# US 12,374,532 B2 · Plasma processing method

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- Number: US 12,374,532 B2
- Document ID: US12374532B2
- Status: Granted
- Kind: B2
- Application number: 18/279,299
- Filed: 2022-04-11
- Published: 2025-03-06
- Granted: 2025-07-29
- Earliest claimed: 2022-04-11
- Assignees: Hitachi High-Tech Corporation
- Applicants: Hitachi High-Tech Corporation
- Inventors: Mai Isomoto; Hitoshi Kobayashi; Ryota Takahashi; Satoshi Une
- Web page: https://patentgrep.com/patent/US12374532B2

## CPC

- H01J 37/32697: {Electrostatic control}
- H01J 37/32165: {Plural frequencies}
- H01J 37/32293: {using particular waveforms, e.g. polarised waves}
- H01J 37/32715: {Workpiece holder}
- H10P 50/242: {of Group IV materials}
- H10P 50/28: of insulating materials
- H01J 2237/3341: Reactive etching
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

An object of the invention is to provide a plasma processing method for preventing generation of deposition from an underlying metal film and attaining an anisotropic shape in hard mask etching. The plasma processing method for forming a mask using a film to be etched whose underlying layer is a metal film according to the invention includes: a first step of etching, using a plasma generated by mixed gas containing O2 gas, CHF3 gas, NF3 gas, Ar gas, and He gas, while supplying pulse-modulated radio frequency power to a sample stage on which a sample having the film to be etched is placed; and a second step of etching while supplying continuous wave (CW) radio frequency power to the sample stage after the first step. The film to be etched is a TEOS film and a silicon nitride film, and the continuous wave (CW) radio frequency power is smaller than a product of the pulse-modulated radio frequency power and a pulse-modulated duty ratio and is smaller than 50 W.

## Claims

### Claim 1

A plasma processing method for forming a mask using a film to be etched whose underlying layer is a metal film, the plasma processing method comprising:
a first step of etching, using a plasma generated by mixed gas containing oxygen (O2) gas, trifluoromethane (CHF3) gas, nitrogen trifluoride (NF3) gas, argon (Ar) gas, and helium (He) gas, the film to be etched while supplying pulse-modulated radio frequency power to a sample stage on which a sample having the film to be etched is placed; and
a second step of etching the etched film to be etched while supplying continuous wave (CW) radio frequency power to the sample stage after the first step, wherein
the film to be etched is a tetra ethyl ortho silicate (TEOS) film and a silicon nitride film, and
the continuous wave (CW) radio frequency power is smaller than a product of the pulse-modulated radio frequency power and a pulse-modulated duty ratio and is smaller than 50 W.

### Claim 2 (depends on 1)

The plasma processing method according to claim 1, wherein
a flow rate of the helium (He) gas is higher than a flow rate of the argon (Ar) gas.

### Claim 3 (depends on 1)

The plasma processing method according to claim 1, wherein
as etching gas in the second step, mixed gas containing sulfur hexafluoride (SF6) gas and the trifluoromethane (CHF3) gas is used.

### Claim 4 (depends on 1)

The plasma processing method according to claim 1, wherein
the continuous wave (CW) radio frequency power is 10% or less of the product of the pulse-modulated radio frequency power and the pulse-modulated duty ratio.

### Claim 5 (depends on 1)

The plasma processing method according to claim 1, wherein
radio frequency power for generating a plasma in the second step is larger than radio frequency power for generating a plasma in the first step.

### Claim 6 (depends on 5)

The plasma processing method according to claim 5, wherein
the radio frequency power for generating the plasma in the first step and the radio frequency power for generating the plasma in the second step is radio frequency power of a microwave, and
a current for forming a magnetic field in the second step is larger than a current for forming a magnetic field in the first step.

### Claim 7 (depends on 1)

The plasma processing method according to claim 1, wherein
the mask for etching the film to be etched is an amorphous carbon layer (ACL) film.