Low OHMIC contacts containing germanium for gallium nitride or other nitride-based power devices

• US 20110140173A1
• Filed: 11/30/2010
• Published: 06/16/2011
• Est. Priority Date: 12/16/2009
• Status: Abandoned Application

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Ramdani, Jamal
• Application Number:
  US12/927,948
• Publication Number:
  US 20110140173A1
• Time in Patent Office: Days
• US Class Current: 257/194
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/452 on AIII-BV compounds
• CPC Class Codes: H01L 29/66462 with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
• CPC Class Codes: H01L 29/7786 with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT

Abstract

An apparatus includes a substrate, a Group III-nitride layer over the substrate, and an electrical contact over the Group III-nitride layer. The electrical contact includes a stack having multiple layers of conductive material, and at least one of the layers in the stack includes germanium. The layers in the stack may include a contact layer, where the contact layer includes aluminum copper. The stack could include a titanium or titanium alloy layer, an aluminum or aluminum alloy layer, and a germanium or germanium alloy layer. At least one of the layers in the stack could include an aluminum or titanium alloy having a germanium content between about 1% and about 5%.

Claims

1. An apparatus comprising:

a substrate;

a Group III-nitride layer over the substrate; and

an electrical contact over the Group III-nitride layer, the electrical contact comprising a stack having multiple layers of conductive material, at least one of the layers in the stack comprising germanium.

2. The apparatus of claim 1, wherein the layers in the stack include a contact layer, the contact layer comprising aluminum copper.

3. The apparatus of claim 2, wherein:

the contact layer has a copper content between about 0.5% and about 1.0%; and

the contact layer has a thickness between about 100 nm and about 150 nm.

4. The apparatus of claim 1, wherein the stack comprises:

a titanium or titanium alloy layer;

an aluminum or aluminum alloy layer; and

a germanium or germanium alloy layer.

5. The apparatus of claim 1, wherein at least one of the layers in the stack comprises an aluminum or titanium alloy having a germanium content between about 1% and about 5%.

6. The apparatus of claim 1, wherein the Group III-nitride layer comprises a buffer layer and at least one barrier layer, the buffer and barrier layers comprising Group III-nitride epitaxial layers.

7. The apparatus of claim 1, wherein:

the electrical contact comprises one of multiple electrical contacts; and

the apparatus further comprises a gate contact between the electrical contacts.

8. A system comprising:

a semiconductor structure comprising a substrate and a Group III-nitride layer over the substrate;

a Group III-nitride integrated circuit device in or over the Group III-nitride layer; and

multiple electrical contacts in electrical connection to the Group III-nitride integrated circuit device, each electrical contact comprising a stack having multiple layers of conductive material, at least one of the layers in the stack comprising germanium.

9. The system of claim 8, wherein the Group III-nitride integrated circuit device comprises a Group III-nitride high electron mobility transistor (HEMT).

10. The system of claim 8, wherein the layers in the stack include a contact layer, the contact layer comprising aluminum copper.

11. The system of claim 10, wherein:

the contact layer has a copper content between about 0.5% and about 1.0%; and

the contact layer has a thickness between about 100 nm and about 150 nm.

12. The system of claim 8, wherein the stack comprises:

a titanium or titanium alloy layer;

an aluminum or aluminum alloy layer; and

a germanium or germanium alloy layer.

13. The system of claim 8, wherein at least one of the layers in the stack comprises an aluminum or titanium alloy having a germanium content between about 1% and about 5%.

14. The system of claim 8, wherein the Group III-nitride layer comprises a buffer layer and at least one barrier layer, the buffer and barrier layers comprising Group III-nitride epitaxial layers.

15. The system of claim 8, wherein the Group III-nitride integrated circuit device further comprises a gate contact between the electrical contacts.

16. A method comprising:

forming a Group III-nitride layer over a substrate; and

forming an electrical contact over the Group III-nitride layer, the electrical contact comprising a stack having multiple layers of conductive material, at least one of the layers in the stack comprising germanium.

17. The method of claim 16, further comprising:

forming a Group III-nitride integrated circuit device using the Group III-nitride layer, the electrical contact in electrical connection to the Group III-nitride integrated circuit device.

18. The method of claim 16, wherein the layers in the stack include a contact layer, the contact layer comprising aluminum copper.

19. The method of claim 18, wherein:

the contact layer has a copper content between about 0.5% and about 1.0%; and

the contact layer has a thickness between about 100 nm and about 150 nm.

20. The method of claim 16, wherein at least one of the layers in the stack comprises an aluminum or titanium alloy having a germanium content between about 1% and about 5%.