JP4470147B2 - Thin film wiring layer - Google Patents

Description

  The present invention relates to a thin film wiring layer used in a flat panel display (hereinafter referred to as FPD) manufactured by forming a thin film on a substrate.

  For example, FPDs manufactured by laminating thin films on glass substrates or Si wafers include liquid crystal displays (hereinafter referred to as LCDs), plasma display panels (hereinafter referred to as PDPs), field emission displays (hereinafter referred to as FEDs), Various new products such as electroluminescence display (hereinafter referred to as ELD) and electronic paper are actively researched and developed.

FPD conductive films include oxide ITO (Indium-Tin-Oxide), which is a transparent conductive film, and lower resistance than ITO when higher definition display is required, adhesion to the substrate, and heat resistance. Cr, Ta, which are excellent refractory metals, and alloy films thereof are used. Further, when further low resistance is required, a thin film wiring layer in which these refractory metal films and Al or an Al alloy are laminated is used.
Among them, the Cr film is excellent in corrosion resistance and heat resistance, can be wet-etched using a chemical solution, has high adhesion to a substrate such as a glass substrate or Si wafer, and is a particularly useful material as a thin film material. Therefore, Cr can be used as a coating layer such as an underlayer such as Al, Ag, Cu, or an alloy obtained by adding an additive element to these, or an upper coating layer. However, in recent years, there has been a problem such as the generation of waste liquid containing hexavalent Cr when manufacturing flat display elements, discarding and recycling Cr films, and the use of Cr films has been reduced for global environmental conservation. There is a need to.

Therefore, development of a highly reliable material that replaces Cr is desired. As a material that substitutes for Cr, a Mo alloy has been proposed as a material having a resistance equal to or less than that.
Since Mo is a high-melting point material like Cr, it has high heat resistance and good adhesion to a glass substrate for flat display devices, Si wafers, and the like. Furthermore, there is an advantage that wet etching is possible. In addition, Mo alloy is proposed instead of pure Mo. Since Mo is a metal that is easily corroded, the etching rate difference with the main wiring layer such as Al during wet etching is alleviated; This is for improving the resistance against dry etching gas such as gas and chlorine-based gas. As specific additive elements, Cr, Ti, Zr, Hf, Nb, Ta and the like have been proposed. (See Patent Documents 1, 2, 3, etc.)
JP 2000-284326 A Japanese Patent Laid-Open No. 2001-242483 JP 2001-350159 A

Application of the Mo alloy described above is effective as a thin film wiring layer of a flat display device because a highly reliable wiring layer can be obtained by securing wet etching property and heat resistance by Mo.
Incidentally, in the manufacture of flat display devices such as liquid crystal display devices, resistance to environmental atmospheres, particularly humidity, has become an important characteristic. This is because the property (contact property) deteriorates as an electrical contact point due to the phenomenon that the film changes in quality due to the influence of humidity, that is, it rusts due to oxidation.
Although this inventor examined the moisture resistance of Mo alloy, since it was Mo base, it did not lead to the remarkable improvement in moisture resistance.

  An object of the present invention is to provide a novel thin film wiring layer capable of ensuring heat resistance and improving moisture resistance.

As a result of the study, the present inventor has found that the above object can be achieved by using a specific additive element based on Ni instead of using Mo as a base.
That is, the present invention is a thin film wiring layer formed on a substrate made of a coating layer that covers the main conductor layer and the main conductor layer mainly composed of C u, the coating layer, the Nb 1 to 7 This is a thin-film wiring layer that is an alloy layer that contains atomic percent and contains Mo and / or W in a total amount of 3 to 15 atomic percent with Nb, with the balance being substantially Ni.

  Since the wiring layer of the present invention can improve moisture resistance while ensuring heat resistance, it is extremely effective as a wiring layer for TFTs for flat display devices that require high-speed driving and dislike changes in thin film characteristics. Become.

An important feature of the present invention resides in that a Ni alloy layer is applied in place of the Mo alloy layer conventionally applied to a wiring layer having a structure composed of a main conductor layer and a covering layer covering the main conductor layer.
The Ni alloy layer applied to the present invention will be described below.

Since Ni has a high electrode potential and is not easily oxidized, it can ensure remarkably superior moisture resistance compared to Mo. This is the most important feature of the present invention.
Further, since Ni has a melting point near 1400 ° C. as the coating layer, the heat resistance of the main conductor layer mainly composed of Ag or Cu can be ensured to some extent.

  Note that pure Ni is inferior to Mo, which is a refractory metal, in terms of heat resistance, and therefore it is effective to use an additive element to suppress film alteration during heating. In the present invention, in order to improve heat resistance, Ni contains 3 to 15 atomic% of one or more additive elements selected from (Ti, Zr, Hf, V, Nb, Ta, Mo, W). Let

In the present invention, if the additive element is less than 3 atomic%, the effect for improving the heat resistance is small, and if it exceeds 15 atomic%, the etching process cannot be performed.
In the present invention, the additive element is preferably 5 atom% to 10 atom%, more preferably 7 atom% to 10 atom%.
When a sputtering method is used for forming the wiring layer, a target having the same composition as that of the coating layer is required. However, Ni is a magnetic substance, and there is a problem that the efficiency of magnetron sputtering is poor. The additive element of the present invention also has an effect of reducing magnetism, and reducing or eliminating magnetism also has an advantage for production efficiency. From the viewpoint of eliminating magnetism, the additive element is preferably 7 atomic% or more.
Further, the additive element is an element that increases the resistance value of Ni, but adopting a structure having a main conductor layer as in the present invention can ensure basic conductivity by the main conductor layer. There is an advantage.

When the main conductor layer is a layer containing Ag as a main component, it is desirable that the additive element in the coating layer be one or more additive elements selected from (Ti, Zr, Hf).
These additive elements can easily form Ag and a compound, and can improve the adhesion between the main conductor layer and the coating layer.

In addition, when the main conductor layer is a layer containing Cu as a main component, it is desirable that the additive element in the coating layer be one or more additive elements selected from (Nb, Ta, Mo, W).
These additive elements are elements that do not dissolve in Cu or easily form a surface compound, and have a high effect of preventing the main conductor layer and the coating layer from being excessively diffused.

Further, among the additive elements to Ni, V, Nb, and Ta are less likely to increase in resistivity by addition than the 6A group elements of Mo and W, and have a more solid solution region with respect to Ni than the 4A group such as Ti. This is because the heat resistance can be increased more widely. Further, since the progress of oxidation does not stop in the oxidizing atmosphere when V is added, Nb and Ta are desirable among V, Nb and Ta, and Nb is preferred from the viewpoint of cost.
Moreover, Mo and W have the widest solid solution region among the additive elements described above, and have the highest effect of making the thin film structure fine. Therefore, as an additive element, at least Nb is contained in 1 to 7 atomic%, and Mo and / or W is contained in a total of 3 to 10 atomic% with Nb, thereby improving the Nb etching property, Mo and It is possible to achieve both the effect of improving the pattern accuracy by miniaturizing the film by W / or W.

  The board | substrate which forms the thin film wiring layer of this invention is not specifically limited, It can apply to a silicon substrate, Al substrate, a glass substrate, a resin substrate, etc. In particular, when a wiring layer is formed on a glass substrate, it is particularly suitable because of the effect of improving the adhesion. The main conductive layer and the coating layer in the thin film wiring layer of the present invention can be formed by sputtering using a target material having substantially the same composition as each layer.

In addition, a typical form as a coating layer in the present invention includes a base layer 4 as a coating layer formed on the substrate 1 as shown in FIG. 1, a main conductor layer 2 formed on the base layer 4, and The cover layer 3 is a cover layer formed on the main conductor layer. The underlayer provided between the substrate 1 and the main conductor layer 2 may be omitted.
However, since the Ni alloy film of the present invention is excellent in adhesion to various substrates, it can be used as a base film for the main wiring layer. Ag and Cu are films having lower adhesion to glass substrates and Si wafers than conventional Al and Cr. For this reason, it is possible to improve the reliability by improving the adhesion of the Ag or Cu film by using the Ni alloy film as a base film.

Nb and W, which are high-purity metal raw materials, are added to high-purity electrolytic Ni by a predetermined weight, melted in a vacuum induction melting furnace, cast into a metal mold having a thickness of 50 mm, a width of 200 mm, and a height of 300 mm. An ingot having the composition shown in FIG. Thereafter, a solid solution treatment was performed at 1150 ° C., and then a plate was formed by plastic working and further machined to obtain predetermined sizes of target materials having various compositions. The target material is attached to a magnetron sputtering apparatus, the argon pressure is 0.5 Pa, the input power is 500 W, and the Ni alloy having a film thickness of 100 nm is placed on a 1737 glass substrate made by Corning, 0.7 mm (t) × 100 mm × 100 mm. A sample on which a film was formed was prepared.
Further, in the same manner as a comparative example, Mo-8 atomic% Nb and Mo-10 atomic% W targets were prepared, and similar film samples were obtained.

The basic humidity resistance test of the present invention was conducted by a test that was allowed to stand for 240 hours in an environment of a temperature of 85 ° C. and a relative humidity of 85%. The results are shown in Table 1.
As a result, in all of the Mo-based comparative examples, a clear purple discoloration was confirmed, but it was confirmed that the Ni-based alloy had no discoloration and was excellent in moisture resistance.

Hereinafter, a thin film sample having an alloy composition shown in Table 2 was produced in the same manner as in Example 1 to obtain a film sample. In addition, since the magnetron sputtering apparatus was used for the evaluation, it has been confirmed that the total use amount of the additive element of 7 atomic% or more at which the magnetism as the target disappears makes the target use efficiency.
In addition, the samples shown in Table 2 were subjected to the same moisture resistance test as in Table 1. However, no discoloration was observed in all samples containing pure Ni, and it was confirmed that the samples had good moisture resistance. .

The results of measuring resistance characteristics and heat resistance are shown below.
Here, the resistance characteristic is measured using a four-terminal thin film resistivity meter (MCP-T400, manufactured by Mitsubishi Yuka Co., Ltd.) as the film characteristic of the formed Ni alloy film. did.
As a heat resistance test, each sample was heated in a clean oven at a temperature of 300 ° C. for 1 hour.

  As shown in Table 2, the specific resistance of pure Ni is low, but white spots occur on the film surface after the heat resistance test. In the Ni alloy film of the present invention, the specific resistance value increases as the addition amount increases, but it can be seen that the generation of white spots on the film surface is suppressed. However, when the amount of each additive element increases by 15 atomic%, the specific resistance exceeds 100 μΩcm, which is not desirable for a conductive film. The white spot is a raised part of the film surface due to partial film growth or oxidation of the film, and if a white spot occurs, it will cause an electrical or optical defect in the next process of the FPD, so it does not occur. It is desirable.

A wiring layer having the configuration shown in FIG. 1 was obtained with the main conductor layer mainly composed of Ag or Cu shown in Table 3 having a thickness of 200 nm and the Ni alloy film as the coating layer (cover layer 3 and base layer 4).
The obtained wiring layer was evaluated for heat resistance and moisture resistance in the same manner as in Example 1 and Example 2. In addition, as a method for evaluating adhesion, after cutting the surface of the film at intervals of 2 mm in a grid pattern, a mending tape 810 (manufactured by Scotch) is applied to the surface of the film, and the film is peeled off at an angle of 45 ° to peel off the film. Checked the situation. The results are shown in Table 3. The thickness of the Ni alloy base film was 50 nm, and the thickness of the cover film was 30 nm. The substrate material was the glass substrate described above, a Si wafer whose surface was thermally oxidized, and a polycarbonate substrate as the resin substrate. The results are shown in Table 3.

  As shown in Table 3, in the layer mainly composed of Ag and Cu, the resistance value is low, but the deterioration occurs in the moisture resistance evaluation, the discoloration occurs in the heat resistance evaluation, and the adhesion with the substrate is inferior. It can be seen that peeling occurs. In contrast, when the Ni alloy film of the present invention is used as the coating layer, the resistance value increases, but it is understood that the moisture resistance, heat resistance, or adhesion to the substrate can be greatly improved.

  As described above, according to the present invention, it is optimal as a conductive film for a flat display device that requires high reliability. In addition, it is particularly suitable as a thin film wiring layer for organic EL displays in which a resin is formed on a conductive film, and is used as a thin film wiring layer for a flat display device for mobile equipment such as a vehicle that requires high reliability. It is expected.

It is a figure which shows an example of the typical form as a wiring layer in this invention.

Explanation of symbols

  1: substrate, 2: main conductor layer, 3: cover layer, 4: underlayer

Claims (1)

A thin film wiring layer formed on a substrate, comprising a main conductor layer containing Cu as a main component and a coating layer covering the main conductor layer, the coating layer containing 1 to 7 atomic% of Nb, and A thin-film wiring layer comprising Mo and / or W in a total amount of 3 to 15 atomic% with Nb, the balance being an alloy layer substantially made of Ni.

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