Multiple Particle Beam Autofocus Lens for Adjustable Working Distance
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Solution Overview
Problem
Conventional multiple particle beam systems struggle with slow autofocus adjustments and limited throughput in inspecting semiconductor wafers with high-precision and high-voltage structures, particularly due to the complexity of magnetic lenses and the need for precise control of working distance, magnification, and landing angle.
Innovation Solution
A multiple particle beam system with a fast autofocus correction lens and a controller that allows for high-frequency adjustments of focal position, maintaining constant magnification and landing angle, using electrostatic lenses and actuators to achieve rapid and precise imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional magnetic lenses are used for focusing particle beams, then the system achieves stable imaging, but the autofocus adjustment speed is slow
Solution Approach 1:
The patent divides the lens system into two independent parts: a magnetic objective lens for stable focusing and an electrostatic correction lens for rapid autofocus adjustments. This segmentation allows each lens type to perform its optimal function without compromising the other.
Solution Approach 2:
The electrostatic correction lens acts as an intermediary element that mediates between the need for fast autofocus response and the stability provided by the magnetic objective lens. It corrects focal position deviations without disrupting the primary imaging function.
2Adaptability or versatility
If the working distance is adjusted for different inspection requirements, then the system becomes more versatile, but the autofocus control complexity increases
Solution Approach 1:
The electrostatic correction lens provides a universal solution for autofocus control that works across multiple working distances and magnifications. A single correction mechanism handles diverse inspection requirements without requiring separate control systems for each condition.
3Productivity
If multiple particle beams are used for high-throughput inspection, then the productivity increases, but the system complexity increases
Solution Approach 1:
The patent merges the autofocus control for multiple particle beams into a single electrostatic correction lens system. Instead of providing separate focus control for each beam, the correction lens collectively adjusts the focal position for the entire beam array, simplifying the control architecture while maintaining high throughput.
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-throughput, high-precision imaging with sub-nanometer accuracy and rapid autofocus adjustments, overcoming limitations of conventional systems by maintaining imaging stability and efficiency in semiconductor wafer inspections.
Implementation Method 1
a magnetic and/or electrostatic objective lens, in particular a magnetic and/or electrostatic immersion lens
Implementation Method 2
a fast autofocus correction lens
Data Source
AI summary
A multiple particle beam microscope and an associated method can provide a fast autofocus around an adjustable working distance. A system can have one or more fast autofocus correction lenses for adapting, in high-frequency fashion, the focusing, the position, the landing angle and the rotation of individual particle beams upon incidence on a wafer surface during the wafer inspection. Fast autofocusing in the secondary path of the particle beam system can be implemented in analogous fashion. An additional increase in precision can be attained via fast aberration correction mechanism in the form of deflectors and/or stigmators.