Charged Particle Beam Scan Signal Calculation for Distortion-Free Rotation
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Solution Overview
Problem
Charged particle beam scanning methods that rotate the scan direction and enlarge the scan-line interval cause distortion in the scan region, particularly at angles other than 0°, 90°, and 180°, leading to inaccuracies in measuring microscopic dimensions of semiconductor devices due to the vulnerability of ArF resist to electron-beam irradiation.
Innovation Solution
A method and apparatus that calculate and adjust the scan signal to maintain a rectangular scan region by reflecting the magnification ratio between the scan-line interval and scan-line directions, allowing for arbitrary angle rotation without distortion, using expressions to calculate and set scan signals that preserve geometric similarity during raster rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the scan direction is rotated and scan-line interval is enlarged to suppress shrink, then measurement accuracy is improved, but the scan region becomes distorted into a parallelogram
Solution Approach 1:
The patent applies dynamics by making the magnification in the vertical direction variable rather than fixed. The control device dynamically adjusts the vertical magnification based on the rotation angle to maintain a rectangular scan region. Specifically, the vertical magnification is set to Mx × tan(θ), where Mx is the horizontal magnification and θ is the rotation angle, allowing the system to adapt to different rotation angles while preserving geometric accuracy.
Solution Approach 2:
The patent changes the magnification parameter in the vertical direction as a function of the rotation angle. By setting the vertical magnification to Mx × tan(θ), the system transforms the scan region from a distorted parallelogram back to a rectangle. This parameter adjustment compensates for the distortion introduced by rotation while maintaining the enlarged scan-line interval needed to suppress shrink.
2Object-affected harmful factors
If the magnification in the vertical direction is set lower than in the horizontal direction to reduce irradiation density, then shrink is suppressed, but the scan region becomes distorted
Solution Approach 1:
The patent dynamically adjusts the vertical magnification parameter based on the rotation angle to maintain a rectangular scan region. The control device sets the vertical magnification to Mx × tan(θ), which allows the scan-line interval to be effectively enlarged (reducing irradiation density and suppressing shrink) while compensating for the distortion that would otherwise occur. This transforms the relationship between magnification and scan region shape from fixed to adaptive.
3Adaptability or versatility
If the scan direction is rotated to measure oblique patterns, then measurement versatility is improved, but configuration changes occur in ArF resist due to electron-beam irradiation
Solution Approach 1:
The patent applies dynamics by making the scan parameters adaptive to different measurement requirements. The control device allows rotation to arbitrary angles for measuring oblique patterns while dynamically adjusting the vertical magnification to maintain a rectangular scan region. This enables versatile measurement of patterns at any angle while suppressing shrink through the enlarged scan-line interval, thus preventing configuration changes in the ArF resist.
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 enables accurate measurement of microscopic dimensions by preventing configuration changes in ArF resist and allowing measurements at arbitrary angles, thereby enhancing measurement accuracy and reducing variations in semiconductor device inspections.
Implementation Method 1
a secondary signal (i.e., secondary electrons, reflected electrons, and electromagnetic waves), which is generated from the sample by the electron-beam irradiation, is detected using a detector that utilizes photoelectric effect
Data Source
AI summary
A method and an apparatus for calculating a scan signal so that the scan region becomes a scan region which is based on magnification ratio between desired magnification in a scan-line interval direction and desired magnification in a scan-line direction, and performing a calculation for rotating the scan direction with respect to the scan signal in order to suppress a distortion which is caused to occur when the technology where the scan direction of a charged particle beam is rotated is applied to the technology where the charged particle beam is scanned such that the scan-line interval is enlarged.