Objective Lens Array for Backscatter Detection Without Cross-Talk
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Solution Overview
Problem
Existing multi-beam inspection systems for semiconductor IC chips struggle with cross-talk and are unable to effectively image backscattered signals due to the detection of secondary electrons, limiting the ability to increase throughput for backscattered detection and obtain information about structures below the surface or measure overlay targets.
Innovation Solution
A charged particle-optical device is designed with a detector array positioned proximate to the sample to repel secondary charged particles and accelerate sub-beams with high landing energy, allowing for the detection of backscattered charged particles using a multi-beam array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a detector array is positioned proximate to the sample to detect backscattered charged particles, then detection throughput and information about subsurface structures are improved, but secondary charged particles interfere with detection causing cross-talk
Solution Approach 1:
The patent extracts and removes secondary charged particles from the detection path using electrostatic repulsion fields generated by the objective lens array. This allows the detector array to be positioned proximate to the sample for high-throughput detection while eliminating the harmful interference from secondary particles that would otherwise cause cross-talk between adjacent detection elements.
Solution Approach 2:
The objective lens array serves as an intermediary element between the sample and detector array. It performs dual functions: accelerating primary charged particles onto the sample to generate backscattered signals, and simultaneously repelling secondary charged particles away from the detector. This mediator role enables the detector to be positioned close to the sample without suffering from secondary particle interference.
2Productivity
If multiple beams are used to increase inspection throughput, then productivity is improved, but cross-talk between adjacent beams increases making it difficult to detect backscattered signals
Solution Approach 1:
The patent divides the inspection system into multiple independent sub-beams that can be processed simultaneously. Each sub-beam is focused by a corresponding objective lens that independently repels secondary particles. This segmentation allows high-throughput multi-beam inspection while maintaining signal purity for each beam, eliminating cross-talk between adjacent beams.
Solution Approach 2:
The patent changes the energy parameter of the charged particle beams by accelerating them to high energies before impact. This high landing energy increases the proportion of backscattered particles relative to secondary particles, improving the signal-to-noise ratio for backscattered detection in multi-beam configurations and enabling high-throughput inspection with maintained precision.
3Loss of information
If high landing energy is used to accelerate charged particle sub-beams, then information about structures below the surface is improved, but secondary charged particle emission increases
Solution Approach 1:
The patent converts the harmful secondary charged particles generated by high-energy beam impact into a managed phenomenon. By using electrostatic repulsion fields from the objective lens array, the system directs secondary particles away from the detector while maintaining the high landing energy needed for subsurface information. The harmful emission is transformed into a controllable flow that can be excluded from the detection path.
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
Enables high-throughput detection of backscattered charged particles, providing information about structures below the surface and enabling measurement of overlay targets, thereby improving the inspection process.
Implementation Method 1
the objective lenses are configured to accelerate the charged particle sub-beams along the sub-beam paths
Implementation Method 2
the charged particle-optical device is configured to repel secondary charged particles emitted from the sample away from the detector
Data Source
AI summary
The embodiments of the present disclosure provide various techniques for detecting backscatter charged particles, including accelerating charged particle sub-beams along sub-beam paths to a sample, repelling secondary charged particles from detector arrays, and providing devices and detectors which can switch between modes for primarily detecting charged particles and modes for primarily detecting secondary particles.