Semiconductor devices with field plates

Patent metadata

Field	Value
Publication number	US-9111961-B2
Application number	US-201414178701-A
Country	US
Kind code	B2
Filing date	Feb 12, 2014
Priority date	Aug 28, 2009
Publication date	Aug 18, 2015
Grant date	Aug 18, 2015

Abstract

A III-N device is described with a III-N material layer, an insulator layer on a surface of the III-N material layer, an etch stop layer on an opposite side of the insulator layer from the III-N material layer, and an electrode defining layer on an opposite side of the etch stop layer from the insulator layer. A recess is formed in the electrode defining layer. An electrode is formed in the recess. The insulator can have a precisely controlled thickness, particularly between the electrode and III-N material layer.

First claim

What is claimed is:

1. A method of forming a III-N device, comprising:
providing a III-N material layer;
forming an insulator layer on a surface of the III-N material layer;
forming a first etch stop layer on an opposite side of the insulator layer from the III-N material layer;
forming a first electrode defining layer on an opposite side of the first etch stop layer from the insulator layer;
forming a stack on an opposite side of the first electrode defining layer from the first etch stop layer, wherein the stack comprises a second etch stop layer and a second electrode defining layer; forming a recess in the stack, the first electrode defining layer and the etch stop layer; forming an electrode in the recess wherein the electrode covers a portion of a top surface of the stack.

2. The method of claim 1 , wherein the recess is also formed through the second electrode defining layer and through the second etch stop layer, and a portion of the electrode is on an opposite side of the second electrode defining layer from the first electrode defining layer.

3. The method of claim 2 , wherein the recess is also formed through the first etch stop layer.

4. The method of claim 3 , wherein the recess is also formed through the insulator layer.

5. The method of claim 4 , wherein the recess extends into the III-N material layer, and the electrode is in a portion of the recess in the III-N material layer.

6. The method of claim 5 , a first portion of the III-N material layer having a first composition and a second portion of the III-N material layer having a second composition, wherein a difference between the first composition and the second composition forms a 2DEG channel in the III-N material layer.

7. The method of claim 6 , wherein the recess extends through the 2DEG channel.

8. The method of claim 1 , further comprising forming a second insulator layer between the first electrode defining layer and the second etch stop layer.

9. The method of claim 8 , further comprising forming a second recess in the second electrode defining layer and in the second etch stop layer, and forming a second electrode in the second recess.

10. The method of claim 9 , wherein the second electrode is electrically connected to the first electrode.

11. The method of claim 1 , further comprising forming one or more additional stacks, wherein a recess is formed in each stack, and an electrode is formed in each recess.

12. The method of claim 1 , wherein a portion of the recess in the first electrode defining layer has angled walls with at least a portion that is at a non-perpendicular angle to a main surface of the first etch stop layer.

13. The method of claim 12 , wherein the non-perpendicular angle is between 5 degrees and 85 degrees.

14. The method of claim 1 , wherein the first etch stop layer and the insulator layer are formed of different materials.

15. The method of claim 14 , wherein the first etch stop layer is formed of aluminum nitride, and the insulator layer is formed of silicon nitride.

16. The method of claim 1 , a first portion of the III-N material layer having a first composition and a second portion of the III-N material layer having a second composition, wherein a difference between the first composition and the second composition forms a 2DEG channel in the III-N material layer.

17. The method of claim 1 , wherein the recess is also formed through the first etch stop layer.

18. The method of claim 1 , wherein the device is a transistor, the electrode is a gate electrode, and the device further comprises a source and a drain.

19. The method of claim 1 , wherein the electrode includes a field plate.

20. A method of forming a III-N transistor, comprising:
providing a III-N material layer;
forming an insulator layer on a surface of the III-N material layer;
forming etch stop layer on an opposite side of the insulator layer from the III-N material layer;
forming an electrode defining layer on an opposite side of the etch stop layer from the insulator layer; and
forming an electrode, wherein a recess is formed in the electrode defining layer and the electrode is formed in the recess, the electrode including a field plate;
wherein a dynamic on-resistance of the transistor, as measured when the transistor is switched from the OFF state, with an OFF state source-drain bias of about 800 V, to the ON state, is equal to or less than 1.4 times a DC on-resistance of the transistor.

21. The method of claim 20 , wherein the recess is also formed through the etch stop layer.

22. The method of claim 20 , wherein the etch stop layer is formed of aluminum nitride, and the insulator layer is formed of silicon nitride.

23. A method of forming a III-N device, comprising:
a providing a III-N material layer;
forming an insulator layer on a surface of the III-N material layer;
forming an etch stop layer on an opposite side of the insulator layer from the III-N material layer;
forming an electrode defining layer on an opposite side of the etch stop layer from the insulator layer, wherein a recess having a first sidewall and a second sidewall is formed in the electrode defining layer, the first sidewall being on an opposite side of the recess from the second sidewall, the first and second sidewalls each extending from a first surface of the electrode defining layer to a second surface of the electrode defining layer, the first surface being adjacent to the etch stop layer and the second surface being opposite the first surface;
forming a gate electrode in the recess and over the first and second sidewalls;
forming a source; and
forming a drain on an opposite side of the recess from the source, the source being proximal to the first sidewall and the drain being proximal to the second sidewall; wherein
a first angle is formed between a surface of the etch stop layer and a portion of the first sidewall, the portion of the first sidewall being adjacent to the surface of the etch stop layer;
a second angle is formed between the surface of the etch stop layer and a portion of the second sidewall, the portion of the second sidewall being adjacent to the surface of the etch stop layer; and
the first angle is greater than the second angle.

24. The method of claim 23 , the first angle being substantially greater than the second angle, wherein a gate-source capacitance of the device is reduced as compared to a similar device in which the first angle is about the same as the second angle.

25. The method of claim 23 , wherein the second angle is between 30 and 45 degrees.

26. The method of claim 25 , wherein the first angle is between 45 and 90 degrees.

27. The method of claim 23 , a first portion of the III-N material layer having a first composition and a second portion of the III-N material layer having a second composition, wherein a difference between the first composition and the second composition forms a 2DEG channel in the III-N material layer.

28. The method of claim 23 , wherein the recess is formed in the etch stop layer.

29. A method of forming a III-N transistor, comprising:
providing a III-N material layer;
forming an insulator layer on a surface of the III-N material layer;
forming an etch stop layer on an opposite side of the insulator layer from the III-N material layer;
forming an electrode defining layer on an opposite side of the etch stop

Assignees

• Transphorm Inc

Inventors

• Chu Rongming
• Coffie Robert

Classifications

• H10P50/646

  of Group III-V materials · CPC title

• H10P50/282

  of inorganic materials · CPC title

• H10P14/69433

  the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz · CPC title

• H10P14/6336

  in the presence of a plasma [PECVD] · CPC title

• H10P14/6334

  using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition (deposition by physical ablation of a target H10P14/6329) · CPC title