JPS61214306A - Method and apparatus for transparent conducting film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a transparent conductive film, and particularly to a method and apparatus for manufacturing a transparent conductive film with low resistivity at a low temperature of 150° C. or lower.

(Prior Art) Generally, a transparent conductive film is necessary or indispensable for transparent infrared shielding plates, transparent electrostatic shielding plates, liquid crystal display elements, electroluminescent display elements, etc. As the film, an indium oxide-tin oxide based transparent conductive film known as an ITO film has been widely used.

(Problems to be solved by the invention) This ITO film has excellent optical properties, electrical properties, and heat resistance, but since the raw material indium is a rare metal, there are resource problems and it is expensive. There was a problem that manufacturing costs were high.

In addition, in order to manufacture an ITO film with low resistivity, 300
Because it requires high-temperature treatment at ~600°C, it cannot be formed on substrates with poor heat resistance such as plastic films, and it also has the problem of high energy consumption and high product costs6.On the other hand, inexpensive zinc oxide has attracted attention as a material for transparent conductive films, but it has been difficult to manufacture one with low resistivity.

Therefore, an object of the present invention is to provide a method and an apparatus for manufacturing a transparent conductive film having high visible light transmittance and low resistivity at a low temperature of 150° C. or lower, at low cost and easily.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a target whose surface is approximately on the same level as the surface of an anode disposed near and parallel to the magnetron cathode. The substrate on which the transparent conductive film is to be formed is placed on the magnetron cathode as shown in FIG. This method performs magnetron sputtering while applying a plasma focusing magnetic field.

As the target, an indium oxide-tin oxide target can be used, but a target made of zinc oxide or a zinc alloy containing at least one type of group Ⅰ element is suitable.

The content of group Ⅰ elements contained in the zinc oxide transparent conductive film is 1 to 20 atomic %, preferably 2 to 6 atomic %, based on zinc atoms.
It is appropriate to express it in atomic percent. This is because if the content is less than 1 atomic %, the effect of addition cannot be obtained, and if it exceeds 20 atomic %, crystallinity deteriorates and resistivity increases.

Examples of group (1) elements include aluminum, scandium, gallium, yttrium, indium, and boron, and these may be contained alone or in combination of two or more. In addition, as a method for incorporating group (I) elements into the zinc oxide transparent conductive film, it is preferable to introduce them in the form of metals, alloys, oxides, halides, etc. into the raw material zinc or zinc oxide during the thin film formation process. be.

As shown in FIGS. 1 and 2, the apparatus for carrying out the method of the present invention includes a magnetron cathode 5 carrying a target 1, and a surface of the target 1 attached to the magnetron cup 1''5, which is approximately parallel to the surface of the magnetron cathode 5 supporting the target 1. 7 no V2 arranged so as to be located at the same level, and a substrate 3 at 3 b approximately perpendicular to and V/or parallel to the surface of the target 1;
3c, a vacuum chamber 6 that houses these members, and a plasma focusing coil 4 that surrounds a plasma formation space.

Specifically, as shown in FIG. 1, the magnetron cathode 5 has a built-in electromagnet or a permanent magnet, and a target 1 is mounted on the surface of the magnetron cathode 5.
It is arranged so as to be located almost at the same level as the surface of No.1'2. The anode 2 has an opening 2a formed in its center, and the target 1 is attached to the magnetron cathode 5 so as to face the opening.

On the other hand, a solenoid coil 4 is arranged around the outer periphery of the vacuum chamber 6, and this solenoid coil 4 generates a magnetic field perpendicular to the target surface and in a direction repelling from the magnetic field of the magnetron cathode in the center of the target to focus the plasma. It's like letting them do it.

The strength of this plasma focusing magnetic field is generally 2×10−
”~10-27 is fine.

A non-metallic substrate holder 7.8, such as ceramic or plastic, is arranged in the space 6 formed above the target, and is adapted to hold the substrate 3 substantially perpendicular and/or parallel to the target surface. Although this embodiment shows an apparatus that incorporates three types of substrate holders, it goes without saying that all of these are not necessarily necessary, and it is sufficient to provide only one type of substrate holder. If the substrate is placed parallel to the target, the use of this non-metallic substrate holder is essential, but in other cases it does not necessarily have to be non-metallic and can be metallic as well. . In addition, if the substrate is placed perpendicular to the target, it is difficult to increase the area as long as a hard substrate such as glass is used, but if the substrate is placed parallel to or on a soft substrate such as film, it is difficult to increase the area. If a target with a large area is used, a transparent conductive film with a large area can be formed.

(Function) In the method of the present invention, the atoms of group Ⅰ elements are introduced into the zinc oxide transparent conductive film, and the fact that magnetron sputtering is performed without applying a plasma focusing magnetic field is effective. This makes it possible to form a low resistivity zinc oxide transparent conductive film on a substrate. The magnetron cathode feature suppresses the temperature rise of the target surface during sputtering, enabling high-speed film formation at low temperatures.

With zinc oxide, an N-type semiconductor degenerate due to donor levels due to intrinsic lattice defects can be obtained relatively easily by film-forming methods such as magnetron sputtering without adding impurities, and the conduction electron density is on the order of 1020 am-'. However, according to the method of the present invention, it is possible to introduce group Ⅰ elements into the zinc oxide thin film at low temperatures, and the atoms of the introduced group Ⅰ elements can effectively act as donors.
-3 order conduction electron density can be achieved.

When the group (III) element is contained in an amount of 1 to 20 at % according to the method of the present invention, the electron mobility does not change significantly compared to the case where the group (III) element is not contained, so that a transparent conductive film with resistivity about one order of magnitude lower can be obtained. Is possible. Furthermore, the plasma focusing magnetic field applied magnetron sputtering according to the present invention
The following effects are provided for lowering the resistivity of a zinc oxide film containing impurities by forming it at a low temperature.

(1) Unlike commonly used sputtering equipment, by using a non-metallic substrate holder, the anode is placed at almost the same level as the target surface rather than on the substrate side, which reduces the resistivity. For example, negatively ionized oxygen (02
-) flying onto the substrate, and serves to prevent a decrease in carrier density and carrier mobility.

(2) Charged particles (argon ions, sputtered ions) in the plasma due to the action of an externally applied magnetic field.

Since the electrons (electrons) are subjected to the Lorentz force, they are given kinetic energy in a direction parallel to the substrate surface, and various particles flying onto the substrate collide with the substrate surface, causing the formation of crystal nuclei and the rearrangement of atoms and molecules. Gives energy to promote.

(3) If metal is not used for the substrate holder, the electric field is not shielded, and since a magnetic field is applied from the outside, stable plasma generation can be achieved at low gas pressure due to the plasma pinch effect. , various particles are given large kinetic energy.

(4) All of these effects improve the crystallinity of the polycrystalline zinc oxide film, thereby increasing carrier mobility. Therefore, the prevention of a decrease in carrier density and carrier mobility due to this mobility increasing effect and the above-mentioned effect of preventing the introduction of ionized oxygen into the film is a factor in achieving low resistivity.

(5) Furthermore, since the externally applied magnetic field focuses the plasma and increases the ionization efficiency of the sputtering gas on the target surface, a high film formation rate can be achieved, making it possible to manufacture transparent conductive films at low cost. .

Examples of the present invention will be described below.

Example 1 Using the apparatus shown in Fig. 1 and Fig. 2, 2 wt.
% of aluminum oxide (AI20'r), 〃 oxide (GazOz), boron oxide (B20.), Zinc oxide (Zn
A rectangular target 1 with a width of 6 cm and a length of 10 cm made of O) is mounted on a magnetron cathode, and using pure argon as a sputtering gas, a substrate 3a is placed almost perpendicular to the surface of the target 1 and parallel to the surface of the target. A substrate 3c was placed on the substrate 3c, and sputtering was performed for 20 minutes under the following conditions to form a transparent conductive film. In addition, the board 3ay
All 3c values were positive, and because sputtering was carried out as the temperature naturally changed from room temperature without any particular temperature control such as heating or cooling, the temperature of the gas increased by about 90 degrees Celsius. Also, the film formation rate at this time is approximately 20% on the vertical substrate 3a.
nm/win, and about 30 nm/win for the parallel substrate 3c. The holder 7.8 that holds the substrate 3 at 3 c is made of ceramic (Micalex manufactured by Toshiba Ceramics)
It was made with

Sputtering conditions> Argon gas pressure: 6,5 Pa High frequency power: Near 0 W Plasma focusing magnetic field: 5 x 10-'T Parallel substrate (placement): 30 mm x 60 mm lath (
32 m5 above the target Vertical substrate (placement): 15 cm x 70 am glass (7) - 5 mm above the board) The resistivity and visible light transmittance (wavelength 400 to 800 nm) of the obtained transparent conductive film were investigated on vertical and parallel substrates. , the results shown in Table 1 were obtained.

As is clear from the results in Table 1, in all cases, transparent conductive films with a resistivity of 10 −4 ΩcI11 or less and a visible light transmittance of 80% or more were obtained. These values are almost uniform over the entire area of the substrate used, and in particular the distribution of resistivity on the substrate is within ±5%.

Also, a vertical substrate provides lower resistivity than a parallel substrate.

Kano Takumi Using a target made of zinc oxide with 2wt% aluminum oxide added, a positive substrate is fixed almost perpendicular to the target surface with a support equipped with a heater, and the surface of the substrate is heated. A transparent conductive film was formed by sputtering under the same conditions as in Example 1 while changing the temperature from 100° C. to 400° C. FIG. 3 shows the substrate temperature dependence of the resistivity of the obtained transparent conductive film.

As is clear from FIG. 3, a low resistivity transparent conductive film was obtained on a low temperature substrate of about 150° C. or lower. Furthermore, the visible light transmittance hardly changed depending on the substrate temperature.

Example 3 The content of aluminum oxide added to zinc oxide was 0.1
A plurality of targets were prepared varying from wt% to 20wt%, and each target was attached to a magnetron cathode, while a glass substrate was placed parallel and perpendicular to the target surface, and sputtering was performed under the same conditions as in Example 1. A transparent conductive film was formed. Since the temperature of the substrate was not intentionally controlled, it rose from room temperature to a maximum of about 120° C. due to natural changes during sputtering. In addition, the film formation rate at this time is as follows when the amount of added aluminum oxide exceeds about 3 wt%.
It gradually decreased, and at 10 wt% it was about 1/2 of that without additives.

FIG. 4 shows the dependence of the resistivity of the obtained transparent conductive film on the aluminum oxide content.

As is clear from FIG. 4, a transparent conductive film with a lower resistivity was obtained with the vertically arranged substrate.

It was also found that in any substrate arrangement, a resistivity of the order of 10<-4 >[Omega]CI6 can be obtained when aluminum oxide is contained in a range of 1 to 5 wt%. This tendency was the same even when gallium oxide, boron oxide, or indium oxide was added to zinc oxide.

Next, under the above sputtering conditions, the target was 2 wt.
FIG. 5 shows the change in resistivity of a transparent conductive film formed using zinc oxide containing % aluminum oxide and varying the strength of the plasma focusing magnetic field.

As is clear from FIG. 5, the lowest resistivity can be achieved by sputtering both the vertically arranged substrate and the parallelly arranged substrate while applying a plasma focusing magnetic field of about 5X10-3T, and even if it is stronger or weaker than this, Resistivity increases. As for the strength of the magnetic field, the component perpendicular to the target surface was measured at a position on the target center plane. From the above facts, it can be seen that application of the plasma focusing magnetic field according to the method of the present invention is essential in order to obtain a transparent conductive film with low resistivity at low temperatures.

Example 4 If a soft substrate 3b such as a plastic film as shown in FIG. 1 is used, it is possible to continuously form a large area transparent conductive film.

Using the apparatus shown in Fig. 1, a flexible substrate 3b made of a plastic film is used as a substrate, and a target made of zinc oxide with 2 wt% aluminum oxide added is used to wind the flexible substrate 3b with a winding mechanism. While removing the sample, sputtering was performed under the same conditions as in Example 1 to form a transparent conductive film. The substrate is a plastic film with a width of 10C and a thickness of 100μ, and a surface of 5Il1m on the 7-node surface.
The target was placed at a height of approximately perpendicular to the target surface (tilted approximately 30° toward the center of the target). t, m
Over an effective substrate area of 100 mm x 15 mm (the parts where the film is not desired to be attached are masked with ceramics), the resistivity is 2 to 3 x 10-' within a film thickness change rate of ±5%.
A transparent conductive film with an Ωe of 1 m was obtained.

In the above example, an oxide is used as a target, but an alloy of zinc (Zn), aluminum (AI), gallium (Ga), boron (B), or indium (In) is used as a target, and argon and argon are used as a sputtering post. Mixtures of oxygen may also be used.

Further, although high frequency power is input in the above embodiment, it is also possible to change this to direct current.

In the case of the vertical substrate arrangement of the above embodiment, the substrates are placed opposite each other and
Place two boards at the same time at the same time.
^L-t-shi11. By changing the distance between the substrates, the strength of the externally applied magnetic field, and the input power, it is possible to produce a large-area transparent conductive film with uniform film thickness and low resistivity. .

In each of the above examples, a zinc oxide thin film is formed, but since the method and apparatus for producing a transparent conductive film according to the present invention can produce a film at a high speed, the ITO film and other transparent conductive films are heated at about 150°C. It can also be used for production at lower temperatures.

(Effects of the Invention) As is clear from the above description, according to the present invention, zinc oxide is used as a material for transparent conductive films because the raw material is inexpensive and crystalline thin films can be formed relatively easily on various low-temperature substrates. By incorporating a small amount of group Ⅰ elements into the film, it is possible to lower the resistivity.

Furthermore, unlike the normally used magnetron sputtering equipment, by adopting a non-metallic substrate holder, the anode is positioned not on the substrate side but at almost the same level as the target surface, and a plasma focusing magnetic field is applied. Therefore, the introduction of oxygen ions into the film, which causes a decrease in carrier density, is reduced, and the kinetic energy of various particles flying onto the film reduces argon gas etc. that are taken into the film, further reducing crystallization. By promoting this, large-scale mobility can be achieved.

In addition, the adoption of a magnetron cathode is the Spa 9 IJ
This helped to suppress the heat generation of the target during the leg, making low-temperature film formation possible. The synergistic effect of these actions makes it possible to further reduce the resistivity even when forming a film on a low-temperature substrate.

By using a non-metallic substrate holder and applying a magnetic field from the outside, it is possible to generate stable plasma at low gas pressure, while at the same time focusing the plasma and reducing the amount of sputtering gas on the target surface. Ionization efficiency can be increased and a high film formation rate can be achieved. Therefore, according to the present invention, a zinc oxide transparent conductive film having characteristics similar to those of ITO II formed by high-temperature treatment at 300°C or higher can be produced in large quantities at low cost on a low-temperature substrate at about 150°C or lower. Effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional front view of a magnetron sputtering apparatus used for carrying out the method of the present invention, FIG. 2 is a schematic cross-sectional side view thereof, and FIG. 3 is a transparent conductive aluminum-containing zinc oxide formed by magnetron sputtering according to the present invention. FIG. 4 is a graph showing the dependence of the resistivity of the film on the substrate temperature; FIG. 4 is a graph showing the dependence of the resistivity on the aluminum content of the aluminum-containing zinc oxide transparent conductive film formed by magnetron sputtering according to the invention; 3 is a graph showing the dependence of resistivity on an externally applied plasma focusing magnetic field. DESCRIPTION OF SYMBOLS 1...Target, 2...Anode, 2a...7 node opening, 3.3a, 3b, 3c...Substrate, 4...Solenoid coil, 5...Magnetron cathode, 6 ...Vacuum chamber, 7.Substrate holder, 8.Non-metallic substrate holder. Patent applicant: Osaka Tokushu Alloy Co., Ltd. Agent: Patent attorney: Aoyama The first of two idiots! ! I Figure 2

Claims (8)

[Claims] (1) Place the target on the magnetron cathode so that the surface of the target is approximately on the same level as the surface of the anode placed near and parallel to the magnetron cathode, and place the substrate on which the transparent conductive film is to be formed as the target. A transparent conductive film that is arranged substantially perpendicular and/or parallel to the target surface and subjected to magnetron sputtering while applying a plasma focusing magnetic field perpendicular to the target surface from the outside and in a direction opposite to the direction of the magnetic field of the magnetron cathode. manufacturing method. (2) The method for manufacturing a transparent conductive film according to claim 1, wherein the target is made of zinc oxide containing at least one group III element. (3) The method for manufacturing a transparent conductive film according to claim 1, wherein the target is made of a zinc alloy containing 1 to 20 atomic % of aluminum, gallium, boron, or indium based on zinc atoms. (4) The method for producing a transparent conductive film according to claim 3, wherein the plasma generating gas is a mixed gas of argon and oxygen. (5) Forming a transparent conductive film with a magnetron cathode that holds a target for forming a transparent conductive film, and an anode that is placed near and parallel to the magnetron cathode so as to be approximately at the same level as the surface of the target. a substrate holding means for holding a substrate to be processed substantially perpendicularly and/or parallelly to the target surface; a vacuum chamber accommodating these members; and a substrate holding means arranged to surround the vacuum chamber and perpendicular to the target surface; A transparent conductive film manufacturing apparatus comprising a plasma focusing coil that applies a plasma focusing magnetic field in a direction opposite to the direction of the magnetic field of the magnetron cathode. (6) The transparent conductive film manufacturing apparatus according to claim 5, wherein the substrate holding means is a substrate holder that holds the substrate substantially perpendicularly to the target surface, and is fixed in a vacuum chamber. (7) The transparent conductive film manufacturing apparatus according to claim 5, wherein the substrate holding means comprises a substrate carrier that moves from one end of the vacuum chamber to the other end. (8) Manufacture of a transparent conductive film according to claim 5, wherein the substrate holding means comprises a substrate moving guide that moves from one end of the vacuum chamber to the other end, and a winding mechanism, and the substrate is made of a film. Device.