Non-overlapping Semiconductor Targets for Overlay Measurement
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is achieving accurate overlay measurement between different layers without overlapping targets, which is crucial for minimizing errors and complexity in scaling down device dimensions.
Innovation Solution
A method involving a first target on one layer and a second target on another layer, both with line features spaced equally apart, but not overlapping, using a lens with a grating to generate interference patterns for overlay measurement, allowing for reduced process deviation and simpler design rules, and enabling multiple overlay results for statistical validation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If targets on different layers are made to overlap for overlay measurement, then overlay measurement can be performed, but process deviation between layers increases measurement error
Solution Approach 1:
The measurement system is segmented into two independent measurement paths: one for the first target on the first layer and another for the second target on the second layer. Each target is measured separately by the same lens system, allowing independent measurement that avoids the compounding errors associated with overlapping targets. The overlay is then calculated by comparing the relative positions obtained from these separate measurements.
2Measurement precision
If overlapping targets are used for overlay measurement, then overlay can be measured, but design rules become more complex
Solution Approach 1:
Instead of using overlapping targets that require complex design rules for proper alignment and measurement, the invention inverts the approach by using non-overlapping targets. The targets are positioned such that they do not interfere with each other spatially, simplifying the design rules while maintaining the ability to measure overlay through comparative position measurement.
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 approach reduces the effect of process deviations between layers and simplifies design rules, enabling precise overlay determination without target overlap, thus improving the quality and reliability of semiconductor devices.
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 a semiconductor device with a grating structure. The semiconductor device includes a first target positioned on a first layer and including a plurality of line features spaced equally apart from each other according to a first pitch; and a second target positioned on a second layer and including a plurality of line features spaced equally apart from each other according to a second pitch. The first layer is different from the second layer. The first target and the second target do not overlap with each other. 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.