Semiconductor Image Correction for Step-Height Defocus
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Solution Overview
Problem
Existing methods for imaging semiconductor patterns with varying heights, such as those described in PTL 1 and PTL 2, suffer from defocus issues due to step-wise height variations, and capturing multiple images to address this can lead to damage, charging, and reduced throughput.
Innovation Solution
A correction method that involves acquiring a target image of a semiconductor pattern with step-wise height variations, calculating and storing image correction values for each area, and applying these values to correct the image post-imaging, thereby reducing defocus through image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focusing is performed on each observation target at each time, then sharpness of the image is maximized, but wear of target areas due to electron beams increases and throughput deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-acquiring height information of the sample surface before imaging. The height map is generated in advance, and during imaging, the focus position is determined by referencing this pre-acquired height data, eliminating the need for repeated electron beam irradiation for focusing adjustments.
Solution Approach 2:
The patent uses a height map as a copy or representation of the actual sample surface topography. Instead of directly measuring or adjusting focus on the target area multiple times, the system creates a digital model (height map) and uses it to determine optimal focus positions, reducing physical electron beam interactions.
2Measurement precision
If a plurality of images are captured focusing on each height of semiconductor pattern, then defocus is reduced, but damage or charging on imaging target increases and throughput deteriorates
Solution Approach 1:
The patent acquires height information of the semiconductor pattern in advance and stores it in a height map. During imaging, the focus position is determined by referencing this pre-acquired height data, allowing single-pass imaging without repeated electron beam irradiation to different focal planes.
Solution Approach 2:
The system creates a digital height map that represents the three-dimensional topography of the semiconductor pattern. This digital model is then used to calculate appropriate focus positions for imaging, eliminating the need to physically refocus the electron beam multiple times on the actual sample.
3Measurement precision
If a plurality of images are captured focusing on each height of semiconductor pattern, then defocus is reduced, but throughput deteriorates due to capturing and combination
Solution Approach 1:
The patent performs preliminary acquisition of height information and stores it in a height map before the actual imaging process. This pre-prepared data allows the system to determine optimal focus positions without needing to capture and combine multiple images, streamlining the workflow into a single imaging pass.
Data Source
AI summary
Provided is a correction method capable of reducing defocus in an image caused by variations in height of a semiconductor pattern by image processing performed after imaging. This correction method for correcting an image includes: acquiring a target image 801 in which a semiconductor pattern having a plurality of areas the height of which varies step-wisely is imaged; storing a plurality of correction coefficients C1 and the like for correcting the respective areas of the acquired target image 801; and correcting the respective areas of the target image 801 using the stored plurality of correction coefficients C1 and the like.