JPH03199373A - Sputtering target for forming electrically conductive transparent ito film - Google Patents

Abstract

PURPOSE:To provide a sputtering target for forming a thin film having improved electrical conductivity by sintering a molded body of powder having a compsn. prepd. by adding a specified amt. of I and Br compds. as well as a specified amt. of SnO2 to In2O3 as a principal component. CONSTITUTION:A molded body of powder having a plate shape or other shape and a compsn. consisting of 5-30wt.% SnO2, 0.1-3wt.% one or more among InI3, InBr3, SnI2 and SnBr2 and the balance In2O3 with inevitable impurities is produced and sintered to obtain a sputtering target. Since the target contains the I and Br compds., in electrically conductive transparent film having improved electrical characteristics such as low resistivity can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sputtering target for forming an ITO transparent conductive film whose resistance is reduced by adding I and/or Br to the ITO thin film.

・ Oxide transparent conductive films such as SnO, In, O, and In, O, films, which are referred to as JITO (Indium-Tin Oxide) films and NESA films, usually have a “deviation” from the stoichiometric composition. ”
In this method, a semiconductor exhibiting n-type conductivity is used, and a dopant is added to the semiconductor to form a low resistance film of 10<-3> to 10<4 >[Omega].(2). In particular, ITO films are the most widely used because they have high conductivity and visible light transparency.

Transparent conductive films such as ITO are used in liquid crystal display devices used in calculators and digital watches, thin film electroluminescence (EL) display devices, radiation detection elements, transparent tablets in terminal equipment,
It has a wide range of uses, including heat-generating films to prevent condensation on window glass, antistatic films, and selectively permeable films for solar collectors.

Methods for forming oxide transparent conductive films include chemical film-forming methods such as the spray method and CVD method, which utilize thermal decomposition of compounds to form oxides on a heated substrate, or vacuum evaporation as a physical film-forming method. sputtering method, sputtering method, etc., but sputtering method has been widely adopted as a means of making it possible to increase the area and obtain a low resistance film with good reproducibility.

In order to improve optical and electrical properties, it is important to control oxygen partial pressure, substrate temperature, annealing conditions, etc. in the sputtering film formation process mentioned above. Creating a resistive film is a fundamental and important issue. Even the ITO thin film, which is said to be an excellent low-resistance transparent film among the above-mentioned oxide-based transparent conductive films, is still insufficient, and there has been a need to further improve its conductivity.

” 4 absorption ΩJLIL In view of the above circumstances, the present invention provides ■ and/or Br
By selecting additives, the carrier concentration N (cm-'') of the ITO transparent conductive film can be greatly increased, and the electrical resistivity ρ (
Ω・cm).

That is, the present invention provides S n 0.5 to 30% (all percentages by weight in this specification, hereinafter omitted) and one or two selected from InI, InBr, SnI, and 5nBr. 0.1 to 3% of seeds and above and the remainder In2
A sputtering target for forming an ITO transparent conductive film in which I and/or Br is added to the target is provided by sintering a powder compact made of O3 and inevitable impurities.

The main components of the ITO transparent conductive film are In, O, and account for about 70 to 95%. This In,O, is a semiconductor that exhibits n-type conductivity due to a "deviation" from the stoichiometric composition, and by adding SnO, which has the same effect, the free electron concentration N (carrier concentration) is increased. It is possible to fabricate a film with resistivity ρ of about 10 −1 to 10 4 Ω· with a resistivity ρ of about 10 −1 to 10 4 Ω·. This is an ITO film.

As mentioned above, by adding SnO to In,O, the ITO film can be significantly improved in its resistance. is still far from sufficient.

The present invention provides a sputtering target for forming an ITO transparent conductive film in which conductivity is further improved by adding I and/or Br to the ITO.

Next, a method for manufacturing an ITO target will be described.

High purity powders are used for In, O, powder and SnO powder, which are the basic components.

The above SnO is added in an amount of 5 to 30%, but less than 5% and 3%.
If it exceeds 0%, the resistance lowering effect of the addition is lost, so the above mixing ratio is used. A particularly preferable addition ratio is 5 to 1
It is 0%. Inl,,■nBr,,SnI,,5nB
The amount of one or more selected from r is 0.1 to
It is 3%. As will be described later, if the amount is less than 0.1% or more than 3%, the effect of lowering electrical properties, that is, resistance, will not be substantially observed compared to a thin film made of ITO alone, so the above-mentioned component proportions are used. A particularly preferred range is 0.5 to 2%.

The raw material powders prepared in this manner are mixed at a predetermined ratio and formed into a plate shape.

The molded product is further sintered, and the sintering can be performed in any of the following atmospheres: air, an oxidizing atmosphere with adjusted oxygen, vacuum, or an inert atmosphere such as Ar. These conditions are appropriately selected depending on the purpose of the sintered body.

Sintering temperature is generally carried out at 1300 to 1600°C,
Lower temperatures are also possible. In the above, the molding and sintering are performed separately, but it can also be manufactured by a hot press method in which they are performed simultaneously.

It is also possible to use an infusion method, but this is not necessarily a good idea from the viewpoint of component adjustment and economic efficiency.

InI, , InBr, , 3nI, , 5n added above
One or more selected from Br decomposes at a relatively low temperature, so during the above sintering, I and/or Br are
Added to O target.

The sintered body obtained by the above manufacturing process is machined into a plate-shaped body having a shape required as a target, such as a rectangle or a disk.

Next, using the ITO sputtering target of the present invention produced as described above (Sn0.10% and InI, ITO target with varying doping concentrations), a gap between the ITO target on the cathode and the anode on the substrate side is about 500
Apply a DC voltage of V, 1~l OX 10-'Tor
FIG. 1 shows the results of a comparison of electrical characteristics when a conductive film is formed by sputtering (DC) in an Ar gas atmosphere of r. For comparison, ITO
A single film was also sputtered in the same manner.

Generally, the electrical characteristics of ITO film, i.e. resistivity ρ (Ωcm)
can be expressed by the following equation.

N(am-”) Carrier concentration μ(cm'/
V -5ec) Mobility e (1,602X 10
-"c) Elementary charge As is clear from this, in order to lower the resistivity ρ, it is necessary to increase μ or N.

As is clear from Figure 1 above, compared to the ITO film alone, the In
1. The thin film formed using a target doped with (0.5-4.0%) is an ITO-only film (addition amount 0% in Figure 1).
The relative carrier concentration N increases, and the resistivity ρ(Ω・cIn
) has been further improved.

Although not shown, similar results were obtained when InBr, 5nBr, and SnI were added. As can be seen from FIG. 1, when the amount added exceeds 3%, the resistivity ρ deteriorates rapidly, and the resistivity is inferior to that of a single ITO film.

Note that the value of resistivity ρ (Ω・an) shown in Fig. 1 is for ITO.
The electrical characteristics are compared with a single film under the same conditions as described above, and it is possible to further improve the resistivity ρ of each film by appropriately adjusting the substrate conditions, heat treatment, etc.

In other words, FIG. 1 was created for relative comparison with an ITO film to show the effect of adding I under the same conditions.

The general optical properties of an ITO film are that the fundamental absorption edge is in the ultraviolet region, and since moderate absorption by free electrons occurs in the near-infrared region, it becomes transparent in the visible region sandwiched between these two regions, and heat rays do not pass in the infrared region. reflect. And the visible transmittance is over 80%, usually over 90%. The visible transmittance of all transparent conductive films formed using the sputtering target of the present invention exceeded 90%.

The sputtering method for forming the above-mentioned ITO film doped with I and/or Br includes high frequency sputtering, plasma sputtering,
DC sputtering, ion beam sputtering, etc. can be used.

Since the conductivity of an ITO film is largely controlled by the "deviation" in stoichiometric composition, it is highly dependent on the composition of the gas during sputtering, mainly on the oxygen partial pressure.

In the case of oxide targets, gas release and changes in target composition are also factors.

It is necessary to control the low substrate temperature, heat treatment, etc. to optimal conditions in order to form a low-resistance film.

Next, the present invention will be explained along with examples.

- High purity In, O, powder, 5nO1 powder, which is the basic component of
In1. Powders of InBr, SnI, and 5nBr were prepared, and plate-shaped molded bodies were prepared in advance at the component mixing ratios shown in Tables 1 and 2. Then, sinter this to 4'φX
Various ITO targets (sample numbers 1 to 7) having a size of 4t and a density of 5g/dl were produced. The sintering temperature is 15
It is 00℃.

Next, thin films were formed by sputtering using these targets, and the resistivity ρ (Ω·cm) was measured.

Table 1 The sputtering conditions are as follows. (Equipment, 5pF-2108 manufactured by Nikkei Anelva) Input power 0.5W/ant Sputtering gas Pure argon method S Pressure 0.5 Pa group
Board temperature 350℃ membrane
Thickness: 1,500 people The above results are shown in Tables 1 and 2.

Comparative example Nll in Tables 1 and 2 uses In as the target material.
This is the ITO film itself to which I3, InBr3, SnI2, and SnBr2 were not added. Resistivity is 2.5X104
It is marked Ω.

Sample number N [L
2 to 9 are all materials N11L1 in Table 1 and Table 2.
The resistivity was improved compared to the above, and the effectiveness of the present invention can be confirmed.

In the case of Comparative Example Sample No. MIO111 in Tables 1181 and 2, the resistivity deteriorated rapidly when the amount added was large (more than 3.0%). Therefore, addition of more than 3.0% is practically meaningless.

As is clear from the above, the present invention further improves the ITO film, which has excellent properties as a transparent conductive film.

As mentioned above, it is possible to further improve the above resistivity by not only using the data described in this specification but also by controlling substrate conditions, heat treatment, oxygen partial pressure during film formation, etc. be. In other words, as in the present invention, by adding trace components, the electrical properties of the target and even the basic composition of the transparent conductive film are fundamentally improved, making it possible to obtain a further improved transparent conductive film. .

Further progress in the transparent conductive film according to the present invention, which has been adopted in many electronic devices such as liquid crystal display devices and selective transmission films, can make a significant contribution to the development of future technologies and devices.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of InI added and the resistivity of the ITO target.

Claims (1)

[Claims] (1) In weight%, SnO_25-30% and InI_3,
0.1 to 3% of one or more selected from InBr_3, SnI_2, and SnBr_2 and the remainder In_2O_3
A sputtering target for an ITO transparent conductive film, which is obtained by sintering a powder compact containing unavoidable impurities and adding I and/or Br to the target.