JPH05179439A - Target for sputtering made of indium oxide-tin oxide sintered compact - Google Patents

Abstract

PURPOSE:To provide a target for sputtering capable of forming an electric conductive transparent film of indium tin oxide used for a gas sensor, the transparent electrode or antistatic coating film of a liq. crystal display device or an electroluminescent display device by sputtering in a short time. CONSTITUTION:This target for sputtering is made of an indium oxidetin oxide sintered compact having a structure of <=1mum average grain diameter and >=85% relative density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film of indium-tin oxide (hereinafter referred to as ITO) used for a liquid crystal display device, a transparent electrode of an electroluminescence display device, an antistatic conductive film coating, a gas sensor and the like. The present invention relates to a target that can perform sputtering while applying a high voltage.

[0002]

2. Description of the Related Art Generally, since an ITO film is transparent and has conductivity, it is widely used as a transparent electrode or a transparent conductive film, and a sputtering method is one of the methods for forming the ITO film. .. The sputtering method uses an In—Sn alloy target and ITO.
There is a method of using a target. In the method of using the above In—Sn alloy target, an ITO target that is relatively easy to form a film is used because a strict control of the oxygen amount is required to obtain a stable film. Method is the mainstream.

[0003]

The above ITO target is difficult to sinter, and the relative density of the ITO target obtained by the usual ceramic sintered body manufacturing method of mixing → crushing → forming → pressureless sintering is at most Only about 60% increase,
Also, the average crystal grain size of the ITO target is 4 μm or more, and if sputtering is performed while applying a high voltage to achieve high-speed film formation using such an ITO target, abnormal discharge is likely to occur and the discharge state is unstable. The target will be consumed unevenly, while if the input power is made small and the voltage is made low, the deposition rate will slow down, and sufficient IT
The O film formation rate could not be obtained.

[0004]

Therefore, the present inventors have
As a result of conducting research to obtain an ITO target for sputtering that can perform high-speed film formation without abnormal discharge even when a high voltage is applied, the density is high and the crystal grain size of the structure is as small as possible. By using the ITO target described above, it has been found that abnormal discharge does not occur even when a higher voltage is applied than in the conventional case, the input power can be increased, and therefore high-speed film formation can be performed.

The present invention was made on the basis of such findings, and has a structure in which the average grain size of crystal grains is 1 μm or less, and the relative density of indium oxide is 85% or more.
It is characterized by an ITO target made of a tin oxide sintered body.

In order to produce an ITO target of the present invention having an average grain size of crystal grains of 1 μm or less and a relative density of 85% or more, the raw material powder has an average grain size of 0.01 to 1 μm
It is manufactured by preparing indium oxide powder or a mixed powder of tin oxide powder and indium oxide powder in which tin oxide of m is dissolved in solid solution, and hot pressing these raw material powders at a temperature of 850 to 1100 ° C. The ratio of tin oxide to indium oxide is usually about 11% by weight, but a range of 30% or less is a permissible range in which a transparent conductive film can be formed.

If the average particle size of this raw material powder is larger than 1 μm, the sinterability will be poor and the sintered density will not increase.
The average crystal grain size of the O target is also larger than 1 μm, which is not preferable. On the contrary, when the average crystal grain size is smaller than 0.01 μm, it is difficult to suppress agglomeration and it is extremely difficult to obtain a powder having high sinterability. Is. Therefore, the average particle size of the raw material powder used for manufacturing the ITO target is
It is preferably in the range of 0.01 to 1 μm, and more preferably in the range of 0.02 to 0.5 μm.

The raw material powder used for manufacturing the ITO target of the present invention may be either indium oxide powder in which tin oxide is solid-solved or a mixed powder of tin oxide powder and indium oxide powder. The indium oxide powder in which is solid-solved is more preferable. The reason for this is that the mixed powder has a low degree of microscopic mixing, and the Sn dispersibility of the obtained target is poor, so the Sn dispersibility of the film obtained by film formation is also poor and the conductivity is also low. Because it gets worse.

The indium oxide powder in which tin oxide is solid-dissolved is added with oxalic acid in an aqueous solution of In salt and Sn salt to adjust pH to 0.
As co-precipitated tin oxalate / indium as 2, 400 to 8
It can be obtained by calcining at 00 ° C., loosening the agglomerated particles, and imparting sufficient dispersibility. Alternatively, it can also be obtained by mixing commercially available tin oxide powder and indium oxide powder, firing at 1350 ° C. or higher to form a solid solution, and then mechanically pulverizing.

The sintering temperature in the hot press is 850.
~ 1300 ° C is good, and if it is lower than 850 ° C, a high sintered density cannot be obtained.
It is not preferable because metal may be deposited.

When sputtering is carried out with an ITO sintered body having an average crystal grain size of more than 1 μm and a relative density of more than 85% as a target, the maximum sputtering voltage is lowered, and therefore, the input power cannot be increased, so that high speed is achieved. No film can be formed.

[0012]

EXAMPLES The present invention will be specifically described based on examples. In ₂ O ₃ powder and SnO ₂ powder were mixed at a ratio of 9: 1, baked in the air, completely dissolved, and then pulverized to produce a raw material powder having an average particle size shown in Table 1. did.

These raw material powders were vacuum hot-pressed at the temperatures and pressures shown in Table 1 to have the average crystal grain size and relative density shown in Table 1, diameter: 80 mm,
Disc-shaped targets 1 to 7 of the present invention and comparative targets 1 and 2 having a thickness of 7 mm were manufactured. For comparison, a conventional target was manufactured by an atmospheric pressure sintering method under the conditions shown in Table 1.

These targets were set in a DC magnetron sputtering apparatus, the substrate temperature: 250 ° C., the pressure: 5 × 10 ^-3 torr, and the current was 1 mA.
Hold constant, increase the voltage until the abnormal discharge occurs in order to increase the input power in order to increase the film formation speed, and measure the voltage immediately before the abnormal discharge (hereinafter referred to as the maximum sputtering voltage), The results are shown in Table 1.

[0015]

[Table 1]

[0016]

From the results shown in Table 1, since the maximum sputtering voltage of each of the targets 1 to 7 of the present invention having an average crystal grain size of 1 μm or less and a relative density of 85% or more is higher than that of the conventional target, the sputtering method is used. When the film is formed, the input electric power can be increased, and therefore the film formation speed can be increased, but the value is outside the conditions of the present invention (values outside the conditions of the present invention are marked with *). It can be seen that since the maximum sputtering voltage of the comparative targets 1 and 2 and the conventional target (shown with) is low, the input power cannot be increased, and therefore high-speed film formation cannot be performed.

Since the target of the present invention has a high maximum sputtering voltage, the input power can be increased to accelerate the film forming rate, and the manufacturing cost can be reduced to make an excellent industrial contribution.

Front Page Continuation (72) Inventor Yukihiro Ouchi 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials (72) Inventor Akio Takahashi 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Mitsubishi Materials Corporation Central research institute

Claims (1)

[Claims] 1. A sputtering target comprising an indium oxide-tin oxide sintered body having a structure in which the average grain size of crystal grains is 1 μm or less and a relative density of 85% or more.