JP2004134785A - Beam homogenizer, laser irradiator and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein structural problems and manufacturing accuracy of a cylindrical lens arrays constituting an optical system cause ununiformity of the energy distribution of the beam spot on the surface to be irradiated. <P>SOLUTION: In an optical system for forming a rectangular shaped beam spot, the optical system for uniformizing the energy distribution in the direction of the short side of the rectangular shaped beam spot on the surface to be irradiated is replaces by an optical waveguide. The optical waveguide is a circuit, having the ability to seal irradiated light in a fixed region, and to guide the flow of energy, in parallel with the axis of a path and transmit it. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention belongs to the technical field of a beam homogenizer that homogenizes a beam spot on a surface to be irradiated in a specific region. In addition, the present invention belongs to the technical field of a laser irradiation device that irradiates the beam spot onto the irradiation surface. Note that a semiconductor device refers to a display device such as a liquid crystal display device or an electroluminescence (EL) display device, an electro-optical device, and an electric appliance, and the present invention belongs to a technical field of a method for manufacturing the semiconductor device.

In recent years, an amorphous semiconductor film or a crystalline semiconductor film (a semiconductor film which is not a single crystal but has a crystallinity such as polycrystal or microcrystal) formed on an insulating substrate such as glass, that is, a non-single-crystal semiconductor film On the other hand, a technique of performing laser annealing to crystallize or improve crystallinity has been widely studied. As the semiconductor film, a silicon film is often used.

Glass substrates are inexpensive, have good workability, and have the advantage that large-area substrates can be easily manufactured, as compared to quartz substrates that have been often used in the past. For this reason, the above research has been actively conducted. A laser is preferably used for crystallization because the melting point of the glass substrate is low. The laser can apply high energy only to the non-single-crystal semiconductor film without significantly changing the temperature of the substrate.

結晶 The crystalline silicon film formed by performing the laser annealing has high mobility. Therefore, a thin film transistor (TFT) using the crystalline silicon film is widely used, for example, a monolithic liquid crystal electro-optical device or the like in which TFTs for a pixel and a driving circuit are formed on one glass substrate. It is widely used. The crystalline silicon film is called a polycrystalline silicon film or a polycrystalline semiconductor film because it is made of many crystal grains.

In addition, a pulsed laser beam with a high output, such as an excimer laser, is processed by an optical system so that a square spot of several cm square or a linear shape with a length of 10 cm or more is formed on the surface to be irradiated. The method of performing laser annealing by scanning the irradiation position of the spot relatively to the irradiated surface is preferably used because it has good mass productivity and is industrially excellent.

In particular, when a linear beam spot is used, unlike when a point-like beam spot that needs to be scanned back and forth and right and left is used, irradiation is performed only in a direction perpendicular to the long axis direction of the linear beam spot. Since the entire surface can be irradiated with the laser beam, high mass productivity can be obtained. Here, the linear beam spot is a rectangular beam spot having a large aspect ratio. Scanning is performed in a direction perpendicular to the long axis direction because it is the most efficient scanning direction. Due to this high mass productivity, the use of a linear beam spot obtained by processing a beam spot of a pulsed excimer laser with an appropriate optical system is currently becoming the mainstream in laser annealing.

FIG. 10 shows an example of an optical system for processing the cross-sectional shape of the beam spot on the irradiated surface into a linear shape. The optical system shown in FIG. 10 is very general. The optical system not only converts the cross-sectional shape of the beam spot into a linear shape, but also at the same time, makes the energy of the beam spot uniform on the irradiated surface. In general, an optical system that equalizes beam energy is called a beam homogenizer. The optical system shown in FIG. 10 is also a beam homogenizer.

If an excimer laser, which is ultraviolet light, is used as a light source, the base material of the optical system may be made of, for example, quartz. This is because a high transmittance can be obtained. Further, it is preferable to use a coating having a transmittance of 99% or more with respect to the wavelength of the excimer laser to be used.

First, a side view of FIG. 10A will be described. The laser beam emitted from the laser oscillator 1201 divides the laser beam spot in one direction by cylindrical lens arrays 1202a and 1202b. The direction will be referred to as a vertical direction. The vertical direction is to bend in the direction of the light bent by the mirror when the mirror enters in the middle of the optical system. In this configuration, there are four divisions. These divided spots are once combined into one spot by the cylindrical lens 1204. The spot separated again is reflected by the mirror 1207, and then combined by the doublet cylindrical lens 1208 on the irradiated surface 1209 into one spot again. The doublet cylindrical lens refers to a lens composed of two cylindrical lenses. Thereby, the energy in the vertical direction of the linear beam spot is equalized, and the length in the vertical direction is determined.

Next, the top view of FIG. 10B will be described. The laser beam emitted from the laser oscillator 1201 divides the spot of the laser beam in a direction perpendicular to the longitudinal direction by a cylindrical lens array 1203. The perpendicular direction is referred to as a lateral direction. In the lateral direction, when a mirror enters in the middle of the optical system, the mirror bends in the direction of the light bent by the mirror. In this configuration, there are seven divisions. Thereafter, the spot divided into seven by the cylindrical lens 1205 is combined into one on the irradiated surface 1209. A broken line after the mirror 1207 is shown by a broken line, and the broken line shows an accurate optical path and the position of the lens and the irradiated surface when the mirror 1207 is not arranged. Thereby, the energy in the horizontal direction of the linear beam spot is made uniform, and the length in the horizontal direction is determined.

As described above, the cylindrical lens array 1202a, the cylindrical lens array 1202b, and the cylindrical lens array 1203 serve as lenses for dividing the spot of the laser beam. The number of divisions determines the uniformity of the energy distribution of the obtained linear beam spot.

The above lenses are made of synthetic quartz in order to support an excimer laser. Further, the surface is coated so as to transmit the excimer laser well, so that, for example, when a XeCl excimer laser is used, the transmittance of the excimer laser per lens becomes 99% or more.

The linear beam spot processed in the above configuration is irradiated while being superposed while gradually shifting the beam spot in the vertical direction of the beam spot. Then, for example, laser annealing can be performed on the entire surface of the non-single-crystal silicon film to crystallize or improve the crystallinity.

Next, a typical method for manufacturing a semiconductor film to be irradiated with a laser beam will be described.
First, a Corning 1737 substrate having a thickness of 0.7 mm and a 5-inch square was prepared as a substrate. An SiO ₂ film (silicon oxide film) having a thickness of 200 nm is formed on the substrate using a plasma CVD apparatus, and an amorphous silicon film (hereinafter referred to as an a-Si film) having a thickness of 50 nm is formed on the surface of the SiO ₂ film. ) Was formed. The substrate was heated in a nitrogen atmosphere at a temperature of 500 ° C. for one hour to reduce the hydrogen concentration in the film. This significantly improved the laser resistance of the film.

XeCl excimer laser (wavelength 308 nm, pulse width 30 ns) L4308 manufactured by Lambda was used as the laser oscillator. The laser oscillator emits a pulsed laser and has an ability to emit 670 mJ of energy per pulse. The spot size of the laser beam is 10 × 30 mm (both half width) at the exit of the laser beam. The exit of the laser beam is defined by a plane immediately after the laser beam is emitted from the laser oscillator and perpendicular to the traveling direction of the laser beam.

The shape of a laser beam generated by an excimer laser is generally rectangular, and falls within a range of 1 to 5 in terms of an aspect ratio. The intensity of the laser beam spot shows a Gaussian distribution that is stronger toward the center of the laser beam spot. The spot size of the laser beam is converted into a linear beam spot having a uniform energy distribution of 125 mm × 0.4 mm by the optical system shown in FIG.

When irradiating the above-mentioned semiconductor film with a laser beam, the overlapping pitch is most suitably about 1/10 of the short width (half width) of the linear beam spot. Thereby, the uniformity of crystallinity in the semiconductor film was improved. In the above example, since the half-width was 0.4 mm, the laser beam was irradiated at an excimer laser pulse frequency of 30 Hz and a scanning speed of 1.0 mm / s. At this time, the energy density on the surface to be irradiated with the laser beam was 450 mJ / cm ² . The method described so far is a very general method used for crystallizing a semiconductor film using a linear beam spot.

Some beam homogenizers use a reflecting mirror (for example, see Patent Document 1).

JP 2001-291681 A

The fabrication of the cylindrical lens array requires high processing accuracy.

The cylindrical lens array is a lens in which cylindrical lenses are arranged in a curvature direction. Here, the curvature direction is a direction perpendicular to the generatrix of the cylindrical surface of the cylindrical lens. In the cylindrical lens array, there is always a junction between the constituent cylindrical lenses. Since the joint does not have a curved surface as a cylindrical lens, light rays incident on the joint are transmitted without being affected by the cylindrical lens. The light beam that reaches the irradiation surface without receiving the above-mentioned action may be one of the causes of the non-uniformity of the energy distribution of the rectangular beam spot on the irradiation surface.

All the cylindrical lenses constituting the cylindrical lens array must be manufactured with the same precision. If the cylindrical lenses have different curvatures, the light beams split by the cylindrical lens array are not superimposed on the same position on the irradiated surface even by the condenser lens. That is, the energy distribution of the rectangular beam spot on the irradiated surface is not uniform.

The causes of the non-uniformity of the energy distribution of the beam spot on the irradiated surface are due to the structural problems and the manufacturing accuracy of the cylindrical lens array constituting the optical system. In other words, the cause of the non-uniformity is that not all the light rays incident on the homogenizer are incident on the portion where the lens action of the cylindrical lens array works, and the light rays split by the cylindrical lens array are all superimposed at the same position. Not in that.

Further, in the case where the energy distribution in the short side direction of the rectangle on the surface to be irradiated has a rectangular beam spot having a Gaussian distribution, the semiconductor film is scanned and crystallized by the method shown in the related art, A stripe pattern is noticeably formed on the semiconductor film in a direction perpendicular to the scanning direction. The stripe pattern is synchronized with the non-uniformity of the crystallinity of the semiconductor film. For example, it appears as a variation in electrical characteristics of a TFT formed using the semiconductor film, and a stripe pattern is displayed on a panel using the TFT.

It is considered that the stripe pattern is caused by instability of the output of the laser oscillator. Therefore, the laser oscillator is improved, and there is no method for eliminating the stripe pattern. However, if the energy distribution in the short side direction of the rectangular beam spot on the irradiation surface is uniform, the output instability of the laser oscillator is unstable. Are averaged out and the stripes become less noticeable. That is, by making the energy distribution in the short side direction of the rectangular beam spot uniform, it is possible to suppress the occurrence of a stripe pattern. Therefore, there is an increasing need for an optical system that makes the energy distribution uniform on the irradiated surface. Of course, a rectangular beam spot having a uniform energy distribution can be obtained using a cylindrical lens array, but a high-precision optical system was required.

According to the present invention, in the above-described optical system for forming a rectangular beam spot, the optical system that equalizes the energy distribution in the short side direction of the rectangular beam spot on the surface to be irradiated is replaced with an optical waveguide. An optical waveguide is a circuit that has the ability to confine emitted light in a certain area, guide the energy flow parallel to the axis of the path, and transmit the energy.

A method for solving the above-mentioned problem is presented below. FIG. 1 shows a schematic diagram of a method for solving the above-mentioned problem. The top view of FIG. 1A will be described. An optical waveguide 1302 having two opposing reflection surfaces and an irradiation surface 1303 are prepared, and light rays are incident from the left side of the drawing. The light rays when the optical waveguide 1302 is present are indicated by solid lines 1301a, and the light rays when the optical waveguide 1302 is not present are indicated by broken lines 1301b.

When the optical waveguide 1302 does not exist, as shown by a light ray 1301b, a light ray incident from the left side of the drawing reaches the areas of the irradiation surfaces 1303a, 1303b, and 1303c.

When the optical waveguide 1302 is present, as shown by the ray 1301a, the ray is reflected by the reflection surface of the optical waveguide 1302, and all reach the area of the irradiation surface 1303b. That is, when the optical waveguide 1302 is present, all the light beams that reach the regions of the irradiation surfaces 1303a and 1303c when the optical waveguide 1302 does not exist reach the region of the irradiation surface 1303b. Therefore, when a light beam enters the optical waveguide 1302, the incident light beam is split, and all the split light beams are superimposed on the irradiation surface 1303b at the same position. In this way, by dividing the incident light beam and superposing the divided light beams at the same position, the energy distribution of the light beam at the superimposed position is made uniform.

In general, the homogenizer increases the uniformity of the energy distribution at the position where the split light beams are superimposed as the number of split light beams increases. In the optical waveguide 1302, the number of light rays divided can be increased by increasing the number of reflections in the optical waveguide 1302. That is, the length of the two reflecting surfaces of the optical waveguide in the light incident direction may be increased. Also, the number of divisions can be increased by reducing the distance between the opposing reflecting surfaces. Desirably, the interval between the two reflecting surfaces is set to 10 mm or less. Thus, the length of the beam spot on the irradiated surface in the short side direction can be reduced to several mm or less.

According to another configuration of the present invention, in the above-described rectangular beam spot forming optical system, the optical system for equalizing the energy distribution in the short side direction of the rectangular beam spot on the irradiation surface is replaced with a light pipe. Things. A light pipe generally refers to a member that is drawn into a shape such as a conical shape, a pyramid shape, or a cylindrical shape that transmits light from one end to the other end by reflection.

A laser device disclosed by the present invention includes a homogenizer having the above-described optical waveguide or light pipe. The energy distribution in the short side direction of the rectangular beam spot on the surface to be illuminated can be made uniform by the optical waveguide or the light pipe having two opposing reflecting surfaces.

In addition, by using the above laser irradiation apparatus in manufacturing a semiconductor device, it is possible to suppress the occurrence of a stripe pattern due to energy non-uniformity of a beam spot on a surface to be irradiated, and to achieve uniformity in crystallinity of a semiconductor film. Can be improved.

The method of the present invention provides a laser beam, passes the laser beam through an optical waveguide, irradiates the semiconductor film with the laser beam that has passed therethrough, and irradiates the semiconductor film to crystallize the semiconductor film (here, the semiconductor The energy distribution of the laser beam on the surface of the film is homogenized by the optical waveguide).

A laser irradiation apparatus disclosed in the present invention has a beam homogenizer provided with an optical waveguide or a light pipe. The light guide or the light pipe has two reflecting surfaces facing each other, and can make the energy distribution in the rectangular short side direction uniform on the irradiated surface.

By using the optical system for forming a rectangular beam spot disclosed in the present invention, a rectangular beam spot having a uniform energy distribution in the short side direction can be irradiated without using an optical lens requiring high manufacturing accuracy. It is possible to form on the surface. When a rectangular beam spot emitted from a laser irradiation device using this optical system is scanned on a semiconductor film in a rectangular short side direction, a stripe pattern caused by non-uniform energy distribution of the beam spot is generated. Thus, the uniformity of the crystallinity in the plane of the substrate can be improved. Further, if the present invention is applied to a mass production line of low-temperature polysilicon TFTs, TFTs having high operation characteristics can be efficiently produced.

The rectangular beam spot forming optical system disclosed in the present invention will be described with reference to FIG.

First, a side view of FIG. 2B will be described. The laser beam emitted from the laser oscillator 1101 is propagated in the direction of the arrow in FIG. First, the laser beam is expanded by the spherical lenses 1102a and 1102b. This configuration is not necessary when the beam spot emitted from the laser oscillator 1101 is sufficiently large.

The beam spot is narrowed in the short side direction of the rectangle by the cylindrical lens 1105 whose second surface has a radius of curvature of -486 mm and a thickness of 20 mm. The sign of the radius of curvature is positive when the center of curvature is on the light exit side with respect to the lens surface, and negative when the center of curvature is on the incident side with respect to the lens surface. The lens surface is a first surface on which light enters, and a second surface is a surface on which light exits. The energy distribution in the short side direction of the rectangular beam spot on the irradiation surface is made uniform by the optical waveguide 1106 having two opposing reflection surfaces 1106a and 1106b placed 1030 mm behind the cylindrical lens 1105. The optical waveguide 1106 has a length of 300 mm in the light incident direction and a distance between the reflecting surfaces of 2 mm.

According to the present invention having the optical waveguide 1302, in the conventional optical system, the structural problem and manufacturing accuracy of the cylindrical lens array, which caused the non-uniformity of the energy distribution of the rectangular beam spot on the surface to be irradiated, and the divided light beam The problem of the manufacturing accuracy of the cylindrical lens which is the condensing lens can be improved.

Light beams emitted from the optical waveguide 1106 in the short side direction of the rectangle are converged by the doublet cylindrical lenses 1107a and 1107b disposed 1250 mm rearward on the irradiated surface 1108 disposed 237 mm rearward from the doublet cylindrical lens. The doublet cylindrical lens refers to a lens composed of two cylindrical lenses. One of the two cylindrical lenses constituting the doublet cylindrical lens is a cylindrical lens having a radius of curvature of the first surface of +125 mm, a radius of curvature of the second surface of +77 mm, and a thickness of 10 mm, and the other is the first lens. This is a cylindrical lens having a surface with a radius of curvature of +97 mm, a second surface with a radius of curvature of -200 mm, and a thickness of 20 mm, and the interval between the two cylindrical lenses is 5.5 mm. Thereby, the energy distribution in the short side direction of the rectangular beam spot is made uniform, and the length in the short side direction is determined. The doublet cylindrical lens does not have to be used, but by using the doublet cylindrical lens, a distance can be secured between the optical system and the irradiation surface, so that there is room in space.

Next, a top view of FIG. 2A will be described. The spot of the laser beam emitted from the laser oscillator 1101 is divided in the long side direction of the rectangle by the cylindrical lens arrays 1103a and 1103b. The cylindrical lens array 1103a is configured by arranging thirty cylindrical lenses having a curvature radius of the first surface of +28 mm, a thickness of 5 mm, and a width of 2 mm in the curvature direction. The cylindrical lens array 1103b is formed by arranging 30 cylindrical lenses having a curvature radius of the first surface of −13.33 mm, a thickness of 5 mm, and a width of 2 mm in the curvature direction. The distance between the cylindrical lens arrays 1103a and 1103b was 88 mm. Thereafter, the laser beam is combined into one on the irradiated surface 1108 by the cylindrical lens 1104 having a radius of curvature of +2140 mm and a thickness of 20 mm on the first surface located 120 mm behind the cylindrical lens array 1103b. Thereby, the energy distribution in the long side direction of the rectangular beam spot is made uniform, and the length in the long side direction is determined.

FIG. 3 shows a result obtained by performing a simulation using optical design software to obtain a beam spot having a uniform energy distribution having a length in the long side direction of 300 mm and a length in the short side direction of 0.4 mm. FIG. 3A is a diagram showing the energy distribution of the beam spot at a portion of ± 0.3 mm in the long side direction and ± 0.2 mm in the short side direction from the center of the rectangular beam spot. FIG. 3B is a cross-sectional view of the energy distribution of the rectangular beam spot in the short side direction at the center of the rectangle.

The laser oscillator used in combination with the optical system of the present invention preferably has a wavelength range that has a large output and is well absorbed by the semiconductor film. In the case where a silicon film is used as the semiconductor film, the wavelength of the laser beam emitted from the laser oscillator used is preferably 600 nm or less in consideration of the absorptance. Laser oscillators that emit such laser beams include, for example, excimer lasers, YAG lasers (harmonics), and glass lasers (harmonics).

Although high output has not yet been obtained with current technology, laser oscillators that emit a laser beam having a wavelength suitable for crystallization of a silicon film include, for example, a YVO ₄ laser (harmonic) and a YLF laser (harmonic). ), There is an Ar laser.

Hereinafter, a method for manufacturing a semiconductor device of the present invention using the beam homogenizer and the laser irradiation apparatus of the present invention will be described. First, a 127 × 127 × 0.7 mm glass substrate (Corning 1737) is prepared as a substrate. This substrate has sufficient durability at temperatures up to 600 ° C. A 200-nm-thick silicon oxide film is formed as a base film on the glass substrate. Further, an amorphous silicon film is formed thereon with a thickness of 55 nm. The film formation is performed by a sputtering method. Alternatively, the film may be formed by a plasma CVD method.

The substrate on which the film has been formed is placed in a nitrogen atmosphere at 450 ° C. for one hour. This step is a step for reducing the hydrogen concentration in the amorphous silicon film. If the amount of hydrogen in the film is too much, the film cannot withstand the laser energy, so this step is performed. The concentration of hydrogen in the film is suitably on the order of 10 ²⁰ / cm ³ . Here, 10 ²⁰ / cm ³ means that there are 10 ²⁰ hydrogen atoms per 1 cm ³ .

In this embodiment, an L4308XeCl excimer laser manufactured by Lambda Physics is used as a laser oscillator. The excimer laser is a pulse laser. The maximum energy of the excimer laser is 670 mJ per pulse, the oscillation wavelength is 308 nm, and the maximum frequency is 300 Hz. During laser processing of one substrate, uniform crystallization can be performed if the energy fluctuation of each pulse of the pulse laser is within ± 10%, preferably within ± 5%.

The variation of the laser energy described here is defined as follows. That is, the difference between the minimum energy or the maximum energy in the period during which one substrate is irradiated and the average value is expressed in%.

The linear laser used has an aspect ratio of 10 or more, and more preferably 100 or more.

The laser beam irradiation is performed, for example, while scanning the stage on which the irradiation surface 1108 shown in FIG. 2 is placed in the short side direction of the rectangular beam spot. At this time, the energy density of the beam spot on the irradiation surface and the scanning speed may be appropriately determined by the practitioner. Rule of thumb is the range of the energy density of ^{200mJ / cm 2 ~1000mJ / cm 2} . If an appropriate scanning speed is selected within a range in which the width of the rectangular beam spot in the short side direction is about 90% or more and overlaps each other, there is a high possibility that uniform laser annealing can be performed. The optimum scanning speed depends on the frequency of the laser oscillator and may be considered to be proportional to said frequency.

Thus, the laser annealing step is completed. By repeating the above steps, a large number of substrates can be processed. Using the substrate, for example, an active matrix liquid crystal display can be manufactured according to a known method.

In the above example, an excimer laser was used as the laser oscillator. An excimer laser has a very small coherent length of several μm and is suitable for the optical system of the above example. Some of the lasers described below have a long coherent length, but a laser having a coherent length changed artificially may be used. The use of a harmonic of a YAG laser or a harmonic of a glass laser is preferable because a similar large output is obtained and the energy of the laser beam is well absorbed by the silicon film. As a laser oscillator suitable for crystallization of a silicon film, there are a YVO ₄ laser (harmonic), a YLF laser (harmonic), an Ar laser, and the like. The wavelength region of these laser beams is well absorbed by the silicon film.

In the above example, an amorphous silicon film is used as the non-single-crystal semiconductor film, but it can easily be estimated that the present invention can be applied to other non-single-crystal semiconductors. For example, a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used as the non-single-crystal semiconductor film. Alternatively, a polycrystalline silicon film may be used as the non-single-crystal semiconductor film.

In this embodiment, an example of an optical system different from the optical system described in the embodiment will be described.

FIG. 4 shows an example of the optical system described in this embodiment. First, a side view of FIG. 4B will be described. The laser beam emitted from the laser oscillator 1401 is propagated in the direction of the arrow in FIG.
The beam spot is narrowed in the short side direction of the rectangle by a cylindrical lens 1402 having a radius of curvature of the second surface of -182 mm and a thickness of 10 mm. The optical waveguide 1405 is placed so that the entrance of the optical waveguide 1405 having two opposing reflecting surfaces 1405a and 1405b is located at the focal position of the cylindrical lens. The energy distribution of the beam spot is made uniform by the optical waveguide 1405. The optical waveguide 1405 has a length of 300 mm in the traveling direction of the light beam, and the distance between the reflecting surfaces is 0.4 mm. An irradiation surface 1406 is placed at a position 0.2 mm away from the exit of the optical waveguide 1405. A rectangular beam spot having a uniform energy distribution and a length of 0.4 mm in the short side direction is formed on the irradiation surface 1406.

Next, a top view of FIG. 4 will be described. The laser beam is propagated from the laser oscillator 1401 in the direction of the arrow in FIG. The first surface passes through a cylindrical lens array 1403 in which seven cylindrical lenses having a radius of curvature of +35 mm and a width of 3 mm are joined in the curvature direction, and the first surface has a first surface with a radius of curvature of +816 mm. The light passes through a cylindrical lens 1404 having a thickness of 5 mm and is superposed on an irradiation surface 1406. As a result, a rectangular beam spot having a uniform energy distribution in the long side direction of the rectangle is formed. When the cylindrical lens 1404 has a long focal length, the light collecting ability is reduced, so that the cylindrical lens 1404 may be omitted.

With the optical system shown in FIG. 4, a rectangular beam spot having a uniform energy distribution with a length of 0.4 mm in the short side direction of the rectangle can be formed. FIG. 5 shows the results of a simulation performed using the optical design software. FIG. 5A is a diagram showing the energy distribution of the beam spot at a portion of ± 0.3 mm in the long side direction and ± 0.2 mm in the short side direction from the center of the rectangular beam spot. FIG. 5B is a cross-sectional view of the energy distribution of the rectangular beam spot in the short side direction at the center of the rectangle.

In this embodiment, an example of an optical system different from the optical system described in the embodiment will be described. FIG. 6 shows an example of the optical system described in this embodiment.

First, a side view of FIG. 6B will be described. In FIG. 6, the laser beam passes through exactly the same optical path as the optical system shown in FIG. 4 until the laser beam reaches the optical waveguide 1605 having two opposing reflecting surfaces 1605a and 1605b. The optical waveguide 1605 has two reflecting surfaces facing each other similarly to the optical waveguide 1405. The optical waveguide 1605 has a length of 900 mm in the traveling direction of the light beam, and the distance between the reflecting surfaces is 2.6 mm. The light beam emitted from the optical waveguide 1605 is formed into a rectangular beam spot in which the energy distribution is made uniform in the short side direction of the rectangle having a length of 2.6 mm in the short side direction. Light rays emitted from the optical waveguide 1605 are converged by doublet cylindrical lenses 1606a and 1606b disposed 1000 mm rearward from the optical waveguide 1605, and collected on an irradiation surface 1607 disposed 220mm rearward from the doublet cylindrical lens. The doublet cylindrical lens has a first surface with a radius of curvature of +125 mm, a second surface with a radius of curvature of +69 mm, a thickness of 10 mm, a first surface with a radius of curvature of +75 mm, a second surface with a radius of curvature of -226 mm, and a thickness of -226 mm. It is composed of a 20 mm cylindrical lens. The interval between the cylindrical lenses was 1 mm. A rectangular beam spot having a uniform energy distribution in the short side direction of the rectangle is formed on the irradiation surface 1607. The doublet lens may be replaced by a cylindrical lens having a first surface having a radius of curvature of +963 mm, a second surface having a radius of curvature of -980 mm, and a thickness of 30 mm. In that case, the position of the cylindrical lens is preferably set at 2000 mm behind the optical waveguide 1605, and the irradiation surface 1607 is preferably set at 2000 mm behind the cylindrical lens.

Next, a top view of FIG. 6A will be described. The laser beam propagates from the laser oscillator 1601 in the direction of the arrow in FIG. A spot that has passed through a cylindrical lens array 1603 in which seven cylindrical lenses each having a radius of curvature of 35 mm, a thickness of 3 mm, and a width of 3 mm on the first surface are joined in the curvature direction, and divided in the long side direction, The light passes through a cylindrical lens 1604 having a radius of curvature of +816 mm and a thickness of 5 mm, and is superposed on an irradiation surface 1606. Thereby, a rectangular beam spot having a uniform energy distribution in the long side direction is formed. When the cylindrical lens 1604 has a long focal length, the light collecting ability is reduced, so that the cylindrical lens 1604 may be omitted.

With the optical system shown in FIG. 6, a rectangular beam spot having a uniform energy distribution with a length in the short side of 0.6 mm can be formed. FIG. 7 shows a simulation result performed by the optical design software. FIG. 7A is a diagram showing the energy distribution of the beam spot at a portion of ± 0.3 mm in the long side direction and ± 0.2 mm in the short side direction from the center of the rectangular beam spot. FIG. 7B is a sectional view of the energy distribution of the rectangular beam spot in the short side direction at the center of the rectangle.

Using the optical system described in this embodiment, laser annealing of the semiconductor film is performed by, for example, the method according to the embodiment. For example, an active matrix liquid crystal display or an electroluminescence (EL) display can be manufactured using the semiconductor film. The production may be performed by a practitioner according to a known method.

In this embodiment, an example of an optical system different from the optical system described in the embodiment will be described. FIG. 8 shows an example of the optical system described in this embodiment.

In FIG. 8, components other than the optical waveguide 1805 pass through exactly the same optical path as the optical system shown in FIG. The optical waveguide 1805 has two reflecting surfaces facing each other similarly to the optical waveguide 1405. In the optical waveguide 1405, the space between two opposing reflection surfaces is hollow, while the space between the reflection surfaces of the optical waveguide 1805 is filled with a medium 1805c having a refractive index n. They differ in this respect. If the refractive index n of the medium is larger than the refractive index of the material of the reflection surface, when the light beam enters the optical waveguide 1805 at an angle smaller than the critical angle, the light beam is totally reflected on the reflection surface. That is, at this time, the light transmittance of the optical waveguide is higher than that in the case where total reflection is not performed. Accordingly, the light from the light source 1801 can be more efficiently condensed on the irradiation surface 1806. Note that the cylindrical lens 1804 may not be provided.

With the optical system shown in FIG. 8, it is possible to form a rectangular beam spot having a uniform energy distribution and a length of 0.4 mm in the short side direction. Here, the refractive index of the medium was 1.521, and the refractive index of the material of the reflecting surface was 1.644. FIG. 9 shows the results of a simulation performed by the optical design software. FIG. 9A is a diagram showing the energy distribution of the beam spot at a portion of ± 0.3 mm in the long side direction and ± 0.2 mm in the short side direction from the center of the rectangular beam spot. FIG. 9B is a sectional view of the energy distribution of the rectangular beam spot in the short side direction at the center of the rectangle.

Using the optical system shown in this embodiment, laser annealing of the semiconductor film is performed, for example, by the method according to the embodiment of the invention. For example, an active matrix liquid crystal display or an electroluminescence (EL) display can be manufactured using the semiconductor film. The production may be performed by a practitioner according to a known method.

The figure explaining the means of the present invention. FIG. 2 is a diagram illustrating an example of a laser irradiation apparatus disclosed by the present invention. Energy distribution of a rectangular beam spot by the optical system presented in FIG. FIG. 2 is a diagram illustrating an example of a laser irradiation apparatus disclosed by the present invention. FIG. 4 is an energy distribution of a rectangular beam spot by the optical system presented in FIG. FIG. 2 is a diagram illustrating an example of a laser irradiation apparatus disclosed by the present invention. Energy distribution of a rectangular beam spot by the optical system presented in FIG. FIG. 2 is a diagram illustrating an example of a laser irradiation apparatus disclosed by the present invention. FIG. 8 is an energy distribution of a rectangular beam spot by the optical system presented in FIG. The figure which shows the conventional laser irradiation apparatus.

Claims (25)

A beam homogenizer for making a beam spot on a surface to be irradiated rectangular.
A beam homogenizer having an optical waveguide for making the energy distribution in the short side direction of the rectangular shape uniform on the irradiated surface. The beam homogenizer according to claim 1, wherein the optical waveguide has two reflecting surfaces facing each other. A beam homogenizer for forming a beam spot on a surface to be irradiated into a rectangular shape,
A beam homogenizer comprising a light pipe for making the energy distribution in the short side direction of the rectangular shape uniform on the irradiated surface. 4. The beam homogenizer according to claim 3, wherein the light pipe has two reflecting surfaces facing each other. A beam homogenizer for forming a beam spot on a surface to be irradiated into a rectangular shape,
An optical waveguide for uniformizing the energy distribution in the rectangular short side direction on the irradiated surface,
A beam homogenizer comprising: one or a plurality of cylindrical lenses that converge light emitted from the optical waveguide in a direction of the short side of the rectangle on the irradiated surface. A beam homogenizer for forming a beam spot on a surface to be irradiated into a rectangular shape,
A light pipe for uniformizing the energy distribution in the short side direction of the rectangular shape on the irradiated surface;
A beam homogenizer, comprising: one or a plurality of cylindrical lenses that converge light emitted from the light pipe in a direction of the short side of the rectangle on the irradiation surface. A beam homogenizer for forming a beam spot on a surface to be irradiated into a rectangular shape,
Means for uniformizing the energy distribution in the long side direction of the rectangular shape on the irradiated surface,
A beam waveguide for making the energy distribution in the short side direction of the rectangular shape uniform on the surface to be irradiated, wherein the means has at least a cylindrical lens array. A beam homogenizer for forming a beam spot on a surface to be irradiated into a rectangular shape,
Means for uniformizing the energy distribution in the long side direction of the rectangular shape on the irradiated surface,
A light pipe for making the energy distribution in the rectangular short side direction uniform on the irradiated surface, wherein the means has at least a cylindrical lens array. 8. The beam homogenizer according to claim 5, wherein the optical waveguide has two reflecting surfaces facing each other. 9. The beam homogenizer according to claim 6, wherein the light pipe has two reflecting surfaces facing each other. The beam homogenizer according to any one of claims 1 to 10, wherein the aspect ratio is 100 or more. A laser irradiation apparatus for forming a beam spot on a surface to be irradiated in a rectangular shape,
A laser oscillator,
Having a beam homogenizer,
The laser irradiation device, wherein the beam homogenizer has an optical waveguide for uniformizing an energy distribution in a short side direction of the rectangular shape. A laser irradiation apparatus for forming a beam spot on a surface to be irradiated in a rectangular shape,
A laser oscillator,
Having a beam homogenizer,
The laser irradiation apparatus, wherein the beam homogenizer has an optical waveguide for equalizing the energy distribution in the rectangular short side direction, and the optical waveguide has two opposing reflecting surfaces. A laser irradiation apparatus for forming a beam spot on a surface to be irradiated in a rectangular shape,
A laser oscillator,
Having a beam homogenizer,
The laser irradiation apparatus, wherein the beam homogenizer includes a light pipe for uniforming an energy distribution in a direction of the rectangular short side. A laser irradiation apparatus for forming a beam spot on a surface to be irradiated in a rectangular shape,
A laser oscillator,
Having a beam homogenizer,
The laser irradiation apparatus, wherein the beam homogenizer has a light pipe for uniformizing an energy distribution in a direction of the rectangular short side, and the light pipe has two facing reflection surfaces. 16. The laser irradiation apparatus according to claim 12, wherein the laser oscillator is any one of an excimer laser, a YAG laser, and a glass laser. The laser oscillator according to any one of claims 12 to 15, YVO ₄ laser, YLF laser, a laser irradiation apparatus which is characterized in that any one of Ar laser. 18. The laser irradiation apparatus according to claim 12, wherein the aspect ratio is 100 or more. In the method for manufacturing a semiconductor device,
Forming a non-single-crystal semiconductor film on the substrate,
Generating a laser beam;
A step of forming the laser beam into a uniform beam spot having a rectangular energy distribution on an irradiated surface by at least a cylindrical lens array and an optical waveguide;
Placing the substrate on which the non-single-crystal semiconductor film is formed on a stage, and matching the surface of the non-single-crystal semiconductor film to the irradiated surface;
Scanning the stage relative to the laser beam while irradiating the rectangular laser beam, laser annealing the non-single-crystal semiconductor film,
Wherein the cylindrical lens array acts in the long side direction of the rectangular beam spot, and the optical waveguide acts in the short side direction of the rectangular beam spot. . In the method for manufacturing a semiconductor device,
Forming a non-single-crystal semiconductor film on the substrate,
Generating a laser beam;
A step of forming the laser beam into a uniform beam spot having a rectangular energy distribution on an irradiated surface by at least a cylindrical lens array and an optical waveguide;
Placing the substrate on which the non-single-crystal semiconductor film is formed on a stage, and matching the surface of the non-single-crystal semiconductor film to the irradiated surface;
Scanning the stage relative to the laser beam while irradiating the rectangular laser beam, laser annealing the non-single-crystal semiconductor film,
Wherein the cylindrical lens array acts in a long side direction of the rectangular beam spot, the optical waveguide acts in a short side direction of the rectangular beam spot, and the optical waveguide has two facing sides. A method for manufacturing a semiconductor device having a reflective surface. In the method for manufacturing a semiconductor device,
Forming a non-single-crystal semiconductor film on the substrate,
Generating a laser beam;
A step of forming the laser beam into a uniform beam spot having a rectangular energy distribution on an irradiated surface by at least a cylindrical lens array and a light pipe,
Placing the substrate on which the non-single-crystal semiconductor film is formed on a stage, and matching the surface of the non-single-crystal semiconductor film to the irradiated surface;
Scanning the stage relative to the laser beam while irradiating the linear laser beam, laser annealing the non-single-crystal semiconductor film,
Wherein the cylindrical lens array acts in a long side direction of the rectangular beam spot, and the light pipe acts in a short side direction of the rectangular beam spot. . In the method for manufacturing a semiconductor device,
Forming a non-single-crystal semiconductor film on the substrate,
Generating a laser beam;
A step of forming the laser beam into a uniform beam spot having a rectangular energy distribution on an irradiated surface by at least a cylindrical lens array and a light pipe,
Placing the substrate on which the non-single-crystal semiconductor film is formed on a stage, and matching the surface of the non-single-crystal semiconductor film to the irradiated surface;
Scanning the stage relative to the laser beam while irradiating the linear laser beam, laser annealing the non-single-crystal semiconductor film,
Wherein the cylindrical lens array acts in the long side direction of the rectangular beam spot, the light pipe acts in the short side direction of the rectangular beam spot, and the light pipe has two facing sides. A method for manufacturing a semiconductor device having a reflective surface. 23. A method for manufacturing a semiconductor device, wherein the oscillator of the laser beam according to claim 19 is any one of an excimer laser, a YAG laser, and a glass laser. Oscillator of the laser beam according to any one of claims 19 to 22, YVO ₄ laser, YLF laser, a method for manufacturing a semiconductor device which is characterized in that any one of Ar laser. 25. The method for manufacturing a semiconductor device according to claim 19, wherein the aspect ratio is 100 or more.