SEM Pitch Walk Inspection Using FFT Phase Analysis
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Solution Overview
Problem
Existing semiconductor manufacturing processes face challenges in accurately inspecting pitch walk, a phenomenon where the pitch of line and space patterns deviate due to multi-patterning technologies, leading to patterning non-uniformity and errors in subsequent processes.
Innovation Solution
A scanning electron microscope (SEM) image-based method that utilizes Fast Fourier Transform (FFT) to analyze line and space patterns, dividing the main pitch into component pitches, and calculating pitch walk by comparing compensated FFT phase graphs, providing an automated and accurate inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-patterning technology is used to form small-pitch L/S patterns, then the ability to pattern below single-patterning limits is improved, but pitch walk occurs causing non-uniformity in patterning
Solution Approach 1:
The patent divides the L/S pattern into multiple components (first L/S pattern and second L/S pattern) formed at different stages through multi-patterning technology. By segmenting the pattern formation process and analyzing each component separately using FFT, the method can identify and measure pitch walk between different pattern sets, enabling precise inspection and control of pitch uniformity across the entire structure.
2Measurement precision
If conventional SEM measurement methods are used for pitch inspection, then simple measurement is possible, but accuracy is affected by SEM CD measurement conditions and spacer width variations
Solution Approach 1:
The patent replaces direct physical measurement of pitch with an FFT-based spectral analysis method. Instead of mechanically measuring dimensions that are sensitive to SEM conditions and spacer variations, the method transforms the spatial pattern into frequency domain data, where pitch information is extracted from FFT phase graphs. This substitution eliminates sensitivity to measurement conditions and provides consistent, accurate pitch and pitch walk measurements.
3Measurement precision
If pitch walk inspection is performed to improve patterning quality, then measurement accuracy is improved, but inspection time and complexity increase
Solution Approach 1:
The patent performs FFT transformation on the L/S pattern data in advance, creating compensated FFT phase graphs that contain encoded pitch information. This preliminary processing allows rapid extraction of pitch and pitch walk measurements without requiring complex real-time analysis during inspection. The pre-computed phase graphs enable quick comparison and accurate pitch walk detection, significantly reducing inspection time while maintaining high measurement precision.
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 enhances the accuracy and speed of pitch walk inspection, reducing errors associated with SEM CD measurement conditions and spacer width variations, thereby improving the reliability and production efficiency of semiconductor devices.
Implementation Method 1
performing a Fast Fourier Transform (FFT) on each graph of the component pitches
Data Source
AI summary
A pitch walk inspection method includes obtaining a scanning electron microscope (SEM) image for a line and space (L/S) pattern formed by a multi-patterning technology (MPT), where L/S pattern includes a plurality of lines and spaces that are alternately arranged; detecting a main pitch of the L/S pattern in the SEM image; dividing a graph of the main pitch into graphs of component pitches, based on the MPT; performing a Fast Fourier Transform (FFT) on each graph of the component pitches; multiplying a phase and an intensity graph of the FFT of each of the graphs of the component pitches with each other and obtaining compensated FFT phase graphs; and calculating a pitch walk for the L/S pattern by obtaining differences between phase peak values of the compensated FFT phase graphs.