Heating treatment device, heating treatment method and fabrication method of semiconductor device Number:7,410,850 from the United States Patent and Trademark Office (PTO) owispatent To provide a method and a device for subjecting a film to be treated to a heating treatment effectively by a lamp annealing process, ultraviolet light is irradiated from the upper face side of a substrate where the film o be treated is formed and infrared light is irradiated from the lower face side by which the lamp annealing process is carried out. According to such a constitution, the efficiency of exciting the film to be treated is significantly promoted since electron excitation effect by the ultraviolet light irradiation is added to vibrational excitation effect by the infrared light irradiation and strain energy caused in the film to be treated by the lamp annealing process is removed or reduced by a furnace annealing process.<H semiconductor, fabrication, Heating, treatme, 7410850.html, Patent, pto, 7410850

Title: Heating treatment device, heating treatment method and fabrication method of semiconductor device

Abstract: To provide a method and a device for subjecting a film to be treated to a heating treatment effectively by a lamp annealing process, ultraviolet light is irradiated from the upper face side of a substrate where the film o be treated is formed and infrared light is irradiated from the lower face side by which the lamp annealing process is carried out. According to such a constitution, the efficiency of exciting the film to be treated is significantly promoted since electron excitation effect by the ultraviolet light irradiation is added to vibrational excitation effect by the infrared light irradiation and strain energy caused in the film to be treated by the lamp annealing process is removed or reduced by a furnace annealing process.

Patent Number: 7,410,850 Issued on 08/12/2008 to Yamazaki, et al.

Inventors: Yamazaki; Shunpei (Setagaya, JP), Ohtani; Hisashi (Tochigi, JP)
Assignee: Semiconductor Energy Laboratory Co., Ltd. (Atsugi-shi, Kanagawa-ken, JP)

Appl. No.: 11/325,513

Filed: January 5, 2006

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10141206	May., 2002	7214574
09038640	Mar., 1998	6423585

Foreign Application Priority Data


Mar 11, 1997 [JP]			9-074425
Apr 17, 1997 [JP]			9-115274

Current U.S. Class: 438/166

Current International Class: H01L 21/268 (20060101); H01L 21/84 (20060101)

Field of Search: 438/166,795

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Primary Examiner: Wilczewski; M.
Attorney, Agent or Firm: Fish & Richardson P.C.

Claims

What is claimed is:

1. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear infrared light using a first light source from an upper side of the substrate while scanning the first linear infrared light; irradiating said film with a second linear infrared light using a second light source from a lower side of the substrate while scanning the second linear infrared light; irradiating said film with a third linear infrared light using a third source from the upper side of the substrate while scanning the third linear infrared light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second and third linear infrared light.

2. The method of forming a semiconductor device according to claim 1, wherein each of the first, second, and third light sources is a lamp light source.

3. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from a lower side of the substrate while scanning the second linear light; irradiating said film with a linear ultraviolet or visible light from the upper side of the substrate while scanning the linear ultraviolet or visible light; irradiating said film with a third linear light from a third light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from the upper side of the substrate while scanning the third linear light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second and third linear light and irradiating the linear ultraviolet or visible light.

4. The method of forming a semiconductor device according to claim 3, wherein each of the first, second and third light sources is a lamp light source.

5. The method of forming a semiconductor device according to claim 3, wherein the linear ultraviolet or visible light is emitted from a lamp light source.

6. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength of 500 nm to 20 .mu.m from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength of 500 nm to 20 .mu.m from a lower side of the substrate while scanning the second linear light; irradiating said film with a linear ultraviolet or visible light from the upper side of the substrate while scanning the linear ultraviolet or visible light; irradiating said film with a third linear light from a third light source and having a wavelength of 500 nm to 20 .mu.m from the upper side of the substrate while scanning the third linear light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second and third linear light and irradiating the linear ultraviolet or visible light.

7. The method of forming a semiconductor device according to claim 6, wherein each of the first, second and third light sources is a lamp light source.

8. The method of forming a semiconductor device according to claim 6, wherein the linear ultraviolet or visible light is emitted from a lamp light source.

9. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear infrared light from a first light source and an upper side of the substrate while scanning the first linear infrared light; irradiating said film with a second linear infrared light from a second light source and a lower side of the substrate while scanning the second linear infrared light; irradiating said film with a linear light having a wavelength region to subject bonds of atoms constituting said film to an electron excitation from the upper side of the substrate while scanning the linear light; irradiating said film with a third linear infrared light using a third light source from the upper side of the substrate while scanning the third linear infrared light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second and third linear infrared light and irradiating the linear light.

10. The method of forming a semiconductor device according to claim 9, wherein each of the first, second and third light sources is a lamp light source.

11. The method of forming a semiconductor device according to claim 9, wherein the linear light is emitted from a lamp light source.

12. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from a lower side of the substrate while scanning the first linear light; irradiating said film with a third linear light front a third light source and having a wavelength region to subject bonds of atoms constituting said film to an electron excitation from the upper side of the substrate while scanning the second linear light; irradiating said film with a fourth linear light from a fourth light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from the upper side of the substrate while scanning the fourth linear light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second, third and fourth linear light.

13. The method of forming a semiconductor device according to claim 12, wherein the first linear light is emitted from a lamp light source.

14. The method of forming a semiconductor device according to claim 12, wherein the second linear light is emitted from a lamp light source.

15. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength of 500 nm to 20 .mu.m from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength of 500 nm to 20 .mu.m from a lower side of the substrate while scanning the second linear light; irradiating said film with a third linear light from a third light source and having a wavelength region to subject bonds of atoms constituting said film to an electron excitation from the upper side of the substrate while scanning the third linear light; irradiating said film with a fourth linear light having wavelength of 500 nm to 20 .mu.m from the upper side of the substrate while scanning the fourth linear light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second, third and fourth linear light.

16. The method of forming a semiconductor device according to claim 15, wherein the first linear light is emitted from a lamp light source.

17. The method of forming a semiconductor device according to claim 15, wherein the second linear light is emitted from a lamp light source.

18. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear infrared light from a first light source from an upper side of the substrate while scanning the first linear infrared light; irradiating said film with a second linear infrared light from a second light source from a lower side of the substrate while scanning the second linear infrared light; irradiating said film with a linear light having a wavelength 10 nm to 600 nm from the upper side of the substrate while scanning the linear light; irradiating said film with a third linear infrared light from a third light source from the upper side of the substrate while scanning the third linear infrared light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second and third linear infrared light and irradiating the linear light.

19. The method of forming a semiconductor device according to claim 18, wherein each of the first, second and third light sources is a lamp light source.

20. The method of forming a semiconductor device according to claim 18, wherein the linear light is emitted from a lamp light source.

21. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational exicitation from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from a lower side of the substrate while scanning the second linear light; irradiating said film with a third linear light from a third light source and having a wavelength 10 nm to 600 nm from the upper side of the substrate while scanning the third linear light; irradiating said film with a fourth linear light having a wavelength region to subject bonds of atoms constituting said film to a vibrational excitation from upper side of the substrate while scanning the fourth linear light; and forming agate electrode with a gate insulating film interposed therebetween after irradiating the first, second, third and fourth linear light.

22. The method of forming a semiconductor device according to claim 21, wherein the first linear light is emitted from a lamp light source.

23. The method of forming a semiconductor device according to claim 21, wherein the second linear light is emitted from a lamp light source.

24. A method of forming a semiconductor device comprising: forming a film comprising silicon over a substrate; irradiating said film with a first linear light from a first light source and having a wavelength 500 nm to 20 .mu.m from an upper side of the substrate while scanning the first linear light; irradiating said film with a second linear light from a second light source and having a wavelength of 500 nm to 20 .mu.m from a lower side of the substrate while scanning the second linear light; irradiating said film with a third linear light from a third light source and having a wavelength of 10 nm to 600 nm from the upper side of the substrate while scanning the third linear light; irradiating said film with a fourth linear light having a wavelength of 500 nm to 20 .mu.m from the upper side of the substrate while scanning the fourth linear light; and forming a gate electrode with a gate insulating film interposed therebetween after irradiating the first, second, third and fourth linear light.

25. The method of forming a semiconductor device according to claim 24, wherein the first linear light is emitted from a lamp light source.

26. The method of forming a semiconductor device according to claim 24, wherein the second linear light is emitted from a lamp light source.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a constitution in the case where lamp annealing is utilized as a heating treatment method frequently used in a fabrication process of a semiconductor device. Particularly, the present invention is effective in fabricating a semiconductor device such as a thin film transistor (TFT) on a glass substrate.

2. Description of Related Art

In recent years, development of TFT formed by utilizing a semiconductor thin film (typically thin film whose major component is silicon) on a glass substrate has significantly been progressed. Further, demand of an electrooptical device in which a pixel matrix circuit, a driver circuit, a logic circuit and the like are monolithically mounted on a glass substrate has been promoted.

The most significant restriction caused in forming TFT on a glass substrate is temperature of process. That is, a restriction whereby a heating treatment cannot be carried out at a heat resistant temperature of glass or higher narrows the margin of process.

Therefore, laser annealing process has been utilized as a means for annealing selectively a thin film. According to the laser annealing process, only a thin film can selectively be heated by elevating instantaneously temperature of a sample by irradiating a pulse laser beam onto the sample. However, there has been posed a problem in view of mass production steps in which an optical system is complicated to deal with a laser beam and the uniformity is difficult to ensure.

Hence, a lamp annealing process using a strong beam emitted from an arc lamp, a halogen lamp or the like has recently been spotlighted. This technology is referred to as RTA (Rapid Thermal Annealing) or RTP (Rapid Thermal Processing) in which a film to be treated is heated by irradiating a strong beam in a region of wavelength that is apt to be absorbed by the film to be treated.

Normally, the lamp annealing process utilizes a region of visible light to infrared light as strong beam. The light in this wavelength region is difficult to absorb by a glass substrate and accordingly, the heating of the glass substrate can be restrained to a minimum. Further, time periods for temperature rise and temperature drop are extremely short and accordingly, high temperature treatment at 1000.degree. C. or higher can be carried out in a short period of time of several seconds to several tens seconds.

Further, a complicated optical system such as used in a fabrication process by using a laser beam is not needed and therefore, the process is suitable for treating a comparatively large area with excellent uniformity. Also, the yield and throughput are promoted since the high temperature treatment is basically carried out by a sheet by sheet process.

It is a problem of the present invention to improve the above-described lamp annealing process and to provide a method for effectively subjecting a film to be treated to a heating treatment.

Further, according to the conventional lamp annealing process, light has been irradiated only from an upper face side of a film to be treated and therefore, when a layer which does not transmit the light (for example, electrode made of a metal) or a layer which hinders irradiation of light is present at a portion or a total face of the film to be treated, the film to be treated beneath the layer could not be annealed.

Particularly, when the conventional lamp annealing process was used in a step of activating impurities doped in a semiconductor thin film, an electrode made of a metal and an insulating film which were laminated on the semiconductor thin film hindered irradiation of light and source/drain regions excellent in uniformity could not be formed.

It is one of the problems of the present invention to provide a semiconductor thin film having source/drain regions excellent in uniformity by activating impurities through a step using a heating treatment method improving the conventional lamp annealing process in a semiconductor thin film doped with impurities and by heat treatment at later steps.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention disclosed in the specification, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source,

wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation is irradiated from an upper face side of the thin film and simultaneously therewith a strong light in a wavelength region capable of subjecting the bonds to a vibrational excitation is irradiated from a lower face side of the thin film.

In the first aspect of the present invention, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is a light included in a wavelength region of 10 through 600 nm; and

the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is a light included in a wavelength region of 500 nm through 20 .mu.m.

In the first aspect of the present invention, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is an ultraviolet light, and

the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is an infrared light.

Further, according to a second aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source,

wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation is irradiated from an upper face side of the thin film and simultaneously therewith a strong light in a wavelength region capable of subjecting the bonds to a vibrational excitation is irradiated from a lower face side of the thin film, and

wherein the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.

According to a third aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source:

wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation and a strong light in a wavelength capable of subjecting the bonds to the vibrational excitation are irradiated from an upper face side of the thin film and simultaneously therewith a strong light in the wavelength capable of subjecting the bonds to the vibrational excitation is irradiated from a lower face side of the thin film; and

wherein the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.

In the third aspect of the present invention, an infrared light irradiated from the upper face side of the thin film is irradiated to regions of the thin film immediately before and/or immediately after a region of the thin film where an ultraviolet light is irradiated.

In the second aspect or the third aspect of the present invention, all of the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and the strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned in a state of irradiating a same portion of the thin film.

In the second aspect or the third aspect of the present invention, a first region where the strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are irradiated includes a second region where the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is irradiated and is wider than the second region.

In the above-described aspects, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is a light included in a wavelength region of 10 through 600 nm, and

the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is a light included in a wavelength region of 500 nm through 20 .mu.m.

In the above-described aspects, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is an ultraviolet light, and

the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is an infrared light.

Further, according to a fourth aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source, said method comprising the steps of,

subjecting bonds of atoms constituting the thin film to an electron excitation by irradiating an ultraviolet light from an upper face side of the thin film,

subjecting the bonds to a vibrational excitation by irradiating an infrared light from a lower face side of the thin film, and

wherein the step of subjecting the thin film to the electron excitation and the step of subjecting the thin film to the vibrational excitation are carried out simultaneously.

Additionally, in carrying out the present invention comprising the above-described aspects, there is needed a heating treatment device comprising at least,

an ultraviolet light lamp arranged on an upper face side of a substrate to be treated,

an infrared light lamp arranged on a lower face side of the substrate to be treated, and

wherein the ultraviolet light lamp and the infrared light lamp are arranged to interpose the substrate to be treated.

Further, in carrying out the above-described aspects of the present invention, there is needed a heating treatment device comprising at least,

an ultraviolet light lamp and an infrared light lamp arranged on an upper face side of a substrate to be treated;

an infrared light lamp arranged on a lower face side of the substrate to be treated, and

wherein the ultraviolet light lamp and the infrared light lamps are arranged to interpose the substrate to be treated.

In the above-described aspects of the heating treatment device, the infrared light lamp arranged on the upper face side of the substrate to be treated is an auxiliary lamp for irradiating a region different from a region irradiated by the ultraviolet light lamp.

Further, according to the inventors, the most preferable constitution of the present invention is a constitution where infrared light and ultraviolet light are fabricated in a linear shape and irradiated. In that case, a heating treatment device in which an ultraviolet light lamp and an infrared light lamp are in a rod-like shape or a cylindrical shape having a longitudinal direction in a direction in parallel with a substrate to be treated may be used. Further, it is effective to also arrange cylindrical lenses between the ultraviolet light lamp and the substrate to be treated and between the infrared light lamp and the substrate to be treated.

Further, according to a fifth aspect of the present invention, there is provided a method of fabricating a semiconductor device for subjecting a semiconductor thin film formed on a substrate having a light transmitting performance to a heating treatment by irradiating a strong light, said method comprising the steps of,

irradiating strong beams emitted from at least one lamp light source provided on an upper face side of the semiconductor thin film and at least one lamp light source provided on a lower face side of the semiconductor thin film to the semiconductor thin film, and

carrying out a heat treatment on the semiconductor thin film after the step of irradiating the strong beams.

According to a sixth aspect of the present invention, there is provided a method of fabricating a semiconductor device for irradiating a semiconductor thin film doped with impurities and subjecting the semiconductor thin film to a heating treatment thereby activating the impurities, said method comprising the steps of,

irradiating strong lights emitted from at least one lamp light source provided on an upper face side of the semiconductor thin film and at least one lamp light source provided on a lower face side of the semiconductor thin film to the semiconductor thin film, and

carrying out a heat treatment on the semiconductor thin film after the step of irradiating the strong beams.

In the fifth aspect or the sixth aspect of the present invention, the heat treatment is carried out by a furnace annealing process at 500 through 700.degree. C.

In the fifth aspect or the sixth aspect of the present invention, strain energy of the semiconductor thin film is reduced by the heat treatment.

In the fifth aspect or the sixth aspect of the present invention, the strong lights are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.

In the fifth aspect or the sixth aspect of the present invention, all of the strong lights are scanned in a state of irradiating a same portion of the thin film.

In the fifth aspect or the sixth aspect of the present invention, the strong light from the upper face side is a light whose major component is in a wavelength region capable of subjecting bonds of atoms of the semiconductor thin film to an electron excitation, and

the strong beam from the lower face side is a light whose major component is in a wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to a vibrational excitation.

Further, in the above-described aspects of the present invention, the strong light in the wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to the electron excitation is an ultraviolet light, and

the strong light in the wavelength region capable of subjecting the bonds of the atoms of the thin film to the vibrational excitation is an infrared light.

Further, in the above-described aspects of the present invention, the wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to the electron excitation falls in a range of 10 through 600 nm, and

the wavelength region capable of subjecting the bonds of the atoms of the thin film to the vibrational excitation falls in a range of 500 nm through 20 .mu.m.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are views showing a constitution of a heating treatment according to the present invention;

FIGS. 2A and 2B are views showing a constitution of a heating treatment according to the present invention;

FIG. 3 is a view showing a constitution of a heating treatment according to the present invention;

FIG. 4 is a view showing a constitution of a heating treatment according to the present invention;

FIG. 5 is a diagram showing a difference between thermal energy and optical energy;

FIG. 6 is a view showing a constitution of a heating treatment according to the present invention;

FIGS. 7A and 7B are views showing a constitution of a heating treatment according to the present invention;

FIGS. 8A and 8B are views showing a heating treatment device used in the present invention;

FIGS. 9A and 9B are views showing a heating treatment device used in the present invention; and

FIGS. 10A, 10B, 10C, 10D, 10E and 10F are views showing semiconductor devices as applied products.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One feature of the present invention resides in irradiating a combination of ultraviolet light (UV light) and infrared light (IR light) to a film to be treated.

Further, another feature of the present invention resides in a semiconductor device and a fabrication method of a semiconductor device using a semiconductor thin film provided by a device of irradiating light from both face sides to a film to be treated, particularly irradiating a combination of ultraviolet light (UV light) and infrared light (IR light) from an upper face side and a lower face side thereof.

Incidentally, although ultraviolet light has been described as representative light providing photon energy, visible light can be included so far as it is a light in a wavelength region capable of subjecting a film to be treated to electron excitation. Representatively, light in a wavelength region of 10 through 600 nm can be used.

Further, similarly, although infrared light has been described as representative light providing vibrational energy (may be referred to as thermal energy), visible light can also be included so far as it is a light in a wavelength region capable of subjecting a film to be treated to vibrational excitation. Representatively, light in a wavelength region of 500 nm through 20 .mu.m can be used.

Further, although the above-described wavelength regions overlap in a visible light region of 500 through 600 nm, this is because a wavelength region capable of subjecting a film to be treated to electron excitation or vibrational excitation differs depending on the film to be treated. That is, this does not signify that electron excitation and vibrational excitation are simultaneously caused by light in the same wavelength region.

The above-described ultraviolet light can be obtained with lamps emitting ultraviolet ray such as a low pressure metal vapor lamp, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a halogen arc lamp, a hydrogen arc lamp, a metal halide lamp, a heavy hydrogen lamp, a rare gas resonance line lamp, a rare gas molecular light emitting lamp and the like as light sources.

Further, the above-described infrared light can be obtained with lamps emitting infrared ray such as a halogen lamp, a halogen arc lamp, a metal halide lamp and the like as light sources.

According to light irradiation treatment using ultraviolet light, energy provided to photon is given to a film to be treated in a form of light absorption and directly excites bonds of molecules constituting the film to be treated. Such an excitation phenomenon is referred to as electron excitation. Further, ultraviolet light is preferably irradiated from an upper face side of a film to be treated since the light is apt to be absorbed by a glass substrate.

Meanwhile, according to light irradiation treatment by infrared light, vibrational energy is given in a form of lattice vibration and indirectly excites bonds of molecules constituting a film to be treated as excitation energy. Such an excitation phenomenon is referred to as vibrational excitation. Further, infrared light can be irradiated from a lower face side of the film to be treated since it is difficult to be absorbed by a glass substrate.

Steps of the present invention can achieve effects explained below.

First, in addition to vibrational excitation (excitation by thermal energy) according to the conventional irradiation of infrared light, electron excitation excited by irradiation of ultraviolet light is caused and therefore, the efficiency of exciting a crystalline silicon film 103 is surprisingly promoted by a synergetic effect of these.

That is, bonds of molecules constituting the crystalline silicon film 103 are totally loosened by lattice vibration caused by irradiation of infrared light and are connected to each other in a state in which molecules are extremely active in view of electrons by irradiation of ultraviolet light. Accordingly, a crystalline silicon film 112 which has been subjected to a heating treatment according to the present invention, is formed of a very active state (state where degree of freedom of bond is high).

Therefore, in the crystalline silicon film 112 provided by carrying out the present invention, crystal defects such as unpaired bonds are very few. Further, a grain boundary is formed by a bond having excellent compatibility and therefore, almost all of the grain boundary is formed by an inert boundary such as an inclined boundary.

Further, it seems that since the basic absorption edge of silicon is substantially 1 eV, ultraviolet light is absorbed only by a surface having a thickness of about 10 nm through 1 .mu.m. However, according to the case of embodiments of the present invention, a film thickness of a crystalline silicon film is extremely as thin as 10 through 75 nm (representatively, 15 through 45 nm) and accordingly, sufficient excitation effect can be expected.

Further, the conventional lamp annealing was a lump treatment in respect of all the faces and therefore, when the treatment time period was long, there was a concern where heat is propagated from a film to be treated to a glass substrate and the glass substrate is warped or contracted.

However, according to the present invention, a linear infrared light lamp 108 is used as the light source of an infrared light 111 and therefore, propagation heat conducted from the crystalline silicon film 103 to a substrate 101 is only local. Therefore, the substrate 101 can be prevented from being warped or contracted by heat.

Further, although in this embodiment, a heating treatment method of the present invention is applied to steps of improving the crystalline performance of a crystalline silicon film, the present invention can naturally be applied to a step of crystallizing an amorphous silicon film.

In this way, according to the present invention, the excitation effect of a film to be treated can further be promoted by irradiating ultraviolet light simultaneously with irradiation of infrared light in a heating treatment using a lamp annealing process. That is, an effect of significantly promoting the efficiency of a heating treatment is achieved.

Meanwhile, FIG. 5 shows a conceptual diagram representing a difference between thermal energy and optical energy in which the abscissa designates energy and the ordinate designates energy density. As shown by FIG. 5, the thermal energy is provided with average energy of kT in view of energy and is provided with an energy distribution in a wide range. Meanwhile, the optical energy is provided with a certain value determined by wavelength, that is, energy of hv per se.

Accordingly, when crystals of, for example, a silicon film are grown, although the thermal energy includes also energy for destructing crystals or the like other than energy necessary for growth, the optical energy can efficiently irradiate only energy necessary for growth.

In this way, only a specific thin film can be excited concentratingly by pertinently selecting wavelength of ultraviolet light and therefore, degrees of excitation of different kinds of films to be treated can be controlled or a selective excitation treatment can be carried out. This is one of effects of the present invention where ultraviolet light irradiation is combined with lamp annealing by infrared light.

Also, the present invention is not limited to a combination of lamp annealing by infrared light and ultraviolet light irradiation but, for example, the lamp annealing from an upper face side by infrared light may be combined with lamp annealing by infrared light from a lower face side.

When a lamp annealing process according to the present invention is used in a step of growing crystals of a film whose major component is silicon, an excellent quality semiconductor thin film which is excellent in the uniformity can be provided.

Further, when a lamp annealing process of the present invention is used in a step of activating a film having silicon as a major component and doped with impurities, a source region and a drain region having excellent characteristics can be obtained.

Further, when furnace annealing is conducted after a step of using the lamp annealing process of the present invention, strain energy caused by the step of using the lamp annealing process of the present invention can be reduced or removed.

Accordingly, when the lamp annealing process of the present invention is used, it is preferable to also carry out thermal annealing at later steps.

Embodiment 1

In this embodiment, an explanation will be given of a fabrication method of a semiconductor device in respect of an example of a case where the present invention is applied to a step of improving crystalline performance of a crystalline film whose major component is silicon in reference to FIGS. 1A, 1B and 1C. Incidentally, numerical values, materials, and the like are not limited to those in this embodiment.

First, an underlayer film 102 comprising a silicon oxide film having a thickness of 2000 .ANG. is formed on a glass (or quartz) substrate 101 as a substrate having light transmitting performance. Thereafter, an amorphous silicon film having a thickness of 300 .ANG. through 500 .ANG. or a thickness of 500 .ANG. in this embodiment is piled up directly on the underlayer film by a low pressure thermal CVD (Chemical Vapor Deposition) process or the like.

It is preferable to use means for crystallizing an amorphous silicon film by a heating treatment or laser beam irradiation. Also, it is effective to use means for using a catalyst element promoting crystallization (disclosed in Japanese Unexamined Patent Publication No. JP-A-7-130652). In this way, the crystalline silicon film 103 is obtained. (FIG. 1A) Incidentally, although an explanation will be given of this embodiment with an example of a crystalline silicon film for the crystalline film 103, a compound semiconductor including silicon such as Si.sub.xGe.sub.1-x (O<X<1) or the like can be used.

Further, although the crystalline silicon film includes a single crystal film, a microcrystal film, a polycrystal silicon film or the like, in this embodiment, an explanation will be given with a polycrystal silicon film (so to speak polysilicon film) as an example.

Further, numeral 104 designates a lamp light source emitting ultraviolet light (ultraviolet ray) (hereinafter, simply referred to as ultraviolet light lamp), numeral 105 designates a reflecting mirror and numeral 106 designates a cylindrical lens for converging ultraviolet light 107 emitted from the ultraviolet light lamp 104. Each of the ultraviolet light lamp 104, the reflecting mirror 105 and the cylindrical lens 106 is provided with a shape that is slender in respect of a direction orthogonal to paper face and accordingly, light is irradiated to the crystalline silicon film 103 in a linear shape.

Further, in this embodiment, the ultraviolet light 107 is irradiated from an upper face side of the crystalline silicon film 103. The upper face side indicates a face on the side of a main face opposed to the ultraviolet light lamp 104 in FIG. 1, that is, the side reverse to the glass substrate 101.

Next, numeral 108 designates a lamp light source emitting infrared light (infrared ray) (hereafter, simply referred to as infrared light lamp), numeral 109 designates a reflecting mirror and numeral 110 designates a cylindrical lens for converging infrared light 111 emitted from the infrared light lamp 108. The infrared light 111 is also constituted to form a linear light similar to the ultraviolet light 107.

Further, the infrared light 111 is constituted to irradiate to the crystalline silicon film 103 from a lower face side. Here, the lower face side indicates a face opposed to the side of a rear face side opposed to the infrared light lamp 108 in FIG. 1, that is, the side of the glass substrate 101.

In this case, the infrared light 111 transmits through the glass substrate without being absorbed. That is, even when the infrared light 111 is irradiated from the lower face side, the crystalline silicon film 103 can efficiently be heated. Accordingly, the crystalline silicon film 103 is heated to 600 through 1200.degree. C. (representatively, 700 through 850.degree. C.) by irradiating the infrared light 111. The film face temperature of the crystalline silicon film 103 in this case can be measured (monitored) by using a pyrometer (radiation temperature gage) utilizing a thermocouple.

Further, the glass substrate 101 is supported by a susceptor (not illustrated), the linear ultraviolet light 107 is scanned in a direction of an arrow mark from the upper face side of the glass substrate 101 and the linear infrared light 111 is scanned in a direction of an arrow mark from the lower face side. In this way, a total face of the substrate can be irradiated by scanning the linear lights from one end to other end of the glass substrate 101.

Further, in this embodiment, the ultraviolet light 107 and the infrared light 111 irradiate the same portion of the crystalline silicon film 103. The same portion signifies that ranges of irradiation are located at the same position as shown by FIG. 1B. Naturally, depending on cases, the timings of scanning can intentionally be shifted from each other or the directions of scanning can be made different from each other.

An effect described below can be achieved by the constitution where the ultraviolet light irradiation and the infrared light irradiation are combined as mentioned above.

Further, electron excitation by the ultraviolet light irradiation is caused in addition to vibrational excitation (excitation by thermal energy) by the conventional infrared light irradiation and accordingly, the efficiency of exciting the crystalline silicon film 103 is surprisingly promoted by a synergetic effect of these.

That is, the bonds of molecules constituting the crystalline silicon film 103 are totally loosened by lattice vibration caused by the infrared light irradiation and are connected by constituting a state where the bonds are extremely active by the ultraviolet light irradiation. Therefore, the crystalline silicon film 112 (region designated by hatched lines in FIG. 1) which have been subjected to the heating treatment of the present invention, is formed by a very active state (state having high degree of freedom of bond).

Accordingly, the crystalline silicon film 112 obtained by carrying out the present invention is provided with very few crystal defects such as unpaired bonds. Further, the grain boundary is formed by bonds having excellent compatibility and therefore, almost all of the crystal boundary is formed by an inert boundary such as an inclined boundary.

Further, the basic absorption edge of silicon is substantially 1 eV and accordingly, it seems that ultraviolet light is absorbed only by a surface having a thickness of about 10 nm through 1 .mu.m. However, in the case of the embodiment, the film thickness of the crystalline silicon film is extremely as thin as 10 through 75 nm (representatively, 15 through 45 nm) and therefore, sufficient excitation effect can be expected.

Further, the conventional lamp annealing process is a lump treatment in respect of all the face and therefore, when the treatment time is long, there is a concern where heat is propagated from a film to be treated to a glass substrate and the glass substrate is warped or contracted.

However, the linear infrared light lamp 108 is utilized in the present invention as the light source of the infrared light 111 and therefore, the heat of propagation conducted from the crystalline silicon film 103 to the substrate 101 is only local. Therefore, the substrate 101 can be prevented from being warped or contracted by the heat.

Further, although according to the embodiment, the heating treatment method has been applied in the step of improving the crystalline performance of the crystalline silicon film, the present invention is naturally applicable to a step of crystallizing an amorphous silicon film.

The crystalline silicon film 112 excellent in the crystalline performance has been obtained by carrying out the above-described treatment.

Next, when the above-described treatment has been finished, it is preferable to carry out furnace annealing at 500 through 700.degree. C. (600.degree. C. in this embodiment) for 2 through 8 hours (4 hours in this embodiment). By this heat treatment step, strain energy caused in the semiconductor film by the lamp annealing step described above can be removed or reduced.

When the strain energy remains as it is, it causes film peeling in fabrication process. Further, stress or lattice strain is caused by the strain energy and therefore, electric properties of a semiconductor device are changed. Accordingly, the above-described furnace annealing step is a step which is very effective as a post step of heat treatment accompanied by rapid phase change as in lamp annealing, laser annealing or the like.

Thereafter, the obtained crystalline silicon film is patterned by a photolithography process and separated in islands and an island-like region of a P-