JP2001257174A - Laser annealing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser annealing device that has a simple configuration, drastically improves the pointing stability of a laser beam, at the same time, rarely causes loss of energy, and can achieve uniform polycrystallization. SOLUTION: A laser annealing device 10 is equipped with an excimer laser oscillator 110, and a homogenizer 120 that sets the size of a laser beam L that is outputted from the laser oscillator 110 to a desired long shape and at the same time makes strength distribution uniform, scans a substrate 200 where an amorphous semiconductor film is formed on a surface 200a with the long- shaped laser beam L, and changes the amorphous semiconductor film into a polycrystal. The laser annealing device 10 is also equipped with a means for dividing the laser beam L that is allowed to oscillate from the laser oscillator 110 into two parts, and an optical means 20 for inversing an incident angle where one of the laser beams that are divided into two parts enters the homogenizer 120. In this case, an image rotator is used in the optical means 20, thus easily adjusting the application position of the laser beam L, and hence achieving more uniform polycrystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser annealing apparatus and a laser annealing method for polycrystallizing an amorphous semiconductor film on a substrate, and more particularly to a laser annealing apparatus and a laser annealing method with improved pointing stability of a laser beam. About.

[0002]

2. Description of the Related Art An excimer laser oscillator outputs
A laser annealing apparatus has been developed which irradiates a pulsed laser beam in the ultraviolet region having a relatively high photon energy onto a substrate having an amorphous semiconductor film deposited on its surface to polycrystallize the amorphous semiconductor film at a low temperature. .

[0003] This laser annealing apparatus will be described with reference to FIGS. 7 and 8. FIG. 7 is a block diagram showing a schematic configuration of a conventional laser annealing apparatus 100. FIG. 8 shows that the laser annealing apparatus 100
FIG. 2 is a front view showing a shape of a processing surface 200a and a beam spot S of a laser beam L applied to the processing surface 200a.

As shown in FIG. 7, a main structure of a conventional laser annealing apparatus 100 is an excimer laser oscillator 110.
And the homogenizer 120. The excimer laser oscillator 110 generates an ultraviolet laser beam L having a relatively high photon energy in a pulsed manner.

[0005] The homogenizer 120 includes a front cylinder lens array, a rear cylinder lens array, and a focus lens.
As shown in FIG. 8, the laser beam L of the rectangular beam spot output from the laser beam L is converted into an elongated beam spot S, and the energy intensity distribution of the laser beam L is made uniform. ing.

By irradiating such a laser beam L onto the substrate 200 having an amorphous semiconductor film deposited on its surface, the amorphous semiconductor film can be polycrystallized at a low temperature. Therefore, the conventional laser annealing apparatus 100
By scanning the elongated beam spot S in the direction orthogonal to the long axis direction of the beam spot S as shown by an arrow in FIG. 8, the amorphous semiconductor film on the entire substrate 200 is uniformly polycrystallized.

[0007]

By the way, in the excimer laser oscillator, the vibration of the optical resonator mirror and the supporting column, the minute vibration of the resonator length due to the thermal expansion, the fluctuation of the resonator length, or the heat of the laser tube itself. It is inevitable that the optical axis and the parallelism fluctuate due to the deflection due to the expansion. In the conventional laser annealing apparatus, mainly due to these factors, the incident position and incident angle at which the laser beam output from the excimer laser oscillator enters the homogenizer differs for each pulse, and the laser beam applied to the processing surface of the substrate. Had a problem that the pointing stability of the beam spot was poor.

[0008] Even if the incident position where the laser beam enters the homogenizer is somewhat unstable, if the laser beam enters parallel to the optical axis of the homogenizer, the spot position of the laser beam applied to the processing surface of the substrate is greatly affected. Absent. However, when the laser beam is incident on the optical axis of the homogenizer at an incident angle, the laser beam has a property that the irradiation position of the laser beam shifts substantially in proportion to the incident angle. This property will be specifically described with reference to FIGS.

For example, as shown in FIG. 9A, a laser beam L incident parallel to the optical axis P of the homogenizer 120 is used.
a is irradiated on a predetermined position of the processing surface 200 a of the substrate 200 on the optical axis P of the homogenizer 120. However, FIG.
As shown in (B), the laser beam Lb incident on the optical axis P of the homogenizer 120 at a positive incident angle is incident from the optical axis P of the homogenizer 120 in the positive or negative direction due to the configuration of the lens of the homogenizer 120. The light is applied to a position shifted by a distance proportional to the angle. Similarly, as shown in FIG. 9C, the laser beam Lc incident on the optical axis P of the homogenizer 120 at a negative angle of incidence is moved in the negative or positive direction by the configuration of the lens of the homogenizer 120 in the negative or positive direction.
The light is emitted to a position shifted from the 0 optical axis P by a distance proportional to the incident angle.

Therefore, the conventional laser annealing apparatus 100
In the case, the laser beam L output from the excimer laser oscillator 110 has a different incident angle to the homogenizer 120 for each pulse.
a, the irradiation position of the beam spot S is unstable, the pointing stability of the beam spot S is poor,
This was an obstacle to forming a uniform polycrystal.

In a conventional laser annealing apparatus, as a countermeasure, a method of making the displacement on the substrate 200 zero in principle by a mask imaging method can be considered. However, this method improves the pointing stability of the laser beam, but causes an energy loss because the mask blocks the laser beam to some extent.

As another countermeasure, in a laser annealing process, when a laser beam is scanned along a processing surface of a substrate, a large overlap where irradiation spots overlap is made large, and pointing stability of the laser beam is deteriorated. Also, a method is conceivable in which a laser beam is irradiated as uniformly as possible on the processed surface of the substrate. In this method, although there is almost no energy loss itself, the pointing stability itself of the laser beam is not improved, and it cannot be a drastic measure for uniforming the polycrystal.

[0013] The present invention solves the above problems (problems),
An object of the present invention is to provide a laser annealing apparatus and a laser annealing method capable of radically improving the pointing stability of a laser beam with a simple configuration, hardly causing energy loss, and enabling uniform polycrystallization.

[0014]

According to the first aspect of the present invention, there is provided a laser annealing apparatus comprising: a laser oscillator;
The laser beam output from the laser oscillator has a desired elongate shape, and a homogenizer for making the intensity distribution uniform, and the elongate shape is formed on a substrate having an amorphous semiconductor film formed on its surface. A laser annealing apparatus for scanning the laser beam to polycrystallize the amorphous semiconductor film, wherein the laser beam oscillated from the laser oscillator is divided into two parts, and one of the two divided laser beams is provided by the homogenizer. And an optical means for reversing the angle of incidence at which light is incident.

With this configuration, a laser annealing apparatus capable of drastically improving the pointing stability of a laser beam with a simple configuration, hardly causing energy loss, and capable of uniformly polycrystallizing an amorphous semiconductor film. can do.

In the laser annealing apparatus according to the second aspect, the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer includes:
An optical device in which three total reflection mirrors are appropriately arranged is used.

With this configuration, it is possible to provide a laser annealing apparatus capable of performing uniform polycrystallization by using optical means having the simplest structure.

In the laser annealing apparatus according to the third aspect, the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer includes:
An optical device having an image rotator appropriately constituted by two total reflection mirrors and three mirrors is used.

As described above, when the three-mirror image rotator is used in the optical device, the adjustment of the irradiation position of the laser beam becomes easy, and a laser annealing device capable of more uniform polycrystallization can be obtained. it can.

In the laser annealing apparatus according to the fourth aspect, the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer includes:
An optical device is used in which an image rotator appropriately including two total reflection mirrors and a trapezoidal prism whose bottom surface is formed on a total reflection surface is used.

As described above, when the trapezoidal prism type image rotator is used in the optical device, a variation in the irradiation position of the laser beam can be suppressed, and a laser annealing device capable of more uniform polycrystallization can be obtained.

In the laser annealing apparatus according to the fifth aspect, the laser beam emitted from the laser oscillator
As a means for splitting, a polarizing beam splitter was used.

With this configuration, it is possible to provide a laser annealing apparatus provided with suitable means for dividing a laser beam oscillated from a laser oscillator into two.

In the laser annealing apparatus according to the present invention, the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer has a variable optical path length through which the laser beam passes. did.

With this configuration, by adjusting the optical path length, it is possible to prevent a situation in which the laser beams split into two interfere with each other and the laser beam intensity becomes significantly nonuniform on the processing surface of the substrate.

According to a seventh aspect of the present invention, in the laser annealing apparatus according to any one of the first to sixth aspects, one of the laser beams whose incident angles are inverted by the optical means and the other laser beam. The beam was superimposed on the beam and made incident on the homogenizer, and the fluctuation of the irradiation position of the laser beam was suppressed to improve the pointing stability of the laser beam.

This makes it possible to provide a laser annealing method that enables uniform polycrystallization.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of a laser annealing apparatus and a laser annealing method according to the present invention will be described below with reference to FIGS. 1 and 2. Next, first to third embodiments will be described. Will be specifically described with reference to FIGS.

First, the basic configuration and basic principle of the laser annealing apparatus 10 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of a laser annealing apparatus 10 of the present invention. FIG. 2 shows the substrate 2 using the optical device 20 of the laser annealing device 10 of the present invention.
It is a side view which shows the state which irradiates the beam spot of a laser beam to the processing surface 200a of 00. In FIG. 1, the same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

The main structure of the laser annealing apparatus 10 of the present invention is, as shown in FIG.
As in the case of 00, an excimer laser oscillator 110 as a laser oscillator and a rectangular beam spot output from the excimer laser oscillator 110 are converted into a long beam spot, and the energy intensity distribution of the laser beam L is made uniform. Is provided.

On the other hand, as shown in FIG. 1, the laser annealing apparatus 10 of the present invention has a structural feature that a laser beam L oscillated from the excimer laser oscillator 110 is interposed between the excimer laser oscillator 110 and the homogenizer 120. The optical device 20 includes a unit for dividing the laser beam into two, and an optical unit for reversing an incident angle at which one of the two divided laser beams enters the homogenizer 120. Each embodiment of the optical device 20 will be described later using a specific example.

With the above configuration, the basic principle of the laser annealing apparatus 10 will be described with reference to FIG. 2 and FIG. Laser beam L output from excimer laser oscillator 110
Is split into two laser beams by the optical device 20, and one of the split laser beams has its incident angle incident on the homogenizer 120 inverted by the incident angle inverting means of the optical device 20, and then is superimposed on the other laser beam. The light enters the homogenizer 120.

Then, as shown in FIG. 2, one laser beam LB whose incident angle to the homogenizer 120 is inverted by the optical device 20 is irradiated as a beam spot SB on the processing surface 200a of the substrate 200. The other laser beam LA is applied to the processing surface 2 of the substrate 200.
Irradiated as a beam spot SA on 00a. Note that depending on the lens configuration of the homogenizer 120, SB
And SA may be inverted upside down, but the effects are exactly the same, and the description is omitted below.

Actually, the intensity distribution of the laser beam applied to the processing surface 200a becomes a beam spot S which is a superposition of the beam spot SA and the beam spot SB as shown in FIG. The width of the beam spot S is
It is larger than the case of the conventional laser annealing apparatus 100,
Although the laser beam L fluctuates depending on the angle of incidence on the homogenizer 120, the intensity distribution of the laser beam L is vertically symmetrical about the optical axis P of the homogenizer 120 as shown in FIG. .

Therefore, the conventional laser annealing apparatus 100
In the above, the irradiation position on the processing surface 200a of the substrate 200 was moved up and down around the optical axis P. However, in the laser annealing apparatus 10 of the present invention, the center of the beam spot S of the laser beam L was The laser beam L does not fluctuate in accordance with the optical axis P, so that the pointing stability of the laser beam L can be significantly improved. The problem that the width of the beam spot S increases and the energy density decreases can be easily solved by increasing the overlap and increasing the irradiation time of the laser beam.

The above is the description of the laser annealing apparatus 10 of the present invention.
This is the basic principle that the pointing stability of the laser beam due to is improved. Hereinafter, the laser annealing apparatus 1
FIG. 3 shows the respective embodiments of the optical device 20 used in FIG.
This will be described with reference to FIGS. In the laser annealing apparatus 10 of the present invention, since the excimer laser oscillator 110 and the homogenizer 120 have the same configuration in each embodiment, only the configuration of the optical device 20 is illustrated in each of the following embodiments. I do.

First Embodiment: A first embodiment of the optical device 20A used in the laser annealing device 10 of the present invention will be described with reference to FIG. 3 and FIG. The optical device 20A according to the present embodiment includes a unit that divides the laser beam L output from the excimer laser oscillator 110 into two parts.
As shown in FIG. 3, the first polarization beam splitter 22A
Is used.

Further, the first polarization beam splitter 22A
As an optical means for inverting the incident angle at which one of the laser beams LB split by the laser beam enters the homogenizer 120, as shown in FIG. 3, first, second and third total reflection mirrors 24A, 24B and 24C are used. The optical device 20A configured by appropriately arranging is used.

With the above configuration, the laser beam L output from the excimer laser oscillator 110
Is divided into a laser beam LA and a laser beam LB by a first polarizing beam splitter 22A, and one of the two divided laser beams LB is divided into first, second, and third total reflection mirrors 24A, 24B, As shown by simple geometrical optics, the light is reflected at 24C, and as a result of being reflected an odd number of times, the angle of incidence at the homogenizer 120 is inverted.

One laser beam LB is superimposed on the other laser beam LA divided by the first polarization beam splitter 22A into two laser beams LA and the second polarization beam splitter 22B, and becomes a laser beam L to form a homogenizer 120.
Incident on. Thereby, as shown in the basic principle described above, the other laser beam LA is directly used as the homogenizer 1.
20 and one of the laser beams LB is incident on the homogenizer 120 with the incident angle inverted, so that the irradiation can be performed so that the center of the beam spot S coincides with the optical axis P of the homogenizer 120, and the pointing stability of the laser beam L Can be improved.

In the laser annealing apparatus 10 of the present embodiment, the first, second and third total reflection mirrors 24A and 24B are used as optical means for reversing the incident angle at which one laser beam LB enters the homogenizer 120. , 24C are arranged appropriately, so that the structure can be simplified and the optical path length of one laser beam LB passing through the optical device 20 can be shortened.

Second Embodiment A second embodiment of the optical device 20B used in the laser annealing device 10 of the present invention will be described with reference to FIG. 4 and FIG. Also in the optical device 20B of the present embodiment, similar to the first embodiment,
As means for splitting the laser beam L output from the excimer laser oscillator 110 into two, a first polarization beam splitter 22A is used as shown in FIG.

Further, the first polarization beam splitter 22A
As an optical means for inverting the incident angle at which one of the laser beams LB split by the laser beam is incident on the homogenizer 120, as shown in FIG.
An optical device 20B configured by appropriately disposing an image rotator 26 including 4A, 24B and three mirrors 26a, 26b, 26c is used.

With the above configuration, the laser beam L output from the excimer laser oscillator 110
Is divided into two by a first polarizing beam splitter 22A, and one of the two divided laser beams LB is reflected in order of a first total reflection mirror 24A, an image rotator 26, and a second total reflection mirror 24B, and As a result of the odd number of reflections, the angle of incidence on the homogenizer 120 is inverted, and the pointing stability of the laser beam can be improved as in the first embodiment.

In the laser annealing apparatus 10 of this embodiment, the first and second total reflection mirrors 24A and 24B and the three mirrors are used as optical means for inverting the incident angle at which one laser beam enters the homogenizer 120. 26a, 2
Since the image rotator 26 composed of 6b and 26c is appropriately arranged, the processing surface 2 of the laser beam L is controlled by controlling the image rotator 26.
The irradiation position on 00a can be finely adjusted, which is more effective for uniform polycrystallization.

Third Embodiment A third embodiment of the optical device 20C used in the laser annealing apparatus 10 according to the present invention will be described with reference to FIG. 5 and FIG. In the optical device 20C of the present embodiment, as in the first and second embodiments, as a means for dividing the laser beam L output from the excimer laser oscillator 110 into two, as shown in FIG. Is used.

The first polarization beam splitter 22A
As an optical means for inverting the incident angle at which one of the laser beams LB divided by the laser beam enters the homogenizer 120, as shown in FIG.
An optical device 20C configured by appropriately arranging an image rotator 28 composed of a trapezoidal prism having 4A, 24B and a bottom surface 28a formed on the total reflection surface is used.

With the above configuration, the laser beam L output from the excimer laser oscillator 110
Is divided into two by the first polarizing beam splitter 22A, and one of the two divided laser beams LB is reflected by the first total reflection mirror 24A, refracted by the trapezoidal prism 28, and reflected by the bottom surface 28a, Under the action of refraction, the light is reflected by the second total reflection mirror 24B and sequentially reflected a total of an odd number of times. As a result, the angle of incidence on the homogenizer 120 is inverted. Similarly, the pointing stability of the laser beam L can be improved.

In the laser annealing apparatus 10 of the present embodiment, the first and second total reflection mirrors 24A and 24B and the trapezoidal prism are used as optical means for reversing the incident angle at which one laser beam LB enters the homogenizer 120. Since the image rotator 28 of the mold is appropriately arranged, by controlling the trapezoidal prism 28, the variation of the irradiation position of the laser beam L on the processing surface 200a can be suppressed, and the uniform polycrystallization can be achieved. More effective.

In the first to third embodiments, as shown in FIG. 6, the second assembly A2, which is an optical means for reversing the incident angle at which one laser beam LB enters the homogenizer 120, is used. And the distance T to the first assembly A1 including the first and second polarization beam splitters 22A and 22B that divides the laser beam L into LA and LB and superimposes the laser beam L again. In this case, by adjusting the distance T between the assemblies A1 and A2, one of the two divided laser beams LB and the other laser beam LA interfere with each other, and the processing surface 20 of the substrate 200
At 0a, it is possible to prevent a situation in which the laser beam intensity is significantly non-uniform.

By the way, the laser beam L is divided into two, and one of the laser beams LB passes through an optical path different from that of the other laser beam LA in order to reverse the incident angle at which the laser beam LB enters the homogenizer. 200a
It is assumed that the time to reach is delayed. But,
The degree of this time lag depends on the pulsed laser beam.
It should be noted that the pulse width is sufficiently smaller than the pulse width and negligible.

The laser annealing apparatus and the laser annealing method of the present invention are not limited to the above embodiments, and various modifications can be made. For example, in the above-described embodiment, the first to third examples have been described as means for inverting the incident angle of one of the two split laser beams into the homogenizer. Of course, the present invention is not limited to the embodiment.

[0053]

The laser annealing apparatus and the laser annealing method of the present invention have the following excellent effects because they are configured as described above. (1) A laser annealing apparatus according to the present invention, as described in claim 1, means for splitting a laser beam oscillated from a laser oscillator into two, and an incident angle at which one of the split laser beams is incident on a homogenizer. With the configuration having optical means for inverting the laser beam, the pointing stability of the laser beam is drastically improved with a simple configuration,
In addition, it is possible to provide a laser annealing apparatus which has almost no energy loss and can perform uniform polycrystallization.

(2) As described in claim 2, three total reflection mirrors are appropriately arranged as optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer. When an optical device is used, a laser annealing device capable of uniform polycrystallization can be provided by optical means having the simplest structure.

(3) As described in claim 3, the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer includes two total reflection mirrors and three mirrors. When an optical device in which an image rotator to be used is appropriately arranged is used, the adjustment of the irradiation position of the laser beam becomes easy, and a laser annealing device capable of more uniform polycrystallization can be obtained.

(4) As the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer, two total reflection mirrors and a bottom surface are provided as a total reflection surface. The laser anneal device which can suppress the variation of the irradiation position of the laser beam and can realize more uniform polycrystallization by using an optical device in which an image rotator constituted by a trapezoidal prism formed on the substrate is appropriately arranged. It can be.

(5) As described in claim 5, when a polarizing beam splitter is used as a means for dividing the laser beam oscillated from the laser oscillator into two, the laser beam oscillated from the laser oscillator is divided into two. A laser annealing apparatus having a suitable means for dividing can be provided.

(6) As described in claim 6, when the length of the optical path passing through the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer is made variable, the optical path length becomes By adjusting the distance, it is possible to prevent a situation in which the laser beams split into two interfere with each other to cause significant unevenness of the laser beam intensity on the processing surface of the substrate.

(7) In the laser annealing method according to the seventh aspect, one laser beam whose incident angle is inverted by optical means and the other laser beam are superposed and incident on the homogenizer, and the laser beam is irradiated. Since the fluctuation of the irradiation position is suppressed and the pointing stability of the laser beam is improved, a laser annealing method that enables uniform polycrystallization can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a laser annealing apparatus according to the present invention.

FIG. 2 is a side view for explaining a basic principle in which the pointing stability of a laser beam is improved by the laser annealing apparatus and the laser annealing method of the present invention.

FIG. 3 is a schematic configuration diagram showing a first embodiment of an optical device used for the laser annealing apparatus of the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the optical device used for the laser annealing device of the present invention.

FIG. 5 is a schematic configuration diagram showing a third embodiment of the optical device used for the laser annealing device of the present invention.

FIG. 6 is a conceptual diagram showing a state where the distance between the first and second assemblies is variable in the optical device of the laser annealing apparatus of the present invention.

FIG. 7 is a block diagram showing a basic configuration of a conventional laser annealing apparatus.

FIG. 8 is a front view for explaining a step of performing polycrystallization by scanning a laser beam with a laser annealing apparatus.

FIG. 9 is a side view for explaining that the pointing stability of a laser beam is poor in a conventional laser annealing apparatus.

[Explanation of symbols]

 10: Laser annealing device 20, 20A, 20B, 20C: Optical device 22A, 22B: Polarizing beam splitter 24A, 24B, 24C: Total reflection mirror 26: Three-mirror image rotator 28: Trapezoid prism image rotator 28a: Trapezoid prism Bottom surface 110: excimer laser oscillator (laser oscillator) 120: homogenizer A1: first assembly A2: second assembly L, LA, LB: laser beam S, SA, SB: beam spot

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B23K 101: 40 B23K 101: 40

Claims (7)

[Claims] An amorphous semiconductor film is formed on a surface of a laser oscillator, and a homogenizer for making a laser beam output from the laser oscillator have a desired long shape and uniform intensity distribution. A laser annealing apparatus that scans the formed substrate with the elongated laser beam to polycrystallize the amorphous semiconductor film; and a means for dividing a laser beam oscillated from the laser oscillator into two parts; An optical means for reversing an incident angle at which one of the laser beams is incident on the homogenizer. 2. An optical device in which three total reflection mirrors are appropriately disposed as said optical means for inverting an incident angle at which one of two split laser beams is incident on a homogenizer. The laser annealing apparatus according to claim 1, wherein 3. An image rotator composed of two total reflection mirrors and three mirrors is appropriately disposed as the optical means for inverting the incident angle at which one of the two divided laser beams enters the homogenizer. The laser annealing apparatus according to claim 1, wherein an optical device is used. 4. The optical means for reversing the incident angle at which one of the two split laser beams is incident on the homogenizer includes two total reflection mirrors and a trapezoidal prism having a bottom surface formed on a total reflection surface. 2. The laser annealing apparatus according to claim 1, wherein an optical device having an image rotator appropriately disposed is used. 5. The laser annealing apparatus according to claim 1, wherein a polarizing beam splitter is used as a means for splitting a laser beam emitted from the laser oscillator into two. 6. The optical system according to claim 1, wherein an optical path length of the laser beam passing through the optical means for inverting an incident angle at which one of the two divided laser beams enters the homogenizer is variable. The laser annealing apparatus according to any one of the above. 7. The laser annealing apparatus according to claim 1, wherein one of the laser beams whose incident angles have been inverted by the optical means and the other laser beam are superimposed on each other to form the homogenizer. A laser annealing method characterized by improving the pointing stability of a laser beam by causing the laser beam to be incident and suppressing a change in the irradiation position of the laser beam.