Laser system for target metrology and alteration in an euv light source

Patent metadata

Field	Value
Publication number	US-2021263422-A1
Application number	US-201917277027-A
Country	US
Kind code	A1
Filing date	Aug 12, 2019
Priority date	Sep 25, 2018
Publication date	Aug 26, 2021
Grant date	—

Abstract

Disclosed is a system and method for generating EUV radiation in which a laser is used in a multistage process to illuminate without altering a target material and then irradiate the target material to alter a target material with the illumination stage being used to determine the timing for firing during the irradiation stage or stages.

First claim

1 . Apparatus comprising:
a laser system configured to generate metrology radiation and operational radiation from a single laser source; a first optical system arranged to convey the metrology radiation along a first optical path to an irradiation region; a second optical system arranged to convey reflected metrology radiation reflected by target material in the irradiation region; metrology module arranged to receive the reflected metrology radiation and configured to perform an analysis of the reflected metrology radiation and to generate a control signal based at least in part on the analysis; and a steering module arranged to receive the control signal and configured to steer the operational radiation in response to the control signal, the first optical system conveying the operational radiation to an irradiation site in the irradiation region.

2 . Apparatus as claimed in claim 1 wherein the laser system is further configured to generate only one of the metrology radiation and the operational radiation at a given time.

3 . Apparatus as claimed in claim 1 wherein the laser system is further configured to generate the metrology radiation and the operational radiation from an initial radiation from the single laser source.

4 . Apparatus as claimed in claim 3 wherein the laser system is further configured to divide the initial radiation into the metrology radiation and the operational radiation.

5 . Apparatus as claimed in claim 1 wherein the control module generates the control signal a predetermined time after the control module determines that the reflected metrology radiation satisfies a predetermined criterion.

6 . (canceled)

7 . Apparatus as claimed in claim 5 wherein the predetermined criterion is a magnitude of the reflected metrology radiation exceeding a predetermined threshold.

8 . Apparatus as claimed in claim 5 wherein the predetermined criterion is a timing of the reflected metrology radiation.

9 . Apparatus as claimed in claim 5 wherein the predetermined criterion is the reflected metrology radiation achieving a maximum value.

10 . (canceled)

11 . Apparatus as claimed in claim 1 wherein the metrology radiation has an irradiance below a value capable of significantly perturbing the target material.

12 . Apparatus as claimed in claim 1 wherein the first optical system and the second optical system share at least one optical element.

13 . Apparatus as claimed in claim 1 wherein the metrology radiation is a metrology pulse.

14 . Apparatus as claimed in claim 1 wherein the metrology radiation is quasi-CW laser radiation.

15 . (canceled)

16 . Apparatus as claimed in claim 1 wherein the operational radiation comprises a an ionizing pulse.

17 . Apparatus as claimed in claim 1 wherein the control module generates a focus control signal in response determining that the reflected metrology radiation satisfies a predetermined criterion and further comprising a focusing module located in the first optical path having a first state in which a first beamwidth of radiation in the irradiation region has a first value and a second state in which a second beamwidth of radiation passing in the irradiation region has a second value.

18 . A radiation source having a laser configured to have a first state in which the laser generates metrology radiation and a second state in which the laser generates operational radiation, the radiation source being responsive to a control signal to transition from the first state to the second state.

19 . A radiation source as claimed in claim 18 wherein the metrology radiation has an irradiance below a predetermined value and the operational radiation has an irradiance above the predetermined value.

20 . A radiation source as claimed in claim 19 wherein the predetermined value is a magnitude required to ionize target material into a plasma state.

21 . A radiation source as claimed in claim 18 further comprising:
a first optical system arranged to convey the metrology radiation to a first location along a first path;
a second optical system arranged to convey reflected metrology radiation reflected by target material at the first location; and
a control module arranged to receive the reflected metrology radiation and configured to analyze the reflected metrology radiation and to generate the control signal based on the reflected metrology radiation.

22 . (canceled)

23 . A method of using a radiation source including a laser to irradiate target material, the method comprising the steps of:
causing the laser to emit a metrology pulse; using the target material to reflect at least a portion of a reflected portion of the metrology pulse; determining a timing for the laser to emit an operational pulse based at least in part on whether the at least a portion of the reflected portion meets a predetermined criterion; and causing the laser to emit the operational pulse at the timing as determined.

24 . A method as claimed in claim 23 wherein the predetermined criterion is the presence of any reflected metrology pulse.

25 . A method as claimed in claim 23 wherein the predetermined criterion is the whether the magnitude of the irradiance of the reflected portion of the metrology pulse exceeds a predetermined value.

26 . (canceled)

27 . A method of using a radiation source including a laser to irradiate target material, the method comprising the steps of:
controlling a beamwidth of a focusing module to increase the beamwidth of a beam passing through the focusing module; causing the laser to emit a metrology pulse through the focusing module; using the target material to reflect at least a portion of a reflected portion of the metrology pulse; using the at least a portion of a reflected portion of the metrology pulse to determine a position of the target material; determining a timing for emission by the laser of an operational pulse based at least in part on the position of the target material as determined; controlling the beamwidth of a focusing module to decrease the beamwidth of a beam passing through the focusing module; and causing the laser to emit the operational pulse through the focusing module at the timing as determined.

Assignees

• Asml Netherlands Bv

Inventors

• Rafac Robert Jay
• Fomenkov Igor Vladimirovich

Classifications

• H05G2/0084 Primary

  Control of the laser beam · CPC title

• G03F7/70033

  by plasma extreme ultraviolet [EUV] sources · CPC title

• G03F7/70025

  by lasers · CPC title

• G03F7/70133 Primary

  Measurement of illumination distribution, in pupil plane or field plane · CPC title

• G03F7/70041

  by pulsed sources, e.g. multiplexing, pulse duration, interval control or intensity control · CPC title