JP2000135578A - Laser radiating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser radiating device for evening variation of the radiated laser light energy volume on a substrate. SOLUTION: A processing substrate 2 is held by a holding plate 14. A laser optical system radiates a laser beam 10 having a linear beam cross section of a given width on the surface of the processing substrate 2 held by the holding plate 14. A partial shielding means is arranged on the surface of the processing substrate 2 held by the holding plate 14, spaced from the surface by a given clearance. The partial shielding means shields the laser light transmitted near the both side edges along a line longitudinal direction of the beam cross section out of the laser beams 10 radiated on the surface of the processing substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser irradiation apparatus, and more particularly to a laser irradiation apparatus suitable for laser annealing.

[0002]

2. Description of the Related Art A technique of depositing an amorphous silicon film on a glass substrate and irradiating an excimer laser beam in a pulsed manner to polycrystallize the amorphous silicon film has attracted attention. This glass substrate is used, for example, in an active matrix type liquid crystal display device.

In order to obtain sufficient energy for polycrystallizing amorphous silicon, a laser beam is focused on an amorphous silicon film. By moving the glass substrate while irradiating the laser light and irradiating the laser light to a wide region of the amorphous silicon film, a large-area polycrystalline silicon film can be formed.

In order to irradiate a large area with laser light by one translational movement of the glass substrate, the beam cross section of the laser light is usually long in one direction. By moving the glass substrate in the direction perpendicular to the long direction of the beam cross section,
A large area can be irradiated with laser light.

[0005] The moving speed of the glass substrate is such that a region irradiated by one shot of the excimer laser beam and a region irradiated by the next one shot partially overlap.

[0006]

The irradiation position of the laser beam on the surface of the amorphous silicon film fluctuates by a certain width due to the fluctuation of the central axis of the beam of the excimer laser beam. Since the irradiation position changes for each shot, even if the glass substrate is translated at a constant speed, the overlap ratio of the irradiation regions adjacent to each other changes. Therefore, the energy amount of the laser beam applied to the amorphous silicon film becomes non-uniform in the substrate surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser irradiation apparatus which can make the variation of the energy amount of the irradiated laser light in the substrate plane more uniform.

[0008]

According to one aspect of the present invention, a holder for holding a processing substrate and a linear beam cross section having a certain width are formed on a surface of the processing substrate held by the holder. A laser optical system that irradiates a laser beam having the same, and a laser beam that is disposed on the surface of the processing substrate held by the holding table at a certain distance from the surface and that irradiates the surface of the processing substrate. A laser irradiation apparatus having a partial shielding unit that shields a laser beam propagating in a region near both edges along a line length direction of a cross section is provided.

When the laser beam propagating near both edges along the line length direction of the beam cross section of the laser beam is shielded by the partial shielding means, the position of the laser beam irradiation area on the surface of the processing substrate becomes It is defined by the position of the transmission area of the partial shielding means. By improving the positional stability of the partial shielding means, it is possible to improve the positional stability of the laser beam irradiation area even when the center axis of the laser beam has fluctuation.

[0010]

FIG. 1 is a schematic sectional view of a laser irradiation apparatus according to an embodiment of the present invention. A holding table 14 for holding a processing substrate is disposed inside the processing container 1, and the processing substrate 2 is held on the holding table 14.
An opening 7 is provided in the upper lid of the processing container 1, and the opening 7 is airtightly closed by a quartz window 8 via an O-ring 9. Laser beam 10 that has passed through a beam homogenizer described later
Irradiates the surface of the processing substrate 2 through the quartz window 8. The laser beam 10 has, for example, a long beam cross section in a direction perpendicular to the paper surface of FIG.

On the surface of the processing substrate 2, a partial shielding plate 3 is arranged at a certain distance (for example, about 1 mm) from the surface. The partial shielding plate 3 is formed of, for example, stainless steel. A vertical drive mechanism 5 such as an air cylinder is mounted on the upper lid of the processing container 1. The partial shielding plate 3 is connected to a vertical drive mechanism 5 by a connecting member 4 penetrating the upper lid of the processing container 1. The through hole through which the connecting member 6 penetrates is kept airtight by the bellows 6. Vertical drive mechanism 5
To move the partial shielding plate 3 up and down.

The partial shielding plate 3 has a slit 3A corresponding to the beam cross section of the laser beam 10,
Of 0, laser light propagating in the center of the beam cross section is transmitted, and laser light propagating in the periphery is shielded. The edge of the slit 3A is tapered. For example, the tapered surface is inclined by about 30 ° with respect to the surface of the processing substrate 2.
The portion of the laser beam 10 that enters the edge of the slit 3A is reflected in a direction different from the incident optical axis. For this reason,
The adverse effect caused by the reflected laser beam re-entering the laser optical system can be avoided.

A light absorbing member 11 is arranged so as to surround the optical path of the laser beam 10 in the processing chamber 1. The reflected laser beam 10A reflected at the edge of the slit 3A enters the light absorbing member 11 and is absorbed. Although a part of the laser beam incident on the light absorbing member 11 is reflected, the reflected laser beam partially enters the light absorbing member 11 again, and most of the reflected light is absorbed by the light absorbing member 11.

A coolant passage 12 is thermally connected to the light absorbing member 11. By flowing the refrigerant through the refrigerant channel 12,
The temperature rise of the light absorbing member 11 due to the absorption of the reflected laser beam 10A can be suppressed.

The center axis of the laser beam 10 has a temporal fluctuation. When the partial shielding plate 3 is not provided, the irradiation position of the laser beam 10 in the surface of the processing substrate 2 fluctuates by a certain width due to the fluctuation. When the partial shielding plate 3 is arranged, the irradiation position on the surface of the processing substrate 2 is substantially defined by the position of the slit 3A. By making the position stability of the partial shielding plate 3 higher than the position stability of the center axis of the laser beam 10 with respect to the position in the virtual plane parallel to the surface of the processing substrate 2, the irradiation position of the laser beam 10 is stabilized. (Pointing stability) can be improved. For example, the partial shielding plate 3
When the width (width in the horizontal direction in the drawing) of the laser beam 10 on the surface of the processing substrate 2 is not about 0.6 mm, the width of the slit 3A is about 0.4 mm.

Normally, the laser beam 10 has a light intensity distribution within the beam cross section. If the width of the slit 3A is too large, when the central axis of the laser beam 10 fluctuates, the foot of the light intensity distribution passes through the slit 3A. In this case, the intensity of the laser beam reaching the surface of the processing substrate 2 decreases.

In order to suppress a decrease in the intensity of light irradiating the surface of the processing substrate 2 when the center axis of the laser beam 10 fluctuates, it is preferable to narrow the width of the slit 3A. Specifically, when the position of the central axis of the laser beam 10 fluctuates, the partial shielding plate 3
It is preferable that the light intensity (energy density, unit: mJ / cm ² ) at the outermost periphery of the beam cross section of the laser beam passing through the laser beam is 90% or more of the maximum light intensity of the laser beam 10.

When a part of the laser light having high coherence is shielded by the slit, an interference phenomenon appears. However, since the coherence of the excimer laser light is low, the influence of the interference phenomenon will not be a problem.

By moving the processing substrate 2 in a direction (horizontal direction in FIG. 1) intersecting the long direction of the beam cross section while irradiating the laser beam 10 in a pulsed manner, the laser A beam can be irradiated.
Since the variation in the irradiation position of the laser beam for each shot can be reduced, the variation in the irradiation amount on the surface of the processing substrate 2 can be suppressed.

Next, the configuration and operation of the beam homogenizer that forms the laser beam 10 of FIG. 1 will be described with reference to FIG. Consider an xyz rectangular coordinate system having a z-axis parallel to the optical axis of a light beam incident on a beam homogenizer. FIG. 2A is a cross-sectional view parallel to the yz plane, and FIG.
Shows a sectional view parallel to the xz plane.

As shown in FIG. 2A, the generatrix directions of seven equivalent cylindrical lenses are respectively oriented in the x-axis direction.
The cylinder arrays 15A and 15B are arranged in the y-axis direction and along a virtual plane parallel to the xy plane. The optical axis plane of each cylindrical lens of the cylinder arrays 15A and 15B is parallel to the xz plane, and the generatrix of the cylindrical surface is parallel to the x axis. Here, the optical axis plane means a plane of symmetry of a plane-symmetric imaging system of a cylindrical lens. The cylinder array 15A is arranged on the light incident side (left side in the figure), and the cylinder array 15B is arranged on the light outgoing side (right side in the figure).

As shown in FIG. 2B, the generatrix directions of the equivalent seven cylindrical lenses are respectively oriented in the y-axis direction.
Cylinder arrays 16A and 16B are arranged in the x-axis direction and along an imaginary plane parallel to the xy plane. The optical axis plane of each cylindrical lens of the cylinder arrays 16A and 16B is parallel to the yz plane, and the generatrix of the cylindrical surface is parallel to the y axis. The cylinder array 16A is arranged in front of the cylinder array 15A (left side in the figure), and the cylinder array 16B is arranged between the cylinder arrays 15A and 15B. The optical axis planes of the corresponding cylindrical lenses of the cylinder arrays 15A and 15B match, and the optical axis planes of the corresponding cylindrical lenses of the cylinder arrays 16A and 16B also match.

A converging lens 19 is arranged behind the cylinder array 15B. The optical axis of the converging lens 19 is z
Parallel to the axis.

Referring to FIG. 2A, the state of propagation of a light beam in the yz plane will be described. In the yz plane,
Since the cylinder arrays 16A and 16B are simply flat plates, they do not affect the convergence and divergence of the light beam. A parallel light beam 17 having an optical axis parallel to the z-axis is incident on the cylinder array 16A from the left side of the cylinder array 16A. The parallel light beam 17 has a light intensity distribution that is strong at the central portion and weak at the peripheral portion, as shown by a curve 21y, for example.

The parallel light beam 17 passes through the cylinder array 16A and enters the cylinder array 15A. The incident light beam is divided into seven convergent light beams corresponding to each cylindrical lens by the cylinder array 15A. FIG.
(A) shows only the light beams at the center and both ends as representatives. The seven convergent ray bundles are respectively represented by curves 21ya-2
It has a light intensity distribution indicated by 1yg. Cylinder array 15
The light beam converged by A is transmitted to the cylinder array 15B.
Converges again.

The seven converging light beams 18 converged by the cylinder array 15B form an image in front of the converging lens 19 respectively. This image forming position is closer to the lens than the focal point on the incident side of the converging lens 19. Therefore, the seven light beams transmitted through the converging lens 19 become divergent light beams, respectively, and overlap on the homogenizing surface 20. Homogenized surface 20
The light intensity distributions in the y-axis direction of the seven light beams that irradiate are equal to the distributions obtained by extending the light intensity distributions 21ya to 21yg in the y-axis direction. Light intensity distributions 21ya and 21y
Since g, 21yb and 21yd, and 21yc and 21ye have respective inverted relations with respect to the y-axis direction, the light intensity distribution obtained by superimposing these light beams is represented by a solid line 22y.
Approach a uniform distribution as indicated by.

Referring to FIG. 2B, the state of propagation of a light beam in the xz plane will be described. In the xz plane,
Since the cylinder arrays 15A and 15B are simply flat plates, they do not affect the convergence and divergence of the light beam. The parallel light beam 17 is incident on the cylinder array 16A. Parallel ray bundle 1
7 has a light intensity distribution which is strong at the center and weak at the periphery as shown by a curve 21x, for example.

The parallel light beam 17 is divided by the cylinder array 16A into seven convergent light beams corresponding to each cylindrical lens. FIG. 1B shows only the light beams at the center and both ends as representatives. Each of the seven convergent light beams has a light intensity distribution indicated by curves 21xa to 21xg.

Each ray bundle forms an image in front of the cylinder array 16B, and enters the cylinder array 16B as a divergent ray bundle. Each ray bundle incident on the cylinder array 16B exits at a certain exit angle, and the convergent lens 1
9 is incident.

Each of the seven light beams transmitted through the converging lens 19 becomes a convergent light beam and overlaps on the homogenizing surface 20. The light intensity distribution in the x-axis direction of the seven light beams irradiating the homogenized surface 20 approaches a uniform distribution as shown by a solid line 22x as in the case of FIG.

The light irradiation area on the homogenized surface 20 is y
It has a linear shape that is long in the axial direction and short in the x-axis direction. By arranging the surface of the processing substrate 2 shown in FIG. 1 at the position of the homogenized surface 20, it is possible to irradiate a substantially uniform axial region on the surface in the y-axis direction.

At a position 23 in front of the homogenizing surface 20,
By disposing the partial shielding plate 3 shown in FIG. 1, the positional stability of the light irradiation area on the homogenized surface 20 can be improved.

As shown in FIG. 2, when the light irradiation area has a long linear shape in the y-axis direction, high position stability is required particularly in the x-axis direction. In this case, in a cross section parallel to the xz plane shown in FIG. 2B, by blocking laser light propagating near the side surface of the laser beam, positional stability in the x-axis direction can be improved. When high positional stability is not required in the y-axis direction, FIG.
In the cross section parallel to the yz plane shown in FIG. 2A, it is not necessary to block a part of the laser beam.

As shown in FIG. 2B, the converging lens 19
Are transmitted through different optical paths in the xz plane,
Overlap on the homogenized surface 20. In order to almost uniformly shield the laser beam propagating near the side face of each light beam, it is preferable to dispose the partial shielding plate 3 shown in FIG. 1 at a position where the optical paths of each light beam substantially overlap. . In addition, by bringing the position 23 where the partial shielding plate 3 is disposed closer to the homogenized surface 20, the positional stability of the light irradiation area can be further improved. In FIG. 1, it is preferable that the interval between the partial shielding plate 3 and the treatment substrate 2 is not more than twice the width of the slit 3A.

FIG. 3 is a schematic view of a laser annealing apparatus using the laser irradiation apparatus shown in FIG. The laser annealing apparatus includes a processing chamber 1, a transfer chamber 52, loading / unloading chambers 53 and 54, a homogenizer 42, a CCD camera 58, and a video monitor 59. The homogenizer 42 has a configuration similar to that shown in FIG.

A linear motion mechanism including a bellows 37, coupling members 33 and 35, a linear guide mechanism 34, a linear motor 36, and the like is attached to the processing chamber 1. Less than,
The configuration of the processing chamber 1 and the linear motion mechanism will be described with reference to FIG.

FIG. 4A is a schematic plan sectional view of the processing chamber 1 and the linear motion mechanism, and FIG. 4B is a schematic sectional view taken along a dashed line B1-B1 of FIG. 4A. In addition,
FIG. 4A corresponds to a cross section taken along dashed-dotted line A1-A1 in FIG.

Driving support shafts 32A and 32B are arranged in parallel with each other in an internal cavity of the processing container 1 capable of evacuating the inside. Both ends of each of the driving support shafts 32 </ b> A and 32 </ b> B extend to the outside through the side wall of the processing container 1.

The corresponding one ends of the driving support shafts 32A and 32B are connected to each other by a connecting member 33. The coupling member 33 is supported by a linear guide mechanism 34 so as to be movable in the axial direction of the driving support shafts 32A and 32B.

The other ends of the driving support shafts 32A and 32B are connected to each other by a connecting member 35. The coupling member 35 is driven by a linear motor 36 in the axial direction of the driving support shafts 32A and 32B. By driving the linear motor 36, the driving support shafts 32A and 32B can be translated in the axial direction.

A portion of each of the driving support shafts 32A and 32B led out of the processing vessel 1 is covered with a vacuum bellows 37. One end of the vacuum bellows 37 is the processing vessel 1
The other end is attached to the side of the connecting member 33 or 35
Attached to. The airtightness of the processing container 1 is maintained by the vacuum bellows 37.

A holding table 14 is arranged in the processing container 1. The holding table 14 is fixed to the driving support shafts 32A and 32B. A plurality of pins 38 project from the upper surface of the holding table 14, and the substrate 2 to be annealed is placed on the pins 38. A heater 39 is embedded in the holding table 14 so that the holding table 14 can be heated. The substrate 2 is heated by heat radiation from the holding table 14 or the like. A quartz window 8 is provided on the upper surface of the processing chamber 1, and laser light is introduced into the processing chamber 1 through the quartz window 8. By driving the linear motor 36 to move the driving support shafts 32A and 32B in the axial direction, the substrate 2
Can be translated.

Returning to FIG. 3, the laser annealing apparatus will be described. The processing chamber 1 and the transfer chamber 52 are connected via a gate valve 55, and the transfer chamber 52
And the transfer chamber 53, and the transfer chamber 52 and the transfer chamber 54 are connected via gate valves 56 and 57, respectively. The processing chamber 1 and the loading / unloading chambers 53 and 54 are provided with vacuum pumps 61, 62 and 63, respectively, so that the inside of each chamber can be evacuated.

A transfer robot 64 is housed in the transfer chamber 52. The transfer robot 64 transfers the processing substrate between the processing chamber 1 and the loading / unloading chambers 53 and 54.

A quartz window 8 for transmitting a laser beam is provided on the upper surface of the processing chamber 1. The laser beam output from the excimer laser device 41 having pulsed oscillation enters the homogenizer 42 through the attenuator 46. The homogenizer 42 makes the cross section of the laser beam into an elongated shape. The laser beam that has passed through the homogenizer 42 passes through an elongated quartz window 8 corresponding to the cross-sectional shape of the laser light,
The light enters the partial shielding plate 3 shown in FIG. A part of the laser beam transmitted through the partial shielding plate 3 irradiates the substrate in the processing chamber 1. The relative position between the homogenizer 42 and the substrate is adjusted so that the surface of the substrate coincides with the homogenized surface.

The substrate is translated by the linear motion mechanism described with reference to FIG. By moving the substrate at such a speed that part of the irradiation area for one shot overlaps part of the irradiation area in the previous shot, a large area on the substrate surface can be irradiated.
The substrate surface is photographed by the CCD camera 58, and the substrate surface being processed can be observed on the video monitor 59.

Excimer laser device 41, homogenizer 4
2. The operations of the transfer robot 64, the gate valves 55 to 57, and the linear motor 36 are controlled by the control device 65.

Using this laser annealing apparatus, the amorphous silicon film formed on the surface of the glass substrate can be polycrystallized. By arranging the partial shielding plate 3 shown in FIG. 1, the stability of the irradiation position of the laser beam can be improved, so that the in-plane variation of the energy density of the laser beam irradiated on the substrate can be reduced. it can. Therefore, a high-quality polycrystalline silicon film can be obtained.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0050]

As described above, according to the present invention,
The position stability of the laser beam that irradiates the processing substrate surface can be improved. By relatively moving the laser beam and the processing substrate while irradiating the laser beam, it becomes possible to irradiate the laser beam almost uniformly over a wide area of the substrate surface.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a laser irradiation apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a homogenizer.

FIG. 3 is a schematic view of a laser annealing apparatus using the laser irradiation apparatus shown in FIG.

4 is a sectional view of a linear motion mechanism used in the laser annealing device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing container 2 Processing board 3 Partial shielding plate 4 Connecting member 5 Vertical drive mechanism 6 Bellows 7 Opening 8 Quartz window 9 O-ring 10 Laser beam 11 Light absorption member 12 Refrigerant flow path 14 Holder 15A, 15B, 16A, 16B Cylinder array 17, 18 Ray bundle 19 Converging lens 20 Homogenizing surface 21, 22 Light intensity distribution 32A, 32B Driving spindle 33, 35 Coupling member 34 Linear guide mechanism 36 Linear motor 37 Vacuum bellows 38 Pin 39 Heater 41 Excimer laser device 42 Homogenizer 46 Attenuator 52 Transfer chamber 53, 54 Loading / unloading chamber 55-57 Gate valve 58 CCD camera 59 Video monitor 61, 62, 63 Vacuum pump 64 Transfer robot 65 Control device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsumi Nomura 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hirohisa Tanaka 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F term in the company (reference) 4E068 AH01 CE09 CF02 CF04

Claims (8)

[Claims] 1. A holding table for holding a processing substrate, a laser optical system for irradiating a surface of the processing substrate held on the holding table with a laser beam having a linear beam cross section having a certain width; On the surface of the processing substrate held by the holding table, disposed at a certain distance from the surface, of the laser beam irradiating the surface of the processing substrate, of the edges on both sides along the line length direction of the beam cross section A partial shielding unit for shielding a laser beam propagating in a nearby region. 2. The position stability of the partial shielding means in a virtual plane parallel to the surface of the processing substrate held by the holding table is higher than the position stability of the center axis of the laser beam. A laser irradiation apparatus according to claim 1. 3. The position of the center axis of the laser beam has a fluctuation of a certain width with respect to the partial shielding means,
When the position of the central axis of the laser beam fluctuates by the certain width, the light intensity of the outermost part of the beam cross section of the portion of the laser beam that passes through the partial shielding means is the maximum light intensity of the laser beam. The laser irradiation apparatus according to claim 1, wherein the partial shielding unit is configured to be 90% or more. 4. The laser irradiation apparatus according to claim 1, wherein the partial shielding unit includes a slit corresponding to the beam cross section. 5. The laser beam irradiation apparatus according to claim 1, wherein a region irradiated by the laser beam moves on a surface of the processing substrate held by the holding table in a direction intersecting a longitudinal direction of the beam cross section. The laser irradiation apparatus according to any one of claims 1 to 4, further comprising a moving mechanism that relatively moves a center axis of a beam and the holding table. 6. An edge of the slit of the partial shielding means is tapered, and a laser beam of the laser beam incident on the edge of the slit is reflected in a direction different from an incident optical axis. Item 6. The laser irradiation device according to item 4 or 5. 7. The laser irradiation apparatus according to claim 6, further comprising a light absorbing member arranged to block an optical path of the reflected laser beam reflected by the edge of the slit, and to absorb the reflected laser beam. 8. The laser irradiation apparatus according to claim 7, further comprising cooling means for cooling said light absorbing member.