JPH09115855A - Laser irradiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a non-single crystal semiconductor layer having good electric characteristics by processing an object in a laser irradiation chamber with laser light while sustaining the processing pressure at a constant level when it is reached thereby preventing the non-single crystal semiconductor layer from being mixed with impurities. SOLUTION: A silicon oxide is deposited by 3000Å, as an underlying layer, on a glass substrate 405 by plasma CVD or spattering. A starting material for active layer, i.e., amorphous silicon, is then deposited by 500Å by plasma CVD or low pressure CVD. An irradiation chamber 401 is then evacuated starting from the atmospheric pressure and when a pressure of 0.5Torr is reached, the inner pressure is fixed at that level and the amorphous silicon is irradiated with laser light emitted from a laser oscillator 402 thus crystallizing the amorphous silicon. Since the non-single crystal semiconductor layer is prevented from being mixed with impurities, a non-single crystal semiconductor layer having good electric characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laser irradiation method.

[0002]

2. Description of the Related Art In a chamber for performing laser irradiation (hereinafter referred to as a laser irradiation chamber) when a surface to be formed is processed by laser irradiation or an annealing treatment or a crystallization treatment is performed in semiconductor film production. Employs a process in which before the laser irradiation is started, the processing chamber is once evacuated to a high vacuum with a vacuum pump and then a gas such as oxygen is introduced to restore the pressure to the processing.

However, when crystallization is performed by laser irradiation for producing a semiconductor film after this step is taken, there is a problem that the characteristics of the processed semiconductor film become poor.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a film obtained when a film sensitive to impurities such as a semiconductor film after laser irradiation is processed by laser irradiation. Is intended to be of high quality.

[0005]

The present invention has the following features to attain the object mentioned above.

First configuration: When an object to be processed is treated with a laser beam in a laser irradiation chamber, irradiation with the laser is carried out with the pressure kept constant when the pressure required for the processing is reached. And

Second Configuration When crystallizing the non-single crystal semiconductor layer on the substrate in the laser irradiation chamber, the pressure is kept constant when the pressure required for crystallization is reached, and laser light is applied to the non-single crystal semiconductor layer. It will be irradiated.

Third Structure When the non-single crystal semiconductor layer on the substrate is annealed in the laser irradiation chamber, the pressure is kept constant when the pressure required for the annealing is reached, and the non-single crystal semiconductor layer is irradiated with laser light. I will.

Fourth Structure When crystallizing the non-single crystal semiconductor layer on the substrate in the laser irradiation chamber, the pressure is kept constant when the pressure required for the crystallization is reached, and laser light is applied to the non-single crystal semiconductor layer. At the same time as the irradiation, the laser irradiation chamber is cleaned.

Fifth Structure When annealing the non-single-crystal semiconductor layer on the substrate inside the laser irradiation chamber, the pressure is kept constant when the pressure required for the annealing is reached, and the non-single-crystal semiconductor layer is irradiated with laser light at the same time. The laser irradiation chamber is cleaned.

According to the present invention, when the laser irradiation chamber is depressurized, the vacuum pump is used to create a high vacuum state in the processing chamber and then to return it to a pressure suitable for the processing. The feature is that in the process of reducing the pressure in the chamber, when the pressure suitable for the treatment is reached, the pressure is kept constant and the treatment is started. The constant pressure in the present invention means that after the pressure required for crystallization, annealing, or other laser processing is reached, the pressure is not artificially increased or decreased. is there. The present invention will be described in detail below with reference to examples.

[0012]

【Example】

[Embodiment 1] In this embodiment, the laser irradiation chamber is not evacuated to a high vacuum before laser irradiation, but is gradually changed to a vacuum degree that is necessary for the treatment while flowing a gas in an atmosphere necessary for laser irradiation. It is going.

In this embodiment, the case where the active layer of the thin film semiconductor layer is crystallized by laser will be described as an example. First, a brief description will be given up to the formation of the active layer of the thin film transistor which is the target of laser irradiation.

First, a silicon oxide film is formed as a base film on a glass substrate to a thickness of 3000 Å by plasma CVD or sputtering. Next, an amorphous silicon film as a starting material for forming the active layer is formed by a plasma CVD method or a low pressure CV method.
A thickness of 500Å is produced by the D method. At this time, for the purpose of shifting the threshold value, 1 to 5 ppm of diborane is added to silane which is a reactive gas to form a film.

Laser irradiation using the method of the present invention is now applied to this amorphous silicon film. The glass substrate on which the amorphous silicon film is formed is placed in a laser irradiation chamber, and the laser irradiation chamber is evacuated while introducing oxygen, nitrogen, hydrogen, or a mixture thereof.

The laser irradiation chamber is evacuated while introducing oxygen, for example. FIG. 1 shows how the pressure changes in the laser irradiation chamber at this time. The abscissa represents time, and the ordinate represents the degree of vacuum in the laser irradiation chamber. The higher the vertical axis, the higher the vacuum. In the figure, there is no change in the curve and the part where the degree of vacuum is constant represents the pressure suitable for processing. In the case of this embodiment, the pressure inside the irradiation chamber is reduced from atmospheric pressure to a predetermined pressure, for example, 0.5 Torr.
At that point, the pressure is kept constant and laser irradiation is started to the amorphous silicon film to crystallize the amorphous silicon film.

After that, the resistivity of this crystallized amorphous silicon film was measured and found to be 5 × 10 ⁵ Ωcm.

Comparative Example 1 For the purpose of comparison with Example 1,
As in the conventional vacuum method, the inside of the laser irradiation chamber is once evacuated to a high vacuum and then returned to atmospheric pressure to crystallize the active layer of the thin film semiconductor layer with a laser. explain.

The amorphous silicon film used in the comparative example is the first embodiment.
It was formed on a glass substrate by the same method as shown in.

The glass substrate on which the amorphous silicon film is formed is placed in a laser irradiation chamber, and the laser irradiation chamber is evacuated while introducing oxygen, nitrogen, hydrogen, or a mixture thereof.

At this time, 1 × 10 ⁻⁵ To was obtained by the vacuum pump.
After evacuating to rr, oxygen is introduced to return to atmospheric pressure. The pressure change in the laser irradiation chamber at this time is shown in FIG. The view of FIG. 2 is the same as that of FIG. 1, and represents that the pressure in the irradiation chamber is changed over time as shown in FIG. In the figure, the part where the curve does not change represents atmospheric pressure, and the apex part of the curve represents the pressure of 1 × 10 ⁻⁵ Torr. When the atmospheric pressure is reached, the pressure is kept constant and laser irradiation is started on the amorphous silicon film.

After that, the resistivity of this crystallized amorphous silicon film was measured and found to be 6.5 × 10 ⁶ Ωcm.

Comparative Example 2 For the purpose of comparison with this example,
As in the conventional method of making a vacuum, the active layer of the thin-film semiconductor layer is crystallized by laser by temporarily raising the inside of the laser irradiation chamber to a high vacuum and then returning to the pressure required for laser irradiation processing. The case where is performed will be described.

The amorphous silicon film used in this comparative example was formed on a glass substrate by the same method as shown in Example 1.

The glass substrate on which the amorphous silicon film is formed is placed in a laser irradiation chamber, and the laser irradiation chamber is evacuated while introducing oxygen, nitrogen, hydrogen, or a mixture thereof.

At this time, 1 × 10 ⁻⁵ To was obtained by the vacuum pump.
After exhausting to rr once, introduce oxygen and add 0.5To
Return to rr pressure.

The pressure change in the laser irradiation chamber at this time is shown in FIG. Similarly to FIGS. 1 and 2, FIG. 3 also shows that the pressure in the irradiation chamber is changed over time as shown in FIG. The part where there is no change in the curve in the figure is 0.5
It represents the pressure of Torr, and the apex of the curve is 1 × 10 ^-5
It represents the pressure of Torr. When the pressure reaches 0.5 Torr, the pressure is kept constant and the amorphous silicon film is irradiated with laser to start crystallization of the amorphous silicon film.

Then, the resistivity of this crystallized amorphous silicon film was measured and found to be 6.0 × 10 ⁶ Ωcm. It can be seen from Example 1 and Comparative Examples 1 and 2 that the present invention is effective in producing a film that is electrically good for crystallization of an amorphous silicon film.

[Embodiment 2] In this embodiment, in addition to the method of adjusting the pressure in the laser irradiation chamber before laser irradiation according to the present invention, a step of simultaneously performing etching in the laser irradiation chamber during laser irradiation is added. is there.

According to the present embodiment, by adopting the method of adjusting the pressure in the laser irradiation chamber before laser irradiation according to the present invention, it is possible to reduce the addition of impurities to the laser irradiation target by the subsequent laser irradiation. In addition to the above effect, it is possible to prevent impurities from further mixing into the laser irradiation target by performing etching in the laser irradiation chamber at the same time during laser irradiation.

In this embodiment, a process of manufacturing a thin film transistor will be described as an example in order to explain an example in which the present invention is applied to a process of crystallizing an amorphous silicon film by laser irradiation and an annealing process by laser irradiation. explain.

First, an apparatus for carrying out this embodiment will be described. FIG. 4 shows an example of a laser irradiation device. FIG. 5 shows a view of FIG. 4 seen from above.

In the laser irradiation chamber 401, the laser light emitted from the laser oscillating device 402 is reflected by a mirror 403, and a substrate 405 is passed through a window 404 made of quartz.
It has the function of irradiating to. The laser light has a linear laser pattern in this embodiment.

The substrate 405 is arranged on the substrate stage 411, and is heated and kept at a predetermined temperature (450 to 700 ° C.) by a heater placed under the substrate stage 411.

The substrate stage 411 can be moved in one direction by a moving mechanism 407.

The laser irradiation chamber 401 is equipped with a vacuum exhaust pump 408, and the inside of the laser irradiation chamber 401 can be depressurized or vacuumed as necessary. The laser irradiation chamber 401 also includes a pair of electrodes 409 and a gas supply unit 410.

The pair of electrodes is placed on the side surface of the laser irradiation chamber 401. The laser irradiation chamber 401 has a gate valve 801 so that it can be connected to another processing chamber.

In addition to the laser irradiation chamber shown in FIGS. 4 and 5, a pair of electrodes are provided on the lateral sides of the irradiation chamber.
It may be provided on the upper left. A cross-sectional view of the laser irradiation chamber in that case is shown in FIG. FIG. 7 shows a view from above of the laser irradiation chamber in that case. The same reference numerals are used when displaying the same portions as those in FIGS. 4 and 5.

FIG. 8 is a schematic top view of the laser irradiation apparatus used in this embodiment. FIG. 8 shows that the laser irradiation chamber 401 of FIG. 4 is connected to the substrate transfer chamber 802 via the gate valve 801. An alignment mechanism is arranged in the alignment chamber 803. The alignment mechanism moves up and down by the elevator, and the substrate 804 and the robot arm 80 are moved by the operation mechanism.
5 has a function of correcting the positional relationship with 5. The alignment chamber 803 includes a substrate loading / unloading chamber 806 and a gate valve 8.
It is connected via 07. The heating chamber 808 is for preheating a substrate to be irradiated with laser light to a predetermined temperature. The reason for heating the substrate is to make the irradiation of laser light more effective.

The heating chamber 808 is made of cylindrical quartz. It also has a substrate holder made of quartz. This substrate holder is provided with a susceptor, and is configured to accommodate a large number of substrates. The substrate holder is configured to be slightly moved up and down by the elevator. The heating of the substrate in the heating chamber 808 is performed by a heater. In addition, the heating chamber 808 and the substrate transfer chamber 80
The two are connected by a gate valve 809.

The substrate preheated in the heating chamber 808 for a predetermined time is taken out to the substrate transfer chamber 802 by the robot arm 805. Then, the alignment is performed again by the alignment mechanism.

Thereafter, the robot arm 805 transfers the laser beam to the laser beam irradiation chamber 401. Laser irradiation room 4
01 is the structure as described above. After the laser light irradiation is completed, the substrate 804 is placed on the robot arm 80.
5 is drawn out to the substrate transfer chamber 802,
Transferred to 0. At this time, the alignment mechanism again aligns the substrate with the robot arm.

The slow cooling chamber 810 is connected to the substrate transfer chamber 802 via the gate valve 811, and the substrate placed on the quartz stage is exposed to infrared light from the lamp and the reflecting plate to gradually cool it. It has a mechanism to be cooled.

The substrate gradually cooled in the slow cooling chamber 810 is transferred to the substrate loading / unloading chamber 806 by the robot arm 805, and is again stored in the substrate holder. In this way, the laser beam irradiation process for the substrate 1 is completed.
In the case of irradiating a large number of substrates with laser light, the above steps may be continuously performed.

By laser irradiation using the above apparatus,
By the step of crystallizing the amorphous silicon film and the laser irradiation,
In order to explain the annealing process, a process of manufacturing a thin film transistor will be described below as an example with reference to the process diagram shown in FIG.

First, a silicon oxide film 902 is formed as a base film on a glass substrate 901 to a thickness of 3000 Å by plasma CVD or sputtering.

Next, an amorphous silicon film 903 to be a starting film for forming an active layer is formed by a plasma CVD method or a reduced pressure CV.
A thickness of 500Å is produced by the D method. At this time, for the purpose of shifting the threshold value, 1 to 5 ppm of diborane is added to the reactive gas silane to form a film.

Next, in order to crystallize this amorphous silicon film by irradiating it with a laser beam, the apparatus shown in FIG. 8 is used. As described above, the substrate is loaded into the substrate loading / unloading chamber 806 and transferred to the laser irradiation chamber 401 as described above.

After that, while the substrate is moved by using the laser, the surface of the substrate is irradiated with the laser, and at the same time, the etching in the laser irradiation chamber is simultaneously performed. First, while introducing a gas necessary for etching described below into the laser irradiation chamber 401, the laser irradiation chamber is evacuated to a pressure used for etching.

For example, the inside of the laser irradiation chamber is evacuated while introducing oxygen. The state of the pressure in the laser irradiation chamber at this time is shown in FIG. 1 as a schematic diagram.

Then, when the pressure reaches a predetermined pressure, for example, 0.5 Torr, the pressure is kept constant and laser irradiation is started to the amorphous silicon film, and the laser irradiation chamber 401 is etched as described below. Crystallize the crystalline silicon film. (FIG. 9A)

In FIG. 9, the same reference numerals as those described in FIG. 4 represent the same parts. In FIG. 9, reference numeral 901 denotes a high frequency power source. Reference numeral 919 represents an etching gas.

Next, the gas used for etching and its conditions will be described. When simultaneously removing organic impurities attached to the inner wall of the laser irradiation chamber 401, hydrogen, oxygen, or argon gas is introduced from the gas supply unit 410 to adjust the pressure in the irradiation chamber to, for example, 0.01 to 10 Torr, eg, 0. Keep at 02-0.03 Torr. And high frequency energy is applied to the pair of electrodes 409, here 13.56 MHz.
Was applied at an output of 400W.

By such a method, the organic substances attached to the surface of the substrate can be separated by impact or become volatile oxides and removed.

When metals such as W, Si, Ti, V, As, Ge, P and B attached to the inner wall of the laser irradiation chamber 401 are simultaneously removed, nitrogen trifluoride is supplied from the gas supply unit 410. (NF ₃ ), sulfur hexafluoride (SF ₆ ), C
A gas such as F ₄ or ClF ₃ is introduced to maintain the pressure in the irradiation chamber at, for example, 0.01 to 10 Torr, and the pair of electrodes 40
9. High frequency energy was applied to the high frequency energy of 13.56 MHz here with an output of 5 to 200 W.

Another method for removing the metal such as W, Si, Ti, V, As, Ge, P, B, etc. adhering to the inner wall of the laser irradiation chamber 401 is to use ClF ₃ gas. .

In this case, Cl from the gas supply unit 410
The gas of F ₃ is introduced. In this case no high frequency energy is required. Then react with deposits of the ClF ₃ gas adhered irradiation chamber, the further ClF ₃ gas reaction heat when is activated, the reaction of the deposit and the activated ClF ₃ gas is promoted, irradiated It becomes possible to remove the deposits adhering to the chamber.

The conditions in this case are 0.1 to 100 Torr.
It is preferable that the cleaning is performed under the condition that the temperature of the ClF ₃ gas is the boiling point to 700 ° C. ClF ₃ at a temperature less than the boiling point of the gas may cause damaging the material by condensation on the material ClF ₃ gas constituting the irradiation chamber, configured ClF ₃ gas be greater than 700 ° C. is a still irradiation chamber is activated There is a risk of damaging the material.

If the pressure is less than 0.1 Torr, the cleaning effect cannot be expected, and if it exceeds 100 Torr, the material forming the irradiation chamber may be damaged. After the pressure in the laser irradiation chamber is adjusted by the above method, the amorphous silicon film is crystallized by irradiating the amorphous silicon film with laser light at the same time as cleaning the inside of the laser irradiation chamber.

After the crystallization of the amorphous silicon film is completed, the substrate is transferred to the substrate loading / unloading chamber 806 as described above.

Thereafter, the crystallized crystalline silicon film obtained in the above step is patterned to obtain the active layer 904 of the thin film transistor. Next, a silicon oxide film 905 which functions as a gate insulating film is formed by plasma CVD to a thickness of 1000Å.

Further, an aluminum film for forming a gate electrode is formed by a sputtering method or an electron beam evaporation method.
This aluminum film contains Sc or Y, and one or more kinds of elements selected from lanthanoids and actinides in order to suppress the generation of hillocks and whiskers in the subsequent step. Here, Sc is 0.1
% By weight.

Hillocks and whiskers are needle-like or stab-like protrusions formed on the surface of an aluminum film when the aluminum film is heated to a temperature of 300 ° C. or higher or when the aluminum film is irradiated with laser light. I mean.

In a later step, an extremely thin and dense anodic oxide film (not shown) is formed on the surface of the aluminum film in order to improve the adhesion of the resist mask arranged on the aluminum film. Form.

For this anodic oxidation, an electrolytic solution obtained by neutralizing an ethylene glycol solution containing 3% tartaric acid with aqueous ammonia is used. That is, this anodic oxidation is performed in this electrolytic solution by using the aluminum film as the anode and platinum as the cathode. The dense anodic oxide film formed here has a thickness of 150Å. The thickness of this dense anodic oxide film can be roughly controlled by the applied voltage.

Since this resist mask has a dense anodic oxide film (not shown) formed on the aluminum film,
It can be adhered on the aluminum film without any gap.
Another mask is used to form this resist mask.

Next, patterning is performed using the resist mask 906 to form a gate electrode 907 and a gate wiring (not shown) extending from the gate electrode 907. Thus, FIG.
The state shown in (B) is obtained.

Next, a porous anodic oxide film 907 is formed with the resist mask arranged. This porous anodic oxide film is formed by using a 3% oxalic acid aqueous solution as an electric field solution. Specifically, the aluminum film formed in the step of FIG. 9B is used as an anode, while platinum is used as a cathode, and a current is passed between both electrodes in the above-mentioned aqueous solution.

At this time, since the resist mask is arranged above each pattern made of aluminum, the electrolytic solution does not come into contact with the upper surface of the aluminum pattern, and the anodization proceeds only on the side surface of each pattern.

This anodic oxidation is performed by supplying a current from a wiring for supplying a current at the time of anodic oxidation. The current supply wiring is used to prevent the film thickness of the formed anodic oxide film from being different between the ends of the active matrix region due to the voltage drop. In particular, when the liquid crystal panel has a large area, it is necessary to use the wiring for supplying the current.

The growth distance of this porous anodic oxide film is
It can be controlled by the anodization time. The growth distance of this porous anodic oxide film is 3000Å to 1000
It can be selected between 0Å. Here, the thickness (growth distance) of this porous anodic oxide film is set to 5000 Å. The growth distance of the porous anodic oxide film can roughly determine the size of the low-concentration impurity region to be formed later.

The role of this porous anodic oxide film will be described in detail later, but: formation of a low-concentration impurity region (a region generally called an LDD region), three-dimensional intersection of the first-layer wiring and the second-layer wiring It has a significant role in suppressing the occurrence of defects in parts.

After forming a porous anodic oxide film 909 shown in FIG. 9C, the resist mask 906 is removed, and a dense 150 Å thick anodic oxide film (not shown) is removed.

Next, a dense anodic oxide film 908 is formed.
This dense anodic oxide film is extremely effective in suppressing the formation of hillocks and whiskers.

The dense anodic oxide film is formed by using an ethylene glycol solution containing 3% tartaric acid as an electric field solution neutralized with ammonia water.

In this step, since the electrolytic solution penetrates into the porous anodic oxide film 909, a dense anodic oxide film is formed on the surface of the remaining electrode 910 made of aluminum as indicated by 908. .

Also in this anodization, the current for the anodization is supplied by utilizing the current supply wiring for the anodization. This is to make the thickness of the formed anodic oxide film uniform throughout.

The film thickness of this dense anodic oxide film is 800 Å. Increase the film thickness of this dense anodic oxide film (for example, 20
If the thickness is more than 00Å), the offset gate region can be formed later in the active layer by the thickness thereof. However, forming a dense and dense anodic oxide film requires an applied voltage of 200
It must be as high as V or higher, which is not preferable in terms of work reproducibility and safety. Therefore, here, the thickness of this dense anodic oxide film is set to 800 Å in order to suppress the generation of hillocks and whiskers and improve the breakdown voltage.

In this step, the gate electrode 910 shown in FIG. 9C is formed. The size of the gate electrode 910 is reduced by the anodic oxidation process as compared with the shape shown by 907 in FIG. 9B.

Next, the porous anodic oxide film 909 is removed. The porous anodic oxide film can be selectively removed by using a mixed acid obtained by mixing phosphoric acid, acetic acid and nitric acid.

Thus, the state shown in FIG. 9D is obtained. After the state shown in FIG. 9D is obtained, impurity ions are implanted to form the source region and the drain region of the thin film transistor. Here, P ions are implanted to form an N channel type. P-type instead of N-channel type
If you want to make a channel type thin film transistor,
B ions may be implanted.

In this step, the source region 915 and the drain region 914 are formed in a self-aligned manner. Also,
The low-concentration impurity regions 911 and 913 are also formed in a self-aligned manner. Here, the low-concentration impurity region 913 formed between the channel formation region 912 and the drain region 914 is a region usually called an LDD (lightly doped drain) region. (Fig. 9 (D))

This low-concentration impurity region has a very useful structure for obtaining a thin film transistor having a low OFF current characteristic. In particular, a thin film transistor arranged in a pixel in the active matrix region is required to have a low OFF current characteristic. Therefore, by providing this low concentration impurity region, a low OF
It is useful to have an F current characteristic.

After implanting the impurity ions, laser light is irradiated to activate the implanted impurity ions and anneal the region damaged by the implant of the ions.
Then, at that time, the method of the present invention is carried out as a method for obtaining the pressure necessary for annealing.

As already described, the substrate is loaded into the substrate loading / unloading chamber 806 of the apparatus shown in FIG. 8 and the substrate is transferred to the laser irradiation chamber 401 as described above.

Next, according to the etching described below,
The required etching gas is introduced into the laser irradiation chamber from the gas supply unit, and the pressure is made constant when the pressure becomes suitable for etching.

After that, while the substrate is moved by using the laser, the surface of the substrate is irradiated with the laser, and at the same time, the etching in the laser irradiation chamber is simultaneously performed under the following conditions. (Fig. 9 (E))

When simultaneously removing the organic impurities attached to the inner wall of the laser irradiation chamber 401, the gas supply unit 41 is used.
It may be carried out based on the case of crystallization by laser irradiation by introducing a gas of hydrogen, oxygen or argon from 0.

When metals such as W, Si, Ti, V, As, Ge, P and B attached to the inner wall of the laser irradiation chamber 401 are simultaneously removed, nitrogen trifluoride is supplied from the gas supply unit 410. (NF ₃ ), sulfur hexafluoride (SF ₆ ), C
It may be carried out based on the crystallization by introducing a gas such as F ₄ or ClF ₃ .

Another method for removing metals such as W, Si, Ti, V, As, Ge, P, B, etc. adhering to the inner wall of the laser irradiation chamber 401 is to use ClF ₃ gas. .

In this case, Cl from the gas supply unit 410
The gas of F ₃ is introduced. In this case no high frequency energy is required. Then react with deposits of the ClF ₃ gas adhered irradiation chamber, the further ClF ₃ gas reaction heat when is activated, the reaction of the deposit and the activated ClF ₃ gas is promoted, irradiated It becomes possible to remove the deposits adhering to the chamber.

After the activation of the impurity ions implanted as described above and the annealing of the region damaged by the ion implantation are performed, the substrate is loaded / unloaded in the substrate loading / unloading chamber 80 as described above.
Transferred to 6.

Then, a silicon oxide film functioning as the first interlayer insulating film 916 is formed to a thickness of 4000 Å by the plasma CVD method using TEO gas as a raw material.

As the interlayer insulating film 916, a silicon nitride film or a silicon oxynitride film can be used. If a silicon nitride film is formed, a plasma CVD method using ammonia as a source gas may be used. Further, if the silicon oxynitride film is formed, the plasma CVD method using TEOS and N ₂ O gas may be used.

As the first interlayer insulating film 916, a laminated film in which plural kinds of films selected from a silicon oxide film, a silicon nitride film and a silicon oxynitride film are laminated may be used. After forming the first interlayer insulating film 916, contact holes are formed. The third mask is used in this step.

Then, electrodes and wirings for the second layer (usually referred to as second layer wirings) 917 and 918 are formed. Thus, a thin film transistor is manufactured.

[0098]

According to the present invention, when the non-single-crystal semiconductor layer on the substrate is crystallized in the laser irradiation chamber, the pressure is kept constant when the pressure required for crystallization is reached, and the non-single-crystal semiconductor layer is laser-irradiated. When the non-single crystal semiconductor layer on the substrate is annealed in the laser irradiation chamber, the pressure is kept constant when the pressure required for the annealing is reached, and the non-single crystal semiconductor layer is irradiated with the laser light. By irradiating, it becomes difficult for impurities to be mixed into the non-single-crystal semiconductor layer, so that a non-single-crystal semiconductor layer with favorable electric characteristics can be obtained.

Further, according to the present invention, when the non-single crystal semiconductor layer on the substrate is crystallized in the laser irradiation chamber, the pressure is kept constant when the pressure required for the crystallization is reached, and the non-single crystal semiconductor layer is irradiated with laser light. It was decided to clean the laser irradiation chamber simultaneously with irradiation, or when annealing the non-single-crystal semiconductor layer on the substrate in the laser irradiation chamber,
When the pressure required for annealing is reached, the pressure is kept constant, and the non-single crystal semiconductor layer is irradiated with laser light and the laser irradiation chamber is cleaned at the same time. It becomes possible to obtain a semiconductor layer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in pressure inside a laser irradiation chamber.

FIG. 2 is a diagram showing a change in pressure inside a laser irradiation chamber.

FIG. 3 is a diagram showing a change in pressure inside a laser irradiation chamber.

FIG. 4 is a cross-sectional view of a laser irradiation chamber.

FIG. 5 is a top view showing a laser irradiation chamber.

FIG. 6 is a cross-sectional view of a laser irradiation chamber.

FIG. 7 is a top view showing a laser irradiation chamber.

FIG. 8 is a diagram showing a laser irradiation device.

FIG. 9 is a process drawing for explaining the third embodiment.

[Explanation of symbols]

 401 Laser Irradiation Chamber 402 Laser Oscillator 403 Mirror 404 Window 405 Substrate 406 Substrate Stage 407 Moving Mechanism 408 Vacuum Evacuation Pump 409 Electrode 410 Gas Supply Section

Claims (5)

[Claims] 1. When treating an object to be treated with a laser beam in a laser irradiation chamber, the pressure is kept constant when the pressure required for the treatment is reached, and the treatment using the laser is performed. And laser irradiation method. 2. When crystallizing a non-single-crystal semiconductor layer on a substrate in a laser irradiation chamber, the pressure is kept constant when the pressure required for crystallization is reached, and the non-single-crystal semiconductor layer is irradiated with laser light. A laser irradiation method characterized by the above. 3. When annealing a non-single-crystal semiconductor layer on a substrate in a laser irradiation chamber, irradiating the non-single-crystal semiconductor layer with laser light at a constant pressure when the pressure required for annealing is reached. Characterized laser irradiation method. 4. When crystallizing a non-single-crystal semiconductor layer on a substrate in a laser irradiation chamber, the non-single-crystal semiconductor layer is irradiated with laser light with a constant pressure when the pressure required for crystallization is reached. A laser irradiation method characterized in that the laser irradiation chamber is cleaned at the same time. 5. When annealing a non-single-crystal semiconductor layer on a substrate in a laser irradiation chamber, the pressure is kept constant when the pressure required for annealing is reached, and the non-single-crystal semiconductor layer is irradiated with laser light and at the same time. A laser irradiation method comprising cleaning a laser irradiation chamber.