Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-12-11
2004-11-02
Cao, Phat X. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S342000, C257S401000
Reexamination Certificate
active
06812524
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a semiconductor component, in particular an MOS transistor having first and second connection zones of a first conduction type, a channel zone of a second conduction type and a drift zone of a first conduction type, the drift zone formed between the channel zone and the first connection zone, and the channel zone formed between the second connection zone and the drift zone, a control electrode formed insulated from the second zone for controlling a conductive channel in the second zone between the second zone and the drift zone, a drift zone of the first conduction type formed between the second zone and the first zone, and at least one compensation zone.
Such a semiconductor component, in the form of a vertical MOSFET, is disclosed, for example, in J. Tihanyi: “A Qualitative Study of the DC Performance of SIPMOS Transistors”, Siemens Forschungs-und Entwicklungsbericht, Vol. 9 (1980) No. 4, Springer Verlag, page 181, FIG. 1
c
. Such a MOSFET has an n
+
-doped drain zone in the region of a back of a semiconductor body and an n
+
-doped source zone in the region of a front of the semiconductor body. The source zone is surrounded in the semiconductor body by a p
+
-doped channel zone. Extending between the channel zone and the drain zone is an n
−
-doped drift zone formed adjacently to a p
−
-doped zone that likewise adjoins the channel zone. A gate electrode insulated from the channel zone allows a conductive channel to be formed between the source zone and the drift zone when a driving potential is applied.
Such a semiconductor component in the form of a MOSFET having an n-doped drain zone, an n-doped source zone surrounded by a channel zone, and an n-doped drift path formed adjacently to a p-doped zone is also disclosed in U.S. Pat. No. 5,216,275 to Chen and by U.S. Pat. No. 4,754,310 to Coe.
Such MOS transistors are distinguished by a low turn-on resistance and a high breakdown voltage.
In the MOS transistors, the source zone and the channel zone are normally shorted by a source electrode, so that the p-doped zone adjoining the channel zone is at source potential. Even when the MOSFET is on, i.e., when a conductive channel has been formed in the channel zone between the source zone and the drift zone and there is a voltage between the source zone and the drain zone, a voltage drop is produced across the drift path. Such a configuration results in a potential difference between the p-doped zone and the drift path that is greatest close to the drain zone and causes a space-charge zone to form in the boundary region between the p-doped zone and the drift path. The space-charge zone can pinch off the conductive channel in the drift path.
German Published, Non-Prosecuted Patent Application DE 198 15 907 C1 discloses a semiconductor component that can be controlled by field effect and has an n-doped drain zone, an n-doped source zone, a p-doped channel zone surrounding the source zone, and an n-doped drift path formed between the source zone and the drain zone, with a number of p-doped zones spaced apart being formed in the drift path. For driving, a gate electrode is provided that is formed to be insulated from the channel zone. If the semiconductor component is off and a voltage is applied between the source and drain zones, a space-charge zone propagates starting from the source zone and progressively takes in the p-doped zones disposed apart in the drift path. As such, these zones and the adjoining regions of the drift zone are depleted, that is to say free charge carriers recombine and depletion of free charge carriers occurs in the drift path, which results in a high breakdown voltage. To turn on the semiconductor component again after it has been off, the p-doped regions disposed on a floating basis—that is to say, those not connected to a fixed potential—need to be discharged again. To such an end, an injector is provided that injects p-charge carriers into the drift zone, or into the p-doped zones.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a semiconductor component that can be controlled by field effect that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that has a low turn-on resistance and a high breakdown voltage and in which pinch-off of the conductive channel in the drift zone is reduced in the on state.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a semiconductor component, including a first connection zone of a first conduction type, a second connection zone of the first conduction type, a channel zone of a second conduction type, the channel zone having a conductive channel, a drift zone of the first conduction type, the drift zone formed between the channel zone and the first connection zone, the channel zone formed between the second connection zone and the drift zone, a control electrode for controlling the conductive channel in the channel zone between the second connection zone and the drift zone, the control electrode insulated from the second zone, at least one compensation zone of the second conduction type, the at least one compensation zone formed in the drift zone and having at least two segments disposed at a distance from one another, and the distance between two adjacent ones of the at least two segments being chosen such that a punch-through voltage between the adjacent segments corresponds at most to a voltage across the drift zone at twice a rated current. Preferably, the distance between two adjacent segments is chosen such that a punch-through voltage between the adjacent segments corresponds to a voltage across the drift zone between a rated current and two times the rated current.
The second connection zone is isolated by the channel zone from the drift zone that, starting from the channel zone, extends up to the first connection zone. In addition, a control electrode is used to form a conductive channel in the channel zone between the second connection zone and the drift zone.
The distance between the two adjacent segments is chosen such that the punch-through voltage between the two segments corresponds at most to the voltage that becomes established when, with these miconductor component turned on, the drift path has a current flowing through it that is twice the rated current and when the temperature of the semiconductor body is preferably no more than 150° C.
The rated current is the current at which the semiconductor component is configured for long-term operation. In such a context, the rated current is definitively determined by the housing and its ability to dissipate heat.
In the case of two regions having identical doping and isolated by a complementarily doped region, the “punch-through voltage” is a general term for the value of the potential difference between these regions at which value a space-charge zone starting from one of the two regions takes in the other of the two regions. In absolute values, the punch-through voltage is preferably below 10 V in such a context.
The semiconductor component according to the invention works as an MOS transistor, with the first zone serving as drain zone, the second zone serving as source zone, and the control electrode serving as gate electrode.
With the semiconductor component turned on, those segments of the compensation zone that are disposed on a floating basis in the drift zone, that is to say, the segments that are not connected to the channel zone, assume a potential value that is between the potential on the first connection zone and the potential on the channel zone, or the potential on the second connection zone shorted by the channel zone. The potential difference between these floating segments and the surrounding regions of the drift zone is lower than in the case of the prior art MOS transistors, in which the whole compensation zone is at source potential. Thereby, the “junction effect,” which refers to the conductiv
Ahlers Dirk
Deboy Gerald
Stengl Jens-Peer
Strack Helmut
Tihanyi Jenoe
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