Focusing control method for laser scattering defect detection and defect detection system

Abstract

The invention provides a focusing control method for laser scattering defect detection and a defect detection system, and relates to the field of automatic focusing control for laser scattering defect detection. According to the method, a position sensitive detector is ingeniously placed at the position where the position sensitive detector and the surface of a wafer are in a conjugate object image relation; the position of a light spot on the position sensitive detector is only influenced by the height of the surface of the wafer, and a shading element can be used for avoiding the influence of the lower surface of the transparent wafer on a focusing signal. And finally, the light reflected from the surface of the object to be measured is divided into two beams by using a spectroscope, one beam forms a focusing signal on a position sensitive detector and then controls the height of a rotary lifting platform to realize automatic focusing, and the other beam is used for realizing measurement of morphology corresponding to the reflection intensity and the reflection angle of the surface of the wafer. And finally, imaging and detection of wafer surface defects are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser scattering defect detection control, and in particular to a focusing control method for laser scattering defect detection and a defect detection system. BACKGROUND

[0002] Laser scattering method is a high-sensitivity non-contact detection technology based on the principle of light and matter interaction. When laser irradiates the surface or internal structure of the sample, light will scatter, reflect, interfere or diffract, etc. Through the analysis of the spatial distribution, intensity, phase or time characteristics of the scattering signal, the structural characteristics, material composition and defect information of the measured sample can be obtained.

[0003] With the continuous improvement of manufacturing precision and detection automation level, laser scattering optical detection system is developing towards high resolution, high stability and high throughput. In this process, the automatic focusing ability of the system becomes a key link, which directly affects the acquisition quality of the scattering signal and the overall detection performance. Especially in the scene of high-speed scanning, inconsistent sample height or multiple detection areas, the traditional manual focusing or fixed focus method has been difficult to meet the dual requirements of precision and real-time. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a focusing control method for laser scattering defect detection and a defect detection system. The method ingeniously places a position sensitive detector at a position conjugate to the wafer surface, so that the spot position on the position sensitive detector is only affected by the height of the wafer surface, thereby achieving automatic focusing by controlling the height of the rotating lifting platform.

[0005] In a first aspect, the present application provides a focusing control method for laser scattering defect detection, which is applied to a laser scattering defect detection system. The laser scattering defect detection system at least includes a laser light source, a rotating lifting platform, a first converging lens and a position sensitive detector. The method comprises: When the measured object is placed on the rotating lifting platform, the rotating lifting platform is controlled to rotate, and the laser light source is controlled to emit a laser beam to the measured object, so that the laser beam is reflected to the position sensitive detector. The reflecting surface of the measured object and the receiving surface of the position sensitive detector are conjugate to each other with respect to the first converging lens. The focusing spot corresponding to the laser beam in the position sensitive detector is acquired in real time, and the focusing signal of the measured object is determined by using the position parameter corresponding to the focusing spot. The lifting height corresponding to the rotating lifting platform is determined according to the focusing signal, and the lifting control instruction corresponding to the rotating lifting platform is determined based on the lifting height. The rotating lifting platform is controlled by the lifting control instruction to reach the lifting height.

[0006] Optionally, the step of acquiring the focused light spot corresponding to the laser beam in the position sensitive detector in real time and determining the focusing signal of the object to be measured by using the position parameter corresponding to the focused light spot comprises: controlling the position sensitive detector to acquire the focused light spot after the laser beam is reflected by the rotating lifting platform in real time; determining the position distance between the focused light spot and the center point of the position sensitive detector by using the position parameter corresponding to the focused light spot; determining the focusing signal corresponding to the object to be measured based on the position distance.

[0007] Optionally, the step of determining the lifting height corresponding to the rotating lifting platform according to the focusing signal and determining the lifting control instruction corresponding to the rotating lifting platform based on the lifting height comprises: acquiring the relationship curve between the upper surface height of the object to be measured and the focusing signal of the position sensitive detector; acquiring the upper surface height corresponding to the focusing signal by using the relationship curve, and determining the lifting height corresponding to the rotating lifting platform according to the upper surface height; determining the lifting control instruction corresponding to the rotating lifting platform based on the rotation parameter corresponding to the rotating lifting platform and the lifting height.

[0008] Optionally, the step of determining the lifting control instruction corresponding to the rotating lifting platform based on the rotation parameter corresponding to the rotating lifting platform and the lifting height comprises: determining the acquisition time corresponding to the lifting height according to the rotation parameter corresponding to the rotating lifting platform; calculating the average height value corresponding to the lifting height under the acquisition time, and determining the lifting control instruction by using the acquisition time and the average height value.

[0009] Optionally, the step of determining the lifting height corresponding to the rotating lifting platform according to the focusing signal and determining the lifting control instruction corresponding to the rotating lifting platform based on the lifting height comprises: acquiring the relationship curve between the upper surface height of the object to be measured and the focusing signal of the position sensitive detector; acquiring the upper surface height corresponding to the focusing signal by using the relationship curve, and determining the lifting height corresponding to the rotating lifting platform according to the upper surface height; determining the measurement plane of the object to be measured, and calculating the height difference between the measurement plane and the upper surface of the object to be measured; determining the lifting control instruction corresponding to the rotating lifting platform based on the lifting height and the height difference.

[0010] In a second aspect, the present application provides a focusing control device for laser scattering defect detection, which is applied to a laser scattering defect detection system; the laser scattering defect detection system at least comprises a laser light source, a rotating lifting platform, a first converging lens and a position sensitive detector; The device comprises: a laser emission control module, configured to control the rotating lifting platform to rotate and control the laser light source to emit a laser beam to the object to be detected after detecting that the object to be detected is placed on the rotating lifting platform, so that the laser beam is reflected to the position sensitive detector; wherein the reflecting surface of the object to be detected and the receiving surface of the position sensitive detector are conjugate with respect to the first converging lens; a focusing signal control module, configured to acquire a focusing spot corresponding to the laser beam in the position sensitive detector in real time, and determine a focusing signal of the object to be detected by using a position parameter corresponding to the focusing spot; a control instruction determination module, configured to determine a lifting height corresponding to the rotating lifting platform according to the focusing signal, and determine a lifting control instruction corresponding to the rotating lifting platform based on the lifting height; a lifting control execution module, configured to control the rotating lifting platform to reach the lifting height by using the lifting control instruction.

[0011] In a third aspect, the present application provides a defect detection system, which comprises a laser light source, a rotating lifting platform, a first converging lens and a position sensitive detector; wherein the defect detection system adopts the focusing control method for laser scattering defect detection mentioned in the first aspect in the process of performing laser scattering defect detection on an object to be detected; The laser beam emitted by the laser light source irradiates the object to be detected in the rotating lifting platform, and is focused to the position sensitive detector after being reflected by the reflecting surface of the object to be detected; wherein the reflecting surface of the object to be detected and the receiving surface of the position sensitive detector are conjugate with respect to the first converging lens; The position sensitive detector is configured to generate a focusing signal of the object to be detected according to a position parameter corresponding to a focusing spot generated by the laser beam, and determine a lifting height corresponding to the rotating lifting platform based on the focusing signal; The rotating lifting platform is configured to control the rotating lifting platform to reach the lifting height according to a lifting control instruction corresponding to the lifting height.

[0012] Optionally, the defect detection system further comprises a mirror, a second converging lens, a beam splitter, a polarization beam splitter prism, a first detector and a second detector; The mirror is located between the laser light source and the second converging lens, and is configured to reflect the laser beam emitted by the laser light source to the object to be detected in the rotating lifting platform; The second converging lens is located between the mirror and the rotating lifting platform, and is configured to converge the laser beam so that the laser spot in the object to be detected is minimized; The light splitting mirror is located between the first converging lens and the position sensitive detector; the light splitting mirror is used for splitting the converging light beam after the first converging lens into a first laser beam and a second laser beam; the first laser beam irradiates to the position sensitive detector; the second laser beam irradiates to the polarizing beam splitter to form S polarized light and P polarized light, the S polarized light irradiates to the first detector, and the P polarized light irradiates to the second detector.

[0013] Optionally, the defect detection system further comprises a spatial light shielding element; the spatial light shielding element is arranged between the light splitting mirror and the position sensitive detector and is close to the position sensitive detector. The spatial light shielding element is used for shielding the reflected light formed by the laser beam under the lower surface of the transparent wafer when the object to be detected is a transparent wafer.

[0014] Optionally, the defect detection system further comprises a mirror, a second converging lens, a light splitting mirror, a polarizing beam splitter and a first detector. The mirror is located between the laser light source and the second converging lens, and the mirror is used for reflecting the laser beam emitted by the laser light source to the object to be detected in the rotating lifting platform. The second converging lens is located between the mirror and the rotating lifting platform, and the second converging lens is used for converging the laser beam to make the laser spot in the object to be detected smallest. The light splitting mirror is located between the first converging lens and the polarizing beam splitter, and the light splitting mirror is used for reflecting the converging light beam after the first converging lens to the polarizing beam splitter. The converging light beam irradiates to the polarizing beam splitter to form S polarized light and P polarized light, the S polarized light irradiates to the first detector, and the P polarized light irradiates to the position sensitive detector.

[0015] The embodiment of the present application provides a focusing control method and a defect detection system for laser scattering defect detection. The defect detection system comprises a laser light source, a rotating lifting platform, a first converging lens and a position sensitive detector. In the focusing control process of the defect detection system, when the object to be detected is placed on the rotating lifting platform, the rotating lifting platform is controlled to rotate, and the laser light source is controlled to emit a laser beam to the object to be detected, so that the laser beam is reflected to the position sensitive detector. The reflecting surface of the object to be detected and the receiving surface of the position sensitive detector are in conjugate relationship with the first converging lens. Then, the focusing spot corresponding to the laser beam in the position sensitive detector is acquired in real time, the focusing signal of the object to be detected is determined by using the position parameter corresponding to the focusing spot, the lifting height corresponding to the rotating lifting platform is determined according to the focusing signal, the lifting control instruction corresponding to the rotating lifting platform is determined based on the lifting height, and finally the lifting control instruction is used to control the rotating lifting platform to reach the lifting height. The position sensitive detector is placed at a position in conjugate relationship with the wafer surface, so that the spot position on the position sensitive detector is only affected by the height of the wafer surface, and automatic focusing is realized by controlling the height of the rotating lifting platform. In addition, the defect detection system can use a light shielding element to avoid the influence of the lower surface of the transparent wafer on the focusing signal. Finally, the light reflected from the surface of the object to be detected is divided into two beams by a beam splitter, one beam is used to form the focusing signal on the position sensitive detector to control the height of the rotating lifting platform to realize automatic focusing, and the other beam is used to realize the measurement of the corresponding morphology of the wafer surface reflection intensity and reflection angle, so that the imaging and detection of the wafer surface defects are realized.

[0016] Other features and advantages of the present application will be set forth in the descriptions below, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the structure particularly pointed out in the description, claims and drawings.

[0017] In order to make the above-mentioned objects, characteristics and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 A flowchart of a focusing control method for laser scattering defect detection provided by the embodiment of the present application; Figure 2 A flow chart of step S102 in a focusing control method for laser scattering defect detection provided by an embodiment of the present application; Figure 3 A flow chart of step S103 in a focusing control method for laser scattering defect detection provided by an embodiment of the present application; Figure 4 A relationship curve diagram in a focusing control method for laser scattering defect detection provided by an embodiment of the present application; Figure 5 A flow chart of step S303 in a focusing control method for laser scattering defect detection provided by an embodiment of the present application; Figure 6 A flow chart of step S103 in another focusing control method for laser scattering defect detection provided by an embodiment of the present application; Figure 7 A structural schematic diagram of a focusing control device for laser scattering defect detection provided by an embodiment of the present application; Figure 8 A structural schematic diagram of a first defect detection system provided by an embodiment of the present application; Figure 9 A structural schematic diagram of a second defect detection system provided by an embodiment of the present application; Figure 10 A structural schematic diagram of a third defect detection system provided by an embodiment of the present application; Figure 11 A structural schematic diagram of a fourth defect detection system provided by an embodiment of the present application; Figure 12 A detection principle schematic diagram of a fifth defect detection system provided by an embodiment of the present application.

[0020] Icon: 710 - laser emission control module; 720 - focusing signal control module; 730 - control instruction determination module; 740 - lifting control execution module; 100 - laser light source; 101 - reflecting mirror; 102 - second converging lens; 103 - first converging lens; 104 - beam splitter; 105 - polarization beam splitter prism; 106 - first detector; 107 - second detector; 110 - object to be detected; 120 - rotating lifting platform; 121 - movement axis; 130 - position sensitive detector; 140 - focusing point; 141 - first laser beam; 142 - second laser beam; 143 - central position of position sensitive detector; 300 - lower surface reflected light; 310 - spatial light shielding element; 500 - wafer surface; 510 - wafer lower surface; 520 - wafer inner layer. DETAILED DESCRIPTION

[0021] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0022] Laser scattering is a high-sensitivity non-contact detection technology based on the principle of light-matter interaction. When laser irradiates the surface or internal structure of a sample, light will undergo scattering, reflection, interference or diffraction, etc. By analyzing the spatial distribution, intensity, phase or time characteristics of the scattered signal, the structural characteristics, material composition and defect information of the measured sample can be obtained.

[0023] Laser scattering has the advantages of high resolution, non-destructive, fast response, and adaptability to various materials, and has been widely used in many high-tech fields. For example, in semiconductor manufacturing, laser scattering can be used for wafer surface roughness measurement, sub-micron particle contamination detection, defect identification and photoresist topography monitoring; in the field of thin films and coatings, multi-angle scattering measurement can realize non-destructive characterization of film thickness and multi-layer film structure; in the detection of particles and aerosols, by analyzing the laser scattering angle and intensity, the particle concentration and particle size distribution can be accurately measured, and it is widely used in air quality monitoring and clean room control; in addition, in the fields of precision manufacturing and biomedicine, laser scattering is also used for surface topography detection, cell analysis and protein aggregation detection, etc.

[0024] Autofocus technology plays a key role in high-precision applications such as microscopic imaging, semiconductor detection, and laser processing. Its core goal is to automatically adjust the focus position when the sample height changes, ensuring that the imaging or measurement is always in the best focus state. In the field of semiconductor detection, the commonly used real-time autofocus methods mainly include through-objective autofocus and laser triangulation autofocus.

[0025] Through-objective autofocus focuses laser or white light onto the sample surface through the objective lens, and uses the change in the reflection signal return path to determine the focus position. This method has the advantages of high precision, coaxial path, etc., and is suitable for high-resolution imaging scenarios such as confocal microscopy and high-numerical-aperture systems. However, its structure is relatively complex, requires high stability of the optical path, and is sensitive to sample reflectivity.

[0026] Laser triangulation uses an oblique laser to irradiate the sample, and calculates the height of the sample by detecting the offset of the reflection point on the detector. It has the advantages of fast response, simple structure and low cost, and is suitable for online detection or dynamic focusing system, but its measurement accuracy is limited. Moreover, because the focusing light path and the detection light path are independent of each other, the drift of the automatic focusing light path will lead to the failure of the detection system.

[0027] The semiconductor detection field also uses an asynchronous automatic focusing scheme, such as using a height detection probe to first measure the height of a typical point on the wafer, and then fitting the topography of the entire wafer as the height reference during wafer scanning. This non-real-time automatic focusing method is simple to operate, but cannot take into account the complex warping of the wafer, and the additional focusing scan also consumes time, resulting in a decrease in yield.

[0028] In summary, the prior art cannot simultaneously consider high precision, high speed and system simplification, so there is still a need to design a more real-time, compatible and robust automatic focusing method to meet the imaging or detection requirements in complex scenarios. Based on this, the focusing control method for laser scattering defect detection and the defect detection system disclosed in the embodiments of the present application ingeniously place the position sensitive detector in a position conjugate to the wafer surface, so that the position of the light spot on the position sensitive detector is only affected by the height of the wafer surface, thereby achieving automatic focusing by controlling the height of the rotating lifting platform.

[0029] In order to facilitate the understanding of the present embodiment, first, a focusing control method for laser scattering defect detection disclosed in the embodiments of the present application is described in detail. The method is applied to a laser scattering defect detection system; the laser scattering defect detection system at least includes: a laser light source, a rotating lifting platform, a first converging lens and a position sensitive detector. On this basis, as shown in Figure 1 the method comprises: Step S101: When it is detected that the object to be measured is placed on the rotating lifting platform, the rotating lifting platform is controlled to rotate, and the laser light source is controlled to emit a laser beam to the object to be measured, so that the laser beam is reflected to the position sensitive detector; wherein the reflecting surface of the object to be measured and the receiving surface of the position sensitive detector are conjugate to each other with respect to the first converging lens.

[0030] When it is detected that the object to be measured (such as a wafer, a semiconductor chip or other workpieces to be detected) is placed on the rotating lifting platform, the system first starts the rotating action of the rotating lifting platform, so that the reflecting surface of the object to be measured can be irradiated by the laser in a "scanning" manner; at the same time, the laser light source (such as a laser) is controlled to emit a laser beam, which is guided by the first converging lens and other optical elements, and irradiates the reflecting surface of the object to be measured.

[0031] It is emphasized here that the reflecting surface of the object to be measured and the receiving surface of the position sensitive detector are in a conjugate relationship with respect to the first converging lens. According to the principle of optical conjugate imaging, the light rays of the reflecting surface of the object to be measured will be accurately imaged (or reflected and converged) onto the receiving surface of the position sensitive detector, thereby providing an optical basis for the subsequent detection of the position of the light spot corresponding to the object-image.

[0032] Step S102: Real-time acquisition of the focused light spot corresponding to the laser beam in the position sensitive detector, and determination of the focusing signal of the object to be measured by using the position parameter corresponding to the focused light spot.

[0033] In the process of rotating the rotating lifting platform and continuously irradiating the laser, the focused light spot of the laser received by the position sensitive detector is collected in real time. The position sensitive detector can accurately perceive the position parameter of the light spot (such as the coordinate offset of the center of the light spot on the detector, the spatial distribution position of the light spot, etc.).

[0034] The system can convert the position parameter of the light spot into a focusing signal through a preset algorithm (which can be combined with the corresponding rules of the magnification of the optical system, the position offset of the light spot, and the height deviation of the object surface). The focusing signal directly reflects the deviation degree (size and direction) of the current surface of the object to be measured from the ideal focusing plane of the laser.

[0035] Step S103: Determining the lifting height corresponding to the rotating lifting platform according to the focusing signal, and determining the lifting control instruction corresponding to the rotating lifting platform based on the lifting height.

[0036] According to the focusing signal obtained in step S102, and in combination with the preset relationship between the focusing signal and the height of the wafer surface (such as referring to the relationship curve of the focusing signal with the height of the wafer surface to determine the height deviation value corresponding to the focusing signal), the lifting height (including the rising / falling direction and the specific displacement) that the rotating lifting platform needs to adjust is calculated.

[0037] Subsequently, the system generates a lifting control instruction (the instruction can include key parameters such as “lifting direction” and “target height”) based on the calculated lifting height, thereby providing a control basis for the accurate movement of the lifting platform in the future.

[0038] Step S104: Controlling the rotating lifting platform to reach the lifting height by using the lifting control instruction.

[0039] The generated lifting control instruction is sent to the driving mechanism (such as a servo motor, a precision transmission assembly, etc.) of the rotating lifting platform, and the driving mechanism accurately controls the lifting action of the rotating lifting platform according to the instruction, so that the lifting platform reaches the calculated target height. At this time, the reflecting surface of the object to be measured is adjusted to the best position for laser focusing, thereby ensuring that the subsequent laser scattering defect detection can obtain clear and stable signals, thereby improving the accuracy and reliability of defect detection.

[0040] Optionally, the focusing spot corresponding to the laser beam in the position sensitive detector is acquired in real time, and the focusing signal of the object to be measured is determined by using the position parameter corresponding to the focusing spot, as shown in step S102. Figure 2 As shown in the figure, it comprises: Step S201: controlling the position sensitive detector to acquire the focusing spot of the laser beam reflected by the rotating lifting platform in real time.

[0041] In a specific scenario, the system first sends a control instruction to the position sensitive detector to enter a real-time detection state, continuously capturing the focusing spot formed by the laser beam reflected by the object to be measured on the detector. The preset position is a key reference, which is the position of the spot formed on the position sensitive detector when the laser beam is in the ideal focusing state of the object to be measured (which can be pre-set by system calibration, such as the center coordinates of the detector or a specific calibration marker point). The purpose of real-time acquisition is to dynamically track the position deviation of the focusing spot caused by the change of the surface height of the object to be measured during rotation, and to provide raw data for subsequent focusing judgment.

[0042] Step S202: determining the position distance between the focusing spot and the center point of the position sensitive detector by using the position parameter corresponding to the focusing spot.

[0043] For the focusing spot acquired by the position sensitive detector in real time, the center coordinates (usually represented by the two-dimensional coordinate system of the detector, such as (x, y) pixel coordinates) are extracted by a preset algorithm (such as the light intensity gravity method: calculating the light intensity distribution in the spot area by weighting, and solving the average value of the coordinates by using light intensity as the weight; or the edge detection method: identifying the edge of the spot and fitting the center). Then, the system calculates the position distance between the center coordinates and the center point of the position sensitive detector in real time. The distance can be calculated by the Euclidean distance formula, which directly reflects the degree of deviation of the spot. The greater the deviation distance, the farther the surface height of the object to be measured deviates from the ideal focusing plane.

[0044] Step S203: determining the focusing signal corresponding to the object to be measured based on the position distance.

[0045] The system converts the position distance calculated in step S202 into a focusing signal based on the preset "position distance-focusing signal" mapping relationship (which can be determined by preliminary calibration experiments, such as calibrating the spot deviation distance corresponding to different known height deviations, establishing a mathematical model or a lookup table).

[0046] The focusing signal is usually a quantized electrical signal or a digital quantity, and its value reflects the deviation of the surface height of the object to be measured from the ideal focusing plane (for example, when the distance is 0, the focusing signal is 0, which represents complete focusing; when the distance is positive / negative, the focusing signal is positive / negative, which corresponds to the object surface being too high / too low, respectively). This signal will be directly used as the core basis for subsequent height adjustment of the rotating lifting platform, ensuring that the system can dynamically correct the height deviation and maintain the laser focus on the surface of the object to be measured.

[0047] Optionally, the step S103 of determining the lifting height of the rotating lifting platform corresponding to the focusing signal and determining the lifting control instruction of the rotating lifting platform based on the lifting height includes: Figure 3 As shown in the figure, it includes: Step S301: Obtain a relationship curve corresponding to the focusing signal of the position sensitive detector and the height of the upper surface of the object to be measured.

[0048] The system first calls or generates a core calibration relationship curve, which defines the corresponding relationship between the height of the upper surface of the object to be measured (i.e. the actual height position of the rotating lifting platform) and the focusing signal output by the position sensitive detector.

[0049] This curve is usually obtained from the calibration process in the early stage of the system: by controlling the rotating lifting platform to drive the standard calibration piece (a reference object with known height accuracy) to continuously rise and fall within a predetermined range, the focusing signal corresponding to each height position is recorded (generated by step S203), and finally the functional relationship (which may be a linear relationship, a segmented function or a nonlinear curve, such as the intermediate linear + two-end saturation form analyzed earlier) between the two is fitted. The curve is the reference scale for subsequent height calculation, and directly determines the conversion accuracy of the focusing signal to the actual height.

[0050] Step S302: Obtain the upper surface height corresponding to the focusing signal using the relationship curve, and determine the lifting height of the rotating lifting platform corresponding to the upper surface height.

[0051] In the real-time detection process, the system first inputs the current focusing signal obtained in step S203 into the relationship curve in step S301, and obtains the current upper surface height of the object to be measured corresponding to the signal (i.e. the height value of the current position relative to the system reference plane) by curve reverse lookup (or function solving).

[0052] Subsequently, the ideal focusing height (i.e. the height at which the upper surface of the object to be measured should be when the laser beam is optimally focused, which is usually the reference height preset by the system) is determined according to the detection requirements, and the difference between the "current upper surface height" and the "ideal focusing height" is calculated. This difference is the lifting height that the rotating lifting platform needs to adjust (if the difference is positive, it means that the object surface is too high and needs to be lowered; if it is negative, it means that the surface is too low and needs to be raised).

[0053] Step S303: determining the lifting control instruction corresponding to the rotating lifting platform based on the rotating parameter corresponding to the rotating lifting platform and the lifting height.

[0054] Since the rotating lifting platform is in a continuous rotating state during the detection process (step S101), the lifting action needs to be coordinated with the rotating motion to avoid affecting the continuity of detection due to improper height adjustment timing (such as adjusting the height at a critical angle of defect scanning, which may cause signal loss).

[0055] Therefore, the system needs to first obtain the real-time rotating parameters of the rotating lifting platform, including the current rotating angle (such as the angle value relative to the initial zero position), the rotating speed (such as the angle turned per second), the rotating direction, etc. Based on these parameters, combined with the lifting height calculated in step S302, the coordinated control instruction is generated: the instruction not only contains the direction (up / down) and displacement amount (i.e. lifting height) of lifting, but also may contain details such as adjustment timing (such as performing lifting when rotating to a specific angle interval to ensure matching with the scanning rhythm), lifting speed (set according to the rotating speed to avoid mechanical vibration caused by too fast adjustment), etc.

[0056] Finally, the control instruction is sent to the driving system (such as a servo controller) of the rotating lifting platform to ensure that the lifting action accurately completes the height correction without interfering with the rotating detection, and maintains the laser always focused on the surface of the object to be detected.

[0057] The relationship curve between the upper surface height of the object to be detected and the focusing signal of the position sensitive detector is shown in Figure 4 As shown in the middle region of the curve (the height h is from about -40 μm to about 40 μm), it presents a clear linear growth characteristic: when h≈0, S≈0 (the intercept is approximately 0); the slope k is estimated: from h=0 to h=40 μ, the focusing signal rises from 0 to about 0.5, so the slope k=(0.5-0) / (40-0)=0.0125. Therefore, the approximate relationship of the middle linear segment is: S(h)=0.0125h; where S is the focusing signal, h is the wafer surface height, and the unit is μm. Figure 4 The object to be detected in 201 and 202 is a wafer, and the wafer surface height has a monotonic linear relationship with the signal on the position sensitive detector, which can realize the automatic focusing feedback function with high accuracy in cooperation with the movement of the Z-direction motion axis.

[0058] Optionally, step S303 of determining the lifting control instruction corresponding to the rotating lifting platform based on the rotating parameter corresponding to the rotating lifting platform and the lifting height is as shown in Figure 5 , which includes: Step S501: determining the lifting height corresponding to the acquisition time length according to the rotating parameter corresponding to the rotating lifting platform; Step S502: Calculate the average height value corresponding to the lifting height under the acquisition duration, and determine the lifting control instruction by using the acquisition duration and the average height value.

[0059] The system first extracts the core rotation parameters of the rotating lifting platform, including the current rotation speed (such as the angle rotated per unit time, unit ° / s), the rotation period (the time required to complete 360° rotation), and the preset "effective acquisition angle range" (to reduce the measurement error of a single measurement, it is usually necessary to cover a certain angle range during rotation to collect height data, for example, set to collect height information within a range of 10°).

[0060] According to these parameters, the acquisition duration required to complete the angle range acquisition is calculated: duration = effective acquisition angle range ÷ rotation speed. For example, if the rotation speed is 30° / s, and the height data within a range of 15° needs to be collected, then the acquisition duration = 15° ÷ 30° / s = 0.5s. Because the rotating lifting platform scans at high speed and continuously, in order to avoid over-response of the autofocus and the influence of random defects on the wafer surface on the position of the reflected light spot, the focus signal is filtered or averaged for a certain time and then fed back.

[0061] During the acquisition duration determined in step S501, the system continuously records the real-time height data of the rotating lifting platform (based on the inverse calculation of the focus signal-surface height relationship curve in step S302), and averages the continuous data to obtain the average height value. This average value can smooth out transient fluctuations (such as height jumps caused by rotation vibration, and local deviations caused by surface micro-unevenness), and is closer to the true height of the object surface.

[0062] Subsequently, the acquisition duration and the average height value are combined to generate the lifting control instruction: the instruction needs to specify the target displacement amount of lifting (i.e. the difference between the average height value and the ideal focus height); the lifting speed is determined based on the acquisition duration (speed = target displacement amount ÷ acquisition duration), to ensure that the lifting action matches the rotation period. The instruction can also include a synchronous trigger condition (such as starting lifting when rotating to a specific angle), to ensure that the lifting action seamlessly cooperates with the rotation process and does not interfere with the collection of laser scattering signals.

[0063] Finally, the control instruction is sent to the driving module of the rotating lifting platform, to realize smooth focusing during rotation and ensure that the laser is always accurately focused on the surface of the object to be measured, providing stable optical signals for defect detection.

[0064] Optionally, the step S103 of determining the lifting height corresponding to the rotating lifting platform according to the focus signal, and determining the lifting control instruction corresponding to the rotating lifting platform based on the lifting height, as shown in Figure 6 , includes: Step S601: Obtain a relationship curve of the upper surface height of the object to be measured and the focus signal of the position sensitive detector; Step S602: Obtain the upper surface height corresponding to the focus signal by using the relationship curve, and determine the lifting height corresponding to the rotating lifting platform according to the upper surface height; Step S603: Determine the measurement plane of the object to be measured, and calculate the height difference between the measurement plane and the upper surface of the object to be measured; Step S604: Determine the lifting control instruction corresponding to the rotating lifting platform based on the lifting height and the height difference.

[0065] For some cases that need to detect the lower surface and internal structure of the wafer, the above method of focusing only on the upper surface of the wafer will fail. Therefore, the present embodiment uses the existing autofocus optical path and adopts an asynchronous real-time focusing method. First, the relationship curve of the upper surface height of the object to be measured and the focus signal of the position sensitive detector is obtained to obtain the topographic information of the wafer surface. Then, the upper surface height corresponding to the focus signal is obtained by using the relationship curve, and the lifting height corresponding to the lifting platform is determined according to the upper surface height.

[0066] Subsequently, the measurement plane of the object to be measured is determined, the height difference between the measurement plane and the upper surface of the object to be measured is calculated, and then the lifting control instruction corresponding to the lifting platform is determined based on the lifting height and the height difference. Under this lifting control instruction, the system focuses on the lower surface or a certain layer inside the object to be measured. If multiple layers are scanned in turn, the structural information of the entire wafer inside can be obtained.

[0067] It can be known from the above focus control method for laser scattering defect detection that the position sensitive detector is ingeniously placed at a position that is conjugate to the wafer surface, so that the spot position on the position sensitive detector is only affected by the height of the wafer surface, thereby realizing automatic focusing by controlling the height of the rotating lifting platform.

[0068] Corresponding to the above focus control method for laser scattering defect detection, the present embodiment also provides a focus control device for laser scattering defect detection, as shown in Figure 7 The device is applied to a laser scattering defect detection system; the laser scattering defect detection system at least includes a laser light source, a rotating lifting platform, a first converging lens, and a position sensitive detector; The device includes: The laser emission control module 710 is used to control the rotating lifting platform to rotate and control the laser light source to emit a laser beam to the object to be measured after detecting that the object to be measured is placed on the rotating lifting platform, so that the laser beam is reflected into the position sensitive detector; wherein the reflecting surface of the object to be measured and the receiving surface of the position sensitive detector are in conjugate relationship with respect to the first converging lens; The focus signal control module 720 is used to acquire the focused spot corresponding to the laser beam in the position-sensitive detector in real time, and to determine the focus signal of the object under test by using the position parameters corresponding to the focused spot. The control command determination module 730 is used to determine the lifting height corresponding to the rotary lifting platform based on the focusing signal, and to determine the lifting control command corresponding to the rotary lifting platform based on the lifting height. The lifting control execution module 740 is used to control the rotating lifting platform to achieve the lifting height using lifting control commands.

[0069] As can be seen from the above-mentioned focusing control device for laser scattering defect detection, the device cleverly places the position-sensitive detector at a position that is a conjugate object-image relationship with the wafer surface, so that the position of the light spot on the position-sensitive detector is only affected by the height of the wafer surface, thereby achieving automatic focusing by controlling the height of the rotating lifting platform.

[0070] The focusing control device for laser scattering defect detection provided in this embodiment of the invention has the same implementation principle and technical effect as the aforementioned focusing control method embodiment for laser scattering defect detection. For the sake of brevity, any parts not mentioned in the system embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0071] This embodiment also provides a defect detection system, such as Figure 8 As shown, the system includes: a laser source 100, a rotating platform 120, a first converging lens 103, and a position-sensitive detector 130. During the laser scattering defect detection of the object 110 under test, the defect detection system employs the focusing control method for laser scattering defect detection mentioned in the above embodiments. The laser beam emitted by the laser source 100 illuminates the object 110 under test in the rotating platform 120 and is reflected by the first converging lens 103 to the position-sensitive detector 130. Specifically, the rotation axis of the rotating platform 120 is 121, and the reflecting surface of the object 110 and the receiving surface of the position-sensitive detector 130 are conjugate relative to the first converging lens 103. The position-sensitive detector 130 generates a focusing signal for the object 110 under test based on the position parameters corresponding to the focused spot generated by the laser beam, and determines the corresponding lifting height of the rotating platform 120 based on the focusing signal. The rotating platform 120 is controlled to reach the lifting height according to the lifting control command corresponding to the lifting height.

[0072] Optional, such as Figure 9As shown, the defect detection system further comprises a mirror 101, a second converging lens 102, a beam splitter 104, a polarization beam splitter 105, a first detector 106 and a second detector 107; the mirror 101 is located between the laser light source 100 and the second converging lens 102, and is used to reflect the laser beam emitted by the laser light source to the object 110 to be measured in the rotating lifting platform 120, and form a focus point 140 in the object 110 to be measured; the second converging lens 102 is located between the mirror 101 and the rotating lifting platform 120, and is used to converge the laser beam so that the laser spot in the object 110 to be measured is minimized; the beam splitter 104 is located between the first converging lens 103 and the position sensitive detector 130; the beam splitter 104 is used to divide the converging beam after the first converging lens 103 into a first laser beam 141 and a second laser beam 142; the first laser beam 141 is irradiated to the position sensitive detector 130; the second laser beam 142 forms S-polarized light and P-polarized light after irradiating to the polarization beam splitter 105, the S-polarized light is irradiated to the first detector 106, and the P-polarized light is irradiated to the second detector 107. The signals obtained by the first detector 106 and the second detector 107 can reflect the defect information of the surface of the object to be measured, and the automatic focusing and defect detection are both from the same reflected laser beam of the wafer surface. Specifically, the light reflected from the surface of the object 110 to be measured is divided into two beams by the beam splitter 104, one beam obtains a focusing signal on the position sensitive detector 130 to realize automatic focusing by controlling the height of the rotating lifting platform 120, and the other beam is used to realize the measurement of the corresponding topography of the wafer surface reflection intensity and reflection angle, and finally realize the imaging and detection of the wafer surface defects.

[0073] The laser source 100 emits laser beams of different wavelengths and polarizations, which can be shaped laser beams. The laser beam is obliquely incident on the surface of the object under test (wafer) 110 via a reflector 101. A second converging lens 102 focuses the incident parallel beam, minimizing the spot size at the normal operating height on the wafer surface. Therefore, the laser incident on the surface of the object under test 110 is a focused beam, ensuring the system's spatial resolution and sensitivity. However, due to varying thicknesses of the object under test 110, or warping of the object, the focal point 140 of the laser may deviate from the surface of the object under test, resulting in a decrease in spatial resolution and sensitivity. Therefore, a real-time autofocus mechanism is required. After reflection, the laser incident on the surface of the object under test 110 is refocused by the first converging lens 103 and split into a first laser beam 141 and a second laser beam 142 by a beam splitter 104. The first laser beam 141, after being split, is focused onto the center position 142 of the position-sensitive detector 130. Specifically, the surface position of the position-sensitive detector 130 should be conjugate to the surface of the object under test 110 relative to the first converging lens 103; that is, the focal point 140 on the object under test and the center position 143 on the position-sensitive detector 130 should have a conjugate object-image relationship. When the surface of the object under test 110 deviates from the normal operating height, it will cause the focused spot to move on the position-sensitive detector 130. This can be addressed by adjusting the Z-axis motion 121, such as... Figure 9 As indicated by the double arrows, the surface of the object under test 110 returns to the optimal focusing position. Simultaneously, since the focal point 140 on the object under test 110 and the focal point on the position-sensitive detector 130 are conjugates, the tilting and warping of the object under test 110 do not change the position of the light spot on the position-sensitive detector 130, thus avoiding interference with focusing caused by the tilting and warping of the object under test 110. Because the rotating platform 120 moves continuously at high speed during scanning, to avoid over-response in autofocus and the influence of random defects on the surface of the object under test 110 on the position of the reflected light spot, the focusing signal over a certain period of time can be filtered or averaged before feedback. After being split, the second laser beam 142 is divided into S-polarized light and P-polarized light by the polarization beam splitter prism 105. These are detected by the first detector 106 and the second detector 107, respectively, to detect information such as the reflectivity, morphology, and phase change of the surface of the object under test 110. This method of using an obliquely incident bright-field laser beam for in-situ autofocus achieves both signal detection and autofocus using a single optical path. The structure is compact and overcomes the problem that bright-field detection and autofocus cannot be performed simultaneously in laser scattering systems.

[0074] Optional, such as Figure 10As shown, the defect detection system further comprises a spatial light blocking element 310; the spatial light blocking element 310 is arranged between the beam splitter 104 and the position sensitive detector 130 and close to the position sensitive detector 130; the spatial light blocking element 310 is used to block the reflected light formed by the laser beam on the lower surface of the transparent wafer when the object to be measured 110 is a transparent wafer, so as to ensure that the focusing signal is entirely from the upper surface of the transparent wafer.

[0075] Specifically, the lower surface reflected light 300 is also formed for the transparent wafer, and if the light signal enters the position sensitive detector 130, the focusing signal will be interfered, the reference height of the wafer will be too high, and the focusing will fail. In this case, the spatial light blocking element 310 is arranged in front of the position sensitive detector, including but not limited to a slit and a small hole, the size of which can be selected according to the thickness of the wafer, such as the slit width or the small hole diameter which can be selected as 1mm. After the spatial light blocking element 310 is added, the lower surface reflected light 300 will be effectively blocked, so as to ensure that the automatic focusing of different types of wafers is all focused to the wafer surface.

[0076] Optionally, as shown in Figure 11 The defect detection system further comprises a mirror 101, a second converging lens 102, a beam splitter 104, a polarization beam splitter prism 105 and a first detector 106; the mirror 101 is located between the laser light source 100 and the second converging lens 102, and the mirror 101 is used to reflect the laser beam emitted by the laser light source to the object to be measured 110 in the rotating lifting platform 120; the second converging lens 102 is located between the mirror 101 and the rotating lifting platform 120, and the second converging lens 102 is used to converge the laser beam so that the laser spot in the object to be measured 110 is smallest; the beam splitter 104 is located between the first converging lens 103 and the polarization beam splitter prism 105, and the beam splitter 104 is used to reflect the converged light beam after the first converging lens 103 to the polarization beam splitter prism 105; the converged light beam forms S-polarized light and P-polarized light after irradiating to the polarization beam splitter prism 105, the S-polarized light irradiates to the first detector 106, and the P-polarized light irradiates to the position sensitive detector 130.

[0077] For the power limitation of the bright field light source, or due to the cost and space limitation, there is no independent light splitting, the second detector 107 in Figure 9 may be replaced by the position sensitive detector 130, and the signal detected by the position sensitive detector 130 is directly used for focusing. The change of the wafer surface height will cause the change of the light spot position on the position sensitive detector 130, and there is a monotonic linear relationship between the two, which can be used to focus the wafer surface by using the signal.

[0078] For some cases that need to detect the lower surface and internal structure of the wafer, the above method of focusing only on the upper surface of the wafer will fail. Therefore, the present embodiment uses the existing autofocus optical path and adopts an asynchronous real-time focusing method, as shown in Figure 12 First, the wafer surface 500 is scanned to obtain the topographic information of the wafer surface 500. Then, according to the relationship between the surface topography and the wafer plane direction, when the wafer is scanned, the Z-axis motion shaft 121 is moved upward by a fixed distance, and the optical system will focus on the lower surface 510 or the internal layer 520 of the wafer to obtain the defect information on the layer. If multiple layers are scanned in turn, the internal structure information of the entire wafer can be obtained.

[0079] The defect detection system in the present embodiment has the following technical effects: The existing detection optical path can be used, and the structure is simple and easy to integrate. In the laser scattering defect detection system, the bright field reflection light path can be used for the detection of surface topography and surface film. The present application uses the bright field reflection light path and realizes real-time automatic focusing of the wafer surface by using the principle of laser triangulation.2. By sharing an incident and reflected laser with the automatic focusing system and the detection light path, it can be ensured that when the laser pointing direction drifts, the wafer can still be focused to the best focal plane through automatic focusing, which makes the focusing system avoid the influence of the change of the laser pointing direction.

[0080] 3. By reasonably placing the position of the position sensitive detector, the interference of wafer tilt and wafer warping on automatic focusing is avoided, and the accuracy of automatic focusing is ensured.

[0081] 4. For different application scenarios, whether it is a transparent wafer or an opaque wafer, the influence of the lower surface reflection light can be avoided by adding a light shielding element in front of the automatic focusing detector, and the wafer surface can always be focused. This ensures the universality of the focusing system.

[0082] 5. By using the asynchronous real-time automatic focusing embodiment of the present automatic focusing structure, combined with the confocal detection structure, the defects of any layer inside the wafer can be detected and analyzed, and more application scenarios can be compatible.

[0083] In several embodiments provided in the present application, it should be understood that the disclosed system, device, apparatus and method can be implemented in other manners. The above described system embodiments are merely illustrative. For example, the division of the units is only a logical function division. There can be another division manner for the actual implementation, or a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, or the among different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0084] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. In actual implementation, some or all of the units can be selected according to the actual needs to achieve the purposes of the embodiments of the present application.

[0085] In addition, each functional unit in the various embodiments of the present application can be integrated in one processing unit, or each unit can exist physically as a separate unit, or two or more units can be integrated in one unit.

[0086] If the functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a non-volatile computer readable storage medium executable by a processor. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0087] Finally, it should be noted that the above-described embodiments are merely specific embodiments of the present application, which are used to illustrate the technical solutions of the present application, but not to limit the same. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that any person skilled in the art can still modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, within the technical scope disclosed by the present application. The modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A focusing control method for laser scattering defect detection, characterized in that, The method is applied to a laser scattering defect detection system; the laser scattering defect detection system includes at least: a laser source, a rotary lifting platform, a first converging lens, and a position-sensitive detector. The method includes: When the object to be tested is detected to be placed on the rotating lifting platform, the rotating lifting platform is controlled to rotate, and the laser light source is controlled to emit a laser beam towards the object to be tested, so that the laser beam is reflected into the position sensitive detector; wherein, the reflecting surface of the object to be tested and the receiving surface of the position sensitive detector are conjugate to each other with respect to the first converging lens; The focused spot corresponding to the laser beam in the position-sensitive detector is acquired in real time, and the focus signal of the object under test is determined by the position parameters corresponding to the focused spot. The lifting height of the rotating platform is determined based on the focusing signal, and the lifting control command corresponding to the rotating platform is determined based on the lifting height. The lifting control command is used to control the rotating lifting platform to reach the specified lifting height.

2. The focusing control method for laser scattering defect detection according to claim 1, characterized in that, The step of acquiring the focused spot corresponding to the laser beam in the position-sensitive detector in real time, and determining the focus signal of the object under test using the position parameters corresponding to the focused spot, includes: The position-sensitive detector is controlled to acquire the focused spot of the laser beam after it is reflected by the rotating lifting platform in real time. The positional distance between the focused light spot and the center point of the position-sensitive detector is determined using the position parameters corresponding to the focused light spot. The focus signal corresponding to the object under test is determined based on the positional distance.

3. The focusing control method for laser scattering defect detection according to claim 1, characterized in that, The steps of determining the lifting height corresponding to the rotary lifting platform based on the focusing signal, and determining the lifting control command corresponding to the rotary lifting platform based on the lifting height, include: Obtain the curve showing the relationship between the height of the upper surface of the object under test and the focusing signal of the position-sensitive detector; The height of the upper surface corresponding to the focusing signal is obtained using the relationship curve, and the lifting height of the rotating platform is determined based on the height of the upper surface. The lifting control command for the rotary lifting platform is determined based on the rotation parameters corresponding to the rotary lifting platform and the lifting height.

4. The focusing control method for laser scattering defect detection according to claim 3, characterized in that, The steps of determining the lifting control command corresponding to the rotating lifting platform based on the rotation parameters and the lifting height include: The acquisition duration corresponding to the lifting height is determined based on the rotation parameters corresponding to the rotating platform. Calculate the average height value corresponding to the lifting height under the acquisition duration, and use the acquisition duration and the average height value to determine the lifting control command.

5. The focusing control method for laser scattering defect detection according to claim 1, characterized in that, The steps of determining the lifting height corresponding to the rotary lifting platform based on the focusing signal, and determining the lifting control command corresponding to the rotary lifting platform based on the lifting height, include: Obtain the curve showing the relationship between the height of the upper surface of the object under test and the focusing signal of the position-sensitive detector; The height of the upper surface corresponding to the focusing signal is obtained using the relationship curve, and the lifting height of the rotating platform is determined based on the height of the upper surface. Determine the plane to be measured of the object to be measured, and calculate the height difference between the plane to be measured and the upper surface of the object to be measured; The lifting control command corresponding to the rotary lifting platform is determined based on the lifting height and the height difference.

6. A focusing control device for laser scattering defect detection, characterized in that, The device is used in a laser scattering defect detection system; the laser scattering defect detection system includes at least: a laser source, a rotary lifting platform, a first converging lens, and a position-sensitive detector; The device includes: The laser emission control module is used to control the rotating platform to rotate after detecting that the object to be tested is placed on the rotating platform, and to control the laser source to emit a laser beam toward the object to be tested, so that the laser beam is reflected into the position-sensitive detector; wherein the reflecting surface of the object to be tested and the receiving surface of the position-sensitive detector are conjugate to each other with respect to the first converging lens; The focus signal control module is used to acquire the focused spot corresponding to the laser beam in the position-sensitive detector in real time, and to determine the focus signal of the object under test using the position parameters corresponding to the focused spot. The control command determination module is used to determine the lifting height corresponding to the rotary lifting platform based on the focusing signal, and to determine the lifting control command corresponding to the rotary lifting platform based on the lifting height; The lifting control execution module is used to control the rotating lifting platform to reach the lifting height using the lifting control command.

7. A defect detection system, characterized in that, The system includes: a laser source, a rotating lifting platform, a first converging lens, and a position-sensitive detector; wherein, during the laser scattering defect detection of the object under test, the defect detection system employs the focusing control method for laser scattering defect detection mentioned in any one of claims 1 to 5; The laser beam emitted by the laser source illuminates the object under test in the rotating lifting platform. After being reflected by the reflective surface of the object under test, it is focused by the first converging lens onto the position-sensitive detector. The reflective surface of the object under test and the receiving surface of the position-sensitive detector are conjugate to each other with respect to the first converging lens. The position-sensitive detector is used to generate a focusing signal for the object under test based on the position parameters corresponding to the focused spot generated by the laser beam, and to determine the lifting height corresponding to the rotating lifting platform based on the focusing signal. The rotary lifting platform is used to control the rotary lifting platform to reach the specified lifting height according to the lifting control command corresponding to the specified lifting height.

8. The defect detection system according to claim 7, characterized in that, The defect detection system also includes: a reflector, a second converging lens, a beam splitter, a polarizing beam splitter, a first detector, and a second detector; The reflector is located between the laser source and the second converging lens, and the reflector is used to reflect the laser beam emitted by the laser source to the object to be tested in the rotating lifting platform; The second converging lens is located between the reflector and the rotating lifting platform. The second converging lens is used to converge the laser beam so that the laser spot in the object under test is minimized. The beam splitter is located between the first converging lens and the position-sensitive detector; the beam splitter is used to split the converged beam after passing through the first converging lens into a first laser beam and a second laser beam; the first laser beam illuminates the position-sensitive detector; the second laser beam illuminates the polarization beam splitter prism to form S-polarized light and P-polarized light, the S-polarized light illuminates the first detector, and the P-polarized light illuminates the second detector.

9. The defect detection system according to claim 8, characterized in that, The defect detection system further includes a spatial light-blocking element; the spatial light-blocking element is disposed between the beam splitter and the position-sensitive detector, and is close to the position-sensitive detector; The spatial light-shielding element is used to block the reflected light formed by the laser beam on the lower surface of the transparent wafer when the object under test is a transparent wafer.

10. The defect detection system according to claim 7, characterized in that, The defect detection system also includes: a reflector, a second converging lens, a beam splitter, a polarizing beam splitter prism, and a first detector; The reflector is located between the laser source and the second converging lens, and the reflector is used to reflect the laser beam emitted by the laser source to the object to be tested in the rotating lifting platform; The second converging lens is located between the reflector and the rotating lifting platform. The second converging lens is used to converge the laser beam so that the laser spot in the object under test is minimized. The beam splitter is located between the first converging lens and the polarizing beam splitter prism. The beam splitter is used to reflect the converged beam after passing through the first converging lens into the polarizing beam splitter prism. The converging beam illuminates the polarizing beam splitter to form S-polarized light and P-polarized light. The S-polarized light illuminates the first detector, and the P-polarized light illuminates the position-sensitive detector.

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