JPH10107361A - Excimer laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the temperature increase in a light-transmitting plate by providing a means for cooling with gas, the light-transmitting plate that transmits stimulated emission light, generated in a container and discharges it outside the container. SOLUTION: A part of light generated in a laser container 1 is confined in a light resonator consisting of a pair of reflection mirrors 3, causes stimulated emission, and laser oscillates. When the repetition frequency of pulse oscillation is inputted from a laser oscillation control means 17 to a motor speed control means 16, a proper motor speed is obtained based on it and a motor 14 is driven, so that a blower 12 rotates and agitates a laser medium gas in the laser container 1. A cooling-gas supply pipe 4 is arranged near a light- transmitting plate 2 and a cooling-gas, such as N2 gas is sprayed onto the outer surface of the light-transmitting plate 2, thus suppressing the temperature increase of the light-transmitting plate 2. The speed of the motor increases as the repetition frequency increases, and the flow of the laser medium gas in the laser container 1 becomes faster, thus improving the cooling effect of the light-transmitting plate 2 due to the laser medium gas and suppressing the temperature increase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an excimer laser device.

[0002]

2. Description of the Related Art A laser annealing technique for irradiating a pulsed excimer laser to an amorphous silicon thin film to polycrystallize has attracted attention. This technique is used, for example, for producing a polycrystalline silicon thin film for forming a thin film transistor (TFT) of a liquid crystal display panel.

When polycrystallizing amorphous silicon, a laser beam is focused on a linear region on the surface of the amorphous silicon thin film. Move the irradiation area every shot,
A large area on the surface of the amorphous silicon thin film is irradiated.
The moving direction of the irradiation area is a direction (short axis direction) orthogonal to the long axis direction of the irradiation area, and the moving speed is such that a part of the irradiation area of one shot becomes a part of the irradiation area of the previous shot. It is controlled to overlap.

In order to make the amount of energy applied to the amorphous silicon thin film uniform in the plane, it is preferable to make the light intensity in the major axis direction of the irradiated area constant. Further, it is preferable that the light intensity distribution in the short axis direction is rectangular or trapezoidal, and that the shape is maintained constant in each shot.

[0005]

As the repetition frequency of the pulse oscillation of the excimer laser is increased, the light intensity distribution in the short axis direction of the laser beam irradiation area changes with the passage of time, and the light intensity distribution becomes unstable. In some cases. For this reason, it has not been easy to increase the repetition frequency.

An object of the present invention is to provide an excimer laser device capable of obtaining a stable light intensity distribution even when the repetition frequency of pulse oscillation is increased.

[0007]

According to one aspect of the present invention, a container for containing a laser medium, excitation means disposed within the container for exciting the laser medium,
An optical resonator for resonating light generated in the container, and a light transmitting plate that is hermetically attached to a wall of the container, transmits stimulated emission light generated in the container, and emits the light outside the container; An excimer laser device having an air cooling means for cooling the light transmitting plate with a gas is provided.

[0008] Light generated in the container is confined in the optical resonator, and laser oscillation occurs due to stimulated emission. Since the light transmitting plate is cooled by the air cooling means, the temperature rise can be suppressed. Thermal distortion due to an increase in the temperature of the light transmitting plate is reduced or prevented, and disturbance in the parallelism of the laser light during long-time operation can be suppressed.

According to another aspect of the present invention, a container for accommodating a laser medium, excitation means disposed in the container for exciting the laser medium intermittently with a certain period, and An optical resonator for resonating the generated light, a light transmitting plate that is airtightly attached to the wall of the container, transmits stimulated emission light generated in the container, and emits the light outside the container; An excimer laser device is provided, comprising: a stirring unit that is disposed, forcibly stirs the laser medium in the container, and can change the stirring ability in accordance with the certain period.

When the laser medium is stirred, the light transmitting window is cooled by the laser medium. When the period for exciting the laser medium is shortened, the temperature of the light transmission window tends to increase.
By changing the stirring ability in accordance with the cycle of exciting the laser medium, the light transmission plate can be appropriately cooled.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor conducted a study to determine the cause of an unstable light intensity distribution when the repetition frequency of pulse oscillation of an excimer laser was increased. As a result, it was found that the main instability factor of the light intensity distribution was thermal strain of the light transmitting plate attached to the container of the excimer laser device.

FIG. 4A is a schematic view of an optical system of an excimer laser irradiation apparatus. A light transmitting plate 2 for transmitting laser light is attached to each of mutually facing surfaces of the container 1 of the excimer laser device. A pair of reflecting mirrors 3 are opposed to each other so as to sandwich the container 1 on the optical axis of the laser light transmitted through the light transmitting plate 2 and emitted to the outside. An optical resonator is constituted by the pair of reflecting mirrors 3. One of the reflecting mirrors 3 is a partially transmitting mirror, and a part of the laser beam passes through the reflecting mirror 3 and enters the homogenizer 5.

The homogenizer 5 focuses a laser beam on a linear region on the surface of the substrate 6. FIG. 4A shows a case where the irradiation area of the laser light is a straight line perpendicular to the paper surface. Consider xy orthogonal coordinates on the surface of the substrate 6 with the direction perpendicular to the paper as the x-axis. At this time, the homogenizer 5 converges the laser light in the x-axis direction and diverges the laser light in the y-axis direction. The light intensity distribution in the y-axis direction on the surface of the substrate 6 has a shape close to a trapezoid.

FIG. 4B shows a temperature change of the light transmitting plate 2 when the excimer laser device shown in FIG. The temperature rises during the oscillation period of the excimer laser device, and falls during the oscillation stop period. If there is enough time until the next oscillation,
The temperature of the light transmitting plate 2 drops to the temperature before the start of laser oscillation. For this reason, the temperature of the light transmission plate 2 is maintained within a certain temperature range.

FIG. 4C shows a temperature change of the light transmitting plate 2 when the repetition period T of the pulse oscillation of the excimer laser is shortened. When the repetition period T is shortened, the next oscillation starts before the temperature of the light transmitting plate 2 does not sufficiently decrease during the oscillation stop period. For this reason, the temperature of the light transmission plate 2 rises with time while drawing a sawtooth waveform. According to an experiment performed by the inventor of the present application, when the repetition frequency was set to 30 Hz or more, the temperature was significantly increased.

FIG. 4D schematically shows how laser light propagates when the temperature of the light transmitting plate 2 rises. When the temperature of the light transmitting plate 2 rises, distortion occurs due to thermal expansion of the light transmitting plate. Since the periphery of the light transmitting plate 2 is airtightly fixed to the container 1, the light transmitting plate 2 is curved. The curved light transmitting plate 2 has a lens effect. For this reason, the laser light transmitted through the reflecting mirror 3 is no longer parallel light.

The homogenizer 5 is adjusted so that a desired image is formed on the surface of the substrate 6 when parallel light enters. Therefore, when the incident light is not parallel light, a desired image is not formed on the surface of the substrate 6. For this reason, the light intensity distribution in the y-axis direction may be distorted from a shape close to a trapezoid, resulting in a shape like a normal distribution.

Next, an excimer laser device according to an embodiment of the present invention will be described. FIG. 1A is a schematic sectional view of an excimer laser device according to an embodiment. Laser container 1
An electrode 10 for exciting the laser medium is arranged in the inside. Light transmitting plates 2 are hermetically attached to the wall of the laser vessel 1 at positions facing each other with the electrode 10 interposed therebetween. A pair of reflecting mirrors 3 is arranged outside the laser container 1 so as to sandwich the two light transmitting plates 2 to constitute an optical resonator.

The laser container 1 is filled with, for example, XeCl gas as a laser medium. Part of the light generated in the laser vessel 1 is confined in an optical resonator composed of a pair of reflecting mirrors 3, causing stimulated emission and causing laser oscillation. One of the reflecting mirrors 3 is a partially transmitting mirror, and a part of the laser light is transmitted through the reflecting mirror 3 and emitted to the outside of the optical resonator.

A blower 12 is arranged in the laser vessel 1. As shown in FIG. 1B, the blower 12 includes a center shaft 12A and a plurality of fins 12B.
The central axis 12A of the blower 12 is rotatably supported by a bearing 13 attached to the inner wall of the laser vessel 1. One end of the center axis of the blower 12 is led out of the laser container 1.

A motor 14 is arranged outside the laser vessel 1, and a rotation axis of the motor 14 and a center axis 12 A of the blower 12 are provided.
, A belt 15 is stretched. By driving the motor 14, the blower 12 rotates. Blower 12
Agitates the laser medium gas in the laser vessel 1.

The laser oscillation control means 17 applies a voltage to the electrode 10 at a predetermined repetition frequency. Laser pulse oscillation occurs in the optical resonator including the pair of reflecting mirrors 3 according to the repetition frequency of the applied voltage.

The pulse oscillation repetition frequency is input from the laser oscillation control means 17 to the motor rotation speed control means 16. The motor rotation speed control means 16 determines an appropriate motor rotation speed based on the input repetition frequency, and drives the motor 14 at that rotation speed. An appropriate motor speed will be described later.

A cooling gas supply pipe 4 is provided near the light transmitting plate 2.
Is arranged. The cooling gas supply pipe 4 is connected to the light transmitting plate 2.
A cooling gas such as N ₂ gas is blown to the outer surface of the light transmitting plate 2 to suppress the temperature rise of the light transmitting plate 2.

Inside the laser container 1, a wind direction changing plate 11 is attached. The wind direction changing plate 11 directs the flow of the laser medium gas formed by the blower 12 toward the light transmitting plate 2. Since the laser medium gas is blown onto the light transmitting plate 2, the laser medium gas acts as a cooling gas, and the temperature rise of the light transmitting plate 2 is suppressed.

When the repetition frequency of the pulse oscillation is increased, the temperature rise of the light transmitting plate 2 increases. As the repetition frequency increases, the motor rotation speed control means 16 increases the rotation speed of the motor 14. The flow of the laser medium gas in the laser vessel 1 is increased, and the cooling effect of the laser medium gas on the light transmitting plate 2 is enhanced. Thus, blower 1
By changing the rotation speed of the light transmission plate 2 according to the repetition frequency of the pulse oscillation, it is possible to obtain an appropriate cooling effect corresponding to the temperature rise of the light transmission plate 2. A preferred rotation speed of the blower 12 corresponding to the repetition frequency of the pulse oscillation is:
It is preferable to obtain the value by an evaluation experiment in which the repetition frequency is changed in advance.

In the above embodiment, the cooling gas supply pipe 4, the wind direction changing plate 11, and the motor speed control means 16 are provided for cooling the light transmitting plate 2. However, it is not always necessary to provide all of them at the same time. Absent. When a sufficient cooling effect can be obtained with only one type of cooling means, only one type of cooling means may be provided.

Next, a laser annealing apparatus using the excimer laser apparatus shown in FIG. 1 will be described.

FIG. 2 is a schematic plan view of the laser annealing apparatus. The housing 50 includes a processing chamber 51, a transport chamber 52, a loading chamber 53, a loading chamber 54, a homogenizer 42, a CCD camera 58, and a video monitor 5.
9 is attached.

The processing chamber 51 and the transfer chamber 52 are connected via a gate valve 55, and the transfer chamber 52 and the load chamber 53, and the transfer chamber 52 and the discharge chamber 54 are connected via gate valves 56 and 57, respectively. I have. Processing chamber 51, loading chamber 53
The vacuum pump 61,
62 and 63 are attached, and the inside of each chamber can be evacuated.

A transfer robot 64 is accommodated in the transfer chamber 52. The transfer robot 64 transfers the processing substrate between the processing chamber 51, the loading chamber 53, and the unloading chamber 54.

On the upper surface of the processing chamber 51, a window 60 for transmitting a laser beam is provided. The laser beam output from the excimer laser device 41 according to the embodiment described with reference to FIG. 1 passes through the attenuator 46 and enters the homogenizer 42. 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 has an elongated window 60 corresponding to the cross-sectional shape of the laser beam.
And irradiates the processing substrate in the processing chamber 51.

The processing substrate moves in parallel in a direction orthogonal to the long axis direction of the window 60. By moving the processing substrate at such a speed that a part of the irradiation area for one shot overlaps a part of the irradiation area in the previous shot, a large area on the surface of the processing substrate can be irradiated. Processing substrate surface is CC
The substrate surface being photographed by the D camera 58 and being processed can be observed on the video monitor 59.

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

FIG. 3 is a schematic diagram showing an optical system of the laser annealing apparatus shown in FIG. The laser beam output from the excimer laser device 41 passes through the attenuator 46, is reflected by the turn mirrors 47 and 48, and enters the homogenizer 42. The laser beam that has passed through the homogenizer 42 is reflected by the turn mirror 49, passes through the glass window 60, and is introduced into the processing chamber 51.

The homogenizer 42 and the turn mirror 49
The parallel movement along the optical axis of the incident laser light can be performed while maintaining the mutual relative positional relationship. Turn mirror 4
When the laser beam reflected at 9 is at position c in the figure, the processing substrate 51 in the processing chamber 51 is irradiated with laser light.

In the processing chamber 51, a power meter 7 is provided.
2 are arranged. When the laser beam is moved to the position d, the laser beam is irradiated on the power meter 72, and the intensity of the laser beam can be measured. Further, a power meter 73 is also provided outside the processing chamber 51, and by moving the laser beam to the position b, the intensity of the laser beam before being introduced into the processing chamber 51 can be measured.

Outside the processing chamber 51, a beam profiler 74 in which optical sensors are linearly arranged is arranged. By moving the laser beam to the position a and irradiating the laser beam to the beam profiler 74, it is possible to measure the intensity distribution of the laser beam having a linear cross-sectional shape in the long-axis direction in the cross section.

A power meter 70 is arranged between the attenuator 46 and the turn mirror 47, and a power meter 71 is arranged between the turn mirror 48 and the homogenizer 42. The power meters 70 and 71 can measure the intensity of the laser beam at that position.

As described in the embodiment of FIG. 1, the parallelism of the laser beam emitted from the excimer laser device 41 can be kept high by the above configuration. Since the laser beam having a high degree of parallelism is always incident on the homogenizer 42, it is possible to suppress the time variation of the light intensity distribution in the short axis direction of the laser beam irradiation area on the processing substrate. For this reason, it is possible to suppress variation in the work amount (product of energy and time) of the laser beam in the short axis direction of the irradiation region, and to perform more uniform irradiation. In particular, the effect is great when the repetition frequency of pulse oscillation is increased. Since the repetition frequency of the pulse oscillation can be increased, the moving speed of the processing substrate can be increased. Therefore, an improvement in throughput can be expected.

The output signals of the power meters 70, 71, 72, 73 and the beam profiler 74 are
Is input to Power meter 72 in processing chamber 51
If the intensity of the laser light detected by the above is within a normal range, the processing substrate is irradiated with the laser light as it is to polycrystallize amorphous silicon.

When the intensity of the laser beam detected by the power meter 72 is insufficient, the homogenizer 42 and the turn mirror 49 are moved to the position b, and the intensity of the laser beam is measured by the power meter 73. The intensity of the laser beam detected by the power meter 73 is compared with a predetermined normal intensity. If the intensity is normal, it is considered that the transmission characteristics of the glass window 60 have deteriorated.

Similarly, by comparing the intensity of the laser light detected by the power meters 71 and 70 with the normal value at each position, the deterioration state of each optical component can be known. Further, by analyzing the detection signal from the beam profiler 74, the normality of the intensity distribution in the major axis direction of the cross section of the laser beam can be confirmed.

Although FIG. 3 shows the case where a power meter is used to detect the intensity of the laser beam, a Joule meter may be used instead of the power meter. The power meter can measure the work of the laser light, and the joule meter can measure the energy of the laser light. Generally, a Joule meter can obtain higher measurement accuracy. Further, when the work of the laser beam becomes large, it is difficult to measure with a Joule meter, and it is preferable to use a power meter. It is preferable to appropriately select which one to use depending on the purpose of use and the allowable accuracy.

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.

[0046]

As described above, according to the present invention,
The temperature rise of the light transmitting plate for emitting laser light from the laser container can be suppressed, and the occurrence of distortion due to thermal expansion of the light transmitting plate can be prevented. For this reason, disturbance of the parallelism of the laser beam due to the distortion of the light transmitting plate can be prevented. Since laser light with a high degree of parallelism can always be obtained, instability of the light intensity distribution in the cross section of the laser light can be eliminated when the laser light is converged and diverged by the optical system.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an excimer laser device according to an embodiment of the present invention, and a partially broken perspective view of a blower.

FIG. 2 is a plan view of a laser annealing device using the excimer laser device of FIG.

FIG. 3 is a schematic view of an optical system of the laser annealing apparatus shown in FIG.

FIGS. 4A and 4D are schematic diagrams of a laser annealing device, and FIGS. 4B and 4C are graphs showing a temperature change of a light transmitting plate of the laser annealing device. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Light transmission plate 3 Reflecting mirror 4 Cooling gas supply pipe 5 Homogenizer 6 Substrate 10 Electrode 11 Wind direction change plate 12 Blower 13 Bearing 14 Motor 15 Belt 16 Blower rotation speed control means 17 Laser oscillation control means 41 Excimer laser device 42 Homogenizer 46 Attenuators 47, 48, 49 Turn mirror 50 Housing 51 Processing chamber 52 Transport chamber 53, 54 Loading / unloading chamber 55-57 Gate valve 58 CCD camera 59 Video monitor 60 Window 61, 62, 63 Vacuum pump 64 Transport robot 65 Control device 70 , 71, 72, 73 Power meter

Claims (5)

[Claims] A container for accommodating a laser medium; an excitation unit disposed in the container to excite the laser medium; and an optical resonator for resonating light generated in the container. An excimer that is hermetically attached to a wall of the container, transmits a stimulated emission light generated inside the container, and emits the light outside the container, and an air cooling unit for cooling the light transmission plate with gas. Laser device. 2. The excimer laser device according to claim 1, wherein said air cooling means blows a cooling gas onto said light transmitting plate from outside said container. 3. A stirring means disposed in the container, for stirring the laser medium to forcibly form a flow of the laser medium in the container, and a flow of the laser medium formed by the stirring means. The excimer laser device according to claim 1, further comprising: a wind direction changing unit for turning a direction toward the light transmitting plate. 4. A container for accommodating a laser medium, an excitation means disposed in the container for exciting the laser medium intermittently at a certain period, and for resonating light generated in the container. An optical resonator, airtightly attached to a wall of the container, transmitting a stimulated emission light generated in the container, and emitting the light to the outside of the container; and An excimer laser apparatus comprising: a stirring means capable of stirring a laser medium in a container and changing a stirring capacity in accordance with the certain cycle. 5. The excimer laser device according to claim 4, further comprising wind direction changing means for directing the flow of the laser medium formed by said stirring means toward said light transmitting plate.