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US 7,923,751 B2Granted
Bipolar transistor with a low saturation voltage
AssigneeZetex PLC
InventorDavid Casey
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AssigneeZetex PLC
InventorDavid Casey
Estimating the term…
A bipolar transistor with a specific area resistance less than about 500 mOhms·mm2 comprises a first semiconductor region of a first conductivity type defining a collector region (2). A second semiconductor region of a second conductivity type defines a base region (3). A third semiconductor region of the first conductivity type defines an emitter region (4). A metal layer provides contacts (6, 7) to said base (3) and emitter regions (4). The metal layer has thickness greater than about 3 μm.
A bipolar transistor suitable for operation as a saturated switch comprising:
A method of manufacturing a bipolar transistor having reduced saturation resistance, the method comprising:
Dependencies are inferred from the claim text.
From the US filing history. Foreign family members aren’t listed.
Drawings are temporarily unavailable. Open the PDF at USPTO
Semiconductor regions connected to electrodes carrying current to be rectified, amplified or switched, e.g. source or drain regions: emitter…
Vertical BJTs: having both emitter-base and base-collector junctions ending at the same surface of the body
Electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. sources, drains, anodes or cathodes: emitter or collector…
Electrodes not carrying the current to be rectified, amplified, oscillated or switched, e.g. gates: base electrodes for bipolar transistors
Term ended 12 Jul 2024 (estimated)
The present invention relates to a bipolar transistor with a low saturation voltage.
With bipolar transistors, the collector-emitter saturation voltage is a key parameter determining the power loss of the transistor and its efficiency. In a circuit where the bipolar transistor is operated as a saturated switch a small base current is used to switch on a much larger collector to emitter current, the size of this current being determined by the voltage supply and the load resistance connected to either the collector or the emitter. When a bipolar transistor is operated in saturation the voltage drop from the collector to the emitter is reduced to a minimum value known as the saturation voltage VCE(sat). It is desirable to reduce this saturation voltage to as low a value as possible in order to minimise the power loss within the transistor.
There a number of known techniques to reduce the saturation voltage for a bipolar transistor, through either ensuring that the emitter/base junction is biased as evenly as possible across the whole junction area, or reducing the parasitic series resistance from the collector contact to the emitter contact.
Low VCE(sat) transistors with specific area resistances of below 500 mOhm·mm2 are now widely available. Nevertheless it remains desirable to find new ways of reducing the VCE(sat) of bipolar transistors. Accordingly it is an object of the present invention is to provide a new approach to reducing the specific area resistance and thus VCE(sat) of bipolar transistors.
According to the present invention there is provided a bipolar transistor, comprising:
a first semiconductor region of a first conductivity type defining a collector region;