Voltage Contrast Defect Detection With Dual-Mode Beam Apertures
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Solution Overview
Problem
Current charged-particle beam inspection tools face challenges in maintaining high imaging resolution and throughput due to increased Coulomb interaction effects when switching between flooding and inspection modes, particularly in defect detection for small IC components, where the large beam current in flooding mode can negatively impact resolution in the inspection mode.
Innovation Solution
A charged-particle beam apparatus with a current-limiting aperture plate and beam-limiting aperture array, allowing for the same apertures to be used in both modes, reducing Coulomb interaction effects by blocking peripheral electrons in the inspection mode without sacrificing image resolution, and using a detector protection mechanism to prevent high-energy signal electrons from damaging detectors during flooding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large beam current is used in flooding mode to increase throughput, then inspection throughput is improved, but Coulomb interaction effects increase and negatively impact imaging resolution in inspection mode
Solution Approach 1:
The patent divides the charged particle beam into two separate portions using aperture arrays: a first portion for flooding the sample surface to generate voltage contrast, and a second portion for inspecting the sample. This segmentation allows each beam portion to be optimized independently - the first portion can have high current for throughput while the second portion uses reduced current to minimize Coulomb interaction effects and maintain imaging resolution.
Solution Approach 2:
The patent extracts the harmful peripheral charged particles from the beam using aperture arrays positioned at different locations. By blocking these peripheral particles that cause excessive Coulomb interactions, the system maintains high throughput from the flooding mode while preserving imaging resolution in inspection mode by removing the detrimental effects of space charge.
2Ease of operation
If the same apertures are used in both flooding and inspection modes to simplify operation, then ease of operation is improved, but imaging resolution deteriorates due to Coulomb interaction effects
Solution Approach 1:
The patent employs aperture arrays that serve multiple functions: they define the beam portions for both flooding and inspection modes, and simultaneously block peripheral charged particles to reduce Coulomb interaction effects. This multi-functionality allows the system to maintain ease of operation with fixed apertures while preserving imaging resolution by inherently limiting the harmful space charge regardless of the operational mode.
3Productivity
If high beam current is maintained in inspection mode to preserve throughput, then inspection throughput is improved, but image resolution is degraded due to increased Coulomb interaction effects
Solution Approach 1:
The patent applies different beam current characteristics to different spatial regions and functional zones: the first beam portion used for flooding can have high current density, while the second beam portion used for inspection has reduced current density. This local differentiation allows the system to maintain high overall throughput while ensuring that the inspection region operates with optimized current levels that preserve image resolution by minimizing Coulomb interactions.
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 maintains high inspection throughput while preserving image resolution by minimizing Coulomb interaction effects and protecting detectors from high-energy electrons, enabling efficient defect detection in small IC components.
Implementation Method 1
a condenser lens configured to focus the at least a first portion of the primary charged-particle beam
Implementation Method 2
the increased Coulomb interaction effects may negatively impact the resolution
Data Source
AI summary
Systems and methods of providing a probe spot in multiple modes of operation of a charged-particle beam apparatus are disclosed. The method may comprise activating a charged-particle source to generate a primary charged-particle beam and selecting between a first mode and a second mode of operation of the charged-particle beam apparatus. In the flooding mode, the condenser lens may focus at least a first portion of the primary charged-particle beam passing through an aperture of the aperture plate to form a second portion of the primary charged-particle beam, and substantially all of the second portion is used to flood a surface of a sample. In the inspection mode, the condenser lens may focus a first portion of the primary charged-particle beam such that the aperture of the aperture plate blocks off peripheral charged-particles to form the second portion of the primary charged-particle beam used to inspect the sample surface.