Self-Aligned Multiple Patterning Overlay Metrology Pattern Symmetry
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Solution Overview
Problem
Self-aligned multiple patterning in semiconductor manufacturing faces challenges in overlay metrology accuracy due to poor symmetry of metrology patterns caused by differences in topographies of peripheral fins, which are sensitive to etch cavity environments and difficult to distinguish optically.
Innovation Solution
A method is introduced that includes providing an overlay metrology pattern with a front layer pattern comprising segmented grating structures, forming core structures and spacers, and selectively removing outermost fin structures to improve symmetry and accuracy, involving a photomask, photoresist layers, and etching processes to create a modified metrology structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the original line is segmented into dozens of fins to form the metrology pattern, then the pattern can be formed in self-aligned multiple patterning, but the peripheral fins have different topographies due to etch cavity environment differences, causing poor symmetry
Solution Approach 1:
The patent removes the two outermost fin structures from the metrology pattern to eliminate the source of asymmetry. By extracting these problematic peripheral fins that experience different etch cavity environments, the remaining inner fins can form a symmetric pattern, directly resolving the symmetry issue while maintaining the self-aligned multiple patterning manufacturing capability
Solution Approach 2:
The patent applies different treatment to different parts of the fin structure. Specifically, the two outermost fins are removed while the inner fins are retained and used for metrology measurement. This local differentiation ensures that only the fins with uniform topography (the inner ones) are used for measurement, while the problematic peripheral fins are excluded, achieving local optimization of pattern quality
2Quantity of substance
If the line is segmented into dozens of fins, then the pattern density is doubled, but the fins become excessively sensitive to etch cavity environment, making their topography difficult to control
Solution Approach 1:
The patent extracts the two outermost fins that are most sensitive to etch cavity environment variations. By removing these highly sensitive peripheral fins, the remaining inner fins experience more uniform etch conditions, enabling better topography control while maintaining the high pattern density achieved through fin segmentation
Solution Approach 2:
The patent differentiates the fate of different fins based on their sensitivity to etch cavity environment. The inner fins, which experience more uniform conditions, are retained for metrology, while the outermost fins, which are most sensitive to environmental variations, are removed. This local quality differentiation optimizes both pattern density and topography control
3Device complexity
If conventional OVL metrology pattern design is used in self-aligned multiple patterning, then the process is simple, but the obtained line consists of only a circle of very thin fins that cannot be distinguished optically
Solution Approach 1:
The patent segments the metrology line into multiple discrete fin structures rather than using a continuous line or a single circle of fins. This segmentation creates distinct, separable fin features that can be individually resolved and detected optically, solving the distinguishability problem while maintaining relative simplicity in the overall pattern design
Solution Approach 2:
The patent creates local variations in the fin structure by removing the two outermost fins, leaving a central cluster of inner fins. This local modification creates optical contrast and distinguishability between the metrology features, enabling optical detection while keeping the overall design approach simple and consistent with self-aligned multiple patterning
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 symmetry of the overlay metrology pattern, reduces the impact of etch cavity environments, and improves metrology accuracy by modifying the fin structures and their formation process.
Implementation Method 1
forming core structures and spacers, and selectively removing outermost fin structures to improve symmetry and accuracy, involving a photomask, photoresist layers
Implementation Method 2
etching processes to create a modified metrology structure
Implementation Method 3
forming core structures and spacers
Data Source
AI summary
The present application provides a method for improving overlay metrology accuracy of self-aligned multiple patterning, overlay metrology pattern comprising a front layer pattern and a current layer pattern, the front layer pattern comprising a plurality of first grating structures overlaid on the periphery of the current layer pattern, the first grating structure being composed of a plurality of repeatedly arranged strip elements; segmenting the strip element in the first grating structure, so that each of the strip elements forms a sub-grating structure comprising a plurality of repeatedly arranged strip structures; forming a plurality of repeatedly arranged core structures corresponding to the plurality of repeatedly arranged strip structures; form a gate structure comprising a plurality of repeatedly arranged fin structures; removing two outermost fin structures of the gate structure; the gate structure and the current layer pattern structure together forming an overlay metrology structure.