JP2001028477A - Formation method of metal wiring and metal wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent undercut from easily occurring in metal wiring, and to achieve microminiaturization even if a power-feeding film is overetched by using a reactive ion etching that is dry etching for eliminating the unnecessary part of the power-feeding film. SOLUTION: First, the sputtering method or the like is used for forming a power-feeding film 2 consisting of a W thin film on an aluminum substrate 1. Then, the substrate 1 is dipped in an Ni plating bath, the power-feeding film 2 is energized, and an adhesive layer 4 consisting of an Ni thin film is formed at an opening part 6 of a resist pattern 3. Successively, the substrate 1 is immersed in an Au plating bath, the power-feeding film 2 is energized, and an electroplating layer 5 made of Au is deposited at the opening part 6 of the resist pattern 3. The substrate 1 is dipped in resist release liquid, and the resist pattern 3 is removed for washing by demineralized water for drying. Finally, the reactive ion etching device of a parallel flat plate is used, the electroplating layer 5 made of Au is used as mask, and CF 4 plasma is used for etching the unnecessary part of the power-feeding film 2 for removing, thus completing metal wiring with the lamination structure of Au/Ni/W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor integrated circuit,
The present invention relates to a method for forming a metal wiring used for a semiconductor device, a high-frequency device, a wiring board, and the like, and more particularly, to a method for forming a fine metal wiring using an electrolytic method.

[0002]

2. Description of the Related Art In recent years, as expectations for higher performance and higher integration of electronic components such as semiconductor devices and high-frequency devices have increased, metal wiring used for these electronic components has been required to be further miniaturized. It is becoming.

Conventionally, a semi-additive method has been used for forming a metal wiring by an electrolytic plating method. A method for forming a metal wiring using the semi-additive method will be described with reference to FIGS. FIG.
(E) is a sectional process view showing a method of forming a metal wiring using a semi-additive method.

First, a power supply film 12 for electrolytic plating is formed on the entire surface of a substrate 11 (FIG. 2A). As a power supply membrane,
When electrolytic Cu plating is performed later, a two-layer film having a laminated structure of Cu / Ti is used.
A two-layer film having a laminated structure of d / Ti is generally used. Next, after forming a resist pattern 13 for electrolytic plating on the power supply film 12 (FIG. 2B), the power supply film 12 is energized to selectively form an electrolytic plating layer 15 in the opening 16 of the resist pattern 13. (FIG. 2C). Subsequently, the resist pattern 13 is removed (FIG. 2D), and unnecessary portions of the power supply film 12 are removed by etching (FIG. 2E). Wet etching is used for etching the power supply film 12. As an etchant, a mixed solution of acetic acid and hydrogen peroxide is generally used for removing Cu, a hydrofluoric acid is used for removing Ti, and a mixed solution of nitric acid and hydrochloric acid is used for removing Pd.

[0005]

However, the conventional metal wiring forming method using the semi-additive method has the following problems. That is, in the conventional method for forming a metal wiring, since wet etching is used for removing the power supply film by etching, as shown in FIG. 2E, the metal wiring is undercut due to over-etching of the power supply film, which limits the miniaturization. Had occurred. Specifically, the limit of miniaturization is that the line / space of the metal wiring is about 10 μm. However, in order to cope with higher performance and higher integration of electronic components, further miniaturization of metal wiring is required.

The method of forming a metal wiring according to the present invention has been made in view of the above-mentioned problems, and solves these problems. It is an object of the present invention to provide a method for forming a metal wiring by an electrolytic plating method and a metal wiring, which can be realized.

[0007]

In order to achieve the above object, a method for forming a metal wiring according to the present invention comprises a step of forming a power supply film for electrolytic plating on a substrate and a step of forming a resist pattern on the power supply film. Forming an adhesion layer that enhances adhesion between the power supply film and the electrolytic plating layer formed on the power supply film in the opening of the resist pattern; and, on the power supply film in the opening of the resist pattern, by electrolytic plating. The method includes a step of forming an electrolytic plating layer, a step of removing a resist pattern, and a step of removing unnecessary portions of the power supply film by dry etching. Further, it is desirable that the dry etching is reactive ion etching.

As described above, in the present invention, reactive ion etching, one of dry etching, is used instead of removing unnecessary portions of the power supply film by wet etching in the conventional method of forming a metal wiring using the semi-additive method. It is characterized by the following. This is because reactive ion etching can perform anisotropic etching, so that undercutting of a metal wiring hardly occurs even when overetching of a power supply film is performed as in wet etching. Further, since reactive ion etching can perform fine etching, it can be said that reactive ion etching is very suitable for forming fine metal wiring as the object of the present invention.

The power supply film is made of a material capable of reactive ion etching. This is because an unnecessary portion of the power supply film needs to be removed by reactive ion etching in the final step.

Preferably, the power supply film is made of one or more of Mo, W, and Pt, or a material mainly containing an alloy thereof. Examples of the material of the power supply film that can be removed by reactive ion etching include Al, Ta, Mo, W, and Pt.
However, since Al or Ta forms a passivation on the surface, an electrolytic plating layer cannot be deposited thereon, and does not function as a power supply film. On the other hand, Mo, W, and Pt have poor adhesion to the electrolytic plating layer, but can barely deposit the electrolytic plating layer. Therefore, in the present invention, Mo, W, P
t is used as a material for the power supply film. First, a metal layer having good adhesion to the power supply film is formed on the power supply film, and an electrolytic plating layer is formed thereon. The layer can be deposited stably. That is, an adhesion layer formed of a metal layer is formed between the power supply film and the electrolytic plating layer to enhance the adhesion between the power supply film and the electrolytic plating layer.

In the present invention, the adhesion layer is not formed on the entire surface of the power supply film, but is formed only on the opening of the resist pattern. When the adhesion layer is formed on the entire surface of the power supply film, it is necessary to etch the adhesion layer thereon before etching unnecessary portions of the power supply film. However, in the present invention, since the adhesion layer is selectively formed only under the electrolytic plating layer,
Unnecessary portions of the power supply film to be etched after the removal of the resist pattern are exposed, so that it is not necessary to etch the adhesion layer, and the process is facilitated. In order to form the adhesion layer in the opening of the resist pattern, it is desirable to use an electrolytic plating method using a power supply film for forming an electrolytic plating layer.

The metal wiring formed by using the method for forming a metal wiring according to the present invention as described above includes a power supply film formed on a substrate and made of a material capable of reactive ion etching, and a power supply film formed on the power supply film. A metal wiring having an electroplated layer, and an adhesion layer formed between the power supply film and the electrolytic plating layer, the adhesion layer improving the adhesion between the power supply film and the electrolytic plating layer. , Pt, or one or more of them, or an alloy thereof as a main component.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a metal wiring according to an embodiment of the present invention will be described below with reference to FIGS. 1 (a) to 1 (f). 1A to 1F are cross-sectional process diagrams showing a method for forming a metal wiring according to the present invention.

First, a power supply film 2 made of a W thin film is formed on an alumina substrate 1. The power supply film 2 is formed by a sputtering method or the like, and has a thickness of about 100 nm over the entire surface of the substrate 1.
(FIG. 1A). The power supply film 2 is not limited to a W single-layer film, and may be a multilayer film in which an adhesive layer with the substrate 1 and a diffusion prevention layer are formed below the W thin film. It is desirable that the thickness of the power supply film 2 as described above is 5 nm to 1000 nm. The power supply film 2 becomes a power supply film for an adhesion layer and an electrolytic plating layer formed by an electrolytic plating method in a later step. Subsequently, using photolithography technology on the power supply film 2,
A resist pattern 3 having a line / space of 5 μm and a film thickness of 6 μm is formed (FIG. 1B).

Next, the substrate 1 is immersed in a Ni plating bath, and electricity is supplied to the power supply film 2 so that Ni
An adhesion layer 4 made of a thin film is formed to a thickness of about 100 nm (FIG. 1C). Since Ni has good adhesion to W,
Adhesion layer 4 made of Ni thin film on feed film 2 made of W thin film
Is formed, the subsequently formed electrolytic plating layer can be stably deposited on the power supply film 2. That is, the adhesion between the power supply film 2 and the electrolytic plating layer can be improved. Further, since the adhesion layer 4 is formed in the opening after the formation of the resist pattern 3, the adhesion layer 4 can be selectively formed only on the portion of the power supply film 2 where the electrolytic plating layer is to be formed. After the formation of the adhesion layer 4, the substrate is washed with pure water.

Subsequently, the substrate 1 is immersed in an Au plating bath, and the power supply film 2 is energized to deposit the Au electrolytic plating layer 5 in the opening 6 of the resist pattern 3 to a thickness of, for example, about 5000 nm (FIG. 1). (D)). It is desirable that the total thickness of the power supply film 2, the adhesion layer 4, and the electrolytic plating layer 5, that is, the thickness of the metal wiring is 100 nm to 10,000 nm. W
Is a material that is unlikely to cause the electrolytic plating layer to be deposited. However, since the adhesion layer 4 made of the Ni thin film is formed on the power supply film 2 made of the W thin film in the above process, A
The u electrolytic plating layer 5 can be easily deposited. A
After the formation of the u electrolytic plating layer 5, the substrate is washed with pure water and dried.

Next, the substrate 1 is immersed in a resist stripper to remove the resist pattern 3, and then washed with pure water and dried (FIG. 1 (e)). Finally, by using a parallel plate reactive ion etching apparatus, unnecessary portions of the power supply film 2 are removed by etching using CF ₄ plasma with the Au electrolytic plating layer 5 as a mask, thereby forming a laminated structure of Au / Ni / W. A metal wiring having a line / space of 5 μm is completed (FIG. 1F).

As described above, since unnecessary portions of the power supply film 2 are removed by using reactive ion etching, undercutting occurs in the metal wiring even when the power supply film 2 is over-etched as in the case of using wet etching. Hateful. Further, since the alumina substrate 1 used in this embodiment is hardly chemically damaged by CF ₄ gas, an unnecessary portion of the power supply film 2 can be completely removed by a sufficient over-etching process. The material of the substrate 1 may be any material as long as it is difficult to be etched by the etching gas to be used, and can be appropriately selected depending on the type of the etching gas.

Since the Au electrolytic plating layer 5 used in this embodiment is not etched by reactive ion etching using CF ₄ gas, only the power supply film 2 can be selectively etched.

Furthermore, the adhesion layer 4 is not formed on the entire surface of the power supply film 2 but is selectively formed only below the Au electrolytic plating layer 5. When the adhesion layer is formed on the entire surface of the power supply film, it is necessary to etch the adhesion layer thereon before etching the unnecessary portion of the power supply film. In the present invention, as shown in FIG. Since the unnecessary portion of the power supply film 2 to be etched after the removal of the resist pattern 3 is exposed, the adhesion layer 4 does not need to be etched before the power supply film 2 is etched, thereby facilitating the process.

Through the steps described above, a metal wiring having a line / space of 5 μm exceeding the miniaturization limit of the conventional semi-additive method can be realized.

In the above embodiment, the case where a metal wiring having a laminated structure of Au / Ni / W is formed is described. However, the present invention is not limited to these materials.
The present invention can be applied to the case of forming a metal wiring having a laminated structure of Au / Cr / Mo using Cr as the material of the adhesion layer and Au as the material of the electrolytic plating layer. In this case, similarly to the above-described embodiment, Mo as the power supply film is a material that does not easily deposit the electrolytic plating layer.
Since the adhesion layer made of Cr, which has good adhesion to the electrode, is formed, the Au electrolytic plating layer can be easily deposited on the Mo power supply film, and the adhesion between the Mo power supply film and the Au electrolytic plating layer is improved. be able to.

The power supply film material is described in the above embodiments.
Not limited to W and Mo, Cl_Two, BCl_Three, SiCl_Four, C
Cl_Four, CCIF_Three, CCl_TwoF_Two, CCl_ThreeF, CHCl
F_Two, CHCl_TwoF, CHCl_Three, CH_TwoCl_Two, CH_Four, C
HF_Three, CH_TwoF_Two, C_TwoF₆, C _ThreeF₈, C_FourF₈, CBr
F_Three, CBr_TwoF_Two, F_Two, NF_ThreeFew selected from
At least one etching gas containing one or more gases
Those that are subjected to reactive ion etching can be used. concrete
Has very poor adhesion to the electrolytic plating layer like W etc.
Although it is possible, it is possible to deposit an electrolytic plating layer
Pt or the like can also be used as a power supply film material.

Further, the electrolytic plating layer is not limited to the Au electrolytic plating layer used in the above embodiment, but may be an electrolytic plating layer containing Cu, Pd, Pt or the like as a main component. When removing unnecessary portions of the power supply film by reactive ion etching, if the material of the electrolytic plating layer is not etched by the etching gas used, only the power supply film can be selectively etched. On the other hand, even if the material of the electrolytic plating layer is etched by the etching gas used, the thickness of the electrolytic plating layer is extremely large compared to the thickness of the power supply film, and thus the electrolytic plating layer is simultaneously etched with the power supply film. Even if the surface is partially etched, there is no significant effect.

In the above embodiment, a photoresist formed by photolithography is used as the resist pattern. However, the present invention is not limited to this, and an electron beam resist or the like may be used. Further, other organic materials or inorganic materials that can be patterned can also be used.

[0026]

As described above, according to the present invention, reactive ion etching is used instead of removing unnecessary portions of the power supply film by wet etching in the conventional method of forming a metal wiring using the semi-additive method. Undercutting of the metal wiring hardly occurs even when the power supply film is over-etched, and a metal wiring having a line / space of 5 μm exceeding the miniaturization limit of the conventional semi-additive method can be realized.

[Brief description of the drawings]

FIGS. 1A to 1F are cross-sectional process diagrams illustrating a method for forming a metal wiring according to the present invention.

FIGS. 2A to 2E are cross-sectional process views showing a conventional method for forming a metal wiring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Substrate 2, 12 Power supply film 3, 13 Resist pattern 4 Adhesion layer 5, 15 Electroplating layer

Claims (6)

[Claims] 1. A step of forming a power supply film for electrolytic plating on a substrate; a step of forming a resist pattern on the power supply film; and a power supply film in an opening of the resist pattern and an electrolytic plating formed on the power supply film. A step of forming an adhesion layer that enhances the adhesion of the layer, a step of forming an electrolytic plating layer in the opening of the resist pattern by an electrolytic plating method, a step of removing the resist pattern, and dry etching of an unnecessary portion of the power supply film. And forming the metal wiring. 2. The method according to claim 1, wherein the dry etching is reactive ion etching. 3. The power supply film according to claim 1, wherein the power supply film is made of a material capable of reactive ion etching.
3. The method for forming a metal wiring according to 1. 4. The metal according to claim 1, wherein the power supply film is mainly composed of one or more of Mo, W, and Pt, or an alloy thereof. Method of forming wiring. 5. The method according to claim 1, wherein the adhesion layer is formed by an electrolytic plating method. 6. A power supply film formed of a material capable of reactive ion etching formed on a substrate, an electrolytic plating layer formed on the power supply film, and a power supply formed between the power supply film and the electrolytic plating layer. An adhesion layer that enhances the adhesion between the film and the electrolytic plating layer;
Wherein the power supply film is Mo,
A metal wiring comprising one or more of W and Pt alone or an alloy thereof as a main component.