Search

CN-121996924-A - Correction method, device and storage medium for ellipsometry

CN121996924ACN 121996924 ACN121996924 ACN 121996924ACN-121996924-A

Abstract

The invention discloses a correction method, equipment and a storage medium for ellipsometry, wherein the method comprises the steps of collecting energy intensity distribution of light spots at the position of an exit pupil plane of an incident arm lens, adaptively generating a discretized intensity distribution lattice based on the energy intensity distribution, calculating normalization weights of all points, establishing a discretized numerical aperture distribution function based on the intensity distribution lattice, the normalization weights and lens numerical aperture parameters, and correcting depolarization effects in spectral ellipsometry by using the numerical aperture distribution function to obtain a measurement result of optical critical dimensions or film thickness. According to the invention, an accurate numerical aperture model is established through the real light spot characteristics, the problem of measurement errors caused by light spot deformation caused by a diaphragm is effectively solved, the accuracy and reliability of optical critical dimension or film thickness measurement are remarkably improved, and meanwhile, the method has the advantages of low implementation cost and strong adaptability.

Inventors

  • MA YANZHONG
  • GAO HAOZHE
  • CHEN LU

Assignees

  • 深圳中科飞测科技股份有限公司

Dates

Publication Date
20260508
Application Date
20251231

Claims (13)

  1. 1. A method for correcting ellipsometry, comprising: Collecting energy intensity distribution of light spots at the position of an exit pupil plane of an incident arm lens; based on the energy intensity distribution, a discretized intensity distribution lattice is adaptively generated, and the normalized weight of each point is calculated; establishing a discretized numerical aperture distribution function based on the intensity distribution lattice, the normalized weights and lens numerical aperture parameters; and correcting the depolarization effect in the spectroscopic ellipsometry by using the numerical aperture distribution function to obtain the measurement result of the optical critical dimension or the film thickness.
  2. 2. The method of claim 1, wherein adaptively generating a discretized intensity distribution lattice based on the energy intensity distribution and calculating a point normalization weight comprises: According to the energy intensity distribution, an effective area of the light spot is identified by adopting a self-adaptive threshold method; Matching lattice configuration based on shape parameters and/or light spot energy distribution of the effective area; and calculating the normalized weight of each point based on the lattice configuration and the energy intensity distribution.
  3. 3. The method for correcting ellipsometry according to claim 2, wherein said identifying the effective area of the spot using an adaptive thresholding method comprises: and selecting a pixel area with energy intensity larger than the maximum intensity by a preset percentage as the effective area.
  4. 4. The method of claim 2, wherein matching the lattice configuration based on the shape parameters of the active area comprises: calculating the rectangular degree or roundness of the effective area; When the rectangle degree is higher than a first threshold value, judging that the light spot shape is rectangular, and matching lattice configuration adapted to rectangular light spots; and when the roundness is higher than a second threshold value, judging that the shape of the light spot is elliptical or circular, and matching and adapting to the lattice configuration of the elliptical or circular light spot.
  5. 5. The method of claim 2, wherein matching the lattice configuration based on the spot energy distribution of the active area comprises: extracting spatial distribution characteristics of the light spot energy distribution of the effective area, and identifying whether step characteristics formed by energy jump exist in the energy distribution by calculating the energy gradient of the light spot energy distribution; If the energy steps are identified, edge detection is carried out on the light spot energy distribution, the detected step edges at all levels are used as space boundaries, and the effective area is divided into discrete areas which are configured by an adaptive lattice; If no obvious energy step is identified, presetting a plurality of equal-level envelope curves based on the peak value proportion or curvature change rate of the energy distribution so as to virtually divide the effective area and obtain a plurality of areas of the adaptive lattice configuration.
  6. 6. The method for correcting ellipsometry according to claim 2, wherein said calculating the normalized weights of the points comprises: mapping the matched lattice configuration to the effective area, and regarding each point as an integral unit; Respectively calculating the sum of energy intensities of all pixels in each integration unit to obtain integrated light intensity of each unit; summing all the integrated light intensities to obtain total light intensity; Dividing the integrated light intensity of each unit by the total light intensity to obtain the normalized weight corresponding to the point.
  7. 7. The method of claim 1, wherein the creating a discretized numerical aperture distribution function comprises: According to the normalized coordinates of each sampling point on the exit pupil plane and the lens numerical aperture parameters, calculating the incidence angle and azimuth angle corresponding to each sampling point through a geometric optical relation, and forming a group of triplet sequences consisting of the incidence angle, the azimuth angle and the normalized weight as the discretized numerical aperture distribution function.
  8. 8. The method for correcting ellipsometry according to claim 1, wherein correcting the depolarization effect in the spectroscopic ellipsometry using the numerical aperture distribution function to obtain the measurement result of the optical critical dimension or the film thickness comprises: Testing a target sample to obtain an ellipsometry spectrum and a first sample Mueller matrix spectrum; Calculating a first model average muller matrix spectrum based on the numerical aperture distribution function; fitting the first sample Mueller matrix spectrum and the first model average Mueller matrix spectrum to obtain the optical critical dimension or film thickness.
  9. 9. The method for correcting an ellipsometry according to claim 1, wherein before correcting an depolarization effect in a spectroscopic ellipsometry using the numerical aperture distribution function, further comprising: carrying out ellipsometry by using a standard sample with known film thickness to obtain a second sample Mueller matrix spectrum; calculating a second model average mueller matrix spectrum based on the numerical aperture distribution function; fitting the second sample Mueller matrix spectrum and the second model average Mueller matrix spectrum to obtain a fitted film thickness value; And fine-tuning the lens numerical aperture parameters based on the fitted film thickness values to optimize the numerical aperture distribution function.
  10. 10. Correction method for ellipsometry according to claim 8 or 9, wherein the first sample muller matrix spectrum and the first model average muller matrix spectrum are fitted using a non-linear regression algorithm or a library matching algorithm and/or the second sample muller matrix spectrum and the second model average muller matrix spectrum are fitted using a non-linear regression algorithm or a library matching algorithm.
  11. 11. A correction device for ellipsometry, characterized by comprising the following steps: The acquisition module is used for acquiring the energy intensity distribution of the light spots at the position of the exit pupil surface of the incident arm lens; The generation module is used for adaptively generating a discretized intensity distribution lattice based on the energy intensity distribution and calculating the normalized weight of each point; the establishing module is used for establishing a discretized numerical aperture distribution function based on the intensity distribution lattice, the normalized weight and the lens numerical aperture parameter; And the correction module is used for correcting the depolarization effect in the spectroscopic ellipsometry by utilizing the numerical aperture distribution function to obtain the measurement result of the optical critical dimension or the film thickness.
  12. 12. A computer device comprising a processor, a memory coupled to the processor, the memory having stored therein program instructions that, when executed by the processor, cause the processor to perform the steps of the ellipsometry correction method of any of claims 1-10.
  13. 13. A storage medium storing program instructions for implementing the method for correcting ellipsometry according to any one of claims 1-10.

Description

Correction method, device and storage medium for ellipsometry Technical Field The present application relates to the field of semiconductor manufacturing and precise optical measurement technologies, and in particular, to a method, apparatus and storage medium for correcting ellipsometry. Background In the fields of semiconductor manufacture and precise optical element production, the method is very important for high-precision measurement of micro-nano structures such as film thickness, critical dimension and the like. As a key element in these fields, the accuracy of the optical critical dimension or film thickness measurement technique directly affects the performance and yield of the product. The spectroscopic ellipsometry technique is widely used because of its non-contact, high precision and other features. Numerical aperture is a common equipment-induced depolarization source in optical systems, whose accurate setting and model correction are crucial for obtaining high quality measurements. In the conventional ellipsometry system architecture, the introduction of the diaphragm is one of common means for realizing light path regulation and control and optimizing measurement conditions. However, the aperture inevitably changes the original ideal circular shape of the spot by limiting the propagation range of the beam, so that the actual spot assumes a complex rectangular, elliptical or other irregular shape. The method currently in common use is to give a hypothetical numerical aperture distribution function by empirical or simple lens modeling, usually derived based on an ideal circular spot. After the light spot is deformed due to the action of the diaphragm, the numerical aperture calculation formula deduced based on the circular light spot cannot accurately map the real transmission path and the energy distribution characteristic of the light in the optical system at the moment. When the system analysis and the measurement result correction are carried out continuously by using the traditional numerical aperture data, the actual working state of the measurement system is difficult to accurately reflect, the corresponding correction is difficult to effectively improve the measurement effect, and finally the measurement accuracy of the optical critical dimension or the film thickness is limited. Disclosure of Invention In view of the above, the present application provides a correction method, apparatus and storage medium for ellipsometry, so as to solve the problem of insufficient measurement accuracy caused by mismatch between a factor aperture model and an actual light spot in the prior art. In order to solve the technical problems, the application adopts a technical scheme that the method for correcting the ellipsometry comprises the following steps: Collecting energy intensity distribution of light spots at the position of an exit pupil plane of an incident arm lens; Based on the energy intensity distribution, self-adaptively generating a discretized intensity distribution lattice, and calculating the normalized weight of each point; Establishing a discretized numerical aperture distribution function based on the intensity distribution lattice, the normalized weight and the lens numerical aperture parameters; and correcting the depolarization effect in the spectroscopic ellipsometry by using a numerical aperture distribution function to obtain the measurement result of the optical critical dimension or the film thickness. As a further improvement of the present application, based on the energy intensity distribution, a discretized intensity distribution lattice is adaptively generated, and normalized weights of points are calculated, including: According to the energy intensity distribution, an effective area of the light spot is identified by adopting a self-adaptive threshold method; matching the lattice configuration based on the shape parameters of the effective area and/or the light spot energy distribution; Based on lattice configuration and energy intensity distribution, calculating normalized weights of each point. As a further improvement of the present application, identifying an effective area of a light spot using an adaptive thresholding method includes: and selecting a pixel area with energy intensity larger than the maximum intensity by a preset percentage as an effective area. As a further improvement of the present application, matching the lattice configuration based on the shape parameter of the effective region includes: calculating the rectangular degree or roundness of the effective area; when the rectangle degree is higher than a first threshold value, judging that the shape of the light spot is rectangle, and matching the lattice configuration of the rectangular light spot; And when the roundness is higher than a second threshold value, judging that the shape of the light spot is elliptical or circular, and matching the lattice configuration of the elliptical or circular