JPH08293466A - Manufacture of semiconductor thin film - Google Patents

Abstract

PURPOSE: To provide a semiconductor thin film in which the dimensional accuracy by scanning is enhanced and at the same time which is uniform and high quality throughout the whole surface of a large-area substrate. CONSTITUTION: The laser beam C of a high output continuously irradiates the non- single-crystal semiconductor film of an irradiation substrate 12 on a tray 11, and the crystal particle diameter of the thin film is expanded or the thin film is made into a single crystal and at the same time, in a laser annealing device, high-intensity light B is radiated together with the laser beam C in a larger area than the area of a substrate for a longer period of time than the irradiation time of the laser beam C with a lower density than the irradiation energy density of the laser beam C from a high-intensity light unit 13, and the crystal growth is performed by the molten recrystallization of the non-single-crystal semiconductor film, thereby obtaining a semiconductor thin film crystalline layer with a uniform property of matter and a high-quality crystalline property. Also, since the heating of the whole of the substrate 12 is performed by the high-intensity light B, the tray scanning mechanism of the laser annealing device dispenses with a heating mechanism unlike a conventional one, and since only a scanning mechanism is used, the high dimensional accuracy by scanning can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in thin film transistors (hereinafter referred to as TFTs) for active matrix type image display devices and image sensors.
The present invention relates to a method for manufacturing a semiconductor thin film for polycrystallizing a non-single-crystal semiconductor thin film.

[0002]

2. Description of the Related Art Conventionally, T has been formed on an insulating substrate such as glass.
As a semiconductor device having an FT, an active matrix type liquid crystal display device using an TFT for driving a pixel, an image sensor and the like are known. A thin film silicon semiconductor is generally used for the TFT used in these devices. As this thin film silicon semiconductor,
Amorphous silicon semiconductors (a-Si) and crystalline silicon semiconductors are roughly classified. This amorphous silicon semiconductor is the most commonly used because it has a low film formation temperature, can be relatively easily manufactured by the vapor phase method, and has high mass productivity. Since it is inferior to silicon semiconductors, which have properties,
In the future, in order to obtain higher speed characteristics, there has been a strong demand for establishment of a method for manufacturing a TFT made of a crystalline silicon semiconductor. Note that as a crystalline silicon semiconductor, polycrystalline silicon, microcrystalline silicon, amorphous silicon containing a crystalline component, semi-amorphous silicon having an intermediate state between crystalline and amorphous are known. .
As a method for obtaining these thin film silicon semiconductors having crystallinity, (1) a film having crystallinity is directly formed at the time of film formation.

(2) A semiconductor film is formed and crystallinity is imparted by applying heat energy.

(3) A semiconductor film is formed and crystallinity is imparted by the energy of laser light.

The above methods (1) to (3) are known.

However, in the method (1), since crystallization progresses at the same time as the film forming step, it is indispensable to increase the thickness of the silicon film in order to obtain crystalline silicon having a large grain size. It is technically difficult to uniformly form a film having a film on the entire surface of the substrate. Further, since the film forming temperature is as high as 600 ° C. or higher, there is a cost problem that an inexpensive glass substrate cannot be used.

The method (2) has an advantage that it can be applied to a large area, but requires a heat treatment for several tens of hours at a high temperature of 600 ° C. or higher for crystallization. That is, considering the use of an inexpensive glass plate and the improvement of throughput, it was necessary to simultaneously solve the conflicting problems of lowering the heating temperature and crystallizing in a shorter time.

Further, in the method (3), the polycrystalline or amorphous semiconductor on the substrate is scanned while being irradiated with a laser beam of a high-energy beam to obtain a coarse-grained polycrystalline or single crystal having a fine grain boundary. A crystallization treatment method for forming a semiconductor layer (Japanese Patent Laid-Open No. 56-103417) has been proposed. However, since it is not possible to obtain an output enough to irradiate the entire substrate at one time, it is difficult to improve the uniformity when the beams are overlapped and irradiated. FIG. 4 shows a scanning method of a laser beam of a high energy beam, which is often used in a conventional method for obtaining a semiconductor layer having crystallinity.

FIG. 4 is a diagram showing an outline of a conventional method of manufacturing a semiconductor thin film, wherein a is a top view of an apparatus including a substrate for irradiating laser light, and b is a side view of the apparatus for irradiating the substrate with laser light. FIG. 1C is a diagram showing the relationship between the oscillation time of laser light and energy output, and FIG. 3D is a top view of an apparatus including a substrate when laser light is sequentially irradiated.

As shown in FIG. 4a, the irradiation substrate 2 is placed on the tray 1, and the surface of the irradiation substrate 2 is irradiated with the laser beam 3 having the oscillation time shown in FIG. Also,
As shown in FIG. 4d, it is necessary to repeatedly irradiate the irradiation region 4 of the laser light 3 while sequentially superimposing the irradiation region 4 of the laser light 3 so as not to form an unirradiated region of the laser light 3 by scanning the tray 1 in the direction of the arrow (Japanese Patent Laid-Open No. Sho 60). -245124 and JP-A-3-286518). Further, as shown in FIG. 4b, the irradiation substrate 2 on the tray 1 is irradiated with the laser beam 3 while being heated by the heating mechanism 5 composed of a heating wire provided below the tray 1, thereby obtaining good crystallinity. It is known that a semiconductor thin film having the same can be obtained (JP-A-1-196116).

[0011]

In order to obtain a semiconductor layer having uniform physical properties and good crystallinity in the above-mentioned conventional method for manufacturing a semiconductor thin film, the shape of the laser beam, the energy uniformity, and the in-beam uniformity are required. It is necessary to scan the substrate with a good laser beam with high accuracy. In particular, a TFT that can be used for an active matrix type image display device or image sensor provided on an insulating substrate such as glass
In the semiconductor thin film used for
The accuracy is high because it is narrow in m units, and the tray scanning mechanism of the laser annealing apparatus is required to have the same dimensional accuracy as that of an exposure device that patterns a semiconductor thin film. However, it has been difficult to scan the laser beam with high accuracy using a tray having a mechanism for transporting the irradiation substrate while heating it.

The present invention solves the above-mentioned conventional problems, and provides a method for manufacturing a semiconductor thin film, which can improve the dimensional accuracy by scanning and can obtain a uniform and good quality semiconductor thin film over the entire surface of a large area substrate. The purpose is to do.

[0013]

A method of manufacturing a semiconductor thin film according to the present invention is a method of manufacturing a semiconductor thin film in which a non-single crystal semiconductor film is annealed by laser light to be polycrystallized. After the heating step of irradiating with light and heating, the non-single crystal semiconductor film is irradiated with the laser light at the same time as the strong light on the non-single crystal semiconductor film, and the non-single crystal semiconductor film And a polycrystallization step for performing crystallization, whereby the above object is achieved.

The method of manufacturing a semiconductor thin film of the present invention is
In a method for manufacturing a semiconductor thin film in which a non-single-crystal semiconductor film is annealed by laser light to be polycrystallized, the entire non-single-crystal semiconductor film is irradiated with strong light whose irradiation energy density is lower than the irradiation energy density of the laser light. And heating the non-single crystal semiconductor film simultaneously with the intense light, and irradiating the non-single crystal semiconductor film with the laser light in a strong light irradiation region to polycrystallize the non-single crystal semiconductor film. And a polycrystallization step, whereby the above object is achieved.

Further, in the method for producing a semiconductor thin film of the present invention, a non-single-crystal semiconductor film is formed on an insulating substrate or an insulating film provided on the insulating substrate, and the non-single-crystal semiconductor film is irradiated with laser light. In the method of manufacturing a semiconductor thin film which is annealed to be polycrystallized by irradiation with intense light, the irradiation energy density of which is lower than the irradiation energy density of the laser light so that the irradiation area is larger than that of the insulating substrate. And a polycrystal for performing polycrystallization of the non-single-crystal semiconductor film by irradiating the non-single-crystal semiconductor film with the intense light at the same time as the intense light irradiation with the laser light after the heating step. The above-mentioned object is achieved by that.

Further, preferably, the irradiation time of the strong light in the method for manufacturing a semiconductor thin film of the present invention is longer than the irradiation time of the laser light.

Further preferably, the laser light used in the method for producing a semiconductor thin film of the present invention has a wavelength of 400 nm.
Use the following UV rays: Further, it is preferable to use ultraviolet rays having an oscillation time of 60 nsec (seconds) or less as laser light in the method for manufacturing a semiconductor thin film of the present invention.

[0018]

In the present invention, the non-single crystal semiconductor film is continuously irradiated with a laser beam of a high-power energy beam, and at the same time as this laser beam, the area of the insulating substrate is larger than the irradiation time of the laser beam. The non-single-crystal semiconductor film is polycrystallized by irradiating the whole non-single-crystal semiconductor film with intense light having a lower irradiation energy density of the laser light.

As described above, since the non-single-crystal semiconductor film is heated by intense light, it is not necessary to provide the tray scanning mechanism of the laser annealing apparatus with a heating mechanism as in the conventional case, and if only the scanning mechanism is provided. Since it is good, it is possible to scan the laser beam with the same dimensional accuracy as that of an exposure device that patterns a semiconductor thin film. In addition, since the entire substrate is heated at once by irradiating an area larger than the substrate with strong light, the substrate temperature is excellent in uniformity, and in terms of throughput, for example, there is no need to preheat the tray, which is advantageous. Further, for example, if the scanning mechanism is provided on the tray of the substrate, the optical system can be fixed, so that it becomes possible to form the laser light having good shape, energy uniformity, and in-beam uniformity.

The wavelength of this laser light is 400
If ultraviolet rays having a wavelength of nm or less are used, it is possible to efficiently heat the semiconductor silicon film with a wavelength matching the absorption coefficient of the semiconductor silicon film, for example.

[0021]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing an outline of a method for manufacturing a semiconductor thin film in one embodiment of the present invention, which is a configuration diagram of a laser annealing apparatus.

In FIG. 1, the irradiation substrate 1 is placed on the tray 11.
2 is placed and conveyed in the left-right direction (scanning direction) of arrow A. Above the irradiation substrate 12 on the tray 11, a strong light unit 13 that heats the entire substrate by irradiating the strong light B of ultraviolet rays from an oblique direction is provided. This strong light unit 1
Irradiation substrate 1 by means of 3 ultraviolet (UV) lamps 13a
2, the irradiation substrate 12 is heated to a predetermined temperature by irradiating strong light B having an irradiation energy density lower than the irradiation energy density of the laser light so that the irradiation area is larger than that of the irradiation substrate 12. A beam shaping unit 14, which is, for example, a homogenizer, is provided directly above the irradiation substrate 12 on the tray 11, and the laser beam C for polycrystallization from the laser oscillator 15 is reflected by the reflecting mirror 16 to perform beam shaping. The beam is guided to the unit 14, and the beam shaping unit 14 shapes the beam into a predetermined beam and irradiates the irradiation substrate 12 with the beam. At this time, the laser light C has a wavelength of 400 nm.
Hereinafter, the oscillation time is set to 60 nsec or less. The laser annealing device is configured as described above.

Thus, by irradiating the laser while heating the substrate, it is possible to obtain a crystal layer of a semiconductor thin film having good crystallinity. Further, the tray scanning mechanism of the laser annealing apparatus does not need to have a heating mechanism as in the conventional case, and the whole substrate is heated by the strong light B, so that the accuracy of the tray scanning mechanism and the optical system can be improved.

First, the irradiation substrate 12 will be described below.

FIG. 2 is a sectional view of the irradiation substrate 12 shown in FIG.

In FIG. 2, a base coat film 22 is provided on an insulating substrate 21, and an amorphous silicon film 23 serving as a semiconductor thin film, for example, a polycrystalline silicon film is provided on the base coat film 22 by laser light C. Has been. This forms the irradiation substrate 12.

A method of manufacturing the irradiation substrate 12 will be described.

As shown in FIG. 2, after cleaning the surface of an insulating substrate (for example, a glass substrate) 21 of about 300 mm □, silicon dioxide is used as a base coat film 22 on the insulating substrate 21 and a thickness of 300 nm is formed by using a sputtering device. Deposit to a degree. The required film thickness of the base coat film 22 varies depending on the surface condition of the insulating substrate 21, is sufficiently flat,
Also, it can be omitted if the substrate has a sufficiently low concentration of ions such as sodium ions which adversely affect the semiconductor characteristics. Conversely, if the surface condition is such that scratches or irregularities are severe, the above film It should be deposited thicker than thick. On this base coat film 22, a chemical vapor deposition method (C
The amorphous silicon film 23 is deposited to a thickness of about 50 nm by using the VD method) or the sputtering method. The irradiation substrate 12 is obtained by the above.

Next, a method for manufacturing a semiconductor thin film of the present invention will be described below.

FIG. 3 is a diagram showing an outline of a method of manufacturing a semiconductor thin film in one embodiment of the present invention, in which a is a laser beam C.
And a top view of an apparatus including a substrate for irradiating strong light B, b is a side view of an apparatus including a substrate for irradiating laser light C and strong light B, and c is a time and energy output of laser light C and strong light B. It is a figure which shows a relationship.

As shown in FIGS. 3a to 3c, the irradiation substrate 1
The entire surface of the amorphous silicon film 23 of No. 2 is irradiated with strong light B to heat the irradiation substrate 12 to a predetermined temperature. After this heating,
The strong light B is irradiated onto the amorphous silicon film 23, and the laser light C is simultaneously irradiated in the strong light irradiation region at the same time as the strong light B is irradiated to cause crystal growth by melt recrystallization of silicon. A crystalline layer of a semiconductor thin film having uniform physical properties and good crystallinity is obtained.

At this time, the irradiation area 17 of the laser light C is
It is included in the irradiation region 18 of the strong light B. This laser light C
The oscillation wavelength of XeCl excimer laser was 308 nm, the energy output was 700 mJ / pulse, the oscillation time (pulse width) was about 50 ns, and the oscillation frequency was 300 Hz. The beam shape is 300 × 0.5 mm and the energy density on the substrate surface is about 300 mJ / cm ² .

As a method of scanning the irradiation substrate 12, the tray 11 is moved at a speed of 15 mm / sec in the left and right direction of the arrow A.
Are operated to sequentially scan the laser light C.

Further, for the strong light B, the UV lamp 1
The surface of the irradiation substrate 12 is heated by irradiation with a capillary type high pressure mercury lamp 3a before irradiation with the laser beam C so that the irradiation area is larger than the substrate area within a range of about 350 mm □. Was set to a predetermined temperature of about 400 ° C. Further, as shown in FIG. 3c, the irradiation time of the strong light B indicated by the dotted line is longer than the oscillation irradiation time of the laser light C indicated by the solid line. As a result, it becomes possible to perform an annealing to obtain a semiconductor thin film crystal layer having uniform physical properties and good crystallinity. The intense light B may be irradiated for a certain period of time even after the irradiation of the laser light C is completed. Actual laser light C
The optimum value of the irradiation conditions of No. ² differs depending on the film thickness and the like, but the energy density of the laser light C is 200 to 400 mJ / cm ²
The surface temperature of the irradiation substrate 12 by the strong light B is about 200
Set to about 500 ° C.

As described above, the amorphous silicon film 2 deposited on the insulating substrate 21 by using the heating mechanism of the laser annealing apparatus in the method of manufacturing a semiconductor thin film crystal layer of the present invention.
3 is continuously irradiated with the laser light C, and at the same time as the laser light C, strong light larger than the area of the insulating substrate 11, longer than the oscillation irradiation time of the laser light C, and lower than the irradiation energy density of the laser light C. B is irradiated to polycrystallize the non-single-crystal semiconductor film.

That is, in the present invention, a laser beam of a semiconductor thin film for irradiating the amorphous silicon film 23 with a laser beam C of a high-power energy beam continuously and sequentially to enlarge the crystal grain size of the film or to single crystallize the film. In the light irradiation method and the laser annealing apparatus, strong light B that is larger than the substrate area at the same time as the laser light C, is longer than the irradiation time of the laser light C, and is lower than the irradiation energy density of the laser light C, And a heating method using a laser annealing apparatus for obtaining a semiconductor thin film crystal layer having uniform physical properties and good crystallinity by crystallizing the amorphous silicon film 23 which is a single crystal semiconductor film by melt recrystallization. ing.

With the above structure, since the entire irradiation substrate 12 is heated by the strong light B, the tray scanning mechanism of the laser annealing apparatus does not need to have a heating mechanism as in the conventional case, but only the scanning mechanism needs to be provided. Since it is good, scanning accuracy equivalent to that of an exposure device for patterning a semiconductor thin film is possible. In addition, since the whole substrate is heated at once by irradiating the area larger than the irradiation substrate 12 with the strong light B, the substrate temperature is excellent in uniformity, and in terms of throughput, there is no need to preheat the tray, which is advantageous. is there. In addition, since the optical system can be fixed by providing the scanning mechanism on the tray of the substrate, it becomes possible to form the laser light with good shape, energy uniformity, and in-beam uniformity.

In this embodiment, the light source of the strong light B is the ultraviolet (UV) lamp 13a, but laser light, infrared lamp, visible light lamp, etc. are conceivable, and the irradiation energy density of the entire substrate is laser light. It suffices that strong light B lower than the irradiation energy density of C can be irradiated. Further, it is possible to apply the present invention to the activation of the ion-implanted layer and make the annealed region uniform.

Further, in the present embodiment, the oscillation wavelength of the laser light is set to 308 nm of the XeCl excimer laser and the oscillation wavelength of the laser light is set to 400 nm or less. This is due to the absorption coefficient of the semiconductor film, for example, the semiconductor silicon film. It is necessary that the wavelengths are matched, and in order to efficiently heat the semiconductor silicon film, the oscillation wavelength is 4
This is because it is necessary to irradiate ultraviolet rays having a wavelength of 00 nm or less. For example, the wavelength of light from a halogen lamp is 1μ
In the case of a wide wavelength having a peak at about m, most of this light (probably 90% or more) passes through the semiconductor silicon film, and the semiconductor silicon film is not sufficiently heated.

[0041]

As described above, according to the present invention, since the substrate and the entire non-single-crystal semiconductor film are heated by strong light, the tray scanning mechanism of the substrate needs to have a heating mechanism as in the conventional case. However, it is sufficient to provide only the scanning mechanism, and the dimensional accuracy in scanning can be improved. Therefore, the dimensional accuracy of the overlapping portion of the laser irradiation is improved and the uniform heating eliminates variations in the physical properties of the semiconductor thin film in the annealed region. As a result, a uniform and good-quality crystal layer of a semiconductor thin film can be formed, and for example, an active matrix substrate having a high definition and a large area can have TFT characteristics practically sufficient.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a method for manufacturing a semiconductor thin film in one embodiment of the present invention, which is a configuration diagram of a laser annealing apparatus.

FIG. 2 is a sectional view of an irradiation substrate 12 of FIG.

FIG. 3 is a diagram showing an outline of a method for manufacturing a semiconductor thin film in one embodiment of the present invention, in which a is a top view of an apparatus including a substrate for irradiating laser light and strong light, and b is laser light and strong light. FIG. 3 is a side view of an apparatus including a substrate for irradiating with, and c is a diagram showing a relationship between time and energy output of laser light and intense light.

FIG. 4 is a diagram showing an outline of a conventional method for manufacturing a semiconductor thin film, in which a is a top view of an apparatus including a substrate for irradiating laser light, and b is a side view of an apparatus including a substrate for irradiating laser light.
c is a diagram showing a relationship between an oscillation time of laser light and energy output, and d is a top view of an apparatus including a substrate when laser light is irradiated.

[Explanation of symbols]

 12 irradiation substrate 17 irradiation area of laser light C 18 irradiation area of strong light B 23 amorphous silicon film (non-single crystal semiconductor film) B strong light C laser light

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/336

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor thin film in which a non-single-crystal semiconductor film is annealed by laser light to be polycrystallized, wherein a heating step of irradiating the entire non-single-crystal semiconductor film with intense light to heat it, and the heating step. After that, simultaneously with the intense light on the non-single-crystal semiconductor film, the laser light is irradiated in the intense light irradiation region to polycrystallize the non-single-crystal semiconductor film, Production method. 2. A method of manufacturing a semiconductor thin film in which a non-single-crystal semiconductor film is annealed by laser light to be polycrystallized, wherein the irradiation energy density is lower than the irradiation energy density of the laser light over the entire non-single-crystal semiconductor film. A heating step of irradiating with intense light and heating, and after the heating step, the non-single-crystal semiconductor film is irradiated with the laser light at the same time as the intense light in the intense light irradiation region. A method of manufacturing a semiconductor thin film, comprising a polycrystallization step of performing polycrystallization. 3. A semiconductor thin film in which a non-single-crystal semiconductor film is formed on an insulating substrate or an insulating film provided on the insulating substrate, and the non-single-crystal semiconductor film is annealed by laser light to be polycrystallized. In the manufacturing method of 1., a heating step of irradiating and heating with intense light having an irradiation energy density lower than the irradiation energy density of the laser light so that the irradiation area is larger than that of the insulating substrate, and after the heating step A method of manufacturing a semiconductor thin film, comprising: a polycrystallizing step of irradiating the non-single crystal semiconductor film with the intense light at the same time as the intense light irradiation with the laser light to polycrystallize the non-single crystal semiconductor film. . 4. The method for manufacturing a semiconductor thin film according to claim 1, 2 or 3, wherein the intense light irradiation time is longer than the laser light irradiation time. 5. The laser light having a wavelength of 400 nm
The method for producing a semiconductor thin film according to claim 1, wherein the following ultraviolet rays are used.