A self-focusing wafer 3D morphology precision inspection device and method

Abstract

This invention proposes a self-focusing precision inspection device and method for three-dimensional wafer morphology, comprising a superluminescent diode, an optical fiber coupler, a microscopic reference arm with a reference arm microscope objective, a self-focusing wafer scanning platform with a microscopic scanning platform, a near-infrared reflectance spectrometer, and a host computer. During inspection, the near-infrared broadband light emitted by the diode is coupled into the optical fiber coupler and split into a probe light and a reference light. The wafer under test is moved to the focal point of the probe light. The probe light is focused onto the wafer sample, forming a measurement light carrying information about the sample surface. This measurement light is then backscattered by the sample surface and interferes with the reference light at the optical fiber coupler. The resulting interference signal is captured by the near-infrared reflectance spectrometer and transmitted to the host computer. The wafer sample is moved at the focal point of the probe light, and XY-axis scanning is performed to obtain the three-dimensional morphology data of the wafer. This invention enables high-precision non-destructive inspection of the three-dimensional morphology of a chip without damaging the chip sample.

Description

Technical Field

[0001] This invention relates to the field of non-contact optical coherence microscopy imaging technology, and in particular to a self-focusing wafer three-dimensional morphology precision detection device and method. Background Technology

[0002] With the development of technology, wafers have gradually become a key component of modern products. Chip ball bonding technology is a process of covering or embedding bumps or flip-chip solder balls on a chip onto a substrate or module. This technology not only significantly increases the connection density between the chip and the substrate or module, but also helps improve the heat transfer capability and optimize the electrical performance of the device. The quality of the solder balls directly affects the operating performance and stability of the device. Therefore, measuring the surface morphology is crucial for further improving ball bonding technology and chip design.

[0003] Compared to traditional inspection methods, modern manufacturing processes place higher demands on wafer surface morphology inspection, such as high resolution, large measurement range, and high measurement speed. Taking the microelectronics industry as an example, the lateral dimensions of sapphire substrates and silicon wafers are typically 4 to 16 inches, while axial measurement accuracy requires sub-micron to nanometer levels. Due to the high throughput of production lines, automated inspection efficiency also needs to be improved accordingly. Although traditional surface morphology measurement techniques, such as atomic force microscopy and scanning electron microscopy, can achieve nanometer-level accuracy, their measurement efficiency is low and they are difficult to meet the needs of large-scale measurements. Therefore, it is essential to propose a method for measuring wafer surface morphology in current industrial environments. Summary of the Invention

[0004] This invention proposes a self-focusing wafer three-dimensional morphology precision inspection device and method, which can achieve high-precision non-destructive inspection of the chip morphology without damaging the chip sample.

[0005] The present invention adopts the following technical solution.

[0006] A self-focusing precision wafer morphology inspection device includes a superluminescent diode (1), an optical fiber coupler (2), a microscopic reference arm with a reference arm microscope objective (5), a self-focusing wafer scanning platform (13), a near-infrared reflectance spectrometer, and a host computer. During inspection, the wafer sample to be inspected is fixed at the self-focusing wafer scanning platform. The near-infrared broadband light emitted by the superluminescent diode is coupled into the optical fiber coupler and split into probe light input to the microscopic probe arm and reference light input to the microscopic reference arm. The self-focusing wafer scanning platform moves the wafer under test to the focal point of the probe light. The probe light is focused onto the wafer sample by the microscope probe of the microscope probe arm, forming a measurement light carrying information about the sample surface. The light is then backscattered by the sample surface and interferes with the reference light at the fiber coupler. The resulting interference light signal is captured by the near-infrared reflectance spectrometer and transmitted to the host computer. By controlling the self-focusing wafer scanning platform to move the wafer sample at the focal point of the probe light, the sample is scanned along the X and Y axes to obtain the three-dimensional morphology data of the wafer.

[0007] The self-focusing wafer scanning platform includes a wafer loading tray (11) located on the micro-scanning platform (13), a motion controller (14), and a micro sample arm fixed to the motorized focusing lens mount (7). The micro sample arm is driven by the motorized focusing lens mount. When the host computer processes the collected interference signal, it accurately calculates the Z-axis position of the wafer and feeds it back to the self-focusing wafer scanning platform. It accurately controls the motorized focusing lens mount to make the micro sample arm focus. The wafer loading tray is fixed on the micro-scanning platform. The micro-scanning platform moves according to the XY coordinate system through the signal acquisition device and the host computer software.

[0008] A photodetector (12) is provided at the focal length wafer scanning platform. The photodetector includes a photoelectric switch and a baffle located at the microscopic scanning platform. When the microscopic scanning platform moves a preset distance along the X direction, the baffle will block the light beam between the emitter and receiver of the photoelectric switch. The signal output by the photoelectric switch switches from low level to high level to form a trigger signal, which triggers the linear array camera (16) of the near-infrared reflective spectrometer and starts to collect interference signals. After a predetermined number of images are collected, the system enters a state of waiting for the next trigger signal.

[0009] The optical input end of the near-infrared reflective spectrometer includes an optical fiber APC connector, a scaling sleeve, a spectrometer collimating lens (19), a holographic reflective grating (18), a focusing lens, and a linear array camera, wherein the linear array camera is a linear array CCD camera;

[0010] When inspecting the wafer, the interference light signal is incident through the APC connector. After the interference light is collimated by adjusting the scaling sleeve, the resulting parallel light is incident on the surface of the holographic reflective grating at a predetermined angle. After the holographic reflective grating undergoes first-order diffraction, the collimated beam is split according to wavelength and then focused by the focusing lens onto the linear CCD camera. This causes the interference light signal to be converted into an interference signal in the form of an electrical signal through the optical path and transmitted to an external host computer, which is a computer (15).

[0011] The microscopic reference arm includes an optical fiber APC connector, a reference arm collimating lens (3), a reference arm aperture (4), a reference arm microscope objective (5), and several sleeves;

[0012] When inspecting a wafer, the reference light enters the micro reference arm, first enters the sleeve through the fiber APC connector, and becomes a parallel beam after passing through the collimating lens of the reference arm. After adjusting the aperture of the reference arm to change the size of the beam, it is then focused on the upper surface of the quartz glass (6) by the microscope objective of the reference arm. After the beam is reflected, it returns to the fiber coupler through the original optical path.

[0013] The micro probe arm is provided with a probe arm collimating lens (8) and a probe arm microscope objective (9) in sequence in the direction of probe light input.

[0014] A self-focusing wafer three-dimensional topography precision inspection method, using a self-focusing wafer three-dimensional topography precision inspection device, includes the following steps;

[0015] Step S1: During device initialization, the reference arm aperture is set to zero, and the quartz glass is placed at the micro-detection end of the micro-detection arm of the micro-scanning platform. Based on the detection light intensity collected by the linear CCD, the motorized focusing lens is controlled to make the focal length of the quartz glass surface, the reference arm aperture is opened, and the optical path difference and aperture are adjusted to make the interference signal have the required good signal-to-noise ratio. The interference signal is collected and the focal length position is calculated.

[0016] Step S2: Initialize the position of the microscopic scanning platform and place the wafer sample to be tested in the wafer loading tray (11); perform spectral correction on the collected interference signal and collect the interference signal of the current detection point; calculate the initial position of the current wafer and the focal distance to be moved after spectral correction of the interference signal, and drive the electric focusing lens to move and focus in the Z-axis direction;

[0017] Step S3: Input the scanning range and scanning step size of the wafer, and start acquiring interference signals with wafer surface position information;

[0018] Step S4: Construct the physical equation between wafer surface position data and geometric dimensions;

[0019] Step S5: Substitute the interference signal obtained in step S3 into the Hanning window energy centroid method to obtain the wafer surface position data, and calculate the three-dimensional morphology of the chip according to the equation established in step S4.

[0020] In actual detection, the linear CCD camera described in step S1 can only acquire the real part of the interference signal. Specifically, the real part of the interference spectrum signal is:

[0021]

[0022] Where k = 2π / λ is the wave number of the light wave. Let S be the spectral power distribution function of the light reflected from the reference end. S(z) Let a be the spectral power distribution function of the reflected light from the z-th layer in the sample. S Let be the reflection coefficient of the z-th layer structure in the sample; the first term The first term is a constant, representing the DC component in the real interference signal; the second term... The superposition of the reflectance spectral signals from different depth layers in the sample and a series of cosine functions represents the encoding of the z-th layer's structural tomographic information at a frequency of 2kHz. S In the cosine function; the third term This is a self-coherent term, describing the self-interference phenomenon between the z-th and z′-th layers along the sample depth direction; the energy of the self-coherent term is much smaller than the energy of the light reflected from the reference end, and will not affect the accuracy of the system tomographic imaging, so it is ignored in the calculation;

[0023] Performing a Fourier transform on the second term in the spectral interference signal that carries sample structure information, we get:

[0024]

[0025] In the above formula δ represents convolution, δ is the Eurac function, δ(z) is the tomographic structure information of the sample, and δ(-z) is the conjugate mirror image of the sample about the zero optical path axis.

[0026] The calculation of the focal length distance in step S2 uses the Hanning window energy centroid method to calculate the information of the focal position and the initial position, and to obtain the focal length distance to be moved, specifically as follows:

[0027] H = Δz × (f1 - f2)

[0028] Where Δz is the axial resolution of the system, and f1 and f2 are the focal position frequency and initial position frequency obtained after correction by the Hanning window energy centroid algorithm, respectively.

[0029] The formula for the energy centroid algorithm of the Hanning window is:

[0030]

[0031] in, Let f be the normalized frequency of the harmonic signal, k be the spectral line number corresponding to the point of maximum amplitude, G be the amplitude corresponding to the i-th spectral line, and f be the frequency of the harmonic signal. s Where N is the sampling frequency and N is the number of sampling points.

[0032] In step S4, the physical equation between the wafer surface position data and the geometric dimensions is:

[0033] Z = Δz × (ff) org )

[0034] Where N is the distance between the wafer surface and the origin of the Z-axis, Δz is the axial resolution of the system, and f is the wafer surface position frequency obtained after correction using the Hanning window energy centroid algorithm. org The frequency of the interference signal is when the wafer is at the origin of the Z-axis.

[0035] In step S2, the micro probe arm is placed at the micro sample arm of the motorized focusing lens mount. The motorized focusing lens mount is controlled by the host computer software to move and focus in the Z-axis direction. The wafer loading disk is fixed on the micro scanning platform. The micro scanning platform moves according to the XY coordinate system through the signal acquisition device and the host computer software.

[0036] The wafer sample to be tested is fixed on a self-focusing wafer scanning platform. The measurement light and reference light, which reflect the surface information of the wafer sample, interfere at the fiber coupler. After being captured by a near-infrared reflectance spectrometer, the host computer calculates the initial position and focusing distance of the current detection point and drives the self-focusing wafer scanning platform to focus. Finally, the scanning platform is driven to move and scan according to the input scanning range, and the three-dimensional morphology of the wafer is calculated.

[0037] The fiber optic coupler is a single-mode fiber optic coupler.

[0038] This invention addresses the method for measuring the surface morphology of wafers in existing industrial environments, enabling high-precision non-destructive testing of the three-dimensional morphology of chips without damaging the chip samples.

[0039] This invention proposes a high-precision wafer morphology detection device that can focus quickly and accurately, achieving ultra-precision detection of the three-dimensional morphology of the chip with nanometer-level accuracy without damaging the chip structure. Attached Figure Description

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] Appendix Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention;

[0042] Appendix Figure 2 This is a schematic diagram of the signal acquisition process according to an embodiment of the present invention;

[0043] Appendix Figure 3 This is a schematic diagram of a semiconductor photolithography wafer-mounted chip according to an embodiment of the present invention;

[0044] Appendix Figure 4 This is a schematic diagram illustrating the principle of the self-focal distance algorithm in an embodiment of the present invention;

[0045] Appendix Figure 5 This is a schematic diagram of the three-dimensional morphology measurement results of the wafer surface in an embodiment of the present invention;

[0046] Appendix Figure 6 This is a schematic diagram of the cross-sectional morphology measurement results corresponding to the three-dimensional morphology of the wafer surface in an embodiment of the present invention.

[0047] In the figure: 1 is a superluminescent diode, 2 is an optical fiber coupler, 3 is a collimating lens for the reference arm, 4 is an aperture for the reference arm, 5 is a microscope objective for the reference arm, 6 is quartz glass, 7 is a motorized focusing mount, 8 is a collimating lens for the probe arm, 9 is a microscope objective for the probe arm, 10 is a wafer sample, 11 is a wafer loading tray, 12 is a photodetector, 13 is a microscopic scanning platform, 14 is a motion controller, 15 is a computer, 16 is a linear CCD camera, 17 is a focal lens for the spectrometer, 18 is a holographic reflective grating, and 19 is a collimating lens for the spectrometer. Detailed Implementation

[0048] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below for detailed explanation:

[0049] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0050] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0051] As shown in the figure, a self-focusing wafer three-dimensional morphology precision inspection device includes a superluminescent diode 1, an optical fiber coupler 2, a microscopic reference arm with a reference arm microscope objective 5, a self-focusing wafer scanning platform 13, a near-infrared reflectance spectrometer, and a host computer. During inspection, the wafer sample to be tested is fixed at the self-focusing wafer scanning platform. The near-infrared broadband light emitted by the superluminescent diode is coupled into the optical fiber coupler and split into probe light input to the microscopic probe arm and reference light input to the microscopic reference arm. The self-focusing wafer scanning platform moves the wafer under test to the focal point of the probe light. The probe light is focused onto the wafer sample by the microscope probe of the microscope probe arm, forming a measurement light carrying the surface information of the sample. It is then backscattered by the sample surface and interferes with the reference light at the fiber coupler. The resulting interference light signal is captured by the near-infrared reflectance spectrometer and transmitted to the host computer. By controlling the self-focusing wafer scanning platform to move the wafer sample at the focal point of the probe light, the sample is scanned along the X and Y axes to obtain the three-dimensional morphology data of the wafer.

[0052] The self-focusing wafer scanning platform includes a wafer loading tray 11 located at the micro scanning platform 13, a motion controller 14, and a micro sample arm fixed at the motorized focusing lens mount 7.

[0053] The microscopic sample arm is driven by an electric focusing lens mount. When the host computer processes the acquired interference signal, it accurately calculates the Z-axis position of the wafer and feeds it back to the self-focusing wafer scanning platform. It precisely controls the electric focusing lens mount to focus the microscopic sample arm. The wafer loading tray is fixed on the microscopic scanning platform. The microscopic scanning platform moves according to the XY coordinate system under the control of the host computer software through the signal acquisition device.

[0054] A photodetector 12 is provided at the focal length wafer scanning platform. The photodetector includes a photoelectric switch and a baffle located at the microscopic scanning platform. When the microscopic scanning platform moves a preset distance along the X direction, the baffle will block the light beam between the emitter and receiver of the photoelectric switch. The signal output by the photoelectric switch switches from a low level to a high level to form a trigger signal, which triggers the linear array camera 16 of the near-infrared reflectance spectrometer and begins to collect interference signals. After a predetermined number of images are collected, the system enters a state of waiting for the next trigger signal.

[0055] The optical input end of the near-infrared reflective spectrometer includes an optical fiber APC connector, a zoom sleeve, a spectrometer collimating lens 19, a holographic reflective grating 18, a focusing lens, and a linear array camera, wherein the linear array camera is a linear array CCD camera.

[0056] During wafer inspection, the interference light signal is incident through the APC connector. After the interference light is collimated by adjusting the scaling sleeve, the resulting parallel light is incident on the surface of the holographic reflective grating at a predetermined angle. After first-order diffraction, the holographic reflective grating splits the collimated beam according to wavelength, and then the focusing lens focuses it onto the linear CCD camera. This converts the interference light signal into an electrical interference signal through the optical path and transmits it to an external host computer, which is computer 15.

[0057] The microscopic reference arm includes an optical fiber APC connector, a reference arm collimating lens 3, a reference arm aperture 4, a reference arm microscope objective 5, and several sleeves.

[0058] When inspecting a wafer, the reference light enters the micro reference arm, first enters the sleeve through the fiber optic APC connector, and becomes a parallel beam after passing through the collimating lens of the reference arm. After adjusting the aperture of the reference arm to change the size of the beam, it is then focused on the upper surface of the quartz glass 6 by the microscope objective of the reference arm. After reflection, the beam returns to the fiber coupler through the original optical path.

[0059] The micro probe arm is provided with a collimating lens 8 and a microscope objective lens 9 in sequence in the direction of probe light input.

[0060] A self-focusing wafer three-dimensional topography precision inspection method, using a self-focusing wafer three-dimensional topography precision inspection device, includes the following steps;

[0061] Step S1: During device initialization, the reference arm aperture is set to zero, and the quartz glass is placed at the micro-detection end of the micro-detection arm of the micro-scanning platform. Based on the detection light intensity collected by the linear CCD, the motorized focusing lens is controlled to make the focal length of the quartz glass surface, the reference arm aperture is opened, and the optical path difference and aperture are adjusted to make the interference signal have the required good signal-to-noise ratio. The interference signal is collected and the focal length position is calculated.

[0062] Step S2: Initialize the position of the microscopic scanning platform and place the wafer sample to be tested in the wafer loading tray 11; perform spectral correction on the acquired interference signal and acquire the interference signal at the current detection point; calculate the initial position of the current wafer and the focal length to be moved after spectral correction of the interference signal, and drive the motorized focusing lens to move and focus in the Z-axis direction;

[0063] Step S3: Input the scanning range and scanning step size of the wafer, and start acquiring interference signals with wafer surface position information;

[0064] Step S4: Construct the physical equation between wafer surface position data and geometric dimensions;

[0065] Step S5: Substitute the interference signal obtained in step S3 into the Hanning window energy centroid method to obtain the wafer surface position data, and calculate the three-dimensional morphology of the chip according to the equation established in step S4.

[0066] In actual detection, the linear CCD camera described in step S1 can only acquire the real part of the interference signal. Specifically, the real part of the interference spectrum signal is:

[0067]

[0068] Where k = 2π / λ is the wave number of the light wave. Let S be the spectral power distribution function of the light reflected from the reference end. S(z) Let a be the spectral power distribution function of the reflected light from the z-th layer in the sample. S Let be the reflection coefficient of the z-th layer structure in the sample; the first term The first term is a constant, representing the DC component in the real interference signal; the second term... The superposition of the reflectance spectral signals from different depth layers in the sample and a series of cosine functions represents the encoding of the z-th layer's structural tomographic information at a frequency of 2kHz. S In the cosine function; the third term This is a self-coherent term, describing the self-interference phenomenon between the z-th layer and the z-th layer in the sample depth direction; the energy of the self-coherent term is much smaller than the energy of the light reflected from the reference end, and will not affect the accuracy of the system tomographic imaging, so it is ignored in the calculation;

[0069] Performing a Fourier transform on the second term in the spectral interference signal that carries sample structure information, we get:

[0070]

[0071] In the above formula δ represents convolution, δ is the Eurac function, δ(z) is the tomographic structure information of the sample, and δ(-z) is the conjugate mirror image of the sample about the zero optical path axis.

[0072] The calculation of the focal length distance in step S2 uses the Hanning window energy centroid method to calculate the information of the focal position and the initial position, and to obtain the focal length distance to be moved, specifically as follows:

[0073] H = Δz × (f1 - f2)

[0074] Where Δz is the axial resolution of the system, and f1 and f2 are the focal position frequency and initial position frequency obtained after correction by the Hanning window energy centroid algorithm, respectively.

[0075] The formula for the energy centroid algorithm of the Hanning window is:

[0076]

[0077] in, Let f be the normalized frequency of the harmonic signal, k be the spectral line number corresponding to the point of maximum amplitude, G be the amplitude corresponding to the i-th spectral line, and f be the frequency of the harmonic signal. s Where N is the sampling frequency and N is the number of sampling points.

[0078] In step S4, the physical equation between the wafer surface position data and the geometric dimensions is:

[0079] Z = Δz × (ff) org )

[0080] Where Z is the distance between the wafer surface and the origin of the Z-axis, Δz is the axial resolution of the system, and f is the wafer surface position frequency obtained after correction using the Hanning window energy centroid algorithm. org The frequency of the interference signal is when the wafer is at the origin of the Z-axis.

[0081] In step S2, the micro probe arm is placed at the micro sample arm of the motorized focusing lens mount. The motorized focusing lens mount is controlled by the host computer software to move and focus in the Z-axis direction. The wafer loading disk is fixed on the micro scanning platform. The micro scanning platform moves according to the XY coordinate system through the signal acquisition device and the host computer software.

[0082] The wafer sample to be tested is fixed on a self-focusing wafer scanning platform. The measurement light and reference light, which reflect the surface information of the wafer sample, interfere at the fiber coupler. After being captured by a near-infrared reflectance spectrometer, the host computer calculates the initial position and focusing distance of the current detection point and drives the self-focusing wafer scanning platform to focus. Finally, the scanning platform is driven to move and scan according to the input scanning range, and the three-dimensional morphology of the wafer is calculated.

[0083] The fiber optic coupler is a single-mode fiber optic coupler.

[0084] Example:

[0085] This example includes a superluminescent diode, a fiber optic coupler, a microscopic reference arm, a self-focusing wafer scanning platform, a near-infrared reflectance spectrometer, and a host computer. The microscopic sample arm is fixed to a motorized focusing lens mount, whose Z-axis movement and focusing are controlled by the host computer software. The wafer loading disk is fixed to the microscopic scanning platform, which moves according to the XY coordinate system via a signal acquisition device controlled by the host computer software.

[0086] In this example, the wafer sample to be tested is fixed on a self-focusing wafer scanning platform. The superluminescent diode is turned on, and the measurement light carrying sample surface information and the reference light interfere at the fiber coupler. This interference is captured by a near-infrared reflectance spectrometer. The computer calculates the initial position and focusing distance of the current detection point and drives the self-focusing wafer scanning platform to focus. Finally, based on the input scanning range, the scanning platform moves and scans, and the three-dimensional morphology of the wafer is calculated.

[0087] like Figure 1 As shown, a self-focusing wafer 3D morphology precision inspection device includes a superluminescent diode, an optical fiber coupler, a microscopic reference arm, a self-focusing wafer scanning platform, a near-infrared reflectance spectrometer, and a host computer. The wafer sample to be tested is fixed on the self-focusing wafer scanning platform. The superluminescent diode emits near-infrared broadband light that is coupled into the optical fiber coupler and split into a probe beam and a reference beam. The probe beam is focused onto the wafer sample by a microscopic probe. The measurement beam, carrying information about the sample surface, is backscattered and interferes with the reference beam at the optical fiber coupler. The interference beam is captured by the near-infrared reflectance spectrometer and transmitted to the host computer. The self-focusing wafer scanning platform moves the wafer to the focal point of the probe beam. The self-focusing wafer scanning platform is controlled to perform XY-axis scanning to obtain the wafer's 3D morphology data.

[0088] The self-focusing wafer scanning platform includes a microscopic scanning platform 13, a wafer loading tray 11, a motion controller 14, a motorized focusing lens mount 7, and a microscopic sample arm. The microscopic sample arm is fixed to the motorized focusing lens mount. The host computer processes the acquired interference signals to accurately calculate the wafer's Z-axis position and feeds this information back to the scanning platform, precisely controlling the motorized focusing lens mount for focusing. The wafer loading tray is fixed to the microscopic scanning platform, and the microscopic scanning platform moves according to the XY coordinate system under the control of the host computer software via a signal acquisition device.

[0089] The near-infrared reflective spectrometer includes a collimating lens 19, a holographic reflective grating 18, a focusing lens 17, and a linear CCD camera 16. Interference light is incident through an APC connector. After collimation by adjusting the zoom sleeve, the parallel light is incident on the grating surface at a certain angle. After first-order diffraction, the grating splits the collimated beam according to wavelength, and then the lens focuses it onto the linear CCD camera. The interference signal is converted into an electrical interference signal through the optical path and transmitted to an external host computer.

[0090] The microscopic reference arm includes a collimating lens 3, an aperture 4, a microscope objective 5, a quartz glass 6, and several sleeves. The light source enters the sleeves via an APC fiber optic connector, becomes parallel light after passing through the collimating lens, the aperture is adjusted to change the beam size, and then the light is focused onto the upper surface of the quartz glass by the microscope objective. After reflection, the light returns to the fiber coupler via the original optical path. The structure of the microscopic probe arm is the same as that of the microscopic reference arm.

[0091] like Figure 2 As shown, the photodetector 12 includes a baffle and a photoelectric switch. When the microscopic scanning platform moves a preset distance along the X-axis, the baffle blocks the light beam between the photoelectric switch's emitter and receiver, and the signal output by the photoelectric switch switches from a low level to a high level. At this time, the line scan camera begins to acquire interference signals. After acquiring a predetermined number of images, the system enters a state of waiting for the next trigger signal.

[0092] A self-focusing method for precise inspection of the three-dimensional morphology of wafers includes the following steps:

[0093] Step S1: During device initialization, the reference arm aperture is set to zero, and the quartz glass is placed on the microscopic probe end of the microscopic scanning platform. Based on the probe light intensity acquired by the linear CCD, the motorized focusing frame is controlled to bring the focal length to the surface of the quartz glass. The reference arm aperture is opened, and the optical path difference and aperture are adjusted to achieve a better signal-to-noise ratio for the interference signal. The interference signal is then acquired, and the focal length position is calculated.

[0094] Step S2: Initialize the position of the microscopic scanning platform and place the wafer sample to be tested in the wafer loading tray. Perform spectral correction on the acquired interference signal and acquire the interference signal at the current detection point. After spectral correction, calculate the initial position of the wafer and the focal length to be moved, and drive the motorized focusing lens mount to move and focus in the Z-axis direction.

[0095] Step S3: Input the scanning range and scanning step size of the wafer, and start acquiring interference signals with wafer surface position information.

[0096] Step S4: Construct the physical equation between wafer surface position data and geometric dimensions;

[0097] Step S5: Substitute the interference signal obtained in S3 into the Hanning window energy centroid method to obtain the wafer surface position data, and calculate the three-dimensional morphology of the chip according to the equation established in S4.

Claims

1. A self-focusing wafer three-dimensional morphology precision inspection device, characterized in that: The device includes a superluminescent diode (1), an optical fiber coupler (2), a microscopic reference arm with a reference arm microscope objective (5), a self-focusing wafer scanning platform with a microscopic scanning platform (13), a near-infrared reflectance spectrometer, and a host computer. During detection, the wafer sample to be tested is fixed at the self-focusing wafer scanning platform. The near-infrared broadband light emitted by the superluminescent diode is coupled into the optical fiber coupler and split into a probe light input to the microscopic probe arm and a reference light input to the microscopic reference arm. The self-focusing wafer scanning platform moves the wafer to be tested to the focal point of the probe light. The probe light is focused onto the wafer sample to be tested by the microscope probe of the microscopic probe arm, forming a measurement light carrying information about the sample surface. The light is then backscattered by the sample surface and interferes with the reference light at the optical fiber coupler. The interference light signal is captured by the near-infrared reflectance spectrometer and transmitted to the host computer. By controlling the self-focusing wafer scanning platform to move the wafer sample at the focal point of the probe light, the sample is scanned along the XY axis to obtain the three-dimensional morphology data of the wafer. A photodetector (12) is provided at the focal length wafer scanning platform. The photodetector includes a photoelectric switch and a baffle provided at the microscopic scanning platform. When the microscopic scanning platform moves a preset distance along the X direction, the baffle will block the beam between the emitter and receiver of the photoelectric switch. The signal output by the photoelectric switch will switch from low level to high level to form a trigger signal, which will trigger the linear array camera (16) of the near-infrared reflective spectrometer and start to collect interference signals. After a predetermined number of images are collected, the system will enter a state of waiting for the next trigger signal. The optical input end of the near-infrared reflective spectrometer includes an optical fiber APC connector, a scaling sleeve, a spectrometer collimating lens (19), a holographic reflective grating (18), a focusing lens, and a linear array camera, wherein the linear array camera is a linear array CCD camera; When inspecting the wafer, the interference light signal is incident through the APC connector. After the interference light is collimated by adjusting the scaling sleeve, the resulting parallel light is incident on the surface of the holographic reflective grating at a predetermined angle. After the holographic reflective grating undergoes first-order diffraction, the collimated beam is split according to wavelength and then focused by the focusing lens onto the linear CCD camera. This causes the interference light signal to be converted into an interference signal in the form of an electrical signal through the optical path and transmitted to an external host computer, which is a computer (15).

2. The self-focusing wafer three-dimensional morphology precision inspection device according to claim 1, characterized in that: The self-focusing wafer scanning platform includes a wafer loading tray (11) located on the micro-scanning platform (13), a motion controller (14), and a micro sample arm fixed to the motorized focusing lens mount (7). The micro sample arm is driven by the motorized focusing lens mount. When the host computer processes the collected interference signal, it accurately calculates the Z-axis position of the wafer and feeds it back to the self-focusing wafer scanning platform. It accurately controls the motorized focusing lens mount to make the micro sample arm focus. The wafer loading tray is fixed on the micro-scanning platform. The micro-scanning platform moves according to the XY coordinate system through the signal acquisition device and the host computer software.

3. The self-focusing wafer three-dimensional morphology precision inspection device according to claim 1, characterized in that: The microscopic reference arm includes an optical fiber APC connector, a reference arm collimating lens (3), a reference arm aperture (4), a reference arm microscope objective (5), and several sleeves; When inspecting a wafer, the reference light enters the micro reference arm, first enters the sleeve through the fiber APC connector, and becomes a parallel beam after passing through the collimating lens of the reference arm. After adjusting the aperture of the reference arm to change the size of the beam, it is then focused on the upper surface of the quartz glass (6) by the microscope objective of the reference arm. After the beam is reflected, it returns to the fiber coupler through the original optical path. The micro probe arm is provided with a probe arm collimating lens (8) and a probe arm microscope objective (9) in sequence in the direction of probe light input.

4. A method for precise inspection of the three-dimensional morphology of a self-focusing wafer, using the self-focusing three-dimensional morphology precision inspection device as described in claim 1, characterized in that: Includes the following steps; Step S1: During device initialization, the reference arm aperture is set to zero, and the quartz glass is placed at the micro-detection end of the micro-detection arm of the micro-scanning platform. Based on the detection light intensity collected by the linear CCD, the motorized focusing lens is controlled to make the focal length of the quartz glass surface, the reference arm aperture is opened, and the optical path difference and aperture are adjusted to make the interference signal have the required good signal-to-noise ratio. The interference signal is collected and the focal length position is calculated. Step S2: Initialize the position of the microscopic scanning platform and place the wafer sample to be tested in the wafer loading tray (11); The acquired interference signal is spectrally corrected, and the interference signal at the current detection point is acquired. After spectral correction, the interference signal is used to calculate the initial position of the current wafer and the focal length to be moved, and to drive the motorized focusing lens to move and focus in the Z-axis direction. Step S3: Input the scanning range and scanning step size of the wafer, and start acquiring interference signals with wafer surface position information; Step S4: Construct the physical equation between wafer surface position data and geometric dimensions; Step S5: Substitute the interference signal obtained in step S3 into the Hanning window energy centroid method to obtain the wafer surface position data, and calculate the three-dimensional morphology of the chip according to the equation established in step S4.

5. The method for precise detection of three-dimensional morphology of a self-focusing wafer according to claim 4, characterized in that: The linear CCD camera described in step S1 can actually acquire the real part of the interference signal during actual detection. Specifically, the real part of the interference spectrum signal is: Where k = 2π / λ is the wave number of the light wave. Let S be the spectral power distribution function of the light reflected from the reference end. S(z) Let a be the spectral power distribution function of the reflected light from the z-th layer in the sample. S Let z be the reflection coefficient of the z-th layer structure in the sample; Item 1 The first term is a constant, representing the DC component in the real interference signal; the second term... The superposition of the reflectance spectral signals from different depth layers in the sample and a series of cosine functions represents the encoding of the z-th layer's structural tomographic information at a frequency of 2kHz. S In the cosine function; the third term This is a self-coherent term, describing the self-interference phenomenon between the z-th layer and the z-th layer in the sample depth direction; the energy of the self-coherent term is much smaller than the energy of the light reflected from the reference end, and will not affect the accuracy of the system tomographic imaging, so it is ignored in the calculation; Performing a Fourier transform on the second term in the spectral interference signal that carries sample structure information, we get: In the above formula δ represents convolution, δ is the Eurac function, δ(z) is the tomographic structure information of the sample, and δ(-z) is the conjugate mirror image of the sample about the zero optical path axis.

6. The method for precise detection of three-dimensional morphology of a self-focusing wafer according to claim 4, characterized in that: The calculation of the focal length distance in step S2 uses the Hanning window energy centroid method to calculate the information of the focal position and the initial position, and to obtain the focal length distance to be moved, specifically as follows: H = Δz × (f1 - f2) Where Δz is the axial resolution of the system, and f1 and f2 are the focal position frequency and initial position frequency obtained after correction by the Hanning window energy centroid algorithm, respectively. The formula for the energy centroid algorithm of the Hanning window is: in, Let f be the normalized frequency of the harmonic signal, k be the spectral line number corresponding to the point of maximum amplitude, G be the amplitude corresponding to the i-th spectral line, and f be the frequency of the harmonic signal. s Where N is the sampling frequency and N is the number of sampling points.

7. The method for precise detection of three-dimensional morphology of a self-focusing wafer according to claim 4, characterized in that: In step S4, the physical equation between the wafer surface position data and the geometric dimensions is Z = Δz × (ff) org ) Where Z is the distance between the wafer surface and the origin of the Z-axis, Δz is the axial resolution of the system, and f is the wafer surface position frequency obtained after correction using the Hanning window energy centroid algorithm. org The frequency of the interference signal is when the wafer is at the origin of the Z-axis.

8. The method for precise detection of three-dimensional morphology of a self-focusing wafer according to claim 4, characterized in that: In step S2, the micro probe arm is placed at the micro sample arm of the motorized focusing lens mount. The motorized focusing lens mount is controlled by the host computer software to move and focus in the Z-axis direction. The wafer loading disk is fixed on the micro scanning platform. The micro scanning platform moves according to the XY coordinate system through the signal acquisition device and the host computer software. The wafer sample to be tested is fixed on a self-focusing wafer scanning platform. The measurement light and reference light, which reflect the surface information of the wafer sample, interfere at the fiber coupler. After being captured by a near-infrared reflectance spectrometer, the host computer calculates the initial position and focusing distance of the current detection point and drives the self-focusing wafer scanning platform to focus. Finally, the scanning platform is driven to move and scan according to the input scanning range, and the three-dimensional morphology of the wafer is calculated.

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