Overlay Metrology Structure for Accurate Semiconductor Alignment
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Solution Overview
Problem
Existing optical overlay control methods in semiconductor manufacturing fail to accurately represent the actual overlay error between structures in the device area due to differences in interaction between layers, leading to inaccurate measurements.
Innovation Solution
A semiconductor structure and method that uses a combination of third and fourth structures in an optical overlay metrology area to mimic the interaction between first and second structures in the device area, ensuring accurate representation of the overlay error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical overlay control methods are used without mimicking structures, then the measurement process is simpler and faster, but the overlay error measurement is inaccurate due to differences in layer interaction
Solution Approach 1:
The patent creates a copy of the device area structures (first and second structures) in the overlay metrology area as third and fourth structures. This copy allows the metrology measurement to accurately represent the actual device overlay error by replicating the same material interactions and layer configurations, thereby resolving the inaccuracy caused by conventional simplified measurement structures.
Solution Approach 2:
The patent divides the semiconductor structure into two distinct areas: a device area where actual device structures are formed, and an overlay metrology area where measurement structures are formed. This segmentation allows the metrology area to be optimized specifically for accurate overlay measurement while keeping the device area focused on device fabrication, resolving the conflict between measurement accuracy and process simplicity.
2Reliability
If the overlay metrology area uses different material interactions than the device area, then the measurement process is easier to implement, but the measured overlay error does not represent the actual device overlay error
Solution Approach 1:
The patent ensures that the third structure in the metrology area is formed from the same material as the first structure in the device area, and the fourth structure is formed from the same material as the second structure. This material homogeneity ensures that the physical and chemical interactions between layers are identical in both areas, making the overlay error measurement reliable and representative of actual device performance.
3Measurement precision
If optical detection is performed without mimicking the device structure combination, then the measurement speed is faster, but the overlay error determination is inaccurate
Solution Approach 1:
The patent performs overlay error measurement on the third and fourth structures in the metrology area before final device fabrication steps. By using the mimicking structures to predict the overlay error that will occur in the actual device, the process allows for preliminary correction of masking layer alignment, preventing the need for time-consuming rework and improving both accuracy and efficiency.
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
The solution provides a more accurate determination of overlay error by mimicking the interaction between layers, allowing for precise correction of masking layer alignment and improving the overlay control process.
Implementation Method 1
optically detecting a second distance between a feature of the fourth structure, corresponding to the feature of the second masking structure, and the feature of the fifth structure
Data Source
AI summary
A semiconductor structure includes a device area that includes a first structure in a first layer having a top surface above a top surface of the first layer, and a second structure in a second layer on top of the first layer, where the first structure is pinned in the second structure; an overlay metrology area for optically evaluating an overlay error between the second and first structure, including: a third structure in the first layer, having a top surface above the top surface of the first layer, a fourth structure in the second layer, where the combination of the third and fourth structures mimics the combination of the first structure and the second structures, and a fifth structure in the first layer, for use as a reference structure.