JP3969197B2 - Laser irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser irradiation apparatus that uniformly irradiates an irradiation object using a laser light source having high coherency.
[0002]
[Prior art]
FIG. 3 is a schematic diagram of a laser irradiation apparatus. In this figure, a laser beam 1 is generated and emitted by a laser light source 52 controlled by a laser controller 51. The laser beam 1 passes through the optical system 54 and the homogenizer 55, is reflected downward by the mirror 56, and is irradiated onto the upper surface of the substrate 58 through an opening (not shown) provided in the reaction vessel 57.
[0003]
The laser beam 1 scans the substrate by, for example, swinging the mirror 56 or moving the optical system 54. The stage controller 59 can move the substrate 58 two-dimensionally. Further, the inside of the reaction vessel 57 (chamber) is controlled to a predetermined gas atmosphere by the pump system 60 and the gas introduction part 61.
[0004]
4 is a plan view of the optical system 54 and the homogenizer 55 of FIG.
[0005]
In this example, the optical system 54 includes an expander 54a (cylindrical concave lens) that widens the width of the laser beam 1 (vertical direction in the figure) and a cylindrical convex lens 54b that returns the laser beam to parallel light. Further, the homogenizer 55 includes a cylindrical lens array 55a composed of a plurality of cylindrical lenses and a focusing lens 55b. In the example of FIG. 3, the focal plane S is the upper surface of the substrate 58, and the mirror 56 is located between the focal plane S and the focusing lens 55b.
[0006]
With the configuration of FIG. 4, the circular cross-section laser beam 1a emitted from the laser light source 52 becomes an elongated laser beam 1b by the expander 54a and the cylindrical convex lens 54b, and is incident on the cylindrical lens array 55a. The collimated light (laser beam 1b) incident on the lens array 55a is divided into a beam group 1c having a rectangular beam profile by a rectangular lens group, and each beam group is condensed by the lens array 55a and exceeds the focal plane. spread. The focusing lens 55b (convex lens) refracts each beam group 1c and condenses it on the focal plane S.
[0007]
Therefore, on the focal plane S, all the beam groups 53c overlap to make the intensity distribution uniform, and a leveled intensity distribution can be obtained. A cylindrical concave lens can be used instead of the cylindrical convex lens 54b.
[0008]
As a related technique, “light beam incoherent device” (Japanese Patent Laid-Open No. 61-75523), “method for improving uniformity of laser beam irradiation” (Japanese Patent Laid-Open No. 10-314970), and the like are disclosed.
[0009]
[Problems to be solved by the invention]
However, in the conventional laser irradiation apparatus described above, if a highly coherent light source such as a YAG laser is used as the laser light source, an interference action occurs after the laser beam passes through the homogenizer, and the irradiation object cannot be irradiated uniformly. There was a problem. Furthermore, the lens array that constitutes the homogenizer is obtained by bonding individually manufactured lenses, and when a laser beam is incident on the lens array, interference fringes due to diffracted light or reflected light are generated at the joint surfaces of the lenses. Therefore, there is a problem that high beam uniformity cannot be obtained.
[0010]
The present invention has been developed to solve the above-described problems. In other words, an object of the present invention is to provide a laser irradiation apparatus capable of uniformly irradiating an irradiation object without generating interference fringes due to diffracted light or reflected light on the joint surface even when a highly coherent laser light source is used. is there.
[0011]
[Means for Solving the Problems]
According to the present invention, in a laser irradiation apparatus that irradiates an irradiation object by transforming a laser beam from a circular cross-sectional shape to a linear cross-sectional shape, a laser light source that emits a laser beam having a circular cross-sectional shape, A lens system that deforms into a shape, a homogenizer that homogenizes the intensity distribution of the laser beam that exits the lens system, and an interference reduction device that is provided between the homogenizer and the lens system to reduce the interference action of the laser beam. The homogenizer includes a cylindrical lens array and a focusing lens formed of a plurality of cylindrical lenses, and the interference reduction device has a width B equal to a width B of each of the plurality of cylindrical lenses included in the cylindrical lens array. A plurality of transparent lengths that are successively longer by a predetermined length X that is longer than the coherent length. Providing an optical path length correction member made of a glass plate, and a photomask that shields the laser beam incident on the boundary surfaces of the plurality of transparent glass plate constituting the optical path length correction member, it laser irradiation apparatus according to claim is Is done.
[0013]
The photomask is a metal mask obtained by depositing a thin film that absorbs a laser beam on a glass substrate and performing a partial etching process.
[0014]
According to the configuration of the present invention, the optical path length correction member has a width B equal to the width of each of the plurality of cylindrical lenses constituting the cylindrical lens array , and is sequentially increased by a predetermined length X longer than the coherent length. Since the optical path for the laser beam divided into each cylindrical lens becomes longer by the length of the glass, each laser beam has an optical path difference longer than the coherent length. There is no effect and the beams do not interfere with each other.
[0015]
In addition, since the photomask shields the laser beam that is incident on the boundary surface of the plurality of transparent glass plates constituting the optical path length correction member, the generation of diffraction and reflected light at the boundary surface is prevented, and the diffraction and reflected light is incident. Interference on the irradiation surface with light can be prevented.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.
[0017]
FIG. 1 is a block diagram of a laser irradiation apparatus according to the present invention, and FIG. 2 is a block diagram of the main part of FIG. As shown in FIGS. 1 and 2, a laser irradiation apparatus 10 of the present invention is a laser irradiation apparatus that irradiates an irradiation object by transforming a laser beam 1 from a circular cross-sectional shape to a linear cross-sectional shape. A system 14 and an interference reduction device 20 are provided.
[0018]
The laser light source 12 is a laser oscillator that emits a laser beam 1a having a circular cross section. The laser light source 12 is not limited to a highly coherent YAG laser device, but may be a multimode oscillation excimer laser device.
[0019]
The lens system 14 includes an expander 14a (cylindrical concave lens) that expands the width of the laser beam 1 (vertical direction in the figure) and a cylindrical convex lens 14b that returns the laser beam to parallel light. The laser beam 1a having a circular cross-sectional shape is linearly cross-sectionally shaped. Transforms into A cylindrical concave lens may be used instead of the cylindrical convex lens 14b.
With this configuration, the laser beam 1a having a circular cross section emitted from the laser light source 12 becomes a laser beam 1b having an elongated linear cross section by the expander 14a and the cylindrical convex lens 14b.
[0020]
The homogenizer 16 includes a cylindrical lens array 16a composed of a plurality of cylindrical lenses 16a and a focusing lens 16b, and homogenizes the intensity distribution of the laser beam 1b. In the example of FIG. 3, the focal plane S is the upper surface of the substrate 58, and the mirror 56 is located between the focal plane S and the focusing lens 55b.
[0021]
The interference reduction device 20 includes a photomask 21 and an optical path length correction member 22 and is provided between the lens system 14 and the homogenizer 16.
[0022]
The photomask 21 shields the laser beam incident on the boundary surface of the optical path length correction member 22 (a plurality of transparent glass plates 22a described later). The photomask 21 is a metal mask in which a thin film 21b that absorbs light, such as Cr, is deposited on the surface of a glass substrate 21a (for example, quartz glass) to a thickness of about 10 nm to 100 nm, and the portions other than the portion to be absorbed are removed by etching. There should be.
As the metal mask, a known mask can be used as long as the thin film 21b has a characteristic of absorbing the laser beam and the thickness is sufficiently smaller than the wavelength of the laser beam.
[0023]
A mask manufactured by machining or the like has a film thickness of about several tens of μm because of its manufacturing accuracy. Therefore, the film thickness is larger than the wavelength of the laser beam (for example, 532 nm), and diffraction from the mask surface (especially the thickness surface) is difficult. There is a risk of reflection. On the other hand, in the photomask 21 of the present invention, since the film thickness is about several tens of nm, it is sufficiently smaller than the wavelength of the laser beam, and diffraction and reflection hardly occur. In the case of a Cr film, the transmittance of the mask is about 0.1% with a laser having a wavelength of 532 nm, which is sufficiently small.
[0024]
The optical path length correction member 22 includes a plurality of transparent glass plates 22a, and the transparent glass plates 22a have a width B equal to the width of each of the plurality of cylindrical lenses constituting the cylindrical lens array 16a . That is, the interval between the thin films 21b of the photomask 21, the width of the transparent glass plate 22a, and the cylindrical lens 16a all have the width B.
The lengths of the plurality of transparent glass plates 22a are also sequentially increased by a predetermined length X that is longer than the coherent length. In addition, in this example, although the length of the some transparent glass plate 22a is lengthened in order from one side, this invention is not limited to this, It may arrange | position long from the center reversely, or may arrange | position at random. . Furthermore, although the number of the transparent glass plates 22a is seven in this example, it may be 6 or less or 8 or more as long as it matches the number of the cylindrical lenses 16a.
[0025]
According to the configuration of the present invention described above, the circular cross-section laser beam 1a emitted from the laser light source 12 becomes an elongated laser beam 1b by the expander 14a and the cylindrical convex lens 14b, and the individual transparent glass plates of the optical path length correction member 22. Incident on 22a.
[0026]
Since the photomask 21 is positioned in front of the transparent glass plate 22a, the laser beam incident on the boundary surface of the transparent glass plate 22a is shielded by the thin film 21b, and the thin film 21b prevents diffraction and reflected light from being generated at the boundary surface. Interference on the irradiated surface between the diffracted and reflected light and the incident light is prevented.
[0027]
Further, since the optical path length correction member 22 is composed of a plurality of transparent glass plates 22a having a width B equal to the cylindrical lens 16a constituting the homogenizer 16 and sequentially lengthened by a predetermined length X longer than the coherent length, each cylindrical The optical path for the laser beam divided into the lenses 16a becomes longer by the length of the glass, and each laser beam has an optical path difference of a distance longer than the coherent length. Therefore, there is no influence of coherency, and the beams do not interfere with each other. .
[0028]
Next, the laser beam that has passed through the optical path length correction member 22 enters the lens array 15a while being divided, and is divided into beam groups 1c having a rectangular beam profile by the rectangular lens group, and each beam group is divided into the lens array 15a. The light is condensed by the light and spreads beyond the focal plane. The focusing lens 15b (convex lens) refracts each beam group 1c and condenses it on the focal plane S.
Accordingly, in the focal plane S, all the beam groups 13c overlap to cause homogenization of the intensity distribution, and a leveled intensity distribution can be obtained.
[0029]
In addition, this invention is not limited to the Example and embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0030]
【The invention's effect】
As described above, the laser irradiation apparatus according to the present invention does not generate interference fringes due to diffracted light or reflected light on the joint surface even when a highly coherent laser light source is used. Has an excellent effect.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a laser irradiation apparatus according to the present invention.
FIG. 2 is a configuration diagram of a main part of FIG. 1;
FIG. 3 is a schematic diagram of a conventional laser irradiation apparatus.
4 is a configuration diagram of a main part of FIG. 3;
[Explanation of symbols]
1, 1a, 1b, 1c laser beam,
10 laser irradiation device, 12 laser light source,
14 lens system, 14a expander,
14b cylindrical convex lens,
16 Homogenizer,
16a cylindrical lens array,
16b Focusing lens,
20 interference reduction device,
21 photomask, 21a glass substrate, 21b thin film,
22 Optical path length correction member , 22a Transparent glass plate

Claims (2)

In a laser irradiation apparatus that irradiates an irradiation object by transforming a laser beam from a circular cross-sectional shape to a linear cross-sectional shape,
A laser light source that emits a laser beam having a circular cross-sectional shape, a lens system that transforms the laser beam into a linear cross-sectional shape, a homogenizer that homogenizes the intensity distribution of the laser beam exiting the lens system, and the homogenizer and lens system An interference reduction device for reducing the interference effect of the laser beam provided between,
The homogenizer comprises a cylindrical lens array composed of a plurality of cylindrical lenses and a focusing lens,
The interference reduction device is composed of a plurality of transparent glass plates having a width B equal to the width B of each of the plurality of cylindrical lenses constituting the cylindrical lens array and sequentially lengthened by a predetermined length X longer than the coherent length. An optical path length correction member;
A laser irradiation apparatus comprising: a photomask that shields a laser beam incident on a boundary surface of a plurality of transparent glass plates constituting the optical path length correcting member . 2. The laser irradiation apparatus according to claim 1 , wherein the photomask is a metal mask obtained by depositing a thin film that absorbs a laser beam on a glass substrate and performing a partial etching process. 3.

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