Neural Denoising of Electron Microscope Images Without Clean Ground Truth
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Solution Overview
Problem
Conventional image processing techniques for electron microscope images, particularly in the semiconductor industry, struggle with significant noise levels that affect accurate measurements of line-edge roughness, line-width roughness, and critical dimensions, and existing deep learning methods require clean ground-truth images for training, which are often unavailable or difficult to obtain.
Innovation Solution
A method using a neural network trained through unsupervised learning to denoise electron microscope images without requiring clean ground-truth images, by iteratively replacing pixel values with randomly selected values from the same image and applying statistical dependencies to estimate noiseless components, allowing for efficient denoising and calibration curve generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image processing techniques are used to denoise EM images, then noise is reduced, but edge information is smoothed away and measurement precision deteriorates
Solution Approach 1:
The patent replaces conventional mechanical image processing techniques (like Gaussian blur or median filtering) with a deep learning-based neural network approach. The neural network learns to distinguish between noise and genuine edge information through training on synthetic images with known ground truth, allowing it to denoise while preserving sharp edges and fine structural details that would otherwise be lost in traditional filtering methods.
Solution Approach 2:
The patent changes the fundamental parameter of how denoising is achieved by moving from deterministic mathematical operations to data-driven learning. The neural network models the noise characteristics and learns optimal denoising transformations through training, enabling adaptive noise removal that preserves edge information better than fixed-parameter filtering methods.
2Measurement precision
If deep learning methods are used for denoising, then measurement precision improves, but the requirement for clean ground-truth training data creates additional complexity and resource requirements
Solution Approach 1:
The patent creates synthetic copies of the actual EM images by adding controlled noise patterns to clean versions. These synthetic noisy images serve as training data, allowing the neural network to learn denoising without requiring access to the original clean ground-truth images. The synthetic images replicate the noise characteristics of real EM data while providing the clean targets needed for supervised learning.
Solution Approach 2:
The patent uses synthetic images as disposable training data that can be generated on demand from the actual EM images. Instead of requiring rare and valuable clean ground-truth images, the system creates numerous synthetic training pairs by processing the same real images through controlled noise addition, providing abundant training data without compromising the scarcity of real clean data.
3Quantity of substance
If synthetic images are generated for training, then training data becomes available, but additional conditional files create artifacts and affect measurement accuracy
Solution Approach 1:
The patent extracts the essential training information directly from the actual EM images by adding controlled noise to create synthetic training pairs. This approach eliminates the need for external conditional files and synthetic generation pipelines that introduce artifacts. The training data is derived directly from the real measurement data itself, ensuring that the learned denoising model reflects actual measurement characteristics without introducing spurious artifacts from synthetic generation processes.
Data Source
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AI summary
The invention relates generally to image processing. In particular, the invention relates to a method (60) for analyzing a sample, in particular a die comprising memory structures. The method (60) comprises the steps of: recording (61) an electron microscope, EM, image of a section of the sample with a scanning electron microscope, SEM, wherein the EM image is recorded in a voltage contrast mode of the SEM; denoising (62) the recorded EM image; performing (63) a spatially resolved inspection measurement of the section of the sample, wherein the inspection measurement comprises determining electrical property values, preferably conductivity values; at different locations of the section of the sample; correlating (64) the pixel values of the denoised EM image (89) to the electrical property values determined at the different locations of the section of the sample; and generating (65) a property map (91) based said correlation, wherein the property map indicates the electrical properties of structures visible in the EM image (89).