JPH06252048A - Method for manufacturing polycrystalline semiconductor thin film - Google Patents

Abstract

(57) [Summary] [Object] Production of a polycrystalline semiconductor thin film capable of uniformly polycrystallizing the entire amorphous semiconductor thin film by equalizing the overlapping amount of laser beams in each part of the amorphous semiconductor thin film. Provide a way. [Configuration] The amorphous semiconductor thin film 6 provided on the substrate,
A pulse energy beam l ₂ having a hexagonal cross section in the irradiation direction is emitted, and the pulse energy beam l ₂ is scanned while overlapping a predetermined area in a direction in which predetermined sides of the hexagon are arranged. . Further, a cross-sectional shape of the irradiation direction of the pulse energy beam is a rhombus, and the pulse energy beam is scanned while overlapping a predetermined area in a diagonal direction of the rhombus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a uniform polycrystalline semiconductor thin film on an insulating substrate such as a glass substrate by using a low temperature process.

[0002]

2. Description of the Related Art In recent years, research on thin film semiconductors has been actively conducted as a semiconductor material for driving elements such as liquid crystal displays and contact type image sensors. This is because, unlike a conventional single crystal semiconductor, this thin film semiconductor has the characteristics that it can be formed on an insulating substrate such as glass and that the area can be easily increased. Amorphous silicon thin films have hitherto been the mainstream of such thin film semiconductors, but their mobility is very low (μ _e = 0.1 to ¹ cm ² V ⁻¹ s ⁻¹ ) and their application The field is limited. Therefore, as a material replacing the amorphous silicon thin film, research on a polycrystalline silicon thin film capable of forming a large-area thin film using a low temperature process has been activated. This polycrystalline silicon thin film has a carrier mobility that is nearly three orders of magnitude higher than that of an amorphous silicon thin film. Therefore, if a method for manufacturing a polycrystalline silicon thin film can be established, an integrated circuit (IC) chip that has been manufactured on a silicon wafer can be mounted on a substrate and connected by wire bonding or the like. Peripheral drive circuits can be integrated on the same substrate as a thin film drive circuit, and it is possible to reduce manufacturing costs for mounting, wiring, etc., and achieve compactness.

One of the methods for producing a polycrystalline silicon thin film is
There is a recrystallization method using a short wavelength laser light such as an excimer laser. FIG. 5 is a schematic configuration diagram of a high energy beam recrystallization device. In the figure, 1 is an excimer laser, 2 is
Is a mirror, 3 is a uniform optical system including a homogenizer,
Reference numeral 4 is a vacuum chamber provided with a quartz window 5. In order to polycrystallize an amorphous silicon thin film using this high energy beam recrystallization apparatus, first, a glass substrate 7 having an amorphous silicon thin film 6 formed thereon is placed at a predetermined position in a vacuum chamber 4. The inside of the vacuum chamber 4 is evacuated to a predetermined vacuum degree. An inert gas such as Ar may be introduced into this vacuum if necessary. Then, a laser beam (pulse energy beam) l ₁ is emitted from the excimer laser 1. This laser beam l ₁ is reflected by the mirror 2, and when passing through the uniform optical system 3, the cross-sectional shape in the irradiation direction is rectangular and the beam is made uniform, passes through the quartz window 5, and passes through the glass substrate 7. Amorphous silicon thin film 6 on
Is irradiated. The amorphous silicon thin film 6 is polycrystallized by rapid heat treatment on the order of nanoseconds by the laser beam l ₁ .

When the amorphous silicon thin film 6 has a large area, as shown in FIG. 6, the cross-sectional shape of the laser beam l _{1 in} the irradiation direction is square or rectangular, and the laser beam l _{1 is formed.}
Are scanned in two directions within the plane of the amorphous silicon thin film 6, that is, in the X-axis direction or the Y-axis direction to polycrystallize the amorphous silicon thin film 6 to form a polycrystalline silicon thin film 8. In this case, in order to make the polycrystalline silicon thin film 8 uniform, the laser beam l ₁ having a square cross section shown in FIG. 7A is changed to a predetermined laser beam l ₁ as shown in FIG. 7B. Scanning is performed while overlapping a predetermined area in the array direction of the sides (X-axis direction in the figure), and as shown in FIG. 7C, a predetermined side adjacent to the side of the laser beam l ₁ is scanned. The laser beam ₁₁ is moved in the arrangement direction (Y-axis direction in the figure) while overlapping with a predetermined area, and again scanned with the laser beam l ₁ while overlapping a predetermined area in the X-axis direction. By repeating the above operation, a large-area amorphous silicon thin film 6 can be obtained.
Can be polycrystallized.

In this recrystallization method, since the pulse width of the laser beam is a high-speed heat treatment of the order of nanoseconds, the recrystallization time is extremely short, only the surface is locally heated, and the substrate is not thermally affected. Since there is almost no glass substrate, an inexpensive glass substrate can be used. Further, since it is a process of once melting an amorphous silicon thin film and then recrystallizing it, it is comparatively often used in another method for manufacturing a low-temperature polycrystalline silicon thin film, for example, 600 by using an electric furnace. It is possible to obtain a thin film having excellent crystallinity with few defects such as twins inside the crystal grains as compared with the method of annealing for several tens of hours at a temperature of about C (solid phase growth method). Therefore, in a thin film transistor (TFT) manufactured by using this thin film, a thin film having high mobility can be easily obtained, and this is the most promising method.

[0006]

However, in this recrystallization method, as shown in FIG. 7 (c), the laser beam l ₁ is moved in the X-axis direction and the Y-axis direction in the overlapping portion k. to scanned while overlap by _x and the overlapping part k _y, the amount of overlap in the X-axis direction (number of pulses) and the amount of overlap in the Y-axis direction (the number of pulses) has a overlapping portion k _x and overlapping portions k _y,
The overlapping part k _x and the overlapping part k _y are different in each overlapping part k _z . Since the polycrystalline silicon thin film depends on the irradiation pulse number, when the overlapping amount of the laser beam l ₁ is different in each portion, the crystallinity is also different in each portion. For example, in FIG. 7C, the non-overlapping part k ₀ , the overlapping parts k _x and k _y , and the overlapping parts k _x and k.
The crystallinity of each part of _y and the overlapping part k _z is different,
Therefore, the characteristics of the manufactured device are such that the non-overlapping part k ₀ ,
There is a problem that the overlapping portions k _x , k _y and the overlapping portion k _z are different from each other.

Therefore, as shown in FIG. 8, if the feed pitch in the X direction is finely set, the uniformity in the X direction can be improved, but the overlapping amount in the Y axis direction is the overlapping portion k ₀ and the overlapping portion k. _y
However, there is a problem in that a non-uniform portion is also generated due to the difference between and.

The present invention has been made in view of the above circumstances, and makes the entire amorphous semiconductor thin film uniformly polycrystallized by equalizing the overlapping amounts of the laser beams in the respective portions of the amorphous semiconductor thin film. It is an object of the present invention to provide a method for manufacturing a polycrystalline semiconductor thin film that can be made into a semiconductor.

[0009]

In order to solve the above problems, the present invention adopts the following method for manufacturing a polycrystalline semiconductor thin film. That is, in the method for producing a polycrystalline semiconductor thin film according to claim 1 of the present invention, the amorphous semiconductor thin film provided on the substrate is irradiated with a pulse energy beam, and the pulse energy beam is applied to the amorphous semiconductor thin film. In the method for producing a polycrystalline semiconductor thin film, which comprises polycrystallizing the amorphous semiconductor thin film by scanning in the plane direction, a cross-sectional shape of the irradiation direction of the pulse energy beam is hexagonal, and the pulse energy beam is It is characterized in that scanning is performed while overlapping a predetermined area in the arrangement direction of predetermined sides of the polygon.

According to a second aspect of the present invention, there is provided a method of manufacturing a polycrystalline semiconductor thin film, wherein an amorphous semiconductor thin film provided on a substrate is irradiated with a pulse energy beam, and the pulse energy beam is applied to the amorphous semiconductor thin film. In the method for manufacturing a polycrystalline semiconductor thin film in which the amorphous semiconductor thin film is polycrystallized by scanning in the plane direction, a cross-sectional shape in the irradiation direction of the pulse energy beam is a rhombus, and the pulse energy beam is a rhombus. It is characterized by scanning while overlapping a predetermined area in the diagonal direction.

[0011]

In the method for producing a polycrystalline semiconductor thin film according to claim 1 of the present invention, the cross-sectional shape of the pulse energy beam in the irradiation direction is hexagonal, and the pulse energy beam is arranged on a predetermined side of the hexagon. The scanning is performed while overlapping a predetermined area in the direction. As a result, the overlapping amounts of the laser beams in the respective parts of the amorphous semiconductor thin film are made equal to uniformly polycrystallize the entire amorphous semiconductor thin film.

Further, in the method of manufacturing a polycrystalline semiconductor thin film according to claim 2, the cross-sectional shape in the irradiation direction of the pulse energy beam is rhombic, and the pulse energy beam is
Scanning is performed while overlapping a predetermined area in the diagonal direction of the diamond. As a result, the overlapping amounts of the laser beams in the respective parts of the amorphous semiconductor thin film are made equal to uniformly polycrystallize the entire amorphous semiconductor thin film.

[0013]

Embodiments of the method for manufacturing a polycrystalline semiconductor thin film according to the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a conceptual diagram showing a method of manufacturing a polycrystalline silicon thin film according to a first embodiment of the present invention. The manufacturing method of the polycrystalline silicon thin film shown in FIG. 1 differs from the conventional manufacturing method of the polycrystalline silicon thin film shown in FIG. 5 in that the laser beam (pulse energy beam) l ₂ has a hexagonal sectional shape in the irradiation direction. The point is to scan the amorphous silicon thin film 6 with the laser beam l ₂ overlapping a predetermined area in the arrangement direction of the predetermined sides of the hexagon (X-axis direction in the drawing).

The manufacturing method of this polycrystalline silicon thin film will be described in more detail below with reference to FIGS. 1 and 5. First, an amorphous silicon thin film is formed on an insulating substrate. As the insulating substrate, a glass substrate 7 having a SiO ₂ film as a buffer layer formed on the surface of non-alkali glass is used. On the glass substrate 7, plasma CVD method, LPCVD
The amorphous silicon thin film 6 having a thickness of 300 to 1500 angstroms is formed by using a sputtering method, a sputtering method, or the like. Since the amorphous silicon thin film formed by the plasma CVD method or the like contains a large amount of hydrogen immediately after its formation, it is 550
It is necessary to perform a dehydrogenation treatment at a temperature near 0 ° C. to prevent the film from being roughened due to the sudden release of hydrogen during laser irradiation.

Then, the glass substrate 7 on which the amorphous silicon thin film 6 is formed is placed at a predetermined position in the vacuum chamber 4, and the inside of the vacuum chamber 4 is evacuated to a predetermined degree of vacuum. An inert gas such as Ar may be introduced into this vacuum if necessary. Then, the excimer laser 1 emits a laser beam l ₂ . The cross-sectional size of the laser beam l ₂ depends on the optical design, and the length of one side is about 1 mm to 1 mm.
It can be arbitrarily set within a range of up to about 5 mm. As the excimer laser 1, an excimer laser using F ₂ , ArF, KrF, XeCl, XeF or the like, which is a short pulse laser, is preferably used, and its energy density is preferably 200 to 500 mJ / cm ^2. .

This laser beam l ₂ is reflected by the mirror 2, and when passing through the uniform optical system 3, the cross-sectional shape in the irradiation direction is made hexagonal, and the beam is made uniform, and passes through the quartz window 5. The amorphous silicon thin film 6 on the glass substrate 7 is irradiated. The amorphous silicon thin film 6 is polycrystallized by rapid heat treatment on the order of nanoseconds by the laser beam l ₂ .

In this method, as shown in FIG.
The laser beam l ₂ has a length of 1 between a pair of opposite sides of the hexagon in the array direction (X-axis direction in the figure) of a predetermined side of the hexagon that is the cross-sectional shape of the irradiation direction of the laser beam l ₂ . Scan the amorphous silicon thin film 6 by moving by 1/2, and
As shown in FIG. 1C, the laser beam l ₂ is moved in the diagonal direction of the hexagon (Y-axis direction in the figure) while overlapping a predetermined area, and the laser beam l ₂ is again moved to the hexagonal direction. The amorphous silicon thin film 6 is scanned by moving it by ½ of the length between the pair of opposite sides of the prism. By repeating the above operation, the entire large-area amorphous silicon thin film 6 can be uniformly polycrystallized.

According to this method, X of the amorphous silicon thin film 6 is
The overlapping amount in the axial direction (the number of pulses) and the overlapping amount in the Y-axis direction (the number of pulses) are both twice, so that the overlapping amount of the laser beam in each part of the amorphous silicon thin film 6 can be made equal over the large area substrate. Recognize. Therefore, it can be seen that the entire amorphous silicon thin film 6 is uniformly polycrystallized.

FIG. 2 is a diagram showing the characteristic distribution of the TFT element in the directions of the X ₁ cross section and the Y ₁ cross section in FIG. 1 when the TFT element is manufactured on the polycrystalline silicon thin film of the above embodiment (Example). FIG. 3 is a diagram showing a characteristic distribution of the TFT element in the directions of the X ₂ cross section and the Y ₂ cross section in FIG. 7 when the TFT element is manufactured on the conventional polycrystalline silicon thin film (conventional example). Is.

In the embodiment, the field effect mobility is constant in both the X ₁ section and the Y ₁ section, and the characteristics of the TFT element are uniform, whereas in the conventional example, the overlapping portion k _{x of the} X ₂ section is used. Field effect mobility of the non-overlapping part k _{0 is} similar to that of the overlapping part k _z of the Y ₂ cross section with respect to the overlapping part k _x . It can be seen that it is uniform. From these figures, it is understood that when the TFT element is manufactured on the polycrystalline silicon thin film of the above-mentioned embodiment, the uniformity of the TFT element is significantly improved as compared with the conventional example, and therefore, the polycrystalline silicon thin film is It is obvious that the uniformity of the crystals is significantly improved as compared with the conventional one.

As described above, according to this method for producing a polycrystalline silicon thin film, the overlapping amount of the laser beam in each part of the amorphous silicon thin film 6 can be made equal over the whole area of the large area substrate. The entire silicon thin film 6 can be uniformly polycrystallized. Therefore, when a device is manufactured by using this polycrystalline silicon thin film, there is an effect that a device and a circuit having no characteristic variation in the entire substrate can be obtained.

Even when the overlapping amount is made finer, the same effect can be obtained if the feed pitch is an integral multiple of the beam length in the scanning direction. Further, the overlap amount may be halved as described above, and the whole may be scanned many times. Regarding the nonuniformity of the characteristics of the laser beam edge portion, the nonuniformity of the characteristics of the laser beam edge portion is reduced by making the shape of this portion as steep as possible, that is, by reducing the area of the edge region as much as possible. be able to. In this case, the width of this region can be set to 20 μm or less by optimizing the optical design. In addition, the substrate temperature during laser irradiation is 40
By performing laser annealing in a state of being heated and maintained at about 0 ° C., it is possible to avoid the non-uniformity of the crystal to a further problem-free level.

(Second Embodiment) FIG. 4 is a conceptual diagram showing a method of manufacturing a polycrystalline silicon thin film according to a second embodiment of the present invention. The manufacturing method of the polycrystalline silicon thin film shown in FIG. 4 is different from the manufacturing method of the polycrystalline silicon thin film of the first embodiment shown in FIG. 1 in that the cross-sectional shape of the laser beam l _{3 in} the irradiation direction is a rhombus, This is a point where l ₃ is scanned on the amorphous silicon thin film 6 while overlapping a predetermined area in the diagonal direction of the rhombus (X-axis direction in the figure).

In this method, as shown in FIG.
The laser beam l ₃ is moved by ½ of the length of the diagonal line of the rhombus in the direction of the diagonal line of the rhombus (X-axis direction in the drawing) which is the cross-sectional shape of the irradiation direction of the laser beam l ₃ and is amorphous. The silicon thin film 6 is scanned, and as shown in FIG. 4 (c), the laser beam l ₃ is moved in the other diagonal direction of the rhombus (Y-axis direction in the figure) to 1 / l of the length of the diagonal line. 2 is moved, the laser beam l ₃ again, in a diagonal direction of the rhombus (in the figure the X-axis direction), thereby scanning the amorphous silicon thin film above 6 are moved 1/2 increments of length of the diagonal line of該菱type . By repeating the above operation, the entire large-area amorphous silicon thin film 6 can be uniformly polycrystallized.

Also in this method, the overlapping amount (pulse number) in the X-axis direction and the overlapping amount (pulse number) in the Y-axis direction of the amorphous silicon thin film 6 are each twice, and each part of the amorphous silicon thin film 6 is changed. It can be seen that the overlapping amounts of the laser beams can be made equal, and therefore the entire amorphous silicon thin film 6 can be uniformly polycrystallized. As described above, this polycrystalline silicon thin film manufacturing method also has the same effect as the polycrystalline silicon thin film manufacturing method of the first embodiment.

[0026]

As described above, according to the first aspect of the present invention.
Alternatively, according to the method for producing a polycrystalline semiconductor thin film described in 2,
The overlapping amount of laser beams in each part of the amorphous semiconductor thin film can be made equal, and the entire amorphous semiconductor thin film can be uniformly polycrystallized. Therefore, when a device is manufactured by using this polycrystalline silicon thin film, it is possible to improve the variation in characteristics due to the overlapping amount of laser beams, which has been a problem in the past, and to obtain a device with no characteristic variations in the entire substrate. There is an effect that a circuit can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a method of manufacturing a polycrystalline silicon thin film according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a polycrystalline silicon thin film according to a first embodiment of the present invention with T
It is a figure which shows the characteristic distribution of a TFT element at the time of producing an FT element.

FIG. 3 is a diagram showing a characteristic distribution of a TFT element when the TFT element is manufactured on a conventional polycrystalline silicon thin film.

FIG. 4 is a conceptual diagram showing a method for manufacturing a polycrystalline semiconductor thin film according to a second embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a high energy beam recrystallization device.

FIG. 6 is a conceptual diagram of a high energy beam recrystallization method.

FIG. 7 is a conceptual diagram showing a conventional method for manufacturing a polycrystalline semiconductor thin film.

FIG. 8 is a conceptual diagram showing another conventional method for manufacturing a polycrystalline semiconductor thin film.

[Explanation of symbols]

1 Excimer Laser 2 Mirror 3 Uniform Optical System 4 Vacuum Chamber 5 Quartz Window 6 Amorphous Silicon Thin Film (Amorphous Semiconductor Thin Film) 7 Glass Substrate l ₂ , l ₃ Laser Beam

Claims (2)

[Claims] 1. An amorphous semiconductor thin film provided on a substrate is irradiated with a pulse energy beam, and the pulse energy beam is scanned in a plane direction of the amorphous semiconductor thin film to form the amorphous semiconductor thin film. In the method of manufacturing a polycrystalline semiconductor thin film for polycrystallizing, the cross-sectional shape of the irradiation direction of the pulse energy beam is hexagonal, and the pulse energy beam is overlapped with a predetermined area in the arrangement direction of the predetermined sides of the hexagon. A method for manufacturing a polycrystalline semiconductor thin film, which comprises scanning while performing scanning. 2. An amorphous semiconductor thin film provided on a substrate is irradiated with a pulse energy beam, and the pulse energy beam is scanned in the plane direction of the amorphous semiconductor thin film to form the amorphous semiconductor thin film. In the method for producing a polycrystalline semiconductor thin film that is polycrystallized, the cross-sectional shape of the irradiation direction of the pulse energy beam is a rhombus, and the pulse energy beam is scanned while overlapping a predetermined area in a diagonal direction of the rhombus. A method for producing a polycrystalline semiconductor thin film, which is characterized.