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WO2014084575A1 - Procédé et dispositif de détection de microdéfauts - Google Patents

Procédé et dispositif de détection de microdéfauts Download PDF

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Publication number
WO2014084575A1
WO2014084575A1 PCT/KR2013/010798 KR2013010798W WO2014084575A1 WO 2014084575 A1 WO2014084575 A1 WO 2014084575A1 KR 2013010798 W KR2013010798 W KR 2013010798W WO 2014084575 A1 WO2014084575 A1 WO 2014084575A1
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WO
WIPO (PCT)
Prior art keywords
sample
light source
defect
irradiated
pump
Prior art date
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Ceased
Application number
PCT/KR2013/010798
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English (en)
Korean (ko)
Inventor
장기수
최우준
유선영
김건희
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Korea Basic Science Institute KBSI
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Korea Basic Science Institute KBSI
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Publication date
Application filed by Korea Basic Science Institute KBSI filed Critical Korea Basic Science Institute KBSI
Publication of WO2014084575A1 publication Critical patent/WO2014084575A1/fr
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/72—Investigating presence of flaws
    • 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
    • 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 present invention relates to a technique for detecting fine defects, and more particularly, by irradiating a pump laser beam to a sample to induce a change in the periodic reflection intensity due to the photothermal effect of the defect present in the irradiation area, and to the probe A method and apparatus for detecting minute defects in a sample by irradiating a beam and measuring a change in reflection intensity.
  • microdefects in the thin film may be It can act as a local hot source to increase the ambient temperature, and this change in temperature and the difference in coefficient of thermal expansion in the thin film results in thermal stress, resulting in a laser-induced laser damage threshold.
  • damage threshold LIDT
  • the lowering of the laser damage threshold caused by laser exposure ultimately results in damage and permanent destruction of the thin film, thereby degrading the performance of the optoelectronic device and further shortening the life of the device.
  • Photothermal microscopy [B. Bertussi et al ., "High-resolution photothermal microscope: a sensitive tool for the detection of isolated absorbing defects in optical coatings," Appl. Opt., 45 (7) 2006, US patent, "Photothermal imaging scanning microscopy", registration number: 07075058, registration date: July 11, 2006, is one of the most widely used thin film defect detection techniques. It is a method of estimating a defect location by checking a change in refractive index around a defect due to a stimulus to a degree of deflection / refraction of a probe beam.
  • the method obtains defect distribution by raster scanning using a sample stage, the data acquisition time is long (more than a few minutes), and the photothermal effect around the defect predominates when the pump beam size is larger than the measurement defect. There was a problem that the accuracy of the detection falls.
  • the light-heat signal is very sensitive to the relative position of the probe beam and the pump beam, it is difficult to precisely adjust the probe beam irradiation angle for each sample measurement.
  • an object of the present invention is to provide a novel technique using a reflection mode photothermal reflection microscopy technique that measures the position of the defect through the degree of change in reflectance instead of the change in refractive index due to the photothermal effect.
  • a first aspect of the invention is a step of irradiating a pump laser beam of a predetermined frequency (f) to the sample; Changing the periodic reflection intensity by changing the defect surface temperature due to the photothermal effect of the defect in the area irradiated with the pump laser beam; And irradiating a probe beam to the sample to measure a change in the reflection intensity.
  • the sample for detecting the microdefects is not particularly limited, such as a thin film, a thick film, a wafer, a bulk material, and can be various kinds.
  • the method further comprises the step of measuring from the change in reflectance of the sample by phase-locked heat reflection and converting it into a heat distribution.
  • the detector may further include triggering a sample at a multiple of the frequency for temperature-modulating the sample.
  • the light source for generating the pump laser beam may be configured using a wavelength tunable laser diode and a wavelength selection filter (not shown) to irradiate the beam of various wavelengths.
  • the pump laser beam is preferably irradiated with a surface light source, but may also be modified to be irradiated in the form of a line light source.
  • the probe beam imaging plane may be moved into the sample through vertical movement of the sample stage, three-dimensional defect information of the sample may be realized through the stage Z-axis scan.
  • sample mounting unit for mounting a sample;
  • a pump light source for irradiating the pump laser beam at a predetermined frequency f on the sample;
  • a probe light source for irradiating visible light onto the sample;
  • a detector for detecting light reflected by the probe light source and reflected from the surface of the sample;
  • a control unit and an image processing unit at multiple times of a period in which the sample is temperature-modulated by irradiation of the pump laser beam.
  • the apparatus further includes a light splitter, and transmits the beam emitted from the probe light source to the sample and delivers the beam transmitted from the sample to the detector.
  • a light splitter transmits the beam emitted from the probe light source to the sample and delivers the beam transmitted from the sample to the detector.
  • the probe beam irradiation area is acquired at a time without a separate scan, thereby greatly reducing the imaging time (several seconds or more), and the probe beam and the pump beam. Since high-precision light alignment of the liver is not required, there is an effect that the defect site can be identified more quickly.
  • FIG. 1 is a flowchart illustrating a method of detecting microdefects according to an embodiment of the present invention.
  • FIG. 2 is a schematic structural diagram of a system for implementing a method for detecting microdefects of the present invention.
  • 3 to 5 are views for explaining a method of irradiating a sample to the pump light source according to the present invention.
  • FIG. 6 is a photograph showing an example of detecting impurities in a uniform medium using a method for detecting microdefects according to an embodiment of the present invention.
  • Figure 7 is a photograph showing the results confirmed through the system for the micro-defects inside the uniform PDMS produced additionally.
  • FIG. 1 is a flowchart illustrating a method of detecting microdefects according to an embodiment of the present invention.
  • the defect in the sample absorbs the pump beam and the absorbed light energy is converted into thermal energy and transferred around the defect.
  • This thermal energy increases the temperature around the defect, which results in a change in refractive index (thermal lens effect). Therefore, as a result, the change in the refractive index leads to a change in the light reflection intensity, and the relationship between the relative change in the light reflection intensity and the temperature change can be expressed as follows.
  • ⁇ R, R, , ⁇ T represent the change of light reflection intensity, background reflection intensity, heat reflection correction coefficient, and temperature change of sample surface, respectively.
  • One feature of the present invention is in determining the defect position, so that the relative reflectance change amount ⁇ R / R can be used as a parameter for measuring the defect position.
  • the probe beam can be used to measure it.
  • the sample reflected light can be detected by a CCD camera which is recondensed by the objective and operates at a frequency of 4f.
  • FIG. 2 is a schematic structural diagram of a system for implementing a method for detecting microdefects of the present invention.
  • thermal reflection microscopy is an optical technique for measuring the microscopic distribution of thermal changes in an optoelectronic circuit, which can calculate the actual temperature by measuring the relative reflection intensity change of the sample caused by the temperature change.
  • a band pass filter 270 in front of the CCD camera to block the pump beam reflected light by the sample.
  • the reflected light intensity recorded on the CCD arbitrary pixels (x, y) can be expressed as follows.
  • Is the reflectivity of the sample Represents the change in the relative reflection intensity of the sample due to pump beam excitation, Denotes the phase retardation values caused by the modulation frequency and the optical thermal modulation of the reflected beam, respectively. Since the CCD camera is synchronized with the pump beam, it is possible to extract only the relative reflectance variation from the reflected light intensity recorded in the CCD camera by using homodyne lock-in detection, which is known as a low frequency signal demodulation technique. .
  • the system of the present invention includes a probe light source 100, a pump light source 120, a detector 300, a controller, and an image processor 400, and further includes an optical splitter 250.
  • the beam emitted from 100 may be transferred to the sample, and the beam transmitted from the sample may be transferred to the detector 300.
  • various lenses C and L may be disposed at the front end of the light source or the detector to assist in converging light.
  • the probe light source 100 is a light source that provides light in which light rays having a plurality of wavelengths are mixed in the visible light wavelength region.
  • the type includes a wavelength filter (not shown) that selects only a predetermined wavelength together with a light source capable of obtaining a wide wavelength line width such as a white light, an LED, a solid light source having a broad wavelength line width, or a line width of about 10 nm to 50 nm. LEDs having a specific wavelength band can be used.
  • the pump light source 120 is for irradiating a sample with a beam of frequency f, and may be irradiated using a laser diode of 808 nm. It is, of course, also possible to use a multi-mode fiber or a bundle of fiber to guide the pump light source 120 to the sample.
  • the pump light source 120 may be configured using a wavelength tunable laser diode and a wavelength selection filter (not shown) to irradiate beams of various wavelengths. That is, more effective defect imaging can be realized by selecting a wavelength having good transmittance and light absorption by irradiating beams of various wavelengths and using a filter for wavelength selection.
  • the stage Z-axis scan is performed.
  • Three-dimensional defect information of the sample can be implemented. In the case of a large area sample, this process is followed by a scan of the transverse axis of the sample stage, thereby making it possible to obtain three-dimensional defect information on the entire area of the sample. In the case of a large area, it is possible to implement three-dimensional defect information on the entire area of the sample by stitching by moving the sample stage horizontally by one step.
  • the beam irradiated to the surface light source from the pump light source 120 enables to intensively obtain information about a certain depth in the depth direction inside the sample (for example, a thin film), and relatively outside the corresponding depth There is a vulnerable problem. Therefore, it is also possible to scan in the depth direction in such a way that the pump light source 120 adjusts the depth irradiated in the sample. Specifically, by adjusting the distance between the pump light source 120, the condenser lens 295, and the sample 500, a focal plane in which the beam irradiated from the pump light source 120 is mainly intensively irradiated deeply. It is possible to change in the direction.
  • changing the wavelength of the pump light source 120 to change the depth irradiated intensively in the sample it is possible to ensure whether the internal defects in the three-dimensional image.
  • changing the wavelength of the pump light source has an effect of changing the image plane according to the wavelength when the lens is used, but the light absorption of the defect is changed according to the wavelength, so it is difficult to obtain the same defect information.
  • the detector 300 may include a plurality of optical signal detectors including a charged coupled device (CCD), a photo detector, an avalanche photo diode (APD), and a photo multiplier tube (PMT).
  • CCD charged coupled device
  • APD avalanche photo diode
  • PMT photo multiplier tube
  • the system controller and the image processor 400 generate a signal for synchronizing the pump light source 120 and the detector 300, and are composed of hardware and software for processing the measured image information.
  • the phase lock nib is applied by applying an optical signal that is a sample, and simultaneously illuminating the object with visible light through an optical microscope to detect the distribution of reflected light, for example, by using a CCD camera.
  • the exothermic distribution of the object is measured by measuring by means of law.
  • the sample is temperature-modulated by the pump beam at a particular frequency f, with heating and cooling repeated periodically.
  • periodic heating and cooling drive signals cause periodic temperature changes around defects in the sample.
  • the CCD which is the detector 300 can detect the light reflected from the sample.
  • the detector 300 is triggered by multiple times (eg, 4 times) the frequency that modulates the sample, thereby generating a series of images multiple times (eg, 4 times) within one period of temperature modulation of the sample. It can be secured.
  • the data secured through the CCD is sent to the controller and the image processor 400 to process the data.
  • FIG. 3 to 5 are views for explaining a method of irradiating a sample to the pump light source according to the present invention.
  • FIG. 3 illustrates a case where the pump light source is irradiated in an off-axis manner
  • FIG. 4 illustrates a case where the pump light source is irradiated in a collinear manner
  • FIG. 5 illustrates a case where the pump light source is irradiated in an inverted manner.
  • FIG. 6 are photographs showing an example of detecting impurities in a uniform medium using a method for detecting microdefects according to an embodiment of the present invention.
  • a PDMS polydimethylsiloxane
  • FIG. 6 (b) is a light heat reflection image when the pump beam is operated
  • FIG. 6 (c) is a light heat reflection image when the pump beam is turned off. Indicates.
  • the image acquisition time was about 50 seconds after 50 averaging processes and the acquired image size was 200 ⁇ m (X) ⁇ 148 ⁇ m (Y).
  • Figure 7 is a photograph showing the result of confirming the micro-defects inside the uniform PDMS produced further through the system. 7 is a result of detecting the micro defects in the PDMS for each depth, (a), (c) is an optical microscope image and a light-heat reflection image corresponding to the optical microscopy image at a depth of 15 ⁇ m, 20 ⁇ m from the PDMS surface is (b), (d )to be. Submicron impurities are more clearly displayed in the expanded rectangular box.
  • FIGS. 7 (a) and 7 (c) are optical microscopic images at depths of 15 ⁇ m and 20 ⁇ m from the PDMS surface, respectively, and as shown in the drawing, no defects appear to the naked eye. However, during pump beam operation, locally located submicron impurities (enlarged box markings) were found at each position, as shown in FIGS. 7 (b) and 7 (d).
  • the present invention relates to a method and apparatus for detecting submicron micro defects in a sample, by applying a two-dimensional image sensor-based heat reflection microscopy technique, by measuring a relative change in reflectance caused by the photothermal effect of impurities, where Can be imaged.
  • image acquisition time is tens of times faster than conventional detection systems, and a separate optical alignment process is not required for defect measurement, so that defect inspection can be performed more quickly.
  • the three-dimensional defect inspection can be performed much faster than the conventional inspection equipment of the scan driving method, which can be said to be of great technical value and industrial application.

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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)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

Abstract

La présente invention porte sur un procédé de détection de microdéfauts, comprenant les étapes de : irradier un faisceau laser de pompage d'une fréquence constante sur un échantillon ; changer une intensité de réflexion périodique en permettant à la température d'une surface défectueuse de changer en raison d'un effet photothermique d'un défaut dans une zone sur laquelle le faisceau laser de pompage est irradié ; et mesurer un changement de l'intensité de réflexion par irradiation d'un faisceau de sonde sur l'échantillon.
PCT/KR2013/010798 2012-11-27 2013-11-26 Procédé et dispositif de détection de microdéfauts Ceased WO2014084575A1 (fr)

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KR10-2012-0135493 2012-11-27
KR1020120135493A KR20140067793A (ko) 2012-11-27 2012-11-27 미세결함을 검출하는 방법 및 장치

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CN104882394B (zh) * 2015-06-07 2017-10-17 上海华虹宏力半导体制造有限公司 颗粒物缺陷的监控方法
KR102074593B1 (ko) * 2018-11-09 2020-02-06 한국기초과학지원연구원 레이저 스캐닝 기반 현미경 장치 및 이의 동작 방법
JP2022539847A (ja) 2019-07-09 2022-09-13 ビーコ インストゥルメント インク 溶融検出システム及びその使用方法
US20250327758A1 (en) * 2024-04-19 2025-10-23 Onto Innovation Inc. Metrology based on time resolved non-acoustic signals

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US20050200850A1 (en) * 2002-03-01 2005-09-15 Borden Peter G. Apparatus and method for measuring a property of a layer in a multilayered structure
JP2004311580A (ja) * 2003-04-03 2004-11-04 Toshiba Corp 半導体評価装置及び半導体評価方法
JP2006319193A (ja) * 2005-05-13 2006-11-24 Nec Electronics Corp 検査装置及び方法
KR100794555B1 (ko) * 2006-08-10 2008-01-17 한국전기연구원 다중 파장 광원 장치 및 이를 이용한 생체 조직의 광학특성 분석 시스템

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SMITH, W.L. ET AL.: "Direct Measurement of Stress-Induced Void Growth by Thermal Wave Modulated Optical Reflectance Imaging.", IEEE /IRPS., March 1990 (1990-03-01), pages 200 - 208 *

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