JPH09139346A - Method and device for laser anneal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make annealing effects constant, in the case of performing a laser anneal to a silicon film, even when the irradiation energy densities of a laser beam are different from each other. SOLUTION: According to the variation width of the irradiation energy density of an irradiating laser beam on a silicon film, the heating temperature of the silicon film is set. When the variation width of the irradiation energy density of the irradiating laser beam is large or small, the heating temperature of the substrate of the silicon film is set relatively low or high.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD [0001] The invention disclosed in this specification is:
TECHNICAL FIELD The present invention relates to a method for annealing a semiconductor by irradiating a laser beam, and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, there is known a technique of irradiating an amorphous silicon film formed by a gas phase method such as a plasma CVD method with a laser beam to obtain a crystalline silicon film.

By using this technique, a crystalline silicon film can be obtained on a glass substrate, and a thin film transistor having high characteristics can be obtained by using this crystalline silicon film.

Forming a thin film transistor having high characteristics on a glass substrate is necessary for manufacturing an active type flat panel display represented by an active matrix type liquid crystal electro-optical device.

The method using the above-mentioned annealing technique by irradiation with laser light is promising because it can suppress thermal damage to the substrate, but it has a problem that the oscillation characteristic of the laser used is unstable.

In general, as a laser beam for annealing,
An excimer laser capable of obtaining a wavelength (ultraviolet region) region is used for annealing a silicon film. The excimer laser oscillates a suitable gas by obtaining a special excited state called an excimer state by electromagnetic energy.

However, as is clear from the oscillation principle,
When the gas is contaminated, the oscillation condition changes and the oscillation power changes. There is also a problem that a stable irradiation energy density cannot always be obtained.

In order to industrially utilize this annealing by laser irradiation, it is necessary to continuously perform laser annealing one after another. Therefore, it is not preferable that the stability of the irradiation energy density changes while the steps are repeated in order to obtain a predetermined annealing effect.

Further, when a plurality of laser oscillators are used and the stability of the irradiation energy density is different, it is necessary to devise a constant annealing effect.

[0010]

DISCLOSURE OF THE INVENTION The invention disclosed in the present specification provides a structure capable of making the annil effect constant when the stability of the irradiation energy density of laser light is changed. Is an issue.

It is another object of the present invention to provide a technique in which the annealing effect using each laser oscillator is constant when the irradiation energy densities of different laser oscillators are different.

[0012]

In order to solve the above problems, the present invention is a method for annealing a silicon film by irradiating a laser beam, wherein the silicon film is formed according to the displacement width of the irradiation energy density of the radiated laser beam. The laser annealing method is characterized in that the heating temperature of is set.

In the laser annealing method, for example, when the irradiation energy density of the irradiated laser light has a large displacement width, the heating temperature of the substrate is set relatively low, and the irradiation energy density of the irradiated laser light changes. When the width is small, the heating temperature of the substrate is set to be relatively high.

Another structure of the present invention is an annealing method for a silicon film by irradiating a laser beam, wherein a displacement width (mJ) of an irradiation energy density of the radiated laser beam.
/ Cm ² ) is Y and the heating temperature (° C) of the silicon film is X, the heating temperature of the silicon film at the time of laser light irradiation is a value represented by Y = (370/24) (24-X) The laser annealing method is characterized by the following settings.

In the laser annealing method of this structure, the formula X = (370/24) (24-Y) is derived from the experimental data of the present inventors.

In the laser annealing method of each of the above-mentioned structures, a particularly remarkable effect can be obtained when a crystalline silicon film, that is, a thermally crystallized silicon film is used as the silicon film.

Another structure of the present invention is a laser annealing apparatus, which has means for changing a heating temperature of a silicon film according to a displacement width of an irradiation energy density of a laser beam to be irradiated. It is an annealing device.

In the above laser annealing apparatus, the means for changing the heating temperature of the silicon film makes the heating temperature of the substrate relatively low when the irradiation energy density of the irradiation laser beam has a large displacement width, and the irradiation is performed. When the displacement width of the irradiation energy density of the laser light is small, the heating temperature of the substrate is controlled to be relatively high.

Specifically, when the displacement width (mJ / cm ² ) of the irradiation energy density of the irradiated laser light is Y and the heating temperature (° C.) of the silicon film is X, the irradiation time of the laser light is The heating temperature of the silicon film is X = (370/24) (24
-The function has the function of setting the value less than or equal to the value indicated by Y).

The present invention will be described in detail below with reference to examples.

【Example】

[Example 1] This example relates to a method for obtaining a crystalline silicon film having a predetermined film quality.

According to the research conducted by the present inventors, in the process of obtaining a crystalline silicon film by applying an annealing treatment by irradiating a laser beam to an amorphous silicon film formed by a vapor phase method,
It has been found that there is a relationship between the irradiation energy density (mJ / cm ² ) of the irradiated laser beam on the surface to be irradiated and the crystallinity as described below.

Studies by the present inventors have revealed that the film quality of the crystalline silicon film obtained by laser annealing can be determined by the refractive index of the film obtained by measurement by ellipsometry.

The film quality of the crystalline silicon film is comprehensively judged by its crystallinity, surface flatness, film uniformity and the like. However, according to the experiment, when the irradiation energy density of the laser beam is within a range of about 280 mJ / cm ² or less, by setting the refractive index of the film (crystalline silicon film) after the laser irradiation to about 3.4, a predetermined film quality can be obtained. It is known that it can be determined that the

On the other hand, it has been found that there is a difference in the annealing effect by the laser light irradiation depending on the heating temperature of the sample during the laser light irradiation.

FIG. 5 shows the relationship between the refractive index of the obtained crystalline silicon film and the irradiation energy density of the laser beam when the sample temperature is changed.

The data shown in FIG. 5 is the result of measuring the refractive index of the obtained crystalline silicon film by irradiating the sample with laser light at various irradiation energy densities while heating the sample to a predetermined temperature. .

In the experiment for collecting the data shown in FIG. 5, the irradiation energy density was determined with great care, and the reliability of the value was sought to be as high as possible.

As is clear from FIG. 5, the combination of the irradiation energy of the laser beam and the heating temperature of the sample
The refractive index of the obtained crystalline silicon film changes greatly.

Here, the refractive index of the obtained crystalline silicon film is
Focus on the plot points of the laser energy density when it falls within the range of 3.4 ± 0.02.

Then, it can be seen that the higher the heating temperature of the sample, the narrower the range of allowable irradiation energy density.

That is, from the data of FIG. 5, when the sample temperature is low, the allowable range of fluctuation of the irradiation energy density of the laser beam required to obtain a predetermined film quality may be large, while the sample temperature is high. In this case, it is suggested that the permissible range of the fluctuation of the irradiation energy density of the laser beam required to obtain a predetermined film quality must be small.

In order to evaluate this quantitatively, the displacement width of laser energy (allowable value for blurring) when the refractive index falls within the range of 3.4 ± 0.02 was obtained from the curve connecting the plotted points. . FIG. 1 shows the relationship between the displacement width of the irradiation energy density of laser light and the heating temperature.

The irradiation energy density of the laser light shown in FIG. 1 is obtained by measuring the irradiation energy on the surface to be irradiated with a power meter and dividing the value by the area of the surface to be irradiated with the laser light. OPHI as a power meter
FL150A EXRP manufactured by R Co. was used.

As is apparent from FIG. 1, when the sample temperature is certainly low, a predetermined film quality (film quality with a refractive index of 3.4 ± 0.02) is obtained even if the value of the laser irradiation energy density is relatively large. To be

For example, if the sample temperature is near room temperature without heating (expressed as RT), the irradiation energy density is 20 mJ /
A predetermined film quality can be obtained even if the displacement is cm ² or more.

However, when the heating temperature of the sample is set to about 300 ° C., the displacement width of the irradiation energy density of the laser beam required to obtain a predetermined film quality is 6 mJ / c.
Only about m ² is allowed.

When the displacement width (mJ / cm ² ) of the irradiation energy density of the laser light to be irradiated is Y and the heating temperature (° C.) of the silicon film is X, the relationship between the two can be derived from FIG. = (370/24) (24-Y).

A specific laser light irradiation process will be described below. Here, a manufacturing process of a thin film transistor will be described as an example. FIG. 2 shows a manufacturing process of a thin film transistor.

First, as shown in FIG. 2, a 127 mm square Corning 1737 is prepared as the substrate 201. Then, a silicon oxide film 202 as a base film is formed to a thickness of 2000 Å by the plasma CVD method.

Further, an amorphous silicon film is further formed thereon in a thickness of 300 to 3
A film is formed to a thickness of 000Å, for example, 500Å by the low pressure thermal CVD method. Next, a 10 ppm nickel acetate aqueous solution is applied onto the amorphous silicon film by spin coating.

Thus, the nickel acetate layer is formed. It is more preferable to add a surfactant to the nickel acetate aqueous solution. Since the nickel acetate layer is extremely thin, it is not always in the form of a film, but there is no problem in the subsequent steps.

Next, the substrate 201 on which each film is laminated as described above is subjected to thermal annealing at 600 ° C. for 4 hours. As a result of this step, the amorphous silicon film is crystallized and the crystalline silicon film 2
03 is formed. (Fig. 2 (A))

At this time, the added nickel element plays a role of a nucleus of crystal growth and promotes crystallization. 600
The crystallization can be performed in a short time at a low temperature of 4 ° C. for 4 hours due to the function of nickel. Details are described in JP-A-6-244104.

The concentration of the catalytic element is 1 × 10 ^{15 to} 5 × 10 5.
It is preferably within the range of ¹⁹ atoms / cm ³ . 5x
At a high concentration of 10 ¹⁹ atoms / cm ³ or more, it should be noted that the crystalline silicon film exhibits metallic properties and the characteristics as a semiconductor are impaired.

In this embodiment, the concentration of the metal element in the crystalline silicon film is 1 × 10 ^{17 to} 5 which is the minimum value in the film.
× 10 ¹⁸ atoms / cm ³ . These values were analyzed and measured by secondary ion mass spectrometry (SIMS).

The crystalline silicon film 20 thus obtained
In order to further improve the crystallinity of No. 3, laser annealing is performed using an excimer laser.

FIG. 3 shows a top view of the laser annealing apparatus in the embodiment. Here, the multi-chamber type laser annealing apparatus shown in FIG. 3 is used.

FIG. 4 shows a laser irradiation chamber in the embodiment. FIG. 4 is a side sectional view of the laser irradiation chamber. FIG.
A view showing a cross section taken along line AA ′ in FIG.

In FIG. 4, the laser irradiation chamber 101 is
The pulse laser beam emitted from the laser oscillator 102 and processed into a linear cross section by the optical system 112 is reflected by the mirror 103, and the window 10 made of quartz is used.
4 has a function of irradiating the substrate 105 to be processed.

The laser oscillating device 102 is, here, X
One that oscillates an eCl excimer laser (wavelength 308 nm) is used. In addition, a KrF excimer laser (wavelength 2
48 nm).

The substrate 105 to be processed is placed on the stage 111 provided on the table 106, and is heated to a predetermined temperature (100 to 700 by a heater installed in the table 106).
° C).

The table 106 is moved by the moving mechanism 107 in the direction perpendicular to the linear direction of the linear laser beam, and enables the upper surface of the substrate 105 to be processed to be irradiated with the laser beam while being scanned.

Laser irradiation chamber 101 capable of controlling atmosphere
Has a vacuum exhaust pump 108 as a means for reducing pressure and exhausting. Further, as a gas supply means, a gas supply pipe 109 connected to an oxygen cylinder via a valve and a gas supply pipe 110 connected to a cylinder of nitrogen or another gas via a valve are provided.

The laser irradiation chamber 101 includes a gate valve 3
01 is connected to the substrate transfer chamber 302.

In FIG. 3, the laser irradiation chamber 10 shown in FIG.
1 is connected to the substrate transfer chamber 302 via the gate valve 301.

The apparatus shown in FIG. 3 will be described. In the load / unload chamber 306, a cassette 312 containing a large number of substrates 105 to be processed, for example, 20 is arranged. The robot arm 305 moves one substrate from the cassette 312 to the alignment chamber.

The substrate 1 to be processed is placed in the alignment chamber 303.
05 and the robot arm 305 are arranged with an alignment mechanism for correcting the positional relationship. The alignment chamber 303 is connected to the load / unload chamber 306 via a gate valve 307. Also, as will be described later,
The alignment chamber 303 is provided with a light irradiation section 313 and a light receiving section 314 that form an ellipsometer, and is configured to measure the refractive index of the silicon film as needed.

The preheating chamber 308 preheats the substrate to be laser-annealed to a predetermined temperature, shortens the time required for heating the substrate in the laser irradiation chamber 101, and improves the throughput.

The inside of the preheating chamber 308 is made of cylindrical quartz. The cylindrical quartz is surrounded by a heater. It also has a substrate holder made of quartz. The substrate holder is provided with a susceptor capable of accommodating a large number of substrates. The substrate holder is moved up and down by the elevator. The substrate is heated by the heater. The preheating chamber 308 is connected to the substrate transfer chamber 302 by a gate valve 309.

In the preheating chamber 308, the substrate preheated for a predetermined time is pulled back to the substrate transfer chamber 302 by the robot arm 305 and realigned in the alignment chamber 303, and then the robot arm 305 is used to irradiate the laser irradiation chamber 101. Be transferred to.

After the laser irradiation is completed, the substrate 105 to be processed is drawn out to the substrate transfer chamber 302 by the robot arm 305 and transferred to the slow cooling chamber 310.

The slow cooling chamber 310 is connected to the substrate transfer chamber 302 via a gate valve 311, and the substrate 105 to be processed placed on the quartz stage is irradiated with infrared light from a lamp or a reflector. Bathed in and gradually cooled.

The substrate 10 to be processed which has been slowly cooled in the slow cooling chamber 310.
5 is transferred to the load / unload chamber 306 by the robot arm 305 and stored in the cassette 312.

Thus, the laser annealing process is completed. Thus, by repeating the above steps,
A large number of substrates can be processed one by one continuously.

A process of performing laser annealing using the apparatus shown in FIGS. 3 and 4 will be described. First, the target substrate 105
The (substrate 201 having the crystalline silicon film 203) is washed with an HF aqueous solution or a mixed aqueous solution of HF and H ₂ O ₂ to remove the natural oxide film, and then stored in the cassette 312, and the cassette 312 is loaded / loaded. It is arranged in the unload chamber 306.

In FIG. 3, the load / unload chamber 30
The substrate 105 to be processed conveyed from 6 is aligned, then conveyed to the preheating chamber 308 and appropriately heated, and then conveyed to the laser irradiation chamber 101.

The inside of the laser irradiation chamber 101 is evacuated by the vacuum exhaust pump 108, and then oxygen is supplied from the gas supply pipe 109 and nitrogen is supplied from the gas supply pipe 110, respectively, and oxygen content of 20% oxygen and 80% nitrogen is contained. It becomes an atmosphere.

By performing laser annealing in an oxygen-containing atmosphere or in a state where the silicon oxide film 204 is formed on the upper surface of the crystalline silicon film 203 in an oxygen-containing atmosphere, the crystallinity and homogeneity of the crystalline silicon film by laser annealing, The energy efficiency of laser light can be improved.

However, air is not preferable because it contains many impurities and adversely affects the film quality and film characteristics.

The purity of both oxygen and nitrogen supplied to the laser irradiation chamber is 99.9% (3N) to 99.999.
99% (7N), here 7N. If the purity is less than 3N, the amount of impurities is large and the film quality is adversely affected. Also, 7
Even if the purity is higher than N, the effect is not changed and the cost becomes high.

The oxygen-containing atmosphere is preferably oxygen alone or a mixed gas of oxygen and an inert gas such as nitrogen, helium or argon. In the case of a mixed gas, it is preferable that oxygen is contained in an amount of 1% or more, preferably 5% or more.

If the oxygen content is less than 1%, the formation of a silicon oxide film will be insufficient or impossible. Above 5%,
The effect of using the oxygen-containing atmosphere or providing the silicon oxide film can be stably obtained.

The atmosphere at the time of laser annealing may be a hydrogen-containing atmosphere. In this case, the threshold value of the thin film transistor manufactured using the crystalline silicon film after laser annealing is shifted to the positive (plus) side by about 2 to 4V. Moreover, the current rising characteristic in the current-voltage characteristic of the thin film transistor does not deteriorate even if the threshold value shifts. Therefore, it is possible to eliminate the need for boron doping, which is often performed for controlling the threshold value, by laser annealing in a hydrogen-containing atmosphere.

The hydrogen-containing atmosphere is preferably a mixed gas of hydrogen and an inert gas such as nitrogen, helium or argon.
It is preferable that the mixed gas contains hydrogen at 1 ppm or more, preferably 0.1% or more, and more preferably 1% or more. When the hydrogen content in the atmosphere is high, the threshold shift amount is also high.

The pressure during the annealing in the oxygen-containing atmosphere or the hydrogen-containing atmosphere may be atmospheric pressure or lower, particularly, reduced pressure of 0.01 Torr or more and 700 Torr or less. By performing the laser annealing under reduced pressure, it is possible to reduce the roughness of the surface of the crystalline silicon film after annealing and the entire film. Below 0.01 Torr, the effect of the atmosphere containing oxygen or hydrogen cannot be obtained.

The substrate 105 to be processed transferred to the laser irradiation chamber 101 is placed on the stage 111,
It is heated to 200 ° C. by the heater in the table 106. When heated in an oxygen-containing atmosphere, the upper surface of the crystalline silicon film 203 is oxidized and a silicon oxide film 204 of 10 to 100Å, for example, 30Å is formed.

Since the silicon oxide film 204 is formed in a high-purity oxygen-containing atmosphere, impurities such as carbon hardly exist. Therefore, excellent characteristics are obtained without adversely affecting various characteristics of the crystalline silicon film after laser annealing.

In FIG. 4, the linear laser beam with which the substrate 105 to be processed is irradiated has a width of 0.34 mm and a length of 1.
35 mm. The linear laser beam is scanned by moving the table 106 in one direction at 2.5 mm / s. The oscillation frequency of the laser is set to 200 Hz, and focusing on one point of the object to be irradiated, a laser beam of 10 to 50 shots is irradiated.

In this way, the crystalline silicon film 203 is annealed by laser to improve the crystallinity.
(FIG. 2 (B))

Next, after the substrate 105 to be processed is taken out of the laser annealing chamber, it is moved to the alignment chamber 303 and ellipsometry is performed by an ellipsometer to measure the refractive index of the crystalline silicon film. The refractive index may be measured after the substrate 105 to be processed is gradually cooled in the slow cooling chamber 310.

The ellipsometer is a measuring device which makes polarized light incident on the surface of a sample (thin film) to be measured from an oblique direction and obtains information relating to the refractive index and film thickness of the thin film from changes in the polarization state of this incident light. is there. For example, if the thickness of the thin film of the sample is known, the refractive index of the thin film can be obtained.

The refractive index is measured by irradiating the light irradiation unit 313 on the upper surface of the substrate 105 to be processed arranged in the alignment mechanism.
Is irradiated with light of a specific wavelength at a predetermined angle from the light receiving unit 3
This is performed by inputting the reflected light to 14. The time required for measurement is several seconds to several tens of seconds. The ellipsometer may be provided in the laser irradiation chamber.

The term "refractive index" as used herein refers to the refractive index of a crystalline silicon film formed on a glass substrate using an ellipsometer (SD-2000LA, manufactured by MSETEC Co., Ltd., measurement light: wavelength 129).
It is measured by using a semiconductor laser of 4 nm and an incident angle of 60 °. More specifically, ellipsometry has a characteristic that, when the flatness of the film to be measured is poor, it exhibits a value slightly lower than the refractive index of the actual film. The value (apparent refractive index) including this characteristic is defined as the refractive index here.

The surface condition of the crystalline silicon film after laser annealing is observed by an electron microscope, and when a sample having a preferable surface condition is selected, the refractive index of the crystalline silicon film is
The crystalline silicon film having a crystallinity in the range of 3.40 ± 0.02 has a high crystallinity, a uniform film quality in the plane, and no film roughness, and is an excellent crystalline silicon film.

In this embodiment, the heating temperature of the sample during laser annealing is 200 ° C. Therefore, from the graph shown in FIG. 1, the displacement width of the laser irradiation energy density is in the range of about 10 mJ / cm ² , in other words, ± 5 mJ /
It will be allowed in the range of about cm ² .

In this embodiment, the heating temperature is 200 ° C.
An example was given. However, if the stability of the laser oscillator used is high, the heating temperature can be further increased.

Although not clear from the refractive index, the higher the heating temperature of the sample during laser irradiation, the better from the viewpoint of obtaining a crystal structure closer to a single crystal. This is clarified by the observation of Raman spectrum.

From the viewpoint of reducing the load on the laser oscillator, it is preferable to raise the heating temperature of the sample and reduce the irradiation energy density of the laser light. It is clear from the data shown in FIG. 5 that the required irradiation energy density can be reduced by increasing the heating temperature of the sample.

After the laser annealing treatment, the silicon oxide film 204 has been scattered by the irradiation of the pulsed laser a plurality of times.

The substrate 1 to be processed after completion of laser annealing
05 is transferred to the slow cooling chamber 310, and after slow cooling, is stored in the cassette 312 of the load / unload chamber 306.

Next, using the produced crystalline silicon film 203, a thin film transistor (TFT) is produced. First, the crystalline silicon film 203 is etched to form island regions 205.

Next, a silicon oxide film to be the gate insulating film 206 is formed with a thickness of 1200Å by the plasma CVD method. TEOS and oxygen are used as source gases. The substrate temperature during film formation is 250 ° C. to 380 ° C., for example, 300 ° C. (Fig. 2 (C))

Next, a gate electrode is produced. Aluminum film is sputtered to a thickness of 3000Å ~ 8000
Å, for example, 6000Å is deposited. 0.1 to 2% of silicon may be contained in the aluminum film. The gate electrode 207 is formed by etching the film.

Next, impurities are added. In the case of manufacturing an N-channel TFT, phosphorus ions are implanted in the island region 205 by the ion doping method using the gate electrode as a mask. Phosphine (PH ₃ ) is used as a doping gas. The acceleration voltage is 10 to 90 kV, for example 80 kV, and the dose is 1 × 10 ^{14 to} 5 × 10 ¹⁵ atoms / cm ² , for example, 1 × 10 ¹⁵ atoms / cm ² . The substrate temperature is room temperature. As a result, the channel formation region 21
A source 208 and a drain 209 are formed as 0 and N-type impurity regions.

In the case of manufacturing a P-channel type TFT,
In this case, boron ions are ionized using the gate electrode as a mask.
It is driven into the island region 205 by the wrapping method. Do
Hydrogen as a wrapping gas at 1-10%, for example 5%
Diluted diborane (B_Two H ₆ ) Is used. Acceleration voltage is
60 to 90 kV, for example 65 kV, the dose amount is 2 × 1
0^Fifteen~ 5 × 10^FifteenAtom / cm^Two , For example, 3 × 10^Fifteenoriginal
Child / cm^Two And The substrate temperature is room temperature. As a result,
As the channel forming region 210 and the P-type impurity region,
A source 208 and a drain 209 are formed. (Figure 2
(D))

Next, in order to activate the doped impurities, laser annealing is performed again with a linear laser beam using the laser annealing apparatus shown in FIG. The atmosphere in the laser irradiation chamber 101 is air (atmospheric pressure). The irradiation energy density of the laser beam on the irradiation surface is 100 mJ / cm ^{2 to} 350 mJ / c.
In the range of m ² , for example, 160 mJ / cm ² . Scan a linear laser beam. Focusing on one point of the object to be irradiated, a laser beam of 20 to 40 shots is irradiated. The substrate temperature is 200 ° C. Then, thermal annealing is performed at 450 ° C. for 2 hours in a nitrogen atmosphere. (Figure 2
(E))

Subsequently, a silicon oxide film having a thickness of 6000 Å is formed by the plasma CVD method to form an interlayer insulating film 211. Next, a contact hole is formed in the interlayer insulating film 211 by etching. Further, by forming and etching a metal material, for example, a multilayer film of titanium and aluminum, the source electrode / wiring 212 and the drain electrode / wiring 213 are formed through the contact holes.

Finally, in a hydrogen atmosphere of 1 atm, 200 ~
A thermal annealing process at 350 ° C. is performed.

In this way, a plurality of N-type or P-channel type crystalline TFTs are formed. These TFTs are
It is an excellent material having a mobility of 70 to 120 cm ² / Vs for the N channel type and 60 to 90 cm ² / Vs for the P channel type. (Fig. 2 (F))

[Embodiment 2] This embodiment relates to a laser beam irradiation method used in the following situations.

For example, when there are two laser oscillators and the annealing process is continuously performed by using both of them alternately, the stability of the two laser oscillators is often different.

Further, the stability of oscillation greatly changes due to replacement of the laser oscillation gas for maintenance such as cleaning.

Further, the stability of laser oscillation may gradually change with repeated use.

In such a case, it is useful to use the configuration shown in this embodiment. First, the heating temperature of the sample (amorphous silicon film) is determined from the graph shown in FIG. 1 according to the variation of the irradiation energy density of the laser oscillator.

That is, the displacement width of the energy density of the laser light on the surface to be irradiated, which is required to obtain a predetermined film quality (refractive index) (this value should be measured in advance or data of its tendency should be taken. It is necessary to keep the above), and the heating temperature as high as possible is selected using FIG.

For example, there are two laser oscillators, the displacement width of the irradiation energy density of the laser emitted from the first oscillator is 10 mJ / cm ² , and the irradiation energy density of the laser emitted from the second oscillator is It is assumed that the displacement width may be 20 mJ / cm ² .

In this case, the heating temperature of the sample is set to 200 ° C. when the first oscillator is used. When the second oscillator is used, the sample heating temperature is room temperature.

By doing so, even when two laser oscillators are used, a laser having a refractive index of about 3.4 can always be obtained.

[Embodiment 3] This embodiment relates to a structure which always obtains a predetermined annealing effect when using a laser oscillator in which the stability of the irradiation energy density gradually changes during use. .

First, the change in the stability of the energy of the laser light emitted from the laser oscillator, that is, the change width of the irradiation energy density that changes over time is measured in advance.

Then, according to this data, the heating temperature of the sample is changed appropriately according to the data shown in FIG. 1 every time annealing is repeated.

Generally, the range of displacement of the irradiation energy density of laser light gradually increases, so the heating temperature of the sample may be gradually lowered as the process is repeated.

It is also useful to measure the refractive index of the sample constantly or intermittently using an ellipsometer and control the irradiation energy of the laser light so that the refractive index falls within the required range.

In this case, if the irradiation energy density of the laser beam is increased, the annealed silicon film (crystalline silicon film)
Has a smaller refractive index, and the smaller the irradiation energy density, the larger the refractive index of the annealed silicon film (crystalline silicon film). (This is understood from the data shown in FIG. 5)

[0115]

By utilizing the invention disclosed in this specification, even when a plurality of laser oscillators having different stability is used or a laser oscillator whose stability is gradually changed is used, A crystalline silicon film having a predetermined film quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a displacement width of irradiation energy density and a heating temperature.

2A to 2C are diagrams showing a manufacturing process of a thin film transistor in an example.

FIG. 3 is a top view of the laser annealing apparatus according to the embodiment.

FIG. 4 is a diagram showing a laser irradiation chamber in an example.

FIG. 5 is a diagram showing the relationship between the refractive index of the obtained crystalline silicon film and the irradiation energy density of laser light when the sample temperature is changed.

[Explanation of symbols]

 101 Laser Irradiation Chamber 102 Laser Oscillator 103 Mirror 104 Window 105 Processed Substrate 106 Units 107 Moving Mechanism 108 Vacuum Evacuation Pump 109, 110 Gas Supply Pipe 111 Stage 112 Optical System 201 Substrate 202 Silicon Oxide Film (Base Film) 203 Crystallized Silicon Film 204 Silicon oxide film 205 Island region 206 Gate insulating film 207 Gate electrode 208 Source 209 Drain 210 Channel forming region 211 Interlayer insulating film 212 Source electrode / wiring 213 Drain electrode / wiring 301 Gate valve 302 Substrate transfer chamber 303 Alignment chamber 305 Robot Arm 306 Load / unload chamber 307 Gate valve 308 Preheating chamber 309 Gate valve 310 Slow cooling chamber 311 Gate valve 312 Cassette 313 Light irradiation unit 314 Light reception Department

[Procedure amendment]

[Submission date] March 19, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title: Laser annealing method and laser annealing apparatus

Claims (7)

[Claims] 1. A laser annealing method for irradiating a silicon film by irradiating a laser beam, wherein a heating temperature of the silicon film is set according to a displacement width of an irradiation energy density of the radiated laser beam. 2. The displacement width of the irradiation energy density of the irradiated laser light is set relatively low when the displacement width of the irradiation energy density of the irradiated laser light is large. A laser annealing method characterized in that the heating temperature of the substrate is set to be relatively high when is small. 3. A method of annealing a silicon film by laser light irradiation, wherein a displacement width (mJ / cm ² ) of irradiation energy density of the laser light to be irradiated is Y, and a heating temperature (° C.) of the silicon film is set. When X is set, the heating temperature of the silicon film at the time of laser light irradiation is set to a value shown by X = (370/24) (24-Y) or less. 4. The laser annealing method according to claim 1, wherein the silicon film is a crystalline silicon film. 5. A laser annealing apparatus comprising a means for changing a heating temperature of a silicon film according to a displacement width of an irradiation energy density of laser light to be irradiated. 6. The means for changing the heating temperature of a silicon film according to claim 5, wherein the heating temperature of the substrate is relatively lowered when the displacement width of the irradiation energy of the irradiated laser light is large. A laser annealing apparatus having a function of relatively increasing the heating temperature of a substrate when the displacement width of irradiation energy of laser light is small. 7. The heating means for changing the heating temperature of the silicon film according to claim 5, wherein the displacement width (mJ / cm ² ) of the irradiation energy density of the irradiated laser light is Y, and the heating temperature of the silicon film (° C.) ) Is X, the laser annealing has a function of setting the heating temperature of the silicon film at the time of irradiating the laser light to a value shown by X = (370/24) (24-Y) or less. apparatus.