JPS6239821A - Manufacture of double-layer interconnection substrate - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process, and to improve the yield of a product by utilizing a variation of a chemical property by a heat treatment of an ITO film which is formed by a low temperature spattering method, and forming an upper picture element electrode by means of etching. CONSTITUTION:An insulating layer 3 is formed on a glass base material 1 on which a lower transparent electrode 2 consisting of ITO is formed, and a through-hole 4 for obtaining an electric conduction between the upper and the lower electrodes is formed on the layer 3. Subsequently, an upper picture element electrode use ITO film 6 is formed on the whole surface by a low temperature spattering method, on the layer 3, and a photoresist pattern 7 is formed on the ITO film in order to form the upper picture element electrode pattern, and thereafter, chemical etching of the upper picture element electrode use ITO film is executed without exerting an influence on the electrode 2 by using an inorganic acid solution, and thereafter, the pattern 7 is removed and a heat treatment is executed. In such a way, a protecting process of the electrode 2 is not required, the process is simplified, the reliability is improved, and the yield can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing a two-layer wiring board for a liquid crystal display.

(Prior Art and its Problems) In recent years, as the practical use of liquid crystal displays has become common and the fields of their application have expanded, attempts have been made to increase the number of display pixels of the display.

A liquid crystal display substrate using tanu double-layer wiring is being considered to improve the decrease in pixel area occupancy (hereinafter simply referred to as aperture ratio) with respect to the screen due to the increase in the number of display pixels. In other words, in a conventional single-layer board, the wiring to each pixel is
Since it is installed in the space between pixels, as the number of pixels increases, the area occupied by this wiring space increases, resulting in a decrease in the aperture ratio.

Therefore, this wiring is installed under each pixel via an insulating layer, and each pixel and the wiring are connected to each other through a through hole formed in the insulating layer.This two-layer wiring structure can be expected to improve the aperture ratio. .

FIG. 1 is a schematic diagram of a two-layer wiring board for a liquid crystal display.

It consists of an insulator on a glass substrate (i) having a lower transparent electrode (2). An insulating layer (3) is formed, and an upper pixel electrode (5) made of a transparent conductive film is formed thereon. The upper pixel electrode (5) and the lower transparent electrode (2) have a structure in which conduction is obtained through a through ball (4) formed in the insulating layer (3). When manufacturing a two-layer wiring board for a liquid crystal display having such a structure, a major problem arises in the process of forming the upper pixel electrode (5).

That is, the upper pixel electrode (5) is formed by forming a transparent conductive film on the entire surface of the insulating layer (3) and then processing it into a predetermined pattern by photo-etching.At this time, the lower transparent electrode (2) is formed later. The transparent conductive film for the upper pixel electrode causes a short circuit between the electrodes. Furthermore, since the upper pixel electrode (5) and the lower transparent electrode (2) are made of the same material, when the upper pixel electrode (5) is chemically etched, the lower transparent electrode (2) is also etched, resulting in loss of pattern and resistance. Defects such as an increase in value occur. In the conventional method, this problem is eliminated (in order to avoid this problem, the lower transparent electrode (
2) A process in which a protective mask is formed on the exposed portion, a transparent conductive film is formed on the entire surface, the upper pixel electrode (5) is patterned by chemical etching, and the lower transparent electrode protective mask is removed by a lift-off method, or After forming a transparent conductive film for the upper pixel over the entire surface using a lift-off pattern that serves both of protecting the exposed portion of the lower transparent electrode and forming the upper pixel electrode, a process is performed to form the upper pixel electrode (5) using the lift-off method. It was However, both processes have drawbacks such as poor product yield due to the complexity of the process and low reliability of the lift-off process, and an unavoidable increase in product costs.

(Object of the Invention) The present invention relates to a method of simplifying the manufacturing process of a two-layer wiring board for a liquid crystal display and improving the yield of the product in view of the drawbacks existing in the conventional method.

(Specific means for solving problem C) That is, by utilizing the change in chemical properties caused by heat treatment of the ITO1 film formed by the low-temperature sputtering method in which the film is formed at a substrate temperature of 150°C or lower, the lower transparent electrode The present invention relates to a method of forming an upper pixel electrode by etching without forming a protective mask. More specifically, IT formed into a film by low-temperature sputtering method,
The O film has poor chemical stability (particularly resistance to hydrogen chloride), and usually obtains a certain level of chemical stability by heat treatment in the air at a temperature of 250 to 350° C. after film formation. The present invention
Focusing on this point, an ITO film is formed by a low-temperature snow splattering method on a chemically stable heat-treated lower transparent electrode, and the chemical instability of this ITO film, that is, its ease of etching, is utilized. However, the upper pixel electrode can be formed by chemical etching without forming a protective mask for the lower transparent electrode, using an acidic etching solution such as dilute hydrochloric acid that can chemically etch the ITO film for the upper pixel electrode without corroding the lower transparent electrode. The present invention also relates to a method for easily obtaining a two-layer wiring board for a liquid crystal display by performing heat treatment at a temperature of 250° C. or higher in order to improve the chemical stability of the upper pixel electrode.

(The process according to the detailed description of the invention will be explained in detail using FIGS. 2 to 6.

FIG. 2 shows a glass substrate (i) on which a lower transparent electrode (2) made of ITO is formed. The ITO lower transparent electrode (2) may be formed by any method, but it must be heat-treated at a temperature of 200° C. or higher during or after film formation. Figure 3 shows an insulating layer (
3).

A through hole (4) is formed in the insulating layer (3) to provide electrical continuity between the upper and lower electrodes. The through hole (4) is generally formed in the insulating layer (3) using a photoetching method or a lift-off method, but the through hole (4) is formed by directly using a photosensitive polymer in the insulating layer (3). 4) can also be formed by photophosphorography. Further, as a substrate for a liquid crystal display, the insulating layer (3) is preferably made of a material with high light transmittance.

Next, as shown in FIG. 4, an ITO film (6) for the upper pixel electrode is formed on the entire surface of the insulating layer (3) by low-temperature sputtering.
Deposit a film. The low-temperature sputtering method refers to a method in which sputtering film formation is performed while maintaining the substrate temperature at 150°C or less during film formation, and the ITO film (6) for the upper pixel electrode obtained by this method has good etching properties. , that is, the lower transparent electrode (2
) has the property of being easily chemically etched. The temperature of the glass substrate (i) is desirably as low as possible; if it is higher than 150°C, etching selectivity will be impaired;
Set to C or lower.

As the sputtering apparatus, a magnetron type sputtering apparatus is suitable in order to avoid an increase in the temperature of the base material, but this is not limited to other apparatuses as long as they satisfy the above conditions.

Regarding the raw material for the ITO film, that is, the target, both a reactive sputtering method using an indium-tin alloy target and an oxygen atmosphere or a normal sputtering method using an ITO target are applicable.

Next, in order to form the upper pixel electrode pattern as shown in FIG. ) The ITO film for the upper pixel electrode was chemically etched without providing any color tube.At this time, as the inorganic acid used, hydrochloric acid was the most desirable, and dilute hydrochloric acid of 2 to 10% by volume was the best.

Figure 6 shows the two-layer wiring board after removing the photoresist (7) pattern, and shows the patterned upper pixel electrode (5).
) By heat-treating this substrate at a temperature of 250° C. or higher, it is possible to obtain performance comparable to that of the conventional ①TO film.

(Effects of the Invention) As described above, when manufacturing a conventional two-layer wiring board for liquid crystal displays, a protection process for the lower transparent electrode is essential.
This has caused problems such as complicating the manufacturing process and reducing reliability and yield, which has been a major cause of cost increases.However, according to the present invention, there is no need to protect the lower transparent electrode at all, making the process easier. This enables simplification, improved reliability, and improved yield, making it possible to significantly reduce costs.

Examples are shown below.

[Example 1] An ITO film was formed on a silica-coated (thickness: 1500K) soda glass substrate using an ITO target using a magnetron-type high-frequency sputtering device.

The film forming atmosphere at this time was argon gas at 0-3 Tonr.

The film thickness was 400^, and the base material was heated. After film formation, baking was performed in the air at a temperature of 350° C. for 30 minutes.

Next, in order to form a lower transparent electrode, a pattern was formed by chemical etching using a positive resist (0FPR2 manufactured by Tokyo Ohka Co., Ltd.). The composition of the etching solution at this time was concentrated hydrochloric acid 7.
5% by volume, 25% by volume of ferric chloride solution, and the liquid temperature was 5% by volume.
It was 0°C. This base material was coated with highly transparent photosensitive polyimide, exposed and developed to form through holes, and formed into an insulating layer. Again, an ITO target was used and a magnetron type high frequency sputtering device was used to form an ITO film to a thickness of 400 mm over the entire surface of the substrate while keeping the substrate at room temperature. (The film forming conditions are the same as the previous time.) Next, positive resist (TOKYO OHKA OF PR) was applied.
After exposure, development, and baking using 2), chemical etching was performed with dilute hydrochloric acid at a concentration of 5% by volume to form a pixel electrode. After that, I peeled off the resist and tested the chemical resistance of the upper pixel electrode.

[Example 2] A lower transparent electrode was formed on a soda glass substrate on which an ITO film (thickness: 1000″A) was formed by vacuum evaporation, and chemical etching was performed using a positive resist (Sibley AZ-1350). Next, using the same positive resist, a lift-off pattern for forming through holes was formed, and a SiO2 film was formed to a thickness of 6000 mm using a magnetron type high frequency sputtering device to form an insulating layer. After forming through-holes by lift-off, reactive sputtering is performed using a magnetron DC sputtering device using an n-Sn alloy (8N 9% by weight) as a target and keeping the substrate temperature at 40°C. An ITO film was formed on the entire surface with a thickness of 600 mm.The sputtering atmosphere at this time had an oxygen partial pressure of 5.OX 10' Torr and an argon partial pressure of 4.0 Torr.
X I O'' Torr. Next, a resist pattern was formed using a positive resist (Sibley AZ-1350), and then chemical etching was performed with dilute hydrochloric acid at a concentration of 3% by volume to form an upper pixel electrode.

After peeling off the resist, baking was performed in the air at 350° C. for 30 minutes to improve the chemical resistance of the upper pixel electrode and complete a two-layer wiring board for a liquid crystal display.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a two-layer wiring board according to the present invention, and FIGS. 2 to 6 are explanations sequentially showing one embodiment of the method for manufacturing a two-layer wiring board according to the present invention. It is a diagram. (i)...Glass base material (2)...Lower transparent electrode (3)...Insulating layer (4)...Through hole (5)...Upper pixel electrode (6)...Top ITO film for pixel electrode (7)...photoresist

Claims (1)

[Claims] 1) An upper pixel electrode made of ITO (indium-tin oxide) is formed on a glass substrate having a lower transparent electrode made of ITO (indium-tin oxide) via an insulating layer made of an organic or inorganic material. , in a method for manufacturing a two-layer wiring board for a liquid crystal display having a structure in which conduction between the upper pixel electrode and the lower transparent electrode is obtained by a through hole formed in an insulating layer, (i) a substrate temperature of 150 during sputtering film formation; A step of selectively photoetching the ITO transparent conductive film for the upper pixel electrode formed by a low-temperature sputtering method performed at temperatures below ℃ using an etching solution that does not damage the lower transparent electrode to form the upper pixel electrode, (ii) Completion of etching A method for manufacturing a two-layer wiring board for a liquid crystal display, comprising: heating a base material at a temperature of 250° C. or higher.