US 5,323,040 AGranted

Silicon carbide field effect device

AssigneeNorth Carolina State University at Raleigh

InventorBantval J. Baliga

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Abstract

A silicon carbide field effect device includes vertically stacked silicon carbide regions of first conductivity type, extending from a lowermost drain region to an uppermost source region. In between the drain and source regions, a drift region and a channel region are provided. The drift region extends adjacent the drain region and the channel region extends between the drift region and the source region. Control of majority carrier conduction between the source and drain regions is provided by a plurality of trenches, which extend through the source and channel region, and conductive gate electrodes therein. To provide high blocking voltage capability and low on-state resistance, the doping concentration in the drift region is selected to be greater than the doping concentration of the channel region but below the doping concentration of the drain and source regions. Preferably, the material used for the gate electrodes, the spacing between adjacent trenches and the doping concentration of the channel region are chosen so that the channel region is depleted of majority charge carriers when zero potential bias is applied to the gate electrodes.

Claims24

Dependent claims

A silicon carbide field effect transistor comprising:

a silicon carbide substrate having first and second opposing faces;
a silicon carbide drain region of first conductivity type in said silicon carbide substrate, extending to said first face;
a silicon carbide drift region of first conductivity type on said silicon carbide drain region opposite said first face, said silicon carbide drift region having a first conductivity type dopant concentration below that of said silicon carbide drain region;
a silicon carbide channel region of first conductivity type on said silicon carbide drift region opposite said silicon carbide drain region, said silicon carbide channel region having a first conductivity type dopant concentration below that of said silicon carbide drift region;
a silicon carbide source region of first conductivity type on said silicon carbide channel region, said silicon carbide source region extending to said second face and having a first conductivity type dopant concentration above that of said silicon carbide channel region;
a first trench in said silicon carbide substrate at said second face, said first trench having a sidewall extending between said silicon carbide drift region and said silicon carbide source region;
and
a second trench in said silicon carbide substrate at said second face, adjacent said first trench, said second trench having a sidewall extending between said silicon carbide drift region and said silicon carbide source region to thereby define a mesa of first conductivity type in said silicon carbide channel region and said silicon carbide source region, between said first trench and said second trench.

5 more elements

A silicon carbide field effect transistor comprising:

a silicon carbide substrate having first and second opposing faces;
a silicon carbide drain region of first conductivity type in said silicon carbide substrate, extending to said first face;
a silicon carbide drift region of first conductivity type on said silicon carbide drain region opposite said first face, said silicon carbide drift region having a first conductivity type dopant concentration below that of said silicon carbide drain region;
a silicon carbide channel region of predetermined conductivity type on said silicon carbide drift region opposite said silicon carbide drain region, said silicon carbide channel region having a first conductivity type dopant concentration below that of said silicon carbide drift region;
a silicon carbide source region of first conductivity type on said silicon carbide channel region, said silicon carbide source region extending to said second face and having a first conductivity type dopant concentration above that of said silicon carbide channel region;
and
at least one trench in said silicon carbide substrate at said second face, said trench extending between said second face and said silicon carbide drift region and having a sidewall which defines a mesa, extending between said silicon carbide drift region and said second face.

4 more elements

A silicon carbide field effect transistor comprising:

a silicon carbide substrate having first and second opposing faces;
a silicon carbide drain region of first conductivity type in said silicon carbide substrate, extending to said first face;
a silicon carbide drift region of first conductivity type on said silicon carbide drain region opposite said first face, said silicon carbide drift region having a first conductivity type dopant concentration below that of said silicon carbide drain region;
a silicon carbide channel region of first conductivity type on said silicon carbide drift region opposite said silicon carbide drain region, said silicon carbide channel region extending to said second face and having a first conductivity type dopant concentration below that of said silicon carbide drift region;
a first trench in said silicon carbide substrate at said second face, said first trench having a first sidewall extending between said silicon carbide drift region and said second face;
and
a second trench in said silicon carbide substrate at said second face, adjacent said first trench, said second trench having a second sidewall, opposite said first trench sidewall, extending between said silicon carbide drift region and said second face.

4 more elements

A silicon carbide rectifier, comprising:

a monocrystalline silicon carbide substrate having first and second opposing faces;
a silicon carbide drain region of first conductivity type in said silicon carbide substrate, extending to said first face;
a silicon carbide drift region of first conductivity type on said silicon carbide drain region opposite said first face, said silicon carbide drift region having a first conductivity type dopant concentration below that of said silicon carbide drain region;
a silicon carbide channel region of first conductivity type on said silicon carbide drift region opposite said silicon carbide drain region, said silicon carbide channel region having a first conductivity type dopant concentration below that of said silicon carbide drift region;
a silicon carbide source region of first conductivity type on said silicon carbide channel region, said silicon carbide source region extending to said second face and having a first conductivity type dopant concentration above that of said silicon carbide channel region;
a first trench in said silicon carbide substrate at said second face, said first trench having a sidewall extending between said silicon carbide drift region and said silicon carbide source region;
a second trench in said silicon carbide substrate at said second face, adjacent said first trench, said second trench having a sidewall extending between said silicon carbide drift region and said silicon carbide source region to thereby define a mesa of first conductivity type in said silicon carbide channel region and said silicon carbide source region, between said first trench and said second trench;
a first insulating region on said first trench sidewall and a second insulating region on said second trench sidewall;
a first conductive gate electrode in said first trench on said first insulating region and a second conductive gate electrode in said second trench on said second insulating region;
a drain contact on said silicon carbide drain region, at said first face;
and
a source contact on said silicon carbide source region, at said second face, said source contact electrically connected to said first conductive gate electrode and said second conductive gate electrode.

9 more elements

Dependencies are inferred from the claim text.