# US 2026/0107718 A1 · Methods for conditioning a surface prior to etching to optimize etch performance

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2026/0107718 A1
- Document ID: US20260107718A1
- Status: Published application
- Kind: A1
- Application number: 18/914,968
- Filed: 2024-10-14
- Published: 2026-04-16
- Earliest claimed: 2024-10-14
- Assignees: Tokyo Electron Limited
- Applicants: Tokyo Electron Limited
- Inventors: Kate Abel
- Web page: https://patentgrep.com/patent/US20260107718A1

## CPC

- H10P 50/667: {by liquid etching only}
- H10P 70/27: {during, before or after processing of conductive materials, e.g. polysilicon or amorphous silicon layers}
- H10P 95/70: Chemical treatments
- H10P 95/90: Thermal treatments, e.g. annealing or sintering
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

New methods are provided for conditioning a surface of a material to be etched prior to etching the material. More specifically, the present disclosure provides various embodiments of methods for conditioning a surface of a metal layer prior to etching the metal layer using etch chemistry optimized for the bulk metal layer. In some embodiments, the techniques disclosed herein may be used to condition a surface of a ruthenium (Ru) layer prior to etching the ruthenium layer using halogenating etch chemistries in a wet atomic layer etching (ALE) process.

## Claims

### Claim 1

A method for conditioning a surface of a metal layer to be etched prior to etching the metal layer, the method comprising:
receiving a substrate having the metal layer formed thereon, wherein a metal surface is exposed on a surface of the substrate;
annealing the substrate in a reducing atmosphere to at least partially reduce the metal surface;
exposing the substrate to a gas-phase L-type ligand to form a passivation layer on the metal surface; and
etching the metal layer using a wet etch process, wherein the passivation layer formed on the metal surface increases an etch rate of the metal layer during the wet etch process, compared to an etch rate achieved without the passivation layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein the metal layer is a ruthenium (Ru) layer, a cobalt (Co) layer, a copper (Cu) layer, a tungsten (W) layer, a molybdenum (Mo) layer, a tantalum (Ta) layer, a niobium (Nb) layer, a titanium (Ti) layer, a zirconium (Zr) layer or a hafnium (Hf) layer.

### Claim 3 (depends on 2)

The method of claim 2, wherein said etching the metal layer comprises performing multiple cycles of a wet atomic layer etching (ALE) process, wherein each cycle comprises:
exposing the metal surface to a first etch solution comprising a halogenation agent dissolved in a non-aqueous solvent to form a metal halide or oxyhalide passivation layer, which is self-limiting and insoluble in the non-aqueous solvent;
rinsing the substrate with a first purge solution to remove the first etch solution from the surface of the substrate;
exposing the metal halide or oxyhalide passivation layer to a second etch solution to selectively remove the metal halide or oxyhalide passivation layer and expose an unmodified metal surface underlying the metal halide or oxyhalide passivation layer; and
rinsing the substrate with a second purge solution to remove the second etch solution from the surface of the substrate and etch the metal layer.

### Claim 4 (depends on 2)

The method of claim 2, wherein the passivation layer formed on the metal surface increases the etch rate of the metal layer by: (a) reversing oxidative passivation of the metal surface, which occurred before said receiving the substrate, and/or (b) preventing oxidative passivation of the metal surface during said etching the metal layer.

### Claim 5 (depends on 1)

The method of claim 1, wherein said annealing the substrate comprises exposing the substrate to a gaseous reducing agent and a temperature ranging between 100° C. and 500° C.

### Claim 6 (depends on 5)

The method of claim 5, wherein the gaseous reducing agent comprises hydrogen (H2), hydrazine (N2H4), carbon monoxide (CO), ammonia (NH3), methane (CH4), formic acid (CH2O2) or another volatile carboxylic acid.

### Claim 7 (depends on 5)

The method of claim 5, wherein the metal layer is a ruthenium (Ru) layer having a ruthenium surface exposed on the surface of the substrate, and wherein said annealing the substrate comprises exposing the substrate to a hydrogen (H2) gas and a temperature ranging between 150° C. and 250° C. to at least partially desorb any oxide, hydroxide or hydrate groups bound to the ruthenium surface.

### Claim 8 (depends on 1)

The method of claim 1, wherein said exposing the substrate to the gas-phase L-type ligand is performed immediately after said annealing the substrate without exposing the substrate to air or other oxidizing environments.

### Claim 9 (depends on 1)

The method of claim 1, wherein said exposing the substrate to the gas-phase L-type ligand comprises exposing the substrate to the gas-phase L-type ligand while the substrate is exposed to a temperature ranging between 25° C. and 400° C.

### Claim 10 (depends on 9)

The method of claim 9, wherein the gas-phase L-type ligand is carbon monoxide (CO), cyclohexadiene (C6H8) or another alkene, ammonia (NH3), an alkyl amine or a phosphine.

### Claim 11 (depends on 9)

The method of claim 9, wherein the metal layer is a ruthenium (Ru) layer having a ruthenium surface exposed on the surface of the substrate, wherein said exposing the substrate to the gas-phase L-type ligand comprises exposing the substrate to carbon monoxide (CO) while the substrate is exposed to a temperature less than 75° C. to form a carbonyl passivation layer on the ruthenium surface, and wherein the carbonyl passivation layer formed on the ruthenium surface increases an etch rate of the ruthenium (Ru) layer during the wet etch process, compared to an etch rate achieved without the carbonyl passivation layer.

### Claim 12

A method for conditioning a surface of a ruthenium (Ru) layer to be etched prior to etching the ruthenium layer, the method comprising:
receiving a substrate having the ruthenium layer formed thereon, wherein a ruthenium surface is exposed on a surface of the substrate;
annealing the substrate in a reducing atmosphere to at least partially reduce the ruthenium surface;
exposing the substrate to a carbon monoxide (CO) gas to form a carbonyl passivation layer on the ruthenium surface; and
etching the ruthenium layer using a wet etch process, wherein the carbonyl passivation layer formed on the ruthenium surface increases an etch rate of the ruthenium layer during the wet etch process, compared to an etch rate achieved without the carbonyl passivation layer.

### Claim 13 (depends on 12)

The method of claim 12, wherein said annealing the substrate comprises exposing the substrate to a hydrogen (H2) gas and a temperature ranging between 150° C. and 250° C. to at least partially desorb any oxide, hydroxide or hydrate groups bound to the ruthenium surface.

### Claim 14 (depends on 12)

The method of claim 12, wherein said exposing the substrate to the carbon monoxide (CO) gas is performed immediately after said annealing the substrate without exposing the substrate to air or other oxidizing environments.

### Claim 15 (depends on 12)

The method of claim 12, wherein said exposing the substrate to the carbon monoxide (CO) gas comprises exposing the substrate to the carbon monoxide (CO) while the substrate is exposed to a temperature less than 75° C. to form the carbonyl passivation layer on the ruthenium surface.

### Claim 16

A method for conditioning a surface of a ruthenium (Ru) layer to be etched prior to etching the ruthenium layer in a wet atomic layer etching (ALE) process, the method comprising:
receiving a substrate having the ruthenium layer formed thereon, wherein a ruthenium surface is exposed on a surface of the substrate;
annealing the substrate in a reducing atmosphere to at least partially reduce the ruthenium surface;
exposing the substrate to a gas-phase L-type ligand to form a passivation layer on the ruthenium surface; and
etching the ruthenium layer by performing multiple cycles of the wet ALE process, wherein each cycle comprises:
exposing the ruthenium surface to a first etch solution comprising a chlorinating agent dissolved in a non-aqueous solvent to form a ruthenium chloride or oxychloride passivation layer, which is self-limiting and insoluble in the non-aqueous solvent;
rinsing the substrate with a first purge solution to remove the first etch solution from the surface of the substrate;
exposing the ruthenium chloride or oxychloride passivation layer to a second etch solution to selectively remove the ruthenium chloride or oxychloride passivation layer and expose an unmodified ruthenium surface underlying the ruthenium chloride or oxychloride passivation layer; and
rinsing the substrate with a second purge solution to remove the second etch solution from the surface of the substrate and etch the ruthenium layer;
wherein the passivation layer formed on the ruthenium surface increases an etch rate of the ruthenium layer during said etching, compared to an etch rate achieved without the passivation layer.

### Claim 17 (depends on 16)

The method of claim 16, wherein said annealing the substrate comprises exposing the substrate to a gaseous reducing agent and a temperature ranging between 100° C. and 500° C. to at least partially desorb any oxide, hydroxide or hydrate groups bound to the ruthenium surface.

### Claim 18 (depends on 17)

The method of claim 17, wherein the gaseous reducing agent comprises hydrogen (H2), hydrazine (N2H4), carbon monoxide (CO), ammonia (NH3), methane (CH4), formic acid (CH2O2) or another volatile carboxylic acid.

### Claim 19 (depends on 16)

The method of claim 16, wherein said annealing the substrate comprises exposing the substrate to a hydrogen (H2) gas and a temperature ranging between 150° C. and 250° C. to at least partially desorb any oxide, hydroxide or hydrate groups bound to the ruthenium surface.

### Claim 20 (depends on 16)

The method of claim 16, wherein said exposing the substrate to the gas-phase L-type ligand is performed immediately after said annealing the substrate without exposing the substrate to air or other oxidizing environments.

### Claim 21 (depends on 16)

The method of claim 16, wherein said exposing the substrate to the gas-phase L-type ligand comprises exposing the substrate to the gas-phase L-type ligand while the substrate is exposed to a temperature ranging between 25° C. and 400° C.

### Claim 22 (depends on 17)

The method of claim 17, wherein the gas-phase L-type ligand is carbon monoxide (CO), cyclohexadiene (C6H8) or another alkene, ammonia (NH3), an alkyl amine or a phosphine.

### Claim 23 (depends on 16)

The method of claim 16, wherein said exposing the substrate to the gas-phase L-type ligand comprises exposing the substrate to carbon monoxide (CO) while the substrate is exposed to a temperature less than 75° C. to form a carbonyl passivation layer on the ruthenium surface.

### Claim 24 (depends on 16)

The method of claim 16, wherein said annealing the substrate comprises exposing the substrate to a carbon monoxide (CO) gas and a first temperature ranging between 150° C. and 250° C. to at least partially desorb any oxide, hydroxide or hydrate groups bound to the ruthenium surface, and wherein said exposing the substrate to the gas-phase L-type ligand comprises continuing to expose the substrate to the carbon monoxide (CO) gas while the substrate is exposed to a second temperature less than 75° C. to form a carbonyl passivation layer on the ruthenium surface.

### Claim 25 (depends on 16)

The method of claim 16, wherein the passivation layer formed on the ruthenium surface prevents formation of ruthenium dioxide (RuO2) and/or other ruthenium species having oxidation states higher than 3+ on the ruthenium surface during said etching the ruthenium layer.