Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Multiple housings
Reexamination Certificate
2002-12-17
2004-03-16
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Multiple housings
C257S678000, C257S685000, C257S734000, C257S737000, C257S738000, C257S777000, C257S778000, C257S784000, C257S786000
Reexamination Certificate
active
06707143
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device in which a stack of semiconductor chips is mounted on a wiring board.
Recently, to downsize electronic units and improve the reliability thereof, a semiconductor device in which multiple semiconductor chips are included in one package has been in high demand. In view of this, to realize high performance and high packaging density, a semiconductor device (an LSI package) made by stacking a plurality of semiconductor chips on a wiring board has attracted more and more attention.
Hereinafter, a known semiconductor device will be described with reference to the drawing.
FIG. 6
shows a cross-sectional structure for a known semiconductor device with a stack of LSI chips. As shown in
FIG. 6
, first and second LSI chips
102
and
103
are secured to each other on a wiring board
101
so that the non-circuitry sides of these chips
102
and
103
face each other, i.e., so that the top of the chip
102
faces the bottom of the chip
103
.
The circuitry side of the first LSI chip
102
faces the principal surface of the wiring board
101
and is electrically connected to the wiring board
101
via raised electrodes
104
. In other words, the first LSI chip
102
is flip-chip bonded to the wiring board
101
. External electrodes
105
on the circuitry side of the second LSI chip
103
are electrically connected to the wiring board
102
via metal fine wires
106
.
However, in the known semiconductor device, because of recent remarkable increase in number of pins in an LSI chip, the external electrodes
105
on the second LSI chip
103
are often located almost right over the raised electrodes
104
on the first LSI chip
102
as viewed vertically downward from over the principal surface of the wiring board
101
. Thus, during a wire bonding process in which the external electrodes on the second LSI chip
103
are bonded to the wiring board
101
, if a load is applied downward vertically to the principal surface of the wiring board
101
with a bonding jig, the raised electrodes
104
and surrounding portions thereof (which will be herein referred to as “flip-chip bonding terminals”) are mechanically damaged. As a result, the electrical connection between the first LSI chip
102
and wiring board
101
via the raised electrodes
104
deteriorates due to the mechanical damage or the bonding terminals might be crushed. That is to say, if the thicknesses of the LSI chips
102
and
103
are reduced to 300 &mgr;m or less to meet the demand of thinning a semiconductor device, it should be difficult for the thinner LSI chips
102
and
103
to internally attenuate the load applied thereto by the bonding jig.
In addition, even if a low-melting metal with a mechanical strength greater than that of a conductive adhesive or resin is used for the raised electrodes
104
, the mechanical strength of the bonding terminals will not increase so much as compared to the bonding terminals made of the conductive adhesive or resin. This is because the size of the raised electrodes
104
is several tens &mgr;m at the most.
Further, the first and second LSI chips
102
and
103
are secured together so that their non-circuitry sides face each other. Thus, it is difficult to mount a stack of three or more LSI chips on one wiring board
101
. Accordingly, it is not so easy for the know techniques to further improve the performance and further increase packaging density.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to solve these problems of a semiconductor device with a stack of multiple semiconductor chips. Specifically, a first object of the present invention is to establish more reliable electrical connection by suppressing the deterioration of the flip-chip bonding terminals during a wire bonding process. A second object of the present invention is to get three or more semiconductor chips mounted on a wiring board.
To achieve the first object, a first inventive semiconductor device includes: a wiring board; a first semiconductor chip, which has a circuitry side and a non-circuitry side that face each other vertically and which is electrically connected to the wiring board via a raised electrode, the circuitry side of the first chip facing the principal surface of the wiring board; and a second semiconductor chip, which has a circuitry side and a non-circuitry side that face each other vertically and which includes an external electrode on the circuitry side thereof. The non-circuitry sides of the first and second semiconductor chips are secured to each other. The external electrode of the second semiconductor chip is connected to the wiring board via a metal fine wire. The external and raised electrodes are so disposed as not to overlap each other as viewed vertically downward from over the principal surface of the wiring board.
In the first inventive semiconductor device, the external and raised electrodes are so disposed as not to overlap each other as viewed vertically downward from over the principal surface of the wiring board. Thus, the load applied to the external electrode during a wire bonding process does not propagate to a flip-chip bonding terminal on the first semiconductor chip so easily. As a result, electrical connection does not deteriorate at the flip-chip bonding terminal.
To achieve the second object, a second inventive semiconductor device includes: a wiring board; a first semiconductor chip, which has a circuitry side and a non-circuitry side that face each other vertically and which is electrically connected to the wiring board via a raised electrode, the circuitry side of the first chip facing the principal surface of the wiring board; and at least second and third semiconductor chips, each of which has a circuitry side and a non-circuitry side that face each other vertically and each of which includes an external electrode on the circuitry side thereof. The non-circuitry sides of the second and third semiconductor chips are secured to the non-circuitry side of the first semiconductor chip. The external electrodes of the second and third semiconductor chips are connected to the wiring board via metal fine wires.
In the second inventive semiconductor device, the non-circuitry sides of the second and third semiconductor chips are secured to the non-circuitry side of the first semiconductor chip. Thus, a stack of three or more semiconductor chips can be mounted on the wiring board. As a result, high performance and high packaging density are realized.
To obtain the second object, a third inventive semiconductor device includes: a wiring board; at least first and second semiconductor chips, each of which has a circuitry side and a non-circuitry side that face each other vertically and each of which is electrically connected to the wiring board via a raised electrode, the circuitry sides of the first and second chips facing the principal surface of the wiring board; and a third semiconductor chip, which has a circuitry side and a non-circuitry side that face each other vertically and which includes an external electrode on the circuitry side thereof. The non-circuitry side of the third semiconductor chip is secured to the non-circuitry side of the first semiconductor chip and/or the non-circuitry side of the second semiconductor chip. The external electrode of the third semiconductor chip is connected to the wiring board via a metal fine wire.
The third inventive semiconductor device includes at least the first and second semiconductor chips which are electrically connected to the wiring board via raised electrodes. In this device, the non-circuitry side of the third semiconductor chip is secured to the non-circuitry side of the first semiconductor chip and/or the non-circuitry side of the second semiconductor chip. Thus, a stack of three or more semiconductor chips can be mounted on the wiring board. As a result, high performance and high packaging density are realized.
In the second or third semiconductor device, the external and raised electrodes are preferably so dispose
Fujimoto Hiroaki
Kunitomo Yoshinobu
Yui Takashi
Flynn Nathan J.
Greene Pershelle
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Studebaker Donald R.
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