JPH11307450A - Reforming method of thin film and device used for its operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reforming method of a thin film which prevents contraction of a substrate due to heating of a substrate and warp of a substrate, permits precise laser casting on a desired position which can be mechanically controlled, enables casting of a fine pattern of a line width of about 1 μm on a substrate and permits heating of a substrate to 500 deg.C or higher, while restraining contraction and warp of a substrate, and a device used for its operation. SOLUTION: When a semiconductor silicon thin film 102 on an insulating glass substrate 101 is crystallized by XeCl excimer laser 103, CO2 laser 104 of a wavelength of 9 to 11 μm is cast on the substrate 101 simultaneously or before or after it to selectively heat a part of the substrate 101 in an area near an interface between the substrate 101 and the semiconductor thin film 102. According to this constitution, contraction of a substrate and warp of a substrate due to heating of a substrate can be prevented and precise irradiation to a desired position which can be mechanically controlled is possible. As a result, a fine pattern of a small focus depth and a line width of about 1 μm can be cast on a substrate by the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying a thin film effective for forming a semiconductor thin film such as a silicon thin film constituting a crystalline silicon thin film transistor, and an apparatus used for implementing the method. TECHNICAL FIELD The present invention relates to a method for modifying a thin film for crystallizing and a device used for carrying out the method.

[0002]

2. Description of the Related Art A thin film transistor (TF) is formed on a glass substrate.
Representative techniques for forming T) include a hydrogenated amorphous semiconductor TFT technique and a polycrystalline silicon TFT technique. The former has a maximum temperature in the fabrication process of about 300 ° C. and realizes a carrier mobility of about 1 cm ² / Vsec. The latter is, for example, 100 mm using a quartz substrate.
By using a high-temperature process similar to an LSI having a temperature of about 0 ° C., a performance with a carrier mobility of 30 to 100 cm ² / Vsec can be obtained. The realization of such high carrier mobility is possible, for example, when the above-mentioned TFT is applied to a liquid crystal display, the peripheral driving circuit portion can be formed simultaneously on the same glass substrate simultaneously with the pixel TFT driving each pixel. This is extremely advantageous in terms of cost and size.

However, the latter polycrystalline silicon TF
In the T technology, when the above-described high temperature process is used, an inexpensive low softening point glass that can use the former process of the hydrogenated amorphous semiconductor TFT technology cannot be used. Therefore, there is a demand for a reduction in the temperature of the polycrystalline silicon TFT process. Therefore, a low-temperature forming technique of a polycrystalline silicon film using a laser crystallization technique has been researched and developed (Japanese Patent Application Laid-Open No. 6-89905, JP-A-7-106247, JP-A-9-235
172).

FIG. 11 is a schematic diagram showing an example of a conventional pulsed laser irradiation apparatus used for laser crystallization of this polycrystalline silicon film. A silicon thin film 16 as an object to be irradiated is formed on a glass substrate 15.
Is set on the xy stage 17. The laser light supplied from the pulsed laser light source 11 passes through an optical path 17 defined by a mirror 12 and a group of optical elements such as a beam homogenizer 14 installed to equalize the spatial intensity. The light is incident on the silicon thin film 16. Since the area per one irradiation is smaller than that of the entire glass substrate, the laser irradiation to an arbitrary position on the substrate can be performed by moving the glass substrate 15 on the xy stage 17. After the irradiation of the laser beam, the substrate 15 is stored in the cassette 18 by the substrate transport mechanism 19.

When a silicon thin film is crystallized by such laser irradiation, if the laser light on the spot is irradiated while moving stepwise, the film quality becomes non-uniform.
In order to prevent the film quality from becoming non-uniform, 300 to 500
A technique of heating a substrate to ° C. is disclosed in Japanese Patent No. 2525101.

[0006]

However, in the method of heating the substrate to 300 to 500 ° C. as described above,
Expansion and warping of the substrate occur, so that positional accuracy for irradiating the laser beam to a desired position and a large depth of focus for the irradiated laser beam are required. There is a problem that it is difficult to irradiate without defocusing. Also, 500
Heating the substrate to a high temperature of ° C. has a problem that the material of the substrate is greatly restricted and a material having a low softening point cannot be used. For example, when the above-described conventional technique is used for manufacturing a thin film transistor for a liquid crystal display, processing on the order of μm is required for photolithography, and shrinkage of the substrate due to heating of the substrate causes misalignment in a subsequent process.

[0007] Also, JS Im et al. Applied Phisics
Lette, vol. 64, (1994), pp. 2303,
It has been suggested that setting the temperature to 00 ° C. or higher, for example, 600 ° C. or 800 ° C., increases the particle size during laser crystallization. However, as mentioned above, practically 500
It is difficult to heat the substrate to a temperature above ℃.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to prevent a substrate from shrinking and warping due to heating of a substrate, and to enable precise laser irradiation to a mechanically controllable desired position. And a method of modifying a thin film, which enables irradiation of a substrate with a fine pattern having a line width of about 1 μm, and furthermore, enables the substrate to be heated to 500 ° C. or more while suppressing shrinkage and warpage of the substrate. It is intended to provide a device for use in implementation.

[0009]

According to a method of modifying a thin film according to the present invention, when a thin film on an insulating substrate is irradiated with an excimer laser for modification, the thin film is more easily transmitted through the thin film than the excimer laser. Irradiating light selectively heats a substrate portion near an interface between the substrate and the thin film.

In this method for modifying a thin film, for example, the thin film is a silicon thin film, the insulating substrate is a silicon dioxide substrate, and light for selectively heating the substrate has a wavelength of 9 to 11 μm. Light. In this case, the light for heating the substrate is preferably a CO ₂ laser. And the irradiation of the light for heating the substrate,
The irradiation can be performed simultaneously with the irradiation of the excimer laser, before the irradiation of the excimer laser, or after the irradiation of the excimer laser. The light for heating the substrate may be pulsed light or light having a wavelength of 9 mm.
Scanning may be performed in a region irradiated with an excimer laser with continuous light of 11 μm to 11 μm.

An insulating film may be formed on the thin film, and a silicon dioxide thin film may be formed as the insulating film. In the modification of these thin films, the modification includes, for example, crystallization from an amorphous silicon film to a polycrystalline silicon film, coarsening of a crystal grain from a small grain silicon film to a large grain silicon film, and crystal defects. This is a process for making the properties of the silicon thin film as desired, such as reducing defects from a film having a large number of defects to a film having a small number of crystal defects.

The thin film reforming apparatus according to the present invention comprises a substrate stage on which an insulating substrate on which a thin film is formed is installed, a first light source for generating an ultraviolet pulse having a wavelength of 400 nm or less, and a wavelength of 9 to 11 μm. A second light source that generates continuous light or pulsed light having a wavelength of, and irradiates the substrate on the substrate stage by processing light from the first and second light sources into a predetermined irradiation shape and intensity distribution. And a group of optical elements.

In the present invention, for example, when a semiconductor thin film on an insulating substrate is crystallized by an excimer laser,
For example, by irradiating a CO ₂ laser beam, a substrate portion near an interface between the substrate and the semiconductor thin film is selectively heated. In this manner, by irradiating the excimer laser with light that is more efficiently absorbed by the substrate than by the semiconductor thin film, the vicinity of the interface in contact with the semiconductor thin film, not the entire substrate, can be selectively heated. Accordingly, it is possible to selectively heat only a required portion of the substrate without causing the substrate to warp or shrink, thereby making the film quality uniform.

In general, the energy I of light passing through a certain film thickness d is expressed by the following equation 1 using the energy I _{0 of} irradiation light and the absorption coefficient α.

[0015]

[Number 1] in the case of a thin film transistor used in the I = I ₀ e-αd liquid crystal display, the thickness of the glass substrate is about 0.5Mm～1.1Mm, the thickness of the silicon thin film to be used 10 200n
m, more ideally about 30 to 100 nm. The absorption coefficient of silicon for light having a wavelength of about 10.6 μm is 1.5 (1 / cm), and the absorption coefficient of silicon dioxide is 1.
Since it is 22 × 10 ³ (1 / cm), a light having a wavelength of 10.6 μm is transmitted by a silicon thin film (for example, a thickness of 100 nm) of 99.99% or more on the surface, and silicon dioxide is compared. The substrate absorbs more than 70% of the light at 10 μm on its surface. When the wavelength is about 9.3 μm, the selectivity of the light absorption coefficient depending on the material becomes even more remarkable. The absorption coefficient of silicon is 0.64 (1 / cm), and the absorption coefficient of silicon dioxide is 3.05 × 10 ^4. (1 / cm)
The silicon existing on the surface (for example, with a thickness of 100
nm) transmits more than 99.999%, and silicon dioxide absorbs more than 95% of light at 1 μm on the surface.

Therefore, a substrate portion near the interface between the substrate and the semiconductor thin film is selected by using a carbon dioxide laser capable of obtaining 50 or more oscillation lines in a wavelength region of 9 to 11 μm and selecting a desired wavelength. Heating is possible.

Further, on a silicon thin film on an insulating substrate,
In the case where a semiconductor device having a structure in which an insulating film (for example, a silicon dioxide film) is selectively disposed is crystallized by irradiation with an excimer laser, light having a wavelength of 9 to 11 μm is irradiated before, after, or simultaneously with the irradiation of the excimer laser. By doing so, the silicon thin film can be heated from both upper and lower directions, and new effects such as an increase in crystal grain size due to a reduction in cooling rate in the excimer laser crystallization process can be obtained. Furthermore, by selectively arranging the silicon dioxide film on top of the silicon thin film, the heat capacity of that portion increases, and the recrystallization of silicon below the silicon dioxide film precedes the surroundings, and good crystals are formed. To be formed, lateral growth proceeds from there to nuclei towards regions without silicon dioxide on top.

Further, by scanning a region irradiated with an excimer laser using continuous light having a wavelength of 9 to 11 μm,
A temperature distribution (gradient) can be formed in an excimer laser irradiation area. The direction of crystallization can be controlled at the time of recrystallization after excimer laser irradiation by the temperature gradient formed on the substrate side, so that the grain size can be increased and the crystal grain position can be controlled.

By irradiating a light having a wavelength of 9 to 11 μm to a laminate of a silicon thin film and an insulating film (silicon dioxide thin film), the interface between the silicon thin film and the insulating film can be maintained at 1000 ° C. or more without damaging the substrate. , It is possible to form a good MOS interface.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a first embodiment of the present invention. In this embodiment, a glass substrate 101 (0.7 m thick) containing silicon dioxide as a main component is used.
m) formed on the silicon thin film 102 (thickness 100 n
m) is irradiated with a XeCl excimer laser 103. Simultaneously with or before or after the irradiation of the XeCl excimer laser 103, a CO ₂ laser 104 is applied to the substrate 101.
Irradiate toward

In this case, for example, even if a silicon dioxide layer having a higher purity of silicon dioxide than the glass substrate exists between the glass substrate 101 and the silicon thin film 102, or the purpose is to control valence electrons in silicon. Impurities may be added. XeC is applied to such a silicon thin film.
Irradiating the excimer laser 103, the silicon thin film 1
By irradiating with a sufficiently high irradiation intensity compared to the film thickness of 02, the silicon thin film can be modified by melting and recrystallization. That is, for example, crystallization from an amorphous silicon film to a polycrystalline silicon film, coarsening of crystal grains from a small grain silicon film to a large grain silicon film, and a film with many crystal defects to a film with few crystal defects. It is possible to modify the silicon thin film 102 to reduce defects.

In this embodiment, since the CO ₂ laser 104 is irradiated during the crystallization process using the excimer laser 103, the interface between the silicon thin film 102 and the glass substrate 101 is heated to a high temperature, It is possible to reduce the cooling rate during the recrystallization process and increase the grain size of the obtained polycrystalline silicon.

Table 1 below shows the optical constants of silicon and silicon dioxide at each wavelength. The data in Table 1 is
Handbook of Optical Constants of Solids, E. Palik
Ed., 1985, published by Academic Press.

[0024]

[Table 1]

That is, as shown in Table 1, based on the optical constants of silicon and silicon dioxide when the irradiation wavelength is about 10.6 μm and about 9.3 μm, and the absorption coefficient obtained therefrom, each film was formed. When the absorption depth is determined, the wavelength is 1
Silicon at the surface (eg, 100 nm thick) transmits 0.6 μm or more of 99.99% light, and silicon dioxide absorbs 70% or more light at 10 μm of the surface. When the wavelength is about 9.3 μm, such selectivity of light absorption or transmission becomes more remarkable, and silicon (for example, 100 nm thick) existing on the surface is transmitted at 99.999% or more, and silicon dioxide is present on the surface. At 1 μm, 95% or more of the light is absorbed.

On the other hand, an excimer laser having a shorter wavelength than the XeF excimer laser having a wavelength of 351 nm, for example, XeCl
And KrF laser absorption coefficient to silicon is 10 ⁶ c
up to m ^-1 . Therefore, absorption on the glass substrate hardly occurs.

From the above, the excimer laser 1
03 and the substrate heating by the CO ₂ laser 104 can be performed simultaneously. Moreover, since the substrate heating by the CO ₂ laser 104 is about 1 to 10 μm as described above, by using the pulsed CO ₂ laser controlled at 50 nsec to 100 μsec, the substrate can be prevented from warping and contracting. In addition, the outermost surface of the glass substrate can be set at a high temperature of 1000 ° C. or higher.

There are various modes for the laser irradiation timing at this time, as shown in FIGS. FIG.
9 to 9, the solid line is an excimer laser, and the broken line is CO _2.
Laser. As shown in FIG. 7, a method of delaying the irradiation of the CO ₂ laser rather than the irradiation of the excimer laser;
As shown in FIGS. 9 and 10, there is a method of irradiating an excimer laser with a predetermined delay time after irradiating a CO ₂ laser. In addition, an excimer laser is generally radiated from the back surface of the substrate using a substrate that easily transmits light having a wavelength of about 351 nm, for example, OA-2 glass manufactured by Nippon Electric Glass.
_{2 A} method of irradiating a laser from the substrate surface is also possible. Of course, a CW type CO ₂ laser may be used depending on desired heating conditions.

FIGS. 2A to 2G and FIGS. 2D to 2F are sectional views showing the steps in the case where the first embodiment is applied to a method of manufacturing a thin film transistor. 2 (d ') to (f') are cross-sectional views in a direction perpendicular to the cross sections of (d) to (f). As shown in FIG.
A glass substrate 501 having a flat surface (for example, OA-2 glass manufactured by Nippon Electric Glass Co., Ltd., or 1737 glass manufactured by Corning Inc., including a quartz substrate) is washed with acid or alkali, and then a silicon dioxide film 508 is formed on the substrate. To form
As the formation method, LPCVD, TEOS (Tetra
An ethoxysilane (teos) method, a plasma CVD method using silane, oxygen or ozone, or the like, and a normal pressure CVD method can be used. Further, a silicon dioxide film can also be formed by heating and baking a coating film of high order silane, organic silica, or the like.

Next, after the substrate is washed again, the substrate is washed by LPCVD using disilane gas as a raw material.
At 75 ° C., a 75 nm amorphous silicon thin film is deposited. After the deposition, cleaning is performed again immediately before performing the next step.

Thereafter, the substrate with the Si film formed as described above is placed in a laser annealing apparatus. Once the inside of the process chamber is evacuated (about 10 ^-2 to 10 ^-6 torr), Ar gas is introduced from the gas inlet, and
The gas flow meter and the exhaust valve are controlled so that torr can be maintained. Until it reaches 700 torr, this A
Instead of the gas inlet for maintaining the r gas pressure, the Ar gas may be introduced using another inlet capable of increasing the flow rate. Ar gas pressure is 700t
After reaching orr, the excimer laser is operated to start laser irradiation on the substrate. Xe as a pulse laser light source
Cl (wavelength 308 nm), XeF (351 nm), Kr
F (248 nm) can be used. At this time, a pulsed CO ₂ laser is irradiated at the same time. The irradiation range is desirably slightly larger than the irradiation region of the excimer laser, and therefore, its beam intensity profile is appropriately selected.

As shown in FIG. 2B, the amorphous silicon film is crystallized by this laser irradiation, and a polycrystalline silicon film 502 is formed.

Thereafter, as shown in FIG. 2C, a silicon dioxide film 503 is formed to a thickness of 10 nm. This silicon dioxide film 503 can be formed by the same forming means as that used for the formation of the silicon dioxide film 508. In this case, after the formation of the polycrystalline silicon film 502, it is more preferable that the polycrystalline silicon film 502 be transported to a chamber for forming a silicon dioxide film without being exposed to the atmosphere to form a silicon dioxide film 503.

Thereafter, as shown in FIG. 2D, the polysilicon film 502 and the silicon dioxide film 503 are formed into an island pattern. At this time, the silicon dioxide film 503
By patterning the pattern slightly smaller, it is possible to suppress the occurrence of gate leak.

Next, as shown in FIG. 2E, after forming a silicon dioxide film 504 and covering the polycrystalline silicon film, an n ⁺ silicon film is formed by a plasma CVD method or phosphorus is added. After forming a doped amorphous silicon film, it is formed by activating the film by laser or lamp heating or the like, and then, after forming an Al layer by sputtering, a laminate of these Al / n ⁺ silicon films is formed. Is patterned to form a gate electrode 505. In addition,
Not limited to Al, tungsten, molybdenum, tantalum,
A metal such as copper, a silicide film such as tungsten silicide or molybdenum silicide thereof, or a laminate thereof may be used. After forming a gate electrode 505 made of an Al / n ⁺ silicon laminated film, the lower silicon dioxide films 504 and 503 are patterned using this as a mask,
Further, the source / drain region 509 is formed by an ion doping method capable of selecting only desired ions by an ion doping method, a plasma doping method, or a mass separating method without performing mass separation.

Thereafter, as shown in FIG. 2G, an interlayer insulating film 506 is formed, a contact hole is formed in the interlayer insulating film, an Al wiring 507 is formed, and a TFT is formed.

By forming a TFT and a liquid crystal display or an image sensor using the TFT as an active element by the above-described method, process reproducibility and long-term stability at the time of laser irradiation are secured, and the product yield is improved. Can be done.

Next, a second embodiment of the present invention will be described. As shown in FIG. 3A, a silicon thin film 102 (75 nm thick) is formed on a glass substrate 101 (1.1 mm thick).
Is deposited thereon, and a silicon dioxide film 105 (thickness: 100 nm) is deposited thereon, and is patterned into a desired shape.
Such a laminate is irradiated with an excimer laser 103 and a CO ₂ laser 104 by the same means as described above. Since the heat capacity of the region where the silicon dioxide film 105 exists is increased by that amount, the temperature rise of the silicon thin film 102 due to both laser irradiations is smaller than that of the peripheral portion, and
Since the solidification at the time of recrystallization also starts earlier than the surroundings, in the silicon thin film 102, the crystal growth centered on the small grain size region 106 under the silicon dioxide film 105 proceeds in the lateral direction, and the large grain size region 107 To form Moreover, since the crystal growth of the portion of the silicon thin film 102 below the silicon dioxide film 105 is promoted as compared with the case where the substrate is not heated by the CO ₂ laser, the crystal grain size serving as a nucleus is large, and as a result, the crystal grows around. There is an advantage that the size of the crystal becomes larger.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. As shown in FIG. 4A, a glass substrate 101 on which a silicon thin film 102 is deposited is irradiated with a CW type CO ₂ laser 104 having a predetermined beam size, and the glass substrate 101 is scanned in a scanning direction 110. By performing this scanning, as shown in FIG. 4B, the substrate surface temperature with respect to the substrate position at a certain time is determined. This can be arbitrarily set according to the laser irradiation intensity, the silicon film thickness, the laser wavelength, the scanning speed, and the like. By irradiating the CO ₂ laser as described above prior to or together with the excimer laser irradiation, a temperature gradient is generated in the silicon thin film irradiated with the excimer laser, so Crystal growth proceeds, and crystal grains can be formed at desired positions by controlling the irradiation place.

Next, a fourth embodiment of the present invention will be described with reference to FIG. By the heating assist method of excimer laser crystallization using the infrared laser as described above, the interface between the silicon thin film that has already been recrystallized and the silicon dioxide thin film that is formed on the upper or lower part is more electrically defective. It is possible to change to a structure having few levels. That is, as shown in FIG. 5, by irradiating the CO ₂ laser 104 from the top SiO ₂ film 105, an upper SiO ₂
The lower glass substrate 101 is heated simultaneously with the film 105.

As described above, at a wavelength of about 9.3 μm, in the case of the SiO ₂ film 105 (100 nm thick) existing on the surface, about 26% of energy is absorbed, and silicon (100 nm thick) is 99% thick. .999% or more, and 1 μm on the surface of the substrate 101 made of silicon dioxide.
In this way, the remaining 69% or more of the light is absorbed. Therefore, by using a pulse light source of several tens to several thousand nsec, heat treatment of the silicon / silicon dioxide interface existing on the surface becomes possible without heating the entire substrate.

FIGS. 6A to 6G and FIGS. 6D to 6F are sectional views showing a case where the fourth embodiment is applied to a method of manufacturing a thin film transistor in the order of steps. In FIG. 6, (d ') to (f') are (d) to (f).
It is sectional drawing which looked at from the side. As shown in FIG. 6A, a glass substrate 501 having a flat surface (for example, OA-2 glass manufactured by NEC Corporation, 1737 glass manufactured by Corning Inc., and a quartz substrate) is cleaned using an acid or an alkali. After that, a silicon dioxide film 508 is formed on the substrate. The method of forming the silicon dioxide film 508 is shown in FIG.
The same method as in the case of (a) can be used.

Next, after the substrate is washed again, an amorphous silicon thin film of 75 nm is deposited at 450 ° C. by LPCVD using disilane gas as a raw material. After this deposition,
Washing is performed again immediately before performing the next step.

Then, the substrate with the Si film formed as described above is placed in a laser annealing apparatus as in the case of FIG. Once the process chamber is evacuated (10 ^-2 ~
After 10 ^-6 torr), Ar gas is introduced from the gas inlet and the gas flow meter and the exhaust valve are controlled so that the Ar gas pressure can be maintained at 700 torr.

After the pressure of the Ar gas reaches 700 torr, the excimer laser is operated to start laser irradiation on the substrate. As a pulse laser light source, XeCl (wavelength 3
08 nm), XeF (351 nm) or KrF (248
nm) can be used.

The polycrystalline silicon film 50 is irradiated by laser irradiation.
After the formation of No. 2, a silicon dioxide film 503 is formed to a thickness of 10 nm. In this case, a forming method similar to the film forming method used for forming the silicon dioxide film 508 described above can be employed. Further, after the formation of the polycrystalline silicon film 502, the polycrystalline silicon film 502 is transferred to a silicon dioxide formation chamber without being exposed to the atmosphere, and a silicon dioxide film 503 is formed.

Then, as shown in FIG. 6C, a pulse type CO ₂ laser is irradiated. The irradiation range is desirably slightly larger than the irradiation region of the excimer laser, and the beam intensity profile is set appropriately. A continuous wave type laser beam may be used, but a pulse type is more preferable in order to suppress damage to the substrate. After that, the polycrystalline silicon film 502 and the silicon dioxide film 503
Is island-patterned. At this time, by patterning the silicon dioxide film 503 such that the silicon dioxide film 503 is slightly smaller, it is possible to suppress the occurrence of gate leak.

Next, as shown in FIG. 6E, after forming a silicon dioxide film 504 and covering it with polycrystalline silicon, an n ⁺ silicon film is formed by a plasma CVD method or an amorphous structure doped with phosphorus. After silicon is formed, it is formed by a method of activating by means such as laser or lamp heating. Next, an Al layer is formed by sputtering, and then patterned to form a gate electrode 505 made of an Al / n ⁺ silicon laminated film. Not only Al but also a metal such as tungsten, molybdenum, tantalum, and copper, a silicide film such as tungsten silicide and molybdenum silicide, or a laminate thereof.

Next, as shown in FIG.
After forming a gate electrode 505 composed of an n ⁺ silicon laminated film, the silicon dioxide films 504 and 5
03 is patterned. After that, the source / drain region 509 is formed by an ion doping method without mass separation, a plasma doping method, an ion implantation method capable of selecting only desired ions by mass separation, or the like.

Next, as shown in FIG. 6G, an interlayer insulating film 506 is formed, a contact hole is formed in the interlayer insulating film 506, and an Al wiring 507 is formed.
FT is completed.

At the time when the polycrystalline silicon film is formed or when the amorphous silicon film is formed, application to modification of the silicon dioxide film by carbon dioxide laser irradiation, activation of impurities, and the like are also possible.

By forming a TFT or a liquid crystal display or an image sensor using the TFT as an active element by the above-described method, it is possible to ensure process reproducibility and long-term stability during laser irradiation and to increase product yield. Can be.

Next, an embodiment of the present invention will be described with reference to FIG. The excimer laser is irradiated from a pulse laser light source 811 to a glass substrate 815 on an xy stage 817 disposed in a vacuum chamber 818 and a silicon thin film 816 thereon via a mirror 812, a beam homogenizer 814, and the like. Infrared pulse laser light source 821 that can control oscillation synchronization with an excimer laser
Denotes an infrared beam homogenizer 824 and an infrared mirror 8
22 and the like, like the excimer laser,
Irradiation is carried out toward 15.

With such a configuration, heating of the outermost surface of the substrate by infrared laser and melting and recrystallization of the silicon thin film 816 by ultraviolet short pulse laser can be performed.
The infrared light source is not limited to the pulse laser, but may be a continuous wave laser, and may include a mechanism for scanning a beam (for example, a polygon mirror or the like). 351 nm
By using an ultraviolet light source of the order, it becomes possible to relatively easily excimer laser crystallization from the back surface of the substrate,
It is also possible to introduce ultraviolet light from below the substrate and infrared light from above the substrate.

The optical element group may be moved instead of the xy stage 817, or the optical element group and the stage may be moved in combination. Laser irradiation can be performed in a vacuum chamber 818 in a vacuum or in a high-purity gas atmosphere.

[0056]

As described above, according to the present invention,
Shrinkage of the substrate and warpage of the substrate due to heating of the substrate can be prevented, and precise irradiation to a desired position that can be controlled mechanically becomes possible. Thus, according to the present invention, it is possible to irradiate the substrate with a fine pattern having a small depth of focus and a line width of about 1 μm. Further, according to the present invention, the substrate can be heated to 500 ° C. or higher while preventing shrinkage and warpage of the substrate, and the performance of the silicon thin film used for the crystalline silicon thin film transistor can be significantly improved. It makes a significant contribution to the expansion of the technical field used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIGS. 2A to 2G and 2D to 2F are cross-sectional views sequentially showing steps when the present embodiment is applied to a method for manufacturing a thin film transistor.

FIGS. 3A and 3B are schematic diagrams showing a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a third embodiment of the present invention.

FIG. 5 is a schematic diagram showing a fourth embodiment of the present invention.

FIGS. 6A to 6G are cross-sectional views sequentially showing steps when this embodiment is applied to a method of manufacturing a thin film transistor.

FIG. 7 is a schematic diagram showing irradiation timings of an excimer laser and a CO ₂ laser.

FIG. 8 is a schematic diagram showing irradiation timings of an excimer laser and a CO ₂ laser.

FIG. 9 is a schematic diagram showing irradiation timings of an excimer laser and a CO ₂ laser.

FIG. 10 is a schematic view showing an embodiment of the device of the present invention.

FIG. 11 is a schematic view showing a conventional apparatus.

[Explanation of symbols]

101: Glass substrate 102: Silicon thin film 103: XeCl excimer laser 104: CO ₂ laser 105: SiO ₂ film 501: Glass substrate 502: Polycrystalline silicon film 503, 504: Silicon dioxide film 505: Gate electrode 811: Pulsed laser light source 812 : Mirror 814: beam homogenizer 815: glass substrate 816: silicon thin film 817: xy stage 821: infrared pulse laser

Claims (10)

[Claims] 1. A method of irradiating a thin film on an insulating substrate with an excimer laser for modification by irradiating the thin film on the insulating substrate with light that is more easily transmitted through the thin film than the excimer laser. A method for modifying a thin film, comprising selectively heating a substrate portion. 2. The method according to claim 1, wherein the thin film is a silicon thin film, the insulating substrate is a silicon dioxide substrate, and light for selectively heating the substrate is light having a wavelength of 9 to 11 μm. The method for modifying a thin film according to claim 1. 3. The method according to claim 2, wherein the light for heating the substrate is a CO ₂ laser. 4. The method according to claim 1, wherein the irradiation with the light for heating the substrate is performed simultaneously with the irradiation with the excimer laser, before the irradiation with the excimer laser, or after the irradiation with the excimer laser. Item 14. The method for modifying a thin film according to item 4. 5. The method of modifying a thin film according to claim 1, wherein an insulating film is formed on the thin film. 6. The method according to claim 2, wherein the light for heating the substrate is continuous light having a wavelength of 9 to 11 μm, and the continuous light is scanned in a region irradiated with an excimer laser. The method for modifying a thin film according to claim 1. 7. The method according to claim 2, wherein the insulating film is a silicon dioxide thin film. 8. The method for modifying a thin film according to claim 1, wherein the modification of the thin film is crystallization of the thin film. 9. A substrate stage on which an insulating substrate on which a thin film is formed is placed, a first light source for generating an ultraviolet pulse having a wavelength of 400 nm or less, and continuous light or pulsed light having a wavelength of 9 to 11 μm. A second light source that generates
An optical element group configured to process the light from the first and second light sources into a predetermined irradiation shape and intensity distribution and to irradiate the substrate on the substrate stage with an optical element group. 10. The thin film reforming apparatus according to claim 9, wherein the thin film is crystallized by irradiation with an ultraviolet pulse from the first light source.