IGBT with self-aligning cathode pattern and method for producing it
First Claim
1. An insulated-gate bipolar transistor comprisinga semiconductor substrate of a first conduction type which is bounded by a first and a second main area;
- a cathode which is allocated to the first main area, and an anode which is formed by a metallization covering the second main area;
an emitter layer of a second conduction type which is inserted into the semiconductor substrate from the anode-side main area;
a plurality of collector regions of the second conduction type which are inserted into the semiconductor substrate from the cathode-side main area, the semiconductor substrate penetrating to the cathode-side main area between two adjacent collector regions;
a gate electrode which is formed by a conducting layer which is arranged and insulated above the cathode-side main area and extends from a collector region over the semiconductor substrate penetrating to the surface to the adjacent collector region;
a number of source regions of the first conduction type which are inserted into the collector regions and which exhibit a length L and at right angles thereto a width W in the direction of an adjacent collector region;
whereinthe length L of the source regions is selected such that there are at least two channel regions produced for each source region, the channel regions comprising a part of a collector region which penetrates to the cathode-side main area between the source region and semiconductor substrate and which is covered by the gate electrode,the width of the source regions is selected to be of the order of magnitude of microns such that holes which flow from the anode to the cathode underneath the source regions polarize a PN-junction which is formed by the source regions and the adjacent collector regions in the forward direction, and such that a voltage drop across said PN-junction remains below the inbuilt forward voltage of the PN junction at any time.
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Abstract
An insulated-gate bipolar transistor (IGBT) is specified, the collector (7) and source regions (8) of which can be produced by means of a self-aligning method. This provides an IGBT which is distinguished by a homogeneous turn-off current distribution. For this purpose, the width W of the source regions (8) is selected to be so small that holes can flow laterally into the surrounding collector region. In this connection it must be ensured that the voltage drop across the PN junction of the source regions and collector regions remains below the inherent forward voltage at any time. In consequence, the IGBT according to the invention is particularly insensitive to latch-up.
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Citations
15 Claims
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1. An insulated-gate bipolar transistor comprising
a semiconductor substrate of a first conduction type which is bounded by a first and a second main area; -
a cathode which is allocated to the first main area, and an anode which is formed by a metallization covering the second main area; an emitter layer of a second conduction type which is inserted into the semiconductor substrate from the anode-side main area; a plurality of collector regions of the second conduction type which are inserted into the semiconductor substrate from the cathode-side main area, the semiconductor substrate penetrating to the cathode-side main area between two adjacent collector regions; a gate electrode which is formed by a conducting layer which is arranged and insulated above the cathode-side main area and extends from a collector region over the semiconductor substrate penetrating to the surface to the adjacent collector region; a number of source regions of the first conduction type which are inserted into the collector regions and which exhibit a length L and at right angles thereto a width W in the direction of an adjacent collector region;
whereinthe length L of the source regions is selected such that there are at least two channel regions produced for each source region, the channel regions comprising a part of a collector region which penetrates to the cathode-side main area between the source region and semiconductor substrate and which is covered by the gate electrode, the width of the source regions is selected to be of the order of magnitude of microns such that holes which flow from the anode to the cathode underneath the source regions polarize a PN-junction which is formed by the source regions and the adjacent collector regions in the forward direction, and such that a voltage drop across said PN-junction remains below the inbuilt forward voltage of the PN junction at any time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. Method for producing an IGBT which comprises the steps of:
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patterning a cathode-side surface after creation of the anode and any edge termination, by means of the following steps; deposition of a gate oxide layer; deposition of a polysilicon layer which is covered with an SiO2 masking layer; removal of the polysilicon layer at the locations where no gate electrode is to be created; implantation and diffusion of the collector regions, the polysilicon layer being used as implantation mask; covering of the collector regions with resist at the locations where no source region is to be created; implantation and diffusion of the source regions and simultaneous doping of the silicon layer to become the gate electrode, the polysilicon layer for the source regions, in turn, being used as implantation masks; and insulation of the gate electrode, contact hole opening and metallization of the cathode. - View Dependent Claims (15)
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Specification