JP5123785B2 - Method for forming antireflection film and antireflection film - Google Patents

Description

The present invention relates to a film forming method and the antireflection film of the antireflection film, More particularly, flat panel displays: used (FPD Flat Panel Display) display surface of the operation surface such as a touch panel, the light receiving surface or the like of the solar cell Te is relates to a film forming method and the antireflection film of a suitable anti-reflection film.

In recent years, various antireflection films have been used for antireflection in flat panel displays (FPD), touch panels, solar cells, and the like.
As an antireflection film conventionally used, a multilayer antireflection film in which a high refractive index layer and a low refractive index layer are sequentially laminated on a transparent substrate has been proposed.
In such an antireflection film, for example, TiO ₂ (refractive index: 2.3 to 2.55), ZrO ₂ (refractive index: 2.05), and the like are included in the high refractive index layer. For example, SiO ₂ (refractive index: 1.45 to 1.46) is used as the layer (Patent Documents 1 and 2).

In such an antireflection film, desired antireflection performance can be obtained by changing the film thickness and material of the high refractive index layer and the low refractive index layer.
Such an antireflection film is formed by forming a low refractive index layer on a transparent substrate by sputtering using a target of a low refractive index material such as SiO ₂ , and then forming TiO ₂ or the like on the low refractive index layer. It can be obtained by forming a high refractive index layer by sputtering using a target of a high refractive index material such as ZrO ₂ .
JP-A-7-130307 JP-A-8-75902

By the way, in order to form a conventional antireflection film having a multilayer structure by sputtering, it is necessary to prepare films with different targets for each layer. That is, it is necessary to form a film by sputtering the TiO ₂ target and the SiO ₂ target in order, or to form the film by sputtering the Ti target and the Si target in order while introducing a reactive gas such as oxygen gas. is there.
In particular, when sputtering a SiO ₂ target, it is necessary to use an RF power source because sputtering cannot be performed using a DC power source or an AC power source. However, the RF power source is expensive and the device configuration is complicated. There was a problem.

  On the other hand, when the Ti target and Si target are sputtered while introducing a reactive gas such as oxygen gas, a DC power source or an AC power source can be used, but a large amount of oxygen gas must be introduced. Therefore, there is a problem that the film cannot be formed in the same atmosphere as the transparent conductive film made of a metal oxide.

The present invention has been made to solve the above-described problems, and in a method for forming an antireflection film using a zinc oxide-based transparent conductive film, a zinc oxide-based target is used, and oxygen gas, hydrogen A plurality of refractive index layers having different refractive indexes are laminated by sputtering while changing the ratio of each gas in a reactive gas containing two or three selected from the group of gas and water vapor. It is an object of the present invention to provide a method for forming a zinc oxide-based antireflection film capable of obtaining antireflection performance and an antireflection film.
In addition, an antireflection film in which a plurality of refractive index layers having different refractive indexes are stacked can be formed by one apparatus. Further, using the same zinc oxide target, oxygen / It is an object of the present invention to provide a film forming apparatus for forming an antireflection film in which a plurality of refractive index layers having different refractive indexes are stacked by sputtering while changing the hydrogen ratio.

  As a result of intensive studies on a method for forming an antireflection film using a zinc oxide-based transparent conductive film, the present inventors have used a target made of a zinc oxide-based material, and a plurality of materials having different refractive indexes by sputtering. Each of the reactive gases in the reactive gas containing two or three selected from the group of oxygen gas, hydrogen gas, and water vapor is formed when the zinc oxide antireflection film formed by laminating the refractive index layers is formed. If sputtering is performed by changing the gas ratio, an antireflection film having a desired reflection performance in which a second zinc oxide thin film having a different refractive index is laminated on the first zinc oxide thin film can be efficiently produced. The inventors have found that a film can be formed and have completed the present invention.

  That is, the method for forming an antireflection film according to the present invention is a method for forming an antireflection film in which a second zinc oxide-based thin film is laminated on a first zinc oxide-based thin film. A first zinc oxide-based thin film is formed by sputtering using a first zinc oxide-based target in a first reactive gas containing two or three selected from the group of gas and water vapor. 1 film forming step, and on the first zinc oxide-based thin film, the composition contains two or three selected from the group of oxygen gas, hydrogen gas, and water vapor, and has a composition different from that of the first reactive gas. And a second film-forming step of forming a second zinc oxide-based thin film by sputtering using a second zinc oxide-based target in a second reactive gas.

In this manufacturing method, the first zinc oxide target is formed in the first reactive gas containing two or three selected from the group of oxygen gas, hydrogen gas, and water vapor by the first film forming step. A first zinc oxide-based thin film is formed by sputtering used, and the second film forming step includes two or three selected from the group of oxygen gas, hydrogen gas, and water vapor, and the first A second zinc oxide-based thin film is formed by sputtering using a second zinc oxide-based target in a second reactive gas having a composition different from that of the reactive gas.
This makes it possible to stack a plurality of refractive index layers having different refractive indexes using a zinc oxide target, and as a result, efficiently form an antireflection film having a desired antireflection performance. It becomes possible.

In the method for forming an antireflection film of the present invention, it is preferable that the second reactive gas has a different content ratio of the first reactive gas and the hydrogen gas.
The second reactive gas preferably has a different content rate of the first reactive gas and oxygen gas.
The second zinc oxide based target is preferably the same as the first zinc oxide based target.
The second film forming step is preferably performed by replacing the first reactive gas with the second reactive gas in the same vacuum chamber as the first film forming step.
The first zinc oxide target and the second zinc oxide target are preferably an aluminum-added zinc oxide target or a gallium-added zinc oxide target.

  The antireflection film of the present invention is an antireflection film obtained by the method for forming an antireflection film of the present invention, and is laminated on the first zinc oxide-based thin film and the first zinc oxide-based thin film. The second zinc oxide thin film having a refractive index different from that of the first zinc oxide thin film is provided.

  The antireflection film includes a first zinc oxide-based thin film and a second zinc oxide-based thin film laminated on the first zinc oxide-based thin film and having a refractive index different from that of the first zinc oxide-based thin film. This makes it possible to provide a zinc oxide-based antireflection film having a desired antireflection performance, which is formed by laminating a plurality of refractive index layers having different refractive indexes.

In the antireflection film of the present invention, it is preferable that at least one of the first zinc oxide-based thin film and the second zinc oxide-based thin film has a specific resistance of 1.0 × 10 ³ μΩ · cm or less.

  According to the method for forming an antireflection film of the present invention, the first zinc oxide-based target in the first reactive gas containing two or three selected from the group of oxygen gas, hydrogen gas, and water vapor Selected from the group consisting of oxygen gas, hydrogen gas, and water vapor on the first zinc oxide-based thin film, and a first film forming step of forming a first zinc oxide-based thin film by sputtering using A second zinc oxide-based thin film is formed by sputtering using a second zinc oxide-based target in a second reactive gas containing seeds or three types and having a composition different from that of the first reactive gas. A plurality of refractive index layers having different refractive indexes can be easily stacked using a zinc oxide-based target, and as a result, a desired antireflection performance is obtained. An antireflection film can be efficiently formed.

  According to the antireflection film of the present invention, the first zinc oxide-based thin film and the second zinc oxide-based thin film laminated on the first zinc oxide-based thin film and having a refractive index different from that of the first zinc oxide-based thin film Therefore, it is possible to provide a zinc oxide-based antireflection film having a desired antireflection performance obtained by laminating a plurality of refractive index layers having different refractive indexes.

  According to the film forming apparatus of the present invention, the vacuum vessel includes a vacuum vessel, a target holding unit that holds the target in the vacuum vessel, and a power source that applies a sputtering voltage to the target, and the vacuum vessel is a hydrogen gas introduction unit. Since two or more of oxygen gas introducing means and water vapor introducing means are provided, when a plurality of refractive index layers having different refractive indexes are stacked on a substrate by sputtering using a target made of a zinc oxide material. Can be a reactive gas atmosphere in which the ratio of reducing gas to oxidizing gas is harmonized. Therefore, an antireflection film having a desired antireflection performance can be formed with one apparatus using a target made of a zinc oxide-based material.

  In addition, an antireflection film consisting of a plurality of refractive index layers with different refractive indexes can be easily formed by using only one type of target made of a zinc oxide-based material and changing the composition of the introduced gas. can do. Further, a DC power source or an AC power source can be used, and film formation can be performed at a speed higher than the conventional film formation rate.

The best mode for carrying out the method for forming an antireflection film, the antireflection film, and the film forming apparatus of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

“First Embodiment”
FIG. 1 is a cross-sectional view showing an antireflection film according to a first embodiment of the present invention. The antireflection film 1 is a film having a laminated structure formed on a surface 2a of a transparent substrate 2, and the transparent substrate 2, a plurality of zinc oxide thin films having different refractive indexes, for example, a transparent film 11 having a high refractive index and a transparent film 12 having a low refractive index are stacked so that the refractive index gradually decreases outward from the surface 2a side. ing.

Examples of these zinc oxide-based thin films include aluminum-added zinc oxide (AZO) to which aluminum oxide (Al ₂ O ₃ ) is added, gallium-added zinc oxide (GZO) to which gallium oxide (Ga ₂ O ₃ ) is added, and the like. A zinc oxide-based material as a main component is preferably used.

For example, in the case of a laminated structure using aluminum-added zinc oxide (AZO), the transparent film 11 with a high refractive index having a refractive index of, for example, 1.91 is argon (Ar) with aluminum-added zinc oxide (AZO) as a target. It can be obtained by forming a film in a gas atmosphere or an argon (Ar + O ₂ ) gas atmosphere containing oxygen.
In addition, the transparent film 12 having a low refractive index of, for example, 1.64 is used in the hydrogen (H ₂ ) gas atmosphere or the water vapor (H ₂ O) atmosphere with the above-described aluminum-added zinc oxide (AZO) as a target. Obtained by film formation.

The specific resistance of at least one of these zinc oxide thin films, for example, at least one of the high refractive index transparent film 11 and the low refractive index transparent film 12 is 1.0 × 10 ³ μΩ · cm or less. preferable.
Thus, by setting the specific resistance of at least one of the transparent films 11 and 12 to 1.0 × 10 ³ μΩ · cm or less, the transparent film can be provided with a function as a transparent conductive film.

FIG. 2 is a cross-sectional view showing a modification of the antireflection film of the present embodiment. When the specific resistance of the low refractive index transparent film 12 is high, the transparent conductive film 3 is formed on the transparent film 12. It is an example.
By setting it as such a structure, the function of a transparent conductive film can be provided to the antireflection film 1.

FIG. 3 is a schematic configuration diagram showing a sputtering apparatus (film forming apparatus) used for forming the antireflection film of this embodiment, and FIG. 4 is a cross-sectional view showing the main part of the film forming chamber of the sputtering apparatus.
The sputtering apparatus 21 is an inter-back type sputtering apparatus. For example, a loading / unloading chamber 22 for loading / unloading a substrate such as a glass substrate (not shown), and a zinc oxide-based antireflection coating on the substrate. A film forming chamber (vacuum container) 23 for forming a film is provided.
The preparation / removal chamber 22 is provided with a roughing exhaust means 24 such as a rotary pump for roughly evacuating the chamber, and a substrate tray 25 for holding and transporting the substrate is movably disposed in the chamber. ing.

  On the other hand, a heater 31 that heats the substrate 26 is provided vertically on one side surface 23a of the film forming chamber 23, and a target 27 made of zinc oxide material is held on the other side surface 23b to provide a desired sputtering voltage. A cathode (target holding means) 32 to be applied is provided in a vertical type, and further, a high vacuum evacuation means 33 such as a turbo molecular pump for evacuating the chamber to a high vacuum, a power supply 34 for applying a sputtering voltage to the target 27, and a chamber. Gas introduction means 35 for introducing gas is provided.

The cathode 32 is made of a plate-like metal plate, and is used for fixing the target 27 by bonding (fixing) with a brazing material or the like.
The power source 34 is for applying a sputtering voltage to the target 27 and includes a direct current (DC) power source (not shown).
The gas introduction means 35 includes a sputtering gas introduction means 35a for introducing a sputtering gas such as Ar, a hydrogen gas introduction means 35b for introducing hydrogen gas, an oxygen gas introduction means 35c for introducing oxygen gas, and a water vapor for introducing water vapor. And introducing means 35d.

  In the gas introduction means 35, the hydrogen gas introduction means 35b to the water vapor introduction means 35d may be selectively used as necessary. For example, the hydrogen gas introduction means 35b, the oxygen gas introduction means 35c, and the hydrogen gas introduction means You may comprise by two means like 35b and the water vapor introducing means 35d.

Next, a method of sequentially forming the zinc oxide-based antireflection film 1 and the transparent conductive film 3 on the transparent substrate 2 using the sputtering apparatus 21 will be described.
Here, a non-alkali glass substrate is used as the transparent substrate 2, and a two-layer structure made of a zinc oxide-based material such as aluminum-added zinc oxide (AZO) or gallium-added zinc oxide (GZO) is used as the antireflection film 1. The case will be described.

"Deposition of antireflection film"
(A) Formation of High Refractive Index Transparent Film In order to form the high refractive index transparent film 11, a zinc oxide target 27 is bonded and fixed to the cathode 32 with a brazing material or the like. Here, as the target material, a zinc oxide-based material, for example, aluminum-added zinc oxide (AZO) added with 0.1 to 10% by mass of aluminum oxide (Al ₂ O ₃ ) or gallium oxide (Ga ₂ O ₃ ) is used. Examples include gallium-doped zinc oxide (GZO) added in an amount of 0.1 to 10% by mass.

Next, in a state in which the substrate 26 is stored in the substrate tray 25 of the preparation / removal chamber 22, the preparation / removal chamber 22 and the film formation chamber 23 are roughly evacuated by the roughing exhaust unit 24, and the preparation / removal chamber 22 and film formation are performed. After the chamber 23 reaches a predetermined degree of vacuum, for example, 0.27 Pa (2.0 × 10 ⁻³ Torr), the substrate 26 is carried into the film forming chamber 23 from the loading / unloading chamber 22, and the substrate 26 is set. Is placed in front of the heater 31 in a state of being turned off, the substrate 26 is opposed to the target 27, and the substrate 26 is heated by the heater 31 to be within a temperature range of 100 ° C. to 600 ° C.

Next, the film formation chamber 23 is evacuated by the high vacuum exhaust means 33, and the film formation chamber 23 has a predetermined high vacuum, for example, 2.7 × 10 ⁻⁴ Pa (2.0 × 10 ⁻⁶ Torr). Thereafter, Ar gas is introduced into the film forming chamber 23 by the sputtering gas introduction means 35a, or Ar gas and O ₂ gas are introduced by the sputtering gas introduction means 35a and the oxygen gas introduction means 35c. The inside of the film chamber 23 is an Ar gas atmosphere or an Ar gas (Ar + O ₂ ) atmosphere containing O ₂ gas.

Next, a sputtering voltage is applied to the target 27 by the power supply 34.
This sputtering voltage is preferably 340 V or less. By reducing the discharge voltage, it becomes possible to form a zinc oxide-based transparent film with a well-organized crystal lattice.
As the sputtering voltage, a high frequency voltage may be superimposed on a DC voltage. By superimposing the high frequency voltage on the DC voltage, the discharge voltage can be further reduced.
When a sputtering voltage is applied, plasma is generated on the substrate 26, and ions of a sputtering gas such as Ar excited by the plasma collide with the target 27. From the target 27, aluminum-added zinc oxide (AZO), gallium-added zinc oxide Atoms constituting the zinc oxide-based material such as (GZO) are ejected, and a transparent film made of the zinc oxide-based material is formed on the substrate 26.

In this film formation process, the atmosphere in the film formation chamber 23 is an Ar gas atmosphere or an Ar gas (Ar + O ₂ ) atmosphere containing O ₂ gas. Therefore, if sputtering is performed in this atmosphere, the obtained transparent film The number of oxygen vacancies in the zinc oxide crystal is controlled, and the transparent film 11 with a high refractive index having a desired high refractive index, for example, around 2.0, and a desired specific resistance (conductivity) is obtained.

Incidentally, when it is desired to shift the refractive index of the transparent film 11, the atmosphere during film formation, the Ar gas (Ar + _{O 2)} atmosphere containing Ar gas atmosphere or _{O 2} gas, Ar containing Ar gas or _{O 2} gas the gas may be the atmosphere plus _{H 2} gas and / or the _{H 2} O gas (water vapor).
This is realized by performing either one or both of introduction of H ₂ gas by the hydrogen gas introduction unit 35b and introduction of H ₂ O gas (water vapor) by the water vapor introduction unit 35d into the film forming chamber 23. be able to.

(B) Film formation of low refractive index transparent film Introduction of H ₂ gas by hydrogen gas introducing means 35b into the film forming chamber 23 with the zinc oxide target 27 left in the film forming chamber 23, By performing either one or both of the introduction of H ₂ O gas (water vapor) by the water vapor introducing means 35d, the inside of the film forming chamber 23 is made an H ₂ gas and / or H ₂ O gas (water vapor) atmosphere. .

When forming the low refractive index transparent film, the same zinc oxide target 27 as that of the high refractive index transparent film is used, and the atmosphere during film formation includes H ₂ gas and / or H ₂ O gas (water vapor). The atmosphere. Thereby, a low refractive index transparent film in which the refractive index of the transparent film is shifted to the low refractive index side is formed.
Here, H ₂ gas and / or H ₂ O gas (water vapor) is introduced into the film forming chamber 23 using the hydrogen gas introducing means 35b and the water vapor introducing means 35d.
Note that the film formation chamber 23 also contains Ar gas (Ar + O ₂ ) containing Ar gas or O ₂ gas, so that each of H ₂ gas, H ₂ O gas (water vapor), and Ar + O ₂ gas is separated. By controlling the pressure, the refractive index and specific resistance (conductivity) of the obtained transparent film can be controlled.

For example, the ratio _{R (P} H2 _/ P _O2) of the partial pressures of _{(P H2)} and oxygen gas of hydrogen gas _{(P O2),}
R = P _H2 / P _O2 ≧ 5 (1)
When the above condition is satisfied, the atmosphere in the film forming chamber 23 is a reactive gas atmosphere in which the hydrogen gas concentration is five times or more the oxygen gas concentration, and this reactive gas atmosphere satisfies R = P _H2 / P _O2 ≧ 5. A transparent film 12 having a refractive index of about 1.6 is obtained.

Also, the partial pressure of hydrogen gas _{(P H2)} and water vapor ratio _{R (P} H2 _/ P _H2O) with the partial pressure of (gas) _{(P H2 O)} is,
R = P _H2 / P _H2O ≧ 5 (2)
When satisfying, the atmosphere in the film forming chamber 23 is a reactive gas atmosphere in which the hydrogen gas concentration is five times or more the water vapor concentration, and this reactive gas atmosphere satisfies R = P _H2 / P _H2O ≧ 5, A transparent film 12 having a refractive index of around 1.6 is obtained.

Thus, the specific resistance (conductivity) of the obtained transparent film 12 also changes by making the inside of the film formation chamber 23 into H ₂ gas and / or H ₂ O gas (water vapor) atmosphere. Therefore, in the case of the transparent film 12 that requires conductivity, it is necessary to form the film in an H ₂ gas atmosphere. However, in the case of the transparent film 12 that does not require conductivity, an H ₂ gas atmosphere, H ₂ O Any of gas (water vapor) atmospheres may be used.
Thus, since the low refractive index transparent film 12 formed in an atmosphere of H ₂ gas and H ₂ O gas (H ₂ + H ₂ O) has a low specific resistance, it can also serve as a transparent conductive film. In this case, the transparent conductive film 3 becomes unnecessary.

On the other hand, the transparent film 12 having a low refractive index formed in an H ₂ O gas atmosphere has a high specific resistance, and thus the transparent conductive film 3 is necessary.
Next, a method for forming the transparent conductive film 3 on the transparent film 12 having a high specific resistance and a low refractive index will be described.

"Deposition of transparent conductive film"
In order to form the transparent conductive film 3, the zinc oxide target 27 is used, the temperature of the substrate 26 is set within a temperature range of 100 ° C. to 600 ° C. in the same manner as the antireflection film, and the sputtering gas is used. A sputtering gas such as Ar is introduced by the introducing means 15a, and any two or three of the hydrogen gas introducing means 15b to the water vapor introducing means 15d are selected from the group of hydrogen gas, oxygen gas, and water vapor. Two or three gases are introduced.

Here, if you choose the hydrogen gas and oxygen gas, partial pressures of _{(P H2)} and oxygen gas of hydrogen gas _{(P O2)} ratio of _{R (P} H2 _/ P _O2) is,
R = P _H2 / P _O2 ≧ 5 (3)
When the above condition is satisfied, the atmosphere in the film forming chamber 23 is a reactive gas atmosphere in which the hydrogen gas concentration is five times or more the oxygen gas concentration, and this reactive gas atmosphere satisfies R = P _H2 / P _O2 ≧ 5. A transparent conductive film having a specific resistance of 1.0 × 10 ³ μΩ · cm or less is obtained.

Also, if you choose the hydrogen gas and water vapor (gas), the partial pressure of hydrogen gas _{(P H2)} and water vapor ratio _{R (P} H2 _/ P _H2O) with the partial pressure of (gas) _{(P H2 O)} is,
R = P _H2 / P _H2O ≧ 5 (4)
When satisfying, the atmosphere in the film forming chamber 23 is a reactive gas atmosphere in which the hydrogen gas concentration is five times or more the water vapor concentration, and this reactive gas atmosphere satisfies R = P _H2 / P _H2O ≧ 5, A transparent conductive film having a specific resistance of 1.0 × 10 ³ μΩ · cm or less is obtained.

Next, a sputtering voltage of 340 V or less, preferably a sputtering voltage in which a high frequency voltage is superimposed on a DC voltage is applied to the target 27 by the power source 34.
As a result, plasma is generated on the substrate 26, and ions of a sputtering gas such as Ar excited by the plasma collide with the target 27. From the target 27, aluminum-added zinc oxide (AZO), gallium-added zinc oxide (GZO) The atoms constituting the zinc oxide-based material such as) are ejected to form the transparent conductive film 3 made of the zinc oxide-based material on the transparent film 12.

  In this film forming process, the atmosphere in the film forming chamber 23 becomes a reactive gas atmosphere consisting of two or three kinds selected from the group of hydrogen gas, oxygen gas, and water vapor. The resulting transparent conductive film 3 is controlled in the number of oxygen vacancies in the zinc oxide crystal to become a film having a desired conductivity, and its specific resistance is lowered and the desired specific resistance is reduced. It becomes the value of.

In particular, when the concentration of each gas in the film forming chamber 23 is 5 times or more than the oxygen gas concentration, a reactive gas atmosphere in which the ratio of the hydrogen gas to the oxygen gas is harmonized is obtained. If sputtering is performed in this reactive gas atmosphere, the obtained transparent conductive film 3 is a film having a desired conductivity by highly controlling the number of oxygen vacancies in the zinc oxide crystal. The resistance also decreases to the equivalent of the ITO film, and becomes a desired specific resistance value.
Moreover, the obtained transparent conductive film 3 maintains the transparency with respect to visible light, without a possibility of producing metallic luster.
In this way, the substrate 26 on which the zinc oxide-based transparent conductive film 3 having a low specific resistance and good transparency to visible light is formed is obtained.

Next, the experimental results conducted by the present inventors will be described for the method of manufacturing the zinc oxide-based transparent conductive film and antireflection film of the present embodiment.
An aluminum-added zinc oxide (AZO) target to which 2% by mass of Al ₂ O ₃ having a size of 5 inches × 16 inches is added is used as a brazing material to a parallel plate cathode 32 to which a direct current (DC) voltage is applied. Fixed with. Next, a non-alkali glass substrate is placed in the preparation / removal chamber 22, and the inside of the preparation / removal chamber 22 is roughly evacuated by the rough evacuation unit 24. The film formation chamber 23 was carried and placed opposite to the AZO target.

Next, after introducing Ar gas to a pressure of 5 mTorr by the gas introduction means 35, the partial pressure of H ₂ O gas is 5 × 10 ⁻⁵ Torr, the partial pressure of O ₂ gas is 1 × 10 ⁻⁵ Torr, The AZO target attached to the cathode 32 is sputtered by applying 1 kW of electric power to the cathode 32 from the power source 34 in an atmosphere of H ₂ O gas or O ₂ gas. An AZO film was deposited on an alkali glass substrate.

FIG. 5 is a graph showing the effect of H ₂ O gas (water vapor) in non-heated film formation, in which A represents the transmittance of the zinc oxide-based transparent conductive film when no reactive gas is introduced, and B represents The transmissivity of the zinc oxide-based transparent conductive film when introduced so that the partial pressure of H ₂ O gas is 5 × 10 ⁻⁵ Torr, C is the partial pressure of O ₂ gas is 1 × 10 ⁻⁵ Torr The transmittance of the zinc oxide-based transparent conductive film when introduced as described above is shown.

When no reactive gas was introduced, the film thickness of the transparent conductive film was 207.9 nm, and the specific resistance was 1576 μΩcm.
When H ₂ O gas was introduced, the film thickness of the transparent conductive film was 204.0 nm, and the specific resistance was 64464 μΩcm.
When O ₂ gas was introduced, the film thickness of the transparent conductive film was 208.5 nm and the specific resistance was 2406 μΩcm.

According to FIG. 5, it was found that the peak wavelength of transmittance can be changed without changing the film thickness by introducing H ₂ O gas. Moreover, the transmittance was also increased as a whole compared with A in which no reactive gas was introduced.
In addition, when H ₂ O gas is introduced, the specific resistance is high and the resistance deterioration is large, but since the transmittance is high, it can be applied to an optical member that does not require low resistance such as an antireflection film. I understood.
Furthermore, it was found that an optical device having a laminated structure with a changed refractive index can be obtained with a single target by repeatedly performing the film forming conditions with no introduction of H ₂ O gas and introduction or the amount of introduction changed.

FIG. 6 is a graph showing a simulation result of the reflectance of the antireflection film that has been optically designed using the refractive index calculated from the spectra of B and C in FIG.
Here, the peak value (λ) 796 nm of the wavelength obtained from the spectrum of C in FIG. 5 and each value of the film thickness (d) 208.5 nm are simply expressed by the equation “2nd = mλ” (where, The refractive index (n) of the transparent film having a high refractive index was calculated to be 1.91 when d is a film thickness, λ is a wavelength, and n and m are integers, and m = 1.
On the other hand, the wavelength peak value (λ) 668 nm obtained from the spectrum of B in FIG. 5 and the film thickness (d) 204.0 nm are simply expressed by the equation “2nd = mλ” (where d Is a film thickness, λ is a wavelength, and n and m are integers). When m = 1, the refractive index (n) of the transparent film having a low refractive index is calculated to be 1.64.

Next, a transparent film having a high refractive index with a refractive index (n) of 1.91 is formed on the glass substrate so that the film thickness (d) is 64.0 nm. A low refractive index transparent film having a refractive index (n) of 1.64 was formed so as to have a film thickness (d) of 89.5 nm.
According to FIG. 6, it can be seen that when the wavelength (λ) is 550 nm, the reflectance of the antireflection film is 0.167%, and the multilayered antireflection film is continuously formed using one target. It was found that the film can be made.

Next, an AZO film was deposited on the alkali-free glass substrate in the same manner as described above except that the alkali-free glass substrate was heated to 250 ° C.
FIG. 7 is a graph showing the effect of H ₂ O gas (water vapor) in heating film formation with a substrate temperature of 250 ° C., where A is the zinc oxide-based transparent conductive film when no reactive gas is introduced. The transmittance is B, the transmittance of the zinc oxide-based transparent conductive film when introduced so that the partial pressure of H ₂ O gas is 5 × 10 ⁻⁵ Torr, and C is the partial pressure of O ₂ gas is 1 ×. The transmittance of the zinc oxide-based transparent conductive film when introduced so as to be 10 ⁻⁵ Torr is shown. As the cathode, a parallel plate type cathode to which a direct current (DC) voltage was applied was used.

When no reactive gas was introduced, the film thickness of the transparent conductive film was 201.6 nm, and the specific resistance was 766 μΩcm.
When H ₂ O gas was introduced, the film thickness of the transparent conductive film was 183.0 nm and the specific resistance was 6625 μΩcm.
When O ₂ gas was introduced, the film thickness of the transparent conductive film was 197.3 nm and the specific resistance was 2214 μΩcm.

According to FIG. 7, it was found that the same effect as in the non-heated film formation can be obtained in the heat film formation.
When H ₂ O gas is introduced, the film thickness is slightly reduced, but when the substrate temperature is heated to 250 ° C. because the peak wavelength is shifted more than the peak wavelength shift due to film thickness interference. It was also found that the same effect as that obtained without heating can be obtained.

Next, H ₂ O gas is replaced with H ₂ gas, a parallel plate type cathode capable of superimposing a direct current (DC) voltage and a high frequency (RF) voltage is used as a cathode, and a high frequency (350 W) is applied to DC power of 1 kW by a power source 34. An AZO film was deposited on a non-alkali glass substrate in the same manner as described above except that sputtering power superimposed with (RF) power was applied to the cathode 12 and constant current control of 4 A was performed.

FIG. 8 is a graph showing the effect when H ₂ gas and O ₂ gas are simultaneously introduced in the thermal film formation at a substrate temperature of 250 ° C., where A is the partial pressure of H ₂ gas is 15 × 10. ⁻⁵ Torr, O ₂ gas partial pressure is 1 × 10 ⁻⁵ Torr when introduced simultaneously, the transmittance of the zinc oxide-based transparent conductive film is B, O ₂ gas partial pressure is 1 × 10 ⁻⁵ The transmittance of the zinc oxide-based transparent conductive film when introduced so as to be Torr is shown.

When H ₂ gas and O ₂ gas were introduced at the same time, the film thickness of the transparent conductive film was 211.1 nm.
When only O ₂ gas was introduced, the film thickness of the transparent conductive film was 208.9 nm.
According to FIG. 8, when the H ₂ gas and the O ₂ gas are introduced at the same time, the peak wavelength is shifted more than the shift of the peak wavelength due to the film thickness interference as compared with the case where only the O ₂ gas is introduced. I understood that. Moreover, it turned out that the transmittance | permeability is also improving.

FIG. 9 is a graph showing the effect when H ₂ gas and O ₂ gas are introduced at the same time in heating film formation with a substrate temperature of 250 ° C., and the partial pressure of O ₂ gas is 1 × 10 ⁻⁵ Torr (flow rate). The specific resistance of the zinc oxide-based transparent conductive film when the H ₂ gas partial pressure is changed between 0 and 15 × 10 ⁻⁵ Torr (flow rate partial pressure). ing. The film thickness of the transparent conductive film was approximately 200 nm.
According to this figure, the specific resistance sharply decreases when the pressure of H ₂ gas is from 0 Torr to 2.0 × 10 ⁻⁵ Torr, but when the pressure exceeds 2.0 × 10 ⁻⁵ Torr, the specific resistance is stabilized. I knew it would come.
When the reactive gas was not introduced under the same conditions, the specific resistance of the transparent conductive film was 422 μΩ · cm. Therefore, it was found that even when H ₂ gas and O ₂ gas were introduced at the same time, the specific resistance was hardly deteriorated. .

In particular, a transparent conductive film used for a display or the like is required to have low resistance in addition to high transmittance in the visible light region. The transparent electrode of a general display is required to be 1.0 × 10 ³ μΩ · cm or less. In FIG. 9, the specific resistance is 1.0 × 10 ³ μΩ · cm or less when the pressure of the H ₂ gas is 5.0 × 10 ⁻⁵ Torr or more. Since the pressure of the O ₂ gas is 1 × 10 ⁻⁵ Torr, it is preferable that R = P _H2 / P _O2 ≧ 5 in order to set the specific resistance to 1.0 × 10 ³ μΩ · cm or less. I understand.

FIG. 10 is a graph showing the effect of H ₂ gas in non-heated film formation, in which A is a zinc oxide-based transparent when introduced so that the partial pressure of H ₂ gas is 3 × 10 ⁻⁵ Torr. B shows the transmittance of the conductive film, and B shows the transmittance of the zinc oxide-based transparent conductive film when introduced so that the partial pressure of O ₂ gas becomes 1.125 × 10 ⁻⁵ Torr. As the cathode, a counter-type cathode to which a direct current (DC) voltage was applied was used.

When H ₂ gas was introduced, the film thickness of the transparent conductive film was 191.5 nm and the specific resistance was 913 μΩcm.
When O ₂ gas was introduced, the film thickness of the transparent conductive film was 206.4 nm and the specific resistance was 3608 μΩcm.
According to FIG. 10, it was found that the peak wavelength of transmittance can be changed without changing the film thickness by introducing H ₂ gas.
Further, transmittance was found to be higher than the case of introducing O ₂ gas.
Thus, the process of introducing H ₂ gas, by optimizing the H ₂ gas introduction rate, zinc oxide-based transparent conductive film having a high transmittance and low specific resistance could be obtained.

  According to the film formation method of the antireflection film of this embodiment, since sputtering is performed in a reactive gas atmosphere containing two or three kinds selected from the group of hydrogen gas, oxygen gas, and water vapor, The zinc oxide-based antireflection film 1 excellent in transparency and the zinc oxide-based transparent conductive film 3 having low specific resistance and excellent transparency to visible light can be easily formed.

According to the film forming apparatus of the present embodiment, the gas introduction means 35 includes a sputtering gas introduction means 35a for introducing a sputtering gas such as Ar, a hydrogen gas introduction means 35b for introducing hydrogen gas, and an oxygen for introducing oxygen gas. Since the gas introduction means 35c and the water vapor introduction means 35d for introducing water vapor are configured, the zinc oxide antireflection film 1 and the transparent conductive film 3 are controlled by controlling the sputtering gas introduction means 35a to the water vapor introduction means 35d. The atmosphere in forming the film can be a reactive gas atmosphere in which the ratio of the reducing gas to the oxidizing gas is harmonized.
Therefore, it is possible to form a zinc oxide antireflection film or a transparent conductive film only by improving a part of the conventional film forming apparatus.

  In the antireflection film 1 of this embodiment, the antireflection film has a two-layer structure in which a transparent film 11 having a high refractive index and a transparent film 12 having a low refractive index are sequentially formed on the surface 2a of the transparent substrate 2. The laminated structure of the antireflection film 1 is not limited to the above two-layer structure, and may be a multilayer structure of three or more layers so as to satisfy the required antireflection performance of the antireflection film. For example, a multilayer structure in which a transparent film 11 having a high refractive index and a transparent film 12 having a low refractive index are repeatedly formed a plurality of times may be used.

“Second Embodiment”
FIG. 11 is a cross-sectional view showing a main part of a film forming chamber of an inter-back magnetron sputtering apparatus (film forming apparatus) used for forming an antireflection film according to the second embodiment of the present invention.
The magnetron sputtering apparatus 41 is different from the sputtering apparatus 21 described above in that a sputtering cathode mechanism (target holding means) that holds a target 27 of a zinc oxide-based material on one side surface 23b of the film forming chamber 23 and generates a desired magnetic field. ) 42 is provided vertically.

  The sputter cathode mechanism 42 includes a back plate 43 in which the target 27 is bonded (fixed) with a brazing material or the like, and a magnetic circuit (magnetic field generating means) 44 disposed along the back surface of the back plate 43. The magnetic circuit 44 generates a horizontal magnetic field on the surface of the target 27. A plurality of magnetic circuit units (two in FIG. 11) 44a and 44b are connected and integrated by a bracket 45, and the magnetic circuit unit 44a, Each of 44b includes a first magnet 46 and a second magnet 47 having different polarities on the surface on the back plate 43 side, and a yoke 48 for mounting them.

In the magnetic circuit 44, a magnetic field represented by a magnetic force line 49 is generated by the first magnet 46 and the second magnet 47 having different polarities on the back plate 43 side. Thereby, on the surface of the target 27 between the first magnet 46 and the second magnet 47, a position 50 where the vertical magnetic field is 0 (the horizontal magnetic field is maximum) is generated. The high-density plasma is generated at the position 50, so that the film forming speed can be improved.
The maximum value of the horizontal magnetic field intensity on the surface of the target 27 is preferably 600 gauss or more. The discharge voltage can be lowered by setting the maximum value of the horizontal magnetic field strength to 600 gauss or more.

The magnetron sputtering apparatus 41 of the present embodiment can achieve the same effects as the sputtering apparatus 21 of the first embodiment.
In addition, since the sputtering cathode mechanism 42 for generating a desired magnetic field is provided on the one side surface 23b of the film forming chamber 23 in a vertical type, the sputtering voltage is set to 340 V or less, and the maximum horizontal magnetic field strength on the surface of the target 27 is 600 gauss. With the above process, a zinc oxide-based antireflection film or a transparent conductive film with a well-organized crystal lattice can be formed.
This zinc oxide-based antireflection film and transparent conductive film are hardly oxidized even after annealing at a high temperature after film formation, can suppress a decrease in transmittance and an increase in specific resistance, and have excellent heat resistance. A zinc oxide-based antireflection film or a transparent conductive film can be obtained.

“Third Embodiment”
FIG. 12 is a schematic configuration diagram showing a carousel type sputtering apparatus (film forming apparatus) according to a third embodiment of the present invention.
The sputtering apparatus 51 rotates in a film forming chamber (vacuum container) 52 around the central axis of the film forming chamber 52 and supports a plurality of substrates 26 on its outer peripheral surface in a detachable manner. 12 are provided, and a plurality of cathodes that hold a target 27 of a zinc oxide-based material and apply a desired sputtering voltage to the inner surface of the film forming chamber 52. 32 (two in FIG. 12) are provided, and when the rotating body 54 is rotated about its axis and stopped at a position facing the cathode 32, the substrate supported by the substrate holder 53 of the rotating body 54 26 faces the target 27 held by the cathode 32.

The film forming chamber 52, the partition plate 55 is provided for partitioning the chamber into two sputter areas _S 1, _{S 2,} these two sputter areas _S 1, _{S 2} each, rough exhaust means 24 and A high vacuum evacuation unit 33 is provided, and a gas introduction unit 35 including a sputtering gas introduction unit 35a, a hydrogen gas introduction unit 35b, an oxygen gas introduction unit 35c, and a water vapor introduction unit 35d for introducing water vapor is further provided. .

In this film forming chamber 52, by introducing one or both of Ar gas introduction, Ar gas containing O ₂ gas (Ar + O ₂ ), or both into the sputtering region S ₁ , The sputtering region S ₁ is made to have an Ar gas (Ar + O ₂ ) atmosphere containing Ar gas or O ₂ gas, and sputtering is performed in this atmosphere, whereby a high refractive index transparent material having a desired high refractive index on the substrate 26. A film 11 is formed.

Then, by rotating the rotating member 54 about its axis, a substrate 26 having a transparent film 11 of the high refractive index has been deposited is moved to the sputtering region S _2, this sputter region S _2, the gas introducing means 35 the introduction of _{H 2} gas, the introduction of the _{H 2} O gas (water vapor), either one, or by performing both, the sputter area _S in _{2 H 2} gas and / or the _{H 2} O gas (water vapor) atmosphere The low refractive index transparent film 12 having a desired low refractive index is formed on the high refractive index transparent film 11 by performing sputtering in this atmosphere.
As described above, the zinc oxide antireflection film 1 according to the first embodiment can be formed using the sputtering apparatus 51.

In the film forming chamber 52, either or both of Ar gas introduction and Ar gas containing O ₂ gas (Ar + O ₂ ) are introduced into the entire sputtering regions S ₁ and S ₂ by the gas introduction means 35. In this atmosphere, the substrate 26 is rotated to perform sputtering, whereby the transparent film 11 having a high refractive index is formed on the substrate 26. Then, gas is introduced into the entire sputtering regions S ₁ and S _2. Also by performing either one or both of introduction of H ₂ gas and introduction of H ₂ O gas (water vapor) by means 35, and performing sputtering by rotating the substrate 26 in this changed atmosphere, The zinc oxide-based antireflection film 1 of the first embodiment can be formed.

Even if the sputtering apparatus 51 of this embodiment is used, the same effect as the sputtering apparatus 21 of the first embodiment can be obtained.
In addition, a rotating body 54 having a substrate holder 53 that rotates about the central axis of the film forming chamber 52 and detachably supports the plurality of substrates 26 is provided in the film forming chamber 52. Since the plurality of cathodes 32 for holding the target 27 of zinc oxide-based material are provided on the inner surface, the substrate 26 is attached to the rotating body 54, and the rotating body 54 is rotated around its axis, so that different atmospheres can be obtained. A film having a multilayer structure can be formed at Therefore, it is suitable when a multilayer film is repeatedly formed.

It is sectional drawing which shows the antireflection film of the 1st Embodiment of this invention. It is sectional drawing which shows the modification of the antireflection film of the 1st Embodiment of this invention. It is a schematic block diagram which shows the sputtering device of the 1st Embodiment of this invention. It is sectional drawing which shows the principal part of the film-forming chamber of the sputtering device of the 1st Embodiment of this invention. Is a graph showing the effect of the H _{2 O} gas in the unheated film deposition (vapor). It is a graph which shows the simulation result of the reflectance of an antireflection film. Is a graph showing the effect of the H _{2 O} gas in the heating film formation a substrate temperature of 250 ° C. (steam). Is a graph showing the effect in the case of introducing H ₂ gas and O ₂ gas at the same time in the heating film formation a substrate temperature of 250 ° C.. Is a graph showing the effect in the case of introducing H ₂ gas and O ₂ gas at the same time in the heating film formation a substrate temperature of 250 ° C.. It is a graph showing the effect of H ₂ gas in the unheated film deposition. It is sectional drawing which shows the principal part of the film-forming chamber of the inter-back-type magnetron sputtering apparatus of the 2nd Embodiment of this invention. It is a schematic block diagram which shows the carousel type sputtering device of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antireflection film 2 Transparent substrate 2a Surface 3 Transparent conductive film 11 Transparent film with high refractive index 12 Transparent film with low refractive index 21 Sputtering device 22 Preparation / take-out chamber 23 Deposition chamber 24 Roughing exhaust means 25 Substrate tray 26 Substrate 27 Target 31 Heater 32 Cathode 33 High vacuum evacuation means 34 Power supply 35 Gas introduction means 35a Sputter gas introduction means 35b Hydrogen gas introduction means 35c Oxygen gas introduction means 35d Water vapor introduction means 41 Magnetron sputtering apparatus 42 Sputter cathode mechanism 43 Back plate 44 Magnetic circuit 44a , 44b Magnetic circuit unit 45 Bracket 46 First magnet 47 Second magnet 48 Yoke 49 Magnetic field line 50 Position where the vertical magnetic field becomes 0 51 Sputtering device 52 Deposition chamber 53 Substrate holder 54 Rotating body 55 Partition plate S ₁ , S ₂ Sputtering region Area

Claims (8)

A method for forming an antireflection film in which a second zinc oxide-based thin film is laminated on a first zinc oxide-based thin film,
A first zinc oxide-based thin film is formed by sputtering using a first zinc oxide-based target in a first reactive gas containing two or three selected from the group consisting of oxygen gas, hydrogen gas, and water vapor. A first film forming step of forming a film;
In a second reactive gas containing two or three selected from the group of oxygen gas, hydrogen gas, and water vapor on the first zinc oxide-based thin film and having a composition different from that of the first reactive gas A second film-forming step of forming a second zinc oxide-based thin film by sputtering using a second zinc oxide-based target at
A method for forming an antireflection film, comprising:   2. The method of forming an antireflection film according to claim 1, wherein the second reactive gas has different contents of the first reactive gas and hydrogen gas. 3.   2. The method of forming an antireflection film according to claim 1, wherein the second reactive gas has different contents of the first reactive gas and oxygen gas. 3.   4. The method of forming an antireflection film according to claim 1, wherein the second zinc oxide-based target is the same as the first zinc oxide-based target. 5.   The second film forming step is performed by replacing the first reactive gas with the second reactive gas in the same vacuum chamber as the first film forming step. The method for forming an antireflection film according to claim 1.   The reflection according to any one of claims 1 to 5, wherein the first zinc oxide-based target and the second zinc oxide-based target are an aluminum-added zinc oxide target or a gallium-added zinc oxide target. Method for forming a prevention film. An antireflection film obtained by the method for forming an antireflection film according to any one of claims 1 to 6,
A first zinc oxide thin film, and a second zinc oxide thin film laminated on the first zinc oxide thin film and having a refractive index different from that of the first zinc oxide thin film, Anti-reflective coating. The antireflection according to claim 7, wherein at least one of the first zinc oxide-based thin film and the second zinc oxide-based thin film has a specific resistance of 1.0 × 10 ³ μΩ · cm or less. film.

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