A method, system, apparatus and storage medium for measuring a remaining silicon thickness

Abstract

The application provides a residual silicon thickness measurement method, system, device and storage medium, the distance between the objective lens and the sample is changed, a sampling image set is obtained, the definition of the sampling image set is evaluated, the corresponding clear image is obtained by screening based on the definition evaluation value data set and using a preset condition; finally, the clear image, the objective lens position corresponding to the clear image and a preset algorithm are used for calculation, and a high-precision residual silicon thickness measurement result can be quickly obtained. Meanwhile, by using the self-made rough surface silicon wafer and the imaging corresponding objective lens position, the objective lens position corresponding to the smooth surface wafer surface can be measured, the residual silicon thickness of the smooth surface wafer is measured, and the precision of the residual silicon thickness measurement of the wafer is further improved.

Description

Technical Field

[0001] This invention relates to measurement technology, and more particularly to a method, system, apparatus, and storage medium for measuring residual silicon thickness. Background Technology

[0002] Through-Silicon Via (TSV) technology originated from the need for miniaturization and high integration of semiconductor devices. As Moore's Law advanced, traditional two-dimensional packaging technologies could no longer meet the ever-increasing demands for integration, thus TSV technology emerged. TSV technology achieves three-dimensional interconnection between chips by creating vertical vias inside the chip, thereby significantly improving the integration and packaging efficiency of electronic components.

[0003] In practical applications of TSV technology, wafer backside thinning is a crucial process step. Thinning the wafer backside reduces package mounting height, chip package size, and improves thermal diffusion efficiency and electrical performance. During wafer backside thinning, precise measurement of the residual silicon thickness (RST) is essential to ensure the thinned wafer meets design requirements and quality standards. However, common methods for measuring RST have drawbacks: for example, laser confocal microscopy is limited by the wafer structure, leading to a significant decrease in measurement accuracy; X-ray microscopy requires a demanding operating environment and is easily affected, resulting in low measurement efficiency; acoustic measurements also have high operating environment requirements and low efficiency. In summary, existing RST measurement techniques all suffer from low measurement accuracy and low efficiency. Summary of the Invention

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

[0005] On one hand, the present invention provides a method for measuring the remaining silicon thickness, the method comprising the following steps:

[0006] The distance between the objective lens and the sample is changed to obtain a set of sampled images; the set of sampled images is formed by light passing sequentially through the objective lens and a rough-surface silicon wafer and converging onto the sample, and then being reflected by the sample and passing sequentially through the rough-surface silicon wafer, the objective lens, and an imaging lens; the sample includes a smooth-surface wafer with several cylindrical holes;

[0007] Determine a number of clear images in the sampled image set that meet preset clarity conditions, and the objective lens positions corresponding to the number 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 residual silicon thickness of the sample is calculated.

[0009] Further, the determination of the several clear images in the sampling image set whose clarity degree meets the preset condition and the objective lens positions corresponding to the several clear images comprises:

[0010] Based on the sampling image set and the clarity degree evaluation function, a clarity degree evaluation value data set is obtained.

[0011] Based on the clarity degree evaluation value data set and the preset condition, several clear images whose clarity degree meets the preset condition are obtained; the several clear images whose clarity degree meets the preset condition include the clear image of the bottom of the cylindrical hole of the smooth surface wafer, the clear image of the rough surface silicon wafer and the clear image of the rough surface silicon wafer reflection virtual image.

[0012] Based on the several clear images, the corresponding objective lens positions are obtained.

[0013] Further, the obtaining of the several clear images whose clarity degree meets the preset condition based on the clarity degree evaluation value data set and the preset condition comprises:

[0014] Based on the clarity degree evaluation value data set, several clarity degree evaluation maximum values are obtained.

[0015] Based on the several clarity degree evaluation maximum values, the several clear images are obtained.

[0016] Further, the calculation of the residual silicon thickness of the sample based on the several clear images, the objective lens positions corresponding to the several clear images and the preset algorithm comprises:

[0017] The thickness value of the rough surface silicon wafer is obtained.

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

[0019] Further, the preset algorithm comprises:

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

[0021] Hrst= h2- h1- d + ht, wherein Hrst is the residual silicon thickness of the sample, h1 is the objective lens position corresponding to the clear image of the real object of the rough surface silicon wafer, h2 is the objective lens position corresponding to the clear image of the reflected virtual image of 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] In another aspect, the present application also provides a system for measuring residual silicon thickness, 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 to load the sample;

[0025] The column 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. After being deflected by the beam splitter, the light passes through the objective lens, the rough surface silicon wafer and the sample in sequence, and then passes through the rough surface silicon wafer, the objective lens, the beam splitter and the imaging lens in sequence after being reflected by the sample, 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] Further, the rough surface silicon wafer comprises a grid, and the grid shape comprises a strip shape, a square shape and a circular shape.

[0032] In another aspect, the present application also provides a device for measuring residual 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 test method.

[0036] In another aspect, the present application also provides a computer readable storage medium, wherein a processor executable program is stored, and the processor executable program is used for executing the above-mentioned measurement method when executed by a processor.

[0037] In summary, the embodiments of the present application can achieve the beneficial effects including:

[0038] The present application provides a kind of remaining silicon thickness measurement method, system, device and storage medium, by changing the distance between objective lens and sample, obtains sampling image set, carries out definition evaluation to sampling image set, based on definition evaluation value data set, utilize preset condition and obtain corresponding clear image by screening;Finally, according to clear image, clear image corresponding objective lens position and pre-set algorithm calculation, high-precision remaining silicon thickness measurement result can be quickly obtained.Simultaneously, using self-made rough surface silicon wafer and its imaging corresponding objective lens position, the objective lens position corresponding to the surface of the wafer with smooth surface can be measured, the remaining silicon thickness of the wafer with smooth surface is measured, and the accuracy of the remaining silicon thickness measurement of the wafer is further improved.Therefore, the remaining silicon thickness measurement system provided by the present application can effectively improve the measurement accuracy and measurement efficiency in the measurement technology of the remaining silicon thickness. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a step flowchart of the remaining silicon thickness measurement method provided by the embodiment of the present application;

[0040] Figure 2 It is a structure block diagram of the remaining silicon thickness measurement system provided by the embodiment of the present application;

[0041] Figure 3 It is a step flowchart of another remaining silicon thickness measurement method provided by the embodiment of the present application;

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

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

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

[0045] Figure 7 It is a structure block diagram of a kind of storage medium provided by the embodiment of the present application;

[0046] Legend: 1 - broadband 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 rail, 14 - stand, 15 - mirror cavity, 21 - rough surface silicon wafer real object, 22 - rough surface silicon wafer reflected virtual image, d - thickness of rough surface silicon wafer, h1 - objective lens position corresponding to self-made silicon wafer image, h2 - objective lens position corresponding to clear image of rough surface silicon wafer reflected virtual image, h3 - objective lens position corresponding to sample wafer smooth surface, htx - objective lens position corresponding to bottom of columnar hole (x = 1, 2, 3…). DETAILED DESCRIPTION

[0047] The application will be further described in detail below in conjunction with the drawings and specific embodiments. For the step numbers in the following embodiments, only the setting is for the convenience of explaining and illustrating, and the order between the steps is not limited in any way, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0048] The related technologies involved in the present application are introduced as follows:

[0049] Laser confocal microscope measurement: Laser confocal microscope measures the TSV inner wall and the remaining silicon thickness by detecting the reflected light signal, provides high-resolution depth information, has the advantage of non-contact measurement, and is suitable for online monitoring in wafer manufacturing process. This method is usually measured from the front to capture the TSV surface features. However, as the aspect ratio of TSV increases, the light reflection signal decays seriously, and the scattering effect is intensified 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 the TSV structure with X-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 complex to operate, not suitable for large-scale detection on production line, and requires high operating personnel.

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

[0052] Electrical Measurement: Electrical measurement method deduces the remaining silicon thickness by measuring the resistance, capacitance and other characteristics of TSV under the application of electrical signal. This method is usually performed from the front side, although it has certain practicality, its measurement accuracy depends on the material properties of TSV, and it is difficult to ensure high accuracy in all scenarios, especially for TSV structures with large material performance changes.

[0053] The following terms related to this application are explained as follows:

[0054] Through-Silicon Via (TSV): A revolutionary semiconductor packaging and interconnection solution. It realizes high-speed, low-loss electrical connection between chips or different levels within a chip by directly manufacturing vertical conductive channels inside the chip, significantly improving data transmission rate 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 technologies in modern electronics industry.

[0055] Remaining Silicon Thickness (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 semiconductor manufacturing process. This parameter is crucial for device performance and reliability, affecting the electrical conductivity, thermal conductivity efficiency and mechanical strength of the circuit. Precise control of the remaining silicon thickness can optimize the electrical and thermal characteristics of the device, improve the integration and working frequency of integrated circuits, and is an indispensable part of semiconductor process.

[0056] Aspect Ratio: Refers to the ratio of the depth of the silicon structure after etching or processing to its lateral dimension (such as diameter or width). This parameter is important for evaluating the processing accuracy, structural stability and performance characteristics of the silicon wafer. By measuring the aspect ratio, we can more comprehensively understand the distribution of the remaining silicon thickness, providing important basis for subsequent process control and optimization.

[0057] Scattering Effect: In the measurement of remaining silicon thickness, it refers to the scattering of part of the light (such as laser) when it irradiates the surface of the silicon wafer. The direction and intensity distribution of these scattered light is closely related to the surface topography, roughness and remaining silicon thickness of the silicon wafer. By analyzing the characteristics of scattered light, we can indirectly deduce the information of the remaining silicon thickness, providing important basis for the processing and quality control of the silicon wafer.

[0058] Sharpness evaluation function: In the measurement of residual silicon thickness, the sharpness of the image or video is evaluated by the sharpness, resolution, contrast and noise of the image or video edge, so as to indirectly reflect the thickness information of the silicon wafer, and provide an important reference for high-precision silicon wafer thickness measurement. The following is a sharpness evaluation function that can be used in the measurement method of the residual silicon thickness provided by the present application, wherein x and y represent the coordinates of the pixel points in the picture:

[0059] Sharpness evaluation function: the gradient of each pixel point is determined by calculating the square sum of the gray value difference between the adjacent pixels in the x-axis and y-axis directions. The gradient values of all pixel points are accumulated to obtain the final image sharpness evaluation result.

[0060]

[0061] Roberts operator: the gray value difference of adjacent pixels on the diagonal line is calculated. The square sum of the gray values of the four adjacent pixels is subtracted and squared to obtain the gradient value of each pixel. The gradient values of all pixels are accumulated to form the numerical value of the sharpness evaluation function.

[0062]

[0063] Tenengrad function: the gradient values of the pixel points in the horizontal and vertical directions are obtained by the Sobel operator. The function is defined as the square sum 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 of the pixel point (x,y)

[0066]

[0067] where and are the gradient values of the pixel points in the horizontal and vertical directions.

[0068]

[0069] where is the convolution symbol, g x , g y are the horizontal and vertical templates of the Sobel operator.

[0070] Gradient filter method, also known as Brenner function, only needs to perform difference operation on the points separated by two pixels on the x-axis, that is, to calculate the second order gradient, so as to reduce the calculation amount.

[0071]

[0072] The variance function shows the dispersion of gray-level distribution in an image. When an image is out of focus, the range of gray-level values ​​is small, the dispersion is low, and therefore the variance is also small; while when an image is in focus, the range of gray-level values ​​is large, the dispersion is high, and therefore the variance is large.

[0073]

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

[0075]

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

[0077]

[0078] Where b is generally taken as 2, g represents the image gray value, G represents the maximum value of the image gray value, k represents the defocused image sequence, and P(g) represents the probability of gray value g appearing in the k-th image.

[0079]

[0080] Where MN represents the total number of pixels, and n represents the number of pixels with a gray value of g in the k-th image.

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

[0082] S100: Change the distance between the objective lens and the sample to acquire a set of sampled images.

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

[0084] For the wafer with smooth surface and rough surface, the remaining silicon thickness (RST) is calculated by subtracting the height corresponding to the bottom of the through silicon via (TSV) from the height corresponding to the wafer surface. The height of the wafer surface is relatively complex to determine for the wafer with smooth surface, while the height of the wafer surface is easy to confirm for the wafer with rough surface. Therefore, the present application mainly designs the measurement method for the remaining silicon thickness measurement of the wafer with smooth surface, determines the height of the wafer with smooth surface and the height corresponding to the bottom of the through silicon via by image sampling and analysis, and calculates the remaining silicon thickness of the wafer with smooth surface.

[0085] Optionally, the light rays are emitted by a wide-bandwidth light source, which includes a component capable of penetrating silicon and a component incapable of penetrating silicon.

[0086] Because the imaging light rays include the component capable of penetrating silicon, the sampling image set can include the sampling images of the inside, surface and outside of the wafer. The present application adopts the measurement from the back, which can effectively solve the problem that the light rays cannot irradiate to the bottom in the high aspect ratio TSV structure. The traditional optical measurement method is often limited in the deep hole and high aspect ratio TSV structure, and cannot accurately obtain the depth information. By the light rays from the back, the present application can better irradiate to the bottom of the TSV, and significantly improves the accuracy of the measurement.

[0087] S200: determining a clear image with a certain degree of definition and an objective lens position corresponding to the clear image from the sampling image set.

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

[0089] Based on the definition evaluation value data set and the preset condition, a clear image with a certain degree of definition is obtained; and based on the clear image, the corresponding objective lens position is obtained.

[0090] In some embodiments, the process of obtaining the clear image with a certain degree of definition based on the definition evaluation value data set and the preset condition in step S200 can be realized by the following steps:

[0091] S210: obtaining a definition evaluation maximum value based on the definition evaluation value data set.

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

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

[0094] Based on the plurality of definition evaluation maximum values and the corresponding sampling images, clear images of the bottom of the cylindrical hole of the smooth surface wafer, clear images of the rough surface silicon wafer, and clear images of the rough surface silicon wafer reflection virtual image are screened out.

[0095] S300: Calculate the residual 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.

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

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

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

[0099] S320: Calculate the residual silicon thickness of the sample based on the objective lens positions corresponding to the clear images of the bottom of the cylindrical hole of the smooth surface wafer, the objective lens positions corresponding to the clear images of the rough surface silicon wafer, the objective lens positions corresponding to the clear images of the rough surface silicon wafer reflection virtual image, the thickness value, and the preset algorithm.

[0100] By inserting the rough surface silicon wafer, the clear images of the rough surface silicon wafer and the clear images of the rough surface silicon wafer reflection virtual image are used to determine the objective lens positions corresponding to the surface of the smooth surface wafer, and further combined with the objective lens positions corresponding to the clear images of the bottom of the cylindrical hole of the smooth surface wafer, the residual silicon thickness of the smooth surface wafer sample can be calculated.

[0101] As Figure 2As shown, the embodiment of the present application also provides a measurement system for the remaining silicon thickness, which comprises a light source 1, an aperture diaphragm 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 for fixing the column 14 and the leveling device 11.

[0103] The leveling device 11 is used for loading a sample.

[0104] The column 14 is used for fixing the movable guide rail 13.

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

[0106] Optionally, the movable guide rail can be provided with a speed variation law, and the mirror cavity is moved by the guide rail, so as to further move the objective lens in the measurement system. Because the speed variation law of the movable guide rail can be set according to actual requirements, and the position of the objective lens can be determined in real time by recording the time of the movable guide rail (the distance of 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 for measuring the remaining silicon thickness.

[0107] The processor is used for realizing the measurement method.

[0108] The light emitted by the light source 1 passes through the aperture diaphragm 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 then passes through the rough surface silicon wafer 9, the objective lens 8, the beam splitter 7 and the imaging lens 6 in sequence after being reflected by the sample 10, and finally enters the camera.

[0109] Optionally, the light source comprises a wide-band light source, which comprises a silicon-penetrable part and a silicon-impenetrable part.

[0110] Further, the measurement system provided by the present application can use visible light and infrared light for measurement, which can realize high-resolution imaging of the wafer surface and effectively measure the internal structure of the wafer. This innovative method can comprehensively obtain depth information and adapt to the measurement requirements of various materials and structures.

[0111] The measurement system provided by this invention acquires a set of sampled images by changing the distance between the objective lens and the sample. The sharpness of these images is evaluated, and based on the sharpness evaluation dataset, corresponding sharp images are selected using preset conditions. Finally, based on the sharp images, the corresponding objective lens positions, and a preset algorithm, a high-precision measurement result of the remaining silicon thickness can be quickly obtained. Unlike traditional contact measurement methods, this invention uses imaging for measurement, maintaining the advantages of non-contact detection and avoiding potential damage to devices caused by physical contact. This detection method is more suitable for rapid inspection on production lines, ensuring the safety and integrity of the equipment.

[0112] It is evident that the content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0113] like Figure 3 As shown, Figure 3 This is a schematic flowchart of another method for measuring residual silicon thickness provided in an embodiment of the present invention; the present invention also provides another method for measuring residual silicon thickness, applied to... Figure 2 The aforementioned system for measuring residual silicon thickness includes the following steps:

[0114] S500: Optical Path Setup: (Followed by...) Figure 2 The optical path has been completed as shown.

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

[0116] S510: Perform a scan on the sample to determine if it is smooth.

[0117] Specifically, the objective lens is moved to perform an image sampling of the entire sample. Computer analysis is then used to determine whether the surface of the sample wafer is smooth. If the sample wafer surface is rough, a corresponding image of the rough surface can be directly obtained; otherwise, the sample wafer has a smooth surface.

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

[0119] S520: Change the distance between the objective lens and the sample to obtain a set of sampled images.

[0120] By 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 one closest to the surface of the sample wafer is selected). In actual measurement, the objective lens is first moved downward to a position 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 constant speed, and images are collected at a constant speed to form a set of sampling images.

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

[0122] Further, the moving speed of the movable guide rail is designed to be constant, the mirror cavity is moved by the guide rail, and the objective lens in the measurement system is moved at a constant speed. Since the movable guide rail is designed to move at a constant speed, the position of the objective lens can be determined in real time by recording the time of the movable guide rail (the distance of the movement of 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: According to the set of sampling images, clear images of key positions are determined and their corresponding objective lens positions are confirmed.

[0124] While collecting images at a constant speed, the sharpness evaluation value of each collected image is calculated in real time according to the sharpness evaluation function, until a plurality of maximum values of the sharpness evaluation are obtained. Three maximum values of the sharpness evaluation are selected, and the corresponding images are the clear images of the bottom of the cylindrical hole of the smooth surface wafer, the clear image of the rough surface silicon wafer, and the clear image of the rough surface silicon wafer reflection virtual image. If the surface of the sample wafer is rough, the surface of the sample wafer can be directly imaged. In the measurement, only two maximum values of the sharpness evaluation and their corresponding images need to be selected, which are the clear image of the surface of the sample wafer and the clear image of the bottom of the cylindrical hole of the sample wafer.

[0125] Further, the rough surface silicon wafer is self-made and can be repeatedly used. The pattern on the surface of the rough surface silicon wafer is known, so the clear images corresponding to the maximum values of the sharpness evaluation value can be selected by analyzing the image information to determine the clear images of the rough surface silicon wafer and its reflection virtual image.

[0126] S540: According to the image positions corresponding to the key positions, the remaining silicon thickness of the sample is calculated.

[0127] In the case that the surface of the sample wafer is smooth, the positional relationship between the rough surface silicon wafer reflection virtual image and the bottom of the cylindrical hole includes Figures 4-6The three cases are that the virtual image of the rough surface silicon wafer is above all the bottom of the columnar holes, the virtual image of the rough surface silicon wafer is between the bottom of the columnar holes and the virtual image of the rough surface silicon wafer is below all the bottom of the columnar holes.

[0128] In any case, the real image and the virtual image of the rough surface silicon wafer satisfy the plane mirror imaging rule, and the rough surface silicon wafer is reflected and imaged through the smooth surface of the sample wafer. Therefore, the objective lens position corresponding to the smooth surface of the sample wafer is obtained through the objective lens positions corresponding to the real image and the virtual image of the rough surface silicon 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] In the formula, d is the thickness of the rough surface silicon wafer, h1 is the objective lens position corresponding to the clear image of the real object of the rough surface silicon wafer, h2 is the objective lens position corresponding to the real object of the self-made silicon wafer, and h3 is the objective lens position corresponding to the smooth surface of the sample wafer.

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

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

[0134] In the formula, d is the thickness of the rough surface silicon wafer, h1 is the objective lens position corresponding to the clear image of the real object of the rough surface silicon wafer, h2 is the objective lens position corresponding to the clear image of the virtual image of the rough surface silicon wafer, h3 is the objective lens position corresponding to the smooth surface of the sample wafer, and h tx is the objective lens position corresponding to the bottom of the columnar hole (x=1, 2, 3…).

[0135] Further, in the measurement, the measurement system provided by the present application can image multiple columnar hole bottoms, and can automatically calculate the number of columnar holes on the picture (there can be multiple columnar hole bottoms at the same objective lens position).

[0136] On the other hand, in the case of a rough sample wafer surface, a self-made rough surface silicon wafer is not required; the remaining silicon thickness of the sample can be calculated by the following formula:

[0137] Remaining silicon thickness Hrst=H-h tx

[0138] In the formula, H is the objective lens position corresponding to the clear image of the rough wafer surface, and h tx is the objective lens position corresponding to the bottom of the columnar hole (x=1, 2, 3…).

[0139] As Figure 7 shown, the embodiment of the present application also provides a remaining silicon thickness measurement device, which comprises:

[0140] at least one processor;

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

[0142] The at least one program, when executed by the at least one processor, causes the at least one processor to implement the method steps of the above method embodiments.

[0143] The memory, as a kind of non-transient computer readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs.The memory can include high-speed random access memory, and can also include non-transient memory, such as at least one disk storage device, flash memory device, or other non-transient solid-state memory device.In some embodiments, the memory can optionally include remote memory arranged remotely relative to the processor, which can be connected to the processor through 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 content in the above method embodiments is applicable to the present device embodiments, the device embodiments specifically implement the same functions as the above method embodiments, and achieve the same beneficial effects as the above method embodiments.

[0145] In addition, 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 executes the above-mentioned method.

[0146] The present application also 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-mentioned method when executed by the processor.Similarly, the content in the above method embodiments is applicable to the present storage medium embodiments, the storage medium embodiments specifically implement the same functions as the above method embodiments, and achieve the same beneficial effects as the above method embodiments.

[0147] It is to be understood that all or some of the steps, systems, etc. in the methods disclosed above can be performed by software, firmware, hardware, and / or any suitable combination thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a micro-processing unit, as hardware, or as an integrated circuit, such as an application- specific integrated circuit. Such software can be distributed on computer readable media, which can comprise computer storage media (or non-transitory media), and communication media (or transitory media). As is well known to those of ordinary skill in the art, computer storage media includes all computer-readable media in which data, computer executable instructions, or other computer readable data is / are publicized, embodied, or otherwise accessed. Computer storage media does not include communication media unless the communication media embodies computer readable instructions, data structures, program modules or other data. Computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Further, it should be appreciated 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 includes any information delivery media.

[0148] The above description is that of the preferred embodiments of the application. Various equivalents and alternatives to those preferred embodiments that are with in the scope of the present application are possible in light of the teachings herein and such equivalents and alternatives are within the scope of the appended claims.

Claims

1. A method for measuring residual silicon thickness, characterized in that, include: By changing the distance between the objective lens and the sample, a set of sampled images can be obtained; The sampled image set is formed by light rays passing sequentially through an objective lens and a rough-surface silicon wafer and converging onto the sample. After being reflected by the sample, the light rays pass sequentially through the rough-surface silicon wafer, the objective lens, and the imaging lens. The sample includes a smooth-surface wafer with several cylindrical holes. Determine several clear images in the sampled image set that meet preset clarity conditions, and the objective lens positions corresponding to several of the clear images; Based on several clear images, the objective lens positions corresponding to the clear images, and a preset algorithm, the remaining silicon thickness of the sample is calculated. The step of determining a plurality of sharp images in the sampled image set that meet preset sharpness conditions, and the objective lens positions corresponding to the plurality of sharp images, includes: Based on the sampled image set and the sharpness evaluation function, a sharpness evaluation value dataset is calculated; Based on the resolution evaluation value dataset and preset conditions, several clear images whose resolution meets the preset conditions are determined; the several clear images whose resolution 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 actual rough surface silicon wafer, and a clear image of the virtual image reflected by the rough surface silicon wafer. Based on several clear images, the corresponding objective lens position is obtained; The calculation of the remaining silicon thickness of the sample based on several clear images, the objective lens positions corresponding to the clear images, and a preset algorithm includes: Obtain the thickness value of the silicon wafer with the rough surface; 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 actual 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. The preset algorithm includes: Wherein, Hrst is the remaining silicon thickness of the sample, h1 is the objective lens position corresponding to the clear image of the actual rough surface silicon wafer, 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.

2. The measurement method as described in claim 1, characterized in that, Based on the sharpness evaluation value dataset and preset conditions, several sharp images whose sharpness meets the preset conditions are obtained; including: Based on the aforementioned sharpness evaluation value dataset, several sharpness evaluation maxima are obtained; Based on several sharpness evaluation maxima, several sharp images are obtained.

3. 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 to load the sample; The column 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 as described in any one of claims 1 to 2; The mirror cavity includes: an aperture stop, a collimating lens unit, a beam splitter, an objective lens, and an imaging lens; the collimating lens unit includes a first collimating lens and a second collimating lens; The light emitted by the light source passes sequentially through the aperture stop, the first collimating lens, the second collimating lens, and the beam splitter. After being deflected by the beam splitter, the light passes sequentially through the objective lens, the rough-surface silicon wafer, and the sample. After being reflected by the sample, the light passes sequentially through the rough-surface silicon wafer, the objective lens, the beam splitter, and the imaging lens, and finally enters the camera.

4. The measurement system as described in claim 3, characterized in that, The light source includes a wide bandwidth light source; the wide bandwidth light source includes components that are permeable to silicon and components that are not permeable to silicon.

5. A measurement system as described in claim 3, characterized in that, The rough-surface silicon wafer includes a grid, the grid shape of which includes strips, squares, and circles.

6. 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 performs the method as described in any one of claims 1 to 2.

7. A computer-readable storage medium storing a processor-executable program, characterized in that, The processor-executable program, when executed by the processor, is used to perform the method as described in any one of claims 1 to 2.

Images