JP2979648B2 - ITO sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indium oxide-tin oxide sintered body, that is, an ITO sintered body used as a sputtering target or a vapor deposition pellet used for forming a transparent conductive film.

[0002]

2. Description of the Related Art As a transparent conductive film obtained by a sputtering method or a vapor deposition method, ITO made of indium oxide-tin oxide has attracted attention as a promising film due to its low specific resistance. For example, by physically depositing ITO under appropriate conditions on a substrate heated to a high temperature of about 300 ° C.,
A high-quality ITO film having good transparency and a specific resistance of 2.0 × 10 ⁻⁴ Ω · cm or less can be obtained. For forming an ITO film having a low specific resistance value on a substrate heated to such a high temperature,
As a TO sintered body, JP-A-62-21751 discloses that an appropriate amount of In ₂ O ₃ powder and SnO ₂ powder are blended, mixed and pulverized, molded, calcined, and then re-sintered. An ITO sintered body manufactured by pulverizing into a powder, and further molding and firing the obtained calcined powder is disclosed.

[0003]

In recent years, an ITO film has been coated on a color filter for a color liquid crystal display. In addition, in order to reduce the weight of the display, a plastic substrate has been coated with an ITO film. However, since these color filters and plastic substrates are inferior in heat resistance, conventional high-temperature sputtering cannot be performed, and the substrate heating temperature is limited to 200 ° C. or less. In the ITO sintered body disclosed in the above-described prior art, a film having a low specific resistance can be obtained by sputtering by heating the substrate at a high temperature, but can be obtained by sputtering by heating the substrate at a low temperature of 200 ° C. or lower. IT
The specific resistance of the O film is 5 × 10 ⁻⁴ Ω · cm or more, making it difficult to obtain a film having a low specific resistance.

Accordingly, an object of the present invention is to provide a sputtering target material or a vapor deposition pellet capable of forming an ITO film having a low specific resistance value even at a low substrate temperature.

[0005]

According to the present invention, there is provided an ITO sintered body substantially consisting of indium, tin and oxygen, which has a plane spacing of 2.86 to 2.89 ° by X-ray diffraction.
A phase having a diffraction plane of 3.05 to 3.08 ° is formed, and the integrated intensity of these diffraction peaks is In
0.1 of integrated intensity of diffraction peak of (222) plane of ₂ O ₃ phase
% Or more is provided.

In the ITO sintered body of the present invention, the plane spacing by X-ray diffraction is 2.86 to 2.89 ° and 3.05 to 3.0.
It is a remarkable feature that a phase having a diffraction plane of 8 ° is formed. That is, the conventionally known ITO sintered body is In
₂ O ₃ phase, SnO ₂ phase, or (In _x Sn _1-x ) ₂ O
₃ Consisting of a thermally stable crystalline phase such as an intermediate compound phase having a structure of [x = 0.6 to 0.7], and a diffraction peak due to the above-mentioned plane-to-plane diffraction plane is observed. Not.

The phase having a diffraction peak peculiar to the sintered body of the present invention is composed of an atomic group (cluster) which is regularly arranged in units of several tens to several tens of atoms. This phase is considered to be a thermally unstable phase formed at a reaction interface between the In ₂ O ₃ phase and the SnO ₂ phase when the substrate temperature is low due to the presence of such a phase. It is believed that an ITO film having a low specific resistance value can be formed. That is, since the cluster interface has a low bond energy of atoms, when the ITO film is formed by sputtering, it is easily released from the sintered body in a cluster state by excited argon ions, and the released cluster remains as it is on the substrate. It is easier to reach. By the way, in general, as the substrate heating temperature decreases, the formation and growth of crystal grains on the substrate become difficult, and the structure of the formed ITO film changes from crystalline to amorphous. It is known that the transition becomes easy, the mobility of electrons decreases, and the resistivity of the ITO film increases. However, the ITO of the present invention
In the sintered body, the atoms emitted from the sintered body are in a cluster form. When the atoms reach the substrate as they are, even if the substrate temperature is low, the cluster becomes a crystal nucleus and is released from other phases. The isolated ITO atoms adhere so as not to disturb the arrangement, whereby a crystalline ITO film is formed. Therefore, according to the present invention, it is possible to form an ITO film having a low specific resistance even when the substrate temperature is low.

[0008] In the present invention, the surface spacing is from 2.86 to
The integrated intensities of the diffraction peaks appearing at 2.89 ° and 3.05 to 3.08 ° are (22) of the In ₂ O ₃ phase, respectively.
2) It is also important that the integrated intensity of the diffraction peak on the plane is 0.1% or more, preferably 0.3% or more. That is, when the integrated intensity ratio is less than 0.1%, since the phase of the thermally unstable compound that has not been completely crystallized is small, it is released from the sintered body when forming the ITO film. Clusters decrease, which makes it difficult to form a crystalline ITO film.

The composition of the ITO sintered body of the present invention is the same as that of a conventionally known ITO sintered body except that it has a compound phase having the above-mentioned specific diffraction peak. Is 3 to 15% by weight, and the average composition of indium is in the range of 60 to 80% by weight.

The above-described ITO sintered body of the present invention is manufactured by the method described below. First, the average particle size is 0.1
Submicron indium oxide powder with an average particle size of 0.1
A tin oxide powder having a diameter of not more than micron is blended in accordance with the desired composition of the ITO sintered body, and if necessary, an appropriate amount of paraffin wax is added, followed by mixing with a wet ball mill. This mixing is usually desirably performed for 24 hours or more in order to finely and uniformly disperse the tin oxide powder.

Next, the above mixed powder is mixed with 900 to 120
By performing heat treatment at a temperature of 0 ° C. in an oxygen atmosphere such as the air, a small amount of Sn atoms are diffused on the In ₂ O ₃ surface. At this heat treatment temperature, SnO ₂ is stable and, for example, generation of an intermediate compound phase in a conventional sintered body is suppressed. Further, by performing the heat treatment in an oxygen atmosphere, scattering of tin due to reduction can be prevented. Usually, such heat treatment is preferably performed for 24 hours or more.

The ITO sintered body of the present invention in which a phase having a specific diffraction peak as described above is formed by performing press molding using the heat-treated powder and performing sintering at a temperature of 1350 to 1450 ° C. The body is obtained. Press molding can be performed by a method known per se, for example, using a suitable mold at a pressure of 1 ton / cm ² or more. The sintering time varies depending on the temperature, but is generally 5 hours or less, preferably 1 to 3 hours.

[0013]

EXAMPLE 1 An In ₂ O ₃ powder having an average particle diameter of 0.07 μm as measured by the bed method and a SnO ₂ powder having an average particle diameter of 0.09 μm were mixed with 10% by weight of SnO _2. And 1% by weight of paraffin wax as a binder was added thereto, and the mixture was mixed and pulverized in a ball mill for 40 hours. About this powder, 100
After heat treatment at 0 ° C. for 48 hours, mixing and pulverization were performed again in a ball mill for 20 hours. After drying this powder, press molding was performed at a pressure of 1 ton / cm ² ,
A disk-shaped molded body having a diameter of 5 mm and a thickness of 5 mm was obtained. This compact was sintered at a temperature of 1400 ° C. for 3 hours,
An O-sinter was obtained.

After polishing the cross section of the obtained sintered body, X-ray diffraction was performed, and the plane spacing of two diffraction peaks and (2) of the In ₂ O ₃ phase, which were not observed in the conventional ITO sintered body, were observed.
22) The integrated intensity ratio to the diffraction peak of the plane was determined. As a result, the plane spacing of each peak was 2.87 ° and 3.06 °, and the integrated intensity of each peak was (22) of the In ₂ O ₃ phase.
2) 0.5% and 0.5% of the integrated intensity with respect to the diffraction peak of the plane.
4%. The plane distance (d) was calculated from the diffraction angle (2θ) obtained from the midpoint of the half width by the following equation. d = (λ / 2) sin ⁻¹ (θ) where λ is the wavelength of the X-ray.

Using the above sintered body as a target, DC
A film was formed to a thickness of 1000 ° on a polyethylene terephthalate (PET) film by magnetron sputtering. The sputtering conditions are as follows:
r: O ₂ = 99: 1, sputter pressure 0.5 Pa, sputter output 200 W, distance between target substrates 60 mm. The sputtering was performed at a substrate temperature of 200 ° C. and 100 ° C. The specific resistance of the obtained film was measured by a four probe method. The results are shown in Table 1.

Comparative Example 1 In with an average particle diameter of 0.5 micron
₂ O ₃ powder and SnO having the same average particle diameter of 1 micron
_{The two} powders were blended so that SnO ₂ became 10% by weight, 1% by weight of polyvinyl alcohol was added as a binder, and wet ball mill mixing was performed for 24 hours to perform drying and granulation. Using this powder, 2to
Press molding was performed under a pressure of n / cm ² to obtain a disk-shaped molded body having a diameter of 77 mm and a thickness of 5 mm. About this molded article, 140
Sintering was performed at a temperature of 0 ° C. for 5 hours to obtain an ITO sintered body. When X-ray diffraction was performed on the obtained sintered body, the peak of the In ₂ O ₃ phase, the peak of a small amount of SnO ₂ ,
And only the peak of the intermediate compound phase (In _0.6 O _0.4 ) ₂ O ₃ was observed, and the interplanar spacing was 2.86 to 2.89 ° and 3.05.
No phase having a diffraction plane of 33.08 ° was observed. Using this sintered body as a sputtering target, a film formation test by sputtering was performed in the same manner as in Example 1, and the film characteristics were evaluated. The results are shown in Table 1.

Table 1

[0018]

According to the present invention, an ITO film having a low specific resistance can be formed by sputtering even when the substrate temperature is low, for example, 200 ° C. or less. Therefore, the ITO sintered body of the present invention can be effectively used for forming an ITO film on a plastic substrate.

Continuation of the front page (56) References JP-A-4-160047 (JP, A) JP-A-4-77344 (JP, A) JP-A-4-104936 (JP, A) JP-A-3-126655 (JP) , A) JP-A-62-21751 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/00 C23C 14/34

Claims (1)

(57) [Claims] 1. An ITO sintered body consisting essentially of indium, tin and oxygen, having a plane spacing of 2.8 by X-ray diffraction.
Phases having diffraction planes of 6 to 2.89 ° and 3.05 to 3.08 ° are formed, and the integrated intensities of these diffraction peaks are the same as those of the (222) plane of the In ₂ O ₃ phase. IT characterized by being at least 0.1% of the integrated intensity
O sintered body.