JP2005079130A - Thin film wiring layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film wiring layer effective as the wiring layer of a flat surface display in which moisture resistance can be improved while ensuring wet etching properties and heat resistance. <P>SOLUTION: The thin film wiring layer being formed on a substrate consists of a main conductor layer principally comprising Al and a coating layer covering the main conductor layer wherein the coating layer contains 7-15 atom% of one kind or more than two kinds of additive element selected from (Ti, Zr, Hf, V, Nb, Ta, Mo, W) and the remainder is an alloy layer substantially comprising Ni. Preferably, the coating layer contains at least 1-7 atom% of Nb and total 7-10 atom% of Mo and/or W and Nb. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 being actively researched and developed.

The conductive film of FPD is ITO (Indium-Tin-Oxide), which is a transparent conductive film, and, when higher definition display is required, ITO is used as a display electrode and has lower resistance and adheres to the substrate. Cr, Ta, and their alloy films, which are high-melting-point metals having excellent heat resistance and heat resistance, 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 or an Al alloy 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. In addition, 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, not only wet etching properties but also resistance to environmental atmospheres, particularly humidity, have become important characteristics. 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 improving moisture resistance while ensuring wet etching property and heat resistance.

As a result of the study, the present inventor has found that the above object can be achieved by adding a specific element based on Ni, not based on Mo.
That is, the present invention is a thin-film wiring layer formed on a substrate, comprising a main conductor layer containing Al as a main component and a coating layer covering the main conductor layer, the coating layer comprising (Ti, Zr, Hf , V, Nb, Ta, Mo, W), which is a wiring layer that is an alloy layer containing 3 to 15 atomic% of one or more additive elements selected from the group consisting of Ni.

  In the present invention, the additive element is preferably one or more selected from (V, Nb, Ta), and more preferably contains at least 1 to 7 atomic% of Nb and contains Mo and / or W. The total amount is 3 to 10 atomic% with Nb.

  In the present invention, it is effective as a thin film wiring layer formed on a glass substrate generally used for a flat display device, and more specifically, for a thin film transistor (TFT) such as a liquid crystal display or an organic EL (electroluminescence) display. It is effective as a wiring layer.

  The wiring layer of the present invention can improve the moisture resistance while ensuring wet etching property and heat resistance. Therefore, the wiring layer of the present invention is extremely suitable as a TFT wiring layer for flat display devices that require high-speed driving and dislike changes in thin film characteristics. It becomes effective.

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 a coating layer, heat resistance of the main conductor layer mainly composed of Al can be ensured to some extent.
Furthermore, in terms of wet etching, Ni has a feature that it is soluble in a general aqueous solution of phosphoric acid, nitric acid and acetic acid, so it can be etched simultaneously with the main conductor layer containing Al as the main component. Is possible.

Note that pure Ni, like Mo, has a high dissolution rate during wet etching with respect to Al or Al alloy as a main wiring layer and is easily corroded, resulting in over-etching and a problem in patterning properties. In addition, pure Ni is inferior to Mo, which is a high melting point metal, in terms of heat resistance. Therefore, it is effective to use an additive element for suppressing film alteration during heating.
In the present invention, in order to improve these properties, 3 to 15 atomic% of one or more additive elements selected from (Ti, Zr, Hf, V, Nb, Ta, Mo, W) are added to Ni. Contain.
These elements have the property of improving etching resistance, can alleviate the phenomenon of Ni being corroded during wet etching, which was a problem with pure Ni, and can be simultaneously wet with the main wiring layer mainly composed of Al. Patterning by etching becomes possible. Moreover, heat resistance is also improved.

In the present invention, if the additive element is less than 3 atomic%, the coating layer is excessively etched compared to the main wiring layer during wet etching, and if it exceeds 15 atomic%, the etching cannot be performed. Preferably, 5 atomic% to 10 atomic%, more preferably 7 atomic% to 10 atomic%.
When a sputtering method is used for forming the wiring layer, a target material 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 the magnetism of Ni, and the reduction or disappearance of magnetism is an advantage for the production efficiency due to the effect of improving the formation rate of the Ni alloy film and the efficiency of using the target material. Also become. From the viewpoint of eliminating magnetism, the additive element is preferably 7 atomic% or more.

Further, among the additive elements, V, Nb, and Ta have a small increase in resistivity due to the addition as compared with the 5A group elements of Mo and W, and have a wider solid solution region with respect to Ni than the 3A group such as Ti. This is because the sex can be further enhanced. In addition, 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 preferable 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 due to the effect of improving adhesion.
The main conductive layer and the covering 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.

Further, a typical form as a wiring layer in the present invention is a covering layer 3 serving as a cover layer located on the upper side of the main conductor layer 2 formed on the substrate 1 as shown in FIG. It is also effective as a base layer provided between the main conductor layers 2.
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 a film mainly composed of Al as a main wiring layer. It is also effective to adapt to a resin substrate having low adhesion to a film containing Al as a main component or a silicon substrate that easily diffuses into a film containing Al as a main component and has an increased resistance value. In addition, it can be used as a base film for obtaining electrical contact with ITO, which is a transparent electrode film that cannot provide electrical contact with a film containing Al as a main component in the process of manufacturing a flat display device or the like. It is.

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, and 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 target materials of various compositions having predetermined sizes. The target material is attached to a magnetron sputtering apparatus, the argon pressure is 0.5 Pa, the input power is 500 W, and a Ni alloy with a film thickness of 100 nm 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.
Similarly, as a comparative example, a target material of Mo-8 atomic% Nb and Mo-10 atomic% W was produced, and the same film sample was 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 was confirmed that the total amount of additive elements of 7 atomic% or more at which the magnetism as the target material disappears has a good usage efficiency of the target material.
In addition, the samples shown in Table 2 were subjected to the same moisture resistance test as in Table 1. However, no discoloration or the like 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 specific resistance value is a specific resistance value (μΩcm) related to conductivity as a film characteristic of the formed Ni alloy film, using a four-terminal thin film resistivity meter (MCP-T400, manufactured by Mitsubishi Yuka). It was measured.
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, although the specific resistance is low in pure Ni, 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 the film surface It can be seen that the occurrence of white spots and the like is suppressed. However, when the amount of each additive element increases by 15 atomic%, the specific resistance value exceeds 100 μΩcm, which is not desirable as a conductive film. The white spot is a raised part of the film surface due to partial film growth or oxidation of the film. When a white spot occurs, an electrical short circuit or disconnection in the next process of the FPD, or a display device is obtained. It is desirable not to occur because it leads to visual defects.

  In order to evaluate the patterning property in wet etching, each main wiring layer containing Al as a main component was formed on a 200 nm substrate, and a Ni alloy film having the same composition as that of Example 2 was formed thereon with 30 nm. A wiring layer having a configuration was formed. 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.

  An OFPR-800 positive resist made by Tokyo Ohka Co., Ltd. is formed on the Ni alloy film by spin coating, and the resist is exposed to ultraviolet rays using a photomask, and then developed with an organic alkali developer NMD-3. In S), a 25 μm resist pattern was prepared. Then, using a mixed aqueous solution of phosphoric acid, nitric acid and acetic acid, etch until the part without the resist pattern is dissolved and permeate, and then check the resist pattern, the surrounding residue, the shape of the pattern edge, and the deviation of the pattern width with an optical microscope. Observed. At that time, a wiring pattern was formed, and no residue was evaluated as good. Further, in the pattern shape, it is most desirable that the etched portion is straight, but the edge straightness is low and the difference between the maximum width and the minimum width exceeds 3 μm, x is 1.5 to 3 μm, and 1 .Gamma. Moreover, the thing of 1 micrometer or less was evaluated as (double-circle).

  After that, after immersing in an organic solvent, washing with pure water, spin drying, and removing the resist by performing oxygen ashing, the laminated film pattern is observed with an optical microscope, and its shape and discoloration are good. It was. The results are shown in Table 3.

  Good when etching a laminated film in which an Ni alloy film containing an additive element selected from (Ti, Zr, Hf, V, Nb, Ta, Mo, W) is formed on a film containing Al as a main component. A thin film pattern is obtained. Pure Ni has a high etching rate, a large side etching, and a non-uniform pattern shape. For this reason, the Al film surface is not sufficiently covered, and the film surface is altered after passing through the resist stripping step. In the Ni alloy film of the present invention, no residual is generated and the patterning property is good, and the film surface is not discolored after the resist is removed. The improvement effect is insufficient if the addition amount is less than 3 atomic%, and if it exceeds 15 atomic%, the patterning property is lowered, etching cannot be performed, and a thin film pattern that can withstand practical use cannot be obtained. For this reason, it is understood that the addition amount is preferably 3 to 15 atomic%.

As described above, the thin film wiring layer of the present invention can provide a thin film pattern having both moisture resistance and patterning properties. Furthermore, in order to increase the definition and brightness of the FPD, it is necessary to make the thin film wiring narrower. Particularly, in the case of a thin film wiring layer having a width of 10 μm or less, the accuracy and safety of the pattern shape are also important. . In order to cope with this, it is necessary to further carefully select additive elements to be added to Ni. As shown in Table 3, among the additive elements, V, Nb, and Ta have little difference from the resist pattern, but the pattern edge linearity is slightly inferior to Mo and W. In V, white spots may occur after resist removal. Ti, Zr, and Hf are slightly inferior in straightness, and have a tendency that the pattern width becomes wide and reverse taper. The reverse taper shape may be unfavorable because the step angle becomes steep when a protective film is formed. In addition, Mo and W have good straightness of the edge, but overetching tends to be large and the pattern width tends to be narrow.

  Furthermore, it can be seen that a Ni alloy / Al laminated film with good pattern accuracy and pattern shape can be obtained by combining Nb with good pattern accuracy and Mo and W with good pattern shape. In this case, when considering together with Example 2, it can be seen that the addition amount is 10 atomic% or less, and the heat resistance, moisture resistance, patterning property and low resistance value are combined.

  According to the present invention, since high reliability can be secured as a thin film wiring layer, it is expected to be widely used as wiring applied to various FPDs, in particular, mobile devices such as in-vehicle.

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: Covering layer

Claims (4)

A thin film wiring layer formed on a substrate, comprising a main conductor layer mainly composed of Al and a coating layer covering the main conductor layer, the coating layer comprising (Ti, Zr, Hf, V, Nb, A thin film wiring layer comprising 3 to 15 atom% of one or more additive elements selected from Ta, Mo, W), and the balance being an alloy layer substantially made of Ni. The thin film wiring layer according to claim 1, wherein the additive element is one or more selected from (V, Nb, Ta). 2. The thin film wiring layer according to claim 1, wherein the thin film wiring layer includes at least 1 to 7 atomic% of Nb as additive elements and 3 to 10 atomic% of Mo and / or W in total with Nb. 4. The thin film wiring layer according to claim 1, wherein the thin film wiring layer is a wiring layer formed on a glass substrate.

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