Non-Overlapping Overlay Targets with Grating-Based 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 in semiconductor manufacturing.
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 measurements through lens shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional overlapping targets are used for overlay measurement, then measurement capability is achieved, but process deviation effects between layers increase and design rules become more complex
Solution Approach 1:
The measurement target is divided into two separate non-overlapping targets on different layers, rather than using a single overlapping target structure. This segmentation allows each target to be independently designed and measured, reducing the complexity of design rules while maintaining overlay measurement capability through the lens shifting mechanism
Solution Approach 2:
The invention transitions from a single-layer overlapping target to a multi-layer non-overlapping target configuration. By utilizing the third dimension (layer depth) to separate the targets, the system eliminates the need for complex overlapping design rules while preserving overlay measurement functionality through optical path integration
2Measurement precision
If traditional overlapping targets are used for overlay measurement, then measurement capability is achieved, but the effect of process deviation between layers increases
Solution Approach 1:
By segmenting the measurement into two separate non-overlapping targets on different layers, the invention isolates the process deviation effects for each layer. This allows independent optimization of each target structure, reducing the cumulative effect of process deviations while maintaining accurate overlay measurement through the lens shifting and interference pattern analysis
3Reliability
If multiple overlay measurements are taken through lens shifting, then statistical validation is improved, but measurement time increases
Solution Approach 1:
The invention employs periodic lens shifting to capture multiple interference patterns at different positions. This periodic action enables statistical validation of overlay measurements by collecting multiple data points, while the systematic nature of the shifting allows for efficient data collection and processing
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 less complex design rules, while providing precise overlay measurements through statistical validation of multiple 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.