JP2002141302A - Optical system for laser annealing and laser annealing apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system that controls a laser light irradiated profile to form a thin film having excellent crystallization necessary for manufacturing a high-performance thin film transistor in a laser heat treatment. SOLUTION: The optical system for irradiating a silicon film with a rectangular beam has an intensity distribution forming unit for forming the cross-sectional intensity distribution of a laser beam irradiated from a laser oscillator, and an intensity distribution forming unit for forming a rectangular beam on an amorphous or polycrystalline silicon film. In the direction of the short side of the rectangular beam, the laser beam is condensed on the amorphous or polycrystalline silicon film by a condenser and in the direction of the long side, a part of laser beams are reflected plural times and then superposed and applied directly to the amorphous or polycrystalline silicon film. This can heat the silicon film uniformly in the direction of thickness, can produce a thin film having excellent crystallization necessary for manufacturing a high- performance thin film transistor in the laser heat treatment, and can reduce the number of optical components and thus size and cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for laser heat treatment for forming an amorphous silicon film formed on a substrate into a polycrystalline silicon film having excellent crystallinity, and an apparatus using the same. About.

[0002]

2. Description of the Related Art A pixel portion of a liquid crystal panel uses a polycrystalline silicon film formed on a glass or quartz substrate to form an image by switching thin film transistors formed on the polycrystalline silicon film. I have. Such a polycrystalline silicon film is usually formed by first forming an amorphous silicon film on a substrate, heating the polycrystalline silicon film to form a polycrystalline silicon film, and using the polycrystalline silicon film as a substrate. A pixel transistor circuit is formed. In a conventional liquid crystal panel, driver circuits for driving these pixel transistors are independently arranged outside. However, it is expected that the driver circuits can be simultaneously configured close to the pixel transistors. If this is the case, there will be significant advantages in terms of liquid crystal panel manufacturing cost and reliability.

However, since the crystallinity of the silicon film constituting the active layer of the transistor is poor, the performance of the thin film transistor is low, as represented by the mobility, and the production of an integrated circuit that requires high speed and high functionality is required. It was difficult. Therefore, in order to realize a high mobility thin film transistor,
As a method for improving the crystallinity of a silicon film, a laser heat treatment for increasing the crystallinity by irradiating a laser to a silicon film formed on a substrate has been performed.

[0004] The relationship between the crystallinity of the silicon film and the mobility of the thin film transistor is explained as follows. The silicon film obtained by the laser heat treatment is generally polycrystalline, but the crystal grain boundaries of the polycrystal are composed of defects, and these defects scatter carriers in the thin film transistor active layer and hinder movement. Therefore, in order to increase the mobility of the thin film transistor, it is important to reduce the number of times the carrier crosses the crystal grain boundary during the movement of the active layer, and thus it is necessary to reduce the crystal defect density. The purpose of laser heat treatment is to form a polycrystalline silicon film having a large crystal grain size and few crystal defects at crystal grain boundaries.

[0005]

The present inventors have proposed an optical system for laser heat treatment in Japanese Patent Application No. 11-179233, which uses a laser beam from a laser oscillator by an optical system. The irradiation laser beam shape is linearly distributed on the silicon film surface, and the linear beam is swept relatively on the silicon film in a direction orthogonal to the beam.In the process of moving the linear beam, The beam-irradiated portion of the silicon film is once melted linearly, and the melted portion is cooled as the beam-irradiated portion moves away to crystallize the silicon film into coarse grains.

FIG. 6 shows a schematic diagram of this optical system. A laser beam 2 emitted from a laser oscillator 1 passes through an intensity distribution shaping means 30 and a beam shape shaping means 40 and is placed on a substrate 50. The silicon film 5 is irradiated.

In this optical system, a laser beam 2 emitted from a laser oscillator 1 has a beam shape PA on an entrance surface A of an intensity distribution shaping means 30, for example, as shown in FIG. The intensity distribution XA in the x direction in the A plane and the intensity distribution YA in the y direction in the A plane are substantially Gaussian. The intensity distribution shaping means 30 includes, for example,
The intensity distribution in the x direction is stored as a Gaussian distribution, and only the intensity distribution in the y direction is smoothed. For this reason, the beam shape PB of the laser beam on the exit surface B of the intensity distribution shaping means 30 is converted into a substantially rectangular shape, and the intensity distribution XB in the x direction on the B surface is obtained.
The intensity distribution XA in the x direction on the surface A is maintained, and the intensity distribution YB in the y direction on the surface B is shaped almost like a top hat distribution. This laser beam is applied to
The magnification in the x direction and the y direction is adjusted by 0, and the silicon film 5 is irradiated with a rectangular beam shape and heated.

Here, the y direction is taken in the longitudinal direction of the irradiation laser beam which is rectangular or linear on the upper surface C of the silicon film, and x
Although the direction is taken in the narrow direction of the irradiation laser beam, the intensity distribution XC in the x direction on the C plane becomes a shape in which the intensity distribution XA in the x direction on the A plane is reduced, and the properties such as the directivity of the oscillation laser beam 2 are reduced. On the other hand, the intensity distribution YC in the y direction on the C plane becomes a substantially uniform distribution.

The object to be irradiated with the laser is an amorphous silicon film formed by depositing a silicon oxide film as a base film 51 on a substrate 50 made of glass or the like and forming the silicon oxide film thereon. The substrate 50 is mounted and fixed on a moving stage, and performs laser irradiation while moving in the narrow direction of the linear irradiation laser beam, that is, in the x direction. When the amorphous or polycrystalline silicon film 5 is irradiated with laser light, the amorphous or polycrystalline silicon film 5
Is absorbed by the laser beam, heated and melted into a rectangle.
At this time, the longitudinal direction of the irradiation laser beam, that is, the y direction is
Since the intensity distribution of the laser beam 2 is uniform, no temperature gradient occurs,
A temperature gradient occurs only in the x direction. When the melted portion is crystallized, the crystal grows in accordance with the temperature gradient, so that the crystal grows in one direction in the moving direction of the substrate 50, that is, in the x direction, and large crystal grains having a crystal grain size of about several μm are formed.

In the case of performing heat treatment using a rectangular beam in the heat treatment using a laser as a light source, the profile in the width direction greatly affects the recrystallization growth process, and the distribution in the longitudinal direction affects the region where the crystal grows. In order to manufacture a thin film transistor excellent in the above, an appropriate profile must be selected. However, in the conventional optical system for forming a linear beam, after shaping the beam intensity distribution, the shape of the irradiation laser beam is shaped using a transfer optical system or the like. The area has increased.

The present invention has been made in order to solve such problems, and provides a laser optical system capable of controlling a laser beam irradiation profile in order to form a thin film having excellent crystallinity in a laser heat treatment method. Another object of the present invention is to provide a small and high-performance laser annealing apparatus.

[0012]

According to the laser optical system of the present invention, in order to irradiate a laser beam onto the upper surface of a semiconductor film in the form of a rectangular laser beam, the intensity distribution shaping means must be perpendicular to the laser beam optical axis. A condensing lens for condensing a laser beam on the semiconductor film in one direction in a plane, and overlapping after reflecting a part of the laser beam a plurality of times in a direction perpendicular to the one direction in the vertical plane And a waveguide that directly irradiates the semiconductor film. The semiconductor film is heated and melted and polycrystallized by scanning the surface of the semiconductor film with an irradiation laser beam in the one direction.

The intensity distribution shaping means has a cylindrical lens for converging light in the above-mentioned one direction, ie, the x direction, and a reflecting surface having a reflection surface which repeats reflection of the laser beam from the cylindrical lens only in the above-mentioned orthogonal direction, ie, the y direction. An integrated wave path can be used.

By arranging a plurality of such intensity distribution shaping means and arranging a plurality of rectangular or linear irradiation laser beams in the longitudinal direction thereof, the irradiation area in one pass can be widened. In the present invention, a laser oscillator and a plurality of laser beams are each provided with an intensity distribution shaping means, and a plurality of irradiation laser beams are arranged on the substrate or the upper surface of the semiconductor film.

[0015] Preferably, the formed irradiation laser beams are arranged substantially straight in the longitudinal direction by a plurality of intensity distribution forming means. The plurality of irradiation laser beams may be arranged so that adjacent irradiation laser beams do not overlap with each other.

The laser optical system of the present invention is applied to a silicon film as a semiconductor film, so that it can be used as a silicon substrate for forming a thin film transistor used for a pixel portion of a liquid crystal display.

In the laser oscillator, 350 nm to 800 n
A device that emits a laser beam having an oscillation wavelength of m is preferable for uniform heating in the thickness direction of the silicon film. A harmonic of a solid-state laser is used as an oscillator for laser light having such a wavelength.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 This embodiment is
A cylindrical lens 32 as a condensing lens for the laser beam emitted from the laser oscillator 1;
And a waveguide 33 arranged on the front side of the cylindrical lens 32, and in combination with the laser oscillator 1, constitutes a laser optical system. In the laser optical system, when a heat treatment is used, a substrate 50 on which a silicon film to be processed is formed in advance is arranged on the front side of the waveguide 33 of the intensity distribution shaping means 30. The laser annealing apparatus is mounted and fixed on a (not shown), and allows either the stage or the laser optical system to relatively scan and move by a scanning mechanism.

FIG. 1 shows the intensity distribution shaping means 30. As shown in FIG. 1, a cylindrical lens is used as the condenser lens 32. The cylindrical lens is capable of condensing light on the optical axis side and has an axis (y) parallel to the y direction. A convex surface which is a cylindrical surface around (axis) is formed on one surface. The cylindrical lens focuses light only in the x direction. A cylindrical lens is placed on the entrance side of the waveguide, and this example is close.

As the other waveguide 33, a transparent solid block provided with a reflecting surface facing in the y direction in parallel or in a tapered shape can be used, and the block is formed of, for example, transparent glass. Is a total reflection surface of a transparent body or a mirror surface. Instead of a block, the waveguide 33 can also be a hollow body in which a pair of reflecting mirrors are arranged in space in parallel with the y direction, or a pair of reflecting mirrors are inclined or tapered.

Further, in this example, the strength distribution forming means 30
In addition, a diverging lens 34 (in this example, a concave lens) that diverges the beam from the laser oscillator 1 and expands the lens surface area of the condenser lens 32 is located behind the diverging lens 34 (incident side).
Are located in

In such an intensity distribution shaping means, as shown in FIG.
The light transmitted through the diverging lens 34 is diverged toward the condenser lens 32, and the laser light incident on the cylindrical lens, which is the condenser lens 32, is refracted by the curved cylindrical surface in the x direction. In 1 (A), the light converges in the x direction,
Passing through the space or block transparent body inside the waveguide 33,
In this example, the light is almost condensed on the surface of the silicon film 5. However, in the other y direction, as shown in FIG. 1B, the divergent laser light entering from the diverging lens 34
The second cylindrical lens does not refract so much,
And a part of the incident light is between the reflection surfaces of the waveguide 33,
It is synthesized while repeating reflection, and y
The directional component has a uniform and long intensity distribution. The irradiation laser beam projected on the surface of the silicon film 5 in this way is, as shown in FIG.
Above, the irradiation laser beam shape is rectangular or linear, shows a uniform intensity distribution YC in the y direction, and in the x direction,
A steep peak-like intensity distribution XC is shown.

The optical system of the present invention irradiates an amorphous or crystalline silicon film to achieve coarse and sound crystallization. Such a silicon film is preferably formed on a substrate. A coated amorphous silicon coating can be used. For example, LPCVD (Low Pressure Chemical Vapor)
The film can be formed by a por deposition method. For such a silicon film, a silicon oxide film having a thickness of, for example, about 200 nm is formed in advance as a base film 51 on a quartz glass substrate 50 by a CVD (Chemical Vapor Deposition) method, and a thickness of about 50 nm is formed on the base layer. Molded into

The substrate 50 is mounted and fixed on a stage. The stage is provided with a scanning mechanism capable of scanning and is movable in one direction or two orthogonal directions. The laser irradiation is performed while moving the irradiation laser beam in the narrow direction, that is, the x direction, on the silicon film on the substrate.

In the use of the optical system of the present invention, when the amorphous or polycrystalline silicon film 5 is irradiated with laser light,
The silicon film 5 absorbs the laser beam and is heated at the irradiation site corresponding to the rectangular shape of the irradiation laser beam, and is melted once the temperature exceeds the melting point.

In the present invention, the irradiation laser beam having a rectangular or linear intensity distribution is irradiated onto the silicon film so that a molten portion is formed. Then, the irradiation laser beam is applied in the narrow direction (x Moving in the direction), the silicon film at the heated melt site cools sequentially as the irradiated laser beam moves away, thus creating a temperature gradient in the scan direction at the melt site. At this time, the irradiation laser beam has a uniform intensity distribution in the longitudinal direction, that is, the y direction, so that substantially no temperature gradient occurs in the y direction.
A temperature gradient occurs only in the x direction. When the melted portion crystallizes, the crystal grows according to this temperature gradient, so that it becomes one-dimensional growth (unidirectional growth) in the moving direction of the substrate 50, that is, in the x-direction. Crystal grains as large as about μm are formed.

The process of preferential growth in the x direction is greatly affected by the temperature distribution formed in the x direction in the amorphous or polycrystalline silicon film 5, ie, in the width direction of the irradiated rectangular beam. Greatly influenced by the intensity distribution of The heat introduced into the silicon film 5 by the laser beam irradiation is uniformly dissipated to the substrate. That is, the temperature distribution in the x direction in the amorphous or polycrystalline silicon film 5 decreases uniformly. Therefore, the crystal grows laterally from a portion where the temperature first falls below the melting point to a portion where the temperature falls below the melting point first. This crystal growth is stopped by microcrystals grown by the generation of natural nuclei in the process of lowering the temperature, and the crystal growth in the x direction is stopped. In other words, it is only necessary that the crystal grains grow as long as possible until the time when the natural nucleation occurs. For that purpose, a high crystal growth rate is required. Generally, the crystal growth rate v in a certain minute region is represented by v = kΔT / Δx. Here, k is a rate constant, ΔT is a temperature difference in a minute region, and Δx is a width of the minute region. In other words, in the x direction in the silicon film, if the temperature distribution in a region having a temperature equal to or higher than the melting point has a steep gradient, the crystal growth rate is high, and as a result, a polycrystal having a large crystal grain size is generated in the silicon film. In addition, a thin film having excellent crystallinity can be formed and can be used for a silicon substrate for a high-performance thin film transistor.

In the optical system shown in this embodiment, since the beam intensity distribution in the narrow direction of the irradiation laser beam preserves the properties such as the directivity of the oscillation laser beam 2, the irradiation laser beam is emitted by the oscillation laser beam. Light can be collected to the limit limited by the properties of the light 2, a maximum intensity gradient can be obtained on the silicon film 5, and an arbitrary intensity distribution equal to or less than the maximum intensity gradient can be obtained. It is possible to control the temperature distribution in the x direction.

The laser oscillator according to the present invention has a wavelength of 320 nm.
A laser having an oscillation wavelength between ８００800 nm is used. Laser light having a wavelength of 320 nm to 800 nm particularly has a relatively small absorption coefficient with respect to amorphous silicon. Therefore, the silicon film is substantially uniformly heated in the film thickness direction to the inside by penetration of the laser light in the film thickness direction. The lateral temperature distribution in the silicon film generated by the laser irradiation is formed only in the x direction. Therefore, the beam portion having a certain intensity or higher in the amorphous or polycrystalline silicon film 5 as the film material on the substrate is melted in the entire depth direction. Using the laser light in the above wavelength range, the thickness direction of the silicon film can be uniformly heated,
A thin film having excellent crystallinity can be obtained.

As a laser in this wavelength range, a solid-state laser harmonic generation source can be used. This includes the second harmonic (532 nm) and the third harmonic (355 nm) of the Nd: YAG laser.
nm), the second harmonic of the Nd: YLF laser (524n
m), the third harmonic (349 nm), or Yb: YA
The second harmonic (515 nm) and the third harmonic (3
44 nm). Ti: A fundamental wave or a second harmonic of a sapphire laser may be used. By using a solid-state laser, laser light having an oscillation wavelength between 320 nm and 800 nm can be efficiently obtained with a compact device, and stable operation can be performed for a long time.

Embodiment 2 FIG. 2 shows an example in which the condensing lens 32 and the waveguide 33 shown in the first embodiment are formed as an integral part of the intensity distribution shaping means 30. This example
The intensity distribution molding means 30 uses a transparent block,
The incident-side end face 35 is formed of a partial cylindrical surface around the y-axis, and the side part includes a pair of parallel or tapered reflecting surfaces 34, 34 facing in the y-direction.
It is a plane. In this example, the intensity distribution forming means 30
However, the irradiation end face is arranged close to the silicon film on the substrate.

This optical system is similar to that of the first embodiment except that the intensity distribution shaping means 30 is integrated. The effect of the irradiation laser beam on the amorphous or polycrystalline silicon film 5 is the same as that described in the first embodiment. By integrating, the number of optical components can be reduced, the size and cost can be reduced, and the adjustment of the optical system becomes easy.

Embodiment 3 A laser optical system including the laser oscillator 1 of the optical system described in the first embodiment and the intensity distribution shaping means 30 is regarded as one set, and a plurality of sets of laser optical systems can be configured in parallel. This makes it possible to extend the intensity distribution of the irradiation laser beam without changing the irradiation energy density of the irradiation laser beam of the rectangular shape, thereby extending the length of the irradiation laser beam.

FIG. 3 shows this laser optical system. In this example, three sets of laser optical systems are used, and the respective laser beams 2a, 2b, 2c emitted from the laser oscillators 1a, 1b, 1c are used. Are divergent optical systems 34, respectively.
a, 34b, 34c, strength distribution forming means 30a, 30
b, 30c and an amorphous or polycrystalline silicon film 5
Irradiated on top. The effect of each irradiation laser beam on the amorphous or polycrystalline silicon film 5 is the same as that described in the first embodiment, but in this embodiment, each irradiation laser beam has a rectangular or linear shape. It has an intensity distribution and can irradiate a silicon film by arranging multiple irradiation laser beams in the longitudinal direction of the beam. The length of the melted portion is formed. The melted portion gradually cools and solidifies as the irradiated laser beam moves in the narrow direction (in the x-direction) and moves away, thus causing a temperature gradient in the scan direction.
At this time, the irradiation laser beams arranged in a plurality of longitudinal directions can have a uniform intensity distribution in the longitudinal direction, that is, the y direction, and therefore, there is substantially no temperature gradient in the y direction. , A temperature gradient occurs only in the x direction. When the melted portion crystallizes, the crystal grows according to this temperature gradient, so that it becomes one-dimensional growth (unidirectional growth) in the moving direction of the substrate 50, that is, in the x-direction. Large crystal grains of about μm to about several tens μm are formed.

By arranging a plurality of sets of optical systems in parallel, a large area of laser light can be irradiated on the substrate 50 in a single pass, which has the advantage of improving productivity. .

Embodiment 4 FIG. FIGS. 4 and 5 show the arrangement of the irradiation laser beam on the amorphous or polycrystalline silicon film 5 by the laser optical system constituted by the parallel arrangement of the plurality of optical systems shown in the fourth embodiment.

As shown in FIG. 3 of the third embodiment, the intensity distribution shaping means 30 is formed by using a plurality of sets of optical systems.
Irradiation laser beam 8a on substrate 50 from a to 30c
To 8c are arranged in a straight line in the beam longitudinal direction (y direction). In the intensity distribution shaping means 30 used in the present embodiment, the irradiation end face 36 of the waveguide 33 is spaced apart from the amorphous or polycrystalline silicon film 5 without being in close contact with the amorphous film or the polycrystalline silicon film 5. Of the intensity distribution becomes gentle. Therefore, the peripheral portion of the irradiation laser beam (for example, 8a) is disposed so as to appropriately overlap with the peripheral portion of the irradiation laser beam (for example, 8b) from another adjacent intensity distribution shaping means, and a plurality of intensity distributions are provided. Forming means 3
Laser light emitted from Oa to 30c can be synthesized almost uniformly in the y direction on the amorphous or polycrystalline silicon film 5.

In FIG. 5, the irradiation laser beams 8a to 8c on the silicon film on the substrate 50 can be alternately arranged so as not to overlap. That is, in the irradiation range on the silicon film where the irradiation laser beam is moved in the x direction, the intensity distribution of the peripheral portion 82 of the irradiation laser beam (for example, 8b) and the uniformity of the irradiation laser beams 8a and 8c adjacent thereto are uniform. The region 81 of the intensity distribution is arranged so as to be appropriately overlapped, and the region 81 of the uniform intensity distribution in the y direction of the irradiation beam is overlapped on the irradiation path in the x direction. Under these conditions, if the irradiation laser beams adjacent to each other are not overlapped and are close to each other, the heat input to the silicon film 5 can be substantially uniformized in the y direction, and the unidirectionality in the x direction can be improved. Crystal growth can be ensured,
In one pass, a wide crystallization zone corresponding to the irradiation laser beam width is obtained. Further, it is possible to prevent the silicon film 5 from being damaged due to the high laser intensity due to the overlapping of the laser beams.

The staggering of the irradiation laser beams 8a to 8c can be realized by, for example, slightly shifting the optical axes of the laser beams 2a to 2c in the x direction in FIG.

Embodiment 5 The laser annealing apparatus includes a stage for fixedly mounting the substrate on which the silicon film is formed on the laser optical system, and a scanning mechanism for scanning the laser optical system or the stage. The scanning mechanism preferably scans the stage in two directions, x and y, and irradiates a rectangular laser beam to the silicon film of the substrate mounted on the scanning stage from a fixed laser optical system, and scans the silicon with the scanning stage. Scan the membrane. The scanning moves in the x direction of the irradiation laser beam to form a crystallization zone of a silicon film having a width of the irradiation laser beam,
The irradiation laser beam is swept across the required surface area of the silicon film at intervals of the width to prepare a polycrystalline silicon film having large crystal grains.

[0041]

According to the laser optical system of the present invention, the intensity distribution for forming a cross-sectional intensity distribution of a laser beam emitted from a laser oscillator to form an irradiation laser beam shape irradiated on a semiconductor film on a substrate into a rectangular shape. A laser optical system including shaping means, wherein the intensity distribution shaping means focuses the laser beam on the semiconductor film in one direction in a plane perpendicular to the laser beam optical axis; A waveguide that reflects a part of the laser beam a plurality of times in the orthogonal direction orthogonal to one direction, and then superimposes and directly irradiates the semiconductor film directly onto the semiconductor film, so that the irradiation has a uniform intensity distribution in the longitudinal direction. A laser beam can be realized with a small number of optical components, which is effective for reducing the size and cost of a laser optical system.

In the laser annealing optics, if the intensity distribution shaping means is constituted integrally by the cylindrical lens and the waveguide,
The number of optical components can be reduced, and the size and cost can be further reduced.

If the laser optical system is constituted by the same number of intensity distribution shaping means corresponding to a plurality of laser oscillators, the intensity distribution shaping means are arranged in the longitudinal direction, and one scanning pass can be performed.
Laser light irradiation of a large area becomes possible, and productivity can be improved.

Further, by a plurality of intensity distribution forming means,
By arranging a plurality of irradiation laser beams almost in a straight line in the longitudinal direction, it is possible to irradiate a large area of laser light in one scanning pass, and obtain a uniform irradiation light intensity in the longitudinal direction with a wide irradiation laser beam. As a result, a uniform polycrystalline semiconductor film can be formed, and a thin film having excellent crystallinity required for manufacturing a high-performance thin film transistor can be formed.

Further, since the irradiation laser beams from the plurality of intensity distribution shaping means are configured not to overlap,
In a single scanning pass, laser light irradiation of a large area becomes possible, wide productivity can be improved, and a substantially uniform irradiation light intensity can be obtained in the y direction with a wide irradiation laser beam, and a uniform polycrystalline semiconductor film can be obtained. Can be formed, and a thin film having excellent crystallinity required for manufacturing a high-performance thin film transistor can be formed.

The laser optical system is applied to a silicon film as a semiconductor film, so that it can be used as a silicon substrate for forming a high-speed thin film transistor used for a pixel portion of a liquid crystal display.

Further, the oscillation wavelength of the laser oscillator is set to 35
When the thickness is in the range of 0 nm to 800 nm, in particular, the thickness direction of the amorphous silicon film can be uniformly heated, and a thin film having excellent crystallinity required for manufacturing a high-performance thin film transistor by a laser heat treatment method can be obtained. Can be

If a harmonic of a solid-state laser is used for the laser oscillator, the laser oscillator can be made compact and the thickness direction of the amorphous or polycrystalline silicon film can be uniformly heated. The thin film having excellent crystallinity required for manufacturing the thin film transistor of the above is obtained.

In the laser annealing apparatus of the present invention, the laser optical system is combined with a laser oscillator and a stage for mounting and fixing a substrate, and the irradiation laser beam is irradiated on a silicon substrate by relative movement of the stage or the optical system. Since the silicon film is polycrystallized by scanning the irradiation laser beam in one direction on the film surface, a polycrystallized silicon film having large crystal grains and a low lattice defect density is obtained. The device can be manufactured and used, and the device can be realized with a small number of optical components having a small number of optical systems, and the size and cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view (A, B) of a laser optical system according to an embodiment of the present invention, an intensity distribution (C) of a laser beam from a laser oscillator, and an intensity of an irradiation laser beam on a silicon film. The distribution (D) is shown.

FIG. 2 is a view similar to FIG. 1 of a laser optical system according to another embodiment of the present invention.

FIG. 3 is a sectional view of a laser optical system according to another embodiment of the present invention.

FIG. 4 shows an intensity distribution of an irradiation laser beam on a silicon film by a laser optical system according to an embodiment of the present invention.

FIG. 5 shows an intensity distribution of an irradiation laser beam on a silicon film by a laser optical system according to another embodiment of the present invention.

FIG. 6 is a schematic sectional view (A) of the laser optical system, a partial sectional view thereof (B), an intensity distribution (C) of a laser beam from a laser oscillator, and an intensity distribution (D) at an intensity distribution forming means outlet. ) And the intensity distribution (E) of the irradiation laser beam on the silicon film.

[Explanation of symbols]

Reference Signs List 1 laser oscillator, 2 laser beam, 30 intensity distribution shaping means, 32 condenser lens, 33 waveguide, 34 divergence optical system, 5 silicon film, 50 substrate.

Continuation of the front page (72) Inventor Yukio Sato 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Junichi Nishisaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric In-house F term (reference) 5F052 AA02 BA01 BA07 BA18 BB02 BB07 CA07 DA02 DB02 5F072 AB01 AB20 KK12 QQ02 RR03 SS06 YY08 5F110 AA01 AA30 BB02 DD03 DD13 GG02 GG13 GG25 GG47 PP03 PP04 PP05 PP06 PP07 PP23

Claims (9)

[Claims] An intensity for shaping an intensity distribution of a laser beam emitted from a laser oscillator to irradiate an amorphous or polycrystalline semiconductor film formed on a substrate with an irradiation laser beam having a rectangular shape. A laser optical system including a distribution shaping means, wherein the intensity distribution shaping means focuses the laser beam on the semiconductor film in one direction in a plane perpendicular to the laser beam optical axis; A waveguide in which a part of the laser beam is reflected a plurality of times in a direction orthogonal to the one direction and then superimposed and directly irradiated onto the semiconductor film, and the laser beam is irradiated on the surface of the semiconductor film in the one direction. A laser optical system for laser annealing in which a semiconductor film is polycrystallized by scanning in a laser beam. 2. The laser optical system according to claim 1, wherein the intensity distribution shaping means includes a cylindrical lens as a condenser lens, and the waveguide is integrated with the cylindrical lens. 3. An optical system comprising: a plurality of laser oscillators;
A plurality of intensity distribution shaping means corresponding to the laser oscillator;
3. The laser optical system according to claim 1, further comprising: a plurality of irradiation laser beams having a rectangular shape from the plurality of intensity distribution shaping units, which are arranged in a longitudinal direction of the irradiation laser beams. 4. The laser optical system according to claim 3, wherein said plurality of irradiation laser beams are arranged substantially in a line in said longitudinal direction. 5. The laser optical system according to claim 3, wherein the plurality of irradiation laser beams are arranged so that adjacent irradiation laser beams do not overlap with each other. 6. The laser optical system according to claim 1, wherein the semiconductor film is a silicon film. 7. The laser oscillator has a wavelength of 330 nm to 800 n.
A laser optical system comprising the laser optical system according to any one of claims 1 to 6, wherein the laser optical system is a pulsed laser oscillator having an oscillation wavelength between m. 8. The laser optical system according to claim 7, wherein the laser oscillator is a harmonic of a solid-state laser. 9. A laser optical system and a laser oscillator according to claim 1; and a stage for mounting and fixing the substrate, wherein the irradiation laser beam is moved by relative movement of the stage or the optical system. A laser annealing apparatus that scans the surface of a silicon film on a substrate with an irradiation laser beam in one direction to polycrystallize the silicon film.