# US 11,452,197 B2 · Shock wave visualization for extreme ultraviolet plasma optimization

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- Number: US 11,452,197 B2
- Document ID: US11452197B2
- Status: Granted
- Kind: B2
- Application number: 16/655,116
- Filed: 2019-10-16
- Published: 2020-04-30
- Granted: 2022-09-20
- Earliest claimed: 2018-10-29
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Yen-Shuo Su; Jen-Hao Yeh; Jhan-Hong Yeh; Ting-Ya Cheng; Yee-Shian Henry Tong; Chun-Lin Chang; Han-Lung Chang; Li-Jui Chen; Po-Chung Cheng
- Web page: https://patentgrep.com/patent/US11452197B2

## CPC

- H05G 2/0027: {Arrangements for controlling the supply; Arrangements for measurements}
- G01V 8/12: using one transmitter and one receiver
- H05G 2/0035: {the material containing metals as principal radiation-generating components}
- H05G: X-RAY TECHNIQUE (investigating or analysing materials by the use of X-rays G01N23/00; apparatus for X-ray photography G03B42/02; X-ray tubes H01J35/00; TV systems having X-ray input H04N5/321)
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

A method for monitoring a shock wave in an extreme ultraviolet light source includes irradiating a target droplet in the extreme ultraviolet light source apparatus of an extreme ultraviolet lithography tool with ionizing radiation to generate a plasma and to detect a shock wave generated by the plasma. One or more operating parameters of the extreme ultraviolet light source is adjusted based on the detected shock wave.

## Claims

### Claim 1

A method, comprising:
irradiating a first target droplet in an extreme ultraviolet (EUV) light source apparatus of an EUV lithography tool with a focused radiation beam to generate EUV radiation and a plasma;
detecting a shock wave generated by the plasma of the first target droplet; and
adjusting one or more operating parameters of the EUV light source apparatus based on the detected shock wave, wherein by the adjusting the one or more operating parameters, an impact of the shock wave associated with the first target droplet on a next droplet is minimized.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
irradiating the shock wave with a non-ionizing light from a radiation source of a shock wave illumination module; and
capturing one or more images of the shock wave by an image sensor of a shock wave detection module.

### Claim 3 (depends on 2)

The method of claim 2, further comprising:
capturing consecutive images of the shock wave;
detecting shock wave parameters based on the captured images of the shock wave; and
adjusting the one or more operating parameters of the EUV light source apparatus based on the shock wave parameters.

### Claim 4 (depends on 1)

The method of claim 1, wherein the one or more operating parameters of the EUV light source apparatus comprise one or more parameters of one or both of a droplet generator or a source of the focused radiation beam.

### Claim 5 (depends on 4)

The method of claim 4, wherein the one or more operating parameters of the EUV light source apparatus comprise one or both of a first time delay between pulses generated by the source of the focused radiation beam or a second time delay between droplets generated by the droplet generator.

### Claim 6 (depends on 5)

The method of claim 5, wherein by adjusting one or both of the first time delay and the second time delay, the impact of the shock wave associated with the first target droplet on the next droplet is avoided.

### Claim 7 (depends on 2)

The method of claim 2, further comprising:
irradiating, with a non-ionizing light from a radiation source of a droplet illumination module, a path between a droplet generator and a zone of excitation, wherein the zone of excitation is where the first target droplet is irradiated by the focused radiation beam; and
detecting a light reflected and/or scattered by droplets in the path to capture one or more images of the path by an image sensor of a droplet detection module.

### Claim 8 (depends on 7)

The method of claim 7, further comprising
capturing consecutive images of the path by the droplet detection module;
determining droplet parameters of at least one droplet based on the captured images; and
adjusting the one or more operating parameters of the EUV light source apparatus based on the droplet parameters.

### Claim 9

A method, comprising:
irradiating a zone of excitation of an EUV light source, wherein a first target droplet is configured to interact with a focused radiation beam at the zone of excitation and create a plasma;
determining whether a shock wave is generated by the plasma; and
after determining the shock wave is generated, adjusting one or more operating parameters of the EUV light source, wherein by the adjusting the one or more operating parameters, an impact of the shock wave associated with the first target droplet on a next droplet is avoided.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
irradiating a path between a droplet generator and the zone of excitation; and
detecting a light reflected and/or scattered by droplets in the path to capture one or more images of the path by an image sensor of a droplet detection module.

### Claim 11 (depends on 10)

The method of claim 10, further comprising:
capturing consecutive images of the shock wave by an image sensor of a shock wave detection module;
detecting shock wave parameters based on the captured images of the shock wave; and
adjusting the one or more operating parameters of the EUV light source based on the shock wave parameters.

### Claim 12 (depends on 9)

The method of claim 9, wherein the one or more operating parameters of the EUV light source comprise one of a first time delay between pulses generated by a source of the focused radiation beam or a second time delay between droplets generated by a droplet generator.

### Claim 13 (depends on 9)

The method of claim 9, wherein a source of the focused radiation beam is a pulsed laser.

### Claim 14 (depends on 11)

The method of claim 11, wherein the shock wave parameters comprise a direction of expansion and a velocity of expansion of the shock wave.

### Claim 15

An apparatus for monitoring shock waves in an extreme ultraviolet light source, comprising:
a shock wave illumination module comprising a radiation source configured to illuminate a zone of excitation, wherein a first target droplet interacts with a focused radiation beam at the zone of excitation to generate an extreme ultraviolet light and a plasma;
a shock wave detection module comprising one or more image sensors and configured to capture one or more images of the zone of excitation; and
a controller coupled to the shock wave illumination module and the shock wave detection module and configured to:
determine whether a shock wave is generated based on the captured images of the zone of excitation;
determine shock wave parameters of the shock wave; and
adjust one or more operating parameters of the extreme ultraviolet light source based on the shock wave parameters, wherein the one or more operating parameters are adjusted such that an impact of the shock wave associated with the first target droplet on a next droplet is avoided.

### Claim 16 (depends on 15)

The apparatus of claim 15, further comprising:
a droplet illumination module comprising a radiation source configured to illuminate a path between a droplet generator and the zone of excitation; and
a droplet detection module configured to detect a light reflected and/or scattered by droplets in the path to capture one or more images of the path;
wherein the controller is further configured to:
determine droplet parameters of at least one droplet based on the captured images of the path; and
adjust the one or more operating parameters of the extreme ultraviolet light source based on the droplet parameters.

### Claim 17 (depends on 15)

The apparatus of claim 15, wherein the one or more operating parameters of the extreme ultraviolet light source comprise both of a first time delay between pulses generated by a source of the focused radiation beam and a second time delay between droplets generated by a droplet generator.

### Claim 18 (depends on 16)

The apparatus of claim 16, wherein the radiation source of the shock wave illumination module and the radiation source of the droplet illumination module are non-ionizing.

### Claim 19 (depends on 16)

The apparatus of claim 16, wherein the radiation source of the shock wave illumination module and the radiation source of the droplet illumination module are non-ionizing lasers, and at least one of the non-ionizing lasers have a wavelength of about 1064 nm.

### Claim 20 (depends on 16)

The apparatus of claim 16, further comprising a synchronizer that is configured to synchronize the droplet illumination module with the droplet detection module and also synchronize the shock wave illumination module with the shock wave detection module.