Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Reexamination Certificate
2000-02-07
2001-09-04
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
C257S080000, C257S082000, C257S081000
Reexamination Certificate
active
06285084
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having a pair of elements which are adapted to be coupled to each other in an electrically isolated state for signal transmission.
2. Description of Related Art
Devices having a transmitter element and a receiver element in pair which are adapted to be optically or magnetically coupled to each other in an electrically isolated state for signal transmission are generally referred to as isolators. Exemplary isolators are photo-couplers which include a light-emitting element such as a light-emitting diode and a light-receiving element such as a photo MOS transistor or a photo diode.
Typical constructions of the conventional photo-couplers, which are described in NIKKEI ELECTRONICS Jul. 1, 1991, pp83-92, are respectively shown in
FIGS. 8 and 9
.
FIG. 8
illustrates a photo-coupler of opposed type in which a semiconductor chip
110
formed with a light-emitting element is opposed to a semiconductor chip
120
formed with a light-receiving element.
FIG. 9
illustrates a photo-coupler of planar type in which a semiconductor chip
110
formed with a light-emitting element and a semiconductor chip
120
formed with a light-receiving element are disposed in substantially the same plane.
In either of the photo-diodes, the semiconductor chips
110
,
120
are mounted on different lead frames
111
,
121
, and a transparent resin
101
is interposed between the semiconductor chips
110
and
120
to provide a light path therebetween. In this state, the semiconductor chips
110
,
120
are encapsulated with a mold resin in a package
103
, and distal edges of the lead frames
111
,
121
are led out of the package
103
.
In the case of the opposed type, light is transmitted through the transparent resin
101
between the opposed semiconductor chips
110
and
120
, and direct light from the light-emitting element of the semiconductor chip
110
is incident on the light-receiving element of the semiconductor chip
120
. In the case of the planar type, on the other hand, light emitted from the light-emitting element of the semiconductor chip
110
is reflected on an interface between the transparent resin
101
and the mold resin, and the reflected light is incident on the light-receiving element of the semiconductor chip
120
.
Since the aforesaid photo-couplers are constructed such that the light-emitting element and the light-receiving element are resin-sealed with the intervention of the transparent resin
101
therebetween, size reduction thereof is difficult.
Further, the semiconductor chips
110
and
120
are respectively mounted on the different lead frames
111
and
121
, so that circuits for the light-emitting element and the light-receiving element cannot be integrated. This also hinders the size reduction.
Particularly in the case of the opposed type construction, it is difficult to properly position the semiconductor chips
110
and
120
respectively mounted on the different lead frames
111
and
121
. That is, the positioning of the light-emitting element with respect to the light-receiving element is difficult, so that the efficiency of the coupling between the light-emitting element and the light-receiving element is likely to be reduced.
Where an attempt is made to achieve multi-channeling by providing a plurality of light-emitting element/light-receiving element pairs in a single package in either of the aforesaid constructions, there is a difficulty in optical signal isolation between respective channels. Therefore, it is impossible to realize a multi-channel device.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device which includes a pair of elements capable of signal transmission therebetween in an electrically isolated state.
It is another object of the invention to provide a semiconductor device which features easier positioning of a pair of elements adapted for signal transmission therebetween in an electrically isolated state.
It is further another object of the invention to provide a semiconductor device which has a construction advantageous for multi-channel signal transmission in an electrically isolated state.
The semiconductor device according to the present invention comprises: a first semiconductor chip; and a second semiconductor chip stacked on the first semiconductor chip and bonded to a surface of the first semiconductor chip. The first semiconductor chip and the second semiconductor chip are formed with a first element and a second element, respectively, which are provided in an opposed relation. The first element and the second element are adapted to be coupled to each other in an electrically isolated state for signal transmission. The first semiconductor chip has an external connector isolated from the first element and electrically connected to the second element.
The signal transmission between the first element and the second element maybe achieved through photo-coupling. Alternatively, the signal transmission between the first element and the second element may be achieved through magnetic coupling (coupling by mutual inductance). Further, one of the first element and the second element may be a signal transmitting element, and the other may be a signal receiving element. In this case, which of the first and second elements is the signal transmission element is not critical.
The first semiconductor chip and the second semiconductor chip may respectively have chip connectors, through which the connection between the second element and the external connector may be achieved. In this case, the chip connectors of the first and second semiconductor chips are preferably located in opposed positions when the first and second elements are bonded to each other in an opposed relation.
A chip interconnection member may be interposed between the chip connectors of the first and second semiconductor chips. The chip interconnection member may be a metal protuberance provided on at least one of the chip connectors of the first and second semiconductor chips. The metal protuberance may be a bump formed as a relatively thick film by plating, or a thin metal film (metal deposition film) having a thickness much smaller than the bump.
The connection between the chip connectors and the external connector may be achieved by an internal interconnection provided in the first semiconductor chip, or by a surface interconnection provided on the surface of the first semiconductor chip. Where the chip interconnection member is provided on the first semiconductor chip, the surface interconnection is preferably composed of the same material as the chip interconnection member. Thus, the formation of the surface interconnection can be achieved simultaneously with the formation of the chip interconnection member.
The semiconductor device preferably further comprises a wall member provided between the opposed surfaces of the first and second semiconductor chips as surrounding the first and second elements. Thus,a coupling space (e.g., a light transmission path for optical coupling) can assuredly be provided between the first and second elements when the first and second semiconductor chips bonded to each other are resin-sealed.
In accordance with the present invention, the semiconductor device has a so-called chip-on-chip structure in which the second semiconductor chip is bonded onto the first semiconductor chip in a stacked relation. The first element and the second element respectively provided in the first semiconductor chip and the second semiconductor chip are opposed to each other. The chip-on-chip structure makes it possible to dispose the first element and the second element in a very close relation for a higher coupling efficiency. Where the first element and the second element are to be coupled to each other by an optical signal, for example, a light transmission path can assuredly be provided between the first element and the second element without the provision of a transparent resin therebetween. Thus, an i
Hikita Junichi
Mochida Hiroo
Clark Sheila V.
Rader Fishman & Grauer
Rohm & Co., Ltd.
LandOfFree
Semiconductor device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2458771