JP2003248184A - Beam mode shaping optical system and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply realize a beam mode shaping optical system for surely shaping a light emitted from a light source into a beam having a circular cross- section and a small diameter. <P>SOLUTION: The beam mode shaping optical system 1 comprises an optical fiber 24, an introducing lens 23 for introducing emitted light emitted from a semiconductor laser 21 to an incident end 24a of the fiber 24, and a collimator lens 25 for collimating the light emitted from the emitting end 24 of the single- mode optical fiber 24. The diameter of the fiber 24 is reduced in its core and clad in a tapered state from the incident end 24a to an emitting end 24b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam mode shaping optical system and an exposure apparatus equipped with this beam mode shaping optical system.

[0002]

2. Description of the Related Art Semiconductor lasers, excimer lasers, or light emitting diodes (hereinafter referred to as "semiconductor lasers").
The beam emitted from the device includes a transverse mode, and the cross-sectional shape of the beam becomes linear, crescent-shaped, or elliptical. Therefore, in an optical device that employs a semiconductor laser or the like as a light source, where the spot shape is desired to be circular, the mode pattern of the beam emitted from the semiconductor laser or the like is shaped into a circle in advance. There is.

More specifically, conventionally, a parallel lens and a condenser lens are spaced apart from each other and face each other, and a cylindrical lens type beam mode in which a cylindrical lens having different vertical and horizontal focusing rates is interposed between the respective lenses. A beam emitted from a semiconductor laser or the like has been shaped by using a shaping optical system or an anamorphic (pair prism) type beam mode shaping optical system formed by combining a pair of prisms.

[0004]

However, in the above-mentioned conventional beam mode shaping optical system, it was difficult to surely shape the mode pattern of the beam into a circular shape. That is,
In the conventional beam mode shaping optical system, it is difficult to remove the transverse mode of the semiconductor laser or the like as a light source when the transverse mode is bad, and the transverse mode remains in some cases, resulting in a cross-sectional shape of the emitted light flux. It sometimes became elliptical, linear, or crescent-shaped.

Further, since the above-mentioned conventional beam mode shaping optical system is formed by combining a plurality of lenses and prisms,
There has been a problem that the structure of the entire optical device equipped with this becomes complicated and that adjustment such as optical axis alignment is difficult.

Further, in the above-mentioned conventional beam mode shaping optical system, since the diameter of the output beam depends on the size of the light emitting point in the semiconductor laser or the like, the spot shape of the projected light is circular, as in an exposure apparatus or the like. In addition to the above, there is a problem that it is difficult to apply the method to a device in which a small spot diameter is particularly desired from the viewpoint of drawing accuracy.

The present invention has been made in view of the above circumstances, and provides a technique for surely shaping the cross-sectional shape of a beam emitted from a light source into a circular shape and sufficiently reducing the beam diameter. With the goal. Another object of the present invention is to provide a beam mode shaping optical system which has a simple structure and is easy to adjust such as optical axis alignment. Further, the present invention is
The purpose is to realize an exposure apparatus with a simple structure at low cost.

[0008]

A beam mode shaping optical system according to a first aspect of the present invention which achieves the above object introduces an optical fiber and an outgoing light emitted from a light source to an incident end of the optical fiber. A beam mode shaping optical system comprising: a lens; and a collimating lens for collimating light emitted from the emitting end of the optical fiber, wherein a core and a clad of the optical fiber are tapered from an incident end to an emitting end. It is characterized in that it is configured with a reduced diameter.

Here, the light source is, for example, a semiconductor laser (L
D), excimer laser, or light emitting diode (LED)
Etc. can be used.

In the beam mode shaping optical system according to the first aspect, the light emitted from the light source is introduced into the incident end of the optical fiber by the introduction lens. The light introduced at the incident end propagates through the optical fiber while being substantially totally reflected at the boundary surface between the core and the clad, and is emitted from the emitting end. By thus introducing the light emitted from the light source into the optical fiber, the divergence angle of the light emitted from the emission end of the optical fiber can be made uniform without depending on the divergence angle of the light source. In addition, since the core and the clad of the optical fiber are tapered in diameter from the incident end to the emitting end, the light introduced into the incident end is not the first in the process of propagating through the optical fiber. The point difference is reliably removed, the second mode is the single mode, and the third mode is the diameter reduction. As a result, a beam having a small diameter and a circular cross section can be obtained from the emission end of the optical fiber. Thus, the emitting end of the optical fiber can be regarded as an ideal point light source. Further, since the core and the clad of the single mode optical fiber are tapered in diameter from the entrance end to the exit end, the core diameter at the entrance end is larger than the core diameter at the exit end. Therefore, with the diameter of the light emitted from the emitting end kept sufficiently small, it is possible to secure a core diameter at the incident end that can reliably and easily perform positioning of the introducing lens or coupling with the fiber. Further, this allows the light emitted from the light source to be emitted even if the shape of the light introduced by the introducing lens varies, or the optical axes of the introducing lens and the incident end face are slightly deviated due to vibration or the like. It can be introduced at the entrance end without loss even with low loss. Thus, a beam mode shaping optical system having a simple structure and easy adjustment such as optical axis alignment is realized. Further, since the optical fiber has flexibility, the design of the location of the light source can be changed flexibly. Further, the light emitted from the emission end of the optical fiber is collimated by the collimator lens, but since the emission end of the single mode optical fiber is an ideal point light source, a perfect collimated light flux is obtained by the collimator lens. Therefore, in the latter optical system, this parallel light beam may be condensed by a lens having a long focal length without any problem.

A beam mode shaping optical system according to a second aspect of the present invention which achieves the above object is the beam mode shaping optical system according to the first aspect, which includes a semiconductor laser as the light source. Characterize.

The beam mode shaping optical system according to the second aspect includes a semiconductor laser as a light source. As described above, in this beam mode shaping optical system, the cross-sectional shape of the emitted light emitted from the semiconductor laser is circular. Since the semiconductor laser can be shaped and the beam diameter can be made sufficiently small, this semiconductor laser can be used as a substitute for, for example, a gas laser. That is, by applying a beam mode shaping optical system as an alternative to the gas laser to an optical device that has conventionally used a gas laser with a small divergence angle as a light source, the configuration of the optical device can be significantly simplified and the manufacturing cost can be reduced. it can.

Further, an exposure apparatus according to a third aspect of the present invention which achieves the above object is to expose the beam mode shaping optical system according to the first or second aspect and the light emitted from the collimator lens to an exposure target. It is characterized by comprising a scanning means for scanning the irradiation target on the exposure target while irradiating.

The exposure device referred to here is a direct laser type drawing device for printing a predetermined pattern without using a mask by irradiating a substrate coated with a photosensitive material with a beam, or a liquid photo-curing device. It includes a photo-curing modeling apparatus for irradiating a resin with a laser to cure a part of the resin and modeling an arbitrary three-dimensional shape.

In the exposure apparatus according to the third aspect, the scanning means causes the light emitted from the collimating lens of the beam mode shaping optical system to irradiate the exposure target while scanning the irradiation position on the exposure target. As a result, a predetermined pattern is exposed on the exposure target. As mentioned above,
By providing the beam mode shaping optical system, it is possible to obtain a beam having a circular cross-sectional shape and a small diameter. Therefore, according to this exposure apparatus, drawing accuracy and drawing density can be improved.

Further, an exposure apparatus according to a fourth aspect of the present invention which achieves the above object is the exposure apparatus according to the third aspect, wherein said scanning means causes the light emitted from said collimating lens to fθ lens. It is a gimbal type scanner mirror that irradiates the exposure target through the.

According to the exposure apparatus of the fourth aspect,
Since the gimbal type scanner mirror is adopted as the scanning means, the configuration of the entire apparatus can be remarkably simplified. Further, since the rotation center of the mirror is at one point, the field curvature can be reduced. Further, the light emitted from the collimator lens is f
The object to be exposed is irradiated through the θ lens,
The emitting end of the optical fiber can be regarded as an ideal point light source, and since perfect collimated light is formed by the collimating lens, it is possible to use an fθ lens having a long focal length. As a result, an exposure apparatus that is small but has a large exposure area is realized.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. [First Embodiment] FIG. 1 is a schematic plan view schematically showing the structure of an exposure apparatus according to the first embodiment, and FIG. 2 is a schematic front view thereof. The exposure apparatus 1 irradiates a beam mode shaping optical system 2 that emits a beam whose cross-sectional shape is circular and a substrate W to be exposed with the emitted light emitted from the beam mode shaping optical system 2. And a scanning unit 3 that scans the substrate W.

Here, the substrate W corresponds to, for example, a semiconductor wafer or a liquid crystal substrate. The exposed surface of the substrate W is coated with a photosensitive material such as photoresist.

The beam mode shaping optical system 2 includes a semiconductor laser (LD) 21 as a light source and an LD collimating lens 2.
2. A condensing lens 23 as an introducing lens, a tapered optical fiber 24, and a collimating lens 25 are arranged in this order along the optical path. The wavelength of the emitted light emitted from the semiconductor laser 21 is about 400 [nm].

The taper type fiber 24 is made of an optical fiber having flexibility, and as shown in FIG. 3, the core 2 goes from the incident end 24a side toward the output end 24b side.
41 and the clad 242 are formed in a tapered shape.
The ratio of the core diameter at the entrance end 24a to the core diameter at the exit end 24b is approximately 3: 1. The core diameter at the emitting end 24b is about 3 [μm]. However, the size of the tapered fiber 24 is not particularly limited to these values, and when a semiconductor laser having a wavelength of about 600 to 700 [nm] is adopted as a light source, the emitting end 24b
The core diameter may be about 6 [μm]. Further, the taper may be provided only on the emission end portion of the optical fiber 24.

The scanning unit 3 includes a pair of galvanometer mirrors 31,
32, the fθ lens 33, and a control unit (not shown). One galvanometer mirror 31 is driven by a first motor (not shown) and rotates about a rotation axis perpendicular to the paper surface of FIG. The other galvanometer mirror 32 is driven by a second motor (not shown) and rotates about a rotation axis in the plane of the drawing of FIG. The first motor and the second motor are drive-controlled by a control unit (not shown). By this, the postures of the respective mirrors 31, 32 are controlled, and f
The beam scans the exposure target W via the θ lens 33. The fθ lens 33 makes the angle of the beam incident on the lens 33 proportional to the position of the spot, and as shown in FIG.
1 and 32 and the exposure target W.

The operation of the exposure apparatus 1 configured as described above is as follows. The emitted light emitted from the semiconductor laser 21 is first collimated by the LD collimator lens 22. The collimated light passes through the introduction lens 23.
Is collected by the incident end 2 of the tapered optical fiber 24.
4a. Incident end 24 of tapered optical fiber 24
The light introduced into a is propagated through the tapered optical fiber 24 while being totally reflected by the boundary surface between the core 241 and the clad 242, and is emitted from the emission end 24b. The light emitted from the emission end 24b of the tapered optical fiber 24 is collimated by the collimator lens 25 and emitted to the galvanometer mirror 31.

The light emitted to the galvanometer mirror 31 is reflected by the galvanometer mirror 31 and the galvanometer mirror 32. As shown by the broken line in FIG. 2, the reflected beam of light is scanned through the fθ lens 33 with a uniform spot diameter over the entire area of the main surface of the exposure target W.
In the process, the controller (not shown) controls the first motor and the second motor (not shown) so that the locus of the spot draws a given pattern.
Control the motor. Exposure is performed in this manner.

According to the exposure apparatus described above, the following effects can be obtained. (1) The optical fiber 2 emits the light emitted from the semiconductor laser 21.
By introducing the optical fiber 24 into the optical fiber 24,
The divergence angle of the light emitted from 4b can be made uniform without depending on the divergence angle of the semiconductor laser 21.

(2) Core 241 of tapered optical fiber 24
Since the cladding 242 is tapered in diameter from the entrance end 24a to the exit end 24b, the light introduced into the entrance end 24a is propagated through the optical fiber 24,
Firstly, the astigmatic difference is surely removed, secondly it is made into a single mode, and thirdly, its diameter is narrowed. This allows
From the emission end 24b of the tapered optical fiber 24, a beam having a circular cross section and a sufficiently small spot diameter can be obtained. Therefore, the emitting end 24b of the tapered optical fiber 24 can be regarded as an ideal point light source.

(3) Since the core 241 and the clad 242 of the tapered fiber 24 are tapered in diameter from the entrance end 24a to the exit end 24b, the diameter of the core 241 at the entrance end 24a is equal to that at the exit end 24b. Core 241
Larger than the diameter of. Therefore, with the diameter of the light emitted from the emitting end 24b being sufficiently narrowed, it is possible to secure a core diameter at the incident end 24a that allows reliable and easy positioning of the introducing lens 23 or coupling with the fiber 24.
When the exit end of an optical fiber is to be regarded as an ideal point light source without providing a taper, a single mode optical fiber is used as the fiber and the incident end has a very high accuracy of about 0.05 μm. It is necessary to position the introduction lens properly.

(4) Since the diameter of the core 241 at the entrance end 24a is larger than the diameter of the core 241 at the exit end 24b, the shape of the light introduced by the introduction lens 23 may vary, or it may be caused by vibration or the like. Even if the optical axes of the introducing lens 23 and the surface of the incident end 24a are slightly deviated, the light emitted from the semiconductor laser 21 and collimated by the LD collimator lens 22 can be introduced to the incident end 24a without leakage.

(5) Emitting end 24 of tapered optical fiber 24
The light emitted from b is collimated by the collimator lens 25, but the emission end 24 b of the tapered optical fiber 24.
Is an ideal point light source, a perfect collimated light beam is obtained by the collimator lens 25. Therefore, in the latter optical system, this parallel light beam may be condensed by a lens having a long focal length. Specifically, in the exposure apparatus 1, since the collimator lens 25 obtains a perfect parallel light flux,
A lens having a long focal length can be adopted as the fθ lens 33. Thereby, a wide exposure area can be secured.

(6) Since the core 241 and the clad 242 of the tapered fiber 24 are tapered in diameter from the entrance end 24a to the exit end 24b, the entrance end 24a thereof
The diameter of the light introduced into the fiber is narrowed in the process of propagating through the fiber 24. As a result, the spot diameter of the beam projected onto the exposure target W via the fθ lens 33 can be made sufficiently small.

(7) Since the tapered optical fiber 24 has flexibility, the semiconductor laser 21 and the like can be flexibly arranged in the specific design of the exposure apparatus 1. Further, shortening the tapered fiber 24 contributes to downsizing of the exposure apparatus 1.

(8) The semiconductor laser 21 has a larger beam diameter and divergence angle than a gas laser or the like, but according to the beam mode shaping optical system 2, the semiconductor laser 21 is used as a light source and emitted from the semiconductor laser 21. Since the cross-sectional shape of the emitted light thus emitted can be shaped into a circle and the beam diameter thereof can be made sufficiently small, the semiconductor laser 21 can be used as a substitute for, for example, a gas laser. That is, by applying this beam mode shaping optical system to an exposure apparatus which has conventionally used a gas laser having a small divergence angle as a light source, the exposure apparatus can be realized inexpensively and simply.

The LD collimator 22 and the condenser lens 23 may be omitted in the beam mode shaping optical system 2. That is, as shown in FIG. 4, the emitted light from the semiconductor laser 21 may be directly introduced into the tapered optical fiber 24. Then, the configuration of the beam shaping optical system can be further simplified. In this case, the semiconductor laser 21 is brought as close as possible to the incident end face of the tapered optical fiber 24, and the incident end 2 of the tapered optical fiber 24 is
It is preferable to secure the core diameter in No. 4 so that coupling with the semiconductor laser 21 can be performed without loss.

[Second Embodiment] An exposure apparatus according to the second embodiment is similar to the exposure apparatus 1 according to the first embodiment, except that the galvano mirrors 31 and 32 are used instead of the exposure apparatus shown in FIG. The gimbal type scanner mirror 4 shown is provided.

The gimbal type scanner mirror 4 shown in FIG.
Are constructed on the basis of a body 40 obtained by etching a silicon substrate. The main body 40 made of silicon has a central portion 4 which is arranged in the center and has a rectangular shape in plan view.
1 and an outer frame portion 42 arranged so as to surround this central portion
It is composed of and. Au (gold) is provided in the central portion 41.
A mirror surface 411 is formed by depositing the above.
A coil pattern 41 is provided around and around the mirror surface 411.
Two are provided.

The central portion 41 and the outer frame portion 42 are connected only by a pair of torsion bars 413 and 414 extending in the X-axis direction (the horizontal direction in FIG. 5). Outer frame part 4
2, the coil pattern 421 is provided over the entire circumference. Further, a pair of torsion bars 422, 423 extend from the outer frame portion 42 in the Y-axis direction (vertical direction in FIG. 5). Incidentally, the torsion bars 413, 41
Since 4,422 and 423 are made of silicon, they have flexibility. Further, four permanent magnets 43, 44, 45, 46 are fixed around the outer frame portion 42.

In the gimbal type scanner mirror 4 thus constructed, the coil pattern 4 is formed by each permanent magnet.
A static magnetic field is always applied to each of 12 and 421.
When a current is supplied to each of the coil patterns 412 and 421 in this state, a rotational torque due to the Lorentz force is generated in each coil due to the interaction between the magnetic field generated by the coil and the static magnetic field provided by the permanent magnet.

At this time, the central portion 41 uses the pair of torsion bars 413, 414 as rotation axes, and the torsion restoring force of each of the torsion bars 413, 414 and the coil 412.
It rotates to the position where it balances with the rotation torque generated by. Along with this, the mirror surface 411 swings around the X axis. On the other hand, the outer frame portion 41 rotates about the pair of torsion bars 422 and 423 as rotation axes to a position where the torsional restoring force of each of the torsion bars 422 and 423 and the rotational torque generated by the coil 421 are balanced. Along with this, the mirror surface 411 swings around the Y axis.

The magnitude of the rotational torque generated by each coil 412, 421 has a value corresponding to the magnitude of the current supplied to each coil. Therefore, the respective coils 412, 4
Mirror surface 4 by controlling the current value supplied to 21
The posture of 11 can be changed arbitrarily. This allows
The spot position of the beam reflected by the mirror surface 411 is
It is possible to freely scan in the XY plane (main surface of the exposure target).

The exposure apparatus according to the second embodiment eliminates the need for the first motor and the second motor, which were required in the exposure apparatus 1 according to the first embodiment, and thus the overall configuration of the exposure apparatus is improved. It can be significantly simplified. Further, since the center of rotation of the mirror surface 411 for scanning the spot is one point, it is possible to reduce the curvature of field as compared with the first embodiment.

[0041]

As described above, according to the present invention, it is possible to surely shape the cross-sectional shape of the beam emitted from the light source into a circular shape and to sufficiently reduce the beam diameter. Further, according to the present invention, there is provided a beam mode shaping optical system which has a simple structure and is easy to adjust such as optical axis alignment. Further, according to the present invention, the exposure apparatus can be realized at a low cost with a simple structure.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a configuration of an exposure apparatus according to an embodiment.

FIG. 2 is a schematic front view showing the configuration of the exposure apparatus according to the embodiment.

FIG. 3 is a cross-sectional view schematically showing the structure of a tapered optical fiber.

FIG. 4 is a schematic diagram showing a beam mode shaping optical system according to another embodiment.

FIG. 5 is a diagram showing a configuration of a gimbal type galvanometer mirror according to still another embodiment.

[Explanation of symbols]

2 beam mode shaping optics 3 Scanning section (scanning means) 4 Gimbal type scanner mirror (scanning means) 21 Semiconductor laser (light source) 23 Condensing lens (introducing lens) 24 Tapered optical fiber (optical fiber) 25 Collimating lens W substrate (exposure target)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryoichi Ogoshi             17-2 Shimotakahagi Nitta, Hidaka City, Saitama Prefecture             Machine Co., Ltd. F-term (reference) 2H045 AB03 AB06 AB13 AB16 BA12                       CB24 DA11                 2H050 AC83

Claims (4)

[Claims] 1. An optical fiber, an introduction lens that guides outgoing light emitted from a light source, and a collimator lens that collimates the light emitted from the outgoing end of the optical fiber at the incident end of the optical fiber. A beam mode shaping optical system, wherein the optical fiber has a core and a clad that are tapered in diameter from an entrance end to an exit end. 2. The beam mode shaping optical system according to claim 1, further comprising a semiconductor laser as the light source. 3. The beam mode shaping optical system according to claim 1 or 2, and a scanning means for irradiating the object to be exposed with the light emitted from the collimator lens, and scanning the irradiated portion on the object to be exposed. An exposure apparatus characterized by having. 4. The exposure apparatus according to claim 3, wherein the scanning means is a gimbal type scanner mirror that irradiates the light emitted from the collimator lens to the exposure target through the fθ lens. .