Residual silicon thickness measuring method, system and device and storage medium

Abstract

The invention provides a method, a system and a device for measuring the thickness of residual silicon and a storage medium. The method comprises the following steps: acquiring a sampling image set by changing the distance between an objective lens and a sample, performing definition evaluation on the sampling image set, and based on a definition evaluation value data set, performing screening by using a preset condition to obtain a corresponding clear image; and finally, according to the clear image, the objective lens position corresponding to the clear image and a preset algorithm, a high-precision residual silicon thickness measurement result can be quickly obtained. Meanwhile, the position of the objective lens corresponding to the surface of the wafer with the smooth surface can be measured by utilizing the self-made rough surface silicon wafer and the position of the objective lens corresponding to imaging of the rough surface silicon wafer, the thickness of the residual silicon of the wafer with the smooth surface is measured, and the precision of measuring the thickness of the residual silicon of the wafer is further improved.

Description

Technical Field

[0001] The present invention relates to measurement technology, and in particular to a method, system, device and storage medium for measuring residual silicon thickness. Background Art

[0002] TSV (Through-Silicon Via) technology, or through-silicon via technology, originates from the demand for miniaturization and high integration of semiconductor devices. With the advancement of Moore's Law, traditional two-dimensional packaging technology can no longer meet the growing demand for integration, so TSV technology came into being. TSV technology achieves three-dimensional interconnection between chips by making vertical vias inside the chip, thereby greatly improving the integration and packaging efficiency of electronic components.

[0003] In the practical application of TSV technology, wafer backside thinning is an important process step. By thinning the back side of the wafer, the package mounting height can be reduced, the chip package volume can be reduced, and the thermal diffusion efficiency and electrical performance of the chip can be improved. During the wafer backside thinning process, the remaining silicon thickness (RST) of the wafer needs to be accurately measured to ensure that the thinned wafer meets the design requirements and quality standards. However, the common remaining silicon thickness measurement methods still have shortcomings: for example, laser confocal microscope measurement is limited by the wafer structure, resulting in a significant decrease in measurement accuracy; the measurement process of the x-ray microscope has high requirements for the operating environment and is easily affected, resulting in low measurement efficiency; acoustic measurement has high requirements for the operating environment and low measurement efficiency; in summary, the remaining silicon thickness measurement technologies in the existing technology all have the disadvantages of low measurement accuracy and low measurement efficiency. Summary of the invention

[0004] In view of this, in order to solve one of the above problems, an embodiment of the present invention aims to provide a method, system, device and storage medium for measuring the remaining silicon thickness, which can effectively improve the measurement accuracy and efficiency in the measurement technology of the remaining silicon thickness.

[0005] In one aspect, the present invention provides a method for measuring the thickness of residual silicon, the method comprising the following steps:

[0006] The distance between the objective lens and the sample is changed to obtain a sampling image set; the sampling image set is formed by light rays passing through the objective lens and the rough surface silicon wafer in sequence, converging onto the sample, and then passing through the rough surface silicon wafer, the objective lens and the imaging lens in sequence after being reflected by the sample; the sample comprises a smooth surface wafer with a plurality of cylindrical holes;

[0007] Determine a plurality of clear images in the sampled image set whose clarity meets a preset condition and the objective lens positions corresponding to the plurality of clear images;

[0008] Based on the several clear images, the objective lens positions corresponding to the several clear images and a preset algorithm, the remaining silicon thickness of the sample is calculated.

[0009] Furthermore, the step of determining a plurality of clear images in the sampled image set whose clarity meets a preset condition and the objective lens positions corresponding to the plurality of clear images includes:

[0010] Based on the sampled image set and the clarity evaluation function, obtaining a clarity evaluation value data set;

[0011] Based on the clarity evaluation value data set and the preset conditions, a plurality of clear images whose clarity meets the preset conditions are obtained; the plurality of clear images whose clarity meets the preset conditions include a clear image of the bottom of the cylindrical hole of the smooth surface wafer, a clear image of the rough surface silicon wafer, and a clear image of the virtual image reflected by the rough surface silicon wafer;

[0012] Based on the plurality of clear images, the corresponding objective lens position is acquired.

[0013] Furthermore, based on the definition evaluation value data set and the preset conditions, a plurality of clear images whose definition meets the preset conditions are obtained; including:

[0014] Based on the clarity evaluation value data set, obtaining a plurality of clarity evaluation maximum values;

[0015] Based on the plurality of maximum clarity evaluation values, a plurality of clear images are obtained.

[0016] Further, the calculating of the remaining silicon thickness of the sample based on the plurality of clear images, the objective lens positions corresponding to the plurality of clear images and a preset algorithm comprises:

[0017] Obtaining the thickness value of the rough surface silicon wafer;

[0018] Based on the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer, the objective lens position corresponding to the clear image of the real rough surface silicon wafer, the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, the thickness value and the preset algorithm, the remaining silicon thickness of the sample is calculated.

[0019] Furthermore, the preset algorithm includes:

[0020] Hrst=(h2+h1-d) / 2-ht

[0021] Among them, Hrst is the remaining silicon thickness of the sample, h1 is the objective lens position corresponding to the clear image of the real silicon wafer with rough surface, h2 is the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, d is the thickness value, and ht is the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer.

[0022] On the other hand, the present invention also provides a system for measuring the remaining silicon thickness, the system comprising a camera, a mirror cavity, a light source, a rough surface silicon wafer, a leveling device, a platform, a column, a movable guide rail and a processor; wherein,

[0023] The platform is used to fix the column and the leveling device;

[0024] The leveling device is used for loading samples;

[0025] The upright post is used to fix the movable guide rail;

[0026] The movable guide rail is used to fix the mirror cavity;

[0027] The mirror cavity comprises: an aperture stop, a collimating lens unit, a beam splitter, an objective lens, and an imaging lens;

[0028] The processor is used to implement the measurement method as described in the above aspect;

[0029] The light emitted by the light source passes through the aperture stop, the first collimating lens, the second collimating lens and the beam splitter in sequence; the light deflected by the beam splitter passes through the objective lens, the rough surface silicon wafer and the sample in sequence, and after being reflected by the sample, passes through the rough surface silicon wafer, the objective lens, the beam splitter and the imaging lens in sequence, and finally enters the camera.

[0030] Further, the light source comprises a wide-bandwidth light source; the wide-bandwidth light source comprises a component that can penetrate silicon and a component that cannot penetrate silicon.

[0031] Furthermore, the rough surface silicon wafer comprises a grid, and the grid shapes include strip, square and circle.

[0032] On the other hand, the present invention also provides a device for measuring the remaining silicon thickness, comprising:

[0033] at least one processor;

[0034] at least one memory for storing at least one program;

[0035] When the at least one program is executed by the at least one processor, the at least one processor implements the above-mentioned testing method.

[0036] On the other hand, the present invention further provides a computer-readable storage medium storing a program executable by a processor, wherein the program executable by the processor is used to execute the above-mentioned measurement method when executed by the processor.

[0037] In summary, the embodiments of the present invention can achieve the following beneficial effects:

[0038] The present invention provides a method, system, device and storage medium for measuring the thickness of residual silicon. By changing the distance between the objective lens and the sample, a sampling image set is obtained, and the clarity of the sampling image set is evaluated. Based on the clarity evaluation value data set, the corresponding clear image is screened using preset conditions; finally, according to the clear image, the objective lens position corresponding to the clear image and the preset algorithm calculation, a high-precision measurement result of the thickness of residual silicon can be quickly obtained. At the same time, by using the self-made rough surface silicon wafer and the objective lens position corresponding to its imaging, the objective lens position corresponding to the surface of the smooth surface wafer can be measured, so as to measure the residual silicon thickness of the smooth surface wafer, and further improve the accuracy of measuring the residual silicon thickness of the wafer. Therefore, the residual silicon thickness measurement system provided by the present invention can effectively improve the measurement accuracy and efficiency in the measurement technology of the residual silicon thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic flow chart of the steps of a method for measuring the remaining silicon thickness provided by an embodiment of the present invention;

[0040] Figure 2 is a structural block diagram of a system for measuring residual silicon thickness provided by an embodiment of the present invention;

[0041] Figure 3 It is a schematic flow chart of another method for measuring the remaining silicon thickness provided by an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the position of a virtual image of a silicon wafer with a rough surface in a measurement method provided by an embodiment of the present invention;

[0043] Figure 5 This is another schematic diagram of the position of a virtual image of a silicon wafer with a rough surface in the measurement method provided by an embodiment of the present invention;

[0044] Figure 6 This is another schematic diagram of the position of a virtual image of a silicon wafer with a rough surface in the measurement method provided by an embodiment of the present invention;

[0045] Figure 7 is a structural block diagram of a storage medium provided by an embodiment of the present invention;

[0046] Labels: 1-wide bandwidth light source, 2-aperture diaphragm, 3-first collimating lens, 4-second collimating lens, 5-camera, 6-imaging lens, 7-beam splitter, 8-objective lens, 9-rough surface silicon wafer, 10-sample, 11-leveling device, 12-platform, 13-movable guide rail, 14-column, 15-mirror cavity, 21-real object of rough surface silicon wafer, 22-virtual image reflected by rough surface silicon wafer, d-thickness of rough surface silicon wafer, h1-objective lens position corresponding to the image of homemade silicon wafer, h2-objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, h3-objective lens position corresponding to the smooth surface of the sample wafer, htx-objective lens position corresponding to the bottom of the cylindrical hole (x=1, 2, 3...). DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0048] The relevant technologies involved in this application are introduced as follows:

[0049] Laser confocal microscopy measurement: Laser confocal microscopy measures the TSV inner wall and remaining silicon thickness by detecting reflected light signals, providing high-resolution depth information. It has the advantage of non-contact measurement and is suitable for online monitoring during wafer manufacturing. This method usually measures from the front to capture TSV surface features. However, as the TSV aspect ratio increases, the light reflection signal attenuates severely, and the scattering effect intensifies when the TSV aperture is small, resulting in a significant decrease in measurement accuracy.

[0050] X-ray microscope measurement: X-ray microscope can obtain accurate depth information in high aspect ratio TSV by penetrating TSV structure with rays. This method can measure from the front and back, has high spatial resolution, and can image the inner and outer walls of TSV. However, X-ray microscope equipment is expensive and complicated to operate, which is not suitable for large-scale inspection of production lines, and has high requirements for operators.

[0051] Acoustic measurement: Acoustic measurement uses the propagation characteristics of ultrasound in silicon materials to measure TSV depth and remaining silicon thickness by analyzing the reflected signal. Ultrasonic waves can penetrate materials and obtain internal structural information, but in high-aspect ratio TSVs, signal attenuation and multiple reflections affect the accuracy and reliability of measurement. Acoustic measurement can be measured from both the front and back sides, but its complex equipment and environmental requirements limit its application in mass production.

[0052] Electrical measurement: The electrical measurement method applies an electrical signal to the TSV and measures its resistance, capacitance and other characteristics to deduce the remaining silicon thickness. This method is usually performed from the front side. Although it has certain practicality, its measurement accuracy depends on the material properties of the TSV, and it is difficult to ensure high accuracy in all scenarios, especially for TSV structures with large changes in material properties.

[0053] Several terms involved in this application are explained as follows:

[0054] Through-Silicon Via (TSV) technology is a revolutionary semiconductor packaging and interconnection solution. It achieves high-speed, low-loss electrical connections between chips or between different layers within a chip by directly manufacturing vertical conductive channels inside the chip, significantly improving data transmission rates and system performance. TSV technology is widely used in high-performance computing, 3D integrated circuits, large-capacity memory stacking and other fields, and is one of the indispensable and important technologies in the modern electronics industry.

[0055] Through Silicon Via Technology (RST) refers to the thickness of the remaining silicon material layer on the silicon wafer after a series of etching, grinding or polishing steps in the semiconductor manufacturing process. This parameter is crucial to the performance and reliability of the device, affecting the conductivity, thermal conductivity and mechanical strength of the circuit. Precise control of the remaining silicon thickness can optimize the electrical and thermal properties of the device, improve the integration and operating frequency of the integrated circuit, and is an indispensable part of the semiconductor process.

[0056] Aspect ratio: refers to the ratio between the depth of the silicon structure after etching or processing and its lateral size (such as diameter or width). This parameter is important for evaluating the processing accuracy, structural stability and performance characteristics of silicon wafers. By measuring the aspect ratio, we can have a more comprehensive understanding of the distribution of the remaining silicon thickness, providing an important basis for subsequent process control and optimization.

[0057] Scattering effect: In the measurement of remaining silicon thickness, it means that when a light beam (such as a laser) is irradiated onto the surface of a silicon wafer, part of the light will be scattered. The direction and intensity distribution of these scattered lights are closely related to the surface morphology, roughness, and remaining silicon thickness of the silicon wafer. By analyzing the characteristics of the scattered light, the information on the remaining silicon thickness can be indirectly inferred, providing an important basis for the processing and quality control of silicon wafers.

[0058] Clarity evaluation function: In the measurement of the remaining silicon thickness, the clarity of the image or video is determined by comprehensively evaluating the sharpness, resolution, contrast and noise of the image or video edge, thereby indirectly reflecting the thickness information of the silicon wafer and providing an important reference for high-precision silicon wafer thickness measurement. The following is a clarity evaluation function that can be used for a method for measuring the remaining silicon thickness provided by the present invention, where x and y represent the coordinates of the pixel points in the picture:

[0059] Clarity evaluation function: Determine the gradient of each pixel by calculating the sum of the squares of the grayscale differences between adjacent pixels in the x-axis and y-axis directions. Add up the gradient values ​​of all pixels to get the final image clarity evaluation result.

[0060]

[0061] Roberts operator: By calculating the grayscale difference between adjacent pixels on the diagonal line, the square sum of the grayscale values ​​of four adjacent pixels is subtracted and used as the gradient value of each pixel. The gradient values ​​of all pixels are accumulated to form the value of the clarity evaluation function.

[0062]

[0063] Tenengrad function: The Sobel operator is used to obtain the gradient values ​​of the pixel in the horizontal and vertical directions. The function is defined as the sum of the squares of the gradient values ​​of the pixel points, and a threshold T is set to adjust the sensitivity of the function.

[0064]

[0065] Where G(x,y) is the gradient at the pixel point (x,y)

[0066]

[0067] in and It is the gradient value of the pixel in the horizontal and vertical directions.

[0068]

[0069] in is the convolution symbol, g x , g y It is the horizontal template and vertical template of Sobel operator.

[0070] The gradient filter method, also known as the Brenner function, only needs to perform differential operations on points two pixels apart on the x-axis, that is, to calculate the second-order gradient, thereby reducing the amount of calculation.

[0071]

[0072] Variance function: It shows the dispersion of the grayscale distribution of the image. When the image is out of focus, the grayscale value has a smaller range of variation and a lower degree of dispersion, so the variance is also smaller; when the image is in focus, the grayscale value has a larger range of variation and a higher degree of dispersion, so the variance is larger.

[0073]

[0074] Where μ is the average gray value of the image

[0075]

[0076] Information entropy clarity evaluation method: In the field of information theory, entropy is an indicator to measure the richness of information. Using the evaluation function of information entropy, the diversity of grayscale distribution of in-focus images can be analyzed. When the grayscale values ​​of pixels are widely distributed and significantly different from each other, the entropy value is correspondingly high; for out-of-focus images, the situation is just the opposite.

[0077]

[0078] Among them, b is generally 2, g represents the image grayscale value, G represents the maximum image grayscale value, k represents the defocused image sequence, and P(g) represents the probability of grayscale value g appearing in the kth image.

[0079]

[0080] Among them, MN represents the total number of pixels, and n represents the number of pixels with gray value g in the kth image.

[0081] like Figure 1 As shown, an embodiment of the present invention provides a method for measuring the remaining silicon thickness, which includes the following steps:

[0082] S100: changing the distance between the objective lens and the sample to obtain a sampling image set.

[0083] Optionally, the sampling image is formed by light passing through an objective lens and a rough-surface silicon wafer in sequence and converging onto the sample, and then passing through the rough-surface silicon wafer, the objective lens and an imaging lens in sequence after being reflected by the sample; the sample includes a smooth-surface wafer with a plurality of cylindrical holes.

[0084] For both smooth and rough surface wafers, the height corresponding to the bottom of the through silicon via (TSV) is subtracted from the height corresponding to the wafer surface to calculate the remaining silicon thickness (RST). For a smooth surface wafer, the determination of its surface height is relatively complicated, while the surface height of a rough surface wafer is easy to confirm. Therefore, the present invention mainly designs a measurement method for the remaining silicon thickness of a smooth surface wafer. Through image sampling and analysis, the height of the smooth surface wafer and the height corresponding to the bottom of the through silicon via are determined, and the remaining silicon thickness of the smooth surface wafer is calculated.

[0085] Optionally, the light is emitted by a broad bandwidth light source and includes a component that can penetrate silicon and a component that cannot penetrate silicon;

[0086] Because the imaging light includes components that penetrate silicon, the sampled image set can include sampled images of the inside, surface, and outside of the wafer. The present invention uses a method of measuring from the back side, which can effectively solve the problem that light cannot irradiate to the bottom of the high aspect ratio TSV structure. Traditional optical measurement methods are often limited in deep holes and high aspect ratio TSV structures and cannot accurately obtain depth information. By incident light from the back side, the present invention can better irradiate the bottom of the TSV, significantly improving the accuracy of the measurement.

[0087] S200: Determine a plurality of clear images in the sampled image set whose clarity meets a preset condition and objective lens positions corresponding to the plurality of clear images.

[0088] Based on the sampled image set and the clarity evaluation function, a clarity evaluation value data set is calculated; the clarity evaluation function includes but is not limited to an energy gradient function, a Roberts function, a Tenengrad function, a Brenner function, a Variance function, a Laplace function, and a clarity evaluation function based on information entropy.

[0089] Based on the clarity evaluation value data set and preset conditions, a plurality of clear images whose clarity meets the preset conditions are obtained; based on the plurality of clear images, corresponding objective lens positions are obtained.

[0090] In some embodiments, the process of obtaining a plurality of clear images whose clarity meets the preset conditions based on the clarity evaluation value data set and the preset conditions in step S200 can be implemented by the following steps:

[0091] S210: Based on the clarity evaluation value data set, a plurality of clarity evaluation maximum values ​​are obtained.

[0092] The data trend in the clarity evaluation value data set is analyzed to obtain a plurality of clarity evaluation maximum values ​​in the clarity evaluation value data set that conform to the maximum value data trend. When the clarity evaluation value corresponding to the image is a maximum value, it is proved that the image is a clear image.

[0093] S220: Acquire a plurality of clear images based on the plurality of maximum clarity evaluation values.

[0094] Based on the analysis of several clarity evaluation maxima and their corresponding sampled images, a clear image of the bottom of the cylindrical hole of the smooth surface wafer, a clear image of the real object of the rough surface silicon wafer and a clear image of the virtual image reflected by the rough surface silicon wafer are screened out.

[0095] S300: Based on the plurality of clear images, the objective lens positions corresponding to the plurality of clear images and a preset algorithm, the remaining silicon thickness of the sample is calculated.

[0096] Through the clear images of several key positions and their objective lens positions, the objective lens position of the smooth surface wafer of the sample can be determined, and then the remaining silicon thickness of the sample can be calculated according to a preset algorithm.

[0097] In some embodiments, the process of calculating the remaining silicon thickness of the sample based on the plurality of clear images, the objective lens positions corresponding to the plurality of clear images and a preset algorithm in step S300 can be implemented by the following steps:

[0098] S310: Obtaining the thickness value of the rough surface silicon wafer.

[0099] S320: Based on the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer, the objective lens position corresponding to the clear image of the real object of the rough surface silicon wafer, the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, the thickness value and the preset algorithm, calculate the remaining silicon thickness of the sample.

[0100] By inserting a rough surface silicon wafer and using the clear image of the rough surface silicon wafer and the clear image of the reflected virtual image of the rough surface silicon wafer, the objective lens position corresponding to the surface of the smooth surface wafer is determined, and then further combined with the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer, the remaining silicon thickness of the smooth surface wafer sample can be calculated.

[0101] like Figure 2As shown, an embodiment of the present invention further provides a system for measuring the remaining silicon thickness, the system comprising a light source 1, an aperture stop 2, a first collimating lens 3, a second collimating lens 4, a camera 5, an imaging lens 6, a beam splitter 7, an objective lens 8, a rough surface silicon wafer 9, a sample 10, a leveling device 11, a platform 12, a movable guide rail 13, a column 14 and a processor; wherein,

[0102] The platform 12 is used to fix the column 14 and the leveling device 11;

[0103] The leveling device 11 is used to load the sample;

[0104] The column 14 is used to fix the movable guide rail 13;

[0105] The movable guide rail 13 is used to fix the mirror cavity 15; the mirror cavity 15 includes an aperture stop 2, a first collimating lens 3, a second collimating lens 4, a camera 5, an imaging lens 6, a beam splitter 7, and an objective lens 8.

[0106] Optionally, the movable rail can be set with a speed variation rule, and the mirror cavity is driven to move by the rail, so as to further move the objective lens in the measurement system. Because the speed variation rule of the movable rail can be set according to actual needs, by recording the time of the movable rail, the position of the objective lens movement can be determined in real time (the distance moved by the objective lens can be obtained in real time by setting the starting point of the objective lens as a reference point), which is used to measure the remaining silicon thickness.

[0107] The processor is used to implement the above-mentioned measurement method;

[0108] The light emitted by the light source 1 passes through the aperture stop 2, the first collimating lens 3, the second collimating lens 4 and the beam splitter 7 in sequence; the light deflected by the beam splitter 7 passes through the objective lens 8, the rough surface silicon wafer 9 and the sample 10 in sequence, and after being reflected by the sample 10, passes through the rough surface silicon wafer 9, the objective lens 8, the beam splitter 7 and the imaging lens 6 in sequence, and finally enters the camera.

[0109] Optionally, the light source comprises a broad bandwidth light source comprising a portion that is transparent to silicon and a portion that is not transparent to silicon.

[0110] Furthermore, the measurement system provided by the present invention can combine visible light and infrared light for measurement, which can not only achieve high-resolution imaging of the wafer surface, but also effectively measure the internal structure of the wafer. This innovative method can fully obtain depth information and meet the measurement needs of various materials and structures.

[0111] The measurement system provided by the present invention obtains a sampled image set by changing the distance between the objective lens and the sample, performs clarity evaluation on the sampled image set, and screens the corresponding clear image based on the clarity evaluation value data set using preset conditions; finally, according to the clear image, the position of the objective lens corresponding to the clear image, and the preset algorithm calculation, a high-precision measurement result of the remaining silicon thickness can be quickly obtained. Unlike the traditional contact measurement method, the present invention measures by imaging, maintains the advantages of non-contact detection, and avoids possible damage to the device caused by physical contact. This detection method is more suitable for rapid detection on the production line to ensure the safety and integrity of the equipment.

[0112] It can be seen that the contents of the above method embodiments are all applicable to the present system embodiments, the functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0113] like Figure 3 As shown, Figure 3 1 is a schematic diagram of the steps of another method for measuring the thickness of remaining silicon provided by an embodiment of the present invention; the present invention also provides another method for measuring the thickness of remaining silicon, which is applied to Figure 2 The system for measuring the remaining silicon thickness comprises the following steps:

[0114] S500: Optical path setup: press Figure 2 The optical path is completed as shown.

[0115] Specifically, the light emitted by the light source passes through the aperture stop, the first collimating lens, the second collimating lens and the beam splitter in sequence; the light deflected by the beam splitter passes through the objective lens, the rough surface silicon wafer and the sample in sequence, and after being reflected by the sample, passes through the rough surface silicon wafer, the objective lens, the beam splitter and the imaging lens in sequence, and finally enters the camera.

[0116] S510: Scan the sample once to determine whether the sample is smooth.

[0117] Specifically, the objective lens is moved to sample the entire sample once. The surface of the sample wafer is determined to be smooth by computer analysis. If the surface of the sample wafer is rough, the corresponding image of the rough surface wafer surface can be directly obtained, otherwise the sample wafer is a smooth surface wafer.

[0118] Specifically, when the scanning direction is not perpendicular to the wafer surface, the leveling device 11 can be controlled by image sampling information to compensate for the tilt angle.

[0119] S520: Change the distance between the objective lens and the sample to obtain a sampling image set.

[0120] Through the image sampling of step S510, the objective lens position corresponding to the bottom of the cylindrical hole of the sample wafer can be confirmed (if there are multiple cylindrical holes, the cylindrical hole that is closest to the sample wafer surface that can be clearly imaged is selected). When actually measuring, the objective lens is first moved downward so that it is located below the objective lens position corresponding to the bottom of the cylindrical hole of the sample wafer. Then the objective lens is moved upward at a uniform speed, and images are collected at a uniform speed to form a sample image set.

[0121] Optionally, if the surface of the sample wafer is rough, the silicon wafer with the rough surface is removed from the system and step S520 is performed again.

[0122] Furthermore, the moving speed of the movable guide rail is designed to be uniform, and the mirror cavity is driven to move by the guide rail, so that the objective lens in the measurement system is further moved at a uniform speed; since the movable guide rail is designed to be uniform, the position of the objective lens movement can be determined in real time by recording the time of the movable guide rail (the distance moved by the objective lens can be obtained in real time by setting the starting point of the objective lens as a reference point), which is used to measure the remaining silicon thickness.

[0123] S530: Determine the clear image of the key position and confirm the corresponding objective lens position according to the sampled image set.

[0124] While collecting images at a uniform speed, the clarity evaluation value of each collected image is calculated in real time according to the clarity evaluation function until several maximum values ​​of the clarity evaluation appear, from which three maximum values ​​of the clarity evaluation are screened out, and the corresponding images are a clear image of the bottom of the cylindrical hole of a wafer with a smooth surface, a clear image of the actual silicon wafer with a rough surface, and a clear image of the virtual image reflected by the silicon wafer with a rough surface; if the surface of the sample wafer is rough, the surface of the sample wafer can be imaged directly, and in the measurement, only two maximum values ​​of the clarity evaluation and their corresponding images need to be screened out, specifically a clear image of the surface of the sample wafer and a clear image of the bottom of the cylindrical hole of the sample wafer.

[0125] Furthermore, the rough surface silicon wafer is made by itself and can be used repeatedly. The pattern on the surface of the rough surface silicon wafer is known, so the clear images corresponding to several maximum values ​​of the clarity evaluation value can be screened by analyzing the image information to determine the clear image of the rough surface silicon wafer and its reflected virtual image.

[0126] S540: Calculate the remaining silicon thickness of the sample according to the image position corresponding to the key position.

[0127] When the sample wafer surface is smooth, the positional relationship between the virtual image reflected by the rough surface silicon wafer and the bottom of the cylindrical hole includes: Figures 4 to 6There are three cases shown, namely, the virtual image of the rough surface silicon wafer is located above the bottom of all cylindrical holes, the virtual image of the rough surface silicon wafer is located between the bottoms of the cylindrical holes, and the virtual image of the rough surface silicon wafer is located below the bottom of all cylindrical holes.

[0128] In either case, the real image and virtual image of the rough surface silicon wafer satisfy the imaging law of the plane mirror, and the rough surface silicon wafer is imaged by reflection from the smooth surface of the sample wafer. Therefore, the objective lens position corresponding to the real image and virtual image of the rough surface silicon wafer can be used to obtain the objective lens position corresponding to the smooth surface of the sample wafer.

[0129] Specifically, the objective lens position corresponding to the smooth surface of the sample wafer is calculated by the following formula:

[0130] h3=(h2-h1-d) / 2

[0131] Among them, d is the thickness of the rough surface silicon wafer, h1 is the objective lens position corresponding to the clear image of the rough surface silicon wafer, h2 is the objective lens position corresponding to the homemade silicon wafer, and h3 is the objective lens position corresponding to the smooth surface of the sample wafer.

[0132] Furthermore, the remaining silicon thickness of the sample can be calculated by the following formula:

[0133] Remaining silicon thickness Hrst = (h2-h1-d) / 2-htx

[0134] Among them, d is the thickness of the rough surface silicon wafer, h1 is the objective lens position corresponding to the homemade silicon wafer image, h2 is the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, h3 is the objective lens position corresponding to the smooth surface of the sample wafer, and htx is the objective lens position corresponding to the bottom of the cylindrical hole (x=1, 2, 3...).

[0135] Furthermore, during measurement, the measurement system provided by the present invention can image the bottoms of multiple cylindrical holes and automatically calculate the number of cylindrical holes on the image (there may be multiple cylindrical hole bottoms located at the same objective lens position).

[0136] On the other hand, in the case where the sample wafer surface is rough, there is no need to use a homemade rough surface silicon wafer; the remaining silicon thickness of the sample can be calculated by the following formula:

[0137] Remaining silicon thickness Hrst = H-htx

[0138] In which, H is the objective lens position corresponding to the clear image of the rough surface wafer surface, and htx is the objective lens position corresponding to the bottom of the cylindrical hole (x=1, 2, 3...).

[0139] like Figure 7 As shown, an embodiment of the present invention further provides a device for measuring the remaining silicon thickness, comprising:

[0140] at least one processor;

[0141] at least one memory for storing at least one program;

[0142] When the at least one program is executed by the at least one processor, the at least one processor implements the method steps described in the above method embodiment.

[0143] Among them, the memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs. The memory may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a remote memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0144] It can be seen that the contents of the above method embodiments are all applicable to the present device embodiments, the functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0145] In addition, the embodiment of the present application also discloses a computer program product or a computer program, which is stored in a computer-readable storage medium. The processor of the computer device can read the computer program from the computer-readable storage medium, and the processor executes the computer program, so that the computer device performs the above method.

[0146] The embodiment of the present invention further provides a computer-readable storage medium, which stores a program executable by a processor, and the program executable by the processor is used to implement the above method when executed by the processor. Similarly, the contents of the above method embodiment are all applicable to the present storage medium embodiment, and the functions specifically implemented by the present storage medium embodiment are the same as those of the above method embodiment, and the beneficial effects achieved are also the same as those achieved by the above method embodiment.

[0147] It is understood that all or some steps and systems in the disclosed method above can be implemented as software, firmware, hardware and appropriate combinations thereof. Some physical components or all physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, and the computer-readable medium can include a computer storage medium (or a non-transitory medium) and a communication medium (or a temporary medium). As known to those of ordinary skill in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical disk storage, magnetic cassette, magnetic tape, disk storage or other magnetic storage device, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0148] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for measuring the thickness of residual silicon, characterized in that: include: The distance between the objective lens and the sample is changed to obtain a set of sampled images; The sampling image set is formed by light rays passing through an objective lens and a rough surface silicon wafer in sequence, converging onto the sample, and then passing through the rough surface silicon wafer, the objective lens, and an imaging lens in sequence after being reflected by the sample; the sample comprises a smooth surface wafer with a plurality of cylindrical holes; Determine a plurality of clear images in the sampled image set whose clarity meets a preset condition and objective lens positions corresponding to the plurality of clear images; Based on the plurality of clear images, the objective lens positions corresponding to the plurality of clear images and a preset algorithm, the remaining silicon thickness of the sample is calculated.

2. The measuring method according to claim 1, characterized in that: The step of determining a plurality of clear images in the sampled image set whose clarity meets a preset condition and the objective lens positions corresponding to the plurality of clear images comprises: Based on the sampled image set and the clarity evaluation function, a clarity evaluation value data set is calculated; Based on the clarity evaluation value data set and the preset conditions, a plurality of clear images whose clarity meets the preset conditions are determined; the plurality of clear images whose clarity meets the preset conditions include a clear image of the bottom of the cylindrical hole of the smooth surface wafer, a clear image of the rough surface silicon wafer, and a clear image of the virtual image reflected by the rough surface silicon wafer; Based on the plurality of clear images, the corresponding objective lens position is acquired.

3. The measuring method according to claim 2, characterized in that: The method of obtaining a plurality of clear images whose clarity meets the preset conditions based on the clarity evaluation value data set and the preset conditions comprises: Based on the clarity evaluation value data set, obtaining a plurality of clarity evaluation maximum values; Based on the plurality of maximum clarity evaluation values, a plurality of clear images are obtained.

4. The measuring method according to claim 2, characterized in that: The method of calculating the remaining silicon thickness of the sample based on the plurality of clear images, the objective lens positions corresponding to the plurality of clear images and a preset algorithm comprises: Obtaining the thickness value of the rough surface silicon wafer; Based on the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer, the objective lens position corresponding to the clear image of the real rough surface silicon wafer, the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, the thickness value and the preset algorithm, the remaining silicon thickness of the sample is calculated.

5. The measuring method according to claim 4, characterized in that: The preset algorithm includes: Hrst=(h2+h1-d) / 2-ht Among them, Hrst is the remaining silicon thickness of the sample, h1 is the objective lens position corresponding to the clear image of the real silicon wafer with rough surface, h2 is the objective lens position corresponding to the clear image of the virtual image reflected by the rough surface silicon wafer, d is the thickness value, and ht is the objective lens position corresponding to the clear image of the bottom of the cylindrical hole of the smooth surface wafer.

6. A system for measuring residual silicon thickness, characterized in that: The measurement system includes a camera, a mirror cavity, a light source, a rough surface silicon wafer, a leveling device, a platform, a column, a movable guide rail and a processor; wherein, The platform is used to fix the column and the leveling device; The leveling device is used for loading samples; The upright post is used to fix the movable guide rail; The movable guide rail is used to fix the mirror cavity; The processor is used to implement the measurement method according to any one of claims 1 to 5; The mirror cavity comprises: an aperture stop, a collimating lens unit, a beam splitter, an objective lens, and an imaging lens; The light emitted by the light source passes through the aperture stop, the first collimating lens, the second collimating lens and the beam splitter in sequence; the light deflected by the beam splitter passes through the objective lens, the rough surface silicon wafer and the sample in sequence, and after being reflected by the sample, passes through the rough surface silicon wafer, the objective lens, the beam splitter and the imaging lens in sequence, and finally enters the camera.

7. A measurement system according to claim 6, characterized in that: The light source comprises a broad bandwidth light source; the broad bandwidth light source comprises a silicon-transmissive component and a silicon-impermeable component.

8. A measuring system according to claim 6, characterized in that: The rough surface silicon wafer comprises a grid, and the shapes of the grid include strip, square and circle.

9. A device for measuring residual silicon thickness, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method according to any one of claims 1 to 5.

10. A computer-readable storage medium storing a program executable by a processor, characterized in that: The processor-executable program is used to perform the method according to any one of claims 1 to 5 when executed by the processor.

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