Method of forming solder bumps on a semiconductor device...

Details Method of forming solder bumps on a semiconductor device... Method of forming solder bumps on a semiconductor device...

2000-06-09

2002-08-13

Sherry, Michael J. (Department: 2829)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S616000

Reexamination Certificate

active

06432807

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bump transfer plate used for a semiconductor package and the like, a manufacturing method of the bump transfer plate, a manufacturing method of a semiconductor device with the bump transfer plate, and the semiconductor device manufactured by the method, and more specifically to a bump transfer plate with high reliability, a manufacturing method thereof, a manufacturing method of a semiconductor device with the bump transfer plate, and the semiconductor device manufactured by the method.
2. Description of Related Art
Recently, new types of semiconductor devices have been successively developed to meet the demands of high functionality, miniaturization and lightening, and the speeding up of electronic equipment. For example, size reduction and width reduction are achieved by using bumps of solder or the like for external terminals in a semiconductor device that adopts a package such as Ball-Grid-Array or Chip-Size-Package.
Such bumps are used to electrically connect an electrode formed in a semiconductor element with a wiring pattern of a package to each other, and mount the semiconductor element on a printed board. A transfer method, in which bumps are formed on electrodes formed in a semiconductor element by transfer can be mentioned as one of the methods of forming bumps. In the transfer method, bump formation materials such as solder are first formed on a base so as to meet the arrangement of the electrodes of a semiconductor element. Thereafter, the bump formation materials and the electrodes of the semiconductor element are caused to coincide with each other to adjust each position, and the base and the semiconductor element are overlapped. The bump formation materials are transferred to the electrodes of the semiconductor element, and thereby bumps are formed on the semiconductor element. FIG.
1
A through
FIG. 1C
show a bump transfer plate for the conventional transfer method. FIG.
2
A through
FIG. 2E
are sectional views showing the sequential steps for manufacturing the conventional bump transfer plate.
FIG. 1A
is a top view,
FIG. 1B
is a sectional view, and
FIG. 1C
is an enlarged view of FIG.
1
B.
As shown in
FIG. 1A
, in a conventional bump transfer plate
121
, solder bumps
122
of eutectic solder or high melting point solder are formed on a base
123
made of Al or stainless steel. The solder bumps
122
are arranged to meet the arrangement of electrodes of a semiconductor element to be connected in a later process.
When the bump transfer plate
121
is manufactured, a photo resist layer
124
is first formed on the main surface of the base
123
of
FIG. 2A
, as shown in FIG.
2
B. Thereafter, the photo resist layer
124
is exposed with a mask of a predetermined pattern and developed, thereby forming holes
125
, as shown in
FIG. 2C
, in order to form solder bumps in the later process. Subsequently, the holes
125
are filled with bump formation materials
126
as shown in
FIG. 2D
, and the photo resist layer
124
is removed as shown in
FIG. 2E
, thereby forming solder bumps
122
. Thus, the bump transfer plate
121
is obtained.
FIG.
3
A and
FIG. 3B
are sectional views showing the sequential steps of a conventional method for manufacturing a semiconductor device, and FIG.
4
A through
FIG. 4D
are sectional views showing the manufacturing method of
FIGS. 3A and 3B
in detail.
When a semiconductor device is manufactured by the use of the bump transfer plate
121
manufactured as mentioned above, the bump transfer plate
121
is first disposed on a table
17
such that the surface on which the solder bumps
122
are disposed faces a surface on which electrodes
7
of a semiconductor element
1
are disposed, as shown in FIG.
3
A and FIG.
4
A. An insulating film
3
made of polyimide or the like is formed around the electrodes
7
of the semiconductor element
1
. However, the insulating film
3
is not formed on the electrodes
7
. Therefore, concave-shaped structures are formed by the insulating film
3
and the electrodes
7
. That is, the insulating film
3
and the electrodes
7
form concave portions
8
.
The electrodes
7
are then adjusted to coincide with the positions of the solder bumps
122
and is brought into contact therewith as shown in FIG.
3
B and FIG.
4
B. Thereafter, as shown in
FIG. 4C
, the solder bumps
122
are transferred onto the electrodes
7
by the reflow of the solder bumps
122
, and the base
123
is removed as shown in FIG.
4
D.
Another method of forming bumps on a semiconductor element according to the transfer method is disclosed in Japanese Laid-open Patent Publication No. Hei 9-148330. FIG.
5
A through
FIG. 5H
are sectional views showing the sequential steps of the manufacturing method of this publication.
In the method disclosed in the publication, a resist layer
144
is first formed on a base
143
by means of a spin coater, as shown in
FIG. 5A
, and then holes
145
are formed in the resist layer
144
, so that a bump transfer plate
141
is formed. Thereafter, a bump formation materials
142
a
are formed on the base
143
by metal plating, as shown in
FIG. 5B
, and the bump formation materials
142
a
are melted by reflow. If the wettability of the bump formation materials
142
a
and the base
143
is low at this time, the molten bump formation materials
142
a
are shaped almost spherical as shown in FIG.
5
C. Thereafter, electrodes
7
of a semiconductor element
1
are adjusted to coincide with the positions of the bump formation materials
142
a
in a state in which the bump formation materials
142
a
are melted, as shown in FIG.
5
D. The bump formation materials
142
a
and the electrodes
7
are then bonded together as shown in
FIG. 5E
, and solder bumps
142
b
are obtained.
After the solder bumps
142
b
are formed, the base
143
is removed as shown in
FIG. 5F
, and a metallic plate
146
is pressed against the solder bumps
142
b
. As a result, the surfaces of the solder bumps
142
b
are flattened as shown in
FIG. 5G
, in other words, the solder bumps
142
b
undergoes coining, and a flat part
142
c
is formed for each of the solder bumps. Thereafter, the solder bumps
142
b
are bonded to lands
5
of a package substrate
2
as shown in FIG.
5
H.
However, the following problems reside in the bump transfer plates and the semiconductor devices.
In general, the concave portions
8
are formed on the surface of the semiconductor element
1
as shown in FIG.
4
A and FIG.
5
D. Therefore, when the solder bumps
122
are transferred to the electrodes
7
of the semiconductor element
1
by using the bump transfer plate
121
shown in
FIG. 1
, gaps
120
are generated in the concave portions
8
, as shown in
FIG. 4B
, in transferring the solder bumps
122
to the electrodes
7
if the tops of the solder bumps
122
are flat. Therefore, voids
127
exist, as shown in
FIG. 4D
, in the solder bump
122
obtained after the transfer, because of air remaining in the gaps
120
. The strength of a junction between the solder bump
122
and the electrode
7
is weakened if the void
127
thus exists in the solder bump
122
. Additionally, in a heat treatment process or the like required in, for example, a process of mounting the semiconductor element
1
and the package substrate
2
, the possibility that the void
127
expands, and breakage is caused in the junction will increase. As a result, there is a problem in that yield decreases, and productivity decreases.
Especially, in the conventional method of manufacturing the bump transfer plate disclosed in Japanese Laid-open Patent Publication No. Hei 9-148330, the bump formation material
142
a
is bonded to the electrode
7
while being melted, as mentioned above. At this time, the bump formation material
142
a
is bonded to the electrode
7
, in most cases, in a state in which the material
142
a
is shaped almost spherical because of melting. It is, however, difficult to cause the molten bump formation material
142
a
to coincide with the

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