SCHOTTKY DIODE

• US 20140145213A1
• Filed: 01/31/2014
• Published: 05/29/2014
• Est. Priority Date: 09/11/2011
• Status: Active Grant

• Current Assignee: Wolfspeed, Inc.
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Henning, Jason Patrick, Zhang, Qingchun, Ryu, Sei-Hyung, Palmour, John Williams, Allen, Scott, Agarwal, Anant Kumar
• Granted Patent: US 9,231,122 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/05552 in top view
• CPC Class Codes: H01L 2224/05554 being square
• CPC Class Codes: H01L 2224/05567 the external layer being at least partially embedded in the surface
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05639 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/0661 specially adapted for altering the breakdown voltage by removing semiconductor material at, or in the neighbourhood of, a reverse biased junction, e.g. by bevelling, moat etching, depletion etching
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/8611 Planar PN junction diodes
• CPC Class Codes: H01L 29/872 Schottky diodes
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/1301 Thyristor
• CPC Class Codes: H01L 2924/1305 Bipolar Junction Transistor [BJT]
• CPC Class Codes: H01L 2924/13055 Insulated gate bipolar transistor [IGBT]

Abstract

The present disclosure generally relates to a Schottky diode that has a substrate, a drift layer provided over the substrate, and a Schottky layer provided over an active region of the drift layer. The metal for the Schottky layer and the semiconductor material for the drift layer are selected to provide a low barrier height Schottky junction between the drift layer and the Schottky layer.

Claims

1. A Schottky diode comprising:

a drift layer having a first surface associated with an active region and an edge termination region substantially adjacent the active region, the active region being provided on a mesa in the drift layer and including a mesa guard ring;

a Schottky layer over the active region of the first surface to form a Schottky junction;

an array of junction barrier elements formed in the drift layer below the Schottky junction, wherein at least one junction barrier element of the array junction barrier elements forms a junction barrier junction with the drift layer; and

an edge termination structure formed in a bottom surface of the edge termination recess that is non-planar with the mesa guard ring.

2. The Schottky diode of claim 1, wherein during forward biased operation, the Schottky junctions are configured to turn on before the junction barrier junction.

3. The Schottky diode of claim 1, wherein during reverse bias conditions, depletion regions form adjacent to the junction barrier junction, where the junction barrier junction expands to block reverse current through the Schottky diode.

4. The Schottky diode of claim 1, wherein the active region occupies an active surface area and the array of junction barrier elements occupies a portion of the active surface area where a ratio of surface area occupied by the array of junction barrier elements to the active surface area is between about 2% and 40%

5. The Schottky diode of claim 1 wherein:

the Schottky layer formed from a low barrier height capable metal comprising tantalum;

the edge termination recess extends substantially about the active region; and

the edge termination structure comprises a plurality of guard rings that extend substantially about the active region.

6. The Schottky diode of claim 5 wherein the mesa guard ring extends substantially about the Schottky layer such that the mesa guard ring resides between the Schottky layer and the plurality of guard rings.

7. The Schottky diode of claim 6 wherein a recess well is formed in the drift layer below the bottom surface of the edge termination recess, and the recess well is doped with a doping material of a second conductivity type, which is opposite the first conductivity type.

8. The Schottky diode of claim 5 wherein the drift layer comprises silicon carbide.

9. The Schottky diode of claim 1 wherein the edge termination structure comprises as least one guard ring.

10. The Schottky diode of claim 1 wherein the edge termination recess extends substantially about the active region and the edge termination structure comprises a plurality of guard rings that extend substantially about the active region.

11. The Schottky diode of claim 10 wherein the mesa guard ring extends substantially about the Schottky layer such that the mesa guard ring resides between the Schottky layer and the plurality of guard rings.

12. The Schottky diode of claim 11 wherein the first surface of the drift layer about the active region comprises a mesa guard ring recess such that the mesa guard ring is a doped region that extends into the drift layer about the mesa guard ring recess, and the doped region is doped with a doping material of a second conductivity type, which is opposite the first conductivity type.

13. The Schottky diode of claim 10 wherein a recess well is formed in the drift layer below the bottom surface of the edge termination recess, and the recess well is doped with a doping material of a second conductivity type, which is opposite the first conductivity type.

14. The Schottky diode of claim 10 wherein the bottom surface of the edge termination recess comprises a plurality of guard ring recesses such that at least some of the plurality of guard rings are doped regions that extend into the drift layer about corresponding ones of the plurality of guard ring recesses, and the doped regions are doped with a doping material of a second conductivity type, which is opposite the first conductivity type.

15. The Schottky diode of claim 1 wherein the first surface of the drift layer comprises a plurality of junction barrier element recesses in the active region such that at least certain junction barrier elements of the array of junction barrier elements are doped regions that extend into the drift layer about corresponding ones of the plurality of junction barrier element recesses, and the doped regions are doped with a doping material of a second conductivity type, which is opposite the first conductivity type.

16. The Schottky diode of claim 1 wherein the drift layer is predominantly doped with the doping material of the first conductivity type in a graded fashion wherein the drift layer has a lower doping concentration near the first surface and an intentionally higher doping concentration near a second surface of the drift layer, the second surface being substantially opposite the first surface.

17. The Schottky diode of claim 1 wherein the drift layer comprises silicon carbide.

18. A Schottky diode comprising:

a drift layer having a first surface associated with an active region and an edge termination region substantially adjacent the active region, the active region being provided on a mesa in the drift layer and including a mesa guard ring;

a Schottky layer over the active region of the first surface to form a Schottky junction;

a first junction barrier element formed in the drift layer having a first size;

a second junction barrier element formed in the drift layer having a second size different from the first size, wherein the first junction barrier element forms a first junction barrier junction with the drift layer and the second junction barrier element forms a second junction barrier junction with the drift layer; and

an edge termination structure formed in a bottom surface of the edge termination recess that is non-planar with the mesa guard ring.

19. The Schottky diode of claim 18, wherein when the Schottky diode is forward biased only past a first threshold, the Schottky junction turns on.

20. The Schottky diode of claim 19, wherein when the Schottky diode is forward biased past a second threshold greater than the first threshold, the second junction barrier junction turns on.

21. A Schottky diode comprising:

a drift layer having a first surface associated with an active region and an edge termination region substantially adjacent the active region, the active region being provided on a mesa in the drift layer and including a mesa guard ring;

a Schottky layer over the active region of the first surface to form a Schottky junction; and

an array of junction barrier elements formed in the drift layer below the Schottky junction, wherein at least one junction barrier element of the array junction barrier elements forms a junction barrier junction with the drift layer, wherein during forward biased operation, the Schottky junctions are configured to turn on before the junction barrier junction.