Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
2001-08-29
2003-05-13
Cao, Phat X. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S347000
Reexamination Certificate
active
06563200
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an interface device for connecting a control unit and a field apparatus such as sensor and actuator in a network which are, for example, used in a production line, and an interface system using the same.
2. Conventional Art
A conventional electric line connection to the field apparatus such as a sensor and an actuator which are used in a production line was generally constituted through an individual wiring.
Although, these days, such connection is being shifting toward a field network which permits a flexible system construction, however, in such instance an interface device for connecting to a network is necessitated.
Now, an interface necessitates a power source, and in a case of a system where many numbers of field apparatuses are connected to a network having a long laying distance via an interface, the electric power is usually supplied from the network to the interface.
In order to receive such electric power supply, the interface is required to include a regulator unit which converts the voltage supplied from the network into a voltage usable in the interface system, a transceiver for performing signal transmission and reception with the network, a controller unit such as microcomputer which controls a communication system and the field apparatus and an isolator which electrically isolates the network from the field apparatus.
Now, when the scale of the system enlarges, at an interface device located remote from the power source, a voltage drop due to the network increases and the interface device likely becomes inoperable, for this reason structure of the network is limited and the advantages of the field network can not fully make use of, therefore, it is necessary to reduce power consumption of such interface device.
In a conventional interface device a photo coupler is generally used as the isolator, however, the power consumption of such photo coupler is comparatively large and the size reduction thereof is difficult, because the photo coupler is a dedicated part for respective ICs.
For countermeasuring the above problem, for example, JP-A-11-317445 (1999) and JP-A-11-136293 (1999) disclose a semiconductor device of on-chip structure in which a dielectric isolation (DI) substrate such as a silicon on insulator (SOI) substrate is used as a circuit substrate and a static capacitor type isolator is mounted thereon.
By means of the above prior art, the electrical isolation is obtained by the static capacitor not using the photo coupler, therefore, if the interface device is constituted with such means, both small sizing and low power consumption can be easily achieved.
However, the above conventional art did not take into account the noise propagation by the dielectric isolation substrate which causes problems of erroneous operation of the circuits and deterioration of the elements.
When an interface device which is formed by integrating a transceiver unit and a capacitive type isolator unit on an SOI substrate is operated through power supply from the network, the interface device possibly operates erroneously due to noises from the network.
Namely, if noises come into the transceiver unit from the network, a voltage is induced even on a thin film semiconductor layer via a semiconductor support substrate and an erroneous operation due to noises is resultantly caused.
Further, in such instance, performance of the elements on the thin film semiconductor layer is possibly deteriorated due to the noises, which is caused by such as electric charge accumulation in a buried insulation film and occurrence of charge depletion.
Now, the influences of the noises in the conventional art will be further explained in detail with reference to
FIG. 3
, in a semiconductor device using a dielectric isolation substrate a buried insulation film
41
is formed within a semiconductor substrate as shown in the drawing, thereby, the semiconductor substrate is divided into two parts in its thickness direction, in that an isolated structure is formed one (the lower side in the drawing) as a semiconductor support substrate region
411
and the other (the upper side in the drawing) as a semiconductor region used for circuit element formation.
Further, the semiconductor region used for circuit element formation is further divided in its face direction by a region insulation portion ( insulation channel)
410
into two kinds of thin film silicon layers of a controller side region
407
and a network side region
408
.
Namely, in this instance, one piece of semiconductor substrate is divided into three kinds of regions by the region insulation portion
410
and the buried insulation film
412
.
Herein, circuits formed in the controller side region
407
is electrically isolated from circuit formed in the network side region
408
and a necessary signal transmission passage is provided by an isolator portion via a static capacitor coupling.
The circuits in the network side region
408
are supplied by a power source V+ and V− in the network and the circuits in the controller side region
407
are supplied by a power source VDD
2
and GND
2
in the controller side.
On the other hand, the semiconductor support substrate region
411
is connected nowhere and is kept floating. Herein, the power source V+ and V− in the network is, for example, 24V and if a high voltage noise is induced in the network, the high voltage noise is applied to the network side region
408
. The noise voltage at such instance sometimes reaches up to, for example, 500V.
Such noise is directly and electrostatically applied to the controller side region
407
from the network side region
408
via the region insulation portion
410
as well as since the semiconductor support substrate region
411
is kept floating, after inducing a noise voltage at the semiconductor support substrate region
411
via the buried film
412
, the noise voltage is applied to the controller side region via the buried insulation film
412
in a voltage divided manner by a static capacitor.
At this moment, since the static capacitance formed by the region insulation portion
410
between the controller side region
407
and the network side region
408
shows merely a small value because of the thin thickness of respective regions
407
and
408
, the noises directly applied via this portion does not cause a substantial problem.
On the other hand, since the semiconductor support substrate
410
adjoins with the controller side region
407
and the network side regions
408
through a single plane, a static capacitance formed between them is comparatively large and a noise voltage induced at the controller side region
407
from the network side region
408
via the buried insulation film
412
reaches comparatively high voltage.
At this moment, since the buried insulation film
412
accumulates charges and is depleted, the performance of the elements is deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an interface device using a dielectric isolation substrate which sufficiently suppresses an erroneous operation due to noises and performance deterioration, and a system using the same.
The above object is achieved by an interface device which is provided with at least two semiconductor regions separated from a support substrate region via a dielectric body and in which an electrical isolation between an integrated circuit formed in the respective semiconductor regions is provided by a static capacitance, and is further provided with means for keeping the potential of one of the semiconductor regions, in which the integrated circuits being connected to a network are formed, at a potential of a power source line for the network.
At this instance, the integrated circuits being connected to the side of the network can include a communication function for an integrated circuit in another interface device connected to the network.
Further, at this instance, the interface device can include a package and the suppor
Amishiro Masatsugu
Kikuchi Mutsumi
Murabayashi Fumio
Sase Takashi
Watanabe Atsuo
Cao Phat X.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Hitachi , Ltd.
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