JPH09266318A - Manufacture of thin film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a thin film transistor which is capable of further activating impurities and recovering damages simultaneously. SOLUTION: An oxide film 15 is formed on a glass board 10 based on a CVD method. An amorphous silicon thin film 20 is formed thereon based on the CVD method. A resist 30 whose pattern is identical to a gate electrode, is formed on this layer. With this as a mask, phosphorous (P) is ion-doped with a low energy of 10 keV and below and under the condition of about 1E15 (cm-<2> ), thereby forming a source drain area 60. And the resist 30 is removed so that the surface of the amorphous silicon thin film 20 may be exposed, thereby irradiating it with an excimer laser 50 whose energy exceeds 300mJ/cm<2> and in a range which does not allow an abrasion to be produced, which serves to crystallize and activate impurities and recover the damages thus received. Then, when a gate insulation film 70 and a gate electrode 80 are formed on the silicon thin film 20, a thin film transistor is available.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor used in, for example, a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, high temperature annealing treatment in hydrogen plasma has been carried out in order to activate impurities in a source / drain region of a thin film transistor. In addition, the above-mentioned "activation" means from the implanted impurity atoms or molecules,
This means that carriers that contribute to electrical conduction (conductivity) are released.

[0003]

However, when an amorphous silicon thin film or a polysilicon thin film is doped with impurities, the thin film is damaged. This damage is that when an impurity atom or molecule having high energy collides with the thin film, a lattice defect occurs, and if this damage is large, a transition loop may occur. The lattice defect has a problem that it affects mobility of transistor characteristics and deterioration of reliability. In particular, damage in the vicinity of the source / drain in the channel region has a great influence on the characteristics of the transistor. Therefore, the activation process of the impurities needs to recover the damage at the same time as the implantation. However, the conventional method could activate the impurities but not recover the damage.

In order to solve the conventional problems described above, an object of the present invention is to provide a method of manufacturing a thin film transistor capable of simultaneously activating impurities and recovering damage to the thin film transistor.

[0005]

In order to achieve the above object, the first method of manufacturing a thin film transistor according to the present invention is to implant a donor or acceptor type impurity into an amorphous silicon thin film formed on a glass substrate. Then, a configuration is adopted in which the activation of the impurities, the crystallization of the amorphous silicon thin film, and the recovery of the damage caused by the implantation of the impurities are simultaneously performed by a laser annealing process.

That is, in order to recover the damage at the time of implantation, energy for returning the distorted crystal lattice to the original state must be applied, but the present inventors have conducted various studies on the method of applying this energy. . As a result, I got the idea of using a laser, and when I conducted a series of research based on this idea, I was able to activate impurities by laser irradiation and at the same time give energy to the crystal lattice,
The inventors have found that the distorted crystal structure can be restored by the injection, and have reached the present invention. The thin film transistor obtained by the present invention, without the carriers being captured,
It will be a high-performance device with high mobility, and will also be highly resistant to the reliability degradation phenomenon in which carriers are captured over time. The same applies to the following second and third thin film transistor manufacturing methods of the present invention.

"Activation of impurities" means activation by releasing carriers that contribute to conductivity from the injected impurities by laser annealing.
In the first method of manufacturing a thin film transistor according to the present invention, when the damage caused by the impurity implantation is a crystal lattice defect caused by the ion implantation, laser annealing treatment is performed to repair the lattice defect. .

In the first method of manufacturing a thin film transistor of the present invention, a polysilicon thin film may be used instead of the amorphous silicon thin film. Next,
A second method of manufacturing a thin film transistor according to the present invention comprises forming a resist having the same pattern as a gate electrode on an amorphous silicon thin film formed on a glass substrate, and implanting a donor or acceptor type impurity using the resist as a mask. Then, the resist is peeled off, the activation of the implanted impurities by laser annealing, the crystallization of the amorphous silicon thin film, and the recovery of the damage caused by the implantation of the impurities are simultaneously performed to crystallize the silicon thin film. A gate insulating film is formed on the gate insulating film, and a gate metal is deposited on the gate insulating film to form the gate electrode.

In the second method of manufacturing a thin film transistor according to the present invention, a polysilicon thin film may be used instead of the amorphous silicon thin film. In the second method for manufacturing a thin film transistor of the present invention, instead of forming a resist, an insulating film is formed on an amorphous silicon thin film, and a gate metal is deposited on the insulating film to form a gate electrode. Impurities may be implanted using the gate electrode as a mask, the gate electrode may be removed thereafter, and laser annealing may be performed through the gate insulating film. This has the advantages that the process is simplified and the manufacturing efficiency is improved, and that dust is not generated due to resist deterioration during implantation.

Next, in the third method of manufacturing a thin film transistor according to the present invention, a laser is applied to an amorphous silicon thin film formed on a glass substrate to form a gate insulating film on the amorphous silicon thin film. A gate metal is deposited on the gate insulating film to form a gate electrode, and in this state, a donor or acceptor type impurity is injected into the amorphous silicon, and laser annealing treatment activates the injected impurity and the impurity. The damage caused by the injection of is simultaneously recovered.

In the third method of manufacturing a thin film transistor of the present invention, prior to the laser annealing treatment,
The gate insulating film on the source and drain of the amorphous silicon thin film may be removed. This makes it possible to more effectively activate the impurities and recover the damage in the source and drain regions.

Further, in the laser annealing treatment of the third method of manufacturing a thin film transistor of the present invention, when the laser irradiation is performed at an angle smaller than 90 degrees with respect to the irradiation surface,
Laser energy can also be applied to the channel region of the amorphous silicon thin film. In this case, when the laser irradiation is performed while rotating the glass substrate, the laser energy can be uniformly applied to the wide portion of the channel region.

Then, in the laser annealing treatment of the third method of manufacturing a thin film transistor of the present invention, a reflector for reflecting laser light is provided in advance between the glass substrate and the amorphous silicon thin film, and laser irradiation is performed in this state. It is preferable to utilize the reflected light to activate the interface corresponding to directly under the gate electrode of the amorphous silicon thin film. In this way, the laser irradiation is spread over a wide range.

Further, in the laser annealing treatment of the third method of manufacturing a thin film transistor of the present invention, it is preferable to irradiate a laser from the back surface of the glass substrate, because the laser energy can be applied to a wide area.

In the implantation of impurities in all of the thin film transistor manufacturing methods of the present invention, the implantation energy is preferably 10 keV or less, particularly preferably 1 to 8 keV, for the purpose of reducing damage.

Further, an excimer laser can be used as a laser in the laser annealing treatment of all the thin film transistor manufacturing methods of the present invention. And
As an impurity implantation method in all the thin film transistor manufacturing methods of the present invention, an ion doping method of implanting without selecting an ion species can be used.

[0017]

Embodiments of the present invention will be described below. The following embodiments are examples in which the present invention is applied to a liquid crystal display device.

[0018]

First Embodiment A first embodiment according to the present invention will be described with reference to FIG. That is, first, as shown in FIG. 1A, about 20 glass substrates (# 7059 or # 1737, manufactured by Corning Incorporated) 10 are formed by a vapor phase chemical growth (CVD) method.
The oxide film 15 is formed to a thickness of 00A (200 nm), and amorphous silicon is similarly deposited to about 500 to about 500 by the CVD method.
An amorphous silicon thin film 20 is formed by depositing it with a thickness of 1000 A (50 to 100 nm). The oxide film 15
Is for suppressing impurities in the glass substrate and can be formed by, for example, a normal pressure CVD method or a low pressure CVD method.

Then, as shown in FIG. 3B, a resist material is placed on the amorphous silicon thin film 20 and is shaped into the same pattern as the gate electrode to form a resist 30.

Next, as shown in FIG. 2C, the resist 30 is used as a mask and ion-doped 40 with phosphorus (P) at a low energy of 10 keV or less under a condition of about 1E15 (cm ⁻² ), A source / drain region 60 is formed as shown in FIG. Then, the resist 30
Is removed, the surface of the amorphous silicon thin film appears again, and this is irradiated with the excimer laser 50. By this irradiation, the amorphous silicon thin film 20 is crystallized, and the impurity phosphorus is activated, and at the same time, the damage of the thin film is recovered. The energy of the excimer laser is preferably 300 mJ / cm ² or more, but if it is made too high, ablation occurs, so the upper limit is the value of the energy causing this ablation.

After the irradiation with the excimer laser 50, a gate insulating film 70 is formed with a thickness of about 1000 A (100 nm) by the CVD method as shown in FIG. The gate insulating film 70 is formed, for example, by a plasma CVD method, a low pressure CV.
It can be formed by the D method or the atmospheric pressure CVD method. Further, as shown in FIG. 3F, Ta is used as a gate metal on the gate insulating film 70 by a sputtering method to obtain 2000 A (200 nm).
The target thin film transistor is obtained by forming the gate electrode 80 by depositing the thin film with a thickness of.

The reliability characteristics of the thin film transistor thus manufactured were evaluated together with those obtained by the conventional manufacturing method. This evaluation is performed by applying an AC stress for 1000 seconds and monitoring the change in its characteristics. The above characteristics were measured by measuring the drain current. Further, in the conventional manufacturing method, activation of impurities is performed by high temperature annealing treatment in hydrogen plasma.

The result of this evaluation is shown in the graph of FIG.
As shown in FIG. 7A, the thin film transistor obtained according to the first embodiment of the present invention has an initial (after 0 second) characteristic and
The characteristics after 000 seconds were almost the same, and there was no large deviation. On the other hand, as shown in FIG. 6B, the thin film transistor obtained by the conventional manufacturing method had a large difference between the initial (after 0 second) characteristics and the characteristic after 1000 seconds.

[0024]

Second Embodiment A second embodiment according to the present invention will be described with reference to FIG. As shown in FIG.
Amorphous silicon is deposited thereon to a thickness of about 500 to 1000 A (50 to 100 nm) in the same manner as in Embodiment 1 to form an amorphous silicon thin film 20. Then, as shown in FIG. 6B, the amorphous silicon thin film is crystallized by using an excimer laser 50.
The energy of laser irradiation at this time is 200 to 40
It is 0 mJ / cm ² .

Next, as shown in FIG. 3C, a resist material is applied on the crystallized silicon thin film,
A resist 30 having the same pattern as the gate electrode is formed, and then phosphorus (P) is ion-doped 40 under the conditions of about 10 keV and 1E15 (cm ⁻² ) using the resist 30 as a mask.

After removing the resist 30, as shown in FIG. 3D, excimer laser irradiation 50 is performed to activate the impurities (phosphorus). In the figure,
Reference numeral 60 is a source / drain region. The energy of the laser irradiation 50 is 300 (m) as in the first embodiment.
J / cm ² ) or more is desirable, and the upper limit is also the same. By this laser irradiation 50, the activation of impurities (phosphorus) in the source / drain region 60 and the damage caused by the ion doping 40 can be recovered.

Further, as shown in FIGS. 7E and 7F, a gate insulating film 70 having a thickness of about 1000 A (100 nm) is formed on the silicon thin film 20 in the same manner as in the first embodiment. By forming the gate electrode 80 thereon, a target thin film transistor can be manufactured.

[0028]

Third Embodiment A third embodiment according to the present invention will be described with reference to FIG. As shown in FIG.
Amorphous silicon is deposited thereon to a thickness of about 500 to 1000 A (50 to 100 nm) in the same manner as in Embodiment 1 to form an amorphous silicon thin film 20. Next, as shown in FIG.
Is used to crystallize the amorphous silicon thin film 20 in the same manner as in the second embodiment. Then, as shown in FIGS. 3C and 3D, a gate insulating film 70 of about 1000 A is formed on the silicon thin film 20 in the same manner as in the first embodiment.
(100 nm) in thickness, and the gate electrode 8 is formed thereon.
0 is formed, and phosphorus (P) is ion-doped 40 under the conditions of about 80 keV and 1E15 (cm ⁻² ) using the gate electrode 80 as a mask. After that, as shown in FIG. 6E, the excimer laser 5 is processed in the same manner as in the first embodiment.
0, and impurities (phosphorus) in the source / drain region 60
Is simultaneously activated and the damage caused by the ion doping 40 is recovered.

[0029]

Fourth Embodiment A fourth embodiment according to the present invention will be described with reference to FIG. As shown in FIG.
Amorphous silicon is deposited thereon to a thickness of about 500 to 1000 A (50 to 100 nm) in the same manner as in Embodiment 1 to form an amorphous silicon thin film 20. Then, as shown in FIG. 3B, the excimer laser 50 is irradiated to the amorphous silicon thin film 20 in the same manner as in the second embodiment to crystallize it. Next, as shown in FIGS. 7C and 7D, the gate insulating film 70 is coated with about 1000 A (100 nm) in the same manner as in the second embodiment.
And the gate electrode 80 is formed on the gate electrode 80.
Ion doping 40 is performed under the condition of E15 (cm ⁻² ).
After that, as shown in FIG. 7E, the gate insulating film 70 is removed by etching using the gate electrode 80 as a mask. The source / drain region 60 is formed by this etching.
Is exposed, and as shown in FIG.
In the same manner as the above, the excimer laser 50 is irradiated to activate the impurities (phosphorus) in the source / drain regions 60 and at the same time, the damage caused by the ion doping is recovered.
The etching can be performed by dry etching or wet etching using reactive ions, for example.

[0030]

Fifth Embodiment A fifth embodiment according to the present invention will be described with reference to FIG. As shown in FIG. 1A, the glass substrate 1
0, the amorphous silicon thin film 20 is formed by depositing amorphous silicon to a thickness of about 500 to 1000 A (50 to 100 nm) in the same manner as in the first embodiment.
Then, as shown in FIG. 2B, the amorphous silicon thin film 20 is irradiated with an excimer laser 50 in the same manner as in the second embodiment, and is crystallized. Next, as shown in FIGS. 7C and 7D, the gate insulating film 70 is formed with about 1000 A (100 nm) in the same manner as in the second embodiment.
And a gate electrode 80 is formed on the gate electrode 80.
Ion doping 40 is performed under the condition of E15 (cm ⁻² ).
After that, as shown in FIGS. 8E and 8F, the excimer laser 50 is irradiated at an angle. It is preferable that this angle be as small as possible (at least less than 90 degrees) with respect to the glass substrate 10 (laser-irradiated surface), because the laser is also irradiated directly below the gate electrode 80 and activation can be performed in a wide range. Further, since there is a place behind the gate electrode 80, it is preferable to irradiate again at an angle from the opposite direction. Furthermore, when the glass substrate 10 is rotated and the laser irradiation is performed at an angle, the activation of impurities and the recovery of damage are performed in a wider range, which is particularly preferable.

[0031]

Sixth Embodiment A sixth embodiment according to the present invention will be described with reference to FIG. As shown in FIG. 1A, the glass substrate 1
0, the amorphous silicon thin film 20 is formed by depositing amorphous silicon to a thickness of about 500 to 1000 A (50 to 100 nm) in the same manner as in the first embodiment.
Then, as shown in FIG. 2B, the amorphous silicon thin film 20 is irradiated with an excimer laser 50 to crystallize it, as in the second embodiment. Then, as shown in FIGS. 7C and 7D, a gate insulating film 70 is formed on the crystallized silicon thin film 20 in a thickness of about 1000 A (100 nm) in the same manner as in the second embodiment. A gate electrode 80 is formed on top of this, and phosphorus is used at 80 keV, 1E15 (cm) with this gate electrode 80 as a mask.
Ion doping 40 is performed under the condition of ^-2 ). Next, as shown in FIG. 7E, the excimer laser 50 is irradiated from the back surface (the surface opposite to the surface on which the amorphous silicon thin film is formed) of the glass substrate 10 in the same manner as in the second embodiment. By this laser irradiation from the back surface side, there is no interruption by the gate electrode 80, and damage is recovered in a wide range including immediately below the gate electrode 80.

[0032]

Seventh Embodiment A seventh embodiment according to the present invention will be described with reference to FIG. That is, first, as shown in the figure, a reflecting plate 90 that reflects laser light is formed on the glass substrate 10, and the oxide film 15 is formed thereon, as in the first embodiment. The reflector 90 can be formed, for example, by depositing a refractory metal (for example, titanium, film thickness 100 nm) by a sputtering method. Next, in the same manner as in the first embodiment, about 500 to 1000 A (5
The amorphous silicon thin film 20 is formed by depositing the amorphous silicon thin film 20 with a thickness of 0 to 100 nm. Then, similarly to the second embodiment, the excimer laser 50 is irradiated to crystallize this. Next, a gate insulating film 70 is formed on the crystallized silicon film 20 in the same manner as in the second embodiment by about 1000 A (10 A).
The gate electrode 80 is formed on the gate electrode 80, and phosphorus is used for 80 k
Ion doping under the conditions of eV and 1E15 (cm ^-2 ) 4
0. After that, excimer laser irradiation 50 is performed again in the same manner as in the second embodiment to activate the impurities in the source / drain regions 60 and at the same time, recover the damage caused by the ion doping. At this time, the laser light is reflected by the reflection plate 90, and a part of the laser light is also radiated directly under the gate electrode 80, so that the damage is widely recovered.

[0033]

Eighth Embodiment An eighth embodiment according to the present invention will be described with reference to FIG. As shown in FIG. 9A, the glass substrate 10
About 2000A on the top surface by chemical vapor deposition (CVD) method
The oxide film 15 is formed with a thickness of (200 nm), and similarly,
Amorphous silicon thin film 20 is about 500-
It is formed with a thickness of 1000 A (50 to 100 nm). On top of that, as shown in FIG.
It is formed by sputtering using a. And FIG. 9 (c)
As shown in FIG.
1E15 (cm ^-2 ) phosphorus at low energy below keV
Ion doping 40 is performed under moderate conditions to form source / drain regions 60 as shown in FIG. Then, when the gate electrode 80 is temporarily removed, the surface of the amorphous silicon thin film 20 is exposed again. Then, as shown in FIG. 9D, the surface of the amorphous silicon thin film 20 is irradiated with an excimer laser 50. By this irradiation, the amorphous silicon thin film 2
0 is crystallized, impurities are activated, and damage is recovered. Next, as shown in FIG. 9E, after the excimer laser irradiation, about 100
It is formed with a thickness of 0 A (100 nm). And in FIG.
As shown in (f), again on the gate insulating film 70,
A thin film transistor can be manufactured by forming the gate metal Ta by depositing it by a sputtering method.

As described above, when the gate metal (electrode) is used as a mask during ion doping, dust is less and there is no possibility of contaminating the doping chamber as compared with the case where a resist is used as the mask.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. Further, in these embodiments, no reference is made to the insulating film that prevents the impurities in the glass substrate from diffusing into the silicon substrate, but it is irrelevant to the effect of the present invention. Therefore, the insulating film can be appropriately formed by a conventionally known method, if necessary. Further, although the amorphous silicon thin film is formed in these embodiments, the same can be done by forming a polysilicon thin film, and the polysilicon thin film can be formed by a CVD method.

[0036]

As described above, according to the method of manufacturing a thin film transistor of the present invention, it is possible to activate impurities and simultaneously recover damage such as crystal lattice defects. In the thin film transistor thus obtained, carriers carrying an electric current are not captured by crystal lattice defects, and the initial characteristics and the reliability deterioration characteristics are improved. Further, when the thin film transistor thus obtained is formed into an array, variations in characteristics are also suppressed. Further, in the method of manufacturing the thin film transistor of the present invention, the activation of impurities and the recovery of damage are performed at the same time, so that the process is simplified and the manufacturing efficiency is improved as compared with the conventional manufacturing method.

[Brief description of drawings]

FIG. 1A to FIG. 1F are cross-sectional views showing an embodiment of a method of manufacturing a thin film transistor according to the present invention, step by step.

2A to 2F are cross-sectional views showing another embodiment of the method of manufacturing a thin film transistor according to the present invention, step by step.

FIG. 3A to FIG. 3E are cross-sectional views showing still another embodiment of the method of manufacturing a thin film transistor according to the present invention, step by step.

FIG. 4A to FIG. 4F are cross-sectional views showing, step by step, still another embodiment of the method of manufacturing a thin film transistor according to the present invention.

5A to 5F are cross-sectional views showing, in process steps, still another embodiment of the method of manufacturing a thin film transistor according to the present invention.

FIG. 6A to FIG. 6E are cross-sectional views showing still another embodiment of the method of manufacturing a thin film transistor according to the present invention, step by step.

FIG. 7 is a cross-sectional view showing still another embodiment of the method of manufacturing a thin film transistor of the present invention.

FIG. 8A is a graph showing characteristics of the thin film transistor obtained according to the embodiment, and FIG.
[Fig. 4] is a graph showing characteristics of a thin film transistor obtained by a conventional manufacturing method.

9A to 9F are cross-sectional views showing, in process steps, still another embodiment of the method of manufacturing a thin film transistor according to the present invention.

[Explanation of symbols]

 10 glass substrate 15 oxide film 20 amorphous silicon thin film 30 resist 40 ion doping 50 excimer laser 60 source / drain region 70 gate insulating film 80 gate electrode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/268 H01L 29/78 616M (72) Inventor Hiroshi Tsutsumi 1006 Kadoma, Kadoma-shi, Osaka Matsushita Denki Sangyo Co., Ltd. (72) Inventor Tatsuo Yoshioka 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Mamoru Furuta 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Shigeki Maekawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Yutaka Miyata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (16)

[Claims] 1. An amorphous silicon thin film formed on a glass substrate is implanted with a donor or acceptor type impurity, and then laser annealing is performed to activate the impurity, crystallize the amorphous silicon thin film, and implant the impurity. A method for manufacturing a thin film transistor, which simultaneously recovers the damage that has occurred. 2. The method of manufacturing a thin film transistor according to claim 1, wherein the activation of the impurities is activation by releasing carriers that contribute to conductivity from the implanted impurities by a laser annealing process. 3. The method of manufacturing a thin film transistor according to claim 1, wherein the damage caused by the impurity implantation is a lattice defect caused by the ion implantation, and a laser annealing process is performed to repair the lattice defect. 4. The method of manufacturing a thin film transistor according to claim 1, wherein a polysilicon thin film is used instead of the amorphous silicon thin film. 5. A resist having the same pattern as a gate electrode is formed on an amorphous silicon thin film formed on a glass substrate, a donor or acceptor type impurity is implanted using the resist as a mask, and the resist is peeled off. A gate insulating film is formed on the crystallized silicon thin film by removing and activating the implanted impurities by laser annealing, crystallizing the amorphous silicon thin film, and recovering damage caused by the impurity implantation. And forming a gate metal on the gate insulating film to form the gate electrode. 6. The method of manufacturing a thin film transistor according to claim 5, wherein a polysilicon thin film is used instead of the amorphous silicon thin film. 7. Instead of forming a resist, a gate insulating film is formed on an amorphous silicon thin film, a gate metal is deposited on the gate insulating film to form a gate electrode, and impurities are implanted using this gate electrode as a mask. 7. The method of manufacturing a thin film transistor according to claim 5, wherein the gate electrode is removed thereafter, and laser annealing is performed through the gate insulating film. 8. An amorphous silicon thin film formed on a glass substrate is irradiated with a laser to form a gate insulating film on the amorphous silicon thin film, and a gate metal is deposited on the gate insulating film to form a gate electrode. To form
A method of manufacturing a thin film transistor, in which a donor or acceptor type impurity is implanted into the amorphous silicon in this state, and activation of the implanted impurity by laser annealing and recovery of damage caused by the implantation of the impurity are performed simultaneously. 9. The method of manufacturing a thin film transistor according to claim 8, wherein the gate insulating film on the source and drain of the amorphous silicon thin film is removed prior to the laser annealing process. 10. The method of manufacturing a thin film transistor according to claim 8, wherein in the laser annealing treatment, laser irradiation is performed at an angle smaller than 90 degrees with respect to the irradiation surface. 11. The laser irradiation is performed while rotating the glass substrate in the laser annealing treatment.
A method for manufacturing the thin film transistor according to the above. 12. In the laser annealing process, a reflection plate for reflecting laser light is provided in advance between the glass substrate and the amorphous silicon thin film, laser irradiation is performed in this state, and the reflected light is used to make a gate electrode of the amorphous silicon thin film. The interface corresponding to the portion directly below is activated.
1. The method for manufacturing a thin film transistor according to any one of 1. 13. The method of manufacturing a thin film transistor according to claim 8, wherein a laser is applied from the back surface of the glass substrate in the laser annealing process. 14. The method of manufacturing a thin film transistor according to claim 1, wherein the implantation energy is set to 10 keV or less in the impurity implantation. 15. The method of manufacturing a thin film transistor according to claim 1, wherein an excimer laser is used as a laser in the laser annealing process. 16. The ion doping method of implanting without selecting an ion species is used as the impurity implantation method.
16. The method for manufacturing a thin film transistor according to any one of items 15 to 15.