Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified configuration
Reexamination Certificate
2000-12-04
2003-06-17
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified configuration
C257S783000
Reexamination Certificate
active
06580173
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to semiconductor devices and, more particularly, to a semiconductor device using an organic substrate formed by an organic material such as a resin material.
The organic substrate is used for substrates of semiconductor devices due to its easiness in handling and processing. As a typical organic substrate, there is a glass-epoxy substrate or a polyimide substrate. In a semiconductor device using the organic substrate, it is general to fix a semiconductor chip to the organic substrate by an adhesive.
However, the organic substrate has a high moisture-absorption characteristic, thereby having a nature to easily absorb moisture in an atmosphere. An amount of moisture absorbed by the organic substrate can be reduced if the semiconductor device is stored in a low humidity atmosphere. However, there may be a problem related to a static electricity if the humidity is low. Thus, it is required to maintain the humidity at a certain level.
Accordingly, the organic substrate is used on the assumption that the organic substrate absorbs a certain amount of moisture, and a semiconductor device using an organic substrate is generally provided with means for preventing problems caused by moisture absorbed by the organic substrate.
2. Description of the Related Art
The moisture absorbed by an organic substrate in a semiconductor device remains at an interface between the organic material and an adhesive or under fill material that fixes a semiconductor chip onto the organic substrate. When such moisture is heated due to a heat for mounting the semiconductor device, the moisture is abruptly evaporated, which increases an inner pressure. Thus, there is a problem in that the adhesive is separated from the organic substrate at the interface therebetween. Such a separation is referred to as a popcorn phenomenon.
As measures for preventing the popcorn phenomenon, a method is used in which a plurality of small though holes generally referred to as vent holes are formed in the organic substrate so as to release a water vapor, which is generated at the interface between the adhesive and the organic substrate, via the through holes.
FIG. 1
is a cross-sectional view of a conventional semiconductor device produced by a wire bonding method. A semiconductor chip
2
is fixed to an organic substrate
6
via an adhesive
4
. Electrodes of the semiconductor chip
2
are connected by bonding wires
8
to electrode pads
10
formed on the organic substrate
6
, respectively. The semiconductor chip
2
and the bonding wires
8
are encapsulated by a seal resin
12
. Additionally, the electrode pads
10
of the organic substrate
6
are electrically connected to solder balls
14
, which are external connection electrodes, via a circuit pattern (not shown in the figure) formed on the organic substrate
6
.
In the semiconductor device shown in
FIG. 1
, a plurality of vent holes
16
, which are through holes, are previously formed in the organic substrate
6
so as to prevent the above-mentioned popcorn phenomenon. Since the vent holes
16
are formed by punching or drilling, a diameter of each of the vent holes
16
ranges from 0.1 mm to 0.3 mm. The semiconductor device is formed by fixing the semiconductor chip
2
by the adhesive
4
onto the organic substrate
6
having the thus-formed vent holes
16
.
Additionally, there is a method in which the vent holes
16
are not previously formed on the organic substrate
6
but a plurality of through holes are formed as the vent holes
16
in the organic substrate
16
by using a laser apparatus
18
after fixing the semiconductor chip
2
to the organic substrate
6
and encapsulating by a resin.
FIG. 3
is a cross-sectional view of a conventional semiconductor device produced by a flip chip method. The semiconductor chip
2
is mounted to the organic substrate
6
by bonding stud electrodes
20
to the electrode pads
10
formed on the organic substrate
6
. An under fill material
22
is filed between the semiconductor chip
2
and the organic substrate
6
so as to securely fix the semiconductor chip
2
to the organic substrate
6
. Additionally, the electrode pads
10
of the organic substrate
6
is electrically connected to the solder balls
14
, which are external connection electrodes, via the circuit pattern (not shown in the figure) formed on the organic substrate
6
. The under fill material
22
corresponds to the adhesive
4
in FIG.
1
.
Accordingly, similar to the semiconductor device shown in
FIG. 1
, the vent holes, which are a plurality of through holes, are previously formed in the organic substrate
6
. Since the vent holes
16
are formed by punching or drilling, a diameter of each of the vent holes
16
ranges from 0.1 mm to 0.3 mm. The semiconductor device is formed by fixing the semiconductor chip
2
onto the organic substrate
6
having the thus-formed vent holes
16
and filling the under fill material
22
between the organic material
6
and the semiconductor chip
2
.
Additionally, there is a method in which the vent holes
16
are not previously formed on the organic substrate
6
but a plurality of through holes are formed as the vent holes
16
in the organic substrate
16
by using the laser apparatus
18
after fixing the semiconductor chip
2
onto the organic substrate
6
.
In the semiconductor device shown in
FIG. 1
, since the vent holes
16
are previously formed in the organic substrate
6
, there is a problem in that the adhesive
4
leaks through the vent holes
16
when the liquid or paste-like adhesive
4
before curing is supplied between the semiconductor chip
2
and the organic substrate
6
.
The adhesive
4
is mixed with filler having a particle diameter ranging from 50 &mgr;m to 60 &mgr;m, and, thus, the filler easily passes through the vent holes
16
, and the vent holes
16
are not clogged by the filler. However, the leakage of the adhesive
4
cannot be prevented by the filler.
If the adhesive
4
leaks through the vent holes
16
, the leaking adhesive may cause a problem during a mounting operation of the semiconductor device. That is, the leaked and cured adhesive
4
may adhere to the electrodes of the mounting substrate when the semiconductor device is mounted onto the mounting substrate, which may cause incomplete soldering.
In order to eliminate the above-mentioned problem caused by the leakage of the adhesive
4
, the vent holes
16
are formed by laser machining after the adhesive
4
is cured as shown in FIG.
2
. Thereby, the leakage of the adhesive
4
can be prevented, but there is a problem in that a surface of the semiconductor chip
2
is damaged by a laser beam penetrating the adhesive
4
and reaching the surface of the semiconductor chip
2
. In recent years, semiconductor chips have become thin, and, therefore, a crack may be generated in the semiconductor chip
2
when the semiconductor chip receives only a small damage. When the semiconductor chip
2
receives damage, an operation failure may occur in the semiconductor device.
Additionally, in the semiconductor device shown in
FIG. 3
, there is the same problem as the above-mentioned semiconductor device shown in FIG.
3
. That is, in a case in which the vent holes
16
are previously formed in the organic substrate
6
, there is a problem in that the under fill material
22
leaks through the vent holes
16
. Additionally, as shown in
FIG. 4
, in a case in which the vent holes
16
are formed in the organic substrate
6
by laser machining after the under fill material is cured, the surface of the semiconductor chip
2
may be damaged by the laser beam.
Especially, in the semiconductor chip produced by the flip chip mounting as shown in
FIGS. 3 and 4
, since the circuit forming surface of the semiconductor chip
2
faces the organic substrate
6
, the circuit forming surface is damaged by the laser machining. Accordingly, the circuit of the semiconductor chip is directly influenced even if the damage is very small, which results in an operati
Aiba Kazuyuki
Hiraoka Tetsuya
Okada Akira
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Owens Douglas W.
Thomas Tom
LandOfFree
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