Charged-particle beam deflection control for aberration reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor micro circuit fabrication, the advanced downscaling of patterns requires precise length measurement with reduced shrinkage and deflection aberration, but existing methods struggle with high-speed focus correction and astigmatism control, leading to image blur and distortion, especially when the visual field is expanded in the Y-direction for high-magnification observations in the X-direction.
Innovation Solution
A charged-particle beam device with a scanning optical system, including first and second deflectors, an image acquiring unit, and an evaluation unit that determines optimal deflection intensity ratios and rotation angles to minimize deflection aberrations, allowing for accurate length measurement and reduced image distortion across a larger visual field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the visual field is expanded in the Y-direction for high-magnification observations in the X-direction, then the measurement area is increased, but deflection aberration increases causing image blur and distortion
Solution Approach 1:
The patent divides the deflection operation into two independent stages: a first deflector handles deflection in the X-direction (measurement direction) while a second deflector handles deflection in the Y-direction (visual field expansion direction). This segmentation allows each deflector to be optimized independently, reducing the cumulative deflection aberration that would occur with a single deflection system.
Solution Approach 2:
The patent applies different deflection characteristics to different directions: the first deflector is designed with high precision for the X-direction where nanometer-level measurement is required, while the second deflector is designed for the Y-direction where larger visual field coverage is prioritized. This local optimization of deflection quality resolves the contradiction between expanded visual field and maintained image quality.
2Reliability
If magnetic fields are used for focus correction and astigmatism control, then correction capability is provided, but response speed is slow preventing high-speed adjustment
Solution Approach 1:
The patent replaces the conventional magnetic field-based focus correction and astigmatism control system with an electrostatic field-based system. The electrostatic deflectors and correctors respond much faster than their magnetic counterparts, enabling high-speed focus and astigmatism adjustment while maintaining the necessary correction capabilities. This substitution of the physical field type (from magnetic to electrostatic) resolves the speed limitation.
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 solution enables efficient measurement of line patterns and reduces image blur and distortion, enabling high-resolution length measurement in the X-direction while expanding the visual field in the Y-direction, thus addressing the challenges of shrinkage, wiggling, and sample electrification.
Implementation Method 1
a scanning optical system that scans a charged particle beam over the sample
Implementation Method 2
an electron beam emitted from an electron source is focused on the surface of a sample through an electron lens formed by a magnetic field or an electric field
Implementation Method 3
the electron beam is deflected using a magnetic field or an electric field to scan the surface of the sample
Implementation Method 4
the electron beam is deflected using a magnetic field or an electric field to scan the surface of the sample
Implementation Method 5
an electron beam emitted from an electron source is focused on the surface of a sample through an electron lens formed by a magnetic field or an electric field
Implementation Method 6
the electron beam is applied to detect secondary electrons emitted from the sample
Data Source
AI summary
This charged-particle beam device changes conditions for combining an intensity ratio between upper and lower deflectors and rotation angles of the deflectors in multiple ways when obtaining images having different pixel sizes in the vertical and horizontal directions. Then, the charged-particle beam device determines an optimal intensity ratio between the upper and lower deflectors and rotation angles of the deflectors on the basis of variations in size value measured in the larger pixel size direction (Y-direction) of the image. As a result, it is possible to extend the field of view in the Y-direction while reducing deflection aberrations when measuring at high precision in the X-direction.