Atomic layer etching of GaN and other III-V materials

• US 10,056,264 B2
• Filed: 06/03/2016
• Issued: 08/21/2018
• Est. Priority Date: 06/05/2015
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Yang, Wenbing, Ohba, Tomihito, Tan, Samantha, Kanarik, Keren Jacobs, Marks, Jeffrey, Nojiri, Kazuo
• Primary Examiner(s): Olsen, Allan
• Application Number:
  US15/173,358
• Publication Number:
  US 20160358782A1
• Time in Patent Office: 809 Days
• Field of Search: None
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01L 21/30621 Vapour phase etching
• CPC Class Codes: H01L 21/67207 comprising a chamber adapted to a particular process
• CPC Class Codes: H01L 29/1066 Gate region of field-effect devices with PN junction gate
• 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 29/7786 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

Provided herein are ALE methods of removing III-V materials such as gallium nitride (GaN) and related apparatus. In some embodiments, the methods involve exposing the III-V material to a chlorine-containing plasma without biasing the substrate to form a modified III-V surface layer; and applying a bias voltage to the substrate while exposing the modified III-V surface layer to a plasma to thereby remove the modified III-V surface layer. The disclosed methods are suitable for a wide range of applications, including etching processes for trenches and holes, fabrication of HEMTs, fabrication of LEDs, and improved selectivity in etching processes.

Claims

1. A method of etching a III-V material on a substrate, comprising:

a) exposing the III-V material to a chlorine-containing plasma without biasing the substrate to form a modified III-V surface layer, wherein the chlorine-containing plasma includes essentially no ionic species; and

b) applying a bias voltage to the substrate while exposing the modified III-V surface layer to an inert plasma to thereby remove the modified III-V surface layer.

2. The method of claim 1, further comprising repeating (a) and (b) one or more times.

3. The method of claim 1, wherein the bias voltage is at a level such that the removal is in a self-limiting regime.

4. The method of claim 1, wherein the chlorine-containing plasma is generated from a process gas including a boron-containing compound, wherein about 0.5% to 10% (volumetric) of the process gas is the boron-containing compound.

5. The method of claim 1, further comprising performing one or more additional cycles of (a) and (b), wherein the bias voltage is lowered during the one or more additional cycles.

6. The method of claim 1, wherein the III-V material is GaN.

7. The method of claim 6, wherein GaN is removed without removing an underlayer.

8. The method of claim 7, wherein the underlayer is AlGaN.

9. The method of claim 1, wherein the bias voltage is between about 20 V and 120 V.

10. The method of claim 1, wherein the bias voltage is between about 50 V and 120 V.

11. The method of claim 1, wherein the bias voltage is between about 50 V and 100 V.

12. The method of claim 1, wherein the chlorine-containing plasma is generated from a mixture of a chlorine-containing gas and a boron-containing gas.

13. The method of claim 1, wherein the chlorine-containing plasma is generated from a mixture of a Cl₂ and BCl₃.

14. The method of claim 1, wherein the inert plasma in (b) is an argon-containing plasma.

15. The method of claim 1, wherein the bias voltage is at level such that the etch is selective to an underlying material.

16. A method of etching a III-V material on a substrate, comprising:

a) exposing the III-V material to a chlorine-containing plasma without biasing the substrate to form a modified III-V surface layer, wherein the chlorine-containing plasma is generated from a mixture of Cl₂ and BCl₃, wherein about 0.5% to 10% (volumetric) of the mixture is BCl₃ and the remainder is Cl₂; and

b) applying a bias voltage to the substrate while exposing the modified III-V surface layer to an inert plasma to thereby remove the modified III-V surface layer.

17. The method of claim 16, wherein about 5% of the mixture is BCl₃.

18. A method of selectively etching a first III-V material relative to a second III-V material that underlies the first III-V on a substrate, comprising:

(a) exposing the first III-V material to a chlorine-containing plasma without biasing the substrate to form a first modified III-V surface layer,

(b) applying a first bias voltage to the substrate while exposing the first modified III-V surface layer to an inert plasma to thereby remove the first modified III-V surface layer,

(c) after (b), exposing the first III-V material to a chlorine-containing plasma without biasing the substrate to form a second modified III-V surface layer,

(d) applying a second bias voltage to the substrate while exposing the second modified III-V surface layer to an inert plasma to thereby remove the second modified III-V surface layer, wherein the second bias voltage is lower than the first bias voltage.

19. The method of claim 18, wherein at the first bias voltage, the etch selectivity of the first III-V material relative to the second III-V material is less than infinity.

20. The method of claim 19, wherein at the second bias voltage, the etch selectivity of the first III-V material relative to the second III-V material is infinity.