JPH01297620A - Formation of transparent electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of forming a transparent electrode in a predetermined pattern on a substrate surface.

[Conventional technology]

For example, when forming transparent electrodes in a predetermined pattern on the surface of a glass substrate used in a liquid crystal display element, conventionally, a transparent conductive film made of a metal oxide such as ITO is formed over the entire surface of the substrate, and then this transparent conductive film is formed on the entire surface of the substrate. A resist mask with a predetermined pattern is formed thereon, and the transparent conductive film is patterned by wet etching or dry etching to form transparent electrodes.

[Problem to be solved by the invention]

However, in the conventional method described above, unnecessary parts of the transparent conductive film are not completely etched because the physical properties of the transparent conductive film made of metal oxides such as ITO are unstable and the etching rate changes depending on the influence of temperature. This has caused problems such as short-circuiting between the transparent electrodes, or conversely, over-etching, which deteriorates the precision of the shape of the transparent electrodes.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a method for forming a transparent electrode that can pattern a transparent conductive film into a predetermined electrode shape without using etching. Our goal is to provide the following.

[Means to solve the problem]

The method for forming a transparent electrode of the present invention involves forming a transparent conductive film made of a metal oxide on a substrate surface, forming a mask material in a predetermined electrode pattern on the transparent conductive film, and heat-treating it in a reducing gas. Accordingly, the area of the transparent conductive film that is not covered with the mask material is made into an insulating film, and the area of the transparent conductive film that is not covered with the insulating film is made into a transparent electrode.

[Effect]

According to the method for forming a transparent electrode of the present invention, since the region of the transparent conductive film made of a metal oxide other than the region that will become the transparent electrode is turned into an insulating film by heat treatment in a reducing gas, the transparent conductive film is etched. Since this transparent conductive film can be patterned into a predetermined electrode shape without etching, problems such as unnecessary transparent conductive film remaining after etching and over-etching that occur when forming a transparent electrode by etching a transparent conductive film can be avoided. can be eliminated.

[Example] Hereinafter, a first example of the present invention will be described with reference to FIG. 1 regarding the formation of a transparent pixel electrode formed on the surface of a glass substrate for an active matrix liquid crystal display element.

In FIG. 1, 1 is a glass substrate, 2 is a thin film transistor formed on one surface of this substrate and drives a pixel electrode,
The thin film transistor 2 includes a gate electrode G made of a metal film formed on a surface of a substrate 1, and a gate insulating film 3 made of a transparent insulating film such as SIN formed on the gate electrode G over almost the entire surface of the substrate 1. , an a-8i (amorphous silicon) layer 4 formed on the gate insulating film 3 facing the gate electrode G and serving as a channel region, and an n layer formed on this semiconductor layer 3 as a source and drain region. It is composed of "-3i layers 5S and 5D, and a drain electrode made of a metal film is formed on the n"-3i layer 5D, which serves as a drain region. Note that this drain electrode is connected to the integrated data line,
The gate electrode G is connected to an integral gate line. Further, 6 is a transparent flattening film made of 5oG (spin-on glass) or the like, which is formed on the surface of the substrate 1 to cover the thin film transistor 2, and the transparent pixel electrode a is formed on this flattening film 6.

This pixel electrode a is formed as follows.

First, prior to forming the pixel electrode a, as shown in FIG. A contact hole 7 for connection is made, and a transparent conductive film 8 made of a metal oxide such as ITO is deposited to a predetermined thickness on the entire upper surface of the flattened film 6 by sputtering or the like as shown in FIG. 1(b). (the thickness of the pixel electrode a to be formed), and further, a mask material 9 is formed on the entire upper surface.The transparent conductive film 8 is also deposited in the contact hole 7 of the planarization film 6. n”-S1 which becomes the source area
It is electrically connected to the layer 5s, and this portion becomes the source electrode S of the thin film transistor 2. Next, as shown in FIG. 1(c), a resist mask 10 is formed on the mask material 9 according to the shape including the source electrode S portion of the pixel electrode a to be formed, and the mask material 9 is wetted. Patterning is performed by an etching method or a dry etching method to expose a region of the transparent conductive film 8 other than the region that will become the pixel electrode a. After this,
After the resist mask 10 is peeled off, the entire substrate is heat-treated in a vacuum chamber at 250° C., 0.8 Torr, and a reducing gas (here, H2) atmosphere of about 100 W for about 30 minutes.

When this heat treatment is performed in the reducing gas (H2), the area covered with the mask material 9 of the transparent conductive film (ITO film) 8, that is, the area that will become the pixel electrode a, remains unchanged; The uncovered area undergoes a reduction action and becomes an insulating film. FIG. 1(d) shows this state, and the box in the figure indicates the area where the transparent conductive film 8 is made into an insulating film. This conversion of the transparent conductive film 8 into an insulating film is achieved by heat treatment in a reducing gas, where the region of the transparent conductive film 8 exposed to the reducing gas has a mixture of completely reduced metallic parts and insulating parts. This is thought to be because the entire region becomes insulating (semi-reduced state). Furthermore, although the insulating film area of the transparent conductive film 8 becomes white, this area does not affect the display of the liquid crystal display element, and when this area becomes white, the upper surface of the substrate 1 Since light from the substrate is already blocked by this region, it is possible to prevent light from the upper surface of the substrate from hitting the channel region of the thin film transistor and causing the transistor to malfunction. Note that the transparent conductive film 8
Since the process of partially converting into an insulating film is carried out at a high temperature of about 250°C, if the mask material 9 is a resist, there is a risk that the resist will carbonize and lose its function as a mask material 9. As the material, it is desirable to use metal or a highly heat-resistant insulating material. After this, see Figure 1 (e
), the masking material 9 can be removed by etching, and when this masking material 9 is removed, the region of the transparent conductive film 8 that was covered with the masking material 9, that is, the area covered with the masking material 9, which is exposed to the reducing action during heat treatment in a reducing gas, is removed. The conductive region that has not received the current becomes the transparent pixel electrode a.

That is, the method for forming the transparent electrode is to form a mask material 9 in a predetermined electrode pattern on the transparent conductive film 8 and heat-treat it in a reducing gas, so that the transparent conductive film 8 is covered with the mask material 9. The non-conductive region of the transparent conductive film 8 is made into an insulating film, and the non-insulating region of the transparent conductive film 8 is used as the transparent pixel electrode a. According to this method, the transparent pixel electrode of the transparent conductive film 8 made of metal oxide is Since the area other than the area a is turned into an insulating film by heat treatment in a reducing gas, it is possible to pattern the transparent conductive film 8 into a predetermined electrode shape without etching the transparent conductive film 8. Because I can,
Problems such as unnecessary etching residue and over-etching that occur when a transparent conductive film is etched to form a transparent electrode can be eliminated. Also,
Conventionally, transparent electrodes are formed by etching a transparent conductive film, so if the thickness of the film is increased to lower the resistance value of the pixel electrode, the difference in level between the pixel electrode and the area in between increases, causing the pixel electrode to become thicker. In some cases, the alignment film formed on the formation surface becomes extremely thin or breaks at the step portion, but according to the above method, since the transparent conductive film 8 is not etched, the formed The part between the pixel electrodes 8 (
The insulating film region b) of the transparent conductive film 8 is flush with the surface of the pixel electrode 8, so that the alignment film formed on the pixel electrode forming surface can be a flat film having a uniform thickness over the entire surface. can.

In the above embodiment, a part of the pixel electrode a is used as the source electrode S of the thin film transistor 2, but this pixel electrode a
is n”-3i which becomes the source region of the thin film transistor 2
A source electrode made of metal may be formed on the layer 5s and connected to this source electrode.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the transparent conductive film 8 formed on the surface of the substrate 1 is also used as a contact layer with the a-S 1 layer 4 of the thin film transistor 2. In this embodiment, the planarizing film 6 in the first embodiment is omitted, and the pixel electrode a is formed on the gate insulating film 3.

The transparent pixel electrode a according to this embodiment is formed as follows.

First, as shown in FIG. 2(a), the gate electrode G of the thin film transistor 2, the gate insulating film 3, and the
After forming one layer 4, a transparent conductive film 8 such as ITO is formed over the entire surface of the substrate, and a mask material 9 made of a low-resistance metal is further formed over the entire upper surface. Next, as shown in FIG. 2(b), a resist mask having a shape corresponding to the drain contact region and source contact region of the thin film transistor 2 and the pixel electrode forming region connected to the source contact region is placed on the mask material 9. 10a
The mask material 9 is patterned by an etching method to expose regions of the transparent conductive film 8 other than the above-mentioned regions. Thereafter, the resist mask 10a is peeled off, and the transparent conductive film 8 is heat-treated in a reducing gas (H2) atmosphere in the same manner as in the first embodiment described above, so that it becomes transparent as shown in FIG. 2(c). The region of the conductive film 8 that is not covered with the mask material 9 is made into an insulating film, and the transparent conductive film 8 is electrically connected to the drain contact layer 8D of the thin film transistor 2, the source contact layer 8s, and the transparent pixel electrode a. Insulate and separate. Next, as shown in FIG. 2(d), the transparent conductive film 8
A thin film is placed on the remaining mask material 9;・Lansistor 2
A resist mask 10b is formed to cover only the drain contact region and the source contact region, and the mask material 9 is etched to expose the portion of the transparent conductive film 8 that will become the transparent pixel electrode a, and the remaining resist mask is etched. The metal mask material 9 below 10b is made into metal layers 9D and 9s for lowering the resistance values of the drain contact layer 8D and source contact layer 8s made of the transparent conductive film 8. After this, the resist mask 10b may be peeled off as shown in FIG. 2(e).

In this embodiment, the pixel electrode a is formed by partially converting the transparent conductive film 8 made of a metal oxide such as ITO into an insulating film by heat treatment in a reducing gas.
Similar to the first embodiment described above, the transparent conductive film 8 can be patterned into a predetermined electrode shape without etching the transparent conductive film 8. The conductive film 8 is a-S of the thin film transistor 2.
Since they are also used as contact layers 8o and 8s with the first layer 4, the step of forming an n''-St layer on the a-S1 layer 4 can be omitted in the formation of the thin film transistor 2. , in this example:
The mask material 9 is made of metal, and this mask material 9 is left as a metal layer 9D+98 for lowering the resistance value of the drain contact layer 8D and the source contact layer 8s made of the transparent conductive film 8. When forming the mask material 9 to be sufficiently thick, the mask material 9 is used as the drain contact layer 8.
It may be removed without leaving anything on D and the source contact layer 8s, and in that case, an insulating material may be used as the mask material 9.

Note that in the first and second embodiments described above, the transparent conductive film 8
H2 is used as a reducing gas to partially form an insulating film, but chlorine gas of BCCa2 may also be used as this reducing gas (if this chlorine gas is used, the transparent conductive film 8 (The surface of the insulating film area may be etched to some extent.) Further, in the above embodiment, the formation of transparent pixel electrodes formed on the substrate surface of an active matrix type liquid crystal display element was explained, but the present invention provides a striped transparent scanning electrode and a transparent pixel electrode formed on a pair of substrate surfaces, respectively. It goes without saying that the present invention can also be applied to the formation of the transparent scanning electrodes and transparent signal electrodes formed on the substrate surface of a matrix type liquid crystal display element forming signal electrodes.

〔Effect of the invention〕

According to the method for forming a transparent electrode of the present invention, since the region of the transparent conductive film made of a metal oxide other than the region that will become the transparent electrode is turned into an insulating film by heat treatment in a reducing gas, the transparent conductive film is etched. Since this transparent conductive film can be patterned into a predetermined electrode shape without etching, unnecessary transparent conductive film remains etched and over-etching occurs when a transparent conductive film is etched to form a transparent electrode. You can eliminate the problem.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of forming a transparent pixel electrode showing a first embodiment of the present invention, and FIG. 2 is a process diagram of forming a transparent pixel electrode showing a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Thin film transistor, 3... Gate insulating film, 6... Flattening film, 8... Transparent conductive film,
a... Transparent pixel electrode, b... Insulating film region, 9...
-Mask material, 10.10a, 10b...resist mask. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In a method of forming transparent electrodes in a predetermined pattern on a substrate surface, a transparent conductive film made of metal oxide is formed on the substrate surface, a mask material is formed in a predetermined electrode pattern on the transparent conductive film, and a reducing gas is A transparent electrode characterized in that the area of the transparent conductive film that is not covered with the mask material is made into an insulating film by heat treatment inside the transparent conductive film, and the area of the transparent conductive film that is not covered with the mask material is made into a transparent electrode. Formation method.