JPS58110677A - Etching solution for copper - Google Patents

Abstract

PURPOSE:To provide a copper etching soln. which can etch copper films quickly and uniformly without increasing the rate of side etching by consisting the same of an aq. (NH4)2S2O8 soln. added with NH4Cl. CONSTITUTION:An etching soln. for copper prepd. by adding NH4Cl at <=10g/l rate to an aq. ammonium persulfate[(NH4)2S2O8]soln. The above-described etching soln. for copper that can etch copper films quickly is obtd. by adding said NH4Cl. Further, the effect of suppressing the generation of hydrogen foam in the stage of etching is obtained by the addition of the NH4Cl, whereby the uniformity of etching is improved as well. This etching soln. for copper is usable for a large amt. of etching treatments in the case of working copper films finely to desired patterns with semiconductor elements.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copper etching solution used for fine processing.

Figure 1 (4-4) shows a part of the manufacturing process of a flip-chip device that requires processing of such a copper film, in which an aluminum conductor 2 is provided on a silicon substrate 1, and nitride M3 is formed on it. A photoresist 4 is formed on the coated film (FIG. 1) in a desired pattern, and a part of the nitride film 3 is removed by plasma etching (agllM(B)). Next, two layers of titanium film 5 and copper film 6 are deposited on exposed aluminum film 2 and nitride film 3 (FIG. 1 (Cl)).

Furthermore, the desired areas are coated with photoresist, and copper p
Etch a6 (Fig. 1(D)). This remaining copper [6! Solder bumps 9 are formed through the nickel plating layer 8.
(Fig. 1E). In this case, the etching solution for the copper film shown in Figure 1 (DJ) is generally 1 mol/lO.
) concentrated ferric chloride aqueous solution or ammonium persulfate aqueous solution was used. However, when these etching solutions are used, the uniformity of etching is poor due to the generation of hydrogen bubbles during etching, and the amount of side etching is large, so that they are insufficient for microfabrication etching of copper films. Particularly, when processing a large number of silicon plates at the same time, there is a problem because the amount of side etching increases due to the temperature rise of the etching solution. The amount of side etching is relatively small in the case of a low concentration aqueous solution of ammonium persulfate, but this has the disadvantage that the etching speed is slow and workability is poor. ! ! Figure 2 shows the ammonium peroxide acidity and copper etching rate (line 2) when etching a 1 μm copper film.
1) Side etching amount measured by g and microscope (
The relationship [22] is shown. The allowable side etching lid during microfabrication is generally about 3 μm or less, and therefore (
The concentration of NH4) 2820g is preferably 50g/l or less. In that case, the etching speed becomes very slow, and it takes 3 minutes to etch 1 μm.

In view of this, it is an object of the present invention to provide a copper film etching solution that has good etching uniformity, a high etching rate, and less side etching.

This objective can be achieved by filtering an aqueous ammonium solution to which ammonium chloride has been added.

The present invention is based on g* that the etching rate of copper in ammonium persulfate solution can be increased by adding ammonium chloride without significantly increasing the amount of side etching. However, the amount of ammonium chloride added needs to be suppressed to 10 g or less per 11, and if it exceeds this, the amount of side etching will increase.

Figure 3 shows the etching rate of a 1 μm thick copper film when ammonium chloride was added to the ammonium persulfate solution at 25g/1O) and the change in etching violet. (NH4Cl0) on the side etching lid.
Addition lid degree was 10 g/l.It did not increase much in the city, and 3
It can be seen that the pupils are smaller than μm. Etching speed is NH
After adding 4C/10g/l, it became 90A/sec, and the (NH4)2S2 (7825g/l) shown in Figure 2
Etching speed It 45 A/s e
It will be twice as much as c. In other words, it takes 50 fυ minutes for IC to etch 1 .mu.m, and the average side etching amount is 2.5 .mu.m. NH4C as shown in Figure 3
The improvement in etching speed due to the addition of No. 7 and the fact that the amount of side etching does not increase much when added below 10 g/l, but suddenly increases when it exceeds (N) 14) 2
8204 Even if the concentration of the liquid changes, it will appear in the same way.

Furthermore, the addition of ammonium chloride according to the present invention has the effect of suppressing the generation of hydrogen bubbles during etching, thereby improving the uniformity of etching.

As described above, the present invention provides a copper etching solution that can quickly etch a copper film without increasing the amount of side etching by simply adding ammonium chloride to an ammonium persulfate aqueous solution. It is extremely effectively applied and publicly used because it enables mass etching processing when finely processing a desired pattern.

[Brief explanation of the drawing]

FIG. 1 (5) to 7) show an example in which the etching solution according to the present invention is used. A cross-sectional view showing the manufacturing process of a lip chip element, FIG. 2 is a relationship diagram showing the concentration, etching rate, and side etching lid of a conventional ammonium persulfate etching solution, and FIG. 3 is a diagram showing the present invention for the ammonium persulfate etching solution. Etching rate of ammonium chloride addition by 8
FIG. 3 is a relationship diagram showing the influence on the side etching lid and side etching lid.

Claims (1)

[Scope of Claims] 1] A copper etching solution characterized by being an ammonium persulfate aqueous solution to which ammonium chloride is added. 2. A copper etching solution according to claim 1, characterized in that the amount of ammonium chloride added is 10 g/l or less.