Isolation structure in gallium nitride devices and integrated circuits

• US 9,171,911 B2
• Filed: 07/02/2014
• Issued: 10/27/2015
• Est. Priority Date: 07/08/2013
• Status: Active Grant

• Current Assignee: Efficient Power Conversion Corporation
• Original Assignee: Efficient Power Conversion Corporation
• Inventors: Zhou, Chunhua, Cao, Jianjun, Lidow, Alexander, Beach, Robert, Nakata, Alana, Strittmatter, Robert, Zhao, Guangyuan, Kolluri, Seshadri, Ma, Yanping, Liu, Fang Chang, Cao, Jiali, Chiang, Ming-Kun
• Primary Examiner(s): Nguyen, Dao H
• Application Number:
  US14/322,659
• Publication Number:
  US 20150008442A1
• Time in Patent Office: 482 Days
• Field of Search: 257/59, 257/76, 257/77, 257/192, 257/194, 257/206, 257/E29.104, 257/E27.061, 257/E21.159, 257/E21.403, 438/47, 438/172, 438/275, 438/400
• US Class Current: 1/1
• CPC Class Codes: H01L 21/76 Making of isolation regions between components
• CPC Class Codes: H01L 27/0605 integrated circuits made of compound material, e.g. AIIIBV
• CPC Class Codes: H01L 29/2003 Nitride 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 29/778 with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface H01L29/803 takes precedence
• 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 integrated semiconductor device which includes a substrate layer, a buffer layer formed on the substrate layer, a gallium nitride layer formed on the buffer layer, and a barrier layer formed on the gallium nitride layer. Ohmic contacts for a plurality of transistor devices are formed on the barrier layer. Specifically, a plurality of first ohmic contacts for the first transistor device are formed on a first portion of the surface of the barrier layer, and a plurality of second ohmic contacts for the second transistor device are formed on a second portion of the surface of the barrier layer. In addition, one or more gate structures formed on a third portion of the surface of the barrier between the first and second transistor devices. Preferably, the one or more gate structures and the spaces between the gate structures and the source contacts of the transistor devices collectively form an isolation region that electrically isolates the first transistor device from the second transistor device.

Claims

1. An integrated semiconductor device comprising:

a buffer layer disposed on a substrate layer;

a gallium nitride layer disposed on the buffer layer;

a barrier layer disposed on the gallium nitride layer;

a plurality of first device contacts for a first transistor device formed on a first portion of an exposed surface of the barrier layer;

a plurality of second device contacts for a second transistor device formed on a second portion of the exposed surface of the barrier layer;

at least one gate structure formed on a third portion of the surface of the barrier,

wherein the gate structure is disposed between the plurality of first device contacts and the plurality of second device contacts to form an isolation region of the integrated semiconductor device that electrically isolates the first transistor device from the second transistor device.

2. The integrated semiconductor device according to claim 1, wherein the plurality of first device contacts comprise source, gate and drain contacts for the first transistor device, and the plurality of second device contacts comprise source, gate and drain contacts for the second transistor device.

3. The integrated semiconductor device according to claim 2, wherein the gate structure is disposed between the respective source contacts of the first and second transistor devices.

4. The integrated semiconductor device according to claim 2, wherein the gate structure and the gate contacts of the first and second transistor devices comprise a common film stack.

5. The integrated semiconductor device according to claim 2, wherein the gate structure and the gate contacts of the first and second transistor devices are fabricated from common process sequences.

6. The integrated semiconductor device according to claim 2, wherein the gate structure is electrically coupled to a source contact of one of the first transistor device and the second transistor device.

7. The integrated semiconductor device according to claim 2, wherein the gate structure is biased at a most negative voltage in the integrated semiconductor device.

8. The integrated semiconductor device according to claim 7, wherein the barrier layer comprises a thickness between 50 Å

and 300 Å

.

9. The integrated semiconductor device according to claim 1, wherein the gallium nitride layer is un-doped and has a thickness between 0.5 and 10 μ

m.

10. The integrated semiconductor device according to claim 1, wherein the barrier layer comprises AlGaN with an aluminum composition from 10% to 35%.

11. The integrated semiconductor device according to claim 1, wherein the first transistor device and the second transistor device are adjacent.

12. The integrated semiconductor device according to claim 1, wherein the barrier layer between the first transistor device and the second transistor device is continuous.

13. An integrated semiconductor device comprising:

a buffer layer disposed on a substrate layer;

a gallium nitride layer disposed on the buffer layer;

a barrier layer disposed on the gallium nitride layer;

a plurality of first device contacts for a first transistor device formed on a first portion of an exposed surface of the barrier layer;

a plurality of second device contacts for a second transistor device formed on a second portion of the exposed surface of the barrier layer;

a pair of gate structures formed on a third portion of the surface of the barrier,

wherein the pair of gate structures are disposed between the plurality of first device contacts and the plurality of second device contacts to form an isolation region of the integrated semiconductor device that electrically isolates the first transistor device from the second transistor device.

14. The integrated semiconductor device according to claim 13, wherein the plurality of first device contacts comprise source, gate and drain contacts for the first transistor device, and the plurality of second device contacts comprise source, gate and drain contacts for the second transistor device.

15. The integrated semiconductor device according to claim 14, wherein the pair of gate structures are disposed between the respective source contacts of the first and second transistor devices.

16. The integrated semiconductor device according to claim 14, wherein the pair of gate structures and the gate contacts of the first and second transistor devices comprise a common film stack.

17. The integrated semiconductor device according to claim 14, wherein the pair of gate structures and the gate contacts of the first and second transistor devices are fabricated from common process sequences.

18. The integrated semiconductor device according to claim 14, further comprising an ohmic contact formed on the third portion of the surface of the barrier between the pair of gate structures, such that the pair of gate structures and the ohmic contact form the isolation region.

19. The integrated semiconductor device according to claim 18, wherein the pair of gate structures are enhancement-mode structures.

20. The integrated semiconductor device according to claim 19, wherein the pair of gate structures and the ohmic contact are not electrically connected to an external bias voltage.

21. The integrated semiconductor device according to claim 19, wherein the pair of gate structures and the ohmic contact are shorted to each other and are connected to a lowest voltage reference of the integrated semiconductor device.

22. The integrated semiconductor device according to claim 14, wherein the pair of gate structures are disposed adjacent to the source contacts of the first and second transistor devices, respectively, and an isolation window is formed between the pair of gate structures.

23. The integrated semiconductor device according to claim 22, wherein the isolation window is defined in the third portion of the surface of the barrier layer and a portion of the gallium nitride layer under the third portion of the barrier layer.

24. The integrated semiconductor device according to claim 23, wherein the isolation window is formed by etching or ion implantation to remove a two-dimensional electron gas of the gallium nitride layer.

25. The integrated semiconductor device according to claim 13, wherein the first transistor device and the second transistor device are adjacent.

26. The integrated semiconductor device according to claim 13, wherein the barrier layer between the first transistor device and the second transistor device is continuous.