Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Patent
1993-06-01
1995-09-05
Loke, Steven H.
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
257173, 257379, 257467, 257541, H01L 2976, H01L 2974, H01L 2900
Patent
active
054480922
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an insulated gate bipolar transistor equipped with a current detection function.
BACKGROUND ART
In order to prevent a switching element from being broken down due to an over-current and prevent circuit parts other than the power element from being broken down due to a current above a permissible current value in a system equipped with a power switching element, the system is required to be provided with a function for monitoring a current value flowing into the power switching element and restricting the current.
As means of providing the current detection function as described above in an insulated gate bipolar transistor (IGBT) element has been proposed as disclosed in Japanese Laid-open Patent Application No. 60-94772 or Japanese Laid-Open Patent Application No. 2-138773, for example. However, in the former, a resistor for obtaining a current detection signal is required to be set up at the outside thereof, and thus it has a problem that an assembly cost is increased and the size of an assembly is increased. In addition, there is a problem that a part of an element current is sacrificed because the current is partially diverted. On the other hand, the latter proposes such a construction that no resistor is required to be set up at the outside, however, in this construction a signal detection electrode is provided in the neighborhood of a channel portion of a cell area, so that a p-base area of this construction is required to be longer in lateral direction than a usual length to set up a contact area. Therefore, there is a problem that latch-up current value is depressed due to an increase of holes flowing into the p-base area.
This invention has been implemented in view of the above various problems, and has an object to provide an IGBT equipped with a current detection structure which requires no signal detecting resistor at the outside thereof, and induces no depression of latch-up current value.
DISCLOSURE OF INVENTION
In order to attain the above object, the IGBT according to this invention has been designed on the basis of an idea that an impurity-diffused area is formed at an area different from an unit cell area on the surface of an element, and a voltage drop due to carriers flowing through a lateral resistance of the impurity-diffused area is detected to perform a current detection, and specifically the IGBT comprises a unit cell area including a first semiconductor layer of a first conductivity type formed at a drain electrode side, of a second semiconductive layer of a second conductivity type, which is formed on the first semiconductor layer of the first conductivity type and whose conductivity is modulated by injection of carriers, a third semiconductor layer of the first conductivity type which is selectively formed on the surface of the second semiconductor layer, a fourth semiconductor layer of the second conductivity which is selectively formed on the surface of the third semiconductor layer, a gate electrode which is formed at least on a gate insulated film on the surface of the third semiconductor layer between the second semiconductor layer and the fourth semiconductor layer, and a source electrode which is formed on the surface of the third semiconductor layer and the surface of the fourth semiconductor layer, and a current signal detection area provided in the vicinity of the unit cell area and including a fifth semiconductor layer of the first conductivity type which is formed on the surface of the second semiconductor layer independently of the third semiconductor layer, and two contact areas which are away from each other at a predetermined interval in the fifth semiconductor layer, wherein the fifth semiconductor layer is contacted with the source electrode through one of the two contact areas, and contacted with a signal detection electrode formed independently of the source electrode or the gate electrode through the other contact area.
According to the construction as described above, when the surface of the third semiconduct
REFERENCES:
patent: 4783690 (1988-11-01), Walden et al.
patent: 4962411 (1990-10-01), Tokura et al.
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Tokura, U.S. patent Appln. No. 08/56,946; Okabe, U.S. patent Appln. No. 07/849,689 & Tokura, U.S. patent Appln. No. 07/735,512.
Okabe Naoto
Tokura Norihito
Loke Steven H.
Nippondenso Co. Ltd.
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