JPH0273970A - Formation of thin film - Google Patents

Abstract

PURPOSE:To form a thin film on a base body arranged oppositely to a target by accelerating the ions in a nearly columnar plasma flow caused by arc discharge toward the target held at electric potential negative for the plasma flow and performing sputtering. CONSTITUTION:Magnetic field 7 is formed by two or more blank-core coils 6 and a high-density plasma flow caused by arc discharge is drawn into a vacuum chamber 3 from a plasma generating source 1. Both a target 10 and a base body 9 are arranged so as to pinch the plasma flow 11 and sputtering voltage is impressed to the target 10 from a sputtering power source 12 so that the target 10 is made negative for the plasma 11. Therefore an electrically- conductive transparent film low in specific resistance can be coated even on an organic film, etc., which can not be heated. Further erosion of the target is made more uniform and the utilizing effect of the target is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film forming method using arc discharge plasma flow.

[Prior Art] Transparent conductive oxide films such as indium oxide containing tin, tin oxide containing fluorine, tin oxide containing antimony, and zinc oxide containing aluminum are coated on transparent substrates such as inorganic glass or organic films. It is used as a transparent electrode for display devices such as liquid crystals and El-, and a typical example thereof is an indium oxide film (ITO) added with tin. Conventionally, ITO films with low resistivity (2XIO-'Ωcm) have been produced by heating an inorganic glass substrate to 300 to 400°C and using electron beam evaporation (EBB) to increase the reactivity and crystallinity of the substrate. The film was formed by a vapor deposition method, or a C magnetron sputtering method as shown in FIG.

[Problems to be Solved by the Invention] On the other hand, EB evaporation or DC magnetron sputtering is also used when an organic material is used as a substrate or when coating an ITO film on inorganic glass with a color filter that is used as a substrate for a liquid crystal color display. The film is formed by the method. However, since these substrates cannot be heated above 200°C, the reaction and crystallization of indium and oxygen on the substrate cannot take place sufficiently, making it impossible to achieve a low resistivity 11゛0 film (≧4X In-'Ωcm). Therefore, activation methods using plasma such as ion plating are also used as an alternative method for heating the substrate, but ion blating and magnetron sputtering based on EB evaporation utilize so-called glow discharge to generate plasma. As a result, the degree of ionization of the gas or raw material is as low as about 1%, and the chemically active ions and intermediates necessary to efficiently form transparent conductive oxides such as r = t o. The number of sexually active species is not sufficient. Therefore, although the film quality is improved to some extent, the substrate temperature is 300 to 400℃.
It is difficult to form a transparent film with low resistivity, such as when heated to . Therefore, in order to obtain low sheet resistance, the film thickness must be increased, and in order to obtain transparency, the film formation rate must be extremely slow, and even compared to film formation on a high-temperature substrate,
What was the drawback of requiring a very long film formation time?

[Means for Solving the Problems] The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to solve the above-mentioned drawbacks of the prior art. The present invention provides a new thin film forming method that can form a film at a significantly faster film forming rate than that of the previous method.

That is, the present invention was made in order to solve the problems mentioned in 011, and it is an object of the present invention to direct ions in a substantially cylindrical arc discharge plasma flow generated by arc discharge to the substantially cylindrical arc discharge plasma flow. Thin film formation characterized by performing accelerated sputtering on a target kept at a negative potential and forming a thin film on a substrate placed facing the target with the substantially cylindrical arc discharge plasma flow in between. The present invention provides a method.

FIG. 1 shows an example of an apparatus used for coating according to the method of the present invention.

In the present invention, a plasma flow generated by arc discharge is used. Such an arc discharge plasma flow is generated by applying a DC power source 4 for plasma generation between the arc discharge plasma flow generation source 1 and the anode 2 to perform arc discharge.

The arc discharge plasma flow generation source 1 is preferably a composite cathode type plasma generation device, a pressure gradient type plasma generation device, or a plasma generation device combining both. Such a plasma generator is described in Shinku Vol. 25, No. 10 (published in 1982).

A composite cathode type plasma generator consists of an auxiliary cathode with a small heat capacity and a main cathode made of L a B6, concentrates the initial discharge on the auxiliary cathode, and uses it to generate the main cathode L.
ane and main cathode fan. This is a plasma generating device in which the final cathode is used to generate arc discharge. For example, a device as shown in FIG. 3 can be mentioned. The auxiliary cathode may be a coil or a vibrator made of a high melting point metal such as W, Ta, or Mo.

In such a composite cathode type plasma generation bag,
The auxiliary cathode 52, which has a small heat capacity, is intensively heated by the initial discharge, operates as an initial cathode, and indirectly achieves 1. Since the method heats the main cathode 51 of aBe and ultimately transitions to arc discharge by the main cathode 51 of L a B a,
Before the auxiliary cathode 52 reaches a high temperature of 2,500'C or more, which affects its life, the main cathode 51 of L a B a reaches 1,500'C.
C. to 1800.degree. C. and can emit a large current of electrons, which has a great advantage in that further temperature rise of the auxiliary cathode 52 can be avoided.

A pressure gradient plasma generator is one in which an intermediate electrode is interposed between the cathode and the anode, and discharge is performed while maintaining the cathode region at about I Torr and the anode region at about 10 Torr. In addition to not damaging the cathode due to ion backflow from the anode region, the gas efficiency of the carrier gas used to create the discharge electron flow is dramatically higher than in discharge types without an intermediate electrode, and large current discharge is possible. It has the advantage of being possible.

The composite cathode type plasma generator and the pressure gradient type plasma generator each have the above-mentioned advantages.
A plasma generating device that combines both, that is, a plasma generating device that uses a composite cathode as a cathode and also has an intermediate electrode, is very preferable as the arc discharge plasma flow source 1 of the present invention because it can simultaneously obtain the above advantages.

FIG. 1 shows a composite cathode 2I as shown in FIG. 3 as an arc discharge plasma generation source l, a first intermediate electrode 2Z including an annular permanent magnet, and a second intermediate electrode 23 having a second intermediate electrode including an air core fill. The case is shown in which a device with .

In the present invention, the plasma generation source 1 and the at 2 are arranged so that the sputtering region 5 is located between them, and the magnetic field 7 directed from the plasma generation source 1 toward the anode 2 by two or more air-core coils 6. is formed, and a high-density plasma flow due to arc discharge generated from the plasma generation source 1 is drawn into the vacuum chamber 3.

Then, the target 10 and the base 9 are arranged to sandwich the arc discharge plasma flow 11, and a sputtering voltage is applied to the target 10 by the sputtering power source 12 so that the target 0 becomes negative with respect to the sheet plasma 11.

A discharge gas is introduced from the gas inlet 13. or,
It is desirable that the vacuum chamber 3 is maintained at a pressure of about 10-3 Torr or less by an exhaust means.

In the present invention, a substantially cylindrical plasma flow refers to a plasma flow whose cross section is circular, approximately circular, oval, etc., for example, approximately circular as shown in FIG. 4.

As the target IO used in the present invention, targets made of metals, alloys, their oxides, borides, carbides, silicides, or mixtures containing one or more of these can be used, and there are no particular limitations. However, when forming a metal oxide film, it is preferable to use a metal oxide target because the film forming conditions can be easily controlled and a high quality film can be obtained. In particular, when forming an indium oxide film containing tin, an indium oxide target containing 5 to 10% by weight of tin is preferred because a film with very low resistance can be obtained.

Further, in the present invention, the discharge gas introduced into the vacuum chamber 3 from the gas inlet 13 is not particularly limited, but may include the following:
Inert gases such as Ar and lle are preferred. When lle is used as an inert gas, since lle has a small atomic radius, it is unlikely to cause internal stress even if it is mixed into the film, so a film with large internal stress, such as a TiN film, is formed. It is advantageous in some cases. The gas atmosphere inside the vacuum chamber 3 includes, in addition to an inert gas such as a sputtering gas, a gas atmosphere inside the vacuum chamber 3, which is not shown in FIG.
0□ as a reaction gas by the gas introduction means provided in
, N2, etc. may be added in an amount of 0 to 40% by volume.

In the present invention, the substrate 9 on which the thin film is formed can be a substrate or film made of glass, plastic, metal, etc., and is not particularly limited, but materials with low heat resistance, such as a substrate or film made of plastic, can be used. Alternatively, the present invention can be sufficiently applied to a glass plate having an organic polymer film in advance, for example, a glass substrate for a liquid crystal color display having a color filter film.

In the present invention, the thin film formed on the substrate 9 may be a metal film, an alloy film, a metal oxide, a nitride, a boride, a silicide, or a mixture containing one or more of these. Although not particularly limited, the method of the present invention is optimal for obtaining a transparent conductive film with low resistance and high transmittance. Suitable examples of such a transparent conductive film include an indium oxide film containing tin, a tin oxide film containing antimony, and a zinc oxide film containing aluminum.

The method of the present invention can also be applied to the production of transparent electrodes for displays such as liquid crystal display elements, electrodes for solar cells, heat ray reflective glass, electromagnetic shielding glass, low-emissivity glass, and the like.

In the present invention, during film formation, the substrate 9 may be stationary or may be transported. In particular, in Fig. 1, it is advantageous in terms of equipment arrangement to carry out sputtering while conveying the paper vertically from the front to the back side, or from the back side to the front. This is preferable because film formation can be carried out using the same method.

In the present invention, by adjusting the DC power supply 4 applied to the arc discharge plasma flow generation source 1, the annular permanent magnet built in the intermediate electrode 22, 23, the current of the air core coil, etc., the diameter can be reduced to 3 cm", 10 cm, A cylindrical arc discharge plasma flow with a length of approximately 30 cm to 2 m can be easily formed.

Further, in the present invention, the distance between the surface of the arc discharge plasma flow 11 and the base body 9 is preferably about 1 to 30 cm. If the distance is closer than this, the temperature of the substrate will rise significantly by -L, making it impossible to apply it to substrates with weak heat resistance.

Furthermore, if the distance is greater than this, the particles ejected from the target by sputtering will no longer adhere to the substrate effectively.
do.

Further, in the present invention, it is preferable that the distance between the surface of the arc discharge plasma flow 11 and the tarp 10 is about 1 to 10 cm. If it is brought closer than this, the temperature of the target will drop significantly, making it impossible to use a target with a low melting point. Furthermore, if the distance is greater than this, the sputtering power will not be applied effectively.

In the present invention, a film formation rate of about 1,000 to 10,000 persons/min can be obtained, and a high-quality film can be formed at a speed about 2 to 5 times faster than conventional film formation methods such as magnetrosputtering.

For example, with an indium oxide target containing tin! When forming a TO film, 2000 to 5000 people/
An ITO film with a low resistance of 3 x In-'Ω·cm or less can be obtained at a film forming speed of about 1 minute.

[Function] Since the plasma used in the present invention utilizes arc discharge, the density of the plasma is 50 to 100% higher than that of the glow discharge type plasma used in conventional magnetron sputtering and ion blating. The degree of ionization of the gas is several tens of percent higher, and the ion density, electron density, and neutral active species density are also extremely high. By placing the target and substrate facing each other in such high-density plasma and applying a negative voltage to the target, it is possible to extract a large number of ions in the direction of the target, compared to conventional magnetron sputtering. By doing so, it is possible to realize sputtering that is 2 to 5 times faster. Furthermore, many of the atmospheric gases such as oxygen and argon take highly reactive ions and neutral active f1 states, and in addition, sputtered particles and reactive gas particles such as oxygen atoms also It passes through a high-density arc discharge plasma flow and becomes highly reactive ions and neutral active species. As a result, the reactivity at the substrate is increased, and a transparent conductive film with low resistivity can be realized at a faster deposition rate than before, even without heating the substrate.

[Example] Example 1 Using a suba-interning apparatus as shown in FIG. 1 in which a pressure gradient type arc discharge plasma flow source 1 having a composite cathode 21 as shown in FIG. A sintered body of indium oxide containing 75% by weight of
A non-alkali glass substrate (AN glass manufactured by Asahi Glass Co., Ltd. (product name)
, 10 cm x 30 cm) J- was coated with 1'O film by the following method.

First, the inside of the vacuum chamber 3 is evacuated to below] Ta. After this, the sputtering pressure was I x 10-” Torr and the oxygen partial pressure was 2
% of argon and oxygen gas in vacuum chamber 3.
introduced within. Here, a sputtering voltage of 1,400 μm was applied to the target by the sputtering power source 12, and an ITO film was formed for 1 minute while the substrate was stationary. The distance between the target 10 and the arc discharge plasma flow 11 was approximately 1 cm, the distance between the arc discharge plasma flow 11 and the substrate 9 was approximately 1 cm, and the distance between the target 10 and the substrate 9 was approximately 8 cm. The sputtering current at this time was 8Δ, and the substrate temperature increase during film formation was 200° C. or less. The characteristics of the coded ITO film are: film thickness: 300Q, resistivity: 2.8X
Transmittance 287% at 10''Ωcm and wavelength 550nm
Met.

[Comparative Example] Using a C magnetron sputtering apparatus as shown in FIG. 2 having a target size similar to that of Example 1, 7.5% by weight of tin as in Example 1 was used as the target 32.
Using the added indium oxide sintered body, an ITO film was coated on the same glass substrate as in Example 1 by the following method.

First, inside the sputtering equipment] X IQ-'Tor
After evacuation to below r, the sputtering pressure is 1×IO-
Argon and oxygen gases were introduced into the sputtering chamber through the gas inlet 35 at a pressure of 2.5 Torr and an oxygen partial pressure of 2%. Here, target 32 -
Sputtering power supply 3 with sputtering voltage of 400V
4, and an ITO film was formed for 1 minute with the substrate stationary. The sputtering current at this time was 3.0A. The distance between the target 32 and the substrate 31 was about 8 cm, and the temperature of the substrate increased by +50'C or more during film formation.

The characteristics of the coated ITO film are: film thickness: 1800
Person, specific resistance: 7.2X 10-4Ωcm, wavelength 55
The transmittance at 0 nm was 280%.

As described above, the thin film forming method according to the present invention is similar to the conventional D
A transparent conductive oxide film with low resistivity can be formed at a deposition rate 1.5 to 5 times faster than C magnetron sputtering.

[Effects of the Invention] The present invention can be applied to organic films that cannot be heated, inorganic glass substrates coated with organic films, etc. at a film formation rate 1.5 to 5 times faster than conventional film formation methods such as magnetron sputtering. This method has an excellent effect in that a transparent conductive film can be coated with a specific resistance equal to or lower than that of a film made by conventional methods. Furthermore, unlike magnetron sputtering, the present invention does not use a magnet on the back surface of the target, so it has the excellent effect of making the erosion of the target more uniform and improving the utilization efficiency of the target.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of an apparatus used for coating according to the method of the present invention, FIG. 2 is a sectional view showing an example of an apparatus for a conventional magnetron sputtering method, and FIG. FIG. 4 is a cross-sectional view showing an example of a composite cathode as a cathode of a plasma generation source. FIG. 4 is a cross-sectional view showing an example of a substantially cylindrical arc discharge plasma flow cross section used in the present invention. 1: Arc discharge plasma flow source 2 Gonode 3: Vacuum chamber 4: DC power supply for plasma generation 5 Varnish buttering area 6: Air core coil 7: Direction of magnetic field created by the air core coil 9: Base 10: Target 11: Arc Discharge plasma flow 12 Varnish buttering power source 13: Gas inlet 21: Composite cathode 22: First intermediate electrode 23 with built-in annular permanent magnet: Second intermediate electrode 31 with built-in air core coil: Substrate 32: Target 33: Permanent magnet 34 Varnish buttering power source 35: Gas inlet 36: Plasma 37: Erosion area 51: LaBa main cathode 52: 53: 54: 55: 56: 57: 58: Ta vibe auxiliary cathode Disc made of W for protecting the cathode Cylinder made of Mo. Disc-shaped heat shield made of Mo. Cooling water. Cathode support stand made of stainless steel. Gas inlet. Diagram. Procedure amendment. December 1999.

Claims (1)

[Claims] 1. Ions in a substantially cylindrical arc discharge plasma flow generated by arc discharge are accelerated to a target maintained at a negative potential with respect to the substantially cylindrical arc discharge plasma flow. A method for forming a thin film, comprising performing sputtering to form a thin film on a substrate disposed facing the target with the substantially cylindrical arc discharge plasma stream in between. 2. The thin film forming method according to claim 1, wherein the transparent conductive film is formed on a transparent or semitransparent substrate.