# US 12,215,430 B2 · Method for increasing the surface roughness of a metal layer

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- Number: US 12,215,430 B2
- Document ID: US12215430B2
- Status: Granted
- Kind: B2
- Application number: 17/535,147
- Filed: 2021-11-24
- Published: 2022-06-02
- Granted: 2025-02-04
- Earliest claimed: 2020-11-27
- Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Applicants: Commissariat à L'éNergie Atomique Et Aux éNergies Alternatives
- Inventors: Nicolas Posseme; Laurent Grenouillet; Olivier Pollet
- Web page: https://patentgrep.com/patent/US12215430B2

## CPC

- C23F 1/02: Local etching
- C23F 4/00: Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
- H01J 37/32522: {Temperature}
- H10B 63/22: {of the metal-insulator-metal type}
- H10N 70/011: {Manufacture or treatment of multistable switching devices}
- H10N 70/063: {by etching of pre-deposited switching material layers, e.g. lithography}
- H10N 70/20: Multistable switching devices, e.g. memristors
- H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices}
- H10N 70/841: {Electrodes}
- H10N 70/8833: {Binary metal oxides, e.g. TaOx}
- H01J 2237/2001: Maintaining constant desired temperature
- H01J 2237/3341: Reactive etching
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- H10B: ELECTRONIC MEMORY DEVICES
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A method for increasing the surface roughness of a layer based on a metal having a catalytic power, includes fixing fluorine or chlorine on the surface of the metal based layer, by exposing the metal based layer to a plasma formed from a reactive gas containing fluorine or chlorine; exposing the surface of the metal based layer to a humid environment to produce an acid, by reaction of hydrogen from the humid environment with the fluorine or the chlorine fixed on the surface of the metal based layer, the acid reacting with the metal to form residues, the whole of the residues forming a pattern on the surface of the metal based layer, and etching the metal based layer through the residues, so as to transfer the pattern into the metal based layer.

## Claims

### Claim 1

A method for increasing a surface roughness of a metal layer based on titanium, tantalum, tungsten, gold, nickel and/or aluminum, comprising:
fixing fluorine or chlorine on the surface of the metal layer, by exposing the metal layer to a plasma formed from a reactive gas containing fluorine or chlorine;
after fixing fluorine or chlorine on the surface of the metal layer, exposing the surface of the metal layer to a humid environment to produce an acid, by reaction of hydrogen from the humid environment with the fluorine or the chlorine fixed on the surface of the metal layer, the acid reacting with the metal to form residues, the whole of the residues forming a pattern on the surface of the metal layer, and
after forming the residues, etching the metal layer through the residues, so as to transfer the pattern into the metal layer.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the metal layer is etched by an etching method having a selectivity with respect to the residues comprised between 1 and 2.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the metal layer is etched until all the residues are removed.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the reactive gas is a non-polymerising gas containing fluorine.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the reactive gas is sulphur hexafluoride (SF6) or nitrogen trifluoride (NF3).

### Claim 6 (depends on 1)

The method according to claim 1, wherein the plasma is formed from a mixture of reactive gases comprising a fluorocarbon gas (CxFY) and a depolymerising gas.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the humid environment is ambient air.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the humid environment is generated in a chamber of a plasma reactor.

### Claim 9 (depends on 1)

The method according to claim 1, further comprising a step of oxidation of the surface of the metal layer before the step of formation of the residues.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the metal layer is made of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), titanium oxynitride or titanium oxynitride.

### Claim 11 (depends on 1)

The method according to claim 1, wherein the plasma used to fixe fluorine or chlorine on the surface of the metal layer has no etching role.