High Breakdown Voltage Wide Band-Gap MOS-Gated Bipolar Junction Transistors with Avalanche Capability

• US 20110012130A1
• Filed: 07/15/2009
• Published: 01/20/2011
• Est. Priority Date: 07/15/2009
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Zhang, Qingchun
• Granted Patent: US 8,541,787 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/7395 Vertical transistors, e.g. vertical IGBT
• CPC Class Codes: H01L 29/7397 and a gate structure lying on a slanted or vertical surface or formed in a groove, e.g. trench gate IGBT

Abstract

High power wide band-gap MOSFET-gated bipolar junction transistors (“MGT”) are provided that include a first wide band-gap bipolar junction transistor (“BJT”) having a first collector, a first emitter and a first base, a wide band-gap MOSFET having a source region that is configured to provide a current to the base of the first wide band-gap BJT and a second wide band-gap BJT having a second collector that is electrically connected to the first collector, a second emitter that is electrically connected to the first emitter, and a second base that is electrically connected to the first base.

Claims

1. A high power wide band-gap MOSFET-gated bipolar junction transistor (“

MGT”

), comprising;

a first wide band-gap bipolar junction transistor (“

BJT”

) having a first collector, a first emitter and a first base;

a wide band-gap MOSFET having a source region that is configured to provide a current to the base of the first wide band-gap BJT;

a second wide band-gap BJT having a second collector that is electrically connected to the first collector, a second emitter that is electrically connected to the first emitter, and a second base that is electrically connected to the first base.

2. The high power wide band-gap MGT of claim 1, wherein the second base is thinner than the first base.

3. The high power wide band-gap MGT of claim 1, wherein the first and second wide band-gap BJTs are formed on a substrate, and wherein a drift region is provided on the substrate, and wherein a distance between the first base and the drift region exceeds the distance between the second base and the drift region.

4. The high power wide band-gap MGT of claim 1, wherein a breakdown voltage of the high power wide band-gap MGT may exceed at least 5,000 volts.

5. The high power wide band-gap MGT of claim 1, wherein the first and second wide band-gap BJTs and the wideband MOSFET are formed of silicon carbide (“

SiC”

).

6. The high power wide band-gap MGT of claim 1, wherein the second BJT provides a non-destructive avalanche current path within an active area of the MGT.

7. The high power wide band-gap MGT of claim 2, wherein a maximum thickness of the drift region is at least 1.2 times a maximum thickness of the first base.

8. The high power wide band-gap MGT of claim 1, wherein the device is configured so that the minority carrier injection from the first emitter into the first base exceeds the minority carrier injection from the first collector into the first base when the MGT is turned on.

9. The high power wide band-gap MGT of claim 1, further comprising a tunnel diode between the source and the drain of the wide band-gap MOSFET.

10. The high power wide band-gap MGT of claim 1, wherein the first and second wide band-gap BJTs and the wide band-gap MOSFET form a unit cell, the high power wide band-gap MGT including a plurality of additional unit cells, wherein the unit cell and the plurality of additional unit cells are electrically connected in parallel.

11. The high power wide band-gap MGT of claim 10, wherein only some of the plurality of additional unit cells include two BJTs.

12. The high power wide band-gap MGT of claim 11, wherein at least 75% of the plurality of additional unit cells include only a single BJT.

13. A high power wide band-gap MOSFET-gated bipolar junction transistor (“

MGT”

), comprising;

a silicon carbide (“

SiC”

) bipolar junction transistor (“

BJT”

) having a collector, an emitter and a base;

a SiC MOSFET having a source region that is configured to provide a current to the base of the SiC BJT;

wherein a breakdown voltage of the SiC BJT exceeds at least 5,000 volts.

14. The high power MGT of claim 13, wherein the MGT supports collector current densities of at least 30 A/cm².

15. The high power MGT of claim 14, wherein the SiC substrate comprises an n-type SiC substrate, wherein the SiC BJT comprises an n-p-n BJT that has an n-type drift layer, wherein the base layer is a p-type base layer, wherein the SiC MOSFET comprises an n-MOSFET that includes an n-type drain region, and wherein the source region comprises an n-type source region that is spaced apart from the n-type drain region.

16. The high power MGT of claim 13, further comprising:

a SiC substrate of a first conductivity type, wherein the substrate includes the collector of the SiC BJT thereon;

a drift layer of the first conductivity type on the SiC substrate opposite the collector;

a base layer of a second conductivity type that is opposite the first conductivity type, the base layer provided on the drift layer opposite the SiC substrate,

an emitter layer of the first conductivity type on the base layer opposite the drift layer,

wherein the base is part of the base layer, and

wherein the collector is electrically connected to the n-type drain region.

17. The high power MGT of claim 13, wherein the SiC MOSFET is configured to operate at a gate voltage of between about 5 volts and about 16 volts

18. A high power wide band-gap MOSFET-gated bipolar junction transistor (“

MGT”

), comprising;

an n-type bulk single crystal silicon carbide (“

SiC”

) substrate;

an n-type SiC drift layer on the n-type conductivity bulk single crystal SiC substrate, the n-type drift layer having a first carrier concentration that is less than a second carrier concentration of the n-type SiC substrate;

a patterned p-type SiC layer in the n-type SiC drift layer, the patterned p-type SiC layer including a base region and a source isolation region that includes a channel region;

a patterned n-type SiC layer in the p-type SiC layer, the patterned n-type SiC layer including a source region that is located in the source isolation region of the patterned p-type SiC layer and an emitter region in the base region of the patterned p-type SiC layer;

an insulating layer on the source region, the channel region, and the n-type drift layer;

a gate electrode on the insulating layer;

a collector contact on a surface of the SiC substrate opposite the n-type drift layer;

an emitter contact on the emitter region of the patterned n-type SiC layer,

wherein the source region is electrically connected to the base region, and

wherein a breakdown voltage of the MGT exceeds at least 5,000 volts.