System and method for defect detection using multi-spot scanning

Patent metadata

Field	Value
Publication number	US-9810643-B1
Application number	US-201314037304-A
Country	US
Kind code	B1
Filing date	Sep 25, 2013
Priority date	Sep 25, 2012
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

A system that may include a radiation source to generate a beam of coherent radiation; traveling lens optics to focus the beam so as to generate multiple spots on a surface of a sample and to scan the spots together over the surface; collection optics to collect the radiation scattered from the multiple spots and to focus the collected radiation so as to generate a pattern of interference fringes; and a detection unit to detect changes in the pattern of interference fringes.

First claim

The invention claimed is:

1. A system, comprising:
a radiation source adapted to generate a beam of coherent radiation;
traveling lens optics adapted to focus the beam to generate first, second and third spots on a surface of a sample and to scan the spots together over the surface;
a controller operatively coupled to the traveling lens optics, the controller being configured to transmit a signal to the traveling lens optics to cause the traveling lens optics to generate the first, second and third spots;
a collimating lens disposed between the radiation source and the traveling lens optics, the collimating lens being adapted to collimate the beam;
collection optics adapted to collect the radiation scattered from the first, second and third spots and to focus the collected radiation to generate a pattern of interference fringes;
a detection unit adapted to detect changes in the pattern of interference fringes; and
a processing device adapted to reconstruct phase and amplitude data of a near field radiation in proximity to the surface of the sample from the detected changes in the pattern of interference fringes; and classify defects on the surface of the sample using the reconstructed phase and amplitude data.

2. The system according to claim 1 , wherein the traveling lens optics comprise an acousto-optic Bragg cell and an acoustic transducer coupled to the cell adapted to produce, in response to receiving the signal transmitted by the controller, first, second and third frequency-modulated acoustic pulses, which travel along a length of the cell, such that when the beam of radiation passes through the cell, it is focused by the first, second and third pulses so as to generate and scan the first, second and third spots, respectively.

3. The system according to claim 2 , wherein the transducer is adapted to vary, in response to receiving a control signal from the controller, a relative timing and phase of the acoustic pulses to control a spacing and relative phase of the first, second and third spots.

4. The system according to claim 3 , wherein:
the second spot is formed between the first and third spots; and
wherein the traveling lens optics are adapted to generate the first and third spots as being of a same phase and to generate the second spot as being phase shifted from the first and third spots.

5. The system according to claim 3 , wherein the traveling lens optics are adapted to control, in response to receiving the signal transmitted by the controller, at least one of a phase and amplitude of each one of the first, second and third spots to cause the pattern of interference fringes to remain substantially stationary at a certain optical plane regardless of topographic differences between different portions of the surface of the sample.

6. The system according to claim 1 , wherein the collection optics comprises a beam stop which is arranged to block at least one interference fringe of the pattern of interference fringes from impinging on a detector of the detection unit.

7. The system according to claim 1 , wherein the traveling lens optics are adapted to generate, in response to receiving the signal transmitted by the controller, at least one additional spot on each side of the first, second and third spots to form an array of spots that comprises more than three spots and wherein all the spots of the array of spot participate in a generation of the pattern of interference fringes.

8. The system according to claim 7 , wherein:
the traveling lens optics are further adapted to generate the second spot such that the second spot is positioned at a center of the array of spots; and
wherein phases of spots of the array of spots are symmetrical about the second spot.

9. The system according to claim 1 , wherein the traveling lens optics are adapted to vary, in response to receiving the signal transmitted by the controller, at least one optical character of at least one spot of the first, second and third spot in alternation while scanning the first, second and third spots over the surface to facilitate a generation of multiple images of non-continuous portions of the surface of the sample.

10. The system according to claim 9 , wherein the traveling lens optics are further adapted to vary, in response to receiving the signal transmitted by the controller, a phase of the at least one spot in alternation between at least three different phase values to generate at least three images, each of the at least three images corresponds to a different phase value.

11. The system according to claim 1 , wherein the traveling lens optics are adapted to modulate, in response to receiving the signal transmitted by the controller, at least one optical character of at least one spot of the first, second and third spot during the scanning of the surface of the sample.

12. The system according to claim 1 wherein the traveling lens optics are adapted to vary, in response to receiving the signal transmitted by the controller, a phase differently between the second spot and a phase of the third and first spots while maintaining the second spot between the first and third spots.

13. A method comprising:
generating, by a radiation source, a beam of coherent radiation;
focusing, by traveling lens optics, the beam to generate first, second and third spots on a surface of a sample and scanning the spots together over the surface;
collecting, by collection optics, the radiation scattered from the first, second, and third spots and focusing the collected radiation to generate a pattern of interference fringes;
detecting, by a detection unit, changes in the pattern of interference fringes;
reconstructing, by a processing device, phase and amplitude data of a near field radiation in proximity to the surface of the sample from the detected changes in the pattern of interference fringes; and
classify, by the processing device, defects on the surface of the sample using the reconstructed phase and amplitude data.

Assignees

• Applied Materials Israel Ltd
• Applied Materials Israel Ltd

Inventors

• Shoham Amir
• Berlatzky Yoav
• Feldman Haim

Classifications

• G01B2290/30

  Grating as beam-splitter · CPC title

• G01N21/95607 Primary

  using a comparative method · CPC title

• G01N21/95623

  using a spatial filtering method (per se G02B) · CPC title