JPH10256179A - Device and method for laser light irradiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uniformity of optically split and synthesized laser light. SOLUTION: The in-plane uniformity of laser light is improved by utilizing an optical system constituted by combining multi-cylindrical lens arrays 301, 302, 304, and 305 with a multi-micro-lens array 401. Therefore, the ununiformity of the projecting energy density of the laser light in an irradiated plane is modified. In addition, the degree of modification of the ununiformity is further improved by rotating the lens array 401.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to an apparatus for irradiating a laser beam having excellent uniformity in a beam plane and a method for irradiating such a laser beam.

[0002] A laser irradiation apparatus and a laser irradiation method using the invention disclosed in this specification can be used, for example, for annealing a semiconductor material, various exposures, and the like.

[0003]

2. Description of the Related Art A technique of irradiating a semiconductor material with laser light to anneal the semiconductor material is known. Also, a technique using laser light in a photolithography process is known.

[0004] In such a technique, the problem is how to make the laser light correspond to a large area.

As a means for solving this problem, there is a method in which a laser beam is linearly beam-processed, and the beam is scanned and irradiated.

[0006]

When a laser beam is linearly beam-processed, unevenness of the irradiation energy density in the extending direction (longitudinal direction of the linear beam) becomes a problem.

FIG. 1 shows an outline of a linear laser beam irradiation apparatus developed and used by the present inventors.

The apparatus shown in FIG. 1 is an apparatus developed and used for annealing (crystallization and activation) of a silicon thin film.

This apparatus converts the laser light oscillated by an oscillator 101 into homogenizers 102, 103, 104, 1
The light is guided to the lenses 106, 107, and 108 via the lens 105, further reflected by the mirror 109, and irradiated from the lens 110 to the irradiation surface 111 as linear laser light.

[0010] The linear laser light emitted by this apparatus has a width of several mm and a length of more than ten cm.

The homogenizers 102 and 105 have a function of adjusting (more precisely, appropriately dispersing) the energy distribution in the beam in the width direction of the laser beam processed linearly.

The homogenizer has a structure as shown in FIG. Its function is to correct the difference in energy density in the beam cross section in the split direction by splitting the beam and combining them.

The homogenizers 103 and 104 have a function of adjusting (more precisely, appropriately dispersing) the energy distribution in the beam in the longitudinal direction of the laser beam to be linearly processed.

Here, the role of the homogenizers 102 and 105 is not significant. This is because the width of the linear laser beam is several mm. (That is, the in-plane distribution of the irradiation energy density is compressed and inconspicuous.)

On the other hand, the influence of the homogenizers 103 and 104 on the irradiation energy distribution is very large. this is,
By the laser beam being elongated in a longitudinal shape,
This is because the in-plane distribution of the irradiation energy density is enlarged.

The homogenizer has a structure in which a large number of lenses each having a cam-like shape, a semi-cylindrical shape, or a shape obtained by vertically dividing a columnar body are arranged in parallel as shown in FIG.

In such a structure, since there is interference of light from each lens, a periodic interference fringe appears. The interference fringes appear as unevenness in the irradiation energy density of the laser beam.

As shown in FIG. 5, the laser beam output from the oscillator also has partial energy unevenness. In the case of the pulse oscillation type laser, this uneven state is caused by each of oscillations 501, 502, 503, and 504 in FIG.
Will be different as shown by.

It is considered that this unevenness is caused by a difference in the oscillation position and a difference in the discharge start position for each pulse in the oscillator.

It is difficult to correct such unevenness of the irradiation energy density of the laser beam by using a homogenizer alone (although a certain effect can be obtained), and it appears as unevenness of an annealing effect and unevenness of exposure.

If the number of divisions of the homogenizer is increased, the above-mentioned problem of unevenness can be reduced. However, it takes time and effort to manufacture the lens, resulting in high cost.

In addition, this method is not suitable for forming a linear laser beam which will require a length of several tens cm to 1 m or more in the future. That is, there is a limit in increasing the number of divisions of the homogenizer, and several tens of
It cannot cope with the formation of a linear laser beam that would require a length of m to 1 m or more.

It is conceivable that the homogenizer is not used in order to avoid the occurrence of interference fringes caused by using the homogenizer. However, in this case, it is not possible to obtain the effect of correcting the deviation of the in-plane energy density in the laser beam output from the oscillator, and interference fringes are generated due to other factors, which also produces undesirable results.

The invention disclosed in the present specification is directed to an irradiation surface caused by unevenness of energy density in a laser beam caused by using the above-described homogenizer and unevenness of energy density of laser light oscillated from a laser oscillator. It is an object to provide a technique for suppressing unevenness of irradiation energy density in the inside.

[0025]

Means for Solving the Problems One of the inventions disclosed in this specification is an apparatus for irradiating a laser beam, a homogenizer for dividing the laser beam into a plurality of beams in a predetermined direction, and a laser beam in a matrix. A laser beam output from a laser oscillator is passed through the homogenizer and the microlens array, and then shaped into a desired beam shape by an optical system.

According to another aspect of the invention, there is provided an apparatus for irradiating a laser beam, comprising: a first homogenizer for dividing a plurality of laser beams in a first direction; a microlens array for dividing a laser beam into a matrix; And a second homogenizer that divides the laser light into a plurality of pieces in the second direction,
The first and second homogenizers are arranged before and after the microlens array, and the laser beam output from the laser oscillator is sequentially passed through one homogenizer, the microlens array, and the other homogenizer. It is characterized in that a desired beam shape is formed later by an optical system.

According to another aspect of the invention, a plurality of homogenizers for dividing incident light in a predetermined direction are provided, and at least one microlens array for dividing laser light in a matrix between the plurality of homogenizers is provided. The plurality of homogenizers are arranged, and a dividing direction of the plurality of homogenizers with respect to incident light is set to a plurality of directions.

According to another aspect of the invention, a laser beam is made incident on a homogenizer that divides the laser beam into a plurality of beams in a predetermined direction, and then the laser beam is further made incident on a microlens array that divides the laser beam into a matrix. It is characterized by being shaped into a beam and irradiating the surface to be irradiated.

According to another aspect of the invention, a laser beam is made incident on a microlens array which divides the laser beam into a matrix, and then the laser beam is made incident on a homogenizer which divides the laser beam into a plurality of beams in a predetermined direction. It is characterized by being shaped into a shape and irradiating the surface to be irradiated.

In the above invention, it is preferable to use the microlens array by rotating it.

A homogenizer for dividing a laser beam into a plurality of beams in a predetermined direction basically has a structure as shown in FIG. This has a structure in which lenses having a semicircular shape or a cross-section similar thereto and having a longitudinal shape in one direction are arranged in parallel.

The homogenizer having such a structure has a function of dividing incident light by a number of lenses in a specific direction (this direction corresponds to the direction in which the lenses having a longitudinal shape are arranged). .

The microlens array has a configuration in which a large number of circular lenses or rectangular lenses or lenses similar thereto are arranged in a matrix as shown by 303 in FIG. 3 and 401 in FIG.

This lens has a function of dividing incident light into a matrix.

[0035]

【Example】

Embodiment 1 FIG. 3 shows an outline of the present embodiment. In FIG.
An optical system for improving in-plane uniformity of energy density of laser light output from an oscillator is shown. After passing through the optical system shown in FIG. 3, the laser light is incident on an optical system (not shown) for determining the beam shape, and is irradiated on the surface to be irradiated.

The configuration shown in FIG. 3 has a structure in which a laser beam from an oscillator is incident from the right side of the page and a laser beam with reduced in-plane non-uniformity is output to the left side of the page. I have.

First, the laser light incident on the homogenizer 301 is divided into seven in the y direction, and the laser light incident on the homogenizer 302 is divided into seven in the x direction. Since the x-axis and the y-axis are orthogonal to each other, the laser light incident on the two homogenizers is conveniently divided by 7 × 7.

The 49 divided laser beams pass through the microlens array 303 and are further divided.

In the microlens array, lenses having a circular or rectangular shape or a similar shape in a matrix are arranged in a matrix.

The laser light further divided into a matrix by the microlens array enters the homogenizers 304 and 305 and is further divided into 49.

The laser beam that has passed through the optical system shown in FIG. 3 is synthesized by an optical system (not shown), and further shaped into a required beam shape. Then, irradiation is performed on the irradiation surface.

With this configuration, even if there is a protruding region in a part of the energy distribution of the laser beam, it is dispersed and superposed, so that the irradiation energy density in the final laser beam is increased. Uneven distribution can be greatly corrected.

In the conventional configuration, the micro lens array 3
There is no 03, so that stripe-like unevenness (irradiation energy density) corresponding to the extending direction of the cam-shaped (or vertically-shape-shaped column) lens constituting the homogenizer is generated.

However, in the configuration shown in FIG. 3, a large number of laser beams passing through the homogenizers 301 and 302 are further superimposed by the microlens array, so that the above-described stripe-shaped unevenness is less likely to appear. it can.

The optical system shown here can be used for a laser annealing technique of irradiating a semiconductor material with a beam processed in a linear shape, an exposure in a photolithography step, and the like.

[Embodiment 2] This embodiment is an example in which the configuration shown in Embodiment 1 is further improved.

FIG. 4 shows a schematic configuration of this embodiment. In this embodiment, a laser beam from an oscillator is incident from the right side of the paper, and a laser beam with improved in-plane non-uniformity is output to the left side of the paper.

First, the laser light incident on the homogenizer 301 is divided into seven in the y direction, and the laser light incident on the homogenizer 302 is divided into seven in the x direction. The laser light incident on these two homogenizers is conveniently divided into 7 × 7.

The 49 divided laser beams pass through the rotating microlens array 401, and enter the homogenizer 304 in a state where each of the 49 divided laser beams is superimposed.

At this time, since the microlens array 401 is rotating, the state of the laser beam passing through the microlens array (in-plane distribution of energy density) also varies with time. That is, the energy distribution state of the laser beam is spatially and temporally dispersed.

The laser beam in which the in-plane distribution of the energy density dispersed both spatially and temporally is dispersed is further divided into 49 by the homogenizers 304 and 305. The 49 divided laser beams are superposed by an optical system (not shown) and formed into a required beam shape.

By passing through the optical system shown in FIG. 4, it is possible to disperse the in-plane distribution of the irradiation energy density of the laser beam and, at the same time, to temporally disperse the energy density. Is greatly improved.

[Embodiment 3] In the configurations shown in Embodiments 1 and 2, the two homogenizers forming a pair have the dividing directions (or the longitudinal directions of the lenses) orthogonal to each other. (FIG. 6 (A))

However, in order to further improve the uniformity of the energy distribution in the beam, a configuration using a plurality of homogenizers may be employed.

In this embodiment, as shown in FIG.
A configuration in which three homogenizers intersect at an angle of 0 ° will be described. By doing so, the uniformity of the energy distribution in the beam can be further improved.

[0056]

By using the invention disclosed in this specification, the irradiation energy density in the laser beam caused by the unevenness of the in-plane distribution of the energy density of the laser beam output from the oscillator and the use of the homogenizer Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a system for irradiating a linear laser beam.

FIG. 2 is a diagram showing an outline of a homogenizer.

FIG. 3 is a diagram showing a configuration of an optical system using the present invention.

FIG. 4 is a diagram showing a configuration of an optical system using the present invention.

FIG. 5 is a diagram showing an energy distribution in a beam of laser light emitted from an oscillator.

FIG. 6 is a diagram showing a combination angle of a homogenizer.

[Explanation of symbols]

 Reference Signs List 101 laser oscillator 102 homogenizer 103 homogenizer 104 homogenizer 105 homogenizer 106 beam forming lens 107 beam forming lens 108 beam forming lens 109 mirror 110 beam forming lens 111 illuminated surface 301 Homogenizer 302 Homogenizer 303 Micro lens array 304 Homogenizer 305 Homogenizer 401 Rotating micro lens array

Claims (10)

[Claims] An apparatus for irradiating a laser beam, comprising: a homogenizer that divides the laser beam into a plurality of beams in a predetermined direction; and a microlens array that divides the laser beam into a matrix. A laser beam passing through the homogenizer and the microlens array, and thereafter forming the beam into a desired beam shape by an optical system. 2. The laser beam irradiation device according to claim 1, wherein the microlens array rotates. 3. The laser light irradiation device according to claim 1, wherein the laser light is incident on the microlens array after passing through the homogenizer. 4. The laser beam irradiation apparatus according to claim 1, wherein the laser beam is incident on the homogenizer after passing through the microlens array. 5. An apparatus for irradiating a laser beam, comprising: a first homogenizer for dividing a plurality of laser beams in a first direction; a microlens array for dividing a laser beam into a matrix; And a second homogenizer that divides the laser beam output from the laser oscillator into one of the first and second homogenizers before and after the microlens array. An apparatus for irradiating a laser beam, wherein the laser beam is sequentially passed through a homogenizer, the microlens array, and the other homogenizer, and then shaped into a desired beam shape by an optical system. 6. A plurality of homogenizers for dividing incident light in a predetermined direction, and at least one microlens array for dividing laser light into a matrix sandwiched by the plurality of homogenizers, is provided. The irradiation direction of the homogenizer is divided into a plurality of directions with respect to the incident light. 7. The laser beam irradiation device according to claim 6, wherein the microlens array rotates. 8. A laser beam is incident on a homogenizer which divides the laser beam into a plurality of beams in a predetermined direction. Thereafter, the laser beam is further incident on a microlens array which divides the laser beam into a matrix. Irradiating a surface to be irradiated with a laser beam. 9. A laser beam is made incident on a microlens array which divides the laser beam into a matrix, and then the laser beam is made incident on a homogenizer which divides the laser beam into a plurality of beams in a predetermined direction. A method for irradiating a laser beam, which comprises irradiating a surface to be irradiated. 10. The laser beam irradiation device according to claim 8, wherein the microlens array is rotated.