Etching a substrate: processes – Forming or treating electrical conductor article
Reexamination Certificate
2001-01-17
2004-10-26
Mills, Gregory (Department: 1763)
Etching a substrate: processes
Forming or treating electrical conductor article
C216S018000, C216S040000, C216S100000, C205S080000, C205S123000, C205S125000, C205S223000, C205S169000, C205S157000, C205S186000, C438S727000, C438S643000, C438S648000, C438S653000
Reexamination Certificate
active
06808641
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of wiring formation and manufacturing electronic components, and more specifically, it relates to methods of fine wiring formation using a semi-additive process.
2. Description of the Related Art
In semiconductor integrated circuits, semiconductor devices, wiring substrates, etc., fine and low-resistance wiring patterns are necessary. Therefore, an aspect ratio (wiring thickness/wiring width) of the wiring pattern must be large. In order to form a wiring pattern having a high aspect ratio, a semi-additive process has been generally used.
A method of formation of the wiring pattern by the conventional semi-additive process is shown in
FIGS. 1A
to
1
D. A feeder film
22
is formed on the entire surface of the substrate
21
, thereafter a photoresist is coated thereon. Then, the photoresist is patterned to form a resist pattern
23
, for a selective electrolytic plating, on the feeder film
22
as shown in FIG.
1
A. As the feeder film
22
, generally, a two-layer film composed of an upper layer made of Cu and a lower layer made of Ti, is used in the case of Cu plating, and an upper layer made of Pd and a lower layer made of Ti, is used in the case of Au plating.
Then, by immersing the substrate
1
into an electrolytic plating solution, and passing a current through the feeder film
22
as an electrolytic plating electrode, as shown in
FIG. 1B
, the plating metal is deposited on the feeder film
22
in an area exposed from the resist pattern
23
, and a plated wiring
24
is formed. After the completion of the electrolytic plating, the substrate
21
is washed, then, the resist pattern
23
is peeled away as shown in FIG.
1
C.
Thereafter, by completely etching the feeder film
22
exposed from the plated wiring
24
, the wiring pattern, having a desired pattern, composed of the feeder film
22
and the plated wiring
24
as shown in
FIG. 1D
is obtained.
In the aforementioned method of fine wiring formation, as shown in
FIG. 1D
, the exposed portion of the feeder film
22
is removed by the etching after forming the plated wiring
24
, and dry etching or wet etching methods are used.
The dry etching methods include ion milling, reactive ion etching (RIE), and others. By using these methods, it is possible to form the fine wiring pattern in which the line and space (hereafter described as L/S) is 5 &mgr;m or less.
In the dry etching methods, however, expensive apparatuses are required, and therefore, the manufacturing cost is very high. Furthermore, in the ion milling, it is not possible to selectively etch only the feeder film, but the plated wiring and the substrate are etched together with the feeder film so that problems of etching residues and substrate damage occur. In the reactive ion etching, there is a problem in that a suitable material for the feeder film has not been identified.
On the other hand, in the wet etching methods, hydrofluoric acid is used in the case of the feeder film made of Cu or Ti, and a mixture of nitric acid and hydrochloric acid is used in the case of the feeder film made of Pd. The wet etching methods is very low in the cost compared to the dry etching methods, and it is easy to selectively etch only the feeder film.
Because the wet etching is isotropic, however, when the feeder film
22
is wet etched, as shown in
FIG. 2
, the feeder film
22
under the plated wiring
24
is also side-etched to cause an undercut
25
under the plated wiring
24
so that defects such as insufficient adhesion and peeling of the wiring may be caused. Therefore, in the wet etching, there is a limit in accuracy at L/S=5 &mgr;m to 10 &mgr;m, and then a fine wiring in which the L/S is 5 &mgr;m or less could not been obtained.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a method of wiring formation wherein fine wiring is accurately formed by the semi-additive process using wet etching to remove the feeder film, and to provide an electronic component.
According to one preferred embodiment of the present invention, a method of wiring formation includes the steps of forming a feeder film partially on a substrate, forming on the substrate a plating base film by using a physical film making method such that the plate base film partially overlaps the feeder film, forming a plated wiring on the plating base film using an electrolytic plating, and selectively removing at least an area of the feeder film which is exposed from the plated wiring, using a wet etching.
The types of substrates used in the methods of preferred embodiments of the present invention are not particularly limited, and semiconductor integrated circuits and semiconductor devices, semiconductor substrates and ceramic substrates for wiring substrates, glass epoxy substrates, and other suitable substrates may be used.
The step of forming the plating base film on the substrate such that the plating base film has a desired pattern, may include forming a substrate metal on the entire substrate, thereafter by etching the substrate metal, or the plating base film may be formed by a lift-off method after depositing the substrate metal on the substrate from above a resist pattern.
According to preferred embodiments of the present invention, because the plating base film is formed so as to overlap the feeder film on the substrate using the physical film making method, and the plated wiring is formed thereon, even if all of the feeder film were removed by etching during the etching of the feeder film, only a portion of the plating base film is caused to be elevated and separated from the substrate due to an undercut and a space caused in a portion of the plating base film, most of the plating base film is not peeled off the substrate. Therefore, the process is usable for wiring patterns containing patterns of fine wire width, so that it becomes possible to form wiring patterns of fine wire width by using the semi-additive process in which the feeder film is removed using wet etching.
Preferred embodiments of the present invention include the case in which the steps are applied to a portion of the wiring pattern. For example, a conventional method may be used for a portion containing relatively wide wire width, and the methods of preferred embodiments of the present invention may be applied only to a portion containing fine wire width.
According to another preferred embodiment of the present invention, the method of wiring formation includes the steps of forming a feeder film partially on a substrate, forming on the substrate a resist pattern which has an opening defining a wiring forming area, such that a portion of the feeder film is exposed by the opening of the resist pattern, forming a plating base film at least on the substrate in the opening using a physical film making method, forming a plated wiring on the plating base film in the opening using an electrolytic plating, removing the resist pattern, and selectively removing at least an area in the feeder film which is exposed from the plated wiring, using a wet etching.
According to the method of this preferred embodiment, because the feeder film is exposed in a portion of the opening portion of the resist pattern, and the plating base film is formed at least in the opening of the resist pattern using the physical film making method, the plating base film can be formed to overlap the feeder film by the plating base film, even if all of the feeder film were removed by etching during the etching of the feeder film, only a portion of the plating base film is elevated and separated from the substrate due to an undercut caused in a portion of the plating base film, and the plating base film is not peeled off the substrate. Therefore, the steps of this method are usable for wiring patterns containing patterns of fine wire width, so that it becomes possible to form wiring patterns of fine wire width by the semi-additive process in which the feeder film is removed using the wet
Koshido Yoshihiro
Tonami Yoshiyuki
Kackar Ram N
Kenneth & Bennett LLP
Mills Gregory
Murata Manufacturing Co. Ltd
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