JPH10308548A - Device and method for irradiating pulse laser light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform irradiation, wherein the intensity of a laser beam is stabilized, and to suppress the useless laser oscillation, which does not contribute to the formation of a polycrystalline silicon thin film at the same time, by controlling the initial pulse part of a pulse laser, which is oscillated again for the n-th irradiation so as to shield the puls part. SOLUTION: The oscillating period of a laser and the moving period of a stage 18 of a glass substrate 15 are controlled, and the shielding period of an optical path by a light shielding device 13 is controlled. Thus, the laser irradiating period to the substrate 15 is determined. That is to say, when the n-th laser-oscillation starting time is made to be the reference, the stage 18 is stopped at this time, and the optical path is shielded. When the unstable period of the intrinsic oscillation of the laser light source has passed, the optical- path shielding state is released, and the laser irradiation to the substrate 15 is started. After the intended number of purses are irradiated on the substrate 15, the laser oscillation is stopped, and the stage 18 is moved. At the same time of the stop of the stage 18, the optical path is shielded again, and the oscillation starting of the laser in the sequence of n+1 is waited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for irradiating a pulsed laser beam. More specifically, the present invention relates to a pulsed laser beam irradiation apparatus and method for manufacturing a polycrystalline silicon thin film used for various semiconductor products.

[0002]

2. Description of the Related Art FIG. 8A is a control timing chart of a conventional example, FIG. 8B is a second control timing chart of a conventional example, and FIG. 8C is a third control timing chart of a conventional example. is there.

A thin film transistor (TF) is formed on a glass substrate.
Representative techniques for forming T) include hydrogenated amorphous semiconductor TFT technology and polycrystalline silicon TFT technology. The former has a maximum fabrication process temperature of about 300 ° C. and realizes a carrier mobility of about 1 cm ² / (Volt · sec). The latter uses, for example, a quartz substrate and a high-temperature process similar to an LSI at about 1000 ° C. to provide a carrier mobility of 30 to 100 cm ^2.
/ (Volt · sec) performance can be obtained. The realization of such a high carrier mobility can be achieved, for example, by using the T
When the FT is applied to a liquid crystal display, there is an advantage in terms of low cost and miniaturization that a pixel TFT for driving each pixel and a peripheral drive circuit portion can be simultaneously formed on the same glass substrate. However, in the case of using the above-described high-temperature process in the polycrystalline silicon TFT technology, an inexpensive low softening point glass that can be used in the former process cannot be used. Therefore, it is necessary to reduce the temperature of the polycrystalline silicon TFT process, and a technology for forming a polycrystalline silicon film at a low temperature using a laser crystallization technology has been researched and developed.

As an example, a technique of crystallizing an amorphous silicon thin film on an amorphous substrate using a short wavelength pulsed laser beam and applying the crystallized thin film to a thin film transistor is disclosed in Japanese Patent Publication No. Hei 7-118443.
(Japanese Unexamined Patent Publication No. 60-245142, Japanese Patent Application No. 59-10018)
0). According to this method, since amorphous silicon can be crystallized without raising the temperature of the entire substrate, it is possible to fabricate inexpensive semiconductor devices and semiconductor integrated circuits on a large-area substrate such as a liquid crystal display and glass. There are advantages. However, as described in the above publication, irradiation intensity of about 50 to 500 mJ / cm ² is required for crystallization of an amorphous silicon thin film by a short wavelength laser. On the other hand, the light emission output of currently generally available pulse laser devices is about 1 J / pulse at maximum, and the area that can be irradiated at one time even by simple conversion is ^{2 to 20} cm ^2.
Only about. Therefore, for example, the substrate size 47
In order to laser crystallize the entire surface of a × 37 cm substrate, laser irradiation is required at least at 87 to 870 points.

In order to uniformly form a thin-film semiconductor element group on a large-area substrate by the above-mentioned method, Japanese Patent Application Laid-Open No.
No. 1167 (Japanese Patent Application No. 3-315863), an element group is divided into smaller elements than the laser beam size, or an element group smaller than the beam size is formed, and several pulses are irradiated by step-and-repeat. It is known that a method of repeating the movement of the irradiation area and the irradiation container + the irradiation of several pulses + the movement of the irradiation area +... Is effective. As shown in FIG. 8B, this is a method in which laser oscillation and movement of a stage (and thus a substrate) or a beam are performed alternately. However, a pulse laser device with a variation in oscillation intensity of about ± 5% (at the time of continuous oscillation) which can be obtained at present also by this method is used.
When irradiation of about 20 pulses / location is repeated, there is a problem that oscillation intensity variation exceeds ± 5%, and the resulting polycrystalline silicon thin film and polycrystalline silicon thin film transistor characteristics are not sufficiently uniform. In particular, generation of intense light due to instability of discharge at the beginning of laser oscillation, which is called spiking, is a problem of non-uniformity.
As a method of avoiding such spiking, FIG.
As shown in FIG. 8A, a method of avoiding laser oscillation by starting before the start of irradiation of the element formation region is known. However, as shown in FIG. There is a problem that it cannot be applied when the movement is intermittently repeated.

In order to avoid these problems, Japanese Patent Application Laid-Open No. 5-90191 (Japanese Patent Application No. 3-251984) discloses that a pulse laser light source is continuously oscillated, and a light shielding device is used to irradiate a substrate during a moving period of a stage. Methods have been proposed to prevent this. That is, as shown in FIG. 8C, the laser is continuously oscillated at a certain frequency, and the movement of the stage to the desired irradiation position and the shielding of the optical path are synchronized, so that the laser light having a stable pulse-to-pulse intensity can be obtained. Irradiation to the irradiation position was enabled. However, although this method enables stable irradiation of the substrate with the laser beam, the productivity of the polycrystalline silicon thin film and the production efficiency of the polycrystalline silicon thin film with respect to the power required for laser oscillation and the like are reduced.
There has been a problem that the production cost is increased.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable stable irradiation of laser beam intensity and suppress unnecessary laser oscillation that does not contribute to the formation of a polycrystalline silicon thin film. A pulsed laser beam irradiation device that can improve the productivity of the polycrystalline silicon thin film with respect to the life of the light source and the excitation gas and the production efficiency of the polycrystalline silicon thin film with respect to the power required for laser oscillation and the like, and prevent an increase in production cost. An object of the present invention is to provide a pulsed laser beam irradiation method for manufacturing a semiconductor such as a polycrystalline silicon thin film.

[0008]

A first pulse laser light irradiation apparatus according to the present invention comprises at least one pulse laser light source and a laser light oscillated from the pulse laser light source which is located within a single irradiation range of the laser light. In a pulse laser light irradiation device having a laser beam or a substrate moving scanning mechanism for irradiating a large substrate, and further having at least one laser light shielding device between the pulse laser light source and the irradiation position on the substrate A period during which the pulse laser stops oscillating during a transition period from the (n-1) th irradiation range to the nth irradiation range on the substrate, and the initial period of the pulse laser re-oscillated for the nth irradiation. The pulse unit is controlled so as to be shielded by the shielding device.

A second pulse laser beam irradiation apparatus according to the present invention comprises at least one pulse laser beam source and a laser beam for irradiating a laser beam oscillated from the pulse laser beam source onto a substrate larger than one laser beam irradiation range. In a pulsed laser light irradiation device having a light or substrate moving scanning mechanism, a laser beam emitted from a pulsed laser light source has distribution means for decomposing the laser light into a plurality of optical paths according to a predetermined time, and is distributed. A moving mechanism is provided on the extension of the optical path, and the distributing means sequentially supplies the laser light to the first optical path and the second optical path, and an irradiation area on the substrate on the extension of each optical path is an arbitrary laser. After receiving the irradiation light, it moves to a desired position before the next irradiation light is supplied.

In the pulse laser beam irradiation apparatus, the wavelength of the laser beam oscillated from the pulse laser light source is 400 nm.
It is preferable that the following is satisfied, and it is also preferable that the pulse laser light source is an excimer laser.

According to the pulse laser beam irradiation method of the present invention, in the pulse laser beam irradiation method for irradiating the semiconductor material with the pulse laser beam, one irradiation range of the pulse laser beam is smaller than the size of the semiconductor material to be irradiated. The laser irradiation on the entire surface of the semiconductor material or on an arbitrary region, the pulse irradiation and the movement of the irradiation region are sequentially repeated, and the pulse laser light source repeats the oscillation period and the stop period at a constant cycle in accordance with the movement, and The laser light emitted during a part of the n-th oscillation period is irradiated on the n-th irradiation region.

The semiconductor material is preferably silicon or a laminate of silicon and a dielectric material that transmits laser light.

By these means, the apparatus according to the first aspect of the invention can prevent the substrate from being irradiated with a laser pulse having an unstable intensity at the initial stage of oscillation, which is generated when the oscillation period is intermittently repeated. Become. In addition, laser oscillation is stopped during a part of the beam or substrate movement period, compared to the case where continuous oscillation is performed, so that useless oscillation can be suppressed and the life of the laser light source or the excitation gas can be extended. become.

The apparatus according to the second aspect of the present invention makes it possible to use all the laser beams having a stable intensity for producing polycrystalline silicon or modifying various semiconductor materials.

The wavelength of the laser to be oscillated is 400n.
When the pulse laser light source is an excimer laser, the absorption coefficient for silicon or other semiconductor materials becomes large, and the material can be efficiently modified. The effect of preventing an increase in production and operation costs caused by the above is enhanced.

Further, the method of the present invention makes it possible to minimize an increase in reforming cost due to irradiation.
Therefore, for example, it is possible to reduce the production cost of a liquid crystal display or the like that requires a large area element group as a display device.

[0017]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of a pulse laser beam irradiation apparatus according to the present invention, and FIG.
One embodiment of a control timing chart from laser oscillation to laser irradiation to the substrate, FIG. 3 is a second embodiment of the same control timing chart, and FIG. 4 is a light shielding corresponding to the control timing chart of FIG. FIG. 4 is a schematic cross-sectional view in a direction perpendicular to the light traveling of the device.

The pulse laser beam irradiation apparatus shown in FIG. 1 has a pulse laser light source 11, a plurality of (three in the figure) mirrors 1
2. It comprises a beam homogenizer 14 and has a light shielding device 13 on the laser beam path. The laser oscillation period and the moving period of the stage 18 of the glass substrate 15 are controlled in a relationship as shown in FIG. 2, and the light shielding period of the optical path by the light shielding device 13 is controlled as shown in FIG. As shown in FIG. 2, the laser irradiation period on the substrate 15 is determined. That is, based on the n-th laser oscillation start timing,
At this time, the stage 18 is stopped, and the optical path is blocked. After the unstable period of the oscillation unique to the laser light source has elapsed, the optical path blocking state is released and the laser irradiation to the substrate is started. After irradiating the substrate with a desired number of pulses, laser oscillation is stopped and the stage is moved. At the same time as the stage is stopped, the optical path is blocked again, and the oscillation of the (n + 1) th laser is started.

At this time, the irradiation position on the substrate can be changed by moving the optical element instead of moving the stage, that is, the substrate, and the x-axis direction can be changed on the stage and the other y-axis direction can be changed. It is also possible to adopt a method of moving the optical element. The movement of the stage or the optical element may include an alignment operation for correctly stopping at a desired irradiation position.

In FIG. 2, after irradiating the substrate with a desired number of pulses, the laser oscillation is stopped, the stage is moved, and at the same time as the stage is stopped, the optical path is again blocked and n +
While waiting for the first laser oscillation to start, it is also possible to block the optical path and start laser oscillation in the second half of the stage movement period as shown in FIG. Also, in FIG. 1, the laser light shielding device 13 is located in the middle of the optical path 17, but it is desirable to install it as close as possible to the light source 11 in order to extend the life of optical elements such as mirrors and lenses.

An embodiment of the light shielding device corresponding to the control chart shown in FIG. 3 will be described with reference to FIG. The shielding device 13 is rotated at a constant speed about a center thereof by a driving motor or the like. The beam optical path 22 is blocked by a shielding section 23, and can transmit when the transmitting section 24 approaches the beam optical path. The material can be selected according to the wavelength of a light source such as an ultraviolet pulse laser, a YAG laser, or the like, but a metal painted black that can withstand laser heating or the like is desirable. In the present embodiment, a black paint is applied to an alloy containing aluminum as a main component. The transmission part 24 was hollow. Further, the reference mark 21 can be formed by a hole like the transmission portion 24, and can be synchronized with the laser oscillation start timing by using a transmission type optical sensor. The light shielding device 13 that rotates at a constant speed unblocks the optical path after T ₁ time from the start of laser oscillation and transmits light. Then T ₂ hours,
Transmits light, after enabling the irradiation of the substrate T ₃ hours waiting, to shield the optical path. Where the shielding of the optical path passed T ₄ hours, the reference mark 21 reaches the transmission optical sensor position, the laser starts to oscillate again. At this time the stage 18 is stopped between ₁ hour T, it starts operating between of T ₃ hours.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a schematic configuration diagram of a pulsed laser beam irradiation apparatus provided with a beam distribution means according to the second embodiment, and FIG. 6 is a diagram illustrating the steps from laser oscillation to laser irradiation on a substrate in FIG. Example of control timing chart of FIG.
(A) is a schematic top view of one embodiment of FIG. 5, (B) is
It is an optical path side view of (A).

The pulse laser beam irradiation apparatus shown in FIG. 5 includes a pulse laser light source 31, a plurality of mirrors 32 ₁ , 32 ₂ , 3
2a, 32b, a beam homogenizer 34, and a beam distributing means 39 on a laser beam path 37. The beam distributing means 39 performs the laser supply to the glass substrate 35b by moving the mirror 32b up and down, so that the supply to the glass substrate 15a can be alternately selected.
According to FIG. 6, the laser is supplied to the optical path 37a during the oscillation start period of the laser.
Avoid irradiating the desired substrate. After the oscillation intensity becomes stable,
The beam is changed to the optical path 37b using the beam distribution means. At this time, a desired area of the glass substrate 35b disposed on the stage 38b and the silicon thin film 36b deposited on the surface is irradiated with the laser light. At this time, the stage 38a moves to a region of the glass substrate 35a and the silicon thin film 36a deposited on the surface to be irradiated with the laser. After irradiating the glass substrate 35b with a desired number of pulses, the beam is changed to the optical path 37a using the beam distribution means 39. By repeating this operation, it is possible to alternately irradiate the glass substrate 15a and the glass substrate 15b with a beam having a stable intensity. Of course, it is necessary for the beam distribution means 39 to operate within one stop time in the oscillation cycle of the pulse laser.

This embodiment will be described with reference to a schematic top view of FIG. FIG. 7A shows an amorphous silicon (a-Si) using an excimerizer as a pulse laser.
1 shows an example of a pulsed laser beam irradiation device for crystallizing a thin film. This apparatus includes vacuum loadable / unloadable substrate load / unload chambers 47a and 47b, a substrate transfer chamber 49, and substrate heating chambers 42a and 42b and laser irradiation chambers 44a and 44b.

The movement of the substrate is shown using the mechanism on the left side of the figure. The glass substrate 35a on which the silicon thin film 36a is deposited is put into the load / unload chamber 47a,
9 and transferred to the substrate heating chamber 42a by a robot. Here, the glass substrate 35a is placed in the laser irradiation chamber 44a after being heated to about 200 ° C. to 400 ° C. If there is no need to heat the substrate 35a, the substrate heating chamber 42a
No need to go through. If a mechanism for forming amorphous silicon (a-Si) is added to the substrate heating chamber 42a, the glass substrate 35a is loaded, and then the a-S
The formation of the i-thin film 36a and the laser crystallization in the laser irradiation chamber 44a can be performed continuously without exposing to the atmosphere.

The same function is provided on the right side of FIG. In the vacuum apparatus described above, the supply path 41 of the excimer laser, the rotary beam distributor 46, and the beam introduction window 45 are provided.
By arranging a and 45b, a silicon crystallization apparatus using an excimer laser is configured. The laser beam supplied from the excimer laser supply path 41 can be periodically distributed to the optical path 43 and the optical path 43b by a rotary beam distribution device 46 (that is, by rotating a mirror at a certain period). The beam distributed to each optical path is reflected by a mirror 32a or 32b and a beam introduction window 4.
Through 5a or 45b, it reaches glass substrates 36a and 36b (on which a silicon thin film is deposited) arranged in a vacuum vessel.

By controlling the silicon crystallization apparatus using the excimer laser configured as described above according to the timing chart shown in FIG. 6, silicon crystallization with high throughput can be realized. According to the present method, it is desirable that the beam distribution means 39 operate within one stop time in the oscillation cycle of the pulse laser. However, due to the configuration of the optical path, unless the operation of the distribution means 39 is completed, the beam distribution to the reflecting mirror is not performed. Since no beam is supplied, it is possible to prevent irradiation errors due to malfunctions.

[0030]

FIG. 6 shows an embodiment in which the laser off operation and the stage operation start timing and the laser oscillation start timing and the stage stop timing are matched with each other by using the configuration shown in FIG. Examples are shown below in comparison with the prior art.

As prerequisites, the number of irradiation areas is 1500 (= 50 × 30) places / substrate Laser oscillation frequency 10 Hz The number of irradiation pulses is 10 pulses / place The initial unstable pulse during intermittent operation 5 pulse Stage moving time 1 second / 1 moving distance I do.

[0032]

As described above, the present invention enables stable irradiation of the laser beam intensity by controlling the oscillation shielding or the like of the pulsed laser beam or controlling the distribution of the optical path. At the same time, unnecessary laser oscillation that does not contribute to polycrystalline silicon thin film formation is reduced,
The productivity of the polycrystalline silicon thin film with respect to the life of the laser light source and the excitation gas, and the production efficiency of the polycrystalline silicon thin film with respect to the power required for laser oscillation, etc., are increased. As a result, it is possible to prevent an increase in reforming cost due to laser irradiation There is an effect that a simple pulsed laser beam irradiation device and a pulsed laser beam irradiation method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a pulse laser beam irradiation device according to the present invention.

FIG. 2 is an embodiment of a control timing chart from laser oscillation to laser irradiation on a substrate in FIG. 1;

FIG. 3 is a second embodiment of the control timing chart.

FIG. 4 is a schematic cross-sectional view in a direction perpendicular to light traveling of a light shielding device corresponding to the control timing chart of FIG. 3;

FIG. 5 is a schematic configuration diagram of a pulsed laser beam irradiation device including a beam distribution unit according to the second embodiment.

FIG. 6 is an embodiment of a control timing chart from laser oscillation to laser irradiation on a substrate in FIG. 5;

FIG. 7A is a schematic top view of one embodiment of FIG. 5,
(B) is an optical path side view of (A).

8A is a control timing chart of a conventional example, FIG. 8B is a second control timing chart of a conventional example, and FIG. 8C is a third control timing chart of a conventional example.

[Explanation of symbols]

11, 31 pulsed laser light source 12, 32 ₁ , 32 ₂ , 32a, 32b mirror 13 light shielding device 14, 34 beam homogenizer 15, 35a, 35b glass substrate 16, 36a, 36b silicon thin film 17, 37a, 37b, 43a, 43b Light path 18, 38a, 38b Stage 21 Reference mark 22 Beam light path 23 Shielding part 24 Transmission part 39 Beam distribution means 41 Beam supply path 42a, 42b Heating chamber / a-Si forming chamber 44a, 44b Irradiation chamber 45a, 45b Beam introduction window 46 Rotary beam distribution device 47a, 47b Load / unload chamber 49 Substrate transfer chamber

Claims (6)

[Claims] 1. At least one pulsed laser light source;
The laser light emitted from the pulsed laser light source to irradiate a substrate larger than the single irradiation range of the laser light or the laser beam or the substrate moving scanning mechanism, further from the pulsed laser light source What is claimed is: 1. A pulsed laser light irradiation device having at least one laser light shielding device up to an irradiation position on a substrate, comprising: a pulsed laser during a transition period from the (n-1) th irradiation range to the nth irradiation range on the substrate. A pulse laser beam irradiation controlled so that an initial pulse portion of the pulse laser re-oscillated for the n-th irradiation is shielded by the shielding device. apparatus. 2. At least one pulsed laser light source;
A pulse laser light irradiation device including: a laser beam for irradiating a laser beam oscillated from the pulse laser light source onto a substrate larger than one irradiation range of the laser beam; A distributing unit for decomposing the laser light oscillated from the light source into a plurality of optical paths according to a predetermined time; and having the moving mechanism on an extension of the distributed optical path; Are sequentially supplied to the first optical path and the second optical path, and the irradiation area on the substrate that is on the extension of the respective optical paths, after receiving any laser irradiation light, until the next irradiation light is supplied. A pulse laser beam irradiation device, which moves to a desired position in between. 3. The pulse laser beam irradiation device according to claim 1, wherein the wavelength of the laser beam oscillated from the pulse laser light source is 400 nm or less. 4. The pulse laser beam irradiation device according to claim 1, wherein the pulse laser light source is an excimer laser. 5. A pulse laser beam irradiation method for irradiating a semiconductor material with a pulse laser beam, wherein one irradiation range of the pulse laser beam is smaller than the size of the semiconductor material to be irradiated, and The laser irradiation to the region is performed by sequentially repeating irradiation of several pulses and movement of the irradiation region, and the pulsed laser light source repeats an oscillation period and a stop period at a constant cycle in accordance with the movement, and performs the n-th oscillation. A pulsed laser beam irradiation method, wherein the laser beam oscillated during a part of the period is irradiated on the n-th irradiation region. 6. The pulse laser beam irradiation method according to claim 5, wherein the semiconductor material is silicon or a laminate of silicon and a dielectric material that transmits the laser beam.