JP2018195675A - Laser annealing apparatus and laser annealing method - Google Patents

Abstract

To reduce, by a homogenizer, the unevenness of interference in a laser annealing apparatus.SOLUTION: A laser annealing apparatus comprises: a light source for generating laser light; a homogenizer for substantially uniformizing an intensity distribution of laser light launched from the light source; a condenser lens for collecting the laser light uniformized by the homogenizer in intensity distribution; and a cylindrical lens for converting the laser light collected by the condenser lens into a line beam. The line beam is applied to a target for exposure to light in a state in which a scan direction is inclined at a given angle to interference fringes which can be formed on the target for exposure to light by interference of laser light having passed through the homogenizer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser annealing apparatus for annealing a substrate with a laser.

  Conventionally, a laser annealing technique is known as a technique for converting amorphous silicon of a silicon substrate into polysilicon. Laser annealing is generally a technique for forming a polysilicon film by heating a silicon film at a low temperature by irradiation with a laser, and is known as a technique for producing a substrate such as a liquid crystal panel. Patent Document 1 discloses an example of such a laser annealing technique.

JP 2012-182348 A

  By the way, in such laser annealing, it is known that the intensity distribution of a laser oscillated from a light source that emits a laser is made uniform by a homogenizer, and then a beam is formed to perform annealing. The homogenizer is composed of, for example, a fly-eye lens, but highly coherent lasers that have passed through each of the plurality of lenses constituting the fly-eye lens interfere with each other, resulting in interference unevenness on the substrate. There is a problem of generating. Needless to say, it is not preferable that such interference unevenness is formed on the substrate.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a laser annealing apparatus and method that can reduce interference unevenness due to laser interference through a homogenizer.

  In order to solve the above problems, a laser annealing apparatus according to an aspect of the present invention includes a light source that generates laser light, a homogenizer that makes the intensity distribution of laser light emitted from the light source substantially uniform, and an intensity distribution using the homogenizer. A condenser lens that condenses the laser light that has been made uniform and a cylindrical lens that converts the laser light condensed by the condenser lens into a line beam, and is formed on the object to be irradiated by the interference of the laser light that has passed through the homogenizer The irradiation target is irradiated with the line beam in a state where the scanning direction is inclined by a predetermined angle with respect to the interference fringes that can be performed.

  In the laser annealing apparatus, the intensity distribution may be made substantially uniform by condensing the laser light from the light source with the homogenizer rotated by a predetermined angle so that a predetermined angle is formed. .

  The laser annealing apparatus further includes a mounting table for mounting the irradiation target and a drive unit that drives the mounting table in the scanning direction, and the irradiation target is mounted on the mounting table in a state inclined at a predetermined angle. Then, the line beam may be irradiated.

  In the laser annealing apparatus, the predetermined angle is an angle at which the start end of the first stripe and the end of the second stripe adjacent to the first stripe coincide with each other in the scanning direction in the interference fringe of the line beam. It is good also as being.

  The laser annealing method according to one embodiment of the present invention includes an irradiation step of irradiating a laser beam from a light source, a uniformizing step of making the intensity distribution of the laser beam irradiated from the light source substantially uniform by a homogenizer, and an intensity by the homogenizer. Condensing step of condensing laser light with uniform distribution by condenser lens, conversion step of converting laser light condensed by condenser lens into line beam by cylindrical lens, and interference of laser light passing through homogenizer An annealing step of irradiating the irradiation target with a line beam in a state where the scanning direction is inclined by a predetermined angle with respect to the interference fringes that can be formed on the irradiation target.

  In the laser annealing apparatus according to one embodiment of the present invention, interference unevenness that may be generated by interference of laser light that has passed through a homogenizer is tilted with respect to the scanning direction, so that interference fringes generated by the line beam are tilted. The integrated value can be made substantially uniform. Therefore, the laser annealing apparatus can suppress the occurrence of interference unevenness due to the interference of laser light by the homogenizer.

(A) is a top view of a laser annealing apparatus, (b) is a side view of a laser annealing apparatus. It is a figure for demonstrating the interference nonuniformity formed in a panel. (A) is a figure which shows the relationship between the homogenizer, the interference nonuniformity formed, and the energy distribution of a line beam. (B) is a figure which shows the relationship between the interference nonuniformity formed and the energy distribution of a line beam in the state which inclined the homogenizer by the predetermined angle. It is a flowchart which shows operation | movement of a laser annealing apparatus. It is a figure which shows the generation | occurrence | production direction of an interference nonuniformity, the angle with respect to a scanning direction, and the suppression effect of an interference nonuniformity. It is a figure which shows another example of the annealing method.

  The laser annealing apparatus according to the present invention will be described in detail with reference to the drawings.

<Embodiment>
<Configuration>
FIG. 1 is a diagram showing a configuration of a laser annealing apparatus 100, (a) is a plan view of the laser annealing apparatus 100 viewed from the top, and (b) is a side view of the laser annealing apparatus 100 viewed from the side. FIG.

  The laser annealing apparatus 100 condenses the light source 101 that generates laser light, the homogenizer 111 that makes the intensity distribution of the laser light emitted from the light source substantially uniform, and the laser light whose intensity distribution is made uniform by the homogenizer 111. A condenser lens 112 and a cylindrical lens 113 that converts the laser light collected by the condenser lens into a line beam, and for interference fringes that can be formed on the irradiation target by the interference of the laser light that has passed through the homogenizer 111, The irradiation target (panel) 200 is irradiated with a line beam in a state where the scanning direction is inclined by a predetermined angle.

  The light source 101 is a light source for irradiating laser light for laser annealing, and is, for example, a laser oscillator that oscillates a UV pulse laser.

  The homogenizer 111 makes the intensity distribution of the laser beam 201 oscillated from the light source 101 substantially uniform. The homogenizer 111 can be realized by, for example, two fly-eye lenses facing each other. The intensity distribution of the laser beam 202 that has passed through the homogenizer 111 is not completely uniform because the laser beams that have passed through a plurality of lenses constituting the homogenizer interfere with each other. In addition, the homogenizer 111 may use an aspherical lens or a diffraction optical element. In the present embodiment, the homogenizer 111 is configured so that the interference fringes generated by the coherence of the laser light 202 that has passed through the fly-eye lens are inclined at a predetermined angle with respect to the target panel 200. Annealing is performed with the angle rotated. Further details of the homogenizer 111 will be described later.

  The condenser lens 112 condenses the laser light 202 that has passed through the homogenizer 111 and has a substantially uniform intensity distribution.

  The cylindrical lens 113 converts the laser beam 203 collected by the condenser lens 112 into a line beam.

  The mirror 115 is a mirror that reflects the line beam 204 that has passed through the cylindrical lens 113 toward the panel 200 to be irradiated.

  The cylindrical lens 116 converts the line beam 204 reflected by the mirror 115 into a line beam having a width suitable for irradiating the panel 200 to be irradiated.

  The panel 200 to be irradiated is a substrate on which a silicon film is formed, and is placed on the stage 300.

  The stage 300 is a mounting table for mounting the panel 200 to be laser annealed. The stage 300 is driven by a driving device (not shown). Thereby, the panel 200 moves and the surface of the panel 200 is made into polysilicon. In the example of FIG. 1B, the stage 300 moves toward the light source 101. The moving direction may be referred to as a scanning direction.

  Further, the homogenizer 111, the condenser lens 112, the cylindrical lens 113, the mirror 115, and the cylindrical lens 116 are combined to form a uniform line beam optical system 110.

  Here, interference unevenness that may occur in the panel 200 when the laser beam that has passed through the homogenizer 111 is directly irradiated onto the panel 200 will be described.

  The intensity distribution of the laser light 201 oscillated from the light source 101 is made substantially uniform by the homogenizer 111. However, in the laser beam 201, the laser beams that have passed through the plurality of lenses constituting the homogenizer 111 interfere with each other, and the intensity distribution of the laser beam 202 is not completely uniform. Therefore, when this laser beam 202 is converted into a line beam as it is and laser annealing is performed, as shown in the panel 200 of FIG. 2, a polysilicon film having interference unevenness (interference fringes) is formed. .

  The upper part of FIG. 2 shows an example of the panel 200 on which interference fringes are formed, and the lower part shows the energy intensity distribution of the line beam at that time. As shown in the lower graph of FIG. 2, the line beam has a substantially periodic energy intensity distribution. The laser annealing apparatus 100 performs annealing by shooting the line beam in units of 20 μm width in the y direction shown in the upper part of FIG. 2, but because of the strength of the energy distribution in the x direction of the line beam shown in the lower part of FIG. Interference fringes are formed on the panel 200. 2 indicate the same direction as the x direction and the y direction shown in FIG. That is, interference fringes in the same direction as the scanning direction are formed on the panel 200.

  Therefore, in the present embodiment, as shown in FIG. 3B, the homogenizer 111 is fixed while being rotated by a predetermined angle, and the laser beam 201 from the light source 101 is made incident. Hereinafter, a description will be given in comparison with FIG.

  FIG. 3A shows from the left the state when facing the light source 101 of the homogenizer 111 (left), and the interference unevenness in the panel 200 that occurs when laser annealing is performed without rotating the homogenizer 111. The state (middle stage) and the energy distribution of the line beam at that time (right stage) are shown.

  When annealing is performed without tilting the homogenizer 111 with respect to the scanning direction as shown in the left part of FIG. 3A, the panel 200 has a scan as shown in the middle part of FIG. Interference fringes occur in the direction. This is because the line beam having the same energy distribution is uniformly irradiated along the scanning direction as shown in the right side of FIG.

  Therefore, in the laser annealing apparatus 100 according to the present embodiment, as shown in FIG. 3B, the homogenizer 111 is provided in the uniform line beam optical system 110 while being rotated by a predetermined angle (n °). Then, as shown in the middle part of FIG. 3B, the panel 200 is scanned with a feeling that the interference fringes are inclined. As a result, as shown in the graph of energy distribution on the right side of FIG. 3B, the energy per line of the panel is integrated, and the laser has a substantially uniform energy distribution as shown by a broken line 310. Annealing can be performed. As a result, the laser annealing apparatus 100 can perform laser annealing while suppressing the generation of interference fringes due to the laser light that has passed through the homogenizer 111.

<Operation>
From here, the annealing operation by the laser annealing apparatus 100 will be described. FIG. 4 is a flowchart showing the operation.

  First, the operator inputs the conditions of the light source 101 and the uniform line beam optical system to the simulator, and calculates a generation distribution in which interference unevenness occurs on the panel 200 (step S401). The specification is synonymous with specifying the energy distribution of the line beam. The conditions of the light source 101 and the uniform line beam optical system refer to the frequency and intensity of the laser oscillated from the light source 101, the arrangement position, curvature, and characteristics of various lenses constituting the optical system. Here, the location where the interference unevenness is generated is specified by the simulator, but the location where the interference unevenness is actually generated may be specified.

  The operator rotates the homogenizer 111 by a predetermined angle (n °) according to the calculated occurrence distribution (step S402). Details of the predetermined angle will be described later.

  Then, the operator drives the laser annealing apparatus 100 to irradiate the laser from the light source 101. The laser annealing device 100 drives the driving device to perform laser annealing while moving the stage 300 (step S403).

  Thereby, the laser annealing apparatus 100 can provide the panel 200 in which amorphous silicon having no interference unevenness is made into polysilicon.

  Note that the processing in steps S401 and S402 is not an operation of the laser annealing apparatus 100 but a preparation process for laser annealing, and an operator using the laser annealing apparatus 100, a simulator used by the operator, and a projection mask 114 are generated. This is processing by the generation device.

<Rotation angle of homogenizer>
In order to prevent interference unevenness from occurring on the panel 200, it is preferable that the integrated value of energy by the line beam irradiated to the panel 200 be as uniform as possible. Therefore, it is preferable that the predetermined angle at which the homogenizer 111 is rotated is such that one of the oblique interference fringes is overlapped with one of the other adjacent interference fringes.

  FIG. 5 is a diagram illustrating the inclination of interference fringes and the level of the effect of suppressing interference unevenness that occurs when laser annealing is performed according to the inclination.

  The upper part of FIG. 5 shows an example in which laser annealing is performed without rotating the homogenizer 111. In this case, as shown in the energy distribution of FIG. Since a line beam having a uniform distribution is irradiated, interference fringes as shown in the upper part of FIG. 5 are generated.

  However, as shown in the middle and lower stages of FIG. 5, when laser annealing is performed with the homogenizer 111 rotated, the energy distribution is integrated as shown in FIG. As a result, the energy of the line beam irradiated to the entire panel 200 becomes uniform. As a result, the occurrence of uneven interference can be suppressed.

  As shown in the middle part of FIG. 5, it is preferable that the distances h1 and h2 between the oblique interference fringes are set to zero. That is, the first interference fringe is at the start end side in the scanning direction of the first interference fringe and at the end portion closer to the second interference fringe and at the end side in the scanning direction of the second interference fringe. It is desirable to rotate the homogenizer 111 so that the end portion closer to is located on the same straight line parallel to the scanning direction. As a result, the energy distribution of the line beam that is eventually irradiated to the entire panel 200 can be made uniform, and the occurrence of uneven interference can be suppressed. At this time, the distance between the end portions of the region where the energy is higher than a predetermined value may be zero.

  In this case, the configuration in which the interference fringes are tilted by a predetermined angle with respect to the scanning direction is realized by rotating the homogenizer 111 by a predetermined angle. A similar effect can be obtained by scanning in an inclined state. That is, as shown in FIG. 6, the panel 200 may be obliquely placed on the stage 300, and the laser annealing apparatus 100 may drive the stage 300 in the scan direction shown in the figure.

<Summary>
As described above, according to the laser annealing apparatus 100 according to the present invention, the line irradiated to the panel 200 can be obtained by rotating the homogenizer 111 more than a predetermined value or by tilting the panel 200 when placing it on the stage 300. The beam can be tilted. As a result, the integrated value of the energy of the line beam is applied to the panel 200 for annealing, so that interference unevenness can be suppressed and amorphous silicon can be made into polysilicon.

  Conventionally, in laser annealing, the above-described interference fringes are suppressed by moving an optical system including a homogenizer using a low-speed laser (for example, about 600 Hz). However, the inventors have found that there is a limit to the suppression of interference fringes by moving the optical system when annealing is performed by shooting a higher-speed line beam (for example, about 6 kHz). Therefore, as shown in the above-described embodiment, the inventors make the line beam oblique with respect to the panel 200 so that the interference fringes are not generated (the interference fringes that can be generated are oblique). In other words, the present invention has been made so that the energy applied to the entire panel 200 is made uniform to suppress interference unevenness.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, in the uniform line beam optical system 110, if the line beam is irradiated so that the interference fringes are oblique with respect to the panel 200 as a result, the arrangement of the components constituting the optical system may be moved back and forth. .

DESCRIPTION OF SYMBOLS 100 Laser annealing apparatus 101 UV pulse laser irradiation apparatus 110 Uniform line beam optical system 111 Homogenizer 112 Condenser lens 113 Cylindrical lens 115 Mirror 116 Cylindrical lens 200 Panel 300 Stage

Claims (5)

A light source for generating laser light;
A homogenizer that makes the intensity distribution of the laser light emitted from the light source substantially uniform;
A condenser lens for condensing the laser light whose intensity distribution is made uniform by the homogenizer;
A cylindrical lens that converts the laser beam condensed by the condenser lens into a line beam,
A laser annealing apparatus that irradiates the irradiation target with the line beam in a state where a scanning direction is inclined by a predetermined angle with respect to an interference fringe that can be formed on the irradiation target by interference of laser light that has passed through the homogenizer. The intensity distribution is substantially uniform by condensing the laser light from the light source in a state where the homogenizer is rotated by a predetermined angle so that the predetermined angle is formed. The laser annealing apparatus as described. The laser annealing apparatus further includes:
A mounting table for mounting the irradiation object;
A driving unit that drives the mounting table in the scanning direction;
2. The laser annealing apparatus according to claim 1, wherein the irradiation target is placed on the mounting table while being tilted at the predetermined angle, and the line beam is irradiated. In the line beam interference fringes, the predetermined angle is an angle at which a first fringe start end and a second fringe end adjacent to the first fringe coincide in the scan direction. The laser annealing apparatus according to any one of claims 1 to 3, wherein the apparatus is a laser annealing apparatus. An irradiation step of irradiating a laser beam from a light source;
A homogenizing step of making the intensity distribution of the laser light emitted from the light source substantially uniform by a homogenizer;
A condensing step of condensing the laser light having a uniform intensity distribution by the homogenizer with a condenser lens;
A conversion step of converting the laser light collected by the condenser lens into a line beam by a cylindrical lens;
An annealing step of irradiating the irradiation target with the line beam in a state where a scanning direction is inclined by a predetermined angle with respect to interference fringes that can be formed on the irradiation target by interference of laser light that has passed through the homogenizer.

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