JPS6058795B2 - Ni thin film etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for etching an Al/N2 double-layer thin film, in particular a Ni thin film, consisting of an Al thin film as a lower layer and a N2 thin film as an upper layer, which prevents pollution and facilitates waste liquid treatment. Moreover, the present invention relates to a selective etching method with high work safety.

For example, a thin film EL display device is provided with two types of orthogonal electrode stripe groups.

One is an Al back electrode and the other is a transparent electrode made of indium oxide doped with stannous oxide. Since each of these electrodes is arranged in an orderly positional relationship, the bond connection terminals for supplying signals to the electrodes must also be arranged in an orderly manner at the end portions, similar to the electrode stripe group.

FIG. 1 is a plan view showing the electrode structure of the thin film EL display device, in which striped back electrodes 1, 10...l
m and the transparent electrodes 21, 22, . . . 2n are arranged in a relationship that is orthogonal to each other.

At one end of each striped electrode lj, 2j are terminals 3, 30, 4, 42, . . . for connecting lead wires.
... is provided, and an Al film (4500 to 6
An Al film (3000A) and a N2 film (3000A) are laminated on the transparent electrode stripe group 2j, while an In film forming a stripe electrode is formed at the end 4j of the transparent electrode stripe group 2j. O. :
SnO. Membrane (3000Λ)N on top of membrane (14508)
Two films (3000Λ) are laminated. In forming the ends of the Al/Ni double-layer thin film described above, etching away the Al/Ni double-layer thin film itself is quite easy, and various types of etching solutions have been devised.

For example, an etching solution made by mixing equal volumes of hydrochloric acid and ferric chloride solution (42°Be') and heating it to around 50°C will instantly etch the Al/N2 bilayer thin film. Dew. However, with such an etching solution with a fast reaction rate, the hydrogen bubbles generated when the Al/Ni double-layer thin film is etched become high pressure and push up the resist film, resulting in the adhesion of the resist film being weakened at the edge of the stripe. This may cause the electrode stripes to become wavy and disordered in this area. In fields such as thin film EL display devices that require highly accurate display, non-uniform pixel shapes significantly degrade display quality and represent a fatal defect. Therefore, a mixed solution of hydrochloric acid and ferric chloride solution cannot be used as an etching solution. Two types of etching solutions can be considered for the Al/N, two-layer thin film.

1 A liquid that can etch both thin films, 2 A liquid that can etch only one of A 1 or N.

Type 1 includes the aforementioned mixture of hydrochloric acid and ferric chloride solution and the mixture of hydrochloric acid and cupric chloride solution.

However, as mentioned above, satisfactory results can be obtained in terms of stripe shape, and since highly concentrated hydrochloric acid is used,
This etching solution penetrates through the film defects that occur during the deposition of the ZnS:Mn light-emitting layer of the thin film EL device, and the ZnS:Mn
There is a risk that the n-emitting layer will be eluted and the characteristics of the thin film EL device will be significantly deteriorated. For the reasons mentioned above, it is not appropriate to use one type of etching solution.

It is desirable to use an etching solution that has selective etching properties like the second type of etching solution.

Typical etching solutions for A1 thin films are aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, or an aqueous solution of potassium hydroxide to which potassium iodate is added. On the other hand, acid types include phosphoric acid,
There is a mixture of water and nitric acid. In any case, the etching solution for the A1 film has been used in various fields and does not pose any particular problem. Etching solution for N, thin film is used when etching a film consisting of only a single layer of Ni thin film, and when etching a two-layer structure thin film such as a Ni thin film on top of the A1 thin film, which is the target of the present invention. It cannot help but be different depending on when you do it.

Dilute nitric acid is sufficiently effective for etching a single Ni thin film on a glass substrate. However, in order to etch the N1 thin film in the AI/N1 double-layer thin film, this solution is too thin! One cannot expect the required speed of etching. This is because if a Ni film is continuously formed on the A1 film without breaking the vacuum, the N
This is probably because a considerable amount of Al has precipitated into the film, and the N film containing the A1 metal component cannot be etched with nitric acid alone. In this case, the Al/N thin film was immersed in an aqueous solution of sodium hydroxide to remove A1 in the film, and then diluted with N containing nitric acid: acetic acid: acetonate in a ratio of 1:1:1.
The Ni film can be etched away by immersing it in a thin film etching solution. Here, the process of immersing in an alkaline solution is called a pre-etch process. Although the etchant for N1 thin film with the above composition can effectively etch Ni thin films even at room temperature, the reaction in which the acetone in the component is oxidized by nitric acid and changes to acetic acid occurs very suddenly, resulting in work safety issues. It can damage the environment and become a source of pollution. The present invention has been made in view of the problems in the conventional N1 thin film etching method, and provides an etching method that can stably produce fine patterns by selecting an etching solution.

The etching solution for the N thin film according to the present invention is 60% nitric acid and 2
Mixed with double the volume of 15% hydrogen peroxide solution, i.e. nitric acid 2
A mixture of 0% hydrogen peroxide and 10% hydrogen peroxide in water is used as the etching solution. The hydrogen peroxide solution in the etching solution oxidizes and removes the hydrogen molecular layer on the surface of the N film, thereby promoting smooth and uniform etching of the N thin film by nitric acid.

In addition to not being a source of pollution, this etching solution is easy to dispose of as a waste solution and has good work safety. There is no need to worry about deterioration in the performance of the etching solution due to decomposition of the hydrogen peroxide solution itself, as it can withstand use for a week if used at room temperature. The suitable composition range of nitric acid and hydrogen peroxide solution for carrying out the present invention is 10 to 30% nitric acid and 10 to 20% hydrogen peroxide solution.

The details of the present invention will be explained based on Examples.

FIG. 2 shows A1/N for the striped electrode pattern and vapor deposition ranges 3 and 4 of the lead connection terminal film. The deposition conditions for the lower N film and the upper N1 film are as follows.

The A1 film 1 for the back electrode is deposited at the same time as the underlying N film that will become the lead connection terminal.

A photoresist is applied to the thus prepared substrate using a spinner, and prebaked at 110° C. for 3 minutes.

After lowering the substrate temperature to around room temperature, it is exposed and developed. 14
After baking at 0°C for 3 minutes, the substrate temperature is lowered to about room temperature and the etching process begins.

If the substrate is immersed in an N etching solution having the above composition and the solution is stirred, the N1 film will disappear in about 1 minute. At this time, the underlying A1 film appears and the reflectance changes, making it easy to determine the etching end point. N. When the etching of the film is completed, the substrate is taken out of the tank and washed with water, and the process moves on to A1 etching for the back electrode and lead connection terminal. There are acidic and alkaline A1 film etching solutions, but either can be used depending on the properties of the resist. However, when using an acidic etching solution, the following points must be noted.

That is, since the adhesion of the A1 film to the transparent conductive film is inferior to the adhesion of the N film to the glass substrate, the etching solution seeps in from the interface between the transparent electrode and the N film, and the N film under the resist film is removed.
The membrane is etched. The hydrogen bubbles generated at this time push up the N film, which may lead to peeling of the lead connection terminal film if it is severe. This does not occur with N films on glass substrates. Regarding etching of the A1 film, alkaline type etching liquids are also used, but there is no need to worry much when using alkaline type etching liquids due to the difference in the activity of the etching liquid. The above problem can be prevented by designing a pattern so that the width of the transparent electrode stripe is smaller than the lead connection terminal film.

Further, after A1 etching, it is necessary to take measures such as rinsing with water as easily as possible, drying the substrate quickly, and not continuing to etch the A1 film more than necessary. A careful cleaning process can be performed after resist stripping. As described above, according to the present invention, it is possible to etch an A1/N, two-layer thin Ni film with a solution containing 1IN03 and H2O2, and there is no fear of causing pollution in the treatment of etching solution waste, and it is extremely effective. It is possible to obtain a suitable etching state, and the processing accuracy of fine patterns can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the electrode structure of a thin film EL display device, and FIG. 2 is a plan view for explaining an embodiment of the present invention.

Claims (1)

[Claims] 1 The lower layer formed on a non-metallic plate is an Al thin film, and the upper layer is an N film.
In photoetching of an Al/Ni bilayer thin film composed of an i thin film, HNO_310-30%, H_2O_2
A Ni thin film etching method characterized by etching a Ni thin film into a desired pattern with an etching solution having a composition of 10 to 20% and using H_2O_2 as an oxidizing agent.