Electron Beam Deflector for Substrate Inspection Aberration Control
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Solution Overview
Problem
Existing substrate inspection methods using electron beams suffer from increased aberration due to the space charge effect in the overlapping space between the primary and secondary electron beams, particularly at their focus positions, which affects image resolution and signal quality.
Innovation Solution
A substrate inspection method and apparatus that includes a deflector between the multistage quadrupole lenses and the Wien filter to control the primary electron beam trajectory, reducing the overlapping space and suppressing aberration caused by the space charge effect, while maintaining the Koehler illumination for the primary electron beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the primary electron beam trajectory is adjusted to reduce overlapping space with the secondary electron beam, then aberration caused by space charge effect is suppressed, but the Koehler illumination may be impaired
Solution Approach 1:
The patent divides the electron optical system into separate trajectory control zones. The deflector is positioned to specifically adjust the primary electron beam trajectory in the region where overlap with secondary electrons occurs, while leaving other regions unchanged to maintain Koehler illumination. This segmented approach allows localized correction of the overlapping space charge effect without compromising overall illumination quality.
Solution Approach 2:
The invention applies local quality by making the primary electron beam trajectory non-uniform only in the specific overlapping region with the secondary electron beam. The deflector creates a localized trajectory modification that reduces space charge interaction precisely where it occurs, while the rest of the beam path maintains the conditions necessary for optimal Koehler illumination.
2Measurement precision
If a deflector is added to control the primary electron beam trajectory, then aberration is suppressed, but device complexity increases
Solution Approach 1:
The deflector acts as an intermediary component between the primary electron beam source and the specimen. It introduces a controlled electric or magnetic field that modifies the primary beam trajectory only in the critical overlapping region, serving as a mediator to reduce space charge aberration without requiring complete redesign of the entire electron optical system.
Solution Approach 2:
The deflector provides dynamic control of the primary electron beam trajectory, allowing real-time adjustment of the beam path to optimize the reduction of overlapping space with secondary electrons. This dynamic capability enables adaptive aberration suppression while maintaining flexibility in operation.
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
The method effectively reduces aberration in the secondary electron beam, improving image resolution and signal quality without impairing the primary electron beam's illumination, enabling more accurate substrate inspection.
Implementation Method 1
a primary electron beam is deflected by a Wien filter as an electron beam deflector
Implementation Method 2
the aberration of the secondary electron beam is increased by the significant influence of the electron-electron interaction, i.e. the so-called space charge effect due to the high electron density in this overlapping space
Implementation Method 3
magnifying and projecting the induced electron as a secondary electron beam so as to form an image of the secondary electron beam
Implementation Method 4
generating an electron beam and irradiating the electron beam as a primary electron beam to a substrate as a specimen
Data Source
AI summary
A substrate inspection method includes:generating an electron beam and irradiating the electron beam as a primary electron beam to a substrate as a specimen;inducing at least any of a secondary electron, a reflected electron and a backscattering electron which are emitted from the substrate receiving the primary electron beam, and magnifying and projecting the induced electron as a secondary electron beam so as to form an image of the secondary electron beam; a trajectory of the primary electron beam and a trajectory of the secondary electron beam having an overlapping space and space charge effect of the secondary electron beam occurring in the overlapping space,detecting the image of the secondary electron beam to output a signal representing a state of the substrate; andsuppressing aberration caused by the space charge effect in the overlapping space.