Multi-Beam Electron Lens for Crosstalk Reduction
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Solution Overview
Problem
In multi-beam image acquisition systems, reducing the pitch between electron beams to achieve high resolution leads to increased crosstalk and aberration in the detection optical system, making it difficult to detect multiple secondary electron beams individually.
Innovation Solution
A multi-beam image acquisition apparatus and method that includes a stage, an objective lens to image primary electron beams, a separator with electrodes and magnetic poles to separate secondary electron beams, a deflector to deflect these beams, and a lens to image them at a deflection point, followed by detection, which reduces aberration and allows for individual separation of secondary electron beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitch between electron beams is reduced to achieve high resolution, then the resolution is improved, but crosstalk between beams increases and secondary electron beams spread on the E×B separator making it difficult to detect them individually
Solution Approach 1:
A lens is introduced as an intermediary component between the E×B separator and the detector. This lens forms an intermediate image of the secondary electron beams, acting as a mediator that prevents direct spread of beams on the separator while enabling individual detection. The lens conjugates the object surface to the intermediate image position, creating a controlled imaging path that separates beam trajectories before detection.
Solution Approach 2:
The patent introduces a new spatial dimension by forming an intermediate image at a conjugate position between the separator and detector. This additional imaging plane allows beams to be separated in the lateral dimension while maintaining vertical detection, effectively adding a dimensional layer to the beam separation process that prevents crosstalk without reducing pitch.
2Device complexity
If multiple secondary electron beams are detected without forming an intermediate image, then the detection system is simpler, but aberration increases and beams overlap on the detector
Solution Approach 1:
The lens performs preliminary imaging action by forming an intermediate image of the secondary electron beams before they reach the detector. This preliminary formation of the intermediate image at the conjugate position prepares the beams for accurate detection, preventing aberration and overlap issues that would occur without this pre-imaging step.
3Reliability
If the E×B separator is arranged at the field conjugate position of the primary electron beam, then the influence of E×B on primary beams is minimized, but secondary electron beams spread without forming an intermediate field
Solution Approach 1:
The lens serves as an intermediary that bridges the gap created by the E×B separator arrangement. By introducing this lens between the separator and detector, the system compensates for the lack of intermediate field formation by the separator, creating a new intermediate image that enables proper secondary beam detection while maintaining primary beam stability.
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 solution effectively reduces aberration and enables the separation of secondary electron beams, improving the resolution and accuracy of pattern inspection in semiconductor wafer imaging by aligning the deflection point with the detection surface, preventing beam overlap and enhancing detection capabilities.
Implementation Method 1
a separator configured to have two or more electrodes for forming an electric field and two or more magnetic poles for forming a magnetic field and configured to separate multiple secondary electron beams emitted due to the substrate being irradiated with the multiple primary electron beams from trajectories of the multiple primary electron beams by the electric field and the magnetic field formed
Implementation Method 2
a separator configured to have two or more electrodes for forming an electric field and two or more magnetic poles for forming a magnetic field and configured to separate multiple secondary electron beams emitted due to the substrate being irradiated with the multiple primary electron beams from trajectories of the multiple primary electron beams by the electric field and the magnetic field formed
Implementation Method 3
an E×B (E cross B) separator is arranged on the trajectory of the primary electron beam to separate the secondary electron beam from the primary electron beam
Implementation Method 4
an objective lens configured to image multiple primary electron beams on the substrate
Implementation Method 5
a lens arranged between the objective lens and the deflector and configured to image the multiple secondary electron beams at a deflection point of the deflector
Implementation Method 6
a deflector configured to deflect the multiple secondary electron beams separated
Implementation Method 7
a detector configured to detect the deflected multiple secondary electron beams
Data Source
AI summary
According to one aspect of the present invention, a multi-beam image acquisition apparatus, includes: an objective lens configured to image multiple primary electron beams on a substrate by using the multiple primary electron beams; a separator configured to have two or more electrodes for forming an electric field and two or more magnetic poles for forming a magnetic field and configured to separate multiple secondary electron beams emitted due to the substrate being irradiated with the multiple primary electron beams from trajectories of the multiple primary electron beams by the electric field and the magnetic field formed; a deflector configured to deflect the multiple secondary electron beams separated; a lens arranged between the objective lens and the deflector and configured to image the multiple secondary electron beams at a deflection point of the deflector; and a detector configured to detect the deflected multiple secondary electron beams.