A silicon wafer nanotopography optimization method and device, and a double-sided thinning apparatus
Patent Information
- Application Number
- CN202611113841.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-24
- Publication Date
- 2026-09-25
AI Technical Summary
[0002]在硅片的双面减薄技术中，易出现“中心鱼眼”及“边缘台阶”等形貌缺陷，导致抛光后硅片纳米形貌（NanoTopography，简称NT）数值异常
[0014]本申请公开了一种硅片纳米形貌优化方法、装置及双面减薄设备，根据每个所述气压计采集的气压值，确定间隙差值，在所述间隙差值大于预设补偿触发阈值的情况下，根据所述间隙差值确定所述磨削砂轮的位置补偿量，从而调整所述磨削砂轮的进给位置，建立间隙差值与硅片纳米形貌之间的关联关系，同时间隙值是由气压值所确定，以此可基于气压差值与抛光后硅片纳米形貌的关联关系，在减薄工序主动调控并优化纳米形貌，提升工艺一致性。
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Figure CN122807707A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and in particular to a method, apparatus and double-sided thinning device for optimizing the nanostructure of silicon wafers. Background Technology
[0002] In the double-sided thinning technology of silicon wafers, morphological defects such as "central fisheye" and "edge steps" are prone to occur, resulting in abnormal nanotopography (NT) values after polishing. However, due to the influence of grinding marks on the surface during the thinning process, the true NT value is usually difficult to determine at the same stage. Only after the polishing process can the nanoscale morphological changes on the wafer surface be identified, thus leading to a relatively slow optimization of nanotopography. Summary of the Invention
[0003] A method, apparatus, and double-sided thinning device for optimizing the nanomorphology of silicon wafers are provided to optimize the nanomorphology of silicon wafers in a timely manner.
[0004] In a first aspect, this application provides a method for optimizing the nanostructure of a silicon wafer, applied to a double-sided thinning device. The double-sided thinning device includes support pads disposed opposite to both sides of the silicon wafer and grinding wheels disposed opposite to both sides of the silicon wafer. Each support pad is equipped with a barometer. The method includes: Based on the air pressure value collected by each of the barometers, a gap difference value is determined, which is used to characterize the difference in gap value between the silicon wafer and the bearing pads on both sides; If the gap difference is greater than a preset compensation trigger threshold, the position compensation amount of the grinding wheel is determined based on the gap difference, and the position compensation amount is used to adjust the feed position of the grinding wheel.
[0005] In some embodiments, the number of barometers on each of the support pads is multiple, and the barometers on two support pads are respectively provided; The step of determining the gap difference based on the air pressure values collected by each of the barometers includes: The first gap value is determined based on the air pressure values collected by the multiple barometers on the first bearing pad; The second gap value is determined based on the air pressure values collected by the multiple barometers on the second support pad. The first support pad is the support pad located on one side of the silicon wafer, and the second support pad is the support pad located on the other side of the silicon wafer. The difference between the first gap value and the second gap value is determined as the gap difference value.
[0006] In some embodiments, determining the position compensation amount of the grinding wheel based on the clearance difference includes: The position compensation value is determined based on the absolute value of the gap difference; Based on the relationship between the first gap value and the second gap value, the offset direction of the silicon wafer relative to the center position is determined; The position compensation amount for each grinding wheel is determined based on the offset direction and the position compensation value.
[0007] In some embodiments, determining the position compensation value based on the absolute value of the gap difference includes: The position compensation value is determined as half of the absolute value of the gap difference.
[0008] In some embodiments, the number of barometers on each of the support pads is three, and the three barometers are distributed along the front, middle and rear directions of the support pads.
[0009] In some embodiments, determining the first gap value based on the air pressure values collected by the plurality of barometers on the first bearing pad includes: The pressure values collected by each barometer on the first bearing pad are filtered and temperature compensated, and the processed pressure values are converted into the first intermediate gap value. The average value of all the first intermediate gap values is determined as the first gap value; The step of determining the second gap value based on the air pressure values collected by the multiple barometers on the second bearing pad includes: The pressure values collected by each barometer on the second bearing pad are filtered and temperature compensated, and the processed pressure values are converted into second intermediate gap values. The average value of all the second intermediate gap values is determined as the second gap value.
[0010] In some embodiments, before determining the gap difference based on the pressure values collected by each of the barometers, the method further includes: It is confirmed that the silicon wafer has been ground to the target thickness.
[0011] In some embodiments, after determining the position compensation amount of the grinding wheel based on the clearance difference, the method further includes: The position compensation amount is superimposed on the target feed coordinates of the grinding wheel to generate the corrected grinding wheel position parameters; Before the next silicon wafer is ground, the grinding wheel is driven to move to the compensated starting position according to the corrected grinding wheel position parameters.
[0012] Secondly, this application provides a silicon wafer nanostructure optimization device, applied to a double-sided thinning equipment, the double-sided thinning equipment including support pads disposed opposite to both sides of the silicon wafer and grinding wheels disposed opposite to both sides of the silicon wafer, each support pad being equipped with a barometer; the device includes: The processing module is used to determine the gap difference value based on the air pressure value collected by each barometer, and the gap difference value is used to characterize the difference in gap value between the silicon wafer and the bearing pads on both sides; The compensation module is used to determine the position compensation amount of the grinding wheel based on the gap difference when the gap difference is greater than a preset compensation trigger threshold. The position compensation amount is used to adjust the feed position of the grinding wheel.
[0013] Thirdly, this application provides a double-sided thinning apparatus, comprising: Each of the support pads disposed on both sides of the silicon wafer is equipped with a barometer. Grinding wheels are positioned opposite each other on both sides of the silicon wafer; A control device for performing the method.
[0014] This application discloses a method, apparatus, and double-sided thinning device for optimizing the nanomorphology of silicon wafers. Based on the air pressure values collected by each barometer, a gap difference is determined. When the gap difference exceeds a preset compensation trigger threshold, the position compensation amount of the grinding wheel is determined based on the gap difference, thereby adjusting the feed position of the grinding wheel and establishing a correlation between the gap difference and the nanomorphology of the silicon wafer. Since the gap value is determined by the air pressure value, the nanomorphology can be actively controlled and optimized during the thinning process based on the correlation between the air pressure difference and the nanomorphology of the polished silicon wafer, improving process consistency. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.
[0017] Figure 1 A flowchart of a silicon wafer nanomorphology optimization method provided as an exemplary embodiment of this application; Figure 2 A schematic diagram of a silicon wafer nanomorphology optimization device module provided in an exemplary embodiment of this application; Figure 3 A schematic diagram of the grinding principle of a double-sided thinning device provided as an exemplary embodiment of this application; Figure 4 A schematic diagram of the grinding wheel rotation direction of the double-sided thinning device provided in an exemplary embodiment of this application; Figure 5 A schematic diagram of grinding components in a double-sided thinning device provided as an exemplary embodiment of this application; Figure 6 A top view of a double-sided thinning device provided as an exemplary embodiment of this application; Figure 7 The attached figure shows the correlation between the air pressure difference and the nanomorphic data in Embodiment 1 of this application; Figure 8 The attached figure shows the correlation between the air pressure difference and the nanomorphic data in Example 1 of this application; Figure 9 The attached figure shows the correlation between the air pressure difference and the nanomorphic data in Embodiment 2 of this application; Figure 10 The attached figure shows the correlation between the air pressure difference and the nanomorphic data in Example 2 of this application.
[0018] 100. First bearing pad; 101. First pneumatic gauge; 1011. First front barometer; 1012. First middle barometer; 1013. First rear barometer; 110. First grinding wheel; 120. Second bearing pad; 121. Second pneumatic gauge; 1201. Second front barometer; 1202. Second middle barometer; 1203. Second rear barometer; 130. Second grinding wheel; 140. Silicon wafer; 150. Drive gear; 160. Carrier ring. Detailed Implementation
[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.
[0020] In the embodiments of this application, "at least one" refers to one or more; "multiple" refers to two or more. In the description of this application, the terms "first," "second," "third," etc., are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.
[0021] References such as “one embodiment” or “some embodiments” as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms “comprising,” “including,” “having,” and variations thereof, as used in this specification, mean “including, but not limited to,” unless otherwise specifically emphasized.
[0022] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.
[0023] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.
[0024] In recent years, double-sided thinning technology has become a key process for achieving ultra-thin, uniform, and high-quality wafer processing due to its advantages of low damage, low breakage rate, environmental friendliness, and cost.
[0025] However, during the thinning process of the grinding wheel, morphological defects such as "central fisheye" and "edge step" are prone to occur. These problems are difficult to completely eliminate through subsequent processes, which in turn degrades the geometric parameters and surface morphology of the silicon wafer, resulting in abnormal nano-morphological values of the silicon wafer after polishing.
[0026] Here, the measurement of silicon wafer nanomorphology values relies on non-contact optical surface profilometers (such as laser interferometers) to acquire three-dimensional morphology data of the silicon wafer surface through scanning, and quantifies its flatness based on specific algorithms. As a core indicator of silicon wafer geometric quality, silicon wafer nanomorphology values have a decisive impact on the yield of subsequent photolithography and thin film processes. For example, in existing technologies, equipment such as the KLA WaferSight2i can be used to measure the nanomorphology of silicon wafers after polishing based on laser interferometry; however, due to the influence of grinding marks at the thinning station, it is difficult to directly obtain accurate nanomorphology values that can guide process control at the thinning station.
[0027] Therefore, due to the influence of grinding marks on the surface of the thinning process, it is currently difficult to determine the true value of the nano-morphology of the silicon wafer at the current station. Only after the polishing process can the nano-level morphology changes on the wafer surface be identified. At present, there is a lack of effective means to monitor the nano-morphology of silicon wafers in the front-end thinning process.
[0028] To address these issues, this study proposes a method, apparatus, and double-sided thinning device for optimizing the nanostructure of silicon wafers.
[0029] Firstly, referring to Figure 1 This application provides a method for optimizing the nanostructure of silicon wafers, applied to a double-sided thinning device. The double-sided thinning device includes support pads disposed opposite to both sides of the silicon wafer 140 and grinding wheels disposed opposite to both sides of the silicon wafer 140. Each support pad is equipped with a barometer. The method includes: Step S101: Determine the gap difference value based on the air pressure value collected by each barometer. The gap difference value is used to characterize the difference in gap value between the silicon wafer 140 and the bearing pads on both sides. Step S102: When the gap difference is greater than the preset compensation trigger threshold, determine the position compensation amount of the grinding wheel based on the gap difference. The position compensation amount is used to adjust the feed position of the grinding wheel.
[0030] Here, the 140-nanometer morphology of the silicon wafer is a key parameter for evaluating the overall flatness of the silicon wafer 140. It is used to characterize the microscopic undulation deviations of the front and back surfaces of the silicon wafer 140 in the qualified quality area within a spatial wavelength range of approximately 0.2–20 mm. These deviations manifest as morphological features such as depressions, protrusions, or ripples on the surface of the silicon wafer 140, with peak-to-valley height variations typically ranging from several nanometers to hundreds of nanometers. In this embodiment, the 140-nanometer morphology of the silicon wafer 140 refers to the surface flatness data obtained by a flatness measurement machine after the silicon wafer 140 has undergone post-polishing. It is defined as an uneven deviation on the entire front surface of the silicon wafer 140 within the qualified quality area within a spatial wavelength range of approximately 0.2–20 mm. The depressions, protrusions, or ripples on the surface of the silicon wafer 140 have height variations from peak to valley ranging from several to hundreds of nanometers. The 140-nanometer morphology data can be directly output by the machine and is an important parameter for evaluating the final surface quality of the silicon wafer 140.
[0031] In this embodiment, the gap difference is determined based on the air pressure value collected by each barometer. When the gap difference is greater than a preset compensation trigger threshold, the position compensation amount of the grinding wheel is determined based on the gap difference, thereby adjusting the feed position of the grinding wheel and establishing a correlation between the gap difference and the nano-morphology of the silicon wafer. Since the gap value is determined by the air pressure value, the nano-morphology can be actively controlled and optimized in the thinning process based on the correlation between the air pressure difference and the nano-morphology of the polished silicon wafer, thereby improving process consistency.
[0032] In this embodiment, when the pneumatic gauge compensation function is activated, the relationship between the gap difference and the preset compensation trigger threshold is further determined, and the position compensation amount of the grinding wheel is determined based on the gap difference.
[0033] Here, with the pneumatic gauge compensation function activated, the pneumatic gauge on the support pad is used to establish the pneumatic gauge compensation function to correct the air pressure difference. The range of nano-topography data is used as the input value to output the air pressure difference control boundary. After the air pressure difference control boundary is derived from the 140-nanometer topography data of the ideal silicon wafer, the air pressure difference is controlled through automatic compensation, thereby controlling the air pressure difference within a stable and low-level ideal range.
[0034] In some embodiments, there are multiple barometers on each support pad, and barometers on two support pads are respectively set accordingly; In step S101, the gap difference is determined based on the air pressure value collected by each barometer, including: Step S1011: Determine the first gap value based on the air pressure values collected by multiple barometers on the first bearing pad 100; Step S1012: Determine the second gap value based on the air pressure values collected by multiple barometers on the second support pad 120. The first support pad 100 is a support pad located on one side of the silicon wafer 140, and the second support pad 120 is a support pad located on the other side of the silicon wafer 140. Step S1013: Determine the difference between the first gap value and the second gap value as the gap difference value.
[0035] Among them, reference Figure 3 The key point of this embodiment is to obtain the gap difference value corresponding to the air pressure difference value of the front and rear barometers configured on the edge of the bearing pad. This is because the rear barometer difference value and the front barometer are set on the same horizontal line and their positions correspond to each other. In the actual grinding process, the change trend of the two is consistent. Only by monitoring the gap corresponding to the air pressure difference value of the front barometer can the current position state of the silicon wafer 140 be obtained.
[0036] Meanwhile, the pressure difference value corresponding to the pair of front barometers on both sides of each silicon wafer 140 corresponds to a silicon wafer 140 nanometer morphology data. The pressure difference value is directly output by the machine during the double-sided thinning process and can be used as a process parameter in the double-sided thinning process. In addition, this embodiment also regards the pressure difference value corresponding to the middle barometer as a secondary key monitoring object, and combines it with the front and rear barometers to jointly monitor the pressure difference value data of the silicon wafer 140, thereby improving the accuracy of monitoring the position status of the silicon wafer 140 during the grinding process.
[0037] Here, the specific steps for calculating the gap difference in this embodiment include: When the process is completed, the silicon wafer 140 grinding feed is completed and has been ground to the target thickness. The machine sends a synchronization signal and locks the time of air pressure value acquisition. Using the front barometers (second front barometer 1201 and first front barometer 1011) located on the left and right sides of the silicon wafer 140, the air pressure values (left front air pressure value and right front air pressure value) are collected respectively. At this time, the formula for calculating the air pressure difference ΔP is: ΔP=P 右前 P 左前 ; Among them, P 右前 and P 左前 These represent the instantaneous output right front air pressure value and left front air pressure value, respectively. The air pressure difference ΔP is used to characterize the gap difference between the current silicon wafer 140 and the left and right sides. The calculated gap difference value is bound to the ID of the current silicon wafer 140 and directly output from the machine to the data log or process report.
[0038] In some embodiments, in step S102, determining the position compensation amount of the grinding wheel based on the clearance difference includes: Step S1021: Determine the position compensation value based on the absolute value of the gap difference; Step S1022: Determine the offset direction of the silicon wafer 140 relative to the center position based on the relationship between the first gap value and the second gap value; Step S1023: Determine the position compensation amount for each grinding wheel based on the offset direction and position compensation value.
[0039] Among them, reference Figure 4 In this embodiment, barometers on the two side bearing pads of the current silicon wafer 140 are symmetrically arranged, and an automatic compensation rule is preset for the pressure difference of any pair of barometers.
[0040] For example, the automatic compensation rule includes: compensate 1 mm for a 1 mm difference, that is, when the horizontal offset of silicon wafer 140 is 1 mm, then 1 mm is compensated when grinding the next silicon wafer 140.
[0041] Furthermore, in this embodiment, the absolute value of the horizontal offset of the silicon wafer at 140° is obtained, wherein, If the current horizontal offset of silicon wafer 140 |Δx| > the compensation trigger threshold, the current silicon wafer 140 is marked as having an out-of-tolerance offset and the offset vector is recorded. Here, the offset vector is the position compensation amount in different offset directions, thereby triggering the pneumatic gauge compensation function and automatically calculating the position compensation amount of the double-sided grinding wheel when grinding the next silicon wafer 140.
[0042] For example, the grinding wheel position compensation amount is the compensation displacement of the right grinding wheel: Δx / 2; Left grinding wheel compensation displacement: +Δx / 2; If the current silicon wafer 140 is offset to the left by 12 micrometers, the right grinding wheel needs to compensate 6 micrometers towards the center, and the left grinding wheel needs to compensate 6 micrometers in the opposite direction.
[0043] In some embodiments, in step S1021, determining the position compensation value based on the absolute value of the gap difference includes: Half of the absolute value of the gap difference is determined as the position compensation value.
[0044] In this embodiment, the air pressure value is converted into a gap value, and the nano-morphology data of the silicon wafer 140 is further optimized based on the gap value, thereby establishing a correlation between the air pressure value and the nano-morphology data of the silicon wafer 140. The actual grinding position of the silicon wafer 140 is directly characterized by the obtained air pressure difference value. If the silicon wafer 140 deviates from the ideal center position, it will cause an imbalance in the distribution of the normal load (positive pressure) applied to the silicon wafer 140 by the grinding wheels on both sides, which will indirectly affect the magnitude of the friction force during grinding, and ultimately cause asymmetry in the grinding removal rate on both sides and deterioration of the surface accuracy, resulting in problems such as abnormal nano-morphology data of the silicon wafer 140.
[0045] Furthermore, the correlation between the pressure difference and the 140 nm morphology of the silicon wafer in this embodiment changes with the process conditions. Through analysis of the process data in the process conditions, it can be clearly seen that there is a significant correlation between the pressure difference and the 140 nm morphology of the polished silicon wafer in the double-sided thinning process.
[0046] Here, when process conditions (e.g., grinding wheel type, feed rate, material properties, and grinding removal amount) change, the air pressure difference control boundary will be recalibrated. Specifically, nano-morphology data is used as the core limiting index of the air pressure difference control boundary. Data fitting is used for regression analysis to accurately determine the air pressure difference control boundary and preset automatic compensation rules under different process conditions, thereby optimizing the grinding process and improving its stability.
[0047] This embodiment effectively improves the 140nm morphology of silicon wafers in subsequent processes by strictly controlling the range of gas pressure difference during the double-sided thinning process.
[0048] For example, for high-precision requirements of preset nano-morphological data less than 10 nanometers, regression analysis using data fitting can determine that the ideal control boundary for the pressure difference is no more than |20| micrometers.
[0049] In other embodiments, in step S102, after determining the position compensation amount of the grinding wheel based on the clearance difference, the position compensation amount is used to adjust the feed position of the grinding wheel, including: Based on the correlation between air pressure value and nano-morphology data of silicon wafer 140, an air pressure difference control boundary is set according to the nano-morphology data. When the air pressure difference exceeds the air pressure difference control boundary and the position compensation amount exceeds the compensation trigger threshold, the pneumatic gauge compensation function is automatically activated during the grinding of the next silicon wafer 140, and the pneumatic gauge compensation function is used to compensate for the position deviation of the center position of silicon wafer 140 in the horizontal direction.
[0050] Furthermore, the position compensation verification of the grinding wheels is performed. Before grinding the next silicon wafer 140, the silicon wafer 140 is first loaded on the grinding machine. By automatically calling the corrected position parameters of the two grinding wheels, the grinding wheels on both sides of the silicon wafer 140 are driven to move horizontally to the starting point after position compensation, that is, the ideal center position, and the grinding operation of the next silicon wafer 140 is performed.
[0051] Meanwhile, the over-value trigger threshold of the pneumatic gauge is preset. When the air pressure difference exceeds the air pressure difference control boundary and the position compensation exceeds the over-value trigger threshold, an alarm is triggered and the position compensation of the grinding wheel is manually adjusted.
[0052] In this embodiment, when the air pressure difference exceeds the over-value trigger threshold, the grinding machine will activate the over-value alarm function, and if necessary, manual intervention will be required to readjust the position of the grinding wheel.
[0053] In some embodiments, the number of barometers on each support pad is three, and the three barometers are distributed along the front, middle and rear directions of the support pad.
[0054] Here, each support pad is equipped with a pneumatic gauge, which consists of three barometers distributed along the front, middle and rear directions. In the double-sided thinning machine, the pneumatic gauge monitors the value of the pneumatic gauge through the air gap and air volume, thereby outputting the gap data between the silicon wafer 140 and the support pad.
[0055] Optionally, in this embodiment, three barometers positioned at the front, middle, and rear of each support pad are used to monitor the air pressure between the silicon wafer 140 and the support pad, and the air pressure signals are collected synchronously. When the gap between the nozzle of the barometer and the surface of the silicon wafer 140 changes slightly, the space for airflow to escape changes, causing air pressure fluctuations in the cavity formed by the gap. At this time, the air pressure signal is filtered and temperature compensated to convert it into gap data at various points of the silicon wafer 140. Based on the gap data, the final position data of each silicon wafer 140 after grinding is located, and the position compensation of the silicon wafer 140 is performed by monitoring the gap data. Position compensation is used to solve the problem that the grinding of the edge of the silicon wafer 140 during the double-sided thinning process affects the nanometer morphology of the silicon wafer 140.
[0056] Reference Figure 6In this embodiment, by obtaining the pressure difference values corresponding to the front, middle and rear three pairs of barometers, and using the pressure difference values as process monitoring parameters associated with the 140-nanometer morphology of the polished silicon wafer, the deviation between the overall position of the silicon wafer 140 and the preset ideal middle position can be accurately determined, thereby improving the controllability of the 140-nanometer morphology of the silicon wafer.
[0057] Furthermore, in this embodiment, the air pressure values of three pairs of barometers are obtained through a pneumatic gauge, and the gap data between the silicon wafer 140 and the support pad is output. The correlation between the air pressure difference and the nano-morphology is established by combining the nano-morphology data measured after polishing, clarifying the influence law of the air pressure difference on the nano-morphology. Then, by activating the automatic compensation function of the pneumatic gauge, the air pressure difference parameter can be adjusted in real time, thereby optimizing the nano-morphology data of the silicon wafer 140, and ultimately providing a guarantee for obtaining a silicon wafer 140 with higher flatness.
[0058] In some embodiments, in step S1011, determining the first gap value based on the air pressure values collected by multiple barometers on the first support pad 100 includes: The pressure values collected by each barometer on the first bearing pad 100 are filtered and temperature compensated, and the processed pressure values are converted into the first intermediate gap value. The average of all first intermediate gap values is determined as the first gap value; In step S1012, the second gap value is determined based on the air pressure values collected by multiple barometers on the second bearing pad 120, including: The pressure values collected by each barometer on the second bearing pad 120 are filtered and temperature compensated, and the processed pressure values are converted into the second intermediate gap values. The average of all second intermediate gap values is determined as the second gap value.
[0059] In this embodiment, during the grinding process of silicon wafer 140, the horizontal center position of silicon wafer 140 relative to the machine is deduced using the first gap value and the second gap value. The specific deduction calculation process includes: Center position coordinate calculation. Read the barometer gap data at the front, middle, and rear positions of the single-sided support pad, respectively. Set the first intermediate gap value as gLf for the barometer at the front position on the first support pad of silicon wafer 140, gLm for the barometer at the middle position on the first support pad, gLb for the barometer at the rear position on the first support pad, gRf for the barometer at the front position on the second support pad, gRm for the barometer at the middle position on the second support pad, and gRb for the barometer at the rear position on the second support pad.
[0060] The formula for calculating the first gap value is: ; The formula for calculating the second gap value is: ; Horizontal offset calculation. The calculated center position coordinates are compared with the preset ideal center position (usually the origin of the machine tool coordinate system) to obtain the horizontal offset Δx.
[0061] At this point, the formula for calculating the horizontal offset of silicon wafer 140 is: ; Furthermore, when the silicon wafer 140 is in the ideal center position (the mechanical coordinate origin of the grinding machine), the distance between the silicon wafer 140 and the pneumatic gauges located on its two sides is equal. At this time, the difference between the first gap value and the second gap value on the left and right sides of the silicon wafer 140 is 0, that is, the horizontal offset Δx of the silicon wafer 140 is 0.
[0062] In some embodiments, before determining the gap difference value based on the air pressure value collected by each barometer in step S101, the method further includes: It has been confirmed that silicon wafer 140 has been ground to the target thickness.
[0063] In this embodiment, the silicon wafer 140 is selected with a thickness of approximately 880 micrometers. During actual grinding, the initial thickness value of the silicon wafer 140 is first preset, and then the grinding process conditions are adaptively adjusted to achieve compatible processing of silicon wafers 140 with different thicknesses.
[0064] Furthermore, the air pressure difference value output by the machine is not a continuous signal, but a specific moment value collected at the moment when each silicon wafer 140 ends a single grinding stage, thereby precisely controlling the grinding thickness of the silicon wafer 140, ensuring uniform grinding of the silicon wafer 140, avoiding grinding warping problems, and further improving the grinding yield of the silicon wafer 140.
[0065] In some embodiments, after determining the position compensation amount of the grinding wheel based on the clearance difference in step S102, the method further includes: The position compensation is superimposed on the target feed coordinates of the grinding wheel to generate the corrected grinding wheel position parameters; Before grinding the next silicon wafer 140, the grinding wheel is driven to move to the compensated starting position according to the corrected grinding wheel position parameters.
[0066] In this embodiment, by superimposing the position compensation of the two-sided grinding wheels into the target feed coordinates of the grinding wheels, a new NC (Numerical Control) code or servo setting value is generated before grinding the next silicon wafer 140, so as to realize the coordinate correction control during the grinding process of silicon wafer 140. The positive and negative signs correspond to different grinding wheels on different sides, and the position of the grinding wheels on different sides is adjusted according to the positive and negative signs.
[0067] In other embodiments, when the pneumatic gauge compensation function is not activated, the accumulated grinding error of the silicon wafer 140 is used for process stability diagnosis and equipment maintenance during the grinding of the silicon wafer 140.
[0068] In this embodiment, when the pneumatic gauge compensation function is not activated, the pressure difference is used to adjust the gap difference to adjust the 140 nm morphology data of the silicon wafer. Therefore, there is a correlation between the pressure difference and the 140 nm morphology data of the silicon wafer. Thus, the pressure difference in this embodiment is correlated with the 140 nm morphology data of the silicon wafer after polishing, and can be used as a way to monitor nanomorphology risks in the front-end double-sided thinning process.
[0069] Meanwhile, without activating the pneumatic gauge compensation function, the air pressure difference value output by the machine is still the value collected at a specific moment when each silicon wafer 140 ends at the designated grinding stage, but the position compensation action for the next silicon wafer 140 will not be triggered based on this air pressure difference value.
[0070] Furthermore, if silicon wafer 140 continuously deviates from its ideal center position due to factors such as mechanical drift or load asymmetry, the machine will not automatically adjust the grinding wheel coordinates, but will still record the air pressure difference data corresponding to each silicon wafer 140. In this mode, since a closed-loop pneumatic gauge compensation function is not introduced, the position compensation of silicon wafer 140 may produce cumulative errors, resulting in a clear monotonic trend in the air pressure difference over time (for example, continuously increasing or decreasing; if the pneumatic gauge compensation function is turned off and the initial air pressure difference is adjusted to 42 micrometers, the air pressure deviation rises to 48 micrometers, and the nano-morphology data remains at a high level and continues to rise, consistent with the trend of the air pressure difference). This trend serves as a reference for process stability diagnosis or equipment maintenance.
[0071] This demonstrates a significant positive correlation between the pressure difference and the nano-morphology data of silicon wafer 140; that is, as the pressure difference increases, the nano-morphology data of silicon wafer 140 also increases accordingly. This indicates that the grinding position of silicon wafer 140, as reflected by the pressure difference parameter, can serve as an important correlation parameter for the final nano-morphology data of silicon wafer 140, thus providing effective support for process control.
[0072] In addition, during the double-sided thinning process, the pressure difference can be monitored and adjusted by configuring a pneumatic gauge compensation function in the machine, thereby maintaining the pressure difference in a stable and low ideal range (within |20| micrometers), thus suppressing potential fluctuations in the 140-nanometer morphology data of the silicon wafer in advance at the critical process node before polishing.
[0073] Therefore, by establishing an active intervention mechanism based on the pressure difference and the 140 nm morphology data of the silicon wafer in this embodiment, not only can the process stability be improved, but also more favorable initial conditions are created for the subsequent polishing process. Ultimately, this plays a positive role in achieving the overall optimization goal of the 140 nm morphology data of the silicon wafer after polishing.
[0074] Example 1: A double-sided thinning machine (model WDSG12-ZJS) was used to thin the silicon wafer 140. At the same time, a flatness tester (model KLA WaferSight2i) was used to measure the nano-morphology of the polished silicon wafer 140. Here, a 12-inch diamond wire cut silicon wafer 140 was used.
[0075] The experimental scheme in this embodiment 1 is shown in Table 1: Table 1: Experimental scheme in Example 1 1 Double-sided thinning √ Turn off the pneumatic gauge compensation function. 2 corrosion √ 3 Double-sided polishing √ 4 Flatness test √ FrontNT (10mm SquarePV) The experimental steps included: determining the processing path as double-sided thinning, etching, double-sided polishing, and flatness testing; disabling the automatic compensation function of the pneumatic gauge on the double-sided thinning machine during the double-sided thinning path; using a 12-inch diamond wire-cut silicon wafer 140 as the source, with a thickness of 880 micrometers; continuous grinding; and recording the air pressure difference value output by the machine and the nano-morphology data after polishing for each silicon wafer 140 during grinding. A 10 mm × 10 mm square detection window was opened on the silicon wafer 140, and the flatness of the front NT (nano-morphology of the front side of silicon wafer 140) was tested to determine the influence of the air pressure difference value on the nano-morphology data.
[0076] like Figure 7 The figure shows the relationship between air pressure difference and nano-morphology data. When the pneumatic gauge compensation function is turned off, the air pressure difference increases with the number of silicon wafers 140 being ground. This may be due to the relative displacement of the center position of silicon wafer 140 relative to the left and right barometers during the grinding process, and the displacement gradually increases. The nano-morphology on the front side of silicon wafer 140 and the air pressure difference show a highly consistent upward trend, as shown in the figure. Figure 8 As shown, the correlation is as high as 0.8439, indicating a strong correlation.
[0077] Example 2: This embodiment is used to further explore the relationship between the compensation function of the machine's pneumatic gauge and nanoscale morphology data.
[0078] The experimental scheme in this embodiment 2 is shown in Table 2: Table 2: Experimental Scheme in Example 2 1 Double-sided thinning With compensation enabled, all pressure differences are kept within 30 micrometers. Pneumatic gauge compensation begins <|30| micrometers 2 Double-sided thinning With compensation enabled, the initial pressure difference is at the |50| micrometer level. Pneumatic gauge compensation begins ≈|50| micrometers 3 Double-sided thinning Compensation is off, initial pressure difference is at the |50| micrometer level. Pneumatic gauge compensation off The experimental steps include: based on the experimental steps of Example 1, three experimental conditions are set in the double-sided thinning processing path, including compensation on, all air pressure difference values are controlled within |30| micrometers, at which time the pneumatic gauge compensation starts <|30| micrometers; compensation on, the initial air pressure difference value is at the |50| micrometer level, at which time the pneumatic gauge compensation starts ≈|50| micrometers; compensation off, the initial air pressure difference value is at the |50| micrometer level, at which time the pneumatic gauge compensation is off.
[0079] In this embodiment 2, the experimental endpoint values are obtained based on the preset range of nanomorphological data and the correlation between the pressure difference and the nanomorphological data. When the preset nanomorphological data is low (e.g., controlled within 10 nanometers), the pressure difference range corresponding to the reference embodiment 1 is limited to within |30| micrometers; if the preset nanomorphological data is high (e.g., 17 nanometers), the pressure difference range is extended to the |50| micrometer level.
[0080] Therefore, by designing three sets of comparative experiments with different pressure difference levels, we can accurately verify whether there is a positive correlation between pressure difference and nanomorphological data, and evaluate the improvement effect of the automatic compensation function of the pneumatic gauge on nanomorphological data.
[0081] Furthermore, such as Figure 9 As shown, when performing grinding operations on multiple silicon wafers 140, activating the pneumatic gauge compensation function can continuously correct the grinding position of the grinding wheels on both sides, thereby continuously optimizing the 140-nanometer morphology data of the silicon wafer and reducing the correlation coefficient between the air pressure difference and the 140-nanometer morphology data of the silicon wafer. Figure 10 The correlation between the pressure difference and the nanomorphic data is 0.4978.
[0082] Furthermore, after activating the pneumatic gauge compensation function, the air pressure difference can be controlled within |30| micrometers, and the maximum initial air pressure difference is less than |20| micrometers. At this time, the air pressure difference fluctuates at a low level and the fluctuation is stable. If the initial air pressure difference is adjusted to 46 micrometers, after activating the pneumatic gauge compensation function, the air pressure difference gradually decreases, indicating that the compensation function is working and performing the position deviation repair function. This allows for continuous adjustment of the center position of the silicon wafer 140 during the grinding process, reducing the grinding offset of the silicon wafer 140, thereby reducing the unevenness and defects caused by inconsistent grinding on both sides, and finally stabilizing at the level of |20| micrometers. At the same time, the morphology data of the silicon wafer 140 nanometers shows a downward trend.
[0083] Secondly, referring to Figure 2 This application provides a silicon wafer nanostructure optimization device, applied to a double-sided thinning equipment. The double-sided thinning equipment includes support pads disposed opposite to both sides of the silicon wafer 140 and grinding wheels disposed opposite to both sides of the silicon wafer 140. Each support pad is equipped with a barometer. The device includes: The processing module is used to determine the gap difference value based on the air pressure value collected by each barometer. The gap difference value is used to characterize the difference between the gap value between the silicon wafer 140 and the bearing pads on both sides. The compensation module is used to determine the position compensation amount of the grinding wheel based on the gap difference when the gap difference is greater than the preset compensation trigger threshold. The position compensation amount is used to adjust the feed position of the grinding wheel.
[0084] In this embodiment, a grinding wheel is used to grind both sides of the current silicon wafer 140. A gap is formed between the grinding wheel and both sides of the current silicon wafer 140. Gas is introduced into the gap and pressure is generated during the grinding of the current silicon wafer 140. In the processing module, the pressure value is obtained using a barometer on the support pad, and the absolute value of the pressure difference is calculated. The pressure difference is converted into a gap difference value. After the current silicon wafer 140 is ground, a pneumatic gauge compensation function is established and activated using a pneumatic gauge on the support pad. In the compensation module, if the gap difference value is greater than a preset compensation trigger threshold, the position compensation amount of the grinding wheel is determined based on the gap difference value. Before grinding the next silicon wafer 140, the position of the grinding wheel is adjusted, and position compensation is performed on the next silicon wafer 140 based on the position compensation amount to optimize the nanometer morphology of the silicon wafer 140.
[0085] Thirdly, this application provides a double-sided thinning apparatus, comprising: Each of the support pads positioned on both sides of the silicon wafer 140 is equipped with a barometer. Grinding wheels are positioned opposite each other on both sides of the silicon wafer 140; Control equipment, and the method used by the control equipment to perform.
[0086] Among them, reference Figure 5 The double-sided thinning device in this embodiment includes a carrier ring 160 and a drive gear 150. A first pneumatic gauge 101 is mounted on the first support pad 100, and a second pneumatic gauge 121 is mounted on the second support pad 120. The first pneumatic gauge 101 includes a first front barometer 1011, a first middle barometer 1012, and a first rear barometer 1013. The second pneumatic gauge 121 includes a second front barometer 1201, a second middle barometer 1202, and a second... The rear barometer 1203 also includes a second grinding wheel 130 and a first grinding wheel 110 disposed opposite to each other on the silicon wafer 140. In this embodiment, a pneumatic gauge compensation function is established using a pneumatic gauge on the support pad. This function is used to adjust the grinding position of the grinding wheel in the next silicon wafer 140 according to the position compensation amount after grinding the previous silicon wafer 140. This effectively suppresses the process drift problem during the grinding of the silicon wafer 140 and significantly improves and optimizes the nano-morphology of the final silicon wafer 140.
[0087] During the grinding process, the pneumatic gauge continuously feeds back the position data of the silicon wafer 140, which can fine-tune the detected residual position offset data (such as due to mechanical lag) to ensure that the grinding wheel always grinds both sides of the silicon wafer 140 symmetrically around the ideal center position. At the same time, in this embodiment, the compensation effect is verified. After the grinding is completed, the final position of the silicon wafer 140 is detected again. If the offset is restored to within the set threshold, the compensation is successful; otherwise, the compensation parameters of the next wafer will be iteratively adjusted according to the new error value.
[0088] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0089] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.
Claims
1. A method for optimizing the nanostructure of silicon wafers, characterized in that, The method is applied to a double-sided thinning equipment, which includes support pads disposed opposite to both sides of the silicon wafer and grinding wheels disposed opposite to both sides of the silicon wafer. Each support pad is equipped with a barometer. Based on the air pressure value collected by each of the barometers, a gap difference value is determined, which is used to characterize the difference in gap value between the silicon wafer and the bearing pads on both sides; If the gap difference is greater than a preset compensation trigger threshold, the position compensation amount of the grinding wheel is determined based on the gap difference, and the position compensation amount is used to adjust the feed position of the grinding wheel.
2. The method for optimizing the nanostructure of silicon wafers according to claim 1, characterized in that, The number of barometers on each of the bearing pads is multiple, and the barometers on two bearing pads are respectively set accordingly; The step of determining the gap difference based on the air pressure values collected by each of the barometers includes: The first gap value is determined based on the air pressure values collected by the multiple barometers on the first bearing pad; The second gap value is determined based on the air pressure values collected by the multiple barometers on the second support pad. The first support pad is the support pad located on one side of the silicon wafer, and the second support pad is the support pad located on the other side of the silicon wafer. The difference between the first gap value and the second gap value is determined as the gap difference value.
3. The method for optimizing the nanostructure of silicon wafers according to claim 2, characterized in that, Determining the position compensation amount of the grinding wheel based on the gap difference includes: The position compensation value is determined based on the absolute value of the gap difference; Based on the relationship between the first gap value and the second gap value, the offset direction of the silicon wafer relative to the center position is determined; The position compensation amount for each grinding wheel is determined based on the offset direction and the position compensation value.
4. The method for optimizing the nanostructure of silicon wafers according to claim 3, characterized in that, Determining the position compensation value based on the absolute value of the gap difference includes: The position compensation value is determined as half of the absolute value of the gap difference.
5. The method for optimizing the nanostructure of silicon wafers according to claim 2, characterized in that, The number of barometers on each of the bearing pads is three, and the three barometers are distributed along the front, middle and rear directions of the bearing pad.
6. The method for optimizing the nanostructure of silicon wafers according to claim 2, characterized in that, Determining the first gap value based on the air pressure values collected by the multiple barometers on the first bearing pad includes: The pressure values collected by each barometer on the first bearing pad are filtered and temperature compensated, and the processed pressure values are converted into the first intermediate gap value. The average value of all the first intermediate gap values is determined as the first gap value; The step of determining the second gap value based on the air pressure values collected by the multiple barometers on the second bearing pad includes: The pressure values collected by each barometer on the second bearing pad are filtered and temperature compensated, and the processed pressure values are converted into second intermediate gap values. The average value of all the second intermediate gap values is determined as the second gap value.
7. The method for optimizing the nanostructure of silicon wafers according to claim 1, characterized in that, Before determining the gap difference based on the pressure values collected by each barometer, the method further includes: It is confirmed that the silicon wafer has been ground to the target thickness.
8. The method for optimizing the nanostructure of silicon wafers according to claim 1, characterized in that, After determining the position compensation amount of the grinding wheel based on the clearance difference, the method further includes: The position compensation amount is superimposed on the target feed coordinates of the grinding wheel to generate the corrected grinding wheel position parameters; Before the next silicon wafer is ground, the grinding wheel is driven to move to the compensated starting position according to the corrected grinding wheel position parameters.
9. A device for optimizing the nanostructure of silicon wafers, characterized in that, An apparatus for use in a double-sided thinning device includes support pads disposed opposite to both sides of a silicon wafer and grinding wheels disposed opposite to both sides of the silicon wafer, each support pad being equipped with a barometer; the apparatus includes: The processing module is used to determine the gap difference value based on the air pressure value collected by each barometer, and the gap difference value is used to characterize the difference in gap value between the silicon wafer and the bearing pads on both sides; The compensation module is used to determine the position compensation amount of the grinding wheel based on the gap difference when the gap difference is greater than a preset compensation trigger threshold. The position compensation amount is used to adjust the feed position of the grinding wheel.
10. A double-sided thinning device, characterized in that, include: Each of the support pads disposed on both sides of the silicon wafer is equipped with a barometer. Grinding wheels are positioned opposite each other on both sides of the silicon wafer; A control device for performing the method as described in any one of claims 1-8.