CN-121639680-B - TDI camera focusing position calibration method and wafer detection equipment

Abstract

The application provides a TDI camera focusing position calibration method and wafer detection equipment, which belong to the semiconductor optical detection technology, wherein the TDI camera focusing position calibration method comprises the steps of generating a focusing matrix, trombone coordinate alignment, registering the focusing matrix and generating an optimal focusing position; the method solves for the best focus position by GRID SEARCH algorithm. The application provides the calibration method of the optimal focusing position of the TDI camera for wafer bright field defect detection, calculates the optimal focusing position by registering the focusing matrix generated by two-dimensional search, reduces the influence caused by system errors, improves the calibration precision of the TDI camera, and is convenient to popularize and apply in the field of wafer optical detection.

Inventors

• CAI XIONGFEI
• PENG JIAXIN
• ZHANG HONGBIN

Assignees

• 苏州矽行半导体技术有限公司

Dates

Publication Date

20260508

Application Date

20260203

Claims (6)

1. 1. The method for calibrating the focusing position of the TDI camera is characterized by comprising the following steps of: s1, generating a focusing matrix, wherein in the two-dimensional searching and focusing process, the whole focusing process generates a complete image definition matrix, namely the focusing matrix, based on different Z-axis and Trombone mechanism positions of a wafer detection system corresponding to an image definition value; S2, trombone coordinates are aligned, trombone has the error of Alignment of the Trombone mechanism coordinates prior to registration to calibrate the matrix And reference matrix Trombone coordinates of (a) are consistent, and the search range is limited to be ; S3, registering the focusing matrix, and calibrating the matrix Selecting a window area Move and move And reference matrix Comparing the different areas of the two images, and searching the area with the minimum average absolute error to obtain the search position with the minimum average absolute value Namely, the offset value of the optimal focusing position is used for realizing registration; s4, generating an optimal focusing position based on registration Calculating a focus matrix Corresponding best focusing position , In the middle of Z-axis and Trombone-position coordinates corresponding to the best focal plane position 。
2. 2. The method of calibrating a focus position of a TDI camera according to claim 1, wherein the two-dimensional search includes generating a focus matrix Is the first of (2) The row indicates that the Z-axis coordinate is fixed as Moving Trombone the mechanism to perform one-dimensional searching; First of matrix Column representation Trombone mechanism coordinates are fixed as And (3) moving the Z axis to perform one-dimensional searching.
3. 3. The method for calibrating a focus position of a TDI camera according to claim 1, wherein the optimal focus position is the best focus position The solving step of (1) comprises: S31, giving a reference matrix Calibration matrix Initializing Is a value of (2); S32, finding a window area And (3) with A value of image sharpness for the corresponding position; S33, accumulating absolute errors of the window areas, and calculating average absolute error values; S34, traversing the rest Repeating S32-S33, and calculating all average absolute error values; S35, screening the search position corresponding to the smallest error value in all the average absolute error values As the best focus position, an offset value of the best focus position is thereby obtained.
4. 4. The method for calibrating a focusing position of a TDI camera according to claim 3, wherein the optimal focusing position is solved by GRID SEARCH algorithm 。
5. 5. The method for calibrating the focusing position of the TDI camera according to claim 1, wherein the method for calibrating the focusing position of the TDI camera is suitable for optical detection of a wafer.
6. 6. Wafer inspection equipment, which comprises an EFEM device (100) and an inspection device (200), wherein the EFEM device (100) comprises an EFEM controller (1) arranged at an EFEM chamber and a mechanical arm (2) with a sheet fork, the inspection device (200) comprises an inspection frame (3) arranged at the inspection chamber, a motion carrier (4), an optical-mechanical module (5) and an inspection processor (6), and the wafer inspection equipment is characterized in that: the detection processor (6) controls the Z-axis and Trombone mechanism of the optical machine module (5) based on the TDI camera focusing position calibration method according to any one of claims 1-4 to realize the optical focusing of the TDI camera.

Description

TDI camera focusing position calibration method and wafer detection equipment Technical Field The invention belongs to the semiconductor optical detection technology, and particularly relates to a TDI camera focusing position calibration method and wafer detection equipment. Background The bright field defect detection BFI (Bright Field Inspection, bright field defect detection) of the wafer is to detect the surface defect of the wafer after photoetching by using a high-resolution TDI camera, can rapidly and accurately detect the surface defect of 10+ nanometer level, and is very important detection equipment in the field of semiconductor manufacturing. The TDI (TIME DELAYED Integration, time delay Integration) camera is an industrial camera commonly used in BFI wafer detection systems, performs multiple exposure on the same moving target through a multi-stage photosensitive unit, improves the signal to noise ratio and sensitivity of an image by utilizing charge line-by-line superposition, has the advantages of high response speed, wide dynamic range and the like, and the focusing process of the TDI camera can be controlled through object distance and image distance and respectively corresponds to the Z axis and Trombone position of a hardware system indirectly, generally through a two-dimensional searching method, namely different Z axis and Trombone positions are sequentially adjusted, and the optimal focusing position (shown in figure 1) is determined through the change of image definition. In semiconductor inspection equipment (particularly high-end optical systems for photolithography, reticle inspection, wafer metrology, etc.), trombone generally refers to an optical delay line or optical path adjustment mechanism that can precisely adjust the optical path length. The key function is optical path compensation/matching, in precise optical systems such as interferometers, white light interferometry, phase shift measurement and the like, optical Path Difference (OPD) between reference light and sample light needs to be accurately adjusted to be equal or to keep a specific difference value so as to generate interference fringes or optimized signals, and a Trombone structure is used for linearly changing the optical path length by moving a reflector group, and the sliding mechanism of the Trombone structure is similar to a U-shaped telescopic tube of a trombone (Trombone), so that the structure is named. The high-magnification objective lens and the tiny defect size of the TDI camera have higher requirements on the calibration precision of the camera, and the subsequent detection precision can be seriously influenced by the system error of hardware, the change of environment and the attenuation of an optical device. Conventional calibration methods rely heavily on hardware readings, introducing significant amounts of systematic errors and environmental noise, and therefore require recalibration within a particular period to maintain the accuracy of the best focus position. Disclosure of Invention In order to overcome the defects in the prior art, the invention aims to provide a TDI camera focusing position calibration method and wafer detection equipment, which can solve the problems. The design principle is that the focusing curve of the TDI camera is very sensitive to the positions of the Z axis and Trombone, and small changes can be detected through the change of the image definition. The focusing curve can accurately reflect the relation among the object distance, the image distance and the image quality, is determined by the optical characteristics of the light path, and the instability of hardware can not cause the change of the focusing curve. In order to reduce dependence on hardware reading and improve stability of calibration of an optimal focusing position of the TDI camera, the invention provides a novel calibration method of the optimal focusing position of the TDI camera by utilizing the characteristic, which can effectively avoid huge errors and failure risks caused by independent dependence on hardware reading, improves calibration precision of the TDI camera and is convenient for subsequent defect detection. The overall design content is that the calibration method stores a two-dimensional search focusing matrix as reference data and a Z-axis corresponding to the optimal focusing and a Trombone reading position (called as the optimal focusing position for short) as reference positions when initial calibration is performed, new focusing data are compared with the reference data in the subsequent calibration process, an offset value of the optimal focusing position is obtained, and the initial optimal focusing position is corrected to obtain the calibrated optimal focusing position. The specific scheme is as follows. A calibration method for the focusing position of TDI camera includes such steps as generating a focusing matrix, generating a complete image definition matrix, that is, a focus