High-voltage GaN high electron mobility transistors

• US 10,541,323 B2
• Filed: 07/29/2016
• Issued: 01/21/2020
• Est. Priority Date: 04/15/2016
• Status: Active Grant

• Current Assignee: MACOM Technology Solutions Holdings, Inc.
• Original Assignee: MACOM Technology Solutions Holdings, Inc.
• Inventors: Boles, Timothy E., Carlson, Douglas, Kaleta, Anthony
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US15/223,614
• Publication Number:
  US 20170301781A1
• Time in Patent Office: 1,271 Days
• CPC Class Codes: H01L 29/0653 adjoining the input or output region of a field-effect device, e.g. the source or drain region
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/205 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/401 Multistep manufacturing processes
• CPC Class Codes: H01L 29/402 Field plates
• CPC Class Codes: H01L 29/404 Multiple field plate structures
• CPC Class Codes: H01L 29/41758 for lateral devices with structured layout for source or drain region, i.e. the source or drain region having cellular, interdigitated or ring structure or being curved or angular H01L29/41733 - H01L29/4175 take precedence
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/42312 Gate electrodes for field effect devices
• CPC Class Codes: H01L 29/42316 for field-effect transistors
• CPC Class Codes: H01L 29/42376 characterised by the length or the sectional shape
• CPC Class Codes: H01L 29/475 on AIII-BV compounds
• CPC Class Codes: H01L 29/517 the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence
• 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
• CPC Class Codes: H01L 29/7787 with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET

Abstract

High-voltage, gallium-nitride HEMTs are described that are capable of withstanding reverse-bias voltages of at least 900 V and, in some cases, in excess of 2000 V with low reverse-bias leakage current. A HEMT may comprise a lateral geometry having a gate, gate-connected field plate, and source-connected field plate.

Claims

1. A high electron-mobility transistor (HEMT) comprising:

a buffer layer;

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source;

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60 degrees;

one or more additional gates that are connected with the gate to a common gate contact;

one or more additional sources that are connected with the source to a common source contact; and

one or more additional drains that are connected with the drain to a common drain contact.

2. The HEMT of claim 1, further comprising an oxidation layer between about 10 Angstroms and about 50 Angstroms thick formed between the gate and the barrier layer.

3. The HEMT of claim 1, wherein a first extension of the first gate-connected field plate towards the drain is larger than a second extension of the first gate-connected field plate towards the source.

4. The HEMT of claim 3, wherein the second extension is between approximately 10% and approximately 75% of the length of the first extension.

5. The HEMT of claim 4, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

6. The HEMT of claim 3, wherein the first extension is between approximately 0.3 μ

m and approximately 0.8 μ

m beyond a first edge of the gate toward the drain and the second extension is between approximately 0.1 μ

m and approximately 0.4 μ

m beyond a second edge of the gate toward the source.

7. The HEMT of claim 1, wherein the barrier layer comprises AlGaN having a mole fraction of Al between approximately 24% and approximately 29%.

8. The HEMT of claim 7, wherein the barrier layer has a thickness between approximately 10 nm and approximately 50 nm.

9. The HEMT of claim 8, wherein the first insulating layer comprises silicon nitride and has a thickness between approximately 20 nm and approximately 100 nm.

10. The HEMT of claim 9, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

11. The HEMT of claim 1, wherein the gate comprises a first conductive material that physically contacts the barrier layer but does not physically contact the conduction layer.

12. The HEMT of claim 11, wherein the first conductive material comprises a multi-layer composition selected from the following group:

Ni/Pd/Au/Ti, Ni/Pt/Au/Ti, Ni/Ti/Al/W, Ni/W/Al/W, Ni/Ta/Al/Ta, Ni/Ta/Al/W, Ni/NiO/Al/W, Ni/NiO/Ta/Al/Ta, Ni/NiO/Ta/Al/W, W/Al/W, Ni/WN/Al/W, Ni/NiO/W/Al/W, Ni/NiO/WN/Al/W, WN/Al/W, and Pt/Au/Ti.

13. The HEMT of claim 11, wherein the source and drain comprise a second conductive material that electrically contacts the conduction layer.

14. The HEMT of claim 13, wherein the second conductive material comprises a multi-layer composition selected from the following group:

Ti/Al/Ni/Au, Ti/Al/W, and Ta/Al/Ta.

15. The HEMT of claim 1, wherein the first gate-connected field plate comprises a multi-layer composition selected from the following group:

Ti/Pt/Au, Al/Cu, and TiN/Cu.

16. The HEMT of claim 1 configured to drive up to approximately 1 Amp/mm of peripheral gate length at modulation rates up to approximately 1 GHz.

17. The HEMT of claim 1 configured to drive up to approximately 1 Amp/mm of peripheral gate length at modulation rates up to approximately 10 GHz.

18. The HEMT of claim 1 configured to drive up to approximately 1 Amp/mm of peripheral gate length at modulation rates up to approximately 30 GHz.

19. A high electron-mobility transistor (HEMT) comprising:

a buffer layer;

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source;

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60degrees, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

20. The HEMT of claim 19, further comprising a cap layer formed of GaN located over the barrier layer.

21. The HEMT of claim 19, further comprising an oxidation layer between about 10 Angstroms and about 50 Angstroms thick formed between the gate and the barrier layer.

22. The HEMT of claim 19, further comprising:

a source-connected field plate comprising a conductor that is electrically connected to the source and extends over the gate; and

a second insulating layer separating the source-connected field plate and the gate.

23. A high electron-mobility transistor (HEMT) comprising:

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source;

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60degrees; and

a cap layer formed of GaN located over the barrier layer.

24. The HEMT of claim 23, wherein a thickness of the cap layer is between approximately 1 nm and approximately 30 nm.

25. The HEMT of claim 24, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

26. The HEMT of claim 23, further comprising:

a source-connected field plate comprising a conductor that is electrically connected to the source and extends over the gate; and

a second insulating layer separating the source-connected field plate and the gate.

27. The HEMT of claim 23, further comprising an oxidation layer between about 10 Angstroms and about 50 Angstroms thick formed between the gate and the barrier layer.

28. A high electron-mobility transistor (HEMT) comprising:

a buffer layer;

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source; and

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60 degrees, wherein the gate-to-drain distance is between about 10 μ

m and about 20 μ

m and the gate is located closer to the source than to the drain.

29. The HEMT of claim 28, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

30. A high electron-mobility transistor (HEMT) comprising:

a buffer layer;

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source;

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60 degrees; and

a second gate-connected field plate electrically connected to the gate and extending beyond edges of the first gate-connected field plate toward the drain and source over a second insulating layer.

31. The HEMT of claim 30, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.

32. A high electron-mobility transistor (HEMT) comprising:

a buffer layer;

a gallium-nitride conduction layer formed over the buffer layer;

a barrier layer formed over the gallium-nitride conduction layer;

a gate, source, and drain formed over the barrier layer;

a first insulating layer formed in regions between the gate and drain and between the gate and source;

a first gate-connected field plate electrically connected to the gate and extending beyond edges of the gate toward the drain and source over the first insulating layer, wherein a combined thickness of the buffer layer and gallium-nitride layer is greater than approximately 4.5 μ

m and sidewalls of the gate are sloped outward between approximately 5 degrees and approximately 60degrees;

a source-connected field plate comprising a conductor that is electrically connected to the source and extends over the gate; and

a second insulating layer separating the source-connected field plate and the gate, wherein the source-connected field plate extends beyond the first gate-connected field plate.

33. The HEMT of claim 32, wherein the source-connected field plate extends beyond the first gate-connected field plate a distance that is between approximately 1.5 μ

m and approximately 3.5 μ

m.

34. The HEMT of claim 32, wherein an edge of the source-connected field plate near the drain may be between approximately 4 μ

m and approximately 10 μ

m.

35. The HEMT of claim 32, wherein a thickness of the second insulating layer is between approximately 300 nm and approximately 600 nm.

36. The HEMT of claim 35, wherein a thickness of the first insulating layer is between approximately 20 nm and approximately 100 nm.

37. The HEMT of claim 32, wherein a length of the gate L_g is between 0.15 μ

m and 2 μ

m, and the HEMT is capable of withstanding reverse-bias voltages between 900 volts and approximately 1200 volts.