Low voltage MOSFET
First Claim
Patent Images
1. A low voltage planar power MOSFET comprising:
- a silicon wafer having a junction receiving surface;
at least first and second shallow spaced base diffusions of one conductivity type formed in said junction receiving surface and spaced by a common conduction region of said wafer;
each of said first and second bases having a respective source region of the other conductivity type diffused therein, each source region being substantially wholly contained within a respective base to define at least first and second spaced substantially, coplanar invertible channel regions, said first and second bases having a diffusion depth of less than about 1.5 microns;
a thin gate insulation layer overlying said invertible channel regions and the surface of said common conduction region between said invertible channel regions; and
a conductive polysilicon gate electrode layer overlying said gate insulation layer;
whereinthe polysilicon line width of said polysilicon layer measured in the direction spanning across said common conduction region is between about 0.7 microns and about 3.8 microns.
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Abstract
A low voltage planar MOSFET has a polyline width of less than 3.8 microns and a channel (base) region depth of less than 1.5 microns to produce a device having a reduced figure of merit (or product of QGD and RDSON).
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Citations
20 Claims
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1. A low voltage planar power MOSFET comprising:
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a silicon wafer having a junction receiving surface; at least first and second shallow spaced base diffusions of one conductivity type formed in said junction receiving surface and spaced by a common conduction region of said wafer; each of said first and second bases having a respective source region of the other conductivity type diffused therein, each source region being substantially wholly contained within a respective base to define at least first and second spaced substantially, coplanar invertible channel regions, said first and second bases having a diffusion depth of less than about 1.5 microns; a thin gate insulation layer overlying said invertible channel regions and the surface of said common conduction region between said invertible channel regions; and a conductive polysilicon gate electrode layer overlying said gate insulation layer;
whereinthe polysilicon line width of said polysilicon layer measured in the direction spanning across said common conduction region is between about 0.7 microns and about 3.8 microns. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A planar MOSFET having a breakdown voltage lower than about 30 volts, said MOSFET comprising:
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a silicon wafer having a junction receiving surface; a plurality of symmetrically spaced polygonal base diffusions of one conductivity type formed in said junction receiving surface, each of said bases having a diffusion depth less than about 1.5 microns; the material of said wafer disposed between said bases defining a common conduction region for the vertical conduction of charge carriers across at least a portion of the thickness of said wafer; each of said bases having an annular source diffusion therein to define a polygonal invertible channel region around periphery of each of said bases; a thin gate insulation layer lattice which overlies each of said invertible channel regions and the surface of said common conduction region; a conductive polysilicon electrode layer in substantial registry with and overlying said gate insulation member; the polysilicon line width of said polysilicon layer as measured in a direction across said common conduction region being between about 0.7 microns and about 3.8 microns. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A power MOSFET comprising:
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a polysilicon gate; a channel region; a source region; and a drain region; said polysilicon gate having a polysilicon line width; said power MOSFET having a gate to drain capacitance which produces a gate to drain charge QGD; said power MOSFET having an on resistance between said source region and said drain region expressed as RDSON; the value of QGD being generally a linear function of said polysilicon line width; the value of RDSON being non-linearly related to said polysilicon line width; and said polysilicon line width being between about 0.7 microns and about 3.8 microns, chosen to minimize the product of QGD and RDSON.
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Specification