Methods for wet etching of noble metals

Patent metadata

Field	Value
Publication number	US-12276033-B2
Application number	US-202217986160-A
Country	US
Kind code	B2
Filing date	Nov 14, 2022
Priority date	Oct 19, 2021
Publication date	Apr 15, 2025
Grant date	Apr 15, 2025

Abstract

The present disclosure provides improved wet etch processes and methods for etching noble metals. More specifically, the present disclosure provides various embodiments of wet etch processes and methods that utilize new etch chemistries for etching noble metals, such as ruthenium (Ru), gold (Au), platinum (Pt) and iridium (Ir), in a wet etch process. In general, the disclosed embodiments expose a noble metal surface to a first etch solution to chemically modify the noble metal surface and form a noble metal salt passivation layer, which can then be selectively dissolved in a second etch solution to etch the noble metal surface.

First claim

What is claimed is:

1. A method of etching, the method comprising:
receiving a substrate having a noble metal formed thereon, wherein a noble metal surface is exposed on a surface of the substrate;
exposing the surface of the substrate to a surface modification solution such that the surface modification solution is in contact with the noble metal surface, wherein the surface modification solution includes a persulfate salt, a chloride ion source and a cation, and wherein the persulfate salt reacts with the chloride ion source to form dichloride radical ions, which oxidize the noble metal surface to form a noble metal salt passivation layer;
removing the surface modification solution from the surface of the substrate subsequent to forming the noble metal salt passivation layer;
exposing the surface of the substrate to a dissolution solution that reacts with the noble metal salt passivation layer to form soluble species that are dissolved by the dissolution solution; and
removing the dissolution solution and the soluble species from the substrate.

2. The method of claim 1 , wherein the noble metal is ruthenium (Ru), gold (Au), platinum (Pt) or iridium (Ir), and wherein the noble metal salt passivation layer is a chloro-metalate salt, an oxychlorometalate salt, or a hydrate of the chloro-metalate salt or the oxychlorometalate salt.

3. The method of claim 1 , wherein the persulfate salt is an ammonium or quaternary ammonium cation salt of the persulfate or peroxymonosulfate ion.

4. The method of claim 1 , wherein the chloride ion source is hydrochloric acid (HCl) or a non-acidic chloride ion source comprising (1) potassium chloride (KCl), (2) tetrabutylammonium chloride (TBAC), (3) tetramethyl ammonium chloride (TMAC), (4) 1-butyl-3-methylimidazolium chloride and/or other soluble metal chlorides, (5) ammonium chlorides, (6) imidazolium chlorides, and (7) chloride salts of phosphoniums, pyrrolidiniums, guanidiniums, triazoliums, quinoliniums and/or other organic cations.

5. The method of claim 1 , wherein the dissolution solution is an aqueous dissolution solution containing an acid comprising hydrochloric acid (HCl), nitric acid and/or sulfuric acid.

6. The method of claim 1 , wherein the dissolution solution is a solvent comprising deionized water, acetonitrile, alcohols, acetates, ethers and/or ketones.

7. The method of claim 1 , wherein the surface modification solution comprises: (a) ammonium persulfate (APS) or tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt, and (b) tetrabutylammonium chloride (TBAC) as the chloride ion source, and wherein said exposing the surface of the substrate to the surface modification solution oxidizes the noble metal surface and forms the noble metal salt passivation layer in a continuous oxidation process.

8. The method of claim 1 , wherein the surface modification solution comprises: (a) ammonium persulfate (APS) or tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt, (b) potassium chloride (KCl) as the chloride ion source, and (c) a base, and wherein said exposing the surface of the substrate to the surface modification solution oxidizes the noble metal surface and forms the noble metal salt passivation layer in a self-limiting oxidation process.

9. The method of claim 1 , wherein the surface modification solution comprises: (a) ammonium persulfate (APS) or tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt, and (b) hydrochloric acid (HCl) as the chloride ion source, and wherein said exposing the surface of the substrate to the surface modification solution oxidizes the noble metal surface and forms the noble metal salt passivation layer in a self-limiting oxidation process.

10. A method of etching, the method comprising:
receiving a substrate having a noble metal formed thereon, wherein a noble metal surface is exposed on a surface of the substrate;
exposing the surface of the substrate to a surface modification solution such that the surface modification solution is in contact with the noble metal surface, wherein the surface modification solution includes: (a) a chloride ion source, (b) a persulfate salt that reacts with the chloride ion source to form dichloride radical ions, which oxidize the noble metal surface to form a noble metal salt passivation layer, and (c) an acid or a base to adjust a pH of the surface modification solution and control an oxidation behavior of the noble metal salt passivation layer;
removing the surface modification solution from the surface of the substrate subsequent to forming the noble metal salt passivation layer;
exposing the surface of the substrate to a dissolution solution that reacts with the noble metal salt passivation layer to form soluble species that are dissolved by the dissolution solution; and
removing the dissolution solution and the soluble species from the substrate.

11. The method of claim 10 , wherein the noble metal is ruthenium (Ru), gold (Au), platinum (Pt) or iridium (Ir), and wherein the noble metal salt passivation layer is a chloro-metalate salt, an oxychlorometalate salt, or a hydrate of the chloro-metalate salt or the oxychlorometalate salt.

12. The method of claim 10 , wherein the surface modification solution includes an ammonium or quaternary ammonium cation salt of the persulfate or peroxymonosulfate ion as the persulfate salt.

13. The method of claim 12 , wherein the surface modification solution further includes a non-acidic chloride ion source and the acid, wherein the acid decreases the pH of the surface modification solution to oxidize the noble metal surface and form the noble metal salt passivation layer in a continuous oxidation process.

14. The method of claim 13 , wherein the surface modification solution includes tetrabutylammonium chloride (TBAC) as the non-acidic chloride ion source, tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt, and hydrochloric acid (HCl) as the acid.

15. The method of claim 12 , wherein the surface modification solution further includes a non-acidic chloride ion source and the base, and wherein the base increases the pH of the of the surface modification solution to oxidize the noble metal surface and form the noble metal salt passivation layer in a self-limiting oxidation process.

16. The method of claim 15 , wherein the surface modification solution includes potassium chloride (KCl) as the non-acidic chloride ion source, tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt, and potassium hydroxide (KOH) as the base.

17. The method of claim 12 , wherein the surface modification solution further includes an acidic chloride ion source as the chloride ion source and the acid, wherein the acidic chloride ion source changes a ratio of cations in the surface modification solution to oxidize the noble metal surface and form the noble metal salt passivation layer in a self-limiting oxidation process.

18. The method of claim 17 , wherein the surface modification solution includes tetrabutylammonium peroxymonosulfate (TBAPMS) as the persulfate salt and hydrochloric acid (HCl) as the acidic chloride ion source.

19. A method of etching a substrate using a wet atomic layer etching (ALE) process, the method comprising:
a) receiving the substrate, the substrate having a noble metal layer thereon;
b) exposing the noble metal layer to a first etch solution containing a non-acidic chloride ion source, a base and an oxidizer that reacts with the non-acidic chloride ion source to form dichloride radical ions, which oxidize an exposed su

Assignees

• Tokyo Electron Ltd

Inventors

• Abel Paul

Classifications

• C22B11/06

  Chloridising · CPC title

• C23F1/40

  for etching other metallic material · CPC title

• C23G1/10

  Other heavy metals · CPC title

• C23C22/58

  Treatment of other metallic material · CPC title

• C23F1/30 Primary

  for etching other metallic material · CPC title