Multi-Beamlet Assembly for High Throughput Wafer Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional scanning electron microscopes with single beams struggle to achieve high throughput and resolution during wafer inspection due to challenges in directing, scanning, and correcting multiple beams, which leads to aberrations and prolonged inspection times.
Innovation Solution
A charged particle beam apparatus with a multi-beamlet generation and correction assembly, including a first multi-aperture electrode for creating beamlets, a second multi-aperture electrode for field curvature correction, and multipoles for individual beamlet control, along with a single transfer lens for collimation and an objective lens for focusing, allows for simultaneous inspection of multiple locations with reduced aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple beamlets are propagated next to each other over an extended distance within a column, then high throughput inspection is achieved, but electron-electron interactions cause beam widening and deflection deteriorating resolution
Solution Approach 1:
The patent segments the beam propagation path into distinct regions using multiple intermediate focus planes. Each plane contains beamlets at different separation distances, creating zones where electron-electron interactions are minimized. This segmentation allows beamlets to travel extended distances while maintaining resolution by periodically resetting their spatial configuration.
Solution Approach 2:
The patent employs curved or spheroidal trajectories for beamlet propagation between focus planes. By using curved paths instead of straight parallel propagation, the beamlets naturally diverge and converge in a controlled manner, reducing the time they spend in close proximity and thereby minimizing electron-electron interaction effects while maintaining high throughput.
2Productivity
If multiple beams are directed and scanned in a single column, then high throughput inspection is achieved, but correcting aberrations such as field curvature becomes challenging
Solution Approach 1:
The patent divides the single column into multiple functional sections separated by intermediate focus planes. Each section handles specific beamlet subsets with dedicated correction elements, segmenting the complex aberration correction task into manageable sections. This reduces the overall complexity compared to correcting all beamlets simultaneously in a single column.
Solution Approach 2:
The patent introduces the dimension of multiple intermediate focus planes along the beam propagation path. Instead of attempting to correct all aberrations at a single plane, the system distributes correction across multiple planes, adding a spatial dimension to the correction process. This dimensional approach simplifies the correction of field curvature and other aberrations by addressing them at different stages of beam propagation.
3Measurement precision
If a conventional single-beam SEM is used for wafer inspection, then resolution can be maintained, but inspection time becomes excessively long
Solution Approach 1:
The patent segments the inspection task by dividing the beam into multiple beamlets that can simultaneously inspect different regions of the wafer. This parallel segmentation of the inspection process maintains the resolution quality of individual beamlets while dramatically reducing total inspection time through concurrent operation of multiple beams.
Solution Approach 2:
The patent performs preliminary focusing and arrangement of beamlets at intermediate focus planes before the final inspection plane. This preliminary action ensures that when multiple beamlets simultaneously inspect the wafer, each maintains optimal focus and resolution, preventing degradation that would otherwise occur with parallel beam propagation.
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 solution enables quick and accurate inspection of specimens with multiple beamlets, improving resolution and throughput by minimizing electron-electron interactions and aberrations, while maintaining a compact apparatus design.
Implementation Method 1
a charged particle beam emitter for generating a charged particle beam propagating along an optical axis
Implementation Method 2
a multi-beamlet generation- and correction-assembly, including: a first multi-aperture electrode with a first plurality of apertures for creating the plurality of beamlets from the charged particle beam
Implementation Method 3
an objective lens for focusing each of the plurality of beamlets to a separate location on the specimen
Implementation Method 4
a single transfer lens for beamlet collimation arranged between the multi-beamlet generation- and correction-assembly and the objective lens
Implementation Method 5
at least one second multi-aperture electrode with a second plurality of apertures of varying diameters for the plurality of beamlets for providing a field curvature correction
Data Source
AI summary
A charged particle beam apparatus for inspecting a specimen with a plurality of beamlets is described. The charged particle beam apparatus includes a charged particle beam emitter (105) for generating a charged particle beam (11) propagating along an optical axis (A) and a multi-beamlet generation- and correction-assembly (120), including a first multi-aperture electrode (121) with a first plurality of apertures for creating the plurality of beamlets from the charged particle beam, at least one second multi-aperture electrode (122) with a second plurality of apertures of varying diameters for the plurality of beamlets for providing a field curvature correction, and a plurality of multipoles (123) for individually influencing each of the plurality of beamlets, wherein the multi-beamlet generation- and correction-assembly (120) is configured to focus the plurality of beamlets to provide a plurality of intermediate beamlet crossovers. The charged particle beam apparatus further includes an objective lens (150) for focusing each of the plurality of beamlets to a separate location on the specimen, and a single transfer lens (130) for beamlet collimation arranged between the multi-beamlet generation- and correction-assembly and the objective lens. Further, a method of inspecting a specimen with a charged particle beam apparatus is described.