WO2005026706A1 - Method for high efficiency multipass article inspection - Google Patents

Method for high efficiency multipass article inspection Download PDF

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Publication number
WO2005026706A1
WO2005026706A1 PCT/US2004/027910 US2004027910W WO2005026706A1 WO 2005026706 A1 WO2005026706 A1 WO 2005026706A1 US 2004027910 W US2004027910 W US 2004027910W WO 2005026706 A1 WO2005026706 A1 WO 2005026706A1
Authority
WO
WIPO (PCT)
Prior art keywords
inspection
cameras
area
multipass
integrated circuits
Prior art date
Application number
PCT/US2004/027910
Other languages
French (fr)
Inventor
Emanuel Elyasef
Ron Naftali
Shimon Yalov
Original Assignee
Applied Materials Israel, Ltd.
Applied Materials, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Applied Materials Israel, Ltd., Applied Materials, Inc. filed Critical Applied Materials Israel, Ltd.
Publication of WO2005026706A1 publication Critical patent/WO2005026706A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • 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
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/82—Auxiliary processes, e.g. cleaning or inspecting
    • G03F1/84—Inspecting
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/9501—Semiconductor wafers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • 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
    • G01N2021/8854—Grading and classifying of flaws
    • G01N2021/8867—Grading and classifying of flaws using sequentially two or more inspection runs, e.g. coarse and fine, or detecting then analysing
    • G01N2021/887—Grading and classifying of flaws using sequentially two or more inspection runs, e.g. coarse and fine, or detecting then analysing the measurements made in two or more directions, angles, positions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects
    • G01N2021/95676—Masks, reticles, shadow masks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/94—Investigating contamination, e.g. dust
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/063—Illuminating optical parts
    • G01N2201/0636—Reflectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/066—Modifiable path; multiple paths in one sample
    • G01N2201/0662—Comparing measurements on two or more paths in one sample

Definitions

  • the present invention relates to systems and methods for inspecting integrated circuits fabricated on semiconductor wafers and/or masks used in the manufacture of such integrated circuits.
  • Optical inspection systems using CCD/CMOS cameras can suffer from contamination or scratches on the optical surfaces as well as various detector problems (e.g., blemishes, dead pixels, etc.). Such defects can cause artifact images at the CCD plane of the inspection system, especially under high coherence illumination.
  • Figure 1 illustrates an example of an image 10 showing such artifacts.
  • the contamination artifacts dynamically change depending on the article pattern, since it defines the diffraction pattern of the particle contamination at the CCD plane. Such a pattern cannot be neutralized by any calibration for that reason.
  • Using a number of cameras with the double inspection technique may help to keep a reasonable inspection throughput while solving the problem of the CCD/optics defects.
  • the main disadvantage of such a method is low transmission for each camera channel, which is expressed in high fluence at the article plane required to achieve a high dynamic range of the camera. For high magnification configurations the optimal fluence can overcome the damage threshold of the article layers that limits the system performance.
  • a mask is inspected by imaging an area thereof at least twice using an imaging beam passing through different optical paths, each including mirrors, to three or more cameras, each of which is used to capture an image of the area
  • Figure 1 illustrates an example of a CCD image showing artifacts as a result of defects in the imaging system.
  • Figure 2 illustrates an imaging system configured for use in accordance with an embodiment of the present invention.
  • Figure 3 illustrates an example of multiple images of an area on a mask obtained during a multipass inspection in accordance with an embodiment of the present invention.
  • Figure 4 illustrates an example of different fields of view obtained by imaging an article in accordance with the methods of the present invention.
  • FIG. 1 An example of an inspection system 20 configured in accordance with the present invention is illustrated in Figure 2.
  • Systems configured in accordance with the present invention allow scanning of an article (e.g., a mask) while preventing FAs due to contamination or other defects on the CCD and other optical surfaces of the system and maintaining high throughput and high optical transmission, which enables inspection at high magnifications without causing any damage to the inspected article.
  • the present invention allows inspection system operation in two different modes with minor changes required to switch between them.
  • the first mode is called "process window inspection", in which three (or more) cameras have the same FOV but are placed in different defocus areas.
  • This mode can be used to check printability of a mask within a defocus range defined by a lithography process window.
  • This mode can be operated by switching two beam splitters (BS1 and BS2 in Figure 2) into corresponding positions.
  • the second mode of operation is intended for fast scanning at maximum
  • the beam splitters are removed from the system.
  • the mirrors M ⁇ and M 12 which can be implemented on the same substrate with an uncoated area for a transmitted beam, and mirror M 2 will split the beam spatially so that each camera has its own FOV without overlapping.
  • the camera positions F 2 and F 3 should be corrected along the optical axis since the total track is changed.
  • the transmission of each channel is kept as high as that if only single camera was used.
  • the FOV of the imaging system should be increased and the shape of the camera should be rectangular with the ratio between the sides equal to the number of cameras if the separation is done in one direction.
  • the beam is split by a set of mirrors to bring the beamlets to the cameras. Each camera has its own FOV in the article plane without overlapping. Other mirror configurations are also possible.
  • the scanning scheme depends on the mode of operation. Scanning in fast mode (where the effect of contamination defects is negligible) requires moving the article stage between the laser pulses by a distance corresponding to one camera FOV multiplied by the number of cameras. This concept is illustrated graphically in Figure 4.
  • the scanning scheme for the multi pass inspection to improve the system detection capability is different. That is explained by the fact that each inspected area must be imaged at least twice on different camera(s) areas, as shown in Figure 3. ;!

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

Abstract

The present invention relates to a method for inspecting integrated circuits fabricated on semiconductor wafers and/or masks used in the manufacture of such integrated circuits. An objesct of the invention isto reduce the number of false alarms due the misdection of defect, for example due to contamination on the optical surfaces of the inspection system. A mask is inspected by imaging an area thereof at least twice using an imaging beam passing through different optical paths, each including mirrors (M11,M12,M2), to three or more cameras, each of which is used to capture an image of the area.

Description

METHOD FOR HIGH EFFICIENCY MULTIPASS ARTICLE INSPECTION
RELATED APPLICATIONS
[0001] The present application is related to and hereby claims the priority benefit of U.S. provisional patent application 60/500,574, filed 4 September 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to systems and methods for inspecting integrated circuits fabricated on semiconductor wafers and/or masks used in the manufacture of such integrated circuits.
BACKGROUND
[0003] Optical inspection systems using CCD/CMOS cameras can suffer from contamination or scratches on the optical surfaces as well as various detector problems (e.g., blemishes, dead pixels, etc.). Such defects can cause artifact images at the CCD plane of the inspection system, especially under high coherence illumination. Figure 1 illustrates an example of an image 10 showing such artifacts. The contamination artifacts dynamically change depending on the article pattern, since it defines the diffraction pattern of the particle contamination at the CCD plane. Such a pattern cannot be neutralized by any calibration for that reason.
[0004] Both of the effects described above limit the detection capability of the article area corresponding to the described artifacts and significantly increases false alarm (FA) rate thereby resulting in misdetection of defects. A compromise in the detection rate can be made to limit the FA rate, but such is often unacceptable in the field of mask detection.
[0005] One solution for the above-described problem is a double inspection process using single camera. This solution exploits the fact that contaminations and camera blemishes have approximately constant frame position. Meanwhile, the article defects have constant reticle coordinates. These facts enable distinction between real defects and nuisance ones: real defects will be detected in different coordinates between consecutive frames with a known displacement. The drawback of this technique is that it results in a more than two-fold reduction in the inspection throughput. [0006] Another solution involves the use of two or more cameras with common field of view (FOV) separated by beam splitters. This technique allows for scanning at the original speed (i.e., not the reduced speed required for the double inspection process). In this case the CCD defects can be eliminated, however the contamination/cosmetic defects of the optical surfaces will continue to affect the detector, since they overlap the same inspection area for all cameras.
[0007] Using a number of cameras with the double inspection technique may help to keep a reasonable inspection throughput while solving the problem of the CCD/optics defects. The main disadvantage of such a method, however, is low transmission for each camera channel, which is expressed in high fluence at the article plane required to achieve a high dynamic range of the camera. For high magnification configurations the optimal fluence can overcome the damage threshold of the article layers that limits the system performance.
SUMMARY OF THE INVENTION
[0008] In an embodiment of the present invention, a mask is inspected by imaging an area thereof at least twice using an imaging beam passing through different optical paths, each including mirrors, to three or more cameras, each of which is used to capture an image of the area
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which:
[0010] Figure 1 illustrates an example of a CCD image showing artifacts as a result of defects in the imaging system.
[0011] Figure 2 illustrates an imaging system configured for use in accordance with an embodiment of the present invention.
[0012] Figure 3 illustrates an example of multiple images of an area on a mask obtained during a multipass inspection in accordance with an embodiment of the present invention.
[0013] Figure 4 illustrates an example of different fields of view obtained by imaging an article in accordance with the methods of the present invention.
DETAILED DESCRIPTION
[0014] Described herein are systems and methods for inspecting integrated circuits fabricated on semiconductor wafers and/or masks used in the manufacture of such integrated circuits. An example of an inspection system 20 configured in accordance with the present invention is illustrated in Figure 2. Systems configured in accordance with the present invention allow scanning of an article (e.g., a mask) while preventing FAs due to contamination or other defects on the CCD and other optical surfaces of the system and maintaining high throughput and high optical transmission, which enables inspection at high magnifications without causing any damage to the inspected article. Although discussed with reference to several illustrated embodiments, however, the present invention should only be measured in terms of the claims that follow this detailed description.
[0015] The present invention allows inspection system operation in two different modes with minor changes required to switch between them. The first mode is called "process window inspection", in which three (or more) cameras have the same FOV but are placed in different defocus areas. This mode can be used to check printability of a mask within a defocus range defined by a lithography process window. This mode can be operated by switching two beam splitters (BS1 and BS2 in Figure 2) into corresponding positions.
[0016] The second mode of operation is intended for fast scanning at maximum
speed V = Vl - N (or for multipass inspection at V = Vl ■ N/2 ), where V is a speed using
one camera (or three cameras in the first configuration), and Ν is the number of cameras. In this second mode the beam splitters are removed from the system. The mirrors Mπ and M12, which can be implemented on the same substrate with an uncoated area for a transmitted beam, and mirror M2 will split the beam spatially so that each camera has its own FOV without overlapping. The camera positions F2 and F3 should be corrected along the optical axis since the total track is changed. The transmission of each channel is kept as high as that if only single camera was used. [0017] The FOV of the imaging system should be increased and the shape of the camera should be rectangular with the ratio between the sides equal to the number of cameras if the separation is done in one direction. The beam is split by a set of mirrors to bring the beamlets to the cameras. Each camera has its own FOV in the article plane without overlapping. Other mirror configurations are also possible.
[0018] The scanning scheme depends on the mode of operation. Scanning in fast mode (where the effect of contamination defects is negligible) requires moving the article stage between the laser pulses by a distance corresponding to one camera FOV multiplied by the number of cameras. This concept is illustrated graphically in Figure 4. The scanning scheme for the multi pass inspection to improve the system detection capability is different. That is explained by the fact that each inspected area must be imaged at least twice on different camera(s) areas, as shown in Figure 3. ;!
[0019] Thus, systems and methods for inspecting integrated circuits fabricated on semiconductor wafers and/or masks used in the manufacture of such integrated circuits have been described.

Claims

CLAIMSWhat is claimed is:
1. A method of inspecting a mask, comprising imaging an area of a mask at least twice using an imaging beam passing through different optical paths, each including mirrors, to three or more cameras, each of which is used to capture an image of the area.
PCT/US2004/027910 2003-09-04 2004-08-26 Method for high efficiency multipass article inspection WO2005026706A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US50057403P 2003-09-04 2003-09-04
US60/500,574 2003-09-04

Publications (1)

Publication Number Publication Date
WO2005026706A1 true WO2005026706A1 (en) 2005-03-24

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006019446A2 (en) * 2004-07-19 2006-02-23 Applied Materials Israel, Ltd. Double inspection of reticle or wafer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2060876A (en) * 1979-10-16 1981-05-07 Zeiss Jena Veb Carl Testing photomasks
JPH02159545A (en) * 1988-12-13 1990-06-19 Nippon Seiko Kk Method and apparatus for extracting defect of pattern
EP0838679A2 (en) * 1996-10-23 1998-04-29 Nec Corporation Method and apparatus for inspecting high-precision patterns
US6327033B1 (en) * 1999-06-21 2001-12-04 International Business Machines Corporation Detection of phase defects on photomasks by differential imaging

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2060876A (en) * 1979-10-16 1981-05-07 Zeiss Jena Veb Carl Testing photomasks
JPH02159545A (en) * 1988-12-13 1990-06-19 Nippon Seiko Kk Method and apparatus for extracting defect of pattern
EP0838679A2 (en) * 1996-10-23 1998-04-29 Nec Corporation Method and apparatus for inspecting high-precision patterns
US6327033B1 (en) * 1999-06-21 2001-12-04 International Business Machines Corporation Detection of phase defects on photomasks by differential imaging

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 0144, no. 15 (P - 1102) 7 September 1990 (1990-09-07) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006019446A2 (en) * 2004-07-19 2006-02-23 Applied Materials Israel, Ltd. Double inspection of reticle or wafer
WO2006019446A3 (en) * 2004-07-19 2006-05-04 Applied Materials Israel Ltd Double inspection of reticle or wafer

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