JPH03177585A - Method for etching metal layer - Google Patents

Abstract

PURPOSE:To facilitate the control of etching of a metal layer and to shorten the time required to etch the layer by removing an oxidized film on the surface of the metal layer with an active selective etching soln. and then dissolving the metal layer with a selective etching soln. CONSTITUTION:When a metal layer 22 on a glass substrate 21 as a work is etched with a selective etching soln. 17 dissolving a specified metal, an oxidized film 22a covering the surface of the metal layer 22 is previously removed with an active selective etching soln. 16 contg. the same principal component as the soln. 17 and having higher chemical activity than the soln. 17 and then the metal layer 22 is dissolved with the soln. 17. The deterioration of the accuracy of patterning of the metal layer can be prevented.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for etching a metal layer used for forming electrode patterns, etc., without impairing the patterning accuracy of the metal layer.
A method for etching a metal layer using a selective etching solution that dissolves a specific metal, the purpose of which is to facilitate control of the etching process and shorten the required time. After removing the oxide film covering the surface of the metal layer using an active selective etching solution having a chemical activity higher than that of the selective etching solution, the metal layer is continuously dissolved by the selective etching solution. It is composed of the following characteristics.

[Industrial application field]

The present invention relates to a method for etching a metal layer used for forming electrode patterns.

The removal (patterning) of metal layers by etching is widely practiced in the public sector in the formation of fine electrodes for various electronic devices (child devices) including plasma display panels (FDPs), and has improved mass productivity. There is a need for an etching method that is easy to control and capable of forming highly accurate patterns.

[Conventional technology]

In an FDP, a pair of transparent substrates on the display side and the back side are arranged facing each other with a discharge gap, and discharge cells defined by electrodes provided inside the transparent substrates can selectively emit light.
has been admonished.

For example, in the manufacture of an AC (alternating current) drive system facing electrode type PDP, on the surface of each of a pair of glass substrates,
A plurality of strip-shaped electrodes, a dielectric layer, and a protective film are sequentially formed, and both glass substrates are arranged with a predetermined gap so that the electrodes on each glass substrate face each other in a grid pattern, and the surroundings are surrounded by a sealing glass. After sealing, gas for discharge is filled.

The electrode is a metal layer with a three-layer structure of chromium (Cr)-copper (Cu)-chromium (film thickness is 5000 mm) on the surface of the glass plate.
~10,000 people), resist coating, pattern exposure, resist development, and C
It is formed by a photolithography process consisting of so-called wet etching (chemical etching) using an etching solution that is selective to r or Cu, respectively.

Conventionally, as an etching solution for Cr, an aqueous solution containing hydrogen chloride (HC') as a main component, that is, hydrochloric acid, has been used.

[Problem to be solved by the invention]

Generally, in wet etching, the time required for the material to be etched to be immersed in the etching solution (wet state) by spraying or dipping, that is, the time required for the etching process, is the time required for the material to be etched to dissolve. (hereinafter referred to as "etching time") and an overetching time that takes into account an error in the etching time.

The etching time can be calculated based on the etching rate determined by the concentration and temperature of the etching solution and the layer thickness of the material to be etched.

However, as mentioned above, when Cr is dissolved with hydrochloric acid at a predetermined concentration, an acid-resistant chromium oxide (Cro) film is formed on the surface of Cr when it comes into contact with the atmosphere.
As a result, the dissolution of Cr does not start easily even after the wet state has been established, resulting in a problem that the time required for the etching process becomes longer.

In addition, the delay time for the start of dissolution of C varies depending on the formation state (film thickness) of the Cro film, so the PDP
In mass production, the required time must be set in consideration of delay time depending on the state of formation of the Cro film. In other words, it is not possible to set the time required for etching processing,
The control of the etching process becomes complicated, and if the actual delay time is shorter than the time expected at the time of setting, the overetching time will actually become longer.
There is a problem in that the excess etching amount (side etching amount) of Cr (material to be etched) in the lower part of the resist layer increases and the patterning accuracy is impaired.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to make it possible to easily control the etching process and shorten the required time without impairing the precision of patterning the metal layer.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a method of etching a metal layer 22 using a selective etching solution 17 that dissolves a specific metal, as shown in FIG. After the oxide film 22a covering the surface of the metal layer 22 is removed by an active selective etching solution 16 which is made of the following ingredients and has a higher chemical activity than the selective etching solution 17, the oxide film 22a covering the surface of the metal layer 22 is removed by the selective etching solution 17. The structure is characterized in that the metal layer 22 is melted.

[For production]

Before the metal layer 22 is dissolved by the selective etching solution 17 that dissolves a specific metal, the surface of the metal layer 22 is etched by an active selective etching solution 16 that has the same main components as the selective etching solution 17 and has a high chemical activity. The oxidized M22a covering the surface is removed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional front view schematically showing the groove bottom of an etching apparatus 1 according to the present invention, and FIG. 2 is a cross-sectional view taken along arrows 1--2 in FIG.

The etching apparatus 1 includes an etching tank 101 provided with an inlet 10a and an outlet 10b, conveying rollers 11, 11, . . .
, liquid stopper rollers 12 and 13, a nozzle 14 for spouting the first etching solution 16, a nozzle 15 for spouting the second etching solution 17, etc., and are used as a pattern etching means for forming electrodes of FDP on the production line. incorporated into. Note that illustrations of the support shafts and driving means of each roller are omitted.

A metal layer 22 made of Cr is sputter-deposited on the upper surface of the glass substrate 21 as a workpiece in a previous step, and a resist layer (not shown) for patterning the metal II 22 is further provided thereon. The surface layer of the metal 1122 is oxidized by contact with the atmosphere, and the metal layer 2
Oxide layer 22a made of CrO that inhibits the etching of No. 2
It becomes.

The glass substrate 21 is transferred to the etching tank 10 from the entrance 10a.
While being transported at a predetermined speed in the direction of the arrow M1 by the transport roller 11, it undergoes a two-step etching process using first and second etching solutions 16 and 17, and is discharged from the exit 10b. The conveyance speed is variable, which allows the time required for the entire machining/nching process to be set.

The nozzle 14 is arranged on the front side with respect to the nozzle 15 in the transport direction M1. Therefore, the upper surface of the glass substrate 21 is first made wet by the first etching solution 16 separated from the second etching solution 17 by the liquid stopping roller 13, and after passing through the liquid stopping roller 13, the second etching solution 17 is wetted. This results in a wet state. The first and second etching solutions 16 and 17 that wet the upper surface of the glass substrate 21 flow down from both ends of the glass substrate 21 to the lower part of the etching tank 10, and are deposited in a liquid reservoir 10c separated by a partition wall 10e. , 10d, and then passes through a circulation path (not shown) and is ejected again from nozzles 14 and 15.

In the etching apparatus 11fl, the first etching solution 16
Hydrochloric acid with a concentration of 30% is used as the second etching solution 17, and hydrochloric acid with a concentration of 10% is used as the second etching solution 17.

FIG. 3 is a graph showing the relationship between the concentration of the etching solution and the time TS required for the etching process.

In the same figure, the black circle indicates the point at which C' actually begins to dissolve (
The white circle indicates the point at which all Cr has actually dissolved (the end of etching). Therefore, the time from the black circle to the white circle is the etching time TE of Cr.
becomes. The start and end of etching can be confirmed by hydrogen bubbles generated by the reaction between Cr and hydrochloric acid.

As shown in the figure, the etching time TE does not vary greatly depending on the concentration of hydrochloric acid, but the required time TS becomes shorter as the concentration increases, regardless of the temperature of the hydrochloric acid. In other words, the higher the concentration of hydrochloric acid, the stronger the removal effect on CrO covering the Cr surface, and the shorter the time from the wet state to the start of etching. Shortening is possible.

However, in general, the higher the concentration, the more the amount of side etching tends to increase.

For this reason, if Cr is etched using high concentration hydrochloric acid after CrO is removed, the amount of side etching during over-etching time will be larger than when using low concentration hydrochloric acid, resulting in poor patterning accuracy. This will result in a decline.

Therefore, in the etching device 1, the etching process is divided into two stages as described above. In the first stage, CrO is removed using high concentration hydrochloric acid, and in the second stage, Cr is dissolved using low concentration hydrochloric acid, which has a weak side etching effect. conduct.

In other words, by removing CrO with high concentration hydrochloric acid,
Since the required time TS can be set short, the set time and the actual required time T, which occur depending on the formation state of C
The error with S is smaller than the error when the required time TS is set longer, and the error in the overetching time is also smaller. Furthermore, by dissolving Cr with low concentration hydrochloric acid, the amount of side etching during overetching time is reduced.

Therefore, even if the required time TS is set uniquely, highly accurate patterning can be performed on Cr, and the required time TS can be set according to the Cr0O type precept state as in the past.
There is no need to change the settings, and the enching process can be easily controlled, which improves the mass productivity of PDPs.

According to the embodiments described above, the first and second etching solutions 1
Since the main components (H(1)) of 6.17 are the same, there is no need to strictly separate them. In other words, even if some mixing occurs, the etching effect will not be extremely impaired, so one In the etching tank 10, CrO is removed and C
Therefore, as in the case where two types of etching solutions with different main components are used, cleaning and transportation between etching tanks can be performed between the two-step etching process. There is no need to carry out this process, and the inconvenience of Cr being exposed to the atmosphere and forming CrO again after CrO removal does not occur.

In the above embodiment, as the first etching solution 16, hydrochloric acid whose chemical activity toward CrO was increased by making the concentration higher than that of the second etching solution 17 was used. By using hydrochloric acid of the same concentration as .17 and making the temperature of the first etching solution 16 higher than that of the second etching solution 17, the chemical activity toward CrO was increased as shown in FIG. It may be increased.

In addition to varying the concentration and liquid temperature, the chemical activity may be increased by adding an activator such as hydrogen peroxide to change the composition.

In the above embodiment, etching of the metal layer 22 made of C was exemplified, but etching with selectivity for metal layers made of Mo (molybdenum), W (tungsten), Ti (titanium), etc. The present invention can also be applied when patterning is performed using a solution.

[Effects of the Invention] According to the present invention, it is possible to easily control the etching process and shorten the required time without impairing the precision of patterning gold KN.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional front view showing the general configuration of an etching apparatus according to the present invention, Fig. 2 is a cross-sectional view taken along the ■-■ arrow in Fig. 1, and Fig. 3 shows the concentration of the etching solution and the time required for the etching process. FIG. 4 is a graph showing the relationship between the temperature of the etching solution and the time required for the etching process. In the figure, 1G is a first etching solution, I7 is a second etching solution, 22 is a metal layer, and 22a is an oxide film. (Activated cremation etching solution 16...First etching solution 17...Second etching solution 22...Metal layer 22a...Oxide film (Activated selective etching solution (Selective etching solution 16)...Etching device of the present invention FIG.

Claims (1)

[Claims] (1) Selective etching solution that dissolves specific metals (17
) of a metal layer (22), the method comprises: using an active selective etching solution (16) consisting of the same main components as the selective etching solution (17) and having a higher chemical activity than the selective etching solution (17);
), the oxide film (
A method for etching a metal layer, characterized in that after removing 22a), the metal layer (22) is continuously dissolved by the selective etching solution (17).