JP5541693B2 - Laser annealing equipment - Google Patents

Description

The present invention relates to Relais Zaaniru device can be suitably used when, for example manufacturing a polycrystalline or monocrystalline semiconductor film of the thin film transistor used in a pixel switch and a driving circuit for a liquid crystal display or an organic EL display.

As a semiconductor thin film used for a flat panel display substrate or the like, a semiconductor thin film using an amorphous film or a crystalline thin film is known. With respect to this crystal thin film, a method of manufacturing an amorphous film by annealing and crystallizing has been proposed (for example, see Patent Document 1).
In the annealing treatment, there is known a method of crystallizing a target object by irradiating the target object such as an amorphous film with laser light so that the laser light enters the target object and gives thermal energy. . Laser light is output from a laser oscillator and irradiated onto an object to be processed through an optical system including a lens, a mirror, and the like.
An annealing process is also known which is performed for the purpose of modifying defects such as removing defects and improving crystallinity by irradiating a crystalline film with laser light.

JP 2008-147487 A

By the way, when the object to be processed is irradiated with laser light, it is inevitable that the laser light is reflected on the surface of the object to be processed. For example, an amorphous silicon film has a property of reflecting excimer laser light (wavelength: 308 nm) by 50% on the film surface. Therefore, when annealing an amorphous silicon thin film with excimer laser light, there is a problem that the energy utilization rate is only about 50% due to surface reflection of the silicon thin film.
Further, when the laser beam reflected on the surface of the object to be processed travels backward through the optical system, the laser oscillator may be irradiated to cause damage to the laser oscillator. For this reason, a method is also proposed in which a predetermined incident angle (> 0) is set on the surface of the object to be processed and the laser beam is irradiated from an oblique direction on the surface of the object to be processed. Has been.

  The apparatus is shown in FIG. Laser light output from a laser oscillator (not shown) is appropriately shaped by the optical system 30 and guided by the optical system 30. The laser beam 40 emitted from the optical system 30 is applied to the object 50 at an incident angle φ. Then, the laser beam 40 penetrates into the object to be processed 50 while being refracted by the object to be processed 50, and gives laser beam energy to the object to be processed 50. At this time, a part of the laser beam 40 is reflected by the reflection angle φ according to the incident angle φ on the surface of the workpiece 50. As a result, it is possible to prevent the laser beam 41 reflected from the surface of the workpiece from traveling backward as it is through the optical system 30 and reaching the laser oscillator. However, even in this case, the energy of the reflected laser light 41 is not used effectively for irradiating the object to be processed 50 and is wasted as described above.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to increase the energy efficiency of a laser beam and efficiently perform the annealing process when performing an annealing process on an object to be processed using a laser beam. To do.

That is, the laser annealing apparatus of the present invention is a laser annealing apparatus for irradiating a surface of an object to be processed with laser light to anneal the object to be processed. A first optical system for irradiating and a second optical system comprising an optical system different from the first optical system for guiding and reirradiating the laser beam irradiated and reflected on the object to be processed It has a door,
The second optical system is the same as the irradiation position through the first optical system at an incident angle different from the incident angle of the laser light by the first optical system through a mirror and a concave mirror located on the downstream side of the optical path. The laser beam is re-irradiated to the object to be processed at the position of .

  According to the present invention, the laser beam reflected from the surface of the object to be processed can be irradiated again on the surface of the object to be processed for annealing, and the energy utilization efficiency is remarkably improved. In addition, it is possible to increase the maximum energy density in the irradiated portion of the object to be processed. Furthermore, when laser light is shaped into a line, etc., the energy density decreases as the irradiation area is increased, so the shape to be shaped is also limited (for example, the long axis length of the line beam). By improving the efficiency, for example, the long axis length of the line beam can be increased to perform the annealing treatment, and the effect of improving productivity can be obtained.

  Note that the laser light re-irradiated on the object to be processed through the second optical system is normally irradiated at the same position as the irradiation position by the first optical system, but the present invention is not limited to this. It is also possible to irradiate a position different from the irradiation position. For example, the irradiation position by the second optical system is slightly shifted with respect to the irradiation position by the first optical system, or irradiation is performed on the front side in the scanning direction and used for preheating, or the rear side in the scanning direction. It is also possible to irradiate and use for post-heating. However, when it is desired to increase the irradiation energy at the irradiation position, the laser beam that has passed through the first optical system and the laser beam that has passed through the second optical system irradiate the same position of the object to be processed.

The laser light described above is focused so as to converge near the surface of the object to be processed when irradiating the object to be processed. Therefore, when this laser beam is reflected by the surface of the object to be processed, it travels along the optical path while diffusing. For this reason, in the second optical system, it is desirable to irradiate the laser beam while condensing it when re-irradiating the surface of the object to be processed. The condensing can use a convex lens or a concave mirror, and the concave mirror can re-irradiate the surface of the object to be processed with reflection and condensing simultaneously.
In the re-irradiation of laser light through the second optical system, re-irradiation can be performed such that the beam shape is the same as that of the laser light irradiated through the first optical system. As a result, the surface of the object to be processed can be annealed with the same shape and area. However, in the present invention, the beam shape of the laser light passing through the first optical system may be different from the beam shape of the laser light passing through the second optical system. The beam shape of the laser beam that passes through the optical system may be shaped.

  The re-irradiation may be performed on the laser light irradiated and reflected through the first optical system, or may be re-irradiated with the laser light re-irradiated and reflected on the surface of the object to be processed. Is not particularly limited. When the laser beam is reflected by 50% on the surface of the object to be processed, an energy utilization rate of 75% can be obtained by one re-irradiation, and an energy utilization rate of less than 90% can be obtained by two re-irradiations. An energy utilization rate of slightly less than 94% can be obtained by three re-irradiations.

  In addition, since the laser beam irradiated directly on the surface of the object to be processed travels backward through the same optical path when regularly reflected, the configuration and arrangement of the second optical system are limited. In order to avoid this, when the laser beam is irradiated onto the object to be processed through the first optical system, the incident angle can be determined (> 0 degrees) and the irradiation can be performed from an oblique direction. This facilitates the arrangement of the second optical system.

Further, when the object to be processed is re-irradiated with the laser beam reflected from the surface of the object to be processed at the same angle, the laser light is reflected at the same angle as the incident angle and easily moves backward to the laser oscillator side. For this reason, by making the incident angle at the time of re-irradiation different from the angle at which it was reflected by the workpiece before that time, it is possible to avoid re-reflected laser light being reflected and going back to the laser oscillator as it is. it can. In order to make the incident angle of re-irradiation different from the previous reflection angle, an appropriate deflecting member such as a mirror or a prism can be used.
In addition, when re-irradiating repeatedly, the energy of the reflected light gradually decreases. Therefore, in the second and subsequent re-irradiations, the problem caused by the backward movement is reduced even if re-irradiation is performed at the same angle as the previous reflection angle.

  In the present invention, the object to be processed is not particularly limited as long as it can be annealed. For example, a semiconductor thin film formed on a substrate is used as the object to be processed. Can do. The semiconductor thin film may be an amorphous thin film that is crystallized by the above-described annealing treatment, or the crystalline thin film may be subjected to modification such as defect removal by annealing treatment.

  Further, according to the laser annealing apparatus of the present invention, in the laser annealing apparatus for irradiating the surface of the object to be processed with the laser beam to perform the annealing process, the laser light is guided to the object to be irradiated and irradiated. Since the first optical system and the second optical system that guides and re-irradiates the laser beam irradiated and reflected on the object to be processed are executed efficiently and reliably. can do.

It is the schematic which shows the laser annealing apparatus of one reference form of this invention. Similarly, it is an enlarged perspective view showing the vicinity of the irradiation position of the laser beam. It is the schematic which shows the laser annealing apparatus of one Embodiment of this invention. It is the schematic which shows the laser annealing apparatus of further another embodiment of this invention. Similarly, it is an enlarged perspective view showing the vicinity of the irradiation position of the laser beam. It is the schematic which shows the conventional laser annealing apparatus.

Hereinafter, one reference form will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of a laser annealing apparatus, and FIG. 2 shows the vicinity of a laser beam irradiation position.
The laser annealing apparatus 1 includes a laser oscillator 2 that outputs an excimer laser. At the output destination of the laser oscillator 2, an attenuator 3 for adjusting the output of the laser beam 2a output from the laser oscillator 2 is disposed. The attenuator 3 can adjust the output of the laser beam, for example, by adjusting the transmittance of the laser beam. At the destination of the laser beam 2a whose output is adjusted by the attenuator 3, an optical system 4 is provided that shapes the laser beam 2a into a line beam-like laser beam 100 and guides it to the object to be processed in the processing chamber 5. . In the figure, only the convex lens 4a and mirror 4b of the optical system 4 are shown. The optical system 4 corresponds to the first optical system of the present invention. A stage 6 is located at the emission destination of the optical system 4.
The stage 6 can be reciprocated at least in one horizontal direction by a driving device (not shown). A substrate 20 on which an amorphous silicon thin film 21 is formed is placed on the stage 6. The amorphous silicon thin film 21 corresponds to an object to be processed of the present invention.

The optical system 4 is set so that the laser beam 100 is incident on the amorphous silicon thin film 21 at an incident angle φ (φ> 0) with respect to the major axis direction. For example, the amorphous silicon thin film 21 is irradiated while being condensed by an objective lens (not shown). At that time, the laser beam 100 converges near the surface of the amorphous silicon thin film 21.
In the direction of the reflection angle φ with respect to the incident angle φ, a long concave mirror 7 having a concave cross section is disposed as a second optical system, and the concave surface is directed to a reflection site in the amorphous silicon thin film 21. The concave mirror 7 is focused so that the laser beam 101 reflected and re-irradiated to the amorphous silicon thin film 21 is converged near the surface of the amorphous silicon thin film 21.

Next, the operation of the laser annealing apparatus 1 will be described.
First, the substrate 20 on which the amorphous silicon thin film 21 is formed is placed on the stage 6 in the processing chamber 5.
The laser oscillator 2 outputs a laser beam 2a that is an excimer laser beam having a wavelength of 308 nm. The laser beam 2a passes through the attenuator 3 and is adjusted to a desired output. The laser beam 2a is shaped into a line beam-like laser beam 100 after being condensed by the lens 4a and reflected by the mirror 4b in the optical system 4. The laser beam 100 is applied to the amorphous silicon thin film 21 on the substrate 20 placed on the stage 6 at an incident angle φ.
At this time, the movement of the stage 6 is controlled by a control device (not shown) and is moved at a constant feed rate in the minor axis direction of the line beam at the time of laser irradiation at a predetermined feed rate.

About 50% of the laser light 100 irradiated to the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21 and the energy is absorbed to heat the amorphous silicon thin film 21. The heated amorphous silicon thin film 21 is subjected to annealing treatment such as crystallization according to heating and cooling.
On the other hand, about 50% of the laser light 100 irradiated to the amorphous silicon thin film 21 is reflected on the surface. At this time, as shown in FIGS. 1 and 2, the laser beam is reflected at the reflection angle φ according to the incident angle, and the reflected laser beam 101 enters the concave mirror 7 in the traveling direction.

  Contrary to the laser light 100, the laser light 101, which is reflected light, is further reflected and collected by hitting the concave mirror 7 while being diffused by reflection. Due to the reflection, the laser beam 101 is applied to the irradiated portion of the amorphous silicon thin film 21 on which the laser beam 100 is incident. At this time, the laser beam 101 is condensed according to the curved surface of the concave mirror 7 and converges near the surface of the amorphous silicon thin film 21 at the same position and shape as the laser beam 100. About 50% of the laser light 101 irradiated to the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21 and contributes to the annealing process, while about 50% is reflected on the surface of the amorphous silicon thin film 21. Is done.

  As described above, about 75 (≈100 / 50 + 50/2)% of the laser light 100 can penetrate into the amorphous silicon thin film 21 and contribute to the annealing process. Conventionally, the energy utilization rate is about 50%. On the other hand, a significant energy utilization improvement effect can be obtained.

Next, an embodiment of the present invention will be described with reference to FIG. In addition, about the structure similar to the said reference form, the same code | symbol is attached | subjected and the description is simplified.
In the laser neil device 10 of this embodiment, the laser oscillator 2 that outputs the excimer laser, the attenuator 3 that adjusts the output of the laser beam 2a, and the laser beam 2a that is output-adjusted by the attenuator 3 are line beams as in the above embodiment. The optical system 14 is shaped to be shaped into a laser beam 100 and guided to an object to be processed in the processing chamber 5. In this figure, only the lens 14 a and the mirror 14 b are shown as the optical system 14.
The stage 6 in the processing chamber 5 is located at the emission destination of the optical system 14. The stage 6 can reciprocate at least in the horizontal direction as in the above embodiment. The stage 6 is provided with a substrate 20 on which an amorphous silicon thin film 21 is formed as in the above embodiment.

  The optical system 14 is set so that the laser beam 100 is incident on the amorphous silicon thin film 21 at an incident angle φ1 (φ1> 0) with respect to the major axis direction. For example, the amorphous silicon thin film 21 is irradiated while being condensed by an objective lens. At that time, the laser beam 100 converges near the surface of the amorphous silicon thin film 21.

A mirror 11 for reflecting and deflecting the laser beam 101 reflected by the surface of the amorphous silicon thin film 21 is disposed in the direction of the reflection angle φ1 with respect to the incident angle φ1, and the concave surface faces the reflection direction of the mirror 11. The concave mirror 12 is disposed on the surface of the amorphous silicon thin film 21. The concave surface of the concave mirror 12 also faces the surface of the amorphous silicon thin film 21.
The reflection direction of the concave mirror 12 is directed to the irradiation part of the amorphous silicon thin film 21 irradiated with the laser beam 100, and the incident angle of the laser beam 101 reflected by the concave mirror 12 is φ2 (φ2>φ1> 0). Is set to The concave mirror 12 is focused so that the laser light 101 re-irradiated on the amorphous silicon thin film 21 converges near the surface of the amorphous silicon thin film 21.
The mirror 11 and the concave mirror 12 correspond to the second optical system in the present invention.

Next, the operation of the laser annealing apparatus 1 will be described.
The laser beam 2a irradiated from the laser oscillator 2 and adjusted to a desired output by the attenuator 3 is shaped into a line beam-shaped laser beam 100 after being condensed by the lens 14a and reflected by the mirror 14b in the optical system 14. . The laser beam 100 is applied to the amorphous silicon thin film 21 on the substrate 20 placed on the stage 6 at an incident angle φ1.
At this time, the movement of the stage 6 is controlled by a control device (not shown) and is moved at a constant feed rate in the minor axis direction of the line beam at the time of laser irradiation at a predetermined feed rate.

About 50% of the laser light 100 irradiated to the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21, and about 50% is reflected on the surface. The reflected laser beam 101 is reflected at the reflection angle φ 1 according to the incident angle, and the reflected laser beam 101 enters the mirror 11 in the traveling direction, reflects according to the incident angle, and enters the concave mirror 12.
Contrary to the laser beam 100, the laser beam 101 is incident on and reflected by the mirror 11 and the concave mirror 12 while being diffused by reflection. Due to the reflection at the concave mirror 12, the laser beam 101 is irradiated at an incident angle φ 2 on the incident portion of the amorphous silicon thin film 21 on which the laser beam 100 is incident, and is condensed according to the curved surface of the concave mirror 12. And converges near the surface of the amorphous silicon thin film 21.

  About 50% of the laser light 101 irradiated to the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21 and contributes to the annealing process, while about 50% is reflected on the surface of the amorphous silicon thin film 21. Is done. As described above, about 75% of the energy of the laser beam 100 enters the amorphous silicon thin film 21 and contributes to the annealing process. About 50% of the re-irradiated laser beam 101 is reflected again on the surface of the amorphous silicon thin film 21 at the reflection angle φ2. In this embodiment, the incident angle φ1 where the laser beam 100 is incident is different from the incident angle φ2 where the laser beam 102 is incident, and a part of the laser beam 101 is reflected again on the surface of the amorphous silicon thin film 21. In this case, the reflected laser beam 102 can be prevented from going backward to reach the laser oscillator 2.

Next, still another embodiment will be described with reference to FIGS. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and the description is simplified.
In the laser neil device 10 of this embodiment, the laser oscillator 2 that outputs the excimer laser, the attenuator 3 that adjusts the output of the laser beam 2a, and the laser beam 2a that is output-adjusted by the attenuator 3 are line beams as in the above embodiment. The optical system 14 is shaped to be shaped into a laser beam 100 and guided to an object to be processed in the processing chamber 5. Similarly to the above embodiment, the optical system 14 is set so that the laser beam 100 is incident on the amorphous silicon thin film 21 at an incident angle φ1 (φ1> 0) with respect to the major axis direction. The laser beam 100 irradiates the amorphous silicon thin film 21 while being condensed by, for example, an objective lens of the optical system 4 and converges near the surface of the amorphous silicon thin film 21.

A mirror 11 that reflects and deflects the laser beam 101 reflected by the surface of the amorphous silicon thin film 21 is disposed in the direction of the reflection angle φ1 with respect to the incident angle φ1, and the concave mirror is arranged so that the concave surface faces the reflection direction of the mirror 11. 12 is arranged. The reflecting direction of the concave mirror 12 is directed to the irradiated portion of the amorphous silicon thin film 21 irradiated with the laser beam 100, and the incident angle is φ2 (φ2>φ1> 0). The concave mirror 12 is focused so that the laser beam 101 re-irradiated on the amorphous silicon thin film 21 converges near the surface of the amorphous silicon thin film 21. In the direction of the reflection angle φ2 with respect to the incident angle φ2, a concave mirror 13 is disposed so as to face the irradiation site. The laser beam 102 reflected by the surface of the amorphous silicon thin film 21 by being irradiated with the laser beam 101 is incident on the concave mirror 13 and reflected, and is irradiated again to the amorphous silicon thin film 21. The concave mirror 13 is focused so that the laser beam 102 re-irradiated on the amorphous silicon thin film 21 converges near the surface of the amorphous silicon thin film 21.
The mirror 11, concave mirror 12 and concave mirror 13 correspond to the second optical system of the present invention.

Next, the operation of the laser annealing apparatus 1 will be described.
The laser beam 2 a irradiated from the laser oscillator 2 and adjusted to a desired output by the attenuator 3 is shaped into a line beam-shaped laser beam 100 in the optical system 14. The laser beam 100 is applied to the amorphous silicon thin film 21 on the substrate 20 placed on the stage 6 at an incident angle φ1.

About 50% of the laser light 100 irradiated on the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21, about 50% is reflected on the surface, and the reflected laser light 101 is reflected at the reflection angle φ1, and its traveling direction. And is incident on the concave mirror 12. Contrary to laser beam 100, laser beam 101 strikes mirror 11 and concave mirror 12 while being diffused by reflection, and is reflected. In the reflection, the laser beam 101 is irradiated to the incident portion of the amorphous silicon thin film 21 on which the laser beam 100 is incident at an incident angle φ2, and converges near the surface of the amorphous silicon thin film 21 at the same position and the same shape as the laser beam 100. A part of the laser light 101 irradiated to the amorphous silicon thin film 21 is reflected at the reflection angle φ2 on the surface of the amorphous silicon thin film 21 and is incident and reflected while diffusing to the reflecting mirror 13 in the traveling direction.
In the reflection, the laser beam 102 is irradiated on the irradiated portion of the amorphous silicon thin film 21 on which the laser beam 100 is incident, condensed according to the curved surface of the concave mirror 13, and the surface of the amorphous silicon thin film 21 at the same position and shape as the laser beam 100. Converge around.

About 50% of the laser light 102 irradiated to the amorphous silicon thin film 21 penetrates into the amorphous silicon thin film 21 and contributes to the annealing process, while about 50% is reflected on the surface of the amorphous silicon thin film 21. Is done. As described above, about 90% (≈100 / 2 + 50/2 + 25/2) of the laser beam 100 penetrates into the amorphous silicon thin film 21 and contributes to the annealing process.
In this embodiment, the incident angle φ1 at which the laser beam 100 is incident and the incident angle φ2 at which the laser beam 102 is incident are different from each other, but a part of the laser beam 101 passes through the optical system 14 by subsequent reflection. Although it is possible to reversely move, the energy of the backwardly moving laser beam is considerably lowered by repeated re-irradiation, and there is almost no influence on the laser oscillator 2.

In each of the above embodiments, the laser beam shaped into a line has been described. However, the present invention is not limited to the beam shape of the laser beam. For example, in the case of a spot laser beam. The same applies.
Although the present invention has been described based on the above embodiment, the present invention is not limited to the contents of each of the above embodiments, and appropriate modifications can be made without departing from the scope of the present invention. is there.

DESCRIPTION OF SYMBOLS 1 Laser annealing apparatus 2 Laser oscillator 2a Laser beam 4 Optical system 5 Processing chamber 7 Concave mirror 10 Laser neil apparatus 11 Mirror 12 Concave mirror 13 Concave mirror 100 Laser beam 101 Laser beam 102 Laser beam

Claims (7)

In a laser annealing apparatus that irradiates a surface of an object to be processed and anneals the object to be processed, a first optical system that irradiates the object to be processed in the form of a pulsed laser beam, A second optical system that is composed of an optical system different from the first optical system and reflects the laser beam irradiated and reflected on the object to be processed, and re-irradiates the object.
The second optical system is the same as the irradiation position through the first optical system at an incident angle different from the incident angle of the laser light by the first optical system by a mirror and a concave mirror located on the downstream side of the optical path. A laser annealing apparatus characterized by re-irradiating the object to be processed with the laser beam at a position .   2. The laser annealing apparatus according to claim 1, wherein the second optical system is configured to repeatedly guide the laser beam irradiated and reflected to the object to be processed to re-irradiate the object to be processed.   When the second optical system repeatedly irradiates and re-irradiates the laser beam irradiated and reflected on the object to be processed, the laser by the first optical system is used in the first re-irradiation. The re-irradiation is performed at an incident angle different from the incident angle of light, and in the second and subsequent re-irradiations, the re-irradiation is performed at the same incident angle as the incident angle of laser light in the previous re-irradiation. The laser annealing apparatus according to claim 2.   The second optical system re-irradiates the object to be processed with the same beam shape as that of the laser light irradiated to the object to be processed through the first optical system. The laser annealing apparatus according to claim 1, wherein the apparatus is a laser annealing apparatus.   The laser annealing apparatus according to claim 1, wherein the second optical system includes a light collecting member that condenses laser light.   The laser annealing apparatus according to claim 1, wherein the second optical system includes a concave mirror that collects the laser light while reflecting the laser light.   The first optical system is set so that the object to be processed is irradiated with a laser beam with an angle difference with respect to a direction orthogonal to the surface of the object to be processed. The laser annealing apparatus according to any one of 1 to 6.

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