Voltage Control Plate for Fast Electron Beam Focus Correction
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Solution Overview
Problem
Existing charged-particle beam inspection systems face challenges in accurately focusing high landing-energy electron beams to image both the top and bottom surfaces of 3D structures while maintaining detection efficiency and throughput, as conventional focus adjustment techniques interfere with signal detection and collection, leading to low-quality images and reduced inspection efficiency.
Innovation Solution
Incorporation of a voltage control plate between the backscattered electron detector and the magnetic lens polepiece, which adjusts the electrostatic field to correct the focal length of the primary electron beam without affecting backscattered electron collection, using an electrically conducting material like metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional focus adjustment techniques are used to image 3D structures, then the focal length can be adjusted between top and bottom surfaces, but the focus adjustment interferes with signal detection by the charged-particle detector
Solution Approach 1:
The patent divides the focus adjustment function from the detector by introducing a separate voltage control plate between the detector and polepiece. This segmentation allows the detector to maintain its signal detection function while the voltage control plate independently handles focus adjustment through electrostatic field modulation.
Solution Approach 2:
The voltage control plate acts as an intermediary element between the detector and the magnetic lens polepiece. It mediates the focus adjustment process by creating an electrostatic field that corrects spherical aberration without directly interfering with the detector's signal collection path, thus resolving the conflict between focus adjustment and signal detection.
2Measurement precision
If high landing energy beams are used to image high aspect ratio structures, then imaging capability is improved, but focus adjustment techniques reduce inspection throughput
Solution Approach 1:
The patent replaces mechanical or conventional electromagnetic focus adjustment mechanisms with an electrostatic field-based voltage control plate. This substitution enables faster, software-controlled focus adjustments that do not require complex mechanical movements or lengthy electromagnetic field reconfigurations, thereby maintaining high imaging quality while improving inspection throughput.
3Measurement precision
If focus adjustment is performed to maintain resolution on 3D structures, then imaging resolution is preserved, but signal collection efficiency is reduced
Solution Approach 1:
The voltage control plate serves as an intermediary that corrects spherical aberration through electrostatic field modulation without blocking or interfering with the path of signal electrons to the detector. This allows resolution to be maintained through focus correction while preserving signal collection efficiency.
Solution Approach 2:
The patent changes the electrical parameter (voltage) applied to the voltage control plate to dynamically adjust the electrostatic field strength. By modulating this voltage parameter, the system can optimize focus correction for different 3D structures while maintaining efficient signal electron collection, as the electrostatic field adjustments do not impede electron trajectories to the detector.
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
Enables high-quality imaging of 3D structures with maintained resolution and throughput by adjusting the focal length of the primary electron beam, ensuring efficient detection of backscattered electrons.
Implementation Method 1
adjusting an electrostatic field experienced by a primary charged-particle beam passing through the cavity
Implementation Method 2
an objective lens comprising a magnetic lens
Data Source
AI summary
Systems and methods of imaging a sample using a charged-particle beam apparatus are disclosed. The apparatus may include a charged-particle source configured to emit charged particles, the emitted charged particles forming a primary charged-particle beam along a primary optical axis; an objective lens comprising a magnetic lens; a charged-particle detector located downstream from the objective lens with respect to a path of the primary charged-particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and a voltage control plate located between the charged-particle detector and a pole-piece of the magnetic lens. The voltage control plate may comprise a horizontal portion comprising an opening; and an elongated portion extending downward from the opening with respect to the path of the primary charged-particle beam, into a hole of the charged-particle detector.