# US 11,029,324 B2 · Particle image velocimetry of extreme ultraviolet lithography systems

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- Number: US 11,029,324 B2
- Document ID: US11029324B2
- Status: Granted
- Kind: B2
- Application number: 16/579,660
- Filed: 2019-09-23
- Published: 2020-04-02
- Granted: 2021-06-08
- Earliest claimed: 2018-09-28
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: En Hao Lai; Chi Yang; Shang-Chieh Chien; Li-Jui Chen; Po-Chung Cheng
- Web page: https://patentgrep.com/patent/US11029324B2

## CPC

- G01P 5/20: using particles entrained by a fluid stream (G01P5/22 takes precedence)
- G02B 27/0006: {with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation (G02B1/18 takes precedence; cleaning in general B08B)}
- G03F 1/42: Alignment or registration features, e.g. alignment marks on the mask substrates
- G03F 7/20: Exposure; Apparatus therefor (photographic printing apparatus for making copies G03B27/00)
- G03F 7/70025: {by lasers}
- G03F 7/70033: {by plasma extreme ultraviolet [EUV] sources}
- H05G 2/0027: {Arrangements for controlling the supply; Arrangements for measurements}
- H05G 2/0035: {the material containing metals as principal radiation-generating components}
- H05G 2/008: {involving an energy-carrying beam in the process of plasma generation}
- H05G 2/0094: {Reduction, prevention or protection from contamination; Cleaning}
- G01P 5/26: by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- 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)

## Abstract

A method includes irradiating a target droplet in an extreme ultraviolet light source of an extreme ultraviolet lithography tool with light from a droplet illumination module. Light reflected and/or scattered by the target droplet is detected. Particle image velocimetry is performed to monitor one or more flow parameters inside the extreme ultraviolet light source.

## Claims

### Claim 1

A method, comprising:
irradiating a target droplet in an extreme ultraviolet (EUV) light source of an extreme ultraviolet lithography tool with non-ionizing light from a droplet illumination module;
detecting light reflected and/or scattered by the target droplet; and
performing particle image velocimetry, based on the detected light, to monitor one or more flow parameters inside the EUV light source.

### Claim 2 (depends on 1)

The method of claim 1, further comprising adjusting one or more operating parameters of the EUV light source based on the monitored flow parameters.

### Claim 3 (depends on 2)

The method of claim 2, wherein the monitored flow parameters include:
one or more of a flow pattern of gases, droplets, or debris in the EUV light source;
the droplets and debris propagation direction; and
spatial evolution of a plasma shockwave.

### Claim 4 (depends on 3)

The method of claim 3, further comprising:
monitoring a rate of an amount of droplet and debris depositing on a collector mirror of the EUV light source; and
adjusting the one or more operating parameters of the EUV light source to reduce the rate.

### Claim 5 (depends on 4)

The method of claim 4, further comprising:
mapping the amount of droplet and debris deposited on the collector mirror; and
triggering a cleaning mechanism to clean the collector mirror based on the mapping.

### Claim 6 (depends on 4)

The method of claim 4, further comprising:
mapping the amount of droplet and debris deposited on the collector mirror; and
triggering a replacement mechanism to change the collector mirror based on the mapping.

### Claim 7 (depends on 1)

The method of claim 1, wherein the non-ionizing light irradiating the target droplet has a wavelength of about 1064 nm.

### Claim 8 (depends on 1)

The method of claim 1, wherein a source of the non-ionizing light of the droplet illumination module is a laser.

### Claim 9 (depends on 1)

The method of claim 1, wherein the light reflected and/or scattered by the target droplet is detected by a droplet detection module.

### Claim 10 (depends on 9)

The method of claim 9, wherein the droplet detection module comprises a digital camera.

### Claim 11

A method, comprising:
irradiating one or more of tin droplets and tin debris in an extreme ultraviolet light source of an extreme ultraviolet lithography tool with non-ionizing light from a droplet illumination module;
detecting light reflected and/or scattered by the one or more of the tin droplets and the tin debris; and
performing particle image velocimetry, based on the detected light, to monitor a rate of an amount of the tin droplets and the tin debris depositing on a collector mirror of the extreme ultraviolet light source.

### Claim 12 (depends on 11)

The method of claim 11, further comprising:
adjusting one or more operating parameters of the extreme ultraviolet light source to reduce the rate.

### Claim 13 (depends on 11)

The method of claim 11, further comprising:
mapping the amount of tin droplets and tin debris deposited on the collector mirror; and
triggering a replacement mechanism to change the collector mirror based on the mapping.

### Claim 14 (depends on 11)

The method of claim 11, further comprising:
mapping the amount of tin droplets and tin debris deposited on the collector mirror; and
determining a half life time of the collector mirror based on the mapping.

### Claim 15

An apparatus for monitoring flow parameters of particles in an extreme ultraviolet light source of an extreme ultraviolet lithography system, comprising:
a droplet illumination module comprising a radiation source configured to illuminate a target droplet;
a droplet detection module configured to detect light reflected and/or scattered by the target droplet; and
a controller coupled to the droplet illumination module and the droplet detection module and configured to:
perform particle image velocimetry to monitor one or more flow parameters inside the extreme ultraviolet light source.

### Claim 16 (depends on 15)

The apparatus of claim 15, wherein the controller is further programmed to adjust one or more operating parameters of the extreme ultraviolet light source based on the monitored flow parameters.

### Claim 17 (depends on 15)

The apparatus of claim 15, wherein the radiation source comprises a laser.

### Claim 18 (depends on 17)

The apparatus of claim 17, wherein the laser produces a non-ionizing light having a wavelength of about 1064 nm.

### Claim 19 (depends on 15)

The apparatus of claim 15, further comprising a synchronizer that synchronizes the droplet illumination module and the droplet detection module.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein the controller is further configured to control the synchronizer.