JPH0794514A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To provide a semiconductor device having a construction capable of forming high reliability plated Au by a non-cyanogen process. CONSTITUTION:This semiconductor device has a backing metal layer 4 for electrolytic plating formed on GaAs substrate 1, an Au thin film 4 which was formed on the backing metal layer 4 with the thickness removable by dry etching, and a plated Au layer 7 formed by electrolytic plating on the Au thin film 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device provided with Au (plating Au) formed by electrolytic plating.

[0002]

2. Description of the Related Art In recent years, a large-scale integrated circuit formed by integrating a large number of transistors, resistors, etc., on one chip in an important part of a computer or communication equipment so as to achieve an electric circuit ( LSI) is frequently used. Therefore, the performance of the entire device is largely linked to the performance of the LSI alone.

The improvement of the performance of the LSI alone can be realized by, for example, reducing the resistance of the wiring.
This is a very important technical issue. In order to reduce the resistance of the wiring, Au wiring by electrolytic plating has been widely used from the past.

However, in the conventional electrolytic plating process,
Since a chemical containing a cyanide compound is used to remove the plating solution and the base metal, there is a problem in terms of safety and workability.

Therefore, there is an increasing demand for establishment of a non-cyan process, and as a result, a non-cyan type plating solution is commercially available. On the other hand, dry etching instead of Au is used as a base metal directly under the Au wiring. Possible uses of Mo and W are under consideration.

However, when Mo or W is used, the growth of Au on the surface of the wafer by electrolytic plating becomes uneven, and the adhesion between Au and the underlying metal (Mo or W) is poor, so that the reliability is high. There is a problem that the Au wiring cannot be formed.

[0007]

As described above, the conventional Au wiring technique using a cyanide compound has problems in safety and workability. Therefore, a non-cyan process was proposed, but as a base metal immediately below the Au wiring,
If Mo or W that can be dry-etched is used instead of u, there is a problem that the growth of plated Au becomes non-uniform, and a highly reliable Au wiring cannot be formed.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a highly reliable plating A.
It is to provide a semiconductor device having a structure in which u can be formed by a non-cyan process.

[0009]

In order to achieve the above object, a semiconductor device of the present invention comprises a base metal layer for electrolytic plating formed on a substrate and a dry metal layer formed on the base metal layer. An Au thin film having a thickness that can be removed by etching, and an Au thin film formed on the Au thin film by electrolytic plating.
And a layer.

The method of manufacturing a semiconductor device according to the present invention comprises a step of forming a metal wiring on a substrate, a base metal layer for electrolytic plating on the entire surface, and a thickness A which can be removed by dry etching.
a step of sequentially forming a u thin film; a step of selectively forming an Au layer on the metal wiring by electrolytic plating;
And a step of selectively removing the Au thin film other than the lower part of the layer by dry etching.

The thickness of the Au thin film is preferably 1 nm or less.

[0012]

According to the present invention, the thickness of the Au thin film directly below the plating Au is selected so that it can be removed by dry etching. Therefore, after forming the plating Au, the unnecessary portion of the above Au in the unnecessary portion is formed without using the cyanide compound. The thin film can be removed.

Even with such a thin Au thin film, Au can be grown by electrolytic plating.
Also has good adhesion to the base metal, there is no problem that the reliability of the plated Au is lowered.

Further, if the thickness of the Au thin film is selected to be 1 nm, unnecessary Au will be irrelevant regardless of parameters such as the pattern area.
The thin film can be reliably removed without etching.

[0015]

Embodiments will be described below with reference to the drawings.

FIG. 1 is a process sectional view showing a method of forming an Au wiring according to an embodiment of the present invention.

First, as shown in FIG. 1A, an insulating film, for example, a SiO ₂ film 2 having a thickness of 600 nm is formed on a semi-insulating substrate, for example, an undoped GaAs substrate 1. Then, an Au wiring 3 made of a laminated film of a Ti film having a thickness of 5 nm, a Mo film having a thickness of 600 nm, and an Au film having a thickness of 1000 nm is formed on the SiO ₂ film 2, and then a base metal layer for electrolytic plating is formed on the entire surface. 4, for example, Ti having a thickness of 5 nm
A laminated film of the film and a Mo film having a thickness of 50 nm is formed using an E-gun vapor deposition device. Subsequently, an Au thin film 5 having a thickness of 1 nm is continuously formed on the entire surface by an E-gun vapor deposition device.

Next, as shown in FIG. 1B, the Au wiring 3
A resist pattern 6 having an opening having the same width as the above is formed on the Au wiring 3. Then, for example, with an RIE device, O ₂
After performing the plasma treatment for 1 minute, for example, Fine Form Au100, which is a non-cyan type Au plating solution manufactured by Nippon Electropreting Engineering Co., Ltd., is used to fill the opening by electrolytic plating.
The u layer 7 is formed. As a result, the thickness of the Au wiring 3 can be increased and the wiring resistance can be reduced.

Next, as shown in FIG. 1C, after removing the resist pattern 6 by O ₂ plasma ashing,
The Au thin film 5 is lightly sputtered out with CF ₃ ⁺ ions by RIE etching using CF ₄ , and unnecessary A
u Remove the thin film.

Finally, as shown in FIG. 1D, the underlying metal 4 for electrolytic plating is removed by CDE to complete the low resistance Au / Au laminated wiring 8.

According to this embodiment, since the Au thin film 5 having a thickness of 1 nm is used as the underlying metal immediately below the plated Au layer 7, the Au thin film 5 is removed by wet etching using a solution containing cyan. However, since it can be performed by dry etching such as RIE etching, safety and workability are improved.

Further, as in the prior art, the plated Au layer 7
Since Mo or W is not used as the underlying metal immediately below the substrate, the plated Au layer 7 having a uniform film quality can be formed.

FIGS. 2 and 3 are diagrams showing this, and FIG. 2 shows the state of the plated Au layer 7 when the Au thin film 5 is used as the base (the present invention), and FIG. Plated Au layer 7 when W metal 5a is used (conventional)
The state of a is shown.

From FIG. 2, it can be seen that the surface of the plated Au layer 7 is whitish when the Au thin film 5 is used. This is because the plated Au layer 7 has a uniform surface and is in the same situation as when light is reflected by the mirror.

On the other hand, it can be seen from FIG. 3 that the surface of the plated Au layer 7a is dark when the metal 5a of Mo or W is used. This is because the surface of the plated Au layer 7a is non-uniform, which is the same as the situation where light is diffusely reflected.

Also, the adhesion between the Au thin film 5 and the plated Au layer 7 was good.

Thus, according to the present embodiment, the non-cyan process is performed by using an Au thin film having a thickness that can be removed by dry etching, instead of using a metal such as Mo or W as a base metal immediately below the plated Au. However, highly reliable plated Au can be formed.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the thickness is 1 nm.
The case where the Au thin film was used was described, but the same effect can be expected in the present invention even when the Au thin film having a thickness of 5 nm is used. However, when an Au thin film with a thickness of 1 nm is used,
There is an advantage that the Au thin film in the unnecessary region can be surely formed regardless of the parameters such as the pattern area.

[0029]

As described in detail above, according to the present invention, since an Au thin film having a thickness that can be removed by dry etching is used as a base metal directly under the plated Au, reliability can be obtained by a non-cyan process. It is possible to form a highly plated Au.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for forming an Au wiring according to an embodiment of the present invention.

FIG. 2 is a photograph showing a fine pattern of plated Au formed on a substrate (Au thin film).

FIG. 3 is a photograph showing a fine pattern of plated Au formed on a substrate (Mo film or W film).

[Explanation of symbols]

1 ... GaAs substrate 2 ... SiO ₂ film 3 ... Au wire 4 ... underlying metal layer 5 ... Au film 6 ... resist pattern 7 ... plated Au layer 8 ... Au / Au laminated wiring

Claims (4)

[Claims] 1. A metal wiring formed on a substrate, a base metal layer for electrolytic plating formed on the metal wiring, and a thickness of the base metal layer which can be removed by dry etching formed on the base metal layer. A semiconductor device comprising an Au thin film and an Au layer formed on the Au thin film by electrolytic plating. 2. The semiconductor device according to claim 1, wherein the thickness of the Au thin film is 1 nm or less. 3. A step of forming a metal wiring on a substrate, a step of sequentially forming an underlying metal layer for electrolytic plating and an Au thin film having a thickness removable by dry etching on the entire surface, and Au on the metal wiring. A method of manufacturing a semiconductor device, comprising: a step of selectively forming a layer by electrolytic plating; and a step of selectively removing an Au thin film other than the lower part of the Au layer by dry etching. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the thickness of the Au thin film is 1 nm or less.