TWI674335B - Etchant composition, method for manufacturing array substrate for liquid crystal display device and array substrate using the same - Google Patents

Abstract

The present invention relates to an etchant composition, and a method and an array substrate for manufacturing an array substrate of a liquid crystal display device using the same. When the copper-based metal layer is etched using the etchant composition of the present invention, an excellent etched cross section and a large number of processed boards are obtained.

Description

Etchant composition, method for manufacturing array substrate of liquid crystal display device using the same, and array substrate Technical field

The present invention relates to an etchant composition, a method for manufacturing an array substrate of a liquid crystal display device, and an array substrate using the same.

Background technique

Thin film transistors (TFTs) are typical electronic circuits that drive semiconductor devices and flat panel displays. The manufacturing process of a TFT generally includes forming a metal layer as a gate line and a data line material on a substrate, forming a photoresist on a selected area of the metal layer, and then using the photoresist as a mask A mold etches the metal layer.

The gate and data lines use copper with good electrical conductivity and low resistance, and in the case of copper, coating and patterning a photoresist may be difficult in terms of process, and therefore, copper-based metals Layers have recently been used as gate and data lines instead of separate copper layers. Among the copper-based metal layers, a titanium / copper double layer is generally used. However, when the titanium / copper double layer is etched at the same time, it has the disadvantages of poor etch profile and difficulty in post-processing. Copper elution has occurred, which results in a small number of processed plates. In view of the foregoing, an etchant composition for a copper-based metal layer has been actively studied, and as an example, Korean Patent Application Publication No. 2015-0059800 provides a liquid composition including a maleic acid ion source, copper ions Source and fluoride ion source, and has a pH value of 0 to 7. However, the liquid composition has disadvantages in that it has a poor etching profile and the number of processed plates is reduced.

Therefore, there has been a need for an etchant composition having an excellent etching profile and a large number of processed plates when etching a copper-based metal layer such as a titanium / copper double layer.

[Existing technical literature] [Patent Literature]

Korean Patent Application Publication No. 2015-0059800

Summary of invention

An object of the present invention is to provide an etchant composition for a copper-based metal layer, which has an excellent etching profile and a large number of processed plates.

In view of the above, one aspect of the present invention provides an etchant composition for a copper-based metal, which contains 0.5% to 10% by weight of a copper compound relative to the total weight of the composition; 0.01% to 2% 1% to 10% by weight of one or more types of inorganic acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid and perchloric acid; 0.1% to 10% by weight of one or more types of fluorine compounds A chlorine compound selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride, ammonium chloride, methanesulfonyl chloride, and ethylsulfonate A group consisting of chlorobenzene, chlorobenzenesulfonyl chloride, benzenesulfonyl chloride, and chloroethanesulfonyl chloride; 1 to 10% by weight of one or more types of organic acids selected from the group consisting of acetic acid, butyric acid, citric acid, Formic acid, gluconic acid, glycolic acid, oxalic acid, valeric acid, sulfobenzoic acid, sulfosuccinic acid, sulfophthalic acid, salicylic acid, sulfosalicylic acid, benzoic acid, lactic acid, glyceric acid, apple A group consisting of an acid, tartaric acid, isocitric acid, profenoic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid, or a salt thereof; 0.1 to 10% by weight of one or more types of nonmetallic inorganic salts , Which is selected from the group consisting of ammonium sulfate, sodium sulfate, potassium sulfate, calcium sulfate, ammonium hydrogen sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, calcium hydrogen sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, and calcium nitrate; 0.01 weight % To 5% by weight of a cyclic amine compound; 0.5% to 10% by weight of a chelating agent; and the balance of water, wherein the chelating agent is 1) a cis-dicarboxylic acid or a salt thereof, 2) selected from the group consisting of horses Maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic acid, 4-sulfophthalic acid Quinolinic acid, cis-5-norbornene-exo-2,3-dicarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid and cis, cis, cis, cis-1,2,3 , One or more types of the group consisting of 4-cyclopentanetetracarboxylic acid, or a salt thereof, or 3) one or more types selected from the group consisting of malonic acid, succinic acid and glutaric acid, Or its salt.

In one embodiment, the chelating agent may be selected from the following One or more types in the group: maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, phenylmaleic Anhydride, 2,3-dihydro-1,4-disulfide [2,3-C] furan-5,7-dione (2,3-dihydro-1,4-dithino [2,3-C] furan -5,7-dione), phthalic anhydride, 4-methylphthalic anhydride, pyromellitic dianhydride, 3-oxabicyclo [3,1,0] -hexane-2,4-di Ketone, cis-1,2,3,4-cyclopentanetetracarboxylic dianhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, cis-5-norbornene-exo-2 , 3-dicarboxylic anhydride, cis-1,2,3,6-tetrahydrophthalic anhydride, maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzenetetracarboxylic acid , Pyromellitic acid and 4-sulfophthalic acid; or a salt thereof.

In another embodiment, the copper-based metal layer may be a double layer of titanium or a titanium alloy and copper or a copper alloy.

Another aspect of the present invention provides a method of manufacturing an array substrate for a liquid crystal display device, the method comprising: a) forming a gate line on the substrate; b) forming a gate insulating layer on the substrate including the gate line C) forming a semiconductor layer on the gate insulating layer; d) forming a source and a drain electrode on the semiconductor layer; and e) forming a pixel electrode connected to the drain electrode, wherein a) or The step d) includes forming a copper-based metal layer on the substrate or semiconductor layer, and etching the copper-based metal layer with the etchant composition to form a gate line, or source and drain electrodes, and the etching Agent composition, with respect to the total weight of the composition, comprising 0.5% to 10% by weight of a copper compound; 0.01% to 2% by weight of a fluorine compound; 1% to 10% by weight of one or more types Inorganic acid selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid and perchloric acid; 0.1% to 10% by weight of one or more types of chlorine compounds selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride, chloride A group consisting of ammonium, methanesulfonyl chloride, ethanesulfonyl chloride, chlorobenzenesulfonyl chloride, benzenesulfonyl chloride and chloroethanesulfonyl chloride; 1 to 10% by weight of one or more types of organic acids, Free acetic acid, butyric acid, citric acid, formic acid, gluconic acid, glycolic acid, oxalic acid, valeric acid, sulfobenzoic acid, sulfosuccinic acid, sulfophthalic acid, salicylic acid, sulfosalicylic acid, A group consisting of benzoic acid, lactic acid, glyceric acid, malic acid, tartaric acid, isocitric acid, propionic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid, or a salt thereof; 0.1 to 10% by weight Type non-metal inorganic salt, which is selected from the group consisting of ammonium sulfate, sodium sulfate, potassium sulfate, calcium sulfate, ammonium hydrogen sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, calcium hydrogen sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, and calcium nitrate Group; 0.01% to 5% by weight of cyclic amine compound; 0.5% to 10% by weight Mixture; and the balance water.

In one embodiment, the array substrate of the liquid crystal display device may be a thin film transistor (TFT) array substrate.

In another embodiment, the chelating agent may be one or more types selected from the group consisting of: maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, 3,4, 5,6-tetrahydrophthalic anhydride, phenylmaleic anhydride, 2,3-dihydro-1,4-disulfide [2,3-C] furan-5,7-dione, phthalate Formic anhydride, 4-methylphthalic anhydride, pyromellitic dianhydride, 3-oxabicyclo [3,1,0] -hexane-2,4-dione, cis-1,2,3,4 -Cyclopentane tetracarboxylic dianhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, cis-5-norbornene-exo-2,3-dicarboxylic anhydride, cis-1, 2,3,6-tetrahydrophthalic anhydride, maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic acid and 4-sulfophthalic acid; or a salt thereof.

In another embodiment, the copper-based metal layer may be a double layer of titanium or a titanium alloy and copper or a copper alloy.

Another aspect of the present invention provides an array substrate of a liquid crystal display device manufactured by the above method.

The object and nature of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which: FIG. 1 shows when titanium is etched using the etchant composition of Example 1 and Comparative Example 12 Cross section when the copper / copper double layer is used; FIG. 2 shows the cross section when the titanium / copper double layer is etched using the etchant composition of Example 17 and Comparative Example 27; and FIG. The cross-section of an etchant composition when etching a titanium / copper double layer.

detailed description

The present invention relates to an etchant composition and a method for manufacturing an array substrate of a liquid crystal display device.

When the etchant composition of the present invention etches a copper-based metal layer by containing a certain content of a specific chelating agent, it has an excellent etching profile and a large number of processed plates.

Hereinafter, the present invention will be described in detail.

Etching composition

In the present invention, the copper compound acts as an oxidant and acts as an etch The CD offset remains unchanged when the etchant etches the metal layer, and preferably accounts for 0.5% to 10% by weight relative to the total weight of the etchant. When the content is less than 0.5% by weight, etching of copper or a metal layer containing copper cannot be achieved, or the etching rate is very low and the initial etching is uneven. When the content is more than 10% by weight, the effect of increasing the number of processed plates cannot be obtained. The copper compound preferably uses one or more types selected from the group consisting of copper sulfate, copper chloride, and copper nitrate.

The fluorine compound is a main component for etching titanium or a metal layer containing titanium, and functions to remove residues that may occur during etching. The fluorine compound preferably accounts for 0.01 to 2% by weight based on the total weight of the etchant. When the content of the fluorine compound is less than 0.01% by weight, the etching rate of titanium or a metal layer containing titanium is reduced, resulting in a residue, and when the content is more than 2.0% by weight, formation of a substrate such as on the substrate may occur. Damage to the glass of the metal wire and damage to the insulating layer containing silicon formed with it. The fluorine compound may be a compound in which a fluorine ion or a polyatomic fluorine ion is dissociated in a solution, and one or more selected from the group consisting of ammonium fluoride, sodium fluoride, potassium fluoride, ammonium hydrogen fluoride, sodium hydrogen fluoride, and potassium hydrogen fluoride is preferably used. Types of.

One or more types of inorganic acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, and perchloric acid are auxiliary oxidants for etching copper or a metal layer containing copper and titanium or a metal layer containing titanium, and are preferably relative to The total weight of the etchant is 1% to 10% by weight. When the content of the inorganic acid is less than 1% by weight, the etching rate of copper or a copper-containing metal layer and titanium or a titanium-containing metal layer is reduced, which may cause etching profile defects and residues When the content is more than 10% by weight, over-etching and photoresist cracking occur, which may cause wire short-circuiting due to penetration of liquid chemicals.

One selected from the group consisting of hydrochloric acid, sodium chloride, potassium chloride, ammonium chloride, methanesulfonyl chloride, ethanesulfonyl chloride, chlorobenzenesulfonyl chloride, benzenesulfonyl chloride, and chloroethanesulfonyl chloride or Various types of chlorine compounds function as a secondary oxidant for the metal layer, and control the etching rate and the angle of the metal layer, and have the advantages of preventing wire opening. The chlorine compound preferably accounts for 0.1 to 10% by weight relative to the total weight of the composition. When the content of the chlorine compound is less than 0.1% by weight, the etching rate for copper is reduced, causing an increase in the etching time in the process, which may cause a problem of productivity. In addition, when the content is more than 10% by weight, overetching may occur because the etching rate to copper cannot be controlled.

One or more types of organic acids selected from the group consisting of acetic acid, butyric acid, citric acid, formic acid, gluconic acid, glycolic acid, oxalic acid, valeric acid, sulfobenzoic acid, sulfosuccinic acid, sulfophthalic acid, water A group consisting of salicylic acid, sulfosalicylic acid, benzoic acid, lactic acid, glyceric acid, malic acid, tartaric acid, isocitric acid, propionic acid, iminodiacetic acid and ethylenediaminetetraacetic acid, or a salt thereof. The solubility of copper ions occurring during precipitation plays a role in controlling the etch rate and chelator, and lowers the pH. The organic acid or a salt thereof preferably accounts for 1 to 10% by weight based on the total weight of the etchant. When the content of the organic acid or the organic acid salt is less than 1% by weight, the effect of increasing the number of processed plates cannot be obtained, and when the content is more than 10% by weight, over-etching occurs, which may cause a short circuit of the wire.

Selected from ammonium sulfate, sodium sulfate, potassium sulfate, calcium sulfate, sulfuric acid One or more types of non-metal inorganic salts in the group consisting of ammonium hydrogen, sodium hydrogen sulfate, potassium hydrogen sulfate, calcium hydrogen sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, and calcium nitrate, which play a role of auxiliary etching control agents for metal layers. Function and has the effect of improving a poor etching profile, which is a disadvantage of an etchant containing a chlorine compound. The non-metal inorganic salt preferably accounts for 0.1 to 10% by weight with respect to the total weight of the composition. When the content is less than 0.1% by weight, the effect of the auxiliary etching control agent and the effect of improving the etching profile cannot be achieved, and when the content is more than 10% by weight, over-etching may occur.

The cyclic amine compound is an etching control agent that controls batch etching and the angle of copper or a metal layer containing copper. The cyclic amine compound preferably accounts for 0.01 to 5% by weight based on the total weight of the composition. When the content is less than 0.01% by weight, uniform etching of the metal layer cannot be obtained, and when the content is more than 5% by weight, the etching rate can be reduced. The cyclic amine compound is preferably selected from the group consisting of 5-aminotetrazole, triazole, phenyltetrazole, imidazole, indole, purine, pyrazole, pyridine, pyrimidine, pyrrole, pyrrolidine, pyrroline, and 5-methyltetrazol. One or more types from the group consisting of azoles.

Water means deionized water, and water for semiconductor processing is used, and water of 18 MΩ / cm or more is preferably used. With respect to the total content of the etchant, water accounts for the balance so that the total weight of the etchant becomes 100% by weight.

The chelating agent of the present invention functions as a main component for increasing the number of processed boards.

Specifically, the chelating agent may be 1) cis-dicarboxylic acid or a salt thereof, and 2) selected from the group consisting of maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzene tetra Carboxylic acid, pyromellitic acid, 4-sulfophthalic acid, quinolinic acid, cis-5-norbornene-exo-2,3-dicarboxylic acid, 1,2,3,4-cyclobutane tetra One or more types of carboxylic acid and cis, cis, cis, cis-1,2,3,4-cyclopentanetetracarboxylic acid, or a salt thereof, or 3) selected from the group consisting of malonic acid, amber One or more types of the group consisting of an acid and glutaric acid, or a salt thereof.

The cis-dicarboxylic acid or a salt thereof may be one or more types selected from the group consisting of maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, 3,4,5 , 6-tetrahydrophthalic anhydride, phenylmaleic anhydride, 2,3-dihydro-1,4-disulfide [2,3-C] furan-5,7-dione, phthalic acid Acid anhydride, 4-methylphthalic anhydride, pyromellitic dianhydride, 3-oxabicyclo [3,1,0] -hexane-2,4-dione, cis-1,2,3,4- Cyclopentane tetracarboxylic dianhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, cis-5-norbornene-exo-2,3-dicarboxylic anhydride, cis-1,2 , 3,6-tetrahydrophthalic anhydride, maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic acid and 4-sulfophthalic acid Formic acid; or a salt thereof.

The chelating agent preferably accounts for 0.5 to 10% by weight relative to the total weight of the composition. When the content is less than 0.5% by weight, the effect of increasing the number of processed plates cannot be obtained, and when the content is more than 10% by weight, the etching rate of the metal layer is increased, which may cause over-etching.

In the present invention, the etchant composition may further include a metal ion chelator, a corrosion inhibitor, and the like.

Method for manufacturing array substrate of liquid crystal display device

A method of manufacturing an array substrate for a liquid crystal display device, the method comprising: a) forming a gate line on a substrate; b) forming a gate insulating layer on the substrate including the gate line; c) forming a semiconductor layer on the gate insulating layer; d) on the semiconductor layer Forming source and drain electrodes; and e) forming a pixel electrode connected to the drain electrode, wherein step a) or d) includes forming a copper-based metal layer on the substrate or semiconductor layer, and using the invention The etchant composition etches the copper-based metal layer to form gate lines, or source and drain electrodes.

The array substrate of the liquid crystal display device may be a thin film transistor (TFT) array substrate, but is not limited thereto, and may also be used for manufacturing other electronic devices including metal wires formed with a copper-based metal layer, for example, for manufacturing a memory semiconductor Display panel.

Hereinafter, the present invention will be described in more detail with reference to examples, comparative examples, and test examples. However, the following examples, comparative examples, and test examples are for illustrative purposes only, and the scope of the present invention is not limited to the following examples, comparative examples, and test examples, and may be variously modified and changed.

Examples 1 to 48 and Comparative Examples 1 to 46. Preparation of Etchant Composition

The etchant composition was prepared with the composition and content (unit: weight%) listed in Table 1, Table 2 and Table 3 below.

(A): Cu (II) SO4

(B): Ammonium fluoride

(C): Nitric acid

(D): Citric acid

(E): Ammonium chloride

(F): Ammonium sulfate

(G): 5-methyltetrazole

(H): cis-cyclobutane-1,2-dicarboxylic acid

(I): cis-1,2,3,4-cyclopentane tetracarboxylic dianhydride

(J): trans-cyclobutane-1,2-dicarboxylic acid

(K): trans-4-cyclohexene-1,2-dicarboxylic acid

(L): phthalic acid; benzene-1,2-dicarboxylic acid

(M): terephthalic acid; benzene-1,4-dicarboxylic acid

(N): Malonic acid

(O): Succinic acid

(P): glutaric acid

(Q): Adipic acid

Test example. Evaluation of etching properties

Etching was performed using each of the etchant compositions of Examples 1 to 48 and Comparative Examples 1 to 46. Using a spray etching type test equipment (model: ETCHER (TFT), SEMES Co., Ltd.), the temperature of the etchant composition during the etching process was set at about 30 ° C. The etching time varies depending on the etching temperature, however, the etching is usually performed for 30 to 80 seconds during the LCD etching process. During the etching process, the cross section of the cross section of the titanium / copper double layer etched during the etching process was observed with a SEM (product of Hitachi, Ltd., model S-4700). The results are shown in Tables 4, 5, and 6 below. Table 6, Figure 1, Figure 2 and Figure 3 are shown.

Unetched: Cu not etched in non-patterned units and no pattern etched. Section defect: refers to straightness defects in Cu lines of patterned units and defects in oblique planes in SEM measurement.

As shown in Tables 4 to 6, Examples 1 to 48 exhibited superior properties in the number of processed plates and the etching cross section as compared to Comparative Examples 1 to 46.

Specifically, as shown in FIG. 1, Example 1 exhibited an excellent etching profile as compared with Comparative Example 12 in which no inorganic salt (ammonium sulfate) was added.

In addition, as shown in FIG. 2, Example 17 exhibited an excellent etching profile as compared with Comparative Example 27 in which no inorganic salt (ammonium sulfate) was added.

In addition, as shown in FIG. 3, Example 32 exhibited an excellent etched cross section as compared with Comparative Example 42 in which no inorganic salt (ammonium sulfate) was added.

When the copper-based metal layer is etched using the etchant composition of the present invention, an excellent etched cross section and a large number of processed boards can be obtained.

Claims (5)

An etchant composition for a copper-based metal layer, which contains 0.5 to 10% by weight of a copper compound relative to the total weight of the composition; 0.01 to 2% by weight of a fluorine compound; 1 weight % To 10% by weight of one or more types of inorganic acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid and perchloric acid; 0.1% to 10% by weight of one or more types of chlorine compounds selected from hydrochloric acid, A group consisting of sodium chloride, potassium chloride, ammonium chloride, methanesulfonyl chloride, ethanesulfonyl chloride, chlorobenzenesulfonyl chloride, benzenesulfonyl chloride and chloroethanesulfonyl chloride; 1% to 10% by weight One or more types of organic acids selected from the group consisting of acetic acid, butyric acid, citric acid, formic acid, gluconic acid, glycolic acid, oxalic acid, valeric acid, sulfobenzoic acid, sulfosuccinic acid, sulfophthalic acid, A group consisting of salicylic acid, sulfosalicylic acid, benzoic acid, lactic acid, glyceric acid, malic acid, tartaric acid, isocitric acid, propionic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid, or a salt thereof; 0.1 % To 10% by weight of one or more types of non-metallic inorganic salts selected from ammonium sulfate, A group consisting of sodium sulfate, potassium sulfate, calcium sulfate, ammonium hydrogen sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, calcium hydrogen sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, and calcium nitrate; 0.01% to 5% by weight of the ring Amine compounds; 0.5% to 10% by weight of chelating agents; and The balance of water, wherein the chelating agent is 1) selected from the group consisting of maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, 3,4,5,6-tetrahydrophthalic anhydride , Phenylmaleic anhydride, 2,3-dihydro-1,4-disulfide [2,3-C] furan-5,7-dione, phthalic anhydride, 4-methylphthalic acid Anhydride, pyromellitic dianhydride, 3-oxabicyclo [3,1,0] -hexane-2,4-dione, cis-1,2,3,4-cyclopentanetetracarboxylic dianhydride, ring Butane-1,2,3,4-tetracarboxylic dianhydride, cis-5-norbornene-exo-2,3-dicarboxylic anhydride, cis-1,2,3,6-tetrahydrophthalic acid One or more types from the group consisting of formic anhydride; or a salt thereof, 2) selected from the group consisting of maleic acid, citraconic acid, phthalic acid, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic acid , 4-sulfophthalic acid, quinolinic acid, cis-5-norbornene-exo-2,3-dicarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid and cis, cis Cis, cis-1,2,3,4-cyclopentanetetracarboxylic acid, one or more types, or a salt thereof, or 3) selected from the group consisting of malonic acid, succinic acid, and glutaric acid One or more types in the group, or a salt thereof. The etchant composition for a copper-based metal layer according to claim 1, wherein the copper-based metal layer is a double layer of titanium or a titanium alloy and copper or a copper alloy. A method of manufacturing an array substrate for a liquid crystal display device, the method comprising: a) forming a gate line on the substrate; b) forming a gate insulating layer on the substrate including the gate line; c) forming a semiconductor layer on the gate insulating layer; d) forming a source and a drain electrode on the semiconductor layer; and e) forming a pixel electrode connected to the drain electrode, wherein a) or d The step) includes forming a copper-based metal layer on the substrate or semiconductor layer, and etching the copper-based metal layer with the etchant composition according to claim 1 to form a gate line, or source and drain electrodes. The method for manufacturing an array substrate of a liquid crystal display device according to claim 3, wherein the array substrate of the liquid crystal display device is a thin film transistor array substrate. The method for manufacturing an array substrate of a liquid crystal display device according to claim 3, wherein the copper-based metal layer is a double layer of titanium or a titanium alloy and copper or a copper alloy.