Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-10-20
2002-05-28
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S612000, C438S725000, C438S745000
Reexamination Certificate
active
06395626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, more particularly, to a semiconductor device having bump(s) (projecting electrode(s) for connection) for electrical and mechanical connection to a wiring pattern of a circuit board when mounted on the circuit board and a method of fabricating the same.
2. Description of the Related Art
Semiconductor devices of the surface-mounting type are increasingly used as a semiconductor device constituting an integrated circuit (IC) or a large scale integrated (LSI) circuit.
Some semiconductor devices of surface-mounting type have multiple bumps provided on the surfaces thereof for electrical and mechanical connection to a wiring pattern of a circuit board when mounted on the circuit board. As an example, the configuration of a bump in a straight wall shape is shown in FIG.
20
.
FIG. 20
is a sectional view showing a portion of a conventional semiconductor device. On a semiconductor substrate
12
having an integrated circuit formed therein, multiple electrode pads
14
(only one is shown in
FIG. 20
) are provided for connection to an external circuit. An insulating film
16
having opening portions
16
a
each formed to cover the edge of each electrode pad
14
and to expose the inside portion thereof is provided on the entire surface of the semiconductor substrate
12
. A lower electrode
19
is provided to be closely contacted with the periphery of the opening portion
16
a
of the insulating film
16
and the exposed portion of the electrode pad
14
.
Additionally, provided on the lower electrode
19
, there is a bump
36
formed in a straight wall shape.
In this semiconductor device, the bump electrode
36
is formed in a straight wall shape. In contrast, some semiconductor devices have bumps each formed in a mushroom shape in which the upper portion is larger than the base portion. However, a straight wall shape bump can have a less extended area in the lateral direction along the semiconductor substrate
12
to allow more bumps to be arranged at an increased density, thereby obtaining a finer pitch for connection to an external circuit.
Next, as an example of mounting a semiconductor device having the bump
36
formed as described above onto a circuit board, a structure for mounting on a glass substrate of a liquid crystal display panel is shown in FIG.
21
.
The liquid crystal display panel is designated with reference numeral
40
, in which a liquid crystal
43
is filled in between two glass substrates
41
,
42
by a sealing material
44
, and an area
8
corresponding to an extended portion of the lower glass substrate
42
with regard to the upper glass substrate
41
is an area for mounting a semiconductor device
10
which drives the liquid crystal display panel
40
.
On the upper surface of the glass substrate
42
, multiple wiring patterns
45
extending from the inside where the liquid crystal is filled toward the area
8
and multiple wiring patterns
46
serving as a connection terminal to the outside are formed.
To mount the semiconductor device
10
on the liquid crystal display panel
40
, first, an anisotropic conductive adhesive
50
obtained by mixing conductive particles
52
into an insulating adhesive is applied on the area
8
of the glass substrate
42
. Next, the semiconductor device
10
is disposed above the area
8
of the glass substrate
42
in alignment with the wiring patterns
45
,
46
for connection to each bump
36
, in an orientation upside down with respect to that of the semiconductor device
10
shown in FIG.
20
.
In this way, with the semiconductor device
10
set on the substrate
42
applied with the anisotropic conductive adhesive
50
, the semiconductor device
10
is pressed on the glass substrate
42
and is subjected to an annealing treatment so that each bump
36
is electrically connected to the wiring patterns
45
,
46
through the conductive particles
52
in the anisotropic conductive adhesive
50
. Simultaneously, the semiconductor device
10
is attached and fixed to the glass substrate
42
with the insulating adhesive in the anisotropic conductive adhesive
50
.
Also, a flexible printed circuit (FPC) board
60
is disposed at its end portion above the portion of the glass substrate
42
that is formed with the wiring pattern
46
. This FPC
60
is formed with a wiring pattern made of copper foil for providing an input signal to the semiconductor device
10
.
This wiring pattern is also electrically connected to the wiring pattern
46
on the glass substrate
42
through the conductive particles
52
in the anisotropic conductive adhesive
50
and the end portion of the FPC is attached and fixed to the glass substrate
42
.
Such a configuration ensures connections by the conductive particles
52
in the anisotropic conductive adhesive
50
between the bump
36
and the wiring pattern
45
on the glass substrate
42
as well as between the wiring pattern of the FPC
60
and the wiring pattern
46
on the glass substrate
42
, respectively, thereby forming respective electrical connections. Mechanical connections are also formed by the insulating adhesive.
Thereafter, a mold resin
62
is applied on the upper surface of the connections for the semiconductor
10
and the FPC
60
and the surrounding regions thereof. This prevents moisture from entering the connections of the bump
36
and the wiring pattern
45
and the connections of the FPC
60
and the wiring pattern
46
, and can provide mechanical protection to enhance reliability.
It is a matter of course that the semiconductor device having the bump as described above can be mounted not only on a liquid crystal display panel but also on various circuit boards in which a wiring pattern is formed on a resin substrate, ceramic substrate, and so on.
Next, the method of fabricating the conventional semiconductor device having a bump in a straight wall shape will be described using sectional views in
FIG. 17
to FIG.
20
.
First, as shown in
FIG. 17
, on the semiconductor substrate
12
having multiple electrodes pads
14
formed on the upper surface, the insulating film
16
is formed to cover the entire surface thereof. The opening portion
16
a
is formed by a photoetching technique on each electrode pad
14
such that the insulating film
16
is left only on the edge of each electrode pad
14
to expose the inside portion thereof.
Next, a common electrode film
32
is formed above the entire surface of the semiconductor substrate
12
having the electrode pad
14
and the insulating film
16
by a sputtering.
The common electrode film
32
is obtained by sequentially forming aluminum in the thickness of 0.8 &mgr;m, chromium at 0.01 &mgr;m, and copper at 0.8 &mgr;m from the side of the semiconductor substrate
12
to make a three-layered structure. The common electrode film
32
serves both as a barrier layer for connecting to the electrode pad
14
and for preventing interdiffusion to the electrode pad
14
, and as an electrode for forming the bump by an electroplating.
Thereafter, a photoresist (photoresistive resin)
18
shown in
FIG. 18
is formed on the entire surface of the common electrode film
32
by a spin coating. An opening portion
18
a
is then formed in the portion in which the bump is to be formed by a photolithography technique.
As shown in
FIG. 19
, gold plating is plated onto the common electrode
32
in the opening portion
18
a
of the photoresist
18
to thereby form the bump
36
in a straight wall shape in a thickness ranging from 10 to 15 &mgr;m.
After the photoresist
18
is removed, the bump
36
is used as a mask to etch the common electrode film
32
by a wet etching. Thus, as shown in
FIG. 20
, the common electrode film
32
is left only below the bump
36
to serve as the lower electrode
19
.
After the above-mentioned steps, the semiconductor substrate
12
is cut into single pieces of a semiconductor chip in a dicing step to complete the semiconductor device.
However, the formation of the bump
36
through the above-mention
Citizen Watch Co. Ltd.
Nguyen Ha Tran
Niebling John F.
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