Photocathode Film Layout for Multi-Beam Electron Throughput

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Solution Overview

Problem

Increasing the number of electron beamlets in electron-beam devices, such as scanning electron microscopes, to enhance throughput is challenging due to issues with homogenous angular intensity distribution, field curvature, astigmatism, and distortion.

Innovation Solution

An electron-beam device that includes a photocathode film with a pattern of emission and non-emission regions, illuminated from the back side by a laser, to emit multiple electron beamlets, which are then extracted and controlled using electrodes to achieve desired shapes and directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the emission angle of the electron source is increased to create more beamlets, then the number of beamlets increases and throughput improves, but the angular intensity distribution becomes less homogenous

Engineering Contradiction:

ImprovethroughputVSAvoidangular intensity distribution homogeneity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent divides the electron source into multiple discrete emission regions on the photocathode film, each corresponding to a specific beamlet. By illuminating the back side of the photocathode with a laser, electrons are emitted at controlled locations and angles, creating multiple beamlets with homogeneous angular intensity distribution while maintaining high throughput

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of controlling the front side of the photocathode as in conventional approaches, the patent illuminates the back side of the photocathode film with a laser. This inverted approach allows for better control of electron emission angles and homogeneous angular intensity distribution across multiple beamlets

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If the number of beamlets is increased to improve throughput, then the field of view increases, but field curvature, astigmatism, and distortion increase

Engineering Contradiction:

ImprovethroughputVSAvoidimage quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies different properties to different regions of the photocathode film, with each emission region optimized for its specific location and angle. This allows each beamlet to maintain high quality with minimal aberrations while collectively providing a large field of view and high throughput

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent controls emission parameters (angle, position, energy) by varying the illumination conditions on the back side of the photocathode. By changing these parameters across different emission regions, the system achieves both large field of view and high image quality with minimal distortion

Inventive Principle:

Principle #35Parameter changes

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 enables the creation of multiple electron beamlets with controlled shapes and directions, improving the throughput and inspection capabilities of electron-beam devices while minimizing distortions and aberrations.

Implementation Method 1

The photocathode film has a front side and a back side and emits a plurality of electron beamlets when illuminated from the back side using the laser

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS12283453B2Creating multiple electron beams with a photocathode film

Publication Date: 2025.04.22 KLA CORP

AI summary

An electron-beam device includes a laser and a photocathode film. The photocathode film has a front side and a back side and emits a plurality of electron beamlets when illuminated from the back side using the laser. The electron-beam device also includes electrodes to extract the plurality of electron beamlets from the front side of the photocathode film and to control shapes of the plurality of electron beamlets.