Spatial-Frequency Matched Wafer Alignment Marks
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Solution Overview
Problem
Conventional alignment mark designs in semiconductor manufacturing fail to accurately reflect device pattern shifts during pattern transfer, leading to misalignment issues despite precise etching and polishing, due to larger mark elements etching less repeatably and reliably with CMP and other techniques.
Innovation Solution
The use of alignment marks with spatial frequency spectra corresponding to device patterns, allowing for more accurate modeling and measurement of wafer patterns by distributing marks throughout the substrate to receive similar processing as device patterns, thereby enhancing overlay accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment mark designs with large mark elements are used, then alignment marks can be easily detected and measured, but the mark elements etch less repeatably and reliably with CMP and other processing techniques
Solution Approach 1:
The patent changes the spatial frequency parameter of alignment marks to match the device pattern spectrum. By transforming the alignment mark design from conventional large elements to patterns with spatial frequencies corresponding to actual device patterns (e.g., 0.5-2.0 cycles/µm), the marks undergo similar processing effects as device patterns during CMP and etching, thereby improving etching repeatability while maintaining detectability through spectral matching.
2Reliability
If alignment mark designs are subdivided into segments to satisfy design rules, then etching repeatability improves, but the marks fail to accurately reflect actual device pattern shifts during pattern transfer
Solution Approach 1:
The patent applies local quality by making alignment marks have the same spatial frequency characteristics as the local device patterns they represent. Instead of using uniform segmented designs across all marks, each alignment mark's spatial frequency is tailored to match the corresponding device pattern's spectral content, enabling accurate reflection of local pattern shifts while maintaining etching reliability through appropriate size segmentation.
Solution Approach 2:
The patent transforms alignment mark designs by changing their spatial frequency parameters to match device pattern spectra. This parameter transformation ensures that segmented alignment marks experience similar processing effects as actual device patterns, allowing them to accurately reflect pattern shifts while satisfying design rules for etching repeatability.
3Manufacturing precision
If alignment marks are distributed throughout the wafer to receive similar processing as device patterns, then overlay accuracy improves, but the complexity of mark design and measurement increases
Solution Approach 1:
The patent applies universality by creating alignment marks that serve dual functions: they maintain the spatial frequency characteristics of device patterns for accurate overlay measurement, while also undergoing similar processing effects during CMP and etching. This multi-functionality allows distributed marks to improve overlay accuracy without requiring entirely separate measurement systems, as the same marks used for alignment also reflect processing effects.
Data Source
AI summary
Alignment patterns that are selected based on device pattern spatial frequencies are defined on a reticle. The alignment patterns can include periodic arrays of lines, spaces, dots, of other pattern elements. Such patterns can be defined as sets associated with a common spatial frequency or frequency range, or some or all sets can include alignment marks having mark elements associated with different spatial frequencies.