Overlay Measurement Using Non-Overlapping Targets and Grating Interference
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Solution Overview
Problem
Challenges arise in achieving improved quality, yield, performance, and reliability in semiconductor devices due to issues during the scaling-down process, particularly in minimizing overlay errors and applying complex design rules.
Innovation Solution
A method and system for overlay measurement using non-overlapping targets on different layers, employing a lens with a grating to generate interference patterns, allowing for reduced process deviation and less complex design rules, and enabling multiple overlay results through lens shifting for statistical validation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional overlapping targets are used for overlay measurement, then measurement can be performed, but process deviation effects between layers increase and design rules become more complex
Solution Approach 1:
The measurement system is segmented into separate first and second targets on different layers, where each target is independently formed. This segmentation eliminates the need for overlapping structures, thereby reducing design rule complexity while maintaining measurement precision through interference pattern generation.
2Measurement precision
If traditional overlapping targets are used for overlay measurement, then measurement can be performed, but the effect of process deviation between layers increases
Solution Approach 1:
By forming separate first and second targets on different layers instead of using overlapping structures, the measurement system reduces the impact of process deviations. Each target can be independently optimized and formed, minimizing cumulative process variation effects while maintaining measurement precision.
3Ease of manufacture
If non-overlapping targets on different layers are used, then design rules become simpler and process deviation effects are reduced, but multiple lens positioning operations are required
Solution Approach 1:
The lens is periodically shifted to different positions to sequentially measure multiple non-overlapping targets. This periodic repositioning allows the system to maintain simple design rules and reduce process deviation effects while systematically collecting measurement data from multiple targets for statistical validation.
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
Reduces the effect of process deviations between layers and allows for a less complex design rule, improving precision and accuracy in overlay measurement without requiring target overlap, and facilitating statistical validation of overlay results.
Implementation Method 1
The first target is configured to generate an interference pattern when being illuminated by a lens including a grating configured thereon. The second target is configured to generate an interference pattern when being illuminated by the lens including the grating configured thereon.
Data Source
AI summary
The present application discloses present disclosure provides a method for overlay measurement. The method includes forming a first target on a first layer; forming a second target on a second layer different from the first layer, wherein the first target and the second target are not overlapped to each other; positioning a lens including a grating configured thereon at a first location to completely overlap with the first target and the second target to generate an interference pattern of the first target and an interference pattern of the second target; and determining an overlay between the first target and the second target through the interference pattern of the first target and the interference pattern of the second target.