Power switching devices having controllable surge current capabilities

• US 8,193,848 B2
• Filed: 11/02/2009
• Issued: 06/05/2012
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Zhang, Qingchun, Richmond, James Theodore, Agarwal, Anant K., Ryu, Sei-Hyung
• Primary Examiner(s): Wells, Kenneth B.
• Application Number:
  US12/610,582
• Publication Number:
  US 20100301929A1
• Time in Patent Office: 946 Days
• Field of Search: 327/318, 327/483, 327/319, 361/56
• US Class Current: 327/318
• CPC Class Codes: H01L 21/8213 the substrate being a semiconductor, using SiC technology H01L21/8258 takes precedence
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/06181 On opposite sides of the body
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 25/072 the devices being arranged next to each other
• CPC Class Codes: H01L 25/18 the devices being of types provided for in two or more different subgroups of the same main group of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N
• CPC Class Codes: H01L 27/0605 integrated circuits made of compound material, e.g. AIIIBV
• CPC Class Codes: H01L 27/0705 comprising components of the field effect type
• CPC Class Codes: H01L 27/088 the components being field-effect transistors with insulated gate
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/7302 structurally associated with other devices assemblies of devices H01L25/00; integrated circuits H01L27/00; IGBT H01L29/7393
• CPC Class Codes: H01L 29/739 controlled by field-effect, e.g. bipolar static induction transistors [BSIT] unijunction transistors H01L29/705
• CPC Class Codes: H01L 29/7803 structurally associated with at least one other device assemblies H01L25/00; integrated circuits H01L27/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/1305 Bipolar Junction Transistor [BJT]
• CPC Class Codes: H01L 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]

Abstract

Semiconductor switching devices include a wide band-gap power transistor, a wide band-gap surge current transistor that coupled in parallel to the power transistor, and a wide band-gap driver transistor that is configured to drive the surge current transistor. Substantially all of the on-state output current of the semiconductor switching device flows through the channel of the power transistor when a drain-source voltage of the power transistor is within a first voltage range, which range may correspond, for example, to the drain-source voltages expected during normal operation. In contrast, the semiconductor switching device is further configured so that in the on-state the output current flows through both the surge current transistor and the channel of the power transistor when the drain-source voltage of the power transistor is within a second, higher voltage range.

Claims

1. A semiconductor switching device, comprising:

a wide band-gap power transistor;

a second wide band-gap transistor coupled in parallel with the wide band-gap power transistor; and

a wide band-gap driver transistor that is configured to provide a base current to the second wide band-gap transistor;

wherein a gate of the wide band-gap power transistor, a gate of the wide band-gap driver transistor and a contact for an emitter of the second wide band-gap transistor are on a first side of the semiconductor switching device, and wherein a contact for a collector of the second wide band-gap transistor is on a second side of the semiconductor switching device that is opposite the first side; and

wherein a first current path length between a source contact of the wide band-gap power transistor and a drain contact of the wide band-gap power transistor is substantially the same as a second current path length between the contact for the emitter of the second wide band-gap transistor and the contact for the collector of the second wide band-gap transistor.

2. The semiconductor switching device of claim 1, wherein the semiconductor switching device is configured so that in its on-state substantially all of an output current of the semiconductor switching device flows through a channel of the wide band-gap power transistor when a drain-source voltage of the wide band-gap power transistor is within a first voltage range;

and

the semiconductor switching device is further configured so that in its on-state the output current flows through both the second wide band-gap transistor and the channel of the wide band-gap power transistor when the drain-source voltage of the wide band-gap power transistor is within a second voltage range having voltages that are higher than the voltages in the first voltage range.

3. The semiconductor switching device of claim 2, wherein the wide band-gap power transistor comprises a wide band-gap power MOSFET, wherein the wide band-gap driver transistor comprises a wide band-gap driver MOSFET and the second wide band-gap transistor comprises a wide band-gap bipolar junction transistor (“

BJT”

), and wherein the semiconductor switching device is configured to saturate a surge current flowing through the semiconductor switching device.

4. The semiconductor switching device of claim 3, wherein the saturation level is a function of a drain-source voltage of the wide band-gap power MOSFET and a bias voltage that is applied to the gates of the wide band-gap power MOSFET and the wide band-gap driver MOSFET.

5. The semiconductor switching device of claim 1, wherein the second wide band-gap transistor, the wide band-gap power transistor and the wide band-gap driver transistor each comprise a silicon carbide based device.

6. The semiconductor switching device of claim 2, wherein the second wide band-gap transistor, the wide band-gap power MOSFET and the wide band-gap driver MOSFET each comprise a silicon carbide based device, and wherein a gate of the wide band-gap power MOSFET is electrically connected to a gate of the wide band-gap driver MOSFET, wherein a first source/drain region of the wide band-gap power MOSFET is electrically connected to a the collector of the second wide band-gap transistor, and wherein a second source/drain region of the wide band-gap power MOSFET is electrically connected to the emitter of the second wide band-gap transistor.

7. The semiconductor switching device of claim 6, wherein a first source/drain region of the wide band-gap driver MOSFET is electrically connected to the collector of the second wide band-gap transistor and a second source/drain region of the wide band-gap driver MOSFET is electrically connected to a base of the second wide band-gap transistor.

8. The semiconductor switching device of claim 2, wherein the semiconductor switching device comprises:

an n-type silicon carbide drift layer;

a p-type silicon carbide base layer and a p-type silicon carbide p-well on the n-type silicon carbide drift layer;

an n-type silicon carbide emitter region on the p-type silicon carbide base layer;

a first n-type source/drain region of the wide band-gap driver MOSFET in an upper portion of the silicon carbide p-well; and

a first n-type source/drain region of the wide band-gap power MOSFET in an upper portion of the silicon carbide p-well.

9. The semiconductor switching device of claim 8, wherein the switching device further comprises:

a heavily-doped p-type silicon carbide region on the p-type silicon carbide base layer adjacent the n-type silicon carbide emitter region; and

an electrical connection between the heavily-doped p-type silicon carbide region and the first n-type source/drain region of the wide band-gap driver MOSFET.

10. The semiconductor switching device of claim 9, wherein the n-type silicon carbide drift layer comprises the collector of the second wide band-gap transistor, the second source/drain region of the wide band-gap power MOSFET and the second source/drain region of the wide band-gap driver MOSFET.

11. The semiconductor switching device of claim 1, wherein the collector of the wide band-gap BJT comprises a semiconductor layer that is directly on an underlying semiconductor substrate.

12. The semiconductor switching device of claim 1, wherein the semiconductor switching device comprises a monolithic device on a single semiconductor substrate.

13. A power semiconductor switch that conducts an output current when in an on-state, comprising:

a silicon carbide drift layer having a first conductivity type;

a silicon carbide base layer on the silicon carbide drift layer, the silicon carbide base layer having a second conductivity type that is different than the first conductivity type;

a silicon carbide well having the second conductivity type on the silicon carbide drift layer;

a silicon carbide emitter region having the first conductivity type on the silicon carbide base layer opposite the silicon carbide drift layer;

a first source/drain region having the first conductivity type in an upper portion of the silicon carbide well that is opposite the silicon carbide drift layer; and

a second source/drain region having the first conductivity type in the upper portion of the silicon carbide well;

wherein the first source/drain region and the silicon carbide drift layer are part of a unipolar wide band-gap semiconductor device that has a first switching speed;

wherein the silicon carbide base layer, the silicon carbide emitter region and the silicon carbide drift layer comprise, respectively, the base, emitter and collector of a wide band-gap bipolar junction transistor (“

BJT”

) that has a second switching speed that is slower than the first switching speed;

wherein the power semiconductor switch is configured so that the output current flows through the unipolar wide band-gap semiconductor device for a first range of output current levels; and

the power semiconductor switch is further configured so that the output current flows through both the unipolar wide band-gap semiconductor device and the wide band-gap BJT for a second range of output current levels that are higher than the output current levels in the first, range of output current levels,

wherein the unipolar wide band-gap semiconductor device and the wide band-gap BJT are both vertical devices.

14. The power semiconductor switch of claim 13, wherein the unipolar wide band-gap semiconductor device comprises a power MOSFET that has a gate terminal and a first source/drain region contact on a first side of the device and a second source/drain region contact that is on a second side of the device that is opposite the first side of the device, and wherein the wide band-gap BJT has a base and a second contact on the first side of the device and a third contact that is on the second side of the device.

15. The power semiconductor switch of claim 14, wherein the BJT and the power MOSFET are implemented in parallel so that the second contact of the wide band-gap BJT and the first source/drain region contact of the power MOSFET form a first common node, and the third contact of the BJT and the second source/drain region contact of the power MOSFET form a second common node.

16. The power semiconductor switch of claim 15, further comprising a driver MOSFET that is configured to provide a base current to a base of the BJT.

17. The power semiconductor switch of claim 16, wherein the BJT, the power MOSFET and the driver MOSFET each comprise a silicon carbide semiconductor device.

18. The power semiconductor switch of claim 13, wherein n-type silicon carbide drift layer comprises the collector of the wide band-gap BJT, and wherein the n-type silicon carbide drift layer is directly on an underlying semiconductor substrate.

19. The power semiconductor switch of claim 16, further comprising a conductive element that is at least partly external to the base of the BJT that electrically connects a source/drain region of the driver MOSFET to the base of the BJT.

20. The power semiconductor switch of claim 13, wherein a first current path length between a source contact of the unipolar wide band-gap semiconductor device and a drain contact of the wide band-gap semiconductor device is substantially the same as a second current path length between the contact for the emitter of the wide band-gap BJT and the contact for the collector of the wide band-gap BJT.

21. A power switching device, comprising:

a first wide band-gap MISFET having a gate, a first source/drain region and a second source/drain region;

a second wide band-gap MISFET having a gate, a first source/drain region and a second source/drain region; and

a wide band-gap bipolar junction transistor (“

BJT”

) having a base, a collector and an emitter;

wherein the gate of the first wide band-gap MISFET is electrically connected to the gate of the second wide band-gap MISFET;

wherein the first source/drain region of the first wide band-gap MISFET is electrically connected to the first source/drain region of the second wide band-gap MISFET and to the collector;

wherein the second source/drain region of the first wide band-gap MISFET is electrically connected to the emitter; and

wherein the second source/drain region of the second wide band-gap MISFET is electrically connected to the base,

wherein the power switching device comprises a vertical device in which the gates of the first and second wide band-gap MISFETs are on a first side of the power switching device and wherein the contact for the collector is on a second side of the power switching device that is opposite the first side of the device, and

wherein the source for the first wide band-gap MISFET and the source for the second wide band-gap MISFET are positioned in a common well that is formed in the collector.

22. The high power switching device of claim 21, wherein the BJT is configured to provide a current carrying path for at least a portion of surge currents that flow through the power switching device.

23. The high power switching device of claim 21, wherein the BJT, the first wide band-gap MISFET and the second wide band-gap MISFET comprise silicon carbide based devices.

24. The high power switching device of claim 21, wherein the switching device comprises:

an n-type silicon carbide drift layer that comprises the collector, the first n-type source/drain region of the power MISFET and the first n-type source/drain region of the driver MISFET;

a p-type silicon carbide base layer that comprises the base on the n-type silicon carbide drift layer;

a p-type silicon carbide p-well on the n-type silicon carbide drift layer;

an n-type silicon carbide emitter region that comprises the emitter on the p-type silicon carbide base layer;

a first gate electrode on the p-well and separated from the second n-type source/drain region of the driver MISFET and the n-type silicon carbide drift layer by a first gate insulation layer; and

a second gate electrode on the p-well and separated from the second n-type source/drain region of the power MISFET and the n-type silicon carbide drift layer by a second gate insulation layer;

wherein the first source/drain region of the driver MISFET comprises an n-type silicon carbide region in an upper portion of the silicon carbide p-well; and

wherein the first n-type source/drain region of the power MISFET comprises an n-type silicon carbide region in an upper portion of the silicon carbide p-well.

25. The high power switching device of claim 24, wherein the switching device further comprises:

a heavily-doped p-type silicon carbide region on the p-type silicon carbide base layer adjacent the n-type silicon carbide emitter region; and

an electrical connection between the heavily-doped p-type silicon carbide region and the first n-type source/drain region of the driver MISFET.

26. The power switching device of claim 21, wherein a first current path length between a source contact of the first wide band-gap MISFET and a drain contact of the first wide band-gap MISFET is substantially the same as a second current path length between a contact for the emitter of the wide band-gap BJT and the contact for the collector of the wide band-gap BJT.

27. A method of operating a semiconductor switching device that includes a wide band-gap power transistor, a wide band-gap surge current transistor coupled in parallel with the wide band-gap power transistor and a wide band-gap driver transistor that is configured to provide a base current to the wide band-gap surge current transistor, the method comprising:

operating the semiconductor switching device so that a drain-source voltage of the wide band-gap power transistor is within a first voltage range and substantially all of an output current of the semiconductor switching device flows through a channel of the wide band-gap power transistor; and

operating the semiconductor switching device so that the drain-source voltage of the wide band-gap power transistor is within a second voltage range having voltages that are higher than the voltages in the first voltage range and the output current flows through both the wide band-gap surge current transistor and the channel of the wide band-gap power transistor with more than half of the output current flowing through the wide band-gap surge current transistor.

28. The method of claim 27, wherein a gate of the wide band-gap power transistor, a gate of the wide band-gap driver transistor and a contact for an emitter of the wide band-gap surge current transistor are on a first side of the semiconductor switching device, and wherein a contact for a collector of the wide band-gap surge current transistor is on a second side of the semiconductor switching device that is opposite the first side.

29. The method of claim 28, wherein a first current path length between a source contact of the wide band-gap power transistor and a drain contact of the wide band-gap power transistor is substantially the same as a second current path length between the contact for the emitter of the wide band-gap surge current transistor and the contact for the collector of the wide band-gap surge current transistor.

30. The method of claim 27, further comprising saturating a surge current flowing through the semiconductor switching device.