JPH0371510A - Transparent conductive film - Google Patents

Abstract

PURPOSE:To make a conductive film thinner, to cut time for etching, to improve yield, and to maintain good light transmittance for a transparent conductive film whose matrix is indium oxide by including one kind of nickel oxide or of phosphorus oxide therein. CONSTITUTION:To a transparent conductive film whose matrix is indium oxide, one kind of nickel oxide or of phosphorus oxide is added. The amount to be added is defined as 2-25mol% for nickel oxide, and 1-10mol% for phosphorus oxide. For the preparation of the transparent conductive film, sputtering, electron beam deposition, ion-plating, chemical evaporation, or application are employed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a transparent conductive film, and particularly to a transparent conductive film suitable for use in transparent electrodes of liquid crystal displays, electroluminescent displays, electrochromic displays, and the like.

[Prior art] As a transparent conductive film, metals such as gold and platinum, tin oxide,
A device in which a film of an oxide such as indium oxide is formed on a substrate is known. Among these, ITO (Indi O), which is made by adding tin oxide to indium oxide, is used for liquid crystal displays.
umu-Tin Oxide) is the mainstream. This is because ITO has good etching properties, chemical stability, adhesion to substrates, etc. as well as high transparency and low resistance.

In addition to ITO, there are the following examples of techniques for reducing the resistance of transparent conductive films using a semiconductor mechanism based on valence control.

In JP-A-59-163707, ruthenium oxide, lead oxide, and copper oxide are added to ITO, and the best value is specific resistance 0.7X 10-'Ω"ClR5lR5 light transmission power 88%.
I am getting . In JP-A-59-71205, 1.01 to 3 wt% of phosphorus oxide was added to ITO and the best value was determined.
1000 thick, resistance 0.3Ω/mouth (specific resistance 3
10-'Ω·C■) and a light transmittance of 90%. In JP-A No. 61-294703, aluminum fluoride is added to indium oxide, and the resistance is 220Ω/hole (13X 10-'Ω・C11
), it has a light transmittance of 85%. Unexamined Japanese Patent Publication 1986-7
In 8404, aluminum fluoride is added to ITO, and the best value is 5Ω/hole (0,7
5X 10-'Ω·C■) and a light transmittance of 84%.

In JP-A-63-178414, tellurium oxide is added to ITO, and the best value is 1. I X 10-'Ω・C
11+ resistance film, ITO in JP-A-64-10507
0.1 to 5 wt% of silicon oxide is added to the film, and a film with a resistance of 1.96x io-'Ω·Cl11 is found as the best value.

On the other hand, an example of reducing the resistance of a transparent conductive film by converting it into a semiconductor based on reduction is USP 4,399.194.

According to USP 4.399.194, zirconium oxide is added to indium oxide in an amount of 40 to 60 wt% to obtain characteristics of specific resistance of 4.4 x in-'Ω·can and light transmittance of 80%.

Methods for forming the transparent conductive film include physical vapor deposition methods such as vacuum evaporation, ion blasting, and sputtering, chemical vapor deposition methods that use chemical reactions such as thermal decomposition, and coating methods such as spraying and dipping. Among these methods, the physical vapor deposition method, especially the sputtering method, has become mainstream because it has good film density and can easily produce a low resistance film.

[Problem to be solved by the invention 1 In recent years, liquid crystal displays have been widely used for word processors, televisions, etc., and as a result of the increasing size of the liquid crystal screens, the conventional transparent 1
111 When it becomes necessary to improve the light transmittance without reducing the specific resistance value of the conductive film, maintaining the specific resistance value at a low resistance requires reducing the film thickness of the electrode. Therefore, good etching performance is also possible.If the film thickness of the transparent conductive film exceeds 200 mm, the etching time becomes longer, causing pattern breakage and resistance non-uniformity due to deterioration of the film surface condition. This causes a decrease in yield.

The present invention improves the specific resistance of the conventionally used transparent conductive film.
In addition to maintaining the specific resistance of X 10-' Ω・cm, we aimed for an even lower specific resistance value, made the conductive film more thick, shortened the etching time, improved the yield, and achieved a light transmittance of 90%. The objective of the present invention is to ensure the same level of performance, and we have investigated the addition of elements not found in the prior application.

[Means for Solving the Problems] The present inventor focused on the fact that when a certain metal oxide is added with an element having a valence different from that of the metal, it becomes a semiconductor by controlling the valence, and developed a method using indium oxide (In20a) as the main component. When lowering the resistance of a transparent conductive film by adding an element other than trivalent, it is necessary to add an element that is smaller than the trivalent indium ion radius and can exist as an interstitial ion, so that lattice distortion does not become large. As a result of various studies, we have arrived at the present invention.

That is, we have found a transparent conductive film whose main component is indium oxide (In2O3), which is characterized by containing one type of nickel oxide (Nip) or phosphorus oxide (paos).

Adding NiO or P2O5 to In□O8 lowers the resistance. In particular, when NiO is added in an amount of 2 to 25 mo1% or PJS is added in an amount of 1-11-10%, the specific resistance becomes less than 2 x 10-'Ω·Cl1l, which is preferable.

In addition, some of the SnO□ added in conventional ITO is replaced with P.
A similar good effect can be obtained by replacing it with 2O.

In this case, Snug contained in ITO is 20 mo1
% or less is effective.

Sputtering and electron beam evaporation are commonly used to form transparent conductive films, but there are other methods such as ion blating, chemical vapor deposition, and coating. The method is selected as appropriate.

In the sputtering method and the electron beam evaporation method, a sintered body of indium and an oxide of an additive element or an alloy thereof is used as the evaporation material.

Oxide sintered bodies as vapor deposition materials use oxides, metals, hydroxides, chlorides, nitrates, sulfates, etc. as raw materials, and compounds containing these indium and additional elements are mixed in a ball mill or the like. , NiO added at 400-1400'C, P2O,.

After calcining in powder form at 400 to 700°C, binders such as PVA and PVB are added and granulated by spray drying, etc. to produce 500 to 2,000 kg/c d.
It is made by molding and sintering.

The sintering temperature is 800 to 1600℃ for those with NiO added.
, the one with P2O5 added is 400-700°C.

When forming a film by sputtering, after setting the sintered body or alloy as the vapor deposition material and the substrate on which the film is to be formed,
After evacuation to Torr or less, oxygen and Ar are mixed in a molar ratio ranging from 0.5:9.5 to 4:6, especially in the case of alloys in a strongly oxidizing atmosphere of about 4:6. , I x
Introduce the mixed gas to about 10-” to 5 x 10-” Torr, and reduce the deposition rate to 1 at a substrate temperature of 200 to 350°C.
The film is formed at a rate of 0λ/sec or less.

At this time, if the 0□ partial pressure is too lower than the value in L, the membrane transmittance will be low and the resistance value will be high. As the 02 partial pressure increases, the transmittance increases and the resistance value decreases, but if it becomes too high, the resistance value increases. Further, if the substrate temperature is less than 200°C, the transmittance and resistance value will be poor, and if it exceeds 350°C, the resistance value will be poor again. Even if the deposition rate exceeds 0 s/sec, the film's transmittance and resistance are poor.

Considering the above, if the membrane transmittance is 90% or more,
The sputtering conditions that provide the lowest resistance value are selected.

Also, when forming a film by electron beam evaporation.

The process of not introducing Ar gas but introducing oxygen gas and heating the substrate is similar to sputtering, and the deposition rate is determined by the voltage, current, and beam diameter of the electron beam. By appropriately selecting the 0□ partial pressure, substrate temperature, and deposition rate, a film with a transmittance of 90% or more and the lowest resistance value is obtained. The initial vacuum level is 10
−'TorrLu, and then 0□ partial pressure is O, 5X
10-'~4 x 10-'Torr, substrate temperature 20
0~400℃, deposition rate 0.5~107%/see
is an appropriate condition.

Among film forming methods such as sputtering, electron beam evaporation, chemical vapor deposition, and surface coating methods, sputtering is known to yield a low-resistance film over the widest range of additive amounts.

As the substrate on which the film is formed, glass, plastic sheets, films, etc., or those coated with a protective film or a functional film are used.

[Example J The present invention will be explained in detail below using examples.

Examples 1 to 5, Comparative Examples 1 to 2 Table L for those in which NiO is added to Inz03
Weigh InzL and NiO so that the composition is as shown in
Ethanol was added and mixed for 48 hours in a nylon ball mill at a slurry concentration of 50%. The obtained slurry was dried at 60°C and calcined at 1400°C in the air for 10 hours. Next, it was pulverized 24 hours a day in a nylon ball mill. To this pulverized powder, 20 wt % of a 2.5% PVA aqueous solution was added and granulated to an average particle size of 20 μm using a spray dryer.

The granules were press-molded at 1 ton/crr1' and had a diameter of 7
A molded body having a diameter of 0 nm+mφ and a thickness of 1 Omm was obtained.

This molded body was fired in the atmosphere at 1450°C for 15 hours,
I made a sputtering target.

This target was set in a high-frequency magnetron sputtering device and evacuated to I 76X 26X 1 mn1) 300 substrates
A transparent conductive film was prepared under the conditions of heating to 0.degree. C. and a film formation rate of 3 s/see.

The film thickness, light transmittance, and specific resistance characteristics of the obtained transparent conductive film were measured, and these are also listed in Table 1.

The film thickness was determined by masking during film formation, and after film formation, the difference in height between the film and the substrate from which the masking was removed was determined by measuring the difference in height using Rank-Taylor Bobson (Structure Talystep).

The light transmittance is the transmittance of 550 nm light using a spectrometer manufactured by Tokai Kogaku@4.

Further, the specific resistance was measured by a four-terminal method by soldering conductive wires to the membrane at four locations along a straight line -L.

Strictly speaking, the composition after film formation deviates from the sputtering target composition, but the deviation in the content of additive elements is ±0.05.
It was confirmed by chemical analysis that the mole content was about 1%.

As can be seen from Table 1, as the amount of NiO added increases, the resistivity gradually decreases, but when it exceeds about 9.5 mo1%, the resistivity increases.

In the range shown in Table l, the light transmittance is 90% or more,
When the amount of NiO added is in the range of 2 to 25 mo1%
It showed a specific resistance superior to the value of TO 2 x 10-'Ω·CJ.

Examples 6 to IO1 Comparative Examples 2 to 4 For those in which p2o is added to In2oi, the calcination temperature is 400°C and the firing temperature is 550°C for the composition shown in Table 1.
Except for the above, a sputtering target was prepared in the same manner as in Examples 1 to 5, and sputtering was performed under the same conditions to create a transparent conductive film. Their film properties are also shown in Table 1.

As the amount of p2o added increased, the specific resistance initially decreased, but when it exceeded 6 mo1%, it increased.

Addition of PzOs 311.1-10 mo1% aili
It showed excellent characteristics with a specific resistance of less than 2×10-'Ω·Cl11.

Examples 11-13 The 5nO of ITO with Snug added to InJs
The compositions shown in Table 1 were investigated, assuming that PzOs was added to a part of the addition of z. Example 6 shows how to make a sputtering target and sputtering conditions.
- The same procedure as in 10 was carried out. The film characteristic values are also shown in Table 1.

(Left below) [Advantageous Effects of the Invention 1] The transparent conductive film obtained by adding NiO or PO to InzOa of the present invention has properties superior to those of conventional ITO, and the film thickness can be made thinner, making it easier to etch. This results in improved properties and an associated improvement in yield.

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Claims (1)

[Claims] A transparent conductive film containing indium oxide (In_2O_3) as a main component and containing one type of nickel oxide (NiO) or phosphorus oxide (P_2O_5).