JP3126862B2 - Metal pattern forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal pattern.

[0002]

2. Description of the Related Art Conventionally, a metal pattern is formed by an electrolytic plating method. 6 and 7 are process diagrams for explaining a conventional method of forming a metal pattern by an electrolytic plating method.

First, a SiN _x film 12 is laminated as an interlayer insulating film on a GaAs substrate 10 on which electric circuit elements are formed. Thereafter, the Ti film 14 is sequentially formed on the SiN _x film 12.
a, a Pt film 14b and an Au film 14c are laminated to form a current film 14 having a three-layer structure composed of these films 14a to 14c (FIG. 6A). Next, a resist mask 16 that exposes the pattern forming region P and covers the pattern non-forming region Q is formed on the current film 14 (FIG. 6B). Next, an Au plating film 18 is laminated on the current film 14 in the pattern formation region P using the current film 14 as a cathode for electrolytic plating (FIG. 6).
(C)). Since the resist mask 16 has an insulating property, the Au plating film 18 can be selectively laminated on the pattern formation region P, and as a result, a metal pattern composed of the Au plating film 18 is obtained. Wiring, electrode pads and other electric circuit elements are formed by this metal pattern.

Next, the resist mask 16 is removed (FIG. 7A). Thereafter, using the Au plating film 18 as an etching mask, the current film 14 in the pattern non-formation region Q is formed by an ion milling method or another etching method.
Is removed (FIG. 7B).

[0005]

However, in the above-described conventional method, the Au plating film 18 as a metal pattern is not used.
Is used as an etching mask, so that when removing the current film 14 in the pattern non-formed region Q, the Au plating film 18 is also etched. Accordingly, the thickness and width of the Au plating film 18 are reduced, so that the Au plating film 18
When using as a wiring, it becomes difficult to control the wiring resistance. Also, control of line and space becomes difficult.

An object of the present invention is to provide a method of forming a metal pattern in which the dimensional variation of the metal pattern is reduced to solve the above-mentioned conventional problems.

[0007]

In order to achieve this object, a method of forming a metal pattern according to the present invention comprises a step of laminating a current film on a base and a step of exposing a pattern formation region and covering a pattern non-formation region. Insulating mask,
A step of forming a pattern on the current film, a step of performing electroplating through an insulating mask to selectively laminate a metal pattern on the current film in the pattern formation area, and a step of covering the pattern formation area and forming a pattern non-formation area Forming an etching mask having the same material and thickness as the current film on the metal pattern, and, after removing the insulating mask, etching the etching mask and the current film in the pattern non-formation area in parallel. Removing step.

[0008]

According to the present invention, when removing the current film in the pattern non-formation area, the current film is etched while the metal pattern is protected by the etching mask. In addition, the material and thickness of the etching mask are the same as those of the current film. Therefore, when the current film in the pattern non-formation area is removed, the etching mask is also removed in parallel with the removal, and the end of the removal of the current film and the end of the removal of the etching mask can be made substantially the same. For this reason, the dimensional fluctuation of the metal pattern can be reduced or eliminated.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The drawings are only schematically shown to the extent that the invention can be understood, and thus the invention is not limited to the illustrated examples.

FIGS. 1 to 3 are process diagrams for explaining a reference example of the present invention. In forming a metal pattern,
First, a current film is formed on the base 20.

In this reference example, a wiring or an electrode pad is formed as a metal pattern, and a base 20 having an insulating property is prepared. Here, the base 20 includes a GaAs semiconductor substrate 20a on which an electric circuit element is formed, and a SiN _x interlayer insulating film 20b provided on the electric circuit element. Then, a Ti film 22a, a Pt film 22b, and an Au film 22c are sequentially stacked on the interlayer insulating film 20b of the base 20 by an evaporation method or a sputtering method, and a current film 22 having a three-layer structure including these films is formed (FIG. FIG.
(A)). The thicknesses of these films 22a, 22b, and 22c are 1000, 500, and 1000 degrees.

Next, an insulating mask 24 exposing the pattern forming region P and covering the pattern non-forming region Q is formed on the current film 22.

In this reference example, a resist is applied on the current film 22, and then the resist is exposed and developed to be processed into a predetermined shape to obtain an insulating mask 24 made of a resist having a predetermined shape (FIG. 1). (B)). Insulating mask 2
4 has an opening 24a exposing the pattern formation region P. Here, in order to form an etching mask 28 described later by a lift-off method, the insulating mask 24 is formed of a resist for lift-off, and the opening shape of the insulating mask 24 is an overhang shape.

Next, electrolytic plating is carried out through an insulating mask 24 so that the current film 2 in the pattern formation region P is formed.
The metal pattern 26 is selectively formed on the substrate 2.

In this embodiment, a jet-type electrolytic plating apparatus is used. Then, the current film 22 in the pattern forming region P is immersed in a non-cyan Au plating solution, and the solution temperature is set to 50 ° C.
And a plating solution jet velocity of 3 l / min. Electrolytic plating is performed. Pattern forming area P of current film 22
Is exposed through the opening 24a and the pattern non-formation region Q is covered with the insulating mask 24, so that the pattern formation region P
An Au plating film can be selectively deposited on the current film 22 of the above, and a metal pattern 26 made of this Au plating film can be obtained. The metal pattern 26
For example, an Au plating film, a Cu plating film, or any other suitable plating film can be formed.

Next, an etching mask 28 that covers the pattern forming region P and exposes the pattern non-forming region Q is formed on the metal pattern 26.

In this reference example, an etching mask forming material 30 is applied to a metal pattern 26 via an insulating mask 24.
It is laminated on top (FIG. 2 (A)). A Ti film is deposited at 1500 ° as an etching mask forming material. Thereafter, the etching mask forming material 30 in the non-pattern forming region Q is removed together with the insulating mask 24 to form the etching mask 28 (FIG. 2B). The etching mask 28 is formed of the etching mask forming material 3 remaining on the metal pattern 26.
Consists of zero.

After removing the insulating mask 24, etching is performed through an etching mask 28 to form a metal pattern 26.
Is to selectively remove the current film 22 in the pattern non-formation region Q so as not to be etched.

In this reference example, ion milling is performed using Ar gas at an acceleration voltage of 0.75 KW to remove the current film 22 in the non-pattern forming region Q (FIG. 2C).

In removing the current film 22 in the pattern non-formation region Q, it is most preferable to etch only the current film 22 without etching the metal pattern 26. The current film 22 may be etched at a rate higher than the etching rate of the metal pattern 26 to minimize the etching of the metal pattern 26. As such etching, it is preferable to use ion milling, RIE (Reactive Ion Etching), or other anisotropic etching. Further, the etching mask 28 is used for a period until the removal of the current film 22 in the pattern non-formation region Q is completed.
It is sufficient that the etching mask 28 has such a film thickness and material.

After the selective removal of the current film 22, the etching mask 28 is selectively etched away so as not to etch the metal pattern 26 (FIG. 3). The current film 22 remaining in the pattern forming region P also forms a metal pattern 32 integrated with the metal pattern 26. Therefore, it is most preferable to etch only the etching mask 28 without etching both the metal patterns 26 and 32. However, the etching rate of the etching mask 28 is set to be higher than the etching rate of the metal pattern 26 or 32. Etching mask 2
8, the etching of the metal pattern 26 or 32 may be suppressed as much as possible. As such etching, for example, chemical etching using hydrofluoric acid as an etchant or wet etching can be used. When using hydrofluoric acid, the Au metal pattern 26
Can be removed without etching the Ti. Ti of metal pattern 32 by hydrofluoric acid
The film 22a is etched. For example, when the etching mask 28 is etched in parallel when the current film 22 is removed to reduce the thickness of the mask when the etching mask 28 is removed, the etching for removing the etching mask 28 is performed. The time can be reduced, so that the Ti film 22a
Can be minimized. It is more preferable that the current film 22 to be the metal pattern 32 be formed using a material that is not etched by hydrofluoric acid, for example, Pt, W, or TiN. In this case, the current film 22 is made of Pt or W
Or a two-layer structure of TiN and Pt sequentially provided on the underlayer 20.

FIG. 4 is a process chart for explaining a modification of the above-mentioned reference example. Hereinafter, points different from the above-described reference example will be described, and detailed description of the same points as the above-described reference example will be omitted.

The steps up to the formation of the metal pattern 26 are the same as in the above-described reference example (FIG. 4A). However, in this modification, since the etching mask 28 is formed by electrolytic plating, it is not necessary to make the shape of the insulating mask opening 24a overhang. In the illustrated example, the opening 24a
Is a wall surface substantially perpendicular to the current film 22.

Then, by performing electroplating through the insulating mask 24, an etching mask forming material 30 is selectively laminated on the metal pattern 26 to form an etching mask 28 (FIG. 4B).

FIG. 5 is a process chart for explaining an embodiment of the present invention. Hereinafter, points different from the above-described reference example will be described, and detailed description of the same points as the above-described reference example will be omitted.

The steps up to the formation of the etching mask 28 are the same as in the above-described reference example. However, the etching mask 28 has the same material and thickness as the current film 22. Therefore, in this embodiment, the Ti film 30 sequentially laminated on the metal pattern 26 via the insulating mask 24 is used.
a, the Pt film 30b and the Au film 30c are used as the etching mask forming material 30 (see FIG. 2A). Ti film 30
a, the thicknesses of the Pt film 30b and the Au film 30c are determined by the Ti film 22a, the Pt film 22b and the Au film 2 of the current film 22.
2c. Then, the etching mask forming material 30 in the pattern non-forming region Q is removed together with the insulating mask 24, and the Ti film 30 remaining in the pattern forming region P is removed.
a, an etching mask 28 having a three-layer structure composed of the Pt film 30b and the Au film 30c is obtained (FIG. 5A).

After the removal of the insulating mask 24, the etching mask 28 and the current film 22 in the non-pattern forming region Q are removed by etching in parallel (FIG. 5B). Since the material and the thickness of the etching mask 28 are the same as those of the current film 22, the removal of the current film 22 in the pattern non-formation region Q and the removal of the etching mask 28 can be completed almost simultaneously (FIG. 5).
(C)).

In this embodiment, the etching mask 28 is formed by the lift-off method as in the reference example. However, the etching mask 28 may be formed by electrolytic plating as in the modification of the reference example. In this case, by performing electrolytic plating via the insulating mask 24, the etching mask forming material 3 is selectively formed on the metal pattern 26.
0a, 30b and 30c are laminated to form an etching mask 2
8 may be formed (see FIG. 4).

The present invention is not limited to the above-described embodiment, and the dimensions, shapes, arrangement positions, forming methods, forming materials, and others of the components can be changed as desired.

[0030]

As is clear from the above description, according to the metal pattern forming method of the present invention, the dimensional fluctuation of the metal pattern can be reduced or eliminated, so that the line and space of the metal pattern can be reduced. Can be easily controlled. In the case where a wiring is formed as a metal pattern, a change in wiring resistance can be reduced.

[Brief description of the drawings]

FIGS. 1A to 1C are process diagrams for explaining a reference example of the present invention.

FIGS. 2A to 2C are process diagrams for explaining a reference example of the present invention.

FIG. 3 is a process chart for explaining a reference example of the present invention.

FIGS. 4A and 4B are process diagrams for explaining a modification of the reference example of the present invention.

5 (A) to 5 (C) are process diagrams for explaining an embodiment of the present invention.

6 (A) to 6 (C) are process diagrams for explaining a conventional method.

FIGS. 7A and 7B are process diagrams for explaining a conventional method.

[Explanation of symbols]

 20: Underlayer 22: Current film 24: Insulating mask 26, 32: Metal pattern 28: Etching mask 30: Etching mask forming material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-162728 (JP, A) JP-A-3-34324 (JP, A) JP-A-60-14453 (JP, A) JP-A-50- 42376 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/3205 H01L 21/321 H01L 21/3213 H01L 21/768 H01L 21/28-21/288 H01L 21/44 -21/445 H01L 29/40-29/51 H01L 29/872 H01L 21/3065

Claims (3)

(57) [Claims] 1. A step of laminating a current film on an underlayer, a step of forming an insulating mask on the current film that exposes a pattern forming region and covers a pattern non-forming region, Performing a process of electroplating and selectively laminating a metal pattern on the current film in the pattern forming region; and covering the pattern forming region to expose the non-pattern forming region, and using the same material and thickness as the current film. Forming an etching mask on the metal pattern, and, after removing the insulating mask, etching and removing the etching mask and a current film in a pattern non-formation region in parallel. Method for forming a metal pattern. 2. The method for forming a metal pattern according to claim 1, wherein an etching mask forming material is laminated on the metal pattern via an insulating mask, and thereafter, the etching mask forming material in a pattern non-formation region is removed. A method for forming a metal pattern, comprising removing an etching mask together with an insulating mask. 3. The method for forming a metal pattern according to claim 1, wherein the electrolytic plating is performed through an insulating mask.
A method for forming a metal pattern, characterized in that an etching mask is formed by selectively laminating an etching mask forming material on a metal pattern.