JPS6248757B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an etchant for transparent conductive films. Transparent conductive films have conventionally been widely used for display electrodes, but patterned transparent conductive films have become indispensable in recent liquid crystal displays. Transparent electrodes that are generally widely used include those based on indium oxide, such as indium oxide doped with about 5 to 10 wt% tin oxide, and those based on tin oxide, such as tin oxide and pentoxide. Those doped with 0.01 mol% to 1.0 mol% of antimony are mainly used. The former, mainly made of indium, has low resistance and high transmittance, and can be easily immersed in etching with hydrochloric acid or hydrochloric acid containing ferrous chloride. The production cost has been extremely high due to the sputtering method. Furthermore, because its electrochemical stability is inferior to that of the latter tin oxide, it is necessary to insulate the electrode with an inorganic material such as SiO ₂ or an organic material such as polyimide, which has been a barrier to manufacturing liquid crystal panels.

On the other hand, the latter transparent conductive film mainly composed of tin oxide is produced at low cost by CVD from anhydrous stannic chloride, and has superior electrochemical stability compared to the former.
Transmittance and resistance equivalent to the former can also be obtained by doping with antimony pentoxide (anhydrous antimony pentachloride as a CVD source). However, the only drawback is that immersion etching is not possible in the past, and even if it is possible, the life of the solution is short.

The etching method commonly used up until now is
It is said that powders of Zn, Al, etc. are sprinkled on a transparent electrode, and hydrochloric acid is poured over it, and then the dust is removed with a brush or the like. With this method, even if nascent hydrogen is used, it is impossible to produce fine patterns because it requires brushing. It has been impossible to stably mass-produce fine patterns of about 10 to 50 μm because the resist peels off during patterning and the transparent conductive film breaks due to overetching. on the other hand
An immersion method using the redox reaction of divalent chromium and chromium trioxide as seen in USP No. 4009061 has also been considered, but divalent chromium is replaced by trivalent chromium due to the reduction reaction of oxygen in the air. The lifespan of the etching solution was very short because it got hot. For example 60℃
If you leave it in the air for one hour, the etching speed will drop to about 1/3.

This makes it industrially difficult to obtain a stable fine pattern. The present invention is intended to solve these drawbacks, and aims to provide a tin oxide etchant that stably produces fine patterns.

The transparent conductive film mainly composed of tin oxide of the present invention includes only tin oxide, and tin oxide with 0.01 to 1.0 mol% of a pentavalent metal oxide, such as antimony pentoxide.
Such as phosphorus pentoxide.

Antimony pentoxide is primarily used, which is CVDed from anhydrous antimony pentachloride in a gas mixture with an anhydrous stannic chloride source.

CVD on insulating substrate (glass, ceramic, etc.)
These transparent conductive films mainly composed of tin oxide are patterned using a positive or negative photoresist, and then immersed in the etchant of the present invention (in a broad sense such as ultrasonic immersion or etchant shower) for etching. Do this.

The etchant is an acidic aqueous solution containing at least 0.5 g/or more of ammonium fluoride, preferably about 2 g/-20 g/. If the amount is less than 2 g/min, the etching speed will drop significantly.

Also, if it exceeds 20g/speed, the speed will be almost saturated and the liquid will be wasted.

The acid used here is one or more selected from inorganic acids such as nitric acid, sulfuric acid, phosphoric acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid. Nitric acid, hydrochloric acid, and phosphoric acid are preferable, and for aqueous solutions
It is 0.1N to 6N, preferably 0.5N to 4N.

The present invention will be described in detail below with reference to Examples.

Example 1 Borosilicate glass was coated with a SnO ₂ -Sb ₂ O ₅ transparent conductive film of about 300 Å by CVD at a substrate temperature of 500° C. using anhydrous stannic chloride and anhydrous antimony pentachloride as sources. The proportion of SnO ₂ −Sb ₂ O ₅ is approximately
99.9: 0.1 mol%.

After cleaning, about 1 μm of negative type photoresist was coated and a predetermined photo process was performed to pattern the resist. This resist width is about 10μ.

Next, dissolve 10 c.c. of nitric acid in 100 c.c. of water and add 0.8
g of ammonium fluoride was dissolved to make an etchant. Using this etchant, the photo-patterned glass substrate was immersed and etched. FIG. 1 is a graph of the etching rate at each temperature. In the case of a 300 Å transparent conductive film, it takes about 30 seconds at 90°C. Etched surface is insoluble
The formation of a substance thought to be SnF ₄ causes white flakes to peel off from the substrate, which can then be easily removed with a sponge, brush, etc. Next, when the photoresist was removed with ethyl alcohol, the pattern of the 10 μm transparent conductive film was completely intact. With a length of about 10 cm, there was not a single cut (due to overetching) in the 16 10μ pattern lines.

The present invention has been explained above with reference to the examples, and since the etching solution of the present invention does not use a metal redox system like the conventional etching solution, the solution life is very long.
It can be used for about a week without any problems.

The fine-patterned transparent conductive film obtained by the present invention is used as an electrode for display bodies such as liquid crystals, ECs, EPIDs, and colloidal light valves, and is used in watches, calculators, and the like.

Note that the present invention is not limited to the examples, and of course can be used for transparent conductive films other than conventional fine patterns (for example, 100 to 500μ width) as an etchant for indium oxide-based transparent conductive films. it is obvious.

[Brief explanation of the drawing]

FIG. 1: Relationship between etching rate and temperature using the etchant of the present invention.

Claims (1)

[Claims] 1. An etchant for a transparent conductive film, which comprises an acidic aqueous solution containing at least 0.5 g of ammonium fluoride when etching a transparent conductive film mainly composed of tin oxide.