Charged Particle Beam Overlay Shift Measurement
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Solution Overview
Problem
Current methods for measuring overlay shift amounts between layers in semiconductor manufacturing using charged particle beams face challenges in achieving high accuracy due to noise in signals from lower layers and potential shape changes in upper layers when irradiated multiple times.
Innovation Solution
A charged particle beam system that generates first and second images of a sample's layers, with the number of added images for the lower layer being greater than for the upper layer, to enhance signal-to-noise ratio and accurately measure overlay shift amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are added to improve the signal-to-noise ratio for lower layer measurement, then measurement accuracy improves, but the upper layer pattern shape changes due to repeated charged particle beam irradiation
Solution Approach 1:
The patent segments the image acquisition process into two distinct parts: acquiring fewer images for the upper layer to minimize beam damage, and acquiring more images for the lower layer to improve signal-to-noise ratio. This segmentation allows differential treatment of the two layers based on their different sensitivities to charged particle beam irradiation.
Solution Approach 2:
The patent applies local quality by recognizing that the upper layer and lower layer have different properties regarding beam sensitivity. The upper layer pattern is highly sensitive to shape changes, while the lower layer signal has more noise. Therefore, different numbers of images are added for each layer, optimizing the measurement for each layer's specific characteristics.
2Shape
If the number of added images is reduced to avoid upper layer shape changes, then pattern shape accuracy is maintained, but the signal-to-noise ratio of the lower layer image decreases
Solution Approach 1:
The patent segments the image acquisition process into two distinct parts: acquiring fewer images for the upper layer to minimize beam damage, and acquiring more images for the lower layer to improve signal-to-noise ratio. This segmentation allows differential treatment of the two layers based on their different sensitivities to charged particle beam irradiation.
Solution Approach 2:
The patent applies local quality by recognizing that the upper layer and lower layer have different properties regarding beam sensitivity. The upper layer pattern is highly sensitive to shape changes, while the lower layer signal has more noise. Therefore, different numbers of images are added for each layer, optimizing the measurement for each layer's specific characteristics.
3Ease of manufacture
If the same number of images are added for both layers, then the measurement process is simple, but neither layer achieves optimal measurement accuracy
Solution Approach 1:
The patent applies local quality by recognizing that the upper layer and lower layer have different properties regarding beam sensitivity. The upper layer pattern is highly sensitive to shape changes, while the lower layer signal has more noise. Therefore, different numbers of images are added for each layer, optimizing the measurement for each layer's specific characteristics.
Solution Approach 2:
The patent implements a dynamic measurement approach where the number of images to be added is determined based on the specific characteristics of each layer. The control unit dynamically adjusts the image acquisition parameters for each layer, allowing optimization of measurement accuracy while managing the complexity through automated control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for high-accuracy measurement of overlay shift amounts by optimizing image processing and reducing noise, ensuring precise pattern information from both layers is obtained.
Implementation Method 1
a charged particle beam irradiating unit that irradiates a sample with charged particle beams; a detector that detects a signal from the sample
Data Source
AI summary
Overlay shift amount measurement with high accuracy becomes possible. A charged particle beam system includes a computer system that measures an overlay shift amount between a first layer of a sample and a second layer lower than the first layer based on output of a detector. The computer system generates first images with respect to the first layer and second images with respect to the second layer based on the output of the detector, generates a first added image by adding the first images by a first added number of images, and generates a second added image by adding the second image by a second added number of images greater than the first added number of images. An overlay shift amount between the first layer and the second layer is measured based on the first added image and the second added image.