JP2010080358A - Substrate with transparent conductive film and display element using the same, and solar cell - Google Patents

Abstract

【Task】
For the substrate with a transparent conductive film, when only the ITO portion is recovered later, a simple technique is used.
[Solution]
A substrate (1), a first transparent conductive film (2), and a second transparent conductive film (on the side opposite to the side on which the substrate is disposed) with respect to the first transparent conductive film ( 3), wherein the first transparent conductive film contains an oxide of Zn, Sn, Ti, V, Ni, or Si, and the second transparent conductive film contains indium oxide as a main component. The etching rate of the first transparent conductive film is larger than the etching rate of the second transparent conductive film, the film thickness of the first transparent conductive film is 10 nm or more, and the first transparent conductive film is A substrate with a transparent conductive film, which contains B, Al, or Ga.
[Selection] Figure 1

Description

  The present invention relates to a substrate with a transparent conductive film, a display element using the same, and a solar cell.

  Recently, with the widespread use of various mobile phones, mobile terminals, mobile computers, car navigation systems, etc., there is an increasing demand for small, flat panel displays (FPDs) that are lightweight, high-definition, high-brightness, and inexpensive. . Also, in homes and offices, space-saving desktop displays and flat displays such as wall-mounted televisions are replacing conventional CRT tube displays. In particular, with the spread of the high-speed Internet and the advancement of digital broadcasting, digital signal transmission of hundreds to several gigabits per second has been put into practical use in both wired and wireless, and general users exchange extremely large amounts of information in real time. It is shifting to the times. For this reason, the demand for these flat displays is required to be high-speed display capable of digital signal processing in addition to light weight, high definition, high brightness, and low price. Such FPDs include a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display, an organic light emitting diode (OLED) display, and so on. It has been known. In these displays, by applying an electric field or current to each display pixel, it is necessary to generate light or adjust the amount of light, and at the same time to extract the light to the outside of the element. Transparent electrodes that can be used are used.

  At the same time, the spread of new displays and mobile communications has developed a global scale of economy and has caused significant energy consumption. The demand for solar cells as a form of supplying energy resources has increased, and there is a need for more efficient and resource-saving solar cells. The solar cell was first put to practical use in the Barg type, which cuts silicon single crystals and polycrystals. However, high-quality silicon is depleted, and a thin film type capable of forming an element with less raw materials has attracted attention. In such a solar cell, a transparent electrode capable of transmitting not only visible light but also light having a wide wavelength ranging from ultraviolet rays to infrared rays is required.

Transparent electrode materials are roughly classified into crystalline and amorphous materials. Examples of crystal systems include indium-tin-oxide (ITO) -containing indium oxide In ₂ O ₃ system, zinc oxide ZnO system, tin oxide SnO ₂ system, titanium oxide TiO ₂ system, and cadmium tin oxide CdSnO. Series ₄ is known. In addition, the amorphous type includes indium zinc oxide IZO type (Indium Zinc Oxide, an amorphous phase appearing in an intermediate composition of In ₂ O ₃ and ZnO. Typically, In ₂ O ₃ is 80%). Among these, the transparent electrode material that is overwhelmingly popular is ITO, which is a type of indium oxide In ₂ O ₃ (In ₂ O ₃ crystal substituted with In by 10 to 20% tin Sn). It is. A typical method for forming a thin film using ITO as a transparent electrode is a sputtering method. This is because the ITO target, which is a transparent electrode material, is placed in a vacuum device facing the substrate on which a thin film is to be formed, and the target material is vaporized using argon Ar or oxygen O ₂ gas as the sputtering gas, Let it accumulate. By this method, an ITO thin film with a film thickness of several tens to several hundreds of nanometers is collectively formed on a large substrate of several m square size. In addition, the transparent electrode made of ITO is stable without changing its characteristics due to matching with other members constituting the FPD, patterning processability with a photoresist, heat treatment in the middle, and the like.

However, ITO contains indium In which is a rare metal as a main component, but since In itself has limited underground reserves and is produced only as a by-product of zinc ore, there is a concern about resource depletion. For these reasons, there is a strong demand for an alternative transparent electrode material that can replace ITO. Among transparent electrode materials other than ITO, SnO ₂ and TiO ₂ systems have a conductivity that is one digit or more larger than that of ITO and are difficult to process. The CdSnO ₄ system has not been studied much because of the toxicity of Cd. Since the main component of the IZO system is In, it is difficult to say that it is an alternative material that does not use In. A material that has transparency and conductivity close to those of ITO is a ZnO-based material, which is considered to be the most promising candidate for an alternative material. However, there is currently no level that can completely replace ITO, and there are many remaining issues such as compatibility with mass production processes, patterning properties such as etching, process stability, and long-term stability in addition to the properties as a transparent conductive film. .

  Under such circumstances, the movement to collect and recycle In is more active. According to Non-Patent Document 1, when viewing the ITO flow in the LCD manufacturing process, 70% of the ITO sputter target is recovered without being deposited, and 30% is consumed by the deposition. Of these 30%, 15% masking material adhesion, 5% bell jar inner wall adhesion, 5% etchant, 2% defective panel, and 3% ITO in the final product. The amount is only 0.18 g on a 30-inch LCD TV. Today, recovery of sputter targets, masking materials, and bell jar inner walls has already been promoted. However, the rarity of In still remains unchanged, and ITO contained in the final product carried out of the process is also efficiently recovered. There is a need to do. The technology for recovering ITO from the final product panel is described, for example, in Non-Patent Document 2, in which ITO is dissolved in hydrochloric acid and subjected to various chemical treatments and adsorption treatments to recover In. For this reason, many chemical substances for chemically treating In are required, and the environmental load is increased. In addition, since a large chemical plant is required, the In recovery cost from the final product panel containing only 3% of the ITO sputter target is increased.

Endo Kotaro “Circulation and Recycling of Rare Resources: Using Indium as an Example: Material of the 12th Recycling and Technology Research Group, Material of the Waste Society” (2007/3/26) Takamichi Honma, Toshiaki Muratani, “Material Recovery from LCD Waste Panels”, Sharp Technical Bulletin No. 92 (2005/8)

  Thus, in order to efficiently recover the transparent conductive film mainly composed of indium oxide represented by ITO contained in the product, it is desirable that the recovery method be as simple and low-cost as possible. In particular, by recovering ITO as ITO, it is possible to separate and purify from other members without requiring an extra chemical solution treatment.

  The objective of this invention is providing the board | substrate with a transparent conductive film which can collect | recover only an ITO part later by a simple method.

  In order to solve the above-described problems, the present invention provides a substrate, a first transparent conductive film, and a second transparent film disposed on the opposite side of the first transparent conductive film from the side on which the substrate is disposed. The second transparent conductive film is mainly composed of indium oxide, and the etching rate of the first transparent conductive film is higher than the etching rate of the second transparent conductive film. A substrate with a conductive film.

  The present invention also includes a substrate and a transparent conductive film, the transparent conductive film contains indium as a first element, and the transparent conductive film includes Zn, Sn, Ti, V, Containing Ni or Si, in the transparent conductive film, the concentration of the first element on the surface opposite to the substrate surface in the transparent conductive film is the concentration of the first element on the substrate surface side in the transparent conductive film In the transparent conductive film, the concentration of the second element on the substrate surface side in the transparent conductive film is greater than the concentration of the second element on the surface side opposite to the substrate surface in the transparent conductive film. It is the board | substrate with the transparent conductive film characterized.

  According to the present invention, it is possible to provide a substrate with a transparent conductive film that can later recover only the ITO portion by a simple method, and a display element and a solar cell using the substrate.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The basic structure of the substrate with a transparent conductive film of the present invention will be described with reference to FIGS. The transparent conductive film mainly composed of indium oxide in the present invention is an inorganic compound thin film composed mainly of indium In and oxygen O, and can contain a plurality of elements as additive elements in addition to indium. Examples of such additive elements include boron B, aluminum Al, gallium Ga, indium In, carbon C, silicon Si, germanium Ge, tin Sn, nitrogen N, fluorine F, scandium Sc, titanium Ti, vanadyl V, and nickel Ni. These elements can be included as additive elements other than indium In and oxygen O. Moreover, in this invention, although it is set as the transparent conductive film which has an indium oxide as a main component, ITO (tin addition indium oxide) is mentioned as a typical transparent conductive film in it.

FIG. 1 (a) schematically shows a cross-sectional structure of the substrate with a transparent conductive film of the present invention. The substrate with a transparent conductive film in FIG. 1A is composed of a first transparent conductive film 2 formed on the substrate 1 and a second transparent conductive film 3 formed directly thereon. In order to explain the characteristics of the substrate with a transparent conductive film, the film thickness direction is the z direction, the position of the interface between the substrate 1 and the first transparent conductive film 2 is z ₀ , and the first transparent conductive film 2 and the first transparent conductive film 2 The interface with the second transparent conductive film 3 is z ₁ , and the uppermost surface of the second transparent conductive film 3 is z ₂ . The first transparent conductive film 2 and the second transparent conductive film 3 are formed by laminating two types of transparent conductive materials having different compositions. The composition and the manufacturing method satisfy the conditions as described later. It is desirable. FIG. 1B schematically shows the change in the z direction of the elemental composition ratio of the transparent conductive film shown in FIG. Here, as an example, the case where zinc oxide ZnO is used for the first transparent conductive film 2 and ITO is used for the second transparent conductive film 3 is shown, but in the case of the transparent conductive film as shown in FIG. The ratio of elements constituting each layer (here, oxygen is not shown for convenience) varies discontinuously at z ₁ at the interface between the first transparent conductive film 2 and the second transparent conductive film 3. .

Examples of the first transparent conductive film 2 include zinc oxide ZnO, tin oxide SnO ₂ , and titanium oxide TiO ₂ , which are other oxide-based transparent conductive materials. A transparent conductive material having a low resistance of 1 × 10 ⁻³ Ωcm or less and an average transmittance in the visible light region of 60% or more, such as a SiO ₂ dispersion film in which Ag fine particles are dispersed, can be mentioned. In this case, the main component is Si, but the conductivity is carried by Ag fine particles.

  By optimizing the film thickness ratio and the composition ratio distribution in the film thickness direction of the transparent conductive film constituting the transparent conductive film according to the present invention, the visible light transmittance and conductivity as the transparent conductive film are not impaired. Indium oxide as a main component can be easily recovered. The film thickness of the first transparent conductive film that realizes such characteristics is desirably 10 nm or more. In particular, in order to recover the used indium oxide as half or more indium oxide, it is desirably 20 nm or more. The higher the percentage that can be recovered as indium oxide, the easier it is to recover the transparent conductive film mounted on various products, and it can be reused again as an indium oxide raw material or mixed with alkaline earth metal without using chemicals. Energy saving and low-cost resource recovery such as reduction to metallic indium by smelting becomes possible.

  Here, when the film thickness of the first transparent conductive film is thinner than 10 nm, the second transparent conductive film containing indium oxide as a main component is partially considered in view of film thickness flatness such as actual sputter film formation. An area in contact with the substrate is generated, and it becomes difficult to effectively peel and recover the second transparent conductive film. The upper limit of the film thickness of the first transparent conductive film differs depending on the use of the transparent conductive film. For example, the transparent electrode for LCD is about 300 nm, the transparent electrode for PDP is about 1 μm, the solar In the case of a transparent electrode for battery use, about 1 μm is the upper limit of the film thickness of the transparent electrode as an element, so it is necessary to be smaller than these.

FIG. 2 (a) schematically shows another cross-sectional structure of the substrate with a transparent conductive film of the present invention. The substrate with a transparent conductive film of the present invention in FIG. 2A is composed of a transparent conductive film 5 formed on the substrate 4. In order to explain the characteristics of the transparent conductive film 5, the film thickness direction is the z direction, the interface position between the substrate 4 and the transparent conductive film 5 is z ₀ , and the uppermost surface of the transparent conductive film 5 is z _2. Let z be an arbitrary position. The transparent conductive film 5 is formed so that the elemental composition continuously changes, but the specific composition and manufacturing method preferably satisfy the conditions as described later. FIG. 2B schematically shows changes in the z direction of the elemental composition ratio of the transparent conductive film 5 shown in FIG. Here, as an example, the case where the transparent conductive film 5 composed of three elements of zinc Zn, indium In, and tin Sn is used is shown, but in the case of the transparent conductive film 5 as shown in FIG. The ratio of elements constituting oxygen (for the sake of convenience, oxygen is not shown here) changes continuously in the z-axis direction, particularly rapidly at a certain position z.

  In order to facilitate the recovery from the product while maintaining the characteristics as the transparent conductive film, a specific composition distribution as shown in the examples later is required. At the same time, whether or not the completed transparent conductive film has the configuration of the present invention is known by performing elemental composition analysis in the film thickness direction, for example, AES or TOF-SIMS analysis while sputtering with argon or the like. be able to. Alternatively, when there is a clear difference in the layer structure as shown in FIG. 1A, the analysis can be performed by structural analysis such as a cross-sectional TEM.

  However, depending on the sensitivity of the analysis, for example, even when it consists of a two-layered transparent conductive film as shown in FIG. 1A, the element profile is not as clear as in FIG. ) May appear as a continuous change. As shown later, in the manufacturing process, despite the aim of forming a two-layer transparent conductive film as shown in FIG. 1 (a), a mixed portion of the material occurs at the interface of the completed transparent conductive film. In some cases, a transparent conductive film such as 2 (a) is formed. In any case, the realization of a certain type of composition distribution makes it possible to achieve both the characteristics of the transparent conductive film aimed at by the present invention and the high product recovery efficiency.

  Etching rate is used as a solubility parameter characterizing the transparent conductive film of the present invention. The evaluation is performed by measuring an etching rate with respect to an acetic acid aqueous solution having a concentration of 6 mol / l and a liquid temperature of 20 to 40 ° C. For example, in the case where the transparent conductive film is composed of two transparent conductive films and can be obtained individually, each transparent conductive film is immersed in the above etching solution, and the etching rate is obtained from the relationship between the passage of time and the film decrease. be able to. In addition, for example, a transparent conductive film composed of two transparent conductive films, each of which is not available in a single state or a transparent conductive film whose composition continuously changes in the film thickness direction, is a target. Etching by breaking the transparent conductive film with the substrate in the film thickness direction, immersing the fragments in the above etching solution, and measuring the passage of time and the amount of retraction of the film outer periphery in the film surface direction by an analytical means such as SEM The rate can be determined.

  As a method for obtaining the transparent conductive film of the present invention, a sputtering method of a so-called physical manufacturing method can be mainly used, and specifically, a DC sputtering method, a DC magnet theory sputtering method, an RF sputtering method, an RF magnetron. A sputtering method, an opposed target sputtering method, an ECR sputtering method, a dual magnetron sputtering method, or the like can be used.

  As a substrate for thinning the transparent conductive film of the present invention, a general borosilicate glass such as Corning 1737, a glass substrate such as fused silica, a single crystal substrate such as silicon or quartz, or a metal such as SUS, copper, or aluminum. A substrate, a plastic substrate such as polycarbonate or polyacrylate, or a multilayer substrate combining these can be used. Alternatively, the substrate can be formed by a technique such as cutting and polishing from the base material, injection molding, sand blasting, dicing or the like. As another form, the transparent conductive film of the present invention is formed on a thin film transistor or wiring pattern already formed on the base, or a substrate that has been subjected to such processing and the transparent conductive film of the present invention are separately formed. It is possible to attach the substrate.

  In the process of forming the transparent conductive film or element according to the present invention, various precision processing techniques can be used to produce a required thin film or element structure. For example, precision diamond cutting processing, laser processing, etching processing, photolithography, reactive ion etching, focused ion beam etching and the like can be mentioned. Also, a plurality of thin films or elements that have been processed in advance can be arranged, multilayered, or coupled between them with an optical waveguide, or sealed in that state.

  In the transparent conductive film according to the present invention, the device can be stored in a container filled with an inert gas or an inert liquid. Furthermore, a cooling or heating mechanism for adjusting the operating environment can coexist. Materials that can be used for containers include various metals such as copper, silver, stainless steel, aluminum, brass, iron, and chromium, and alloys thereof, or composite materials in which these metals are dispersed in polymer materials such as polyethylene and polystyrene, A ceramic material or the like can be used. The heat insulating layer may be made of foamed polystyrene, porous ceramics, glass fiber sheet, paper or the like. In particular, it is possible to perform a coating for preventing condensation. Moreover, as an inert liquid with which an inside is filled, liquids, such as water, heavy water, alcohol, a low melting point wax, mercury, or a mixture thereof can be used. Moreover, helium, argon, nitrogen etc. can be mentioned as an inert gas with which an inside is filled. In addition, a desiccant can be added to reduce the humidity inside the container.

  In addition, the transparent conductive film according to the present invention may be subjected to treatment for improving the appearance and characteristics and extending the life after the product is formed. Examples of such post-processing include thermal annealing, radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic field irradiation, and ultrasonic irradiation. Furthermore, the organic electroluminescent device is combined with various types, for example, adhesion, fusion, electrodeposition, vapor deposition, pressure bonding, dyeing, melt molding, kneading, press molding, coating, and the like according to its use or purpose. Can be combined. In addition, an element using the zinc oxide thin film according to the present invention as a transparent conductive film, particularly a display element, can be mounted close to an electronic circuit for driving and can be mounted at high density, and signal exchange with the outside is possible. It can also be integrated with the interface and antenna.

  The substrate with a transparent conductive film according to the present invention can form, for example, a semiconducting or insulating indium oxide thin film depending on a thin film forming method.

  The present invention can be used for various optoelectronic devices such as a liquid crystal display, a plasma display, an organic light emitting diode device, a solar cell, and the like. Alternatively, the transparent conductive film containing indium oxide as a main component of the present invention can be used for various devices using a transparent conductive film such as a touch panel, an electromagnetic wave shield, an inorganic light emitting diode, and a laser diode.

  An example of the display element which uses the board | substrate with a transparent conductive film which concerns on this invention as a transparent electrode is shown in FIGS. The display elements and solar cells shown in FIGS. 3 to 6 are application examples of the present invention, and the specific structure is not limited to these.

  FIG. 3 shows a device structure when the present invention is applied to a liquid crystal display as a display element. In this device, a liquid crystal display of a type in which liquid crystal is sandwiched between substrates with transparent electrodes facing vertically is shown. The transparent electrodes 6 and 6 'are formed on the substrates 11 and 11' opposed to each other in the vertical direction. An RGB color filter 10, a black matrix 8, a transparent electrode 6, an alignment film 7, and the like are formed on the surface of the upper substrate 11, and the surface is in contact with the liquid crystal 9. A polarizing plate 12 is attached to the surface of the substrate 11 opposite to the liquid crystal 9 side. A transparent electrode 6 ′ and an alignment film 7 ′ are formed on the surface of the lower substrate 11 ′, and the surfaces are in contact with the liquid crystal 9. A polarizing plate 12 ′ is attached to the surface of the substrate 11 ′ opposite to the liquid crystal 9 side of the substrate 11, and a light source 14 is provided further below. The upper and lower substrates 11 and 11 ′ are kept at a fixed interval via adhesives 13 and 13 ′, and a liquid crystal 9 is filled between them, and drive circuits 15 and 15 ′ are provided outside thereof. .

  FIG. 4 shows a device structure when the present invention is applied to a plasma display as a display element. In this device, a transparent electrode 16 is provided as a display electrode on a front glass substrate 17, and a bus electrode 18, an upper dielectric layer 19 and a protective layer (MgO) 20 are further formed to suppress a voltage drop. Has been. A structure on the rear glass substrate 25 including the RGB phosphors 24 is formed thereunder, and the structure further includes a display electrode 23, a lower dielectric layer 22, a partition wall 21, and the like.

  FIG. 5 shows a device structure when the present invention is applied to an organic light emitting diode display as a display element. In this device, there is a transparent electrode 26 formed on a glass substrate 29, and an organic layer 27 including an RGB light emitting layer is formed thereon. They are delimited by a partition wall 30, and a cathode 28 is formed so as to cover the whole. The entire element is covered with a sealing can 31 (shown in a simplified manner) and protected so as not to be exposed to the outside air.

  FIG. 6 shows a device structure when the present invention is applied to a solar cell. The solar cell exemplified here is a structure of a two-layered thin film silicon solar cell capable of converting both visible light and near-infrared light into electric energy. In this device, a transparent formed on a glass substrate 32 is used. There is an electrode 33, an amorphous silicon thin film 34 is formed on the electrode 33, a polycrystalline silicon thin film 35 is formed on the upper part, and a back electrode 36 is formed on the uppermost part.

  In the various display elements configured as described above, the zinc oxide thin film as described above is used as a transparent electrode in place of ITO. This zinc oxide thin film has improved conductivity and transmittance stability of the entire zinc oxide thin film, and is thin, lightweight, high definition, high efficiency and long life.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, the technical scope of this invention is not limited to a following example.

  Example 1 will be described using a chart.

Asahi Glass non-alkali glass AN-100 (non-polished product) was used for the substrate. The substrate size is 100 × 100 × 0.7 mm. The glass substrate is subjected to neutral detergent cleaning, pure water ultrasonic cleaning, ethanol vapor cleaning, and pure water ultrasonic cleaning, and then the surface is subjected to UV / O ₃ with an ultraviolet irradiation device (product of Eyegraphic, PL1-406C). Washed. The substrate after the cleaning was carried into the next transparent conductive film forming apparatus as soon as possible.

The transparent conductive film was produced by a dc magnetron sputtering method. In FIG. 7, the outline of the transparent conductive film production apparatus used this time was shown. A transparent conductive film forming apparatus (Hitachi model KR-104) was used as the sputtering apparatus. The main features of the apparatus and film formation are as follows. A vacuum chamber 37 (preparation chamber) for loading a substrate and a first film formation chamber 39 for film formation are partitioned by a gate valve 38. 'Is a load-lock type in which a second film formation chamber 40 for film formation of another material separated by ′ is connected, has an independent exhaust system, and base pressures are 1 × 10 ⁻⁸ and 1 × 10 ⁻ , respectively. ⁷ , 1 × 10 ⁻⁷ Torr. Although not specifically shown, each of the three chambers is provided with a substrate heating mechanism independently and can be heated from room temperature to a maximum of 300 ° C. In particular, the substrate heating mechanism in the preparation chamber is also provided with a cooling mechanism using a water flow, and it is possible to cool a substrate heated at a high temperature and the transparent conductive film formed thereon in a relatively short time.

  The cleaned glass substrate is incorporated into a dedicated stainless steel substrate holder, and the entire substrate holder is carried into the preparation chamber 37 and immediately evacuated. The substrate can be moved horizontally by the transport mechanism for each of the substrate holders (up to 300 mm square substrates can be accommodated). When the predetermined base pressure is reached, the gate valve 38 is opened, the substrate is transferred to the first film forming chamber 39, and the gate valve 38 is closed again.

In the first film formation chamber 39, the first transparent conductive film is formed by sputtering. A 2% aluminum-added zinc oxide target (manufactured by Tosoh Corporation) is used as the target, the target size is 12.7 × 38.1 cm, and the distance between the target and the substrate is 70 mm. As the sputtering gas, pure Ar (purity 6N, flow rate 50.0 sccm, inflow pressure 5.0 × 10 ⁻³ Torr) is used, and the sputtering power is 300 to 500 W. After heating to a substrate temperature of 200 ° C. by the substrate heating mechanism in the chamber, the sputtering target was moved in one direction from the preparation chamber side to the second film formation chamber 40 side, and a film having a predetermined film thickness was formed. The film formation amount was determined in advance under a plurality of movement speeds and sputtering powers, and the film formation conditions for producing the target film thickness were determined. The substrate on which the predetermined film formation has been completed is once transported to the preparation chamber 37 and cooled to room temperature in a vacuum. Thereafter, the gate valves 38 and 38 'are opened, the substrate is transferred to the second film forming chamber 40, and the gate valves 38 and 38' are closed again.

In the second film formation chamber 40, the second transparent conductive film is formed by sputtering. A 10% tin-added indium oxide target (manufactured by Nikko Metal) is used as the target, the target size is 12.7 × 38.1 cm, and the distance between the target and the substrate is 70 mm. As the sputtering gas, O ₂ -added Ar (O ₂ concentration 1%, flow rate 50.0 sccm, inflow pressure 5.0 × 10 ⁻³ Torr) is used, and the sputtering power is 300 to 400 W. After heating to a substrate temperature of 200 ° C. by the substrate heating mechanism in the chamber, the sputtering target was moved in one direction from the preparation chamber side to the second film formation chamber 40 side, and a film having a predetermined film thickness was formed. The film formation amount was determined in advance under a plurality of movement speeds and sputtering powers, and the film formation conditions for producing the target film thickness were determined. Thereafter, the gate valves 38 and 38 'are opened, the substrate is transferred to the preparation chamber 37, and the gate valves 38 and 38' are closed again.

  The substrate conveyed to the preparation chamber 37 is released to the atmosphere and taken out from the apparatus. The extracted substrate with a transparent conductive film is heated to 300 ° C. in the atmosphere and held at that temperature for 1 hour. Thereafter, it is used for necessary measurement and processing (the extracted substrate with a transparent conductive film is hereinafter referred to as a sample).

  The prepared samples were sheet resistance (resistivity measuring instrument, manufactured by Kyowa Riken, K-705RM), film thickness (surface profile measuring device, surface profiler, manufactured by KLA-Tencor, P-10), visible light transmittance (spectrophotometric). Total, U-3900H, manufactured by Hitachi High-Technologies Corporation). The sheet resistance and film thickness of the sample were measured at a plurality of positions (average of 40 points in the plane). The maximum variation in resistance and film thickness was 5% and 10%, respectively. The specific resistance was determined by the average sheet resistance × film thickness.

Table 1 shows the total film thickness z ₁ + z ₂ and the specific resistance ρ when the thickness of the first transparent conductive film of the prepared sample is z ₁ and the film thickness z _{2 of} the second transparent conductive film. Listed. Here, for comparison, an ITO single film was prepared in the same manner, the specific resistance at that time was ρ _0, and the percentage of (ρ−ρ ₀ ) / ρ ₀ was the rate of increase. The specific resistance of the ITO single film was in the range of 1.2 to 1.9 × 10 ⁻⁴ Ωcm in the thickness range of 60 to 200 nm, and the transmittance of each film was 80% or more. On the other hand, when the first transparent conductive film is added, the specific resistance slightly increases. When the film thickness z _{1 of} the first transparent conductive film was 10 nm, the rate of increase was 15% or less in this film thickness range, indicating a characteristic with no practical problem. When the film thickness z _{1 of} the first transparent conductive film is 20 nm, the increase rate is 15% or less when the total film thickness is 140 nm or more. However, when the total film thickness is 80 to 120 nm, the increase rate is in the order of 20% and the minimum is 60 nm. Then, the rate of increase is as high as 33%. When the film thickness z _{1 of} the first transparent conductive film is 30 nm, the rate of increase is 30% or more when the film thickness is 100 nm or less. When the film thickness z _{1 of} the first transparent conductive film is 40 nm, the film thickness is 180 nm. Below, the rate of increase was 30% or more. All of these samples had a transmittance of 80%, and no difference from the ITO single film could be detected. As described above, such a transparent conductive film is mainly composed of ITO, and exhibits a resistance that has almost no problem in practical use.

  The etching rates of the first transparent conductive film and the second transparent conductive film are as follows: each transparent conductive film formed on a glass substrate with the same film thickness as a test piece, with a concentration of 6 mol / l, liquid temperature The film was immersed in an acetic acid aqueous solution at 40 ° C. for several hours and determined from the change in the film thickness. On the other hand, the etching rate for the first transparent conductive film was 10 nm / min or more, while that for the second transparent conductive film was 1 nm / min or less.

  Next, the ease of recovery of the transparent conductive film of the present invention was evaluated from the thin film recovery rate as ITO using a weakly acidic solution as follows. First, a 100 mm square substrate on which a transparent conductive film was formed was cut into 10 mm square using a glass scriber. The cut glass substrate group is put into a 5-liter beaker. Pour 1 liter of 1 wt% dilute hydrochloric acid, put a magnetic stirrer, cover with a film to prevent water droplets from scattering, and stir at room temperature (21 ° C.) for 1 hour. Thereafter, the glass substrate is separated from the peeled transparent electrode and the solution through a 0.5 mm mesh stainless steel sieve, and the glass substrate remaining on the sieve is sufficiently rinsed with pure water in that state. Thereafter, the peeled transparent conductive film and the remaining solution are separated with a funnel and filter paper, and the remaining one on the filter paper is sufficiently washed with pure water. The peeled material remaining on the filter paper is dried in a thermostatic chamber, and then its weight is measured. Four batches of 100 mm square samples could be produced in one batch of film formation, and this was performed for 20 batches, and the peeled material was collected on the same filter paper. Thereafter, the composition of the recovered material was analyzed by AES.

Table 2 shows the thin film recovery rate when the film thickness z _{1 of} the first transparent conductive film is 0 to 40 nm. Here, for the recovery rate evaluation, the thickness of the ITO layer, which is the second transparent conductive film, is fixed at 500 nm, and the total weight of the thin film when the specific gravity is assumed to be 7.0 g / cm ³ (per sheet) The volume ratio of the collected material was 100 mm × 100 mm × 500 nm = 0.005 cm ³ and the weight was 7.0 g / cm ³ × 0.005 cm ³ = 2.8 g). In the absence of the first transparent conductive film, the thin film was not peeled off at all, and the recovery rate was 0%. When the film thickness of the first transparent conductive film was 10 nm, the recovery rate was 5%, 55% was recovered at 20 nm, 84% at 30 nm, and 96% at 40%. When components of the recovered material were analyzed by AES, only In ₂ O ₃ and SnO ₂ were present, the ratio was the same as that of the original ITO, and no component related to Zn was detected. From the above, by making the etching rate of the first transparent conductive film larger than the etching rate of the second transparent conductive film as in the transparent conductive film of the present invention, even with the treatment of dilute hydrochloric acid of about 1 wt%, It was found that it can be easily recovered.

  Example 2 will be described using a chart.

  First, a procedure for manufacturing a substrate with a transparent conductive film in this example will be described. In this case, the glass substrate of the substrate with the transparent conductive film and the cleaning process thereof were the same as those in Example 1, and the same film forming apparatus for the transparent conductive film was used. However, in this example, the first film forming chamber was not used, and the film was formed only in the second film forming chamber. The film formation procedure was also performed in the same manner as in Example 1, while moving the substrate from the preparation chamber side to the second film formation chamber side on the sputter target in the second film formation chamber at a constant speed in one direction. At that time, in order to have a composition distribution, a plurality of additive material chips were arranged on the sputtering target. FIG. 8 shows an example of the arrangement. In the sputter target 41, an erosion region 42 in which sputtering proceeds preferentially occurs corresponding to the magnetic field strength distribution of the electromagnet placed thereunder. In the case of FIG. 8, the shape is like a vertically long ellipse. A plurality of additive material chips 43 are arranged on the outer periphery of the elliptical charging chamber side. Here, chips of zinc oxide ZnO (manufactured by high-purity chemical, purity 4N, size 5 mm × 5 mm × 1 mm) were disposed (the disposition intervals and the number of the illustrated chips are examples). In this way, when the substrate is moved in one direction while sputtering, a large amount of ZnO component is deposited on the substrate side.

FIG. 9 shows an image of elemental composition ratio analysis in the film thickness direction of the substrate with a transparent conductive film formed as described above. Since the material is sputter-deposited from the side close to the glass substrate, the composition of Zn derived from ZnO increases near z ₀ , shows a maximum position in the middle, and then decreases toward the z ₂ side. (In the case of AES depth analysis, composition analysis proceeds from the surface of the transparent conductive film, and immediately after the measurement, the distribution is from the z ₂ side to the z ₀ side with respect to the etching time. The distribution from the z ₀ side to the z ₂ side is shown here.) On the other hand, the In composition ratio is small on the z ₀ side and increases on the z ₂ side in inverse proportion to the increase or decrease of the Zn component. Therefore, the position in the z direction indicating the intermediate concentration R ₃ between the minimum concentration R ₁ and the maximum concentration R ₂ of the In composition ratio (the etching time is given in the depth analysis of the AES analysis. (Converted by thickness) was defined as the characteristic position z _c . The z position indicating the maximum Zn concentration R ₅ was defined as z _a, and the relative atomic concentration of Zn with respect to In, Sn, Zn at z _a was defined as the characteristic addition concentration C _Zn .

Table 3 shows the specific resistance ρ and its rate of increase, and the characteristic position z _c and the characteristic addition concentration C _Zn when the film thickness is changed from 60 to 200 nm. In this case, the increase rate of the specific resistance is suppressed to 15% or less for any film thickness. Although no data was shown in particular, the transmittance was 80% or more, and there was no change. In addition, the characteristic position becomes larger as the film thickness becomes thicker, and this is considered to reduce the substrate transport speed during sputtering in order to form a thick film. Moreover, the characteristic addition concentration was 4.8 to 5.2%.

  The etching rate of the substrate with a transparent conductive film whose composition changes continuously in the film thickness direction is an acetic acid aqueous solution having a concentration of 6 mol / l and a liquid temperature of 40 ° C. The film is immersed in the substrate for several hours, and the amount of receding of the film periphery in the in-plane direction is measured by SEM observation, and is determined from the etching rate in the range of 10 nm on the substrate interface side and the change in film thickness on the film surface side of 10 nm. did. As a result, the etching rate was 10 nm / min or more on the substrate interface side, whereas it was 1 nm / min or less on the film surface side.

  Table 4 shows the ITO recovery rate of these samples. The evaluation method is the same as in Example 1. When the film thickness is in the range of 60 to 200 nm, the recovery rate is about 81 to 93%, which is a relatively high recovery rate (as shown in Example 1, the recovery rate is 0% for the ITO single film).

  As described above, by increasing the indium concentration on the surface opposite to the substrate surface in the transparent conductive film from the indium concentration on the substrate surface side in the transparent conductive film, the same transparent conductivity as that of the ITO single film is ensured. However, a high ITO recovery rate can be achieved.

  Next, in Example 1, the result of examining the change in characteristics when the additive element of the first transparent conductive film is changed will be described.

In Example 1, zinc oxide ZnO added with 2% aluminum Al was used for the first transparent conductive film, and indium oxide In ₂ O ₃ added with 10% tin Sn was used for the second transparent conductive film. Here, as the additive element other than Al, the first transparent conductive film is formed by using 2% boron B, gallium Ga, tin Sn, titanium Ti, and a zinc oxide ZnO target having no additive element, The 1st transparent conductive film was fixed to 30 nm, and the transparent conductive film which changed the film thickness of the 2nd transparent conductive film was formed. The production method and evaluation method of these transparent conductive films are the same as in the previous examples. For the evaluation of the recovery rate, a transparent conductive film having a thickness of the second transparent conductive film of 500 nm was formed, and the recovery procedure was performed in the same manner as in the previous example to evaluate the recovery rate.

  Table 5 shows changes in specific resistance and recovery rate of the obtained transparent conductive film. When the additive element is Al, B, or Ga, the rate of increase in specific resistance is approximately 30% or less, and the recovery rate is stable at 83 to 84%.

  As described above, by adding elements such as Al, B, and Ga, a high ITO recovery rate as a substrate with a transparent conductive film can be achieved, and high conductivity can be achieved.

  In addition, when elements such as Al, B, and Ga are added to the transparent conductive film described in Example 2, the concentration distribution of Al, B, Ga, and the like is substantially equal to the concentration distribution of Zn and the like. By adding to, a high ITO recovery rate as a substrate with a transparent conductive film can be achieved, and high conductivity can be achieved.

  Next, the result of examining the difference from the case where a practically transparent metallic aluminum Al thin film is used for the first transparent conductive film with the same thin film configuration as in Example 1 will be described.

Indium oxide In ₂ O ₃ with 10% tin Sn added to the second transparent conductive film was used. The film thickness of the second transparent conductive film was 500 nm. For the first transparent conductive film, a case where zinc oxide ZnO added with 2% aluminum Al was used and a case where metal aluminum (purity 99.99%) was used were prepared as in Example 1. The thickness of the first transparent conductive film was 30 nm. As in Example 1, changes in film formation, specific resistance, transmittance, and recovery were estimated. Moreover, in order to see the tolerance with respect to an alkali solution, the change of the transmittance | permeability after 30-minute immersion treatment was carried out at 1 degree KOH aqueous solution at the liquid temperature of 35 degreeC. This is for the purpose of estimating the resistance when the transparent conductive film is actually subjected to chemical treatment when various devices are formed.

  The results are shown in Table 6. The increase in specific resistance of the obtained transparent conductive film is slight, but the major difference is the transmittance. When ZnO was used for the first transparent conductive film, the transmittance was almost the same as that of the indium oxide single film. However, when Al was used for the first conductive layer, the transmittance immediately after fabrication was 64%. became. Furthermore, the transmittance after the alkali treatment was 3%, which hardly transmitted light. This is presumably because the battery reaction between Al and indium oxide occurred, the indium oxide was reduced, and the metal In was deposited. The recovery rate was 73%.

  As described above, by using ZnO for the first transparent conductive film, a high ITO recovery rate can be achieved, and a high transmittance can be achieved.

(A), (b) is a schematic block diagram of the board | substrate with a transparent conductive film which concerns on this invention. (A), (b) is a schematic block diagram of the board | substrate with a transparent conductive film which concerns on this invention. It is principal part sectional drawing which shows typically the liquid crystal display using the board | substrate with a transparent conductive film which concerns on this invention. It is principal part sectional drawing which shows typically the plasma display using the board | substrate with a transparent conductive film which concerns on this invention. It is principal part sectional drawing which shows typically the organic light emitting diode display using the board | substrate with a transparent conductive film which concerns on this invention. It is principal part sectional drawing which shows typically the solar cell using the board | substrate with a transparent conductive film which concerns on this invention. It is explanatory drawing of the film-forming apparatus which produced specifically the board | substrate with a transparent conductive film which concerns on this invention. It is explanatory drawing of the sputter target in the film-forming apparatus which produced specifically the board | substrate with a transparent conductive film which concerns on this invention. It is explanatory drawing of the relationship between the composition distribution of Example 2 which concerns on this invention, and a characteristic position.

Explanation of symbols

1, 4, 11, 11 'Substrate 2 First transparent conductive film 3 Second transparent conductive film 5 Transparent conductive film 6, 6', 16, 26, 33 Transparent electrode 7, 7 'Alignment film 8 Black matrix 9 Liquid crystal DESCRIPTION OF SYMBOLS 10 RGB color filter 12, 12 'Polarizing plate 13, 13' Adhesive material 14 Light source 15, 15 'Drive circuit 17 Front glass substrate 18 Bus electrode 19 Upper dielectric layer 20 Protective layer 21, 30 Partition 22 Lower dielectric layer 23 Display Electrode 24 RGB phosphor 25 Back glass substrate 27 Organic layer 28 Cathode 29, 32 Glass substrate 31 Sealing can 34 Amorphous silicon thin film 35 Polycrystalline silicon thin film 36 Back electrode 37 Preparation chamber 38, 38 'Gate valve 39 First film formation chamber 40 Second film forming chamber 41 Target 42 Erosion region 43 Additive material chip

Claims (11)

A substrate,
A first transparent conductive film;
A second transparent conductive film disposed on a side opposite to the side on which the substrate is disposed with respect to the first transparent conductive film;
The second transparent conductive film is mainly composed of indium oxide,
The substrate with a transparent conductive film, wherein an etching rate of the first transparent conductive film is higher than an etching rate of the second transparent conductive film. The substrate with a transparent conductive film according to claim 1,
The substrate with a transparent conductive film, wherein the first transparent conductive film contains an oxide of Zn, Sn, Ti, V, Ni, or Si. The substrate with a transparent conductive film according to claim 1,
The substrate with a transparent conductive film, wherein the film thickness of the first transparent conductive film is 10 nm or more and 1 μm or less. The substrate with a transparent conductive film according to claim 1,
The substrate with a transparent conductive film, wherein the first transparent conductive film has a thickness of 20 nm to 1 μm. The substrate with a transparent conductive film according to claim 1,
The substrate with a transparent conductive film, wherein the first transparent conductive film contains B, Al, or Ga. A substrate,
A transparent conductive film,
The transparent conductive film contains indium as a first element,
The transparent conductive film contains Zn, Sn, Ti, V, Ni, or Si as the second element,
In the transparent conductive film, the concentration of the first element on the surface opposite to the substrate surface in the transparent conductive film is greater than the concentration of the first element on the substrate surface side in the transparent conductive film,
In the transparent conductive film, the concentration of the second element on the substrate surface side in the transparent conductive film is greater than the concentration of the second element on the surface side opposite to the substrate surface in the transparent conductive film. A substrate with a transparent conductive film characterized. The substrate with a transparent conductive film according to claim 6,
The transparent conductive film contains B, Al, or Ga as a third element,
In the transparent conductive film, the concentration of the third element on the substrate surface side in the transparent conductive film is greater than the concentration of the third element on the surface side opposite to the substrate surface in the transparent conductive film; A substrate with a transparent conductive film. A substrate,
A first transparent conductive film;
A second transparent conductive film disposed on a side opposite to the side on which the substrate is disposed with respect to the first transparent conductive film;
The second transparent conductive film is mainly composed of indium oxide,
The display element, wherein an etching rate of the first transparent conductive film is larger than an etching rate of the second transparent conductive film. A substrate,
A transparent conductive film,
The transparent conductive film contains indium as a first element,
The transparent conductive film contains Zn, Sn, Ti, V, Ni, or Si as the second element,
In the transparent conductive film, the concentration of the first element on the surface opposite to the substrate surface in the transparent conductive film is greater than the concentration of the first element on the substrate surface side in the transparent conductive film,
In the transparent conductive film, the concentration of the second element on the substrate surface side in the transparent conductive film is greater than the concentration of the second element on the surface side opposite to the substrate surface in the transparent conductive film. A characteristic display element. A substrate,
A first transparent conductive film;
A second transparent conductive film disposed on a side opposite to the side on which the substrate is disposed with respect to the first transparent conductive film;
The second transparent conductive film is mainly composed of indium oxide,
The solar cell according to claim 1, wherein an etching rate of the first transparent conductive film is larger than an etching rate of the second transparent conductive film. A substrate,
A transparent conductive film,
The transparent conductive film contains indium as a first element,
The transparent conductive film contains Zn, Sn, Ti, V, Ni, or Si as the second element,
In the transparent conductive film, the concentration of the first element on the surface opposite to the substrate surface in the transparent conductive film is greater than the concentration of the first element on the substrate surface side in the transparent conductive film,
In the transparent conductive film, the concentration of the second element on the substrate surface side in the transparent conductive film is greater than the concentration of the second element on the surface side opposite to the substrate surface in the transparent conductive film. Solar cell featuring.

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