Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Ball or nail head type contact – lead – or bond
Reexamination Certificate
1999-07-28
2001-09-04
Clark, Jhihan B (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Ball or nail head type contact, lead, or bond
C257S737000, C257S781000
Reexamination Certificate
active
06285085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device with projection electrodes (bumps) which can be connected electrically and mechanically to a circuit substrate, a method of fabricating a semiconductor device for the same, and a structure for mounting the semiconductor device which electrically and mechanically connect the semiconductor device to the circuit substrate.
For the above-mentioned circuit substrate, a resin substrate made of a fiber glass reinforced epoxy or the like, a ceramic substrate, or a glass substrate or the like for constituting a liquid crystal display panel can be used.
2. Description of the Related Art
Conventionally, there exists a semiconductor device with bumps which can be connected electrically and mechanically to a circuit substrate, for example a semiconductor device
71
as shown in FIG.
15
.
In the semiconductor device
71
, multiple electrode pads
74
are formed on an upper surface
72
a
of a semiconductor chip
72
, and the upper surface
72
a
is covered with an insulating film
76
leaving only the upper surfaces of the electrode pads
74
not covered. Lower electrodes
79
are formed above respective electrode pads
74
. Bumps
82
formed in a substantially vertical straight-walled shape with respect to the upper surface
72
a
of the semiconductor chip
72
are provided above respective lower electrodes
79
.
Next, a method of fabricating the semiconductor device
71
shown in
FIG. 15
will be described with reference to
FIG. 16
to
FIG. 18
as well.
For fabricating the semiconductor device
71
, the insulating film
76
is first formed over the entire surface of the semiconductor substrate
70
on which plural electrode pads are placed in lines in the direction perpendicular to the upper surface of the semiconductor substrate and thereby plural semiconductor chips are to be formed, as shown in FIG.
16
.
Thereafter, the insulating film
76
is patterned to expose the upper surface of the electrode pads
74
with a photolithography treatment and an etching treatment.
Next, a common electrode film
78
is formed on the entire surface of the surface
70
a
of the semiconductor substrate
70
, including on the insulating film
76
and on the electrode pads
74
with a sputtering process.
Incidentally, the common electrode film
78
is made by sequentially forming aluminum in a thickness of 0.8 &mgr;m, chromium at 0.01 &mgr;m, and copper at 0.8 &mgr;m, respectively, from the side of the semiconductor substrate
70
.
The common electrode film
78
having such a multi-layered structure serves as a connecting layer to the electrode pads
74
and a barrier layer for preventing interdiffusion, as well as an electrode used for forming bumps with a plating process.
Next, as shown in
FIG. 17
, a photoresist
80
is formed over the entire surface of the common electrode film
78
in a thickness of 17 &mgr;m with a spin coating process. The photoresist
80
is patterned with a photolithography treatment by using a predetermined photomask to expose the photoresist
80
in an exposure apparatus and then performing a development treatment. By the patterning, the photoresist
80
exposes the common electrode film
78
to open each area in which a bump
82
is designed to be formed later.
Next, the bump
82
, in straight-walled shape and having a thickness ranging from 10 &mgr;m to 15 &mgr;m, is formed in each opening of the photoresist
80
above the common electrode film
78
with a gold plating treatment which uses the common electrode film
78
as an electrode for plating.
After the photoresist
80
is removed, each of the bumps
82
is used as a mask and the common electrode film
78
is etched with a wet etching process to form the lower electrodes
79
in areas aligned with the bumps
82
as shown in FIG.
18
.
Finally, the semiconductor substrate
70
is processed by cutting (dicing) at the boundary parts between the adjacent semiconductor chips of semiconductor substrate
70
into single pieces of a semiconductor chip
72
as shown in
FIG. 15
, thus obtaining plural semiconductor devices
71
.
Incidentally, the wet etching is performed when the common electrode film
78
is etched to form the lower electrodes
79
as described in FIG.
18
and
FIG. 19
for the following reasons.
Specifically, since the common electrode film
78
is formed in a three-layered structure consisting of aluminum in a thickness of 0.8 &mgr;m, chromium at 0.01 &mgr;m, and copper at 0.8 &mgr;m, respectively, from the side of the semiconductor substrate
72
, the use of a dry etching process would need to use a composite etching gas as an etching gas used to obtain an etching selectivity of a layer being etched with respect to the other layers, thereby complicating the selection of the composite etching gas.
Also, the dry etching process is disadvantageous in industrial manufacturing since it takes a very long time for the etching. Furthermore, the dry etching process has a disadvantage in that expensive apparatuses used for the etching treatment are required.
According to the wet etching process however, an etchant allowing for good etching selectivity can be selected to conveniently perform the etching treatment without requiring large-scale equipments.
Next, an example of a conventional structure for mounting a semiconductor device to connect the semiconductor device
71
formed in accordance with the above-mentioned fabricating method to a circuit substrate will be described with reference to
FIG. 19
, with a liquid crystal display panel taken as an example.
In
FIG. 19
, portions other than the semiconductor device
71
, glass substrates
86
a
,
86
b
of liquid crystal display panel
86
, and a flexible printed circuit board (FPC)
68
are shown as a sectional view.
In a liquid crystal display panel
86
shown in
FIG. 19
, a liquid crystal
96
is filled between glass substrates
86
a
and
86
b
. A plurality of transparent electrodes
88
a
,
88
b
are provided on the opposite surface of the glass substrate
86
a
so as to run perpendicular with each other.
To mount the semiconductor device
71
above the glass substrate
86
a
which is the circuit substrate of the liquid crystal display panel
86
, the semiconductor device
71
is disposed upside down with respect to the orientation shown in FIG.
15
. The semiconductor device
71
is disposed with the bumps
82
thus located on the lower positions in alignment with the transparent electrode
88
a
on the glass substrate
86
a.
At this point, an anisotropic conductive adhesive
54
is interposed between the bumps
82
and the glass substrate
86
a.
Incidentally, the anisotropic conductive adhesive
54
is formed by mixing conductive particles
52
into an insulating adhesive.
In this manner, while the semiconductor device
71
is set on the glass substrate
86
a
of the liquid crystal display panel
86
, concurrently with the semiconductor device
71
being pressed on the liquid crystal panel substrate
86
a
, a heating is performed therefor to connect each bump
82
electrically to the respective transparent electrodes
88
a
on the glass substrate
86
a.
Furthermore, an FPC
68
is also disposed above the terminal electrode
88
c
formed on the right side in
FIG. 19
on the glass substrate
86
a
such that an anisotropic conductive adhesive
54
having the conductive particles
52
mixed therein is interposed between the FPC
68
and the terminal electrode
88
c
. While the FPC
68
is pressed on the glass substrate
86
a
, heating is performed therefor.
The FPC
68
is a film patterned with a copper wiring electrode for transmitting electrical power and providing an input signal to the semiconductor device
71
.
The above-mentioned structure holds the conductive particles
52
of the anisotropic conductive adhesive
54
between the bumps
82
and the transparent electrodes
88
a
and between the FPC
68
and the terminal electrode
88
c
, respectively, which provides an electrical connection between the bumps
82
and the transparent elect
Armstrong Westerman Hattori McLeland & Naughton LLP
Citizen Watch Co. Ltd.
Clark Jhihan B
LandOfFree
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