Charged Particle Beam Apparatus for Line Space Pattern Measurement
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Solution Overview
Problem
Existing methods for determining uneven surface height and depression/protrusion on semiconductor wafers, particularly line and space patterns, face challenges such as low S/N ratio and resolution in scanning electron microscopes, leading to errors in determining line and space widths and requiring complex image processing, and issues with oblique beam irradiation causing mismatched images.
Innovation Solution
Irradiating a charged particle beam onto the sample and detecting emitted particles at multiple focal positions to compare signal amounts and profiles, allowing for determination of uneven surfaces and depression/protrusions without complex image processing, specifically suitable for line and space patterns by analyzing changes in signal profiles and half-value widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stereoscopic observation method is used to obtain three-dimensional information, then depression/protrusion determination capability is improved, but image processing complexity and processing time increase significantly
Solution Approach 1:
The patent extracts only the essential information needed for depression/protrusion determination by detecting charged particles at multiple focal positions. Instead of performing full stereoscopic matching of complete images, the method extracts signal amounts and profile characteristics at specific focal depths, thereby simplifying the processing while maintaining measurement precision.
Solution Approach 2:
The patent adds the focal position dimension to the detection process. By detecting particles at multiple focal positions (in-focus and out-of-focus) and analyzing signal amount variations and profile shape changes across this additional dimension, the method determines depression/protrusion states without requiring complex two-image stereoscopic processing.
2Measurement precision
If stereoscopic observation method is used to obtain three-dimensional information, then depression/protrusion determination capability is improved, but processing time increases due to advanced image processing requirements
Solution Approach 1:
The patent performs preliminary detection at multiple focal positions to acquire signal amounts and profile data before final analysis. By pre-categorizing patterns based on signal variations and profile shapes at different focal depths, the method reduces the computational burden during actual measurement, thereby decreasing processing time while maintaining accuracy.
3Ease of operation
If line and space pattern is measured with scanning electron microscope, then pattern observation is achieved, but determination accuracy decreases when line and space have almost equal width
Solution Approach 1:
The patent applies different detection conditions (focal positions) to different depth regions of the pattern. By analyzing signal amount variations and profile shape changes at specific local focal positions, the method enhances the ability to distinguish between lines and spaces of equal width, improving determination accuracy while maintaining ease of operation.
4Measurement precision
If oblique beam irradiation is used to measure pattern dimensions, then dimensional measurement capability is improved, but image matching accuracy deteriorates when beam direction differs
Solution Approach 1:
Instead of relying on oblique beam angles for dimensional measurement, the patent transitions to using the focal position dimension. By detecting particles at multiple focal positions and analyzing signal variations along the depth axis, the method achieves dimensional measurement capability without the image matching problems associated with varying oblique beam directions.
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 method simplifies the determination of uneven surfaces and depression/protrusions, improves accuracy in distinguishing line and space widths, and reduces processing time by eliminating the need for advanced image processing, while ensuring accurate top and bottom surface identification.
Implementation Method 1
a charged particle beam is irradiated onto the sample, and the charged particles emitted from the scanned portion are detected at plural focal positions
Data Source
AI summary
A charged particle beam apparatus for obtaining information of an uneven surface or a depression/protrusion of a sample by irradiating a charged particle beam to a sample having an uneven surface or a depression/protrusion at a plurality of focal positions, measuring signal emitted from the sample, and comparing profile waveforms corresponding to edge portions of the uneven surface.