Radiation-induced false count mitigation and detector cooling

Patent metadata

Field	Value
Publication number	US-10690599-B1
Application number	US-201816170954-A
Country	US
Kind code	B1
Filing date	Oct 25, 2018
Priority date	Jun 5, 2018
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

An inspection system with radiation-induced false count mitigation includes an illumination source configured to illuminate a sample and a liquid-cooling coincidence detector, which includes an illumination detector to detect illumination from the sample, a liquid-cooling device for regulating a temperature of the illumination detector via a liquid, and photodetectors to detect light generated in the liquid in response to particle radiation. The liquid-cooling coincidence detector may also include controllers to identify a set of illumination detection events based on an illumination signal received from the illumination detector, identify a set of radiation detection events based on radiation signals received from the photodetectors, compare the set of radiation detection events to the set of illumination detection events to identify a set of coincidence events, and exclude the set of coincidence events from the set of illumination detection events to generate a set of identified features on the sample.

First claim

What is claimed:

1. An inspection system with radiation-induced false count mitigation, comprising:
an illumination source configured to illuminate a sample;
a liquid-cooling coincidence detector comprising:
an illumination detector configured to detect illumination from the sample positioned on a first side of the illumination detector; and
a radiation sensor, wherein the radiation sensor regulates a temperature of the illumination detector via a liquid circulating through one or more channels disposed on a second side of the illumination detector opposite the first side of the illumination detector, wherein the radiation sensor includes one or more photodetectors configured to detect photons generated in the liquid in response to particle radiation; and

one or more controllers communicatively coupled to the illumination detector and the one or more photodetectors, wherein the one or more controllers are configured to:
identify a set of illumination detection events based on an illumination signal received from the illumination detector;
identify a set of radiation detection events based on one or more radiation signals received from the one or more photodetectors;
compare the set of radiation detection events to the set of illumination detection events to identify a set of coincidence events, wherein the set of coincidence events corresponds to simultaneous occurrences of radiation detection events and illumination detection events; and
exclude the set of coincidence events from the set of illumination detection events to generate a set of identified features on the sample.

2. The system of claim 1 , wherein the liquid comprises:
at least one of water, deionized water, glycol, or a fluorocarbon.

3. The system of claim 1 , wherein the liquid is configured to generate photons in response to particle radiation comprising:
at least one of muons, alpha particles, beta particles, or gamma radiation.

4. The system of claim 1 , wherein the one or more channels are formed from a metal.

5. The system of claim 4 , wherein the one or more channels include one or more transparent windows, wherein the one or more photodetectors detect the photons generated by the liquid in response to particle radiation through the one or more transparent windows.

6. The system of claim 4 , wherein the metal comprises:
stainless steel.

7. The system of claim 1 , wherein interior portions of the one or more channels are polished to provide reflections of the photons generated by the liquid in response to particle radiation.

8. The system of claim 1 , wherein the one or more photodetectors configured to detect photons generated in the liquid in response to particle radiation comprise:
at least one of a photodiode, a silicon photo-multiplier, or a multi-pixel photon counter.

9. The system of claim 1 , wherein the set of radiation detection events based on one or more radiation signals received from the one or more photodetectors comprise:
a summed signal from the one or more photodetectors.

10. The system of claim 1 , wherein the one or more controllers comprise:
a first controller configured to identify a set of illumination detection events based on an illumination signal received from the illumination detector, and
one or more additional controllers configured to:
identify a set of radiation detection events based on one or more radiation signals received from the one or more photodetectors;
compare the set of radiation detection events to the set of illumination detection events to identify a set of coincidence events, wherein the set of coincidence events corresponds to simultaneous occurrences of radiation detection events and illumination detection events; and
exclude the set of coincidence events from the set of illumination detection events to generate a set of identified features on the sample.

11. The system of claim 1 , further comprising:
one or more additional detector assemblies communicatively coupled to the one or more controllers.

12. The system of claim 11 , wherein the one or more controllers are further configured to:
generate one or more additional sets of identified features on the sample based on one or more signals received from the one or more additional detector assemblies, and
compare the set of identified features on the sample to the one or more additional sets of identified features on the sample to generate a modified set of identified features on the sample, wherein the modified set of identified features on the sample corresponds to features identified by at least two detector assemblies.

13. The system of claim 1 , wherein the liquid-cooling coincidence detector includes one or more radiation shields positioned around one or more surfaces of the illumination detector to block radiation from reaching the illumination detector, wherein the one or more radiation shields are open on the first side of the illumination detector to allow illumination from the sample to pass to the illumination detector.

14. The system of claim 13 , wherein the one or more radiation shields are formed from at least one of tungsten or lead.

15. The system of claim 13 , wherein at least a portion the one or more radiation shields is further configured as a heat sink.

16. The system of claim 1 , wherein the illumination detector comprises:
at least one of one or more single-pixel sensors or one or more multi-pixel sensors.

17. The system of claim 16 , wherein the one or more single-pixel sensors comprise:
at least one of one or more photomultiplier tubes (PMTs), one or more photodiodes, or one or more avalanche photodiode (APD) devices.

18. The system of claim 16 , wherein the one or more multi-pixel sensors comprise:
at least one of one or more charge-coupled devices (CCDs), or one or more complementary metal-oxide semiconductor (CMOS) devices.

19. The system of claim 1 , wherein the illumination detector is positioned vertically.

20. The system of claim 1 , wherein the set of identified features on the sample includes one or more defect sites.

21. An inspection system with radiation-induced false count mitigation, comprising:
an illumination source configured to illuminate a sample;
a liquid-cooling coincidence detector comprising:
an illumination detector configured to detect illumination from the sample positioned on a first side of the illumination detector; and
a radiation sensor, wherein the radiation sensor regulates a temperature of the illumination detector via a liquid circulating through one or more channels disposed proximate to a second side of the illumination detector opposite the first side of the illumination detector, wherein the radiation sensor includes one or more photodetectors configured to detect photons generated in the liquid in response to particle radiation; and

one or more controllers communicatively coupled to the illumination detector and the one or more photodetectors, wherein the one or more controllers are configured to:
identify a set of radiation detection events based on one or more radiation signals received from the one or more photodetectors;
generate a set of radiation detection event timestamps associated with the set of radiation detection events;
identify a set of illumination detection events based on the illumination signal received from the illumination detector;
generate a set of illumination detection event timestamps associated with the set of illumination detection events;
compare the set of illumination detection

Assignees

• Kla Tencor Corp

Inventors

• Biellak Stephen
• Trytko Tyler

Classifications

• G01N21/93

  Detection standards; Calibrating {baseline adjustment, drift correction} · CPC title

• G01N21/8851

  Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges (G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002) · CPC title

• G01N21/9501

  Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20) · CPC title

• G01T1/22

  with Cerenkov detectors · CPC title

• G01T1/204 Primary

  the detector being a liquid · CPC title