System and method for optical wafer characterization with image up-sampling

Patent metadata

Field	Value
Publication number	US-12524867-B2
Application number	US-202117492321-A
Country	US
Kind code	B2
Filing date	Oct 1, 2021
Priority date	May 21, 2021
Publication date	Jan 13, 2026
Grant date	Jan 13, 2026

Abstract

A system includes a processing unit communicatively coupled to a detector array of an optical wafer characterization system. The processing unit is configured to perform one or more steps of a method or process including the steps of acquiring one or more target images of a target location on a wafer from the detector array, applying a de-noising filter to at least the one or more target images, determining one or more difference images from one or more reference images and the one or more target images, and up-sampling the one or more difference images to generate one or more up-sampled images. One or more wafer defects are detectable in the one or more difference images or the up-sampled images.

First claim

What is claimed:

1 . A system comprising:
a processing unit communicatively coupled to a detector array of an optical wafer characterization system, wherein the processing unit is configured to:
acquire one or more target images of a target location on a wafer from the detector array;
apply a de-noising filter to the one or more target images to reject spatial frequencies larger than a selected a selected threshold, wherein the selected threshold is dependent on the wavelength of characterization illumination;
determine one or more difference images from one or more reference images and the one or more target images following de-noising; and
up-sample the one or more difference images, via an algorithmic up-sampling process, to generate one or more up-sampled images, wherein one or more wafer defects are detectable in the one or more up-sampled images, wherein the algorithmic up-sampling process comprises an interpolation process;
pass the one or more up-sampled images through an anomaly detector, wherein the anomaly detector is configured to adjust or remove up-sampled image pixel values that exceed a set threshold.

2 . The system of claim 1 , wherein the processing unit is configured to:
acquire the one or more reference images from the detector array, wherein the one or more reference images are of a reference location proximate to the target location on the wafer.

3 . The system of claim 1 , wherein the processing unit is configured to:
determine one or more difference images from the one or more reference images and the one or more target images by subtracting the one or more reference images from the one or more target images.

4 . The system of claim 3 , wherein the de-noising filter is a spatial frequency filter configured to remove a portion of noise in at least the one or more target images acquired by the array detector and configured to reduce alteration of a noise-free image.

5 . The system of claim 4 , wherein the spatial frequency filter is a fast Fourier transform (FFT) filter, wherein the at least the one or more target images are Fourier transformed, multiplied by a function of spatial frequency, and inverse Fourier transformed by the FFT filter.

6 . The system of claim 4 , wherein the spatial frequency filter is a finite-impulse-response (FIR) filter, wherein the at least the one or more target images are convolved by the FIR filter.

7 . The system of claim 1 , wherein the processing unit is configured to:
apply the de-noising filter to the one or more reference images; and determine the one or more difference images from the one or more reference images and the one or more target images after de-noising the one or more reference images and the one or more target images.

8 . The system of claim 1 , wherein the processing unit includes a field programmable gate array (FPGA), an application-specific integrated circuit, a graphical processing unit, or a central processing unit.

9 . The system of claim 1 , wherein the optical wafer characterization system is a broadband plasma (BBP) tool.

10 . The system of claim 1 , wherein the processing unit is configured to:
determine one or more control signals based on one or more wafer defects detected in the one or more up-sampled images, wherein the one or more control signals are configured to make one or more adjustments to at least one of one or more optical wafer characterization components of the optical wafer characterization system or one or more semiconductor fabrication components of a semiconductor fabrication system.

11 . The system of claim 1 , wherein the processing unit is communicatively coupled to a controller, wherein the controller includes one or more processors and memory, wherein the memory is configured to store program instructions, wherein the one or more processors are configured to execute the program instructions causing the one or more processors to:
receive the one or more up-sampled images from the processing unit; and determine one or more control signals based on one or more wafer defects detected in the one or more up-sampled images, wherein the one or more control signals are configured to make one or more adjustments to at least one of one or more optical wafer characterization components of the optical wafer characterization system or one or more semiconductor fabrication components of a semiconductor fabrication system.

12 . A method comprising:
acquiring, via a processing unit, one or more target images of a target location on a wafer from a detector array of an optical wafer characterization system; applying, via the processing unit, a de-noising filter to the one or more target images to reject spatial frequencies larger than a selected a selected threshold, wherein the selected threshold is dependent on the wavelength of characterization illumination; determining, via the processing unit, one or more difference images from one or more reference images and the one or more target images following de-noising; and up-sampling, via the processing unit, the one or more difference images, via an algorithmic up-sampling process, to generate one or more up-sampled images, wherein one or more wafer defects are detectable in the one or more up-sampled images, wherein the algorithmic up-sampling process comprises an interpolation process; and passing, via the processing unit, the one or more up-sampled images through an anomaly detector, wherein the anomaly detector is configured to adjust or remove up-sampled image pixel values that exceed a set threshold.

13 . The method of claim 12 , further comprising:
acquiring, via the processing unit, the one or more reference images from the detector array, wherein the one or more reference images are of a reference location proximate to the target location on the wafer.

14 . The method of claim 12 , wherein the determining the one or more difference images from the one or more reference images and the one or more target images includes subtracting the one or more reference images from the one or more target images following de-noising.

15 . The method of claim 12 , wherein the de-noising filter is a spatial frequency filter configured to remove a portion of noise in at least the one or more target images acquired by the array detector and configured to reduce alteration of a noise-free image.

16 . The method of claim 15 , wherein the spatial frequency filter is a fast Fourier transform (FFT) filter, wherein the at least the one or more target images are Fourier transformed, multiplied by a function of spatial frequency, and inverse Fourier transformed by the FFT filter.

17 . The method of claim 15 , wherein the spatial frequency filter is a finite-impulse-response (FIR) filter, wherein the at least the one or more target images are convolved by the FIR filter.

18 . The method of claim 14 , further comprising:
applying the de-noising filter to the one or more reference images; and determining the one or more difference images from the one or more reference images and the one or more target images after de-noising the one or more reference images and the one or more target images.

19 . The method of claim 12 , wherein the processing unit includes a field programmable gate array (FPGA), an application-specific integrated circuit, a graphical processing unit, or a central processing unit.

20 . The method of claim 12 , wherein the optical wafer characterization system is a broadband plasma (BBP) tool.

21 . The

Assignees

• Kla Corp

Inventors

• Sezginer Abdurrahman
• Zhao Wei
• Wallingford Richard
• Chen Grace Hsiu-Ling
• Liu Xuzhao
• Cong Ge
• Yu Leon
• Virk Kuljit
• Zhang Bosheng
• Patel Amrish
• Mcbride Patrick

Classifications

• H10P74/203 Primary

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title

• G06T2207/20056

  Discrete and fast Fourier transform, [DFT, FFT] · CPC title

• G06T2207/20182

  Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering · CPC title

• G06T2207/20224

  Image subtraction · CPC title