Adjustable Aperture Electron Beam Inspection for Resolution Throughput Trade-off
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Solution Overview
Problem
Conventional electron beam tools for semiconductor manufacturing face a trade-off between sensitivity (resolution) and throughput, where high sensitivity requires low beam current for small defects but results in low throughput, and high throughput requires high beam current, leading to low resolution imaging.
Innovation Solution
The introduction of an adjustable beam-limiting aperture and beam-current selection aperture in the electron gun and column allows for controllable beam current and angular current density, reducing electron-electron interactions and spot blur while maintaining high beam current, enabling both high sensitivity and high throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low beam current is used to improve sensitivity for detecting small defects, then imaging resolution is improved, but throughput decreases
Solution Approach 1:
The patent applies dynamics by making the beam-limiting aperture adjustable rather than fixed. The aperture size can be dynamically changed during operation to optimize the balance between beam current and spot size. This allows the system to switch between high sensitivity mode (small aperture) and high throughput mode (large aperture) depending on inspection requirements, resolving the contradiction between measurement precision and productivity.
2Productivity
If high beam current is used to increase throughput, then productivity is improved, but imaging resolution deteriorates due to spot blur
Solution Approach 1:
The patent applies parameter changes by adjusting the aperture size parameter to control the relationship between beam current and spot size. By optimizing the aperture diameter, the system can achieve higher beam current without proportionally increasing spot blur, as the angular current density is also controlled. This allows throughput to increase while maintaining acceptable imaging resolution.
3Device complexity
If fixed aperture size is used in conventional electron gun, then device complexity is reduced, but adaptability to different inspection requirements decreases
Solution Approach 1:
The patent transforms the static aperture system into a dynamic one by introducing an adjustable beam-limiting aperture. This allows the system to adapt to different inspection requirements (high sensitivity vs. high throughput) by changing the aperture size. The increased adaptability is achieved with moderate additional complexity through the use of a movable aperture mechanism.
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 effectively improves imaging resolution without compromising throughput, overcoming the conventional trade-off between sensitivity and performance by reducing spot blur and enhancing beam current management.
Implementation Method 1
an electron source configured to generate electrons for an electron beam
Implementation Method 2
an objective lens for focusing the electron beam onto the target area
Data Source
AI summary
One embodiment relates to an electron-beam apparatus for defect inspection and/or review of substrates or for measuring critical dimensions of features on substrates. The apparatus includes an electron gun and an electron column. The electron gun includes an electron source configured to generate electrons for an electron beam and an adjustable beam-limiting aperture which is configured to select and use one aperture size from a range of aperture sizes. Another embodiment relates to providing an electron beam in an apparatus. Advantageously, the disclosed apparatus and methods reduce spot blur while maintaining a high beam current so as to obtain both high sensitivity and high throughput.