Multi-Beam Electron Optics With Variable FOV for Wafer Defect Inspection
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Solution Overview
Problem
Conventional yield management tools in the semiconductor manufacturing industry face limitations in throughput and spatial resolution due to the diffraction effect and Coulomb Effect, making it difficult to inspect and review defects on wafers/masks with high resolution and high throughput, especially with single electron beams.
Innovation Solution
A multi-beam apparatus is configured with a variable total Field of View (FOV) in size, orientation, and incident angle, using a source-conversion unit with beamlet-limit openings and electron optics elements to form multiple probe spots from a single electron source, allowing for flexible scanning and detection of secondary electrons across a large observed area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single electron beam with large current is used to improve throughput, then the scanning speed and coverage area increase, but the spatial resolution deteriorates due to the Coulomb Effect
Solution Approach 1:
The invention divides a single electron beam into multiple beamlets (e.g., 7 beamlets) that scan different regions simultaneously. Each beamlet carries a smaller current, avoiding the Coulomb Effect while collectively covering a large area, thus achieving both high throughput and high spatial resolution.
Solution Approach 2:
The invention transitions from single-point sequential scanning to multi-point parallel scanning by spatially distributing multiple beamlets across different regions of the sample. This dimensional expansion from 1D temporal scanning to 2D spatial parallelism enables simultaneous acquisition of multiple scanned regions.
2Measurement precision
If a single electron beam with small current is used to maintain spatial resolution, then the Coulomb Effect is minimized, but the throughput decreases
Solution Approach 1:
The invention merges multiple low-current beamlets into a coordinated scanning system that collectively achieves high throughput. While each individual beamlet maintains low current for high resolution, the combined effect of parallel operation across multiple beamlets delivers the necessary throughput for mass production.
Solution Approach 2:
The invention ensures continuous useful action by having multiple beamlets scan different regions simultaneously without idle time. This parallel continuous scanning eliminates the temporal gaps inherent in sequential single-beam scanning, maintaining high productivity throughout the inspection process.
3Productivity
If multiple electron beams from multiple sources are used to increase throughput, then the scanning coverage and detection speed improve, but the device complexity increases
Solution Approach 1:
The invention makes a single electron source perform multiple functions by generating multiple beamlets from one source. This multi-functional approach eliminates the need for multiple independent electron sources, reducing the complexity of source management, alignment, and synchronization while maintaining the throughput benefits of multi-beam scanning.
Solution Approach 2:
The invention creates virtual copies of the electron source by forming multiple crossovers (virtual sources) from a single physical source. These virtual sources are then imaged onto different scanned regions, achieving the effect of multiple sources without the actual complexity of multiple physical sources.
4Area of stationary object
If the Field of View is increased to cover larger observed areas, then the scanning efficiency improves, but the image resolution may be compromised
Solution Approach 1:
The invention segments the large observed area into multiple smaller scanned regions, each covered by a dedicated beamlet. This segmentation allows each beamlet to maintain high resolution while collectively covering a large total area, overcoming the trade-off between FOV size and image resolution.
Solution Approach 2:
The invention resolves the FOV-resolution trade-off by transitioning from a single large scanned region to multiple smaller scanned regions arranged in space. This spatial distribution across multiple dimensions allows parallel high-resolution imaging of the entire large area simultaneously.
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
The multi-beam apparatus enhances throughput and detection capabilities, enabling high-resolution imaging and increased flexibility in observing various samples, thereby improving defect detection and yield management in semiconductor manufacturing.
Implementation Method 1
an electron source for generating a primary electron beam along a primary optical axis of the apparatus
Implementation Method 2
an objective lens below the source-conversion unit for projecting the plurality of images onto a sample surface
Implementation Method 3
A plurality of secondary electron beams is generated by the plurality of probe spots respectively from the plurality of scanned regions
Data Source
AI summary
A new multi-beam apparatus with a total FOV variable in size, orientation and incident angle, is proposed. The new apparatus provides more flexibility to speed the sample observation and enable more samples observable. More specifically, as a yield management tool to inspect and/or review defects on wafers/masks in semiconductor manufacturing industry, the new apparatus provide more possibilities to achieve a high throughput and detect more kinds of defects.