Charged Particle Source Steering Electrodes Deflect Secondary Particles

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Solution Overview

Problem

Charged particle sources in multi-beam lithography systems face challenges in maintaining operational time and beam stability due to contamination and erosion from residual gases and secondary charged particles, which affect the homogeneity and current density of the particle beam.

Innovation Solution

The design incorporates steering electrodes with intentional deviations from rotational symmetry to deflect secondary charged particles away from the emission surface, using perturbations in the electric potential to redirect them and protect the emitter surface, while maintaining a stable and homogeneous beam.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a conventional charged particle source with rotationally symmetric electrodes is used, then the beam generation is simple and the structure is symmetric, but the emitter surface is exposed to contamination and erosion from secondary charged particles, reducing operational time

Engineering Contradiction:

Improveoperational time of charged particle sourceVSAvoidcontamination and erosion from secondary charged particles

Core Design Contradiction:

Duration of action of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces steering electrodes with intentional deviations from rotational symmetry to create asymmetric electric potential perturbations. These asymmetric fields deflect secondary charged particles away from the emitter surface, protecting it from contamination and erosion while maintaining beam generation functionality.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent converts the harmful effect of secondary charged particles into a beneficial steering mechanism. By introducing controlled asymmetric perturbations, the electric fields that would normally attract secondary particles to the emitter are redirected to steer them away, transforming a harmful interaction into a protective function.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If steering electrodes with asymmetric perturbations are introduced, then the emitter surface is protected from contamination and erosion, but the device complexity increases

Engineering Contradiction:

Improvebeam stability and homogeneityVSAvoidelectrode configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs steering electrodes with controlled asymmetric deviations from rotational symmetry. These electrodes create localized perturbations in the electric potential that steer secondary particles away from the emitter surface while maintaining overall system functionality and beam quality.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The asymmetric perturbations are introduced locally at specific positions of the steering electrodes rather than throughout the entire electrode structure. This localized approach allows protection of the emitter surface while minimizing the overall complexity increase and maintaining beam generation efficiency.

Inventive Principle:

Principle #3Local quality

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 approach extends the operational time of the charged particle source by preventing erosion and contamination, ensuring a stable and homogeneous beam distribution without the need for physical removal or realignment of the source.

Implementation Method 1

an emitter electrode (i.e., an emitter anode or cathode, depending on whether the charged particles carry positive or negative electric charge, respectively), which emitter electrode has an emitter surface configured to emit charged particles of a specific charged particle species

Methodology Applied

Scientific EffectThermionic emission: Thermionic Emission

Implementation Method 2

a counter electrode configured to being applied an electrostatic voltage with respect to the emitter electrode at a sign opposite to that of the electrically charged particles

Methodology Applied

Scientific EffectElectrostatic acceleration: Electric Field

Implementation Method 3

at least one adjustment electrode, which is a steering electrode which interrupts the radial axial-symmetry of the electric potential of the source, configured to force unintended, secondary charged particles away from the emission surface

Methodology Applied

Scientific EffectElectrostatic deflection: Electric Field

Data Source

PatentUS11735391B2Charged-particle source

Publication Date: 2023.08.22 IMS NANOFABTION

AI summary

A charged-particle source for generating a charged-particle comprises a sequence of electrodes, including an emitter electrode with an emitter surface, a counter electrode held at an electrostatic voltage with respect to the emitter electrode at a sign opposite to that of the electrically charged particles, and one or more adjustment electrodes surrounding the source space between the emitter electrode and the counter electrode. These electrodes have a basic overall rotational symmetry along a central axis, with the exception of one or more steering electrodes which is an electrode which interrupts the radial axial-symmetry of the electric potential of the source, for instance tilted or shifted to an eccentric position or orientation, configured to force unintended, secondary charged particles away from the emission surface.