Multi-Beam Electron Optics to Minimize Coulomb Blur
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Solution Overview
Problem
Conventional semiconductor yield management tools using a single electron beam face limitations in throughput due to the Coulomb Effect, which degrades spatial resolution, making them inadequate for high-resolution and high-throughput inspection of defects on wafers/masks in the semiconductor manufacturing industry.
Innovation Solution
A multi-beam apparatus employing a source-conversion unit to deflect multiple beamlets towards an objective lens, allowing for flexible adjustment of deflection angles and current densities of probe spots, thereby reducing aberrations and Coulomb effects, and using a pre-beamlet-forming means to minimize probe spot sizes and improve resolution and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single electron beam with high current is used to increase throughput, then productivity is improved, but manufacturing precision deteriorates due to the Coulomb Effect
Solution Approach 1:
The invention divides a single high-current electron beam into multiple lower-current beamlets using a beamlet-forming plate with multiple openings. Each beamlet maintains lower current density, avoiding the Coulomb Effect that degrades resolution in high-current single beams, while the collective array of beamlets achieves high throughput by simultaneously scanning multiple regions of the sample.
2Productivity
If multiple electron beams are used to improve throughput, then productivity is improved, but device complexity increases
Solution Approach 1:
The invention employs a single objective lens to focus all beamlets onto the sample surface, and a single detector to collect secondary electrons from all scanned regions. This multi-functional approach allows one optical component to serve multiple purposes, achieving high throughput without proportionally increasing device complexity.
Solution Approach 2:
The invention combines multiple beamlets into a unified scanning system where all beamlets share common optical paths, focusing mechanisms, and detection systems. This merging approach consolidates what would otherwise require multiple independent electron microscopes, significantly reducing overall system complexity while maintaining high throughput capability.
3Area of stationary object
If beamlet deflection angles are increased to expand scanning coverage, then area of stationary object is improved, but manufacturing precision deteriorates due to increased aberrations
Solution Approach 1:
The invention dynamically adjusts the deflection angles of individual beamlets based on their position in the array. Beamlets at the center of the array use smaller deflection angles to maintain tight focus, while beamlets at the periphery use progressively larger angles to expand coverage. This dynamic angle adjustment allows the system to maximize observed area while minimizing aberration-induced spot size increases.
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 multi-beam apparatus achieves high-resolution and high-throughput imaging by minimizing probe spot sizes and aberrations, enhancing the ability to inspect and review defects on wafers/masks, aligning with the industry's requirements for advanced semiconductor manufacturing.
Implementation Method 1
a condenser below the electron source, the collimating action of which reduces the divergence of the primary electron beam generated by the electron source
Implementation Method 2
the objective lens focuses the plurality of deflected beamlets onto a being-observed surface of a sample and therefore a plurality of probe spots is formed thereon
Implementation Method 3
the source-conversion unit deflects a plurality of beamlets of the primary electron beam towards the optical axis of the objective lens with different deflection angles
Data Source
AI summary
A multi-beam apparatus for observing a sample with high resolution and high throughput is proposed. In the apparatus, a source-conversion unit forms plural and parallel images of one single electron source by deflecting plural beamlets of a parallel primary-electron beam therefrom, and one objective lens focuses the plural deflected beamlets onto a sample surface and forms plural probe spots thereon. A movable condenser lens is used to collimate the primary-electron beam and vary the currents of the plural probe spots, a pre-beamlet-forming means weakens the Coulomb effect of the primary-electron beam, and the source-conversion unit minimizes the sizes of the plural probe spots by minimizing and compensating the off-axis aberrations of the objective lens and condenser lens.