Multi-beam Electron Source for High-Resolution Semiconductor Inspection
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Solution Overview
Problem
Conventional semiconductor inspection tools using a single electron beam suffer from low throughput due to the diffraction effect and Coulomb Effect, which degrades spatial resolution when trying to increase beam current for higher throughput.
Innovation Solution
A multi-beam apparatus is developed with a source-conversion unit that separates image-forming and aberration-compensation functions, using micro-deflectors and micro-compensators to form parallel beamlets and compensate aberrations, while reducing Coulomb Effect by cutting off peripheral electrons early with Coulomb-effect-reduction openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beam current is increased to improve throughput, then productivity increases, but spatial resolution deteriorates due to Coulomb Effect
Solution Approach 1:
The patent divides a single high-current electron beam into multiple lower-current beamlets using a source conversion unit with micro-deflectors and micro-compensators. This segmentation allows parallel scanning of multiple regions simultaneously, achieving high throughput without the Coulomb Effect that plagues single high-current beams, thereby maintaining spatial resolution while improving productivity.
2Productivity
If optical beam is used instead of electron beam, then throughput is improved, but spatial resolution deteriorates due to diffraction effect
Solution Approach 1:
The patent employs multiple electron beamlets instead of a single beam or optical beam, enabling parallel inspection of multiple regions. This multi-beam approach achieves electron beam resolution without the diffraction limitations of optical beams, while the parallel processing capability delivers high throughput comparable to optical methods.
3Device complexity
If image-forming and aberration-compensation functions are combined in source conversion unit, then device complexity is reduced, but image resolution deteriorates due to additional aberrations from beamlet tilting and shifting
Solution Approach 1:
The patent separates the source conversion unit into independent micro-deflector elements and micro-compensator elements. Each beamlet has its own dedicated compensator that corrects aberrations specific to that beamlet's path, preventing the accumulation of tilting and shifting aberrations that would occur if functions were combined, thereby maintaining high image resolution.
Solution Approach 2:
The patent implements local aberration compensation by providing each beamlet with its own micro-compensator tailored to that specific beamlet's characteristics and path. This localized approach allows precise correction of individual beamlet aberrations without interfering with other beamlets, maintaining optimal image resolution across all parallel beams.
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 improves image resolution and throughput by avoiding additional aberrations from beamlet tilting and shifting, and reduces the impact of Coulomb Effect, enabling faster and more accurate inspection of semiconductor wafers/masks.
Implementation Method 1
a plurality of micro-deflectors converts a single charged-particle beam into a plurality of parallel beamlets and forms a plurality of virtual images of a charged-particle source
Implementation Method 2
a plurality of micro-compensators compensates aberrations of the plurality of virtual images
Implementation Method 3
Each micro-deflector is aligned with one micro-compensator and one beamlet-limit opening... cuts off peripheral electrons of each beamlet and thereby limiting a current thereof
Data Source
AI summary
One modified source-conversion unit and one method to reduce the Coulomb Effect in a multi-beam apparatus are proposed. In the modified source-conversion unit, the aberration-compensation function is carried out after the image-forming function has changed each beamlet to be on-axis locally, and therefore avoids undesired aberrations due to the beamlet tilting/shifting. A Coulomb-effect-reduction means with plural Coulomb-effect-reduction openings is placed close to the single electron source of the apparatus and therefore the electrons not in use can be cut off as early as possible.