JP2002241926A - Method and system for film deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly deposit a zinc oxide type transparent conductive film having widely controllable resistivity on a substrate of large area. SOLUTION: Because the particles of a film material composed essentially of ZnO and containing compounds of group III elements, such as Al2O3, are ionized with high efficiency and implanted in a film by optimum kinetic energy, the surface migration of the group III impurity elements, such as Al, can be accelerated and the dispersion of the impurity elements can be performed more uniformly as compared with that by the other methods. As a result, proper impurity control can be facilitated and material synthesis based on the theoretical prediction can be done, and the zinc oxide type transparent conductive film of low resistivity can be synthesized. Further, by carrying out film deposition while properly controlling the atmospheric pressure of gaseous oxygen and gaseous nitrogen, film characteristics can be widely controlled, e.g. from 2 μΩ to infinity in the case of resistivity.

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 forming a transparent conductive film having a low specific resistance or various specific resistances on a substrate having a large area.

[0002]

2. Description of the Related Art An ITO (indium and tin oxide) film is widely used as a transparent conductive film of a display element such as a liquid crystal. Indium is an expensive metal and a rare metal in terms of resources. Considering the increase in the usage of the display element, it is clear that the film material will soon become tight.

On the other hand, it has long been known that a zinc oxide film also has transparent conductivity. Zinc resources are much more abundant than indium, and if the ITO film can be replaced with a zinc oxide-based transparent conductive film, there are great merits in terms of resources and costs.

[0004] The zinc oxide-based transparent conductive film as described above,
Conventionally, films are formed by various methods such as sol-gel method, spray method, MOCVD method, RF sputtering method, pulsed laser evaporation method, etc., but the specific resistance as low as that of ITO film cannot be obtained or low specific resistance can be obtained. However, it is limited only to a very small substrate size.

[0005] Recently, attempts have been made actively to lower the specific resistance by adding various impurities to a zinc oxide-based transparent conductive film, and it has been demonstrated that characteristics comparable to those of ITO can be obtained. It is becoming.

[0006]

However, even with the above method of adding impurities, a zinc oxide-based transparent conductive film having a uniform and low specific resistance has not been formed on a large-area substrate.

Accordingly, an object of the present invention is to form a zinc oxide-based transparent conductive film having a low specific resistance uniformly on a large-area substrate.

Another object of the present invention is to form a zinc oxide-based transparent conductive film having an arbitrary specific resistance on a substrate.

[0009]

In order to solve the above-mentioned problems, a film forming method according to the present invention comprises the steps of: supplying a plasma beam to a material evaporation source arranged as an anode in a film forming chamber; A film forming method for evaporating a film material of a source and attaching the film material to a surface of a substrate disposed in a film forming chamber, wherein the film material is mainly composed of zinc oxide and oxidized by a Group 3 element or a Group 3 element. It is characterized by being added with a substance.

In the above-mentioned film forming method, the film material is made of zinc oxide as a main component and added with a Group 3 element or an oxide of a Group 3 element. A transparent conductive film can be provided, and a group III element or an oxide of a group III element can suppress deterioration of the film quality due to excessive generation of oxygen vacancies, and can appropriately reduce the specific resistance of the transparent conductive film. Furthermore, in the above-described film forming method, the film material evaporated from the material evaporation source can be activated by the plasma beam, and the film material particles having an appropriate energy can be incident on the substrate. A transparent conductive film having characteristics and good adhesion and strength can be uniformly formed on a large-area substrate.

In a specific embodiment of the above method, an oxygen gas or a gas containing oxygen and a group V element is supplied as an atmosphere gas around the substrate during the film formation. In this case, the amount of oxygen deficiency in the transparent conductive film and the efficiency of addition of the Group 3 impurity element can be controlled, so that the specific resistance of the transparent conductive film can be adjusted to a target value.

Further, since the electronic device of the present invention has the transparent conductive film formed by the above-described film forming method, it can not only exhibit excellent optical characteristics with a high degree of integration but also wastes scarce resources. There is no.

Further, the film forming apparatus of the present invention comprises a plasma source for supplying a plasma beam into a film forming chamber, a hearth arranged in the film forming chamber to guide the plasma beam, and What is claimed is: 1. A film forming apparatus comprising: a substrate holding means for holding a substrate in opposition to a hearth, wherein the film material contains zinc oxide as a main component and an oxide of a Group 3 element or a Group 3 element added thereto. .

In the above film forming apparatus, since the film material is made of zinc oxide as a main component and added with a Group 3 element or an oxide of a Group 3 element, a zinc oxide-based material comprising abundant resources capable of responding to an increase in demand. A transparent conductive film can be provided;
The specific resistance of the transparent conductive film can be reduced by an oxide of a Group 3 element or an oxide of a Group 3 element. Further, in the above-described film forming apparatus, the film material evaporated from the material evaporation source can be activated by the plasma beam, so that a transparent conductive film having excellent electric characteristics and good adhesion and strength can be obtained. It can be formed uniformly on a substrate having an area.

In a specific aspect of the above-mentioned apparatus, the apparatus further comprises a gas supply means for supplying an oxygen gas or an atmosphere gas containing a gas containing oxygen and a group V element into the film forming chamber. In this case, since the composition ratio of oxygen in the transparent conductive film can be controlled, the specific resistance of the transparent conductive film can be adjusted to a target value, and the film remaining in the formed transparent conductive film can be adjusted. Stress can be controlled.

In a specific mode of the above-mentioned apparatus, the apparatus further comprises a magnetic field control member which is composed of a magnet or a magnet and a coil arranged annularly around the hearth and controls a magnetic field above and close to the hearth. The plasma source is a pressure gradient type plasma gun utilizing arc discharge. In this case, the magnetic field control member corrects the plasma beam incident on the hearth with a cusp-shaped magnetic field, thereby forming a film having a more uniform thickness.

[0017]

FIG. 1 is a diagram schematically illustrating an entire structure of a film forming apparatus according to an embodiment of the present invention. The film forming apparatus includes a vacuum chamber 10 serving as a film forming chamber, a plasma gun 30 serving as a plasma source for supplying a plasma beam PB into the vacuum chamber 10, and a plasma beam PB disposed at the bottom in the vacuum chamber 10. An anode member 50 is provided, and a transport mechanism 60 for appropriately moving a substrate holding member WH holding a substrate W on which a film is to be formed above the anode member 50.

The plasma gun 30 is disclosed in Japanese Patent Laid-Open No. 9-1942.
No. 32, etc.
The main body is provided on the side wall of the vacuum vessel 10.
It is mounted on the tubular part 12. This body part is the cathode 3
1 comprises a glass tube 32 one end of which is closed. Moth
In the lath tube 32, a cylinder 3 made of molybdenum Mo is provided.
3 are fixed to the cathode 31 and are arranged concentrically.
LaB inside the cylinder 33 ₆Disk 34 and tongue formed by
And a pipe 35 formed of a barrel Ta.
End of glass tube 32 opposite to cathode 31
And an end of the cylindrical portion 12 provided in the vacuum container 10.
Means that the first and second intermediate electrodes 41 and 42 are concentrically arranged in series.
Is placed. One of the first intermediate electrodes 41 has a plasma
Built-in annular permanent magnet 44 for converging beam PB
Have been. The plasma beam is also provided in the second intermediate electrode 42.
Electromagnetic coil 45 for converging PB is built in
You. In addition, around the cylindrical portion 12, the gas generated on the cathode 31 side is formed.
From the first and second intermediate electrodes 41 and 42
Steering for guiding plasma beam PB into vacuum vessel 10
A coil 47 is provided.

The operation of the plasma gun 30 is controlled by a gun driving device (not shown). This allows
The power supply to the cathode 31 can be turned on / off, the supply voltage to the cathode 31 can be adjusted, and the power supply to the first and second intermediate electrodes 41 and 42, the electromagnet coil 45, and the steering coil 47 can be adjusted. be able to. That is, the intensity and distribution of the plasma beam PB supplied into the vacuum vessel 10 can be controlled.

A pipe 35 disposed at the innermost side of the plasma gun 30 introduces a carrier gas composed of an inert gas such as Ar, which is a source of the plasma beam PB, into the plasma gun 30 and the vacuum vessel 10. It is connected to an inert gas source 90 via a flow meter 93 and a flow control valve 94.

The anode member 50 disposed in the lower portion of the vacuum vessel 10 includes a hearth 51 which is a main anode for guiding the plasma beam PB downward, and an annular auxiliary anode 52 disposed therearound.

The former hearth 51 is formed of a conductive material and is supported by a grounded vacuum vessel 10 via an insulator (not shown). The hearth 51 is controlled to an appropriate positive potential by the anode power supply 80, and the plasma beam PB emitted from the plasma gun 30 is
Is sucked down. The hearth 51 has a through-hole 51a in the center where the plasma beam PB from the plasma gun 30 is incident, into which a rod-shaped material rod 53 as a material evaporation source is loaded. The material rod 53 is obtained by sintering and solidifying a powder obtained by mixing a ZnO powder, which is a main component, and an oxide of a group III element, Al ₂ O ₃ , as a film material. To generate a material vapor for forming a transparent conductive film containing zinc oxide as a main component on the substrate. The material supply device 58 provided at the lower portion of the vacuum vessel 10 has a structure in which the material rods 53 are sequentially loaded into the through holes 51a of the hearth 51 and the loaded material rods 53 are gradually raised. Even if the upper end of the heat sink evaporates and is consumed, the upper end can always be projected from the recess of the hearth 51 by a fixed amount.

The latter auxiliary anode 52 is constituted by an annular container arranged concentrically around the hearth 51. The annular container accommodates an annular permanent magnet 55 made of ferrite or the like and a coil 56 concentrically laminated therewith. The permanent magnet 55 and the coil 56 are magnetic field control members, and form a cusp-shaped magnetic field immediately above the hearth 51. Thereby, the direction and the like of the plasma beam PB incident on the hearth 51 can be corrected.

The coil 56 in the auxiliary anode 52 constitutes an electromagnet.
An additional magnetic field is formed so as to be in the same direction as the magnetic field on the center side generated by. That is, by changing the current supplied to the coil 56, the direction of the plasma beam PB incident on the hearth 51 can be finely adjusted.

The container of the auxiliary anode 52 is formed of a conductive material similarly to the hearth 51. The auxiliary anode 52 is attached to the hearth 51 via an insulator not shown. The electric field above the hearth 51 can be complementarily controlled by changing the voltage applied from the anode power supply 80 to the auxiliary anode 52. That is, when the potential of the auxiliary anode 52 is made the same as that of the hearth 51, the plasma beam PB is also attracted to the plasma beam PB and the plasma beam PB
Supply is reduced. On the other hand, when the potential of the auxiliary anode 52 is reduced to the same degree as that of the vacuum vessel 10, the plasma beam PB is drawn to the hearth 51, and the material rod 53 is heated.

The transfer mechanism 60 functions as a substrate holding means, and includes a plurality of rollers 62 arranged at equal intervals in the horizontal direction in the transfer path 61 to support the edge of the substrate holding member WH. The substrate holding member W is rotated at an appropriate speed.
A driving device (not shown) for moving H in a horizontal direction at a constant speed.

The oxygen gas supply device 71 is a gas supply means for supplying an appropriate amount of oxygen gas to the vacuum vessel 10 at an appropriate timing as an atmospheric gas. A supply line from an oxygen gas source 71a that contains oxygen gas is connected to the vacuum vessel 10 via a flow control valve 71b and a flow meter 71c.

The nitrogen gas supply device 72 is a gas supply means for supplying an appropriate amount of nitrogen gas to the vacuum vessel 10 at an appropriate timing as an atmospheric gas. A supply line from a nitrogen gas source 72a containing nitrogen gas is connected to the vacuum vessel 10 via a flow control valve 72b and a flow meter 72c.

The inert gas supply device 73 is for supplying an atmospheric gas consisting of an inert gas such as Ar to the vacuum vessel 10 at an appropriate timing at an appropriate amount. The atmospheric gas branched from the inert gas source 90 is supplied to the gas supply device 73.
Is directly introduced into the vacuum vessel 10 through the flow control valve 73b and the flow meter 73c.

The exhaust device 76 includes an exhaust pump 76b
Thereby, the gas in the vacuum vessel 10 is appropriately exhausted through the vacuum gate 76a. Further, the vacuum pressure measuring device 77 can measure the partial pressure of oxygen gas, Ar gas and the like in the vacuum vessel 10, and the measurement result is monitored by the pressure control device 78. The pressure control device 78, based on the measurement result of the vacuum pressure measuring device 77, supplies the oxygen gas supply device 71, the nitrogen gas supply device 72, the inert gas supply device 73, and the exhaust device 7
By controlling the operation of Step 6, the partial pressures of oxygen gas, nitrogen gas, Ar gas and the like in the vacuum vessel 10 are controlled to target values.

The operation of the film forming apparatus shown in FIG. 1 will be described below. During film formation by this film forming apparatus, a discharge is generated between the cathode 31 of the plasma gun 30 and the hearth 51 in the vacuum vessel 10, thereby generating a plasma beam PB. The plasma beam PB reaches the hearth 51 while being guided by a magnetic field determined by the steering coil 47 and the permanent magnet 55 in the auxiliary anode 52. The material rod 53 of the hearth 51 is heated by the electric current from the plasma beam PB, and the material rod 53 sublimates, from which vapor of the film material is emitted. This vapor is ionized by the plasma beam PB and adheres to the surface of the substrate W with energy corresponding to the potential of the hearth 51 to form a film.

According to the above-mentioned film forming method, film material particles containing ZnO as a main component and containing a Group 3 element oxide such as Al ₂ O ₃ are ionized with high efficiency and are driven into the film with an optimum kinetic energy. Therefore, the surface migration of the group 3 impurity element such as Al is promoted, and the impurity element can be more uniformly dispersed as compared with other methods. As a result, appropriate impurity control is easily performed, a substance can be synthesized based on theoretical prediction, and a zinc oxide-based transparent conductive film having low specific resistance can be synthesized. Further, at this time, by forming the film while appropriately controlling the atmospheric pressure of the oxygen gas and the nitrogen gas, it became possible to adjust the film quality in a wide range from 2 μΩm to infinity in terms of specific resistance.

The adjustment of the specific resistance will be specifically described. The amount of oxygen vacancies in the transparent conductive film can be adjusted by adjusting the atmospheric pressure of oxygen gas, and by adjusting the atmospheric pressure of nitrogen gas. The efficiency of adding an impurity element such as Al can be adjusted. As a result, the mobility and carrier density of the zinc oxide-based transparent conductive film can be widely adjusted, and by appropriately selecting the film forming conditions, from a low-resistivity film to a high-resistivity film. Can be widely generated.

Further, according to the above method, the magnetic field above the hearth 51 can be adjusted by the permanent magnet 55 and the coil 56 which are magnetic field control members for beam correction, so that the flying direction of the evaporated particles evaporated from the material rod 53 can be adjusted. Can be controlled, and the film-forming rate distribution on the substrate W can be adjusted in accordance with the plasma activity distribution above the hearth 51 and the reactivity distribution on the substrate W, and a uniform thin film can be obtained over a wide area. Can be. To explain this point more specifically, the above-mentioned reactivity on the substrate W refers to the oxidation reaction on the substrate when the metal vapor reaches the substrate and reacts with the oxygen element to form an oxide film. Means ease of progress. It is considered that this reactivity is affected by the plasma activity which affects the activation states of oxygen and metal elements, in addition to the substrate temperature. For example, if a film formation rate distribution is adopted in which the film growth rate is reduced at the end portion of the substrate W where the plasma activity is low and the reactivity tends to be low, the low reactivity is obtained at the end portion of the substrate W. It is possible to form a film in which oxygen is sufficiently taken in over time to compensate. That is, it is possible to make the film quality distribution in which the oxygen content is balanced over the entire substrate W uniform.

FIG. 2 shows an electronic device made by the apparatus of FIG. 1, specifically, an LCD (liquid crystal display).
FIG. 2 is an enlarged sectional view conceptually illustrating the structure of FIG. FIG.
FIG. 2A shows one substrate member constituting the LCD, FIG. 2B shows the other substrate member constituting the LCD,
FIG. 2C shows the structure of the LCD main body formed by joining the pair of substrate members shown in FIGS. 2A and 2B.

In FIG. 2A, on a substrate W made of transparent glass, a plurality of color filter layers CF are formed in an appropriate arrangement via a light shielding area MA. On the color filter layer CF and the light shielding area MA, a zinc oxide-based transparent conductive film T of low specific resistance formed by the apparatus of FIG.
F is formed uniformly.

In FIG. 2B, a transparent conductive film TF of zinc oxide type having a low specific resistance formed by the apparatus of FIG. 1 is formed on a substrate W made of transparent glass. In the transparent conductive film TF, a portion corresponding to the light shielding region MA in FIG. 2A is removed by etching, and an integrated circuit region DA in which circuit elements such as transistors are formed is formed in this portion. .

In FIG. 2C, the liquid crystal material layer LF is sandwiched between a pair of substrate members shown in FIGS. 2A and 2B and they are fixed. At this time, since the transparent conductive films TF of low specific resistance provided on the respective substrate members are arranged to face each other, the optical characteristics of the liquid crystal material layer LF change due to the action of the electric field applied between the transparent conductive films TF. I do.

In the above LCD, the transparent conductive film TF having a small specific resistance can be uniformly formed at a relatively low temperature on a large-area substrate W, so that the integration degree is high, the difference in contrast is large, and high-speed operation is possible. It is possible to provide a display device.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment. For example, as a Group 3 element or an oxide of a Group 3 element added to ZnO, instead of Al ₂ O ₃ , B ₂ O ₃ , G
It can be used _{a 2 O 3, lu 2 O} 3 or the like. Also,
Instead of N ₂ gas of the group V element used as the atmospheric gas,
O, NO ₂ , N ₂ O, P and the like can be used.

Further, the transparent conductive film of the above embodiment is formed of FP
In addition to D, it can be used as a transparent electrode for various electronic devices. For example, a transparent conductive film having a low specific resistance can be formed as a transparent electrode of a solar cell by the above film forming apparatus. Further, a high-resistance ZnO film constituting a surface acoustic wave device can be formed by the above film forming apparatus.

[0042]

As is apparent from the above description, according to the film forming method of the present invention, the film material is composed mainly of zinc oxide.
Since an oxide of a Group III element or a Group III element is added, a zinc oxide-based transparent conductive film comprising abundant resources capable of responding to an increase in demand can be provided. Deterioration of the film quality due to excessive generation of oxygen vacancies is suppressed by the substance, and the specific resistance of the transparent conductive film can be reduced. Furthermore, in the above-described film forming method, the film material evaporated from the material evaporation source can be activated by the plasma beam, and the film material particles having an appropriate energy can be incident on the substrate. A transparent conductive film having characteristics and good adhesion and strength can be uniformly formed on a large-area substrate.

Further, according to the electronic device of the present invention, not only can excellent optical characteristics be exhibited with a high degree of integration, but also rare resources are not wasted.

Further, according to the film forming apparatus of the present invention, since the film material is composed mainly of zinc oxide and added with a Group 3 element or an oxide of a Group 3 element, abundant resources capable of responding to an increase in demand. And a specific resistance of the transparent conductive film can be reduced by a Group 3 element or an oxide of a Group 3 element. further,
In the above film forming apparatus, since the film material evaporated from the material evaporation source can be activated by the plasma beam, the transparent conductive film having excellent electric characteristics and good adhesion and strength can be formed over a large area. It can be formed uniformly on a substrate.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall structure of a film forming apparatus according to a first embodiment.

FIGS. 2A, 2B, and 2C are diagrams illustrating a structure of an LCD formed by the film forming apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vacuum container 30 Plasma gun 50 Anode member 51 Hearth 53 Material rod 58 Material supply device 60 Transport mechanism 71 Oxygen gas supply device 72 Nitrogen gas supply device 73 Inert gas supply device 76 Exhaust device 77 Vacuum pressure measuring device 78 Pressure control device 80 Anode power supply device PB Plasma beam W Substrate

Claims (6)

[Claims] 1. A surface of a substrate disposed in a film forming chamber by supplying a plasma beam to a material vapor source disposed as an anode in a film forming chamber to vaporize a film material of the material vapor source. A film forming method, wherein the film material is a material containing zinc oxide as a main component and a Group 3 element or an oxide of a Group 3 element added thereto. 2. The film forming method according to claim 1, wherein an oxygen gas or a gas containing oxygen and a group V element is supplied as an atmosphere gas around the substrate during the film formation. 3. An electronic device comprising a transparent conductive film formed by the film forming method according to claim 1. 4. A plasma source for supplying a plasma beam into a film forming chamber, a hearth arranged in the film forming chamber to guide the plasma beam, and a substrate held in the film forming chamber so as to face the hearth. A film holding device, comprising: a film material containing zinc oxide as a main component and a Group 3 element or an oxide of a Group 3 element added thereto. . 5. An oxygen gas or oxygen and 5
5. The film forming apparatus according to claim 4, further comprising gas supply means for supplying an atmosphere gas containing a gas containing a group element. 6. A magnetic field control member, comprising a magnet or a magnet and a coil arranged in an annular shape around the hearth, for controlling a magnetic field above and close to the hearth, wherein the plasma source uses an arc discharge. 6. A pressure gradient type plasma gun as set forth in claim 5.
A film forming apparatus according to any one of the above.