JP2008084824A - Manufacturing method of conductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor which excels in conductivity and has proper transparency. <P>SOLUTION: The manufacturing method of a conductor includes a process in which a precursor layer 12' comprising a titanium oxide with an addition of one or a plurality of dopants selected from among a group comprising Nb, Ta, Mo, As, Sb, Al, Hf, Si, Ge, Zr, W, Co, Fe, Cr, Sn, Ni, V, Mn, Tc, Re, P and Bi and a process in which the precursor layer 12' is annealed, under a reducing atmosphere for forming a metal oxide layer 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a conductor.

  In recent years, there is a growing need for large-sized and small-sized liquid crystal display panels. In order to realize this, it is necessary to reduce the power consumption of the display element, and it is indispensable to apply a transparent electrode having a high visible light transmittance and a low resistance value.

  In particular, an organic electroluminescence element that is being developed recently is a self-luminous type and is effective in application to a small portable terminal, but has a problem that power consumption is large due to current driving. In addition, plasma display panels (PDPs) that are currently spreading on the market and field emission displays (FEDs) that are being developed as next-generation displays have a problem of high power consumption. From these points, there is a great expectation for reducing the resistance of the transparent conductive thin film.

  A typical example of the transparent conductive thin film is an indium tin oxide film (hereinafter referred to as an ITO film) made of indium oxide doped with tin. Although the ITO film is excellent in transparency and has high conductivity, the crustal content of In is as low as 50 ppb, and there is a drawback that the cost of raw materials increases with the depletion of resources.

In recent years, titanium dioxide (TiO ₂ ) having both chemical resistance and durability has attracted attention as a material for transparent conductors (for example, Non-Patent Document 1 below).
Patent Document 1 below proposes a method of obtaining a transparent conductor by forming a metal oxide layer made of M: TiO ₂ (M is Nb, Ta, etc.) having an anatase crystal structure on a substrate. Yes. Here, it is shown that a single crystal thin film (solid solution) of M: TiO ₂ having an anatase type crystal structure formed by epitaxial growth remarkably improves electrical conductivity while maintaining transparency.
The following Patent Document 2 discloses a method of forming a transparent conductive thin film laminate by forming a laminate in which transparent high-refractive-index thin film layers containing hydrogen and metal thin film layers are alternately laminated on a transparent substrate. Proposed. The transparent high refractive index thin film layer is made of, for example, titanium oxide.
None of the documents describes annealing after the metal oxide layer is formed.
Applied Physics Vol.73, No.5 (2004), 587-592 International Publication No. 2006/016608 Pamphlet JP 2004-95240 A

The single crystal thin film of M: TiO ₂ having an anatase type crystal structure described in Patent Document 1 is difficult to manufacture and has poor productivity, and thus has low feasibility.
Since the transparent refractive index thin film layer in Patent Document 2 contains hydrogen during film formation, the transparency tends to be insufficient.
Thus, it has not been easy to realize a conductor having a small electrical resistance and excellent transparency.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method capable of producing a titanium oxide-based conductor excellent in conductivity and excellent in transparency with high productivity.

  In order to solve the above problems, the method for producing a conductor of the present invention includes Nb, Ta, Mo, As, Sb, Al, Hf, Si, Ge, Zr, W, Co, Fe, Cr, Sn, Ni, Forming a precursor layer made of titanium oxide to which one or more dopants selected from the group consisting of V, Mn, Tc, Re, P and Bi are added on the surface of the substrate; and It has a step of forming a metal oxide layer by annealing in a reducing atmosphere.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in electroconductivity, a transparent titanium oxide type conductor can be manufactured with sufficient productivity.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a sectional view showing an embodiment of the present invention. In the present embodiment, first, a precursor layer 12 ′ made of titanium oxide to which a specific dopant is added is formed on the surface of a substrate (base) 11, and then the precursor layer 12 ′ is annealed in a reducing atmosphere. Thus, a conductive layer (conductor) 12 made of a metal oxide is obtained. The conductive layer 12 is made of titanium oxide containing a specific dopant, and may hereinafter be referred to as a metal oxide layer 12.

<Substrate>
The material of the substrate is not particularly limited. For example, a single crystal material, a polycrystalline material, or an amorphous material may be used, and a material in which these crystal states are mixed may be used.
Specific examples include a substrate composed of a single crystal or polycrystal of strontium titanate (SrTiO ₃ ); a single crystal substrate or a polycrystal substrate composed of a rock salt type crystal having a perovskite crystal structure or a similar structure; a quartz substrate; a non-alkali substrate Examples thereof include glass substrates such as glass (manufactured by Asahi Glass Co., Ltd., product name: AN100), plastic substrates, and semiconductor substrates such as silicon substrates (thermally oxidized Si substrates) having a thermal oxide film formed on the surface. These may contain dopants, impurities and the like as long as the effects of the present invention are not impaired.
When a single crystal substrate of SrTiO ₃ is used as the substrate 11, a substrate finished so that the substrate surface becomes a (100) plane is preferable.
The present invention can form a good conductive film on the surface of the substrate even if the substrate has an amorphous surface. In the present invention, the crystalline state of the substrate is preferably polycrystalline, amorphous, or a mixture of polycrystalline and amorphous.

The shape of the substrate in the present invention is not particularly limited. For example, it may be a plate-like substrate 11 or a film such as a plastic film.
The thickness of the substrate 11 is not particularly limited. When the transparency of the substrate 11 is required, 1 mm or less is preferable. If a plate-like substrate is required to have mechanical strength and the transmittance may be sacrificed somewhat, it may be thicker than 1 mm. The thickness of the substrate 11 is preferably 0.2 to 1 mm, for example.

The substrate 11 can be polished if necessary. A crystalline substrate such as a SrTiO ₃ substrate is preferably used after being polished. For example, mechanical polishing is performed using diamond slurry as an abrasive. In the mechanical polishing, it is preferable that the particle diameter of the diamond slurry to be used is gradually refined and finally mirror-polished with a diamond slurry having a particle diameter of about 0.5 μm. Then, it may be further flattened by polishing using colloidal silica until the root mean square roughness (rms) is 10 mm (1 nm) or less.

  Prior to the formation of the precursor layer 12 ', the substrate 11 may be pretreated. The pretreatment can be performed by the following procedure, for example. First, the substrate is washed with acetone, ethanol or the like. Next, the substrate is immersed in high-purity hydrochloric acid (for example, EL grade, concentration 36 mass%, manufactured by Kanto Chemical Co., Inc.) for 2 minutes. Next, the substrate is moved into pure water and rinsed with hydrochloric acid or the like. Next, the substrate is moved into new pure water, and ultrasonic cleaning is performed for 5 minutes. Next, the substrate is taken out from the pure water, and nitrogen gas is blown onto the substrate surface to remove moisture from the substrate surface. These treatments are performed at room temperature, for example. These treatments are considered to remove oxides, organic substances, etc. from the substrate surface. Although hydrochloric acid was used in the above example, an acid such as aqua regia or hydrofluoric acid may be used instead. Further, the treatment with an acid may be performed at room temperature, or a heated acid may be used.

<Precursor layer>
The precursor layer 12 ′ is made of Nb, Ta, Mo, As, Sb, Al, Hf, Si, Ge, Zr, W, Co, Fe, Cr, Sn, Ni, V, Mn, Tc, Re, P, and Bi. It consists of titanium oxide to which one or more dopants selected from the group consisting of: The titanium oxide in the present invention is one in which the Ti site of TiO ₂ is substituted with a metal atom M (dopant), and may hereinafter be represented as “M: TiO ₂ ”. In the precursor layer 12 ′, the content of impurities other than the dopant metal atom (M), oxygen atom (O), and titanium atom (Ti) is preferably 0.1 atomic% or less.
In particular, when Nb, Ta, Mo, As, Sb, Al, Hf, Si, Ge, Zr, or W is used as a dopant, an improvement in electrical conductivity can be expected while maintaining the transparency of the metal oxide layer 12. Further, when Co, Fe, Cr, Sn, Ni, V, Mn, Tc, Re, P, or Bi is used as a dopant, a magneto-optical effect and ferromagnetism can be expected.
Among the dopants listed above, it is preferable to use Nb, Ta, Mo, As, Sb, or W, and it is particularly preferable to use Nb and / or Ta from the viewpoint of improving conductivity.

The dopant content in the precursor layer 12 ′ is maintained after annealing. Therefore, the dopant content in the precursor layer 12 ′ is set to be the same as the dopant content in the metal oxide layer 12 to be obtained after annealing.
The content of the dopant in the metal oxide layer 12 is more than 0 atomic% and 50 atomic% when the total amount of titanium atoms (Ti) and the metal atoms (M) of the dopant is 100 atomic% (the same applies hereinafter). The following is preferred. If it exceeds 50 atomic%, the characteristics of TiO _{2 as} a base material in the metal oxide layer 12 after annealing will be reduced. More preferably, it is 20 atomic% or less, and especially 10 atomic% or less. On the other hand, the content of the dopant in the precursor layer 12 ′ is more preferably 1 atomic% or more in order to achieve both good high transparency and low resistance in the annealed metal oxide layer 12.
Moreover, the light transmission characteristic in the metal oxide layer 12 can also be adjusted with content of a dopant. For example, by increasing the Nb doping amount, it is possible to cut the long-wavelength red region and transmit only blue light.

The crystal state of the precursor layer 12 ′ affects the crystal state of the metal oxide layer 12 after annealing. Therefore, the crystal state of the precursor layer 12 ′ is set so that a desired crystal state can be obtained after annealing.
The crystal state of the annealed metal oxide layer 12 is preferably an amorphous state, a polycrystalline state, or a state in which amorphous and polycrystalline are mixed, but the polycrystalline state or the amorphous state in that the resistance tends to be lower. More preferred is a state in which a polycrystal is mixed. Furthermore, from the viewpoint of easy production, a state where a part thereof is amorphous, that is, a mixed state where the presence of amorphous and polycrystal can be confirmed is preferable. When a polycrystal exists in the metal oxide layer 12, an anatase type is preferable because the crystal constituting the polycrystal tends to have a lower resistance.
In addition, since an amorphous structure generally has no birefringence, an amorphous state or a state in which amorphous and polycrystalline are mixed is optically preferable.

If the crystal state of the precursor layer 12 ′ is amorphous, it becomes an amorphous state after annealing or a mixed state of amorphous and polycrystalline depending on annealing conditions. If the annealing temperature is higher than the crystallization temperature, polycrystallization occurs.
If the precursor layer 12 'is in a mixed state of amorphous and polycrystalline, it becomes a mixed state of amorphous and polycrystalline after annealing. It is also possible to obtain a complete polycrystal depending on the conditions.
When polycrystals are present in the precursor layer 12 ′, if the crystals constituting the polycrystals are anatase type, the polycrystals of the metal oxide layer 12 after annealing are anatase types. If the polycrystal is rutile type in the precursor layer 12 ′, the polycrystal of the metal oxide layer 12 is rutile type.

The thickness of the precursor layer 12 ′ may decrease by about 0 to 10% after annealing. Accordingly, the thickness of the precursor layer 12 ′ is preferably set according to the manufacturing conditions so that the thickness of the metal oxide layer 12 after annealing becomes a desired thickness.
The thickness of the metal oxide layer 12 is not particularly limited, and can be set as appropriate depending on the application. For example, 20 to 1000 nm is preferable, and 100 to 200 nm is more preferable.

<Method for forming precursor layer>
The precursor layer can be formed by appropriately using a known film forming method. Specifically, pulsed laser deposition (PLD) method, physical vapor deposition (PVD) method such as sputtering method; chemical vapor deposition (CVD) method such as MOCVD method; sol-gel method, chemical solution method, etc. The film-forming method by the synthesis process from the solution of this is mentioned.
In particular, the PLD method is preferable because a good film state can be easily obtained, and the sputtering method is preferable because a film can be easily formed regardless of the crystallinity of the substrate.

[PLD method]
Hereinafter, as a first example, a method of forming the precursor layer 12 ′ on the substrate 11 by the PLD method will be described.
FIG. 2 is a schematic configuration diagram showing an example of a PLD apparatus 30 preferably used in this method. The PLD apparatus 30 is arranged in a chamber 31 such that the substrate 11 and the target 39 face each other and the facing surfaces are substantially parallel to each other. The chamber 31 is capable of producing a high-quality thin film by maintaining an appropriate degree of vacuum and preventing impurities from entering from the outside.
The substrate 11 can be rotated around a rotation axis 35 perpendicular to the surface of the substrate 11 by a motor (not shown). The target 39 is also rotatable about a rotation axis 38 perpendicular to the surface 39a by a motor (not shown).

An infrared lamp 36 for heating the substrate 11 is installed in the chamber 31. The temperature of the substrate 11 is monitored by a radiation thermometer 37 installed outside the chamber 31 through the window 31b, and is controlled to always be a constant temperature.
A gas supply unit 44 is provided outside the chamber 31, and oxygen gas can be injected into the chamber 31 through an oxygen gas flow rate adjustment valve 45 for adjusting the flow rate of oxygen gas. Further, a turbo molecular pump 42 and a pressure valve 43 are connected to the chamber 31 in order to realize film formation under reduced pressure. The pressure in the chamber 31 is determined by using an oxygen gas flow rate adjustment valve 45 and a pressure valve 43. For example, the oxygen partial pressure is 1 × 10 ⁻⁵ to 1 × 10 ⁻⁴ Torr (1.33 × 10 ⁻³ Pa to 1.3. 33 × 10 ⁻² Pa). The turbo molecular pump 42 is connected to an oil rotary pump 40 and a backflow prevention valve 41, and the pressure on the exhaust side of the turbo molecular pump 42 is always 10 ⁻³ torr (1.33 × 10 ⁻¹ Pa) or less. To be kept.

An optical oscillator 32 is provided outside the chamber 31, and a pulse laser beam oscillated by the optical oscillator 32 reflects a reflecting mirror 33 for adjusting an irradiation position, a lens 34 for controlling a spot diameter, and The light is incident on the surface 39 a of the target 39 facing the substrate 11 through the window 31 a of the chamber 31. The optical oscillator 32 oscillates, for example, a KrF excimer laser having a pulse frequency of 1 to 10 Hz, a laser fluence (laser power) of 1 to ² J / cm ² and a wavelength of 248 nm as the pulse laser light. The oscillated pulsed laser light is spot-adjusted by the reflecting mirror 33 and the lens 34 so that the focal position is in the vicinity of the target 39 and is incident on the surface 39a of the target 39 at an angle of about 45 °.

The target 39 is made of, for example, a Nb: TiO ₂ sintered body containing 6 atomic% Nb. The Nb: TiO ₂ is an example in which the dopant (M) is Nb. The dopant (M) may be any of the dopants in the present invention described above, and a plurality of types of metals may be used in combination.
For example, an Nb: TiO ₂ sintered body can be produced by mixing TiO ₂ and Nb ₂ O ₅ powders weighed so as to have a desired atomic ratio, and then thermoforming the mixed powder. The composition of the target is almost the same as the composition of the film.

In order to form the precursor layer 12 ′ using the PLD apparatus 30, first, the substrate 11 is placed in the chamber 31. Next, in order to remove impurities on the substrate surface and to obtain a flat surface at the atomic level, pretreatment annealing is performed under conditions of an oxygen partial pressure of 10 ⁻⁵ Torr (1.33 × 10 ⁻³ Pa) and a substrate temperature of 500 ° C. You may go. The pretreatment annealing is preferably performed for 1 hour or longer, for example.

Next, the substrate temperature is set to a predetermined value while maintaining the oxygen partial pressure in the chamber at about 1 × 10 ⁻⁵ to 1 × 10 ⁻⁴ Torr (1.33 × 10 ⁻³ Pa to 1.33 × 10 ⁻² Pa). And the substrate 11 is driven to rotate. Further, by intermittently irradiating the pulsed laser light while rotating the target 39, the temperature of the surface of the target 39 is rapidly increased to generate ablation plasma. Ti atoms, Nb atoms, and O atoms contained in the ablation plasma move to the substrate 11 while gradually changing the state while repeating a collision reaction with the oxygen gas in the chamber 31. Then, the particles containing Ti atoms, Nb atoms, and O atoms that have reached the substrate 11 are diffused as they are on the surface of the substrate 11 to be thinned. Thus, the precursor layer 12 ′ is formed on the substrate 11.

[Sputtering method]
Hereinafter, as a second example, a method of forming the precursor layer 12 ′ on the substrate 11 by a sputtering method will be described.
A known sputtering apparatus can be used as appropriate. For example, a reactive DC magnetron sputtering apparatus can be used.
First, the target and the substrate 11 are set in the vacuum chamber of the sputtering apparatus. The substrate 11 is set so as to face the surface of the target. A magnet is disposed on the back side of the target. As the target, for example, a titanium alloy containing a predetermined amount of dopant such as a Ti—Nb alloy containing 6 atomic% of Nb can be used. Alternatively, a metal oxide such as a Nb: TiO ₂ sintered body may be used as a target. The dopant may be any of the dopants in the present invention described above, and a plurality of types of metals may be used in combination. In addition, the content rate of the dopant in a target becomes substantially equivalent to the content rate of the dopant in a film | membrane.
The content of the dopant in the target is preferably more than 0 atomic% and not more than 50 atomic% when the total amount of titanium atoms (Ti) and metal atoms (M) of the dopant is 100 atomic%. If it exceeds 50 atomic%, the characteristics of TiO _{2 as} a base material in the metal oxide layer 12 after annealing will be reduced. More preferably, it is 20 atomic% or less, and especially 10 atomic% or less. On the other hand, the content of the dopant in the target is more preferably 1 atomic% or more in order to satisfactorily achieve both high transparency and low resistance in the annealed metal oxide layer 12.

Next, after the inside of the vacuum chamber is evacuated to 5 × 10 ⁻⁴ Pa or less by a pump, O ₂ gas and inert gas are introduced as sputtering gas and adjusted to a predetermined sputtering pressure. The sputtering pressure is preferably about 0.1 to 5.0 Pa. As the inert gas, one or more selected from Ar, He, Ne, Kr, and Xe can be used. It is preferable to adjust the introduction amount so that the ratio (volume basis) of O ₂ / (inert gas + O ₂ ) in the sputtering gas is 0.001 to 30 vol%.
Subsequently, while maintaining the sputtering pressure, a magnetic field having a predetermined intensity is generated by the magnet on the back surface of the target, and a predetermined voltage is applied to the target to form a precursor layer 12 ′ on the substrate.

(Substrate temperature during film formation)
In any of the film forming methods, if the substrate temperature when the precursor layer 12 ′ is formed on the substrate 11 is too high, rutile crystals are generated in the precursor layer, which is not preferable. Therefore, the upper limit of the substrate temperature is preferably 600 ° C. or lower, and preferably room temperature or lower in order to obtain a metal oxide layer having a lower resistance. When the film is formed at room temperature or lower, the precursor layer 12 'is in an amorphous state. The lower limit of the substrate temperature is not particularly limited as long as it is a temperature capable of forming a film. For example, it is 77K (about -196 ° C) or higher.
The “room temperature” at the substrate temperature at the time of film formation is a temperature range that the substrate temperature can take when the substrate is formed without heating, and is about 25 to 100 ° C. in the PLD method, and 25 to 80 in the sputtering method. It is about ℃. In order to lower the resistance of the metal oxide layer 12, it is more preferable to cool as necessary so that the substrate temperature during film formation is maintained at, for example, about 25 to 50 ° C.

<Annealing>
In the present invention, the metal oxide layer 12 as a conductor is formed through a step of annealing the precursor layer 12 ′ in a reducing atmosphere (hereinafter sometimes referred to as post-annealing).
The reducing atmosphere in the present invention means that the partial pressure of the oxidizing gas in the atmosphere is 0.2 × 10 ⁵ Pa or less. The oxidizing gas means a gas that can give oxygen to the precursor layer 12 ′ in the annealing step, and specific examples include O ₂ , O ₃ , NO, NO ₂ , H ₂ O, and the like. When two or more kinds of oxidizing gases are contained in the atmosphere, the sum of their partial pressures may be within the above range. The partial pressure of the oxidizing gas in the reducing atmosphere is preferably 1 × 10 ⁴ Pa or less, and more preferably 10 Pa or less. About 1 × 10 ⁻⁸ Pa is most preferable. The smaller the value of the partial pressure of the oxidizing gas, the lower the resistance of the metal oxide layer 12 can be obtained.
In order to further reduce the resistance of the metal oxide layer 12, it is preferable that H ₂ and / or CO be present in the reducing atmosphere, and it is more preferable that H _{2 in} a plasma state be present.
Therefore, it is preferable that the annealing atmosphere is once evacuated and then annealed by introducing hydrogen (H ₂ ). In this vacuum state, the atmospheric pressure is preferably in the range of 10 ³ to 10 ⁻⁸ Pa, for example.

The annealing in the present invention refers to an operation of raising the precursor layer 12 ′ to a predetermined temperature (annealing temperature) and then lowering the temperature. When the precursor layer 12 ′ is formed on the substrate 11 as in the present embodiment, the substrate temperature can be applied as the annealing temperature.
The annealing temperature is preferably higher than the crystallization temperature of the precursor layer 12 ′. For example, the crystallization temperature of TiO ₂ to which no dopant is added is about 400 ° C., and when the dopant is added, the crystallization temperature tends to decrease. Therefore, a preferable annealing temperature for satisfactorily reducing the resistance of the metal oxide layer 12 depends on the kind of the dopant, but is preferably 300 ° C. or higher. Further, if the annealing temperature is too high, the anatase type crystal structure may be broken in the annealing step, and therefore, 900 ° C. or lower is preferable. In view of heat resistance of the substrate 11, energy reduction, shortening of temperature raising time, etc., a lower annealing temperature is desirable. A more preferable range of the annealing temperature is 350 to 850 ° C, and 350 to 800 ° C is more preferable.
The time for maintaining the predetermined annealing temperature (annealing time) is not particularly limited. What is necessary is just to obtain a desired characteristic after annealing, for example, it can set within the range of 1-120 minutes. Although depending on other conditions, the annealing time is preferably 1 to 60 minutes, for example.

The metal oxide layer 12 thus obtained has good conductivity. In general, a conductor refers to one having a resistivity at room temperature of 10 ⁰ Ωcm or less, for example. It is preferable for the resistivity at room temperature to be 10 ⁻³ Ωcm or less because the use is further expanded. Further, the transparency is also good, and a good transmittance can be obtained particularly in the visible light range. For example, a transparent conductor having a transmittance in the visible light region of 80% or more and a resistivity of 2 × 10 ⁻⁴ Ωcm or less can be realized. Therefore, it is suitable as a conductor requiring transparency.
In addition, when an M: TiO ₂ single crystal thin film having an anatase type crystal structure described in Patent Document 1 is formed by an epitaxial method, the crystal orientation in the substrate is emphasized, and the manufacturing conditions are also managed. On the other hand, according to the manufacturing method of the present invention, a conductor can be formed not only on a glass substrate but also on a silicon substrate such as a plastic surface or an amorphous silicon substrate. is there. Accordingly, the applicable applications are wide.

In particular, as shown in the examples to be described later, after forming a precursor layer by the PLD method, annealing is performed in H ₂ or in a vacuum, whereby a near-amorphous metal oxide containing polycrystals is formed on a glass substrate. A layer can be formed, and it was confirmed that this metal oxide layer exhibits transparent conductivity. The fact that such metal oxide exhibits transparent conductivity greatly defeats general expectations. It has also been found that by performing post-annealing in a reducing atmosphere such as an H ₂ atmosphere, the carriers are almost activated and the resistivity is further reduced. These things are expected to greatly expand the future application range from the viewpoint of increasing the area of the transparent conductive film and low-temperature growth. Also, the effect of annealing in a reducing atmosphere shown in the following examples can be said to be a characteristic effect that appears when a dopant such as Nb or Ta is included.

Further, as shown in the examples below, was deposited at room temperature by sputtering, by performing the annealing process, the amorphous Nb: Nb containing TiO ₂ film, the anatase type polycrystalline: changes to the TiO ₂ film Confirmed to do. In particular, in the annealing process, the dramatic decrease in resistivity from about 10 ⁵ Ωcm to about 8 × 10 ⁻⁴ Ωcm is a significant result exceeding expectations. In this case, the activation rate of Nb was about 80% (n = 1 to 2 × 10 ²¹ cm ⁻³ ). The hole mobility at room temperature, the sputtering m = 1~3cm ² / Vs or so, in the PLD method was about m = 6~12cm ² / Vs.
Thus, it was found that a TiO ₂ film having a significantly reduced resistivity can be obtained by combining a versatile sputtering method and annealing treatment. These things are expected to greatly expand the range of future applications from the viewpoint of increasing the area and low-temperature growth.

<Application>
The conductor of the present invention has a wide application range, and for example, it can be applied to transparent electrodes such as flat panel displays, solar cells, and touch panels. Further, it can be applied to the shielding of electromagnetic waves used for the antireflection film, a film that prevents dust from sticking due to static electricity, an antistatic film, heat ray reflective glass, and ultraviolet reflective glass. If a multilayer film composed of a layer made of SiO ₂ and a TiO ₂ layer doped with Nb is produced, it can also be applied as an antireflection film.

  Examples of applications include dye-sensitized solar cell electrodes; display panels, organic EL panels, light-emitting elements, light-emitting diodes (LEDs), white LEDs and laser transparent electrodes; surface-emitting laser transparent electrodes; lighting devices; An application that allows light to pass through only a specific wavelength range may be considered.

  Further specific applications can include the following. Transparent conductive film in a liquid crystal display (LCD); Transparent conductive film in a color filter part; Transparent conductive film in an EL (Electro Luminescence) display; Transparent conductive film in a plasma display (PDP); PDP optical filter Transparent conductive film for shielding electromagnetic waves; transparent conductive film for shielding near infrared; transparent conductive film for preventing surface reflection; transparent conductive film for improving color reproducibility; transparent conductive film for preventing damage Optical filter; touch panel; resistive touch panel; electromagnetic induction touch panel; ultrasonic touch panel; optical touch panel; capacitive touch panel; resistive touch panel for personal digital assistants; Panel]; solar cell; amorphous silicon (a-Si) solar cell; microcrystalline Si thin film solar cell; CIGS solar cell; dye-sensitized solar cell (DSC); transparent conductive material for static electricity countermeasures for electronic parts; Transparent conductive material; dimming material; dimming mirror; heating element (surface heater, electrothermal glass); electromagnetic wave shielding glass.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
<Measurement method>
In the following, the following method was used as the measurement method. The measurement temperature was room temperature (20 to 25 ° C.) unless otherwise specified.
[Surface resistance (unit: Ω)] In a sample in which a metal oxide layer was formed on a substrate, an In electrode was crimped onto the metal oxide layer at an electrode interval of 2 mm, and then current-voltage (I- V) The characteristics were measured, and the surface resistance value was calculated from the inclination.
[Transmittance, Reflectance, Absorptivity, Spectral Transmittance Curve] Transmittance (%) and reflectivity (%) were measured with a spectrophotometer manufactured by JEOL. Absorptivity (%) was obtained by subtracting the total of transmittance and reflectance obtained by the measurement from 100. That is, reflectance = 100−transmittance−absorbance was calculated. A spectral transmittance curve was obtained from the measurement result of transmittance.

[SEM (Scanning Electron Microscope) Image] A surface image was obtained with an SEM (scanning electron microscope) manufactured by Hitachi under the condition of an acceleration voltage of 10 kV.
[Profile by X-ray diffraction (XRD)] The profile was measured by an X-ray diffractometer (XRD) manufactured by Bruker.
[Spectrum by X-ray photoelectron spectrometer (XPS)] The spectrum was measured by an X-ray photoelectron spectrometer (XPS) manufactured by ULVAC-PHI.
[Atomic Force Microscope (AFM) Data] Measurement was performed with an atomic force microscope (AFM) manufactured by SEIKO.

(Example 1-1)
A precursor layer was formed on the substrate under the following conditions using the PLD apparatus shown in FIG.
-Substrate: glass substrate made of non-alkali glass (manufactured by Asahi Glass Co., Ltd., product name: AN100) with a thickness of 0.5 mm-Film formation method: PLD method-Oxygen partial pressure during film formation: 1.33 × 10 ^-2 Pa (1 × 10 ⁻⁴ torr)
Target: Nb: TiO ₂ sintered body made of Ti _0.94 Nb _0.06 O ₂ Substrate temperature: 250 ° C.

The obtained precursor layer had an Nb content of 6 atomic%. Next, post-annealing was performed under the following conditions to obtain a sample in which a metal oxide layer having a thickness of 110 nm was formed on the substrate.
<Post annealing conditions>
Annealing atmosphere: After making a vacuum of 10 ⁻¹ Pa once, hydrogen (H ₂ ) was introduced to form an H ₂ atmosphere of 1.013 × 10 ⁵ Pa (1 atm).
Annealing temperature (substrate temperature): 500 ° C
Annealing time: 100 minutes It took 5 minutes for the substrate temperature to reach 500 ° C. from room temperature. After holding at 500 ° C. for 100 minutes, the substrate was cooled to room temperature.
About the metal oxide layer of the obtained sample, resistivity, carrier concentration, and hole mobility were measured. The results are shown in Table 1.

(Comparative Example 1: Single crystal thin film, no post-annealing)
A single crystal thin film of a metal oxide having an anatase type crystal structure described in Patent Document 1 (hereinafter sometimes referred to as an epitaxially grown anatase single phase or anatase type epitaxial film) was produced.
Specifically, using the PLD apparatus shown in FIG. 1, a sample was obtained by forming an anatase single phase of epitaxial growth composed of Nb: TiO ₂ on a substrate under the following conditions. Post-annealing was not performed.
-Substrate: SrTiO ₃ single crystal substrate with (100) substrate surface-Film formation method: PLD method-Oxygen partial pressure during film formation: 1.33 × 10 ^-2 Pa
Target: Nb: TiO ₂ sintered body made of Ti _0.94 Nb _0.06 O ₂ Substrate temperature: 550 ° C.
The formed epitaxially grown anatase single phase had a film thickness of about 100 nm and an Nb content of 6 atomic%.
The resistivity, carrier concentration, and hole mobility were measured for the epitaxially grown anatase single phase of the obtained sample. The results are shown in Table 1.

(Reference Example 1: ITO thin film)
Table 1 shows known typical values for the resistivity, carrier concentration, and hole mobility of the ITO thin film.

  From the results of Table 1, the metal oxide layer of Example 1-1 is equivalent to an anatase single phase with high crystallinity and formed from a single crystal substrate in terms of resistivity and carrier concentration, and is close to ITO. It can be seen that it has characteristics.

(Example 1-2: Room temperature film formation, no cooling)
Under the conditions of Example 1-1, a sample in which a metal oxide layer was formed on a substrate was obtained in the same manner except that the glass substrate was not heated when forming the precursor layer and the substrate temperature was room temperature.
The resistivity of the obtained metal oxide layer was 5.1 × 10 ⁻⁴ Ωcm, which was lower than that of Example 1-1. This shows that a low-resistance metal oxide layer can be obtained when the substrate temperature during film formation by the PLD method is room temperature.

(Example 1-3: Room temperature film formation, with cooling)
Under the conditions of Example 1-2, a metal oxide layer was formed on the substrate in the same manner except that the cooling water was circulated to maintain the substrate temperature at 25 to 50 ° C. when forming the precursor layer. Sample was obtained.
The resistivity of the obtained metal oxide layer was 4.5 × 10 ⁻⁴ Ωcm, which was further lower than that of Example 1-2. This shows that the resistivity of the metal oxide layer is further lowered when the substrate is cooled during film formation at room temperature by the PLD method.
Further, as shown in FIG. 15A (Example 14) and FIGS. 19 to 21 (Example 19) which will be described later, when manufactured under the conditions of this example, the precursor layer before annealing becomes amorphous, and the metal after annealing In the oxide layer, amorphous and polycrystal are mixed.

(Example 2: Substrate temperature during film formation)
In this example, the substrate temperature during the formation of the precursor layer was changed under the conditions of Example 1-1, and the phase structure and the resistance value (surface resistance) before and after annealing were examined. Samples were manufactured in two different annealing atmospheres: the same H ₂ atmosphere as in Example 1-1 and a vacuum atmosphere (10 ⁻¹ Pa). The results are shown in Table 2.
In Table 2, T _s indicates the substrate temperature (unit: ° C.) at the time of film formation of the precursor layer, the numerical value in the parenthesis is the actually measured substrate temperature, and when the numerical value in the parenthesis is not attached, Estimated substrate temperature. An example of annealing in H ₂ at a substrate temperature of 250 ° C. corresponds to Example 1-1.
In Table 2, the number on the left side of the arrow in the column is the resistance value (surface resistance) before annealing, and the number on the right side of the arrow is the resistance value after annealing. In addition, compared with Example 1-1, the sheet resistance 1 kΩ corresponds to a resistivity of about 2.3 × 10 ⁻³ Ωcm.
In addition, the letters “Anatase” or “Rutile” described under the resistance value indicate that anatase-type crystals or rutile-type crystals were confirmed in the amorphous phase in the metal oxide layer. Show. “Slightly Anatase” means a state in which anatase-type crystals are confirmed in an amorphous phase and most of the crystal has an amorphous structure.
Note that the phase structure of the metal oxide layer will be described later using an SEM image or the like.

As shown in the results of Table 2, the resistance values before annealing were as low as 20 kΩ to 13 MΩ. The resistance value was even smaller after annealing than before annealing. In the annealing in H ₂ , the resistance value decreases more greatly by annealing than in vacuum annealing.
When the anatase type crystal is confirmed in the amorphous phase (substrate temperature 200 to 450 ° C.), the rutile type crystal is confirmed in the amorphous phase (substrate temperature 500 ° C.). It can be seen that the resistance value is low both before and after annealing. In particular, when the substrate temperature was 250 ° C. or lower, a very low resistance value of 700Ω was obtained after annealing in H ₂ .

(Example 3-1: Deposition atmosphere is oxygen + hydrogen)
In this example, the atmospheric gas composition at the time of film formation of the precursor layer in Example 1-1 was changed as follows. Others were manufactured in the same manner as in Example 1-1, and the sheet resistance before and after annealing was examined.
-Film formation atmosphere: mixed gas of oxygen and hydrogen-Oxygen partial pressure during film formation: 1.33 × 10 ^-3 Pa
-Hydrogen partial pressure during film formation: 1.33 × 10 ⁻³ Pa
The sheet resistance before and after annealing was about 1 kΩ. Compared with the case of the substrate temperature of 250 ° C. in Table 2, the surface resistance before annealing is lower in this example, and the surface resistance after annealing is higher in this example. From this, it can be seen that when the precursor layer is formed in an atmosphere where hydrogen is present, the resistance is already low before annealing, and the resistance is not lowered even after annealing.

(Example 3-2: Film formation atmosphere is oxygen + hydrogen)
In this example, the oxygen partial pressure and the hydrogen partial pressure at the time of forming the precursor layer in Example 3-1 were changed as follows. The oxygen partial pressure in this example is the same as in Example 1-1. Others were manufactured in the same manner as in Example 3-1, and the sheet resistance before and after annealing was examined. As a result, the sheet resistance before and after annealing was about 1 kΩ as in Example 3-1.
-Oxygen partial pressure during film formation: 1.33 × 10 ⁻² Pa
-Hydrogen partial pressure during film formation: 1.33 × 10 ⁻² Pa

(Example 3-3: partial pressure of oxygen during film formation)
In this example, a sample was manufactured by changing the substrate temperature of the precursor layer and the oxygen partial pressure (P (O ₂ )) during film formation in Example 1-1, and the resistance value (surface resistance) before and after annealing was examined. It was. The oxygen partial pressure during film formation was the same as in Example 1-1, 1.33 × 10 ⁻² Pa and 1.33 × 10 ⁻³ Pa. The annealing conditions were the same as in Example 1-1. The results are shown in Table 3.
The notation in Table 3 is the same as in Table 2.

From the results in Table 3, the same tendency as in Example 2 was observed even when the oxygen partial pressure was changed to 1.33 × 10 ⁻³ Pa. That is, the resistance value before annealing was low, and the resistance value was even smaller after annealing than before annealing. In addition, in the oxygen partial pressure P (O ₂ ) in this range, it can be seen that there is no significant difference in resistance value even if the oxygen partial pressure is different.

(Comparative example 2: no dopant)
In this example, in Example 1-1, the target at the time of film formation of the precursor layer was changed to a TiO ₂ sintered body not containing Nb, and the substrate temperature was 250 ° C. and 350 ° C. same as those in Example 1-1. The precursor layer was formed in the same manner as in Example 1-1 except for two.
Next, annealing was performed in the same manner as in Example 1-1 except that the annealing atmosphere was the same H ₂ atmosphere as in Example 1-1 and a vacuum atmosphere (10 ⁻¹ Pa), and a sample was manufactured.
The obtained metal oxide layer was examined for the phase structure before and after annealing and the resistance value (surface resistance). The results are shown in Table 4. The notation in Table 4 is the same as that in Table 2.

  From the results of Table 4, the surface resistance before annealing is lower in this example than in the case of the substrate temperatures of 250 ° C. and 350 ° C. in Table 2, but the surface resistance increases after annealing. This shows that the dopant is effective for reducing the resistance value by annealing.

(Example 4: film formation at 250 ° C. and 350 ° C.—temperature dependence of resistivity)
In Example 2, a sample temperature obtained by performing annealing in H ₂ at a substrate temperature (Ts) of 250 ° C. (corresponding to Example 1-1) and 350 ° C. at the time of film formation of the precursor layer was measured at a measurement temperature of 10 The resistivity at ~ 300K was measured. The result is shown in the graph of FIG. In this graph, Ts represents the substrate temperature during film formation, the horizontal axis represents the measured temperature, and the vertical axis represents the resistivity.
For comparison, the graph also shows the result of the same measurement performed on the epitaxially grown anatase single phase of the sample obtained under the conditions of Comparative Example 1 (denoted as “Anatase epitaxial film” in the figure). .
From the results of FIG. 3A, it can be seen that the sample obtained under the conditions of Example 2 has a low resistance value and is good as compared with the epitaxially grown anatase single phase. It can also be seen that the resistivity decreases when the substrate temperature during film formation is lowered.

(Example 5: 250 ° C., 350 ° C. film formation—carrier concentration and hole mobility)
In Example 2, a sample temperature obtained by performing annealing in H ₂ at a substrate temperature (Ts) of 250 ° C. (corresponding to Example 1-1) and 350 ° C. at the time of film formation of the precursor layer was measured at a measurement temperature of 10 The carrier concentration and hole mobility at ˜300 K were measured. The results are shown in the graphs of FIGS. 4A and 4B, respectively. In this graph, Ts represents the substrate temperature during film formation, the horizontal axis represents the measured temperature, the vertical axis in FIG. 4A represents the carrier concentration, and the vertical axis in FIG. 4B represents the hole mobility.
For comparison, the graph also shows the result of the same measurement performed on the epitaxially grown anatase single phase of the sample obtained under the conditions of Comparative Example 1 (denoted as “Anatase epitaxial film” in the figure). .
4A, in the sample obtained under the conditions of Example 2 (substrate temperatures 250 ° C. and 350 ° C.), the activation rate of Nb is as high as about 90%, and the anatase type epitaxial metal oxide layer of Comparative Example 1 It can be seen that this is a degenerate semiconductor.
Moreover, according to FIG. 4B, the metal oxide layer of the sample obtained under the conditions of Example 2 is smaller than the anatase type epitaxial film of Comparative Example 1 in terms of hole mobility, but in terms of carrier concentration, It turns out that it is close to an anatase type epitaxial metal oxide layer.

(Example 6-1: 250 ° C. film formation—transmittance T, reflectance R, absorptance)
About the sample obtained on the conditions of Example 1-1, the transmittance | permeability in the predetermined wavelength range, the reflectance, and the absorptivity were measured in the state by which the 110-nm-thick metal oxide layer was laminated | stacked on the glass substrate. Further, the transmittance and reflectance were measured in the same manner in the state where the precursor layer was laminated on the glass substrate before annealing.
The result is shown in FIG. In FIG. 5A, the horizontal axis represents wavelength, and the vertical axis represents transmittance or reflectance. In the figure, symbol T is a transmittance graph, and R is a reflectance graph.
From the results of FIG. 5, the sample metal oxide layer obtained under the conditions of Example 1-1 has good transmittance T, reflectance R, and absorptance both in the visible light region both before and after annealing. It can be seen that this value is shown.

(Example 6-2: Room temperature film formation-transmittance T, reflectance R, absorptance)
About the sample obtained on the conditions of Example 1-3, it carried out similarly to Example 6-1, and measured the transmittance | permeability, reflectance, and absorption rate before and behind annealing. The result is shown in FIG.
From the results shown in FIG. 6, it can be seen that when the precursor layer is formed at room temperature, the increase in the transmittance, the decrease in the reflectance, and the decrease in the absorptance in the visible light region are significantly observed by the H ₂ annealing. .

(Example 6-3: 350 ° C. film formation—transmittance T, reflectance R, absorption rate)
In Example 2, with respect to the sample obtained by annealing in H ₂ at a substrate temperature (Ts) of 350 ° C. during the formation of the precursor layer, the transmittance after annealing and The reflectance was measured. The result is shown in FIG.
From the results shown in FIG. 7, the metal oxide layer of the sample (substrate temperature 350 ° C.) obtained under the conditions of Example 2 shows good values for both transmittance and reflectance, particularly in the visible light region. I understand.

(Example 7: SEM image)
FIG. 8 is an SEM image of the metal oxide layer in the sample obtained under the conditions of Example 1-1. According to this figure, it is understood that almost no grains are observed in the metal oxide layer, and a little anatase type polycrystal is formed in the amorphous phase.

(Example 8: XRD profile)
9A, FIG. 9B, and FIG. 9C show the substrate temperature (Ts) at the time of forming the precursor layer in Example 2 being 200 ° C., 250 ° C. (corresponding to Example 1-1), 350 ° C., and annealing in H _2. It is a measurement result (XRD profile) obtained by performing X-ray diffraction before and after annealing for the sample obtained by performing the above. FIG. 9A shows measurement results at a substrate temperature of 200 ° C., 9B at 250 ° C., and 9C at 350 ° C.
9D shows a sample obtained by annealing in H ₂ at a substrate temperature (Ts) of 250 ° C., 300 ° C., and 350 ° C. when the precursor layer was formed in Example 2. XRD profile. The temperature in FIG. 9D is the substrate temperature during film formation.

In general, the peaks at (101) and (004) are observed in anatase type polycrystals. In the case of perfect polycrystal, the intensity ratio of (101) and (004) is 1000: 185. Therefore, from the results of FIGS. 9A to 9C, it can be seen that the amorphous phase and the anatase-type polycrystal are mixed regardless of before and after annealing.
Further, from the result of FIG. 9D, it can be seen that even when the film forming temperature is changed, the anatase crystal and the amorphous are mixed after the annealing.

(Example 9: XPS spectrum)
FIG. 10 is a diagram showing the results of measuring the state spectrum of the metal oxide layer with an X-ray photoelectron spectrometer (XPS) for the sample obtained under the conditions of Example 1-1. In this figure, the broken line is the measurement result before annealing, and the solid line is the measurement result after annealing.
From the result of this figure, in the metal oxide layer on the glass substrate, a peak of Ti ³⁺ is observed after annealing, and it can be seen that Ti ³⁺ is included in the film. Therefore, it turns out that it is reducing by annealing. The detection of Ti ³⁺ is a phenomenon commonly observed in the low resistance thin film obtained by the method of the present invention regardless of the substrate temperature and the film forming method during film formation.

(Example 10: AFM data)
In Example 2, the sample metal oxide layer obtained by annealing in H ₂ at a substrate temperature (Ts) of 250 ° C. (corresponding to Example 1-1) and 350 ° C. during the formation of the precursor layer Was measured with an AFM (atomic force microscope). The results are shown in FIGS. 11A and 11B.
FIG. 11A shows the result of a sample with a substrate temperature of 250 ° C., FIG. 11B shows the result of a sample with a substrate temperature of 350 ° C. Shows the profile. In the figure, Ra represents a surface roughness value, and RMS represents an average surface roughness value.
From the results of FIGS. 11A and 11B, it was found that the unevenness on the surface of the metal oxide layer was about 10 nm, and a relatively flat surface was formed. The surface roughness is preferably 20 nm or less, although it depends on the application.

Note that the sample of FIG. 11B (substrate temperature 350 ° C.) was analyzed by a technique called electron backscatter diffraction (EBSD), and as a result, there were few crystallized portions and most of the results were amorphous (slightly anatase).
The EBSD (Electron Backscatter Diffraction Pattern) is a technique that is rapidly spreading in combination with a scanning electron microscope (SEM) as a means for analyzing the local crystal orientation of a material. More effective crystal orientation observation is realized by combining with a scanning electron microscope (UHV-SEM).

(Example 11: Variation range of resistivity before and after annealing)
FIG. 12 shows a sample (room temperature film formation) obtained under the conditions of Example 1-3, and in Example 2, the substrate temperature (Ts) during film formation of the precursor layer was 250 ° C. (corresponding to Example 1-1). FIG. 4 is a diagram showing a change in resistivity before and after annealing for a sample obtained by annealing in H ₂ at 350 ° C. FIG.
From the results in this figure, the change in resistivity due to annealing is greatest when the substrate temperature at the time of forming the precursor layer is room temperature. That, _Ti 0.94 _{Nb 0.06} O ₂ thin film obtained by RT grown on a glass substrate, than _Ti 0.94 _{Nb 0.06} O ₂ thin film formed by other substrate temperature condition, _{H 2} atmosphere The decrease in resistivity due to annealing is large.

(Example 12: Temperature dependence of resistivity)
FIG. 13 shows a measurement temperature of 10 to 300 K for the sample obtained under the conditions of Example 1-3 (substrate temperature Ts: room temperature) and the sample obtained under the conditions of Example 1-1 (substrate temperature Ts: 250 ° C.). It is a figure which shows the result of having measured the temperature dependence of the resistivity after annealing in the range of each. FIG. 13 also shows the resistivity value (measurement temperature 300 K) before annealing in the sample obtained under the conditions of Example 1-3.
From this figure, in the samples obtained under the conditions of Example 1-1 and Example 1-3, there is almost no temperature dependence of resistivity, and the Ti _0.94 Nb _0.06 O ₂ thin film after annealing is slightly metal It turned out that it took a typical behavior.
Although not shown in the figure, when the sample obtained under the conditions of Example 1-3 (substrate temperature Ts: room temperature, annealed in H ₂ ) is then annealed in oxygen, the resistance value increases. _When annealed in _two atmospheres, the low resistance state of about 6 × 10 ⁻⁴ Ωcm was obtained again.

(Example 13: Temperature dependence of carrier concentration and hole mobility)
FIG. 14 shows the carrier after annealing for the sample obtained under the conditions of Example 1-3 (substrate temperature Ts: room temperature) and the sample obtained under the conditions of Example 1-1 (substrate temperature Ts: 250 ° C.). It is a figure which shows the result of having measured the temperature dependence of a density | concentration and hole mobility in the range of measurement temperature 10-300K. FIG. 14A shows the carrier concentration, and FIG. 14B shows the hole mobility measurement results.
From the results shown in FIG. 14A, 90% or more of Nb released carriers (active) in any of the samples (substrate temperature: room temperature and 250 ° C.) obtained under the conditions of Example 1-1 and Example 1-3. It can be seen that it is almost degenerate.

(Example 14: XRD profile)
FIG. 15 shows measurement results (XRD profiles) obtained by performing X-ray diffraction before and after annealing on the sample (substrate temperature Ts: room temperature) obtained under the conditions of Example 1-3.
From this result, it can be seen that the material was amorphous before annealing and changed to anatase polycrystal after annealing. That is, it can be seen that the precursor layer formed at room temperature under the conditions of Example 1-3 was in an amorphous state and then changed to polycrystal by annealing in H ₂ . As can be seen from the cross-sectional TEM images shown in FIGS. 20 and 21, which will be described later, under the manufacturing conditions of this example, the amorphous and polycrystalline bodies are mixed after annealing.

(Example 15: 250 ° C. film formation-TEM image)
FIGS. 16 and 17 show cross-sectional TEM (transmission electron microscope) images of the sample metal oxide layer obtained under the conditions of Example 1-1. 16 shows an enlargement ratio of 500,000 times, and FIG. 17 shows an enlargement ratio of 2.5 million times.
In the image of FIG. 16, it can be seen that a polycrystalline thin film is formed, and grain boundaries are also observed. In the image of FIG. 17, every single lattice is observed.
Further, according to the SEM image shown in FIG. 8 (Example 7) and the analysis by EBSD used in Example 10, it can be seen that there are many amorphous materials on the surface, and according to the cross-sectional TEM image of this example, inside the layer, It can be seen that most of them are crystallized, and amorphous parts are also present.

(Example 18: 250 ° C. film formation-electron diffraction pattern)
FIG. 18 is an electron diffraction image inside the metal oxide layer in the sample manufactured under the conditions of Example 1-1. The surface distance d is determined by Lλ / R. Here, R is the distance from the center beam spot, L is the camera length (here, 653.3 mm), and λ is the wavelength of the electron beam (here, 0.0027 nm). The surface distance d indicated by 1 in the figure was 1.73 mm, and the surface orientation was A (211) or (105). In addition, the surface distance d indicated by 2 in the figure was 2.39 mm, and the surface orientation was A (004) (“A” means anatase). Furthermore, the surface interval d indicated by 3 in the figure was 1.70 mm, and the surface orientation was A (211) or (105) (“A” means anatase).
This indicates that the inside of the crystal is also an anatase type crystal.

(Example 19: Room temperature film formation-TEM image)
Samples were prepared under the conditions of Example 1-3, and cross-sectional TEM images of the precursor layer before annealing and the metal oxide layer after annealing were obtained.
FIG. 19 is a cross-sectional TEM image before annealing, and the enlargement ratio is 500,000 times. From this image, it can be seen that the film is completely amorphous.
20 and 21 are cross-sectional TEM images after annealing. FIG. 20 shows an enlargement ratio of 500,000 times, and FIG. 21 shows an enlargement ratio of 2.5 million times.
In the image of FIG. 20, a crystal defect structure such as dislocation is observed, and some crystallization is observed in the vicinity of the glass substrate.
Further, as shown in FIG. 15 described above, since the peak of anatase (101) is observed in the XRD profile, the Ti _0.94 Nb _0.06 O ₂ thin film grown at room temperature is amorphous and polycrystalline when annealed. It can be concluded that the body is in a mixed state.
In FIG. 20 where the enlargement ratio is 500,000 times, almost no crystallization was observed, whereas in FIG. 21, a lattice was observed. This is considered to be due to the fact that when the enlargement ratio was increased to 2.5 million times, the sample was substantially heated by the irradiation of the electron beam concentrated on the sample, and an annealing effect was produced.

FIG. 22 is a cross-sectional TEM image of the metal oxide layer (Nb-doped TiO ₂ thin film) observed at a magnification of 2.5 million in FIG. 21 and observed at a magnification of 500,000 times. From this image, it can be seen that when the magnification is returned to 500,000 times, crystallization has progressed. As described above, this is considered to be a result of bringing the annealing effect to the sample by heating due to squeezing the beam when it was magnified 2.5 million times.
From this, the Ti _0.94 Nb _0.06 O ₂ thin film grown at room temperature becomes a state in which amorphous and polycrystals are mixed when annealed in H ₂ , and then crystallizes when heated in the atmosphere. Is expected to go further.

(Example 20: Annealing time in room temperature film formation)
(Example 20-1: resistivity)
A precursor layer was formed on the substrate in the same manner except that the thickness of the precursor layer was changed to 100 nm under the conditions of Example 1-3.
Next, a sample was prepared in the same manner as in Example 1-3 except that the annealing time was changed in the range of 5 minutes to 100 minutes, and the resistivity of the metal oxide layer was measured. FIG. 23 is a diagram showing the relationship between resistivity and annealing time. FIG. 23 also shows the resistivity value before annealing (annealing time: 0 minutes).
From the results in this figure, it was found that the resistivity decreased by 6 orders of magnitude even when the annealing time was 5 minutes compared to before annealing. This indicates that there is a possibility that the resistance is lowered even if the annealing time is within 5 minutes, but it is sufficient to reduce the resistance if annealing is performed for at least 5 minutes. It was also found that the resistivity hardly fluctuates even after annealing for 5 minutes or longer.

(Example 20-2: XRD profile)
A precursor layer was produced in the same manner as in Example 20-1. Next, (1) an amorphous state in which annealing is not performed, (2) a case in which annealing is performed for 5 minutes and anatase polycrystal and amorphous are mixed, and (3) annealing for 20 minutes is 1 Followed by two 10-minute anneals, resulting in a mixture of anatase polycrystal and amorphous, (4) 100 minutes of anneal and anatase polycrystal and amorphous mixed Four types of samples were prepared.
FIG. 24 shows XRD profiles obtained by performing XRD measurement on the four samples.
In this figure, with respect to the peak of (101), the half width (FWHM) of the sample of (2) is 0.330 °, the FWHM of the sample of (3) is 0.292 °, and the FWHM of the sample of (4) is 0.00. It was 257 °. In the sample (1), the peak (101) was not observed.
From the results in this figure, it can be seen that even if the annealing time is 5 minutes, the amorphous part of the precursor layer is partially changed to a polycrystalline body. Moreover, although there was not much difference in peak intensity by annealing time and the frequency | count of annealing, FWHM was (2)>(3)> (4). A decrease in FWHM indicates an improvement in crystallinity (crystal quality).

(Example 21: Temperature rising time during annealing in room temperature film formation)
(Example 21-1: resistivity)
In Example 1-3, the precursor layer was formed on the substrate in the same manner except that the thickness of the precursor layer was changed to 100 nm.
Next, post-annealing was performed under the following conditions to obtain a sample in which a metal oxide layer was formed on the substrate.
Annealing atmosphere: H ₂ 100%, 1.013 × 10 ⁵ Pa (1 atm)
-Substrate temperature: 500 ° C
Annealing time: 10 minutes In Example 1-3, the temperature rising time until reaching the annealing temperature (500 ° C.) was 5 minutes, but this was changed to 5 minutes, 10 minutes, and 20 minutes. Street samples were made. After holding at 500 ° C. for 10 minutes, the mixture was allowed to cool to room temperature.
The resistivity was measured for the metal oxide layer of the obtained sample.

As a result, the resistivity of the precursor layer that is not annealed is 63.3 Ωcm, 5.5 × 10 ⁻⁴ Ωcm when the heating time is 5 minutes, 5.8 × 10 ⁻⁴ Ωcm when the heating time is 10 minutes, In the case where the temperature raising time was 20 minutes, it was 5.5 × 10 ⁻⁴ Ωcm. From this, it was found that the temperature raising time does not affect the resistivity after annealing.

(Example 21-2: XRD profile)
A precursor layer was produced in the same manner as in Example 21-1. Next, (1) amorphous state in which annealing is not performed, (2) annealing is performed with a heating time of 5 minutes, (3) annealing is performed with a heating time of 10 minutes, (4) heating time XRD measurement was performed on four types of samples that were annealed in 20 minutes. The obtained XRD profile is shown in FIG.
In this figure, there was almost no difference in (2), (3), and (4) for the peak of (101). In the sample (1), the peak (101) was not observed.
Also from this result, it can be seen that there is almost no difference due to the difference in the heating time in the crystalline state after annealing.

(Comparative example 3: no dopant, film formation at room temperature)
A precursor layer (thickness: 110 nm) is formed on the substrate in the same manner as in Example 1-3 except that the target for forming the precursor layer is changed to a TiO ₂ sintered body not containing Nb. In the same manner, annealing was performed to manufacture a sample.
FIG. 26 shows measurement results (XRD profiles) obtained by performing X-ray diffraction before and after annealing. When the resistivity before and after annealing was measured, the precursor layer before annealing was 46.3 Ωcm, and the metal oxide layer after annealing was 0.28 Ωcm.

Compared to the resistivity of the precursor layer and the metal oxide layer made of Nb-doped TiO ₂ shown in FIG. 12 (Example 11) described above, in this example, the resistivity is reduced by annealing in H _2. The width is extremely small. Further, in the XRD profile of the precursor layer and the metal oxide layer made of Nb-doped TiO ₂ shown in FIG. 15A (Example 14), the amorphous precursor layer is annealed to be anatase type. In contrast to the fact that the crystal was changed to a polycrystal, in the XRD profile of this example, not only anatase but also a peak indicating a rutile crystal is present after annealing. When the rutile crystal is generated, the resistivity of the metal oxide layer is increased.
This indicates that Nb contributes to the stabilization of the anatase type crystal and suppresses the generation of the rutile type crystal. That is, the addition of Nb contributes to the stabilization of the anatase crystal as well as the decrease in resistivity.

(Example 22: Room temperature film formation, annealing temperature)
A precursor layer was formed under the conditions of Example 1-3. Next, in a vacuum of 1.33 × 10 ⁻¹ Pa (1 × 10 ⁻³ torr), the substrate temperature is gradually increased from room temperature to 600 ° C. over 200 minutes. Annealing was performed by gradually lowering the temperature. During that time, the resistivity of the metal oxide layer was measured every second. The result is shown in FIG.
As shown in this figure, the resistivity gradually decreased as the substrate temperature increased from room temperature, and the substrate temperature greatly decreased in the vicinity of 320 to 350 ° C. After that, although the resistivity tended to increase gradually as the substrate temperature increased, it was almost flat.
This result in in H ₂ annealing, (the substrate temperature during annealing) annealing temperature it can be seen that satisfactorily low resistance if 350 ° C. or higher.

(Reference Example 2: Upper limit of annealing temperature)
For the epitaxially grown anatase single phase formed under the conditions of Comparative Example 1, post annealing was performed by changing the annealing temperature (substrate temperature) in the range of 250 to 850 ° C., and the resistivity after annealing was measured. The annealing time was 1 hour, the annealing atmosphere was the same H ₂ atmosphere as in Example 1-1, and the oxidizing atmosphere with an oxygen partial pressure of 0.5 × 10 ⁵ Pa. The results are shown in FIG. In the figure, the measured value at the annealing temperature of 0 ° C. is the resistivity before annealing.
From the result of this figure, in the annealing in H ₂ which is a reducing atmosphere, the low resistance was well maintained up to the substrate temperature of 800 ° C. From this, it is presumed that when the annealing temperature exceeds 800 ° C., the stability of the anatase crystal is impaired. If the anatase crystal is broken, the transparency becomes worse.
Further, when annealing was performed in an oxidizing atmosphere (annealing in O ₂ ), the resistivity significantly increased when the annealing temperature (substrate temperature) exceeded 300 ° C.

(Example 23: Thermal oxidation Si substrate, room temperature film formation)
(Example 23-1: XRD profile)
A sample was manufactured in the same manner as in Example 1-3 except that the substrate was changed to a thermally oxidized Si substrate and the thickness of the precursor layer was changed to 200 nm.
FIG. 29 shows measurement results (XRD profiles) obtained by performing X-ray diffraction before and after annealing. Further, when the resistance value (surface resistance) before and after annealing was measured, the precursor layer before annealing was 880 kΩ, and the metal oxide layer after annealing in H ₂ was 171 Ω.
From these results, even when a thermally oxidized Si substrate is used, as in the case of forming a metal oxide layer on a glass substrate, the change from amorphous to polycrystalline and the resistance is greatly reduced by annealing in H _2. It has become clear that this will happen.

(Example 23-2: Nb doping amount)
Under the conditions of Example 23-1, a movable mask was used in combination with the PLD method, and the Nb content was inclined from 0 atomic% to 20 atomic% as a precursor layer on the thermally oxidized Si substrate. A 200-nm thick composition spread thin film (gradient composition film) was formed. Others were the same as in Example 23-1, and a metal oxide layer with a gradient of Nb content was formed.
FIG. 30 is a measurement result (XRD profile) obtained by performing X-ray diffraction on the annealed metal oxide layer. FIG. 30 (b) is an enlarged view showing the vicinity of the peak of anatase (101) in FIG. 30 (a).
As shown in these figures, the peak of anatase (101) shifts to the lower angle side as Nb becomes higher, suggesting solid solution of Nb. As a result, since the c-axis is monotonically extended, it was confirmed that Nb enters the crystal up to 20 atomic% when anatase is formed from amorphous. This also indicates that Nb is not segregated at the grain boundaries.

FIG. 31 is a graph showing the results of measuring the resistance value (surface resistance) of the metal oxide layer with the Nb content gradient obtained above.
As shown in FIG. 32, the resistance value is measured by using the I-V at two terminals at each location where the In electrode is crimped every 1 mm along the direction of increasing Nb concentration in the metal oxide layer. Measurement was performed and the resistance value was calculated from the slope.
From the results of FIG. 31, it was found that the resistance value is sufficiently reduced when the Nb doping amount is 2.5 atomic% or more. Further, it is presumed that the resistance can be lowered even if the Nb doping amount is less than 2.5 atomic%.

(Example 24: vacuum state before reducing atmosphere)
When annealing is performed in H ₂ , a metal oxide layer having a lower resistance value can be formed by introducing a hydrogen gas, which is a gas for making a reducing atmosphere, into a vacuum state once with a pump. found.
For example, in Example 1-3, when performing annealing in H ₂ , hydrogen was introduced into the system after a vacuum state was once generated by a pump. In this case, the resistance value of the metal oxide layer after annealing was 4.5 × 10 ⁻⁴ Ωcm. On the other hand, the resistance value was 5.0 × 10 ⁻⁴ when the vacuum state was not used once and the others were the same as in Example 1-3.

The following is an example in which the precursor layer was manufactured by the sputtering method.
In the following sputtering method examples, the “room temperature” of the substrate temperature is in the range of 25 ° C. or more and 80 ° C. or less. In an actual experiment, it was confirmed that the film was formed by the sputtering method without heating the substrate, and the substrate temperature at that time was in the range of 70 ° C. or higher and 80 ° C. or lower.

(Example 30: Room temperature film formation-XRD profile)
Using a reactive DC magnetron sputtering apparatus, a precursor layer was formed on the substrate under the film forming conditions shown in 1) of Table 5. A non-alkali glass (product name: AN100 manufactured by Asahi Glass Co., Ltd.) having a thickness of 1 mm was used as the substrate.
That is, a Ti—Nb alloy containing 6 atomic% of Nb was set as a target in a vacuum chamber of a reactive DC magnetron sputtering apparatus, and a substrate was set.
The distance (T / S) between the target and the substrate was 70 mm.
Next, after evacuating the vacuum tank to 5 × 10 ⁻⁴ Pa or less with a pump, Ar gas and O ₂ gas are introduced into the vacuum system so that the ratio of O ₂ / (Ar + O ₂ ) becomes a predetermined value. The pressure in the vacuum chamber was adjusted to 1.0 Pa.
Then, with a magnetron magnetic field strength of 1000 G, a voltage was applied to the Ti—Nb alloy target at 150 W to form a titanium oxide film (precursor layer) doped with Nb on the substrate. The substrate was not heated and the substrate temperature was room temperature.
The obtained precursor layer had a film thickness of 150 nm and an Nb content of 6 atomic%. Next, post-annealing was performed under the conditions shown in 2) in Table 5 to obtain a sample in which a metal oxide layer was formed on the substrate. It took 5 minutes for the substrate temperature to reach 500 ° C. from room temperature and 6 minutes for reaching 600 ° C. After holding at a predetermined annealing temperature for 1 hour, it was allowed to cool to room temperature. The obtained metal oxide layer had a film thickness of 140 nm and an Nb content of 6 atomic%.
The ratio of O ₂ / (Ar + O ₂ ) at the time of forming the precursor layer is 10 vol% and 20 vol%, and the annealing temperature (substrate temperature) is 500 ° C. and 600 ° C., and there are 4 conditions in total. Samples were manufactured respectively.

FIG. 33 shows measurement results (XRD profiles) obtained by performing X-ray diffraction on the precursor before annealing and the metal oxide layer after annealing. FIG. 33A shows the case where the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas is 10 vol%, and FIG. 33B shows the case where it is 20 vol%. The temperatures described in the figure are annealing temperatures (500 ° C. or 600 ° C.). The vertical axis represents intensity (arbitrary unit).
In this figure, in the metal oxide layer after post-annealing, the peak (101) seen in the anatase crystal is observed. Moreover, it turns out that a precursor layer is an amorphous state. This shows that anatase type Nb: TiO ₂ is obtained by post-annealing. The metal oxide layer formed in this example is presumed to be in a state where anatase crystals are present in the amorphous phase.

(Example 31: Substrate temperature during film formation-XRD profile)
In Example 30, the substrate temperature when forming the precursor layer was changed to room temperature (corresponding to Example 30), 200 ° C., 350 ° C., and 500 ° C., and the annealing temperature was changed to one of 600 ° C. A sample was manufactured.
FIG. 34 shows measurement results (XRD profile) obtained by performing X-ray diffraction on the precursor before annealing (left side of the arrow) and the metal oxide layer after annealing (right side of the arrow). FIG. 34A shows a case where the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas is 10 vol%, and FIG. 34B shows a case where 20 vol%. The temperature (Ts) described in the figure is the substrate temperature during film formation.

From this figure, it can be seen that when the film is formed at a low substrate temperature, the precursor layer before annealing is in an amorphous state, and crystallization progresses by annealing, resulting in an anatase structure. When the substrate temperature during film formation is increased, a precursor layer crystallized into anatase type is obtained. 34A and 34B, it can be seen that when the precursor layer is formed, the higher the ratio of O ₂ / (Ar + O ₂ ), the lower the substrate temperature.

  In FIG. 34, as the substrate temperature decreases, the (004) peak (peak near 38 °) in the annealed metal oxide layer increases. As shown in FIG. 37 (Example 34), which will be described later, there is data that the hole mobility increases as the substrate temperature decreases. These suggest that the mobility depends on the orientation of the crystal axes.

(Example 32: Presence / absence of dopant-XRD profile)
(Example 32-1: containing Nb)
A sample was produced in the same manner as in Example 30, except that the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas was 10 vol% and the annealing temperature was 600 ° C.
(Example 32-2: No Nb)
A sample was produced in the same manner as in Example 32-1, except that the target was changed to a metal plate made of Ti containing no Nb.

Figure 35 is a metal oxide layer obtained under the conditions of Example 32-1 (Nb: TiO ₂ film) and a metal oxide layer obtained in the conditions of Example 32-2 for (TiO ₂ film), X-ray diffraction It is a measurement result (XRD profile) obtained by performing.
From this figure, it can be seen that the (101) peak and the (004) peak are shifted to the lower angle side by Nb doping. This indicates that the crystal lattice is expanded. Since the ionic radius of Nb ⁵⁺ is 0.069 nm and the ionic radius of Ti ⁴⁺ is 0.068 nm, it is considered that the crystal lattice expanded as a result of substitution of Nb at the Ti site. Therefore, from the XRD profile in this figure, it can be confirmed that Nb is substituted for Ti in the TiO ₂ film doped with Nb.

(Example 33: Presence / absence of dopant, substrate temperature-resistivity)
(Example 33-1: containing Nb)
In Example 30, the substrate temperature when forming the precursor layer was changed to room temperature (corresponding to Example 30), 200 ° C., 350 ° C., and 500 ° C., and the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas was changed. A sample was manufactured in the same manner except that the volume was 10 vol% and the annealing temperature was 600 ° C.
(Example 33-2: No Nb)
A sample was produced in the same manner as in Example 33-1 except that the target was changed to a metal plate made of Ti containing no Nb. However, the substrate temperature at the time of forming the precursor layer was set to room temperature, 200 ° C., and 400 ° C.

FIG. 36 shows a metal oxide layer (Nb: TiO ₂ film, indicated by ◆ in the figure) obtained under the conditions of Example 33-1 and a metal oxide layer (TiO ₂ obtained under the conditions of Example 33-2. It is a figure which shows the result of having measured the resistivity about a film | membrane, (indicated by ◇ in a figure).
From this figure, it can be seen that the resistivity is lowered by 4 to 2 digits by doping Nb. Therefore, as described above, it can be confirmed that Nb is substituted with Ti by XRD, and further, it can be confirmed that the substituted Nb is effectively acting as a donor by this figure.

(Example 34: Substrate temperature, sputtering gas composition-resistivity, carrier concentration, hole mobility)
In Example 30, the substrate temperature at the time of forming the precursor layer was set to four types: room temperature (corresponding to Example 30), 200 ° C., 350 ° C., and 500 ° C. In addition, the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas was set to four types of 7.5, 10 (corresponding to Example 30), 15 and 20 (corresponding to Example 30) vol%. The annealing temperature was one at 600 ° C. Otherwise, 16 samples were produced in the same manner as in Example 30.
The resistivity, carrier concentration, and hole mobility of the obtained metal oxide layer were measured. The result is shown in FIG.

FIG. 37A is a diagram in which the horizontal axis is the oxygen concentration of the sputtering gas, and FIG. 37B is a diagram in which the horizontal axis is the substrate temperature during film formation, and the vertical axis is the carrier concentration and mobility. And resistivity. (A) and (b) are plots of the same data, and are essentially equivalent diagrams except for the difference in parameters.
In the 16 samples obtained in this example, the resistivity of the precursor layer before annealing was about 10 ⁵ Ωcm. As shown in FIG. 37, in the obtained 16 samples, the minimum value of resistivity was 1.1 × 10 ⁻³ Ωcm. From this, it can be seen that, depending on the conditions, the resistivity decreases by 8 digits due to post-annealing.

From (a) of FIG. 37, (1) the carrier concentration tends to decrease with an increase in O ₂ / (Ar + O ₂ ), and (2) the mobility hardly depends on O ₂ / (Ar + O ₂ ). (3) It is understood that the increase in resistivity accompanying the increase in O ₂ / (Ar + O ₂ ) is mainly caused by a decrease in carrier concentration.
From (b) of FIG. 37, (1) the carrier concentration increases as the substrate temperature increases, (2) the mobility decreases as the substrate temperature increases, and (3) from these two relationships, It can be seen that the resistivity is highest at around 350 ° C.

From the above, with respect to the oxygen concentration O ₂ / (Ar + O ₂ ) in the sputtering gas, if it is 7.5 vol% or more and 20 vol% or less, there is a difference in degree, but the resistivity is greatly reduced by annealing. An Nb: TiO ₂ film can be obtained. Further, if the oxygen concentration is 10 vol% or more and 20 vol% or less, an Nb: TiO ₂ film having a resistivity of about 10 ⁻² Ωcm or less can be obtained without depending on the substrate temperature in the sputtering process.

FIG. 38 shows the relationship between the film formation rate and the O ₂ / (Ar + O ₂ ) ratio. According to this figure, the lower the O ₂ / (Ar + O ₂ ), the greater the film formation rate. It turns out that it does not change so much at 15 vol% or more. Therefore, it is considered that the oxygen concentration O ₂ / (Ar + O ₂ ) in the sputtering gas is more preferably 10 vol% in that a high-speed film formation and a low resistance Nb: TiO ₂ film can be obtained. .
Here, the film formation rate (unit: nm / min) is measured by measuring the film thickness (unit: nm) after film formation and dividing the film thickness by the time (unit: minutes) required for film formation. And calculated.

In addition, if the substrate temperature in the sputtering process is set to room temperature to 500 ° C., an Nb: TiO ₂ film whose resistivity is significantly reduced by annealing can be obtained although there is a difference in degree. If the substrate temperature is 200 ° C. or more and 500 ° C. or less, an Nb: TiO ₂ film having a resistivity of about 10 ⁻² Ωcm or less can be obtained without depending on the substrate temperature in the sputtering process. In addition, as shown in FIG. 34 (Example 31) described above, since the strength of the XRD (004) peak of the Nb: TiO ₂ film increases and high mobility can be expected, the substrate temperature in the sputtering process can be expected. Is considered to be preferably room temperature.

(Example 35: Room temperature film formation-transmittance, resistivity, carrier concentration, hole mobility)
Under the conditions of Example 30, the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas was 10 vol%, and the annealing temperature was 600 ° C. Others were produced in the same manner as in Example 30 (same conditions as in Example 32-1).
Table 6 shows electrical characteristics (resistivity, carrier concentration, mobility) and the precursor layer (insulating film) before annealing and the metal oxide layer (Nb: TiO ₂ film, conductive film) after annealing and It is a table | surface which shows the result of having measured the film thickness. Since the resistance of the precursor layer before annealing was very high, it was difficult to measure the carrier concentration and mobility.
FIG. 39 shows the results of measuring spectral transmission characteristics of the obtained precursor layer (insulating film) before annealing and the metal oxide layer (Nb: TiO ₂ film, conductive film) after annealing in the obtained sample. FIG.

From these results, it can be seen that in the visible light region (wavelength 380 nm to 780 nm), the transmittance hardly changes between the precursor layer before annealing and the metal oxide layer after annealing. Therefore, even when the metal oxide layer is applied to an application requiring transparency, it has been found that there is no practical problem due to annealing. Further, it can be seen from these data that the transmittance is reduced by annealing in the near-infrared region (wavelength of 800 nm or more). This shows conductivity after annealing, suggesting that light absorption by free electrons contributing to conductivity occurs. That is, the transmittance measurement results also confirm that the annealed metal oxide layer has conductivity.
In addition, the transmittance shows a good value especially in the visible light region both before and after annealing, indicating that the transparency is excellent.

(Example 36: Room temperature film formation-resistivity, carrier concentration, temperature dependence of hole mobility)
Under the conditions of Example 30, the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas was 10 vol%, and the annealing temperature was 600 ° C. Others were produced in the same manner as in Example 30 (same conditions as in Example 32-1).
FIG. 40 is a diagram showing the results of measuring electrical characteristics (resistivity, carrier concentration, mobility) of the obtained metal oxide layer of the sample while changing the measurement temperature in the range of 10 to 300K. . 40A shows the resistivity, FIG. 40B shows the carrier concentration, and FIG. 40C shows the hole mobility measurement results.
From this figure, it can be seen that the carrier concentration does not depend on the measurement temperature. That is, the obtained metal oxide layer exhibits a metallic behavior. The activation rate was about 80%. It can also be seen that the hole mobility decreases with increasing temperature. Near the room temperature, phonon effects are also observed. It can be seen from these facts that the metal oxide layer obtained is a degenerate semiconductor. This point is common to the metal oxide layer (Nb: TiO ₂ film) formed by the PLD method shown in the above example.

(Example 37: Distance between target and substrate during film formation -XRD)
In Example 30, when the precursor layer is formed, the target-substrate distance T / S in the chamber of the sputtering apparatus is set to 50 mm and 75 mm, and the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas. The sample was produced in the same manner except that the amount of 10 vol% was one.
FIG. 41 is a measurement result (XRD profile) obtained by performing X-ray diffraction on the precursor before annealing and the metal oxide layer after annealing. 41A shows a case where the target-substrate distance T / S is 50 mm, and FIG. 41B shows a case where the T / S is 75 mm. The temperatures described in the figure are annealing temperatures (500 ° C. or 600 ° C.).
From the results in this figure, it can be seen that when the target-substrate distance is increased, the (004) peak increases and the orientation of the sample changes.
In addition, as shown in FIG. 34A, the (004) peak increases as the substrate temperature decreases, so the substrate temperature substantially decreases due to the increase in the target-substrate distance. In addition, it is considered that the increase in the (004) peak as described above occurred.

(Example 38: Distance film between target and substrate during film formation—temperature dependence of resistivity, carrier concentration, hole mobility)
In Example 30, when the precursor layer is formed, the target-substrate distance T / S in the chamber of the sputtering apparatus is 50 mm, and the ratio of O ₂ / (Ar + O ₂ ) in the sputtering gas is 10 vol%. A sample was manufactured in the same manner except that the annealing temperature was 600 ° C.
FIG. 42 is a diagram showing the results of measuring electrical characteristics (resistivity, carrier concentration, mobility) of the obtained metal oxide layer of the sample while changing the measurement temperature in the range of 10 to 300K. . 42A shows a case where the target-substrate distance T / S is 50 mm, and FIG. 42B shows a case where the T / S is 75 mm. (A) shows the resistivity, (b) shows the carrier concentration, and (c) shows the measurement result of the hole mobility.

  Compared with (A) of FIG. 42, in (B), the hole mobility is remarkably increased and the resistivity is slightly decreased. Further, from this and the result of FIG. 41 described above, it can be seen that when the target-substrate distance is increased, the (004) peak increases and the mobility increases. It can also be seen that the resistivity decreases with the orientation of the crystal axis.

<About interpretation of rights>
The present invention has been described above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications or substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.

  It will also be appreciated that illustrative embodiments of the invention achieve the above objects, but that many modifications and other examples can be made by those skilled in the art. The elements or components of each embodiment described in the claims, specification, drawings, and description may be employed in combination with one or more other elements. The claims are intended to cover such modifications and other embodiments, which are within the spirit and scope of the present invention.

It is a figure which shows the state which laminated | stacked the metal oxide layer on the board | substrate. It is a figure which shows the structure of a PLD apparatus. It is the figure which compared the metal oxide layer concerning this invention with the anatase type epitaxial film. It is a figure which shows the carrier hole density | concentration of the metal oxide layer concerning this invention, comparing with an anatase type epitaxial film. It is a figure which shows hole mobility of the metal oxide layer concerning this invention, comparing with an anatase type epitaxial film. It is a figure which shows (a) transmittance | permeability T, reflectance R, and (b) absorptance of the metal oxide layer concerning this invention. It is a figure which shows (a) transmittance | permeability T, reflectance R, and (b) absorptance of the metal oxide layer concerning this invention. It is a figure which shows the transmittance | permeability T and the reflectance R of the metal oxide layer concerning this invention. It is a SEM image of the metal oxide layer concerning this invention. X-ray diffraction by measurement results (XRD profile) shows the results of a comparison with H ₂ atmosphere before and after annealing. X-ray diffraction by measurement results (XRD profile) shows the results of a comparison with H ₂ atmosphere before and after annealing. X-ray diffraction by measurement results (XRD profile) shows the results of a comparison with H ₂ atmosphere before and after annealing. X-ray diffraction by measurement results (XRD profile) shows the results of a comparison with H ₂ atmosphere before and after annealing. It is a figure which shows the state spectrum of the metal oxide layer concerning this invention by X-ray photoelectron spectroscopy analyzer (XPS). It is AFM (atomic force microscope) data of the metal oxide layer concerning this invention. It is AFM (atomic force microscope) data of the metal oxide layer concerning this invention. It is a figure which shows the change of the resistivity before and behind annealing. It is a figure which shows the temperature dependence of a resistivity. It is a figure which shows the temperature dependence of carrier concentration and the temperature dependence of hole mobility. X-ray diffraction by measurement results (XRD profile) shows the results of a comparison with H ₂ atmosphere before and after annealing. It is a cross-sectional TEM image of the Nb dope TiO2 thin film which annealed after forming into a film at 250 degreeC. After forming at 250 ° C., a cross-sectional TEM image of the Nb-doped TiO ₂ thin film was annealed. After forming at 250 ° C., an electron diffraction image of Nb-doped TiO ₂ thin film was annealed. Formed at room temperature, a cross-sectional TEM image of the Nb-doped TiO ₂ thin film before (the as grown) is annealed. After forming at room temperature, a cross-sectional TEM image of the Nb-doped TiO ₂ thin film was annealed. After forming at room temperature, a cross-sectional TEM image of the Nb-doped TiO ₂ thin film was annealed. The Nb-doped TiO ₂ thin film was observed to expand 250 thousand times a cross-sectional TEM images when observed with magnification 500,000 times. It is a figure which shows the relationship between resistance change and annealing time. It is a figure which shows the relationship between XRD and annealing time. It is a figure which shows the influence on the crystallinity of the temperature rising time at the time of annealing. Shows the XRD before and after annealing in the case of non-doped TiO _2. It is a figure which shows the relationship between annealing temperature and resistivity. It is a figure which shows the relationship between the annealing temperature and resistivity in an anatase type epitaxial film. Is a graph showing a result of thermal oxidation Si Nb6at% was formed on a substrate doped TiO ₂ thin film measurement results of X-ray diffraction of the (XRD profile) was compared before and after annealing in _{H 2} atmosphere. It is a figure which shows the XRD data of the composition spread thin film with which Nb inclined from 0at% to 20at% produced on thermal oxidation Si. It is a figure which shows the resistance value of the composition spread thin film with which Nb inclined from 0at% to 20at% produced on thermal oxidation Si. It is a figure which shows the measurement sample for calculation of resistance value. It is a figure which shows the result of having compared the measurement result (XRD pattern) by X-ray diffraction, changing oxygen concentration. It is a figure which shows the film-forming parameter dependence of a XRD pattern. Nb: shows a comparison of the XRD pattern of the TiO ₂ film and the TiO ₂ film. Nb: shows a comparison of the resistivity of the TiO ₂ film and the TiO ₂ film. It is a figure which shows the film-forming parameter dependence of a carrier transport characteristic. It is a graph showing the relationship between the film formation rate and _{O 2 / (Ar + O 2} ) ratio. Nb: shows the spectral transmission characteristic of the TiO ₂ film. Nb: is a diagram showing a temperature dependence of the electrical properties of the TiO ₂ film. It is a figure which shows the relationship between the target-substrate distance in the chamber of a sputtering device, and orientation. It is a figure which shows the improvement of the mobility accompanying an orientation change.

Explanation of symbols

11 Substrate 12 Metal oxide layer 12 ′ Precursor layer 30 PLD device 31 Chamber 32 Optical oscillator 33 Reflector 34 Lens 36 Infrared lamp 39 Target 40 Oil rotary pump 41 Backflow prevention valve 42 Turbo molecular pump 43 Pressure valve 45 Oxygen gas flow rate adjustment valve

Claims (9)

1 selected from the group consisting of Nb, Ta, Mo, As, Sb, Al, Hf, Si, Ge, Zr, W, Co, Fe, Cr, Sn, Ni, V, Mn, Tc, Re, P and Bi Or forming a precursor layer made of titanium oxide to which two or more dopants are added on the surface of the substrate;
A method of manufacturing a conductor, comprising: annealing the precursor layer in a reducing atmosphere to form a metal oxide layer.   The method of manufacturing a conductor according to claim 1, wherein at least a part of the surface of the substrate is amorphous.   The method for producing a conductor according to claim 2, wherein at least a part of the surface of the substrate is made of glass.   The said dopant is Nb, The manufacturing method of the conductor as described in any one of Claims 1-3.   The method for producing a conductor according to any one of claims 1 to 4, wherein a temperature of the base body when the precursor layer is formed is 600 ° C or lower.   The method for producing a conductor according to any one of claims 1 to 5, wherein the precursor layer is formed by a pulse laser deposition method or a sputtering method.   The method of manufacturing a conductor according to claim 6, wherein the precursor layer is formed in a state where the substrate is not heated.   The method for producing a conductor according to any one of claims 1 to 7, wherein a temperature of the base body when the precursor layer is annealed is 300 ° C or higher and 900 ° C or lower.   The thickness of the said metal oxide layer is 20-1000 nm, The manufacturing method of the conductor as described in any one of Claims 1-8.

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