Multi-column SEM Array Spacing for Photomask Inspection
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Solution Overview
Problem
Multi-column scanning electron microscopy (SEM) systems face inefficiencies in inspecting photomasks/reticles and wafers due to suboptimal spacing of electron-optical columns, leading to increased inspection time and potential charging issues, which hinder high-resolution characterization and defect detection in semiconductor manufacturing.
Innovation Solution
A multi-column assembly with electron-optical columns arranged in an array with specific spacings that correspond to the dimensions of inspection areas, allowing for efficient characterization of multiple field areas on a sample surface, minimizing overlap, and optimizing inspection time by aligning images post-processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple electron-optical columns are spaced to cover a larger total inspection area, then the inspection coverage is improved, but the inspection time increases and charging interference occurs
Solution Approach 1:
The patent divides the inspection task into multiple independent electron-optical columns, each responsible for a specific inspection area. The spacing between columns is optimized so that each column inspects a discrete region without excessive overlap, allowing parallel inspection of multiple areas simultaneously while minimizing redundant scanning and total inspection time
Solution Approach 2:
The patent applies different spacing configurations for different columns based on their specific inspection requirements and positions. Columns are strategically positioned and spaced to match the field area dimensions, ensuring optimal coverage without unnecessary overlap that would increase inspection time or cause charging interference
2Area of stationary object
If multiple electron-optical columns are spaced to cover a larger total inspection area, then the inspection coverage is improved, but charging interference occurs
Solution Approach 1:
The inspection area is segmented into discrete regions assigned to individual electron-optical columns with optimized spacing. This segmentation ensures that columns are positioned far enough apart to minimize charging interference while maintaining comprehensive coverage of the field area
Solution Approach 2:
The spacing between columns is locally optimized based on their specific positions and the field area dimensions. Columns near the edges or in sensitive regions are spaced to avoid charging interference, while columns in more robust areas may be spaced closer to maximize coverage
3Productivity
If the number of electron-optical columns is increased, then the inspection throughput is improved, but the system complexity increases
Solution Approach 1:
The system uses multiple independent electron-optical columns that function as separate inspection units. Each column operates independently with its own scanning and detection capabilities, allowing the system to achieve high throughput through parallel processing while maintaining manageable complexity through modular architecture
Solution Approach 2:
The patent optimizes the number, spacing, and positioning of electron-optical columns as key parameters to achieve the desired throughput while controlling complexity. By carefully selecting these parameters based on field area dimensions and inspection requirements, the system achieves optimal performance without unnecessary complexity
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 configuration enhances the sensitivity and throughput of photomask/reticle and wafer inspection processes, reducing the time required for high-resolution characterization and minimizing interference from charging, thereby improving defect detection and semiconductor device quality.
Implementation Method 1
a first electron-optical column of the plurality of electron-optical columns is configured to characterize a first inspection area within a first instance of the particular field
Data Source
AI summary
A multi-column assembly for a scanning electron microscopy (SEM) system is disclosed. The multi-column assembly includes a plurality of electron-optical columns arranged in an array defined by one or more spacings. Each electron-optical column includes one or more electron-optical elements. The plurality of electron-optical columns is configured to characterize one or more field areas on a surface of a sample secured on a stage. The number of electron-optical columns in the plurality of electron-optical columns equals an integer number of inspection areas in a field area of the one or more field areas. The one or more spacings of the plurality of electron-optical columns correspond to one or more dimensions of the inspection areas.