Bidirectional blocking lateral MOSFET with improved on-resistance
First Claim
1. A method for reducing the on-resistance of a bidirectional current blocking power MOSFET, the bidirectional current blocking power MOSFET including a semiconductor substrate, the substrate including a body region doped with P-type dopant to a first doping concentration, wherein the body region is grounded and neither a source region nor a drain region of the power MOSFET is grounded, the method comprising:
- forming a P-type spitaxial layer having a second doping concentration in the semiconductor substrate, the second doping concentration being lower than the first doping concentration;
introducing N-type dopant into the P-type epitaxial layer to form the source region and the drain region; and
forming a P-type threshold adjust layer having a third doping concentration in the spitaxial layer, the third doping concentration being higher than the second doping concentration.
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Abstract
A bidirectional current blocking lateral power MOSFET including a source and a drain which are not shorted to a substrate, and voltages that are applied to the source and drain are both higher than the voltage at which the body is maintained (for an N-channel MOSFET) or lower than the voltage at which the body is maintained (for a P-channel MOSFET). The on-resistance of the MOSFET is improved by decreasing the conductance of the epi region and disposing a thin threshold adjust layer on the surface of the substrate between the source and drain regions. An optional second punchthrough preventing implant is disposed on the substrate surface.
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Citations
8 Claims
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1. A method for reducing the on-resistance of a bidirectional current blocking power MOSFET, the bidirectional current blocking power MOSFET including a semiconductor substrate, the substrate including a body region doped with P-type dopant to a first doping concentration, wherein the body region is grounded and neither a source region nor a drain region of the power MOSFET is grounded, the method comprising:
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forming a P-type spitaxial layer having a second doping concentration in the semiconductor substrate, the second doping concentration being lower than the first doping concentration; introducing N-type dopant into the P-type epitaxial layer to form the source region and the drain region; and forming a P-type threshold adjust layer having a third doping concentration in the spitaxial layer, the third doping concentration being higher than the second doping concentration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification