JP2002016084A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device superior in characteristics and reliability. SOLUTION: The device comprises a blocking film formed on a glass substrate, an oxide film formed on the blocking film, a semiconductor film formed on the oxide film, a gate insulating film formed on the semiconductor film, and a gate electrode formed on the gate insulating film. The semiconductor film and the gate insulating film are irradiated with infrared rays. The blocking film is made of a silicon nitride film, and the semiconductor film is set to a thickness of 30-150 nm, and the gate insulating film is set to a thickness of 70-120 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an insulating gate type semiconductor device having good characteristics and high reliability on an insulating substrate at a low temperature of 400.degree. The semiconductor device according to the present invention is used as a drive circuit for an active matrix such as a liquid crystal display, an image sensor, or the like, or as a thin film transistor in an SOI integrated circuit or a conventional semiconductor integrated circuit (a microprocessor, a microcontroller, a microcomputer, a semiconductor memory, or the like). Is what is done.

[0002]

2. Description of the Related Art In recent years, research on forming an insulated gate semiconductor device (MOSFET) on an insulating substrate has been actively conducted. Forming a semiconductor integrated circuit on an insulating substrate in this manner is advantageous in driving the circuit at high speed. Because
This is because the speed of the conventional semiconductor integrated circuit is mainly limited by the capacitance (stray capacitance) between the wiring and the substrate, but such a floating capacitance does not exist on the insulating substrate. A MOSFET formed on an insulating substrate and having a thin-film active layer is called a thin film transistor (TFT). In a conventional semiconductor integrated circuit, for example, SRA
A TFT is used as the M load transistor.

[0003] Recently, a product that requires a semiconductor integrated circuit to be formed on a transparent substrate has appeared. For example, a driving circuit for an optical device such as a liquid crystal display or an image sensor. Here also, a TFT is used. Since these circuits are required to be formed in a large area, a lower temperature of the TFT manufacturing process is required. Also, for example, in a device having a large number of terminals on an insulating substrate, even when the terminals need to be connected to the semiconductor integrated circuit, in order to reduce the packaging density, the first stage of the semiconductor integrated circuit, Alternatively, it has been considered to form the semiconductor integrated circuit itself monolithically on the same insulating substrate.

Conventionally, a TFT has been coated with an amorphous, semi-amorphous, or microcrystalline semiconductor film.
By performing thermal annealing at a temperature of from 1 to 1200 ° C. or irradiating with strong light such as a laser, the crystallinity is improved, and a high quality (ie, sufficiently large mobility) semiconductor film is improved. Things have been done.
Although there is an amorphous TFT using an amorphous material for the semiconductor film, the mobility is as small as 5 cm ² / Vs or less, usually about 1 cm ² / Vs, and a P-channel TFT can be obtained in terms of operation speed. Its use is greatly restricted because of the lack of it. To obtain a TFT having a mobility of 5 cm ² / Vs or more, annealing at the above temperature was necessary. Further, a P-channel TFT (PTFT) could be formed by such annealing.

[0005]

However, among the above processes, especially in the process requiring a high temperature, the substrate material is significantly restricted. That is, in a so-called high-temperature process (a process in which the maximum process temperature is 900 to 1200 ° C.), a high-quality thermal oxide film can be used as a gate oxide film, but the substrate is expensive and has a large area such as quartz, sapphire, or spinel. Only materials that were difficult to convert could be used.

On the other hand, in a low-temperature process (a process having a maximum process temperature of 750 ° C. or less, including a crystallization process by laser irradiation), a wider range of substrate materials can be selected than in a high-temperature process. A technique for forming a good insulating film at high throughput has also been a problem. Although a sputtering method is used as a method for forming an insulating film at a low temperature, the step coverage is poor and the throughput is not sufficient. On the other hand, an organic material containing silicon atoms (hereinafter, referred to as organic silane) such as tetra-tetoxy silane (TEOS) is vaporized and used as a raw material for plasma CVD and reduced pressure CV.
D, a technique for obtaining a high-throughput silicon oxide film at a low temperature by a chemical vapor deposition method such as atmospheric pressure CVD has been known. However, the film thus obtained has many carbon atoms and hydrocarbons. Groups, which formed clusters and became trap centers. For this reason, the insulating properties are not sufficient, and the interface state density is extremely large, so that it cannot be used as a gate insulating film.

A silicon oxide film formed using such an organic silane as a raw material cannot be used as it is for a material requiring sufficient electrical characteristics, such as a gate insulating film, and is usually used at a temperature of 600 ° C. or higher. Long-term oxidation treatment was required. Such heat treatment damages the substrate,
This is a problem that causes a reduction in throughput.

The present invention has been made in view of such circumstances, and has as its object to form an oxide film having good step coverage at a low temperature, improve the throughput, and further improve the quality of the oxide film. In addition, by accumulating such technologies, the maximum process temperature is 400 ° C or less.
A method for producing T is proposed.

[0009]

The first method of the present invention is as follows.
A silicon oxide film is formed by decomposing and depositing organic silane by various CVD methods, and the characteristics thereof are improved by irradiating a pulsed laser beam. In particular, carbon and hydrocarbon groups contained in the film are eliminated. The purpose is to eliminate the trap center and use it for the gate insulating film of the TFT. As the pulse laser used in the present invention, KrF, ArF, XeCl, XeF
Ultraviolet lasers such as excimer lasers are desirable. It is desirable to use ultraviolet light or infrared light as strong light. The ultraviolet light has an action of eliminating carbon and hydrocarbon groups contained in the film, as described later. The infrared light has the effect of rapidly heating the film and reducing trap centers such as defects and dangling bonds in the film.

[0010] It is also possible to improve the crystallinity of the semiconductor film (for example, change from an amorphous state to a crystallized state) by laser irradiation or infrared light irradiation. Of course, it is also possible to separately improve the crystallinity of the semiconductor film and modify the silicon oxide film.

According to a second method of the present invention, a silicon oxide film is formed by decomposing and depositing an organic silane by various CVD methods, and this is exposed to an oxidizing atmosphere containing oxygen, ozone, nitrogen oxide and the like. Up to 150 to 400 ° C., while being heated, removes carbon and hydrocarbon groups contained in the film by irradiation with ultraviolet light having a wavelength of 300 nm or less,
The purpose is to eliminate the trap center and use it for the gate insulating film of the TFT.

Of course, even more advantages can be obtained by combining the first and second inventions. For example, a silicon oxide film made of an organic silane is exposed to an oxidizing atmosphere,
It may be heated to 150 to 400 ° C. and irradiated with an ultraviolet laser having a wavelength of 300 nm.

[0013] Organic silanes such as TEOS (including those in which some of the hydrocarbon groups, ethoxy groups, hydrogen, etc. are replaced by fluorine) are often liquid at normal pressure and room temperature. In response, the temperature is increased under reduced pressure to vaporize and introduced into the reaction chamber. Plasma CVD
When a silicon oxide film is obtained by a method, an appropriate amount of oxygen is mixed with an organic silane, and an inert gas such as argon or helium is mixed as a carrier gas to carry out a reaction. In the case of manufacturing by low pressure CVD or normal pressure CVD, the reaction may be carried out by mixing organic silane and ozone and, if necessary, mixing the above carrier gas.

As a result, annealing for improving the crystallinity of the semiconductor film no longer determines the maximum process temperature, but other factors (for example, hydrogenation anneal and gate oxide film anneal) determine the maximum process temperature. And the range of substrate selection is significantly improved. Specifically, the maximum process temperature is 400 ° C. or less. In particular, in the related art, the pattern has shifted on a large-area substrate due to the effects of thermal expansion, warpage, and the like. However, in the present invention, since the process is performed at 400 ° C. or lower as described above, no problem occurs. For example, a large number of TFTs can be manufactured with extremely high precision even on a large substrate of 300 mm × 400 mm. For this reason, it is possible to improve the throughput by multi-panning.

Regarding the selection of the substrate, for example, soda glass has a low softening point, and it has been conventionally impossible to form and operate a TFT on the TFT. , The TFT can be operated.

A first application example of the present invention is a peripheral circuit of an active matrix (AM) type liquid crystal display device (LCD) using an amorphous silicon (a-Si) TFT. The a-SiTFT-AMLCD uses a non-alkali glass (for example, Corning 7059) as a substrate and forms an a-SiTFT at a temperature of usually 400 ° C. or less. a-Si TFT has a high OFF resistance,
Although it is ideal as an active matrix switching element, the peripheral drive circuit uses a single crystal integrated circuit (IC) because the operation speed is slow and a CMOS cannot be formed as described above. The terminals of the matrix are connected to the terminals of the IC by a method such as TAB. However, such a mounting method becomes more difficult as the size of the pixel becomes smaller, and the cost required for mounting occupies a large part of the module.

However, in the conventional process, it is difficult to form a peripheral circuit on the same substrate as the matrix because of a thermal problem. However, according to the present invention, a TFT having higher mobility can be formed at the same temperature as that required for forming an a-Si TFT.

A second application is to form a TFT on a material such as soda glass which is less expensive than non-alkali glass. In this case, when the TFT is formed in close contact with soda glass, mobile ions such as sodium contained in the glass enter, so that an insulating film containing silicon nitride or aluminum oxide as a main component is formed on the glass. Further, it is desired to form a TFT by applying the present invention after forming a base insulating film with a material such as silicon oxide thereon. To reduce defects, it is preferable to use a PTFT as a matrix TFT rather than an NTFT. This is because, in the case of NTFT, when mobile ions enter from the substrate, a channel is formed and the TFT is always on. On the other hand, in the case of PTFT, no channel is formed even if mobile ions enter.

As a third application example, there is a peripheral circuit of a simple matrix LCD that performs static driving. For example, a ferroelectric liquid crystal material (FLC) has a memory property, so that a high contrast can be obtained even with a simple matrix, but conventionally, a peripheral circuit is a-SiTFT-AMLC.
As in D, the IC was connected by a method such as TAB. Similarly, an LCD which performs a static operation using a phase change between a cholesteric phase and a nematic phase of a liquid crystal also has a peripheral circuit connected by TAB. LCDs that perform static driving by combining a nematic liquid crystal and a ferroelectric polymer (see, for example,
1152) has also been proposed, but the peripheral circuit is still TA
B connection is assumed.

Since these LCDs are simple matrices, they are characterized in that a large screen can be obtained using an inexpensive substrate and higher definition can be obtained at the same time. In order to achieve high definition, the pitch between terminals must be narrowed, but this makes it difficult to mount ICs.
According to the present invention, a peripheral circuit can be formed monolithically without worrying about a thermal problem even with an inexpensive substrate.

As a fourth application example, a TFT is formed in a semiconductor integrated circuit after a metal wiring is formed.
A so-called three-dimensional IC can be used. Various other applications are also possible. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0022]

[Embodiment 1] FIG. 1 shows an example of manufacturing a TFT according to the present invention. First, a substrate (Corning 705)
9, 300mm x 300mm or 100mm x 10
0 mm) 101 as a base oxide film 102 having a thickness of 100
A silicon oxide film having a thickness of about 300 nm was formed. As a method for forming this oxide film, a sputtering method in an oxygen atmosphere or TEO
A film obtained by decomposing and depositing S by plasma CVD is 450 to 6
Annealing may be performed at 50 ° C.

After that, the amorphous silicon film 103 is formed in a thickness of 30 to 1 by plasma CVD or LPCVD.
Deposited 50 nm, preferably 50-100 nm. Then, as shown in FIG. 1A, the crystallinity of the silicon film 103 was improved by irradiation with a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec). The laser irradiation device shown in FIG. 3B was used. This improvement in crystallinity is achieved by RTA (rapid thermal annealing).
Alternatively, the irradiation may be performed by irradiating a strong light equivalent to a laser beam. It is also effective to anneal the silicon film crystallized by laser light irradiation or heating by the above-mentioned strong light irradiation to further promote the crystallinity. In particular, when infrared light (for example, halogen light having a peak at a wavelength of 1.3 μm) is used as the strong light, the silicon film absorbs more than the glass substrate, so that only the silicon film is selectively heated. Can be useful.

During laser irradiation, the temperature of the sample is set to 150
Heated to ~ 400 ° C. The atmosphere is 10 mtorr
It was as follows. As a result, the crystallinity could be improved. Laser energy density is 200-400mJ /
cm ² , preferably 250 to 300 mJ / cm ² . When the crystallinity of the silicon film 103 thus formed was examined by Raman scattering spectroscopy, the crystallinity was 515 different from the peak of single crystal silicon (521 cm ⁻¹ ).
A relatively broad peak was observed around cm ^-1 .

Next, the silicon layer 103 was patterned into an island shape to form an NTFT region 104 and a PTFT region 105. Furthermore, using TEOS as a raw material, the substrate temperature is 150 to 400 ° C., preferably 200 to 250 ° C. together with oxygen.
Then, the silicon oxide film was decomposed and deposited by the RF plasma CVD method, and this was used as the gate oxide film 106. The pressure ratio between TEOS and oxygen is 1: 1 to 1: 3, and the pressure is 0.05 to
0.5 torr and RF power were 100-250W. In this step, the substrate temperature is set to 150 to 400 ° C., preferably 2 ° C., using TEOS as a raw material together with ozone gas by a low pressure CVD method or a normal pressure CVD method.
It may be formed at 00 to 250 ° C.

Such an oxide film contains a large amount of hydrocarbon groups, so that the film has a large number of trap centers and cannot be used as a gate oxide film as it is. Therefore, laser irradiation was performed by the apparatus shown in FIG. 3B to reduce the number of trap centers in the oxide film. As shown in the figure, an oxygen gas inlet 310, an exhaust port 313, and a quartz window 309 are provided in a chamber 308, and a holder 311 having a heater 314 is disposed in the chamber. 312 is placed. Then, the sample is irradiated with laser light or strong light through the window 309. By performing this strong light irradiation, the number of trap centers in the oxide film can be reduced, and the interface between the semiconductor and the silicon oxide film can be modified and the density of the silicon oxide film can be increased.

This step is performed as follows. First, after the chamber is evacuated to a sufficient vacuum, oxygen, ozone, or nitrogen oxide (NO ₂ , NO, N ₂ O
Etc.) are introduced. Then, irradiation with laser light or strong light is performed. This irradiation is performed under a reduced pressure of 10 torr or less or in an oxidizing atmosphere at atmospheric pressure. Laser is KrF
It is common to use laser light. As the intense light, incoherent ultraviolet light may be used. When laser light is used, the energy density is
Set to 300 mJ / cm ² and the number of shots is 10
Times. At this time, preferably, the temperature is 150 to 400.
° C, typically 300 ° C. It is also useful to perform RTO (rapid thermal oxidation) using infrared light, for example, halogen light (wavelength: 1.3 μm) as strong light. This method reduces the number of trap centers in the oxide film by performing rapid heating using infrared light. When this method is used, the surface to be irradiated is rapidly heated to a temperature of 1000 to 1200 degrees, and the characteristics of the interface between the semiconductor and the gate oxide film are improved. As a result of such annealing, the interface state density of the gate oxide film can be reduced to 10 ¹¹ cm ^-2 or less.

Thereafter, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method, and this is patterned, and as shown in FIG.
07 and 108 were formed. At this time, since aluminum needs to withstand the subsequent laser irradiation, an aluminum film having a high reflectance formed by electron beam evaporation was used. The surface of the aluminum film formed by electron beam evaporation was so flat that the presence of grains could not be confirmed by an optical microscope. As a result of observation with an electron microscope, the size of the grains was 200 nm or less. That is, the particle size must be smaller than the wavelength of the laser used.

Thereafter, impurities were implanted into the island-like silicon film of each TFT in a self-aligned manner by using the gate electrode as a mask by an ion doping method. At this time, first, phosphorus is implanted into the entire surface using phosphine (PH ₃ ) as a doping gas, and then only the island-like region 104 in the figure is covered with a photoresist, and diborane (B ₂ H ₆ ) is used as a doping gas. , Boron was implanted only in the island-like region 105.
The dose amounts are 2 to 8 × 10 ¹⁵ cm ⁻² for phosphorus and 4-1 for boron.
It was set to 0 × 10 ¹⁵ cm ⁻² so that the dose of boron exceeded that of phosphorus.

Further, as shown in FIG. 1D, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns)
ec) was applied to improve the crystallinity of the portion where the crystallinity was deteriorated by introducing the impurity region. In this case, the device shown in FIG. 3B was also used. Laser energy density is 200-400mJ /
cm ² , preferably 250 to 300 mJ / cm ² . The sample was not specifically heated. Thus, the N-type impurities (phosphorus) were formed in the regions 109 and 110, and the P-type impurities (boron) were formed in the regions 111 and 112. The sheet resistance in these regions was 200 to 800 Ω / □. After that, a silicon oxide film having a thickness of 300 nm was formed as an interlayer insulator 113 on the entire surface by using TEOS as a raw material and plasma CVD with oxygen, reduced pressure CVD with ozone, or normal pressure CVD. The substrate temperature is 150-400 ° C,
Preferably, the temperature was set to 200 ° C to 300 ° C.

Then, contact holes are formed in the source / drain of the TFT, and aluminum wirings 114 to 11 are formed.
6 was formed. FIG. 1E shows the left NTFT and PT.
It is shown that an inverter circuit is formed by FT. TFT mobility is 50-100 cm ² for NTFT
/ Vs and 30-100 cm ² / Vs were obtained with PTFT. In this embodiment, since the maximum process temperature is 400 ° C. or less, no shrinkage or warpage of the substrate is caused by non-alkali glass such as Corning 7059. For this reason, even if the substrate is large as in this embodiment, the pattern is hardly displaced, which is convenient when applied to a large-area display or its driving circuit.

Example 2 TF was placed on a soda glass substrate.
An example in which T is formed and an active matrix liquid crystal display element is manufactured will be described. As the substrate 201, a soda glass substrate (thickness: 1.1 mm, 300 × 400 mm) was used. Since soda glass contains a large amount of sodium,
In order to prevent this sodium from diffusing into the TFT, the thickness is 5 to 50 nm, preferably 5 to 2 nm, by plasma CVD over the entire surface.
A 0-nm-thick silicon nitride film 202 was formed. As described above, the technique of coating a substrate with a film of silicon nitride or aluminum oxide to form a blocking layer is disclosed in Japanese Patent Application Nos. 3-238710 and 3-238 filed by the present inventors.
714.

Next, after forming a base oxide film 203 (silicon oxide), a silicon film 204 (thickness: 30 to 150 nm, preferably 3 nm) is formed by LPCVD or plasma CVD.
After dehydrogenation was performed at 400 ° C. for 1 hour, this was patterned to form an island-shaped semiconductor region (TFT active layer). Further, a gate insulating film (thickness of 70 to 120 nm, typically 100 nm) of silicon oxide 20 is formed by plasma CVD in an oxygen atmosphere using tetraethoxysilane (TEOS) as a raw material.
5 was formed. The substrate temperature was set to 400 ° C. or less, preferably 200 to 350 ° C. in order to prevent shrinkage and warpage of the glass. However, at such a substrate temperature, a large amount of hydrocarbon groups are contained in the oxide film, and many recombination centers are present. For example, the interface state density is 10 ¹² cm ⁻² or more, and the oxide film is used as a gate insulating film. Was of an unusable level.

Therefore, as shown in FIG. 2A, a KrF laser beam or an intense light equivalent thereto is irradiated to improve the crystallinity of the silicon film 204 and at the same time, to combine recombination centers (traps) of the gate oxide film 205. (Center) was reduced, and the characteristics of the gate oxide film 205 were improved. That is, in the present step, two actions, which are performed in the first embodiment in two steps, that is, crystallization of the silicon film and improvement of the gate oxide film, are performed in one step. In this case, if strong light is used, an annealing method using infrared light (eg, halogen light having a wavelength of 1.3 μm) is effective.

Preferably, the laser irradiation is 10 torr.
This is performed under reduced pressure in an oxygen excess atmosphere of r or less. This is because carbon atoms in the oxide film are more easily released under reduced pressure. The oxygen partial pressure is, for example, 1 to 10 torr.
And At this time, the energy density of the laser light is 2
The setting was 50 to 300 mJ / cm ^2, and the number of shots was 10 times. Preferably, the temperature is 150-400
° C, typically 300 ° C. The laser irradiation apparatus shown in FIG. 3B was used. As a result, the crystallinity of the silicon film 204 was improved, and the interface state density of the gate oxide film was also reduced to 10 ¹¹ cm ⁻² or less.

Next, an aluminum gate electrode 208 is formed in the same manner as in Example 1, the substrate is immersed in an electrolytic solution, and this is used as an anode. The coating 209 has a thickness of 206
nm. Such anodizing technology is disclosed in Japanese Patent Application Nos. 4-30220 and 4-3863 filed by the present inventors.
7 and 4-54322. FIG. 2B shows a state in which this step is completed. After the anodization step is completed, a negative voltage, for example, -100 to
A voltage of -200 V may be applied for 0.1 to 5 hours. At this time, the substrate temperature is preferably set to 100 to 250C, typically 150C. By this step, mobile ions in the silicon oxide or at the silicon oxide-silicon interface are attracted to the gate electrode (Al). The technique of applying a negative voltage to the gate electrode after or during anodic oxidation is described in Japanese Patent Application No. 4-115503 (filed on Apr. 7, 1992) filed by the present inventors. Have been.

Thereafter, boron as a P-type impurity is implanted into the silicon layer in a self-aligned manner by an ion doping method.
The source / drain 208 and 209 of FT are formed, and further, as shown in FIG. 2C, a KrF laser beam is irradiated to the source / drain 208 and 209 to reduce the crystallinity of the silicon film whose crystallinity is deteriorated due to the ion doping. Was improved. At this time, the energy density of the laser beam is 250 to 300 mJ /
cm ² . By this laser irradiation, this T
FT source / drain sheet resistance is 300-800
Ω / □. In this step, it is also useful to perform annealing by irradiation with strong light, preferably infrared light.

After that, the interlayer insulator 2 is made of polyimide.
10 was formed, and the pixel electrode 211 was formed by ITO. Then, a contact hole is formed, and T
Electrodes 212 and 213 were formed of a chromium / aluminum multilayer film in the source / drain regions of the FT, and one of the electrodes 213 was also connected to ITO. The chromium / aluminum multilayer film has a chromium film of 20 to 200 n underneath.
m, typically 100 nm, with an aluminum film 10
It is made of deposited 0-2000 nm, typically 500 nm. It is desired that these are continuously formed by a sputtering method. Finally, annealing in hydrogen at 200 to 300 ° C. for 2 hours completed the hydrogenation of silicon. Thus, the TFT was completed. A large number of TFTs manufactured at the same time were arranged in a matrix to form an active matrix type liquid crystal display device.

Embodiment 3 FIG. 1 shows an example of manufacturing a TFT according to the present invention. First, a silicon oxide film having a thickness of 100 to 300 nm was formed as a base oxide film 102 on a substrate 101. After that, the amorphous silicon film 103 is formed by plasma CVD or LPCVD to 30 to 1 μm.
Deposited 50 nm, preferably 50-100 nm. Then, as shown in FIG. 1A, the crystallinity of the silicon film 103 was improved by irradiation with a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec). This crystallization may be performed by heating the silicon film to 1000 to 1200 degrees by irradiating strong light equivalent to laser light.

Next, the silicon layer 103 was patterned into an island shape to form an NTFT region 104 and a PTFT region 105. Furthermore, RF plasma CV using TEOS as a raw material
The silicon oxide film was decomposed and deposited by Method D, and this was used as a gate oxide film 106. Such an oxide film contains a large amount of hydrocarbon groups, so that the film has many trap centers and cannot be used as a gate oxide film as it is. Therefore, laser irradiation or an equivalent strong light irradiation was performed by the apparatus shown in FIG. 3A to reduce the number of trap centers in the oxide film. At the same time, the density of the oxide film was increased. Irradiation with intense light is performed by irradiation with ultraviolet light or by rapid heating by irradiation with infrared light. FIG. 3 shows that the chamber 301
Shower-like oxygen gas inlet pipe 305 and exhaust port 30
6. An apparatus in which an ultraviolet lamp 303 is provided, a holder 302 having a heater 307 is disposed in a chamber, a sample 304 is placed thereon, and annealing is performed by irradiation of ultraviolet light. In this case, an ultraviolet lamp whose power consumption is 40 W and whose emission spectrum has a peak around 250 nm is used.

In the chamber, shower-like oxygen, ozone, or nitrogen oxide (NO ₂ , NO, N ₂ O, etc.) was sprayed on the sample. In particular, the chamber was not evacuated to a vacuum. The ultraviolet light irradiation treatment was performed at atmospheric pressure. The photochemical reaction between the ultraviolet light and the oxidizing gas produces oxygen or ozone in an active state, which reacts with carbon, hydrocarbons, etc. in the silicon oxide film to reduce the carbon atoms in the film to a sufficient amount. Could be reduced to Preferably, the temperature of the sample is 150-400 ° C, typically 3
It is good to keep it at 00 ° C. As a result, the interface state density of the gate oxide film was reduced to 10 ¹¹ cm ^-2 or less.

Instead of the device of FIG. 3A, FIG.
May be used. This apparatus includes an oxygen inlet 320 and an exhaust port 321 in a chamber 315,
An ultraviolet lamp 317 is provided, and a heater 316 and a holder 318 thereon are arranged in the chamber, and a sample 319 is placed thereon. In this apparatus, after evacuating the chamber to a sufficient vacuum, an oxidizing gas such as oxygen, ozone, or nitrogen oxide was introduced.

Thereafter, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method, and this is patterned, and as shown in FIG.
07 and 108 were formed. Further, impurities are implanted into the island-like silicon film of each TFT in a self-aligned manner by using the gate electrode portion as a mask by ion doping.
As shown in (D), a KrF excimer laser (wavelength 2
Irradiation of 48 nm and a pulse width of 20 nsec) was performed to improve the crystallinity of the portion where the crystallinity was deteriorated by introducing the impurity region. Thus, the N-type impurity (phosphorus) is
09 and 110 are doped with P-type impurities (boron) in the regions 111 and 1.
No. 12 was formed. The sheet resistance in these regions is 200-
It was 800 Ω / □. Then, an interlayer insulator 11 is formed on the entire surface.
3, a silicon oxide film having a thickness of 30
0 nm was formed.

Then, contact holes are formed in the source / drain of the TFT, and aluminum wirings 114 to 11 are formed.
6 was formed. FIG. 1E shows the left NTFT and PT.
It is shown that an inverter circuit is formed by FT. TFT mobility is 50-100 cm ² for NTFT
/ Vs and 30-100 cm ² / Vs were obtained with PTFT. In addition, in the shift register (five stages) manufactured in this manner, driving at 10 MHz or more at a drain voltage of 20 V was confirmed.

[0045]

According to the present invention, a TFT can be manufactured at a very low temperature and with a high yield. In particular, forming a TFT on a large-area substrate and using it for an active matrix or a driving circuit has a great industrial impact.
Although not shown in the embodiments, the present invention may be used to form a so-called three-dimensional IC in which a semiconductor circuit is further stacked on a single crystal IC or another IC. In the embodiments, examples in which the present invention is mainly applied to various types of LCDs have been described. However, it is obvious that the present invention can be implemented in other circuits required to be formed on an insulating substrate, such as an image sensor. .

[Brief description of the drawings]

FIG. 1 shows a method for manufacturing a TFT according to the present invention.

FIG. 2 shows a method for manufacturing a TFT according to the present invention.

FIG. 3 shows a conceptual diagram of a laser and ultraviolet light processing device used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Insulating substrate 102 Base oxide film 103 Semiconductor region 104 Island semiconductor region (for NTFT) 105 Island semiconductor region (for PTFT) 106 Gate insulating film 107 Gate electrode (for NTFT) 108 Gate electrode (for PTFT) 109, 110 N -Type impurity region 111, 112 P-type impurity region 113 Interlayer insulator 114-116 Metal wiring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H092 JA25 JA33 JA34 JA37 JA41 KA04 KA05 MA05 MA08 MA09 MA25 MA29 MA30 NA21 NA25 NA27 5F052 AA02 AA11 AA17 AA18 AA24 BB07 DA02 DB02 DB03 JA01 5F110 AA17 AA28 BB02 BB04 BB02 BB02 BB02 BB02 BB02 BB04 DD12 DD13 DD14 DD17 EE03 EE34 EE43 FF02 FF29 FF30 FF32 FF36 GG02 GG13 GG25 GG45 GG47 HJ01 HJ04 HJ12 HJ23 HL03 HL04 HL07 HL11 HL23 HM14 NN03 NN04 NN23 NN27 NN35 NN72 PP02 PP03

Claims (6)

[Claims] 1. A blocking film formed on a glass substrate, an oxide film formed on the blocking film, a semiconductor film formed on the oxide film, and a gate insulating film formed on the semiconductor film A semiconductor device, comprising: a film; and a gate electrode formed on the gate insulating film, wherein the semiconductor film and the gate insulating film are irradiated with infrared light. 2. A silicon nitride film formed on a glass substrate, an oxide film formed on the silicon nitride film, a semiconductor film formed on the oxide film, and a silicon nitride film formed on the semiconductor film. A semiconductor device comprising: a gate insulating film; and a gate electrode formed on the gate insulating film, wherein the semiconductor film and the gate insulating film are irradiated with infrared light. 3. A silicon nitride film formed on a glass substrate, an oxide film formed on the silicon nitride film, a semiconductor film having a thickness of 30 to 150 nm formed on the oxide film, and the semiconductor A gate insulating film having a thickness of 70 to 120 nm formed on the film; and a gate electrode formed on the gate insulating film. The semiconductor film and the gate insulating film are irradiated with infrared light. A semiconductor device, comprising: 4. The semiconductor device according to claim 1, wherein said semiconductor film is made of crystalline silicon. 5. The semiconductor device according to claim 1, wherein said infrared light is halogen light. 6. The semiconductor device according to claim 1, wherein the semiconductor device is a thin film transistor used for an active matrix type liquid crystal display device.