Semiconductor Wafer Alignment Markers with Asymmetric Feature Widths
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Solution Overview
Problem
Current semiconductor wafer alignment markers struggle to provide sufficient resolution for precise alignment, as much radiant energy is focused in the first order, which is not sensitive to spatial variations, and existing designs are not suitable for both fine and coarse alignment.
Innovation Solution
The alignment markers are designed with first and second structures having features with unequal widths and specific spacings to enhance the intensity of higher diffraction orders, allowing for improved spatial discrimination and alignment accuracy by directing more energy to higher diffraction orders while maintaining adequate lower order signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment markers use conventional features with equal widths and standard pitch, then the first diffraction order contains most radiant energy, but the first order is not sensitive to spatial variations and provides poor resolution
Solution Approach 1:
The patent applies local quality by making individual features within the alignment marker have different widths rather than uniform widths. Specifically, the marker includes features with widths of 0.5 microns, 1.0 microns, and 1.5 microns at different positions. This non-uniform width distribution locally modifies the diffraction characteristics to enhance energy in higher diffraction orders while maintaining overall marker functionality.
Solution Approach 2:
The patent employs asymmetry by introducing features with unequal widths (0.5 microns, 1.0 microns, 1.5 microns) and non-symmetric spacing within the alignment marker structure. This asymmetric configuration disrupts the conventional symmetric diffraction pattern, redirecting radiant energy from the first order to higher diffraction orders (second, third, and fourth orders), thereby improving spatial sensitivity and measurement precision.
2Measurement precision
If alignment markers are designed to enhance higher diffraction orders, then spatial discrimination improves, but coarse alignment capability may be compromised
Solution Approach 1:
The alignment marker achieves multi-functionality by simultaneously providing both fine alignment (through enhanced higher diffraction orders with improved spatial discrimination) and coarse alignment (through maintained lower diffraction order signals). The non-uniform feature widths and asymmetric spacing are designed to optimize higher order diffraction while preserving sufficient energy in lower orders, allowing the single marker structure to serve dual purposes.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the widths of individual features (0.5, 1.0, 1.5 microns) and their spacing within the marker. These parameter variations are specifically tuned to control the diffraction pattern, enhancing higher diffraction orders for fine alignment while maintaining adequate lower order signals for coarse alignment, thus achieving both functions through controlled parameter optimization.
3Measurement precision
If alignment markers use features with unequal widths and specific spacings, then higher diffraction orders are enhanced, but the device complexity increases
Solution Approach 1:
The alignment marker is segmented into multiple discrete features with specifically assigned widths (0.5 microns, 1.0 microns, 1.5 microns) and positions. This segmentation allows independent optimization of each feature's contribution to the diffraction pattern, enabling precise control over higher diffraction order enhancement while maintaining a manageable structural complexity through systematic segmentation rather than monolithic design.
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 design enhances the ability to accurately and repeatedly align semiconductor wafers during fabrication, improving wafer quality by emphasizing higher diffraction orders without sacrificing coarse alignment capabilities.
Implementation Method 1
The diffraction patterns produced by the alignment marker have multiple diffraction orders (e.g. first order, second order, third order, etc.)
Implementation Method 2
The alignment markers generally include a series of scribe lines or other features that produce an interference pattern when illuminated with radiation at a selected wavelength
Data Source
AI summary
Semiconductor wafer alignment markers and associated systems and methods are disclosed. A wafer in accordance with a particular embodiment includes a wafer substrate having an alignment marker that includes a first structure and a second structure, each having a pitch, with first features and second features positioned within the pitch. The first features are positioned to generate first phase portions of an interference pattern, with at least one of the first features having a width different than another of the first features in the pitch, and with the second features positioned to generate second phase portions of the interference pattern, with the second phase portions having a second phase opposite the first phase, and with at least one of the second features having a width different than that of another of the second features in the pitch. The pitch for the first structure is different than the pitch for the second structure.