Monolithically integrated vertical power transistor and bypass diode
A vertical field-effect transistor (FET) device includes a monolithically integrated bypass diode connected between a source contact and a drain contact of the vertical FET device. According to one embodiment, the vertical FET device includes a pair of junction implants separated by a junction field-effect transistor (JFET) region. At least one of the junction implants of the vertical FET device includes a deep well region that is shared with the integrated bypass diode, such that the shared deep well region functions as both a source junction in the vertical FET device and a junction barrier region in the integrated bypass diode. The vertical FET device and the integrated bypass diode may include a substrate, a drift layer over the substrate, and a spreading layer over the drift layer, such that the junction implants of the vertical FET device are formed in the spreading layer.
1. A semiconductor device comprising:
a substrate, a drift layer on the substrate, and a spreading layer on the drift layer, wherein the substrate, the drift layer, and the spreading layer have a first doping type, and a doping concentration of the spreading layer is greater than a doping concentration of the drift layer; and
a vertical field-effect transistor (FET) comprising:
a pair of junction implants separated by a portion of the spreading layer, each one of the pair of junction implants comprising a source region with the first doping type, and a deep well region with a second doping type opposite the first doping type;
a trench in the spreading layer opposite the drift layer between the pair of junction implants;
an oxide layer on the spreading layer in the trench;
a gate contact on the oxide layer; and
a channel re-growth layer between the oxide layer and the spreading layer in the trench and between the oxide layer and a top surface of the source region, the channel re-growth layer having the first doping type.
2. The semiconductor device of claim 1 wherein each one of the pair of junction implants further comprises a base region with the second doping type, and a doping concentration of the deep well region is greater than a doping concentration of the base region.
3. The semiconductor device of claim 1 wherein the vertical FET further comprises:
a pair of source contacts on the spreading layer opposite the drift layer, such that each one of the pair of source contacts partially overlaps both the source region and the deep well region of one of the pair of junction implants; and
a drain contact on the substrate opposite the drift layer.
4. The semiconductor device of claim 1 wherein the spreading layer and the drift layer comprise silicon carbide.
5. The semiconductor device of claim 1 wherein each one of the pair of junction implants has a depth that is greater than a depth of the trench.
6. The semiconductor device of claim 5 wherein each one of the pair of junction implants is in contact with a sidewall of the trench at least to a depth that is greater than a depth of the gate contact.
7. A semiconductor device comprising:
a substrate;
a drift layer on the substrate;
a spreading layer on the drift layer, wherein the substrate, the drift layer, and the spreading layer have a first doping type, and a doping concentration of the spreading layer is greater than a doping concentration of the drift layer;
a vertical field-effect transistor (FET) comprising:
at least one source contact on the spreading layer;
a drain contact on the substrate opposite the drift layer;
a pair of junction implants separated by a portion of the spreading layer, each one of the junction implants comprising a base region, a source region, and a deep well region, wherein the base region and the deep well region have a second doping type opposite the first doping type, the source region has the first doping type, and a doping concentration of the deep well region is greater than a doping concentration of the base region;
a trench in the spreading layer opposite the drift layer between the pair of junction implants;
an oxide layer on the spreading layer in the trench; and
a gate contact on the oxide layer; and
a channel re-growth layer between the oxide layer and the spreading layer in the trench and between the oxide layer and a top surface of the source region, the channel re-growth layer having the first doping type; and
a junction barrier Schottky (JBS) bypass diode coupled between the drain contact and the at least one source contact of the vertical FET and monolithically integrated adjacent to the vertical FET, the JBS bypass diode comprising:
the deep well region of one of the pair of junction implants of the vertical FET, the deep well region comprising a first junction barrier region of the JBS bypass diode;
a second junction barrier region in the spreading layer opposite the drift layer, the second junction barrier region separated from the first junction barrier region and having the second doping type; and
a first contact on the spreading layer.
8. The semiconductor device of claim 7 wherein:
the first contact of the JBS bypass diode is electrically coupled to the at least one source contact of the vertical FET; and
the JBS bypass diode further comprises a second contact electrically coupled to the drain contact of the vertical FET, wherein the first contact and the second contact are separated from one another by at least the spreading layer, the drift layer, and the substrate.
9. The semiconductor device of claim 7 wherein the substrate, the drift layer, and the spreading layer comprise silicon carbide.
10. The semiconductor device of claim 7 wherein each one of the pair of junction implants has a depth that is greater than a depth of the trench.
11. The semiconductor device of claim 10 wherein each one of the pair of junction implants is in contact with a sidewall of the trench at least to a depth that is greater than a depth of the gate contact.
12. The semiconductor device of claim 7 , wherein the second junction barrier region is provided to a depth between 1.0 μm and 2.0 μm measured from a surface of the spreading layer opposite the drift layer, a depth of the trench is between 0.75 μm and 1.5 μm, and a thickness of the spreading layer is between 1.0 μm and 2.5 μm.