JP2015131998A - Cu-ALLOY WIRING AND Cu-ALLOY SPUTTERING TARGET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-alloy wiring that is used as a protective film of a Cu wiring material, forms an ohmic connection with an ITO film, and has excellent etching property, oxidation resistance, and corrosion resistance.SOLUTION: The Cu-alloy wiring comprises a composition containing at least Ni and Mn, and the balance Cu that may include an inevitable component. When a plane of XY-coordinates is defined by an X axis and a Y axis representing a content of Ni (wt.%) and a content of Mn (wt.%), respectively, the contents of Ni and Mn in the composition are within a range enclosed by the following four points (A), (B), (C), and (D). (A) Ni:20 wt.% and Mn:10 wt.%, (B) Ni:15 wt.% and Mn:20 wt.%, (C) Ni:20 wt.% and Mn:20 wt.%, and (D) Ni:25 wt.% and Mn:15 wt.%. A work function of the Cu-alloy wiring is in a range from 0 eV to -0.2 eV with respect to the work function of ITO.

Description

  The present invention relates to, for example, a Cu alloy wiring connecting ITO and a driving driver in a capacitive touch panel using an ITO film as a sensor, and a Cu alloy sputtering target for forming the wiring by sputtering.

  Recently, capacitive touch panels have been widely adopted for smartphones and tablets. In this method, an X-Y electrode pattern is formed of ITO on glass or a film substrate, and the capacitance is changed when a finger or the like approaches between the electrodes to detect the position.

  The ITO and the drive driver are connected by wiring. For this wiring material, Ag paste, Al, Mo or the like is used. In recent years, gesture operations (enlargement, reduction, movement) have been performed from a single touch panel operation, and further speedup has been demanded. Further, in order to cope with the increase in the screen size of the panel, further narrowing of the frame is required. Therefore, an Al or Mo film that can be miniaturized is formed by sputtering from a conventional Ag paste.

  However, since the Mo film is expensive and has low sputtering efficiency, there is a problem in productivity. In addition, in the case of an Al film, a phenomenon in which metal atoms and vacancies move (electromigration) occurs due to an increase in current density flowing in the wiring, and metal atoms and vacancies are intended to relieve tensile stress applied to the wiring. A phenomenon (stress migration) in which holes move is also generated. Due to the occurrence of voids due to these electromigration and stress migration, there is a problem that the resistance value increases, and further, there is a problem of disconnection due to the occurrence of voids, and reliability is a problem.

  Therefore, from the viewpoint of reducing the cost of the wiring material and reducing the resistance, a wiring material having a lower resistance value than that of the Al or Mo film is required, and the demand for using Cu as the wiring material is increasing. However, Cu is easily oxidized and has a problem in weather resistance. Therefore, a protective film is generally provided on the Cu wiring material.

  High corrosion resistance and good etching characteristics are required as characteristics required for the protective film. In order to solve these problems, for example, techniques described in the following patent documents are disclosed.

  In Patent Document 1, it is a wiring material that constitutes a TFT element for display, and Cu contains Pt, Ir, Pd, Sm in an amount of 0.01 to 0.5 atomic%, or Cu contains Ni, Pt, Ir, Rd. It is disclosed that a Cu alloy wiring film having excellent adhesion to glass can be obtained by containing 0.01 to 0.5 atomic% of Ru, Cr, Nb, and W. However, sufficient weather resistance cannot be obtained with the above composition.

  Patent Document 2 discloses a NiCu alloy sputtering target material containing Co, Mo, and Mn as a protective film for a Cu electrode. However, since Ni is a material with excellent corrosion resistance, the CuNi alloy, which is a protective film of Cu, remains as a residue during wet etching during pattern formation, and the characteristics as an electrode are impaired.

  Patent Document 3 discloses a NiCu alloy sputtering target material used for forming a Cu electrode protective film. However, similar to Patent Document 2, since it has a composition containing a large amount of Ni, it is necessary to use a special chemical for etching.

  In Patent Document 4, a junction electrode structure in which an electrode made of a copper (Cu) alloy is provided on a silicon (Si) semiconductor layer, the thermal diffusion of the interface itself at the interface between the semiconductor layer and the electrode. A junction electrode structure comprising an ohmic contact layer made of a region is disclosed. However, sufficient weather resistance cannot be obtained with the above composition.

WO2008 / 069214 International Publication Pamphlet JP 2011-052304 A JP 2012-193444 A JP 2010-263033 A

  As described in Patent Documents 1 to 4, it is difficult for the protective film for Cu wiring to satisfy the required characteristics such as weather resistance and etching suitability, and the etching rate of the protective film and the underlying Cu wiring match. However, when the wiring pattern is constructed by etching, there is a problem that the Cu wiring is thinned in the cross section and the protective film remains in an eaves shape. For this reason, although a single-layer wiring material that does not require a protective film has been studied, desired performance has not yet been obtained in terms of weather resistance and electrical resistance characteristics.

  In recent years, the wiring pattern has become complicated, and ITO may be further formed on the protective film. At this time, if the work functions of the protective film and the ITO film are different from each other, Schottky connection may occur and the wiring cannot be used. In order for the protective film and the ITO film to be in ohmic connection, it is important that the work function of the protective film is lower than the work function of the ITO film. However, a protective film that has a work function lower than that of the ITO film and satisfies high corrosion resistance and good etching characteristics at the same time has not been obtained so far. There is no disclosure or suggestion in the patent literature.

  Therefore, the present invention has been proposed in view of such a conventional situation, and is used as a substitute for Cu wiring, and has a wiring layer having substantially the same value as the work function of the ITO film and excellent in weather resistance, It aims at providing Cu alloy sputtering target for forming wiring.

  Since CuNi alloy is excellent in weather resistance, it has been conventionally used as a Cu wiring protective film. However, since the work function is higher than that of the ITO film, the connection with the ITO film is not an ohmic connection, which is a problem. In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, it is possible to adjust the work function of the Cu alloy while maintaining the weather resistance by adding Mn to the CuNi alloy. As a result, the present invention has been completed. Specifically, the present invention provides the following.

The first of the present invention is a Cu alloy wiring made of a composition which is Cu which contains at least Ni and Mn, and the balance may contain inevitable components,
The following four points (A) on the XY plane coordinates when the Ni content (Wt%) is the X axis and the Mn content (W t%) is the Y axis are the contents of Ni and Mn in the composition: (B), (C), within the range surrounded by (D),
(A) Ni: 20 wt%, Mn: 10 wt%
(B) Ni: 15 wt%, Mn: 20 wt%
(C) Ni: 20 wt%, Mn: 20 wt%
(D) Ni: 25 wt%, Mn: 15 wt%
The Cu alloy wiring is characterized in that the work function of the Cu alloy wiring is a value in the range of 0 eV to -0.2 eV with respect to the work function of ITO.

  A second aspect of the present invention is the Cu alloy wiring according to the first invention, wherein the reflectance change at 650 nm on the surface of the Cu alloy wiring is within 20% before and after the atmospheric heat treatment at 150 ° C. for 1 hour.

  A third aspect of the present invention is the Cu alloy wiring according to the first invention, wherein the reflectance change at 650 nm on the surface of the Cu alloy wiring is within 20% before and after the salt water treatment with 5% saline for 24 hours.

4th of this invention is Cu alloy sputtering target which consists of a composition which is Cu which contains Ni and Mn at least, and the remainder may contain an unavoidable component,
The following four points (A) on the XY plane coordinates when the Ni content (Wt%) is the X axis and the Mn content (W t%) is the Y axis are the contents of Ni and Mn in the composition: (B), (C), within the range surrounded by (D),
(A) Ni: 20 wt%, Mn: 10 wt%
(B) Ni: 15 wt%, Mn: 20 wt%
(C) Ni: 20 wt%, Mn: 20 wt%
(D) Ni: 25 wt%, Mn: 15 wt%
The Cu alloy sputtering target is characterized in that the work function of the Cu alloy wiring is in the range of 0 eV to -0.2 eV with respect to the work function of ITO.

  For example, a wiring material layered on an ITO film used for a capacitive touch panel, specifically, a Cu alloy wiring / ITO film layered structure in which an ITO film is formed on the wiring is provided. In the pattern wiring, it is possible to provide a Cu alloy wiring material in which the connection with the ITO film is an ohmic connection and excellent in etching property, oxidation resistance and corrosion resistance, and a Cu alloy sputtering target for forming the wiring material.

It is a figure which shows the content range of Ni and Mn in XY plane coordinate.

  Hereinafter, embodiments of the Cu alloy wiring and the Cu alloy sputtering target of the present invention will be described in detail.

<Cu alloy wiring>
In the alloy composition in the case where the Cu alloy wiring of the present invention is Ni, Mn, and the balance is Cu that may contain an inevitable component, Ni and Mn are (A), (B), (C), (D) is an alloy within the four composition ranges (shaded portions in FIG. 1). Here, (A), (B), (C), and (D) are: (A) 20 wt% Ni, 10 wt% Mn, (B) 15 wt% Ni, 20 wt% Mn, (C ) Is 20 wt% Ni, 20 wt% Mn, (D) is 25 wt% Ni, and 15 wt% Mn.

  By using an alloy having the above composition range, the work function difference with the ITO film is reduced, and the connection with the ITO film becomes ohmic connection, and the wiring material is excellent in etching property, oxidation resistance and corrosion resistance. Is.

  The Cu used for the alloy may be, for example, one produced by depositing spongy or dendritic Cu on the cathode by electrolysis in an electrolytic solution such as a copper sulfate solution. In addition, you may use what was manufactured by Cu other than these methods.

  Since Ni is a metal excellent in weather resistance, the weather resistance of the Cu alloy is improved by including Ni. Here, the Ni content is 15 wt% to 25 wt%, preferably 17.5 wt% to 22.5 wt%. If Ni is less than 15 wt%, sufficient weather resistance cannot be obtained, and if it exceeds 25 wt%, it is not preferable because it remains as a residue during the etching process in the wiring pattern formation process.

  Mn is a metal having a low work function and is used for adjusting the work function of the Cu alloy. While the work function of ITO is 4.8 eV, for example, the work function of a copper alloy containing 40 wt% Ni is about 4.9 eV, which is higher than that of ITO. This is because the work function of Ni is as high as 5.1 eV. Therefore, in order to match the work functions of ITO and copper alloy, it is necessary to add a metal having a low work function as the third component. Mn has a work function of 4.1 eV, and the work function of the Cu—Ni alloy can be adjusted. Mn also improves the etching properties of the Cu alloy.

  The work function of the obtained Cu alloy wiring is 4.6 eV or more and 4.8 eV or less, and has a value in the range of 0 eV to −0.2 eV with respect to the work function of the ITO film. A value in the range of 0 eV to -0.1 eV is preferable. When the work function of the Cu alloy wiring is larger than the work function of the ITO film, the ITO film before contact has a higher Fermi level, so the electrons in the ITO film flow into the Cu alloy wiring by contact and the Fermi level matches. To do. The internal energy level of the ITO film decreases by the difference in work function. Electrons flow into the metal at the interface of the ITO film in contact with the Cu alloy wiring, so that positively ionized donors remain to form space charges, creating a potential barrier, and no ohmic connection. Therefore, it is preferable to match the work functions of the Cu alloy wiring and the ITO film as much as possible.

  Even when Ni, Mn, Cu, and elements other than the above inevitable components are included, the content of Ni and Mn in the composition and the value of work function should be within the scope of the claims. Within the scope of the present invention.

  Moreover, since it uses as Cu alloy wiring, it is necessary to be excellent in oxidation resistance and corrosion resistance. The reflectance change at 650 nm of the Cu alloy wiring when heated at 150 ° C. in the atmosphere or immersed in 5% saline for 24 hours by the method described in the examples is preferably 20% or less. The greater the change, the more noticeable the change in appearance. More preferably, it is 10% or less, More preferably, it is 5% or less.

<Method for producing Cu alloy sputtering target>
The Cu alloy wiring as described above is manufactured by sputtering. The sputtering target is manufactured with the same composition as the Cu alloy wiring. In the manufacturing method, Cu, Ni, and Mn elements are first blended so that the Ni content in the sputtering target is 15 to 25 wt% and the Mn content is 10 to 20 wt%. Next, the blended raw materials are alloyed by a melting / casting method. The temperature for alloying is preferably about 1300 to 1600 ° C. The crucible to be used is not particularly specified, but a graphite crucible is not preferable. When a graphite crucible is used, the quality of the resulting ingot may be reduced because it is carburized into Ni as an additive element at about 1300 ° C. The ingot product obtained by the melting / casting method has a uniform composition distribution, and plastic processing is easy.

  Next, a sputtering target is manufactured using the obtained ingot. Any processing method may be used for processing into a sputtering target, hot forging or cold forging may be used, or wire cutting may be used to form a plate material. The obtained plate material can be bonded to a backing plate, which is a sputtering jig, using a brazing material to obtain a Cu alloy sputtering target. The Cu alloy sputtering target includes the state of the sputtering target material before the sputtering target finishing process such as surface grinding and bonding.

<Method for forming wiring>
The wiring formed using the Cu alloy sputtering target of the present invention is produced by the following method. First, wiring is formed on an ITO substrate by sputtering with the Cu alloy sputtering target of the present invention. The thickness of the wiring is 150 to 200 nm. If it is thinner than 150 nm, the electrical resistance may increase. On the other hand, if it is thicker than 200 nm, productivity is lowered or etching becomes difficult, which is not preferable.

  An ITO film is formed on the wiring by sputtering and then etched along the wiring pattern. Since the wiring material of the present invention has an etching property equivalent to that of Cu, conventionally known ferric chloride can be used as the etching solution. Thus, the Cu alloy wiring of the present invention is suitably used for the configuration of Cu wiring / ITO film.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

Example 1
The starting materials are weighed so that Ni is 20.0 wt%, Mn is 10.0 wt%, and the balance is Cu, and a high-frequency induction vacuum melting furnace (manufactured by Fuji Denpa Kogyo Co., Ltd.) is used as the melting furnace, and the raw materials are placed in the alumina crucible. It was charged and heated to 1450 ° C. in an Ar atmosphere, and cast into an iron mold.

  Next, after removing foreign matters on the surface of the obtained ingot with a grinder or the like, it was heated to 900 ° C. by hot rolling, and the ingot was reduced to 80% and processed into a plate shape. The obtained plate material was cut into a diameter of 6 inches by wire cutting, and the cut plate material was processed to a thickness of 5 mm by surface grinding. Thereafter, In was used as a brazing material and attached to a backing plate to produce a sputtering target.

A Cu alloy wiring was formed by magnetron sputtering using this sputtering target. As a sputtering apparatus, a sputtering apparatus manufactured by ULVAC (model number SH-450) was used. After attaching the sputtering target to the sputtering apparatus, attaching the film substrate on which the ITO film of 25 mm × 50 mm is formed facing the sputtering target, and evacuating the inside of the apparatus until the degree of vacuum becomes 6 × 10 ⁻⁴ Pa , Ar gas was introduced until the gas pressure reached 0.5 Pa, and the film substrate on which the ITO film was formed was rotated at 30 rpm, while the input power was 700 W and the film formation time was 180 seconds. A Cu alloy wiring made of a Ni—Mn alloy was obtained.

  The composition of the obtained Cu alloy wiring was the same as that of the sputtering target when the Cu alloy wiring was dissolved with an acid and analyzed with an ICP emission spectroscopic analyzer (model number SPS3500 manufactured by SII Nanotechnology).

(Measurement of work function)
The work function of this Cu alloy wiring was measured with a photoelectron spectrometer (manufactured by Riken Keiki Co., Ltd., model number AC-2). The work function of the Cu alloy wiring formed was 4.78 eV, which was almost the same value as the ITO film 4.8 eV.

(Evaluation of corrosion resistance and oxidation resistance)
As the corrosion resistance test and the oxidation resistance test of the obtained wiring, a salt water immersion test and a heat resistance test were performed, respectively. In the salt water immersion test, the wiring was immersed in 5% saline for 24 hours, and the change in surface reflectance at a wavelength of 650 nm before and after the test was measured with a spectrophotometer (manufactured by Hitachi, Ltd., model number U-4000). In the oxidation resistance test, the Cu alloy wiring was placed in an oven at 150 ° C. for 1 hour, and the change in surface reflectance at a wavelength of 650 nm before and after the test was similarly measured with a spectrophotometer. The reflectance change rate is a value obtained by dividing the value before the test and the value after the test by the value before the test. This is measured as the change in reflectance (%), and when the reflectance change rate is 20% or less, And over 20% was evaluated as x.

(Evaluation of etching properties)
The etching property of the obtained wiring is that etching is performed by immersing a ferric chloride aqueous solution of 42 ° Baume as an etching solution at 35 ° C. and dipping for 80 seconds, and then etching by washing with water. The presence or absence of the residue was confirmed by checking with a microscope.

(Evaluation of ohmic connection)
A Cu alloy wiring was produced on the ITO film under the above-described conditions, and the VI characteristics were examined. When the ohmic connection was made between the ITO film and the Cu alloy wiring, the evaluation was ○, and otherwise it was evaluated as ×.

  The above evaluation results are summarized in Table 1.

(Examples 2 to 6, Comparative Examples 1 to 4)
Except for changing the proportions of Ni, Mn, and remaining Cu as shown in Table 1, Cu alloy wiring was obtained in the same manner as in Example 1, and the results of the same evaluation as in Example 1 are shown in Table 1. .

  FIG. 1 shows a plot of the compositions of Examples 1 to 6 and Comparative Examples 1 to 4 on a plane XY coordinate indicating the Ni—Mg content ratio. As is apparent from Table 1 and FIG. 1, in the example of the present invention, it can be understood that a desired work function is obtained in the composition region in the hatched portion in FIG. 1, and that the corrosion resistance, oxidation resistance, and etching property are excellent. .

Claims (4)

A Cu alloy wiring comprising a composition containing at least Ni and Mn, the balance being Cu which may contain inevitable components,
The following four points (A) on the XY plane coordinates when the Ni content (Wt%) is the X axis and the Mn content (W t%) is the Y axis are the contents of Ni and Mn in the composition: (B), (C), within the range surrounded by (D),
(A) Ni: 20 wt%, Mn: 10 wt%
(B) Ni: 15 wt%, Mn: 20 wt%
(C) Ni: 20 wt%, Mn: 20 wt%
(D) Ni: 25 wt%, Mn: 15 wt%
The Cu alloy wiring, wherein the work function of the Cu alloy wiring is a value in the range of 0 eV to -0.2 eV with respect to the work function of ITO.   The Cu alloy wiring according to claim 1, wherein a change in reflectance at 650 nm on the surface of the Cu alloy wiring is within 20% before and after the atmospheric heat treatment at 150 ° C for 1 hour.   The Cu alloy wiring according to claim 1, wherein the reflectance change at 650 nm on the surface of the Cu alloy wiring is within 20% before and after the salt water treatment with 5% saline for 24 hours. A Cu alloy sputtering target comprising a composition comprising at least Ni and Mn, the balance being Cu that may contain inevitable components,
The following four points (A) on the XY plane coordinates when the Ni content (Wt%) is the X axis and the Mn content (W t%) is the Y axis are the contents of Ni and Mn in the composition: (B), (C), within the range surrounded by (D),
(A) Ni: 20 wt%, Mn: 10 wt%
(B) Ni: 15 wt%, Mn: 20 wt%
(C) Ni: 20 wt%, Mn: 20 wt%
(D) Ni: 25 wt%, Mn: 15 wt%
A Cu alloy sputtering target, wherein a work function of the Cu alloy wiring is in a range of 0 eV to -0.2 eV with respect to a work function of ITO.

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