Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1997-09-30
2001-03-27
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S615000, C029S860000, C029S861000
Reexamination Certificate
active
06207549
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor element in which a bump is formed on an electrode of the semiconductor element by a ball bonding method or the like using a metal thin wire (wire), that is, a method of forming a bump electrode on an IC electrode, a method of fabricating the semiconductor element, a semiconductor device fabricated with the semiconductor element and a method of fabricating the semiconductor device.
In recent years, electronic equipment has been developed to have a compact size, a light weight and a high function, and this has also required electronic components to have a compact size, a light weight and a high function. From this point of view, in regard to a method of forming a bump electrode on an IC electrode relevant to the present invention, a mounting method by means of a wire bonding technique is used.
The method of forming a bump electrode on an IC electrode by the aforementioned prior art wire bonding technique will be described below with reference to the drawings.
FIGS. 17A-17D
show schematic views of a prior art bump electrode forming method. In the figure are shown an Au wire
101
, an Au ball
102
, a bonding capillary
103
, an IC electrode
104
on a board
170
, a ball bond portion
105
and a bump electrode
106
.
The method of forming the bump electrode on the IC electrode will be described next.
In
FIG. 17A
, the Au ball
102
formed at the tip end of the Au wire
101
is supplied onto the IC electrode
104
as shown in FIG.
17
B and bonded onto the IC electrode
104
by the bonding capillary
103
. Subsequently, the bonding capillary
103
is moves upward, sideway and then downward, thereby connecting the Au wire to the ball bond portion
105
as shown in FIG.
17
C. Subsequently, the capillary
103
is moved upward and the cut the Au wire
101
, thereby forming a bump electrode as shown in FIG.
17
D.
The above operation will now be described in greater detail. A method of forming a bump on a semiconductor element by a prior art ball bonding method and a method of connecting the semiconductor element provided with the bump are disclosed in U.S. Pat. No. 4,661,192. The methods will be described.
As shown in
FIG. 18A
, a high voltage of several thousand volts is applied from a torch
160
which serves as a discharge electrode to the tip end
101
a
of a wire
101
protruding from the tip end
103
a
of a capillary
103
. By the application of this high voltage, the wire
101
is increased in temperature and melted from the tip end
101
a
while a discharge current is flowing between the torch
160
and the wire tip end
101
a
, so that a ball-shaped melted portion as shown in
FIG. 18B
is formed. After the ball
102
is formed, the capillary
103
is moved down to the semiconductor element side, so that the ball
102
is made to abut against an electrode
104
of the semiconductor element
170
. By further moving the capillary
103
downwardly with respect to the ball
102
that has abutted against the electrode
104
, the ball
102
is bonded to the electrode
104
and the ball
102
is formed by the tip end portion
103
a
of the capillary
103
, so that a bump base portion
8
as shown in
FIG. 18C
is formed. Next, as shown in
FIG. 18D
, by moving the capillary
103
upwardly away from the semiconductor element while clamping the wire
101
by means of the capillary
103
, the wire
101
is torn off in the vicinity of the bump base portion
8
, thereby forming a bump
30
on the electrode
104
of the semiconductor element
170
. Consequently, a protruding portion
30
a is formed upright on the bump base portion
8
of the bump
30
as shown in FIG.
18
D.
In the semiconductor element
170
where the bump
30
is thus formed on the electrode
104
, as shown in
FIG. 19A
, the bump
30
is pressed against a base material
21
on which a flat surface
21
a
is formed, so that a bump
31
having a flat surface
31
a
formed by flattening the protruding portion
30
a
is formed. Subsequently, as shown in
FIG. 19B
, the bump
31
having the flat surface
31
a
is brought in contact with a conductive adhesive
18
formed on a stage
41
, thereby transferring the conductive adhesive
18
onto the flat surface
31
a
of the bump
31
and its periphery. Subsequently, as shown in
FIG. 19C
, by aligning in position the bump
31
, onto which the conductive adhesive
18
has been transferred, with an electrode
20
on a circuit board
19
and thereafter making the bump
31
abut against the electrode
20
, the bump
31
is bonded to the electrode
20
for the achievement of electrical connection between the semiconductor element
170
and the circuit board
19
.
However, according to the bump electrode forming method as described above, the Au wire
101
comes in contact with the IC electrode portion
104
when the Au wire
101
is cut by the capillary
103
. Consequently, as shown in
FIGS. 20A and 20B
, the electrode
106
a
,
106
b
exhibits an abnormal shape and an IC electrode material adheres to the tip end of the Au wire
101
, causing the issue that the Au ball
102
a
cannot be normally formed, as shown in FIG.
20
C.
SUMMARY OF THE INVENTION
In view of the aforementioned issues, the present invention has an object to provide a method of forming a bump electrode on an IC electrode causing no abnormality in the shape of the electrode.
In accomplishing these and other objects, according to a first aspect of the present invention, there is provided a method of forming a bump electrode on an IC electrode comprising: forming a ball bond portion on an IC electrode by a wire bonding apparatus; moving a bonding capillary; upward (with respect to the IC electrode); moving the bonding capillary sideways and then downward; bonding a wire to the ball bond portion; and cutting the wire, the wire being prevented from coming in contact with a periphery of the ball bond portion (i.e. with portions around the ball bond portion) other than the ball bond portion itself by presetting a descent position of the bonding capillary to a position higher than a ball bond forming position.
According to a second aspect of the present invention, there is provided a method of forming a bump electrode on an IC electrode comprising: forming a ball bond portion pn an IC electrode by a wire bonding apparatus; moving a bonding capillary; upward moving the bonding capillary sideways and then downward; bonding a wire to the ball bond portion; and cutting the wire, the wire being prevented from coming in contact with a periphery of the ball bond portion other than for the ball bond portion itself by setting a chamfer angle of the bonding capillary not greater than 90 degrees to make the ball bond portion have a height greater than a diameter of the wire.
According to a third aspect of the present invention, there is provided a method of forming a bump electrode on an IC electrode comprising: forming a ball bond portion on an IC electrode by a wire bonding apparatus; moving a bonding capillary; upward moving the bonding capillary sideways and then downward; bonding a wire to the ball bond portion; and cutting the wire, the wire being prevented from coming in contact with a periphery of the ball bond portion other than the ball bond portion itself by setting a chamfer diameter of the bonding capillary greater than a diameter of the ball bond.
According to a fourth aspect of the present invention, there is provided a method of forming a bump electrode on an IC electrode comprising: forming a ball bond portion on an IC electrode by a wire bonding apparatus; moving a bonding capillary; upward moving the bonding capillary sideways and then downward; bonding a wire to a ball bond portion; and cutting the wire, the wire being prevented from coming in contact with a periphery of the ball bond portion other than the ball bond portion itself by making a tip end portion of an outer radius portion of the bonding capillary have a tapered thickness for concentration of a cutting force in a wire cutting stage.
According to a fifth aspect of the
Higashi Kazushi
Kitayama Yoshifumi
Otani Hiroyuki
Tsukahara Norihito
Yagi Yoshihiko
Everhart Caridad
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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