Wafer internal flaw detection system

Abstract

The utility model relates to a wafer internal flaw detection system, and the system comprises a bearing unit which is used for bearing a wafer to be detected, and the wafer is divided into a plurality of layers from top to bottom; the flaw capturing unit is used for capturing internal flaws of the wafers of different depth layers at the same time; the image generation unit is used for generating corresponding wafer internal flaw images according to the captured internal flaws of different depth layers; the image analysis unit is used for analyzing the internal defect images of the wafer in different depth layers and obtaining an internal defect distribution diagram of the wafer; wherein the flaw capturing unit comprises a microscope covering a plurality of working wavelengths, and the working distance of each working wavelength falls on one depth layer of the wafer so as to capture the internal flaws of different depth layers of the wafer at the same time. According to the system, defects of different depth layers of the wafer can be imaged at the same time, Z-direction scanning of the wafer is avoided, and the detection efficiency is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wafer defect detection, and in particular to a wafer internal defect detection system. Background Art

[0002] Wafers are silicon chips used to produce silicon semiconductor circuits. Wafer detection is one of the key steps in the chip production and processing process. With the rapid development of integrated circuit technology, the size of wafers has continued to decrease, the chips they carry have become more dense, and the difficulty of detection has also continued to increase.

[0003] CN202311783499.3 discloses a method and device for detecting carbon inclusions in semiconductor substrates. The device includes a microscope lens for capturing images of samples to be detected, a ring-shaped infrared light emitter for irradiating red light on the samples to be detected, a test platform for carrying the samples to be detected, and a focusing sensor for obtaining optimal focusing distance parameters of the samples to be detected.

[0004] This solution uses a microscope lens to capture the sample to be tested that is irradiated with red light according to the optimal focusing position of the multi-layer image. Carbon inclusions of different depths and sizes can be captured, and the carbon inclusions in the captured target image are then captured, achieving the purpose of accurately identifying carbon inclusions.

[0005] Although the above scheme can detect the inside of the semiconductor substrate, the method adopted requires scanning and imaging the sample layer by layer in the Z direction and X / Y direction. The detection is time-consuming and requires a large amount of data to be processed. Utility Model Content

[0006] The purpose of the present invention is to simultaneously detect the inside of a wafer at different depths to improve wafer detection efficiency.

[0007] To achieve the above objectives, the present disclosure provides the following technical solutions:

[0008] A wafer internal defect detection system, comprising:

[0009] A carrying unit, used for carrying a wafer to be inspected, wherein the wafer is divided into several layers from top to bottom;

[0010] A defect capture unit, used for simultaneously capturing internal defects of the wafer at different depth layers;

[0011] An image generating unit generates corresponding wafer internal defect images from the captured internal defects at different depth layers;

[0012] An image analysis unit, which analyzes the internal defect images of the wafer at different depth layers and obtains an internal defect distribution map of the wafer;

[0013] Wherein, the defect capturing unit comprises a microscope covering a plurality of working wavelengths, and the working distance of each working wavelength is located at one of the depth layers of the wafer to simultaneously capture the internal defects of different depth layers of the wafer.

[0014] Preferably, the defect capture unit comprises a dispersion module for providing a plurality of the working wavelengths for the microscope.

[0015] More preferably, the thicknesses of the wafer layers at different depths are respectively smaller than the depths of field of the corresponding working wavelengths, and the depths of field of all the working wavelengths of the microscope cover the entire thickness of the wafer.

[0016] Preferably, it further comprises an imaging unit, which is used to image the internal defects of the wafer at different depth layers captured by the defect capturing unit to the image generating unit.

[0017] More preferably, the image generating unit comprises an image sensor.

[0018] Preferably, the imaging unit comprises a tube lens, the microscope is coupled to the tube lens, and the tube lens is coupled to the image sensor.

[0019] Preferably, the image sensor comprises a CCD camera.

[0020] The technical solution claimed in the present disclosure has achieved the following beneficial effects:

[0021] 1) The detection system disclosed in the present invention can simultaneously image defects at different depth layers of the wafer, efficiently and conveniently detect the distribution of defects inside the wafer, avoid scanning the wafer in the Z direction, greatly reduce the detection time, and improve the detection efficiency.

[0022] 2) The present invention is based on the principles of dispersion and multi-channel imaging, uses the dispersion principle in reverse, and adopts a microscope lens with dispersion function to simultaneously image defects at different depth layers inside the wafer onto the same image plane. The entire system only requires one image sensor to efficiently and conveniently detect the distribution of defects inside the wafer, thereby optimizing the structure of the detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are merely embodiments of the present disclosure, and a person of ordinary skill in the art can obtain other drawings based on the provided drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the module of the wafer internal defect detection system.

[0025] Figure 2 This is the schematic diagram of the wafer internal defect detection system.

[0026] Figure 3 Schematic diagram of the changing relationship between the working distance of the microscope at each working wavelength and the imaging distance of the image sensor.

[0027] Figure 4 This is a trend chart of defect imaging at different depths inside the wafer.

[0028] Figure 5 Schematic diagram of performing "S"-shaped scanning on the wafer in the X / Y direction.

[0029] Figure 6 This is the defect distribution map inside the wafer.

[0030] Reference numerals:

[0031] 1-Detection platform; 2-Microscope objective lens; 3-Tube lens; 4-Image sensor. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and beneficial effects of the embodiments of the present disclosure clearer, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0033] Example 1

[0034] Reference Figures 1 to 2 , this embodiment provides a wafer internal defect detection system, which includes:

[0035] A carrying unit, used for carrying the wafer to be inspected, the wafer being divided into several layers from top to bottom;

[0036] Defect capture unit, used to capture internal defects of wafers at different depth layers simultaneously;

[0037] An image generation unit, including an image sensor (e.g., a CCD camera), generates corresponding wafer internal defect images from captured internal defects at different depth layers;

[0038] An image analysis unit analyzes the internal defect images of the wafer at different depth layers and obtains the internal defect distribution map of the wafer;

[0039] In the solution of this embodiment, the defect capture unit preferably includes a microscope having multiple working wavelengths, and the working distance of each working wavelength falls on one of the depth layers of the wafer, so as to simultaneously capture internal defects of different depth layers of the wafer. In a preferred solution, the defect capture unit includes a dispersion module, such as a microscope equipped with a dispersion lens, and the dispersion module is used to separate the working distances of different working wavelengths so that the working distance of the microscope can cover the thickness of the wafer.

[0040] In the solution of this embodiment, the analysis unit is an image processing system on a computer, and any existing image processing system for processing wafer defect images can be selected for image analysis, which will not be described in detail.

[0041] In a preferred solution, the thicknesses of the divided wafer layers at different depths are respectively smaller than the depths of field of their corresponding working wavelengths, wherein the depths of field of all working wavelengths of the microscope cover the thickness of the entire wafer.

[0042] In a preferred solution, the system in this embodiment further includes an imaging unit, which is used to image the internal defects of the wafer at different depth layers captured by the defect capture unit to the image generation unit. Exemplarily, the imaging unit can use a tube lens. The microscope is coupled to the tube lens, and the tube lens is coupled to the image sensor.

[0043] In the scheme of this embodiment, based on the principles of dispersion and multi-channel imaging, the dispersion principle is utilized in reverse to simultaneously image defects in different depth layers of the wafer, and the entire system only needs to use one image sensor to achieve efficient and convenient detection of defect distribution inside the wafer, avoiding scanning of the wafer in the Z direction, greatly reducing the detection time, and improving detection efficiency.

[0044] Example 2

[0045] This embodiment provides a method for detecting internal defects of a wafer, which is implemented in the system in Embodiment 1.

[0046] The method in this embodiment comprises the following steps:

[0047] Divide the wafer to be inspected into several layers from top to bottom;

[0048] Use the microscope's multiple working wavelengths to simultaneously capture and generate images of defects inside the wafer at different depth levels;

[0049] The internal defect images of the wafer at different depth layers are processed to obtain the internal defect distribution map of the wafer.

[0050] In a more preferred embodiment, the method used in this embodiment specifically includes the following steps:

[0051] S1. Divide the wafer into corresponding layers according to the number of working wavelengths of the microscope;

[0052] S2. Adjust the working distance of the microscope so that the working distances of the various working wavelengths fall on different depth layers of the wafer;

[0053] S3. Calculate the imaging distance of each depth layer of the wafer in the image sensor, and adjust the position of the image sensor according to the imaging distance;

[0054] S4. Using a microscope to simultaneously capture defects at different depth layers of horizontal coordinate points of the wafer, and using an image sensor to generate images of defects inside the wafer in the order of depth layers;

[0055] S5. Analyze the changing trend of the defect image inside the wafer, extract the characteristics of the defects, and obtain the number and depth distribution of the defects at the coordinate points;

[0056] S6. Process the obtained number of defects and three-dimensional coordinates to obtain a distribution diagram of the number of internal defects and three-dimensional coordinates of the wafer.

[0057] In a preferred embodiment, the imaging distance is calculated according to the following formula:

[0058]

[0059] Where D is the imaging distance of the image sensor, WD is the working distance of the microscope, L is the distance between the microscope and the tube lens, Φ 图像传感器 is the size of the image sensor, Φ TL is the entrance pupil diameter of the tube lens, and NA is the numerical aperture of the microscope.

[0060] In a more preferred embodiment, the microscope scans the wafer horizontally in an S-shaped path.

[0061] This embodiment is based on the principles of dispersion and multi-channel imaging, uses the dispersion principle in reverse, and adopts a microscope lens with dispersion function to simultaneously image defects at different depth layers inside the wafer onto the same image plane. The entire system only needs one image sensor to efficiently and conveniently detect the distribution of defects inside the wafer, thereby optimizing the structure of the detection system.

[0062] Application Example 1

[0063] The technical solution in the above embodiment is further described below in conjunction with specific application examples.

[0064] As attached Figure 2As shown, the wafer internal defect detection system in this application example includes a detection platform 1, a microscope objective lens 2, a tube lens 3 and an image sensor 4. The detection platform is used to carry the wafer to be tested, the microscope objective lens is used to capture the defects of the wafer, and the microscope objective lens, the tube lens and the image sensor are coupled in sequence to image the wafer to be tested.

[0065] In this application example, a CCD camera may be used as the image sensor. Microscope objective 2 is a dispersive microscope objective, which can achieve light dispersion through optical devices such as prisms or gratings. Microscope objective 2 captures defects of the wafer to be tested, and tube lens 3 images the defects of the wafer at different depth layers captured by the microscope to image sensor 4.

[0066] The specific process of wafer internal defect detection in this application example is as follows:

[0067] Step 1: Place a wafer of known thickness on the detection platform 1, and divide its thickness into corresponding layers according to the number of working wavelengths of the microscope objective 2. Number the divided wafer layers from top to bottom, and each number corresponds to an imaging channel.

[0068] In this application example, the working wavelength of the microscope objective lens 2 is exemplarily set to 486 nm, 588 nm, and 656 nm. Therefore, the wafer to be tested is divided into three layers from top to bottom, which are respectively recorded as Layer 1, Layer 2, and Layer 3 from top to bottom.

[0069] Step 2: Adjust the distance between the microscope objective lens 2 and the upper surface of the wafer to be measured so that the depth of field of the microscope objective lens covers the entire wafer thickness and the working distances of different wavelengths fall on layers of different depths.

[0070] Among them, the depth of field of the microscope objective at different wavelengths is calculated by the following formula:

[0071]

[0072] In this formula, λ is the wavelength, n is the refractive index of the medium between the sample to be measured and the microscope lens (n=1 for air, n=1.515 for oil immersion objective), NA is the numerical aperture of the microscope objective, M is the magnification, and e is the minimum distance that the microscope objective can resolve.

[0073] The thickness of each layer of the wafer is determined by the depth of field of the lens at the corresponding working wavelength. Among them, the thickness of each layer of the wafer is less than the depth of field of the working wavelength corresponding to the layer, and the depth of field of all working wavelengths of the microscope objective lens covers the entire wafer thickness.

[0074] Step 3: Based on the formula The imaging distance of the image sensor 4 is calculated.

[0075] Where L is the distance between the microscope and the tube lens, Φ 图像传感器is the image sensor size, Φ TL is the diameter of the tube lens entrance pupil, and NA is the numerical aperture of the microscope.

[0076] The working distance and imaging distance of light of different wavelengths are shown in the attached figure. Figure 3 Since this application example designs a dispersive microscope objective coupled with a tube lens, it is possible to image light of different wavelengths onto the same image sensor.

[0077] Step 4: Adjust the position of the image sensor 4 according to the imaging distance obtained in step 3.

[0078] Step 5: Adjust the microscope objective 2 to the scanning starting point, and simultaneously image different depth layers of the horizontal coordinate point of the wafer to be tested, and obtain images of Layer 1-3 in depth order. Analyze the changing trend of the images of different channels, extract the characteristics of the defects, and obtain the number and depth distribution of the defects at the coordinates.

[0079] Specifically, since the microscope has multiple working wavelengths at the same time, the CCD camera can simultaneously capture and generate images of internal defects of the wafer at different depths corresponding to different working wavelengths at horizontal coordinate points. The images are transmitted to the image processing system on the computer, and the group of images is arranged in order from top to bottom according to depth. The image processing system extracts the defect features in each layer of the image, calculates the clarity value of the defect edge, obtains the sharpest image with the largest clarity value, and determines the depth layer where the defect is located based on the clarity value.

[0080] Among them, as attached Figure 4 As shown in Trends 1-4, the defects are located in the layer corresponding to the clearest image. In Trend 1, there is a defect in Layer 3, in Trend 2, there is a defect in Layer 2, in Trend 3, there is a defect in Layer 1, and in Trend 4, there are two defects in Layer 1 and Layer 3 respectively.

[0081] If there are multiple defects at different depths at the same horizontal coordinate, their distribution trend is shown in the attached figure. Figure 4 As shown in Trend 4, the imaging result includes multiple superpositions of clear images and blurred images, and the defects are located in the layer corresponding to the clear image.

[0082] Step 6: Follow the steps below: Figure 5 The "S"-shaped path shown is used to scan the wafer to be tested in the horizontal direction, image the entire wafer to be tested, record the number and depth of defects corresponding to each horizontal coordinate, and obtain the number and three-dimensional coordinate distribution of defects in the entire wafer to be tested.

[0083] Step 7: Process the number and three-dimensional coordinates of the defects obtained to obtain a distribution map of the defects inside the wafer to be tested, as shown in the attached figure. Figure 6 shown.

[0084] In this application example, during inspection, the microscope uses different working wavelengths to simultaneously inspect the inside of multiple depth layers of the wafer. Defects at different depth layers can be imaged to the CCD camera and defect images can be produced. The depth position of the defect can be determined by analyzing the imaging trends at different depths, and by scanning only in the X / Y direction, the number and distribution of defects inside the entire wafer can be obtained.

[0085] The embodiments and application examples described above are merely illustrative descriptions of the present disclosure and are not intended to limit the scope of the present disclosure. Without departing from the design spirit of the present disclosure, various modifications and improvements made to the technical solutions of the present disclosure by ordinary technicians in this field should all fall within the protection scope determined by the present disclosure.

Claims

1. A wafer internal defect detection system, characterized in that: include: A carrying unit, used for carrying a wafer to be inspected, wherein the wafer is divided into several layers from top to bottom; A defect capture unit, used for simultaneously capturing internal defects of the wafer at different depth layers; An image generating unit generates corresponding wafer internal defect images from the captured internal defects at different depth layers; An image analysis unit, which analyzes the internal defect images of the wafer at different depth layers and obtains an internal defect distribution map of the wafer; Wherein, the defect capturing unit comprises a microscope covering a plurality of working wavelengths, and the working distance of each working wavelength falls on one of the depth layers of the wafer so as to simultaneously capture the internal defects of different depth layers of the wafer.

2. The wafer internal defect detection system according to claim 1, characterized in that: The defect capture unit comprises a dispersion module for providing a plurality of the working wavelengths for the microscope.

3. The wafer internal defect detection system according to claim 2, characterized in that: The thicknesses of the wafer layers at different depths are respectively smaller than the depths of field of the corresponding working wavelengths, and the depths of field of all the working wavelengths of the microscope cover the entire thickness of the wafer.

4. The wafer internal defect detection system according to claim 2, characterized in that: An imaging unit is also included, and the imaging unit is used to image the internal defects of the wafer at different depth layers captured by the defect capturing unit to the image generating unit.

5. The wafer internal defect detection system according to claim 4, characterized in that: The image generation unit includes an image sensor.

6. The wafer internal defect detection system according to claim 5, characterized in that: The imaging unit includes a tube lens, the microscope is coupled to the tube lens, and the tube lens is coupled to the image sensor.

7. The wafer internal defect detection system according to claim 5, characterized in that: The image sensor includes a CCD camera.

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