Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-05-31
2003-05-20
Cuneo, Kamand (Department: 2829)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S597000, C438S614000
Reexamination Certificate
active
06566239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of manufacturing a semiconductor device and, more particularly, to a method of manufacturing a semiconductor device having a post electrode as a mounting terminal.
Recently, as a semiconductor device has rapidly been miniaturized and given a higher density, mounting terminals thereof accordingly have been pitched narrowly. Especially for a CSP (Chip Size Package), the above-mentioned narrow pitch makes a serious problem when the CSP has mounting terminals provided on electrode pads formed on the periphery of a semiconductor element, because the semiconductor element has substantially the same size as the package itself.
In order to avoid the above-mentioned problem, mounting terminals and electrode pads are formed in an offset state so that the mounting terminals are formed in a matrix in a package. This structure requires wirings (hereinafter referred to as redistribution layers) to connect the mounting terminals and the electrode pads.
On the other hand, a semiconductor device is required to be manufactured at a low cost. Accordingly, in manufacturing a semiconductor device, the above-mentioned redistribution layers need to be formed at a low cost.
2. Description of the Related Art
Recently, wafer-level techniques have been applied in manufacturing a CSP-type semiconductor device, in which techniques redistribution layers (wirings) and a sealing resin are provided before dicing (separating into pieces) a wafer. Hereinbelow, a description will be given of a conventional method of forming a redistribution layer (a wiring) and providing a sealing resin at the wafer level.
FIG. 1
to
FIG. 12
show a series of steps of manufacturing a conventional semiconductor device. As mentioned above, a wiring (a redistribution layer)
25
and a sealing resin
26
are provided before dicing (separating into pieces) a wafer
11
. However, for convenience' sake in showing and describing,
FIG. 1
to
FIG. 12
do not show the whole wafer
11
, but magnify a part of the wafer
11
in the vicinity of an electrode pad
12
.
An electronic circuit and an electrode pad
12
are formed beforehand on the upper surface of the wafer
11
(a surface on which the wiring
25
is to be formed). Also an insulating film
13
is formed so as to cover the upper surface of the wafer
11
. The insulating film
13
has an opening formed at a position corresponding to the electrode pad
12
so that the electrode pad
12
is exposed from the insulating film
13
.
In forming the wiring
25
, firstly, an underlying metal film
14
is formed on the wafer
11
in the above-mentioned state, as shown in FIG.
1
. The underlying metal film
14
is made of copper (Cu), and is formed by sputtering. The underlying metal film
14
is formed all over the wafer
11
.
After the underlying metal film
14
is formed, a resist
15
made of an insulating material is provided on the underlying metal film
14
, as shown in FIG.
2
. The resist
15
has an opening
16
shaped according to the wiring
25
to be formed. Subsequently, a wiring film
17
is formed on the underlying metal film
14
, as shown in
FIG. 3
, by electroplating using the underlying metal film
14
as an electrode and the resist
15
as a mask.
This wiring film
17
is made also of copper (Cu) as the underlying metal film
14
. In the above-mentioned electroplating, the resist
15
is used as the mask so as to give the wiring film
17
a shape according to the wiring
25
to be formed.
After the wiring film
17
is formed, the resist
15
is removed, as shown in FIG.
4
. Thereafter, a resist
18
is provided on the underlying metal film
14
and the wiring film
17
, as shown in FIG.
5
. The resist
18
has an opening
19
to form a post
20
therein.
Subsequently, the post
20
is formed in the opening
19
, as shown in
FIG. 6
, by electroplating using the underlying metal film
14
as an electrode and the resist
18
as a mask. This post
20
is made also of copper (Cu) as the underlying metal film
14
and the wiring film
17
. The post
20
is formed at a position corresponding to a position at which a solder bump
27
(a mounting terminal) is to be provided in a step described hereinafter.
After the post
20
is formed, an Ni film
21
is formed on the post
20
, as shown in FIG.
7
. Subsequently, an Au film
22
is formed on the Ni film
21
, as shown in
FIG. 8
, so that the post
20
, the Ni film
21
and the Au film
22
together form a post terminal
23
.
After the post terminal
23
is formed, the resist
18
is removed, as shown in FIG.
9
. Thereafter, a resist (not shown in the figures) is provided so as to cover the wiring film
17
(having the shape according to the wiring
25
to be formed) and the post terminal
23
for a patterning of the underlying metal film
14
. Specifically, the underlying metal film
14
except a portion facing the wiring film
17
(having the shape according to the wiring
25
to be formed) is removed by etching, as shown in FIG.
10
. This forms the wiring
25
on the wafer
11
.
After the post terminal
23
and the wiring
25
are formed as above, the sealing resin
26
is formed over the wafer
11
by molding, as shown in FIG.
11
. Then, the solder bump
27
as a mounting terminal is provided on the upper end of the post terminal
23
by, for example, a transferring process. Thereafter, the wafer
11
is diced into pieces so as to form a semiconductor device
10
.
FIG. 12
shows a part of the completed semiconductor device
10
in the vicinity of the electrode pad
12
.
As described above, the wiring
25
and the post terminal
23
are formed by electroplating steps (see FIG.
3
and FIG.
6
). However, using the electroplating steps to form the wiring
25
and the post terminal
23
necessitates an electric supply to be provided to a portion plated by a metal (copper in the above-mentioned steps) in electroplating.
The underlying metal film
14
shown in
FIG. 1
is used to provide the above-mentioned electric supply in electroplating. Therefore, the underlying metal film
14
cannot be removed until all electroplating steps are finished. In other words, the underlying metal film
14
is removed after all the electroplating steps are finished. Specifically, in the above-described conventional method, the underlying metal film
14
is removed by etching shown in FIG.
10
.
Therefore, until the underlying metal film
14
is removed, the sealing resin
26
cannot be provided. Accordingly, in forming metal members including the wiring film
17
and the post
20
, a resist has to be provided and then removed each time. This complicates the manufacturing steps of a semiconductor device.
Specifically, in the conventional method shown in
FIG. 1
to
FIG. 12
, the wiring
25
and the post terminal
23
need to be formed prior to the step of removing the underlying metal film
14
shown in FIG.
10
. Accordingly, the resist
15
has to be provided in the step shown in
FIG. 2
so as to form the wiring
25
(the wiring film
17
), and then the resist
15
has to be removed in the step shown in FIG.
4
. Also, the resist
18
has to be provided in the step shown in
FIG. 5
so as to form the post terminal
23
, and then the resist
18
has to be removed in the step shown in FIG.
9
. Thus, the above-described conventional method requires two sets of steps of providing and removing a resist. This complicates the manufacturing steps of a semiconductor device.
Besides, using a copper (Cu) as a material forming the wiring
25
(the wiring film
17
) entails a consideration for a migration. That is, although a copper (Cu) has a small electrical resistance, and thus has a good electric property as a wire, the copper (Cu) is prone to be affected by a migration so that arranging copper wires (the wiring
25
) adjacent to each other causes a poor insulation. It is well known that coating the copper wire (the wiring
25
) with another metal film such as a nickel (Ni) film effectively prevents this migration.
Considering when
Fujisawa Tetsuya
Makino Yutaka
Matsuki Hirohisa
Watanabe Eiji
Armstrong Westerman & Hattori, LLP
Cuneo Kamand
Fujitsu Limited
Sarkar Asok Kumar
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