JP2002203863A - Thin film transistor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method of a thin film transistor wherein a crystal semiconductor film large in a crystal particulate diameter as compared with the conventional is used. SOLUTION: In the manufacturing method of the thin film transistor irradiating an island-like amorphous semiconductor film on an insulation surface with laser light, scanning an area irradiated with the laser light, crystallizing the island-like amorphous semiconductor film and forming an active layer including a source area, a drain area and a channel formation area by using the crystallized island-like semiconductor film, the laser light is characterized in that it is continuously oscillated from YVO4 laser. Thereby the crystal semiconductor film large in the crystal particulate diameter as compared with the conventional can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for annealing a semiconductor film using a laser beam (hereinafter referred to as "laser annealing") and a laser apparatus (a laser and a laser beam output from the laser) for performing the method. Device including an optical system for guiding to the body). Further, the present invention relates to a semiconductor device manufactured by including the laser annealing in a step 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]

2. Description of the Related Art In recent years, thin film transistors (hereinafter referred to as TFTs) have been developed.
Has been developed, and a TFT using a polycrystalline silicon film (polysilicon film) as a crystalline semiconductor film has attracted attention. In particular, liquid crystal displays (liquid crystal displays)
And EL (electroluminescence) display devices (EL displays) are used as elements for switching pixels and elements for forming a drive circuit for controlling the pixels.

As a means for obtaining a polysilicon film, a technique of crystallizing an amorphous silicon film (amorphous silicon film) into 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 a technique capable of instantaneously heating a semiconductor film and effective as an annealing means for a semiconductor film formed on a substrate having low heat resistance such as a glass substrate or a plastic substrate. Further, the throughput is much higher than that of a heating means using a conventional electric furnace (hereinafter, referred to as furnace annealing).

There are various types of laser light, and generally, laser crystallization using laser light (hereinafter referred to as excimer laser light) using a pulse oscillation type excimer laser as an oscillation source is used. . An excimer laser has an advantage that it has a large output and can be repeatedly irradiated at a high frequency, and has an advantage that an excimer laser beam has a high absorption coefficient with respect to a silicon film.

To form an excimer laser beam, 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 in that if the frequency of gas exchange increases, manufacturing costs increase.

[0007] In addition, replacement of accessory equipment such as a laser tube for laser oscillation and a gas purifier for removing unnecessary compounds generated in the oscillation process is required once every two to three years. Many of these accessories are expensive, and also have the problem of increasing manufacturing costs.

As described above, although a laser device using an excimer laser beam certainly has high performance, it requires a great deal of maintenance, and as a mass-produced laser device, the running cost (here, the cost associated with operation) Cost).

[0009]

SUMMARY OF THE INVENTION The present invention provides a laser device which can obtain a crystalline semiconductor film having a larger crystal grain size as compared with the prior art and has a low running cost, and a laser annealing method using the same. That is the task. It is another object to provide a semiconductor device manufactured using such a laser annealing method and a method for manufacturing the semiconductor device.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method of irradiating a laser beam emitted from a solid-state laser (laser laser having a crystal rod as a resonance cavity) to an upper surface and a lower surface of a semiconductor film. There is a feature.

At this time, it is desirable that the laser beam is processed into a linear shape by an optical system and irradiated. Note that processing the laser light into a linear shape means that the laser light is processed so that the shape of an irradiation surface when the object is irradiated with the laser light is linear. That is, it means that the cross-sectional shape of the laser beam is processed into a linear shape. The term “linear” as used herein does not mean “line” in a strict sense, but means a rectangle (or a long ellipse) having a large aspect ratio. For example, it refers to one having an aspect ratio of 10 or more (preferably 100 to 10,000).

In the above configuration, a generally known solid-state laser can be used, such as a YAG laser (usually indicating an Nd: YAG laser), an Nd: YV laser.
O ₄ laser, Nd: YAlO ₃ laser, ruby laser, Ti: sapphire laser, glass laser and the like can be used. Particularly, a YAG laser which is superior in coherence and pulse energy is preferable. Also, Y
The AG 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.

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 preferred.

In particular, the wavelength of the second harmonic of the YAG laser is 532 nm.
Wavelength range that does not reflect the most amorphous semiconductor film (530 nm
Before and after). In addition, in this wavelength range, since the laser light transmitted through the amorphous semiconductor film has a sufficient light amount, it can be efficiently irradiated by irradiating the amorphous semiconductor film again from the back surface side using the reflector. . The laser energy of the second harmonic is (existing pulse oscillation type Y
1.5 J / pul at maximum (in an AG laser device)
In the case of processing into a linear shape as large as se, the length in the longitudinal direction can be drastically increased, and large area laser light irradiation can be performed at once. Note that these harmonics can be obtained using a nonlinear crystal.

The fundamental wave can be modulated to a second harmonic, a third harmonic or a fourth harmonic by a wavelength modulator including a nonlinear element. The formation of each harmonic may be in accordance with a known technique. In this specification, “laser light using a solid-state laser as an oscillation source” includes not only a fundamental wave but also a second harmonic, a third harmonic, and a fourth harmonic whose wavelength is modulated on the way. .

Also, Q which is often used in a YAG laser
A switch method (Q modulation switch method) may be used. This is a method of outputting a pulse laser having a very high energy value and a steep pulse by rapidly increasing the Q value from a state where the Q value of the laser resonator is sufficiently reduced. This is a known technique.

The solid-state laser used in the present invention can basically output a laser beam if it has a solid crystal, a resonance mirror, and a light source for exciting the solid crystal, and therefore does not require maintenance work like an excimer laser. That is, since the running cost is much lower than that of the excimer laser, the manufacturing cost of the semiconductor device can be significantly reduced. Further, if the number of times of maintenance 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 a reduction in the manufacturing cost of the semiconductor device. Furthermore, the occupied area of the solid-state laser is smaller than that of the excimer laser, which is advantageous for designing a production line.

Furthermore, laser annealing is performed by irradiating laser light to the front and back surfaces of the amorphous semiconductor film, so that the conventional method (when only the surface of the amorphous semiconductor film is irradiated with laser light) is used. It is possible to obtain a crystalline semiconductor film having a larger crystal grain size than that of the semiconductor device. By irradiating the laser light from the front and back surfaces of the amorphous semiconductor film, the applicant has made the cycle of melting and solidification of the silicon film gentle, and the time allowed for crystal growth in the solidification process is relatively small. It is thought that it becomes longer, and as a result, it becomes possible to increase the crystal grain size.

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 a 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 TF having one, preferably zero crystal grain boundary in the channel formation region
T can also be produced. In addition, since individual crystal grains have substantially crystallinity that can be regarded as a single crystal, high mobility (field-effect mobility) equal to or higher than that of a transistor using a single crystal semiconductor can be obtained.

Further, since the number of times carriers cross the crystal grain boundary can be extremely reduced, the on-current value (TFT
It is also possible to reduce variations in the drain current value flowing when the TFT is in the ON state, the OFF current value (the drain current value flowing when the TFT is in the OFF state), the threshold voltage, the S value, and the field effect mobility. Become.

[0021]

[Embodiment 1] One embodiment of the present invention will be described. FIG. 1A is a diagram showing a configuration of a laser device including the laser of the present invention. This laser device comprises a Nd: YAG laser 101, Nd:
An optical system 201 for linearly processing a laser beam (preferably a second harmonic, a third harmonic, or a fourth harmonic) using a YAG laser 101 as an oscillation source, and a stage 102 for fixing a translucent substrate are provided. The stage 102 has a heater 103
And a heater controller 104, and
It can be heated to 00-450 ° C. A reflector 105 is provided on the stage 102, and a substrate 106 on which an amorphous semiconductor film is formed is provided.

When the laser light output from the Nd: YAG laser 101 is modulated to any of the second to fourth harmonics, a wavelength modulator including a nonlinear element is provided immediately after the Nd: YAG laser 101. Just do it.

Next, a method of holding the substrate 106 in the laser device having the structure shown in FIG. 1A will be described with reference to FIG. Substrate 106 held on stage 102
Is installed in the reaction chamber 107, and is irradiated with a linear laser beam having the laser 101 as an oscillation source. The inside of the reaction chamber can be reduced in pressure or in 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.

The stage 102 is mounted on the guide rail 10.
8, the substrate can be moved in the reaction chamber, and the entire surface of the substrate can be irradiated with linear laser light. The laser light enters 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 these chambers are separated by gate valves 112 and 113.

In the loading / unloading chamber 111, a cassette 114 capable of holding a plurality of substrates is provided.
Transfer robot 11 provided in transfer room 109
The substrate is transported by 5. The substrate 106 'represents the substrate being transported. With such a configuration, laser annealing can be continuously performed under reduced pressure or in an inert gas atmosphere.

Next, an optical system 20 for making the laser beam linear
1 will be described with reference to FIG. FIG. 2A is a diagram of the optical system 201 viewed from the side, and FIG. 2B is a diagram of the optical system 201 viewed from the top.

A laser beam having the laser 101 as an oscillation source is split in a vertical direction by a cylindrical lens array 202. The split laser light is further split in the horizontal direction by the cylindrical lens 203. That is,
The laser light is applied to the cylindrical lens arrays 202 and 20.
3 will eventually be divided into a matrix.

Then, the laser light is once collected by the cylindrical lens 204. At this time, the light passes through the cylindrical lens 205 immediately after the cylindrical lens 204. After that, the light is reflected by the mirror 206, passes through the cylindrical lens 207, and reaches the irradiation surface 208.

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 beam transmitted through the cylindrical lens 207 is linear. The homogenization in the width direction (short direction) of the linearly processed laser light is performed by the cylindrical lens array 202, the cylindrical lens 204, and the cylindrical lens 207. The homogenization in the length direction (long direction) of the laser beam is performed by the cylindrical lens array 203 and the cylindrical lens 2.
05.

Next, a configuration for irradiating laser light from the front surface and the back surface of the film to be processed formed on the substrate will be described with reference to FIG. FIG. 3 is a diagram showing a positional relationship between the substrate 106 and the reflector 105 in FIG.

In FIG. 3, reference numeral 301 denotes a light-transmitting substrate, and an insulating film 302 and an amorphous semiconductor film (or a microcrystalline semiconductor film) 303 are provided on the surface thereof (the surface on which a thin film or element is formed). Is formed. In addition, the light-transmitting substrate 301
A reflector 304 for reflecting the laser light is disposed below.

As the translucent substrate 301, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate is used. Further, as the insulating film 302, an insulating film containing silicon such as a silicon oxide film or a silicon nitride oxide film (SiOxNy) may be used. The amorphous semiconductor film 303 can be an amorphous silicon film, an amorphous silicon germanium film, or the like.

The reflector 304 may be a substrate having a metal film formed on the surface (reflection surface for laser light) 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 of aluminum, silver, tungsten, titanium, and tantalum is used.

Also, instead of arranging the reflector 304,
It is also possible to form the above-described metal film directly on the back surface (surface opposite to the front surface) of the substrate 301 and reflect the laser light there. Note that the structure is based on the premise that the metal film formed on the back surface is not removed in the manufacturing process of the semiconductor device.

Then, the amorphous semiconductor film 303 is irradiated with a linearly processed laser beam via the optical system 201 (only the cylindrical lens 207 is shown in the figure) described with reference to FIG.

At this time, the laser light irradiated on the amorphous semiconductor film 303 includes a laser light 305 directly irradiated through the cylindrical lens 207 and a reflector 30.
4 and a laser beam 306 which is reflected once and irradiates the amorphous semiconductor film 303. Note that, in this specification, laser light applied to the front 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.

The laser beam passing through the cylindrical lens 207 is condensed by 45 to 45
It has an incident angle of 90 °. Therefore, the secondary laser light 3
06 is also applied to the back side of the amorphous semiconductor film 303. In addition, the secondary laser light 306 can be obtained more efficiently by providing an uneven portion on the reflection surface of the reflector 304 and irregularly reflecting the laser light.

In particular, the wavelength of the second harmonic of the YAG laser is 532 nm.
Wavelength range that does not reflect the most amorphous semiconductor film (530 nm
Before and after). In addition, in this wavelength range, since the laser light transmitted through the amorphous semiconductor film has a sufficient light amount, it can be efficiently irradiated by irradiating the amorphous semiconductor film again from the back surface side using the reflector. . In addition, 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 it is processed linearly, the length in the longitudinal direction is significantly increased. Laser irradiation can be performed on a large area at once.

As described above, according to the present embodiment, it is possible to process a laser beam having a solid-state laser as an oscillation source into a linear shape, and to use the laser beam as a primary laser beam and a second laser beam. It is possible to irradiate the front and back surfaces of the amorphous semiconductor film by splitting into the next laser light.

[Embodiment 2] In this embodiment, Embodiment 1
Embodiments different from the above will be described. In the present embodiment, an example is shown in which two systems of laser light separated in the middle of the optical system are irradiated from the front surface and the back surface of the amorphous semiconductor film without using the reflector as in the first embodiment.

FIG. 4A is a diagram showing a configuration of a laser device including a 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, the description will be made with the reference numerals of the different parts changed.

This laser device is a Nd: YAG laser 101, and a laser beam (preferably a third or fourth harmonic) using the Nd: YAG laser 101 as an oscillation source.
Optical system 40 that processes the light into a linear shape and splits the light into two systems
1. A light-transmitting stage 402 for fixing a light-transmitting substrate is provided. A substrate 403a is provided on the stage 402, and an amorphous semiconductor film 403b is formed thereon.

When the laser light output from the Nd: YAG laser 101 is modulated into any of the second to fourth harmonics, a wavelength modulator including a nonlinear element is provided immediately after the Nd: YAG laser 101. Just do it.

In the case of this embodiment, since the amorphous semiconductor film 403b is irradiated with the laser beam transmitted through the stage 402, the stage 402 must have a light transmitting property. In addition, since the energy of the laser light (secondary laser light) emitted from the stage 402 side is expected to be attenuated at the time when the laser light passes through the substrate, it is desirable to suppress the attenuation in the stage 402 as much as possible.

FIG. 4B is a view for explaining a method for holding the substrate 403a in the laser device shown in FIG. 4A, except that a light-transmitting stage 402 is used. Since the configuration is the same as that shown in FIG.

Next, the configuration of the optical system 401 shown in FIG. 4A will be described with reference to FIG. FIG. 5B is a diagram of the optical system 401 viewed from the side. Laser light (third harmonic or fourth harmonic) having an Nd: YAG laser 501 as an oscillation source is split vertically by a cylindrical lens array 502. The split laser beam is further split laterally by the cylindrical lens 503. In this manner, the laser light is divided into a matrix by the cylindrical lens arrays 502 and 503.

Then, the laser light is once focused by the cylindrical lens 504. At this time, the light passes through the cylindrical lens 505 immediately after the cylindrical lens 504. Up to this point, it is the same as the optical system shown in FIG.

Thereafter, the laser light is applied to the half mirror 506.
, Where the laser beam is the primary laser beam 507
And a secondary laser beam 508. Then, the primary laser light 507 is reflected by the mirrors 509 and 510, passes through the cylindrical lens 511, and reaches the surface of the amorphous semiconductor film 403b.

The secondary laser light 508 split by the half mirror 506 is reflected by mirrors 512, 513, 514.
After being reflected by and passing through the cylindrical lens 515,
The light passes through the substrate 403a and reaches the back surface of the amorphous semiconductor film 403b.

At this time, similarly to the first embodiment, the laser light projected on the irradiation surface of the substrate shows a linear irradiation surface. The homogenization in the width direction (short direction) of the linearly processed laser light is performed by the cylindrical lens array 502,
This is performed by the cylindrical lens 504 and the cylindrical lens 515. Further, the homogenization in the length direction (long direction) of the laser light is performed by the cylindrical lens array 503, the cylindrical lens 505, and the cylindrical lens 509.

As described above, according to the present embodiment, it is possible to process a laser beam using a solid-state laser as an oscillation source into a linear shape, and to use the laser beam as a primary laser beam by an optical system. In addition, it is possible to irradiate the front surface and the back surface of the amorphous semiconductor film by splitting the light into the secondary laser light.

[Embodiment 3] An embodiment different from Embodiment 2 of the present invention will be described. In the present embodiment, the two types of laser light separated in the middle of the optical system
The surface of the amorphous semiconductor film is made up of the fourth harmonic and the fourth harmonic.
An example in which the back surface is laser-annealed with a third harmonic at a harmonic.

FIG. 6 is a side view of the optical system of the laser device used in this embodiment. The laser beam emitted from the Nd: YAG laser 601 is emitted from the half mirror 60.
2 is split. Although not shown, Nd: YA
A part of the fundamental wave output from the G laser 601 is modulated to a third harmonic having a wavelength of 355 nm before reaching the half mirror 602.

First, the laser light (which becomes the secondary laser light) transmitted through the half mirror 602 is applied to the cylindrical lens arrays 603 and 604 and the cylindrical lens 6.
05, 606, mirror 607, cylindrical lens 6
08, an amorphous semiconductor film 609b via a substrate 609a.
Irradiated on the back surface of

Incidentally, the laser light finally irradiated on the amorphous semiconductor film 609b is linearly processed. The process of linear processing is the same as that of the optical system shown in FIG.

The laser light (which becomes the primary laser light) reflected by the half mirror 602 is modulated into a fourth harmonic having a wavelength of 266 nm by a wavelength modulator 610 including a nonlinear element. After that, the light is applied to the surface of the amorphous semiconductor film 609b via the mirror 611, the cylindrical lens arrays 612 and 613, the cylindrical lenses 614 and 615, the mirror 616, and the cylindrical lens 617.

Incidentally, the laser beam finally irradiated on the amorphous semiconductor film 609b is linearly processed. The process of linear processing is the same as that of the optical system shown in FIG.

As described above, in this embodiment, the surface of the amorphous semiconductor film is irradiated with the fourth harmonic having a wavelength of 266 nm, and the rear surface of the amorphous semiconductor film is irradiated with the third harmonic having a wavelength of 355 nm. The feature is that it irradiates waves. Note that, as in the present embodiment, it is preferable that the cross-sectional shape of the third harmonic and the fourth harmonic be processed into a linear shape because the throughput of laser annealing is improved.

When the substrate 609a is a glass substrate, light having a wavelength shorter than about 250 nm is not transmitted. For example, a Corning # 1737 substrate (1.1 m
m thick) starts transmitting at about 240 nm, about 38% at 300 nm, about 85% at 350 nm, and about 90% at 400 nm.
% Light. That is, when the substrate 609a is a glass substrate, it is preferable to use laser light having a wavelength of 350 nm or more (preferably 400 nm or more) as the secondary laser light.

Therefore, when an Nd: YAG laser is used as the solid-state laser and a glass substrate is used as the substrate on which the amorphous semiconductor film is formed as in the present embodiment, the primary laser light that does not pass through the substrate is applied to the fourth laser. It is desirable that the second laser light transmitted through the substrate be a third harmonic.

As described above, depending on the material of the substrate or the film quality of the amorphous semiconductor film, the laser light (primary laser light) applied to the surface of the amorphous semiconductor film and the laser light applied to the back surface It is effective to make the wavelength of the light (secondary laser light) different.

In the present embodiment, laser light having one laser as an oscillation source is dispersed and used, but two lasers outputting laser lights of different wavelengths can be used.

[0063]

[Embodiment 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 of a driver circuit provided around the pixel portion will be described.

In FIG. 7A, a substrate 701 is made of a glass substrate such as barium borosilicate glass or aluminoborosilicate glass typified by Corning # 7059 glass or # 1737 glass, etc., and polyethylene terephthalate (PET). ), Polyethylene naphthalate (P
EN), a plastic substrate having no optical anisotropy such as polyethersulfone (PES) can be used.

Then, 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 a TFT is to be formed, in order to prevent impurity diffusion from the substrate 701. SiH ₄ by plasma CVD in this embodiment, NH _3, silicon oxynitride is formed from N ₂ O film 702a of 10 to 200 nm (preferably 50 to 100 nm), is similarly prepared from SiH _4, N ₂ O 50 to 200 n of silicon oxynitride hydrogenated film 702b
m (preferably 100 to 150 nm).

The silicon oxynitride film is a conventional parallel plate type
It is formed by a plasma CVD method. Silicon oxynitride
The film 702a is made of SiH_FourTo 10 SCCM, NH_ThreeTo 100 SCC
M, N _TwoO was introduced into the reaction chamber at 20 SCCM, and the substrate temperature was 3
25 ° C, reaction pressure 40Pa, discharge power density 0.41W / c
m^TwoAnd the discharge frequency is 60 MHz. On the other hand, hydrogen oxynitride
The silicon film 702b is made of SiH_FourTo 5 SCCM, N_TwoO to 12
0 SCCM, H_TwoInto the reaction chamber as 125 SCCM
Temperature 400 ° C, reaction pressure 20Pa, discharge power density 0.41
W / cm^TwoAnd the discharge frequency is 60 MHz. These films are
Changing the temperature and changing the reaction gas
It can also be done.

The silicon oxynitride film 702a is formed so that its internal stress becomes a tensile stress, considering the substrate as a center. The silicon oxynitride film 702b also has internal stress in the same direction.
The stress should be smaller than the absolute value.

Next, 25 to 80 nm (preferably 30 to 80 nm)
An amorphous semiconductor film 703 having a thickness of 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 55 nm thick by a plasma CVD method.
Formed to a thickness of At this time, both the base film 702 and the amorphous semiconductor film 703 can be formed continuously. For example, as described above, the silicon oxynitride film 702a
And hydrogenated silicon oxynitride film 702b by plasma CVD
After continuous film formation by the method, SiH ₄ , N ₂ O, H ₂
If you switch to only SiH ₄ and H ₂ or SiH ₄ from
It can be formed continuously without once exposing it to the atmosphere. As a result, contamination of the surface of the hydrogenated silicon oxynitride film 702b can be prevented, and variation in characteristics of a TFT to be manufactured and fluctuation in threshold voltage can be reduced.

Then, first, island-shaped semiconductor layers 704 to 708 having a first shape are formed from the semiconductor layer 703 having an amorphous structure as shown by a dotted line in FIG. 7B. FIG.
0 (A) indicates the island-shaped semiconductor layers 704 and 70 in this state.
11A is a top view of the island-shaped semiconductor layer 708. FIG.

In FIGS. 10 and 11, the island-like semiconductor layer is rectangular and formed so that one side is 50 μm or less. The shape of the island-like semiconductor layer can be arbitrary, and preferably the center is Any polygon or circle may be used as long as the minimum distance from the part to the end is 50 μm or less.

Next, such island-like semiconductor layers 704 to 7
08 is subjected to a crystallization step. In the crystallization step, any of the methods described in Embodiments 1 to 3 can be used. In this embodiment, laser annealing is performed on the island-shaped semiconductor layers 704 to 708 by the method of Embodiment 1. Thus, island-shaped semiconductor layers 709 to 713 formed of a crystalline silicon film indicated by solid lines in FIG. 7B are formed.

Although this embodiment shows an example in which one island-shaped semiconductor layer is formed corresponding to one TFT, a case where the occupied area of the island-shaped semiconductor layer becomes large (one TFT
In the case where the size becomes larger, it is also possible to divide the semiconductor layer into a plurality of island-shaped semiconductor layers and connect a plurality of TFTs connected in series to function as one TFT.

At this time, as the amorphous silicon film is crystallized, the film becomes denser and shrinks by about 1 to 15%. And
A region 714 in which distortion has occurred due to shrinkage is formed at an end of the island-shaped semiconductor layer. Further, such an island-shaped semiconductor layer made of a crystalline silicon film has a tensile stress when the substrate is considered as a center. FIG. 10 (B) and FIG. 11 (B)
Shows top views of the island-shaped semiconductor layers 709, 710, and 713 in this state, respectively. Area 7 indicated by a dotted line in FIG.
04, 705, and 708 are the original island-shaped semiconductor layers 70
4, 705 and 708 are shown.

When the gate electrode of the TFT is formed over the region 714 where such strain is accumulated, this portion has a large number of defect levels as described above and has poor crystallinity, so that the TFT characteristics are not good. Causes deterioration. For example, the off-current value increases, or current concentrates in this region and locally generates heat.

Therefore, as shown in FIG. 7C, the second region 714 in which such distortion has accumulated is removed so that the region 714 is removed.
Island-shaped semiconductor layers 715 to 719 are formed. A dotted line 714 ′ in the figure is a region where the region 714 where the strain is accumulated was present, and shows a state in which the island-shaped semiconductor layers 715 to 719 of the second shape are formed inside the region. The shape of the island-shaped semiconductor layers 715 to 719 having the second shape may be an arbitrary shape. FIG. 10C is a top view of the island-shaped semiconductor layers 715 and 714 in this state. Similarly, FIG. 11C shows the island-shaped semiconductor layer 7.
19 shows a top view of FIG.

Thereafter, the island-shaped semiconductor layers 715 to 719 are formed.
And cover 5 by plasma CVD or sputtering.
A mask layer 720 made of a silicon oxide film having a thickness of 0 to 100 nm is formed. In this state, the island-like semiconductor layer
In order to control the threshold voltage (Vth) of the FT, the impurity element imparting p-type is set to 1 × 10 ^{16 to} 5 × 10 ¹⁷ atoms / cm ^3.
It may be added to the entire surface of the island-shaped semiconductor layer at a concentration of about the same.

As the impurity element imparting p-type to the semiconductor, an element belonging to Group 13 of the periodic table such as boron (B), aluminum (Al), and gallium (Ga) is known.
As the method, an ion implantation method or an ion doping method can be used, but the ion doping method is suitable for treating a large-area substrate. In the ion doping method, diborane (B
Boron (B) is added using ₂ H ₆ ) as a source gas. Such implantation of the impurity element is not always necessary and may be omitted, but it is particularly effective for keeping the threshold voltage of the n-channel TFT within a predetermined range.

In order to form an LDD region of an n-channel TFT of a driver circuit, an impurity element imparting n-type is selectively added to the island-shaped semiconductor layers 716 and 718. Therefore, resist masks 721a to 721e are formed in advance. As an impurity element imparting n-type, phosphorus (P) or arsenic (As) may be used. Here, an ion doping method using phosphine (PH ₃ ) is used to add phosphorus (P).

The formed impurity regions are low-concentration n-type impurity regions 722 and 723, and the phosphorus (P) concentration is 2 ×
The range may be in the range of 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ . In this specification, the impurity regions 722, 7 formed here are
The concentration of the impurity element imparting n-type contained in
^- ). The impurity region 724 is a semiconductor layer for forming a storage capacitor in a pixel portion, and phosphorus (P) is added to this region at the same concentration (FIG. 7D).

Next, the added impurity element is activated.
Perform the process. Activation is performed in a nitrogen atmosphere at 500 to 600
C. for 1 to 4 hours or by laser activation
Can be performed. It is also acceptable to use both together
No. In the case of laser activation method, KrF excimer
Form a linear beam using laser light (wavelength 248 nm)
Oscillation frequency 5-50Hz, energy density 10
0-500mJ / cm ^TwoAs linear beam overlay
The scanning is performed with the tip ratio being 80 to 98%, and the island-shaped semiconductor layer is formed.
Is processed on the entire surface of the substrate on which is formed. Note that the laser light
There are no restrictions on the firing conditions, and
It should be set. This step is performed while leaving the mask layer 720.
May be performed, or may be performed after removal.

In FIG. 7E, a gate insulating film 725 is formed.
Is a film thickness of 4 using a plasma CVD method or a sputtering method.
The insulating film containing silicon is formed to have a thickness of 0 to 150 nm. For example, a silicon oxynitride film with a thickness of 120 nm is preferably used. A silicon oxynitride film formed by adding O ₂ to SiH ₄ and N ₂ O 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 to have a compressive stress considering the substrate as a center.

Then, as shown in FIG. 7E, a heat-resistant conductive layer for forming a gate electrode is formed over the gate insulating film 725. The heat-resistant conductive layer may be formed as a single layer, or may be formed as a multilayer structure including a plurality of layers such as two layers or three layers as necessary. Using such a heat-resistant conductive material, for example, a conductive layer (A) 726 made of a conductive nitride metal film and a conductive layer (B) 727 made of a metal film
Are preferably laminated.

The conductive layer (B) 727 is made of tantalum (Ta),
An element selected from titanium (Ti), molybdenum (Mo), and tungsten (W), an alloy containing the above element as a main component, or an alloy film combining the above elements (typically, a Mo-W alloy film, Mo -Ta alloy film), and the conductive layer (A) 726 is formed using tantalum nitride (TaN), tungsten nitride (WN), titanium nitride (TiN), molybdenum nitride (MoN), or the like. Further, as the conductive layer (A) 726, tungsten silicide, titanium silicide, or molybdenum silicide may be used.

The conductive layer (B) 727 preferably has a reduced impurity concentration in order to reduce the resistance, and particularly preferably has an oxygen concentration of 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.

The conductive layer (A) 726 has a thickness of 10 to 50 nm (preferably 20 to 30 nm), and the conductive layer (B) 727 has a thickness of 200 to 400 nm (preferably 250 to 350 nm).
It is good. In the case where W is used as a gate electrode, an argon (Ar) gas and a nitrogen (N ₂ ) gas are introduced by sputtering using W as a target, and the conductive layer (A) 726 is formed of tungsten nitride (WN) to a thickness of 50 nm. The conductive layer (B) 727 is formed with W to a thickness of 250 nm. As another method, the W film is made of tungsten hexafluoride (WF ₆ )
Can also be formed by a thermal CVD method.

In any case, it is necessary to lower the resistance in order to use it as a gate electrode.
It is desirable to set it to 0 μΩcm or less. The resistivity of the W film can be reduced by enlarging the crystal grains.
When there are many impurity elements such as oxygen therein, crystallization is inhibited and the resistance is increased. Thus, in the case of using the sputtering method, a W target having a purity of 99.9999% is used, and further, the W film is formed with sufficient care so as not to mix impurities from the gas phase during film formation. 9-20μ
Ωcm can be realized.

On the other hand, a TaN film is formed on the conductive layer (A) 726.
When a Ta film is used for the conductive layer (B) 727, it can be formed by a sputtering method in the same manner. TaN film is T
The target film a is formed using a mixed gas of Ar and nitrogen as a sputtering gas, and the Ta film uses Ar as a sputtering gas. When an appropriate amount of Xe or Kr is added to these sputter gases, the internal stress of the film to be formed can be relaxed and the film can be prevented from peeling. The α-phase Ta film has a resistivity of about 20 μΩcm and can be used as a gate electrode, but the β-phase Ta film has a resistivity of about 180 μΩcm and is not suitable for a gate electrode. TaN film is α
Since it has a crystal structure close to a phase, if a Ta film is formed thereon, an α-phase Ta film can be easily obtained.

Although not shown, the conductive layer (A) 726
It is effective to form a silicon film doped with phosphorus (P) with a thickness of about 2 to 20 nm under the layer. Accordingly, the adhesion of the conductive film formed thereover is improved and oxidation is prevented, and at the same time, a small amount of an alkali metal element contained in the conductive layer (A) 726 or the conductive layer (B) 727 is added to the gate insulating film 725. Spreading can be prevented. In any case, the conductive layer (B) 727 has a resistivity of 10 to 50.
It is preferable to be in the range of μΩcm.

Next, using a photomask, the resist masks 728a-728
28f, and the conductive layer (A) 726 and the conductive layer (B) 7
27 are collectively etched to form gate electrodes 729-73.
3 and a capacitor wiring 734 are formed. Gate electrodes 729-7
33 and a capacitor wiring 734 are formed of a conductive layer (A) 729
a to 733a and 729b to 73 made of a conductive layer (B)
3b are integrally formed (FIG. 8A).

The island-like semiconductor layer 71 in this state is
FIG. 10D shows the positional relationship between the gate electrodes 5 and 716 and the gate electrodes 729 and 730. Similarly, FIG. 11D illustrates a relationship between the island-shaped semiconductor layer 719, the gate electrode 733, and the capacitor wiring 734. 10D and 11D, the gate insulating film 725 is omitted.

The method of etching the conductive layer (A) and the conductive layer (B) may be appropriately selected by a practitioner. However, when the conductive layer (A) and the conductive layer (B) are formed of a material containing W as a main component as described above, It is desirable to apply a dry etching method using high-density plasma in order to perform etching at high speed and with high accuracy. Microwave plasma or inductively coupled plasma (Inductively Coup
It is preferable to use an led plasma (ICP) etching apparatus.

For example, W using an ICP etching apparatus
Is an etching method using CF ₄ and Cl ₂ as etching gas.
A seed gas is introduced into the reaction chamber, and the pressure is 0.5 to 1.5 Pa.
(Preferably 1 Pa), and 200 to 10
A high-frequency (13.56 MHz) power of 00 W is applied.
At this time, a high frequency power of 20 W is applied to the stage on which the substrate is placed, and the stage is charged to a negative potential by a self-bias, so that positive ions are accelerated and anisotropic etching can be performed. By using an ICP etching apparatus, even a hard metal film such as W can obtain an etching rate of 2 to 5 nm / sec. 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%. At this time, however, it is necessary to pay attention to the etching selectivity with the base. For example, since the selectivity of the silicon oxynitride film (gate insulating film 725) to the W film is 2.5 to 3, the exposed surface of the silicon oxynitride film is etched by about 20 to 50 nm by such an over-etching process. Being substantially thinner.

Then, the n-channel type TFT of the pixel TFT is used.
In order to form an LDD region, a step of adding an impurity element imparting n-type (n ⁻ doping step) is performed. Using the gate electrodes 729 to 733 as a mask, an impurity element that imparts n-type may be added in a self-aligned manner by an ion doping method. n
The concentration of phosphorus (P) added as an impurity element for imparting a mold is added in a concentration range of 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ . Thus, low-concentration n-type impurity regions 735 to 739 are formed in the island-shaped semiconductor layer as shown in FIG.

Next, in the n-channel TFT, a high-concentration n-type impurity region functioning as a source region or a drain region is formed (n ⁺ doping step). First, using a photomask, resist masks 740a to 740d are used.
Is formed, and an impurity element imparting n-type is added to form high-concentration n-type impurity regions 741 to 746. Phosphorus (P) is used as an impurity element for imparting n-type and its concentration is 1 ×
The ion doping method using phosphine (PH ₃ ) is performed so as to have a concentration range of 10 ²⁰ to 1 × 10 ²¹ atoms / cm ³ (FIG. 8C).

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-aligned manner. At this time, the island-shaped semiconductor films 716, 718, 7 forming the n-channel TFT
Reference numeral 19 denotes a resist mask 747a using a photomask.
747c is formed and the entire surface is covered.

The high-concentration p-type impurity regions 748 and 749 are formed by ion doping using diborane (B ₂ H ₆ ).
The boron (B) concentration in this region is 3 × 10 ^{20 to} 3 × 10 ^21.
atoms / cm ³ (FIG. 8D).

The high-concentration p-type impurity regions 748 and 749
Has phosphorus (P) added in the previous step, and 1 × 10 ²⁰ is added to the high-concentration p-type impurity regions 748a and 749a.
The concentration is about 1 × 10 ²¹ atoms / cm ³ , and the high-concentration p-type impurity regions 748b and 749b have 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms.
Phosphorus is contained at a concentration of s / cm ^{3, and} the concentration of boron (B) added in this step is set to 1.5 to 3 times the concentration of the contained phosphorus, so that the source region of the p-channel TFT and It can function as a drain region without any problem.

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.

Here, when a silicon oxide film is used, tetraethyl orthosilicate (TEOS) and O ₂ are mixed by plasma CVD, the reaction pressure is 40 Pa, the substrate temperature is 300 to 400 ° C., and the high frequency (13.56MHz) Power density 0.5 ~ 0.8W
/ cm ² and can be formed by discharging. In the case of using a silicon oxynitride film, Si
A silicon oxynitride film formed from H ₄ , N ₂ O, and NH ₃ , or a silicon oxynitride film formed from SiH ₄ , N ₂ O may be used. The manufacturing 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 . Alternatively, a hydrogenated silicon oxynitride film formed from SiH ₄ , N ₂ O, and H ₂ may be used. Similarly, the silicon nitride film is formed by SiH ₄ , N
It can be prepared from H _3. Such a protective insulating film is formed so as to have a compressive stress considering the substrate as a center.

Thereafter, a step of activating the impurity elements imparting n-type or p-type added at the respective concentrations is performed. This step is performed by a furnace annealing method 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, the oxygen concentration is 40 ppm or less in a nitrogen atmosphere of 1 ppm or less, preferably 0.1 ppm or less.
The heat treatment is preferably performed at 0 to 700 ° C, typically 500 to 600 ° C. In this embodiment, the heat treatment is performed at 550 ° C for 4 hours. In the case where a plastic substrate having a low heat-resistant temperature is used as the substrate 701, a laser annealing method is used (FIG. 9B).

After the activation step, 3 to 100%
1 to 12 at 300 to 450 ° C. in an atmosphere containing hydrogen
A heat treatment is performed for a long time 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 by thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed. If the heat resistance of the substrate 701 permits, a heat treatment at 300 to 450 ° C. is performed to form the silicon oxynitride nitride film 702 of the base film 702.
b, The island-shaped semiconductor layer may be hydrogenated by diffusing hydrogen in the silicon oxynitride film of the protective insulating film 750.

When the activation and hydrogenation steps are completed,
The interlayer insulating film 751 made of an organic insulator is formed to a thickness of 1.0 to 2.0.
It is formed with an average thickness of μm. As an organic insulator,
Polyimide, acrylic, polyamide, polyimide amide, BCB (benzocyclobutene), or the like can be used. For example, when using a polyimide that is thermally polymerized after being applied to a substrate, a 300 mm clean oven is used.
It is formed by firing at ℃. Also, when using acrylic, use a two-liquid type, after mixing the main material and the curing agent,
After coating the entire surface of the substrate using a spinner, preheating is performed at 80 ° C. for 60 seconds on a hot plate, and further, firing is performed at 250 ° C. for 60 minutes in a clean oven.

The surface can be satisfactorily flattened by forming the interlayer insulating film with an organic insulator. Also,
Since organic insulators generally have a low dielectric constant, parasitic capacitance can be reduced. However, since it has a hygroscopic property and its effect as a protective film is weak, it is preferable to use it 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.

Thereafter, a resist mask having a predetermined pattern is formed using a photomask, and a contact hole reaching a source region or a drain region formed in each island-like semiconductor film is formed. The formation of the contact hole is performed by a dry etching method. In this case, the interlayer insulating film 751 made of an organic insulating material is first etched by using a mixed gas of CF ₄ , O ₂ , and He as an etching gas, and then the protective insulating film 750 is formed by using CF ₄ and O ₂ as the etching gas. Etch. Further, by switching the etching gas to CHF ₃ and etching the gate insulating film 725 in order to increase the selectivity with respect to the island-shaped semiconductor layer, a contact hole can be formed favorably.

Then, a conductive metal film is formed by a sputtering method or a vacuum evaporation method, a resist mask is formed by using a photomask, and the source wirings 752 to 752 are formed by etching.
6 and drain wirings 757 to 761 are formed. 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
A Ti film is formed to a thickness of 50 to 150 nm, a contact is formed with the semiconductor film forming the source or drain region of the island-shaped semiconductor layer, and aluminum (Al) is formed on the Ti film to a thickness of 300 to 400 nm. Then, it is formed as a wiring.

FIG. 10E shows island-shaped semiconductor layers 715 and 716, gate electrodes 729 and 730, source wirings 752 and 753, and drain wirings 757 and 75 in this state.
8 shows a top view. The source wirings 752 and 753 are connected to the island-shaped semiconductor layers 715 and 716 by contact holes provided in an interlayer insulating film and a protective insulating film (not shown).
And 830 and 833 respectively. The drain wirings 757 and 758 are connected to the island-shaped semiconductor layers 715 and 716 at 831 and 832.

Similarly, in FIG. 11E, the island-like semiconductor layer 7 is formed.
19, a gate electrode 733, a capacitor wiring 734, a source wiring 756, and a drain wiring 761 are shown in top views. The source wiring 756 is a contact portion 834 and the drain wiring 7
Numeral 61 denotes contact portions 835, each of which is an island-shaped semiconductor layer 71.
9 is connected.

In any case, in the region inside the island-shaped semiconductor layer having the first shape, the region where the strain remains is removed, and the island-shaped semiconductor layer having the second shape is formed. T
Form FT.

When hydrogenation is performed in this state, favorable results can be obtained for improving the characteristics of the TFT. For example, 3 ~
Heat treatment may be performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 100% hydrogen, or the same effect can be obtained by using a plasma hydrogenation method. In addition, by such heat treatment, the protective insulating film 750 and the base film 702 are formed.
Can be diffused into the island-shaped semiconductor films 715 to 719 for hydrogenation. In any case, the island-like semiconductor layer is desirably defect density and 10 ¹⁶ / cm ³ or less in the 715-719, hydrogen 5 × 10 in order that ¹⁸
It is preferable to provide about 5 × 10 ¹⁹ atoms / cm ³ .
(FIG. 9 (C)).

Thus, the TF of the driving circuit is provided on the same substrate.
A substrate having T and a pixel TFT in a pixel portion can be completed. The drive circuit includes a first p-channel TFT 8
00, a first n-channel TFT 801, a second p-channel TFT 802, a second n-channel TFT 80
3. In the pixel portion, a pixel TFT 804 and a storage capacitor 805 are formed. In this specification, such a substrate is referred to as an active matrix substrate for convenience.

First p-channel type TFT 80 of drive circuit
0, the channel-forming region 80 is formed in the island-shaped semiconductor film 715.
6. Source region 807 including high concentration p-type impurity region
a, 807b and a single drain structure having drain regions 808a, 808b.

In the first n-channel type TFT 801, a channel forming region 809, an LDD region 810 overlapping the gate electrode 730, and a source region 81 are formed on the island-shaped semiconductor film 716.
2. It has 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 set to 0.5 to 3.0 μm, preferably 1.0 to 2.0 μm. By setting the length of the LDD region in the n-channel TFT in this way, a high electric field generated near the drain region can be reduced, hot carriers can be prevented from being generated, and deterioration of the TFT can be prevented.

The second p-channel type TFT 80 of the driving circuit
Similarly, a channel forming region 8 is formed in the island-shaped semiconductor film 717.
13. Source region 814 including high-concentration p-type impurity region
a, 814b and drain regions 815a, 815b.

In the second n-channel TFT 803, a channel forming region 816, LDD regions 817 and 818 partially overlapping 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 with the gate electrode 732 of this TFT is also 0.5 to 3.0 μm, preferably 1.0 to 2.0 μm.
0 μm. The length in the channel length direction of the LDD region that does not overlap with the gate electrode is 0.5 to 4.0 μm, preferably 1.0 to 2.0 μm.

The pixel TFT 804 includes the island-shaped semiconductor film 71.
9, the channel forming regions 821 and 822 and the LDD region 82
3-825, source or drain regions 826-828
have. 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, the storage capacitor 80 is formed from the capacitor wiring 734, the insulating film made of the same material as the gate insulating film, and the semiconductor layer 829 connected to the drain region 828 of the pixel TFT 804.
5 are formed. In FIG. 9C, the pixel TFT 804
Has a double gate structure, but may have a single gate structure or a multi-gate structure provided with a plurality of gate electrodes.

FIG. 12 is a top view showing almost one pixel of the pixel portion. The 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 the island-shaped semiconductor layer 719 thereunder via a 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. Also, 834
Represents a contact portion between the source wiring 756 and the source region 826, and 835 represents a contact portion between the drain wiring 761 and the drain region 828.
Contact part. The storage capacitor 805 is connected to the pixel TF
Semiconductor layer 8 extending from drain region 828 of T804
29 is formed in a region overlapping with the capacitor wiring 734 via the gate insulating film.

The active matrix substrate is completed as described above. In the active matrix substrate manufactured according to this embodiment, a TFT having an appropriate structure is arranged according to the specifications of the pixel portion and the driving circuit. Therefore, it is possible to improve the operation performance and reliability of the electro-optical device using the active matrix substrate.

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 reflection type 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, it is possible to cope with a transmission type liquid crystal display device.

This embodiment is an example of a process for manufacturing a semiconductor device using the present invention, and there is no need to limit the materials and numerical ranges shown in this embodiment. Furthermore, the arrangement of the LDD region and the like may be appropriately determined by the practitioner.

Example 2 In Example 1, an example is shown in which an amorphous semiconductor film is crystallized by laser annealing according to the method described in Embodiments 1 to 3.
Laser annealing can also be performed on the semiconductor film at the stage where crystallization has progressed to some extent.

That is, the laser annealing of the present invention is also effective when the crystalline semiconductor film obtained by crystallizing the amorphous semiconductor film by furnace annealing is further subjected to laser annealing to improve the crystallinity.

More specifically, JP-A-7-161634, JP-A-7-321339, and JP-A-7-13-1
It is possible to use the laser annealing method of Embodiments 1 to 3 in the laser irradiation step (laser annealing step) in the application such as 31034.

After using the present invention in the above publication, a TFT using the formed crystalline semiconductor film can be manufactured. That is, it is possible to combine the present embodiment with the first embodiment.

[Embodiment 3] In this embodiment, a process of manufacturing an active matrix type 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 on the active matrix substrate in the state of FIG. 9C by patterning. In addition, well-known spherical silica or the like can be sprayed and used as the spacer.

In this embodiment, the spacer 9 made of a resin material is used.
Using NN700 manufactured by JSR as 01a to 901f,
After application by a spinner, a predetermined pattern is formed by exposure and development. In a clean oven etc.
Heat and cure at 50-200 ° C. The spacer produced in this manner can have a different shape depending on the conditions of exposure and development processing.However, it is preferable that the top be a columnar shape and the top be flat, when the substrates on the opposite side are combined. Mechanical strength as a liquid crystal display panel can be secured.

The shape is not particularly limited to a conical shape or a pyramid shape. For example, when the shape is a conical shape, specifically, the height H is set to 1.2 to 5 μm and the average radius L1 is set to 5 to 7 μm.
m, the ratio of the average radius L1 to the bottom radius L2 is 1: 1.5.
And At this time, the taper angle of the side surface is set to ± 15 ° or less.

The arrangement of the spacers 901a to 901f may be arbitrarily determined. However, as shown in FIG. 13A, it is preferable that the spacer overlap the contact portion 835 of the drain wiring 761 (pixel electrode) in the pixel portion. It is good to form so that the part may be covered. Since the flatness of the contact portion 835 is impaired and the liquid crystal is not well aligned in this portion, disclination and the like can be prevented by filling the contact portion 835 with a resin for a spacer.

After that, an alignment film 902 is formed. Usually, a polyimide resin is used for the alignment film of the liquid crystal display element. After forming the alignment film, a rubbing treatment is performed so that the liquid crystal molecules are aligned with a certain pretilt angle. It is preferable that the area not rubbed in the rubbing direction from the ends of the spacers 901a to 901f provided in the pixel portion is 2 μm or less. In the rubbing process, the generation of static electricity often poses a problem.
If the spacers 901a to 901e are formed on at least the source wiring and the drain wiring on T, the original role as the spacer in the rubbing step and the effect of protecting the TFT from static electricity can be obtained.

On the opposite substrate 903, a light-shielding film 904, an opposite 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,
It is formed with a thickness of 300 nm. Then, the active matrix substrate on which the pixel portion and the driver circuit are formed and the counter substrate are attached 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 at a uniform interval by the filler 908 and the spacers 901a to 901f.

Thereafter, a liquid crystal material 909 is injected between the two substrates, and completely sealed with a sealant (not shown). A known liquid crystal material may be used as the liquid crystal material. For example, T
In addition to the N liquid crystal, a thresholdless antiferroelectric mixed liquid crystal exhibiting electro-optical response in which the transmittance changes continuously with an electric field can be used. Some thresholdless antiferroelectric mixed liquid crystals exhibit a V-shaped electro-optical response characteristic. See `` H. Furue et al .; Charakteristics and Drivng Scheme '' for details.
of Polymer-Stabilized Monostable FLCD Exhibiting
Fast Response Time and High Contrast Ratio with Gr
ay-Scale Capability, SID, 1998 '', `` T. Yoshida et a
l.; A Full-Color Thresholdless Antiferroelectric LC
D Exhibiting Wide Viewing Angle with Fast Response
Time, 841, SID97DIGEST, 1997 '', `` S.Inui et al.; Thre
sholdless antiferroelectricity in liquid crystals
and its application to displays, 671-673, J.Mater.Ch
em. 6 (4), 1996 "or U.S. Pat. No. 5,594,569.

Thus, the active matrix type liquid crystal display device shown in FIG. 13B is completed. In FIG. 13, the spacers 901 a to 901 e are formed separately on at least the source wiring and the drain wiring on the TFT of the driving circuit.

FIG. 14 is a top view of the active matrix substrate, showing a positional relationship between the pixel portion and the drive circuit portion, the spacers, and the sealant. Pixel section 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 additionally provided.

These drive circuits are connected to the connection wiring 14.
11 connects to the external input / output terminal 1410. In the pixel portion 1400, a group of gate wirings 1404 extending from the scanning signal driving circuit 1401 and the image signal driving circuit 14
02, a source wiring group 1405 extending in a matrix shape intersects to form a pixel, and each pixel has a pixel TF
T804 and a storage capacitor 805 are provided.

The spacer 140 provided in the pixel portion
Reference numeral 6 corresponds to the spacer 901f shown in FIG. 13, and may be provided for all pixels, or may be provided for every several to several tens of pixels arranged in a matrix. That is, the ratio of the number of spacers to the total number of pixels constituting the pixel portion is preferably 20 to 100%. Further, the spacers 1407 to 1409 provided in the driver circuit portion may be provided so as to cover the entire surface thereof, or may be provided in plural pieces in accordance with the positions of the source and drain wirings of each TFT as shown in FIG. May be.

The sealant 907 is formed outside the pixel portion 1400, the scanning signal driving circuit 1401, the image signal driving circuit 1402, and other signal processing circuits 1403 on the substrate 701 and inside the external input / output terminal 1410. I do.

The structure of such an active matrix type liquid crystal display device will be described with reference to the perspective view of FIG. FIG.
5, the active matrix substrate is a glass substrate 7
A pixel unit 1400, a scanning signal driving circuit 1401, an image signal driving circuit 1402, and another signal processing circuit 1403 are formed over the pixel unit 01.

The pixel portion 1400 is provided with a pixel TFT 804 and a storage capacitor 805, and a driving circuit provided around the pixel portion is basically formed of a CMOS circuit. Scanning signal driving circuit 1401 and image signal driving circuit 1402
Are connected to the pixel TFT 804 via a gate wiring 733 and a source wiring 756, respectively. In addition, Flexible Printed Circuit (FPC)
Reference numeral 1413 is connected to the 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 to increase the adhesive strength. Then, a connection wiring 1411 is connected to each drive circuit. Although not shown, the opposing substrate 903 is provided with a light-shielding film and a transparent electrode.

The liquid crystal display device having such a structure can be formed by using the active matrix substrate shown in the first and second embodiments. For example, a reflective liquid crystal display device can be obtained by using the active matrix substrate having the structure in FIG. 9C, and transmission can be achieved by using an active matrix substrate using a transparent conductive film as a pixel electrode as described in Embodiment 1. Type liquid crystal display device.

[Embodiment 4] Embodiments 1 to 3 show examples in which the present invention is applied to a liquid crystal display device. However, the present invention is applicable to any semiconductor device using a TFT. It is possible to implement.

Specifically, an active matrix type E
When manufacturing an L (electroluminescence) display device or an active matrix type EC (electrochromic) display device, the present invention can be implemented in a laser annealing step of a semiconductor film. that time,
Any of the configurations of the first to third embodiments may be used.

Since the invention of the present application is an invention of a laser annealing step, a known TFT manufacturing process can be applied to other parts. Therefore, the active matrix type E
When manufacturing an L display device or an active matrix type EC display device, the present invention may be applied to a known technique. Of course, it is also possible to fabricate by referring to the fabrication steps described with reference to FIGS.

[Embodiment 5] The present invention can be applied to an electronic device (also referred to as an electronic device) having an electro-optical device such as an active matrix type liquid crystal display device or an active matrix type EL display device as a display. It is possible. Electronic devices include personal computers, digital cameras, video cameras, personal digital assistants (mobile computers, mobile phones, e-books, etc.),
Navigation system and the like are raised.

FIG. 16A shows a personal computer, which comprises a main body 2001 provided with a microprocessor and a memory, an image input unit 2002, a display unit 2003, and a keyboard 2004. The present invention relates to a display device 20.
03 and other driving circuits.

FIG. 16B shows 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 210.
6. The present invention can be implemented when the display device 2102 and other driving circuits are manufactured.

FIG. 16C shows a goggle type display, which comprises a main body 2201, a display device 2202, and an arm section 22.
It consists of 03. The present invention can be carried out when the display portion 2202 and other driving circuits (not shown) are manufactured. .

FIG. 16D shows an electronic game machine such as a video game or a video game. A main body 23 on which an electric circuit 2308 such as a CPU and a recording medium 2304 are mounted is shown.
01, controller 2305, display unit 2303, main body 2
The display unit 2302 is incorporated in the display unit 301. The display unit 2303 and the display unit 23 incorporated in the main body 2301
02, the same information may be displayed, the former may be used as the main display device, and the latter may be used as the sub-display device to display information on the recording medium 2304, display the operation state of the device, or display the touch sensor. An operation panel can be provided with additional functions. Further, the main body 2301, the controller 2305, and the display unit 2303 may be wired communication for transmitting signals to each other, or may be wireless communication or optical communication by providing the sensor units 2306 and 2307. The present invention is
This can be performed when the display portions 2302 and 2303 are manufactured. Further, the display portion 2303 can use a conventional CRT.

FIG. 16E shows a player using a recording medium (hereinafter, referred to as a recording medium) on which a program is recorded, and includes a main body 2401, a display section 2402, and a speaker section 24.
03, a recording medium 2404, and operation switches 2405. The recording medium is a DVD (Digital Versati
le Disc) and compact disc (CD)
Playback of music programs, video display, video games (or video games), information display via the Internet, and the like can be performed. The present invention can be implemented when the display portion 2402 and other driving circuits are manufactured.

FIG. 16F shows a digital camera, which includes a main body 2501, a display section 2502, an eyepiece section 2503, operation switches 2504, and an image receiving section (not shown).
The present invention can be implemented when the display portion 2502 and other driver circuits are manufactured.

FIG. 17A shows a front type projector, which comprises 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 illustrates a rear projector, which includes a main body 2701, a light source optical system and a display device 2702, a mirror 2703, and a screen 2.
704. The present invention can be implemented when a display device or another driving circuit is manufactured.

Note that FIG. 17C shows the light source optical system and the display device 26 shown in FIGS. 17A and 17B.
01 and 2702 are shown as examples. The light source optical system and display devices 2601 and 2702 include a light source optical system 2801, mirrors 2802 and 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.
It consists of. The projection optical system 2810 includes a plurality of optical lenses.

FIG. 17C shows an example of a three-plate type using three liquid crystal display devices 2808. However, the present invention is not limited to such a type, and a single-plate type optical system may be used. Also,
In the optical path indicated by the arrow in FIG. 17C, a suitable optical lens, a film having a polarizing function, a film for adjusting a phase, an IR film, or the like may be provided.

FIG. 17D is a diagram showing an example of the structure of the light source optical system 2801 in FIG. 17C.
In this embodiment, the light source optical system 2801 is
11, light source 2812, lens arrays 2813, 281
4. It is composed of a polarization conversion element 2815 and a condenser lens 2816. Note that the light source optical system shown in FIG. 17D is an example, and is not limited to the illustrated configuration.

Although not shown here, the present invention can also be implemented when manufacturing a navigation system or a reading circuit of an image sensor. As described above, the applicable range of the present invention is extremely wide, and the present invention can be applied to manufacturing electronic devices in all fields.

[Embodiment 6] In the first embodiment, an example is shown in which the method of the first to third embodiments is used after patterning is performed. In this embodiment, the first embodiment is performed before the patterning is performed. FIG. 18 shows an example in which a laser beam is irradiated using the method described above.

First, the state shown in FIG. 7A is obtained according to the first embodiment.

Next, a crystallization step is performed on the semiconductor film. A crystallization step used in this embodiment, that is, a configuration in which the front surface and the back surface of the semiconductor film illustrated in FIG. 18 are irradiated with laser light will be described below.

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.
In addition, a reflector 1804 for reflecting laser light is disposed below 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 transmissive substrate 1801 itself can adjust the effective energy intensity of the secondary laser light.
Further, 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 with the insulating film 1802.

In the configuration shown in FIG. 18, the secondary laser light is a laser light that has once passed through the amorphous semiconductor film 1803 and has been reflected by the reflector 1804. Therefore,
The effective energy intensity of the secondary laser light can be adjusted by the amorphous semiconductor film 1803. Further, the amorphous semiconductor film 1803 includes a compound semiconductor film such as an amorphous silicon germanium film in addition to the amorphous silicon film.

Further, the reflector 1804 may be a substrate having a metal film formed on the surface (reflection surface of laser light),
A substrate made of a metal element may be used. In this case, any material may be used for the metal film. Typically, silicon (Si), aluminum (Al), silver (Ag),
Tungsten (W), titanium (Ti), tantalum (T
A metal film containing any element of a) is used. For example,
Tungsten nitride (WN), titanium nitride (TiN), and tantalum nitride (TaN) may be used.

Further, the reflector 1804 may be provided in contact with the light transmitting substrate 1801 or may be provided separately therefrom. Also, instead of disposing the reflector 1804, the substrate 1
It is also possible to form the above-described metal film directly on the back surface (surface opposite to the front surface) of 801 and reflect laser light there. In any case, the effective energy intensity of the secondary laser light can be adjusted by the reflectance of the reflector 1804. In addition, the reflector 1804 is connected to the transparent substrate 1.
When it is set apart from the 801, the energy intensity of the secondary laser light can be controlled by the gas filling the gap.

Then, the amorphous semiconductor film 1803 is irradiated with linearly processed laser light via the optical system 201 (only the cylindrical lens 207 is shown in the figure) described with reference to FIG. The irradiation of the linearly processed laser light is performed by scanning the laser light.

In any case, the cylindrical lens 2
07, the primary laser light 1805 which is irradiated on the surface of the amorphous semiconductor film 1803 and the amorphous semiconductor film 183.
03, the effective energy intensity ratio (I ₀ ′ / I ₀ ) with the secondary laser light 1806 that is once reflected by the reflector 1804 and applied to the back surface of the amorphous semiconductor film 1803 is
It is important to satisfy the relationship 0 <I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ . For this purpose, the reflectance of the reflector 1804 with respect to the laser beam is preferably 20 to 80%. At this time, a desired intensity ratio may be obtained by combining a plurality of means for attenuating the effective energy intensity of the secondary laser light described in this embodiment.

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 focused. Therefore, the secondary laser light 1806 is also applied to the back surface side of the amorphous semiconductor film 1803 so as to reach. In addition, by providing an uneven portion on the reflection surface of the reflector 1804 and irregularly reflecting the laser light, the secondary laser light 1806 can be obtained more efficiently.

As the laser beam, the amorphous semiconductor film 18
Any laser light having a wavelength in the wavelength range (around 530 nm) that has a sufficient light transmission component and absorption component for 03 is acceptable. In this example, crystallization was performed using the second harmonic (wavelength 532 nm) of a YAG laser.

When the second harmonic is used, a part of the irradiated light passes through the amorphous semiconductor film and can be irradiated on the back surface of the amorphous semiconductor film by the reflector. 1806 can be obtained efficiently.

Next, the obtained semiconductor film is patterned to obtain an island-shaped semiconductor film.

In the subsequent steps, according to the first embodiment, an active matrix substrate is obtained.

This embodiment can be combined with the second embodiment. Further, by using the third embodiment, an active matrix type liquid crystal display device can be obtained. Further, this embodiment can be applied to the semiconductor devices shown in Embodiments 4 and 5.

[0170]

According to the present invention, in addition to processing a laser beam into a linear shape at the time of laser annealing to improve throughput, a conventional excimer laser can be used by using a solid-state laser that is easier to maintain. An improvement in throughput can be achieved compared to the laser annealing used. As a result, the manufacturing cost of a semiconductor device such as a TFT or a liquid crystal display device formed with the TFT can be reduced.

Further, laser annealing is performed by irradiating the laser light to the front and back surfaces of the amorphous semiconductor film, so that the conventional method (when only the surface of the amorphous semiconductor film is irradiated with laser light) is performed. It is possible to obtain a crystalline semiconductor film having a larger crystal grain size than that of the semiconductor device. And
By obtaining a crystalline semiconductor film having a large crystal grain size, the performance of a semiconductor device can be significantly 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 the laser device.

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 view showing a laser annealing method of the present invention.

FIG. 6 is a view showing a laser annealing method of the present invention.

FIG. 7 illustrates a manufacturing process of an active matrix substrate.

FIG. 8 is a diagram illustrating a manufacturing process of an active matrix substrate.

FIG. 9 illustrates a manufacturing process of an active matrix substrate.

FIG. 10 illustrates a manufacturing process of an active matrix substrate.

FIG. 11 illustrates a manufacturing process of an active matrix substrate.

FIG. 12 illustrates a pixel structure.

FIG. 13 illustrates a cross-sectional structure of an active matrix liquid crystal display device.

FIG. 14 is a diagram showing 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 illustrates an example of a projector.

FIG. 18 is a view showing a laser annealing method of the present invention.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01L 29/78 616V 618Z 618F (72) Inventor Kenji Kasahara 398 Hase, Atsugi-shi, Kanagawa Pref. ) Inventor Ritsuko Kawasaki 398 Hase, Atsugi-shi, Kanagawa F-term in Semiconductor Energy Laboratory Co., Ltd. CC02 DD01 DD02 DD03 DD12 DD13 DD14 DD15 DD17 DD18 EE01 EE04 EE05 EE06 EE08 EE14 EE15 EE28 EE44 EE45 FF04 FF09 FF28 FF30 GG01 GG02 GG13 GG23 NN25 HL23 GG45 GG45 GG51 GG51 GG22 NN24 NN27 NN35 NN36 NN73 NN78 PP01 PP03 PP04 PP05 PP06 PP07 PP13 PP29 PP35 QQ04 QQ09 QQ11 QQ19 QQ23 QQ24 QQ25

Claims (54)

[Claims] A first step of irradiating the island-shaped amorphous semiconductor film on the insulating surface with a laser beam, and scanning a region irradiated with the laser beam to crystallize the island-shaped amorphous semiconductor film; A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is a laser continuously oscillated from a YVO ₄ laser. A method for manufacturing a thin film transistor, which is light. 2. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. A method for manufacturing a thin film transistor, which is formed without exposure to an atmosphere, wherein the laser light is laser light continuously oscillated from a YVO ₄ laser. 3. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with laser light, and a region irradiated with the laser light is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A gate electrode is formed so as to overlap a part of the LDD region, and a length in a channel length direction of the LDD region overlapping the gate electrode is 0.5 to 3 μm; A method for manufacturing a thin film transistor, wherein a length of a non-overlapping LDD region in a channel length direction is 0.5 to 4 μm. 4. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser beam is continuously oscillated from a YVO ₄ laser, and is formed so that a gate electrode overlaps a part of the LDD region, and the LDD region is overlapped with the gate electrode. The length in the channel length direction is 0.5 to 3 μm, and the length in the channel length direction of the LDD region that does not overlap with the gate electrode is 0.5 to 4 μm. A method for manufacturing a transistor. 5. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser, The method for manufacturing a thin film transistor, wherein the source region and the drain region are activated using excimer laser light. 6. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. A method for manufacturing a thin film transistor, which is formed without exposure to an atmosphere, wherein the laser light is continuously oscillated from a YVO ₄ laser, and the source region and the drain region are activated using excimer laser light. 7. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. The source region and the drain region are activated using excimer laser light, and a gate electrode is formed so as to overlap a part of the LDD region and a channel length direction of the LDD region overlapping the gate electrode. Is 0.5 to 3 μm, and the length in the channel length direction of the LDD region that does not overlap with the gate electrode is 0.5 to 4 μm. A method for manufacturing a thin film transistor. 8. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with laser light, and a region irradiated with the laser light is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface is formed without exposure to the atmosphere above, the laser light is continuously oscillated from YVO ₄ laser, the source region and the drain region is activated by using an excimer laser beam, a part of the LDD region The gate electrode is formed so as to overlap, and the length in the channel length direction of the LDD region overlapping the gate electrode is 0.5 to 3 μm. The channel length direction of the length of the have LDD region, a method for manufacturing a thin film transistor, which is a 0.5 to 4 .mu.m. 9. The method for manufacturing a thin film transistor according to claim 5, wherein the excimer laser beam is scanned with an overlap ratio of 80 to 90%. 10. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is a laser continuously oscillated from a YVO ₄ laser. A method for manufacturing a thin film transistor, which is light, and the number of crystal grain boundaries included in the channel formation region is one or less. 11. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with laser light, and a region irradiated with the laser light is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. The method for manufacturing a thin film transistor, wherein the method is performed without exposure to an atmosphere, the laser light is continuously oscillated from a YVO ₄ laser, and the number of crystal grain boundaries included in the channel formation region is one or less. 12. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with laser light, and a region irradiated with the laser light is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A gate electrode is formed so as to overlap a part of the LDD region, and a length in a channel length direction of the LDD region overlapping the gate electrode is 0.5 to 3 μm; The length of the non-overlapping LDD region in the channel length direction is 0.5 to 4 μm, and the number of crystal grain boundaries included in the channel forming region is one or less. A method for manufacturing a register. 13. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface is formed without exposure to the atmosphere above, the laser light is continuously oscillated from YVO ₄ laser is formed so as the gate electrode overlaps a portion of the LDD region, the LDD region overlapping the gate electrode The length in the channel length direction is 0.5 to 3 μm, and the length in the channel length direction of the LDD region that does not overlap with the gate electrode is 0.5 to 4 μm. The method for manufacturing a thin film transistor, wherein the number of crystal grain boundaries included in the formation region is one or less. 14. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser, The method for manufacturing a thin film transistor, wherein the source region and the drain region are activated using excimer laser light, and the number of crystal grain boundaries included in the channel formation region is one or less. 15. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. is formed without exposure to the atmosphere, the laser light is continuously oscillated from YVO ₄ laser, the source region and the drain region is activated by using an excimer laser beam, the crystal grain boundaries included in the channel formation region Is less than or equal to one. 16. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with a laser beam, and a region irradiated with the laser beam is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. The source region and the drain region are activated using excimer laser light, and a gate electrode is formed so as to overlap a part of the LDD region and a channel length direction of the LDD region overlapping the gate electrode. The length of the LDD region not overlapping with the gate electrode in the channel length direction is 0.5 to 4 μm, and the length of the channel is 0.5 to 3 μm. Wherein the number of crystal grain boundaries included in the pixel formation region is one or less. 17. An island-shaped amorphous semiconductor film on an insulating surface is irradiated with laser light, and a region irradiated with the laser light is scanned to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser light is continuously oscillated from a YVO ₄ laser, the source region and the drain region are activated by using excimer laser light, and a part of the LDD region is formed. The gate electrode is formed so as to overlap, and the length in the channel length direction of the LDD region overlapping the gate electrode is 0.5 to 3 μm, and the LDD region overlaps with the gate electrode. The channel length direction of the length of the no LDD region is 0.5 to 4 .mu.m, the number of grain boundaries included in the channel formation region, a method for manufacturing a thin film transistor which is characterized in that not more than one. 18. The method for manufacturing a thin film transistor according to claim 14, wherein the excimer laser beam is scanned with an overlap ratio of 80 to 90%. 19. The device according to claim 10, wherein the defect density of the channel formation region is 1 × 1.
0 ¹⁶ cm ^-3 or less, the method for manufacturing a thin film transistor. 20. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with a laser beam, and scanning the region irradiated with the laser beam to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor, in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A method for manufacturing a thin film transistor, which has two harmonics. 21. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. A method for manufacturing a thin film transistor, which is formed without exposure to an atmosphere, wherein the laser beam is a second harmonic continuously oscillated from a YVO ₄ laser. 22. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A gate electrode is formed so as to overlap a part of the LDD region, and a length of the LDD region overlapping the gate electrode in a channel length direction is 0.5 to 3 μm. And a length in the channel length direction of the LDD region that does not overlap with the gate electrode is 0.5 to 4 μm. 23. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film; A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser light is formed without being exposed to the atmosphere, and the laser light is a second harmonic continuously oscillated from a YVO ₄ laser, and a gate electrode is formed so as to overlap a part of the LDD region. The length of the LDD region overlapping the gate electrode in the channel length direction is 0.5 to 3 μm, and the length of the LDD region not overlapping the gate electrode in the channel length direction is 0.5 to 4 μm. The method for manufacturing a thin film transistor, characterized in that. 24. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor, in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. The method for manufacturing a thin film transistor, wherein the source region and the drain region have two harmonics and are activated using excimer laser light. 25. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. The laser beam is formed without being exposed to an atmosphere, the laser beam is a second harmonic continuously oscillated from a YVO ₄ laser, and the source region and the drain region are activated using excimer laser beam. Method for manufacturing a thin film transistor. 26. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film; A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. The source region and the drain region are activated by using excimer laser light, and a gate electrode is formed so as to overlap a part of the LDD region. The length of the overlapping LDD region in the channel length direction is 0.5 to 3 μm, and the length of the LDD region not overlapping the gate electrode in the channel length direction is 0.5 to 4 μm. The method for manufacturing a thin film transistor which is characterized in that. 27. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser light is formed without being exposed to the air atmosphere, the laser light is a second harmonic continuously oscillated from a YVO ₄ laser, and the source region and the drain region are activated using excimer laser light. A gate electrode is formed so as to overlap a part of the LDD region, and a length of the LDD region overlapping the gate electrode in a channel length direction is 0.5 to 3 μm, and A method for manufacturing a thin film transistor, wherein a length of an LDD region which does not overlap with a gate electrode in a channel length direction is 0.5 to 4 μm. 28. The method for manufacturing a thin film transistor according to claim 24, wherein the excimer laser beam is scanned with an overlap ratio of 80 to 90%. 29. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor, in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A method for manufacturing a thin film transistor, which has two harmonics, and the number of crystal grain boundaries included in the channel formation region is one or less. 30. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. The laser light is formed without exposure to an atmosphere, the laser light is a second harmonic continuously oscillated from a YVO ₄ laser, and the number of crystal grain boundaries included in the channel forming region is one or less. Method for manufacturing a thin film transistor. 31. Irradiating an island-shaped amorphous semiconductor film on an insulating surface with a laser beam, scanning a region irradiated with the laser beam to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A gate electrode is formed so as to overlap a part of the LDD region, and a length of the LDD region overlapping the gate electrode in a channel length direction is 0.5 to 3 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 μm, and the number of crystal grain boundaries included in the channel formation region is one or less. A method for manufacturing a thin film transistor to be. 32. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with a laser beam, scanning the region irradiated with the laser beam to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser light is formed without being exposed to the atmosphere, and the laser light is a second harmonic continuously oscillated from a YVO ₄ laser, and a gate electrode is formed so as to overlap a part of the LDD region. The length of the LDD region overlapping the gate electrode in the channel length direction is 0.5 to 3 μm, and the length of the LDD region not overlapping the gate electrode in the channel length direction is 0.5 to 4 μm. , The number of grain boundaries included in the channel formation region, a method for manufacturing a thin film transistor which is characterized in that not more than one. 33. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor, in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. A second harmonic, wherein the source region and the drain region are activated using excimer laser light, and the number of crystal grain boundaries included in the channel formation region is one or less. Method of manufacturing. 34. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film; A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film is formed on the insulating surface by air. is formed without exposure to the atmosphere, the laser light is a second harmonic that is continuously oscillated from YVO ₄ laser, the source region and the drain region is activated by using an excimer laser beam, the channel formation The method for manufacturing a thin film transistor, wherein the number of crystal grain boundaries included in the region is one or less. 35. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, scanning the region irradiated with the laser light, crystallizing the island-shaped amorphous semiconductor film, A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the laser light is continuously oscillated from a YVO ₄ laser. The source region and the drain region are activated by using excimer laser light, and a gate electrode is formed so as to overlap a part of the LDD region. The length of the overlapping LDD region in the channel length direction is 0.5 to 3 μm, and the length of the LDD region not overlapping the gate electrode in the channel length direction is 0.5 to 4 μm. There, the number of grain boundaries included in the channel formation region, a method for manufacturing a thin film transistor which is characterized in that not more than one. 36. Irradiating the island-shaped amorphous semiconductor film on the insulating surface with laser light, and scanning the region irradiated with the laser light to crystallize the island-shaped amorphous semiconductor film; A method for manufacturing a thin film transistor in which an active layer including a source region, a drain region, an LDD region, and a channel formation region is formed using a crystallized island-shaped semiconductor film, wherein the amorphous semiconductor film includes an insulating surface The laser light is formed without being exposed to the atmosphere, the laser light is a second harmonic continuously oscillated from a YVO ₄ laser, and the source region and the drain region are activated using excimer laser light. A gate electrode is formed so as to overlap a part of the LDD region, and a length of the LDD region overlapping the gate electrode in a channel length direction is 0.5 to 3 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 μm, and the number of crystal grain boundaries included in the channel formation region is one or less. Production method. 37. The method for manufacturing a thin film transistor according to claim 33, wherein the excimer laser beam is scanned at an overlap ratio of 80 to 90%. 38. The device according to claim 29, wherein the defect density of the channel formation region is 1 × 1.
0 ¹⁶ cm ^-3 or less, the method for manufacturing a thin film transistor. 39. A method for manufacturing a thin film transistor according to claim 1, wherein the crystallized island-shaped semiconductor film is patterned to form an active layer. 40. The thin film transistor according to claim 1, wherein an active layer is formed by etching a region in which the crystallized island-shaped semiconductor film has accumulated strain. Production method. 41. The laser light according to any one of claims 1 to 40, wherein the laser light applied to the island-shaped amorphous semiconductor film is split into a primary laser light and a secondary laser light. Together, the primary laser light is applied to the surface of the island-shaped amorphous semiconductor film, and the secondary laser light is applied to the back surface of the island-shaped amorphous semiconductor film. A method for manufacturing a thin film transistor. 42. A method according to claim 41, wherein an effective intensity ratio between said primary laser light and said secondary laser light is larger than 0 (excluding 1). . 43. The method for manufacturing a thin film transistor according to any one of claims 1 to 42, wherein the laser light is a rectangular laser light having an aspect ratio of 10 or more. 44. The method for manufacturing a thin film transistor according to any one of claims 1 to 42, wherein the laser light is an oblong laser light. 45. The semiconductor device according to claim 1, wherein the channel forming region has a size of 1 × 10 ^{16 to} 5 × 10
^A method for manufacturing a thin film transistor, comprising adding an impurity element imparting p-type at a concentration of ¹⁷ cm ^-3 . 46. The method for manufacturing a thin film transistor according to any one of claims 1 to 45, wherein the irradiation with the laser light is performed under reduced pressure. 47. The method for manufacturing a thin film transistor according to claim 1, wherein the irradiation with the laser light is performed in an inert atmosphere. 48. The thin film transistor according to claim 1, wherein after forming the source region, the drain region, and the channel formation region, the channel formation region is hydrogenated. Production method. 49. The method for manufacturing a thin film transistor according to claim 1, wherein the amorphous semiconductor film is an amorphous silicon film. 50. A thin film transistor manufactured by using the manufacturing method according to any one of claims 1 to 49. 51. A CPU using the thin film transistor according to claim 50. 52. A memory using the thin film transistor according to claim 50. 53. An electro-optical device using the thin-film transistor according to claim 50. 54. An electronic device comprising the electro-optical device according to claim 53.