JP2003218053A - Manufacturing device of thin film semiconductor, and manufacturing method of the thin film semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor manufacturing device, having high throughput by restraining transmission change of a laser beam entering window caused by desorption of silicon during laser crystallization. <P>SOLUTION: An optical inlet chamber and an optical irradiation chamber are separated by means of a gate valve. Even if desorbed silicon is fixed to an optical inlet window provided to an optical inlet chamber, a deposit matter fixing body which can be changed readily is provided to it, and thereby, stabilization of quality and high throughput can be attained by changing the deposited matter fixing body. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor formed on an insulator, a manufacturing device for manufacturing a thin film transistor used as a display pixel of a liquid crystal display device or a liquid crystal driving circuit constituent element, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Semiconductors such as polycrystalline silicon are widely used in thin film transistors (hereinafter referred to as TFTs) and solar cells. In particular, polycrystalline silicon (p-Si) TFTs can be used for liquid crystal display devices (LCD), liquid crystal projectors, etc. by taking advantage of the fact that they can be made on a transparent and insulating substrate such as a glass substrate while allowing high mobility. It has been widely used as a component of a light modulation element or a built-in driver for driving liquid crystal, and has succeeded in creating a new market.

As a method of producing a high-performance TFT on a glass substrate, a manufacturing method called a high temperature process was first put into practical use. This high temperature process is a general term for a process using a high temperature with a maximum process temperature of about 1000 ° C. as a manufacturing method of a TFT. The characteristics of the high temperature process are that a relatively good quality p-Si film can be formed by solid phase growth of silicon, and that a good quality gate insulating film (generally silicon dioxide (SiO ₂ )) and a clean film can be obtained by thermal oxidation. That is, the interface between the p-Si film and the gate insulating film can be formed. Due to these characteristics in the high temperature process, a high-performance TFT having high mobility and high reliability can be stably manufactured. However, in adopting the high temperature process, the substrate for forming the TFT needs to withstand a high temperature heat process of 1000 ° C. or higher, and the quartz glass substrate is the only substrate satisfying this requirement. For this reason, p-Si TFTs manufactured by a high temperature process have been generally formed on a quartz glass substrate that is expensive and small, and it is said that the p-Si TFT is not suitable for increasing the size because of cost problems. In addition, solid phase growth requires heat treatment for a long time of more than ten hours, which is a problem of low productivity. In this method, the thermal deformation of the substrate becomes a big problem due to the entire substrate being heated for a long time, and there is a problem that it is difficult to use a large-sized glass substrate that is substantially inexpensive. This is an obstacle to cost reduction.

On the other hand, a technique called a low temperature process is intended to solve the above drawbacks of the high temperature process and to realize a p-Si TFT having a high mobility. In order to use a relatively inexpensive glass substrate, the p-Si TFT manufacturing process in which the maximum process temperature is approximately 600 ° C. or lower is generally called a low temperature process. Laser crystallization is widely used as a method for manufacturing a p-Si film in a low temperature process.
Laser crystallization is a technique that utilizes the property that an amorphous silicon film on a glass substrate is instantly melted by irradiating it with high-power pulsed laser light and crystallized in the cooling process. Recently, by scanning an amorphous silicon film on a glass substrate while repeatedly irradiating an excimer laser beam, a large area of p-Si is obtained.
The technology of making membranes has become widely used. A relatively high-quality SiO ₂ film can be formed as a gate insulating film by a film forming method using plasma CVD, and it has been put to practical use. With the collection of these technologies, p-Si is now on a large glass substrate that is now several tens of centimeters on a side.
TFTs can be created and mass production is being carried out. However, the problem in this low-temperature process is that the laser-crystallized p-Si film has a high defect density,
This is a factor that greatly affects the mobility of the FT.
The defect density generated by laser crystallization strongly depends on the control of the laser irradiation method particularly in laser crystallization. 2. Description of the Related Art Recently, in a laser crystallization apparatus for a large substrate, a method of shaping a laser beam in a line shape as shown in FIG. 2 and irradiating a semiconductor film with a laser is generally used. This is to put maximum importance on practicality for forming a p-Si film on a large area substrate such as a liquid crystal display device in a short tact time. In this case, in particular, the length 201 of the laser beam in the longitudinal direction that can generate only a limited pulse energy.
Beam width 202 in the minor axis direction is several tens of μ
It is very narrow, from m to several hundred μm. A method is adopted in which pulse irradiation is performed while moving the line beam in the direction of the arrow (203) in FIG. However, when a boundary occurs in the irradiation region of each pulse, it causes crystallinity variation. Therefore, laser irradiation is performed by scanning the irradiation region of each pulse while overlapping each other by about 90%. Therefore, in the laser crystallization device, the semiconductor film on the substrate and the position of the laser beam focused on the line are relatively accurately shifted from several μm to several tens of μm for each laser irradiation pulse to crystallize the entire surface of the substrate. To do.

Laser crystallization utilizes the property that a silicon thin film is heated by a pulsed laser for a very short time, the thin film is melted at a melting point or higher, and then crystallized in a cooling process. Usually, this laser crystallization is performed in a vacuum atmosphere to prevent impurities from being mixed into the film and to control the surface condition. However, since the silicon film reaches the melting point as described above, the temperature of the silicon film is 1000. It has risen above ℃. When such treatment is performed in vacuum, silicon atoms and clusters having thermal energy are released from the film surface. Although the melting time is a short time of several hundred nanoseconds at most, the amount of silicon to be released is very small. However, as described above, a large area of the silicon thin film is crystallized by the high overlapping rate and the multiple laser irradiation. In a mass production apparatus, there is a problem that the above-mentioned thermally desorbed silicon adheres to the laser introduction window and gradually changes the transmittance of laser light.
Even if the amount of silicon adhering to the window is very small, the optical effect on ultraviolet light is great. For example, if about 10 substrates of 300 mm × 300 mm are processed, the transmittance will decrease by about 10%. The optimum energy condition for laser crystallization is only 3 ~
Since there is only 5% range, laser crystallization p-
The quality of the Si film changes. Therefore, it is necessary to remove the laser introduction window and polish the surface to recover the transmittance between treatments.

As a conventional technique for avoiding this problem, there is JP-A-11-26393. This is to prevent the adhesion of silicon particles by performing the treatment while blowing a gas onto the laser light introduction window as shown in FIG.
However, as described above, the particles flying at the thermal speed pass through the window to the window in the normal device structure of about 10 cm in only a few microseconds. In the actual situation, the collision probability is extremely low and little effect can be expected if the gas is blown by pressure under reduced pressure.

For this reason, the effective energy density of the irradiation laser light changes with time, which leads to variations in the quality of the crystallized film, which causes a reduction in yield. In addition, the time required for the maintenance of the device becomes long, which lowers the operating rate and eventually raises the manufacturing cost.

[0008]

In view of the above problems, the present invention reduces the change in transmittance of the light introducing window which is a problem in a semiconductor manufacturing apparatus that performs heat treatment using energetic light in a vacuum atmosphere, In particular, the present invention provides a semiconductor manufacturing apparatus and a method for manufacturing a thin film semiconductor, which has a high operating rate while suppressing variations in the laser crystallized p-Si film.

[0009]

In order to solve the above-mentioned problems, in the present invention, in a thin-film semiconductor manufacturing apparatus for performing heat treatment by irradiating a thin-film semiconductor in a container with energetic light, the container has a light introducing window. It is characterized in that it comprises a light introducing chamber provided and a light irradiating chamber for holding the semiconductor substrate to be processed, which is separated from the light introducing chamber by a gate valve. Here, the light introduction window is a window for transmitting the light with which the semiconductor is irradiated. Therefore, it is formed of a material having a relatively high transmittance at the wavelength of the irradiation light.

Further, the present invention is characterized in that the inside of the container can be under a reduced pressure atmosphere and an arbitrary gas can be introduced.

Therefore, it is possible to process the object to be processed in a cleaner atmosphere than in the atmospheric condition. Further, there is an effect of relatively preventing the deposits from adhering to the light introduction window.

Further, in the present invention, the light introducing chamber is
An exhaust system is provided separately from the light irradiation chamber, and the degree of vacuum can be controlled even after separation by the gate valve.

Further, in the present invention, the light introducing window provided in the light introducing chamber has a surface on the light introducing chamber side,
It is characterized in that it is provided with a light-transmissive substance (which is referred to as a deposit adherent in the present application) for adhering particles thermally desorbed from the object to be treated.

In the present invention, the deposit adherent is thinner than the light introducing window.

Further, the deposit-attached body in the present invention is
It is characterized by being made of a material having a transmittance of ultraviolet rays of 80% or more. As with the light introduction window, the light that irradiates the semiconductor also passes through this deposited material, so it is desirable that the material has a high transmittance at the wavelength of the light that is irradiated. However, since its wavelength is in the ultraviolet range, high transmittance for ultraviolet rays is important.

Further, the deposit-attached body in the present invention is characterized by being quartz. Alternatively, it is characterized by being translucent alumina (Al ₂ O ₃ ). Alternatively, it is a transparent ceramic. Alternatively, it is a heat-resistant ultraviolet transparent film.

Further, in the invention, it is characterized in that the deposit-attached body is fixed to the light introducing window by a supporting mechanism. Here, the support mechanism is a metal frame for fixing the light introduction window, and the deposit attachment body is sandwiched between the lower part of the frame and the light introduction window, and the upper part of the frame is placed thereon. The structure is tightened with screws.

In order to solve the above problems, in the present invention, after the irradiation of energy light to the thin film semiconductor is completed, the gate valve is closed to separate the light introducing chamber and the light irradiating chamber, and then the light introducing window is opened. It is characterized in that it is removed, and the deposit-attached body is replaced. In other words, the melted semiconductor film to be processed adheres and the deposited substance that has become dirty is exchanged each time to stabilize the transmittance.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to FIG.

First, the semiconductor film (403) will be described. Examples of the semiconductor film to which the present invention is applied include silicon-germanium (Si _x G) in addition to semiconductor films of group IV simple substance such as silicon (Si) and germanium (Ge).
e _1-x : 0 <x <1) or silicon carbide (Si
_x C _1-x : 0 <x <1), germanium carbide (Ge _x C _1-x : 0 <x <1), etc. Group IV element composite semiconductors, gallium arsenide (GaAs), indium antimony (InSb) or other complex compound semiconductor film of a Group 3 element and a Group 5 element, or cadmium selenium (CdS)
There is a complex compound semiconductor film of a Group 2 element and a Group 6 element such as e). Or silicon, germanium, gallium,
Arsenic _{(Si x Ge y Ga z As} z: x + y + z = 1) further complex compound such as a semiconductor film and these semiconductor phosphorus (P), arsenic (As), N-type with the addition of donor element such as antimony (Sb) The present invention is also applicable to a semiconductor film or a P-type semiconductor film to which an acceptor element such as boron (B), aluminum (Al), gallium (Ga), indium (In) is added. These semiconductor films are formed by AP-CVD method, LP-CVD method, PE-CV method.
CVD method such as D method or P such as sputtering method or vapor deposition method
It is formed by the VD method. When a silicon film is used as the semiconductor film, disilane (Si ₂ H ₆ ) or the like is deposited as a raw material at a substrate temperature of about 400 ° C. to 700 ° C. in the LP-CVD method. In the PE-CVD method, monosilane (Si
H ₄ ), etc. as a raw material and the substrate temperature is from about 100 ° C.
Deposition is possible at about 00 ° C. If the sputtering method is used, the substrate temperature can be from room temperature to about 400 ° C. The initial state (as-deposit) of the semiconductor film deposited in this way
The ed state) has various states such as amorphous, mixed crystal, microcrystalline, and polycrystalline, but in the present invention, the initial state may be any state. In the specification of the present application, not only amorphous crystallization but also polycrystal recrystallization and microcrystalline recrystallization are collectively referred to as crystallization. The thickness of the semiconductor film is about 20 nm to 1 when it is used for a TFT.
About 100 nm is suitable.

The base insulating film (402) and the semiconductor film (40
After forming 3), the semiconductor film is crystallized by laser irradiation. Usually LP-CVD method, PE-C
A natural oxide film is grown on the surface of the silicon film deposited by the CVD method such as the VD method. Therefore, it is necessary to remove this natural oxide film before irradiating with laser light. As this method, there are a method of wet etching by immersing in a hydrofluoric acid solution, a dry etching in plasma containing fluorine gas, and the like.

Next, the substrate with the semiconductor film is set in the laser irradiation chamber (405). A part of the laser irradiation chamber has an opening, and a metal frame having a light introduction window (415) made of quartz fitted therein is attached to the opening. After the chamber is evacuated to a vacuum, laser light is emitted from this light introduction window. Further, since this light introduction window is itself a constituent part of the vacuum chamber, it needs to have sufficient strength to withstand a vacuum state, and its thickness is about 2 cm.

The irradiated laser light is transferred to the semiconductor film (40
3) It is strongly absorbed on the surface, and the insulating film (402) directly under it.
It is hoped that it will be hardly absorbed by. Therefore, as this laser light, an excimer laser, an argon ion laser, a YAG laser harmonic, or the like having a wavelength in or near the ultraviolet region is preferable. Further, in order to heat the semiconductor film to a high temperature and prevent damage to the substrate at the same time, it is necessary to have a high output and pulse oscillation for an extremely short time.
Therefore, among the above laser lights, especially xenon chloride (XeCl) laser (wavelength 308 nm) and krypton fluoride (KrF) laser (wavelength 248 nm)
Excimer lasers such as are most suitable.

Next, a method of irradiating these laser beams will be described with reference to FIG. Laser pulse intensity half width is 1
It is an extremely short time of about 0 nanoseconds to about 500 nanoseconds.
The laser irradiation is performed at a room temperature (25 ° C.) to about 400 ° C. and a background vacuum degree of about 10 ⁻⁴ Torr to 10 ⁻⁹ Torr. As shown in FIG. 3, the irradiation region shape has a width of about 100 μm (30 μm).
2) Line-shaped (301) with a length of 10 cm or more
Then, crystallization may be advanced by scanning with this linear laser light. In this case, the overlap in the beam width direction for each irradiation (3
The overlap of 03 and 304) is about 5% to 98% of the beam width (302). If the beam width is 300 μm and the overlap for each beam is 95%, the beam advances by 15 μm for each irradiation, so that the same point is subjected to laser irradiation 10 times. Usually, in order to uniformly crystallize the semiconductor film over the entire substrate, laser irradiation is desired to be performed at least about 5 times or more, so that the beam overlap amount for each irradiation is required to be about 80% or more. In order to reliably obtain a highly crystalline polycrystalline film, it is preferable to adjust the overlapping amount from about 90% to about 98% so that the same point is irradiated about 10 to 50 times.

Continuing to use FIG. 4, the light introducing window (415), the deposit material (420), and the upper frame (421) and the lower frame (422) for fixing them are enlarged. Shows.

In FIG. 4, the vacuum container (405) is provided with a gate valve (441) in the semiconductor manufacturing apparatus of the present invention so that the light transmittance of the light introducing window (415) does not decrease even if the laser irradiation is repeated at a high overlapping rate. ) Separates the light introduction chamber (442) and the light irradiation chamber (443).
Laser irradiation is performed on the silicon film (403) on the substrate (401) placed in a vacuum with the gate valve opened. After a series of laser irradiation is completed, the gate valve (441) is closed and the light introduction chamber is separated from the light irradiation chamber.
After this, the light introducing chamber is opened to the atmosphere, and the light introducing window (415)
Then, the set of deposit object adherents (420) is removed. The deposit-attached body has a structure in which the deposit-attached body is placed along the light-introducing window, and the upper and lower sides thereof are sandwiched and tightened by a metal frame, so that it can be easily attached and detached. Here, as also shown in the enlarged portion of FIG. 4, the deposit-attached body is thinner than the light introduction window and does not have sufficient strength to hold a vacuum. Therefore, it is necessary that the vacuum is held at the light introduction window and the O-ring portion (424), and the deposit-deposited body has a structure floating in the vacuum.

In this way, by removing the dirty deposit-attached material and replacing it with a newly prepared deposit-attached material, it is possible to immediately prepare for a new laser crystallization process.

A quartz glass substrate, for example, can be used as the deposit material for the deposit, and the quartz glass substrate of the replaced deposit material can be slightly immersed in the dilute hydrofluoric acid solution for each surface thereof. It can be used several times because the silicon that has been etched and deposited is removed.

In the case of synthetic quartz used for the quartz glass substrate, it has a transmittance of about 92% with respect to the excimer laser having a wavelength of about 300 nm.

This is easier than replacing the quartz window itself, which is also the structure of the vacuum chamber, as in the conventional example, and polishing. Moreover, although the surface of quartz is damaged and the transmittance is reduced by etching and polishing, even if the same quartz is used, the quartz thin plate as a depositor adherent is much cheaper and economical. is there.

Besides, translucent alumina (Al ₂ O ₃ )
Alternatively, translucent ceramics and the like can be used as the deposit-attached body, but each has a transmittance of about 85% for an excimer laser with a wavelength of about 300 nm,
The transmittance does not decrease even at a high temperature of about 1000 ° C. Such translucent ceramics include YAG (Y ₃
A 5 _{G 12)} based and is also used which are those of the material, as good as quartz translucency and heat resistance is obtained.

Further, as a member which transmits ultraviolet rays well and has heat resistance, there are organic compounds and the like. However, even if it is said that it has heat resistance, it cannot have resistance to a temperature of about 1000 ° C. of molten silicon. Therefore, when these are used, it is necessary to replace them with a small amount of treatment so that they are disposable and do not become a source of contamination.

In the conventional example, it takes a long time to maintain the laser light introducing window, and a large number of expensive light introducing windows are used, which causes the running cost to remain high. This makes it possible to improve the operating rate and reduce the running cost. Also in terms of quality, it is possible to suppress variations in the transmittance of the introduction window to a small extent, and stable laser irradiation becomes possible. As a result, it is possible to stably form a high quality p-Si film.

[0034]

EXAMPLE An example of the present invention will be described again with reference to FIG. The substrate and the undercoat protection film used in the present invention conform to the above description, but specifically, a general-purpose non-alkali glass substrate is used as the substrate (401). Board (40
1) PE-C is used for the upper protective film at a film forming temperature of 400 ° C.
A SiO ₂ film (402) having a film thickness of about 500 nm is deposited by the VD method. Then, using a high vacuum LP-CVD apparatus, disilane (Si ₂ H ₆ ) which is a raw material gas is added to 2
An amorphous silicon film (403) is deposited to a thickness of 50 nm at a deposition temperature of 425 ° C. by flowing 00 SCCM. Next, an excimer laser light (41
6) is irradiated to crystallize. This laser crystallizer has an XY stage (407) in a vacuum vessel (405), and a substrate holder (406) above it. The substrate (401) is placed on this substrate holder. The XY stage (407) is moved by the rotation of the ball screw (408), and this ball screw is driven by the pulse motor (409). 1X10 ^{- 6} Torr to move the substrate (401) while the laser irradiation in a vacuum of a silicon thin film of the substrate whole surface is crystallized. Simultaneously with the completion of crystallization, the gate valve (441) is closed, and the crystallized substrate immediately starts to be carried out by a vacuum robot to an adjacent transfer chamber (not shown). After closing the gate valve, the light introducing chamber (442) is opened to the atmosphere and the light introducing window (4) is opened.
15) and the set of deposit deposits (420) are removed. The deposit adherent is a 1.1 mm thick quartz glass substrate,
Replace it with a new one prepared separately. After that, this set is set to the original state, and vacuuming is performed.
Since the size of the light introducing chamber is smaller than that of the light irradiating chamber, the time required for vacuuming is short, and the gate valve is opened when the appropriate vacuum degree is reached, and the next laser irradiation is ready.

The quartz glass substrate after replacement is 3
By dipping it in a dilute hydrofluoric acid solution of about 10%, the surface is slightly etched and the attached silicon is removed, so that it can be reused.

[0036]

According to the conventional technique, the characteristics of the crystalline silicon film vary due to the change in the transmittance of the laser introduction window, and the throughput is lowered due to the reduction in the operating rate of the device. However, as described above, by using the semiconductor manufacturing apparatus and the method for manufacturing a thin film semiconductor of the present invention, it becomes possible to suppress the variation in the transmittance of the laser introduction window to be small, and to improve the uniformity of the characteristics of the crystalline silicon film. In addition to the improvement, it is possible to realize a manufacturing apparatus having high throughput by improving the operation rate of the apparatus.

[Brief description of drawings]

FIG. 1 Description of a conventional device

Figure 2: Laser beam during laser crystallization

FIG. 3 Method of irradiating linear laser beam during laser crystallization

FIG. 4 is a diagram showing a semiconductor device of the present invention.

[Explanation of symbols]

101 substrate 102 Base insulating film 103 semiconductor film 106 quartz window 107 laser light 108 Gas spray nozzle 110 crystalline semiconductor film 415 Light introduction window 420 Depot adherent 427 Vacuum port of light introduction chamber

Claims (12)

[Claims] 1. A thin-film semiconductor manufacturing apparatus for performing heat treatment by irradiating a thin-film semiconductor in a container with energetic light, wherein the container has a light-introducing chamber having a light-introducing window, and the light-introducing chamber is formed by a gate valve. A thin film semiconductor manufacturing apparatus comprising a light irradiation chamber for holding a semiconductor substrate to be processed which is separated. 2. The thin-film semiconductor manufacturing apparatus according to claim 1, wherein the container can be placed in a reduced pressure atmosphere and an arbitrary gas can be introduced. 3. The light introducing chamber has an exhaust system separately from the light irradiating chamber, and the degree of vacuum can be controlled even after separation by the gate valve. Thin film semiconductor manufacturing equipment. 4. The light-introducing window provided in the light-introducing chamber is provided with a translucent deposit deposit on the surface on the light-introducing chamber side. 3. The thin film semiconductor manufacturing apparatus according to item 3. 5. The thin-film semiconductor manufacturing apparatus according to claim 1, wherein the deposit adherent is thinner than the light introducing window. 6. The deposit-attached body has a UV transmittance of 8 or less.
A material comprising 0% or more of claim 1.
5. The thin-film semiconductor manufacturing apparatus according to item 5. 7. The thin film semiconductor manufacturing apparatus according to claim 1, wherein the deposit adherent is quartz. 8. The deposit adherent is made of translucent alumina (A
7. The thin-film semiconductor manufacturing apparatus according to claim 1, wherein the thin-film semiconductor manufacturing apparatus is L ₂ O ₃ ). 9. The thin-film semiconductor manufacturing apparatus according to claim 1, wherein the deposit-attached body is a translucent ceramic. 10. The thin-film semiconductor manufacturing apparatus according to claim 1, wherein the deposit-attached body is a heat-resistant ultraviolet transparent film. 11. The deposit-attached body is supported by a support mechanism.
The thin film semiconductor manufacturing apparatus according to claim 1, wherein the thin film semiconductor manufacturing apparatus is fixed to the light introducing window. 12. After the irradiation of energy light to the thin film semiconductor is completed, the gate valve is closed, the light introducing chamber and the light irradiating chamber are separated, and then the light introducing window is removed to replace the deposit adherent. The method for manufacturing a thin film semiconductor according to claim 1, wherein the method is performed.