JPH1126393A - Laser annealer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable excellent laser annealing by improving a laser annealer. SOLUTION: A gas-feeding valve 1 and a ventilating pipe 3 connected with a gas feeding pump 2 are introduced into a chamber 14 in which laser annealing is performed. A jetting port 4 of the pipe 3 is set in the vicinity of a transparent window 20 of the chamber 14. Ablation generated from a substrate 19 to be treated at the time of laser annealing is blown out by the air blow from the jetting port 4 and prevented from attaching on the transparent window 20. Thereby the transparent window 20 becoming dull and trnasmittance being deteriorated are eliminated. The laser energy loss at the transparent window 20 is restrained, and excellent laser annealing is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser annealing apparatus for forming a good semiconductor film on a substrate.

[0002]

2. Description of the Related Art By using a technique for forming a semiconductor film on a substrate, the degree of integration of an integrated circuit is increased to increase the capacity, or a matrix display is performed on one of a pair of substrates sandwiching a liquid crystal. Thin-film field-effect transistor (TFT: Thin Film Transisto)
r) to enable the display of high-definition moving images with an active matrix liquid crystal display (LCD: Liquid Cry)
stal Display) is being developed.

In particular, MOSF fabricated on a silicon substrate
If a TFT capable of exhibiting characteristics close to ET can be formed on an insulating substrate, not only the switching elements of the LCD matrix display unit but also a CMOS around the LCD and a desired drive signal voltage can be applied to the matrix display unit. It is also possible to integrally form a peripheral driving circuit for supplying, so that mass production of a so-called driver built-in LCD can be performed.

[0004] The LCD with a built-in driver eliminates the need for externally attaching a driver element to the liquid crystal panel.
The number of processes can be reduced and the frame can be narrowed. In particular, narrowing the frame can reduce the size of the product itself in applications such as a portable information terminal or a monitor of a handy video camera in recent years. One of the important issues in the practical use of such an LCD with a built-in driver is to form a high-quality semiconductor film on a transparent insulating substrate such as glass at a temperature within the heat-resistant limit of the substrate. Conventionally, a TFT is formed on a glass substrate by forming an amorphous semiconductor layer, particularly amorphous silicon (a-Si) at a relatively low temperature of about 300 ° C. to 400 ° C. However, such an a-Si TFT has a high on-resistance and can be applied to a switch element of a matrix display unit.
It has not been possible to configure a driver unit that requires a higher-speed operation.

[0005] On the other hand, by using a polycrystalline semiconductor in which a large number of single crystal grains (grains) having a grain size of several hundreds to several thousand degrees are in contact with each other for a channel layer, a driver portion is formed. A TFT that can be applied to any of the above can be formed. In particular, polycrystalline silicon or polysilicon (p-
Si) has a mobility of about several tens to several hundreds cm 2 / V · s, is two orders of magnitude larger than a-Si, and forms a CMOS having a sufficient speed to constitute an LCD driver. .

[0006] Such a driver built-in type p-SiTF
In order to manufacture a TLCD, the most important issue is to form p-Si with good film quality on a glass substrate. Usually, p-Si is formed by a solid phase growth method (SP) that promotes crystallization by performing heat treatment on a-Si formed on a substrate.
C) or a method of directly forming a film by low pressure CVD or the like. Each of these film forming methods is a process at a high temperature of about 700 ° C. to 900 ° C., and a manufacturing process of a p-Si TFT LCD including such a high temperature step is called a high temperature process. In the high temperature process, an expensive substrate such as quartz glass having high heat resistance is required as the substrate, and the cost is high.

[0007] For this reason, the applicant has previously developed a method in which the temperature of the process is set to a maximum of about 600 ° C. or less and an inexpensive alkali-free glass substrate or the like can be used as a substrate in order to reduce costs. I've been. like this,
P- which keeps all processes below the limit temperature of heat resistance of substrate
The manufacturing process of the SiTFT LCD is called a low temperature process.

The low-temperature process has been made possible by excimer laser annealing (ELA) in which a-Si is irradiated with an excimer laser to promote crystallization to form p-Si. The excimer laser is ultraviolet light generated when the excited excimer returns to the ground state. In the ELA, the shape of the laser beam is processed by a predetermined optical system to irradiate the non-processed film. Thereby, thermal energy is particularly applied to the surface of the a-Si, and crystallization is performed at a temperature equal to or lower than the heat-resistant limit temperature of the substrate to form p-Si.

FIG. 3 shows the configuration of such an ELA device. (51) is a laser oscillation source composed of a laser medium, a resonance system, etc., (52) is an optical system in which a lens (55), a mirror (56) and the like are installed in a light shield (57),
(53) is a final irradiation part of a laser beam, (54) is a chamber where laser annealing is actually performed, and (5)
Reference numeral 8) denotes a mounting table for supporting the substrate (59) on which a-Si to be laser-annealed is formed.

The laser light generated by the laser oscillation source (51) is shaped by the optical system (52) so as to show the shape of a predetermined irradiated area, and the transparent part of the chamber (54) is irradiated from the irradiation part (53). Chamber (54) through a transparent window (60)
Irradiated inside. The chamber (54) is maintained at a predetermined pressure and temperature optimum for laser annealing. In the chamber (54), the support table (58) on which the substrate to be processed (59) is mounted moves in a predetermined direction and scans while passing through the laser irradiation area, and laser annealing is performed on the entire surface.

[0011]

In the ELA, an optimum setting of the irradiation laser energy is an important issue. FIG. 4 shows the relationship between the irradiation laser energy and the crystal grain size (grain size) of p-Si. As can be seen from the figure, up to a certain point, as the applied energy increases, the grain size also increases, but beyond a certain point, the grain size sharply decreases, resulting in microcrystallization,
That is, it becomes a microcrystal. Therefore, in order to obtain a sufficiently large grain size (GM) or more, the irradiation laser energy must be optimally set between the lower limit Ed and the upper limit Eu. Based on the relationship of FIG. There is a need to.

FIG. 5 shows the inside of the chamber (54). The laser beam (6) sent from the optical system (52)
1) passes through a transparent window (60) of a chamber (54) made of glass or the like and irradiates a substrate (59) to be processed. This chamber (54) is an airtight chamber, and is replaced with an inert gas atmosphere to prevent the appearance of unnecessary reaction products. However, when the laser beam (61) is irradiated on the substrate (59) to be processed, a
-Si causes ablation, and silicon (62) is scattered and adheres to the opposing transparent window (60) and becomes cloudy (63)
May occur. The laser-annealed film a-Si on the substrate-to-be-processed (59) usually contains a large amount of hydrogen, and this hydrogen is released from the film as hydrogen gas during laser annealing. It is thought that it causes scattering.

As described above, when the transmittance is lowered due to the contamination of the transparent window (60), the substrate (59) is actually irradiated with the laser beam regardless of the optimal setting of the laser power in the laser oscillation source (51). In this case, the laser energy falls below the allowable energy range shown in FIG. 4, the laser annealing is not performed well, and p-Si having a sufficiently large grain size cannot be obtained.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and is directed to a laser oscillation source for generating a laser beam, and a laser beam comprising a plurality of optical components and emitted from the laser oscillation source. In a laser annealing apparatus having an optical system for shaping and forming a predetermined laser beam, and a processing chamber having a mounting table for supporting an object of laser annealing at a position irradiated with the laser beam sent from the optical system. The processing chamber includes a transparent window through which the laser beam sent from the optical system passes, and an airflow generating unit that blows a gas onto an inner surface of the transparent window.

[0015] This prevents scattered matter from the surface of the substrate to be processed from adhering to the opposed transparent window during laser annealing. For this reason, the problem that the transmittance of the transparent window is reduced and good laser annealing is not performed can be prevented. In particular, a ventilation pipe connected to a gas supply source is introduced into the processing chamber, and a blowout portion of the ventilation pipe is close to the transparent window to constitute the airflow generation means.

Thus, since the air supply system for replacing the processing chamber with the inert atmosphere blows out the scattered matter from the processing object, contamination of the transparent window is prevented.

[0017]

FIG. 1 is a configuration diagram of an ELA apparatus according to an embodiment of the present invention. (11) is a laser oscillation source composed of a laser medium, a resonance system, etc., and (12) is a lens (15) and a mirror (1) in a light shield (17).
6) and other optical systems, (13) a final irradiation part of a laser beam, (14) a chamber in which laser annealing is actually performed, and (18) an a-Si to be laser-annealed. A mounting table for supporting the substrate to be processed (19).

The laser light generated by the laser oscillation source (11) is shaped by an optical system (12) to show the shape of a predetermined irradiated area, and the transparent part of a chamber (14) is irradiated from an irradiation part (13). Chamber (14) through a window (20)
Irradiated inside. The chamber (14) is maintained at a predetermined pressure and temperature optimum for laser annealing. In the chamber (14), the mounting table (18) on which the substrate to be processed (19) is mounted moves in a predetermined direction and scans while passing through the laser irradiation area, and laser annealing is performed on the entire surface.

The chamber (14) is an airtight chamber for performing a laser annealing process in an atmosphere of an inert gas such as nitrogen. The air supply valve (1), the air supply pump (2), and the ventilation pipe (3) communicating therewith are provided. ), And an exhaust system including an exhaust valve (6) and an exhaust pump (7). Then, the vent pipe (3) is introduced into the chamber (14), and the outlet (4) is inserted into the chamber (14).
In this configuration, the supply gas is blown to the inner surface of the transparent window (20) in the vicinity of the transparent window (20) incorporated as a part of the outer wall.

FIG. 2 shows the inside of the chamber (14). The laser beam (2) sent from the optical system (12)
1) passes through a transparent window (20) made of glass or the like constituting a part of the outer wall of the chamber (14), enters the chamber (14), and irradiates the substrate (19) to be processed. The outlet (4) of the ventilation pipe (3) of the air supply system is connected to the chamber (14).
Within, adjacent to the transparent window (20). The inert gas supplied from the air supply system is blown out vigorously by the outlet (4), and creates an air flow of the inert gas passing over the inner surface of the transparent window (20). This air blow (2
3) The a-Si on the substrate to be processed (19) is ablated by laser annealing to blow off the scattered silicon (22) and prevent it from adhering to the transparent window (20). For this reason, the transparent window (20) is always kept clean, and the problem that the transmittance is reduced due to fogging is prevented.

[0021]

As is apparent from the above description, in the laser annealing apparatus, it is possible to prevent the transparent window of the chamber into which the laser beam is incident from being contaminated by the scattered matter from the object to be laser-annealed. Was. Since the transparent window is always kept at a high transmittance and unpredictable loss of laser energy is suppressed, good laser annealing with optimally set laser power is performed. For this reason, a semiconductor film having excellent crystallinity is obtained, and a semiconductor element having good characteristics is manufactured using the semiconductor film.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ELA apparatus according to an embodiment of the present invention.

FIG. 2 is a partial configuration diagram of an ELA apparatus according to an embodiment of the present invention.

FIG. 3 is a partial configuration diagram of an optical system of a conventional ELA device.

FIG. 4 is a relationship diagram between irradiation laser energy and grain size.

FIG. 5 is a partial configuration diagram of a conventional ELA device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air supply valve 2 Air supply pump 3 Ventilation pipe 4 Outlet 11 Laser oscillation source 12 Optical system 13 Irradiation unit 14 Chamber 15 Lens 16 Mirror 17 Light shield 18 Mounting table 19 Substrate to be processed 20 Window 21 Laser beam 22 Vaporized silicon 23 Air blow

Claims (2)

[Claims] 1. A laser oscillation source for generating a laser beam, an optical system comprising a plurality of optical parts, shaping a laser beam emitted from the laser oscillation source to form a predetermined laser beam, and transmitting the laser beam from the optical system. And a processing chamber having a mounting table that supports a target of laser annealing at a position to be irradiated with the laser beam, wherein the processing chamber passes the laser beam sent from the optical system. A laser annealing apparatus comprising: a transparent window; and an airflow generating means for blowing a gas to an inner surface of the transparent window. 2. A gas pipe connected to a gas supply source is introduced into the processing chamber, and a blow-out portion of the gas pipe is close to the transparent window to form the gas flow generating means. The laser annealing apparatus according to claim 1, wherein