JPH08158041A - Production of transparent conductive film and device therefor - Google Patents

Abstract

PURPOSE: To prepare a low resistance smooth transparent conductive film with high transmission free from fine particulate deposition. CONSTITUTION: This device for producing the transparent conductive film is composed of a rotating disk 9 provided with substrates 10 along the circumferential part, a vapor deposition boat 1 installed to face the circumference of the rotating disk 9 and for vaporizing a metal 2 consisting essentially of In and devices 3, 4 for plasma-discharging in the area between the vapor depositing boat 1 to the substrates 10. The metal consisting essentially of In is vapor deposited and oxidized in an atmosphere of a gas containing oxygen by plasma- discharging in the area between the vapor depositing boat 1 and the substrate 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing an indium oxide type transparent conductive film.

[0002]

2. Description of the Related Art Conventionally, an optical sensor, a one-dimensional line sensor,
As a transparent conductive film for a light receiving device such as a liquid crystal display, a solar cell, and an imaging device, a transparent conductive film mainly containing indium oxide is widely used, and the conductive film is generally known by the following manufacturing method.

(1) In ₂ O ₃ and S are deposited on a substrate by an RF sputtering method in an argon or oxygen atmosphere.
Sputter a target consisting of a sintered body of nO ₂ ,
A method for obtaining a transparent conductive film mainly composed of indium oxide.

(2) A method of depositing a sintered body of In ₂ O ₃ and SnO ₂ on a heating substrate in an oxygen atmosphere by an electron beam evaporation method to obtain a transparent conductive film mainly containing indium oxide. .

(3) After depositing an In--Sn alloy on a heating substrate in an oxygen atmosphere by electron beam evaporation,
A method of obtaining a transparent conductive film containing indium oxide as a main component by heat treatment in an oxygen gas atmosphere.

(4) A method of vapor-depositing an In--Sn alloy on a heating substrate in an oxygen atmosphere by a resistance heating vapor deposition method to obtain a transparent conductive film mainly containing indium oxide.

[0007] Regarding the above-mentioned method, for example, the document RCA Review Vol. 32, Jun,
289-296 (1971), or Applied Physics, 4th
9, Vol. 1, pp. 2-16 (1980).

[0008]

Of the above-mentioned conventional techniques,
The methods (1) and (2) have good conductivity, but easily generate fine particle defects, and the methods (3) and (4)
Although fine particle-shaped defects are unlikely to occur, there is a drawback that it is not always possible to obtain sufficient conductivity. In the method (4), the vapor deposition boat reacts with the evaporation source material in the oxygen atmosphere,
There was a drawback of melting.

An object of the present invention is to provide a manufacturing method and apparatus which can solve the above problems. Another object of the present invention is to stably provide a smooth, high-quality transparent conductive film having a low resistance and a high transmittance, and having no particulate deposits.

[0010]

Means for Solving the Problems The above-mentioned object is to evaporate a metal mainly composed of In on a substrate heated and held in a gas atmosphere containing oxygen when a region up to the deposition boat and the substrate is plasma-deposited. It is achieved by discharging.

In addition, a vapor deposition boat made of a metal material and an insulating hard ceramic member for evaporating a metal containing In as a main component is used, and a gas atmosphere pressure containing oxygen is 1 mTorr or more and 50 mTorr or less, and a vapor deposition rate is 0. 0.5 nm / m
in or more, 7.0 nm / min or less, substrate temperature 100 ° C or more,
It is achieved by keeping the temperature below 300 ° C.

[0012]

The present inventors have investigated in detail the factors of the decrease in conductivity, the generation of fine particle defects and the reaction with the vapor deposition boat in the prior art. As a result, in the usual resistance heating vapor deposition method, the reaction between the vaporized substance and oxygen is insufficient, so that the resistance value does not decrease, and when a sintered body composed of In ₂ O ₃ and SnO ₂ is used as the vaporization source, the film During the formation, minute fragments of the sintered body fly from the evaporation source and adhere to the substrate to form fine particles, and when the vapor deposition boat material is W or Mo, it reacts with In ₂ O ₃ to form an oxide thereof. And In are generated and evaporated, or T
It was found that the boats of a and Pt were quickly melted and could not continue evaporation.

In the present invention, when a metal mainly composed of In is vaporized in an oxygen atmosphere, a region between the vapor deposition boat and the substrate is plasma-discharged to activate the reaction between the vaporized substance and oxygen, and By using a combination of an insulating hard ceramic member that does not react with the evaporation source material and a metal material in the vapor deposition boat, there are no impurities and there is no interruption of vapor deposition, and it is possible with the conventional resistance heating vapor deposition method. It has become possible to easily form a low resistance In-based transparent conductive film, which has not been possible. As a result, a transparent conductive film having high conductivity and high transmittance free of fine particle defects was obtained.

FIG. 1A is a schematic view showing an example of a vacuum vapor deposition apparatus used in the present invention. In the figure, 1 is a vapor deposition boat, 2 is an evaporation source material, 3 and 4 are plasma discharge electrodes, 5 is a current terminal, 6 is a shield, 7 is a shutter, 8 is a rotating shaft,
Reference numeral 9 is a rotary disk, 10 is a substrate, 11 is a film thickness monitor, 12 is a heater, 13 is a rotary motor, 14 is a bell jar, 15 is a valve, and 16 is an oxygen introduction valve. FIG. 1B is a top view of the rotary disc 9.

The vapor deposition boat 1 shown in FIG. 1A is filled with an evaporation source material 2 made of a metal containing In as a main component, and a rotary disc 9 is provided.
The substrate 10 is placed and the inside of the vapor deposition apparatus is evacuated to a high vacuum. Next, while the oxygen gas is introduced and the inside of the vapor deposition apparatus is maintained at a predetermined pressure, the rotary disk 9 is rotated at a constant speed, and the substrate 12 is heated and maintained at a predetermined temperature by the heater 12. Next, the plasma discharge electrodes 3 and 4 are discharged to form a plasma region between the vapor deposition boat 1 and the substrate 10. Next, the evaporation boat 1
Power is supplied from the power source to heat, melt, and evaporate the metal mainly containing In, and the evaporation amount from the evaporation boat 1 is controlled to be constant. Once you get a stable evaporation,
The shutter 7 is opened, and a metal mainly containing In is vapor-deposited on each substrate 10 on the rotating disk 9 and is oxidized to obtain a transparent conductive film made of an oxide mainly containing In.

In this case, the evaporation amount of the metal mainly consisting of In is always irrespective of whether the shutter is opened or closed, and the film thickness monitor 11
Is used to control the evaporation rate to a predetermined value.
Therefore, according to the present method, it is possible to reproducibly obtain an oxide transparent conductive film mainly composed of In having a low resistance on the substrate.

It is important that the vapor deposition boat does not react with the oxide containing In as a main component and the atmospheric gas. For such a purpose, for example, indirectly heated Al ₂ O ₃ or Al ₂ O ₃ and S having a recess for filling the evaporation source material in the center is used.
hard ceramic boat to the iO ₂ as a main component can be used.

FIG. 2 is an external view showing an example of a vapor deposition boat used in the present invention. In the figure, 17 is an insulating hard ceramic, 18 is a metal wire, and 19 is a circular recess for filling a vapor deposition source material such as a metal mainly containing In. To heat the vapor deposition boat, for example, a metal wire made of a Pt-Rh alloy may be passed through a hole penetrating the side surface of the insulating hard ceramic, and the metal wire may be energized. The metal wire is not necessarily Pt-Rh, and may be Pt, Ir, or an alloy thereof.

As described above, the case where the evaporation source material is mainly composed of In has been described as In and Sn.
It may be one in which a small amount of d, Zn, Ti or the like is additionally doped.

The atmosphere gas for plasma discharge and the reactive gas at the time of vapor deposition are not limited to oxygen, but may be, for example, a mixed gas of oxygen and water vapor, carbon dioxide gas, argon and nitrogen.

FIG. 3 shows an evaporation source material obtained by adding 5% by weight of Sn to In using the vacuum evaporation apparatus of FIG. 1 and the evaporation boat of the present invention of FIG. 2, the substrate temperature is 200 ° C., and the evaporation rate is 2.5 nm.
FIG. 3 is a diagram showing the relationship between the specific resistance and the number of fine particle defects of the oxidized In—Sn-based thin film produced under the condition of / min, the oxygen gas pressure during production, and the presence or absence of plasma discharge.

Oxygen gas pressure 1 with plasma discharge (curve a)
The thin film formed at 0 mTorr has a specific resistance of about 1/2 of that of the case without plasma discharge under the same conditions (curve b), which is about 0.3.
It became mΩ · cm. In addition, the visible light transmittance was 85% or more, indicating good transparent conductivity. Moreover, as shown by the curve (c), the number of fine particle defects is small.

With plasma discharge, oxygen gas pressure 1.0
In the region Rp of ˜50 mTorr, both the specific resistance and the transmittance are good, the smoothness of the film surface is very good, and there are no fine particle defects. On the other hand, when the oxygen gas pressure is 1.0 mTorr or less, the resistance value sharply increases, while when it is 50 mTorr or more, fine particle defects increase.

FIG. 4 shows an evaporation source material obtained by adding 5 wt% of Sn to In using the vacuum vapor deposition apparatus of FIG. 1 and the vapor deposition boat of the present invention of FIG. 2 under the conditions of substrate temperature of 200 ° C. and oxygen gas of 10 mTorr. It is a figure which shows the specific resistance of the produced oxide In-Sn type | system | group thin film, the number of fine particle defects, the vapor deposition rate at the time of production, and the relationship of the presence or absence of plasma discharge. The thin film formed at a deposition rate of 2.5 nm / min with plasma discharge (curve d) has a specific resistance of about 1/2 or about 0 as compared with the case without plasma discharge under the same conditions (curve e). It exhibits good transparent conductivity with a transmittance of visible light of 85% or more at 0.3 mΩ · cm. Further, as shown by the curve (f) in the figure, the number of fine particle defects is small.

With plasma discharge, the deposition rate is 0.5.
In the region (R _V ) of ˜7.0 nm / min, the specific resistance and the transmittance are good, the smoothness of the film surface is very good, and there are no fine particle defects. When the deposition rate is 0.5 nm / min or less, the resistance value suddenly increases and the productivity is poor. On the other hand, 7.
At 0 nm / min or more, fine particle defects increase.

FIG. 5 shows an evaporation source material obtained by adding 5 wt% of Sn to In using the vacuum evaporation apparatus of FIG. 1 and the evaporation boat of FIG. 2 under the conditions of oxygen gas of 10 mTorr and evaporation rate of 2.5 nm / min. FIG. 6 is a diagram showing the relationship between the specific resistance, the transmittance, and the size of the irregularities on the film surface, the substrate temperature during production, and the presence or absence of plasma discharge, of the oxide In—Sn-based thin film produced in FIG. The thin film formed with plasma discharge (curve g) at a substrate temperature of 200 ° C. has a specific resistance of about half that of the case without plasma discharge (curve h) under the same conditions as described above, and is about 0.1. It becomes 3 mΩ · cm, and the visible light transmittance is 80% or more, which shows good transparent conductivity. Further, as shown by the curve (i) in the figure, the unevenness of the film surface is small.

With plasma discharge, the substrate temperature is 100.
In the region ( _RT ) of up to 300 ° C, both the specific resistance and the transmittance are good, the smoothness of the film surface is very good, and there are no fine particle defects. When the substrate temperature is 100 ° C. or lower, the resistance value rapidly increases and the transmittance also deteriorates. On the other hand, 300 ° C
As described above, the crystallinity of the thin film progresses, so that the unevenness of the film surface becomes large and the smoothness deteriorates.

From the above, in the method of forming an oxide conductive thin film containing In as a main component by evaporating a metal containing In as a main component from the vapor deposition boat in the plasma discharge of the present invention, the oxygen gas pressure is 1. 0-50mTorr, vapor deposition rate 0.5-
A range of 7.0 nm / min and a substrate temperature of 100 to 300 ° C. is preferable. In this case, the specific resistance and the transmittance are good, the smoothness of the film surface is very good, and there are no fine particle defects. A high-quality transparent conductive oxide film mainly composed of In can be obtained with good reproducibility. Further, the Sn weight% content of the evaporation source material in the present invention is preferably 1 to 20% in view of the resistance value of the film. The thickness of the thin film formed by the method of the present invention is 10 n.
m or more and 40 nm or less is desirable. Below that, the resistance value becomes large, and above that, the crystallinity of the thin film advances,
The unevenness of the film surface may become large and the smoothness may deteriorate.

Further, when the transparent conductive film according to the present invention is used as a target electrode of an image pickup tube, dark current and white spots are increased as compared with, for example, an image pickup tube using an indium oxide type transparent conductive film formed by a conventional sputtering method. The number of screen defects is small, it is possible to operate by applying a higher voltage, and an image pickup tube with higher sensitivity can be realized.

The transparent conductive film according to the present invention is not limited to the above-described image pickup tube, but is also a light receiving device including at least a transparent substrate, a transparent conductive film, and a photoconductive film, such as an optical sensor, a line sensor, and a two-dimensional sensor. Even when used for a transparent conductive film such as a three-dimensional sensor, a solar cell, a liquid crystal display, and a solid-state image sensor, it is possible to realize a good light-receiving device with less dark current and local image defects as in the case of the above-mentioned image pickup tube. Of course.

[0031]

【Example】

(Example 1) Using the vacuum vapor deposition apparatus of FIG. 1 and the vapor deposition boat of the present invention of FIG. 2, the vapor deposition boat 1 is filled with an evaporation source material made of an alloy of In and Sn 5 wt%. Next, the substrate 10 is placed on the rotary disk 9, the inside of the vapor deposition apparatus is evacuated to a vacuum degree of 2 nTorr or less, the rotary disk is rotated at a constant speed of 50 rpm, and the valve 15 and the oxygen introduction valve 16 are opened. The rate is adjusted to maintain the pressure in the vapor deposition device at 10 mTorr, and
Heat and hold at 0 ° C. Next, the plasma discharge electrodes 3 and 4 are discharged to form a plasma region between the vapor deposition boat 1 and the substrate 10. Next, the vapor deposition boat 1 is heated while maintaining the substrate temperature and the pressure in the vapor deposition device in a steady state. Power supply (not shown)
The vapor deposition is performed by passing an electric current from.

The evaporation rate of the In and Sn 5 wt% alloy was obtained by previously examining the relationship between the evaporation rate instruction value of the film thickness monitor 11 and the vapor deposition amount of the In and Sn 5 wt% alloy actually deposited on the substrate. Set according to the calibration curve provided. In the present embodiment, the vapor deposition rate of In and Sn 5 wt% alloy is 2.
The evaporation rate is set to be 0 nm / min. When the evaporation rate became stable, the shutter 7 on the evaporation boat was opened to form a 25 nm-thick oxidized In—Sn-based transparent conductive film. The specific resistance of the obtained thin film was 0.3 mΩ · cm, the transmittance with visible light was 85% or more, the smoothness of the film surface was extremely good, and no fine particle defects were observed.

(Embodiment 2) FIG. 6 is a schematic sectional view of a target portion of an image pickup tube. First, an In—Sn oxide transparent conductive film having a thickness of 25 nm is formed as a target 21 on the transparent glass substrate 20 by the same method as in the first embodiment. On top of that, another hole deposition blocking layer 22 is formed by another vacuum deposition apparatus.
As a result, a cerium oxide thin film having a film thickness of 15 nm is formed.
Next, an amorphous Se film having a film thickness of 4 μm is formed as the photoconductive film 23, and an electron beam rubbing layer 24 having a film thickness of 100 is formed on the amorphous Se film by vapor deposition in an inert gas atmosphere.
A porous Sb ₂ S ₃ film having a thickness of nm is formed.

The vapor deposition substrate obtained as described above is used as an image pickup tube target and incorporated in an image pickup tube housing containing an electron gun so that the vapor deposition surface faces the electron gun, and the inside is vacuum-sealed to form a photoconductive layer. An image pickup tube was obtained. As a result of mounting the photoconductive type image pickup tube on the camera and measuring the characteristics, an increase in dark current, which is likely to occur in the image pickup tube made by using the conventional transparent conductive film, and white dot-shaped screen defects on the monitor are significantly increased. It is possible to operate at a higher voltage, and when the target voltage is set to 240V, avalanche multiplication of photocarriers occurs in the amorphous Se photoconductive film, and epoch-making high sensitivity characteristics are obtained. Was given.

[0035]

EFFECTS OF THE INVENTION According to the present invention, a high-quality transparent conductive film which activates the reaction between an evaporated substance and oxygen, has a high conductivity and a high transmittance, and is excellent in smoothness without particulate deposits is reproduced. If the transparent conductive film of the present invention is used for a light receiving device such as an image pickup tube, high performance device characteristics that have not been obtained can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a vacuum vapor deposition device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a vapor deposition boat according to an embodiment of the present invention.

FIG. 3 shows oxidized In—Sn obtained by the present invention and a conventional method.
FIG.

FIG. 4 shows oxidized In—Sn obtained by the present invention and the conventional method.
FIG.

FIG. 5: In—Sn oxide obtained by the present invention and the conventional method
FIG.

FIG. 6 is a cross-sectional view of a target portion of an image pickup tube according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Evaporation boat, 2 ... Evaporation source material, 3, 4 ... Plasma discharge electrode, 5 ... Current terminal, 6 ... Shield, 7 ... Shutter,
8 ... Rotating shaft, 9 ... Rotating disk, 10 ... Substrate, 11 ... Film thickness monitor, 12 ... Heater, 13 ... Rotating motor, 14 ... Bell jar, 15 ... Valve, 16 ... Oxygen introducing valve.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/203 Z 9545-4M 21/68 N 31/08

Claims (8)

[Claims] 1. A method for producing a transparent conductive film by evaporating a metal mainly composed of In from a vapor deposition boat in a gas atmosphere containing oxygen and vapor-depositing it on a substrate which is heated and held. A method for manufacturing a transparent conductive film, characterized in that at least a part between the substrate and the substrate is a plasma discharge region. 2. A rotary disk having a substrate arranged along the circumference thereof, a vapor deposition boat for facing the circumference of the rotary disk to vaporize a metal mainly composed of In, and the vapor deposition. An apparatus for producing a transparent conductive film, comprising means for plasma-discharging a region from a boat to the substrate. 3. The vapor deposition boat according to claim 2, wherein the vapor deposition boat has one or more through holes on a side surface thereof, an insulative hard ceramic having a recess at a central portion of an upper surface thereof, and a metal wire penetrated through the hole. Alternatively, an apparatus for manufacturing a transparent conductive film including a thin metal plate. 4. The insulating hard ceramic of the vapor deposition boat according to claim 3, wherein the insulating hard ceramic is made of Al ₂ O ₃ or Al ₂ O ₃ and SiO ₂ , and the metal wire or metal thin plate is Ir, Pt or Pt.
For manufacturing a transparent conductive film made of an alloy of Rh and Rh. 5. The method for producing a transparent conductive film according to claim 1, wherein the pressure of the gas atmosphere containing oxygen is 1 mTorr or more and 50 mTorr or less. 6. The method for producing a transparent conductive film according to claim 1, wherein the vapor deposition rate is 0.5 nm / min or more and 7.0 nm / min or less. 7. The method for producing a transparent conductive film according to claim 1, wherein the substrate temperature is 100 ° C. or higher and 300 ° C. or lower. 8. The step of manufacturing the transparent conductive film in the step of manufacturing an image pickup tube including at least a transparent substrate, a transparent conductive film, and a photoconductive film, the method according to claim 1 or 5. A method for manufacturing a photoconductive type image pickup tube, comprising: