JPH07140475A - Wiring structure of liquid crystal display device - Google Patents

Abstract

PURPOSE:To easily form wiring layers and their protective layers without executing dry etching by forming another metallic wiring layers by electroplating on the metallic wiring layers on an insulating substrate so as to cover these metallic wiring layers. CONSTITUTION:After a Cr film is formed by sputtering on the glass substrate 1, this film is etched to required patterns by photolithography to form a Cr wiring layers 2 and a Cu layer 3 is formed thereon by using an electroplating device; further, a Cr plating layer 4 is formed thereon. After the resist of the glass substrate 1 is removed, silicon nitride films as insulating films are clad and formed by plasma CVD on these metallic wiring layers 2 to 4. As a result, the Cu layers 3 which are inferior in the adhesion property to the glass substrate 1 are easily and surely formed on the glass substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a wiring structure of a liquid crystal display device having reduced electric resistance.

[0002]

2. Description of the Related Art In a liquid crystal display device, in a field where high resolution and fine image display are required, a plurality of pixel electrodes and an active matrix for arranging a switching element for each pixel electrode and switching and driving each pixel electrode. Type liquid crystal display devices are commonly used. In the active matrix type liquid crystal display device, it is required to reduce the signal wiring width by increasing the number of wiring electrodes in the display screen in response to the demand for larger size and higher definition, but in this case, simply Since the required screen display quality cannot be obtained due to the voltage drop just by narrowing the signal wiring width,
It is necessary to reduce the electric resistance of the wiring material together with the miniaturization of the signal wiring.

As a metal material of a signal wiring of an active matrix type liquid crystal display device, a thin film specific resistance value is about 200 μm.
Ω · cm, Ti: about 25-200 μΩ · cm, Ta: about 20-50 μΩ · cm, Cr: about 5
Mo which is 0 μΩ · cm, M which is about 50 μΩ · cm
It is possible to use an o-Ta alloy as well as Al having the same concentration of about 4 μΩ · cm. Particularly, since Al has the lowest thin film resistivity among the above materials, Al has been widely used as a main wiring material.

When forming a signal wiring of an active matrix type liquid crystal display device using Al as a signal wiring,
As shown in FIG. 4, for example, an Al layer is formed on the glass substrate 1 by sputtering, and this is wet-etched into a desired pattern to form an Al wiring layer 5. This A
In general, silicon nitride (SiN) as an insulating layer is formed on the wiring layer.
x) The film 10 is formed by coating.

[0005]

However, in the case of the wiring structure using the conventional Al wiring layer 5 as described above, the insulating layer 10 is used.
The silicon nitride forming
Since the Al wiring layer which has already been formed is deposited at a high temperature of .degree. C., there is a problem that so-called hillocks as fine projections are generated on the surface of the Al wiring layer which has already been formed by the heat at the time of this high temperature treatment. In some cases, the hillocks cause a short circuit between the wiring layers when penetrating the insulating layer of silicon nitride formed between the wiring layers at the intersections of the wirings. Further, the conventional Al wiring layer and the silicon nitride insulating layer are generally formed at the same time as the formation of a thin film transistor (TFT) element (not shown). In this case as well, the Al gate electrode and the source or drain electrode of the TFT element are formed. Also, there is a problem that a short circuit occurs due to the hillock projection of the Al layer via the silicon nitride layer provided between them.

On the other hand, the use of Cu having a thin film specific resistance value of 2.5 Ω · cm, which is lower than that of Al, as a metal material for wiring has attracted attention, but Cu adheres to a glass substrate. Since it is inferior in properties and it is difficult to process by dry etching, it has not yet been put to practical use. Therefore, an object of the present invention is to provide a wiring structure of a liquid crystal display device in which a wiring layer and its protective layer are easily formed without performing dry etching.

[0007]

In order to achieve the above object, the wiring structure of a liquid crystal display device of the present invention comprises a substrate made of an insulating material, and a first metal wiring layer formed on the insulating substrate. A second metal wiring layer formed on the first metal wiring layer by electroplating so as to cover the first metal wiring layer.

In the wiring structure of the present invention, at least a metal of the same type as the first metal wiring and a different metal of the first or second metal wiring are formed so as to cover the second metal wiring layer. It may include a third metal wiring layer formed by electroplating so as to cover the second metal wiring layer with a metal of one side.

[0009]

[Operations and Effects] The wiring structure has a substrate made of an insulating material, a first metal wiring layer formed on the insulating substrate, and an electrical structure so that the first metal wiring layer covers the first metal wiring layer. When the metal wiring is formed by using a second metal wiring layer formed by plating, a metal such as Cu having poor adhesion to the glass substrate or having difficulty in dry etching after deposition is used. C, which has a high adhesion to the glass substrate between the glass substrate and the Cu wiring layer,
When the r wiring layer is provided, the adhesion to the glass substrate is good and the adhesion to the Cu wiring layer is good, and the r wiring layer can be easily formed without requiring a dry etching step. Also,
Even when a metal wiring layer such as Al that is easily affected by heat is used, a metal wiring layer such as Ni, which is more thermally stable, is formed on the upper layer in a self-aligned manner so as to cover the metal wiring layer. Therefore, even when an insulating film such as nitrogen silicon is formed on these metal wirings by plasma CVD or the like under relatively high temperature conditions, the Al wiring layer or the like is made of a metal such as Ni which is more thermally stable than the upper layer. Since it is covered and protected by the wiring layer, thermal effects such as hillocks are effectively prevented.

[0010]

Next, a method for forming a signal wiring of a liquid crystal display device according to the present invention will be described in detail with reference to FIGS. 1 to 3 according to an embodiment. In the present specification, the same or similar parts or elements will be described with the same numbers throughout the specification. The wiring structure of the present invention is formed by using a photolithography technique when forming a thin film transistor (TFT) used for driving a liquid crystal of an active matrix type liquid crystal display device whose description is omitted here.

FIG. 1 shows a cross section of a signal wiring using Cu connected to each TFT element of an active matrix type liquid crystal display device according to a first embodiment of the present invention. In the figure, reference numeral 1 is a cross-sectional view of the main part of one of a pair of glass substrates that holds a liquid crystal used in a liquid crystal display device. First, a Cr film is formed on the glass substrate 1 by sputtering, and then a desired pattern is etched by a photolithography technique to form a C film.
The r wiring layer (first metal wiring layer) 2 is formed to have a layer thickness of about 1000 Å.

Next, a Cu layer 3 is formed on the glass substrate 1 having the Cr wiring layer 2 formed thereon by using the electroplating apparatus shown in FIG. The plating apparatus includes a plating tank 11 that contains a plating solution 12 therein, and a temperature controller that is provided below the plating tank 11 to maintain the plating solution in the plating tank at a desired temperature. 13, a circulation path 14 provided in the plating tank 11 for circulating the plating solution 12 in the plating tank 11, and a circulation path 14 provided in the middle of the circulation path 14 for circulating the plating solution 12 in the plating tank 11. The circulation pump 15 and a filtration filter 16 provided in the middle of the circulation path on the upstream side of the circulation pump 15 are provided. Plating tank 1
In the plating solution 12 contained in 1
The plate 17 and the glass substrate 1 on which the above-mentioned Cr layer as the cathode is formed are connected to the anode and the cathode of the DC power supply 19 through the respective conductive wires. Further, in order to monitor the temperature and pH value of the plating solution 12 in the plating tank 11, a thermometer and a pH are used.
A total of 20 are provided.

The plating tank 11 of the plating apparatus thus constructed is filled with the plating solution 12 which is an aqueous solution in which 180 g / l of copper sulfate and 70 g / l of sulfuric acid are dissolved, and the anode of the DC power source 19 is a Cu plate. After connecting the glass substrate 1 on which the Cr layer is formed on the cathode 17 and the cathode as described above with the non-plated portion thereof covered with a resist through a conductor, a Cu plate 17
Between the Cu plate 17 and the Cr layer 2 of the glass substrate 1 by immersing it in the plating solution 12 with the opposite surface of the glass substrate 1 separated from the glass substrate 1 by about 3 cm and applying a required voltage to the DC power supply 19. The electric current is passed through the plating solution 12 so that the C
A Cu plating layer 3 is formed on the r layer 2. In this case, Cr
By controlling the current density on the layer 2 to be about 280 μA / cm ² and maintaining the temperature of the plating solution 12 at a temperature value of about 40 ° C., about 0.4 μm / min on the Cr layer 2 is obtained.
The Cu plating layer 3 is formed at the film forming speed of. In this way, the Cu plating layer (second metal wiring layer) 3 has a thickness of about 1000.
When the film is formed to a layer thickness of angstrom, the plating is finished, and the required work such as removing the resist on the glass substrate 1 is performed. Since the plating thickness of Cu plating is proportional to the product of current density and processing time, in order to obtain a uniform Cu plating layer, for example, Cu plate 17 of the anode and C of glass substrate 1 of the cathode are used.
By arranging the surface facing the r layer 2 in parallel, the Cr layer 2
It is sufficient to make the above current density uniform.

After forming the Cu plating layer 3 as described above, a Cr plating layer 4 having a layer thickness of about 1000 angstrom is formed on this layer. The formation of this Cr plating layer 4 is carried out by using the above-mentioned plating apparatus, in a plating solution 12 in which chromic acid 250 g / l and sulfuric acid 2.5 g / l are dissolved.
Connect a pure lead plate to the anode, and the above-mentioned Cr layer and C to the cathode.
The glass substrate 1 on which the u layer has been formed is connected in a state in which the required portions are covered with a resist, and the opposing surfaces of both are, for example, 3
It is soaked in a state of being separated from the glass substrate 1 by a direct current power source 19 so that the current density on the Cu layer 3 of the glass substrate 1 is about 5 mA / cm ² . In this case, the plating solution 12 is maintained at a temperature of about 50 ° C. By setting the Cr plating conditions in this way, the Cr plating layer 4 (third layer) is formed on the Cu layer 3 of the glass substrate 1 at a film forming rate of about 0.2 μm / min.
A metal wiring layer) is formed. When the Cr plating layer 4 is formed to a layer thickness of about 1000 angstroms, the plating is terminated, the resist on the glass substrate 1 is removed, and then silicon nitride (Si (Si) (not shown) as an insulating film is formed on these metal wiring layers.
The wiring structure according to the first embodiment of the present invention can be obtained by forming the Nx) film by plasma CVD. As described above, according to the first embodiment of the present invention, it is possible to easily and reliably form the Cu layer, which has poor adhesion to the glass substrate and is difficult to dry-etch, on the glass substrate.

Next, a method of forming a signal wiring according to the second embodiment of the present invention will be described. As shown in FIG. 3, the signal wiring according to the second embodiment of the present invention includes an Al layer 5 having a layer thickness of about 2000 angstroms on the glass substrate 1 and the Al layer.
It consists of about 1000 angstroms of Ni plating layer 6 covering the layer. Hereinafter, Al according to the second embodiment of the present invention will be described.
A method of forming a signal wiring using is described. First,
As shown in FIG.
After forming the l film, the Al wiring layer 5 is formed by etching into a desired pattern by photolithography. After masking a required portion of the glass substrate 1 on which the Al wiring layer 5 is formed with a resist, the glass substrate 1 is immersed in a plating solution 12 in which 250 g / l of nickel sulfate and 40 g / l of boric acid are dissolved to form a pure lead plate. 17 'is connected to the anode, and the glass substrate 1 is connected to the cathode, and the glass substrate 1 and the glass substrate 1 are separated by about 3 cm. As the plating conditions, the current density is about 150 μA / cm ² , and the temperature of the plating solution 12 is about 50.
The temperature and pH are set to about 4. By setting the conditions in this way, N is formed on the Al layer 5 of the glass substrate 1.
The i layer 6 is formed at a film forming rate of about 0.2 μm / min. The plating layer 6 according to this embodiment can be formed by using the above-described plating apparatus in the same manner as the plating in the first embodiment. Thus, after the Ni plating is completed, the resist is removed with an organic solvent or the like, and then a silicon nitride film (not shown) is formed on the upper surface of the metal wiring layer by plasma CVD to form the wiring according to the second embodiment of the present invention. The structure is obtained. According to the wiring structure of the present embodiment, the exposed surface of the Al wiring layer 5 on the glass substrate 1 is covered with the Ni plating layer 6 in a self-aligned manner.
It is possible to effectively prevent the occurrence of hillocks in the Al wiring layer even during high-temperature processing such as plasma CVD of the gate insulating layer of the FT element. Further, although it is generally difficult to dry-etch Ni, by forming it by electroplating as in this embodiment, it is possible to form a coating in a desired pattern without requiring an etching step.

In the above-mentioned second embodiment, Al on the glass substrate is used.
Although the layer is covered with a Ni plating layer, the same effect can be obtained by forming a Cr plating layer instead of the Ni plating layer. If the Ni plating layer formed in the second embodiment is further plated with Cr to form a three-layer wiring structure, the occurrence of hillocks can be prevented more reliably. Needless to say, the electroplating conditions shown in the above embodiments can be changed to desired values as appropriate.

[Brief description of drawings]

FIG. 1 is a sectional view of a wiring structure according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a wiring structure according to a second embodiment of the present invention.

FIG. 3 is a schematic view of a plating apparatus used for forming the wiring structure of the present invention.

FIG. 4 is a cross-sectional view of a conventional wiring structure.

[Explanation of symbols]

 1 Glass Substrate 2 Cr Wiring Layer 3 Cu Plating Wiring Layer 4 Cr Plating Wiring Layer 5 Al Wiring Layer 6 Ni Wiring Layer 11 Plating Tank 12 Plating Liquid 14 Circulation Path 15 Circulation Pump 19 DC Power Supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Hata 21 No. 21 Mizozaki-cho, Saiin, Ukyo-ku, Kyoto City Rome Stock Company

Claims (2)

[Claims] 1. A substrate made of an insulating material, a first metal wiring layer formed on the insulating substrate, and a first metal wiring layer formed on the first metal wiring layer by electroplating so as to cover the first metal wiring layer. 2. A wiring structure for a liquid crystal display device, comprising: a metal wiring layer 2; 2. A metal of the same kind as the first metal wiring and a metal of a different kind from the first or second metal wiring so as to cover the second metal wiring layer. 2. The wiring structure of the liquid crystal display device according to claim 1, further comprising a third metal wiring layer formed by electroplating so as to cover the second metal wiring layer with a metal made of.