Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With extended latchup current level
Reexamination Certificate
2001-03-22
2003-02-18
Loke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With extended latchup current level
C257S139000, C257S140000, C257S146000, C257S132000
Reexamination Certificate
active
06521919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having switching function such as IGBT (Insulated Gate Bipolar Transistor), GCT (Gate Commutated Turn-off Thyristor) or GTO (Gate Turn-off Thyristor).
2. Description of the Background Art
FIG. 8
is a cross section showing a structure of a conventional reverse conducting GTO. Here, there will be explained below GTO as an example of a semiconductor device having a switching function. Normally, the reverse conductive GTO is constituted so that a GTO area is connected to a free wheeling diode area in antiparallel and these areas are integrated in one semiconductor substrate.
In the conventional reverse conducting GTO, a P layer
602
, and an N
E
layer
603
are diffused on a semiconductor substrate N-layer
601
made of silicon or the like in order from a cathode side in a GTO area
620
. Similarly an N
+
layer
604
and a P
E
layer
605
are diffused in order from an anode side. In a diode area
621
, the P layer
602
is diffused on the semiconductor substrate N
−
layer
601
made of silicon or the like from the cathode side, and the N
+
layer
604
and an N
++
layer
606
are diffused in order from the anode side.
In addition, this reverse conducting GTO has a cathode electrode
607
and a gate electrode
608
in the GTO area, a cathode electrode
609
in the diode area and an anode electrode
610
in the whole area. In a separating area which separates the GTO area
620
from the diode area
621
, an etching section
611
is provided on a portion of the P layer
602
which remains on the N
−
layer
601
after a diffusion area of the P layer
602
of about 90 &mgr;m is etched down by about 60 &mgr;m, and the width A of the etching portion is about 5 mm. Resistance of 300 to 500&OHgr; is provided between the GTO area
620
and the diode area
621
and they are separated by the etching area with the width A of about 5 mm. Paying attention to thermal resistance, thermal resistance is generated on the surface of the GTO area
620
at the time of operating GTO, and on the surface of the diode area
621
at the time of operating diode.
Further, relating techniques are disclosed in Japanese Patent Application Laid-Open Nos. 9-191110 (1997) and 2-309676 (1990). Japanese Patent Application No. 9-191110 (1997) discloses an insulating gate bipolar transistor containing a diode. In this transistor, a cathode electrode and a collector electrode are integrated, and an anode electrode and an emitter electrode are integrated so that a size of the whole transistor is reduced.
Japanese Patent Application Laid-Open No. 2-309676 (1990) discloses a reverse conducting-type insulated gate bipolar transistor. In this transistor, a source of IGBT and an anode of a diode are formed by one electrode, and a collector of IGBT and a cathode of the diode are formed by one electrode.
In the conventional reverse conducting GTO (FIG.
8
), since the GTO area
620
and the diode area
621
are separated by high resistance, the separating area is required. Moreover, in this reverse conducting GTO, since thermal resistance is generated on the surface of the GTO area
620
and on the surface of the diode area
621
, there arises a problem that the thermal resistance in the reverse conducting GTO is high. Further, as for both the diodes disclosed in Japanese Patent Application Laid-Open Nos. 9-191110 (1997) and 2-309676 (1990), a switching element and the diode use one electrode so that the whole diode becomes compact. However, a separating area which separates the switching element area from the diode area is required. There arises a problem that an actual operating area is reduced due to this separating area and thus a performance of a semiconductor device is deteriorated.
SUMMARY OF THE INVENTION
The present invention is devised in order to solve the above problems, and it is an object of the present invention to provide a semiconductor device in which a switching ability and a diode ability can be used properly in a regular direction and a reverse direction in one structure, thereby increasing a surface area of a chip and reducing thermal resistance, and a separating area is eliminated, thereby increasing an actual operating area.
In order to achieve the above objects, a first aspect of the invention provides a semiconductor device characterized by including: a semiconductor substrate; wherein the semiconductor includes: a first conducting-type first semiconductor layer; a second conducting-type second semiconductor layer; a first conducting-type third semiconductor layer; a second conducting-type fourth semiconductor layer; and a first conducting-type fifth semiconductor layer; a first main electrode for short-circuiting the first semiconductor layer and the second semiconductor layer; a second main electrode for short-circuit the fourth semiconductor layer and the fifth semiconductor layer; and a control electrode provided on the third semiconductor layer. The semiconductor device is characterized in that the first semiconductor layer and the second semiconductor layer form a joint, the second semiconductor layer and the third semiconductor layer forms a joint, the third semiconductor layer and the fourth semiconductor layer form a joint, and the fourth semiconductor layer and the fifth semiconductor layer form a joint.
In accordance with the semiconductor device of the first aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the second aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first semiconductor layer and the third semiconductor layer are separated by the second semiconductor layer, and the third semiconductor layer and the fifth semiconductor layer are separated by the fourth semiconductor layer.
In accordance with the semiconductor device of the second aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the third aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first semiconductor layer and the second semiconductor layer are exposed from a first main surface of the semiconductor substrate, and the first semiconductor layer is surrounded by the second semiconductor layer.
In accordance with the semiconductor device of the third aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the fourth aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the fourth semiconductor layer and the fifth semiconductor layer are exposed from a second main surface of the semiconductor substrate, and the fifth semiconductor layer is surrounded by the fourth semiconductor layer.
In accordance with the semiconductor device of the fourth aspect of the present invention, the area having the switching ability and the area having the
Hirano Noritoshi
Satoh Katsumi
Yamaguchi Yoshihiro
Loke Steven
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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