Charged Particle Beam Inspection via Dynamic Optical Illumination
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Solution Overview
Problem
Current charged particle beam inspection methods face challenges in distinguishing between open and short/leakage defects in semiconductor devices, particularly in the positive imaging mode, where N+/P-well plugs are difficult to differentiate from normal plugs, leading to low sensitivity and the need for multiple inspections.
Innovation Solution
The method involves selectively illuminating an optical beam during charged particle beam scanning to form multiple images of the same area at different optical beam conditions, allowing for enhanced detection sensitivity of various defects without requiring separate inspections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charged particle beam scanning is performed in positive imaging mode, then short/leakage defects can be detected, but open defects in N+/P-well plugs cannot be distinguished from normal plugs
Solution Approach 1:
The patent applies dynamics by switching between different imaging modes (positive and negative) during the inspection process. The system dynamically changes the charging conditions of the electron beam to create different voltage contrast images, allowing defects that are invisible in one mode to be detected in another mode. This dynamic switching resolves the contradiction by making both open defects and short/leakage defects detectable through sequential imaging.
Solution Approach 2:
The patent changes the imaging parameters by alternating between positive imaging mode (where short/leakage defects are visible) and negative imaging mode (where open defects are visible). By modifying the beam charging conditions and switching imaging modes, the system achieves comprehensive defect detection capability that overcomes the limitation of single-mode inspection.
2Reliability
If multiple separate inspections are performed to detect different defect types, then detection sensitivity is maintained, but inspection time increases
Solution Approach 1:
The patent merges multiple inspection functions into a single integrated inspection process. By combining positive and negative imaging modes in one continuous scanning operation, the system simultaneously achieves detection of both open defects and short/leakage defects without requiring separate inspection steps, thereby maintaining sensitivity while improving throughput.
Solution Approach 2:
The patent maintains continuous useful action by performing both positive and negative imaging modes in sequential order without interrupting the inspection workflow. The electron beam scanning continues uninterrupted, switching between imaging modes to capture different defect types, thus eliminating idle time and maintaining high productivity while ensuring comprehensive defect detection.
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 improves the sensitivity in detecting open and short/leakage defects by altering the optical beam conditions during scanning, enabling more accurate identification and reducing the need for multiple inspections, thus increasing throughput while maintaining sensitivity.
Implementation Method 1
scanning an electron beam over surface patterns of devices formed on a substrate, and collecting the secondary electrons emanated from the surface patterns of scanned devices as inspection signals
Implementation Method 2
an optical beam is, from one line scan to another, selectively illuminated on the area prior to or simultaneously with scanning of the charged particle beam
Data Source
AI summary
An imaging method and apparatus for forming images of substantially the same area on a sample for defect inspection within the area are disclosed. The disclosed method includes line-scanning the charged particle beam over the area to form a plurality of n*Y scan lines by repeatedly forming a group of n scan lines for Y times. During the formation of each group of n scan lines, an optical beam is, from one line scan to another, selectively illuminated on the area prior to or simultaneously with scanning of the charged particle beam. In addition, during the formation of each group of n scan lines, a condition of illumination of the optical beam selectively changes from one line scan to another. The conditions at which individual n scan lines are formed are repeated for the formation of all Y groups of scan lines.