WO2008119550A1 - Appareil et méthode d'inspection - Google Patents

Appareil et méthode d'inspection Download PDF

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Publication number
WO2008119550A1
WO2008119550A1 PCT/EP2008/002585 EP2008002585W WO2008119550A1 WO 2008119550 A1 WO2008119550 A1 WO 2008119550A1 EP 2008002585 W EP2008002585 W EP 2008002585W WO 2008119550 A1 WO2008119550 A1 WO 2008119550A1
Authority
WO
WIPO (PCT)
Prior art keywords
work object
inspection apparatus
sensor
inspection
image
Prior art date
Application number
PCT/EP2008/002585
Other languages
English (en)
Inventor
Taufiq Habib
Alex F. Schreiner
Original Assignee
Viscom Ag
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 Viscom Ag filed Critical Viscom Ag
Publication of WO2008119550A1 publication Critical patent/WO2008119550A1/fr

Links

Classifications

    • 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
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
    • 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
    • G01N21/8806—Specially adapted optical and illumination features
    • 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
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
    • 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
    • G01N21/9505—Wafer internal defects, e.g. microcracks

Definitions

  • the invention relates to an inspection apparatus as defined in the preamble of claim 1 and an inspection method as defined in the preamble of claim 19 for detection of features in a work object. While the invented subject matter may be used in various applications, it will be illustrated herein in the context of the fabrication of silicon wafers. Wafer fabrication involves the drawing of a single continuous ingot which then is sliced into wafers of standard diameters and thickness. These standard wafers are then shipped to a semiconductor processing company for use in creating semiconductor devices, namely, integrated circuits .
  • a semiconductor company will further process the wafer using specialized equipment, in particular grinding equipment. Grinding the unpatterned silicon (e.g. bare), wafers may result in the appearance of structural voids, inclusions and/or pinhole defects that were previously internal to the wafer. These voids, inclusions and/or pinholes may be considered defects rendering the wafer unusable for further processing.
  • Inspection apparatus of the relevant kind for detection of features in a work object are known and include a radiation source directing radiation to the work object in use. Furthermore, the known inspection apparatus include an image capturing system including at least one sensor.
  • near-infrared (NIR) light includes light in a spectrum between 760 nm and 2,500 nm, in particular between 950 nm and 1,300 nm. Particularly preferred is the spectrum between 1,000 and 1,200 nm. Surprisingly, it has been found that particularly in the inspection of silicon wafers, using NIR light results in an excellent image quality.
  • NIR light allows for standard equipment in particular standard cameras to be used.
  • NIR light results in a resolution that is sufficient to image some finer wafer structures .
  • the inventive inspection apparatus includes at least one NIR responsive camera.
  • the image capturing system includes at least one NIR transmissive lens or lens assembly.
  • the work object and the sensor are mounted in fixed relationship to each other.
  • positioning means are provided for positioning the work object and the sensor relative to each other.
  • the work object may be inspected at various locations.
  • one of the work object and the sensor may ⁇ be fixed while the other components may be movable.
  • both the work object and the sensor may be movable.
  • the positioning means are adapted for positioning the work object and the sensor substantially parallel to the surface of the work object. If e. g. the surface of the work object is located within a X-Y-plane, the work object and the sensor are positionable along the X- and the Y-axis. According to a further preferred embodiment, the positioning means are adapted for positioning the work object and the sensor substantially perpendicular to the surface of the work object. If again e. g. the surface of the work object is located within a X-Y plane, in this embodiment the work object and the sensor are positionable relative to each other along the Z axis.
  • control means for controlling the positioning means during an inspection of the work objects are provided wherein according to a further preferred embodiment the work object and the sensor are positioned relative to each other automatically during an inspection of the work object.
  • inspection of the work object may be carried out automatically without human intervention.
  • the image capturing system includes image processing and/or storing means. Said image processing and/or storing means may for example be embodied as a computer.
  • the image processing and/or storing means are adapted to compare acquired image data to a known reference, image characteristics or image representation. In this embodiment, evaluation of the acquired image data may be carried out in a particularly time-saving manner.
  • the work object at least partially is translucent for the near- infrared light, such that the work object is located between the light source and the sensor.
  • the work object at least partially is reflective for the near infrared light such that the light source and the sensor are located at the same side of the work object.
  • the inventive inspection apparatus may be used for inspection of work objects which are translucent for the NIR light as well as for inspection of work objects which are reflective for the NIR light.
  • the inventive inspection apparatus may be used for inspecting various work objects.
  • the apparatus is particularly suitable for inspection of wafers.
  • the work object is at least partially manufactured from semiconductor material, in particular silicon, wherein the work object preferably is a wafer.
  • the work object may be microstructure, in particular a micromechanical structure, wherein the micromechanical structure preferably is a MEMS (Microelectromechanical System) .
  • MEMS Microelectromechanical System
  • At least one feature to be detected is a defect and/or that at least one feature to be detected is an intended structure in the work object.
  • FIG. 1 depicts a system diagram of a first embodiment of an inspection apparatus according to the invention
  • Fig. 2 depicts a system diagram of a second embodiment of an inspection apparatus according to the invention
  • Fig. 3 depicts a system diagram of a third embodiment of an inspection apparatus according to the invention.
  • Fig. 4 is a side view of a wafer and a camera subsection of the inspection apparatus shown in fig. 2,
  • Fig. 5 is a view of the X-Y-Z inspection apparatus shown in fig. 2 operating in conjunction with an X-Y defect inspection apparatus,
  • Fig. 6 is a view of the inspection apparatus shown in fig. 2 configured to operate in the same work space as an X-Y inspection apparatus,
  • Fig. 7 is a view of an X-Y-Z inspection apparatus integrated with an X-Y inspection apparatus using adjustable optics and Fig. 8 shows an example of an NIR image captured by an inspection apparatus according to the invention.
  • Fig. 1 illustrates a first embodiment of an inspection apparatus 2 according to the invention.
  • the inspection apparatus 2 includes a radiation source 4 directing radiation to a work object which in the present embodiment is a wafer 6. Furthermore, the inspection apparatus 2 includes an image capturing system 8 including a camera 10, lens 12, wherein the camera 10 is in data transfer connection with an imaging processing and/or storing means which in the present embodiment is embodied as a computer 14.
  • positioning means 15 For positioning the work object 6 and the camera 10 relative to each other positioning means 15 are provided which in the present embodiment are adapted for positioning the wafer 6 and the camera 10 parallel to the surface of the wafer 6 along the Y and the X axis which in figure 1 are symbolized by arrows 16 and 18 respectively.
  • the radiation source 4 is a NIR light source outputting near infrared light in use.
  • the camera 10 is a NIR responsive camera and the lens 12 is a NIR transmissive lens.
  • the apparatus 2 includes control means for controlling the positioning means 15 during an inspection of the wafer 6, wherein in the present embodiment the control means are constituted by the computer 14.
  • the radiation source 4 irradiates the work object 6 with NIR light, wherein the camera 10 is used to capture images of the wafer 6 as the control means included in the computer 14 positions the camera 10 and the wafer 6 relative to each other.
  • the control means positions the camera 10 and the wafer 6 relative to each other, the camera 10 takes incremental snapshots of the wafer 6, wherein the entire thickness of the wafer 6 is scanned in one image. Defects 24, 24' and 24 '' are detected at various points in the wafer 6. These physical defects 24, 24' and 24'' are stored by the image processing and storing means included in the computer 14. A software system included in the computer 14 can then determine, via image processing or through human intervention, whether the wafer 6 is acceptable or is to be rejected.
  • the inventive inspection apparatus 2 may be manufactured at relatively low costs.
  • Fig. 2 illustrates a second embodiment of the inventive inspection apparatus 2' which differs from the embodiment illustrated in figure 1 mainly in that the positioning means are adapted for positioning the wafer 6 and the camera 10 substantially perpendicular to the surface of the wafer 6, i. e. in the illustrated embodiment along the Z axis. Furthermore, the camera 10 / lens 12 assembly is constructed such that it has a shallow depth of field.
  • the wafer 6 and the camera 10 are positionable relative to each other along the X, Y and Z axis. Consequently, images of the wafer 6 may be captured at arbitrary positions within the volume of the wafer 6 such that the X, Y and Z coordinate values of defects 24, 24', 24'' are determined by means of the inventive inspection apparatus 2.
  • the inspection apparatus 2 may also use known X-Y coordinate values.
  • the X-Y coordinate values may be determined using the apparatus 2 illustrated in figure 1.
  • the known values could be obtained from a stored defect table loaded on an X-Y-Z image processing system of the computer 14.
  • this known data could be determined in real time from the same or different system acquiring the Z image data, or it could be manually input.
  • the defect table may consist of a list of X-Y positions on the wafer 6 where defects have been predetermined.
  • the positioning means 15 positions the camera 10, the light source 4 and the lens 12 to a predetermined location at which the positioning means incrementally adjust the lens 12 to scan the wafer from one side to the other along the Z axis.
  • an image is taken by the camera 10 and processed by the X-Y-Z image processing system of the computer 14.
  • the image processing and/or storing means can then create an X-Y-Z defect table.
  • the X-Y-Z defect table being a list of defects 24, 24', 24'' not only including the X-Y coordinates of the defects but also the depth information (Z axis) , the accuracy of the X- Y-Z defect table being dependent on the positioning means 15, the camera 10 and the image processing means.
  • Fig. 3 illustrates a third embodiment of the inventive inspection apparatus 2' which differs from the embodiment of figure 2 in that the camera 10 and the NIR light source 4 are located at different sides of the wafers 6 such that the NIR light source 4 is configured as a backlight source.
  • Fig. 4 depicts a side view of the wafer 6 with a representative width of 700 ⁇ m.
  • a portion of the inspection apparatus 2 is shown with the camera 10 and the lens 12.
  • the camera 10 / lens 12 assembly is positionable along the Z axis relative to the wafer 6.
  • the camera 10 / lens 12 assembly has a shallow depth of field that is approximately 50 ⁇ m, for example.
  • Three reprentative defects 24, 24' and 24'' are shown in the wafer at depth locations of 0 ⁇ m, 350 ⁇ m and 650 ⁇ m.
  • An inspection of the wafer 6 is carried out using a defect table including X-Y coordinate values of the defects 24, 24', 24''.
  • the first defect 24'' is located without adjusting the camera 10 / lens 12 assembly along the X and Y axis.
  • the inspection apparatus 2' is not limited to storing binary values of whether a defect is located at a particular location along an axis.
  • the apparatus 2' may store the actual image itself and with image postprocessing and interpolation being able to determine Z values that lie between incremental Z steps.
  • the positioning means 15 may position the camera 10 / lens 12 assembly relative to the wafer 6 in a stepwise manner as explained above. However, the positioning means 15 may position the camera 10 / lens 12 assembly relative to the wafer 6 continuously.
  • the apparatus 2 may also be used to detect intended structures within the wafer 6.
  • the embodiment of figure 2 may also be configured to work with other inspection systems as shown in figure 5.
  • a non-infrared inspection system 26 inspects a wafer 6 and records a defect table. The wafer 6 is then transferred by conveyor or a similar mechanism to the apparatus illustrated in figure 2 for X-Y-Z inspection as described above.
  • the X-Y-Z inspection apparatus 2' then views the wafer 6 referencing the X-Y table to determine the Z values of the defects 24, 24', 24'' detected by the inspection system 26.
  • the embodiment of figure 2 may also be configured to work in tandem with the embodiment of figure 1.
  • a wafer 6 is placed in a mount 28.
  • the apparatus 2 of figure 1 (X-Y defect inspection) is mounted on one plane above the wafer 6 and the apparatus 2' of figure 2 (X-Y-Z defect inspection) is mounted on a separate, non- intersecting plane.
  • This configuration allows both systems to potentially work in tandem and sharing a common work space .
  • a single system may be configured with all functions to determining X-Y-Z data.
  • a lens assembly 30 having lenses with different depth of field may be used instead of a single lens 6 .
  • a wider view length 32 is selected by rotating the lens 32 into the position to view the wafer 6.
  • the camera 10 is adjustable on the Z axis.
  • a lens 34 with a smaller depth of field or a lens 36 with an even smaller depth of field may be used.
  • Fig. 8 shows an example of a NIR image of the wafer captured by the inventive inspection apparatus using NIR light.
  • Contrast algorithms consist of taking a known reference image or characteristics of an image that represents a defect- free area in the wafer and comparing it to the captured image or characteristics or a representation of the captured image. The two images are compared and a determination is made whether there are defects present.
  • the defect-free image is processed with an edge-detection algorithm, followed by histogram that computes a single number
  • a defect can be located by comparing a reference value or a computed value of a good wafer with the image recorded for the entire depth of the wafer.
  • modified contrast algorithms are used to determine if there are defects along the Z axis. An image is captured at each depth using the shallow depth of view camera. Each captured image is contrasted with a known reference value. If the algorithm detects sufficient contrast, then the defect is noted in the X-Y-Z defect table.
  • the NIR light emitted by the light source 4 is directed to structures via an internal beam splitter in the lens system.
  • the light, so directed generally is reflected by structures at various intensities (e. g. depending on the bond characteristics and other features and defects of the semiconductor structure) , so as to travel back up through the lens system, to a camera, such camera being based on one or using one or more solid state imaging devices, e. g. CCD or CMOS detectors.
  • the camera detects reflected radiation in the NIR spectrum. Via such detection, an image of the structures is captured.
  • the image, so captured may be provided for further processing via e. g. a computer.
  • the captured image, so processed or otherwise may be employed for test and quality control toward the identifying relevant features of such structures, e. g. where such relevant features are associated with bonded or stacked layers or with other bonded or stacked materials .

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  • 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)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

L'invention porte sur un appareil d'inspection (2) pour la détection de caractéristiques d'un objet usiné (6) comprenant: une source de radiations dirigées sur l'objet, et un système de capture d'images incluant au moins un capteur. Selon l'invention, la source de radiation est une source de lumière en IR proche, et le capteur est sensible à l'IR proche.
PCT/EP2008/002585 2007-04-02 2008-04-01 Appareil et méthode d'inspection WO2008119550A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US90967007P 2007-04-02 2007-04-02
US60/909,670 2007-04-02

Publications (1)

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WO2008119550A1 true WO2008119550A1 (fr) 2008-10-09

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010084314A1 (fr) * 2009-01-22 2010-07-29 Renishaw Plc Procédé et système de mesures optiques
WO2011056282A1 (fr) * 2009-11-05 2011-05-12 Aerospace Corporation Eclairage assisté par réfraction pour l'imagerie
US8110804B2 (en) 2007-04-16 2012-02-07 Viscom Ag Through substrate optical imaging device and method
US8450688B2 (en) 2009-11-05 2013-05-28 The Aerospace Corporation Refraction assisted illumination for imaging
US8461532B2 (en) 2009-11-05 2013-06-11 The Aerospace Corporation Refraction assisted illumination for imaging
US9007454B2 (en) 2012-10-31 2015-04-14 The Aerospace Corporation Optimized illumination for imaging

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003096387A2 (fr) * 2002-05-08 2003-11-20 Phoseon Technology, Inc. Source lumineuse a semi-conducteurs a haut rendement et leurs procedes d'utilisation et de fabrication
US20050002021A1 (en) * 2003-07-03 2005-01-06 Leica Microsystems Semiconductor Gmbh Apparatus, method, and computer program for wafer inspection
US20050231713A1 (en) * 2004-04-19 2005-10-20 Owen Mark D Imaging semiconductor structures using solid state illumination

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003096387A2 (fr) * 2002-05-08 2003-11-20 Phoseon Technology, Inc. Source lumineuse a semi-conducteurs a haut rendement et leurs procedes d'utilisation et de fabrication
US20050002021A1 (en) * 2003-07-03 2005-01-06 Leica Microsystems Semiconductor Gmbh Apparatus, method, and computer program for wafer inspection
US20050231713A1 (en) * 2004-04-19 2005-10-20 Owen Mark D Imaging semiconductor structures using solid state illumination

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8110804B2 (en) 2007-04-16 2012-02-07 Viscom Ag Through substrate optical imaging device and method
WO2010084314A1 (fr) * 2009-01-22 2010-07-29 Renishaw Plc Procédé et système de mesures optiques
WO2011056282A1 (fr) * 2009-11-05 2011-05-12 Aerospace Corporation Eclairage assisté par réfraction pour l'imagerie
US8138476B2 (en) 2009-11-05 2012-03-20 The Aerospace Corporation Refraction assisted illumination for imaging
US8212215B2 (en) 2009-11-05 2012-07-03 The Aerospace Corporation Refraction assisted illumination for imaging
US8450688B2 (en) 2009-11-05 2013-05-28 The Aerospace Corporation Refraction assisted illumination for imaging
US8461532B2 (en) 2009-11-05 2013-06-11 The Aerospace Corporation Refraction assisted illumination for imaging
US9007454B2 (en) 2012-10-31 2015-04-14 The Aerospace Corporation Optimized illumination for imaging

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