JP4429575B2 - Laser irradiation apparatus and method for manufacturing semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser annealing apparatus or a laser irradiation method using laser light. Further, the present invention relates to a method for manufacturing a thin film transistor manufactured through a process including a laser annealing method or a method for manufacturing a semiconductor device including the thin film transistor. The semiconductor device here refers to all devices that can function by utilizing semiconductor characteristics, and includes an electro-optical device such as a liquid crystal display device and a light-emitting device, and an electronic device including the electro-optical device as a component. Shall.
[0002]
[Prior art]
In recent years, a technique for improving crystallinity by applying a laser annealing method to a semiconductor film formed on an insulating substrate such as glass has been widely studied. Silicon is often used for the semiconductor film. In this specification, means for crystallizing a semiconductor film with laser light to obtain a crystalline semiconductor film is called laser crystallization.
[0003]
Compared with a synthetic quartz glass substrate that has been frequently used in the past, a glass substrate is inexpensive and rich in workability, and has an advantage that a large-area substrate can be easily manufactured. This is the reason for the above research. Further, the reason why lasers are used favorably for crystallization is that the melting point of the glass substrate is low. The laser can give high energy only to the semiconductor film without significantly increasing the temperature of the substrate. In addition, lasers have the advantage of a much higher throughput than heating means using an electric furnace.
[0004]
Since a crystalline semiconductor is composed of many crystal grains, it is also called a polycrystalline semiconductor film. A crystalline semiconductor film formed by laser annealing has high mobility. Therefore, for example, it is used for a monolithic liquid crystal electro-optical device or the like in which thin film transistors (TFTs) for pixel driving and driving circuits are formed on a single glass substrate using this crystalline semiconductor film.
[0005]
Also, a pulsed laser beam such as an excimer laser with high output is processed by an optical system so that it becomes a square spot of several cm square or a linear shape with a length of 10 cm or more on the irradiated surface, and the laser beam is scanned. The method of performing the laser annealing method by moving the laser light irradiation position relative to the surface to be irradiated is preferably used because of its high mass productivity and industrial superiority. By the way, processing the laser beam into a line means that the laser beam is processed so that the shape on the irradiated surface becomes a line. That is, it means that the cross-sectional shape of the laser beam is processed into a linear shape. In addition, “linear” here does not mean “line” in a strict sense, but means a rectangular or elliptical shape with a large aspect ratio. For example, the aspect ratio is 10 or more (preferably 100 to 10,000).
[0006]
In particular, when using a linear beam, unlike the case of using a spot laser beam, the entire irradiated surface can be irradiated by scanning only in the direction perpendicular to the longitudinal direction of the linear beam. High productivity. The reason for scanning in the direction perpendicular to the longitudinal (long) direction is that it is the most efficient scanning direction. Due to this high mass productivity, a laser annealing method using a linear beam obtained by processing laser light with an appropriate optical system is used in the manufacturing technology of a liquid crystal display device using TFT.
[0007]
[Problems to be solved by the invention]
There are various types of laser light, but laser crystallization using laser light (hereinafter referred to as excimer laser light) using a pulse oscillation type excimer laser as a light source is generally used. The excimer laser has the advantage that the output is large and can be repeatedly irradiated at a high frequency, and the excimer laser light has the advantage that the absorption coefficient for the silicon film is high.
[0008]
To form excimer laser light, KrF (wavelength 248 nm) or XeCl (wavelength 308 nm) is used as an excitation gas. However, gases such as Kr (krypton) and Xe (xenon) are very expensive, and there is a problem that the manufacturing cost increases when the frequency of gas exchange increases.
[0009]
In addition, replacement of attached equipment such as a laser tube for performing laser oscillation and a gas purifier for removing unnecessary compounds generated during the oscillation process is required every two to three years. Many of these accessory devices are expensive, and there is still a problem that the manufacturing cost increases.
[0010]
As mentioned above, the laser irradiation device using excimer laser light has high performance, but it takes much time for maintenance, and it is a running cost (in this case, it occurs with operation as a mass production laser irradiation device) It also has the disadvantage of high costs.
[0011]
Therefore, in order to realize a laser irradiation device with a lower running cost than an excimer laser and a laser annealing method using the same, there is a method using a solid-state laser (a laser that outputs a laser beam using a crystal rod as a resonance cavity). is there.
[0012]
Therefore, the semiconductor film was irradiated using a YAG laser which is one of typical solid lasers. In the YAG laser, a laser beam (wavelength 532 nm) modulated to a second harmonic by a non-linear optical element is processed into a linear beam whose shape on the irradiation surface is linear by an optical system. Further, the semiconductor film is obtained by forming an amorphous silicon film having a film thickness of 55 nm on a 1737 substrate manufactured by Corning by the plasma CVD method. However, a concentric pattern was formed on the crystalline silicon film obtained by performing a process including a laser annealing method on the amorphous silicon film. This pattern indicates that the physical properties of the crystalline silicon film in the plane are non-uniform. Therefore, when a TFT is manufactured using a crystalline semiconductor in which a concentric pattern is formed, its electrical characteristics are adversely affected. In the present specification, a concentric pattern is referred to as a concentric pattern.
[0013]
Further, in the laser annealing method, as the electro-optical device has a larger screen, the mother glass has a larger area, and a demand for irradiating a semiconductor layer provided on the substrate with a laser at a high speed is increasing.
[0014]
Further, in the laser annealing method, when the semiconductor layer is crystallized, there is an increasing demand for compensating for the insufficient power of the laser for once melting the semiconductor layer.
[0015]
Therefore, the present invention is a laser annealing method using a laser irradiation apparatus having a low running cost to cope with a large substrate, in which a concentric pattern is not formed or a laser annealing method for reducing the formation of a concentric pattern, and It is an object to provide a method for manufacturing a semiconductor device including a laser annealing method in a process.
[0016]
[Means for Solving the Problems]
First, the reason why the concentric pattern is formed will be considered. The laser beam applied to the amorphous silicon film was a linear beam having a linear shape on the irradiated surface. Therefore, even if some pattern is formed on the crystalline silicon film obtained after laser light irradiation, if the semiconductor film, the substrate and the substrate stage are completely flat, the pattern parallel or perpendicular to the linear beam Should be. However, the observed pattern was concentric. Therefore, it is considered that the concentric pattern is not caused by the linear beam. That is, it can be inferred that the cause of the occurrence of this concentric pattern is the film thickness of the semiconductor film, the absorption coefficient for laser light, the substrate and the substrate stage, or a plurality of these.
[0017]
In order to consider the absorption coefficient of the semiconductor film with respect to the laser beam among the causes of the occurrence of the concentric pattern, the reflectance and transmittance of the amorphous silicon film (film thickness 55 nm) with respect to the wavelength were obtained, and the results are shown in FIG. And shown in FIG. The amorphous silicon film is formed on a 1737 substrate by a plasma CVD method. FIG. 10 shows that the reflectance of the YAG laser with respect to the second harmonic (wavelength 532 nm) is 26% and the transmittance is 38%. Then, it is considered that the reflected light from the surface of the amorphous silicon film interferes with the surface where the laser light transmitted through the amorphous silicon film is present. It can be assumed that this is the cause of the concentric pattern.
[0018]
Therefore, in order not to form the concentric pattern or to reduce the formation of the concentric pattern, it is considered necessary to prevent such interference. Therefore, in order to prevent this interference, a plurality of laser beams are condensed, and the semiconductor film on the surface of the substrate is irradiated with the collected laser beams to crystallize the semiconductor film.
[0019]
Therefore, the laser annealing apparatus of the present invention is a laser annealing apparatus having a laser light source that outputs laser light, and a moving mechanism that moves the substrate that is irradiated with the laser light from an oblique direction. In the irradiation region, the moving mechanism reciprocates a distance equal to or longer than the length of one side of the substrate, and the length of the laser light in the Y-axis direction or the direction of the laser light in a direction perpendicular to the reciprocating direction. A laser annealing apparatus having a function of moving at a length equal to or less than a length in the Y-axis direction. By using the laser annealing apparatus of the present invention, the concentric pattern, which has been a problem in laser annealing, is not formed, or the formation of the concentric pattern can be reduced, and the reliability of the manufactured semiconductor device can be improved. Note that even a semiconductor film over a large substrate can be irradiated with uniform laser light.
[0020]
The laser annealing apparatus of the present invention includes a laser light source that outputs laser light, a nonlinear optical element that modulates the laser light, a waveguide that condenses the modulated laser light, and the condensed laser. A laser annealing apparatus having a moving mechanism for moving a substrate irradiated with light from an oblique direction, wherein the moving mechanism reciprocates a distance more than a length of one side of the substrate in the laser light irradiation region. And having a function of moving in the direction perpendicular to the reciprocating direction by a length equal to or shorter than the length of the laser light in the Y-axis direction or the length of the laser light in the Y-axis direction. Laser annealing equipment. By using the laser annealing apparatus of the present invention, by concentrating a plurality of laser beams in one bundle, the concentric pattern, which has been a problem with a bundle of laser beams, is not formed, or the formation of concentric patterns is reduced. The reliability of the manufactured semiconductor device can be improved. Note that even a semiconductor film over a large substrate can be irradiated with uniform laser light.
[0021]
In the method for manufacturing a thin film transistor of the present invention, a semiconductor film is formed over a substrate, and a plurality of laser beams are irradiated to the semiconductor film from an oblique direction while moving the substrate at a constant speed, and perpendicular to the moving direction. The method of manufacturing a thin film transistor is characterized by continuously repeating the movement of the length of the laser beam or a distance equal to or shorter than the length in such a direction. As a result, the concentric pattern, which has been a problem with laser light, is not formed or the formation of the concentric pattern can be reduced, and the reliability of the manufactured thin film transistor and the semiconductor device including the thin film transistor can be improved. Note that even a semiconductor film over a large substrate can be irradiated with uniform laser light.
[0022]
In the thin film transistor manufacturing method of the present invention, a semiconductor film is formed on a substrate, the plurality of laser beams are modulated by a plurality of nonlinear optical elements, the modulated light is condensed through a waveguide, and the substrate is formed. Irradiating the focused laser beam to the semiconductor film from an oblique direction while moving it at a constant speed, and the length of the laser beam or a distance less than the length in a direction perpendicular to the moving direction It is a method for manufacturing a thin film transistor characterized by continuously repeating the movement. As a result, the concentric pattern, which has been a problem with laser light, is not formed or can be reduced, and the reliability of the manufactured thin film transistor and the semiconductor device including the thin film transistor can be improved. Note that even a semiconductor film over a large substrate can be irradiated with uniform laser light.
[0023]
In the method for manufacturing a thin film transistor of the present invention, the constant speed is included in a range of 20 to 200 cm / s. As a result, a laser can be irradiated to a semiconductor layer provided on a large substrate at high speed.
[0024]
Further, the laser light used in the present invention may be processed into an elliptical shape or a linear shape by an optical system.
[0025]
In addition, the present invention is a method for manufacturing a semiconductor device in which the laser light is incident on the semiconductor film at an angle of 5 to 10 ° with respect to a normal direction of the front surface of the substrate or a normal direction of the back surface. It is devised because the concentric pattern does not appear when the process including the laser annealing method is performed by tilting the substrate, and the substrate is irradiated with an angle to the laser beam. By applying the present invention, variation in physical properties of the crystalline semiconductor film due to interference of laser light can be removed or reduced. When a thin film transistor is manufactured using such a crystalline semiconductor film, a film having favorable electrical characteristics can be obtained.
[0026]
In addition, the present invention is a method for manufacturing a thin film transistor in which crystallization progresses in the semiconductor film in a parallel direction of the substrate so as to approach an end surface of the substrate while being irradiated with the laser light. By the method for manufacturing a thin film transistor of the present invention, a thin film transistor having a flat semiconductor layer surface and high electric mobility and a semiconductor device including the thin film transistor can be manufactured.
[0027]
In the present invention, the semiconductor film may be irradiated with laser light from the back surface side (the side opposite to the surface on which the semiconductor film is formed) of the substrate.
[0028]
As the laser beam, a generally known laser beam can be used, and YAG laser (usually Nd: YAG laser), Nd: YLF laser, Nd: YVO _Four Laser, Nd: YAlO _Three A laser, a ruby laser, a Ti: sapphire laser, a glass laser, or the like can be used. In particular, a YAG laser superior in coherency and pulse energy is preferable.
[0029]
For example, if a YAG laser is used, the fundamental wave (first harmonic) of the YAG laser has a long wavelength of 1064 nm, so it is preferable to use the second harmonic (wavelength 532 nm). The first harmonic can be modulated into a second harmonic, a third harmonic, or a fourth harmonic by a wavelength modulator including a nonlinear element. Each harmonic may be formed according to a known technique. Further, in this specification, “laser light using a solid laser as a light source” includes not only the first harmonic but also a harmonic whose wavelength is modulated in the middle.
[0030]
Further, a Q switch method (Q modulation switch method) often used in a YAG laser may be used. This is a method of outputting a sharp pulse laser having a very high energy value by rapidly increasing the Q value from a state in which the Q value of the laser resonator is sufficiently low.
[0031]
Since the solid-state laser used in the present invention can basically output a laser beam if there is a light source for exciting a resonant mirror or a solid crystal, it does not require maintenance work like an excimer laser. That is, since the running cost is very low compared to the excimer laser, the manufacturing cost of the thin film transistor and the semiconductor device can be greatly reduced. Further, if the number of maintenance operations is reduced, the operation rate of the mass production line is also increased, so that the overall throughput of the manufacturing process is improved, which greatly contributes to the reduction of the manufacturing costs of the thin film transistor and the semiconductor device. Furthermore, since the area occupied by the solid-state laser device is smaller than that of the excimer laser device, it is advantageous for designing the production line.
[0032]
If the output of the laser beam is 10 W or more, uniform laser annealing can be performed even with a single beam. Even a single beam can be irradiated with uniform laser light. That is, an output of laser light of 10 W or more is sufficient to melt the semiconductor layer when the semiconductor layer is crystallized.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment mode of the present invention, a laser beam irradiation method will be described with reference to FIG.
[0034]
A crystalline silicon layer is manufactured from an amorphous silicon layer by a crystallization process by laser light irradiation. In this crystallization, a light-transmitting region (transparent window) 601 that transmits laser light is provided on at least one side surface. In a treatment chamber (laser annealing chamber) 602.
[0035]
First, as the substrate, a light-transmitting substrate made of glass such as barium borosilicate glass typified by Corning # 7059 glass or # 1737 glass or aluminoborosilicate glass is used. Note that a quartz substrate or a silicon substrate may be used as the substrate. In this embodiment, a glass substrate having a size of 680 mm × 880 mm and a thickness of 1.1 mm is used. In this specification, a substrate in which a base film is formed over the substrate and a semiconductor film is formed over the base film is referred to as a substrate to be processed.
[0036]
Inside the laser annealing chamber 602, a table 603, a stage 604 provided on the table 603, and a moving mechanism 605 for moving the table 603 are installed, and outside the laser annealing chamber 602. Are provided with an evacuation pump 630, a gas supply pipe 607, and a gate valve 608, which are means for controlling the atmosphere in the processing chamber.
[0037]
The stage 603 is moved in a direction (X-axis direction and Y-axis direction) perpendicular to the normal direction of the substrate 606 to be processed by a moving mechanism 605 for moving, and laser light is applied to the upper surface of the substrate 606 to be processed. Is provided to irradiate. However, the irradiation direction of the laser light is inclined 5 to 10 ° with respect to the normal direction of the substrate 606 to be processed. However, it is assumed that the X axis is perpendicular to the long axis direction of the laser.
[0038]
In this specification, a semiconductor manufacturing apparatus having a stage 604 and a moving mechanism 605 for moving is referred to as a laser annealing apparatus. Further, a table 603 may be provided between the stage 604 and a moving mechanism 605 for moving. Further, the laser annealing device 609, the optical system 610, and the mirror 611 may be referred to as a laser annealing device. The laser annealing chamber, a laser annealing chamber 602 provided with a transparent window 601, a vacuum pump 606, a gas supply pipe 607, and a gate valve 608 are combined to perform an amorphous silicon layer crystallization process. 2 shows the Y-axis direction of the laser annealing apparatus of FIG. FIG. 3 shows a laser annealing apparatus viewed from the mirror side (above the substrate to be processed 606). Note that the moving mechanism 605 can move in the X-axis direction by a distance equal to or longer than the length of one side of the substrate to be processed 606, and in the Y-axis direction perpendicular to the X-axis direction, It can move at a distance less than the length. Note that the length of the laser light is the length of the laser light in a direction perpendicular to the direction of movement by the moving mechanism.
[0039]
As shown in FIG. 1, a laser beam 600 is irradiated from a laser oscillation device 609, and the laser beam 600 whose cross-sectional shape is processed by an optical system 610 is reflected by a mirror 611 and passed through a transparent window 601. Then, the substrate to be processed 606 is irradiated. In addition, the shape of the irradiated light may be a rectangle.
[0040]
FIG. 4 is a view of the substrate 606 as viewed from the normal direction. The end of the substrate to be processed 606 is set to be 100 mm away from the position where the laser beam is irradiated. Next, the moving mechanism 605 for moving in FIG. 1 is moved while accelerating so that the substrate 606 to be processed moves in the direction of the arrow (1). After 0.05 seconds, the substrate 606 is irradiated with the laser beam 600 at a constant speed (here, 20 cm / s). If the position where the laser beam is irradiated is outside the substrate 606, the speed is reduced (FIG. 5). Next, crystallization is performed by performing the same process as the process performed by the arrow (1) in the direction of the arrow (2) which is opposite to the arrow (1). The process applied by the arrow (3) and the process applied by the arrow (4) may be repeated by the process applied by the arrow (1) and the process applied by the arrow (2), respectively. These steps are repeated as necessary, and the entire surface of the substrate to be processed 606 is irradiated with laser light. In the semiconductor film of the substrate to be processed 606, crystallization proceeds in a direction parallel to the substrate to be processed and so as to approach the end surface of the substrate to be processed.
[0041]
The moving speed of the substrate to be processed 606 should be within a range of 20 to 200 cm / s and constant.
[0042]
At this time, the substrate to be processed 606 may be placed on the stage 604, and the substrate to be processed may be kept at a predetermined temperature by a heater that is a heating unit installed in the table 603. This is because the crystal grain size increases when the amorphous silicon layer is crystallized at 450 ° C.
[0043]
Here, the laser oscillation device 609 uses a laser beam 600 that oscillates a CW laser.
[0044]
The laser annealing chamber 602 may include a vacuum exhaust pump 630 provided as a decompression and exhaust means. As gas supply means, a gas supply pipe 607a connected to a hydrogen cylinder through a valve and a gas supply pipe 607b connected to a nitrogen or other gas cylinder through a valve are provided. Note that in this embodiment mode, laser light irradiation is performed at normal temperature and normal pressure.
[0045]
In the present embodiment, the semiconductor film on the surface of the substrate is irradiated with laser light while moving the substrate at a constant speed of 20 to 200 cm / s. Therefore, even in a semiconductor film on a large substrate Laser light can be irradiated.
[0046]
In this embodiment, the output is set to 10 W. However, if the output is set to 10 W or more, uniform laser annealing can be performed even with a single beam. Even a single beam can be irradiated with uniform laser light. A laser light output of 10 W or more is sufficient to melt the semiconductor layer when the semiconductor layer is crystallized.
[0047]
In this embodiment, the beam is emitted from one laser oscillation device, but the beam intensity may be increased by superimposing the beams using a plurality of laser oscillation devices. By condensing the laser light in this manner, the formation of concentric patterns can be reduced, and the reliability of the manufactured semiconductor device can be improved. In this case, if necessary, a plurality of optical systems, a plurality of mirrors, fibers, and the like may be used in combination.
[0048]
In addition, according to the present invention, in addition to processing laser light into an elliptical shape in a process including a laser annealing method to improve throughput, when using a solid laser that is easier to maintain, a conventional excimer laser is used. Throughput can be improved as compared with laser annealing using. As a result, the manufacturing cost of a semiconductor device such as a TFT or a display device formed of the TFT can be reduced.
[0049]
Furthermore, by irradiating the semiconductor film with laser light obliquely, the concentric pattern formed in the semiconductor film can be removed or reduced, and the physical properties of the semiconductor film after the process including the laser annealing method can be made uniform. Can be a thing. In this manner, when a semiconductor device is manufactured using a semiconductor film, the performance of the semiconductor device can be significantly improved.
[0050]
【Example】
[Example 1]
In an embodiment of the present invention, an optical system will be described with reference to FIG.
[0051]
As the laser oscillator 201, a high-power solid-state laser (YAG laser, YVO) _Four It is desirable to use a laser or the like. Of course, a gas laser, a glass laser, or the like may be used for a large output. Then, the laser beam oscillated from the laser oscillator 201 is processed into a laser beam whose irradiation surface has an elliptical shape using an optical system. For the optical system, for example, a long focal length cylindrical lens 205 for enlarging laser light long and a long focal length cylindrical lens 206 for condensing laser light thinly are used. When a cylindrical lens having a long focal length is used, it is possible to suppress the aberration and obtain a laser beam having a uniform energy distribution on the irradiated surface. In addition, the cylindrical lens having a long focal length is also effective in not significantly changing the beam width of light incident on the semiconductor film and the beam width of reflected light from the back surface of the substrate. According to the inventor's experiment, when a cylindrical lens having a focal length of 500 mm or more was used, the influence of aberration could be dramatically reduced.
[0052]
A reflection mirror 207 is provided in front of the cylindrical lens 206 so that the traveling direction of the laser beam can be changed. With the reflection mirror 207, the angle of the laser light incident on the irradiation surface can be adjusted to the target angle θ. If the angle of the cylindrical lens 206 is also changed according to the angle of the reflection mirror 207, more symmetrical laser light can be formed on the irradiation surface.
[0053]
Further, when irradiating the semiconductor film with laser light, irradiation is performed with a superposition ratio of laser light during scanning (laser light in the X-axis direction in this embodiment) being 0 to 80%. In the case of a pulse laser, irradiation may be performed with the overlapping rate (overlap rate) between sequentially irradiated laser beams being 50 to 98%, or without overlapping. Since the optimum conditions vary depending on the state of the semiconductor film, the delay time of the laser beam, and the like, it is preferable that the practitioner determine as appropriate.
[0054]
In this embodiment, a pulse laser (output: 20 W, 30 Hz, YAG) is used as a laser oscillator, modulated to a second harmonic by the nonlinear optical element 202, and laser light having a length of 130 mm and a width of 0.4 mm using an optical system. Then, the semiconductor film is irradiated. At this time, the laser beam is irradiated at an angle of 5 to 10 ° from the normal direction of the substrate 204 to be processed.
[0055]
A stage 208 is provided below the stage 203, and a moving mechanism 209 is provided below the stage 208. With the moving mechanism 209, the substrate 113 to be processed can be moved in the X-axis direction and the Y-axis direction. Note that, for example, a ball, a top, a motor, or the like may be installed below the moving mechanism 209.
[0056]
In the semiconductor film of the substrate to be processed 204, crystallization proceeds in a direction parallel to the substrate to be processed and close to the end surface of the substrate to be processed.
[0057]
By irradiating the semiconductor film of the substrate 204 with laser light obliquely, the concentric pattern formed in the semiconductor film can be removed or reduced, and the physical properties of the semiconductor film after the process including the laser annealing method are obtained. Can be made uniform. In this manner, when a semiconductor device is manufactured using a semiconductor film, the performance of the semiconductor device can be significantly improved.
[0058]
[Example 2]
In this example, a crystallization method of the laser annealing apparatus of the present invention is shown. Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.
[0059]
First, a glass substrate (Corning 1737; strain point 667 ° C.) was prepared as the substrate 1000. Next, a protective film 1001 was formed over the substrate 1000, and a tantalum nitride film 1002a (film thickness of 50 nm) and a tantalum film 1002b (film thickness of 250 nm) were stacked over the protective film by a sputtering method (FIG. 7A). . Thereafter, a gate electrode 1002 having a stacked structure was formed by using a photolithography method which is a known patterning technique. (Fig. 7 (B))
[0060]
Next, a gate insulating film and an amorphous semiconductor film 1004 were sequentially stacked without being exposed to the atmosphere. (FIG. 7C) In this embodiment, a silicon nitride film 1003a (film thickness 50 nm) and a silicon oxide film 1003b are used in order to prevent impurities from the substrate and gate wiring from diffusing into the semiconductor film and the gate insulating film during the manufacturing process. (Thickness 125 nm) was formed by plasma CVD to form a gate insulating film having a stacked structure. In this embodiment, a two-layer insulating film is used as the gate insulating film, but a single layer or a laminated structure of three or more layers may be used. In this embodiment, an amorphous silicon film (amorphous silicon film) having a thickness of 54 nm is formed as the amorphous semiconductor film 1004 on the gate insulating film by a plasma CVD method. In order to prevent contaminants from the atmosphere from adhering to the interface of any layer, the layers were sequentially formed without being opened to the atmosphere.
[0061]
Thereafter, heat treatment (500 ° C., 1 hour) was performed to reduce the hydrogen concentration in the amorphous silicon film which hinders crystallization of the semiconductor film.
[0062]
When the state of FIG. 7C is obtained in this manner, the amorphous semiconductor film 1004 is crystallized by irradiation with infrared light or ultraviolet light (laser crystallization), and a crystalline semiconductor film (semiconductor including a crystal) is obtained. Membrane) 1005 was formed (FIG. 7D). Note that the crystallization direction proceeds in the parallel direction of the 1000 substrate in the amorphous semiconductor film 1004 and closer to the end surface of the substrate 1000.
[0063]
When ultraviolet light is used as a crystallization technique, laser light or strong light generated from an ultraviolet lamp may be used, and when infrared light is used, infrared light or strong light generated from an infrared lamp may be used. In this example, YVO of the CW laser _Four The laser beam is formed into an elliptical shape, tilted by 5 to 10 ° from the normal direction, and the laser beam is set with a superposition ratio of 0 to 80% of the laser beam during scanning (laser beam in the X-axis direction in this embodiment). Irradiated.
[0064]
Note that the conditions for laser crystallization (laser light wavelength, irradiation intensity, repetition frequency, irradiation time, etc.) may be appropriately determined by the practitioner in consideration of the film thickness of the amorphous semiconductor film 1004, the substrate temperature, and the like. .
[0065]
Depending on the laser crystallization conditions, the initial semiconductor film may be crystallized after passing through the molten state, or the initial semiconductor film may be crystallized in the solid state or in the intermediate state between the solid phase and the liquid phase without melting. There is. Through this step, the amorphous semiconductor film 1004 is crystallized and changed into a crystalline semiconductor film 1005. In this embodiment, the crystalline semiconductor film is a polycrystalline silicon film (polysilicon film).
[0066]
[Example 3]
The structure of an active matrix display device manufactured through the method for manufacturing a semiconductor device described in Embodiments 1 and 2 will be described with reference to top views of FIGS.
[0067]
The top view of the active matrix display device shown in FIG. 8 is affixed with a pixel portion 811, a driver circuit (a generic term for a gate line driver circuit 805 and a source line driver circuit 807), and an FPC (Flexible Printed Circuit). An active matrix substrate 801 on which external input terminals 803, wirings 804 that connect the external input terminals to the input portions of each circuit, and a counter substrate 802 on which color filters are formed are attached to each other with a sealant 809 interposed therebetween. Are combined.
[0068]
The gate line driver circuit 805 has a function of inputting a signal to the selected gate wiring 806. The gate wiring 806 is a wiring that is electrically connected to the gate electrode. Then, the selected gate wiring is selected one by one. Of course, an insulating film is provided on the gate wiring. On the other hand, the source line driver circuit 807 has a function of first receiving an image data signal and applying the signal to the pixel electrode connected to the selected gate wiring. The source line driver circuit 807 operates in synchronism with the gate line driver circuit 805. In this manner, switching elements (not shown) of each gate line are sequentially selected, and a desired voltage is applied via the source line 808, whereby an image of the active matrix display device can be obtained.
[0069]
However, color filters of each color of red (R), green (G), and blue (B) formed on the counter substrate side on the pixel portion 811 are provided corresponding to each pixel. In actual display, a color display is formed with three colors of a red (R) color filter, a green (G) color filter, and a blue (B) color filter. The arrangement of the color filters of these colors is arbitrary. Shall.
[0070]
If the direction of crystal growth by laser light irradiation in FIG. 8 is the direction of the arrow, the carrier flow direction (channel direction) in this direction and the semiconductor layer 810 shown in FIG. 9A (schematic diagram of TFT in the pixel portion). ) Does not impair the decrease in electrical mobility. Reference numeral 806 denotes a gate wiring, and 811 denotes a contact hole. Similarly, when the direction of crystal growth by laser light irradiation in FIG. 8 and the carrier flow direction (channel direction) in the semiconductor layer 910 shown in FIG. 9B (schematic diagram of TFT in the driver circuit) match, There is no loss of mobility. Reference numeral 906 denotes a gate wiring, and 911 denotes a contact hole.
[0071]
[Example 4]
An example of a laser annealing apparatus different from that of the first embodiment will be described. A plurality of laser oscillation devices, a plurality of optical systems, and a plurality of mirrors are mounted. Lights oscillated from the laser oscillation devices and processed by the optical systems are collected and irradiated onto the substrate.
[0072]
As shown in FIG. 11, laser beams 1100a-c are irradiated from laser oscillation devices 1109a-c, processed by optical systems 1110a-c, reflected by mirrors 1111a-c, and reflected laser beams are condensed. Then, the substrate 1113 on the stage 1104 is irradiated. A moving mechanism 1105 provided under the stage 1104 can move the substrate 1113 to be processed in the X-axis direction and the Y-axis direction. Note that a ball, a top, a motor, or the like may be installed below the moving mechanism 1105, for example.
[0073]
In this embodiment, the concentric pattern, which has been a problem with laser light, is not formed, or the formation of the concentric pattern can be reduced, and the reliability of the manufactured semiconductor device can be improved.
[0074]
[Example 5]
An example of a laser annealing apparatus different from the first and fourth embodiments will be described. In this embodiment, a plurality of laser oscillation devices, a plurality of nonlinear optical elements and a waveguide are mounted, and light that is irradiated with laser light from each laser oscillation device and modulated by the nonlinear optical elements is collected by the waveguide and collected. Is characterized by irradiating the substrate.
[0075]
As shown in FIG. 12, laser beams 112 a to 112 c irradiated with laser beams from the laser oscillation devices 100 a to 100 c and modulated by the nonlinear optical elements 101 a to 101 c are incident on the fiber array 103 and collected by the waveguide 104. Then, the substrate 113 on the stage 110 is irradiated with the laser light emitted from the fiber array 105. The fiber array 103 is a means for bringing the laser beams 112a to 112c close to each other.
[0076]
A stage 106 is provided below the stage 110, and a moving mechanism 107 is provided below the stage 106. The moving mechanism 107 can move the substrate 113 to be processed in the X-axis direction and the Y-axis direction (not shown). Note that, for example, a ball, a top, a motor, or the like may be installed below the moving mechanism 107.
[0077]
In this embodiment, the concentric pattern, which has been a problem with laser light, is not formed, or the formation of the concentric pattern can be reduced, and the reliability of the manufactured semiconductor device can be improved.
[0078]
[Example 6]
A laser annealing apparatus different from the first, fourth, and fifth embodiments, particularly an example of a moving mechanism for moving the stage will be described with reference to FIG.
[0079]
In general, a stage on which a workpiece to be irradiated with laser light is placed is moved along a guide rail provided in the X-axis direction or the Y-axis direction. An object having a curved surface called a ball (bearing) is sandwiched between the guide rail and the part (slider) that fixes the stage, and the stage can be moved smoothly by reducing the load caused by friction. Such a mechanism is provided.
[0080]
Since this ball is worn by repeated movements of the stage, it is necessary to replace it with regular maintenance, and in order to move the stage more smoothly, it is necessary to reduce the friction generated when moving the stage. there were.
[0081]
FIG. 13A shows a moving mechanism for moving the stage of this embodiment. Reference numeral 1300 denotes a guide rail, and unevenness is formed along one direction in order to move the stage in a certain direction. Reference numeral 1301 denotes a part for fixing a stage called a slider, which can be moved along the guide rail 1300. A plurality of sliders may be provided in a fixed state so as to maintain a constant interval. The rod 1302 is an axis that passes through a hole provided in the slider 1301, and is provided in a direction along the guide rail. The rod 1302 is fixed to the guide rail 1300 by an end plate 1304.
[0082]
A power supply voltage and air are sent to the slider 1301 via a cable 1303. FIG. 13B shows an enlarged view of the slider 1301. The slider 1301 generates a magnetic field that attracts the slider 1301 and the guide rail 1300 by the power supply voltage. Further, the slider 1301 generates a magnetic field in a direction away from the rod 1302 so as not to contact the rod 1302 in the hole provided in the slider 1301, and the slider 1301 moves in the direction of the arrow using the principle of the linear motor. On the other hand, a force acts on the slider 1301 and the guide rail 1300 in the direction attracted by this magnetic field. The air sent to the slider 1301 is discharged between the slider 1301 and the guide rail 1300 from the air hole 1305. Since the force acts in the direction away from the attractive force of the magnetic field and the release of air, a constant interval is maintained.
[0083]
Instead of generating a magnetic field by a power supply voltage applied via a cable, either the guide rail 1300 or the slider 1301 is formed of a magnetic material, and the other is formed of a material that can be attracted by the magnetic material. A magnetic field may be generated. Further, both the guide rail 1300 and the slider 1301 may be magnetic materials.
[0084]
In addition, a magnetic field is not generated by a power supply voltage applied via a cable, but a material having a property in which a force is exerted in a direction in which one of the rod 1302 and the slider 1301 moves away from the magnetic body. A magnetic field may be generated as it is formed. Further, both the rod 1302 and the slider 1301 may be magnetic materials.
[0085]
By using the stage moving mechanism as shown in the present embodiment, it becomes possible to move the stage along the guide rail in a non-contact manner, eliminating the need for periodic ball replacement due to ball wear, Maintenance can be facilitated. Further, since it is non-contact, there is almost no friction, and the stage can be moved more smoothly than when a ball is used.
[0086]
FIG. 13C shows a state in which an object 1311 to be irradiated with laser light is placed on a stage 1310 fixed on a slider 1301. The stage moving means of this embodiment makes the stage move more smoothly, so that the laser beam can be irradiated more uniformly.
[0087]
【The invention's effect】
If the laser annealing apparatus of the present invention is used, a concentric pattern, which has been a problem by condensing a plurality of laser beams in one bundle, is not formed, or the formation of a concentric pattern can be reduced, and the semiconductor device manufactured Reliability can be improved. If the laser annealing apparatus of the present invention is used, sufficient and uniform laser light can be irradiated even on a semiconductor film on a large substrate.
[0088]
Further, according to the present invention, in addition to processing the laser beam into an elliptical shape or a linear shape in the process including the laser annealing method to improve the throughput, a solid laser that is easier to maintain is used. Throughput can be improved over laser annealing using an excimer laser. As a result, the manufacturing cost of a semiconductor device such as a TFT or a display device formed of the TFT can be reduced.
[0089]
Furthermore, the concentric pattern formed in the semiconductor film can be removed or reduced by irradiating the semiconductor film with laser light obliquely, and the physical properties of the semiconductor film after laser annealing are made uniform. Can do. When a semiconductor device is manufactured using such a semiconductor film, the performance of the semiconductor device can be significantly improved.
[Brief description of the drawings]
FIG. 1 illustrates an example of laser light irradiation.
FIG. 2 is a diagram showing an example of the configuration of a laser annealing apparatus.
FIG. 3 is a diagram showing an example of the configuration of a laser annealing apparatus.
FIG. 4 is a diagram for explaining x and y directions of a substrate to be processed.
FIG. 5 is a diagram showing a relationship between a moving time and a speed of a substrate.
FIG. 6 is a diagram showing an example of a laser annealing apparatus of the present invention.
FIGS. 7A to 7C illustrate a manufacturing process of a semiconductor device. FIGS.
FIG. 8 shows a semiconductor device of the present invention.
FIG. 9A is a schematic diagram of a TFT in a pixel portion.
(B) Schematic diagram of TFT in drive circuit
FIG. 10A is a graph showing reflectance with respect to wavelength in an amorphous silicon film (film thickness: 55 nm).
(B) The figure which shows the transmittance | permeability with respect to the wavelength in an amorphous silicon film (film thickness 55nm).
FIG. 11 is a diagram showing an example of the configuration of a laser annealing apparatus.
FIG. 12 is a diagram showing an example of the configuration of a laser annealing apparatus.
FIG. 13 is a diagram showing an example of the configuration of a laser annealing apparatus.

Claims (5)

A guide rail with irregularities formed along one direction;
A slider provided on the unevenness and provided with a hole;
A movement mechanism provided with a rod penetrating the hole and provided in a direction along the one direction;
A stage provided on the slider and on which a workpiece to be irradiated with laser light is placed;
The slider is connected to a power supply voltage that generates a first magnetic field that attracts the guide rail and a second magnetic field that does not contact the rod in the hole,
The laser irradiation apparatus according to claim 1, wherein the slider is provided with an air hole for discharging air toward the guide rail. In claim 1,
The laser irradiation apparatus according to claim 1, wherein the slider moves along the one direction by generating the first magnetic field and the second magnetic field. In claim 1 or claim 2,
The laser beam is a solid laser beam,
The laser irradiation apparatus, wherein the laser beam is irradiated to the object to be processed from an oblique direction. A guide rail with irregularities formed along one direction;
A slider provided on the unevenness and provided with a hole;
A movement mechanism provided with a rod penetrating the hole and provided in a direction along the one direction;
A method of manufacturing a semiconductor device that performs laser light irradiation using a laser irradiation device having a stage provided on the slider,
A substrate on which a semiconductor film is formed is placed on the stage,
Irradiating the laser beam to the semiconductor film while moving the stage in the one direction,
The movement of the stage causes the slider to generate a first magnetic field that attracts the guide rail and a second magnetic field that does not come into contact with the rod in the hole, and releases air toward the guide rail. A method for manufacturing a semiconductor device, which is performed while the method is performed. In claim 4,
The laser beam is a solid laser beam,
The method for manufacturing a semiconductor device, wherein the semiconductor film is irradiated with the laser light from an oblique direction.

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