JP3545213B2 - Laser annealing equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser annealing apparatus that irradiates a thin film on a substrate with a laser beam in a manufacturing process of a thin film transistor (TFT) for a liquid crystal display device and gives energy to the substrate.
[0002]
[Prior art]
As a semiconductor device having a TFT on an insulating substrate such as glass, an active matrix type liquid crystal display device and an image sensor using the TFT for driving pixels are known. In general, a thin film Si semiconductor is used for the TFT used in these devices.
[0003]
Thin-film Si semiconductors are broadly classified into those made of an amorphous Si semiconductor and those made of a crystalline Si semiconductor. Amorphous Si semiconductors are most commonly used because they have a low manufacturing temperature, can be manufactured relatively easily by the CVD method, and have high mass productivity. However, an amorphous Si semiconductor has a drawback that current driving capability is inferior to a crystalline Si semiconductor. Therefore, in order to obtain high-speed characteristics in the future, it is strongly required to establish a method for manufacturing a TFT made of a crystalline Si semiconductor.
[0004]
Known crystalline Si semiconductors include single-crystal Si, polycrystalline Si, microcrystalline Si, amorphous Si containing a crystalline component, or amorphous Si having an intermediate state between crystalline and amorphous. Have been. These crystalline TFTs have higher mobility than amorphous TFTs. Therefore, the driving force is improved, the pixel and the driver circuit can be integrated, and miniaturization can be performed, and a high aperture ratio and a high density can be realized.
[0005]
As a specific method of forming a Si semiconductor thin film having crystallinity, there are a solid phase growth method (SPC method) in which heating is performed in a thermal diffusion furnace, and a laser annealing method in which laser light is applied to melt and solidify to crystallize. And In the SPC method, although amorphous Si can be uniformly crystallized into polycrystalline Si, an inexpensive glass substrate with low heat resistance cannot be used because the heat treatment is performed at a high temperature of around 1000 ° C. Therefore, a laser annealing method using an excimer laser having high light absorption of amorphous Si is regarded as important as a method capable of performing low-temperature processing with little damage to an insulating substrate.
[0006]
As shown in FIG. 4, a conventional laser annealing apparatus irradiates an amorphous Si semiconductor thin film on an insulating substrate 5 of a process chamber 3 with an excimer laser beam through an optical system 2 from a laser oscillator 1 to obtain an insulating property. The substrate 5 is polycrystalline by applying energy.
[0007]
The process chamber 3 is basically configured in a sealed structure, and has a built-in stage 8 on which the insulating substrate 5 is mounted. The insulating substrate 5 is subjected to laser annealing after an amorphous Si semiconductor thin film is deposited on the surface thereof by a plasma CVD method, heated by a heating mechanism of the stage 8 and dehydrogenated. Further, a stage scanning mechanism 9 is connected to the stage 8, and the insulating substrate 5 on the stage 8 is moved and positioned in the XY directions by the stage scanning mechanism 9. Further, a window 4 is fitted into the mounting port 10 on the upper part of the process chamber 3.
[0008]
In the above configuration, if the stage 8 on which the insulating substrate 5 is mounted is moved by a fixed amount of movement, and the amorphous Si semiconductor thin film of the insulating substrate 5 is irradiated with excimer laser light via the window 4 to be melted and solidified. In addition, polycrystalline Si having improved crystallinity and different crystallinity from the surroundings can be formed.
[0009]
Related prior art documents of this type include JP-A-9-17744 and JP-A-9-260303.
[0010]
[Problems to be solved by the invention]
The conventional laser annealing apparatus is configured as described above, and if the excimer laser beam is continuously irradiated, Si evaporated or scattered from the surface of the amorphous Si semiconductor thin film adheres to the window 4, so that the adhered Si is removed. It becomes dirty and absorbs the excimer laser light, resulting in a decrease in transmittance. As a method of solving this problem, there is a method of removing the window 4 from the process chamber 3 and performing cleaning. However, this cleaning method has the drawbacks that it is time-consuming and expensive, and that the maintainability is very poor.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a laser annealing apparatus capable of preventing flying objects and the like from adhering to a window and reducing the time and cost required for cleaning. .
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a process chamber for processing a substrate, a stage for mounting a substrate installed in the process chamber, and a window for guiding a laser beam to a substrate in the process chamber. Irradiating the laser beam to the thin film of the substrate to impart energy to the substrate,
The window is formed in a double structure from a process window located outside the process chamber and a replaceable pollution control window located inside the process chamber, and arranged in a direction toward the inside and outside of the process chamber, The window is substantially the same size as the substrate, and the contamination prevention window is detachably supported by elevating support means for elevating between the upper part of the process chamber and the stage.
[0014]
Here, although there are various types and sizes of substrates in the claims, there is no particular limitation as long as the substrates can be subjected to laser annealing. The thin film includes at least a Si film and an ITO film. The laser annealing apparatus includes a pulse laser annealing apparatus using a ruby, YAG laser, or excimer laser, and a CW (continuos wave) laser annealing apparatus using Ar, Kr, CO ₂ , and an excimer laser. , Any one is fine. Further, the lifting support means can be configured by appropriately combining various types of actuators such as cylinders, electromagnetic solenoids, or motors, and a chuck mechanism, a cam mechanism, a screw mechanism, a gear mechanism, or a link mechanism. In addition, the contamination prevention window is preferably the same size as the size of a substrate to be processed normally, or a size recognized to be substantially the same.
[0015]
According to the present invention, during the annealing process, the material evaporates or scatters from the thin film of the substrate, but this material adheres to the contamination prevention window inside the process chamber and adheres to the process window outside the process chamber. Be regulated. If the pollution control window becomes dirty, it can be replaced with a new pollution control window. Therefore, it is possible to prevent the transmittance of the outer window from decreasing.
[0016]
Also, when replacing a dirty contamination prevention window, the lifting / lowering support means is lowered to move the contamination prevention window from the lifting / lowering support means to the stage, and if this stage is carried out of the process chamber, the contamination prevention window is taken out and a new window is taken out. It can be replaced with a new pollution prevention window. Further, since the contamination prevention window is almost the same size as the substrate, the contamination prevention window can be mounted on the stage, and the stage for mounting the substrate can be effectively used for the maintenance work of the contamination prevention window.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.
As shown in FIG. 1, the laser annealing apparatus according to the present embodiment includes a process chamber 3 in which an excimer laser beam is irradiated from a laser oscillator 1 via an optical system (homogenizer) 2 and a processing substrate in the process chamber 3. A window 4 for guiding excimer laser light to a certain insulating substrate 5 is provided, and this window 4 has a double structure including a process window 12 and a pollution prevention window 13.
[0018]
The irradiation intensity of the excimer laser light (see the arrow in FIG. 1) of the laser oscillator 1 is set to about 200 to 400 mJ / cm ² , the focus is focused by the optical system 2, and the window 4 is placed in the process chamber 3. Incident through. The optical system 2 is configured to be movable in the X and Y directions, and functions to change the size of the excimer laser light and improve the in-plane uniformity.
[0019]
The process chamber 3 is basically formed in a closed structure using a metal that does not transmit laser light, and functions so that the insulating substrate 5 can be processed while being isolated from the atmosphere. An introduction system 6 for an inert gas (such as N ₂ ) and an exhaust system 7 for the inert gas are provided in the process chamber 3, respectively. The pressure, atmosphere, etc. of 3 are adjusted according to the processing steps. The process chamber 3 has a built-in stainless steel stage 8 on which the insulating substrate 5 is mounted. The stage 8 is provided with a heating mechanism (not shown) and a stage scanning mechanism 9 connected thereto. The insulating substrate 5 on the stage 8 is moved and positioned in the XY directions by the scanning mechanism 9.
[0020]
At the center of the upper part of the process chamber 3, a mounting opening 10 for the window 4 is formed, and a pair of support hooks 11 for the pollution prevention window 13 are mounted on the periphery of the mounting opening 10 so as to be able to move up and down. Each support hook 11 is formed in a substantially L-shape, and moves up and down between the inside of the process chamber 3 and the stage 8 (see FIG. 2).
[0021]
The process window 12 is fitted in the mounting opening 10 of the process chamber 3. Since the inside of the process chamber 3 is evacuated when the inert gas is replaced, the process window 12 is made thick using quartz or the like to withstand the vacuum. Furthermore, the pollution prevention window 13 is configured to be larger than the process window 12 and is configured to be thinner to the same size as the insulating substrate 5. It is located directly below with a gap. The other parts are the same as in the conventional example, and the description is omitted.
[0022]
In the above configuration, in order to perform laser annealing on the insulating substrate 5, first, the insulating substrate 5 is set on the stage 8, the stage 8 is loaded into the process chamber 3, and an inert gas is introduced into the process chamber 3. To maintain the atmosphere. Next, while heating the stage 8, the stage 8 on which the insulating substrate 5 is mounted and the optical system 2 are respectively moved in the XY directions by a fixed amount of movement, and an excimer laser is applied to the amorphous Si semiconductor thin film of the insulating substrate 5. If the light is locally irradiated and melted and solidified, the crystallinity can be improved and polycrystalline Si having a different crystallinity from the surroundings can be formed.
[0023]
During the laser annealing treatment, part of the Si evaporates or scatters from the surface of the amorphous Si semiconductor thin film, but part of the Si adheres to the contamination prevention window 13 and It does not adhere to the process window 12 located above.
[0024]
After that, the insulating substrate 5 is taken out of the process chamber 3, and the insulating substrate 5 goes through a predetermined process to manufacture a thin film transistor. When the dirty pollution prevention window 13 is to be replaced, the pair of support hooks 11 is lowered to place the pollution prevention window 13 on the stage 8 and the stage 8 is carried out of the process chamber 3 to open the process chamber 3. The pollution prevention window 13 can be taken out without replacement and replaced with a new pollution prevention window 13 (see FIGS. 2 and 3).
[0025]
According to the above configuration, the evaporated or scattered Si adheres to the contamination prevention window 13, so that the process window 12 can be kept clean and the transmittance thereof can be extremely effectively prevented from lowering. The semiconductor thin film can be reliably irradiated with excimer laser light having a predetermined energy. Further, since the pollution prevention window 13 is of the same size so that it can be handled in the same manner as the insulating substrate 5, it is possible to easily replace the inexpensive pollution prevention window 13 using the stage 8. Therefore, speeding up, smoothing and facilitation of the cleaning operation can be expected. Further, since the replacement of the contamination prevention window 13 is cheaper than the polishing and regeneration of the process window 12, the cost can be reduced.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent flying objects and the like from adhering to the window when irradiating laser light, and to reduce the time and cost required for cleaning the window. Further, since the pollution prevention window is almost the same size as the substrate, the pollution prevention window can be mounted on the stage, and the substrate mounting stage can be effectively used for the maintenance work of the pollution prevention window.
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view showing an embodiment of a laser annealing apparatus according to the present invention.
FIG. 2 is an explanatory sectional view showing an operation of replacing a contamination prevention window in the embodiment of the laser annealing apparatus according to the present invention.
FIG. 3 is an explanatory cross-sectional view showing an operation of unloading a contamination prevention window in the embodiment of the laser annealing apparatus according to the present invention.
FIG. 4 is an explanatory sectional view showing an embodiment of a conventional laser annealing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Optical system 3 Process chamber 4 Window 5 Insulating substrate (substrate)
8 stage 11 support hook (elevation support means)
12 Process window 13 Pollution prevention window

Claims (1)

A process chamber for processing a substrate, a stage for mounting a substrate installed in the process chamber, and a window for guiding a laser beam to a substrate in the process chamber, and irradiating the thin film on the substrate with the laser beam. A laser annealing apparatus for applying energy to the substrate by
The window is formed in a double structure from a process window located outside the process chamber and a replaceable pollution control window located inside the process chamber, and arranged in a direction toward the inside and outside of the process chamber, Laser annealing, wherein the window has substantially the same size as the substrate, and the contamination prevention window is removably supported by elevating support means for elevating between the upper part of the process chamber and the stage. apparatus.

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