System and method for pumping laser sustained plasma with an illumination source having modified pupil power distribution

Patent metadata

Field	Value
Publication number	US-11921297-B2
Application number	US-202217682919-A
Country	US
Kind code	B2
Filing date	Feb 28, 2022
Priority date	Nov 9, 2018
Publication date	Mar 5, 2024
Grant date	Mar 5, 2024

Abstract

A system for generating pump illumination for laser sustained plasma (LSP) is disclosed. The system may include an illumination source configured to output a pump beam, one or more focusing optics, and one or more beam shapers configured to reshape the pump beam to provide a shaped pupil power distribution at an illumination pupil plane of the one or more focusing optics. The shaped pupil power distribution may include at least one of a flat-top distribution or an inverted distribution with a central local intensity minimum. Further, the one or more focusing optics may receive the pump beam from the one or more beam shapers and direct the pump beam to a plasma-forming material, whereby the pump beam at least one of forms or maintains a plasma that emits broadband illumination.

First claim

What is claimed:

1. A system, comprising:
an illumination source configured to output a pump beam;
one or more focusing optics; and
one or more beam shapers configured to reshape the pump beam to provide a shaped pupil power distribution at an illumination pupil plane of the one or more focusing optics, wherein the shaped pupil power distribution comprises at least one of a flat-top distribution or an inverted distribution with a central local intensity minimum, wherein the one or more focusing optics are configured to receive the pump beam from the one or more beam shapers and direct the pump beam to a plasma-forming material, whereby the pump beam at least one of forms or maintains a plasma that emits broadband illumination.

2. The system of claim 1 , wherein the shaped pupil power distribution at the illumination pupil plane is characterized by

D

2
⁢
0

-

D

8
⁢
0

D

F
⁢
W
⁢
H
⁢
M

<

0
.
5

,

where D 20 is an outermost beam diameter at which the intensity of the pump beam reaches 20%, D 80 is an outermost beam diameter at which the intensity of the pump beam reaches 80%, and D FWHM is an outermost beam diameter at which the intensity of the pump beam reaches 50%.

3. The system of claim 2 , wherein the beam profile of the pump beam from the illumination source is characterized by

D

2
⁢
0

-

D

8
⁢
0

D

F
⁢
W
⁢
H
⁢
M

<
0.5

,

where D 20 is an outermost beam diameter at which the intensity of the pump beam reaches 20%, D 80 is an outermost beam diameter at which the intensity of the pump beam reaches 80%, and D FWHM is an outermost beam diameter at which the intensity of the pump beam reaches 50%.

4. The system of claim 1 , wherein the beam profile of the pump beam from the illumination source comprises:
at least one of a bell-shaped distribution, a gaussian distribution, or a near-gaussian distribution.

5. The system of claim 1 , wherein the shaped pupil power distribution is a flat-top distribution.

6. The system of claim 1 , wherein the shaped pupil power distribution is an inverted distribution.

7. The system of claim 6 , wherein an edge region of the shaped pupil power distribution has a greater intensity than a central region of the shaped pupil power distribution.

8. The system of claim 1 , wherein the shaped pupil power distribution is a truncated version of the beam profile from the illumination source.

9. The system of claim 1 , wherein the one or more beam shapers include one or more diffractive optical elements.

10. The system of claim 1 , wherein the one or more beam shapers include one or more axicons.

11. The system of claim 1 , wherein the one or more beam shapers include a delivery fiber imaged on a pupil plane of one or more focusing elements.

12. The system of claim 1 , wherein the one or more beam shapers include a delivery fiber with selectively populated high-order transverse modes.

13. The system of claim 1 , wherein the one or more beam shapers include a limiting aperture.

14. The system of claim 1 , further comprising one or more collection optics configured to receive the broadband illumination and direct the broadband illumination to an output.

15. An optical characterization system, comprising:
an illumination sub-system comprising:
a plasma site configured to contain a plasma-forming material;
an illumination source configured to output a pump beam;
one or more focusing optics;
one or more beam shapers configured to reshape the pump beam to provide a shaped pupil power distribution at an illumination pupil plane of the one or more focusing optics, wherein the shaped pupil power distribution comprises at least one of a flat-top distribution or an inverted distribution with a central local intensity minimum, wherein the one or more focusing optics are configured to receive the pump beam from the one or more beam shapers and direct the pump beam to the plasma-forming material, whereby the pump beam at least one of forms or maintains a plasma that emits broadband illumination; and
one or more collection optics to direct the broadband illumination to a sample;

a collection sub-system comprising:
a detector; and one or more optical elements to direct at least a portion of light from the sample onto the detector; and

a controller communicatively coupled to the detector, the controller including one or more processors configured to execute program instructions causing the one or more processors to generate one or more measurements of the sample based on data from the detector generated in response to illumination of the sample with the broadband illumination.

16. The system of claim 15 , wherein one or more measurements of the sample comprise:
at least one of a metrology measurement or an inspection measurement.

17. The system of claim 15 , wherein one or more measurements of the sample comprise:
an image.

18. The system of claim 15 , wherein the sample comprises:
at least one of a wafer or a photomask.

19. The system of claim 15 , wherein the shaped pupil power distribution at the illumination pupil plane is characterized by

D

2
⁢
0

-

D

8
⁢
0

Assignees

• Kla Corp

Inventors

• Bezel Ilya
• Derstine Matthew
• Stepanov Andrey
• Sherbak Nikolay

Classifications

• H05G2/0086

  Optical arrangements for conveying the laser beam to the plasma generation location · CPC title

• G02B27/0927 Primary

  Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat · CPC title

• G02B5/001

  Axicons, waxicons, reflaxicons · CPC title

• G02B27/0944

  Diffractive optical elements, e.g. gratings, holograms (gratings per se G02B5/18; holograms used as optical elements per se G02B5/32) · CPC title

• G02B27/0955

  Lenses (lenses per se G02B3/00) · CPC title