JP2013074255A - Method and device for manufacturing thin film transistor using oxide semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin film transistor (TFT) using an amorphous metal oxide semiconductor whose processing to give semiconductor characteristics to an oxide is performed at a low temperature and processing time is reduced.SOLUTION: An amorphous metal oxide semiconductor on a work 7 on a work stage 8 is subjected to a step A and a step B. In the step A, light is radiated that includes a wavelength region in which active oxygen is generated and a wavelength region in which the oxide is activated and hydrogen mixed in the oxide is extracted. In the step B, light is radiated that includes a wavelength region for heating the oxide so as to promote diffusion of oxygen into the oxide under a state where hydrogen mixed with the oxide is extracted and active oxygen is generated in the vicinity of the oxide. The step A is performed by radiating light from, for example, a rare gas fluorescent lamp 10 or a flash lamp that radiates light including the light of the wavelength region of a wavelength 230 nm or shorter. The step B is performed by radiating light from, for example, a flash lamp 20 that radiates the light of the wavelength region of a wavelength 800 nm or longer.

Description

  The present invention relates to a method and an apparatus for manufacturing a thin film transistor (TFT) using an oxide semiconductor which is an active element for driving a video display such as a liquid crystal panel and an organic EL display, and more particularly, a TFT using an oxide semiconductor. The present invention relates to a method and an apparatus related to the improvement of the operation.

  FIG. 22 shows a configuration example of a thin film transistor (TFT) which is an active element for driving a video display. FIG. 22 shows a structure example of a bottom gate type TFT as an example. A gate insulating film 102 made of, for example, a SiNx film is applied on an upper portion of the gate 101 made of, for example, Ta, Mo, Al, etc., formed in one pixel region on the substrate 100. Furthermore, the semiconductor layer 103 is superimposed on the upper part. A part of the semiconductor layer 103 is provided with a source 104 and a drain 106 made of, for example, a low resistance Al-based alloy. A source wiring 105 made of, for example, a low resistance Al-based alloy layer is provided in the source 104 of the TFT configured as described above, and a drain wiring 107 made of, for example, a low-resistance Al-based alloy layer is provided in the drain 106. It is done. Although not shown, the gate 101 is provided with a gate wiring.

  An interlayer insulating film (organic insulating film) 108 made of, for example, an acrylic resin is provided so as to cover the upper part of such TFT, source wiring, drain wiring, and gate wiring. A part of the interlayer insulating film 108 is removed by a photoetching process, and a contact hole 109 is formed on the drain wiring 107. A liquid crystal driving electrode 110 (transparent electrode (ITO)), which is a pixel electrode, is provided on the entire surface of the interlayer insulating film 108. Therefore, the liquid crystal driving electrode 110 is connected to the drain wiring 107 through the contact hole 109 and can also be provided above the source wiring 105 and the gate wiring (not shown) through the interlayer insulating film 108. That is, the effective area (aperture ratio) of the liquid crystal driving electrode 110 can be increased.

  In the current video display industry, LCD (liquid crystal panel) using glass as a substrate and using a hydrogenated amorphous silicon (a-Si: H) film as a semiconductor layer of TFT is mainly used. That is, in a video display that has been increasing in size in recent years, a hydrogenated amorphous silicon (a-Si: H) film is formed on a large area substrate at a relatively low temperature (about 250 to 300 ° C.) at which the glass substrate does not melt. ) Is useful as a semiconductor layer of a TFT.

As described above, although it is a-Si: H useful as a semiconductor layer material of TFT, there is a defect that electron mobility is low. Therefore, the characteristics are insufficient for application to a three-dimensional display panel that requires high-speed operation of an active element. Corresponding to this, it is conceivable to employ polycrystalline silicon (p-Si) as a semiconductor layer material whose electron mobility is higher than that of a-Si: H.
However, the p-Si film has a drawback that the manufacturing process is longer than that of the a-Si: H film, and it is difficult to manufacture with a large substrate.

In recent years, research on video displays using a flexible substrate using an organic EL element or an electrophoretic element has been advanced. A plastic film or the like is used as the flexible substrate. Here, a film substrate using a plastic film has a low heat resistance of about 150 ° C., and when a-Si: H is used as a semiconductor layer of a TFT, the film substrate is damaged in the film formation process of the a-Si: H film. Occurs. If an a-Si: H film is formed at 150 ° C. or lower, the TFT performance as an active element is degraded.
Also, when p-Si is used as the semiconductor layer of the TFT, a heat treatment step of 600 ° C. or higher is required in the p-Si film forming step, and it is impossible to form a p-Si film on the film substrate. Impossible.

In contrast to the current situation as described above, in recent years, the semiconductor layer material can be formed at a temperature lower than the heat resistant temperature of the film substrate (for example, about room temperature), and the electron mobility is 10 times or more that of a-Si: H. Oxide semiconductors are attracting attention.
In Patent Document 1, an oxide thin film made of indium (In), gallium (Ga), and zinc (Zn) (hereinafter referred to as IGZO) is used as an oxide semiconductor applied to a semiconductor layer material of a TFT. An example of use as a semiconductor layer is shown.
In the case of an IGZO amorphous thin film, it is possible to form a film at a low temperature by using a general-purpose film forming method such as a sputtering method, and since there is an advantage that there is no crystal grain boundary, flexibility and a low temperature process are required. It is possible to form a film on a film substrate as described above, and to construct a TFT having uniform characteristics over a large substrate.

  As described above, an oxide semiconductor has an electron mobility of 10 times or more that of a-Si: H. Therefore, a liquid crystal panel with high-speed response can be configured by combining with an liquid crystal capable of high-speed operation. Such a liquid crystal panel can also be applied to a three-dimensional display panel. In particular, by combining an active element using an oxide semiconductor TFT and a blue phase liquid crystal, a field sequential color method can be adopted as a display method for a liquid crystal panel.

Comparing a liquid crystal panel mounted with a TFT using an ordinary a-Si: H film and a liquid crystal panel mounted with a TFT using an oxide semiconductor film, the TFT chip using an oxide semiconductor is used when the driving power is equal. Is smaller than the area of the TFT chip using the a-Si: H, so that the liquid crystal panel mounted with the TFT using the oxide semiconductor film has a liquid crystal panel mounted with the TFT using the a-Si: H film. Compared to That is, energy saving by improving the aperture ratio can be achieved in a liquid crystal panel including a TFT using an oxide semiconductor film.
Further, when the area of the TFT chip using the oxide semiconductor and the area of the TFT chip using the a-Si: H are the same, the current that can flow to the former is larger than the current that can flow to the latter. Therefore, it is possible to increase the luminance of an organic EL display in which an organic EL element (organic light-emitting diode (OLED)) and a TFT using an oxide semiconductor film are combined.
Note that as examples of the oxide semiconductor used for the above-described TFT, in addition to amorphous IGZO, two-component In—Zn—O, In—Ga—O, Zn—Sn—O, and three-component Sn—Ga—Zn are used. Non-patent document 1 reports a metal oxide such as —O.

WO2005 / 088726A1 JP 2007-311404 A JP 2010-205798 A

H. Q. Chiang et al, “Thin film transducers with amorphous indium gallium oxide channel layers”, J. Vac. Sci. Technol. B24 (6), p2702-p2705 (2006).

Here, an oxide film such as IGZO usually contains hydrogen, oxygen defects are generated, and does not exhibit semiconductor characteristics. Therefore, in order to recover oxygen defects of an oxide film such as IGZO and impart semiconductor characteristics to the film, heat treatment of the oxide film has been conventionally performed. For example, in Patent Document 2, thermal annealing is performed on an oxide film that is IGZO in an atmosphere of an oxidizing gas (for example, oxygen radical, ozone, water vapor, oxygen) at 200 ° C. or more and 600 ° C. or less. Thus, it is described that semiconductor characteristics are imparted to an oxide film to improve TFT characteristics. Specifically, it is shown that heat treatment is performed for 1 hour at a heat treatment temperature of 400 ° C.
Patent Document 3 describes that a TFT using an amorphous IGZO film is heat-treated in a mixed atmosphere of water vapor and oxygen gas at a temperature of 200 to 500 ° C. for 0.5 to 3 hours.

As described above, in order to provide a practical TFT adopting an amorphous metal oxide semiconductor as a semiconductor layer material, it is necessary to perform thermal annealing after forming an oxide film on the substrate. Therefore, even if an oxide film is formed on the film substrate at a temperature lower than the heat resistant temperature of the film substrate (for example, 150 ° C.) and the TFT is formed on the film substrate, the temperature exceeding the heat resistant temperature of the film substrate is eventually reached. If the thermal annealing treatment is not performed, semiconductor characteristics cannot be imparted to the oxide film, and practical TFT characteristics cannot be obtained. Therefore, it is difficult to construct a TFT having good characteristics on the film substrate.
Further, since the heat treatment time itself must be performed for several hours, the throughput of manufacturing the TFT is increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to manufacture a thin film transistor (TFT) employing an amorphous metal oxide semiconductor as a semiconductor layer material as an active element of a video display. A semiconductor property is imparted to the provided oxide, and further, the treatment of the oxide for improving the TFT property is improved by reducing the property of the oxide imparted with the semiconductor property, thereby shortening the treatment time. A thin film transistor manufacturing method using an oxide semiconductor and an apparatus for manufacturing a thin film transistor using an oxide semiconductor are provided.

The present invention has been made in view of the above circumstances, and a method for manufacturing a thin film transistor using an amorphous metal oxide semiconductor according to the present invention includes, in addition to a conventional thermal annealing process for an oxide film, An active oxygen generation process is performed.
Specifically, in the present invention, an amorphous metal oxide film formed on a substrate in an oxygen-containing atmosphere is irradiated with light including a wavelength range where active oxygen is generated and a wavelength range where the oxide film is activated. A light including a wavelength region for heating the oxide so as to promote diffusion of oxygen into the oxide in a state in which active oxygen is generated and an oxide film is activated at least in a state where the oxide is activated (hereinafter, step A). Includes a thermal annealing step (hereinafter, step B).
In the step A, as the lamp for irradiating light in the wavelength range, a rare gas fluorescent lamp that emits light including a wavelength range of 230 nm or less, or a flash lamp such as a xenon flash lamp can be used. In the step B, as the lamp that irradiates light in the wavelength range, a flash lamp such as a xenon flash lamp that emits light including a wavelength range of 800 nm or more can be used.
That is, in the present invention, the above-described problem is solved as follows.
(1) A method of manufacturing a thin film transistor in which at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film are formed on a substrate, and the semiconductor layer is made of an amorphous metal oxide, in an oxygen-containing atmosphere Then, the process including the following steps A and B is performed on the oxide provided on the substrate.
Step A: Irradiation with light including a wavelength region where active oxygen is generated and a wavelength region where the oxide is activated to extract hydrogen mixed in the oxide.
Step B: In a state where hydrogen mixed in the oxide is extracted and active oxygen is generated in the vicinity of the oxide, a wavelength range for heating the oxide to promote diffusion of oxygen into the oxide is set. Irradiate containing light.
(2) At least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film are formed on a substrate, and the semiconductor layer is held in an oxygen-containing atmosphere in a thin film transistor manufacturing apparatus made of an amorphous metal oxide. At least one first lamp for irradiating the thin film transistor with light, at least one second lamp for irradiating the thin film transistor with light, and light emitted from the first lamp and the second lamp. Is provided to the thin film transistor, and a power supply device for supplying power to the first lamp and the second lamp is provided.
As the first lamp, for the oxide provided on the substrate, light including a wavelength region in which active oxygen is generated and a wavelength region in which the oxide is activated to extract hydrogen mixed in the oxide. In the state in which active oxygen is generated in the vicinity of the oxide by extracting hydrogen mixed into the oxide with respect to the oxide provided on the substrate as the second lamp. In addition, a material that emits light including a wavelength region for heating the oxide so as to promote diffusion of oxygen into the oxide is used.
(3) In the above (2), the first lamp is a rare gas fluorescent lamp that emits light including a wavelength range of 230 nm or less, and the second lamp is light including a wavelength range of 800 nm or more. It is a flash lamp that emits.
(4) In the above (3), the thin-film transistor manufacturing apparatus includes a light-shielding unit that shields light emitted from the flash lamp from being irradiated to the rare gas fluorescent lamp.
(5) In the above (4), the light blocking means is a second reflecting mirror surrounding a part of the rare gas fluorescent lamp.
(6) In the above (4), the light shielding means is a protrusion provided on a part of the reflection surface of the reflecting mirror, and one of the first lamp and the second lamp is the protrusion. The other of the first lamp and the second lamp is disposed at a position facing a flat reflecting surface that is not a protrusion of the reflecting mirror, and the shape of the protrusion, and The arrangement position of one lamp surrounded by this projection, and the arrangement position of the other lamp facing the flat reflecting surface that is not the projection of the reflecting mirror are such that light emitted from one lamp is directed to the other lamp. Is determined not to be irradiated.
(7) In the above (2), the first lamp is a flash lamp that emits light including a wavelength range of 230 nm or less, and the second lamp emits light including a wavelength range of 800 nm or more. It is a flash lamp.

In the present invention, the following effects can be obtained.
(1) For an amorphous metal oxide film formed on a substrate in an oxygen-containing atmosphere, a wavelength region where active oxygen is generated and a wavelength region where the oxide is activated and hydrogen mixed in the oxide is extracted. In the step A of irradiating containing light and in a state where active oxygen is generated in the vicinity of the oxide by extracting hydrogen mixed in the oxide, the oxide is promoted to promote the diffusion of oxygen into the oxide. In the process A, active oxygen having high reactivity is generated in the vicinity of the oxide semiconductor, and the surface of the amorphous metal oxide thin film is formed. In the process B, the amorphous oxide film is heated in step B, and the amorphous oxide film is heated. Hydrogen scan oxide film oxygen is introduced into the bond that has left.
In the process A, since the bond of the amorphous oxide film is cut by light energy as described above, hydrogen can be extracted from the amorphous oxide film in a short time compared to the case of using conventional thermal energy. It becomes possible. Further, the temperature of the amorphous oxide film itself does not rise so much, and even when the semiconductor characteristics are imparted to the amorphous oxide film formed on the film substrate, the film substrate is not damaged by heat.
In Step A, light irradiation is performed on an amorphous oxide film in an oxygen-containing atmosphere (for example, in the air), so that active oxygen having high reactivity is formed in the vicinity of the oxide film, and conventional thermal energy is formed. Oxygen can be introduced into the amorphous oxide film much more dramatically than when using.
In the process B, since the bond of the amorphous oxide film is already cut in the process A and the active oxygen is formed, the entire amorphous oxide film can be heated at a relatively low temperature. It is possible to realize the introduction of oxygen. That is, it becomes possible to heat at a temperature below the heat resistant temperature of the film substrate. In addition, since the process B is responsible only for promoting the diffusion of oxygen into the amorphous oxide film and alleviating the distortion of the oxide film, the heating time is shorter than in the prior art.
(2) In a thin film transistor manufacturing apparatus in which a semiconductor layer is made of an amorphous metal oxide, a first lamp, a second lamp, a first lamp, and a second lamp for irradiating light to a thin film transistor held in an oxygen-containing atmosphere Provided with a reflecting mirror that reflects light emitted from the lamp to the thin film transistor and a power supply device that supplies power to the first lamp and the second lamp. The first lamp is provided on the substrate. As the second lamp, an oxide that emits light including a wavelength region in which active oxygen is generated and a wavelength region in which the oxide is activated to extract hydrogen mixed in the oxide is used. In the state where hydrogen mixed in the oxide is extracted from the oxide provided on the substrate and active oxygen is generated in the vicinity of the oxide, In order to promote the diffusion of oxygen, a material that emits light including a wavelength region that heats the oxide is used, so that the processing including the above-described step A and step B can be performed with one apparatus. it can.
For this reason, hydrogen can be extracted from the amorphous oxide film in a short time and oxygen can be introduced into the amorphous oxide film as compared with the case of using conventional thermal energy. Further, the temperature of the amorphous oxide film itself does not rise so much, and even when the semiconductor characteristics are imparted to the amorphous oxide film formed on the film substrate, the film substrate is not damaged by heat.
(3) A rare gas fluorescent lamp that emits light including a wavelength region of 230 nm or less or a flash lamp is used as the first lamp, and light including a wavelength region of 800 nm or more is used as the second lamp. By using the flash lamp to be emitted, the process including the process A and the process B can be effectively performed.
(4) When a rare gas fluorescent lamp is used as the first lamp, by providing a light shielding means for shielding the light emitted from the flash lamp from being irradiated to the rare gas fluorescent lamp, the fluorescence of the rare gas fluorescent lamp is provided. It is possible to prevent the body layer from being damaged by light having a high peak power emitted from the flash lamp.
(5) By using the protrusion provided on a part of the reflecting surface of the reflecting mirror as the light shielding means, the number of parts can be reduced and the structure can be simplified.

It is a figure which shows the structural example of the manufacturing apparatus of the thin-film transistor of 1st Example of this invention. It is a figure which shows the structural example of a noble gas fluorescent lamp. It is a figure which shows the spectrum radiation spectrum of the light discharge | released from a noble gas fluorescent lamp. It is a figure which shows the structural example of a flash lamp. It is a figure which shows the spectral radiation spectrum of the light discharge | released from a xenon flash lamp. It is a figure which shows the light emission timing chart of the noble gas fluorescent lamp and xenon flash lamp in a 1st Example. It is a figure which shows the gate voltage versus drain current characteristic of the thin-film transistor (TFT) which processed the IGZO oxide film on the four conditions of Experiment 1. FIG. It is a figure which shows the other example of the light emission timing chart of a noble gas fluorescent lamp and a xenon flash lamp. It is a figure which shows the modification of the manufacturing apparatus of the thin-film transistor of 1st Example. It is a figure which shows the structural example of a short arc flash lamp. It is a figure which shows the spectral radiation spectrum of the light discharge | released from a long arc flash lamp when a xenon gas pressure is 0.6 atm (60 kPa) and the current density at the time of light emission is 509 A / cm < ² >. It is a figure (1) which shows the spectrum radiation spectrum of the light discharge | released from a short arc flash lamp using the pressure of the xenon gas enclosed inside as a parameter. It is a figure (2) which shows the spectrum radiation spectrum of the light discharge | released from a short arc flash lamp using the pressure of the xenon gas enclosed inside as a parameter. It is a figure which shows the relationship between the discharge current at the time of light emission of a short arc flash lamp, and the integrating | accumulating radiation intensity in a wavelength range 150-240 nm using the pressure of the xenon gas enclosed inside as a parameter. It is a figure which shows the structural example of the manufacturing apparatus of the thin-film transistor of 2nd Example of this invention. It is a figure which shows another structural example of the manufacturing apparatus of the thin-film transistor in Example 2 of this invention. Second, it is a diagram showing the light emission timing of the sapphire flash lamp and the xenon flash lamp in the embodiment. It is a figure which shows the gate voltage versus drain current characteristic of the thin-film transistor (TFT) which processed the IGZO oxide film on four conditions of Experiment 2. FIG. It is a figure which shows the other example of the light emission timing chart of a sapphire flash lamp and a xenon flash lamp in a 2nd Example. It is a figure which shows the light emission timing chart at the time of using a short arc flash lamp. It is a figure which shows the other example of the light emission timing chart at the time of using a short arc flash lamp. It is a figure which shows the structural example of the thin-film transistor (TFT) which is an active element which drives a video display.

Embodiments of the present invention will be described below.
1. As described above, the present invention activates the wavelength region where active oxygen is generated and the above oxide in an oxygen-containing atmosphere with respect to an amorphous metal oxide film formed on a substrate. In the step A of irradiating light including a wavelength range for extracting hydrogen mixed in the oxide, and in a state where active oxygen is generated in the vicinity of the oxide by extracting hydrogen mixed in the oxide A treatment including the step B of irradiating light including a wavelength region for heating the oxide so as to promote the diffusion of oxygen into the inside is performed.
As a result of intensive studies by the present inventors, by adopting the method for manufacturing a thin film transistor using an oxide semiconductor including the above-described Step A and Step B employed in the present invention, the following effects occur, and the following It was confirmed that there was an effect.

[Process A]
As described above, in the step A, in the oxygen-containing atmosphere (for example, in the air), the wavelength region in which active oxygen is generated and the wavelength that activates the oxide semiconductor film with respect to the amorphous oxide film formed on the substrate. And irradiating light including a region. Specifically, the amorphous oxide semiconductor film is irradiated with light containing ultraviolet rays having a wavelength of 230 nm or less in an oxygen-containing atmosphere.
The following effects occur due to such light irradiation.

(I) Active oxygen generation action When an oxygen-containing atmosphere (for example, in the air) is irradiated with light containing ultraviolet rays (hereinafter also referred to as UV) having a wavelength of 230 nm or less, the following chemical reaction occurs.
Reaction 1: After generation of ozone, oxygen (O ₂ ) + UV → ozone (O ₃ ) in the active oxygen generation atmosphere
Ozone (O ₃ ) + UV → Active oxygen (O _x )
Reaction 2: After oxygen decomposition, oxygen (O ₂ ) + UV → active oxygen (O _x ) in the active oxygen generating atmosphere
That is, highly reactive active oxygen is generated in the vicinity of the oxide semiconductor.

(Ii) Activation Action of Oxide Semiconductor Film When an amorphous metal oxide semiconductor film (for example, an amorphous IGZO film) is irradiated with ultraviolet light having a wavelength of 230 nm or less, the surface of the amorphous metal oxide semiconductor film is activated. Specifically, the chemical bond on the surface of the amorphous IGZO thin film is broken, and hydrogen mixed in the amorphous IGZO thin film is extracted.

[Process B]
(Iii) Thermal annealing action At least, the chemical bond on the surface of the amorphous oxide film is broken and hydrogen mixed in the oxide film is extracted, and active oxygen having high reactivity is present in the vicinity of the amorphous oxide film. In the generated state, light including a wavelength region for heating the oxide is irradiated to heat the amorphous oxide film, whereby oxygen is introduced into the bond from which the hydrogen of the amorphous oxide film is released.

In the process of step A, the surface of the amorphous oxide film is activated and active oxygen having high reactivity is generated in the vicinity thereof. Therefore, even if thermal annealing is not performed, a part of the amorphous oxide film is formed. Then, oxygen is introduced into the bond where the hydrogen of the amorphous oxide film has been released.
However, such oxygen introduction remains in the surface layer of the amorphous oxide film, and oxygen introduction in a portion deeper than the surface layer becomes insufficient. The thermal annealing in step B promotes the diffusion of oxygen into the amorphous oxide film, and realizes oxygen introduction throughout the amorphous oxide film. The semiconductor characteristics are imparted to the amorphous oxide film by the above-mentioned process A and process B.
In addition, since vibration energy is given to the bond of the amorphous oxide film by the thermal annealing in the process B, the molecular structure of the amorphous oxide film vibrates, and as a result, the distortion of the oxide film is relaxed and semiconductor characteristics are imparted. The oxide film becomes a stable film.

  In the case of improving the characteristics of TFTs using oxide semiconductors by imparting semiconductor characteristics to oxide films by conventional thermal annealing, hydrogen is desorbed and oxygen is introduced into oxygen defects by thermal energy. As described above, a high temperature treatment of about 400 ° C. is required, and the treatment time takes several hours. Therefore, it is practically difficult to provide a TFT on a film substrate having a low heat-resistant temperature, and the throughput of manufacturing the TFT is increased.

On the other hand, according to the present invention, the following effects can be obtained by the operations of the process A and the process B as described above.
(1) In Step A, the bonds of the amorphous oxide film are cut by light energy, so that hydrogen can be extracted from the amorphous oxide film in a shorter time compared to the case of using conventional thermal energy. It becomes. Further, the temperature of the amorphous oxide film itself does not rise so much, and even when the semiconductor characteristics are imparted to the amorphous oxide film formed on the film substrate, the film substrate is not damaged by heat.
In step A, since light irradiation is performed on the amorphous oxide film in an oxygen-containing atmosphere (for example, in the air), active oxygen having high reactivity is formed in the vicinity of the oxide film. Therefore, oxygen can be introduced into the amorphous oxide film dramatically more than when using conventional thermal energy.
(2) In the process B, since the bond of the amorphous oxide film has already been cut and the active oxygen is formed in the process A, the entire amorphous oxide film can be heated at a relatively low temperature. It is possible to realize oxygen introduction over a wide range. That is, it becomes possible to heat at a temperature below the heat resistant temperature of the film substrate. In addition, since the process B is responsible only for promoting the diffusion of oxygen into the amorphous oxide film and alleviating the distortion of the oxide film, the heating time is shorter than in the prior art.

  That is, according to the method for manufacturing a thin film transistor (TFT) using an oxide semiconductor including Step A and Step B of the present invention, the oxidation formed on the substrate even when the TFT is formed on the substrate having a low heat-resistant temperature. Semiconductor characteristics can be imparted to an object, and a TFT using a practical oxide film can be manufactured in a shorter time than in the past.

A rare gas fluorescent lamp or a flash lamp can be used as a light source for irradiating ultraviolet rays having a wavelength of 230 nm or less used in the step A.
As a rare gas fluorescent lamp, for example, a rare gas such as xenon, argon, or krypton is sealed in an arc tube, at least a phosphor layer is provided on the inner peripheral surface of the arc tube, and a pair of external electrodes are provided, and a wavelength is 230 nm. A lamp that can be irradiated with the following ultraviolet rays is used.
The flash lamp is a lamp in which, for example, xenon gas is sealed inside the arc tube and a pair of electrodes are provided therein. As will be described later, the flash lamp has an interelectrode distance L equal to or greater than the tube diameter d of the arc tube. A lamp (also referred to as a long arc flash lamp) or a flash lamp (also referred to as a short arc flash lamp) in which the distance L between the electrodes is smaller than the tube diameter d of the arc tube can be used.

As the long arc flash lamp used in the above step A, it is desirable to use a xenon gas sealed pressure in the arc tube of 1.5 atm (152 kPa) or less, and lighting at a current density of 4000 to 9000 A / cm ² . By doing so, strong radiation can be obtained in the vicinity of a wavelength of 230 nm. Further, in order to avoid a problem such as rupture of the arc tube, it is desirable to use alumina having high mechanical strength against shock waves as the arc tube.
As the short arc flash lamp, it is desirable to use a xenon gas sealed pressure in the arc tube of 8 atm (8.10 × 10 ⁵ Pa) or less, and the discharge current at the time of discharge is 1500 A or more. There is a need.

Moreover, as a light source which emits light including a wavelength range of 800 nm or more used in the above-mentioned step B, for example, xenon gas is sealed inside the glass tube, and a pair of electrodes is provided inside the glass tube. A flash lamp (long arc flash lamp) in which the distance L between the electrodes is not less than the tube diameter d of the arc tube can be used.
By setting the current density during discharge of the long arc flash lamp to 1000 to 2000 A / cm ² , strong radiation can be obtained in a wavelength region of 800 nm or more.

In the case where the rare gas fluorescent lamp is used for the process A and the long arc flash lamp is used for the process B, the long arc flash lamp is turned on a plurality of times while the rare gas fluorescent lamp is turned on. Processes A and B can be performed.
When a long arc flash lamp is used for the process A and the long arc flash lamp is used for the process B, the flash lamp for the process A and the flash lamp for the process B are turned on simultaneously. In this case, the light emission time of the long arc flash lamp for the process A is much shorter than the light emission time of the flash lamp for the process B. Even after the light emission of the flash lamp for the process A is finished, the flash lamp for the process B Continues to emit light.
In addition, after the flash lamp for the process B is turned on, while the flash lamp for the process B emits light, hydrogen mixed in the oxide is extracted and active oxygen is generated in the vicinity of the oxide. Alternatively, the flash lamp for the process A may be turned on.
Further, when the short arc flash lamp is used for the process A and the long arc flash lamp is used for the process B, the short arc flash lamp for the process A is caused to emit light a plurality of times. The long arc flash lamp for process B is caused to emit light at substantially the same timing as the light emission timing. In addition, after the short arc flash lamp is turned on a plurality of times, the long arc flash lamp for process B is caused to emit light in a state where hydrogen mixed in the oxide is extracted and active oxygen is generated in the vicinity of the oxide. However, the same effect can be obtained.

2. Configuration Example of Thin Film Transistor Manufacturing Apparatus in the Present Invention Hereinafter, an embodiment of a thin film transistor manufacturing apparatus in the present invention will be described.
[Example 1]
FIG. 1 shows a first embodiment of an apparatus for manufacturing a thin film transistor for carrying out the processes A and B, which are processes for manufacturing a thin film transistor using an oxide semiconductor according to the present invention.
In the manufacturing apparatus shown in FIG. 1, the light source unit 2 for irradiating the amorphous metal oxide semiconductor film formed on the substrate includes the light source responsible for the light irradiation in the process A and the light irradiation in the process B. It consists of two types of light sources.

For example, the rare gas fluorescent lamp 10 is used as the light source in charge of the light irradiation in the process A, and the flash lamp 20 such as a xenon flash lamp is used as the light source in charge of the light irradiation in the process B.
FIG. 2 shows a configuration example of the rare gas fluorescent lamp, and FIG. 4 shows a configuration example of the flash lamp. As is apparent from the structure shown in FIGS. 2 and 4, the shapes of the lamps 10 and 20 are straight tubes. As shown in FIG. 1, a plurality of the lamps 10 and 20 are arranged in parallel. Power supply means 4 for supplying power to 20 is provided.
A work stage 8 is provided below both lamps, and the work 7 is placed on the work stage 8. The work 7 is a substrate having the above-described amorphous metal oxide film.

The number and interval of the plurality of rare gas fluorescent lamps 10 are such that light including ultraviolet rays having a wavelength of 230 nm or less emitted from the rare gas fluorescent lamp 10 is irradiated to the entire work 7 and the light on the work 7 is It is appropriately set so that the irradiance distribution is uniform to some extent.
Similarly, the number and interval of the flash lamps 20 are such that light including infrared rays (IR: for example, wavelength of 800 nm or more) for thermal annealing emitted from the flash lamp 20 is irradiated on the entire work 7 and 7 is set as appropriate so that the irradiance distribution of the light on 7 is uniform to some extent.

In the example shown in FIG. 1, a plurality of straight tube-like rare gas fluorescent lamps 10 and a plurality of straight tube-like flash lamps 20 are alternately arranged so that the light emitted from both lamps 10, 20 can irradiate the entire workpiece 7. And arranged in parallel. However, the arrangement is not limited to this as long as the light from the rare gas fluorescent lamp 10 and the light from the flash lamp 20 are irradiated onto the workpiece 7 in the above-described state.
Reflecting mirrors 3a and 3b are provided above the lamps 10 and 20 to reflect the light emitted from the lamps 10 and 20 to the work 7 disposed below.
Here, as will be described later, the rare gas fluorescent lamp 10 has a structure in which a phosphor layer is provided inside a glass tube. This phosphor layer was found to be damaged when irradiated with light having a high peak power emitted from the flash lamp 20.
Therefore, the light source unit 2 in the thin film transistor manufacturing apparatus of the present invention needs to be configured so that the phosphor layer of the rare gas fluorescent lamp 10 is not irradiated with the light emitted from the flash lamp 20.

In the example shown in FIG. 1, a reflecting mirror 3 b that surrounds a part of the rare gas fluorescent lamp 10 is provided so that the light emitted from the flash lamp 20 is not irradiated onto the rare gas fluorescent lamp 10. The reflecting mirror 3b is provided for all the rare gas fluorescent lamps constituting the light source unit. The reflecting mirror 3b shields light emitted from the flash lamp 20 so that the rare gas fluorescent lamp 10 is not irradiated with the light, and transmits light emitted from the rare gas fluorescent lamp 10 to the light source unit 2. It has a function of reflecting to the workpiece 7 disposed below.
The reflecting mirror 3a is made of, for example, an aluminum plate having a mirror-finished light reflecting surface. Similarly, the reflecting mirror 3b is made of, for example, an aluminum plate having a mirror-finished light reflecting surface.

  The light source unit 2 including the rare gas fluorescent lamp 10, the flash lamp 20, the work 7, and the work stage 8 are disposed in the processing chamber 1 having an atmosphere containing oxygen. Note that only the workpiece 7 and the workpiece stage 8 are arranged in the processing chamber 1 and a light transmitting member that transmits light emitted from the light source unit 2 is provided in the processing chamber 1 so that the light source unit is arranged outside the processing chamber. May be. In this case, the light transmissive member is formed between the light source 2 and the work stage 8 on which the work 7 is placed so that the light emitted from the light source 2 is irradiated onto the work 7 through the light transmissive member. It is provided so as to be located between them.

  The light employed in the process A is a wavelength region where active oxygen is generated and a wavelength that activates the oxide film with respect to the amorphous oxide film formed on the substrate in an oxygen-containing atmosphere (for example, in the air). And is remarkably absorbed in an oxygen-containing atmosphere (for example, in the air). Therefore, depending on the distance between the light source unit 2 and the work 7, the irradiance on the surface of the work 7 becomes small, and the generation of active oxygen and the activation of the oxide semiconductor film in the vicinity of the work 7 may be insufficient. . When such a problem is concerned, the light source 2 including the rare gas fluorescent lamp 10 and the flash lamp 20 and the processing chamber 1 in which the work 7 and the work stage 8 are arranged are light-transmitting as described above. It is desirable to divide spatially using a window member or the like and reduce the oxygen content in the space where the light source part is located as much as possible by purging with an inert gas as much as possible so that only the treatment chamber has an atmosphere containing oxygen.

As described above, ozone is generated in the active oxygen generating action of step A. Since it is not preferable that the generated ozone flows out of the processing chamber 1, the processing chamber 1 is connected to an exhaust unit 5 for discharging ozone generated in the processing chamber 1. Further, the processing chamber 1 is provided with a suction port 6a provided with an air filter 6 for suppressing inflow of contamination in the atmosphere into the processing chamber 1. When the exhaust means 5 is operated and the ozone in the processing chamber 1 is exhausted, an oxygen-containing gas (such as the atmosphere) from which the contamination is almost removed flows into the processing chamber 1 from the suction port 6a.
The operation of the power supply means 4 for supplying power to the light source section 2 and the exhaust means 5 is controlled by the control section 9.

FIG. 2 shows a configuration example of a rare gas fluorescent lamp.
As shown in FIG. 2, the rare gas fluorescent lamp 10 has, for example, a discharge space in which both ends of a straight tubular quartz (SiO ₂ ) glass tube are sealed, and a rare gas such as xenon, argon, krypton is enclosed inside. And a first electrode 11a and a second electrode 11b which are a pair of external electrodes. The first and second electrodes 11a and 11b are strip-like external electrodes that are spaced apart from each other on the outer peripheral surface of the glass tube 13 and are disposed along the tube axis direction. The first and second electrodes 11a 11b is provided with a protective film 17.

An ultraviolet reflection film 14 is provided on the inner surface of the glass tube 13 opposite to the light emitting direction side (see FIG. 2B), and a low softening point glass layer 15 is provided on the inner periphery thereof. A phosphor layer 16 is provided on the inner peripheral surface of the low softening point glass layer 15.
The ultraviolet reflecting film 14 is composed of silica particles (SiO ₂ ) and other particles such as alumina particles (Al ₂ O ₃ ).
The low softening point glass layer 15 is made of hard glass such as borosilicate glass or aluminosilicate glass, for example.
The power supply means 4 for the rare gas fluorescent lamp supplies a high frequency voltage between the first electrode 11a and the second electrode 11b of the rare gas fluorescent lamp 10, and includes, for example, a DC power source, an inverter circuit, and a step-up transformer. Composed. The DC voltage output from the DC power supply is converted into a high-frequency voltage such as a high-frequency AC voltage by an inverter circuit connected to the DC power supply, boosted by a step-up transformer connected to the inverter circuit, and a pair of rare gas fluorescent lamps 10. Are applied to the external electrodes 11a and 11b.

When a high frequency voltage is applied between the first electrode 11a and the second electrode 11b, a discharge is formed with quartz glass (discharge vessel 13) as a dielectric interposed between the electrodes 11a and 11b. As a result, a rare gas excimer molecule excited in the discharge space 18 is formed, and excimer light is emitted when the rare gas excimer molecule transitions to the ground state.
The phosphor is excited by the excimer light, and ultraviolet light is generated from the phosphor layer 16. The ultraviolet light is reflected by the ultraviolet reflecting film 14 and is radiated to the outside from the opening portion where the ultraviolet reflecting film 14 is not provided (radiated in the light radiation direction shown in FIG. 2 (downward in the figure)).
In the rare gas fluorescent lamp 10 used in the present embodiment, xenon gas is sealed inside the glass tube 13, ultraviolet light having a central wavelength of 172 nm is generated by dielectric barrier discharge, and this phosphor is used to excite the phosphor layer. Then, ultraviolet rays including light having a wavelength of 230 nm or less used in Step A were generated.

FIG. 3 shows the spectral emission spectrum of the light emitted from the rare gas fluorescent lamp used in this example, in which the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the relative radiation intensity (%).
FIG. 3 (a) shows a spectral emission spectrum when praseodymium-activated lanthanum phosphate phosphor LaPO ₄ : Pr is used as the phosphor and 21 kPa of xenon gas is sealed inside the glass tube. There is a maximum peak of radiant intensity. On the other hand, FIG. 3B is a spectral emission spectrum in the case where 13.3 kPa of xenon gas is sealed inside a glass tube using neodymium-activated yttrium phosphate phosphor YPO ₄ : Nd as the phosphor, and the wavelength There is a maximum peak of relative radiation intensity around 190 nm.

FIG. 4 shows a configuration example of the flash lamp.
The flash lamp 20 has a structure in which, for example, both ends of a straight tubular quartz glass tube 21 are sealed, and a first electrode 22a and a second electrode 22b are provided at both ends in the longitudinal direction of the lamp.
For example, xenon gas is sealed in the glass tube 21.
The first and second electrodes 22a and 22b are disposed inside a glass tube 21 that is an arc tube, and the arc tube has a sealing portion 23 for sealing an external lead 24 extending from the first electrode 22a. And a sealing portion 23 for sealing the external lead 24 extending from the second electrode 22b.
External leads 24 projecting outward from both ends of the arc tube are connected to the power supply means. The power supply means has a capacitor for storing predetermined energy. When the capacitor is charged, a high voltage is applied between the first electrode 22a and the second electrode 22b, which are a pair of electrodes of the flash lamp 20. In this state, when a trigger is applied between the electrodes 22a and 22b by an igniter means (not shown), a flash discharge is generated in the flash lamp and an arc 25 is generated. As a result, the gas inside the arc tube is excited, Light is emitted.
FIG. 5 shows a spectral emission spectrum of light emitted from the xenon flash lamp used in this example. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents relative radiation intensity (%).

[Experiment 1]
Using the above-described thin film transistor manufacturing apparatus, an IGZO oxide film on the substrate was processed under the following conditions to manufacture a thin film transistor, and the gate voltage versus drain current characteristic of the thin film transistor was examined.
Here, the spectral emission spectrum of the rare gas fluorescent lamp used in Step A is the same as that shown in FIG. 3B, and the spectral emission spectrum of the xenon flash lamp used in Step B is that shown in FIG. Is the same. That is, the light irradiated to the workpiece in the process A is light having a maximum peak of relative radiation intensity near a wavelength of 190 nm and a wavelength region of 230 nm or less. On the other hand, the light irradiated to the workpiece in the process B is light having a wavelength region of about 300 to 1100 nm and a high intensity in the wavelength region of 800 nm or more.

The processing conditions for the IGZO oxide film are as follows. All the workpieces are placed in an air atmosphere, and the temperature is room temperature.
(Condition 1)
IGZO oxide film light irradiation treatment in step A and no light irradiation treatment in step B (as deposition state)
(Condition 2)
Process A: Irradiance 2.5 mW / cm ^{2 on} the workpiece surface of irradiation light from a rare gas fluorescent lamp, irradiation time 500 seconds, that is, energy 2.5 mW / cm ² × 500 seconds = 1.25 J on the workpiece surface / Cm ²
Process B: Flash irradiation of xenon flash lamp 5 times (100s interval), the emission pulse width of each emission pulse is 3 ms (full width at half maximum: FWHM), and the energy on the workpiece surface in each emission is 7 J / cm ²

The light emission timing chart for condition 2 is as shown in FIG. The upper chart in the figure shows the light emission state of the rare gas fluorescent lamp 10, and the lower chart shows the light emission state of the flash lamp 20. The horizontal axis represents time (s), and the vertical axis represents relative light intensity.
That is, after 100 s from the start of light emission of the rare gas fluorescent lamp 10, the first light emission by the xenon flash lamp and the irradiation of the workpiece are performed, and thereafter the light emission of the xenon flash lamp and the irradiation of the workpiece are performed four times (total 5 Times). In FIG. 6A, the emission pulse width of the xenon flash lamp is exaggerated for easy understanding.

(Condition 3)
Process A: Irradiance 2.5 mW / cm ^{2 on} the workpiece surface of irradiation light from a rare gas fluorescent lamp, irradiation time 800 seconds, that is, energy 2.5 mW / cm ² × 800 seconds on the workpiece surface = 2.5 J / Cm ²
Process B: Xenon flash lamp flash irradiation 8 times (100 s interval), the emission pulse width of each emission pulse is 3 ms (full width at half maximum: FWHM), and energy on the workpiece surface in each emission is 7 J / cm ²
The light emission timing chart for condition 3 is as shown in FIG. As described above, the upper chart in the figure shows the light emission state of the rare gas fluorescent lamp 10, and the lower chart shows the light emission state of the flash lamp 20. The horizontal axis represents time (s), and the vertical axis represents relative light intensity.
That is, after 100 s from the start of light emission of the rare gas fluorescent lamp 10, the first light emission by the xenon flash lamp and the irradiation of the workpiece are performed, and thereafter the light emission of the xenon flash lamp and the irradiation of the workpiece are performed seven times (total 8 times). Times). In FIG. 6B, the emission pulse width of the xenon flash lamp is exaggerated for easy understanding.

(Condition 4)
Step A: None Step B: Flash irradiation with a xenon flash lamp once, the emission pulse width of the emission pulse is 3 ms (full width at half maximum: FWHM), and energy on the workpiece surface is 11 J / cm ²

  FIG. 7 shows gate voltage versus drain current characteristics of a thin film transistor (TFT) in which the IGZO oxide film is processed under the four conditions described above. In the figure, a broken line (1) is a characteristic curve in the condition (1), a solid line (2) is a characteristic curve in the condition (2), a solid line (3) is a characteristic curve in the condition (3), An alternate long and short dash line (4) is a characteristic curve in the condition (4).

As is clear from the characteristic curve of the broken line (1) in FIG. 7, in the case of the condition (1) in which the IGZO oxide film is not subjected to the light irradiation treatment, there is almost no change in the drain current even when the gate voltage is changed. It is almost constant at about × 10 ^-10 A. That is, in the case of condition (1), it can be seen that the IGZO oxide film is not given semiconductor characteristics, and the IGZO oxide film is in a state close to an insulating film.

In the case of condition (2), in step A, light energy having a spectral emission spectral characteristic shown in FIG. 3B is given to the IGZO oxide film from the rare gas fluorescent lamp in 1.25 J / cm ² . The IGZO oxide film was irradiated five times from a xenon flash lamp with flash light having the spectral emission spectral characteristics shown in FIG. 5 and having a light energy of 7 J / cm ^{2 on the} workpiece surface. At this time, as is apparent from the characteristic curve of the solid line (2) in FIG. 7, the value of the drain current rapidly increases in the vicinity of the gate voltage of −17V.
That is, when the gate voltage is about −17 V, the TFT performs the on / off operation, so that the semiconductor characteristics are imparted to the IGZO oxide film.

In the case of condition (3), in step A, the light energy having the spectral emission spectral characteristic shown in FIG. 3B is given to the IGZO oxide film from the rare gas fluorescent lamp by 2.5 J / cm ² . The IGZO oxide film was irradiated 8 times from a xenon flash lamp with flash light having the spectral emission spectral characteristics shown in FIG. 5 and having a light energy of 7 J / cm ^{2 on the} workpiece surface. At this time, as is clear from the characteristic curve of the solid line (3) in FIG.
That is, when the gate voltage is about −7 V, the TFT performs the on / off operation, so that the semiconductor characteristics are imparted to the IGZO oxide film.

In the case of condition (4), the ultraviolet irradiation process of the process A was not performed with respect to the IGZO oxide film, and only the process B which is a heat treatment was performed. That is, the IGZO oxide film was irradiated once with flash light having a spectral emission spectral characteristic shown in FIG. 5 from the xenon flash lamp and having a light energy of 11 J / cm ^{2 on the} workpiece surface.
At this time, as is apparent from the characteristic curve of the alternate long and short dash line (4) in FIG. 7, even if the gate voltage is changed, there is almost no change in the drain current, and it is almost constant at about 1 × 10 ⁻⁷ A. That is, in the condition (4), it can be seen that the IGZO oxide film has no semiconductor characteristics, and the IGZO oxide film is in a state close to the conductive film.

From the above results, by adopting a method for manufacturing a thin film transistor (TFT) using an oxide semiconductor including Step A and Step B of the present invention, the oxide formed on the substrate is in a room temperature state. It has been found that semiconductor characteristics can be imparted to the oxide.
Here, when the condition (2) is compared with the condition (3), the threshold voltage Vth of the gate voltage in the condition (2) is about −17V, and the threshold voltage Vth in the condition (3) is about −7V. The shift amount ΔVth (= 0−Vth) of the value of Vth from the gate voltage of 0 V is small in the condition (3).
This is because, in step A, the amount of light energy having the spectral emission spectral characteristics shown in FIG. 3B from the rare gas fluorescent lamp to the IGZO oxide film is greater than that in the condition (2). When the condition (3) is larger than the condition (2), the amount of active oxygen generated in the vicinity of the IGZO oxide film is larger, and the degree of activation of the IGZO oxide film surface is greater. Therefore, it is considered that the extraction of hydrogen mixed in the amorphous IGZO thin film and the repair of oxygen defects were efficiently performed.
Further, in the process B, when the number of times of irradiation of the flash light having the spectral emission spectral characteristics shown in FIG. 6 from the xenon flash lamp to the IGZO oxide film is larger than that in the condition (2) (3), Compared to the condition (2), it is considered that oxygen was sufficiently diffused into the IGZO oxide film.

Furthermore, the amount of light energy having the spectral emission spectrum characteristic shown in FIG. 3B is increased by extending the ultraviolet irradiation treatment time for the IGZO oxide film as compared with the condition (3), and the IGZO oxide film Thus, it is considered that the shift amount ΔVth of the threshold voltage can be further reduced by increasing the number of times of irradiation of flash light having the spectral emission spectral characteristics shown in FIG. 5 from the xenon flash lamp.
On the other hand, in the case of the condition (4) in which the process A is omitted and only the thermal annealing action of the process B is performed, the IGZO oxide film has no semiconductor characteristics. This is presumably because diffusion of the oxygen defect repairing action was not performed because the thermal annealing was performed without performing the hydrogen extraction action and the oxygen defect repairing action in the process A on the IGZO film.
For example, if heat treatment is performed at 400 ° C. for 1 hour as in the prior art, oxygen defects are repaired and semiconductor characteristics are imparted to the IGZO oxide film. Is at room temperature and the energy applied from the xenon flash lamp is about 11 J / cm ² , it is considered that the oxygen defect repairing action as in the prior art has not been achieved. In addition, it is thought that the value of the drain current is increased because impurities on the surface of the IGZO film are diffused inside the IGZO film by the light irradiation in the process B.

  In the above experiment, in step A, the workpiece was irradiated with light having a maximum peak of relative radiation intensity near the wavelength of 190 nm shown in FIG. 3B and a wavelength region of 230 nm or less. Here, in the process A, the same experiment was performed by irradiating the work with light having a maximum peak of the relative radiation intensity near the wavelength of 230 nm shown in FIG. 3A and having a wavelength region of 200 to 300 nm. The experimental results showed the same tendency as the above experiment. That is, the semiconductor characteristics were imparted to the IGZO film only when the workpieces placed in the air atmosphere and having a temperature of room temperature were subjected to the process A and the process B of the present invention.

The effect of improving the threshold voltage shift amount ΔVth is 5 in the case of the light having the spectral emission spectral characteristic shown in FIG. 3B compared to the case of the light having the spectral emission spectral characteristic shown in FIG. It was 10 times larger.
That is, with respect to the irradiation time when the IGZO oxide film is irradiated with light having a maximum relative radiation intensity near the wavelength of 190 nm and a wavelength region of 230 nm or less to reduce the value of ΔVth by a predetermined amount, the wavelength is around 230 nm When the IGZO oxide film is irradiated with light having a maximum peak of relative radiation intensity and a wavelength region of 200 to 300 nm, in order to reduce the value of ΔVth by the same amount as the former, irradiation in the former case is performed. It was necessary to irradiate for 5-10 times longer than the time.
This is because the wavelength region of the former light is shorter than the wavelength region of the latter light, the photon energy of the former light is large, the amount of active oxygen generated in the vicinity of the IGZO oxide film and the surface of the IGZO oxide film This is probably because the degree of activation has increased, and the extraction of hydrogen and the repair of oxygen vacancies in the amorphous IGZO thin film have been performed more efficiently.

In the above conditions (2) and (3), multiple times of flash irradiation with the xenon flash lamp corresponding to step B are performed with substantially the same light intensity and the like after the start of light irradiation with the rare gas fluorescent lamp in step A. Although performed at intervals (100 s), the present invention is not limited to this. For example, as shown in FIG. 8A, flash irradiation with a xenon flash lamp may be started prior to light irradiation with a rare gas fluorescent lamp. Or although illustration is abbreviate | omitted, you may start the flash irradiation by a xenon flash lamp at the timing equivalent to the timing of the light irradiation start by a rare gas fluorescent lamp. In FIG. 8, the horizontal axis represents time (relative value), and the vertical axis represents relative light intensity.
Further, for example, as shown in FIG. 8B, the irradiation may be performed so that the light intensity decreases at every irradiation, although the intervals are equal. Or as shown in FIG.8 (c), although it is substantially the same light intensity, you may irradiate so that an irradiation interval may become large for every irradiation.
Such an irradiation pattern is appropriately determined in consideration of the type of amorphous oxide film, the film formation state, the heat-resistant temperature of the substrate, the degree of oxygen diffusion, the energy given from both lamps to the amorphous oxide film, and the like.

[Modification of Example 1]
FIG. 9 shows a modification of the thin film transistor manufacturing apparatus according to the present invention shown as the first embodiment. As described above, in the thin film transistor manufacturing apparatus shown in FIG. 1, the light emitted from the flash lamp 20 and the rare gas fluorescent lamp 10 is added to the reflecting mirror 3a that reflects the work 7 disposed below, and the flash lamp A reflecting mirror 3b surrounding a part of the rare gas fluorescent lamp 10 is provided so that the light emitted from 20 is not irradiated on the rare gas fluorescent lamp 10.

On the other hand, in the modification shown in FIG. 9, in the reflecting mirror 3 that reflects the light emitted from both the lamps 10 and 20 to the work 7 disposed below, a part of the reflecting surface is opposite to the light reflecting surface. A plurality of convex protrusions 3c are provided on the side surface.
One of the lamps 10 and 20 (the lamp 10 in FIG. 9) is disposed at a position surrounded by the protrusion 3c, and the other lamp (the lamp 20 in FIG. 9) is not at the protrusion of the reflecting mirror 3. It is arranged at a position opposite to a flat reflecting surface.
Here, the shape of the protrusion 3c, the arrangement position of one lamp surrounded by the protrusion 3c, and the arrangement position of the other lamp facing the flat reflecting surface that is not the protrusion of the reflecting mirror 3 are It is determined that the light emitted from one of the lamps is not irradiated to the other lamp. Inevitably, the light emitted from the other lamp is not irradiated to one lamp.

  In the example shown in FIG. 9, the rare gas fluorescent lamp 10 is disposed at a position surrounded by the projection 3c, and the flash lamp 20 is disposed at a position facing the flat reflecting surface. is there. Therefore, the light emitted from the flash lamp 20 is not irradiated to the rare gas fluorescent lamp 10 by determining the shape of the protrusion 3c of the reflecting mirror 3 and the arrangement position of both lamps as described above. That is, since the light having a high peak power emitted from the flash lamp 20 is not irradiated on the phosphor layer of the rare gas fluorescent lamp 10, the phosphor layer is not damaged by the light emitted from the flash lamp 20. The flash lamp 20 may be disposed at a position surrounded by the protrusion 3c, and the rare gas fluorescent lamp 10 may be disposed at a position facing the flat reflecting surface.

In the thin film transistor manufacturing apparatus shown in FIG. 1, the light emitted from the flash lamp 20 is prevented from being irradiated to the rare gas fluorescent lamp 10 by using the reflecting mirror 3a and the plurality of reflecting mirrors 3b which are separate members. Therefore, the number of parts increases, and it is necessary to individually align the plurality of reflecting mirrors 3b with respect to the reflecting mirror 3a.
On the other hand, in the case of the reflecting mirror 3 of this modification example, since it has an integrated structure in which a plurality of protrusions 3c are provided on a part of the reflecting surface of the reflecting mirror 3, the number of parts is small, and the case shown in FIG. The operation of aligning the plurality of reflecting mirrors 3b with respect to the reflecting mirror 3a is also unnecessary.

[Example 2]
In the thin film transistor manufacturing apparatus of Example 1 described above, a rare gas fluorescent lamp that emits light including ultraviolet rays having a wavelength of 230 nm or less was used as a light source in charge of light irradiation in the process A.
In the thin film transistor manufacturing apparatus of the second embodiment, a xenon flash lamp adjusted to emit light having a high relative radiation intensity of light in a wavelength region of 230 nm or less is used as a light source in charge of light irradiation in step A. As a light source in charge of light irradiation in the process B, a xenon flash lamp that emits light having a wavelength region of about 300 to 1100 nm and a high intensity in the wavelength region of 800 nm or more is used as in the first embodiment. Is done.

Generally, the flash lamp has a type in which the distance L between the electrodes is equal to or larger than the tube diameter d of the arc tube (hereinafter also referred to as a long arc flash lamp), and a type in which the distance L between the electrodes is smaller than the tube diameter d of the arc tube. (Hereinafter also referred to as a short arc flash lamp).
The configuration example of the flash lamp previously shown in FIG. 4 is that of a long arc flash lamp. In the example shown in FIG. 4, the interelectrode distance L is significantly longer than the tube diameter d.

Next, FIG. 10 shows a configuration example of a short arc flash lamp in which the interelectrode distance L is smaller than the tube diameter d of the arc tube.
As shown in FIG. 10, in the short arc flash lamp, for example, the distance between a pair of electrodes arranged inside the arc tube is relatively short, and all external leads extending from the pair of electrodes are from one end of the arc tube. It is the structure which protrudes outside.
Specifically, the short arc flash lamp 30 seals a light-transmitting bulb 31 made of container-shaped quartz glass or the like constituting the arc tube, and an opening portion of the light-transmitting bulb 31 (a container-shaped opening portion). This is a structure comprising a stem 34. That is, the inside of the light-transmitting bulb 31 is sealed with the stem 34.
A pair of electrodes 32a and 32b facing in the vertical direction in FIG. 10 are arranged inside the light-transmitting bulb 31 which is an arc tube. Further, between the pair of electrodes 32a and 32b, a pair of trigger electrodes 33a and 33b facing in the left-right direction in FIG. 10 are arranged. Also, xenon gas is sealed inside the light transmissive bulb 31.

  External leads 35 and 36 extending from the pair of electrodes 32a and 32b and the pair of trigger electrodes 33a and 33b protrude from the inside of the light transmissive valve 31 to the outside via the stem 34. Each external lead is sealed by the stem 34, and the sealed state inside the light transmissive bulb is maintained. The respective external leads 35 and 36 projecting outward from the stem 34 are connected to the power supply means. The power supply means has a capacitor for storing predetermined energy. When the capacitor is charged, a high voltage is applied between the first electrode, which is a pair of electrodes of the short arc flash lamp, and the second electrodes 32a and 32b. In this state, when the power feeding means supplies power between the trigger electrodes 33a and 33b and discharge occurs between the trigger electrodes 33a and 33b, flash discharge occurs in the short arc flash lamp.

As described above, in Example 2, as the light source responsible for the light irradiation in Step B, the wavelength region is about 300 to 1100 nm as in Example 1, and the intensity in the wavelength region of 800 nm or more is high. A flash lamp such as a xenon flash lamp that emits light is used. The xenon flash lamp is a long arc flash lamp as shown in FIG.
On the other hand, when a xenon flash lamp adjusted to emit light having a high relative radiation intensity of light in a wavelength region of 230 nm or less is used as a light source in charge of light irradiation in the process A, a long arc flash lamp or a short arc flash is used. Both lamps can be used.

[1] Long Arc Flash Lamp First, a case where a long arc flash lamp is used as a light source in charge of light irradiation in the process A will be considered.
In general, the spectrum of light emitted from a flash lamp depends on the temperature of the plasma generated by the arc discharge. Here, in the long arc flash lamp, the distance L between the electrodes is not less than the tube diameter d of the arc tube, and the plasma generated by the interelectrode discharge grows almost entirely in the arc tube. Therefore, the plasma temperature depends on the cross-sectional area of the arc tube as well as the pressure inside the arc tube and the current value flowing between the electrodes during discharge. Here, when defined as current density = (current value flowing between electrodes during discharge) / (sectional area of arc tube), the spectrum of light emitted from the long arc flash lamp is expressed by the current density and the pressure in the arc tube. It turns out that it depends.

FIG. 11 shows the light emitted from the flash lamp when the arc tube is filled with xenon gas, the pressure inside the arc tube is 0.6 atm (60 kPa), and the current density during light emission is 5096 A / cm ^2. The spectral emission spectrum of is shown. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents relative radiation intensity. In this lamp, there is a maximum peak of radiation intensity in the vicinity of a wavelength of 230 nm. Therefore, this lamp can be employed as a light source in charge of light irradiation in the process A.

On the other hand, as described above, the xenon flash lamp in charge of light irradiation in the process B is also a long arc flash lamp, and the arc tube is filled with xenon gas. As is apparent from the spectral radiation spectrum of the light emitted from the flash lamp shown in FIG. 5, in the present lamp, strong radiation is observed in the wavelength region having a wavelength of 800 nm or more. The light emission conditions at this time were a xenon gas pressure inside the arc tube of 0.6 atm (60 kPa) and a current density during light emission of 1910 A / cm ² .
When the inventors have investigated the relationship between the spectral emission spectrum and current density of the light emitted from a xenon flash lamp, stronger in the vicinity of a wavelength of 230nm as shown in Figure 11 when the current density is 4000~9000A / cm ² Radiation was seen, which proved useful as a light source responsible for the light irradiation of step A. Further, when the current density was 1000 to 2000 A / cm ² , strong radiation was observed in the wavelength region of 800 nm or more as shown in FIG. 5, and it was found useful as a light source in charge of light irradiation in the process B.

Here, when using a long arc xenon flash lamp in which strong radiation is observed in the vicinity of a wavelength of 230 nm as the light source in charge of the light irradiation in the process A, a large current density of 4000 to 9000 A / cm ² is necessary, and the discharge Sometimes the plasma temperature generated is quite high. When the arc tube is made of quartz glass, the quartz glass bulb may be damaged by the high-temperature plasma described above depending on the discharge conditions.
In the case of this lamp, it is desirable to employ an arc tube made of alumina having high heat resistance against high temperature plasma as the arc tube of the lamp. Since alumina has a higher mechanical strength than quartz glass, it is more advantageous than quartz glass against shock waves generated during discharge.
Further, as described above, since the current density during discharge is large, the plasma temperature in the arc tube during light emission becomes considerably high, and the expansion of xenon gas during light emission also increases. As a result of investigations by the inventors, it has been found that in order to avoid problems such as rupture of the arc tube, it is desirable that the xenon gas filling pressure in the arc tube be 1.5 atm (152 kPa) or less. Furthermore, it has been found that it is desirable to set the current density so as not to exceed 9000 A / cm ² in consideration of the strength of the arc tube.

On the other hand, when a long arc xenon flash lamp is used as the light source in charge of light irradiation in the process B, since the distance between the electrodes is long, if the current density is less than 1000 A / cm ² , arc discharge in the arc tube is difficult to occur. I understood that. Therefore, in order to operate the lamp stably, the current density is desirably 1000 A / cm ² or more.

[2] Short Arc Flash Lamp Next, a case where a short arc flash lamp is used as a light source in charge of light irradiation in the process A will be considered.
In the short arc flash lamp, the interelectrode distance L is smaller than the tube diameter d of the arc tube, and the plasma generated by the interelectrode discharge is generated between the electrodes. Therefore, it was found that the plasma temperature that affects the spectrum of light emitted from the short arc flash lamp depends on the pressure in the arc tube, the current value flowing between the electrodes during discharge, and the pressure in the arc tube.

FIG. 12 and FIG. 13 show spectral emission spectra of light emitted from the short arc flash lamp, using the pressure of the xenon gas enclosed in the light transmissive bulb of the short arc flash lamp as a parameter. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents spectral radiation intensity (μJ / cm ² ).
FIG. 12A shows a spectral emission spectrum when the pressure inside the light-transmitting bulb is 2 atm (2.03 × 10 ⁵ Pa). Further, in FIGS. 12B, 13C, and 13D, the pressure inside the light transmissive valve is 3 atm (3.04 × 10 ⁵ Pa), ⁵ atm (5.07 × 10 ⁵ ), respectively. Pa), 8 atm (8.10 × 10 ⁵ Pa). 12 and 13, the horizontal axis represents wavelength (nm) and the vertical axis represents spectral radiation intensity (μJ / cm ² ).

As is apparent from FIGS. 12 and 13, the light emitted from the short arc flash lamp includes light having a wavelength of 230 nm or less in any case where the xenon gas pressure in the light-transmitting bulb is as described above.
In particular, when the xenon gas pressure in the light transmissive bulb is 3 atm, 5 atm, and 8 atm, the light intensity near the wavelength of 170 nm increases. This is thought to be due to the increased emission of xenon excimer.
As a result of investigations by the inventors, it has been found that when the xenon gas pressure in the light transmissive valve exceeds 8 atm, the reliability of the strength of the light transmissive valve decreases.
Therefore, when a short arc flash lamp is employed as the light source in charge of light irradiation in step A of the present invention, the xenon gas pressure inside the light transmissive bulb is preferably set to 8 atm or less.

FIG. 14 shows the relationship between the discharge current at the time of light emission of the short arc flash lamp and the integrated radiation intensity in the wavelength region of 150 to 240 nm, using the pressure of the xenon gas sealed in the light transmissive bulb as a parameter. In FIG. 14, the horizontal axis represents current (A), and the vertical axis represents integrated radiation intensity (relative value) in the wavelength region of 150 to 240 nm. The xenon gas pressure value as a parameter is 2 atm (2.03 × 10 ⁵ Pa), ³ atm (3.04 × 10 ⁵ Pa), ⁵ atm (5.07 × 10 ⁵ Pa), 8 atm (8.10 ×). 10 ⁵ Pa).

As is apparent from FIG. 14, the integrated radiation intensity in the wavelength region of 150 to 240 nm becomes almost zero when the value of the discharge current during short arc flash lamp emission is less than 1500 A, regardless of the xenon gas pressure.
As described above, the action of generating active oxygen in the vicinity of the oxide film and the action of activating the surface of the oxide film in Step A (that is, the action of extracting hydrogen from the oxide film and repairing oxygen defects in the oxide film) are 230 nm in wavelength. It is generated by the following ultraviolet irradiation. Therefore, in order to use the short arc flash lamp described above as a lamp for the process A, it is necessary to use it under an operating condition such that the discharge current is 1500 A or more.

  In summary, the short arc xenon flash lamp employed as the light source in charge of light irradiation in the process A has a xenon gas pressure in the arc tube of 8 atm or less and a discharge current during discharge of 1500 A or more. Need to work.

[Configuration Example of Thin Film Transistor Manufacturing Apparatus of Example 2]
[1] When a long arc flash lamp is used as the light source for the process A FIG. 15 shows a configuration example of a thin-film transistor manufacturing apparatus according to the second embodiment.
The thin-film transistor manufacturing apparatus shown in FIG. 15 is the same as the thin-film transistor manufacturing apparatus of Example 1 shown in FIG. The light source in charge of light irradiation in the process A and the light source in charge of light irradiation in the process B are configured.
Here, the light source in charge of light irradiation in the process A is a long arc xenon flash lamp 40. The material of the arc tube of the xenon flash lamp 40 is alumina. The effective light emission length is 250 mm, the xenon gas pressure inside the arc tube is 0.6 atm (60 kPa), and the current density during light emission is 5096 A / cm ² . The spectral emission spectrum of the light emitted from the flash lamp 40 is as shown in FIG. In FIG. 11, since there is a maximum peak of radiation intensity in the vicinity of a wavelength of 230 nm, this lamp functions as a light source in charge of light irradiation in the process A.

On the other hand, the light source in charge of light irradiation in the process B is also a long arc xenon flash lamp. The material of the arc tube of the xenon flash lamp 20 is quartz glass. The effective light emission length is 250 mm, the xenon gas pressure inside the arc tube is 0.6 atm (60 kPa), and the current density during light emission is 1910 A / cm ² . The spectral emission spectrum of the light emitted from the flash lamp 20 is as shown in FIG.
In FIG. 5, since strong radiation is confirmed in the wavelength region of 800 nm or more, this lamp functions as a light source in charge of the light irradiation in the process B.
Here, for ease of explanation, the long arc xenon flash lamp in charge of process A light irradiation is referred to as a sapphire flash lamp, and the long arc xenon flash lamp in charge of process B light is referred to as a xenon flash lamp. I will do it.

The structure of the sapphire flash lamp 40 for the process A and the xenon flash lamp 20 for the process B are as shown in FIG. Both have a straight tubular shape, and a plurality of the lamps 20 and 40 are arranged in parallel as shown in FIG.
A work stage 8 is provided below both lamps 20.40, and the work 7 is placed on the work stage 8.
The number and interval of the plurality of sapphire flash lamps 40 are such that light including ultraviolet rays having a wavelength of 230 nm or less emitted from the sapphire flash lamp 40 is irradiated on the entire work 7, and the irradiance of the light on the work 7. It is set as appropriate so that the distribution is uniform to some extent.
Similarly, the number and interval of the xenon flash lamps 20 are such that the light including infrared rays for thermal annealing emitted from the xenon flash lamp 20 is irradiated on the entire work 7, and the radiation of the light on the work 7 is emitted. It is appropriately set so that the illuminance distribution becomes uniform to some extent.

In the example shown in FIG. 15, a plurality of straight tubular sapphire flash lamps 40 and a plurality of straight tubular xenon flash lamps 20 are alternately arranged so that light emitted from both lamps 20 and 40 can irradiate the entire workpiece 7. And arranged in parallel. However, the arrangement is not limited to this as long as the light from both lamps 20 and 40 is irradiated onto the workpiece 7 in the above-described state.
The reflecting mirror 3 is made of, for example, an aluminum plate having a mirror-finished light reflecting surface. Similar to the thin film transistor manufacturing apparatus of the first embodiment, the sapphire flash lamp 40, the light source unit 2 including the flash lamp 20, the work 7, and the work stage 8 are arranged in the processing chamber 1 in which the atmosphere contains oxygen. Is done. As described above, only the work 7 and the work stage 8 are disposed in the processing chamber 1, and a light transmitting member that transmits light emitted from the light source unit 2 is provided in the processing chamber 1, so that the light source unit is outside the processing chamber. It may be arranged.
The processing chamber 1 is connected to an exhaust means 5 for discharging ozone generated in the processing chamber 1, and an air filter 6 that suppresses inflow of contamination in the atmosphere into the processing chamber 1 is provided. A suction port 6a is provided. When the exhaust means 5 is operated and the ozone in the processing chamber 1 is exhausted, an oxygen-containing gas (such as the atmosphere) from which the contamination is almost removed flows into the processing chamber 1 from the suction port 6a. Operations of the power supply unit 4 that supplies power to the light source unit 2 and the exhaust unit 5 are controlled by the control unit 9.

[2] When a short arc flash lamp is used as the light source for the process A FIG. 16 shows another configuration example of the thin-film transistor manufacturing apparatus according to the second embodiment.
The configuration example of the thin-film transistor manufacturing apparatus shown in FIG. 16 employs a short arc xenon flash lamp 30 as a light source in charge of light irradiation in process A, and uses a reflecting mirror 3d corresponding to the short arc xenon flash lamp 30. Other than the above, the configuration is the same as the configuration example of the thin film transistor manufacturing apparatus shown in FIG.
The structure of the short arc xenon flash lamp 30 is as shown in FIG. 10. The distance between the electrodes is 3 mm, the xenon gas pressure inside the arc tube is 5 atm (507 kPa), and the current is 5000 A. The spectral emission spectrum of the light emitted from this flash lamp is as shown in FIG. In FIG. 13C, since the maximum peak of the radiation intensity is in the vicinity of a wavelength of 172 nm, this lamp functions as a light source in charge of the light irradiation in the process A.

On the other hand, the light source in charge of light irradiation in the process B is a long arc xenon flash lamp 20 equivalent to that in the thin film transistor manufacturing apparatus shown in FIG. 15, and the structure of the lamp and the spectral emission of light emitted from the lamp. Since the spectrum and the like are the same, detailed description is omitted here.
Here, for ease of explanation, the short arc xenon flash lamp in charge of light irradiation in process A is a short arc flash lamp, and the long arc xenon flash lamp in charge of light irradiation in process B is a long arc flash lamp. Will be called.

In the thin film transistor manufacturing apparatus of Example 2 shown in FIG. 16, the short arc flash lamp 30 used as the light source in charge of light irradiation in Step A of the present invention is a rare gas fluorescent lamp that is a light source for Step A of Example 1. In addition, unlike the long arc flash lamp which is the light source for step A of Example 2 shown in FIG. 15, the light emitting portion is small. Therefore, as shown in FIG. 16, each short arc flash lamp 30 is individually provided with a reflecting mirror 3 d in order to efficiently irradiate the work with light emitted from the short arc flash lamp 30.
On the other hand, the shape of the long arc flash lamp 20 in charge of the light irradiation in the process B is a straight tube shape as shown in FIG. 4, and one or more lamps are arranged between the flash lamps 30 provided with the reflecting mirror 3d.
A work stage 8 is provided below the lamps 20 and 30, and the work 7 is placed on the work stage 8.

The number and interval of the short arc flash lamps 30 including the reflecting mirror 3d are such that light including ultraviolet rays having a wavelength of 230 nm or less emitted from the lamp 30 is irradiated on the entire work 7 and the light on the work 7 is irradiated with the light. The irradiance distribution is appropriately set so that the distribution is uniform to some extent.
Similarly, the number of long arc flash lamps 20 that are the light sources of the process B and the interval thereof are set such that light including infrared rays for thermal annealing emitted from the long arc flash lamp 20 is irradiated on the entire workpiece 7, and The irradiance distribution of the light on the work 7 is appropriately set so as to be uniform to some extent.

In the example shown in FIG. 16, two long arc flash lamps 20 that are light sources for the process B are arranged in parallel between each short arc flash lamp 30 that includes the reflector 3d that is the light source for the process A, and One short arc flash lamp 30 is arranged between a group of long arc flash lamps 20 consisting of two long arc flash lamps 20 and emits from both light sources (light source for process A, light source for process B). If the light to be irradiated is irradiated to the whole workpiece | work substantially uniformly, it will not restrict to this.
For example, a plurality of short arc flash lamps for process A may be provided in a direction perpendicular to the paper surface of FIG.
The configuration and operation of the reflecting mirror 3, the processing chamber 1, the exhaust unit 5, the air filter 6, the power feeding unit 4, the control unit 9 and the like are the same as those in the thin film transistor manufacturing apparatus shown in FIG. The detailed explanation is omitted.

[Experiment 2]
Using the thin film transistor manufacturing apparatus shown in FIG. 15, an IGZO oxide film on the substrate was processed under the following conditions to manufacture a thin film transistor, and the gate voltage versus drain current characteristic of the thin film transistor was examined.
Here, the light source used in the process A is the sapphire flash lamp described above (a long arc xenon flash lamp using alumina as the arc tube), the xenon gas pressure inside the arc tube is 0.6 atm (60 kPa), and the light emission. The spectral emission spectrum of the light emitted from this flash lamp is as shown in FIG. 11 when the current density at the time is 5096 A / cm ² , and the light irradiating the work in the process A has the maximum peak of the radiant intensity around the wavelength of 230 nm. There is light.

On the other hand, the light source used in the process B is the above-mentioned long arc flash lamp (long arc xenon flash lamp), the xenon gas pressure inside the arc tube is 0.6 atm (60 kPa), and the current density during light emission is 1910 A / cm ^2, the spectral emission spectrum of light emitted from the flash lamp is as shown in FIG. 5, the light in the step B is applied to the workpiece, the wavelength region is of the order of 300 to 1100 nm, the above wavelengths 800nm It is light with a large intensity in the wavelength region.

The processing conditions for the IGZO oxide film are as follows. All the workpieces are placed in an air atmosphere, and the temperature is room temperature.
(Condition 1)
IGZO oxide film light irradiation treatment in step A and light irradiation treatment in step B (as deposition state): Same as condition 1 in experiment 1.
(Condition 2)
Process A: Energy on the surface of the workpiece irradiated with light from the sapphire flash lamp is 2.3 J / cm ² , and the emission pulse width of the emission pulse is 0.1 ms (full width at half maximum: FWHM).
Process B: Energy on the workpiece surface of the light irradiated from the long arc flash lamp is 2.7 J / cm ² , and the emission pulse width of the emission pulse is 5 ms (full width at half maximum: FWHM)
(Condition 3)
Process A: The energy of the light irradiated from the sapphire flash lamp on the workpiece surface is 2.8 J / cm ² , and the emission pulse width of the emission pulse is 0.1 ms (full width at half maximum: FWHM).
Process B: Energy on the workpiece surface irradiated with light from the long arc flash lamp is 3.2 J / cm ² , and the emission pulse width of the emission pulse is 5 ms (full width at half maximum: FWHM)

The light emission timing chart for conditions 2 and 3 is as shown in FIG. FIG. 17A shows the light emission timing of the sapphire flash lamp, FIG. 17B shows the light emission timing of the xenon flash lamp, the horizontal axis represents time, and the vertical axis represents the light intensity (relative value).
That is, the light emission of the sapphire flash lamp and the light emission of the long arc flash lamp (xenon flash lamp) were performed at the same timing. As described above, the emission pulse width of the sapphire flash lamp is 0.1 ms (full width at half maximum: FWHM), and the emission pulse width of the long arc flash lamp is 5 ms (full width at half maximum: FWHM). Even after is finished, the long arc flash lamp continues to emit light for a while.
(Condition 4)
Step A: None Step B: Energy 2.5 J / cm ^{2 on} the workpiece surface of the light irradiated from the long arc flash lamp, and the emission pulse width of the emission pulse is 5 ms (full width at half maximum: FWHM)

FIG. 18 shows gate voltage versus drain current characteristics of a thin film transistor (TFT) in which the IGZO oxide film is processed under the above four conditions. In the figure, a broken line (1) is a characteristic curve in the condition (1), a solid line (2) is a characteristic curve in the condition (2), a solid line (3) is a characteristic curve in the condition (3), An alternate long and short dash line (4) is a characteristic curve in the condition (4).
As is apparent from the characteristic curve of the broken line (1) in FIG. 18, in the case of the condition (1) in which the IGZO oxide film is not subjected to the light irradiation treatment, there is almost no change in the drain current even when the gate voltage is changed. It is almost constant at about 10 ^-10 A. That is, in the case of condition (1), it can be seen that the IGZO oxide film is not given semiconductor characteristics, and the IGZO oxide film is in a state close to an insulating film.

In the case of condition (2), in step A, the IGZO oxide film is supplied with 2.3 J / cm ^{2 of} light energy having the spectral emission spectral characteristics shown in FIG. 11 from the sapphire flash lamp. In contrast, 2.7 J / cm ^{2 of} light energy having the spectral emission spectral characteristics shown in FIG. 5 was given from a long arc flash lamp (xenon flash lamp). At this time, as apparent from the characteristic curve of the solid line (2) in FIG. 18, the value of the drain current increases rapidly in the vicinity of the gate voltage of −5V.
That is, when the gate voltage is about −5 V, the TFT performs the on / off operation, so that the semiconductor characteristics are imparted to the IGZO oxide film.

In the case of condition (3), in step A, 2.8 J / cm ^{2 of} light energy having the spectral emission spectral characteristics shown in FIG. 11 is given from the sapphire flash lamp to the IGZO oxide film. In contrast, 3.2 / cm ^{2 of} light energy having the spectral emission spectral characteristics shown in FIG. 5 was given from the long arc flash lamp. At this time, as is apparent from the characteristic curve of the solid line (3) in FIG. 18, the value of the drain current rapidly increases near the gate voltage + 2V.
That is, when the gate voltage is about +2 V, the TFT performs the on / off operation, so that the semiconductor characteristics are imparted to the IGZO oxide film.

In the case of condition (4), the ultraviolet irradiation process of the process A was not performed with respect to the IGZO oxide film, and only the process B which is a heat treatment was performed. That is, 2.5 J / cm ^{2 of} light energy having the spectral emission spectral characteristics shown in FIG. 5 was given from the long arc flash lamp to the IGZO oxide film.
At this time, as is apparent from the characteristic curve of the alternate long and short dash line (4) in FIG. 18, there is almost no change in the drain current even when the gate voltage is changed, and it is almost constant at about 1 × 10 ⁻¹⁰ A. That is, in the condition (4), the semiconductor characteristics are not imparted to the IGZO oxide film, and it can be seen that the state of the IGZO oxide film is not much different from that in the (condition 1) without light irradiation.

  From the above results, by adopting a method for manufacturing a thin film transistor (TFT) using an oxide semiconductor including Step A and Step B of the present invention, the oxide formed on the substrate is in a room temperature state. It has been found that semiconductor characteristics can be imparted to the oxide.

Here, when the condition (2) is compared with the condition (3), the threshold voltage Vth of the gate voltage in the condition (2) is about −5V, the threshold voltage Vth in the condition (3) is about + 2V, The shift amount ΔVth (= 0−Vth) of the value of Vth from the voltage 0V is small in the condition (3).
This is because, in step A, the amount of light energy having the spectral emission spectral characteristics shown in FIG. 11 from the sapphire flash lamp to the IGZO oxide film is larger in the condition (3) than in the condition (2). Compared with the condition (2), the amount of active oxygen generated in the vicinity of the IGZO oxide film is large, the degree of activation of the surface of the IGZO oxide film is large, and the hydrogen extracted from the amorphous IGZO thin film is extracted. It is considered that oxygen defects were repaired efficiently.
In step B, the condition (3) is greater when the amount of light energy having the spectral emission spectral characteristics shown in FIG. 5 from the long arc flash lamp (xenon flash lamp) to the IGZO oxide film is greater than the condition (2). Compared with the condition (2), it is considered that the diffusion of oxygen into the IGZO oxide film was sufficiently performed.

On the other hand, in the case of the condition (4) in which the process A is omitted and only the thermal annealing action of the process B is performed, the IGZO oxide film has no semiconductor characteristics. This is presumably because diffusion of the oxygen defect repairing action was not performed because the thermal annealing was performed without performing the hydrogen extraction action and the oxygen defect repairing action in the process A on the IGZO film.
Further, the light energy having the spectral emission spectral characteristics shown in FIG. 5 given to the IGZO oxide film is 11 J / cm ² in the condition (4) of Experiment 1, whereas the condition (4) of Experiment 2 is. Is as small as 2.5 J / cm ² , it is considered that the state of the IGZO film is not much different from that in the case of (condition 1) without light irradiation.

In the above conditions (2) and (3), the light emission of the sapphire flash lamp and the light emission of the long arc flash lamp (xenon flash lamp) are performed at the same timing, but the present invention is not limited to this. If the light emission of the long arc flash lamp continues for a while after the light emission of the sapphire flash lamp, the long arc flash prior to the light emission of the sapphire flash lamp, for example, as shown in FIGS. It is also possible to set the light emission timing of both lamps so that the lamps emit light.
The setting of the light emission timing of both lamps is appropriately determined in consideration of the type of amorphous oxide film, the film formation state, the heat resistant temperature of the substrate, the degree of oxygen diffusion, the energy given from each lamp to the amorphous oxide film, and the like. The

In addition, a similar experiment was performed using the thin film transistor manufacturing apparatus shown in FIG. 16 which employs a short arc flash lamp as the light source for the process A. As described above, the short arc flash lamp used has a distance between electrodes of 3 mm, a xenon gas pressure inside the arc tube of 5 atm (507 kPa), and a current of 5000 A. The spectral emission spectrum of the light emitted from this flash lamp is as shown in FIG.
Here, the light energy having the spectral emission spectral characteristic shown in FIG. 13C with respect to the IGZO oxide film by light emission of one short arc flash lamp was about 0.072 J / cm ² . The emission pulse width of the emission pulse was 10 μs (full width at half maximum: FWHM).

Compared with the case where the thin film transistor manufacturing apparatus shown in FIG. 15 employing a sapphire flash lamp as the light source for the process A is used, the light provided to the IGZO oxide film by the light emission of the short arc flash lamp once in the process A. The energy is considerably smaller than the light energy given to the IGZO oxide film by one light emission of the sapphire flash lamp.
Therefore, when performing the light irradiation of the process A, the short arc flash lamp is caused to emit light a plurality of times, and the total amount of light energy is substantially equal to the light energy given to the IGZO oxide film by one emission of the sapphire flash lamp. It was made to become.

FIG. 20 shows a schematic diagram of a light emission timing chart corresponding to Condition 2 and Condition 3 of Experiment 2 when a short arc flash lamp is used. FIG. 20A shows the light emission timing of the short arc flash lamp, and FIG. 20B shows the light emission timing of the xenon flash lamp. As shown in FIG. 20A, the short arc flash lamp for the process A is caused to emit a plurality of times, and at the same timing as the last light emission timing of the short arc flash lamp, the process B as shown in FIG. A long arc flash lamp (xenon flash lamp) was used. The light emission frequency of the short arc flash lamp was 30 Hz.
When the experiment was performed in this way, the experimental result showed the same tendency as in the experiment 2. That is, the semiconductor characteristics were imparted to the IGZO film only when the workpieces placed in the air atmosphere and having a temperature of room temperature were subjected to the process A and the process B of the present invention.

The light emission patterns (light emission timing charts) of the short arc flash lamp for process A and the long arc flash lamp for process B (xenon flash lamp) are not limited to those shown in FIG. For example, as shown in FIGS. 21 (a) and 21 (b), the light emission frequency of the short arc flash lamp may be increased, or from the light emission of a plurality of short arc flash lamps and the light emission of one long arc flash lamp. A plurality of light emission pattern sets may be implemented.
Although not shown, the light emission pattern set may be configured by combining a plurality of short arc flash lamps and a plurality of xenon flash lamps.
The setting of the light emission timing of both lamps is appropriately determined in consideration of the type of amorphous oxide film, the film formation state, the heat resistant temperature of the substrate, the degree of oxygen diffusion, the energy given from each lamp to the amorphous oxide film, and the like. The

DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Light source part 3, 3a, 3b, 3d Reflective mirror 3c Projection part 4 Power supply means 5 Exhaust means 6 Air filter 6a Inlet 7 Work piece 8 Work stage 9 Control part 10 Noble gas fluorescent lamp 11a, 11b Electrode 13 Glass tube 14 UV reflection film 15 Low softening point glass layer 16 Phosphor layer 17 Protective film 20 Flash lamp 21 Quartz glass tube 22a, 22b Electrode 23 Sealing portion 24 External lead 30 Short arc flash lamp 31 Light-transmitting bulbs 32a, 32b Electrode 34 Stem 33a, 33b Trigger electrode 35, 36 External lead 40 Sapphire flash lamp

Claims (7)

A method for producing a thin film transistor, comprising at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film formed on a substrate, wherein the semiconductor layer is made of an amorphous metal oxide,
In an oxygen-containing atmosphere,
For the oxide provided on the substrate,
Irradiating light including a wavelength region in which active oxygen is generated and a wavelength region that activates the oxide and extracts hydrogen mixed in the oxide; and
In a state where hydrogen mixed in the oxide is extracted and active oxygen is generated in the vicinity of the oxide, light including a wavelength range for heating the oxide to promote diffusion of oxygen into the oxide is emitted. A process for producing a thin film transistor, comprising the step of irradiating B. An apparatus for manufacturing a thin film transistor, comprising at least a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and a gate insulating film formed on a substrate, wherein the semiconductor layer is made of an amorphous metal oxide,
At least one first lamp for irradiating the thin film transistor with light, and at least one second lamp for irradiating the thin film transistor, which is maintained in an oxygen-containing atmosphere;
A reflecting mirror that reflects the light emitted from the first lamp and the second lamp to the thin film transistor; and a power supply device that supplies power to the first lamp and the second lamp.
The first lamp emits light including a wavelength region where active oxygen is generated and a wavelength region which activates the oxide and extracts hydrogen mixed in the oxide with respect to the oxide provided on the substrate. Is to release,
In the second lamp, the hydrogen provided in the oxide is extracted from the oxide provided on the substrate and active oxygen is generated in the vicinity of the oxide. An apparatus for manufacturing a thin film transistor, which emits light including a wavelength region for heating the oxide so as to promote diffusion of oxygen. The first lamp is a rare gas fluorescent lamp that emits light including a wavelength range of 230 nm or less,
3. The thin film transistor manufacturing apparatus according to claim 2, wherein the second lamp is a flash lamp that emits light including a wavelength range of 800 nm or more. The thin film transistor manufacturing apparatus includes:
4. The thin film transistor manufacturing apparatus according to claim 3, further comprising a light shielding means for shielding light emitted from the flash lamp from being irradiated to the rare gas fluorescent lamp. 5. The thin film transistor manufacturing apparatus according to claim 4, wherein the light shielding means is a second reflecting mirror surrounding a part of the rare gas fluorescent lamp. The light shielding means is a protrusion provided on a part of the reflecting surface of the reflecting mirror,
One of the first lamp and the second lamp is disposed so as to be surrounded by the protrusion,
The other of the first lamp and the second lamp is disposed at a position facing a flat reflecting surface that is not a protrusion of the reflecting mirror,
The shape of the protrusion, the position of one lamp surrounded by the protrusion, and the position of the other lamp facing the flat reflecting surface that is not the protrusion of the reflecting mirror are emitted from one lamp. 5. The thin film transistor manufacturing apparatus according to claim 4, wherein the apparatus is determined so that the other lamp is not irradiated with light. The first lamp is a flash lamp that emits light including a wavelength range of 230 nm or less,
3. The thin film transistor manufacturing apparatus according to claim 2, wherein the second lamp is a flash lamp that emits light including a wavelength range of 800 nm or more.

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