JP2013179265A - Laminate wiring film for electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate wiring film for electronic component using a coating layer which can ensure adhesion to a substrate as a ground layer required for the coating layer, or heat resistance as an upper layer (cap film) for protecting the surface of Cu in a main conductive layer, in the laminate wiring film having a main conductive layer of Cu, and can maintain a low electric resistance value even after a heating process.SOLUTION: The laminate wiring film for electronic component having a metal layer formed on a substrate consists of a main conductive layer containing Cu as a main component, and a coating layer covering at least one surface of the main conductive layer. The coating layer is a Cu alloy having a composition formula represented by Cu-Al, 20≤X≤60 in atomic ratio, and the remainder is inevitable impurities.

Description

  The present invention relates to a multilayer wiring film for electronic parts that requires adhesion to a substrate and heat resistance by heat treatment.

  Flat display devices (flat panel displays, hereinafter) such as liquid crystal displays (hereinafter referred to as LCDs), plasma display panels (hereinafter referred to as PDPs), electrophoretic displays used for electronic paper, etc. for forming thin film devices on glass substrates In addition to thin film electronic components such as various semiconductor devices, thin film sensors, and magnetic heads, a wiring film having a low electric resistance value is required. For example, FPDs such as LCDs, PDPs, and organic EL displays have a large screen, high definition, and high-speed response, and the resistance value of the thin film transistor (TFT) wiring film used as the driving element is reduced. Is required. Furthermore, in recent years, new products such as a touch panel that adds operability to the FPD and a flexible FPD using a resin substrate or an ultrathin glass substrate have been developed.

In recent years, in order to meet the above-described demand for lowering resistance, studies have been made to change the material for forming the main conductive layer from Al to lower resistance Cu. In addition, touch panel substrate screens that provide direct operability while viewing the screen of the FPD are also increasing in size, and studies are underway to use Cu as the main conductive layer to reduce resistance.
In addition, ITO (indium-tin oxide), which is a transparent conductive film, is generally used for position detection electrodes of touch panels used in smartphones, tablet PCs, and the like. Cu can be contacted with ITO, but has low adhesion to the substrate. Therefore, it is necessary to form a laminated wiring film with Mo, Mo alloy or the like as a coating layer in order to ensure adhesion.

In addition, if an etchant containing phosphoric acid and nitric acid used for etching a multilayer wiring film composed of a conventional Mo coating layer and an Al main conductive layer is applied to a multilayer wiring film in which a Mo coating layer and a Cu main conductive layer are stacked. In some cases, the Cu main conductive layer is etched early and a step is generated in the laminated wiring film. When the concentration of the etchant is adjusted to suppress this step, there is a problem that a residue is generated on the substrate.
For such problems, as a coating layer, Cu—Al—Ca alloy is used in an oxygen atmosphere as a coating layer that can be etched together with Cu of the main conductive layer while ensuring adhesion with a substrate similar to conventional Mo. The application of a film formed by sputtering is proposed (see Patent Document 1).

JP 2010-212465 A

The coating layer proposed in Patent Document 1 contains 1 to 10 atomic% Al and 0.1 to 2.0 atomic% Ca, and is a Cu alloy that provides high adhesion by sputtering in an oxygen atmosphere. It is a coating layer.
However, when sputtering is performed in an oxygen atmosphere, nodules, which are reaction products with oxygen, may accumulate on the sputtering target, causing abnormal discharge and generating particles. In addition, depending on the flow direction of the oxygen gas in the sputtering chamber, a difference in the amount of oxygen taken into the sputtered coating layer is likely to occur, which may cause a problem in that the characteristics and adhesion of the coating layer vary.

  In addition, since the signal line cable may be heated in the air when the signal line cable is attached to the terminal portion of the FPD, the laminated wiring film is required to have improved heat resistance. In addition, in a semiconductor film using an oxide, heat treatment may be performed at a high temperature of 350 ° C. or higher in an oxygen-containing atmosphere in order to improve characteristics or stabilize the semiconductor film. In some cases, heat treatment is performed at a high temperature of 350 ° C. or higher after a protective film containing oxygen is formed. Heat resistance is required so that stable characteristics can be maintained as a laminated wiring film even after the heat treatment in an environment in contact with oxygen.

  On the other hand, since the Cu—Al—Ca alloy coating layer sputtered in the oxygen atmosphere disclosed in Patent Document 1 described above is introduced with oxygen, the heat resistance is not sufficient for the above-described requirements, and when coated, There was concern that oxygen would diffuse and increase the electrical resistance value of Cu in the main conductive layer.

  An object of the present invention is to provide an upper layer film (cap layer) that protects the adhesion of a substrate as a base layer required for a coating layer and the Cu surface of the main conductive layer in a laminated wiring film having Cu as a main conductive layer. It is intended to provide a laminated wiring film for an electronic component using a coating layer that can secure heat resistance and maintain a low electric resistance value even after a heating process.

  In view of the above-mentioned problems, the present inventor uses a metal layer obtained by adding a predetermined amount of Al to Cu as the coating layer, thereby ensuring adhesion with the substrate and suppressing oxidation of Cu as the main conductive layer. The present invention has been found.

That is, the present invention is a laminated wiring film for electronic components in which a metal layer is formed on a substrate, comprising a main conductive layer mainly composed of Cu and a covering layer covering at least one surface of the main conductive layer. The coating layer is an invention of a laminated wiring film for electronic parts, in which the composition formula in atomic ratio is represented by Cu _100-X -Al _X , 20 ≦ X ≦ 60, and the balance is a Cu alloy made of inevitable impurities. .
The coating layer is preferably a base layer.
Moreover, it is preferable that the said coating layer is a cap layer.
The covering layer is more preferably an underlayer and a cap layer.
In the present invention, X in the composition formula is preferably 25 ≦ X ≦ 35.

The multilayer wiring film for electronic parts using the Cu alloy of the present invention as a coating layer can be formed stably and easily by performing normal sputtering without using a method of sputtering in a special oxygen atmosphere. And when the coating layer of the present invention is formed as a foundation layer, it can secure adhesion to the substrate, and when it is formed as a foundation layer and a cap layer, it can improve heat resistance, even after a heating process. A low electrical resistance value can be maintained.
Thus, the present invention is a useful technique that can greatly contribute to the stable production of electronic components and the improvement of reliability by being used for various electronic devices, for example, wiring films such as FPD. In particular, it becomes a very useful laminated wiring film for a flexible FPD using a touch panel or a resin substrate.

It is a cross-sectional schematic diagram of the multilayer wiring film for electronic components of the present invention.

  A schematic cross-sectional view of the multilayer wiring film for electronic parts of the present invention is shown in FIG. The multilayer wiring film for electronic parts of the present invention is formed of a coating layer covering at least one surface of the main conductive layer 3 mainly composed of Cu, and is formed on the substrate 1, for example. In FIG. 1, the covering layers 2 and 4 are formed on both surfaces of the main conductive layer 3, but only one surface of the base layer 2 or the cap layer 4 may be covered and can be appropriately selected. When only one surface of the main conductive layer is covered with the coating layer of the present invention, the other surface of the main conductive layer is coated with a coating layer having a composition different from that of the present invention depending on the use of the electronic component. Can be covered.

An important feature of the present invention is that, in the coating layer of the multilayer wiring film for electronic components shown in FIG. 1, by adding a specific amount of Al to Cu, adhesion with the substrate is improved and heat resistance is improved. And a low electrical resistance value can be maintained even after the heating step. The laminated film for electronic parts of the present invention will be described in detail below.
In the following description, “adhesiveness” refers to the difficulty of peeling off from the substrate under the laminated wiring film. “Heat resistance” refers to the difficulty of oxidation of the multilayer wiring film in a high temperature environment and the increase of the electrical resistance value of the multilayer wiring film due to diffusion of Al in the coating layer into the main conductive layer. To do.

The reason why the Cu alloy in which a specific amount of Al is added to Cu is used as the coating layer of the laminated film for electronic parts of the present invention is to improve the adhesion with the substrate when used as the underlayer of the main conductive layer. is there. Cu is an element having low adhesion to an oxide such as a glass substrate. The inventor has found that the adhesion can be significantly improved by adding a specific amount of Al to Cu. The effect becomes clear when 20 atomic% of Al is added to Cu, and is saturated at 25 atomic% or more.
In addition, the Cu layer of the main conductive layer may be oxidized when heated in the atmosphere and the electrical resistance value may be greatly increased. By forming the coating layer made of the Cu alloy of the present invention as a cap layer of the main conductive layer, the surface of the main conductive layer is prevented from being directly exposed to the atmosphere, and the electrical resistance value is increased by oxidation of the Cu layer which is the main conductive layer. Can be suppressed. The effect becomes clear when 15 atomic% or more of Al is added to Cu.
The reason for the manifestation of this effect is not clear, but when a Cu alloy within the scope of the present invention is formed by sputtering as a coating layer, columnar crystals are not formed, and it is presumed that oxygen diffusion is suppressed.

In addition, as a common problem when a coating layer in which a specific amount of Al is added to Cu is formed as an underlayer or cap layer, Al is an element that is easily thermally diffused with respect to Cu, and addition of Al to Cu When the amount exceeds 60 atomic%, Al in the Cu alloy that forms the coating layer easily diffuses into Cu, which is the main conductive layer, in the heating process when manufacturing electronic parts such as FPD, and low electrical resistance. There is a problem that it is difficult to maintain the value. For this reason, the addition amount of Al to Cu forming the coating layer is set to 60 atomic% or less.
From the above, the amount of Al added to Cu as the coating layer was set to 20 to 60 atomic% in order to ensure adhesion and heat resistance.
In addition, when the laminated wiring film in which the coating layer is formed on the main conductive layer is heated at a temperature higher than 250 ° C., Al contained in the coating layer is more easily diffused into Cu of the main conductive layer, so that the lower electric resistance value In order to maintain the above, it is preferable that the amount of Al added is 35 atomic% or less. In order to secure higher adhesion and high heat resistance, the amount of Al added is more preferably 25 to 35 atomic%.

In the multilayer wiring film for electronic parts of the present invention, in order to stably obtain a low electric resistance value, it is preferable to set the film thickness of Cu as the main conductive layer to 100 to 1000 nm. This is because when the thickness of the main conductive layer is less than 100 nm, the electric resistance value is likely to increase due to the influence of electron scattering specific to the thin film. On the other hand, when the thickness is greater than 1000 nm, it takes time to form a film, and the substrate is likely to warp due to film stress.
Moreover, the main conductive layer which has Cu as a main component is preferable at the point from which pure Cu can obtain the lowest electrical resistance value. In consideration of reliability such as heat resistance and corrosion resistance, a Cu alloy layer obtained by adding a transition metal or a semimetal to Cu may be used. At this time, in order to obtain the lowest possible electrical resistance value as the main conductive layer, it is preferable that the amount of element added to Cu is 5 atomic% or less.

In addition, in the multilayer wiring film for electronic parts of the present invention, in order to stably obtain a low electrical resistance value and high adhesion / heat resistance, the film thickness of the Cu alloy layer as the coating layer should be 5 to 100 nm. preferable. This is because if the film thickness is less than 5 nm when used as a base layer, the continuity of the coating layer becomes low, and sufficient adhesion cannot be ensured. The coating layer is more preferably 10 nm or more, which allows more stable and uniform deposition.
The film thickness when used as a cap layer is preferably 20 nm or more, and more preferably 30 nm or more when heated at a higher temperature of 250 ° C. or more. The reason is that it is necessary to sufficiently suppress the entry of oxygen by the coating layer.
In order to suppress the intrusion of oxygen, the thickness of the coating layer is preferably as thick as possible. However, when the thickness exceeds 100 nm, the thickness of the main conductive layer is increased by increasing the thickness of the coating layer under the condition that the total thickness is constant. Therefore, the electrical resistance value of the entire film including the main conductive layer and the covering layer becomes high, and it becomes difficult to obtain a low electrical resistance value when laminated with the main conductive layer. In addition, when the multilayer wiring film for electronic parts is heated at 300 ° C. or higher, the film thickness of the coating layer is used to suppress an increase in electrical resistance due to atomic diffusion of Al in the coating layer to the Cu of the main conductive layer. Is preferably 50 nm or less.

The laminated wiring film for electronic parts of the present invention can sufficiently maintain the effect of protecting the Cu layer of the main conductive layer even when it is configured using a resin film substrate, an ultrathin glass substrate, or the like as the substrate.
In addition, in order to obtain a large FPD screen and high speed driving, the heating temperature during the TFT manufacturing process tends to increase. Since the multilayer wiring film for electronic parts of the present invention has excellent heat resistance by forming a coating layer made of a Cu alloy on the Cu layer of the main conductive layer, it suppresses thermal diffusion to the Cu of the main conductive layer. And a low electric resistance value can be maintained.

In order to form the multilayer wiring film for electronic parts of the present invention, a sputtering method using a sputtering target is suitable. As the sputtering method, a method of forming a film using a Cu or Cu alloy sputtering target having the same composition as the main conductive layer and the coating layer is preferable. Since the present invention can perform normal sputtering, deposition of nodules on the sputtering target can be suppressed, abnormal discharge can be prevented, and film formation can be performed stably and easily without generation of particles.
In order to form the coating layer of the multilayer wiring film for electronic parts of the present invention, the coating layer is stably formed by using a Cu alloy sputtering target containing 20 to 60 atomic% of Al and the balance Cu and unavoidable impurities. it can.
Further, as described above, in order to obtain high adhesion and heat resistance with the substrate as the coating layer, it is preferable that Al contained in the Cu alloy sputtering target is 25 to 35 atomic%.

  In addition, as a method for producing the above-mentioned Cu alloy sputtering target material, a method of producing an ingot produced by melting and casting a raw material prepared to a predetermined composition, or a process of atomizing or grinding an ingot of Cu alloy powder It is possible to manufacture by the method of sintering the obtained powder. Regarding the manufacturing method, it is possible to appropriately apply a method that can be manufactured inexpensively and stably depending on the size and shape of the sputtering target material.

  In the Cu alloy layer that is a coating layer of the multilayer wiring film for electronic parts of the present invention, in order to ensure adhesion with a substrate when used as a base layer and heat resistance when used as a cap layer, an essential element It is preferable that the content of unavoidable impurities other than Cu occupying the balance other than Al is low. However, inevitable impurities such as oxygen, nitrogen and carbon, which are gas components, Fe which is a transition metal, and semi-metallic Si may be included as long as the effects of the present invention are not impaired. For example, oxygen and nitrogen of gas components are each 1000 ppm by mass or less, carbon is 200 ppm by mass or less, Fe is 500 ppm by mass or less, Si is 100 ppm by mass or less, and the purity excluding gas components is 99.9%. The above is preferable.

First, a sputtering target material for forming a Cu alloy layer to be a coating layer was produced. After weighing to a predetermined composition shown in Table 1, it was melted in a vacuum melting furnace and cast to prepare a Cu alloy ingot. Thereafter, a sputtering target material having a diameter of 100 mm and a thickness of 5 mm was produced by machining each ingot.
The Cu sputtering target material for forming the main conductive layer was cut out from an oxygen-free copper (OFC) material manufactured by Hitachi Cable, Ltd. Moreover, the sputtering target material by Sumitomo Chemical Co., Ltd. was used for Al sputtering target material.

Each sputtering target material produced above was brazed to a Cu backing plate and attached to a sputtering apparatus of model number CS-200 manufactured by ULVAC.
Using each prepared sputtering target material on a glass substrate of 25 mm × 50 mm, a Cu alloy layer as a coating layer and a Cu layer as a main conductive layer are respectively shown in Table 1 so as to have the configuration shown in FIG. A multilayer wiring film for electronic parts was obtained by sputtering using the film thickness shown. For comparison, a single layer of pure Cu, a laminated film of Al and Cu, and a laminated film of Mo and Al were similarly formed.

The evaluation of adhesion was performed for each laminated wiring film by a method defined in JIS K5400. First, a transparent adhesive tape (product name: transparent beautiful color) manufactured by Sumitomo 3M Co., Ltd. is pasted on each of the above laminated wiring films, cut into a grid pattern at intervals of 2 mm, and the transparent adhesive tape is peeled off. The remaining squares of the multilayer wiring film for electronic parts were evaluated by obtaining the total fraction. The results are shown in Table 1.
Evaluation of heat resistance was performed by measuring a change in electric resistance value after heating each multilayer wiring film for electronic components at 150 ° C., 200 ° C., 250 ° C., 300 ° C., and 350 ° C. for 1 hour in the air. The electrical resistance value was measured using a 4-terminal thin film resistivity meter, model: MCP-T400, manufactured by Mitsubishi Yuka Co., Ltd. (currently Dia Instruments Co., Ltd.). The results are shown in Table 1.

  As shown in Table 1, the sample No. of the comparative example in which the coating layer is not formed. No. 1 had low adhesion, and when heated in the atmosphere, it was oxidized at 250 ° C. or higher, and continuity could not be obtained and the electric resistance value could not be measured. Sample No. 1 in which a coating layer in which 3 atomic% of Al was added to Cu of Comparative Example was formed. In sample No. 2, sample no. As in No. 1, the adhesion was low, and oxidation occurred at 250 ° C. or higher, so that no electrical continuity was obtained and the electric resistance value could not be measured. Sample No. 1 in which a coating layer in which 15 atomic% of Al was added to Cu of Comparative Example was formed. 3 was confirmed to be inferior in adhesion. Sample No. 1 in which an Al coating layer was formed as the coating layer of the comparative example. Although No. 10 was excellent in adhesiveness, it was confirmed that when it was heated to 250 ° C. or higher, the electrical resistance value was significantly increased and the heat resistance was poor.

In contrast, Sample No. 1 in which a coating layer in which Al was added to Cu within the scope of the present invention was formed. 4-No. The laminated wiring film for electronic parts No. 8 has a high adhesion to the substrate of 90% or more, and has sufficient adhesion that does not peel at all when the Al addition amount is 25 atomic% or more. It was confirmed that high adhesion could be secured.
In addition, the multilayer wiring film for electronic parts of the present invention does not change greatly in the electric resistance value even when heated to 250 ° C. or higher, and has high heat resistance as a cap layer that can suppress oxidation of Cu in the main conductive layer. I was able to confirm.
Sample No. having a coating layer in which 15 atomic% of Al was added to Cu as a comparative example. When the structure of the multilayer wiring film 3 for electronic parts was confirmed by X-ray diffractometry, Cu diffraction lines were mainly confirmed, and the Cu alloy layer was confirmed to be crystalline similar to Cu.
On the other hand, sample No. 1 having a coating layer in which 25 atomic% of Al is added to Cu according to the present invention. In the multilayer wiring film for electronic components of 5, a diffraction line close to a broad amorphous state showing no clear peak in the low angle region is confirmed in addition to the Cu diffraction line, and the Cu alloy layer has a structure close to an amorphous state. It is guessed that. From this result, the grain boundary is reduced by making the Cu alloy layer close to an amorphous structure, oxygen entry into Cu as the main conductive layer is suppressed, and oxidation is prevented, resulting in a low electrical resistance value. It is thought that it is maintained.

Next, the etching property was evaluated. Using an etchant Cu-02 for Cu manufactured by Kanto Kagaku Co., Ltd., a photoresist is applied to only half the area on the multilayer wiring film for electronic parts prepared on the substrate in Example 1 and dried to obtain an etchant solution. Immersion was performed and the uncoated part was etched. The immersion time was maintained for 10 seconds after the completion of etching visually, and the maximum time for the undissolved one was 5 minutes.
The substrate pulled up from the etchant was washed with pure water, dried, and the vicinity of the boundary between the dissolved portion and the undissolved portion coated with the resist was observed with an optical microscope. The results are shown in Table 1.
Sample No. as a comparative example. 10 Al was insoluble in the etchant for Cu. In addition, Sample No. 7-No. In No. 9, it was confirmed that a step or residue was generated in the undissolved portion.
On the other hand, in the examples of the present invention, the etching property is good especially when the Al addition amount is up to 35 atomic%, and there is no step or residue until the Al addition amount is 60 atomic%, and the etching property is good. It was confirmed that there was.

  Using each sputtering target shown in Table 2 prepared in Example 1, a multilayer wiring film for electronic components was formed on a 100 mm × 100 mm polyimide film under the same conditions as in Example 1. Each electronic component laminated wiring film is wound around a glass tube having a diameter of 10 mm, and a transparent adhesive tape (product name: transparent beautiful color) of 25 mm width made by Sumitomo 3M Co., Ltd. is used on the surface of the electronic component laminated wiring film. The film was attached so that no bubbles remained, and was peeled off at an angle of 45 ° to evaluate the adhesion. The results are shown in Table 2.

  As shown in Table 2, sample No. In the 16 Al film, it was confirmed that film peeling occurred in some places. On the other hand, sample no. 12-No. It was confirmed that 15 laminated wiring films for electronic parts had no film peeling and high adhesion even on the film.

1 substrate 2 coating layer (underlayer)
3 Main conductive layer 4 Cover layer (cap layer)

Claims (5)

A laminated wiring film for electronic components in which a metal layer is formed on a substrate, comprising a main conductive layer mainly composed of Cu and a covering layer covering at least one surface of the main conductive layer, the covering layer comprising: A laminated wiring film for an electronic component, characterized in that the composition formula in atomic ratio is Cu _100-X -Al _X , 20 ≦ X ≦ 60, and the balance is a Cu alloy made of inevitable impurities.   The laminated wiring film for electronic parts according to claim 1, wherein the coating layer is a base layer.   The laminated wiring film for electronic components according to claim 1, wherein the coating layer is a cap layer.   The multilayer wiring film for an electronic component according to claim 1, wherein the coating layer is a base layer and a cap layer.   5. The multilayer wiring film for an electronic component according to claim 1, wherein X in the composition formula satisfies 25 ≦ X ≦ 35.