JPH042774A - Method and apparatus for formation of transparent conductive film - Google Patents

Abstract

PURPOSE:To obtain the transparent conductive film of low specific resistance even in low temp. and to prevent the generation of traces of abnormal electric discharge in DC magnetron sputtering by preventing negative-charged particles from rushing into a base plate on which film is to be formed. CONSTITUTION:The electrode 10 for catching the negative-charged particles which is formed in an annular shape made of high melting point metallic wire, such as wire of Mo, of 1mmphi thickness is provided in the middle between an ITO target 1 and a base plate holder 3 in the vacuum vessel 4 of a DC magnetron sputtering apparatus used for the formation of ITO film. The diameter of annular electrode 10 is smaller than that of the target, and set almost right above the errosion area of the target 10. The electrode 10 is kept in earth potential or in positive potential. By this method, the negative-charged particles rushing into the base plate 2 on which film is to be formed from the plasma generated in the vicinity of the target 1 are caught, and the object is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for forming a transparent conductive film.

[Prior Art 1] Conventionally, direct current or high frequency nagnetron sputtering, CVD, a spray method, etc. have been used to form a transparent conductive film. In particular, an ITO film formed by flow magnetron sputtering is widely used for the t-pole arranged by a transparent conductor 1iai of a liquid crystal display such as a simple matrix. FIG. 6 shows a conventional example of a DC magnetron sputtering apparatus used for general ITO film formation.
and the substrate holder 3 are arranged facing each other, and the substrate holder 3
A film-forming substrate 2 made of an insulating material such as glass is fixed to the substrate.

Heating during film formation is performed by a heater 5 in a vacuum container 4.
Inside, a few percent of 02 gas was introduced into the Ar gas, and the pressure was increased to several hundred mPa.
A DC power supply 6 is disposed on the target 1, which is maintained at a pressure of , and a glow discharge is generated by applying a negative voltage to the target 1.

As a result, the target 1 is sputtered, and a sputtered ITO film is formed on the film-forming substrate 2. In order to obtain an ITO film with low resistivity, an optimal oxygen partial pressure in the Ar atmosphere and high temperature heating of the substrate on which the film is to be formed are required. -Radiographically, in order to obtain a film with a specific resistance of about 2XlO-'Ω·Cm, high-temperature heating of 300° C. or higher is performed.

[Problem to be solved by the invention]

However, in the conventional DC magnetron sputtering method described above, the plasma generated near the target spreads to the substrate on which the film is to be deposited, and the ITO film is damaged by the inrush of negatively charged particles in the plasma, resulting in 2XIO'''4Ωcm or less. Therefore, in recent years, as liquid crystal displays have become larger and display elements have become smaller, ITO wiring electrodes have become smaller and smaller. This results in an increase in the resistance value of the ITO film, which has the problem of deterioration of display quality due to voltage drop.Furthermore, when ITO is formed on an organic film, 20
The restriction on the heating temperature of the organic film, which must be below 0°C, is a barrier to obtaining a low resistivity film, which poses problems not only in display quality but also in process design. .

In addition, dielectric breakdown caused by the potential difference between the potential of the substrate to be filmed, which is charged due to exposure to plasma during ITO film formation, and the substrate holder, which is the ground potential, induces abnormal discharge on the ITO film, and the discharge A mark remains in the shape of a lightning bolt,
This has the problem of significantly affecting yield and quality and increasing costs.

The present invention is intended to solve these problems, and its purpose is to provide a transparent conductive film with low specific resistance not only in high-layer film formation but also in low-temperature film formation. An object of the present invention is to provide a method and apparatus for forming a transparent conductive film that can prevent abnormal discharge marks from occurring due to dielectric breakdown occurring on a substrate.

[Means to solve the problem]

The method and apparatus for forming a transparent conductive film of the present invention include, in DC magnetron sputtering, a negatively charged particle trapping electrode is provided between a target and the film-forming substrate facing the target; A means for holding the negatively charged particle trapping electrode at a ground potential or a positive potential is provided, and the negatively charged particles rushing into the substrate to be deposited from the plasma generated near the target are captured in the front stage of the substrate to be deposited. The film is formed while preventing the negatively charged particles from entering the substrate on which the film is formed.

[Function] According to the above configuration of the present invention, in order to capture negatively charged particles that rush into the deposition target substrate from the plasma generated near the target, the film formed on the deposition target substrate is Since the number of negatively charged particles that enter the ITO pus is reduced and the damage to the ITO film is reduced, the crystallinity of the film is not impaired and the resistance can be lowered even at low temperatures. Further, since the charged potential of the substrate to be film-formed due to the inrush of negatively charged particles can be controlled, abnormal discharge can be controlled.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained in detail based on the drawings.

Although FIG. 1 shows a first embodiment of the present invention, the same reference numerals are used for parts corresponding to the conventional example shown in FIG. 6, and detailed explanation thereof will be omitted.

That is, the negatively charged particle trapping electrode 10 of this embodiment is formed into a ring shape with a wire made of a high melting point metal such as molybdenum and has a thickness of 1 mm, and is connected to the target 1 and the substrate holder 3 as shown in FIG. Place it in the middle. Further, the ring diameter of the negatively charged particle capturing electrode 10 is smaller than the target diameter, and is installed almost directly above the erosion area of the target l. And DC power supply 6 is target 1
The DC power supply 11 is arranged at the negatively charged particle trapping electrode 10 and is configured to apply a negative voltage with respect to the ground potential of the vacuum vessel 4, and the DC power supply 11 is arranged at the negatively charged particle capturing electrode 10 and is configured to apply a positive voltage with respect to the ground potential.

Next, the operation of this embodiment will be explained. Figure 2 shows the negatively charged particle trapping electrode 1 when using the device configuration shown in Figure 1.
This is the dependence of the current flowing through the DC power supply 11 on the voltage applied by the DC power supply 11. A constant current is flowing through the target 1 from a DC power supply 6 that is controlled by a constant current, and by increasing the voltage of the DC power supply 11, the current flowing through the negatively charged particle trapping electrode 10 increases, and the current flowing through the target 1 is increased. It saturates when it becomes approximately equal to the flowing current value. That is, a closed current circuit is formed between the target l and the negatively charged particle trapping electrode lO.

The effect on plasma caused by installing the negatively charged particle trapping electrode 10 will be explained. Figure 3 shows the ζ plasma generation conditions, with the discharge pressure set at 0.6 Pa, only Ar introduced, and the discharge current set at 0.4 A. The voltage applied to the negatively charged particle capturing electrode 10 of the Ar emission intensity measured by emission spectroscopy for the plasma between the negatively charged particle capturing electrode 10 and the plasma between the negatively charged particle capturing electrode 10 and the film formation substrate 2 It is dependence. Compared to the conventional example in which the negatively charged particle trapping electrode 10 is not installed, in this example, the emission intensity of the plasma between the target 1 and the negatively charged particle trapping electrode 10 increases as the voltage applied to the negatively charged particle trapping electrode 10 increases. One phenomenon in which the plasma emission intensity between the negatively charged particle trapping electrode l〇 and the film-forming substrate 2 was measured to decrease gradually was that the negative charged particle trapping electrode 1 This means a decrease in plasma density between the electrode 10 and the film-forming substrate 2,
A similar decrease in plasma density was also confirmed in the probe measurement near the film-forming substrate 2.

Moreover, FIG. 4 was obtained by probe measurement.

This is the dependence of the space potential and floating potential near the film-forming substrate 2 on the voltage applied to the negatively charged particle capturing electrode 10.

It can be seen that the space potential and floating potential increase compared to the conventional example. It is known that the charged potential of the substrate 2 to be film-formed is almost equal to the floating potential, and the potential difference between the ground potential and the floating potential is the difference between the grounded substrate holder 3 and the substrate 2 to be film-formed.
This corresponds to the potential difference of . The main cause of abnormal discharge is dielectric breakdown that occurs between the substrate holder 3, which is grounded, and the film-forming substrate 2, which is charged to a floating level t1. This occurs when the potential difference of the film-forming substrate 2 is equal to or higher than the dielectric breakdown voltage threshold, and this threshold value also differs depending on the state of the plasma. However, according to this embodiment, the potential difference between the ground potential and the floating potential can be made smaller than in the conventional example, and it is also possible to eliminate the potential difference.

According to the configuration of this embodiment, the plasma density between the target 1 and the negatively charged particle capturing electrode 10 is maintained or increased, while the plasma density between the negatively charged particle capturing electrode 10 and the deposition substrate 2 is reduced. As a result, damage to the ITO film formed on the film-forming substrate 2 from plasma can be reduced.

Furthermore, the floating potential can be controlled by the voltage applied to the electron trapping electrode, and the insulation potential difference between the substrate holder 3 and the film-forming substrate 2, which are at ground potential, can be reduced.

In the conventional example, for example, the film forming conditions were A with a discharge pressure of 0.6 Pa.
Introducing only r, discharge current 0.4A, film forming temperature 150℃
The specific resistance of the ITO film obtained when
・In contrast, in this example, when the same film-forming conditions were used and the applied voltage of 10 V and the electron trapping voltage was 18 V, the ITO film obtained was as large as 4×10-'Ω・cm. was gotten. In addition, in the conventional example, ITO on the glass substrate surface
On the other hand, abnormal discharge marks on the film surface due to abnormal discharge were confirmed with a probability of nearly 100%, whereas in this example, no abnormal discharge marks occurred at all.

FIG. 5 shows a second embodiment of the present invention, and parts corresponding to the first embodiment are designated by the same reference numerals.
A detailed explanation thereof will be omitted.

In this embodiment, the negatively charged particle capturing electrode 10 is installed in the first
Although it is similar to the embodiment, the positive current side of the DC power supply 6 is arranged in the negatively charged particle capturing electrode lO, and the structure of this embodiment is also short-circuited with the electrode 10 of the DC power supply 11. The voltage applied to the particle trapping electrode 10 can be controlled by the DC power supply 11, and the effects described in the first embodiment can be achieved.

Although each embodiment of the present invention has been described above, the present invention is of course not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, a 1 mmφmm type electrode with a thickness of 1 mm was used for the negatively charged particle capturing electrode 10, but a plate-shaped electrode may also be used, although this may affect the film formation rate to some extent.
Further, the shape of the negatively charged particle capturing electrode is not limited to a circular ring, but may be polygonal, or may be box-shaped surrounding the target.

Furthermore, as the material of the electrode for capturing negatively charged particles in the above embodiments, a metal material for processing such as stainless steel may be used. However, since capturing the negatively charged particles increases the temperature, A metal with a high melting point is preferable because it is a small material and prevents film contamination due to evaporation.

Furthermore, it goes without saying that similar effects can be obtained not only in a stationary opposing type DC magnetron sputtering apparatus but also in a passing type DC magnetron sputtering apparatus.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an ITO film with a lower specific resistance at a lower temperature than in the past, and it is possible to improve the quality of large liquid crystal panels, color displays, etc. Furthermore, the occurrence of defects due to abnormal discharge traces is eliminated, yields are improved, and panel costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the structure of a DC magnetron sputtering apparatus according to a first embodiment of the present invention. FIG. 2 is a graph for explaining the effect of the embodiment. FIG. 3 is a graph for explaining the effect of the embodiment. FIG. 4 is a graph for explaining the effect of the embodiment. FIG. 5 is a sectional view of the structure of a magnetron sputtering apparatus according to a second embodiment of the present invention. FIG. 6 is a sectional view of the configuration of a conventional DC magnetron sputtering apparatus. ITO target Substrate to be deposited Substrate holder Vacuum container DC power supply Magnet Electrode for capturing negatively charged particles Applicant Seiko Epson Corporation Representative Patent attorney Kizobe Suzuki (1 other person) Urgent? 2m!
Standing up - i Yujuku for 11a Denka [V]

Claims (2)

[Claims] (1) In DC magnetron sputtering, negatively charged particles that rush into the substrate to be film-formed from plasma generated near the target are captured at a stage before the substrate to be film-formed, and the negatively charged particles are A method for forming a transparent conductive film characterized by forming the film while preventing the film from penetrating into the substrate. (2) A means for providing a negatively charged particle trapping electrode between the target and the film forming substrate facing the target, and maintaining the negatively charged particle trapping electrode at a ground potential or a positive potential. An apparatus for forming a transparent conductive film, comprising: