JP2625841B2 - Method for producing transparent conductive film, target material and tablet material - Google Patents

Description

The present invention relates to a method for producing a transparent conductive film and its material.

[Prior art] Conventionally, it has been attempted to produce a transparent conductive film by vacuum evaporation and sputtering using a sintered body of indium oxide (ITO) containing tin, and appropriate conditions are selected on a heated substrate. It is known that a transparent conductive film having a specific resistance of about 2 × 10 ⁻⁴ Ω · cm can be obtained by vapor deposition.

Conventionally, ITO sintered bodies have been manufactured by cold pressing or hot pressing. However, they have not been considered from the viewpoint of solid solution of tin atoms in indium crystals, and their solid solubility is low, 40-50% It was about. Therefore, it is not sufficient for the purpose of obtaining a transparent conductive film having a low specific resistance.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned disadvantages of the conventional ITO transparent conductive film manufacturing technology and to provide a specific resistance of 2 × 10 ⁻⁴ Ω · cm.
An object of the present invention is to provide a new method of manufacturing a transparent conductive film for easily realizing an ITO transparent conductive film exceeding the above.

The problem with conventional ITO transparent conductive film production is that the solid solubility of tin in the indium oxide crystal is low, and a target or a tablet for vapor deposition that uses only a mixture of indium oxide and tin oxide is used. As a result, the tin atoms in the formed ITO thin film replace the indium atoms in the indium oxide crystal, the chance of intrusion between lattices is reduced, and the tin atoms segregate at the crystal grain boundaries of the indium oxide. ,
It exists as tin oxide microcrystals and does not work as an n-type dopant. Therefore, in order to further increase the density of electrons contributing to conduction in the ITO thin film, even if the tin concentration in the raw material is increased, the added tin atoms do not work effectively as a dopant, and the crystal of indium oxide does not function effectively. It segregates at the grain boundaries and causes conduction electrons to be scattered, which in turn lowers the mobility and has the disadvantage that the specific resistance of the ITO thin film does not decrease.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and a transparent conductive material is formed by sputtering a target material of indium oxide containing tin on a translucent substrate. In the method for manufacturing a transparent conductive film for forming a film, as a target material of indium oxide containing tin,
The total amount of tin contained in the target material is 8 in terms of tin oxide.
A method of producing a transparent conductive film, characterized in that a solid solution containing at least 70% of the total tin content in indium oxide crystals is used as a solid solution. In a method for producing a transparent conductive film, a transparent conductive film is formed by a vacuum deposition method on a tablet material for indium oxide containing indium oxide, wherein the tablet material for indium oxide containing tin is contained in the tablet material as a tablet material for vapor deposition. The production of a transparent conductive film, characterized in that the total tin content is 3 to 20% by weight in terms of tin oxide, and at least 80% of the total tin content is present as a solid solution in the crystal of indium oxide. It provides a method.

The target material used in the production of the transparent conductive film in the present invention is, in order to introduce a sufficient amount of tin as a dopant by sputtering to reduce the resistance of the transparent conductive film, to convert tin into 8 to 20 wt. % Of tin in a crystal of indium oxide as a solid solution in a crystal of indium oxide for the purpose of easily obtaining a transparent conductive film having a low specific resistance. Is preferred. In addition, the tablet material for vapor deposition used in the production of the transparent conductive film in the present invention oxidizes tin in order to introduce a sufficient amount of tin as a dopant to reduce the resistance of the transparent conductive film by a vacuum vapor deposition method. It consists of a sintered body of indium oxide containing 3 to 20 wt% in terms of tin. For the purpose of easily obtaining a transparent conductive film having a low specific resistance, 90% or more of the total content of tin is a solid solution in the crystal of indium oxide. It is particularly preferred that it exists as

The method for determining the solid solubility of tin is not particularly limited, but can be determined as follows. First, ITO
The sintered body is powdered in a mortar and weighed. Next, hydrochloric acid is added to the ITO powder and dissolved by heating in a warm bath for a long time. At this time, tin dissolved in the indium oxide is dissolved in hydrochloric acid, and tin oxide not dissolved in the indium oxide remains dissolved. The undissolved tin oxide is filtered through filter paper, carbonized and incinerated to determine its weight. The concentration of tin in the filtrate is measured by ICP or atomic absorption spectrometry, and the measured value is defined as the amount of tin dissolved in indium oxide. In this way, the amount of tin dissolved in indium oxide can be determined.

By the sputtering method or the vapor deposition method of the present invention, a substrate for forming a transparent conductive film of indium oxide containing tin is formed at a temperature of about 300 to 400 ° C. so as to obtain adhesion, denseness and a low resistance value of the film. Heating is preferred.

The sputtering gas used in the sputtering according to the present invention depends on the formation of the apparatus, the pumping capacity of the pump, the generation of impurity gas, the sputtering power, and the like. Is preferable, and the oxygen concentration in the case of the mixed gas is 0 to 5
%, And the sputtering pressure is optimally in the range of 2 to 5 × 10 ⁻³ Torr.

In addition, the vacuum deposition according to the present invention has a gas pressure of 1-5 × 10 ^-4.
It is preferably performed in an oxygen atmosphere in the range of Torr.

Further, direct current or high frequency plasma may be introduced into the film forming process. By doing so, it is possible to increase the film formation rate and, consequently, to reduce the specific resistance of the transparent conductive film.

[Operation] The film formation mechanism of the ITO transparent conductive film on the light-transmitting substrate evaporates a material to be a raw material by sputtering or heating the starting raw material by some method. On this occasion,
In addition to decomposing and evaporating the source material to the atomic or molecular state, most of the source material evaporates as clusters consisting of tens to hundreds of molecules, reacts with the atmospheric gas on the substrate, and then regenerates. Crystallizes to form a transparent conductive film. Therefore, when an ITO sintered body having a small amount of tin dissolved in the crystals of indium oxide as a conventional manufacturing method is used as a raw material, the cluster supplied on the substrate also has a solid solubility of tin. When they form a transparent conductive film, tin atoms do not act as n-type dopants, and most of them segregate at crystal grain boundaries of indium oxide or separate phases as fine crystals of tin oxide. As a result, it is considered that even if a large amount of tin is added to lower the specific resistance, the scattering of electrons at the crystal grain boundaries is increased, and the specific resistance is increased.

Therefore, in the present invention, the amount of tin dissolved in the crystals of indium oxide is 70% or more of the total content of ITO.
By using a sintered body, the solid solubility of tin in the thruster supplied on the substrate is also increased, and as a result, most of the tin in the formed ITO film is dissolved in the crystals of indium oxide. Then, it functions effectively as an n-type dopant, and the density of electrons contributing to conduction increases. Further, it is considered that the segregation of tin at the grain boundaries of indium oxide and the reduction of the fine crystals of tin oxide decrease the mobility and decrease the specific resistance.

When the vacuum deposition method is used, the above-mentioned clusters tend to be relatively small, the probability that tin contained in the tablet material evaporates in a solid solution state is low, and tin exists as a solid solution in the crystal of indium oxide. Is smaller than that by sputtering, the amount of tin dissolved in the crystal of indium oxide is preferably at least 80% of the total content.

[Example 1] Tin content was 10 wt% in terms of tin oxide, and indium oxide sintered bodies having different tin solubilities were used as targets, an argon / oxygen ratio of 99: 1, and a gas pressure of 3 × 10 ^-3 Torr
480 V DC voltage is applied in the atmosphere to be pre-sputtered for 10 minutes, and then sputtered for 2 minutes, and heated to 400 ° C. on a glass substrate (Corning Glass Works, USA,
# 7059 glass substrate) ITO transparent conductive film (1000mm thick)
Was formed. As a result, as shown in FIG. 1, when the solid solubility of tin becomes 70% or more, the specific resistance of the ITO transparent conductive film rapidly decreases, and when it exceeds 90%, the value is 1.4 × 10 ⁻⁴ Ω.・ It has dropped to cm.

[Example 2] Tin content was 5 wt% in terms of tin oxide, and indium oxide sintered bodies having different tin solubilities were used as vapor deposition raw materials.
A glass substrate (Corning Glass Works, USA, # #) heated to 400 ° C in an oxygen atmosphere having a gas pressure of 2 × 10 ^-4 Torr using an electron beam heating vapor deposition method.
ITO transparent conductive film (1000mm thickness) on 7059 glass substrate)
Formed. As a result, as shown in FIG. 2, when the solid solubility of tin becomes 80% or more, the specific resistance of the ITO transparent conductive film rapidly decreases, and when it becomes 90% or more, the value becomes 1.3 × 10 ⁻⁴ Ω.・ It has dropped to cm.

[Effect of the Invention] The method for producing a transparent conductive film provided by the present invention is based on an ITO sintered body in which 70% or more of 80% or more of the total tin content is dissolved in indium oxide crystals as a starting material. The method is characterized in that a transparent conductive film is formed on a light-transmitting substrate by a sputtering method, a vacuum evaporation method, or the like. In the present invention,
Since the ITO sintered body having a high solid solubility of tin is used as a starting material, the segregation of tin at the grain boundary and the phase separation of tin oxide microcrystals are small, and the solid solubility of tin in the indium oxide crystal is high, that is, ,
A low-resistance transparent conductive film having a high density of electrons contributing to conduction and a high mobility can be easily realized.

Further, in the present invention, since the added tin atom functions more effectively as an n-type dopant, a transparent conductive film having a lower specific resistance than conventional can be realized with the same amount of tin as in the conventional method. It also has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of Example 1, and FIG. 2 is a graph showing the results of Example 2.

Continuation of the front page (56) References JP-A-62-256311 (JP, A) JP-A-59-149604 (JP, A) JP-A-56-5218 (JP, U) JP-B-50-19125 (JP, A) , B1)

Claims (4)

(57) [Claims] 1. A method for producing a transparent conductive film, wherein a target material of tin-containing indium oxide is sputtered on a light-transmitting substrate to form a transparent conductive film, wherein the target material of tin-containing indium oxide is provided. The use of a target material in which the total amount of tin contained in the target material is 8 to 20 wt% in terms of tin oxide, and 70% or more of the total tin amount is present as a solid solution in the crystal of indium oxide. Characteristic method for producing a transparent conductive film. 2. A method for manufacturing a transparent conductive film, wherein a transparent conductive film is formed on a transparent substrate by coating a tablet material of indium oxide containing tin by a vacuum deposition method. As tablet material,
The total amount of tin contained in the tablet material is 3 in terms of tin oxide.
A method for producing a transparent conductive film, characterized by using a solid solution in which at least 80% of the total tin content is present as a solid solution in indium oxide crystals. 3. The total amount of tin is 8 to 20% by weight in terms of tin oxide, and at least 70% of the total amount of tin is present as a solid solution in the crystal of indium oxide. A target material for sputtering made of sintered indium oxide. 4. A tin-containing alloy, wherein the total tin content is 3 to 20% by weight in terms of tin oxide, and at least 80% of the total tin content is present as a solid solution in the crystal of indium oxide. Tablet material for vacuum evaporation consisting of sintered indium oxide.