JPH01281434A - Electrode forming method for display device - Google Patents

Abstract

PURPOSE:To form an electrode of a display device having a small resistance value by partially forming an insulating film and a low-resistance metallic layer on the surface of the electrode without increasing the photolithography process. CONSTITUTION:An electrode where first and second electrodes 2 and 3 are unified is formed on an insulating substrate 1 by a metallic thin film, and a resist film 29 is stuck on the second electrode. The surface of a first electrode 21 is subjected to anodic oxidation to make an insulating film 23 of the surface of the first electrode 21, and the resist film 29 is removed from the second electrode 3. The surface of the second electrode 3 is electrically plated with a metal having a resistance value smaller than that of the second electrode 3 to form a low-resistance metallic layer 25. That is, the insulating film 23 made by anodic oxidation is used as a mask to electrically plate the surface of the second electrode 3 with the metal whose resistance value is smaller than that of the second electrode 3. Thus, the electrode of the display device has the resistance reduced without complicating the process.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The electrode forming method of the present invention is particularly applicable to a deep matrix type liquid crystal display device that uses nonlinear elements such as thin film transistors and thin film diodes. The present invention relates to the electrode forming method used.

(Prior Art) As mentioned above, nonlinear elements such as IJ thin film transistors and thin film diodes are used in active matrix liquid crystal display devices. An active-ventrix liquid crystal display device using an amorphous silicon thin film as a nonlinear element in the semiconductor layer and 17 is configured as follows, for example. That is, a thin film transistor is connected to each intersection of a matrix electrode consisting of a plurality of scanning electrodes and a plurality of (!) electrodes. This thin film transistor is hereinafter referred to as FT. The gate electrode is connected to the scan electrode, and the drain electrode is connected to the 1, T, 0. (Indume Tin
0xide). This TPT has a laminated electrode structure including a gate electrode, an insulating film, a semiconductor diagram, and source and drain electrodes, which are sequentially patterned by photolithography. Because of this laminated structure, each layer is etched by selective etching that does not corrode other layers. For this reason, an appropriate combination of etching solution and electrode material is selected.The lowest layer of the scanning electrode is made of chromium (Cr), nichrome (NiCr), and tantalum (nickel).
), butane (Ti), tungsten (ti), molybdenum-tantalum alloy, etc. are used.

Furthermore, in MIM diodes made of metal 7/insulating film/'metal, tantalum<1a) or the like is used as the scanning electrode. By using tantalum (Ta) as a scanning electrode, this tantalum (Ta) can be converted into a positive electrode. This is because the fjM film can be used as an insulating film.

(Problems to be Solved by the Invention) Amid such restrictions in device manufacturing, the influence of electrode resistance as display devices become larger has been raised as a serious problem. Chromium (er), nichrome (NiCr), tantalum (choa) used as scanning electrodes
Although the resistance ID of these films is high in itself, the resistance value of a thin film formed by sputtering in an argon atmosphere becomes even larger. The resistance value of tantalum (1a) is 15μ
Ω (180°C), but the resistance value of the thin film formed by sputtering varies from 20 to 200 depending on the sputtering conditions.
μΩcis and human hearing change 1-ru. In this text, such a resistance value is referred to as specific resistance, and is distinguished from the resistance value unique to the material.

Therefore, in a TPT active matrix small LCD TV with a screen diagonal of 3 inches, if the scan electrode is made of tantalum (Ta) with a specific resistance ρ = 40 μΩ and has a thickness of 0.2 μm and an electrode width of 20 μm, the resistance value R of the scan electrode is 6. becomes Ω. Furthermore, if the capacitance component connected to this scanning electrode is estimated using a lumped constant circuit and is about C=120 pF, then the time constant τ at the end of this scanning electrode is calculated as τ=CXR=0.7 μs. In the case of television operation, even if the number of scanning electrodes is 24() and the room frequency is 60i1Z, the address time per scanning electrode is about 67 μs, and the time constant mentioned above can be sufficiently ignored. .

However, in an 8-inch high-definition graphic display device as a large display device, considering the same as the TPT active matrix small LCD TV with a screen diagonal of 3 inches, the resistance value R of the scanning electrode is 16 Ω, and the capacitor capacity f4C.
-350 pF, and the time constant becomes -5.6 μs. If this display device has 800 scanning electrodes and a frame frequency of 100H2, the address time will be approximately 12 μs.
It becomes almost the same as the time constant, and the signal becomes unable to be recorded.

For this reason, it is desired to lower the resistance of the scan electrode, but as mentioned above, the electrode material is determined by the combination of the etching solution and the electrode material, and it is extremely difficult to use a low resistance material as the scan electrode. It is.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming an electric current in a display device, which makes it possible to reduce the resistance of an electrode without complicating the manufacturing process.

[Structure of the Invention] (Means for Solving the Problems) A method for forming electrodes of a display device of the present invention includes an electrode formed by integrally forming a first electrode and a second electrode with a metal thin film on an insulating substrate. a step of forming a resist film on the second electrode; a step of anodizing the surface of the first electrode to make the surface of the first electrode an insulating film;
After removing the resist film from the second electrode 1 (-7) and applying a metal with a lower resistance value than the second electrode 1* to the surface of the second electrode 4- This method is characterized by the steps of forming and covering a low resistance metal layer.

The present invention also includes a step of forming an electrode on an insulating gutter root (in which a first electrode and a second electrode are integrally formed with a bimetallic thin film), and a step of swallowing a resist film on the first electrode. , the second electrode (1) is made by electroplating a metal with a lower resistance than the second electrode to form six low-resistance metal layers, and the insulating layer on which the first electrode is formed. The method is characterized by comprising a step of removing the first electrode from the substrate, and a step of forming an insulating film on the surface of the first electrode by subjecting the surface of the first electrode to chemical oxidation.

(Function) 2) In order to electroplate a metal with a lower resistance value than the second electrode on the second electrode using the insulating film as a mask during the anodic oxidation process, a metal with a resistance value lower than that of the second electrode is applied by electroplating. ,: It is possible to form a low resistance metal layer. Conversely, using the low resistance metal layer as a mask, the first electrode on which the low resistance metal layer is not formed is oxidized, so complex processes such as photolithography are performed. A low resistance metal layer and an insulating film can be formed on the electrode surface without increasing the number of steps. Therefore, the resistance value of the electrode of the display device can be significantly reduced.

(Embodiment) An embodiment of the electrode forming method for a display device according to the present invention will be explained by taking a 1"FT type active matrix liquid crystal display device as an example. FIG. FIG. 2 shows a schematic sectional view along the line a to a' in FIG. 1.
-The electrode and the nonlinear element have a laminated structure on the glass substrate (1). In other words, on the glass substrate (1) are a plurality of scanning electrodes (3) made of tantalum (Ta) and Goo! An electrode (21) is formed on the scanning electrode (3).
A low resistance metal layer (25) is formed on the surface of the gate electrode (21), and an insulating film (23) is formed on the surface of the gate electrode (21).

Six living insulating films (51) are formed over the entire surface of this upper layer, and amorphous silicon (a-3i) is further applied to the semiconductor 1 (41) in the portions corresponding to the electrodes (21,)l.
It is formed as 2. A signal electrode (5) is formed perpendicular to the scanning electrode (3), and a source voltage tz(
il) connects the signal electrode (5) and the semiconductor layer (old). Further, the pixel electrode (61) and the semiconductor 1iq (, 41) are connected by the drain electrode (31). By creating such a structure, scanning type i*(
The video signal from the signal electrode (5) can be applied to the pixel electrode (61) in response to the timing signal from the signal electrode (5).

Figure 3 shows the procedure for forming a 71-Rixmi pole in a T F' T iψ) 7KD matrix liquid crystal display device. Explain in detail.

Kuntal (Ta) was sputter-deposited on an insulating glass substrate (1), and gated km (
21) A plurality of scanning electrodes (3) (first electric whispers) with a thickness of 0.2 μm and a width of 20 μm are integrally formed with +-i V (second electrodes). (a in the figure) Resistors l to (29) are formed on the plurality of scanning electrodes (3) except for the gate electrode (21). (b in the figure) After that, the scanning electrode (3) made of tantalum (Ta>) was used as an anode, and 0.1% citric acid (COOHCH2C(
OH)(COOI-1)CH2COOH-120) Oxidation is performed in a solution with an applied voltage of 50 VFlfJlj. Then, a Ta205 film of 800A is formed as an insulating film (23). (C in the figure) Next, the resist is removed and the sulfuric acid steel (Cu
A scanning electrode (3) without an insulating film (23) formed by passing a current through the scanning electrode (3) using a copper plating solution consisting of S035H20) and sulfur (1''25o4)
A low resistance metal layer (25) is formed thereon by plating with a low resistance metal such as copper (C1). At this time, since an insulating film (23) of Ta205 is formed on the gate electrode (21), this insulating film (23) serves as a mask and plating is not performed on the gate electrode (21). This low resistance metal layer (25) has a thickness of about 0.3 μm, but its resistance value is one order smaller than that of tantalum (Ta).

(d in the figure) On such a glass base (anti-(1)), the interlayer j angle is similar to that of the film (5
As 1), silicon nitride (SiNx) is deposited as a film, and as a pixel electrode (61) 1. Deposit T, O, and films. Then, it is etched into a predetermined shape by phytolithography, and further plasma C9V, D, (Ch
Amorphous silicon (a-3i) is deposited on a semiconductor layer (41
) as a film. (e in the figure) This semiconductor layer (41) is also etched into a predetermined shape using a futuring granoid. (f in the figure) Copper (Cu) is deposited on the entire surface of the glass substrate (1)-1 film, and the source electrode (11) is perpendicular to the scanning mti (3) and connected to the semiconductor layer (41) by notl~lithography. ) to form a signal electrode. At the same time, a drain electrode (31) connected to the pixel electrode (61) and the semiconductor layer (41) is also formed to form the electrode of the active matrix liquid crystal display device. (g in the figure) Here, in addition to copper (Cu), silver (Ag) or the like can be used as the low resistance metal.

As detailed above, to Den 1'! ! ct in the manufacturing process
3 and 7tf~An electrode can be formed using a low-resistance metal at a low cost to a predetermined resistance when forming an insulating film, without involving complicated steps such as lithography. Also, the display screen formed in this way has a diagonal of 8 inches.
In the active polymer type 1 wax liquid crystal display device, the resistance value of the scanning electrode could be reduced to 1/6 of the conventional one. Therefore, the time constant τ at the end of the scanning electrode was 1 μs, and writing on the display screen could be performed satisfactorily.

When tantalum is oxidized using Regime 1~ as a mask, anodic oxidation progresses depending on the film thickness of the resist (29) or the baking temperature, and the insulating film (23) becomes the resist (29) film. It grows by penetrating about 10 μm below the surface. Therefore, if high pattern accuracy is required, a resist (29) is formed on the scanning electrode (3) and a plating process is performed first. Then, using the low resistance metal layer (25) formed by this plating process as a mask, the gate electrode (21) of the scanning electrode (3) is anodized.

If the low resistance metal layer (25) is not anodized, gold (Au) or the like may be used as the low resistance metal layer (25).

Gold is extremely resistant to oxidation, so there is no risk of it becoming oxidized.

Although an example in which the present invention is applied to a TFT type active matrix liquid crystal display device has been described above, the present invention can also be applied to an MIM type active matrix liquid crystal display device. in this case,
An electrode consisting of a scanning electrode (first electrode) and a lower electrode (second electrode) of the MIM element is formed on a glass substrate by sputtering tantalum (Ta), and a resist is deposited on the scanning electrode. . Then, by anodizing the lower electrode, a T2O5 film is grown on the surface of the lower electrode to a thickness of about 800Δ, and this is used as an insulating film.

And @ copper acid (CUSO-5 town O) and arsenic @ acid (1-12
A low-resistance metal layer is formed by plating copper on the scan electrode on which no insulating film is formed by applying a current to the electrode using a copper plating solution consisting of SO4'. Then, form an upper electrode of copper (Cu) or aluminum (A1) on the insulating film so as not to contact the lower electrode, and connect it to the pixel type (1, T, O, formed by * and ()). .

In this manner, an insulating film and a low-resistance metal layer can be locally formed on the electrophoresis surface even in the MIM type active matrix liquid crystal display device without complicating the manufacturing process.

[Effects of the Invention] As described in detail above, in the method for forming electrodes of a display device of the present invention, an insulating film and a low-resistance metal layer can be partially formed on the electrode surface without increasing the photolithography process. By forming this, it is possible to form an electrode of a display device with a low resistance value.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a matrix electrode of a TFT active matrix liquid crystal display device, FIG. 2 is a schematic cross-sectional view taken along line aa in FIG. 1, and FIG. 3 is a display of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a process of an embodiment of a method for forming electrodes of an apparatus, cut along line bb--line in FIG. 1. (1)...Glass base (Anti (3)...Scanning electrode (5)...Signal electrode (21)...Goo 1 to Electron) * (23)...T8 limbus (25) ...Low resistance gold layer agent Patent attorney Nori Chikako Yudo Takehana Kikuto S version! t & Figure 1 1/ Source 3/ Do-in coin■
Figure 2 Figure 3

Claims (2)

[Claims] (1) a step of forming an electrode in which a first electrode and a second electrode are integrally formed using a metal thin film on an insulating substrate; a step of depositing a resist film on the second electrode; forming an insulating film on the surface of the first electrode by anodizing the surface of the first electrode; removing the resist film from the second electrode; A method for forming an electrode for a display device, comprising the step of forming a low-resistance metal layer by electroplating a metal having a lower resistance value than the second electrode. (2) a step of forming an electrode in which a first electrode and a second electrode are integrally formed using a metal thin film on an insulating substrate; a step of depositing a resist film on the first electrode; a step of depositing a low resistance metal layer on a second electrode by electroplating a metal having a resistance value lower than that of the second electrode; and removing the resist film from the insulating substrate on which the first electrode is formed. A method for forming an electrode for a display device, comprising the steps of: forming an insulating film on the surface of the first electrode by anodic oxidizing the surface of the first electrode.