Electron Microscope Dimension Measurement via Differential Waveform
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Solution Overview
Problem
The existing method for measuring the dimension of patterns using electron microscopes is prone to measurement errors due to variations in target shape around the electron beam irradiation position, as the 'penetration BSE' signal changes based on the target shape within the penetration range.
Innovation Solution
An electron microscope apparatus and method that includes a detection unit for reflected electrons, an image generation unit, and a processing unit to generate a differential waveform signal from the image, allowing for accurate dimension measurement of patterns by processing the image using the differential waveform signal and comparing it with a threshold to determine the quality of the dimension measured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high acceleration voltage primary electron beam is used to detect penetration BSE for measuring hole bottom dimension, then the ability to observe deep structures is improved, but measurement error depending on target shape increases
Solution Approach 1:
The patent segments the measurement process into multiple acceleration voltage stages. First, a high acceleration voltage (e.g., 30 kV) is used to generate penetration BSE for observing deep structures like hole bottoms. Then, a low acceleration voltage (e.g., 5 kV) is used to generate surface BSE for precise dimension measurement. This segmentation allows each stage to serve its specific purpose without the interference that causes measurement errors.
Solution Approach 2:
The patent dynamically adjusts the acceleration voltage during the measurement process. The system first applies high acceleration voltage to obtain penetration BSE signals from deep structures, then switches to low acceleration voltage to obtain surface BSE signals for accurate dimension measurement. This dynamic voltage adjustment enables the system to adapt to different measurement requirements and eliminate shape-dependent errors.
2Loss of information
If penetration BSE signal is used for dimension measurement, then deep structure observation is improved, but signal variation due to target shape causes measurement error
Solution Approach 1:
The patent separates the measurement into two distinct phases using different acceleration voltages. The high voltage phase captures penetration BSE for structural information, while the low voltage phase captures surface BSE for precise dimension measurement. This segmentation ensures that the measurement signal is not contaminated by shape variations affecting penetration depth.
Solution Approach 2:
The patent changes the acceleration voltage parameter from high to low between measurement stages. By reducing the acceleration voltage, the electron beam penetration depth is limited to the surface region, making the BSE signal independent of deeper target shape variations. This parameter change transforms the measurement from being shape-dependent to shape-independent.
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 effectively prevents measurement errors caused by target shape variations, enabling precise dimension measurement of patterns regardless of the target shape around the electron beam irradiation position.
Implementation Method 1
detection unit that detects reflected electrons reflected from a sample when the sample is irradiated with primary electrons emitted by a primary electron generation unit
Implementation Method 2
the sample is irradiated with a primary electron beam accelerated by a high acceleration voltage, and the back scattered electrons (BSE) reflected by the sample are detected
Data Source
AI summary
An electron microscope apparatus includes a detection unit that detects reflected electrons reflected from a sample when the sample is irradiated with primary electrons emitted by a primary electron generation unit (electron gun), an image generation unit that generates an image of a surface of the sample with the reflected electrons based on output from the detection unit, and a processing unit that generates a differential waveform signal of the image generated by the image generation unit, processes the image by using information of the differential waveform signal, and measures a dimension of a pattern formed on the sample.