CN118243274B - Optical nondestructive testing system and method for residual stress of substrate - Google Patents
Optical nondestructive testing system and method for residual stress of substrateInfo
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- CN118243274B CN118243274B CN202410536212.5A CN202410536212A CN118243274B CN 118243274 B CN118243274 B CN 118243274B CN 202410536212 A CN202410536212 A CN 202410536212A CN 118243274 B CN118243274 B CN 118243274B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/0047—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes measuring forces due to residual stresses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/241—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet by photoelastic stress analysis
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
本发明公开了一种衬底残余应力的光学无损检测系统及方法，系统包括光源、调制模块、分光镜、样品台、解调模块、图像采集模块；光源、调制模块和分光镜沿着直线A依次布置，分光镜、解调模块和图像采集模块沿着直线B依次布置，直线A垂直于直线B，样品台与分光镜的连线同时垂直于直线A和直线B。测量时，光源发出的激光经过调制模块、分光镜、待测材料和解调模块后到达图像采集模块，被采集形成一系列干涉图像，通过光强信号、光学元器件参数与等倾角和相位差的关系，计算出衬底残余应力的方向和大小。本发明通过垂直入射式反射光弹光路检测系统，改进现有的反射式光弹系统因小角度入射引起的系统误差，实现衬底残余应力的高精度检测。
This invention discloses an optical non-destructive testing system and method for residual stress in substrates. The system includes a light source, a modulation module, a beam splitter, a sample stage, a demodulation module, and an image acquisition module. The light source, modulation module, and beam splitter are arranged sequentially along line A, and the beam splitter, demodulation module, and image acquisition module are arranged sequentially along line B. Line A is perpendicular to line B, and the line connecting the sample stage and the beam splitter is perpendicular to both lines A and B. During measurement, the laser emitted by the light source passes through the modulation module, beam splitter, material under test, and demodulation module before reaching the image acquisition module, where it is acquired to form a series of interference images. The direction and magnitude of the residual stress in the substrate are calculated by considering the relationship between the light intensity signal, optical component parameters, and the inclination angle and phase difference. This invention improves upon existing reflective photoelastic systems by using a vertically incident reflective photoelastic optical path detection system, overcoming the systematic errors caused by small-angle incident light, and achieving high-precision detection of residual stress in substrates.
Description
Technical Field
The invention relates to the technical field of optical detection, in particular to an optical nondestructive detection system and method for residual stress of a substrate.
Background
Currently, common methods for realizing optical nondestructive detection of residual stress of a substrate are mainly Stoney curvature method, raman spectroscopy, X-ray diffraction method, photoelastic method and the like.
The Stoney curvature method is used for indirectly measuring the overall stress distribution of the substrate by measuring the curvature change before and after the substrate coating and combining a mechanical model between the curvature and the residual stress, is generally suitable for a structure of the substrate and a single-layer coating, and is also broken to the precision of local stress and small-size parts. The Raman spectroscopy deduces the distribution condition of the residual stress of the sample by measuring the movement of a Raman spectrum peak value of the sample under the influence of the residual stress, and can realize the on-line monitoring of the single-point stress of the sample. The X-ray diffraction method has high accuracy and high speed, is widely used in the fields of residual stress measurement, phase analysis and the like, but has low penetration depth. The photoelastic method obtains an interference image by utilizing the photoelastic effect of the substrate, and obtains a phase difference distribution diagram and a principal stress direction distribution diagram caused by stress through a phase shift technology. The photoelastic effect is a phenomenon that one beam of light enters a photoelastic model with a double refraction effect to generate two beams of polarized light respectively, wherein the two beams of light with different polarization states are emitted from the same point on the upper surface of the model and interfere with each other in an analyzer. The phase shift method is a technique of obtaining a plurality of interference images with different phase differences by rotating the angles of certain optical elements in an optical system, so as to obtain an isocline phase and an isocline phase through an equation set. The traditional reflective photoelastic system adopts a small-angle incidence mode, and the existing national standard GB/T30020-2023 adopts a 45-degree incidence angle to detect glass defects. In the reflective photoelastic system, when the incident angle is not 0, circularly polarized light incident on the surface of the material is delayed in phase to become elliptically polarized light, and small-angle incidence causes thin film interference to cause errors to influence the detection precision.
Disclosure of Invention
The invention aims to solve the problem that the reflection type photoelastic system in the prior art can cause errors due to small-angle incidence.
The technical scheme adopted for solving the technical problems is that an optical nondestructive testing system for substrate residual stress is provided, and comprises a light source, a modulation module, a spectroscope, a sample stage, a demodulation module and an image acquisition module;
The light source, the modulation module and the spectroscope are sequentially arranged along the straight line A, the spectroscope, the demodulation module and the image acquisition module are sequentially arranged along the straight line B, the straight line A is perpendicular to the straight line B, the connecting line of the sample table and the spectroscope is perpendicular to the straight line A and the straight line B at the same time, laser emitted by the light source reaches a material to be detected which is placed on the sample table after passing through the modulation module and the spectroscope, and reflected light of the material to be detected reaches the image acquisition module after passing through the spectroscope and the demodulation module and is acquired to form a photoelastic image.
Preferably, the modulation module comprises a first linear polarizer and a first wave plate, and the light source, the first linear polarizer, the first wave plate and the spectroscope are sequentially arranged along a straight line A.
Preferably, the demodulation module comprises a second wave plate and a second linear polarizer, and the spectroscope, the second wave plate, the second linear polarizer and the image acquisition module are sequentially arranged along a straight line B.
Preferably, the first wave plate and the second wave plate are 1/4 wave plates
Preferably, the image acquisition module comprises a camera and a matched lens, and the camera adopts a CCD camera or a CMOS camera.
The invention also provides an optical nondestructive testing method for the residual stress of the substrate, which is based on any one of the optical nondestructive testing systems and comprises the following steps:
arranging an optical nondestructive testing system, and placing a material to be tested on a sample stage;
the light source emits laser, and the laser reaches the material to be detected and is reflected to the image acquisition module to form a photoelastic image;
Extracting phase difference and equal inclination angles from the photoelastic image;
the magnitude of the principal stress difference and the principal stress direction are calculated from the phase difference and the isocline.
Preferably, the arrangement detection system specifically comprises:
the modulation module comprises a first linear polaroid and a first wave plate, and the light source, the first linear polaroid, the first wave plate and the spectroscope are sequentially arranged along a straight line A;
the demodulation module comprises a second wave plate and a second linear polarizer, the spectroscope, the second wave plate, the second linear polarizer and the image acquisition module are sequentially arranged along a straight line B, a polarization angle alpha of the first linear polarizer and a fast axis angle zeta of the first wave plate are set, the fast axis angle zeta of the first wave plate is an included angle between a fast axis of the first wave plate and a reference axis, and the reference axis is perpendicular to the propagation direction of detection light and parallel to a tabletop;
Setting an initial value of an analysis angle beta of the second linear polaroid and an initial value of a fast axis angle gamma of the second wave plate, wherein the fast axis angle gamma of the second wave plate is an included angle between a fast axis of the second wave plate and a reference axis;
the rotational speeds of the second linear polarizer and the second wave plate are set.
Preferably, the laser reaches the material to be detected and is reflected to the image acquisition module to form a photoelastic image, specifically, the image acquisition module continuously acquires the photoelastic image within a certain time to form a photoelastic image sequence.
Preferably, the extracting the phase difference and the isocratic angle from the photoelastic image specifically includes:
six photoelastic images are collected, light intensity signals are extracted for each photoelastic image, and the relation between the light intensity signals and the phase difference delta and the equal inclination angle theta is obtained as follows:
where I i denotes the light intensity of the I-th image.
Preferably, the calculating the residual stress principal stress according to the phase difference and the isocline includes:
Converting the equal inclination angle into a main stress direction through a stress circle model, and converting the phase difference into a main stress difference through a stress-optical theorem, wherein the main stress difference is expressed as:
wherein d is the thickness of the material to be measured, (c 1-c2) is the stress optical constant, which is determined by the material to be measured, delta represents the optical path difference, delta represents the phase difference, and lambda is the laser wavelength emitted by the light source. The invention has the following beneficial effects:
(1) The vertical incidence and reflection photoelastic light path is adopted, so that the system error caused by small-angle incidence of the existing reflection photoelastic system is avoided, and the high-precision detection of the residual stress of the substrate is realized;
(2) The vertical incidence type reflection photoelastic system provided by the invention can avoid negative effects brought by other test systems, has no damage to the material to be tested, can fully characterize the stress distribution condition of the material, and is particularly suitable for stress test of a semiconductor substrate.
The present invention will be described in further detail with reference to the drawings and examples, but the present invention is not limited to the examples.
Drawings
FIG. 1 is a system block diagram of an embodiment of the present invention;
fig. 2 is a method step diagram of an embodiment of the present invention.
Detailed Description
Referring to fig. 1, a system structure diagram of an embodiment of the invention is shown, and the system structure diagram comprises a light source, a modulation module, a spectroscope, a sample stage, a demodulation module and an image acquisition module, wherein the sample stage is used for placing a material to be detected, the light source, the modulation module and the spectroscope are sequentially arranged along a straight line A, the spectroscope, the demodulation module and the image acquisition module are sequentially arranged along a straight line B, the straight line A is perpendicular to the straight line B, the connecting line of the sample stage and the spectroscope is perpendicular to the straight line A and the straight line B at the same time, and laser emitted by the light source reaches the image acquisition module after passing through the modulation module, the spectroscope, the material to be detected and the demodulation module and is acquired to form a photoelastic image.
Specifically, the modulation module comprises a polarizer P and a first 1/4 wave plate Q P, laser emitted by the light source firstly transmits linearly polarized light of the polarizer P, and circularly polarized light is obtained through the first 1/4 wave plate Q O, wherein the circularly polarized light is modulated light, and is used for measuring the residual stress of a substrate of a sample to be measured.
Specifically, the demodulation module comprises a second 1/4 wave plate Q A and an analyzer A, the modulated light reaches the material to be detected, is reflected and enters the demodulation module after passing through a spectroscope B, specifically, the 90-degree phase difference introduced by the first 1/4 wave plate Q P in the demodulation module is restored through the second 1/4 wave plate Q A, and then the demodulation function is completed through the analyzer A, so that the demodulated light is obtained.
Specifically, the image acquisition module comprises a camera and a matched lens, the embodiment adopts a CCD camera, and the demodulated light rays are subjected to field expansion through the matched lens and then are acquired into a photoelastic image by the CCD camera.
Referring to fig. 2, a method step diagram of an embodiment of the present invention includes the following steps:
Specifically, the image acquisition module in S202 acquires a photoelastic image, and in this embodiment, a detection system is arranged by using the second 1/4 wave plate Q A and the offset S201, and a material to be detected is placed on a sample stage;
s202, a light source emits laser, and the laser reaches a material to be detected and is reflected to an image acquisition module to form a photoelastic image;
s203, extracting phase difference and equal inclination angles from the photoelastic image;
s204, calculating the magnitude of the main stress difference and the main stress direction according to the phase difference and the equal inclination angle.
Specifically, the arrangement detection system of S201 includes setting a polarization angle α of the polarizer P to 90 degrees, setting an included angle ζ between the fast axis of the first 1/4 wave plate Q P and the reference axis to 45 degrees, setting an included angle θ between the optical axis of the substrate generated by stress and the reference axis, setting an initial value of the included angle γ between the fast axis of the second 1/4 wave plate Q A and the reference axis to 0 degrees, and setting an initial value of the polarization analyzer a to 0 degrees. Rotating the second 1/4 wave plate Q A and the analyzer A at a constant rate ratio of-0.5, i.e., the second 1/4 wave plate Q A and analyzer A are rotated at constant-pi/12 (radians/frame) and pi/6 (radians/frame), respectively, the camera is capable of recording a series of interference images that vary over time. At this time, the light intensity signal output by the camera is the integral of the instantaneous light intensity related to the rotation angle of the analyzer in the exposure time, and the upper and lower limits of the integral are the initial angle and the final angle of the analyzer in the exposure time.
The mirror a rotates by 2 pi as one acquisition period, so that the camera needs to collect 6 images in one acquisition period, and each image has a respective output light intensity equation.
Specifically, in S203, an equation about the light intensity signal, the phase difference and the equal inclination angle is obtained according to the light intensity signal, the polarization angle α of the first linear polarizer, the fast axis angle ζ of the first wave plate, the polarization angle β of the second linear polarizer, and the fast axis angle γ of the second wave plate, where the polarization angle β of the second linear polarizer and the fast axis angle γ of the second wave plate corresponding to each photoelastic image are calculated according to the initial value of the polarization angle β of the second linear polarizer, the initial value of the fast axis angle γ of the second wave plate, the rotation speed of the second linear polarizer, the rotation speed of the second wave plate, and the acquisition time of the photoelastic image. The unknown number is only the phase difference of the material to be measured caused by stress and the inclination angles of interference images, etc., the light intensity equations corresponding to all the photoelastic images of the photoelastic image sequence are formed into an overdetermined equation set, and the overdetermined equation set is brought into known parameters, and finally the obtained equation set is expressed as
Wherein, I i represents the light intensity of the ith image, I a represents the light intensity after passing through the polarizer, I b represents the ambient light intensity, delta represents the phase difference caused by the stress of the material to be measured, and theta represents the equal inclination angle.
The relation between the phase difference, interference image and other inclination angles of the material to be detected caused by stress and the output light intensity of 6 images in one acquisition period can be solved by the equation set as follows:
specifically, in S204, the equal inclination angle θ may be converted into a residual stress main stress direction of the material to be measured through a stress round model, and the phase difference δ may be converted into a main stress difference of the material to be measured through a stress-optical theorem.
Specifically, the phase difference is converted into the principal stress difference by the stress-optics theorem, expressed as:
Wherein d is the thickness of the material to be measured, (c 1-c2) is the stress optical constant, which is determined by the material to be measured, delta represents the optical path difference, delta represents the phase difference, and lambda is the laser wavelength emitted by the light source.
Therefore, the main stress difference distribution and the main stress direction distribution of the material to be tested can be obtained.
Therefore, the vertical incidence type reflected photoelastic light path detection system can improve the systematic error caused by small-angle incidence of the existing reflected photoelastic system and realize high-precision detection of the residual stress of the substrate.
The foregoing is only illustrative of the present invention and is not to be construed as limiting thereof, but rather as various modifications, equivalent arrangements, improvements, etc., within the spirit and principles of the present invention.
Claims (4)
1. The optical nondestructive testing method for the residual stress of the substrate is characterized in that the optical nondestructive testing system comprises a light source, a modulation module, a spectroscope, a sample stage, a demodulation module and an image acquisition module, wherein the light source, the modulation module and the spectroscope are sequentially arranged along a straight line A, the sample stage, the spectroscope, the demodulation module and the image acquisition module are sequentially arranged along a straight line B, the straight line A is perpendicular to the straight line B, laser emitted by the light source passes through the modulation module and the spectroscope and then reaches a material to be tested which is placed on the sample stage, reflected light of the material to be tested passes through the spectroscope and the demodulation module and then reaches the image acquisition module, and the reflected light of the material to be tested is acquired to form a photoelastic image;
the optical nondestructive testing method comprises the following steps:
arranging an optical nondestructive testing system, and placing a material to be tested on a sample stage;
the light source emits laser, and the laser reaches the material to be detected and is reflected to the image acquisition module to form a photoelastic image;
Extracting phase difference and equal inclination angles from the photoelastic image;
Calculating the magnitude of the main stress difference and the main stress direction according to the phase difference and the equal inclination angle;
the modulation module comprises a first linear polaroid and a first wave plate, and the light source, the first linear polaroid, the first wave plate and the spectroscope are sequentially arranged along a straight line A;
the demodulation module comprises a second wave plate and a second linear polarizer, the spectroscope, the second wave plate, the second linear polarizer and the image acquisition module are sequentially arranged along a straight line B, a polarization angle alpha of the first linear polarizer and a fast axis angle zeta of the first wave plate are set, the fast axis angle zeta of the first wave plate is an included angle between a fast axis of the first wave plate and a reference axis, and the reference axis is perpendicular to the propagation direction of detection light and parallel to a tabletop;
Setting an initial value of an analysis angle beta of the second linear polaroid and an initial value of a fast axis angle gamma of the second wave plate, wherein the fast axis angle gamma of the second wave plate is an included angle between a fast axis of the second wave plate and a reference axis;
setting the rotation speeds of the second linear polaroid and the second wave plate;
The phase difference and the isocratic angle are extracted from the photoelastic image, and specifically:
six photoelastic images are collected, light intensity signals are extracted for each photoelastic image, and the relation between the light intensity signals and the phase difference delta and the equal inclination angle theta is obtained as follows:
Wherein I i represents the light intensity of the I-th image, i=1, 2,3,4,5,6;
the method for calculating the magnitude and the main stress direction of the main stress difference according to the phase difference and the equal inclination angle comprises the following steps:
Converting the equal inclination angle into a main stress direction through a stress circle model, and converting the phase difference into a main stress difference through a stress-optical theorem, wherein the main stress difference is expressed as:
Wherein d is the thickness of the material to be measured, delta represents the optical path difference, delta represents the phase difference, and lambda is the laser wavelength emitted by the light source.
2. The method of claim 1, wherein the first wave plate and the second wave plate are each 1/4 wave plates.
3. The method of claim 1, wherein the image acquisition module comprises a camera and a mating lens, and the camera is a CCD camera or a CMOS camera.
4. The method for optical nondestructive testing of residual stress of substrate according to claim 1, wherein the laser reaches the material to be tested and is reflected to the image acquisition module to form a photoelastic image, specifically, the image acquisition module continuously acquires the photoelastic image within a certain time to form a photoelastic image sequence.
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| CN110954253A (en) * | 2019-10-25 | 2020-04-03 | 华南理工大学 | Stress measurement method and stress measurement light path device |
| CN113340810A (en) * | 2021-05-27 | 2021-09-03 | 彭海鲸 | Semiconductor material stress measurement system and method based on photoelastic modulation technology |
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| CN201050980Y (en) * | 2007-05-21 | 2008-04-23 | 天津市奥特梅尔光电科技有限公司 | Dual axis photoelectric autocollimation |
| CN104406544B (en) * | 2014-11-20 | 2017-04-12 | 北京航空航天大学 | Detection device and method for eliminating photoelastic modulator and environment influence based on double beam difference |
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| CN110954253A (en) * | 2019-10-25 | 2020-04-03 | 华南理工大学 | Stress measurement method and stress measurement light path device |
| CN113340810A (en) * | 2021-05-27 | 2021-09-03 | 彭海鲸 | Semiconductor material stress measurement system and method based on photoelastic modulation technology |
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