Self-focusing type wafer three-dimensional shape precision detection device and method

Abstract

The invention provides a self-focusing type wafer three-dimensional shape precision detection device and method. The self-focusing type wafer three-dimensional shape precision detection device comprises a super-radiation light-emitting diode, an optical fiber coupler, a microscopic reference arm provided with a reference arm microscope objective, a self-focal length wafer scanning platform of a microscopic scanning platform, a near-infrared reflection type spectrograph and an upper computer. During detection, near-infrared broadband light radiated by the diode is coupled into the optical fiber coupler and then is divided into detection light and reference light; moving the wafer to be detected to the focal point of the detection light; the detection light is focused on a to-be-detected wafer sample to form measurement light carrying sample surface information, then the measurement light is backscattered by the sample surface and interferes with the reference light at the optical fiber coupler, a formed interference light signal is captured by the near-infrared reflection type spectrometer and then is transmitted into the upper computer, the wafer sample is moved at the focus of the detection light, and the measurement light is transmitted to the lower computer. Performing X-axis and Y-axis scanning to obtain three-dimensional shape data of the wafer; according to the invention, the high-precision nondestructive detection of the three-dimensional shape of the chip can be realized under the condition that the chip sample is not damaged.

Description

Technical Field

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

[0002] With the development of science and technology, wafers have gradually become key components of modern products. Chip balling technology is a process of covering or embedding the bumps or flip-chip solder balls on the chip into the substrate or module. This technology can not only significantly increase the connection density between the chip and the substrate or module, but also help improve the heat transfer capacity of the device and optimize its electrical performance. The quality of the solder balls is directly related to the working performance and stability of the device. Therefore, measuring the surface morphology is crucial to further improve the balling technology and chip design.

[0003] Compared with traditional detection methods, modern processing and manufacturing industries have put forward higher requirements for wafer surface morphology detection, such as high resolution, large range and fast measurement speed. Taking the microelectronics industry as an example, the lateral dimensions of sapphire substrates and silicon wafer chips are usually 4 to 16 inches, and the axial measurement accuracy is required to reach the sub-micron to nanometer level. Due to the high-throughput characteristics of the production line, the efficiency of automatic detection also needs to be improved accordingly. Although traditional surface morphology measurement technologies, such as atomic force microscopy and scanning electron microscopy, can achieve nanometer-level accuracy, their measurement efficiency is low and it is difficult to meet a wide range of measurement needs. Therefore, it is very necessary to propose a method for measuring wafer surface morphology in the existing industrial environment. Summary of the invention

[0004] The present invention provides a self-focusing wafer three-dimensional morphology precision detection device and method, which can realize high-precision non-destructive detection of chip three-dimensional morphology without damaging chip samples.

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

[0006] A self-focusing wafer three-dimensional morphology precision detection device, the device comprising a superluminescent diode (1), an optical fiber coupler (2), a microscopic reference arm provided with a reference arm microscopic objective lens (5), a self-focusing wafer scanning platform of a microscopic scanning platform (13), a near-infrared reflection spectrometer and a host computer; during detection, a wafer sample to be detected is fixed on the self-focusing wafer scanning platform; the near-infrared broadband light radiated by the superluminescent diode is coupled into the optical fiber coupler and is divided into detection light input to the microscopic detection arm, reference light input to the microscopic reference arm, and detection light input to the microscopic detection arm. ; The self-focus wafer scanning platform moves the wafer to be tested to the focus of the detection light; the detection light is focused on the wafer sample to be tested through the microprobe of the microdetection arm to form a measurement light carrying the sample surface information, which is then backscattered by the sample surface and interferes with the reference light at the fiber coupler. The formed interference light signal is captured by the near-infrared reflective spectrometer and transmitted to the host computer. The wafer sample is moved at the focus of the detection light by controlling the self-focus wafer scanning platform, and the sample is scanned on the XY axis to obtain the three-dimensional morphology data of the wafer.

[0007] The self-focusing wafer scanning platform comprises a wafer loading plate (11) arranged at a microscopic scanning platform (13), a motion controller (14), and a microscopic sample arm fixed at an electric focusing frame (7); the microscopic sample arm is driven by the electric focusing frame, and 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, accurately controls the electric focusing frame to focus the microscopic sample arm, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the host computer software to move according to the XY coordinate system through a signal collection device.

[0008] A photoelectric detector (12) is provided at the self-focus wafer scanning platform, and the photoelectric detector comprises 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 light beam between the emitter and the receiver of the photoelectric switch, and the signal output by the photoelectric switch is switched from a low level to a high level to form a trigger signal, so that the linear array camera (16) of the near-infrared reflective spectrometer is triggered and starts to collect interference signals. After a predetermined number of pictures 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 comprises 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;

[0010] When inspecting the wafer, the interference light signal is incident from the APC connector. After adjusting the zoom sleeve to collimate the interference light, the parallel light formed is incident on the surface of the holographic reflective grating at a predetermined angle. After the first-order diffraction, the holographic reflective grating splits the collimated light beam according to the wavelength, and then focuses it to the linear array CCD camera by the focusing lens, so that the interference light signal is 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 comprises an optical fiber APC connector, a reference arm collimating lens (3), a reference arm aperture (4), a reference arm microscopic objective lens (5) and a plurality of sleeves;

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

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

[0014] A self-focusing wafer three-dimensional morphology precision detection method, using a self-focusing wafer three-dimensional morphology precision detection device, comprises the following steps:

[0015] Step S1, when the device is initialized, the reference arm diaphragm is set to zero, and the quartz glass is placed at the microscopic detection end of the microscopic detection arm of the microscopic scanning platform. According to the detection light intensity collected by the linear array CCD, the electric focus frame is controlled to make the focus on the quartz glass surface, the reference arm diaphragm is opened, the optical path difference and the diaphragm are adjusted so that the interference signal has the required good signal-to-noise ratio, and the interference signal is collected and the focal position is calculated;

[0016] Step S2, initializing the position of the microscopic scanning platform, placing the wafer sample to be tested in the wafer loading plate (11); performing spectral correction on the collected interference signal, collecting the interference signal of the current detection point; calculating the initial position of the current wafer and the focal length to be moved after the interference signal is spectrally corrected, and driving the electric focusing frame to perform mobile focusing in the Z-axis direction;

[0017] Step S3, input the scanning range and scanning step length of the wafer, and start collecting the interference signal with the wafer surface position information;

[0018] Step S4, constructing a physical equation between wafer surface position data and geometric dimensions;

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

[0020] In step S1, the linear array CCD camera can only collect the real part of the interference signal in actual detection. The real part of the interference spectrum signal is specifically:

[0021]

[0022] Among them, k = 2π / λ is the wave number of the light wave, is the spectral power distribution function of the reflected light at the reference end, S S(z) is the spectral power distribution function of the reflected light of the zth layer in the sample, a S is the reflection coefficient of the z-th layer structure in the sample; the first term is a constant term, representing the DC component in the real interference signal; the second term It is the superposition of the reflectance spectrum signals of different depth layers in the sample and the product of a series of cosine functions, representing that the z-th layer structural tomography information of the sample is encoded at a frequency of 2kza S In the cosine function of is the self-coherence term, which describes the self-interference phenomenon between the zth layer and the z′th layer in the depth direction of the sample; the energy of the self-coherence term is much smaller than the energy of the reflected light at the reference end, and will not affect the accuracy of the system tomography, so it is ignored in the calculation;

[0023] Perform Fourier transform on the second item in the spectral interference signal that contains the sample structure information, and we have:

[0024]

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

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

[0027] H=Δz×(f 1 -f 2 )

[0028] Where Δz is the axial resolution of the system, f 1 With f 2 are respectively the focal position frequency and the initial position frequency obtained after correction by the Hanning window energy center of gravity algorithm;

[0029] The Hanning window energy center of gravity algorithm formula is:

[0030]

[0031] in, is the normalized frequency of the harmonic signal, k is the spectral line number corresponding to the maximum point of the spectral line amplitude, G is the amplitude corresponding to the i-th spectral line, f s 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 Z-axis origin, Δz is the axial resolution of the system, f is the wafer surface position frequency obtained after correction by the Hanning window energy center of gravity algorithm, and f org is the frequency of the interference signal when the wafer is at the origin of the Z axis.

[0035] In step S2, the microscopic detection arm is arranged at the microscopic sample arm of the electric focusing frame, and the upper computer software controls the electric focusing frame to move and focus in the Z-axis direction, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the upper computer software to move according to the XY coordinate system through the signal acquisition device;

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

[0037] The optical fiber coupler adopts a single-mode optical fiber coupler.

[0038] The present invention is a method for measuring the surface morphology of a wafer in an existing industrial environment, and can realize high-precision nondestructive testing of the three-dimensional morphology of a chip without damaging the chip sample.

[0039] The present invention proposes a high-precision wafer morphology detection device that can focus quickly and accurately, and realizes ultra-precision detection of chip three-dimensional morphology with nanometer-level accuracy without destroying the chip structure. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0041] AttachedFigure 1 A schematic diagram of the system structure of an embodiment of the present invention;

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

[0043] Attached Figure 3 It is a schematic diagram of a semiconductor photolithography wafer ball implant chip according to an embodiment of the present invention;

[0044] Attached Figure 4 Schematic diagram of the principle of the autofocus algorithm according to an embodiment of the present invention;

[0045] Attached Figure 5 A schematic diagram of a wafer surface three-dimensional topography measurement result according to an embodiment of the present invention;

[0046] Attached Figure 6 Schematic diagram of cross-sectional morphology measurement results corresponding to the three-dimensional morphology of the wafer surface according to an embodiment of the present invention

[0047] In the figure: 1 is a superluminescent diode, 2 is a fiber coupler, 3 is a reference arm collimating lens, 4 is a reference arm aperture, 5 is a reference arm microscope objective lens, 6 is a quartz glass, 7 is an electric focus frame, 8 is a detection arm collimating lens, 9 is a detection arm microscope objective lens, 10 is a wafer sample, 11 is a wafer loading plate, 12 is a photodetector, 13 is a microscope scanning platform, 14 is a motion controller, 15 is a computer, 16 is a linear array CCD camera, 17 is a spectrometer focal lens, 18 is a holographic reflective grating, and 19 is a spectrometer collimating lens. DETAILED DESCRIPTION

[0048] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

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

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates 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 detection device comprises a superluminescent diode 1, an optical fiber coupler 2, a microscopic reference arm provided with a reference arm microscope objective lens 5, a self-focusing wafer scanning platform of a microscopic scanning platform 13, a near-infrared reflective spectrometer and a host computer; during detection, the wafer sample to be tested is fixed on the self-focusing wafer scanning platform; the near-infrared broadband light radiated by the superluminescent diode is coupled into the optical fiber coupler and is divided into detection light input into the microscopic detection arm and reference light input into the microscopic reference arm; The self-focus wafer scanning platform moves the wafer to be tested to the focus of the detection light; the detection light is focused on the wafer sample to be tested through the microprobe of the microdetection arm to form a measurement light carrying the sample surface information, which is then backscattered by the sample surface and interferes with the reference light at the fiber coupler. The formed interference light signal is captured by the near-infrared reflective spectrometer and transmitted to the host computer. The wafer sample is moved at the focus of the detection light by controlling the self-focus wafer scanning platform to perform XY axis scanning on the sample to obtain the three-dimensional morphology data of the wafer.

[0052] The self-focus wafer scanning platform includes a wafer loading plate 11 disposed at a microscopic scanning platform 13, a motion controller 14, and a microscopic sample arm fixed at an electric focusing lens frame 7;

[0053] The microscopic sample arm is driven by an electric focusing mirror frame. 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, accurately controls the electric focusing mirror frame to focus the microscopic sample arm, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the host computer software to move according to the XY coordinate system through the signal acquisition device.

[0054] A photoelectric detector 12 is provided at the self-focal length wafer scanning platform, and the photoelectric detector includes a photoelectric switch and a baffle provided at the microscope scanning platform; when the microscope scanning platform moves a preset distance along the X direction, the baffle will block the light beam between the transmitter and the receiver of the photoelectric switch, and the signal output by the photoelectric switch switches from a low level to a high level to form a trigger signal, so that the linear array camera 16 of the near-infrared reflective spectrometer is triggered and starts to collect interference signals. After completing the predetermined number of picture collections, 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] When inspecting the wafer, the interference light signal is incident from the APC connector. After adjusting the zoom sleeve to collimate the interference light, the formed parallel light is incident on the surface of the holographic reflective grating at a predetermined angle. After the first-order diffraction, the holographic reflective grating splits the collimated light beam according to the wavelength, and then focuses it to the linear array CCD camera by the focusing lens, so that the interference light signal is 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.

[0057] The microscopic reference arm comprises an optical fiber APC connector, a reference arm collimating lens 3, a reference arm aperture 4, a reference arm microscopic objective lens 5 and a plurality of sleeves;

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

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

[0060] A self-focusing wafer three-dimensional morphology precision detection method, using a self-focusing wafer three-dimensional morphology precision detection device, comprises the following steps:

[0061] Step S1, when the device is initialized, the reference arm diaphragm is set to zero, and the quartz glass is placed at the microscopic detection end of the microscopic detection arm of the microscopic scanning platform. According to the detection light intensity collected by the linear array CCD, the electric focus frame is controlled to make the focus on the quartz glass surface, the reference arm diaphragm is opened, the optical path difference and the diaphragm are adjusted so that the interference signal has the required good signal-to-noise ratio, and the interference signal is collected and the focal position is calculated;

[0062] Step S2, initializing the position of the microscopic scanning platform, placing the wafer sample to be tested in the wafer loading plate 11; performing spectral correction on the collected interference signal, collecting the interference signal of the current detection point; calculating the initial position of the current wafer and the focal length to be moved after the interference signal is spectrally corrected, and driving the electric focusing frame to move and focus in the Z-axis direction;

[0063] Step S3, input the scanning range and scanning step length of the wafer, and start collecting the interference signal with the wafer surface position information;

[0064] Step S4, constructing a physical equation between wafer surface position data and geometric dimensions;

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

[0066] In step S1, the linear array CCD camera can only collect the real part of the interference signal in actual detection. The real part of the interference spectrum signal is specifically:

[0067]

[0068] Among them, k = 2π / λ is the wave number of the light wave, is the spectral power distribution function of the reflected light at the reference end, S S(z) is the spectral power distribution function of the reflected light of the zth layer in the sample, a S is the reflection coefficient of the z-th layer structure in the sample; the first term is a constant term, representing the DC component in the real interference signal; the second term It is the superposition of the reflectance spectrum signals of different depth layers in the sample and the product of a series of cosine functions, representing that the z-th layer structural tomography information of the sample is encoded at a frequency of 2kza S In the cosine function of is the self-coherence term, which describes the self-interference phenomenon between the zth layer and the zth layer in the depth direction of the sample; the energy of the self-coherence term is much smaller than the energy of the reflected light at the reference end, and will not affect the accuracy of the system tomography, so it is ignored in the calculation;

[0069] Perform Fourier transform on the second item in the spectral interference signal that contains the sample structure information, and we have:

[0070]

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

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

[0073] H=Δz×(f 1 -f 2 )

[0074] Where Δz is the axial resolution of the system, f 1 With f 2 are respectively the focal position frequency and the initial position frequency obtained after correction by the Hanning window energy center of gravity algorithm;

[0075] The Hanning window energy center of gravity algorithm formula is:

[0076]

[0077] in, is the normalized frequency of the harmonic signal, k is the spectral line number corresponding to the maximum point of the spectral line amplitude, G is the amplitude corresponding to the i-th spectral line, f s 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 Z-axis origin, Δz is the axial resolution of the system, f is the wafer surface position frequency obtained after correction by the Hanning window energy center of gravity algorithm, and f org is the frequency of the interference signal when the wafer is at the origin of the Z axis.

[0081] In step S2, the microscopic detection arm is arranged at the microscopic sample arm of the electric focusing frame, and the upper computer software controls the electric focusing frame to move and focus in the Z-axis direction, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the upper computer software to move according to the XY coordinate system through the signal acquisition device;

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

[0083] The optical fiber coupler adopts a single-mode optical fiber coupler.

[0084] Example:

[0085] This example includes a superluminescent diode, a fiber coupler, a microscopic reference arm, a self-focusing wafer scanning platform, a near-infrared reflective spectrometer and a host computer. The microscopic sample arm is fixed on the electric focusing frame, and the host computer software controls the electric focusing frame to move and focus in the Z-axis direction. The wafer loading plate is fixed on the microscopic scanning platform, and the microscopic scanning platform is controlled by the host computer software to move according to the XY coordinate system through the signal acquisition device.

[0086] In this example, the wafer sample to be tested is fixed on the self-focus wafer scanning platform, the superluminescent diode is turned on, and the measurement light and reference light with sample surface information interfere at the fiber coupler. After being captured by the near-infrared reflective spectrometer, the computer calculates the initial position and focus distance of the current detection point, and drives the self-focus 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.

[0087] like Figure 1 As shown, a self-focusing wafer three-dimensional morphology precision detection device comprises a superluminescent diode, a fiber coupler, a microscopic reference arm, a self-focusing wafer scanning platform, a near-infrared reflection spectrometer and a host computer; a wafer sample to be tested is fixed on the self-focusing wafer scanning platform; the superluminescent diode radiates near-infrared broadband light that is coupled into the fiber coupler and is divided into detection light and reference light by the fiber coupler; the detection light is focused onto the wafer sample to be tested through a microscopic probe, and the measuring light carrying the sample surface information is backscattered and interferes with the reference light at the fiber coupler, is captured by the near-infrared reflection spectrometer and then transmitted to the host computer; the self-focusing wafer scanning platform moves the wafer to be tested to the focus of the detection light; and the self-focusing wafer scanning platform is controlled to perform XY axis scanning to obtain wafer three-dimensional morphology data.

[0088] The self-focus wafer scanning platform includes a microscopic scanning platform 13, a wafer loading plate 11, a motion controller 14, an electric focusing frame 7 and a microscopic sample arm. The microscopic sample arm is fixed on the electric focusing frame, and the host computer processes the collected interference signal to accurately calculate the Z-axis position of the wafer and feeds it back to the scanning platform, and accurately controls the electric focusing frame to focus. The wafer loading plate is fixed on the microscopic scanning platform, and the microscopic scanning platform is controlled by the host computer software to move according to the XY coordinate system through the 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 array CCD camera 16. Interference light is incident from the APC connector, and after adjusting the zoom sleeve to collimate the interference light, parallel light is incident on the grating surface at a certain angle. After the grating undergoes first-order diffraction, the collimated light beam is split according to wavelength, and then focused to the linear array CCD camera by the lens. The interference signal is converted into an interference signal in the form of an electrical signal through the optical path and transmitted to an external host computer.

[0090] The microscopic reference arm includes a collimating lens 3 from the reference arm, an aperture 4 from the reference arm, a microscopic objective lens 5 from the reference arm, quartz glass 6, and several sleeves. The light source enters the sleeve through the optical fiber APC connector, becomes parallel light after passing through the collimating lens, adjusts the aperture to change the size of the light beam, and then focuses on the upper surface of the quartz glass through the microscopic objective lens, and returns to the optical fiber coupler through the original light path after reflection; the structure of the microscopic detection 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 direction, the baffle will block the light beam between the photoelectric switch emitter and the receiver, and the signal output by the photoelectric switch will switch from a low level to a high level. At this time, the linear array camera starts to collect interference signals. After completing the collection of a predetermined number of pictures, the system enters a state of waiting for the next trigger signal.

[0092] A self-focusing wafer three-dimensional morphology precision detection method comprises the following steps:

[0093] Step S1, when the device is initialized, the reference arm diaphragm is set to zero, and the quartz glass is placed on the microscopic detection end of the microscopic scanning platform. According to the detection light intensity collected by the linear array CCD, the electric focus frame is controlled to make the focus on the quartz glass surface. The reference arm diaphragm is opened, the optical path difference and the diaphragm are adjusted to make the interference signal have a better signal-to-noise ratio, and the interference signal is collected and the focal position is calculated.

[0094] Step S2, initialize the position of the microscopic scanning platform, place the wafer sample to be tested in the wafer loading tray. Perform spectral correction on the collected interference signal, and collect the interference signal of the current detection point. After the interference signal is spectrally corrected, calculate the initial position of the current wafer and the focal length to be moved, and drive the electric focus frame to move and focus in the Z-axis direction.

[0095] Step S3: input the scanning range and scanning step length of the wafer, and start collecting the interference signal with the wafer surface position information.

[0096] Step S4, constructing a physical equation between wafer surface position data and geometric dimensions;

[0097] Step S5, bringing the interference signal obtained in S3 into the Hanning window energy center of gravity method to obtain the wafer surface position data, and calculating the three-dimensional morphology result of the chip according to the equation established in S4.

Claims

1. A self-focusing wafer three-dimensional morphology precision detection device, characterized in that: The device comprises a superluminescent diode (1), an optical fiber coupler (2), a microscopic reference arm provided with a reference arm microscopic objective lens (5), a self-focus wafer scanning platform of a microscopic scanning platform (13), a near-infrared reflection spectrometer and a host computer; during detection, a wafer sample to be tested is fixed at the self-focus wafer scanning platform; the near-infrared broadband light radiated by the superluminescent diode is coupled into the optical fiber coupler and is divided into detection light input into the microscopic detection arm and reference light input into the microscopic reference arm; the self-focus wafer scanning platform moves the wafer to be tested to the focus of the detection light; the detection light is focused onto the wafer sample to be tested through the microscopic probe of the microscopic detection arm to form measurement light carrying sample surface information, which is then backscattered by the sample surface and interferes with the reference light at the optical fiber coupler; the interference light signal formed is captured by the near-infrared reflection spectrometer and transmitted to the host computer; the wafer sample is moved at the focus of the detection light by controlling the self-focus wafer scanning platform to perform XY axis scanning on the sample to obtain wafer three-dimensional morphology data.

2. The self-focusing wafer three-dimensional shape precision detection device according to claim 1, characterized in that: The self-focus wafer scanning platform comprises a wafer loading plate (11) arranged at a microscopic scanning platform (13), a motion controller (14), and a microscopic sample arm fixed at an electric focusing lens frame (7); The microscopic sample arm is driven by an electric focusing mirror frame. 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, accurately controls the electric focusing mirror frame to focus the microscopic sample arm, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the host computer software to move according to the XY coordinate system through the signal acquisition device.

3. The self-focusing wafer three-dimensional shape precision detection device according to claim 2, characterized in that: A photoelectric detector (12) is provided at the self-focus wafer scanning platform, and the photoelectric detector comprises 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 light beam between the emitter and the receiver of the photoelectric switch, and the signal output by the photoelectric switch is switched from a low level to a high level to form a trigger signal, so that the linear array camera (16) of the near-infrared reflective spectrometer is triggered and starts to collect interference signals. After a predetermined number of pictures are collected, the system enters a state of waiting for the next trigger signal.

4. The self-focusing wafer three-dimensional shape precision detection device according to claim 3 is characterized in that: The optical input end of the near-infrared reflective spectrometer comprises 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; When inspecting the wafer, the interference light signal is incident from the APC connector. After adjusting the zoom sleeve to collimate the interference light, the parallel light formed is incident on the surface of the holographic reflective grating at a predetermined angle. After the first-order diffraction, the holographic reflective grating splits the collimated light beam according to the wavelength, and then focuses it to the linear array CCD camera by the focusing lens, so that the interference light signal is 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).

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

6. A self-focusing wafer three-dimensional morphology precision detection method, using a self-focusing wafer three-dimensional morphology precision detection device, characterized in that: The steps include: Step S1, when the device is initialized, the reference arm diaphragm is set to zero, and the quartz glass is placed at the microscopic detection end of the microscopic detection arm of the microscopic scanning platform. According to the detection light intensity collected by the linear array CCD, the electric focus frame is controlled to make the focus on the quartz glass surface, the reference arm diaphragm is opened, the optical path difference and the diaphragm are adjusted so that the interference signal has the required good signal-to-noise ratio, and the interference signal is collected and the focal position is calculated; Step S2, initializing the position of the microscopic scanning platform, and placing 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; After the interference signal is spectrally corrected, the initial position of the current wafer and the focal length to be moved are calculated, and the electric focusing frame is driven to move and focus in the Z-axis direction; Step S3, input the scanning range and scanning step length of the wafer, and start collecting the interference signal with the wafer surface position information; Step S4, constructing a physical equation between wafer surface position data and geometric dimensions; Step S5, bringing the interference signal obtained in step S3 into the Hanning window energy center of gravity method to obtain the wafer surface position data, and calculating the three-dimensional morphology result of the chip according to the equation established in step S4.

7. The self-focusing wafer three-dimensional topography precision detection method according to claim 6, characterized in that: In step S1, the linear array CCD camera can collect the real part of the interference signal during actual detection. The real part of the interference spectrum signal is specifically: Among them, k = 2π / λ is the wave number of the light wave, is the spectral power distribution function of the reflected light at the reference end, S S(z) is the spectral power distribution function of the reflected light of the zth layer in the sample, a S is the reflection coefficient of the z-th layer structure in the sample; the first term is a constant term, representing the DC component in the real interference signal; the second term It is the superposition of the reflectance spectrum signals of different depth layers in the sample and the product of a series of cosine functions, representing that the z-th layer structure tomography information of the sample is encoded into a frequency of 2jza S In the cosine function of is the self-coherence term, which describes the self-interference phenomenon between the zth layer and the zth layer in the depth direction of the sample; the energy of the self-coherence term is much smaller than the energy of the reflected light at the reference end, and will not affect the accuracy of the system tomography, so it is ignored in the calculation; Perform Fourier transform on the second item in the spectral interference signal that contains the sample structure information, and we have: In the above formula represents convolution, δ is the Eurak function, δ(z) is the tomographic structure information of the sample, and δ(-z) is the conjugate mirror image of the measured sample symmetrical about the zero optical path axis.

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

9. The self-focusing wafer three-dimensional topography precision detection method according to claim 6, 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 Z-axis origin, Δz is the axial resolution of the system, f is the wafer surface position frequency obtained after correction by the Hanning window energy center of gravity algorithm, and f org is the frequency of the interference signal when the wafer is at the origin of the Z axis.

10. The self-focusing wafer three-dimensional topography precision detection method according to claim 6, characterized in that: In step S2, the microscopic detection arm is arranged at the microscopic sample arm of the electric focusing frame, and the upper computer software controls the electric focusing frame to move and focus in the Z-axis direction, and the wafer loading plate is fixed on the microscopic scanning platform. The microscopic scanning platform is controlled by the upper computer software to move according to the XY coordinate system through the signal acquisition device; The wafer sample to be tested is fixed on a self-focus wafer scanning platform. The measurement light and reference light with sample surface information reflected from the wafer sample surface interfere at the fiber coupler and are captured by the near-infrared reflective spectrometer. The host computer calculates the initial position and focusing distance of the current detection point, and drives the self-focus 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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