Charged Particle Beam Signal Processing for High Aspect Ratio Defect Detection
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Solution Overview
Problem
Conventional Scanning Electron Microscopes (SEMs) face difficulties in detecting defects in patterns with high aspect ratios due to the lack of secondary electron emission from the top face, making defect detection and observation impossible.
Innovation Solution
A signal processing method that involves scanning a pattern with a charged particle beam, detecting secondary charged particles using a detector divided into multiple regions, and applying filtering based on the angle of particle entry, enhancing signal-to-noise ratio (S/N) by selectively processing signals from different detector regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary electrons from a pattern are mainly detected to form an image, then image formation is achieved, but defect detection in high aspect ratio patterns becomes impossible
Solution Approach 1:
The detector is divided into multiple regions (first region and second region) that detect secondary electrons from different directions. The first region detects electrons from the top face direction, while the second region detects electrons from the side face direction, enabling detection of defects in high aspect ratio patterns that emit electrons laterally
Solution Approach 2:
Different regions of the detector are assigned different detection functions based on their spatial orientation. The first region is optimized for top-face emission detection while the second region is optimized for side-face emission detection, allowing the system to adapt to different emission characteristics in different pattern regions
2Measurement precision
If a detector is divided into multiple regions to detect secondary charged particles from different directions, then defect detection in high aspect ratio patterns is enabled, but device complexity increases
Solution Approach 1:
The divided detector serves multiple functions: it can detect secondary electrons from different directions simultaneously, provide angular distribution information, and maintain compatibility with conventional SEM operations. The same detector structure handles both top-face and side-face emissions without requiring separate detection systems
3Measurement precision
If filtering is applied to enhance signal-to-noise ratio, then measurement accuracy improves, but processing time increases
Solution Approach 1:
The signal processing apparatus performs filtering operations on detected signals to enhance the signal-to-noise ratio before final analysis. By applying filtering algorithms to the raw detection data, the system improves measurement accuracy while managing processing time through efficient signal enhancement techniques
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
Improves defect detection performance and measurement accuracy for patterns with high aspect ratios by enhancing S/N ratios, allowing for better visibility and depth measurement of defects within complex patterns.
Implementation Method 1
scanning a pattern on a substrate with a charged particle beam, detecting secondary charged particles emitted from the substrate
Implementation Method 2
detecting secondary charged particles emitted from the substrate by using a detector
Data Source
AI summary
In accordance with an embodiment, a signal processing method includes scanning a pattern on a substrate with a charged particle beam, detecting secondary charged particles emitted from the substrate by using a detector, outputting a signal, and filtering the signal. The detector is separated or divided into a plurality of regions, and the secondary charged particles are detected separately in each region of the detector. Intensity of the filtering is defined in dependence on a function f(θ) of an angle θ between a reference axis and a direction along which the secondary charged particles enter a detector plane. The reference axis is an arbitrary direction in a plane parallel to a surface of the substrate.