a plane approximately perpendicular to the optical axis of laser light. A laser exposure device that averages the interference fringes and reduces the unevenness of the illumination of the laser light to perform uniform exposure.

Background technique

A conventional laser exposure apparatus uses a beam expander for enlarging the diameter of the laser beam and an optical integrator such as a fly-eye lens for uniformizing the intensity distribution of the enlarged laser beam in order to uniformly irradiate the object to be exposed with the laser beam. And, in order to utilize the coherence (interferability) of laser light and reduce the interference fringes produced by the transmitted light interference of the fly-eye lens, an optical path difference adjustment member is provided between the beam expander and the fly-eye lens (for example, refer to Patent Document 1).

Patent Document 1: JP-A-2004-12757

However, in this existing laser exposure apparatus, because the optical path difference adjustment member is only arranged between the beam expander and the fly-eye lens, therefore, the interference fringes caused by the transmitted light of the fly-eye lens cannot be completely removed. Illumination unevenness occurs on the object to be exposed due to a small amount of remaining interference fringes, making it difficult to form fine patterns.

Contents of the invention

Therefore, the present invention addresses such a problem, and an object of the present invention is to provide a laser exposure apparatus that can average out interference fringes of laser light generated by a fly-eye lens, reduce uneven illuminance of laser light, and perform uniform exposure.

In order to achieve the above object, the laser exposure apparatus of the present invention is provided with: a laser light source, which emits laser light; After the emitted light is temporarily concentrated, it is radially diverged to expand the cross-sectional shape of the laser light; the first phase difference generating device is arranged on the incident side of the laser light of the first fly-eye lens, so that Each condensing lens of the lens produces a phase difference between the incident laser light respectively; the condensing lens converts the laser light emitted from the first fly-eye lens and expands the cross-sectional shape into parallel light; A plurality of lenses are arranged in parallel in a plane on which the optical axes of the above-mentioned converging lenses are substantially perpendicular, so as to uniformize the light intensity distribution in the illumination area of the photomask brought by the laser light; the second phase difference generating device is arranged on the first The incident side of the laser beam of the second fly's eye lens causes a phase difference between the laser beams respectively incident on the condenser lenses of the second fly's eye lens.

According to such a configuration, the laser light is emitted from the laser light source so that it enters the first phase difference generating device arranged on the incident side of the laser light of the first fly's eye lens without expanding the beam diameter, and the laser beam is incident on the first phase difference generating device by the first phase difference generating device. The laser beams incident on the plurality of condensing lenses arranged in parallel in a plane approximately perpendicular to the optical axis of the first fly's eye lens have a phase difference, which reduces the coherence of the laser beam emitted from the first fly's eye lens. The fly-eye lens temporarily condenses the emitted light from each condenser lens, diverges it radially, and expands the cross-sectional shape of the laser. The second phase difference generating device on the incident side of the laser beam of the lens generates a phase difference between the laser beams respectively incident on the plurality of condenser lenses arranged in parallel in a plane substantially perpendicular to the optical axis of the second fly's eye lens, so that the phase difference from the second fly's eye lens The coherence of the laser light emitted by the second fly-eye lens is reduced again, and the light intensity distribution is uniformized by the second fly-eye lens to irradiate the photomask.

In addition, a transparent plane-parallel rotating plate that is arranged obliquely to the optical axis and rotates around the optical axis is provided on the incident side of the laser light of the condensing lens. Thereby, the transparent plane-parallel rotating plate provided on the incident side of the laser beam of the condenser lens and arranged obliquely with respect to the optical axis is rotated around the optical axis to change the incident angle of the laser beam incident on the second fly's eye lens.

According to the invention of the laser exposure device of the first aspect, the phase difference is generated by the first and second two phase difference generating devices to the plurality of laser beams respectively incident on the condenser lenses of the first and second fly's eye lenses, so that The coherence of the laser light emitted by the first and second fly's eye lenses is reduced, so the interference fringes generated in the illumination area can be further reduced compared with the prior art. In addition, compared to the case of using a single fly-eye lens, the intensity distribution of the laser light can be more uniform, and the unevenness of illumination can be further reduced. Accordingly, it is possible to uniformly illuminate the photomask to perform uniform exposure, and it is easy to perform exposure of a fine pattern on an object to be exposed. In addition, since the first fly-eye lens has both functions of homogenizing the laser light and expanding the beam diameter, it is not necessary to separately provide a beam expander, and the number of parts can be reduced.

In addition, according to the second aspect of the invention, the incident angle of the laser beam incident on the second fly's eye lens can be changed during exposure. Therefore, the illumination area on the photomask brought by the laser light emitted from each condenser lens of the second fly's eye lens can be slightly moved along with the rotation of the parallel plane rotating plate, and the illumination area on the photomask can be adjusted The interference fringes of the generated laser light are averaged to make them inconspicuous. Thereby, the unevenness of the illuminance of a laser beam can be further reduced, and an object to be exposed can be exposed more uniformly.

Description of drawings

FIG. 1 is a front view showing a first embodiment of a laser exposure apparatus of the present invention.

2 is an explanatory view showing the relationship between the position of the plane-parallel rotating plate of the laser exposure apparatus, the incident angle of the laser beam incident on the second fly-eye lens, and the change of the illuminated area on the photomask.

3 is a front view showing a second embodiment of the laser exposure apparatus of the present invention.

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 is a front view showing a first embodiment of a laser exposure apparatus of the present invention. This laser exposure apparatus irradiates laser light to an object to be exposed through a photomask to expose, and includes a laser light source 1 , a first fly-eye lens 2 , a first optical path difference adjusting member 3 , a first converging lens 4 , and a plane-parallel rotating plate 5 . , a second fly-eye lens 6 , a second optical path difference adjusting member 7 , and a second converging lens 8 .

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

A first fly-eye lens 2 is arranged in front of the emission direction of the laser light of the above-mentioned laser light source 1 . The first fly's eye lens 2 temporarily condenses the laser light emitted from the laser light source 1, and then diverges it radially to realize the function of a beam expander that expands the cross-sectional shape of the laser light. At the same time, the second fly's eye lens 6 described later The light intensity distribution in the incident side surface is uniform, and a plurality of condensing lenses 2a are arranged side by side in a matrix, for example, 3 vertically and 3 horizontally in a plane substantially perpendicular to the optical axis of the laser light.

A first optical path difference adjusting member 3 is provided on the laser incident side of the first fly's eye lens 2 . The first optical path difference adjustment member 3 is used to reduce the coherence of the laser light emitted from the first fly's eye lens 2 and to prevent the multiple laser light emitted from each condenser lens 2a of the first fly's eye lens 2 from entering the second fly's eye. Interference occurs on the incident side of the lens 6 to form a first phase difference generating means for causing a phase difference between a plurality of laser beams respectively incident on the condenser lenses 2 a of the first fly's eye lens 2 .

Specifically, the first optical path difference adjustment member 3 corresponds to each condenser lens 2a of the first fly's eye lens 2, and is provided with rod-shaped rods with different lengths in the axial direction parallel to the optical axis and a refractive index greater than 1. The transparent member 3 a is, for example, a member of quartz glass or transparent glass, and functions to change the optical path length of the plurality of laser beams respectively incident on the condenser lenses 2 a of the first fly's eye lens 2 .

A first converging lens 4 is provided on the downstream side of the first fly's eye lens 2 in the traveling direction of the above-mentioned laser light. The first converging lens 4 is used to change the radial laser light emitted from the first fly's eye lens 2 into parallel light, and the incident side of the light is a flat plano-convex lens, so that its front focus position is the same as that of the rear of the first fly's eye lens 2. The focus positions are arranged so as to substantially coincide with each other.

发射的激光的照度不均降低。A parallel plane rotating plate 5 is provided on the optical path between the above-mentioned first fly's eye lens 2 and the first converging lens 4 . The plane-parallel rotating plate 5 is used to change the incident angle of the laser light incident on the second fly-eye lens 6 described later, and is made of a transparent, for example, glass disk tilted with respect to the optical axis and rotated around the optical axis. Thereby, the laser beam illumination region on the photomask 9 is slightly moved, and the interference fringes of the laser beam generated on the photomask 9 by the second fly's-eye lens 6 are averaged and made inconspicuous. In addition, through the first optical path difference adjustment member 3, the first fly-eye lens

The unevenness of the illuminance of the emitted laser light is reduced.

FIG. 2 is an explanatory view showing the relationship between the position of the plane-parallel rotating plate 5 , the incident angle of the laser beam incident on the second fly-eye lens 6 , and changes in the illuminated 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. 2( a ). In this case, when the plane-parallel rotating plate 5 is located at the position shown by the solid line in the same figure (a), the laser light is refracted by the plane-parallel rotating plate 5 as shown by the solid line, and enters the second fly-eye lens 6 at a certain incident angle. The condenser lens 6a is incident.

On the other hand, when the plane-parallel rotating plate 5 rotates and reaches the position shown by the dotted line in FIG. The condenser lens 6a is incident. As a result, the illuminated area 10 on the photomask 9 illuminated by the laser light emitted from the second fly's eye lens 6 moves from the area indicated by the solid line to the area indicated by the dotted line in (b) of the same figure. In this way, by rotating the plane-parallel rotating plate 5 to change the incident angle of the laser beam incident on the second fly-eye lens 6, the intensity unevenness of the laser beam emitted from the first fly-eye lens 2 is averaged, and at the same time, the light The illumination region 10 on the mask 9 moves slightly, and the brightness and darkness of the interference fringes 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 the unevenness of illumination can be averaged. It's not noticeable.

A second fly-eye lens 6 is provided on the downstream side of the first condensing lens 4 in the traveling direction of the above-mentioned laser light. The second fly's-eye lens 6 uniformizes the light intensity distribution in the illuminated area 10 of the photomask 9, and forms, for example, a matrix of 12 vertically by 4 horizontally in a plane approximately perpendicular to the optical axis of the first converging lens 4. A plurality of condensing lenses 6a are arranged in a shape, which is a double fly-eye lens formed by combining two sets of identical fly-eye lenses.

A second optical path difference adjustment member 7 is provided on the incident side of the laser light of the second fly's eye lens 6 . The second optical path difference adjustment member 7 is used to reduce the coherence of the laser light emitted from the second fly's eye lens 6 and suppress the laser light emitted from each condenser lens 6a of the second fly's eye lens 6 The upper interference acts as a second phase difference generating means for causing a phase difference between a plurality of laser beams respectively incident on the condenser lenses 6 a of the second fly's eye lens 6 .

Specifically, the second optical path difference adjustment member 7 corresponds to the condenser lenses 6a in four vertical rows of the second fly's-eye lens 6, and is a plate with a different length in the axial direction parallel to the optical axis and a refractive index greater than 1. Shaped transparent members 7a, such as quartz glass or transparent glass, are overlapped and formed in the lateral direction, and play a role in changing the laser beams in the vertical 4 columns that are respectively incident on the condenser lenses 6a of the second fly's eye lens 6 between adjacent columns in the lateral direction. The optical path length function of the optics.

A second converging lens 8 is provided on the downstream side of the second fly's eye lens 6 in the traveling direction of the laser light. The second converging lens 8 is used to change the laser light emitted from the second fly's eye lens 6 into parallel light and make it incident vertically to the photomask 9. The incident side of the light is formed by combining two flat plano-convex lenses, and The front focus position and the rear focus position of the second fly's eye lens 6 are arranged so that they substantially coincide. In addition, in FIG. 1 , symbols 11 , 12 , and 13 are plane mirrors that bend the optical path.

Next, the operation of the laser exposure apparatus configured in this way will be described.

Laser light emitted from the laser light source 1 is reflected by the two reflection mirrors 11 and 12 , and enters the first optical path difference adjusting member 3 . The first optical path difference adjustment member 3 corresponds to each condenser lens 2a of the first fly-eye lens 2, and is formed by combining a plurality of transparent members 3a having different lengths in the axial direction parallel to the optical axis and having a refractive index greater than 1. Therefore, the plurality of laser beams emitted from the plurality of transparent members 3 a of the first optical path difference adjusting member 3 are out of phase with each other.

A plurality of laser beams emitted from the plurality of transparent members 3 a of the first optical path difference adjusting member 3 enters the corresponding condenser lenses 2 a of the first fly's eye lens 2 . Then, the plurality of laser beams emitted from the condenser lenses 2a of the first fly's eye lens 2 are respectively condensed on the rear focal points of the condenser lenses 3a, and then radially diverge. In this case, since the laser beams incident on the condenser lenses 2 a of the first fly's eye lens 2 are out of phase with each other, the coherence of the laser beams emitted from the first fly's eye lens 2 is lowered. Therefore, on the second fly's eye lens 6 illuminated by a plurality of laser beams emitted from each condenser lens 2a, the interference of each laser beam is suppressed, and the generation of interference fringes is suppressed, and the second fly's eye lens 6 is illuminated substantially uniformly. illumination.

The radial laser light emitted from the first fly's eye lens 3 is converted into parallel light by the first converging lens 4 , and then enters the second fly's eye lens 6 through the second optical path difference adjusting member 7 . At this time, on the incident side of the laser light of the first converging lens 4, a plane-parallel rotating plate 5 in which a transparent disc such as glass is arranged obliquely with respect to the optical axis is arranged. Since it rotates around the optical axis, as shown in FIG. 2 As shown in (a), the incident position of the chief ray of the laser beam refracted by the plane-parallel rotating plate 5 and emitted from the first converging lens 4 changes in the radial direction of the first converging lens 4 . Thereby, as shown in (a), the incident angle of the laser light incident on the second fly's eye lens 6 changes. Simultaneously, 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 converging lens 4 is passed through the second optical path difference adjustment member 7 composed of a combination of a plurality of transparent members 7a having different lengths in the axial direction parallel to the optical axis and having a refractive index greater than 1. It is divided into multiple laser beams to illuminate the second fly-eye lens 6 . At this time, since the optical path lengths of the laser beams passing through the transparent members 7a of the second optical path difference adjusting member 7 are different, a phase difference occurs between the laser beams emitted from the second optical path difference adjusting member 7 . Therefore, the coherence of the laser beams emitted from the second fly's eye lens 6 is reduced, and the interference of the laser beams emitted from the condenser lenses 6 a of the second fly's eye lens 6 and irradiated onto the photomask 9 is suppressed.

The laser light emitted from each condensing lens 6 a of the second fly's eye lens 6 is temporarily condensed at the focal point of each condensing lens 6 a , and then radially diverges to enter the plane mirror 13 . In addition, the laser light is reflected by the plane mirror 13 and converted into parallel light by the second converging lens 8 , and is approximately vertically incident on the photomask 9 to uniformly illuminate the photomask 9 .

Here, in the above-mentioned first embodiment, the second optical path difference adjusting member 7 is formed by overlapping the plate-shaped transparent members 7a having different lengths in the optical axis direction and being long in the vertical direction in the lateral direction. Each condensing lens 6a arranged in the longitudinal direction of the fly's eye lens 6 is incident with the laser light of the same phase, and for each condensing lens 6a arranged in the horizontal direction, the incident laser light with different phases, therefore, the illumination area 10 on the photomask 9 may be There are very few interference fringes caused by the laser beams of the same phase emitted from the condenser lenses 6 a arranged in the longitudinal direction of the second fly's eye lens 6 . However, in the first embodiment described above, the plane-parallel rotating plate 5 is provided on the incident side of the first condensing lens 4 and rotates around its optical axis. Therefore, the incident laser light incident on the second fly-eye lens 6 The angle changes. Therefore, as shown in FIG. 2( b ), the illumination region 10 generated by the laser light on the photomask 9 moves slightly, and the light and dark states of the above-mentioned interference fringes are averaged and made inconspicuous. for uniform exposure.

3 is a front view showing a second embodiment of the laser exposure apparatus of the present invention. This second embodiment differs from the first embodiment in that a collimating mirror 14 is arranged in place of the plane mirror 13 instead of the second converging lens 8 . In this case, the front focus position of the collimating mirror 14 is substantially aligned with the back focus position of the second fly's eye lens 6 . Thereby, the laser light emitted from the second fly's-eye lens 6 can be converted into parallel light so as to be vertically incident on the photomask 9 .

In addition, in the above-mentioned first and second embodiments, the second optical path difference adjustment member 7 corresponds to the condenser lenses 6a in the vertical four rows of the second fly's eye lens 6, respectively, and the length in the axial direction parallel to the optical axis The case where different plate-shaped transparent members 7a are overlapped and formed in the lateral direction has been described, but the present invention is not limited thereto, and may correspond to each condenser lens 6a of the second fly's-eye lens 6 by placing It is formed by combining rod-shaped transparent members having different lengths in the axial direction. In this case, since the phases of the respective laser beams emitted from the respective condensing lenses 6a of the second fly's eye lens 6 are completely different, the possibility of interference of the respective laser beams on the photomask 9 is reduced.

In addition, in the above-mentioned embodiment, the case where the phase difference generator is the optical path difference adjusting member has been described, but the present invention is not limited thereto, and may be a phase plate provided corresponding to each condenser lens of the fly's eye lens.

Symbol Description

1…laser light source

2…The first fly-eye lens (fly-eye lens)

2a...Condenser lens of the first fly-eye lens

3...First optical path difference adjusting member (first phase difference generating device)

3a...Transparent member of the first optical path difference adjusting member

4…first converging lens

5...parallel plane rotating plate

6…second fly eye lens

6a...Condenser lens of the second fly-eye lens

7...second optical path difference adjusting member (second phase difference generating means)

7a...Transparent member of the second optical path difference adjusting member

8...Second converging lens

9…photomask

10…Illumination area on the photomask

Claims (2)

1. A laser exposure device, characterized in that, have: a laser light source emitting laser light; A first fly-eye lens in which a plurality of lenses are arranged in parallel in a plane approximately perpendicular to the optical axis of the laser light, and after temporarily converging the emitted light, it diverges radially to expand the cross-sectional shape of the laser light; A first phase difference generating device, which is arranged on the incident side of the laser light of the first fly's eye lens, so as to generate a phase difference for the laser light incident on each condenser lens of the first fly's eye lens; a converging lens, which converts the laser light emitted from the first fly-eye lens and having an enlarged cross-sectional shape into parallel light; A second fly's-eye lens, which arranges a plurality of lenses in parallel in a plane approximately perpendicular to the optical axis of the condensing lens, and uniformizes the light intensity distribution in the illuminated area of the photomask of the laser; The second phase difference generating device is arranged on the incident side of the laser light of the second fly's eye lens, and generates a phase difference in the laser light incident on each of the condenser lenses of the second fly's eye lens. 2. The laser exposure apparatus according to claim 1, wherein: A transparent plane-parallel rotating plate that is arranged obliquely with respect to the optical axis and that rotates around the optical axis is provided on the incident side of the laser light of the condensing lens.

Images