JP2001144015A - Laser equipment and laser annealing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser annealing method for obtaining a crystalline semiconductor film wherein crystal grain diameter is large. SOLUTION: When an amorphous semiconductor film is crystallized by irradiation of a laser light, the laser light is cast on the surface and the back of the amorphous semiconductor film. In this case, relation of 0 Io'/Io<1 or,1 Io'/Io is maintained in the ratio (Io/Io) between effective energy intensity (Io) of a laser light cast on the surface and effective energy intensity (Io) of a laser light cast on the back.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to annealing of a semiconductor film using laser light (hereinafter referred to as laser annealing).
And a laser apparatus (an apparatus including a laser and an optical system for guiding laser light output from the laser to an object to be processed).

[0002]

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

As a means for obtaining a polysilicon film, a technique of crystallizing an amorphous silicon film (amorphous silicon film) into a polysilicon film is generally used. In particular, recently, a method of crystallizing an amorphous silicon film using laser light has attracted attention. In this specification, means for crystallizing an amorphous semiconductor film with laser light to obtain a crystalline semiconductor film is called laser crystallization.

[0004] Laser crystallization is a technique capable of instantaneously heating a semiconductor film and effective as an annealing means for a semiconductor film formed on a substrate having low heat resistance such as a glass substrate or a plastic substrate. Further, the throughput is much higher than that of a heating means using a conventional electric furnace (hereinafter, referred to as furnace annealing).

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

At present, the most noticeable problem is how to increase the crystal grain size of a crystalline semiconductor film crystallized by laser light. As a matter of course, as one crystal grain (also referred to as a grain) becomes larger, the number of crystal grain boundaries that traverse the TFT, particularly, the channel formation region decreases. Therefore, it is possible to improve variations in typical electric characteristics of the TFT such as the field-effect mobility and the threshold voltage.

Further, the inside of each crystal grain maintains relatively clean crystallinity, and in order to improve the above-mentioned various characteristics of the TFT, the channel forming region is completely contained within one crystal grain. It is desirable to form a TFT in such a manner.

However, it is difficult to obtain a crystalline semiconductor film having a sufficiently large crystal grain size with the current technology.
Although there are reports that they were obtained experimentally, they have not yet reached the level of practical use.

Experimentally, "" High-Mobility Poly-Si Thi
n-Film Transistors Fabricated bya Novel Excimer La
ser Crystallization Method ", K.Shimizu, O.Sugiura
andM.Matumura, IEEE Transactions on Electron Devic
es vol.40, No.1, pp112-117, 1993 ”. This reference discloses that Si / SiO
A three-layer structure of ₂ / n ⁺ Si is formed, and excimer laser light is irradiated from both directions of the Si side and the n ⁺ Si side. It is shown that such a configuration can increase the crystal grain size.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to solving the above-mentioned problems, and is directed to a laser annealing method for obtaining a crystalline semiconductor film having a large crystal grain size and a laser apparatus used for the laser annealing method. The task is to provide

[0011]

SUMMARY OF THE INVENTION The gist of the present invention is that when crystallizing an amorphous semiconductor film, a laser beam is applied to the surface of the amorphous semiconductor film (the surface on which the thin film is superposed) and the back surface ( And the effective energy intensity of the laser light (hereinafter referred to as primary laser light) applied to the front surface and the laser light applied to the back surface (hereinafter referred to as second laser light). (Referred to as secondary laser light).

That is, when the effective energy intensity of the primary laser light is (I ₀ ) and the effective energy intensity of the secondary laser light is (I ₀ ′), the effective energy intensity ratio (I ₀ )
₀ ′ / I ₀ ) to “0 <I ₀ ′ / I ₀ <1” or “1 <I ₀ ′ /
It is characterized by irradiating a laser beam so that the relationship of “I ₀ ” is satisfied. Of course, I ₀ · I ₀ ′ ≠ 0.

In this specification, the term “effective energy intensity” refers to the energy intensity of a laser beam when it reaches the front or back surface of the amorphous semiconductor film, and is an energy intensity in consideration of energy loss due to reflection or the like. Here, the unit is defined as density: mJ / cm ² . Although it cannot be measured, it can be obtained from the calculation of reflectance and transmittance if the medium existing in the path of the laser beam is known.

For example, a specific method of calculating the effective energy intensity when the present invention is applied to the structure shown in FIG. 6 will be described. In FIG. 6, 601 is a reflector made of aluminum, 602 is a Corning # 1737 substrate (0.7 mm thick), 603 is a 200-nm-thick silicon nitride oxide film (hereinafter referred to as SiON film), and 604 is 55 nm
It is a thick amorphous silicon film. A case where such a sample is irradiated with XeCl excimer laser light having a wavelength of 308 nm in the air will be taken as an example.

The energy intensity of the laser light (wavelength 308 nm) immediately before reaching the amorphous silicon film 604 is defined as (I _a ). At this time, the effective energy intensity (I ₀ ) of the primary laser light is given by I ₀ = I _{0 in} consideration of the reflection of the laser light on the surface of the amorphous silicon film.
_a is represented by (1−R _Si ). Here, R _Si is the reflectance of the laser beam. In this case, the I ₀ = 0.45I _a in the calculation.

The effective energy intensity (I ₀ ′) of the secondary laser light is I ₀ ′ = I _a T ₁₇₃₇ R _Al T ₁₇₃₇ (1-R
_SiON-Si ). Here, T ₁₇₃₇ is the transmittance of the # 1737 substrate, R _Al is the reflectance on the aluminum surface, R
_SiON-Si is the reflectivity when entering the amorphous silicon film from inside the SiON film. In addition, SiON
Reflectance when entering the film, transmittance in SiON film, Si
The reflectivity when entering the # 1737 substrate from inside the ON film and the reflectivity when entering the SiON film from inside the # 1737 substrate were not included in the calculation because it was experimentally found to be negligible. In this case, the I ₀ '= 0.13I _a in the calculation.

Accordingly, in the case of the structure shown in FIG. 6, the effective energy intensity (I ₀ ) of the primary laser light is 0.45I _a , and the effective energy intensity (I ₀ ′) of the secondary laser light is 0.13.
Obtained as I _a. That is, the effective energy intensity ratio (I ₀ ′
/ I ₀ ) is 0.29. One of the features of the present invention is that the effective energy intensity ratio obtained as described above satisfies 0 <I ₀ ′ / I ₀ <1.

Further, the present invention can be realized even when the intensity of the primary laser light is smaller than the intensity of the secondary laser light. That is, the effective energy intensity ratio is 1 <I ₀ ′ / I ₀
The present invention is also satisfied when the condition is satisfied.

In order to make the effective energy intensities of the primary laser light and the secondary laser light different, the following method can be used. 1) When irradiating laser light to the front and back surfaces of the amorphous semiconductor film using a reflector provided below the substrate, the effective energy intensity of the secondary laser light is adjusted by adjusting the reflectance of the reflector. Attenuating the laser beam so that it is relatively smaller than the effective energy intensity of the primary laser beam. 2) The primary laser light is split in the middle to form a secondary laser light, and the effective energy intensity of the primary laser light or the secondary laser light is attenuated by a filter (variable attenuator, etc.). And making the effective energy intensities of the two relatively different. 3) A method in which the effective energy intensity of the secondary laser light is attenuated depending on the material of the substrate on which the amorphous semiconductor film is formed, and is relatively smaller than the effective energy intensity of the primary laser light. 4) An insulating film is interposed between the substrate and the amorphous semiconductor film, and the effective energy intensity of the secondary laser light is attenuated by the insulating film so as to be relatively smaller than the effective energy intensity of the primary laser light. Method. 5) By covering the surface of the amorphous semiconductor film with an insulating film and reducing the reflectance of the primary laser light on the surface of the amorphous semiconductor film, the effective energy intensity of the primary laser light is relatively reduced. Method to make the effective energy intensity of the secondary laser light larger than the effective energy intensity. 6) A method in which the amorphous semiconductor film is covered with an insulating film, and the effective energy of the primary laser light is attenuated by the insulating film so as to be relatively smaller than the effective energy of the secondary laser light. . 7) A method in which the primary laser light and the secondary laser light are formed using different lasers as oscillation sources, and the effective energy intensities thereof are different.

The present invention does not depend on the type of laser, but generally known excimer laser (typically, KrF laser or XeCl laser), solid laser (typically, Nd: YAG laser or ruby laser). A gas laser (typically, an argon laser or a helium-neon laser), a metal vapor laser (typically, a copper vapor laser or a helium-cadmium laser), or a semiconductor laser can be used.

When a laser beam having a long fundamental wave (first harmonic: wavelength 1064 nm), such as an Nd: YAG laser, is used, the second, third, or fourth harmonic is used. Is preferred. These harmonics can be obtained using a non-linear crystal (non-linear element).
Further, a known Q-switch method may be used.

[Circumstances leading up to the invention] Here, the background that the present applicant came to the present invention will be described based on experimental results. SEM (Scanning Electron Mi) shown in FIG.
The croscopy photograph is a photograph after the polysilicon film formed by laser crystallization is subjected to Secco etching.
For more information on Seco etching technology, see "F.Secco d'A
ragona: "Dislocation Etch for (100) Planes in Silic
on ".J.Electrochem.soc.Vol.119.No.7.pp.948-950 (197
2) ”.

In both cases, a silicon oxide film (thickness: 200 mm) was placed on a Corning # 1737 substrate (thickness: 0.7 mm).
nm) through an amorphous silicon film (thickness 55n).
m) is formed, and is obtained by irradiating an excimer laser beam. The excimer laser light used in this experiment was a pulse laser light having a wavelength of 308 nm using XeCl gas as an excitation gas, a pulse width was 30 ns, the number of shots was 20, and the energy density was 370 mJ / cm.
^{And 2} .

FIG. 7A shows a polysilicon film (average crystal grain diameter is about 0.3 μm) obtained by irradiating laser light only to the surface of the amorphous silicon film, and FIG. 7B shows the amorphous silicon film. A polysilicon film obtained by irradiating a laser beam to the front and back surfaces of the semiconductor device (the average crystal grain size is about 1.5 μm)
m). According to this, the polysilicon film obtained by irradiating the laser light to the front and back surfaces of the amorphous silicon film has a crystal grain size about 5 times larger than that of the amorphous silicon film, and it has been confirmed that irradiation from both surfaces is very effective. Was done.

In this specification, the definition of the average crystal grain size is in accordance with the definition of the average diameter of the crystal grain region in the specification of Japanese Patent Application No. 10-020566.

As described above, it has been confirmed that the crystal grain size can be increased by irradiating the front and back surfaces of the amorphous semiconductor film with laser light. In the experiments in the literature described in the conventional example, the back surface of the semiconductor film to be crystallized is not directly irradiated with the laser beam, but aims at the heat storage effect using the residual heat of n ⁺ Si. The configuration is completely different from the experiment performed by humans.

Next, the present applicant conducted a similar experiment using a quartz substrate instead of a glass substrate (provided that the energy density of the laser beam was 200 mJ / cm ² ).
As a result, the result as shown in FIG. 8 (SEM photograph after Seco etching) was obtained.

FIG. 8A shows a polysilicon film obtained by irradiating only the surface of the amorphous silicon film with a laser beam, and FIG. 8B shows the polysilicon film obtained by irradiating the laser beam on the front and back surfaces of the amorphous silicon film. This is a polysilicon film obtained by the above method. According to this, when a quartz substrate was used as the substrate, the average crystal grain size was at most about 0.4 to 0.5 μm, and the increase in grain size as shown in FIG. 7B could not be confirmed. In addition, no difference was observed in the crystal grain size when the irradiation was performed from one side or both sides of the substrate. That is, as described above, the effect of increasing the average crystal grain size was not confirmed despite the laser light irradiation on the front and back surfaces of the amorphous semiconductor film.

Then, the present applicant considered the above experimental results, and the difference between the experiments shown in FIGS. 7 and 8 is that the transmittance of the glass substrate (about 50%) and the transmittance of the quartz substrate (about 93%).
%), That is, the difference in the effective energy intensity of the laser light applied to the back surface of the amorphous semiconductor film.
The following experiment was performed for confirmation.

First, in this experiment, a sample having the structure shown in FIG. 6 was manufactured using a quartz substrate as the substrate 602 and a tantalum nitride film as the reflector 601. Then, this sample was irradiated with XeCl excimer laser light under the same conditions as those for obtaining the photograph of FIG. 7 (B), and the average crystal grain size of the obtained polysilicon film was shown on the SEM photograph after Seco etching. Confirmed. The result is shown in FIG.

As can be seen from FIG. 9, it is confirmed that the crystal grains of the obtained polysilicon film are distributed in almost the same state as the polysilicon film of FIG. 7B. In the case of the sample obtained in the photograph of FIG. 7B, the effective energy intensity ratio between the primary laser light and the secondary laser light is 0.5.
29 has already been mentioned. This is substantially the result of the attenuation of the secondary laser light on the glass substrate. Similarly, as a result of calculating the effective energy intensity ratio for the sample of the present experiment, a value of 0.33 was obtained. This is a result of the secondary laser light being substantially attenuated by the reflector.

The sample of FIG. 8B (combination of a reflector made of quartz and aluminum) and the sample of FIG. 9 (combination of a reflector made of quartz and tantalum nitride) are the same except that the material of the reflector surface is different. The structure is different from that of the sample of FIG. 9 only in that the reflectance of the reflector surface is smaller than that of the sample of FIG.

Considering the above results, when the front and back surfaces of the amorphous semiconductor film are crystallized by irradiating laser light, the effective energy intensity of the laser light (primary laser light) on the front surface side is larger than the effective energy intensity. It was found that when the effective energy intensity of the laser beam (secondary laser beam) on the back side was small, an increase in the average crystal grain size was confirmed.

[0034]

[Embodiment 1] One embodiment of the present invention will be described. FIG. 1A is a diagram showing a configuration of a laser device of the present invention. This laser apparatus includes a laser 101, an optical system 201 that linearly transforms laser light using the laser 101 as an oscillation source, and a stage 102 for fixing a light-transmitting substrate.
03 and the heater controller 104 are provided to keep the substrate at a temperature in the range of room temperature to 550 ° C. A reflector 105 is provided on the stage 102, and a substrate 106 on which an amorphous semiconductor film is formed is provided.

Next, a method for holding the substrate 106 in the laser device having the structure shown in FIG. 1A will be described with reference to FIG. Substrate 106 held on stage 102
Is installed in the reaction chamber 107, and is irradiated with a linear laser beam having the laser 101 as an oscillation source. The inside of the reaction chamber can be reduced in pressure or in an inert gas atmosphere by an exhaust system or a gas system (not shown), and can be heated to 100 to 450 ° C. without contaminating the semiconductor film.

The stage 102 is mounted on the guide rail 10.
8, the substrate can be moved in the reaction chamber, and the entire surface of the substrate can be irradiated with linear laser light. The laser light enters from a quartz window (not shown) provided on the upper surface of the substrate 106. In FIG. 1B, a transfer chamber 109, an intermediate chamber 110, and a load / unload chamber 111 are connected to the reaction chamber 107, and these chambers are separated by gate valves 112 and 113.

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

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

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

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

At this time, the laser light projected on the irradiation surface 208 shows a linear irradiation surface. That is, it means that the cross-sectional shape of the laser beam transmitted through the cylindrical lens 207 is linear. Homogenization of the linearly deformed laser light in the width direction (short direction) is performed by the cylindrical lens array 202, the cylindrical lens 204, and the cylindrical lens 207. The homogenization of the laser light in the longitudinal direction (long direction) is performed by the cylindrical lens array 203 and the cylindrical lens 2.
05.

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

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

As the translucent substrate 301, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate is used. The transmissive substrate 301 itself can adjust the effective energy intensity of the secondary laser light. Further, as the insulating film 302, an insulating film containing silicon such as a silicon oxide film or a silicon nitride oxide film (SiOxNy) may be used, and the effective energy intensity of the secondary laser light may be adjusted with the insulating film 302. Further, the amorphous semiconductor film 3
03 includes a compound semiconductor film such as an amorphous silicon germanium film in addition to the amorphous silicon film.

The reflector 304 may be a substrate having a metal film formed on the surface (reflection surface of laser light) or a substrate made of a metal element. In this case, any material may be used for the metal film. Typically, silicon (Si), aluminum (Al), silver (Ag), tungsten (W), titanium (Ti), tantalum (Ta)
A metal film containing any one of the above elements is used. For example, tungsten nitride (WN), titanium nitride (TiN), and tantalum nitride (TaN) may be used.

Further, the reflector 304 is formed on the transparent substrate 3.
01 may be provided, or may be provided separately. Instead of disposing the reflector 304, it is also possible to form the above-described metal film directly on the back surface (the surface opposite to the front surface) of the substrate 301 and reflect the laser light there. In any case, the reflectivity of the reflector 304 can be used to adjust the effective energy intensity of the secondary laser light. When the reflector 304 is provided separately from the light-transmitting substrate 301, the energy intensity of the secondary laser light can be controlled by a gas filling the gap.

Then, the amorphous semiconductor film 303 is irradiated with a linearly deformed laser beam via the optical system 201 (only the cylindrical lens 207 is shown in the figure) described with reference to FIG. The irradiation of the linearly deformed laser light is performed by scanning the laser light.

In any case, the cylindrical lens 2
07, the first laser light 305 irradiating the front surface of the amorphous semiconductor film 303 and the second laser light once reflected by the reflector 304 and irradiating the back surface of the amorphous semiconductor film 303. 306 and the effective energy intensity ratio (I ₀ ′ / I
₀ ) satisfies the relationship of 0 <I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ . For this purpose, the reflector 30
The reflectivity of the laser light of No. 4 is preferably 20 to 80%. At this time, a desired intensity ratio may be obtained by combining a plurality of means for attenuating the effective energy intensity of the secondary laser light described in this embodiment.

The laser beam having passed through the cylindrical lens 207 has an incident angle of 45 to 90 ° with respect to the substrate surface in the process of being focused. Therefore, the secondary laser light 306 is also applied to the back surface side of the amorphous semiconductor film 303 while wrapping around. In addition, the secondary laser light 306 can be obtained more efficiently by providing an uneven portion on the reflection surface of the reflector 304 and irregularly reflecting the laser light.

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

FIG. 4A is a diagram showing the configuration of the laser device of this embodiment. Since the basic configuration is the same as that of the laser apparatus of FIG. 1 described in the first embodiment, the description will be made with the reference numerals of the different parts changed.

This laser apparatus comprises a laser 101, an optical system 401 for linearly transforming a laser beam emitted from the laser 101 as an oscillation source and splitting the laser light into two systems, and a translucent stage for fixing a translucent substrate. 402. A substrate 403a is provided on the stage 402, and an amorphous semiconductor film 403b is formed thereon.

In the case of this embodiment, since the amorphous semiconductor film 403b is irradiated with the laser beam transmitted through the stage 402, the stage 402 must have a light transmitting property. In addition, since the laser light (secondary laser light) emitted from the side of the stage 402 passes through the stage 402, the effective energy intensity of the laser light needs to consider the attenuation when transmitting through the stage 402.

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

Next, the configuration of the optical system 401 shown in FIG. 4A will be described with reference to FIG. FIG. 5 shows an optical system 40.
FIG. 1 is a side view of 1. Laser light having a laser 501 as an oscillation source is split in a vertical direction by a cylindrical lens array 502. The split laser beam is further split laterally by the cylindrical lens 503. In this manner, the laser light is divided into a matrix by the cylindrical lens arrays 502 and 503.

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

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

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

At this time, similarly to the first embodiment, the laser light projected on the irradiation surface of the substrate shows a linear irradiation surface. The homogenization in the width direction (short direction) of the linearly deformed laser light is performed by the cylindrical lens array 502,
This is performed by the cylindrical lens 504 and the cylindrical lens 515. The homogenization of the laser light in the longitudinal direction (long direction) is performed by the cylindrical lens array 503, the cylindrical lens 505, and the cylindrical lens 511.

In any case, the cylindrical lens 5
A primary laser beam transmitted through the laser beam 11 and irradiated on the surface of the amorphous semiconductor film 403b;
Energy intensity ratio (I ₀ ′ / I) with the secondary laser light that is transmitted through the laser beam and irradiates the back surface of the amorphous semiconductor film 403b.
₀ ) satisfies the relationship of 0 <I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ .

In the present embodiment, the above relational expression is satisfied by using a glass substrate (made of a material having a laser beam transmittance of about 50% used here) as the substrate 403a. Of course, in addition to the substrate, the transmittance of the insulating film (not shown) provided on the substrate 403a or the stage (not shown) on which the substrate 403a is installed and the reflectance of the interface are adjusted to adjust the secondary laser light. The effective energy intensity may be attenuated.

Further, in the optical path of the secondary laser light of the optical system 401, a neutral density filter is provided at an arbitrary position,
It is also possible to attenuate the effective energy intensity of the secondary laser light. Conversely, in the optical path of the primary laser light of the optical system 401, a neutral density filter is provided at an arbitrary position to provide the primary laser light. Can be attenuated.

Further, a plurality of means for attenuating the effective energy intensity of the primary laser light or the secondary laser light described in this embodiment may be used in combination to obtain a desired intensity ratio.

[Example 1] In this example, an example in which an amorphous silicon film is crystallized with the configuration shown in the first embodiment will be described. FIG. 3 is used for the description.

In this embodiment, the substrate 301 is 1.1 m
m-thick quartz substrate, 200-nm-thick silicon nitride oxide film (SiON film) as the insulating film 302, and the amorphous semiconductor film 30
As No. 3, an amorphous silicon film was used. At this time,
The SiON film 302 and the amorphous silicon film 303 were formed using a plasma CVD method.

In this embodiment, first, ₄ SCCM of SiH ₄ and N ₂
O was introduced into the reaction chamber at 400 SCCM,
The SiON film 302 was formed at a temperature of 30 ° C., a reaction pressure of 30 Pa, a discharge power density of 0.41 W / cm ² , and a discharge frequency of 60 MHz.
Next, SiH ₄ was introduced into the reaction chamber at 100 SCCM, the film formation temperature was 300 ° C., the reaction pressure was 45 Pa, and the discharge power density was 0.037.
An amorphous silicon film 303 was formed at W / cm ² and a discharge frequency of 13.56 MHz. Actually, the amorphous silicon film was patterned into an island pattern.

Next, laser crystallization of the amorphous silicon film 303 was performed using an excimer laser apparatus as shown in FIG. At this time, the reflector 30 of FIG.
As No. 4, a tungsten nitride film formed on a silicon substrate was used. The reflector 304 and the quartz substrate 3
A gap of 150 μm was provided between the gap and 01.

In this state, as shown in FIG. 3, excimer laser light (primary laser light 305 and secondary laser light 3
06) with respect to the amorphous silicon film 303 at room temperature,
Irradiation was performed in an air atmosphere. The cross section of the excimer laser light is linear (0.4 mm × 16 mm) by the optical system shown in FIG.
0 mm) and scanned from one end of the substrate to the other.
The scanning speed was set to 1 mm / s, and the energy density (energy intensity imagining _Ia in FIG. 6) was 336 mJ / c.
m ² , pulse width 30 ns, repetition frequency 30H
z and the overlapping ratio were 90%. As a result, one shot could be irradiated with 20 shots of laser light.

When laser crystallization is performed in the configuration of this embodiment, the effective energy intensity (I
₀ ) is 151.2 mJ / cm ² , and the effective energy intensity (I ₀ ′) of the secondary laser beam is 77.3 mJ / cm ²
Met. Therefore, the effective energy intensity ratio (I ₀ ′ /
I ₀ ) was 0.51.

FIG. 10 shows an SEM photograph of the polysilicon film crystallized according to this embodiment. Note that FIG.
Is the state after the Seco etching. This secco etching was performed using 50 cc of hydrofluoric acid solution, 25 cc of water and 1.1 cc.
A room temperature etchant to which 4 g of potassium chromate (divalent) was added was used.

As a result, as shown in FIG. 10, relatively large crystal grains having an average crystal grain size of about 0.5 to 0.6 μm were confirmed near the center of the island pattern. Although crystal grains having a small crystal grain size exist at the end of the island-shaped pattern, the positions formed by changing the laser energy density change. In the case where the polysilicon film formed according to the present embodiment is actually used as an active layer of a TFT, the design should be such that such a portion having a small crystal grain size does not hit the channel formation region.

[Embodiment 2] In this embodiment, an example in which an amorphous silicon film is crystallized with the structure shown in the first embodiment will be described. In the laser crystallization performed in this embodiment, the film formed on the surface of the reflector 304 in the first embodiment is a tungsten film, and the laser energy density is 369 mJ /.
Since it was merely changed to cm ² , the detailed description of the other conditions may be referred to Example 1.

FIG. 11 shows an SEM photograph of the polysilicon film crystallized according to this embodiment. Note that FIG. 11 shows a state after the secco etching as in the first embodiment. Seco
The etching conditions may be referred to Embodiment 1.

When laser crystallization is performed in the configuration of this embodiment, the effective energy intensity (I
₀ ) is 166.1 mJ / cm ² and the effective energy intensity (I ₀ ′) of the secondary laser beam is 88.6 mJ / cm ^2.
Met. Therefore, the effective energy intensity ratio (I ₀ ′ /
I ₀ ) was 0.53.

As a result, as shown in FIG. 11, relatively large crystal grains having an average crystal grain size of about 0.6 to 0.7 μm were confirmed in the entire island pattern. In FIG. 11, FIG.
Small crystal grains at the edge of the island-like pattern as shown in FIG. 0 were not remarkably observed. However, there are some conditions that are conspicuous when the laser energy density is changed, so that the laser energy density needs to be optimized.
Even if there is a portion having a small crystal grain size, there is no problem if the design is made so as not to hit the channel forming region of the TFT as in the first embodiment.

[Embodiment 3] In this embodiment, an example in which an amorphous silicon film is crystallized with the structure shown in the first embodiment will be described. In the laser crystallization performed in this embodiment, the film formed on the surface of the reflector 304 in the first embodiment is a titanium nitride film, and the laser energy density is 384 mJ / c.
Since only m ² has been changed, the detailed description of the other conditions may be referred to the first embodiment.

FIG. 12 shows an SEM photograph of the polysilicon film crystallized according to this embodiment. FIG. 12 shows a state after Seco etching as in the first embodiment. Seco
The etching conditions may be referred to Embodiment 1.

When laser crystallization is performed in the configuration of this embodiment, the effective energy intensity (I
₀ ) is 172.8 mJ / cm ² , and the effective energy intensity (I ₀ ′) of the secondary laser light is 57.6 mJ / cm ²
Met. Therefore, the effective energy intensity ratio (I ₀ ′ /
I ₀ ) was 0.33.

As a result, as shown in FIG. 12, large crystal grains having an average crystal grain size of about 0.8 to 1.0 μm were confirmed in the entire island pattern. These crystal grains have a shape that is longer in the horizontal direction toward the paper surface, and it is considered that this suggests the possibility that crystallization has progressed from the horizontal ends of the island pattern. This tendency is slightly confirmed also in FIG.

Further, there are also conditions that are remarkably observed when the laser energy density is changed, so that the laser energy density needs to be optimized. Even if there is a portion having a small crystal grain size, there is no problem if the design is made so as not to hit the channel forming region of the TFT as in the first embodiment.

[Embodiment 4] In this embodiment, an example of forming a polysilicon film to be an active layer of a TFT by the method of Embodiment 1 or Embodiment 2 will be described. FIG. 13 is used for the description.

First, a 200-nm-thick silicon nitride oxide film (not shown) is formed on a glass substrate, and a 50-nm-thick silicon nitride oxide film is formed thereon.
An amorphous silicon film (not shown) having a thickness of nm is formed. Next, the amorphous silicon film is patterned to form an island pattern 701a made of an amorphous silicon film.
701b is formed. (FIG. 13A)

Next, the island patterns 701a and 701b are
Laser crystallization is performed by the method according to the first or second embodiment. The island-shaped patterns 702a and 702b made of a polysilicon film obtained by laser crystallization may have regions 703a and 703b with small crystal grains at end portions.
Further, the end portions of the island-shaped patterns 702a and 702b are regions containing a lot of crystal defects and lattice distortion. (FIG. 13 (B))

The dotted lines 704a and 704b indicate the island-shaped patterns 701 made of an amorphous silicon film.
a, 701b, which means that the island pattern is reduced by about 1 to 15% by laser crystallization. This reduction is considered to occur due to the densification and vaporization of the silicon film, but details are not clear.

Next, the island patterns 702a and 702b made of a polysilicon film are patterned again to form the active layer 705.
a and 705b are formed. Note that dotted lines 706a and 706b are traces of small regions 703a and 703b of crystal grains. (FIG. 13 (C))

Next, covering the active layers 705a and 705b,
A gate insulating film made of a 0-nm-thick silicon nitride oxide film is formed, and a gate electrode 707 is formed thereover. The gate electrode 707 has a stacked structure of a tungsten nitride film and a tungsten film, and has a thickness of 300 nm. (FIG. 13
(D))

After the gate electrode 707 is formed, a step of adding an impurity element imparting n-type is performed, and the source region 708 is formed.
a, a drain region 709a and an LDD region 710 are formed. Further, a step of selectively adding an impurity element for imparting p-type is performed, so that a source region 708b and a drain region 709b are formed.
To form At the same time, the channel formation region 711a,
711b (a region in the active layer to which the impurity element is not added) is formed.

Next, after an interlayer insulating film (not shown) made of a silicon oxide film is formed to a thickness of 1 μm, contact holes are opened, and source wirings 712a, 712b and drain wiring 713 are formed. These wirings may be formed of a low-resistance conductive film mainly composed of an aluminum film. (Figure 1
3 (E))

Through the above steps, a CMOS circuit 7 in which an n-channel TFT 714 and a p-channel TFT 715 having a structure as shown in FIG.
16 are formed.

This embodiment is an embodiment in which the present invention is implemented when forming an active layer of a TFT, and it is not necessary to limit the present invention to this manufacturing process. The present invention relates to any known TF
It can be used for the manufacturing process of T. However, this excludes the case where a light-shielding film or the like is provided below the active layer, that is, the case where it is impossible to simultaneously perform laser annealing on the front and back surfaces of the amorphous semiconductor film.

Although the present embodiment shows an example in which a CMOS circuit is formed, a pixel TFT provided in a pixel portion of an active matrix type image display device can be easily manufactured by using a known technique. It is.

[Embodiment 5] In the embodiment 4, the embodiment in which the present invention is applied to the formation of the active layer of the TFT is shown.
The present invention can be applied to all semiconductor devices using FT. That is, an active matrix type liquid crystal display, an active matrix type EL (electroluminescence) display, an active matrix type EC
(Electrochromics) It may be applied to a display.

Further, SRAMs used for ICs and LSIs
The present invention can be implemented when forming a load transistor of the present invention, and a TFT having a three-dimensional structure can be formed on an IC or LSI.
The present invention is also effective in forming

[Embodiment 6] In this embodiment, FIG.
A case where the structure shown in (A) and (B) is irradiated with laser light under the conditions shown in Example 1 will be described.

In the structure shown in FIG. 14A, reference numeral 801 denotes a 1.1-mm-thick quartz substrate, 802 denotes a 200-nm-thick silicon nitride oxide film, and 803 denotes a 55-nm-thick amorphous silicon film. That is, normal laser crystallization was performed in the structure of FIG.

Further, in the structure of FIG.
4 is a reflector whose surface (reflection surface) is made of a tantalum nitride film;
05 is a quartz substrate having a thickness of 1.1 mm, 806 is a silicon nitride oxide film having a thickness of 200 nm, and 807 is an amorphous silicon film having a thickness of 55 nm. That is, in the structure of FIG. 14B, laser crystallization was performed by implementing the present invention.

The TEM of the resulting polysilicon film
(Transmission Electron Microscopy) Fig. 15
(A) and (B) show. FIG. 15A shows the state shown in FIG.
15B is a TEM photograph of a polysilicon film obtained by crystallizing the amorphous silicon film 803 with the structure shown in FIG.
Is an amorphous silicon film 80 having the structure shown in FIG.
7 is a TEM photograph of a polysilicon film obtained by crystallizing No. 7.

By comparing FIG. 15A and FIG. 15B, it can be confirmed that the polysilicon film of FIG. 15B in which the present invention is implemented has a clearly larger crystal grain size. As described above, it was also confirmed from the TEM photograph that the present invention can increase the average crystal grain size of the crystalline semiconductor film.

Embodiment 7 According to an experiment conducted by the present applicant, the effective energy intensity ratio (I ₀ ′ / I ₀ ) is 0 <I ₀ ′ / I ₀ <1.
Or, when satisfying the relationship of 1 <I ₀ ′ / I ₀ , there was a condition that the average crystal grain size was particularly remarkably enlarged.

In the present embodiment, an experiment will be described in which the material shown in FIG. 6 is changed variously for the substrate (all of which is 1.1 mm thick) or the reflector (strictly, the reflection surface of the reflector). First, Table 1 shows the substrates and reflectors and the effective energy intensity ratios at that time in the samples (A) and (B) used in the experiment.

[0100]

[Table 1]

In Table 1, # 1737 is a product name of a glass substrate manufactured by Corning Incorporated, and AN100 is a product name of a glass substrate manufactured by Asahi Glass Co., Ltd.

As described above, when the effective energy intensity ratio is 0.0
Examples 1 to 7 for samples prepared in the range of 7 to 1.0
XeCl excimer laser light was irradiated under the same conditions as in No. 3, and the resulting polysilicon film was observed in an SEM photograph.

As a result, the effective energy intensity ratio was 0.2
At 9, 0.33, 0.53 or 0.67, the average grain size was confirmed to be about 1 μm, and when the effective energy intensity ratio was 1.0, 0.16, 0.11, 0.07. In, it was confirmed that the average crystal grain size was about 0.3 μm. That is, under the condition that the effective energy intensity of the primary laser light differs from that of the secondary laser light by 20% or more, it is considered that the average crystal grain size significantly increases. Therefore, the above results indicate that the effective energy intensity ratio is I
₀ ′ / I ₀ = 0.2 to 0.9 (preferably 0.3 to ₀ .
It is considered that when the condition (7) is satisfied, it indicates that the optimal crystallization condition exists.

[Embodiment 8] In this embodiment, an example in which an optical system having a structure different from that of the second embodiment is used is shown in FIG.
This will be described with reference to FIG. Specifically, a configuration example in which the length of the linear laser light in the longitudinal direction or the width direction is variable will be described.

When the optical system 10 shown in this embodiment is used,
For semiconductor films that require higher energy for crystallization, the length of the linear laser light in the longitudinal direction is shorter. For semiconductor films that can be crystallized with relatively lower energy, the length of the linear laser light in the longitudinal direction is shorter. Can be set longer. This allows maximum energy efficiency at any time. Further, by making the length in the width direction of the linear laser light variable, the length in the width direction most suitable for crystallization of the semiconductor film can be determined.

The difference between the optical system shown in FIG. 16 and the optical system shown in FIG. 5 is that the optical system shown in FIG. 16 is different from the optical system shown in FIG. And a cylindrical array lens 11 that plays a similar role, and a cylindrical array lens 12 that plays a similar role in addition to the cylindrical array lens 503 that plays a role of dividing in the longitudinal direction.

In this embodiment, since the method of changing the cross-sectional shape of the linear laser beam is the same in both the longitudinal direction and the width direction, here, two cylindrical array lenses that serve to divide in the longitudinal direction are used. I will explain only.

The individual laser beams split in the longitudinal direction of the laser beam by the cylindrical array lens 503 enter the corresponding individual cylindrical lenses forming the cylindrical array lens 12. Specifically, if the cylindrical array lens 503 is divided into seven, the cylindrical array lens 12 that is divided into seven is used. Note that the cylindrical array lens 50
3 and the cylindrical array lens 12 may have the same shape, or may differ only in the radius of curvature of the cylindrical lens.

At this time, the variable region of the length of the laser beam can be determined by the combination of the focal lengths. That is, by changing the distance between the cylindrical array lens 503 and the cylindrical array lens 12, the length of the linear laser light in the longitudinal direction can be controlled.

Also, the cylindrical array lens 503
It is preferable that the distance between the lens and the cylindrical array lens 12 be shorter than twice the focal length of the cylindrical array lens 503. As a result, the laser beams split by the cylindrical array lens 503 can be made to correspond to the individual cylindrical lenses forming the cylindrical array lens 12 on a one-to-one basis.

In this embodiment, a variable transmittance half mirror is used as the half mirror 13. Here, the configuration of the variable transmittance half mirror will be described with reference to FIG. First, an example of the variable transmittance half mirror shown in FIG.

The laser beam 902 incident from the left side of the paper is
Laser light 90 by variable transmittance half mirror 901
3 and a laser beam 904. The variable transmittance half mirror 901 has a structure in which regions 905 to 908 having different transmittances are provided.

By moving the variable transmittance half mirror 901 in the direction of an arrow 909 parallel to the variable transmittance half mirror 901 in the figure, the energy intensity of the transmitted laser beam 903 and the reflected laser beam 904 can be reduced. It can be different. Note that in FIG.
Although two regions 905 to 908 having different transmittances are shown, any number of regions may be used as long as the number is two or more.

Next, another example is shown in FIG. The laser beam 912 incident from the left side of the paper is converted into a laser beam 913 and a laser beam 9 by a variable transmittance half mirror 911.
14 is separated. The variable transmittance half mirror 911 is further divided into a plurality of regions than the variable transmittance half mirror 901 of FIG. 17A, and has a structure in which the transmittance changes finely and stepwise in each region. ing.

Such a variable transmittance half mirror is commercially available. However, even if regions having different transmittances are provided in a stepwise manner in this manner, the laser beam transmitted by moving in the direction of arrow 915 can be obtained. The energy intensities of the light 913 and the reflected laser light 914 can be different.

By using the optical system described above, it is possible to adjust the energy intensity of the laser beam finally irradiated on the semiconductor film. This configuration can be used for the first embodiment.

[Embodiment 9] In this embodiment, an example is shown in which the effective energy intensity ratio is obtained in consideration of the effect of multiple reflection on the reflecting surface of the reflector in the embodiment 7. Samples (A) to (H) used in the experiment are the same as those in Example 7. Further, in the case of the present embodiment, the effective energy intensity (I ₀ ′) of the secondary laser beam is I ₀ ′ = I _a T _sub R _mirror T
_sub (1-R _SiON-Si ) / 1-R _SiON-Si T _sub R _mirror T
_Represented by _sub .

Here, T _sub is the transmittance of the substrate, R _mirror is the reflectance on the surface of the reflector, and R _SiON-Si is the reflectance when entering the amorphous silicon film from inside the SiON film. The reflectance when entering the SiON film from the air, the transmittance in the SiON film, the reflectance when entering from the SiON film to the substrate, and the reflectance when entering from the substrate to the SiON film are experimentally determined. Since it turned out to be negligible, it was not included in the calculation.

Table 2 shows data calculated from the above equations. The data shown in Table 2 is obtained by modifying the data in Table 1 in consideration of the influence of multiple reflection.

[0120]

[Table 2]

Example 7 based on the data shown in Table 2
The optimum crystallization condition described in the above, that is, the effective energy intensity ratio is I ₀ ′ / I ₀ = 0.2 to 0.9 (preferably 0.3 to 0.9).
The condition satisfying 0.7) was not changed.

[Embodiment 10] In this embodiment, effects of the present invention will be described based on experimental results. In this example, the crystallinity was evaluated in five stages relatively.
In the present specification, the crystalline state is evaluated as distinguished as follows.

Crystal state (0): state in which the film has disappeared by ablation. Crystal state (1): As shown in FIG. 18A, a fine crystal state in which fine crystal grains are observed. Crystal state (2): As shown in FIG. 18B, a crystal state having an average crystal grain size of about 300 to 450 nm is observed. Crystal state (3): As shown in FIG. 19A, a crystal state in which relatively large crystal grains having an average crystal grain size of about 600 to 800 nm are observed. Crystal state (4): As shown in FIG. 19B, a crystal state in which very large crystal grains having a major axis exceeding about 3 μm are observed. In this embodiment, the crystal grains in this state are defined as S
The crystal grains are formed by LG (Super Lateral Growth).

On the basis of the above evaluation, the relationship between the laser crystallization conditions and the crystal state was examined. The data shown in Figure 20, (corresponding to an energy intensity I _a of the laser beam just before reaching the amorphous silicon film) irradiation energy
4 shows the results of comparison between the single irradiation and the dual irradiation for the relationship between and single crystal irradiation. Note that single irradiation refers to a case where only the front surface is irradiated with laser light, and dual irradiation refers to a case where the front and back surfaces are irradiated with laser light.

As is clear from FIG. 20, a film having a good crystal state can be obtained with dual irradiation at a lower irradiation energy. In other words, in the case of single irradiation, irradiation energy of about 510 mJ / cm ² is required to cause SLG,
In the case of dual irradiation, irradiation energy of about 440 to 460 mJ / cm ² is sufficient. This indicates that a semiconductor film having higher crystallinity can be obtained with lower irradiation energy in the dual irradiation used in the present invention than in the conventional single irradiation.

It has been experimentally found that the higher the irradiation energy is, the higher the effective energy of the primary laser light is, and the surface roughness of the formed crystalline semiconductor film is increased. This suggests that, in obtaining crystals formed by SLG, dual irradiation can reduce damage to the film surface.

Next, in the case of dual irradiation, experimental results are shown in which the reflectance of the reflector is changed to change the effective energy intensity ratio. FIG. 21A shows the relationship between the irradiation energy and the crystal state, and FIG. 21B shows the relationship between the effective incident energy and the crystal state.

As shown in FIG. 21A, as the reflectivity of the reflector increases (the effective energy intensity of the secondary laser beam increases), the result that the crystal state is improved even with the same irradiation energy was obtained. . This is probably because, for the same irradiation energy, the dual irradiation has a higher effective incident energy. The effective incident energy is
This is the sum of the effective energies incident on the amorphous semiconductor film, and corresponds to the sum of the effective energy intensity of the primary laser light and the secondary effective energy intensity.

Therefore, the relationship between the effective incident energy and the crystal state was examined while fixing the same irradiation energy. Then, as shown in FIG. 21B, the higher the reflectance, the higher the SLG
The effective incident energy required to obtain the crystal (crystal state 4) formed by the above was shifted to a higher energy side. In other words, the lower the reflectivity of the reflector, the easier it is to obtain crystal grains formed by SLG with less effective incident energy, that is, it means that crystallization with less energy loss is possible.

As shown in FIG. 21 (B), as the reflectance of the reflector decreases, the effective incident energy reaching the SLG also decreases. However, when the reflectance is zero, the SLG does not occur. Has been confirmed. From this, it is considered that the reflectance of the reflector has an optimal value for generating SLG.

[0131]

As shown in the present invention, when the amorphous semiconductor film is subjected to laser crystallization, the laser light is simultaneously irradiated on the front and back surfaces of the amorphous semiconductor film and is irradiated on the back surface side. By making the effective energy intensity different from the effective energy intensity applied to the surface side, it is possible to obtain a crystalline semiconductor film having an average crystal grain size larger than that of the related art.

By obtaining a crystalline semiconductor film having a large crystal grain size, the performance of a TFT or a semiconductor device typified by an active matrix display device formed of a TFT can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a laser device.

FIG. 2 is a diagram showing a configuration of an optical system of the laser device.

FIG. 3 is a view showing a laser annealing method.

FIG. 4 is a diagram showing a configuration of a laser device.

FIG. 5 is a diagram showing a configuration of an optical system of the laser device.

FIG. 6 is a diagram for explaining a primary laser beam and a secondary laser beam.

FIG. 7 is an SE showing crystal grains in a polysilicon film.
M photo.

FIG. 8 shows SE showing crystal grains of a polysilicon film.
M photo.

FIG. 9 is an SE showing crystal grains in a polysilicon film.
M photo.

FIG. 10 is an SE showing crystal grains of a polysilicon film.
M photo.

FIG. 11 shows an SE showing crystal grains of a polysilicon film.
M photo.

FIG. 12 shows SE showing crystal grains in a polysilicon film.
M photo.

FIG. 13 is a view showing a manufacturing process of a CMOS circuit using a TFT.

FIG. 14 shows a sample structure.

FIG. 15 is a diagram showing TE showing a state of crystal grains of a polysilicon film.
M photo

FIG. 16 is a diagram showing a configuration of an optical system of a laser device.

FIG. 17 is a diagram illustrating a variable transmittance half mirror.

FIG. 18 is an SEM photograph showing a crystal state of a polysilicon film.

FIG. 19 is an SEM photograph showing a crystal state of a polysilicon film.

FIG. 20 is a diagram showing a relationship between irradiation energy and a crystal state.

FIG. 21 is a diagram showing a relationship between irradiation energy or effective incident energy and a crystal state.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichiro Tanaka 398 Hase, Atsugi-shi, Kanagawa F-Terminator, Semi-Conductor Energy Laboratory Co., Ltd. 5F052 AA02 AA11 BA07 BA15 BB07 CA04 DA02 DB03 JA01 JA04 5F072 AA06 KK15 RR05 YY08 5F110 AA30 BB01 BB02 BB04 BB07 BB11 CC02 DD01 DD02 DD03 DD13 DD14 DD15 EE01 EE04 EE14 FF04 GG01 GG02 GG13 GG16 GG25 GG45 HL03 HM15 NN04 NN23 PP03 PP04 PP06 PP40

Claims (14)

[Claims] An optical system for guiding a laser beam having the laser as an oscillation source to a front surface and a back surface of an object; and a stage for holding the object. A laser device, wherein a reflector is provided between the stage and the laser beam guided to the back surface of the object to be processed is reflected by the reflector and then guided to the back surface of the object to be processed. 2. The laser device according to claim 1, wherein the reflectance of the reflector with respect to the laser light is 20 to 80%. 3. An optical system for guiding a laser beam using the laser as an oscillation source to a front surface and a back surface of an object to be processed, wherein the optical system includes a laser guided to the surface of the object to be processed. A laser device, comprising: a filter for attenuating one of an energy density of light and an energy density of laser light guided to a back surface of the object. 4. A laser device according to claim 1, wherein said laser beam is linearly deformed in cross section by said optical system. 5. When a laser beam is applied to the front and back surfaces of the object, the effective energy intensity (I ₀ ) of the laser beam applied to the surface of the object and the back surface of the object are irradiated. Effective energy intensity of the emitted laser light (I ₀ ')
A laser annealing method, wherein 6. An effective energy intensity (I ₀ ) of the laser light applied to the surface of the object to be processed when the laser light is applied to the front surface and the back surface of the object to be applied and the back surface of the object to be processed. Effective energy intensity of the emitted laser light (I ₀ ')
And 0 <I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ . 7. A step of forming a laser beam using a laser as an oscillation source, and a step of irradiating the laser beam to a front surface and a back surface of the object, and irradiating the back surface of the object. The laser annealing method is characterized in that the laser light to be reflected is reflected by a reflector provided on the back side of the object to be processed and is applied to the back side of the object to be processed. 8. A step of forming a laser beam using a laser as an oscillation source, and a step of irradiating the laser beam to the front and back surfaces of the object to be processed, and irradiating the back surface of the object to be processed. The reflected laser light is reflected by a reflector provided on the back surface side of the object to be processed and is irradiated on the back surface of the object to be processed, and the effective energy intensity of the laser light applied to the surface of the object to be processed ( I ₀₎ and the laser annealing method effective energy intensity of the laser light irradiated on the back surface of the object to be processed (I ₀ ') are different from each other. 9. A step of forming a laser beam using a laser as an oscillation source, and a step of irradiating the laser beam to a front surface and a back surface of the object, and irradiating the back surface of the object. The reflected laser light is reflected by a reflector provided on the back surface side of the object to be processed and is irradiated on the back surface of the object to be processed, and the effective energy intensity of the laser light applied to the surface of the object to be processed ( 0 between I ₀₎ and the effective energy intensity of the laser light irradiated on the back surface of the object to be processed (I ₀ ') <
A laser annealing method characterized by a relationship of I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ . 10. A step of forming a laser beam using a laser as an oscillation source; and a step of irradiating the laser beam on the front and back surfaces of the object to be processed. A laser annealing method, wherein the laser light is divided into a laser beam irradiated on a front surface of a processing object and a laser beam irradiated on a back surface of the processing object. 11. A step of forming a laser beam using a laser as an oscillation source; and a step of irradiating the laser beam to the front and back surfaces of the object to be processed, wherein the laser beam is emitted by an optical system. An effective energy intensity (I ₀ ) of the laser light, which is divided into a laser beam applied to the surface of the object and a laser beam applied to the back surface of the object, and applied to the surface of the object; A laser annealing method characterized in that the effective energy intensity (I ₀ ′) of the laser light applied to the back surface of the object to be processed is different. 12. A step of forming a laser beam using a laser as an oscillation source; and a step of irradiating the laser beam on the front and back surfaces of the object to be processed. An effective energy intensity (I ₀ ) of the laser light, which is divided into a laser beam applied to the surface of the object and a laser beam applied to the back surface of the object, and applied to the surface of the object; 0 <between the laser beam and the effective energy intensity (I ₀ ′) of the laser beam applied to the back surface of the object to be processed.
A laser annealing method characterized by a relationship of I ₀ ′ / I ₀ <1 or 1 <I ₀ ′ / I ₀ . 13. The laser annealing method according to claim 5, further comprising the step of linearly deforming the laser light. 14. The laser annealing method according to claim 5, wherein the object to be processed is an amorphous semiconductor film or a microcrystalline semiconductor film.