JP3920065B2 - Method for manufacturing thin film transistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of annealing a semiconductor film using laser light (hereinafter referred to as laser annealing) and a laser apparatus for performing the method (laser and an optical system for guiding laser light output from the laser to an object to be processed) Apparatus). Further, the present invention relates to a semiconductor device manufactured by including the laser annealing in a process and a manufacturing method thereof. Note that the semiconductor device here includes an electro-optical device such as a liquid crystal display device or an EL display device, and an electronic device including the electro-optical device as a component.
[0002]
[Prior art]
In recent years, thin film transistors (hereinafter referred to as TFTs) have been developed, and TFTs using a polycrystalline silicon film (polysilicon film) as a crystalline semiconductor film have attracted attention. In particular, liquid crystal display devices (liquid crystal displays) and EL (electroluminescence) display devices (EL displays) are used as elements that form elements that switch pixels and drive circuits that control the pixels.
[0003]
As a means for obtaining a polysilicon film, a technique for crystallizing an amorphous silicon film (amorphous silicon film) to form a polysilicon film is generally used. In particular, recently, a method of crystallizing an amorphous silicon film using laser light has attracted attention. In this specification, means for crystallizing an amorphous semiconductor film with laser light to obtain a crystalline semiconductor film is called laser crystallization.
[0004]
Laser crystallization is an effective technique for annealing a semiconductor film formed on a substrate having low heat resistance, such as a glass substrate or a plastic substrate, which can instantaneously heat the semiconductor film. Further, the throughput is much higher than that of a heating means using a conventional electric furnace (hereinafter referred to as furnace annealing).
[0005]
There are various types of laser light. Generally, laser crystallization using laser light (hereinafter referred to as excimer laser light) using a pulsed excimer laser as an oscillation source is used. The excimer laser has the advantage that it has a large output 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.
[0006]
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.
[0007]
In addition, replacement of attached devices 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.
[0008]
As described above, laser devices using excimer laser light have high performance, but they are very laborious to maintain. It also has the drawback of being expensive.
[0009]
[Problems to be solved by the invention]
It is an object of the present invention to provide a laser device and a laser annealing method using the same that can obtain a crystalline semiconductor film having a larger crystal grain size than the prior art and that have a low running cost. It is another object of the present invention to provide a semiconductor device manufactured using such a laser annealing method and a manufacturing method thereof.
[0010]
[Means for Solving the Problems]
The present invention is characterized in that a laser beam using a solid-state laser (a laser that outputs a laser beam having a crystal rod as a resonant cavity) as an oscillation source is irradiated to the front and back surfaces of the semiconductor film.
[0011]
At this time, it is desirable that the laser light be processed into a linear shape by an optical system and irradiated. In addition, processing a laser beam into a line means that the laser beam is processed so that the shape of the irradiated surface when the laser beam is irradiated onto the object to be processed is linear. 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 rectangle (or oval) having a large aspect ratio. For example, the aspect ratio is 10 or more (preferably 100 to 10,000).
[0012]
In the above configuration, a commonly known solid-state laser can be used, such as a YAG laser (usually Nd: YAG 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. Further, YAG laser includes a continuous oscillation type and a pulse oscillation type. In the present invention, it is desirable to use a pulse oscillation type YAG laser capable of irradiating a large area.
[0013]
However, since the fundamental wave (first harmonic) of the YAG laser has a long wavelength of 1064 nm, the second harmonic (wavelength 532 nm), the third harmonic (wavelength 355 nm), or the fourth harmonic (wavelength 266 nm) is used. Is preferred.
[0014]
In particular, the wavelength of the second harmonic of the YAG laser is 532 nm, and when the amorphous semiconductor film is irradiated, it is within the wavelength range (around 530 nm) that is not reflected by the amorphous semiconductor film. Further, in this wavelength range, since the laser beam that passes through the amorphous semiconductor film has a sufficient amount of light, it can be efficiently irradiated by irradiating the amorphous semiconductor film from the back side again using a reflector. . The laser energy of the second harmonic is as large as about 1.5 J / pulse at the maximum (in the existing pulse oscillation type YAG laser device), and when processed into a linear shape, the length in the longitudinal direction is dramatically increased. It can be lengthened, and large area laser light irradiation can be performed at once. These harmonics can be obtained using a nonlinear crystal.
[0015]
The fundamental wave 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 having a solid laser as an oscillation source” includes not only the fundamental wave but also the second harmonic wave, the third harmonic wave, and the fourth harmonic wave whose wavelength is modulated in the middle. .
[0016]
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. This is a known technique.
[0017]
Since the solid-state laser used in the present invention basically has a solid crystal, a resonant mirror, and a light source for exciting the solid crystal, the laser beam can be output, so that 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 semiconductor device can be greatly reduced. Further, if the number of maintenance operations is reduced, the operation rate of the mass production line is increased, so that the overall throughput of the manufacturing process is improved, which also greatly contributes to the reduction of the manufacturing cost of the semiconductor device. Furthermore, since the area occupied by the solid-state laser is smaller than that of the excimer laser, it is advantageous for designing the production line.
[0018]
In addition, by performing laser annealing with a configuration in which laser light is irradiated on the front and back surfaces of the amorphous semiconductor film, compared to the conventional case (when only the surface of the amorphous semiconductor film is irradiated with laser light). A crystalline semiconductor film having a large crystal grain size can be obtained. By irradiating laser light from the front and back surfaces of the amorphous semiconductor film, the applicant has a slow melting and solidification cycle of the silicon film, and the time allowed for crystal growth in the solidification process is relatively It is considered that the crystal grain size can be increased as a result.
[0019]
By obtaining a crystalline semiconductor film having a large crystal grain size, the performance of the semiconductor device can be greatly improved. For example, taking TFT as an example, the number of crystal grain boundaries that can be included in the channel formation region can be reduced by increasing the crystal grain size. That is, a TFT having one crystal grain boundary, preferably zero, in the channel formation region can be manufactured. In addition, since each crystal grain has crystallinity that can be regarded as a single crystal, high mobility (field effect mobility) equivalent to or higher than that of a transistor using a single crystal semiconductor can be obtained.
[0020]
Furthermore, since the number of times the carriers cross the crystal grain boundary can be extremely reduced, an on-current value (drain current value that flows when the TFT is in an on state) and an off-current value (drain current that flows when the TFT is in an off state) Value), threshold voltage, S value, and field-effect mobility can be reduced.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
One embodiment of the present invention will be described. FIG. 1A is a diagram showing a configuration of a laser apparatus including a laser according to the present invention. This laser apparatus is an optical system that linearly processes laser light (preferably second harmonic, third harmonic, or fourth harmonic) using Nd: YAG laser 101 and Nd: YAG laser 101 as an oscillation source. 201 includes a stage 102 for fixing a light-transmitting substrate, and the stage 102 is provided with a heater 103 and a heater controller 104 so that the substrate can be heated to 100 to 450 ° C. A reflector 105 is provided on the stage 102, and a substrate 106 on which an amorphous semiconductor film is formed is provided thereon.
[0022]
When the laser beam output from the Nd: YAG laser 101 is modulated into any of the second to fourth harmonics, a wavelength modulator including a nonlinear element may be provided immediately after the Nd: YAG laser 101. .
[0023]
Next, a method for holding the substrate 106 in the laser device having the structure shown in FIG. 1A will be described with reference to FIG. The substrate 106 held on the stage 102 is set in a reaction chamber 107 and irradiated with linear laser light using the laser 101 as an oscillation source. The reaction chamber can be in a reduced pressure state or an inert gas atmosphere by an exhaust system or a gas system not shown, and can be heated to 100 to 450 ° C. without contaminating the semiconductor film.
[0024]
Further, the stage 102 can move along the guide rail 108 in the reaction chamber, and can irradiate the entire surface of the substrate with linear laser light. The laser light is incident from a quartz window (not shown) provided on the upper surface of the substrate 106. In FIG. 1B, a transfer chamber 109, an intermediate chamber 110, and a load / unload chamber 111 are connected to the reaction chamber 107, and the chambers are separated by gate valves 112 and 113.
[0025]
A cassette 114 capable of holding a plurality of substrates is installed in the load / unload chamber 111, and the substrates are transferred by a transfer robot 115 provided in the transfer chamber 109. Substrate 106 ′ represents the substrate being transferred. With such a configuration, laser annealing can be continuously processed under reduced pressure or in an inert gas atmosphere.
[0026]
Next, the configuration of the optical system 201 that linearizes laser light will be described with reference to FIG. 2A is a view of the optical system 201 as viewed from the side, and FIG. 2B is a view of the optical system 201 as viewed from the top.
[0027]
Laser light using the laser 101 as an oscillation source is divided in the vertical direction by a cylindrical lens array 202. The divided laser light is further divided in the horizontal direction by the cylindrical lens 203. That is, the laser light is finally divided into a matrix by the cylindrical lens arrays 202 and 203.
[0028]
The laser light is once condensed by the cylindrical lens 204. At that time, it passes through the cylindrical lens 205 immediately after the cylindrical lens 204. Thereafter, the light is reflected by the mirror 206, passes through the cylindrical lens 207, and reaches the irradiation surface 208.
[0029]
At this time, the laser light projected on the irradiation surface 208 shows a linear irradiation surface. That is, it means that the cross-sectional shape of the laser light transmitted through the cylindrical lens 207 is linear. The homogenization in the width direction (short direction) of the laser light processed into a linear shape is performed by the cylindrical lens array 202, the cylindrical lens 204, and the cylindrical lens 207. The homogenization of the laser beam in the length direction (long direction) is performed by the cylindrical lens array 203 and the cylindrical lens 205.
[0030]
Next, a structure for irradiating laser light from the front and back surfaces of the film to be processed formed on the substrate will be described with reference to FIG. FIG. 3 shows the positional relationship between the substrate 106 and the reflector 105 in FIG.
[0031]
In FIG. 3, reference numeral 301 denotes a light-transmitting substrate, and an insulating film 302 and an amorphous semiconductor film (or microcrystalline semiconductor film) 303 are formed on the surface (the surface on which a thin film or an element is formed). Yes. A reflector 304 for reflecting the laser light is disposed under the translucent substrate 301.
[0032]
As the light-transmitting substrate 301, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate is used. The insulating film 302 may be an insulating film containing silicon such as a silicon oxide film or a silicon nitride oxide film (SiOxNy). The amorphous semiconductor film 303 can be an amorphous silicon film, an amorphous silicon germanium film, or the like.
[0033]
Further, the reflector 304 may be a substrate on which a metal film is formed on the surface (laser light reflecting surface) or a substrate made of a metal element. In this case, any material may be used for the metal film. Typically, a metal film containing any element of aluminum, silver, tungsten, titanium, and tantalum is used.
[0034]
Further, instead of disposing the reflector 304, it is also possible to form the metal film as described above directly on the back surface (surface opposite to the front surface) of the substrate 301 and reflect the laser beam there. However, the configuration is based on the premise that the metal film formed on the back surface in the manufacturing process of the semiconductor device is not removed.
[0035]
Then, the amorphous semiconductor film 303 is irradiated with a laser beam processed into a linear shape via the optical system 201 described in FIG. 2 (only the cylindrical lens 207 is shown in the drawing).
[0036]
At this time, the laser light irradiated onto the amorphous semiconductor film 303 is irradiated with the laser light 305 directly irradiated through the cylindrical lens 207 and the reflector 304 once reflected by the reflector 304. Laser light 306 to be emitted. Note that in this specification, laser light applied to the surface of the amorphous semiconductor film is referred to as primary laser light, and laser light applied to the back surface is referred to as secondary laser light.
[0037]
The laser beam that has passed through the cylindrical lens 207 has an incident angle of 45 to 90 ° with respect to the substrate surface in the process of being condensed. Therefore, the secondary laser light 306 irradiates around the back surface side of the amorphous semiconductor film 303. Moreover, the secondary laser beam 306 can be obtained more efficiently by providing the undulating portion on the reflecting surface of the reflector 304 to diffusely reflect the laser beam.
[0038]
In particular, the wavelength of the second harmonic of the YAG laser is 532 nm, and when the amorphous semiconductor film is irradiated, it is within the wavelength range (around 530 nm) that is not reflected by the amorphous semiconductor film. Further, in this wavelength range, since the laser beam that passes through the amorphous semiconductor film has a sufficient amount of light, it can be efficiently irradiated by irradiating the amorphous semiconductor film from the back side again using a reflector. . Also, the laser energy of the second harmonic is as large as about 1.5 J / pulse at the maximum value (in the existing YAG laser device), and when processed into a linear shape, the length in the longitudinal direction should be dramatically increased. This enables large area laser light irradiation.
[0039]
As described above, according to the present embodiment, it is possible to process a laser beam using a solid laser as an oscillation source into a linear shape, and the laser beam is converted into a primary laser beam and a secondary laser beam. It is possible to irradiate the surface and the back surface of the amorphous semiconductor film.
[0040]
[Embodiment 2]
In the present embodiment, an embodiment different from the first embodiment will be described. In this embodiment, an example is shown in which a two-system laser beam dispersed in the middle of an optical system is irradiated from the front and back surfaces of an amorphous semiconductor film without using a reflector as in the first embodiment.
[0041]
FIG. 4A is a diagram illustrating a configuration of a laser apparatus including the laser according to the present embodiment. Since the basic configuration is the same as that of the laser apparatus of FIG. 1 described in the first embodiment, different reference numerals are used for the description.
[0042]
This laser apparatus linearly processes laser light (preferably the third harmonic or the fourth harmonic) using the Nd: YAG laser 101 and the Nd: YAG laser 101 as an oscillation source, and splits it into two systems. An optical system 401 and a translucent stage 402 for fixing the translucent substrate are included. A substrate 403a is provided over the stage 402, and an amorphous semiconductor film 403b is formed thereon.
[0043]
When the laser beam output from the Nd: YAG laser 101 is modulated into any of the second to fourth harmonics, a wavelength modulator including a nonlinear element may be provided immediately after the Nd: YAG laser 101. .
[0044]
In the case of this embodiment, the stage 402 must have a light-transmitting property in order to irradiate the amorphous semiconductor film 403b with the laser light transmitted through the stage 402. In addition, the energy of the laser light (secondary laser light) irradiated from the stage 402 side is expected to be attenuated when it passes through the substrate. Therefore, it is desirable to suppress the attenuation at the stage 402 as much as possible.
[0045]
FIG. 4B illustrates a method for holding the substrate 403a in the laser apparatus illustrated in FIG. 4A. FIG. 4B illustrates the method except that the light-transmitting stage 402 is used. Since the configuration is the same, the description thereof is omitted.
[0046]
Next, the structure of the optical system 401 illustrated in FIG. 4A will be described with reference to FIG. FIG. 5B is a view of the optical system 401 as viewed from the side. Laser light (third harmonic or fourth harmonic) using an Nd: YAG laser 501 as an oscillation source is divided in the vertical direction by a cylindrical lens array 502. This divided laser beam is further divided in the lateral direction by a cylindrical lens 503. In this way, the laser light is divided into a matrix by the cylindrical lens arrays 502 and 503.
[0047]
The laser light is once condensed by the cylindrical lens 504. At that time, it passes through the cylindrical lens 505 immediately after the cylindrical lens 504. Up to this point, the optical system is the same as that shown in FIG.
[0048]
Thereafter, the laser light enters the half mirror 506, where the laser light is split into a primary laser light 507 and a secondary laser light 508. The primary laser beam 507 is reflected by the mirrors 509 and 510, passes through the cylindrical lens 511, and then reaches the surface of the amorphous semiconductor film 403b.
[0049]
The secondary laser light 508 dispersed by the half mirror 506 is reflected by the mirrors 512, 513, and 514, passes through the cylindrical lens 515, passes through the substrate 403a, and reaches the back surface of the amorphous semiconductor film 403b. .
[0050]
At this time, similarly to the first embodiment, the laser light projected on the irradiation surface of the substrate shows a linear irradiation surface. Further, the homogenization in the width direction (short direction) of the laser beam processed into a linear shape is performed by the cylindrical lens array 502, the cylindrical lens 504, and the cylindrical lens 515. The homogenization of the laser beam in the length direction (long direction) is performed by the cylindrical lens array 503, the cylindrical lens 505, and the cylindrical lens 509.
[0051]
As described above, according to the present embodiment, it is possible to process a laser beam using a solid laser as an oscillation source into a linear shape, and the laser beam is converted into a primary laser beam and a second laser beam by an optical system. It is possible to irradiate the front surface and the back surface of the amorphous semiconductor film by splitting into the next laser beam.
[0052]
[Embodiment 3]
An embodiment different from the second embodiment of the present invention will be described. In the present embodiment, the two laser beams dispersed in the middle of the optical system are respectively set as the third harmonic and the fourth harmonic, the surface of the amorphous semiconductor film is the fourth harmonic, and the back is the third harmonic. Shows an example of laser annealing.
[0053]
FIG. 6 is a side view of the optical system of the laser apparatus used in this embodiment. Laser light using the Nd: YAG laser 601 as an oscillation source is split by a half mirror 602. Although not shown, a part of the fundamental wave output from the Nd: YAG laser 601 is modulated into a third harmonic wave having a wavelength of 355 nm before reaching the half mirror 602.
[0054]
First, a laser beam (secondary laser beam) transmitted through the half mirror 602 is amorphous through the cylindrical lens arrays 603 and 604, the cylindrical lenses 605 and 606, the mirror 607, the cylindrical lens 608, and the substrate 609a. The back surface of the quality semiconductor film 609b is irradiated.
[0055]
Note that laser light finally irradiated to the amorphous semiconductor film 609b is processed into a linear shape. The process of processing into a linear shape is the same as the description of the optical system in FIG.
[0056]
The laser light reflected by the half mirror 602 (which becomes the primary laser light) is modulated into a fourth harmonic having a wavelength of 266 nm by a wavelength modulator 610 including a nonlinear element. Thereafter, the surface of the amorphous semiconductor film 609b is irradiated through the mirror 611, the cylindrical lens arrays 612 and 613, the cylindrical lenses 614 and 615, the mirror 616, and the cylindrical lens 617.
[0057]
Note that laser light finally irradiated to the amorphous semiconductor film 609b is processed into a linear shape. The process of processing into a linear shape is the same as the description of the optical system in FIG.
[0058]
As described above, in the present embodiment, the surface of the amorphous semiconductor film is irradiated with the fourth harmonic wave with a wavelength of 266 nm, and the back surface of the amorphous semiconductor film is irradiated with the third harmonic wave with a wavelength of 355 nm. It is characterized by In addition, it is preferable to process the cross-sectional shapes of the third harmonic and the fourth harmonic into a linear shape as in the present embodiment because the throughput of laser annealing is improved.
[0059]
When the substrate 609a is a glass substrate, light having a wavelength shorter than that near the wavelength of 250 nm is not transmitted. For example, Corning # 1737 substrate (1.1 mm thick) begins to transmit from about 240 nm and transmits about 38% at 300 nm, about 85% at 350 nm, and about 90% at 400 nm. That is, when the substrate 609a is a glass substrate, it is preferable to use a laser beam having a wavelength of 350 nm or more (preferably a wavelength of 400 nm or more) as the secondary laser beam.
[0060]
Therefore, when an Nd: YAG laser is used as a solid-state laser and a glass substrate is used as a substrate on which an amorphous semiconductor film is formed as in the present embodiment, the first laser beam that does not pass through the substrate is set as the fourth harmonic. It is desirable that the secondary laser light transmitted through the substrate is the third harmonic.
[0061]
As described above, according to the material of the substrate or the film quality of the amorphous semiconductor film, the laser beam (primary laser beam) irradiated on the surface of the amorphous semiconductor film and the laser beam (first laser beam irradiated on the back surface) It is effective to change the wavelength of the secondary laser light.
[0062]
In the present embodiment, laser light using one laser as an oscillation source is spectrally used. However, two lasers that output laser light having different wavelengths may be used.
[0063]
【Example】
[Example 1]
An embodiment of the present invention will be described with reference to FIGS. Here, a method for simultaneously manufacturing a pixel TFT and a storage capacitor in a pixel portion and an n-channel TFT and a p-channel TFT in a driver circuit provided around the pixel portion will be described.
[0064]
In FIG. 7A, a substrate 701 includes polyethylene terephthalate (PET), polyethylene in addition to a glass substrate such as barium borosilicate glass or aluminoborosilicate glass represented by Corning # 7059 glass or # 1737 glass. A plastic substrate having no optical anisotropy such as naphthalate (PEN) or polyethersulfone (PES) can be used.
[0065]
Then, in order to prevent impurity diffusion from the substrate 701, a base film 702 such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed on the surface of the substrate 701 where the TFT is formed. In this example, SiH is used by plasma CVD. _Four , NH _Three , N ₂ A silicon oxynitride film 702a made of O is formed to 10 to 200 nm (preferably 50 to 100 nm), similarly to SiH. _Four , N ₂ A silicon oxynitride silicon film 702b made of O is stacked to a thickness of 50 to 200 nm (preferably 100 to 150 nm).
[0066]
The silicon oxynitride film is formed by using a conventional parallel plate type plasma CVD method. The silicon oxynitride film 702a is formed of SiH. _Four 10SCCM, NH _Three To 100 SCCM, N ₂ O was introduced into the reaction chamber as 20 SCCM, the substrate temperature was 325 ° C., the reaction pressure was 40 Pa, and the discharge power density was 0.41 W / cm. ² The discharge frequency is 60 MHz. On the other hand, the silicon oxynitride silicon film 702b is formed of SiH. _Four 5SCCM, N ₂ O for 120 SCCM, H ₂ Was introduced into the reaction chamber as 125 SCCM, the substrate temperature was 400 ° C., the reaction pressure was 20 Pa, and the discharge power density was 0.41 W / cm. ² The discharge frequency is 60 MHz. These films can be formed continuously only by changing the substrate temperature and switching the reaction gas.
[0067]
Further, the silicon oxynitride film 702a is formed so that the internal stress becomes a tensile stress with the substrate as the center. The silicon oxynitride film 702b also has an internal stress in the same direction, but the stress is smaller than that of the silicon oxynitride film 702a in absolute value.
[0068]
Next, an amorphous semiconductor film 703 having a thickness of 25 to 80 nm (preferably 30 to 60 nm) is formed by a known method such as a plasma CVD method or a sputtering method. For example, an amorphous silicon film is formed to a thickness of 55 nm by plasma CVD. At this time, the base film 702 and the amorphous semiconductor film 703 can be formed continuously. For example, as described above, after the silicon oxynitride film 702a and the silicon oxynitride silicon film 702b are continuously formed by a plasma CVD method, the reaction gas is changed to SiH. _Four , N ₂ O, H ₂ To SiH _Four And H ₂ Or SiH _Four If it is switched to only, it can be continuously formed without being once exposed to the air atmosphere. As a result, contamination of the surface of the silicon oxynitride silicon film 702b can be prevented, and variations in characteristics and threshold voltage of the manufactured TFT can be reduced.
[0069]
First, island-shaped semiconductor layers 704 to 708 having a first shape are formed from the semiconductor layer 703 having an amorphous structure as indicated by a dotted line in FIG. FIG. 10A is a top view of the island-shaped semiconductor layers 704 and 705 in this state, and similarly, FIG. 11A shows a top view of the island-shaped semiconductor layer 708.
[0070]
10 and 11, the island-like semiconductor layer is rectangular and is formed so that one side is 50 μm or less. However, the shape of the island-like semiconductor layer can be arbitrary, and preferably from the center to the end. Any polygon or circle can be used as long as the minimum distance to the part is 50 μm or less.
[0071]
Next, a crystallization process is performed on such island-shaped semiconductor layers 704 to 708. For the crystallization step, any of the methods described in Embodiments 1 to 3 can be used. In this example, laser annealing is performed on the island-shaped semiconductor layers 704 to 708 by the method of Embodiment 1. In this way, island-like semiconductor layers 709 to 713 made of a crystalline silicon film shown by a solid line in FIG. 7B are formed.
[0072]
In this embodiment, an example in which one island-like semiconductor layer is formed corresponding to one TFT is shown. However, when the exclusive area of the island-like semiconductor layer is large (the size of one TFT is large). In the case), it is possible to function as one TFT by dividing a plurality of island-like semiconductor layers and connecting a plurality of TFTs in series.
[0073]
At this time, as the amorphous silicon film crystallizes, the film becomes dense and contracts by about 1 to 15%. A region 714 in which distortion is generated by contraction is formed at the end of the island-shaped semiconductor layer. Moreover, the island-like semiconductor layer made of such a crystalline silicon film has a tensile stress with the substrate as the center. FIGS. 10B and 11B are top views of the island-shaped semiconductor layers 709, 710, and 713 in this state, respectively. In the drawing, regions 704, 705, and 708 indicated by dotted lines indicate the sizes of the original island-shaped semiconductor layers 704, 705, and 708, respectively.
[0074]
When the TFT gate electrode is formed over the region 714 where such strain is accumulated, this portion has a large number of defect levels as described above, and the crystallinity is not good. Cause. For example, the off-current value increases or the current concentrates in this region and locally generates heat.
[0075]
Therefore, as shown in FIG. 7C, the second shape island-shaped semiconductor layers 715 to 719 are formed so that the region 714 in which such strain is accumulated is removed. 714 'indicated by a dotted line in the figure is a region where a region 714 where strain is accumulated exists, and shows a state where island-shaped semiconductor layers 715 to 719 having the second shape are formed inside the region. The shape of the second shape island-shaped semiconductor layers 715 to 719 may be an arbitrary shape. FIG. 10C shows a top view of the island-shaped semiconductor layers 715 and 714 in this state. Similarly, FIG. 11C shows a top view of the island-shaped semiconductor layer 719.
[0076]
Thereafter, a mask layer 720 made of a silicon oxide film having a thickness of 50 to 100 nm is formed by plasma CVD method or sputtering method so as to cover the island-like semiconductor layers 715 to 719. In this state, an impurity element imparting p-type is added to the island-like semiconductor layer for the purpose of controlling the threshold voltage (Vth) of the TFT by 1 × 10 ¹⁶ ~ 5x10 ¹⁷ atoms / cm ^Three You may add to the whole surface of an island-like semiconductor layer with a density | concentration of a grade.
[0077]
As an impurity element imparting p-type to a semiconductor, elements of Group 13 of the periodic table such as boron (B), aluminum (Al), and gallium (Ga) are known. As the method, an ion implantation method or an ion doping method can be used, but an ion doping method is suitable for processing a large-area substrate. In the ion doping method, diborane (B ₂ H ₆ ) As a source gas and boron (B) is added. Such impurity element implantation is not necessarily required and may be omitted, but is particularly effective for keeping the threshold voltage of the n-channel TFT within a predetermined range.
[0078]
In order to form the LDD region of the n-channel TFT of the driver circuit, an impurity element imparting n-type conductivity is selectively added to the island-shaped semiconductor layers 716 and 718. Therefore, resist masks 721a to 721e are formed in advance. As the impurity element imparting n-type conductivity, phosphorus (P) or arsenic (As) may be used. Here, phosphorous (PH) is added to add phosphorus (P). _Three ) Is used.
[0079]
The formed impurity regions are low-concentration n-type impurity regions 722 and 723, and the phosphorus (P) concentration is 2 × 10. ¹⁶ ~ 5x10 ¹⁹ atoms / cm ^Three It may be in the range. In this specification, the concentration of an impurity element imparting n-type contained in the impurity regions 722 and 723 formed here is defined as (n ^- ). The impurity region 724 is a semiconductor layer for forming a storage capacitor of the pixel portion, and phosphorus (P) is added to this region at the same concentration (FIG. 7D).
[0080]
Next, a step of activating the added impurity element is performed. The activation can be performed by a heat treatment at 500 to 600 ° C. for 1 to 4 hours or a laser activation method in a nitrogen atmosphere. Moreover, you may carry out using both together. In the case of the laser activation method, a linear beam is formed using KrF excimer laser light (wavelength 248 nm), and the oscillation frequency is 5 to 50 Hz, and the energy density is 100 to 500 mJ / cm. ² As a result, the entire surface of the substrate on which the island-shaped semiconductor layer is formed is processed by scanning the linear beam with an overlap ratio of 80 to 98%. Note that there are no particular limitations on the irradiation conditions of the laser beam, and the practitioner may make an appropriate decision. This step may be performed while leaving the mask layer 720, or may be performed after the removal.
[0081]
In FIG. 7E, the gate insulating film 725 is formed of an insulating film containing silicon with a thickness of 40 to 150 nm by a plasma CVD method or a sputtering method. For example, it is preferable to form a silicon oxynitride film with a thickness of 120 nm. SiH _Four And N ₂ O to O ₂ A silicon oxynitride film manufactured by adding N is a preferable material for this application because the fixed charge density in the film is reduced. Needless to say, the gate insulating film 725 is not limited to such a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure. In any case, the gate insulating film 725 is formed so as to have a compressive stress about the substrate.
[0082]
Then, as shown in FIG. 7E, a heat-resistant conductive layer for forming a gate electrode is formed over the gate insulating film 725. Although the heat-resistant conductive layer may be formed as a single layer, it may have a laminated structure including a plurality of layers such as two layers or three layers as necessary. Such a heat-resistant conductive material is preferably used, for example, a structure in which a conductive layer (A) 726 made of a conductive nitride metal film and a conductive layer (B) 727 made of a metal film are stacked.
[0083]
The conductive layer (B) 727 is an element selected from tantalum (Ta), titanium (Ti), molybdenum (Mo), and tungsten (W), an alloy containing the element as a main component, or an alloy film in which the elements are combined. (Typically, a Mo—W alloy film or a Mo—Ta alloy film) may be used, and the conductive layer (A) 726 may be a tantalum nitride (TaN), tungsten nitride (WN), titanium nitride (TiN) film, or nitride. It is made of molybdenum (MoN) or the like. For the conductive layer (A) 726, tungsten silicide, titanium silicide, or molybdenum silicide may be used.
[0084]
In addition, the conductive layer (B) 727 is preferably reduced in the concentration of impurities contained in order to reduce resistance, and in particular, the oxygen concentration is preferably 30 ppm or less. For example, tungsten (W) can realize a specific resistance value of 20 μΩcm or less by setting the oxygen concentration to 30 ppm or less.
[0085]
The conductive layer (A) 726 may be 10 to 50 nm (preferably 20 to 30 nm), and the conductive layer (B) 727 may be 200 to 400 nm (preferably 250 to 350 nm). When W is used as a gate electrode, argon (Ar) gas and nitrogen (N ₂ ) Gas is introduced to form the conductive layer (A) 726 with tungsten nitride (WN) to a thickness of 50 nm, and the conductive layer (B) 727 is formed with W to a thickness of 250 nm. As another method, the W film is tungsten hexafluoride (WF). ₆ Can also be formed by a thermal CVD method.
[0086]
In any case, in order to use as a gate electrode, it is necessary to reduce the resistance, and the resistivity of the W film is desirably 20 μΩcm or less. The resistivity of the W film can be reduced by increasing the crystal grains. However, when there are many impurity elements such as oxygen in W, crystallization is hindered and the resistance is increased. Therefore, in the case of sputtering, the resistivity is obtained by using a W target with a purity of 99.9999% and forming a W film with sufficient consideration so that impurities are not mixed in the gas phase during film formation. 9-20 μΩcm can be realized.
[0087]
On the other hand, when a TaN film is used for the conductive layer (A) 726 and a Ta film is used for the conductive layer (B) 727, it can be similarly formed by sputtering. The TaN film is formed using Ta as a target and a mixed gas of Ar and nitrogen as a sputtering gas, and the Ta film uses Ar as a sputtering gas. In addition, when an appropriate amount of Xe or Kr is added to these sputtering gases, the internal stress of the film to be formed can be relaxed and the film can be prevented from peeling. The resistivity of the α-phase Ta film is about 20 μΩcm and can be used as a gate electrode, but the resistivity of the β-phase Ta film is about 180 μΩcm and is not suitable for a gate electrode. Since the TaN film has a crystal structure close to an α phase, an α phase Ta film can be easily obtained by forming a Ta film thereon.
[0088]
Although not shown, it is effective to form a silicon film doped with phosphorus (P) with a thickness of about 2 to 20 nm under the conductive layer (A) 726. This improves adhesion and prevents oxidation of the conductive film formed thereon, and at the same time, an alkali metal element contained in a trace amount in the conductive layer (A) 726 or the conductive layer (B) 727 is added to the gate insulating film 725. It can be prevented from spreading. In any case, the conductive layer (B) 727 preferably has a resistivity in the range of 10 to 50 μΩcm.
[0089]
Next, resist masks 728a to 728f are formed using a photomask using a photolithography technique, and the conductive layer (A) 726 and the conductive layer (B) 727 are collectively etched to form gate electrodes 729 to 733. And the capacitor wiring 734 is formed. The gate electrodes 729 to 733 and the capacitor wiring 734 are integrally formed with 729a to 733a made of a conductive layer (A) and 729b to 733b made of a conductive layer (B) (FIG. 8A).
[0090]
In addition, FIG. 10D illustrates the positional relationship between the island-shaped semiconductor layers 715 and 716 and the gate electrodes 729 and 730 in this state. Similarly, the relation between the island-shaped semiconductor layer 719, the gate electrode 733, and the capacitor wiring 734 is illustrated in FIG. In FIGS. 10D and 11D, the gate insulating film 725 is omitted.
[0091]
The method for etching the conductive layer (A) and the conductive layer (B) may be selected appropriately by the practitioner. In order to perform etching with high accuracy, it is desirable to apply a dry etching method using high-density plasma. As a method for obtaining high-density plasma, microwave plasma or inductively coupled plasma (ICP) etching apparatus may be used.
[0092]
For example, the W etching method using an ICP etching apparatus uses CF as an etching gas. _Four And Cl ₂ These gases are introduced into the reaction chamber to a pressure of 0.5 to 1.5 Pa (preferably 1 Pa), and high frequency (13.56 MHz) power of 200 to 1000 W is applied to the inductive coupling portion. At this time, high-frequency power of 20 W is applied to the stage on which the substrate is placed, and the negative ions are charged by self-bias, whereby positive ions are accelerated and anisotropic etching can be performed. By using an ICP etching apparatus, a hard metal film such as W can obtain an etching rate of 2 to 5 nm / second. Further, in order to perform etching without leaving a residue, overetching is preferably performed by increasing the etching time at a rate of about 10 to 20%. However, it is necessary to pay attention to the etching selectivity with the base at this time. For example, since the selection ratio of the silicon oxynitride film (gate insulating film 725) to the W film is 2.5 to 3, the surface where the silicon oxynitride film is exposed by such over-etching is etched by about 20 to 50 nm. Being substantially thinner.
[0093]
Then, in order to form an LDD region in the n-channel TFT of the pixel TFT, an impurity element addition step (n ^- Doping step) is performed. An impurity element imparting n-type in a self-aligning manner may be added by an ion doping method using the gate electrodes 729 to 733 as a mask. The concentration of phosphorus (P) added as an impurity element imparting n-type is 1 × 10 ¹⁶ ~ 5x10 ¹⁹ atoms / cm ^Three Add in the concentration range of. In this manner, low-concentration n-type impurity regions 735 to 739 are formed in the island-shaped semiconductor layer as shown in FIG.
[0094]
Next, in the n-channel TFT, a high-concentration n-type impurity region that functions as a source region or a drain region is formed (n ⁺ Doping process). First, resist masks 740a to 740d are formed using a photomask, and an impurity element imparting n-type conductivity is added to form high-concentration n-type impurity regions 741 to 746. Phosphorus (P) is used for the impurity element imparting n-type, and its concentration is 1 × 10. ²⁰ ~ 1x10 ^{twenty one} atoms / cm ^Three The phosphine (PH _Three (FIG. 8C).
[0095]
Then, high-concentration p-type impurity regions 748 and 749 serving as a source region and a drain region are formed in the island-shaped semiconductor layers 715 and 717 forming the p-channel TFT. Here, an impurity element imparting p-type is added using the gate electrodes 729 and 731 as a mask, and a high concentration p-type impurity region is formed in a self-aligning manner. At this time, the island-shaped semiconductor films 716, 718, and 719 forming the n-channel TFT are covered with resist masks 747a to 747c by using a photomask.
[0096]
High-concentration p-type impurity regions 748 and 749 are formed of diborane (B ₂ H ₆ ) Using an ion doping method. The boron (B) concentration in this region is 3 × 10 ²⁰ ~ 3x10 ^{twenty one} atoms / cm ^Three (FIG. 8D).
[0097]
The high-concentration p-type impurity regions 748 and 749 are doped with phosphorus (P) in the previous step, and the high-concentration p-type impurity regions 748a and 749a have 1 × 10 6. ²⁰ ~ 1x10 ^{twenty one} atoms / cm ^Three In the high concentration p-type impurity regions 748b and 749b, 1 × 10 ¹⁶ ~ 5x10 ¹⁹ atoms / cm ^Three The concentration of boron (B) added in this step is 1.5 to 3 times the concentration of contained phosphorus, which causes problems as a source region and a drain region of a p-channel TFT. Can function without.
[0098]
After that, as shown in FIG. 9A, a protective insulating film 750 is formed over the gate electrode and the gate insulating film. The protective insulating film may be formed using a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or a stacked film including a combination thereof. In any case, the protective insulating film 750 is formed from an inorganic insulating material. The thickness of the protective insulating film 750 is 100 to 200 nm.
[0099]
Here, when a silicon oxide film is used, tetraethyl orthosilicate (TEOS) and O2 are formed by plasma CVD. ₂ The reaction pressure is 40 Pa, the substrate temperature is 300 to 400 ° C., and the high frequency (13.56 MHz) power density is 0.5 to 0.8 W / cm. ² And can be formed by discharging. When using a silicon oxynitride film, SiH is formed by plasma CVD. _Four , N ₂ O, NH _Three Silicon oxynitride film manufactured from SiH or SiH _Four , N ₂ A silicon oxynitride film formed from O may be used. The production conditions in this case are a reaction pressure of 20 to 200 Pa, a substrate temperature of 300 to 400 ° C., and a high frequency (60 MHz) power density of 0.1 to 1.0 W / cm. ² Can be formed. SiH _Four , N ₂ O, H ₂ Alternatively, a silicon oxynitride silicon film manufactured from the above may be used. Similarly, the silicon nitride film is made of SiH by plasma CVD. _Four , NH _Three It is possible to make from. Such a protective insulating film is formed so as to have a compressive stress with the substrate as the center.
[0100]
Thereafter, a step of activating the impurity element imparting n-type or p-type added at each concentration is performed. This process is performed by furnace annealing using an electric furnace. In addition, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied. In the furnace annealing method, it is preferably performed at 400 to 700 ° C., typically 500 to 600 ° C. in a nitrogen atmosphere having an oxygen concentration of 1 ppm or less, preferably 0.1 ppm or less, and in this example, 550 ° C. for 4 hours. Heat treatment is performed. In the case where a plastic substrate having a low heat resistant temperature is used for the substrate 701, a laser annealing method is used (FIG. 9B).
[0101]
After the activation step, a heat treatment is further performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen to perform a step of hydrogenating the island-shaped semiconductor layer. This step is a step of terminating dangling bonds in the island-shaped semiconductor layer with thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed. In addition, if heat resistance of the substrate 701 permits, heat treatment at 300 to 450 ° C. diffuses hydrogen in the silicon oxynitride silicon film 702 b in the base film 702 and the silicon oxynitride film in the protective insulating film 750 to form an island-shaped semiconductor layer. It may be hydrogenated.
[0102]
After the activation and hydrogenation steps are completed, an interlayer insulating film 751 made of an organic insulator is formed with an average thickness of 1.0 to 2.0 μm. As the organic insulator, polyimide, acrylic, polyamide, polyimide amide, BCB (benzocyclobutene), or the like can be used. For example, when using a type of polyimide that is thermally polymerized after being applied to the substrate, it is formed by baking at 300 ° C. in a clean oven. When acrylic is used, a two-component type is used, and after mixing the main material and the curing agent, applying the entire surface of the substrate using a spinner, preheating at 80 ° C. for 60 seconds with a hot plate. It can be formed by baking at 250 ° C. for 60 minutes in a clean oven.
[0103]
By forming the interlayer insulating film with an organic insulator, the surface can be satisfactorily planarized. Moreover, since an organic insulator generally has a low dielectric constant, parasitic capacitance can be reduced. However, since it is hygroscopic and its effect as a protective film is weak, it is preferably used in combination with a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or the like formed as the protective insulating film 750 as in this embodiment.
[0104]
After that, a resist mask having a predetermined pattern is formed using a photomask, and contact holes reaching the source region or the drain region formed in each island-shaped semiconductor film are formed. Contact holes are formed by dry etching. In this case, CF is used as an etching gas. _Four , O ₂ The interlayer insulating film 751 made of an organic insulator is first etched using a mixed gas of He and He, and then the etching gas is changed to CF. _Four , O ₂ The protective insulating film 750 is etched as follows. Further, in order to increase the selectivity with the island-shaped semiconductor layer, the etching gas is changed to CHF. _Three The contact hole can be satisfactorily formed by switching to the above and etching the gate insulating film 725.
[0105]
Then, a conductive metal film is formed by a sputtering method or a vacuum evaporation method, a resist mask is formed by a photomask, and source wirings 752 to 756 and drain wirings 757 to 761 are formed by etching. A drain wiring 762 indicates a drain wiring of an adjacent pixel. Here, the drain wiring 761 functions as a pixel electrode. Although not shown, in this embodiment, this electrode is formed by forming a Ti film with a thickness of 50 to 150 nm, forming a contact with the semiconductor film forming the source or drain region of the island-like semiconductor layer, and the Ti film Overlaid on top, aluminum (Al) is formed to a thickness of 300 to 400 nm to form wiring.
[0106]
FIG. 10E is a top view of the island-shaped semiconductor layers 715 and 716, the gate electrodes 729 and 730, the source wirings 752 and 753, and the drain wirings 757 and 758 in this state. The source wirings 752 and 753 are connected to the island-shaped semiconductor layers 715 and 716 by 830 and 833, respectively, through contact holes provided in an interlayer insulating film and a protective insulating film (not shown). The drain wirings 757 and 758 are connected to the island-shaped semiconductor layers 715 and 716 by 831 and 832, respectively.
[0107]
Similarly, FIG. 11E shows a top view of the island-shaped semiconductor layer 719, the gate electrode 733, the capacitor wiring 734, the source wiring 756, and the drain wiring 761. The source wiring 756 is a contact portion 834 and the drain wiring 761 is a contact. Each portion 835 is connected to the island-shaped semiconductor layer 719.
[0108]
In any case, an island-like semiconductor layer having a second shape is formed by removing a region where distortion remains in a region inside the island-like semiconductor layer having the first shape, and a TFT is formed. To do.
[0109]
When the hydrogenation treatment is performed in this state, a favorable result can be obtained for improving the characteristics of the TFT. For example, heat treatment may be performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen, or the same effect can be obtained by using a plasma hydrogenation method. Further, by such heat treatment, hydrogen present in the protective insulating film 750 and the base film 702 can be diffused into the island-shaped semiconductor films 715 to 719 to be hydrogenated. In any case, the defect density in the island-like semiconductor layers 715 to 719 is 10 ¹⁶ /cm ^Three It is desirable that the hydrogen content be 5 × 10 5 for this purpose. ¹⁸ ~ 5x10 ¹⁹ atoms / cm ^Three It is preferable to give a degree. (FIG. 9C).
[0110]
In this way, a substrate having the TFT of the driving circuit and the pixel TFT of the pixel portion can be completed on the same substrate. The driver circuit includes a first p-channel TFT 800, a first n-channel TFT 801, a second p-channel TFT 802, a second n-channel TFT 803, and a pixel TFT 804 and a storage capacitor 805 in the pixel portion. Yes. In this specification, such a substrate is referred to as an active matrix substrate for convenience.
[0111]
The first p-channel TFT 800 of the driver circuit has a single drain structure in which an island-shaped semiconductor film 715 includes a channel formation region 806, source regions 807a and 807b made of high-concentration p-type impurity regions, and drain regions 808a and 808b. have.
[0112]
The first n-channel TFT 801 includes an island-shaped semiconductor film 716, a channel formation region 809, an LDD region 810 overlapping with the gate electrode 730, a source region 812, and a drain region 811. In this LDD region, the length in the channel length direction of the LDD region overlapping with the gate electrode 730 is 0.5 to 3.0 μm, preferably 1.0 to 2.0 μm. By making the length of the LDD region in the n-channel TFT in this way, a high electric field generated in the vicinity of the drain region can be relaxed, hot carrier generation can be prevented, and deterioration of the TFT can be prevented.
[0113]
Similarly, the second p-channel TFT 802 of the driver circuit is a single drain having a channel formation region 813, source regions 814a and 814b made of high-concentration p-type impurity regions, and drain regions 815a and 815b on an island-shaped semiconductor film 717. It has a structure.
[0114]
In the second n-channel TFT 803, a channel formation region 816, LDD regions 817 and 818 partially overlapping with the gate electrode 732, a source region 820, and a drain region 819 are formed on the island-shaped semiconductor film 718. The length of the LDD region overlapping the gate electrode 732 of this TFT is also 0.5 to 3.0 μm, preferably 1.0 to 2.0 μm. The length of the LDD region that does not overlap with the gate electrode in the channel length direction is 0.5 to 4.0 μm, preferably 1.0 to 2.0 μm.
[0115]
The pixel TFT 804 includes channel formation regions 821 and 822, LDD regions 823 to 825, and source or drain regions 826 to 828 in an island-shaped semiconductor film 719. The length of the LDD region in the channel length direction is 0.5 to 4.0 μm, preferably 1.5 to 2.5 μm. Further, a storage capacitor 805 is formed from the capacitor wiring 734, an insulating film made of the same material as the gate insulating film, and a semiconductor layer 829 connected to the drain region 828 of the pixel TFT 804. Although the pixel TFT 804 has a double gate structure in FIG. 9C, it may have a single gate structure or a multi-gate structure provided with a plurality of gate electrodes.
[0116]
FIG. 12 is a top view showing almost one pixel in the pixel portion. A cross section AA ′ shown in the drawing corresponds to the cross sectional view of the pixel portion shown in FIG. The gate electrode 733 of the pixel TFT 804 intersects with the island-like semiconductor layer 719 under the gate insulating film (not shown). Although not shown, a source region, a drain region, and an LDD region are formed in the island-shaped semiconductor layer. 834 is a contact portion between the source wiring 756 and the source region 826, and 835 is a contact portion between the drain wiring 761 and the drain region 828. The storage capacitor 805 is formed in a region where a semiconductor layer 829 extending from the drain region 828 of the pixel TFT 804 overlaps with the capacitor wiring 734 with a gate insulating film interposed therebetween.
[0117]
The active matrix substrate is completed as described above. In the active matrix substrate manufactured according to this embodiment, TFTs having appropriate structures are arranged in accordance with the specifications of the pixel portion and the drive circuit. Therefore, it is possible to improve the operation performance and reliability of the electro-optical device using the active matrix substrate.
[0118]
In this embodiment, the drain wiring 761 of the pixel TFT 804 is used as it is as a pixel electrode, and has a structure corresponding to a reflective liquid crystal display device. However, by forming a pixel electrode made of a transparent conductive film so as to be electrically connected to the drain wiring 761, a transmissive liquid crystal display device can be handled.
[0119]
Further, this embodiment is an example of a manufacturing process of a semiconductor device using the invention of the present application, and it is not necessary to limit to the materials and numerical ranges shown in this embodiment. Furthermore, the practitioner may appropriately determine the arrangement of the LDD region.
[0120]
[Example 2]
In Example 1, an example in which an amorphous semiconductor film is crystallized by performing laser annealing by the method described in Embodiments 1 to 3, but the semiconductor is in a stage where crystallization has progressed to a certain extent. Laser annealing can also be performed on the film.
[0121]
That is, the laser annealing of the present invention is effective even when the crystalline semiconductor film obtained by crystallizing the amorphous semiconductor film by furnace annealing is further subjected to laser annealing to improve crystallinity.
[0122]
Specifically, in the laser irradiation process (laser annealing process) in the application of JP-A-7-161634, JP-A-7-321339, or JP-A-7-1331034, the first to third embodiments are applied. A laser annealing method can be used.
[0123]
In addition, after using this invention for the said gazette, TFT using the formed crystalline semiconductor film can be produced. That is, the present embodiment can be combined with the first embodiment.
[0124]
Example 3
In this embodiment, a process of manufacturing an active matrix liquid crystal display device from an active matrix substrate manufactured according to Embodiments 1 and 2 will be described. First, as shown in FIG. 13A, spacers 901a to 901f made of a resin material are formed by patterning on the active matrix substrate in the state of FIG. 9C. In addition, a well-known spherical silica etc. can be sprayed and used as a spacer.
[0125]
In this embodiment, NN700 manufactured by JSR Co. is used as the spacers 901a to 901f made of a resin material, and after applying with a spinner, a predetermined pattern is formed by exposure and development processing. Further, it is cured by heating at 150 to 200 ° C. in a clean oven or the like. The spacers produced in this manner can have different shapes depending on the conditions of exposure and development processing. Preferably, when the spacers are columnar and have a flat top, when the opposing substrates are combined, Mechanical strength as a liquid crystal display panel can be ensured.
[0126]
The shape is not particularly limited, such as a conical shape or a pyramid shape. For example, when the shape is conical, the height H is set to 1.2 to 5 μm, the average radius L1 is set to 5 to 7 μm, and the average radius is set. The ratio of L1 to the bottom radius L2 is 1 to 1.5. At this time, the taper angle of the side surface is ± 15 ° or less.
[0127]
The arrangement of the spacers 901a to 901f may be arbitrarily determined, but preferably, as shown in FIG. 13A, the pixel portion overlaps with the contact portion 835 of the drain wiring 761 (pixel electrode), and the portion is overlapped. It is good to form so that it may cover. Since the flatness of the contact portion 835 is impaired and the liquid crystal is not aligned well in this portion, disclination or the like can be prevented by filling the contact portion 835 with a resin for spacer.
[0128]
Thereafter, an alignment film 902 is formed. Usually, a polyimide resin is used for the alignment film of the liquid crystal display element. After the alignment film is formed, a rubbing process is performed so that the liquid crystal molecules are aligned with a certain pretilt angle. It is preferable that a region that is not rubbed in the rubbing direction from the end portions of the spacers 901a to 901f provided in the pixel portion is 2 μm or less. Further, although the generation of static electricity is often a problem in the rubbing treatment, if the spacers 901a to 901e are formed at least on the source wiring and the drain wiring on the TFT of the driving circuit, the original spacer as the spacer in the rubbing process is formed. The role and the effect of protecting the TFT from static electricity can be obtained.
[0129]
On the counter substrate 903, a light shielding film 904, a counter electrode 905 made of a transparent conductive film, and an alignment film 906 are formed. The light shielding film 904 is made of Ti, Cr, Al or the like with a thickness of 150 to 300 nm. Then, the active matrix substrate on which the pixel portion and the driving circuit are formed and the counter substrate are attached to each other with a sealant 907. A filler 908 is mixed in the sealant 907, and the counter substrate and the active matrix substrate are bonded to each other with a uniform interval by the filler 908 and the spacers 901a to 901f.
[0130]
Thereafter, a liquid crystal material 909 is injected between both the substrates and completely sealed with a sealant (not shown). A known liquid crystal material may be used as the liquid crystal material. For example, in addition to the TN liquid crystal, a thresholdless antiferroelectric mixed liquid crystal exhibiting electro-optical response in which the transmittance continuously changes with respect to the electric field can be used. Some thresholdless antiferroelectric mixed liquid crystals exhibit V-shaped electro-optic response characteristics. For details, see `` H.Furue et al.; Characteristics and Drivng Scheme of Polymer-Stabilized Monostable FLCD Exhibiting Fast Response Time and High Contrast Ratio with Gray-Scale Capability, SID, 1998 '', `` T.Yoshida et al.; A Full- Color Thresholdless Antiferroelectric LCD Exhibiting Wide Viewing Angle with Fast Response Time, 841, SID97DIGEST, 1997 '', `` S.Inui et al.; Thresholdless antiferroelectricity in liquid crystals and its application to displays, 671-673, J.Mater.Chem.6 (4), 1996 "or US Pat. No. 5,594,569.
[0131]
In this way, the active matrix liquid crystal display device shown in FIG. 13B is completed. In FIG. 13, the spacers 901a to 901e are divided and formed on at least the source wiring and the drain wiring on the TFT of the driving circuit. However, the spacers 901a to 901e may be formed to cover the entire surface of the driving circuit.
[0132]
FIG. 14 is a top view of the active matrix substrate, and is a top view showing the positional relationship between the pixel portion and the drive circuit portion, the spacer, and the sealant. Around the pixel portion 1400, a scanning signal driving circuit 1401 and an image signal driving circuit 1402 are provided as driving circuits. Further, a signal processing circuit 1403 such as a CPU or a memory may be added.
[0133]
These drive circuits are connected to an external input / output terminal 1410 by connection wiring 1411. In the pixel portion 1400, a gate wiring group 1404 extending from the scanning signal driving circuit 1401 and a source wiring group 1405 extending from the image signal driving circuit 1402 intersect in a matrix to form a pixel, and each pixel has a pixel TFT 804. And a storage capacitor 805 are provided.
[0134]
The spacer 1406 provided in the pixel portion corresponds to the spacer 901f shown in FIG. 13 and may be provided for all pixels, but is provided every several to several tens of pixels arranged in a matrix. May be. That is, the ratio of the number of spacers to the total number of pixels constituting the pixel portion is preferably 20 to 100%. In addition, the spacers 1407 to 1409 provided in the driver circuit portion may be provided so as to cover the entire surface, or as shown in FIG. May be.
[0135]
The sealant 907 is formed outside the pixel portion 1400 on the substrate 701, the scanning signal driving circuit 1401, the image signal driving circuit 1402, and other signal processing circuits 1403 and inside the external input / output terminal 1410.
[0136]
The structure of such an active matrix liquid crystal display device will be described with reference to the perspective view of FIG. In FIG. 15, the active matrix substrate includes a pixel portion 1400, a scanning signal driving circuit 1401, an image signal driving circuit 1402, and other signal processing circuits 1403 formed on a glass substrate 701.
[0137]
A pixel TFT 804 and a storage capacitor 805 are provided in the pixel portion 1400, and a driver circuit provided in the periphery of the pixel portion is configured based on a CMOS circuit. The scanning signal driving circuit 1401 and the image signal driving circuit 1402 are connected to the pixel TFT 804 by a gate wiring 733 and a source wiring 756, respectively. A flexible printed circuit (FPC) 1413 is connected to an external input terminal 1410 and used to input an image signal or the like. The flexible printed circuit 1413 is fixed with a reinforcing resin 1412 with increased adhesive strength. The connection wiring 1411 is connected to each drive circuit. Further, although not shown, the counter substrate 903 is provided with a light shielding film and a transparent electrode.
[0138]
A liquid crystal display device having such a structure can be formed using the active matrix substrate shown in Embodiments 1 and 2. For example, a reflective liquid crystal display device can be obtained by using an active matrix substrate having the structure of FIG. 9C, and transmission can be achieved by using an active matrix substrate using a transparent conductive film as a pixel electrode as shown in the first embodiment. Type liquid crystal display device can be obtained.
[0139]
Example 4
Examples 1 to 3 show examples in which the present invention is applied to a liquid crystal display device, but the present invention can be applied to any semiconductor device using TFTs.
[0140]
Specifically, when an active matrix type EL (electroluminescence) display device or an active matrix type EC (electrochromic) display device is manufactured, the present invention can be implemented in the laser annealing process of a semiconductor film. It is. At that time, any of the configurations of the first to third embodiments may be used.
[0141]
Since the present invention is an invention of a laser annealing step, a known TFT manufacturing process can be applied to the other parts. Therefore, when an active matrix EL display device or an active matrix EC display device is manufactured, the present invention may be applied to a known technique. Of course, it is also possible to manufacture with reference to the manufacturing steps described with reference to FIGS.
[0142]
Example 5
The present invention can be implemented for an electronic device (also referred to as an electronic device) having an electro-optical device such as an active matrix liquid crystal display device or an active matrix EL display device as a display display. Examples of the electronic device include a personal computer, a digital camera, a video camera, a portable information terminal (mobile computer, mobile phone, electronic book, etc.), a navigation system, and the like.
[0143]
FIG. 16A illustrates a personal computer, which includes a main body 2001 including a microprocessor and a memory, an image input portion 2002, a display portion 2003, and a keyboard 2004. The present invention can be implemented when manufacturing the display device 2003 and other driving circuits.
[0144]
FIG. 16B illustrates a video camera, which includes a main body 2101, a display portion 2102, an audio input portion 2103, operation switches 2104, a battery 2105, and an image receiving portion 2106. The present invention can be implemented when manufacturing the display device 2102 and other driver circuits.
[0145]
FIG. 16C shows a goggle type display which is composed of a main body 2201, a display device 2202, and an arm portion 2203. The present invention can be implemented when manufacturing the display portion 2202 and other drive circuits not shown. .
[0146]
FIG. 16D illustrates an electronic game machine such as a video game or a video game, which is incorporated in a main body 2301, a controller 2305, a display portion 2303, and a main body 2301 on which an electric circuit 2308 such as a CPU and a recording medium 2304 are mounted. The display unit 2302 is configured. The display unit 2303 and the display unit 2302 incorporated in the main body 2301 may display the same information, or display the information on the recording medium 2304 using the former as a main display device and the latter as a sub display device. The operation state can be displayed, or a touch sensor function can be added to provide an operation panel. In addition, the main body 2301, the controller 2305, and the display unit 2303 may perform wired communication in order to transmit signals to each other, or may be provided with sensor units 2306 and 2307 for wireless communication or optical communication. The present invention can be implemented when the display portions 2302 and 2303 are manufactured. The display portion 2303 can also use a conventional CRT.
[0147]
FIG. 16E shows a player using a recording medium (hereinafter referred to as a recording medium) in which a program is recorded. The player 240 includes a main body 2401, a display portion 2402, a speaker portion 2403, a recording medium 2404, and operation switches 2405. A recording medium such as a DVD (Digital Versatile Disc) or a compact disc (CD) can be used to play music programs, display images, display video games (or video games), and display information via the Internet. . The present invention can be implemented when manufacturing the display portion 2402 and other driving circuits.
[0148]
FIG. 16F illustrates a digital camera, which includes a main body 2501, a display portion 2502, an eyepiece portion 2503, an operation switch 2504, and an image receiving portion (not shown). The present invention can be implemented when manufacturing the display portion 2502 and other driving circuits.
[0149]
FIG. 17A illustrates a front projector, which includes a light source optical system, a display device 2601, and a screen 2602. The present invention can be applied to a display device and other driving circuits. FIG. 17B shows a rear projector, which includes a main body 2701, a light source optical system and display device 2702, a mirror 2703, and a screen 2704. The present invention can be implemented when manufacturing a display device or other driving circuits.
[0150]
Note that FIG. 17C illustrates an example of the structure of the light source optical system and the display devices 2601 and 2702 in FIGS. 17A and 17B. The light source optical system and the display devices 2601 and 2702 include a light source optical system 2801, mirrors 2802, 2804 to 2806, a dichroic mirror 2803, a beam splitter 2807, a liquid crystal display device 2808, a phase difference plate 2809, and a projection optical system 2810. The projection optical system 2810 includes a plurality of optical lenses.
[0151]
Although FIG. 17C illustrates a three-plate type example using three liquid crystal display devices 2808, the invention is not limited to such a method, and a single-plate optical system may be used. In addition, an appropriate optical lens, a film having a polarization function, a film for adjusting a phase, an IR film, or the like may be provided in the optical path indicated by an arrow in FIG.
[0152]
FIG. 17D shows an example of the structure of the light source optical system 2801 in FIG. In this embodiment, the light source optical system 2801 includes a reflector 2811, a light source 2812, lens arrays 2813 and 2814, a polarization conversion element 2815, and a condenser lens 2816. Note that the light source optical system illustrated in FIG. 17D is an example and is not limited to the illustrated configuration.
[0153]
Although not shown here, the present invention can also be implemented when manufacturing a navigation system, a reading circuit of an image sensor, or the like. As described above, the scope of application of the present invention is extremely wide, and can be implemented when manufacturing electronic devices in various fields.
[0154]
Example 6
In Example 1, after patterning, an example using the method of Embodiments 1 to 3 was shown. However, in this example, laser light was emitted using the method of Embodiment 1 before patterning. An example of irradiation is shown using FIG.
[0155]
First, according to the first embodiment, the state shown in FIG.
[0156]
Next, a crystallization process is performed on the semiconductor film. A crystallization process used in this embodiment, that is, a structure in which laser light is irradiated on the front and back surfaces of the semiconductor film shown in FIG. 18 will be described below.
[0157]
In FIG. 18, reference numeral 1801 denotes a light-transmitting substrate, on which an insulating film 1802 and an amorphous semiconductor film (or microcrystalline semiconductor film) 1803 are formed. A reflector 1804 for reflecting the laser light is disposed under the light-transmitting substrate 1801.
[0158]
As the light-transmitting substrate 1801, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate is used. The translucent substrate 1801 itself can adjust the effective energy intensity of the secondary laser light. As the insulating film 1802, an insulating film containing silicon such as a silicon oxide film or a silicon nitride oxide film (SiOxNy) may be used, and the effective energy intensity of the secondary laser light may be adjusted by the insulating film 1802.
[0159]
In the configuration of FIG. 18, the secondary laser light is laser light that has once passed through the amorphous semiconductor film 1803 and reflected by the reflector 1804. Therefore, the effective energy intensity of the secondary laser light can be adjusted by the amorphous semiconductor film 1803. In addition to the amorphous silicon film, the amorphous semiconductor film 1803 includes a compound semiconductor film such as an amorphous silicon germanium film.
[0160]
Further, the reflector 1804 may be a substrate on which a metal film is formed on the surface (laser light reflecting surface) or a substrate made of a metal element. In this case, any material may be used for the metal film. Typically, a metal film containing any element of silicon (Si), aluminum (Al), silver (Ag), tungsten (W), titanium (Ti), and tantalum (Ta) is used. For example, tungsten nitride (WN), titanium nitride (TiN), or tantalum nitride (TaN) may be used.
[0161]
Further, the reflector 1804 may be provided in contact with the light-transmitting substrate 1801 or may be provided separately. Further, instead of disposing the reflector 1804, it is also possible to directly form the metal film as described above on the back surface (surface opposite to the front surface) of the substrate 1801 and reflect the laser beam there. In any case, the effective energy intensity of the secondary laser light can be adjusted by the reflectance of the reflector 1804. In the case where the reflector 1804 is placed away from the light-transmitting substrate 1801, the energy intensity of the secondary laser light can be controlled by a gas (gas) filling the gap.
[0162]
Then, the amorphous semiconductor film 1803 is irradiated with a laser beam processed into a linear shape via the optical system 201 described in FIG. 2 (only the cylindrical lens 207 is shown in the drawing). The irradiation of the laser beam processed into the linear shape is performed by scanning the laser beam.
[0163]
In any case, the primary laser light 1805 that passes through the cylindrical lens 207 and is irradiated on the surface of the amorphous semiconductor film 1803 and the amorphous laser film 1803 pass through and are reflected once by the reflector 1804. Effective energy intensity ratio (I) with the secondary laser light 1806 irradiated on the back surface of the amorphous semiconductor film 1803 ₀ '/ I ₀ ) But 0 <I ₀ '/ I ₀ <1 or 1 <I ₀ '/ I ₀ It is important to satisfy this relationship. For this purpose, the reflectance of the reflector 1804 to the laser light is preferably 20 to 80%. At this time, a plurality of means for attenuating the effective energy intensity of the secondary laser light described in the present embodiment may be combined to obtain a desired intensity ratio.
[0164]
Further, the laser beam that has passed through the cylindrical lens 207 has an incident angle of 45 to 90 ° with respect to the substrate surface in the process of being condensed. Therefore, the secondary laser light 1806 irradiates the back surface of the amorphous semiconductor film 1803. Further, by providing an undulation portion on the reflecting surface of the reflector 1804 to diffusely reflect the laser light, the secondary laser light 1806 can be obtained more efficiently.
[0165]
As the laser light, any laser light having a wavelength in a wavelength range (around 530 nm) having sufficient light transmission and absorption components for the amorphous semiconductor film 1803 may be used. In this example, crystallization was performed using the second harmonic (wavelength 532 nm) of a YAG laser.
[0166]
If the second harmonic is used, a part of the irradiated light can pass through the amorphous semiconductor film and can be irradiated to the back surface of the amorphous semiconductor film by the reflector. Can get well.
[0167]
Next, the obtained semiconductor film is patterned to obtain an island-shaped semiconductor film.
[0168]
If the subsequent steps are in accordance with Example 1, an active matrix substrate is obtained.
[0169]
This embodiment can be combined with the second embodiment. Further, if Example 3 is used, an active matrix liquid crystal display device can be obtained. In addition, this embodiment can be applied to the semiconductor devices shown in Embodiment 4 and Embodiment 5.
[0170]
【The invention's effect】
According to the present invention, in addition to processing the laser beam into a linear shape during laser annealing to improve throughput, a solid laser that is easier to maintain is used to make laser annealing using a conventional excimer laser more effective. Can also improve throughput. As a result, the manufacturing cost of a semiconductor device such as a TFT or a liquid crystal display device formed of the TFT can be reduced.
[0171]
Furthermore, by performing laser annealing with a structure in which laser light is irradiated on the front and back surfaces of the amorphous semiconductor film, compared to the conventional case (when only the surface of the amorphous semiconductor film is irradiated with laser light). A crystalline semiconductor film having a large crystal grain size can be obtained. By obtaining a crystalline semiconductor film having a large crystal grain size, the performance of the semiconductor device can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a laser device.
FIG. 2 is a diagram showing a configuration of an optical system of a laser apparatus.
FIG. 3 is a view showing a laser annealing method of the present invention.
FIG. 4 is a diagram showing a configuration of a laser device.
FIG. 5 is a diagram showing a laser annealing method of the present invention.
FIG. 6 is a diagram showing a laser annealing method of the present invention.
FIGS. 7A and 7B are diagrams illustrating a manufacturing process of an active matrix substrate. FIGS.
FIGS. 8A to 8C are diagrams illustrating a manufacturing process of an active matrix substrate. FIGS.
FIGS. 9A and 9B are diagrams illustrating a manufacturing process of an active matrix substrate. FIGS.
FIGS. 10A and 10B are diagrams illustrating a manufacturing process of an active matrix substrate. FIGS.
FIGS. 11A and 11B are diagrams illustrating a manufacturing process of an active matrix substrate. FIGS.
FIG. 12 shows a pixel structure.
13 is a cross-sectional view of an active matrix liquid crystal display device.
FIG 14 illustrates a top structure of an active matrix liquid crystal display device.
FIG. 15 is a perspective view of an active matrix liquid crystal display device.
FIG 16 illustrates an example of an electronic device.
FIG. 17 is a diagram showing an example of a projector.
FIG. 18 is a diagram showing a laser annealing method of the present invention.

Claims (29)

Irradiating the surface of the semiconductor film formed on the translucent substrate with the second harmonic using the YVO ₄ laser as an oscillation source,
Irradiating the back surface of the semiconductor film with a second harmonic having an oscillation source of the YVO ₄ laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. A base film is formed on a translucent substrate,
Forming a semiconductor film on the base film;
Irradiating the surface of the semiconductor film with a second harmonic having an oscillation source of YVO ₄ laser,
Irradiating the back surface of the semiconductor film with a second harmonic having an oscillation source of the YVO ₄ laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. 3. The thin film transistor according to claim 1, wherein the semiconductor film is patterned into an island shape before irradiating the surface of the semiconductor film with a second harmonic using a YVO ₄ laser as an oscillation source. Method. Irradiating the surface of the semiconductor film formed on the translucent substrate with the first laser beam,
Irradiating the back surface of the semiconductor film with a second laser beam reflected by a reflector disposed under the translucent substrate;
An active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film,
The method for manufacturing a thin film transistor, wherein the first and second laser beams are second harmonics continuously oscillated from a YVO ₄ laser. 5. The method for manufacturing a thin film transistor according to claim 1, wherein the second harmonic using the YVO ₄ laser as an oscillation source is a rectangular laser beam having an aspect ratio of 10 or more. Irradiating the surface of the semiconductor film formed on the translucent substrate with a second harmonic using a YAG laser as an oscillation source;
Irradiating the back surface of the semiconductor film with a second harmonic having an oscillation source of the YAG laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. A base film is formed on a translucent substrate,
Forming a semiconductor film on the base film;
Irradiating the surface of the semiconductor film with a second harmonic having a YAG laser as an oscillation source,
Irradiating the back surface of the semiconductor film with a second harmonic having an oscillation source of the YAG laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film.   8. The method for manufacturing a thin film transistor according to claim 6, wherein the semiconductor film is patterned into an island shape before irradiating the surface of the semiconductor film with a second harmonic using a YAG laser as an oscillation source. . Irradiating the surface of the semiconductor film formed on the translucent substrate with the first laser beam,
Irradiating the back surface of the semiconductor film with a second laser beam reflected by a reflector disposed under the translucent substrate;
An active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film,
The method of manufacturing a thin film transistor, wherein the first and second laser beams are second harmonics continuously oscillated from a YAG laser.   10. The method for manufacturing a thin film transistor according to claim 6, wherein the second harmonic using the YAG laser as an oscillation source is a rectangular laser beam having an aspect ratio of 10 or more. Irradiating the surface of the semiconductor film formed on the translucent substrate with a second harmonic using a YAlO ₃ laser as an oscillation source;
Irradiating the back surface of the semiconductor film with a second harmonic having the oscillation source of the YAlO ₃ laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. A base film is formed on a translucent substrate,
Forming a semiconductor film on the base film;
Irradiating the surface of the semiconductor film with a second harmonic using a YAlO ₃ laser as an oscillation source;
Irradiating the back surface of the semiconductor film with a second harmonic having the oscillation source of the YAlO ₃ laser reflected by a reflector disposed under the translucent substrate;
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. 13. The thin film transistor according to claim 11, wherein the semiconductor film is patterned into an island shape before irradiating the surface of the semiconductor film with a second harmonic using a YAlO ₃ laser as an oscillation source. Method. Irradiating the surface of the semiconductor film formed on the translucent substrate with the first laser beam,
Irradiating the back surface of the semiconductor film with a second laser beam reflected by a reflector disposed under the translucent substrate;
An active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film,
The method of manufacturing a thin film transistor, wherein the first and second laser beams are second harmonics continuously oscillated from a YAlO ₃ laser. 15. The method for manufacturing a thin film transistor according to claim 11, wherein the second harmonic using the YAlO ₃ laser as an oscillation source is a rectangular laser beam having an aspect ratio of 10 or more. Irradiating the surface of the semiconductor film formed on the translucent substrate with a second harmonic having a wavelength of 532 nm using a solid laser as an oscillation source;
The back surface of the semiconductor film is irradiated with a second harmonic wave having a wavelength of 532 nm using the solid-state laser reflected by a reflector disposed under the translucent substrate as an oscillation source,
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film. A base film is formed on a translucent substrate,
Forming a semiconductor film on the base film;
Irradiating the surface of the semiconductor film with a second harmonic having a wavelength of 532 nm using a solid laser as an oscillation source,
The back surface of the semiconductor film is irradiated with a second harmonic wave having a wavelength of 532 nm using the solid-state laser reflected by a reflector disposed under the translucent substrate as an oscillation source,
A manufacturing method of a thin film transistor, wherein an active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film.   18. The semiconductor film according to claim 16, wherein the semiconductor film is patterned into an island shape before irradiating the surface of the semiconductor film with a second harmonic having a wavelength of 532 nm using a solid laser as an oscillation source. A method for manufacturing a thin film transistor. Irradiating the surface of the semiconductor film formed on the translucent substrate with the first laser beam,
Irradiating the back surface of the semiconductor film with a second laser beam reflected by a reflector disposed under the translucent substrate;
An active layer including a source region, a drain region, and a channel formation region is formed using the semiconductor film,
The method of manufacturing a thin film transistor, wherein the first and second laser beams are second harmonics having a wavelength of 532 nm continuously oscillated from a solid-state laser.   20. The thin film transistor according to claim 16, wherein the second harmonic wave having a wavelength of 532 nm using the solid-state laser as an oscillation source is a rectangular laser beam having an aspect ratio of 10 or more. Manufacturing method.   18. The method for manufacturing a thin film transistor according to claim 2, wherein the semiconductor film is continuously formed on the base film without being exposed to an air atmosphere.   20. The method for manufacturing a thin film transistor according to claim 4, wherein the semiconductor film is patterned into an island shape before the surface of the semiconductor film is irradiated with the first laser light. .   23. The channel length of the LDD region according to claim 1, wherein the active layer includes an LDD region, the gate electrode is formed to overlap a part of the LDD region, and the LDD region is overlapped with the gate electrode. A method for manufacturing a thin film transistor, wherein a length in a direction is 0.5 to 3 μm, and a length in a channel length direction of an LDD region that does not overlap with the gate electrode is 0.5 to 4 μm.   24. The method for manufacturing a thin film transistor according to any one of claims 1 to 23, wherein an uneven portion is provided on a reflection surface of the reflector.   25. The method for manufacturing a thin film transistor according to any one of claims 1 to 24, wherein the number of crystal grain boundaries included in the channel formation region is one or less.   26. The method for manufacturing a thin film transistor according to any one of claims 1 to 25, wherein the light-transmitting substrate is a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate.   27. The method for manufacturing a thin film transistor according to any one of claims 1 to 26, wherein the semiconductor film has a thickness of 25 to 80 nm.   28. The method for manufacturing a thin film transistor according to any one of claims 1 to 27, wherein the semiconductor film is amorphous.   30. The method for manufacturing a thin film transistor according to claim 1, wherein the semiconductor film is a silicon film.

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