# US 2020/0401050 A1 · Control System and Method

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- Number: US 2020/0401050 A1
- Document ID: US20200401050A1
- Status: Published application
- Kind: A1
- Application number: 16/977,667
- Filed: 2019-02-21
- Published: 2020-12-24
- Earliest claimed: 2018-03-12
- Assignees: ASML Netherlands B.V.
- Applicants: ASML Netherlands B.V.
- Inventors: Herman Philip GODFRIED; Frank EVERTS; Wilhelmus Patrick Elisabeth M OP 'T ROOT
- Web page: https://patentgrep.com/patent/US20200401050A1

## CPC

- G03F 7/70025: {by lasers}
- H01S 3/134: in gas lasers
- G03F 7/70041: {by pulsed sources, e.g. multiplexing, pulse duration, interval control or intensity control}
- G03F 7/70558: {Dose control, i.e. achievement of a desired dose}
- G03F 7/7085: {Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load}
- G03F 9/7026: {Focusing}
- H01S 3/1305: {Feedback control systems}
- H01S 3/097: by gas discharge of a gas laser
- H01S 3/104: in gas lasers
- H01S 3/1306: {Stabilisation of the amplitude}
- 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)
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A control system for controlling a laser, comprising a sensor for sensing a physical value indicative of a characteristic of a laser beam emitted by the laser, a switch, a first controller and a second controller. Each controller is configured, to receive a further sensor value from the sensor, adjust a received setpoint value based on the received further sensor value to give an output value and cause the laser to operate in accordance with the output value. The switch is configured to switch between the controllers such that output values are provided from each controller in a cyclic fashion.

## Claims

### Claim at position 1

-15. (canceled)

### Claim 16

A control system for controlling a laser, the control system comprising:
a sensor configured to sense a physical value indicative of a characteristic of a laser beam emitted by the laser;
a switch;
a first controller and a second controller, wherein each controller is configured, to:
receive a setpoint value;
receive a further sensor value from the sensor;
adjust the received setpoint value based on the received further sensor value to give an output value;
cause the laser to operate in accordance with the output value;
wherein:
an output value from the first controller is different from an output value from the second controller;
the switch is configured to switch between the controllers such that output values are provided from each controller in a cyclic fashion;
the controllers are configured to communicate with one another; and
at least one adjustment to the setpoint value made by the second controller is determined at least in part by at least one adjustment to the setpoint value made by the first controller.

### Claim 17 (depends on 16)

The control system of claim 16, wherein the laser is a pulsed laser and the switch is configured to switch between the controllers on a pulse to pulse basis.

### Claim 18 (depends on 16)

The control system of claim 16, wherein the laser is configured to provide more than one type of output.

### Claim 19 (depends on 18)

The control system of claim 18, wherein each controller is configured to control a respective type of output from the laser.

### Claim 20 (depends on 16)

The control system of claim 16, wherein each controller comprises a limiter configured to adjust the output value in accordance with predetermined limits.

### Claim 21 (depends on 20)

The control system of claim 20, wherein the limiters of each controller are configured to communicate with one another.

### Claim 22 (depends on 16)

The control system of claim 16, wherein each controller comprises a tuning unit configured to adjust the setpoint value based on the received further sensor value to give the output value.

### Claim 23 (depends on 16)

The control system of claim 16, wherein the output value is configured to control the energy dose of the laser.

### Claim 24 (depends on 16)

The control system of claim 16, wherein the output value is configured to control the wavelength emitted by the laser.

### Claim 25 (depends on 16)

A radiation source comprising a laser and a control system according to claim 16, wherein the control system is configured to control the laser of the radiation source.

### Claim 26 (depends on 16)

A lithographic system comprising the radiation source of claim 16, and a lithographic apparatus, the lithographic apparatus comprising:
an illumination system for conditioning a radiation beam emitted by the radiation source;
a support structure for supporting a patterning device, the patterning device serving to impart the radiation beam with a pattern in its cross-section;
a substrate table for holding a substrate; and,
a projection system for projecting the patterned radiation beam onto a target portion of the substrate.

### Claim 27

A method for controlling a parameter of a laser using a first and a second controller, the method comprising:
cycling between a first controller and a second controller, wherein each controller performs the steps of:
a) receive a setpoint value for the parameter;
b) receive a further sensor value from a sensor;
c) adjust the received setpoint value based on the received further sensor value to give an output value;
d) cause the laser to operate in accordance with the output value;
wherein the controllers communicate with one another and wherein at least one adjustment to the setpoint value made by the second controller is determined at least in part by at least one adjustment to the setpoint value made by the first controller.

### Claim 28 (depends on 27)

The method of claim 27, wherein the laser is a pulsed laser and the cycling between the controllers is on a pulse to pulse basis.

### Claim 29 (depends on 27)

The method of claim 27, wherein each controller further controls at least one of:
a respective type of output from the laser; and
the output value in accordance with predetermined limits.

### Claim 30 (depends on 27)

The method of claim 27, wherein the output value is used to control at least one of:
the energy dose of the laser; and
the wavelength emitted by the laser.