Polar coordinate sampling-based data calibration and wafer scanning data alignment method

Abstract

The invention relates to wafer detection, in particular to a data calibration and wafer scanning data alignment method based on polar coordinate sampling, and the data calibration method based on polar coordinate sampling comprises the steps: carrying out the alignment of the collection data of a photoelectric detector and the periodic data of a grating type displacement sensor; determining a time point for starting detection and a time point for ending detection, and cutting the collected data; counting the scanning period of the grating type displacement sensor according to the data width of the current sampling timestamp; scanning the cross-period signals in the clipped acquisition data, and determining the relative offset of each cross-period signal; according to the scanning period of the grating type displacement sensor and the relative offset of each cross-period signal, position offset calibration is carried out on the collected data in each period; according to the technical scheme provided by the invention, the defect that the position deviation of the acquired data caused by the speed fluctuation of the motion shaft is difficult to effectively calibrate and align in the prior art can be effectively overcome.

Description

Technical Field

[0001] The present invention relates to wafer detection, and in particular to a data calibration method based on polar coordinate sampling and a wafer scanning data alignment method. Background Art

[0002] Photoelectric detection uses light sources of varying wavelengths, powers, and modulations, along with corresponding sensors, to detect the appearance and characteristics of an object. This detection process converts optical signals into analog electrical signals, and then further into digital signals, enabling efficient and automated detection using a variety of subsequent digital signal processing circuits and algorithms.

[0003] In semiconductor wafer inspection, lasers are commonly used as light sources to detect material and process defects on and within the wafer. These light sources may include ultraviolet (UV), visible light, or other wavelengths. Lasers are modulated and illuminate the wafer surface. Lenses or other optical devices collect scattered light at different angles, which is then fed into various detectors through optical path design for photoelectric conversion and data collection.

[0004] Semiconductor production places high demands on wafer inspection efficiency. The motion system drives the light source or the wafer itself, allowing the laser spot to rapidly move across the wafer surface, covering the entire wafer under test. XY coordinate-based motion systems require continuous acceleration, deceleration, and translation during each row or column scan. This places high demands on parameters such as repeatability, maximum velocity, and acceleration / deceleration rates.

[0005] To improve wafer inspection efficiency, a spiral scanning method with wafer rotation is commonly used. Since the entire wafer inspection system involves multiple subsystems such as light source, mechanics, and signal acquisition, and inspection must wait until the wafer rotation speed stabilizes before proceeding, accurately identifying the wafer position and calibrating the corresponding inspection data are essential operations during inspection.

[0006] In semiconductor testing, the rotating and translational axes cannot achieve completely uniform speed during movement due to reasons such as manufacturing process, installation method, control logic, and external interference. These speed fluctuations cause the signals collected by the sensors to not be completely true signals of the preset positions. When the speed fluctuation exceeds the allowable error of the system, the collected data needs to be calibrated. Summary of the Invention

[0007] (1) Technical problems solved In response to the above-mentioned shortcomings of the prior art, the present invention provides a data calibration and wafer scanning data alignment method based on polar coordinate sampling, which can effectively overcome the defect of the prior art that it is difficult to effectively calibrate and align the position deviation of the collected data caused by the speed fluctuation of the moving axis.

[0008] (2) Technical solution To achieve the above objectives, the present invention is implemented through the following technical solutions: The data calibration method based on polar coordinate sampling includes the following steps: S11, aligning the collected data of the photoelectric detector with the periodic data of the grating displacement sensor; S12, determining the time points for starting and ending the detection, and cutting the collected data; S13, counting the scanning period of the grating displacement sensor according to the data width of the current sampling timestamp; S14, scanning the cross-cycle signals in the cropped collected data, and determining the relative offset of each cross-cycle signal; S15. Perform position offset calibration on the collected data in each cycle according to the scanning cycle of the grating displacement sensor and the relative offset of each cross-cycle signal.

[0009] Preferably, the step of aligning the collected data of the photoelectric detector with the periodic data of the grating displacement sensor in S11 includes: Aligning the collected data of one or more channels of the photodetector with the periodic data of the grating displacement sensor in time; Among them, the grating displacement sensor includes a grating code disk and a grating scale. The grating code disk is installed on the rotating shaft, and the grating scale is installed on the translation shaft.

[0010] Preferably, determining the time points for starting and ending detection in S12 and trimming the collected data includes: According to the system design process, the time points for starting and ending detection are determined, and the collected data are trimmed according to the periodic data.

[0011] Preferably, in S15, position offset calibration is performed on the collected data in each cycle according to the scanning cycle of the grating displacement sensor and the relative offset of each inter-cycle signal, including: Assume that the scanning period of the grating displacement sensor is L, and the data width of the current scanning period is L C , there are N signal points in the cropped collected data that span the current cycle, that is, cross-cycle signals, and the relative offsets of the N signal points in the current scanning cycle are O i , i=1,2,…,N, for any signal point of the inter-periodic signal, set its numerical coordinate to V. When reaching this position, the number of signal points of the inter-periodic signal is k, k≤N, then the expected offset of the signal point of the inter-periodic signal is: ; Among them, O i,eis the expected offset of the signal point of the i-th cross-period signal.

[0012] The wafer scanning data alignment method, applying the above-mentioned data calibration method based on polar coordinate sampling, includes the following steps: S21, dividing the collected data of the photoelectric detector according to the synchronization signal of the motion axis; S22, counting the actual number of sampling points of the grating displacement sensor in the current scanning cycle; S23, detecting whether there are equivalent signal points in the current scanning cycle, and evaluating their impact range; S24, delaying data buffering until all equivalent signal points in the current scanning cycle have been collected; S25, using a data calibration method based on polar coordinate sampling to calculate the expected offset of the signal points of the cross-cycle signal in the collected data within each cycle, and performing position offset calibration; S26, outputting the collected data after position offset calibration; S27. Repeat S21 to S26, and traverse the collected data in all cycles in turn. After a short delay output, the collected data after position offset calibration in all cycles will be output in turn and completely combined.

[0013] (3) Beneficial effects Compared with the prior art, the data calibration and wafer scanning data alignment method based on polar coordinate sampling provided by the present invention has the following beneficial effects: 1) The data calibration method based on polar coordinate sampling uses the periodic data of the grating displacement sensor as a reference to dynamically calibrate the offset of the cross-period signal in the collected data of the photodetector. This effectively solves the signal misalignment problem caused by the mismatch between the mechanical motion period and the data sampling period in polar coordinate sampling, thereby significantly improving the accuracy and efficiency of wafer inspection. It is particularly suitable for high-speed, high-resolution scanning scenarios. 2) The wafer scanning data alignment method uses synchronous signal segmentation, equivalent signal point detection and dynamic buffering mechanisms, combined with a data calibration method based on polar coordinate sampling, to independently calibrate the collected data within each cycle. This effectively overcomes the periodic data loss or misalignment problems caused by mechanical vibration, motion axis nonlinearity or sampling delay during wafer scanning, and ultimately outputs complete, continuous and high-precision wafer inspection data, providing a reliable basis for subsequent defect analysis and process control. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0015] Figure 1 Schematic diagram of the process of the data calibration method based on polar coordinate sampling in the present invention; Figure 2 Schematic diagram of the process of wafer scanning data alignment method in the present invention. DETAILED DESCRIPTION

[0016] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0017] The following describes the specific process of the data calibration method based on polar coordinate sampling provided by the present invention with reference to specific examples (eg Figure 1 shown) and technical effects.

[0018] 1. Align the collected data of the photoelectric detector with the periodic data of the grating displacement sensor, specifically including: Aligning the collected data of one or more channels of the photodetector with the periodic data of the grating displacement sensor in time; Among them, the grating displacement sensor includes a grating code disk and a grating scale. The grating code disk is installed on the rotating shaft, and the grating scale is installed on the translation shaft.

[0019] 2. Determine the start and end time points for testing and trim the collected data, including: According to the system design process, the time points for starting and ending detection are determined, and the collected data are trimmed according to the periodic data.

[0020] 3. According to the data width of the current sampling timestamp, the scanning period of the grating displacement sensor is counted.

[0021] 4. Scanning the cross-cycle signals in the cropped acquired data and determining the relative offset of each cross-cycle signal; 5. Based on the scanning period of the grating displacement sensor and the relative offset of each cross-period signal, the position offset calibration of the collected data in each period is performed, specifically including: Assume that the scanning period of the grating displacement sensor is L, and the data width of the current scanning period is L C , there are N signal points in the cropped collected data that span the current cycle, that is, cross-cycle signals, and the relative offsets of the N signal points in the current scanning cycle are O i , i=1,2,…,N, for any signal point of the inter-periodic signal, set its numerical coordinate to V. When reaching this position, the number of signal points of the inter-periodic signal is k, k≤N, then the expected offset of the signal point of the inter-periodic signal is: ; Among them, O i,e is the expected offset of the signal point of the i-th cross-period signal.

[0022] The above technical solution uses the periodic data of the grating displacement sensor as a benchmark to align the offset of the cross-period signal in the collected data of the photodetector and perform dynamic calibration, effectively solving the signal misalignment problem caused by the inconsistency between the mechanical motion period and the data sampling period in polar coordinate sampling, thereby significantly improving the accuracy and efficiency of wafer detection, and is particularly suitable for high-speed, high-resolution scanning scenarios.

[0023] On the basis of the data calibration method based on polar coordinate sampling disclosed above, the technical solution of this application also discloses a wafer scanning data alignment method, which applies the data calibration method based on polar coordinate sampling. The specific process of the wafer scanning data alignment method provided by the present invention is described below with reference to specific examples (e.g. Figure 2 shown) and technical effects.

[0024] 1. Split the collected data of the photoelectric detector according to the synchronization signal of the motion axis.

[0025] 2. Count the actual number of sampling points in the current scanning cycle of the grating displacement sensor.

[0026] 3. Detect whether there are equivalent signal points in the current scanning cycle and evaluate their impact range.

[0027] 4. Delay data buffering until all equivalent signal points in the current scan cycle have been collected.

[0028] 5. A data calibration method based on polar coordinate sampling is used to calculate the expected offset of the signal points of the cross-cycle signal in the collected data within each cycle, and position offset calibration is performed.

[0029] 6. Output the collected data after position offset calibration.

[0030] 7. Repeat steps 1 to 6 above, and traverse the collected data in all cycles in turn. After a short delay output, the collected data after position offset calibration in all cycles will be output in turn and completely combined.

[0031] The above technical solution, through synchronous signal segmentation, equivalent signal point detection and dynamic buffering mechanism, combined with a data calibration method based on polar coordinate sampling, independently calibrates the collected data within each cycle, effectively overcoming the periodic data loss or misalignment problems caused by mechanical vibration, motion axis nonlinearity or sampling delay during wafer scanning, and ultimately outputs complete, continuous and high-precision wafer inspection data, providing a reliable basis for subsequent defect analysis and process control.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A data calibration method based on polar coordinate sampling, characterized in that: The following steps are involved: S11, aligning the collected data of the photoelectric detector with the periodic data of the grating displacement sensor; S12, determining the time points for starting and ending the detection, and cutting the collected data; S13, counting the scanning period of the grating displacement sensor according to the data width of the current sampling timestamp; S14, scanning the cross-cycle signals in the cropped collected data, and determining the relative offset of each cross-cycle signal; S15. Perform position offset calibration on the collected data in each cycle according to the scanning cycle of the grating displacement sensor and the relative offset of each cross-cycle signal.

2. The data calibration method based on polar coordinate sampling according to claim 1, characterized in that: In S11, the collected data of the photoelectric detector is aligned with the periodic data of the grating displacement sensor, including: Aligning the collected data of one or more channels of the photodetector with the periodic data of the grating displacement sensor in time; Among them, the grating displacement sensor includes a grating code disk and a grating scale. The grating code disk is installed on the rotating shaft, and the grating scale is installed on the translation shaft.

3. The data calibration method based on polar coordinate sampling according to claim 1, characterized in that: In S12, the time points for starting and ending the detection are determined, and the collected data are trimmed, including: According to the system design process, the time points for starting and ending detection are determined, and the collected data are trimmed according to the periodic data.

4. The data calibration method based on polar coordinate sampling according to claim 1, characterized in that: In S15, position offset calibration is performed on the collected data in each cycle according to the scanning cycle of the grating displacement sensor and the relative offset of each cross-cycle signal, including: Assume that the scanning period of the grating displacement sensor is L, and the data width of the current scanning period is L C , there are N signal points in the cropped collected data that span the current cycle, that is, cross-cycle signals, and the relative offsets of the N signal points in the current scanning cycle are O i , i=1,2,…,N, for any signal point of the inter-periodic signal, set its numerical coordinate to V. When reaching this position, the number of signal points of the inter-periodic signal is k, k≤N, then the expected offset of the signal point of the inter-periodic signal is: ； Among them, O i,e is the expected offset of the signal point of the i-th cross-period signal.

5. A wafer scanning data alignment method, applying the data calibration method based on polar coordinate sampling according to claim 1, characterized in that: The following steps are involved: S21, dividing the collected data of the photoelectric detector according to the synchronization signal of the motion axis; S22, counting the actual number of sampling points of the grating displacement sensor in the current scanning cycle; S23, detecting whether there are equivalent signal points in the current scanning cycle, and evaluating their impact range; S24, delaying data buffering until all equivalent signal points in the current scanning cycle have been collected; S25, using a data calibration method based on polar coordinate sampling to calculate the expected offset of the signal points of the cross-cycle signal in the collected data within each cycle, and performing position offset calibration; S26, outputting the collected data after position offset calibration; S27. Repeat S21 to S26, and traverse the collected data in all cycles in turn. After a short delay output, the collected data after position offset calibration in all cycles will be output in turn and completely combined.

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