JPH0466919A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the defect of an element by the disconnection of Cr by forming the element which has a MIM structure and is formed by electroplating of the Cr after the Cr of upper electrodes is etched to a prescribed size by using photolithiography. CONSTITUTION:Ba borosilicate glass is washed and a substrate consisting of this glass is used. A Ta film is used as the glass protective film. The film is thereafter thermally oxidized in an oxidative atmosphere to form Ta2O6. The Ta film is then formed as the lower electrode and is patterned. An oxide film is formed by an anodic oxidation method. The Cr is sputtered and is etched by using the photolithography. After the photoresist is peeled, the Cr plating is executed by using the Ta of the lower electrode as a cathode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly to a method of manufacturing an active matrix type liquid crystal display device using a nonlinear resistance element for switching.

[Conventional technology]

MIM, which is a nonlinear resistance two-terminal element for switching in active matrix liquid crystal display devices, utilizes the property of insulating layers sandwiched between electrodes that allow current to flow under a high electric field. The mechanism of nonlinear current-voltage characteristics is 5hottky and P4O10-Freukel.
Although it has been explained by mechanisms, there are many points about the mechanism that are unclear.

The manufacture of these elements is formed as follows. First, Ta oxide is formed on a glass substrate as an etching stopper. This material may be formed as required, but a transparent oxide or nitride that is not easily disturbed by Ta etching gas is particularly selected.

Next, as a lower electrode, Ta is formed by well-known sputtering and etched to a predetermined size by photorin etching.

A dry etching method using an etching gas such as CF4+Oz is used. Thereafter, Ta is anodized to form a Ta oxide film as an insulating layer. Anodic oxidation generally uses a 1% citric acid solution. This 'ra oxide film is formed by thermal oxidation or O.

It can also be obtained by plasma oxidation using gas.

Next, Cr is formed thereon as an upper electrode by sputtering. Cr is also formed using photolithography and etching to predetermined dimensions. Furthermore, a pixel electrode is formed. The pixel electrode is made by patterning Injiram tin oxide. A liquid crystal panel is assembled using these element substrates.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology has the following problems.

The thickness of the lower electrode is about 60001× due to resistance issues, and the thickness including the anodic oxide layer is about 5200×. In addition, the etched end face of Ta has an abrupt shape, and it is difficult to obtain sufficient step coverage even if the Cr upper electrode is formed by sputtering. There was a problem in that wire breakage occurred.

[Means to solve the problem]

A plurality of row electrodes and a plurality of column electrodes are arranged on a counter substrate, and a plurality of column electrodes are arranged to intersect with each other. At the intersection of these two electrodes, a nonlinear resistance element for switching and a liquid crystal are arranged in a pixel part formed in a matrix. In an active matrix liquid crystal display device arranged electrically connected in series, the switching element is a Ta lower electrode, the insulating film is a Ta oxide film or an oxynitride film, and the upper electrode is made of Cr. It has an MIM structure (metal insulator metal), and the upper electrode was created by etching Cr to a predetermined size using photolithography and then electroplating Cr [Example] Hooning Co., Ltd. Made of 7059Ba borosilicate glass at 80℃
was washed with hot sulfuric acid. Using this substrate, a 500X Ta film was formed as a glass protective film using a sputtering device.

After that, thermal oxidation was performed at 450°C in an oxidizing atmosphere,
Ta205 was formed. This does not directly affect the characteristics of the switching element (it was created to protect the glass, and if the need for it is small, it does not necessarily need to be formed).

Next, a Ta film for the lower electrode was sputtered for about 5
000'. The Ta was patterned into predetermined dimensions using photolithography and etching techniques. Etching was carried out by a dry etching method using (!?, 60%+0240% gas).

Next, an oxide film was formed by anodic oxidation using 1% citric acid. The thickness of the oxide film is about 5ooX.

Next, Cr was sputtered. The thickness was 150oX. Using well-known photolithography, 6? [i Wet etching with Nicerium ammonium solution.

At this time, about 12 Cr wire breaks occurred out of 153,600 patterns. This is the average number of Cr disconnections for 10 glass substrates. The number of ar disconnections for each is shown in Table 1.

Table I Number of Cr wire breaks (Cr etching) Since 8 or less Cr wire breaks are allowed in a panel, the yield of the panel is 70%.

Next, after stripping off the photoresist, Cr plating was performed in a Sargent bath using Ta as the lower electrode as a cathode.

The Sargent bath composition was 2009/l of chromic anhydride and 21/l of sulfuric acid. A current density of 50°C was applied to a bath kept at a liquid temperature of 55°C.
Plating was carried out using A/dj. The electrode was a lead plate. The plating time was 10 minutes.

After that, the Cr wire breakage was investigated. The results are shown in Table 2.

Table 2 Number of Cr disconnections (after Cr electrolytic plating).

〔Effect of the invention〕

As described above, it can be seen that according to the present invention, the number of Cr disconnections has been drastically reduced. Therefore, there is no element defect due to Cr disconnection, so pixel defects when assembled into a panel can be eliminated, and the yield of the panel can be improved.

As is clear from Table 2 above, the average number of disconnections in Car was drastically reduced to 07. Furthermore, the yield of the panels was 100%.

Looking at the state of Cr precipitation, the plating has grown from the Cr disconnection, and the adhesion is strong.Applicant: Seiko Epson Corporation

Claims (1)

[Claims] It is equipped with a plurality of row electrodes and a plurality of column electrodes arranged on a counter substrate to intersect therewith, and at the intersection of these two electrodes, a nonlinear resistance element for switching and a liquid crystal are electrically connected to a pixel part formed in a matrix. In the active matrix liquid crystal display device, the switching element is a lower electrode of Ta, the insulating film is an oxide film or oxynitride film of Ta, and the upper electrode is made of Cr. It has an MIM structure (metal insulator metal), and after the Cr of the upper electrode is etched to a predetermined size using photolithography, Cr is further etched to a predetermined size.
A method for manufacturing a liquid crystal display device, characterized in that the liquid crystal display device is produced by electrolytic plating.