JP2008190016A - Method for forming electric wiring or electrode for liquid crystal display, which does not have thermal defect and is superior in adhesiveness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming electric wiring or an electrode for a liquid crystal display, which is made from a copper thin film, is superior in adhesiveness to the surface of a glass substrate and does not have such a thermal defect as a hillock and a void. <P>SOLUTION: The method for forming electric wiring or the electrode for the liquid crystal display, which does not have the thermal defect and is superior in adhesiveness, includes: using a copper target having a composition comprising 0.04 to 1 mass% oxygen and the balance Cu with unavoidable impurities; and sputtering the target in an inert gas atmosphere or in an inert gas atmosphere containing 3 vol% or less oxygen. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a wiring or electrode for a liquid crystal display device comprising a copper thin film which is excellent in adhesion to the surface of a glass substrate and does not cause thermal defects such as hillocks and voids.

In general, a liquid crystal display device such as a flat panel display has a wiring made of a metal thin film in close contact with a glass substrate surface, and a TFT transistor is provided at an intersection of the metal thin film. The gate electrode of the TFT transistor is also formed of a metal thin film. The wiring or electrode made of the metal thin film is generally formed by sputtering on the surface of the glass substrate using a target, and the wiring and electrode made of the metal thin film formed on the surface of the glass substrate are a gate insulating film of a liquid crystal display device, In the step of forming an amorphous silicon film or the like by PECVD (plasma chemical vapor deposition), the film is heated to about 300 to 500 ° C. It is known that a pure copper thin film is used as the metal thin film serving as the wiring or electrode. Recently, in order to improve adhesion to the substrate, a copper thin film containing oxygen has been used. The copper thin film is formed by sputtering in an inert gas atmosphere containing oxygen using a pure copper target (see Patent Documents 1 and 2).
JP-A-5-25612 JP-A-8-26889

  Conventional wiring and electrodes made of a copper thin film containing oxygen have excellent adhesion to the glass substrate surface. However, since liquid crystal display devices are becoming more and more precise, it is necessary to make thinner wirings and electrodes made of a copper thin film containing oxygen formed on the glass substrate surface. When wiring and electrodes made of copper thin film containing oxygen are formed on the glass substrate surface, the wiring and electrodes are more susceptible to thermal defects such as hillocks and voids generated by exposure to high temperatures in the heat treatment process. Therefore, it is required to form wirings and electrodes with an oxygen-containing copper thin film that does not generate thermal defects such as hillocks and voids and has further excellent adhesion. .

Accordingly, the present inventors have developed a copper thin film that has excellent adhesion to the glass substrate surface and that does not generate thermal defects such as hillocks and voids in the heating process, and applies this to wiring and electrodes in liquid crystal display devices. I studied as much as possible.
As a result, an oxygen-containing copper atmosphere containing 0.04 to 1% by mass of oxygen containing oxygen more than oxygen-free copper (oxygen content: 0.001% or less) stipulated in JIS standards is used, and an inert gas atmosphere. Alternatively, a copper thin film obtained by sputtering in an inert gas atmosphere containing 3% by volume or less of oxygen has no thermal defects and is more excellent in adhesion, and when used for wiring or electrodes for liquid crystal display devices Research results were obtained, such as no thermal defects and better adhesion.

This invention was made based on the above research results,
(1) Oxygen: Using a copper target having a composition of 0.04 to 1% by mass, the balance being made of Cu and inevitable impurities, there is no generation of thermal defects in sputtering in an inert gas atmosphere, and adhesion Excellent method for forming wiring or electrodes for liquid crystal display devices,
(2) Heat of sputtering in an inert gas atmosphere containing oxygen: 0.04 to 1% by mass, with a balance of Cu and inevitable impurities contained in the copper target and oxygen: 3% by volume or less It is characterized by a method for forming a wiring or an electrode for a liquid crystal display device having no defects and excellent adhesion.

As described above, the reason why the oxygen contained in the copper target used in the method for forming a wiring and electrode for a liquid crystal display device having no thermal defects and excellent adhesion is 0.04 to 1 mass% as described above. The reason is as follows. That is, if the oxygen content contained in the copper target is less than 0.04% by mass, the amount of Cu ₂ O microcrystals formed during sputtering is small, the Cu crystal refinement effect cannot be obtained, and the adhesion of the film On the other hand, if the oxygen content contained in the copper target exceeds 1% by mass, the electrical resistance of the obtained copper thin film increases remarkably and cannot be used as a wiring or an electrode. is there.

As an atmosphere for sputtering using a copper target containing oxygen: 0.04 to 1% by mass, an inert gas such as Ar gas is sufficient, but sputtering is performed in an inert gas atmosphere containing 3% by volume or less of oxygen. You may do it.

The target used in the method for forming a wiring or electrode for a liquid crystal display device having no thermal defects and excellent adhesion according to the present invention is oxygen-free having a purity of 99.9% or more (preferably 99.99% or more). Copper can be produced by high-frequency melting in an inert gas atmosphere, adding CuO powder to the obtained oxygen-free molten copper, casting it in an iron mold, and further hot rolling. The target used in the method of forming a wiring or electrode for a liquid crystal display device having no thermal defects and excellent adhesion according to the present invention is not limited to the melting method, but is composed of copper powder containing oxygen or copper powder and copper oxide powder. The mixed powder can be produced by a hot press method or a hot isostatic pressing method.

  According to the method of the present invention, it is possible to provide a wiring or an electrode in a liquid crystal display device that has no thermal defect and has better adhesion to the surface of the glass substrate, so that peeling occurs during processing such as photolithography or etching. In this case, the manufacturing yield is improved. Further, since the electric resistance is low, the power consumption in the wiring or electrode of the liquid crystal display device which has been increased in definition and increased in size can be reduced.

Example 1
Purity: 99.99 mass% oxygen-free copper (oxygen content: 0.001 mass%) was prepared, and this oxygen-free copper was melted at high frequency in a high-purity MgO crucible in an Ar gas atmosphere, and the resulting molten metal Ingredient composition shown in Table 1 by adding a CuO powder having an average particle size of 5 μm or less to the steel and holding the molten metal at a temperature of 1250 ° C. for 10 minutes, casting into an iron mold, and further hot working Copper targets A to N having a diameter of 154 mm and a thickness of 5 mm were prepared.

Using these targets A to N, and further using Corning 1737 # (length: 50, width: 50, thickness: 0.7 mm) as the substrate glass,
Ultimate vacuum: 5 × 10 ⁻⁵ Pa,
Input power: 600W
Sputtering atmosphere: 100% Ar gas atmosphere,
Pressure: 1Pa,
Substrate heating: None,
A copper thin film having a thickness of 300 nm was formed by sputtering under the following conditions, and the present invention methods 1 to 11, the comparative methods 1 and 2, and the conventional method 1 were carried out.
The copper thin films obtained by carrying out the present invention methods 1 to 11, comparative methods 1 and 2, and the conventional method 1 were charged into an infrared heating furnace, respectively, and a vacuum atmosphere of 2 × 10 ⁻⁴ Pa was reached. Medium, maximum temperature: 350 ° C., 30 minutes holding heat treatment.

The following measurements were performed on the copper thin film subjected to such heat treatment.
(A) Measurement of specific resistance value:
The five-point specific resistance of the copper thin film after the heat treatment was measured by a four-probe method using a Loretas GP MCP-T610 type resistivity meter manufactured by Mitsubishi Chemical, and the average value was obtained. It was shown to.

(B) Cross-cut adhesion test The copper thin film immediately after film formation and the copper thin film after heat treatment are cut into a grid pattern at intervals of 1 mm in accordance with JIS-K5400 to form 100 copper thin-film grids, and then Nichiban A cross-cut adhesion test was carried out to measure the number of squares of the copper thin film peeled off from the glass substrate out of 100 squares on the glass substrate. The adhesion of the copper thin film to the glass substrate was evaluated.

(C) Void measurement:
The copper thin film after the heat treatment was broken and the cross section was observed with TEM. The number of interface voids generated at the 20 μm long copper thin film-glass substrate interface was counted, and the results are shown in Table 2.

  From the results shown in Tables 1 and 2, the copper thin film produced by the present invention methods 1 to 11 has substantially the same specific resistance as the copper thin film produced by the conventional method 1, but has excellent adhesion. Furthermore, it can be seen that the copper thin films prepared by Comparative Methods 1 and 2 under conditions other than the conditions of the present invention show undesirable characteristics such as an increase in specific resistance and a decrease in adhesion.

Example 2
Except that the sputtering atmosphere is an Ar gas atmosphere containing oxygen in the amount shown in Table 3, the inventive methods 12 to 22, the comparative methods 3 to 4 and the conventional method 2 are carried out in the same manner as in Example 1. The results are shown in Table 3.

  From Tables 1 and 3, the copper thin film produced by the inventive methods 12 to 22 has substantially the same specific resistance and adhesion as the copper thin film produced by the conventional method 2, but a copper target containing oxygen was used. It can be seen that the copper thin films produced by the inventive methods 12 to 22 have no voids, whereas the copper thin film produced by the conventional method 2 generates voids by heat treatment. Furthermore, it can be seen that the copper thin films prepared by Comparative Methods 3 to 4 under conditions other than the conditions of the present invention exhibit undesirable characteristics such as an increase in specific resistance and a decrease in adhesion.

Claims (2)

Oxygen: 0.04-1% by mass is contained, a copper target having a composition consisting of Cu and inevitable impurities is used as the balance, and sputtering is performed in an inert gas atmosphere. For forming wiring or electrode for liquid crystal display device having excellent properties. Sputtering is performed in an inert gas atmosphere containing oxygen: 3 vol% or less using a copper target having a composition containing oxygen: 0.04 to 1% by mass, the balance being Cu and inevitable impurities. A method for forming a wiring or electrode for a liquid crystal display device that does not cause thermal defects and has excellent adhesion.