System and method for detecting internal flaws of wafer

Abstract

The invention relates to a wafer internal flaw detection system and method, 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] This disclosure relates to the field of wafer defect detection technology, specifically to a wafer internal defect detection system and method. Background Technology

[0002] A wafer is a silicon wafer used to manufacture silicon semiconductor circuits, and wafer inspection is one of the key steps in the chip manufacturing process. With the rapid development of integrated circuit technology, the size of wafers continues to decrease, and the chips are becoming more densely packed, which also increases the difficulty of inspection.

[0003] CN202311783499.3 discloses a method and apparatus for detecting carbon inclusions in a semiconductor substrate. The apparatus includes a microscope head for capturing images of the sample to be tested, a ring infrared emitter for irradiating the sample to be tested with red light, a test platform for supporting the sample to be tested, and a focusing sensor for obtaining the optimal focusing distance parameters of the sample to be tested.

[0004] This method uses a microscope lens to capture images of the sample to be tested under red light based on the optimal focusing position of multi-layer images. Carbon inclusions of different depths and sizes can be captured. Then, the carbon inclusions in the captured target images are grasped, thus achieving the purpose of accurate identification of carbon inclusions.

[0005] Although the above-mentioned scheme can detect the interior of semiconductor substrates, the method requires scanning and imaging the sample layer by layer in the Z and X / Y directions, which is time-consuming and requires processing a large amount of data. Summary of the Invention

[0006] The purpose of this disclosure is to enable simultaneous inspection of the interior of a wafer at different depths, thereby improving wafer inspection efficiency.

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

[0008] A wafer internal defect detection system includes:

[0009] A carrier unit is used to carry the wafer to be tested, the wafer being divided into several layers from top to bottom;

[0010] A defect capture unit is used to simultaneously capture internal defects of the wafer at different depth layers;

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

[0012] The image analysis unit analyzes images of internal defects in the wafer at different depths and obtains a distribution map of internal defects in the wafer.

[0013] The defect capture unit includes a microscope with multiple working wavelengths, each working distance of which is at one depth layer of the wafer to simultaneously capture the internal defects at different depth layers of the wafer.

[0014] Preferably, the defect capture unit includes a dispersion module for providing multiple operating wavelengths for the microscope.

[0015] More preferably, the thickness of the wafer at different depths is less than the depth of field of the corresponding working wavelength, and the depth of field of all the working wavelengths of the microscope covers the entire thickness of the wafer.

[0016] Preferably, the image generation unit is further included, which is used to image the internal defects of the wafer at different depth layers captured by the defect capture unit onto the image generation unit.

[0017] More preferably, the image generation unit includes an image sensor, and 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.

[0018] Preferably, the image sensor includes a CCD camera.

[0019] To achieve the above objectives, this disclosure also provides the following technical solutions:

[0020] A method for detecting internal defects in a wafer, the method being implemented in any of the preceding systems, includes the following steps:

[0021] The wafer to be tested is divided into several layers from top to bottom;

[0022] Images of internal defects in wafers at different depths are captured and generated simultaneously using multiple working wavelengths of a microscope.

[0023] The images of internal defects of the wafer at different depths are processed to obtain the internal defect distribution map of the wafer.

[0024] More preferably, it includes the following steps:

[0025] S1. Divide the wafer into a corresponding number of layers according to the number of working wavelengths of the microscope;

[0026] S2. Adjust the working distance of the microscope so that the working distance of each working wavelength falls on a different depth layer of the wafer;

[0027] 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;

[0028] S4. The microscope simultaneously captures defects at different depths of the horizontal coordinate points of the wafer, and the image sensor generates images of the internal defects of the wafer in order of depth.

[0029] S5. Analyze the changing trend of the defect image inside the wafer, extract the features of the defects, and obtain the number and depth distribution of defects at the coordinate points;

[0030] S6. Process the obtained number of defects and three-dimensional coordinates to obtain the internal defect number and three-dimensional coordinate distribution map of the wafer.

[0031] Preferably, the imaging distance is calculated according to the following formula:

[0032]

[0033] 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, and Φ 图像传感器 Φ is the size of the image sensor. TL NA is the entrance pupil diameter of the tube lens, and NA is the numerical aperture of the microscope.

[0034] More preferably, the microscope scans the wafer horizontally along an S-shaped path.

[0035] The technical solution claimed in this disclosure achieves the following beneficial effects:

[0036] 1) The detection system disclosed herein can simultaneously image defects at different depths 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.

[0037] 2) Based on the principles of dispersion and multi-channel imaging, this disclosure reverses the dispersion principle and uses a microscope lens with dispersion function to simultaneously image defects at different depths 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, thus optimizing the structure of the detection system. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a wafer internal defect detection system.

[0040] Figure 2 This is a schematic diagram of a wafer internal defect detection system.

[0041] Figure 3 This is a schematic diagram showing the relationship between the working distance of the microscope at various working wavelengths and the imaging distance of the image sensor.

[0042] Figure 4 This is an imaging trend diagram of defects at different depths inside the wafer.

[0043] Figure 5 This is a schematic diagram of an "S"-shaped scan of a wafer in the X / Y directions.

[0044] Figure 6 This is a diagram showing the distribution of defects inside the wafer.

[0045] Figure label:

[0046] 1-Detection platform; 2-Microscopic objective; 3-Tube lens; 4-Image sensor. Detailed Implementation

[0047] To make the objectives, technical solutions, and beneficial effects of the embodiments in this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0048] Example 1

[0049] Reference Appendix Figures 1 to 2 This embodiment provides a wafer internal defect detection system, which includes:

[0050] The carrier unit is used to carry the wafer to be tested, which is divided into several layers from top to bottom;

[0051] The defect capture unit is used to simultaneously capture internal defects in wafers at different depths.

[0052] The image generation unit, including an image sensor (e.g., a CCD camera), generates corresponding images of internal defects in the wafer from internal defects captured at different depth layers;

[0053] The image analysis unit analyzes images of internal defects in wafers at different depths and obtains a distribution map of internal defects in the wafer.

[0054] In this embodiment, the defect capture unit preferably includes a microscope with multiple working wavelengths, each working wavelength's working distance falling on one of the wafer's depth layers, for simultaneously capturing internal defects at different depth layers of the wafer. In a preferred embodiment, the defect capture unit includes a dispersion module, such as a dispersion lens, for separating the working distances of different working wavelengths, enabling the microscope's working distance to cover the wafer thickness.

[0055] In this embodiment, the analysis unit is an image processing system on a computer. Any existing image processing system for processing wafer defect images can be selected for image analysis, which will not be elaborated further.

[0056] In a preferred embodiment, the thickness of the different depth layers of the divided wafer is less than the depth of field of their corresponding working wavelengths, wherein the depth of field of all working wavelengths of the microscope covers the thickness of the entire wafer.

[0057] In a preferred embodiment, the system further includes an imaging unit for imaging internal defects of the wafer at different depths captured by the defect capture unit onto the image generation unit. For example, the imaging unit may be a tube lens. The microscope is coupled to the tube lens, and the tube lens is coupled to the image sensor.

[0058] In this embodiment, based on the principles of dispersion and multi-channel imaging, the dispersion principle is reversed to simultaneously image defects at different depths of the wafer. Furthermore, the entire system only requires one image sensor, enabling efficient and convenient detection of defect distribution inside the wafer. This avoids scanning the wafer in the Z direction, greatly reducing detection time and improving detection efficiency.

[0059] Example 2

[0060] This embodiment provides a method for detecting internal defects in a wafer, which is implemented in the system of Embodiment 1.

[0061] The method in this embodiment includes the following steps:

[0062] The wafer to be tested is divided into several layers from top to bottom;

[0063] Images of internal defects in wafers at different depths are captured and generated simultaneously using multiple working wavelengths of a microscope.

[0064] Images of internal defects in wafers at different depths are processed to obtain a distribution map of internal defects in the wafer.

[0065] In a more preferred embodiment, the method specifically includes the following steps:

[0066] S1. Divide the wafer into the corresponding number of layers according to the number of working wavelengths of the microscope;

[0067] S2. Adjust the working distance of the microscope so that the working distance of each working wavelength falls on a different depth layer of the wafer;

[0068] 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;

[0069] S4. Defects at different depths at horizontal coordinate points on the wafer are captured simultaneously using a microscope, and images of internal wafer defects in order of depth are generated using an image sensor.

[0070] S5. Analyze the changing trend of the defect images inside the wafer, extract the features of the defects, and obtain the number and depth distribution of defects at the coordinate points;

[0071] S6. Process the obtained defect quantity and three-dimensional coordinates to obtain the internal defect quantity and three-dimensional coordinate distribution map of the wafer.

[0072] In a preferred embodiment, the imaging distance is calculated using the following formula:

[0073]

[0074] 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, and Φ 图像传感器 Φ is the size of the image sensor. TL NA is the entrance pupil diameter of the tube lens, and NA is the numerical aperture of the microscope.

[0075] In a more preferred embodiment, the microscope scans the wafer horizontally along an S-shaped path.

[0076] This embodiment is based on the principles of dispersion and multi-channel imaging. It uses the dispersion principle in reverse and employs a microscope lens with dispersion function to simultaneously image defects at different depths 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, thus optimizing the structure of the detection system.

[0077] Application Example 1

[0078] The technical solutions in the above embodiments will be further described clearly below with reference to specific application examples.

[0079] As attached Figure 2As shown, the wafer internal defect detection system in this application example includes a detection platform 1, a microscope objective 2, a tube lens 3, and an image sensor 4. The detection platform is used to hold the wafer under test, the microscope objective is used to capture defects in the wafer, and the microscope objective, tube lens, and image sensor are coupled in sequence to image the wafer under test.

[0080] In this application example, a CCD camera can be used as the image sensor. The microscope objective 2 is a dispersive microscope objective, which can achieve light dispersion through optical devices such as prisms or gratings. Specifically, the microscope objective 2 captures the defects of the wafer under test, and the tube lens 3 images the defects of the wafer at different depth layers captured by the microscope onto the image sensor 4.

[0081] The specific process for detecting internal defects in a wafer in this application example is as follows:

[0082] Step 1: Place the 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 sequentially from top to bottom, with each number corresponding to an imaging channel.

[0083] In this application example, the working wavelength of the microscope objective 2 is exemplarily set to 486nm, 588nm, and 656nm. Therefore, the wafer under test is divided into 3 layers from top to bottom, which are denoted as Layer 1, Layer 2, and Layer 3 respectively.

[0084] Step 2: Adjust the distance between the microscope objective 2 and the upper surface of the wafer under test so that the depth of field of the microscope objective covers the entire thickness of the wafer, and the working distance of different wavelengths falls on different layers.

[0085] The depth of field of the microscope objectives at different wavelengths is calculated using the following formula:

[0086]

[0087] In this formula, λ is the wavelength, n is the refractive index of the medium between the sample and the microscope head (n = 1 for air, n = 1.515 for oil immersion objectives), NA is the numerical aperture of the microscope objective, M is the magnification, and e is the minimum resolvable distance of the microscope objective.

[0088] The thickness of each layer on the wafer is determined by the depth of field of the lens at the corresponding operating wavelength. Specifically, the thickness of each layer on the wafer is less than the depth of field of the corresponding operating wavelength, and the depth of field of all operating wavelengths of the microscope objective covers the entire thickness of the wafer.

[0089] Step 3: According to the formula The imaging distance of image sensor 4 is calculated.

[0090] Where L is the distance between the microscope and the tube lens, Φ 图像传感器For the image sensor size, Φ TL NA is the entrance pupil diameter of the tube lens, and NA is the numerical aperture of the microscope.

[0091] The working distance and imaging distance for different wavelengths of light are shown in the attached figure. Figure 3 As shown. Because this application example uses a dispersive microscope objective coupled to a tube lens, it is possible to image light of different wavelengths onto the same image sensor.

[0092] Step 4: Adjust the position of image sensor 4 according to the imaging distance obtained in step 3.

[0093] Step 5: Adjust microscope objective 2 to the scanning start point, and simultaneously image different depth layers at the horizontal coordinate point of the wafer under test to obtain images of Layers 1-3 in depth order. Analyze the changing trends of the images from different channels, extract the features of defects, and obtain the number and depth distribution of defects at that coordinate.

[0094] Specifically, because the microscope has multiple operating wavelengths, the CCD camera can simultaneously capture and generate images of internal wafer defects at different depths corresponding to different operating wavelengths at a horizontal coordinate point. These images are transmitted to an image processing system on a computer, where they are arranged in descending order of depth. The image processing system extracts defect features from each image layer, calculates the edge sharpness value of the defects, and determines the depth layer where the defect is located based on the sharpness value of the sharpest image.

[0095] Among them, as attached Figure 4 As shown in trends 1-4, the flaws are located in the layers corresponding to the clearest images. In trend 1, there is one flaw in layer 3; in trend 2, there is one flaw in layer 2; in trend 3, there is one flaw in layer 1; and in trend 4, there are two flaws in layers 1 and 3 respectively.

[0096] If multiple defects exist at different depths on the same horizontal coordinate, their distribution trend is illustrated in the attached diagram. Figure 4 As shown in Trend 4, the imaging results contain multiple superimposed sharp and blurry images, with the defects located in the layer corresponding to the sharp image.

[0097] Step 6: Follow as follows Figure 5 The “S”-shaped path shown is used to scan the wafer under test in the horizontal direction, image the entire wafer under test, 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 under test.

[0098] Step 7: Process the obtained defect quantity and 3D coordinates to obtain a defect distribution map inside the wafer under test, as shown in the attached figure. Figure 6 As shown.

[0099] In this application example, during inspection, the microscope simultaneously inspects the interior of the wafer at multiple depths using different operating wavelengths. Defects at different depths can be imaged onto the CCD camera and defect images can be produced. The depth and location of defects can be determined by analyzing the imaging trends at different depths. Furthermore, by scanning only in the X / Y directions, the number and distribution of defects throughout the entire wafer can be obtained.

[0100] The embodiments and application examples described above are merely illustrative descriptions of this disclosure and are not intended to limit the scope of this disclosure. Any modifications and improvements made by those skilled in the art to the technical solutions of this disclosure without departing from the spirit of this disclosure should fall within the protection scope defined by this disclosure.

Claims

1. A wafer internal defect detection system, characterized in that, include: A carrier unit is used to carry the wafer to be tested, the wafer being divided into several layers from top to bottom; A defect capture unit is used to simultaneously capture internal defects of the wafer at different depth layers; The image generation unit generates corresponding wafer internal defect images from the captured internal defects at different depth layers; The image analysis unit analyzes images of internal defects in the wafer at different depths and obtains a distribution map of internal defects in the wafer. The defect capture unit includes a microscope covering multiple working wavelengths, each working wavelength having a working distance falling on one of the depth layers of the wafer 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 includes a dispersion module for providing multiple operating wavelengths for the microscope.

3. The wafer internal defect detection system according to claim 2, characterized in that, The thickness of the wafer at different depths is less than the depth of field of the corresponding working wavelength, and the depth of field of all the working wavelengths of the microscope covers the entire thickness of the wafer.

4. The wafer internal defect detection system according to claim 2, characterized in that, It also includes an imaging unit for imaging internal defects of the wafer at different depth layers captured by the defect capturing unit onto 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, and 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.

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

7. A method for detecting internal defects in a wafer, wherein the method is implemented in the system described in any one of claims 4 to 6, characterized in that, Includes the following steps: The wafer to be tested is divided into several layers from top to bottom; Images of internal defects in wafers at different depths are captured and generated simultaneously using multiple working wavelengths of a microscope. The images of internal defects of the wafer at different depths are processed to obtain the internal defect distribution map of the wafer.

8. The wafer internal defect detection method according to claim 7, characterized in that, Includes the following steps: S1. Divide the wafer into a corresponding number of layers according to the number of working wavelengths of the microscope; S2. Adjust the working distance of the microscope so that the working distance of each working wavelength falls on a different depth layer of the wafer; 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; S4. The microscope simultaneously captures defects at different depths of the horizontal coordinate points of the wafer, and the image sensor generates images of the internal defects of the wafer in order of depth. S5. Analyze the changing trend of the defect image inside the wafer, extract the features of the defects, and obtain the number and depth distribution of defects at the coordinate points; S6. Process the obtained number of defects and three-dimensional coordinates to obtain the internal defect number and three-dimensional coordinate distribution map of the wafer.

9. The wafer internal defect detection method according to claim 8, characterized in that, The imaging distance is calculated using the following formula: 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, and Φ 图像传感器 Φ is the size of the image sensor. TL NA is the entrance pupil diameter of the tube lens, and NA is the numerical aperture of the microscope.

10. The wafer internal defect detection method according to claim 9, characterized in that, The microscope scans the wafer horizontally along an S-shaped path.

Images