Overlay Target with Varying Line Widths for Lens Aberration Correction
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Solution Overview
Problem
Conventional overlay targets in semiconductor device fabrication are unable to correct pattern placement errors caused by lens aberrations in lithography tools, leading to inaccuracies in layer alignment during the fabrication process.
Innovation Solution
The introduction of an overlay target with features of varying line widths, where a second set of features with a narrower line width is arranged parallel to a first set with a wider line width, allowing for the detection of pattern placement errors due to lens aberrations, and these errors are used to adjust the lithography tool's operating parameters for correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional overlay targets with uniform line width features are used, then overlay measurement can be performed, but pattern placement errors arising from lens aberrations cannot be corrected
Solution Approach 1:
The overlay target employs features with different local qualities (different line widths) to enable detection of lens aberration effects. Specifically, the target includes a first set of features with a first line width and a second set of features with a second line width different from the first, allowing differential measurement that reveals placement errors caused by lens aberrations while maintaining standard overlay measurement capability
Solution Approach 2:
The invention adds a new dimension to overlay targets by incorporating line width variation as an additional measurement parameter. Conventional targets only measure positional offset, but this invention uses both positional offset and line width changes to detect and correct lens aberration effects, effectively adding a dimensional aspect to the measurement space
2Reliability
If overlay targets are designed to detect lens aberration effects, then correction capability improves, but target structure complexity increases
Solution Approach 1:
The overlay target is segmented into multiple feature sets with different line widths (first set with first line width, second set with second line width). This segmentation allows the target to independently measure different aspects of lens performance - standard overlay alignment and lens aberration-induced placement errors - without requiring a completely new target design
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 solution enables precise correction of pattern placement errors in two dimensions, improving the accuracy of layer alignment and reducing overlay inaccuracy by compensating for lens aberrations, thereby enhancing the overall quality of semiconductor device fabrication.
Implementation Method 1
exposing a resist in a lithography tool to electromagnetic radiation transferred through a lens and a photomask
Implementation Method 2
exposing a resist in a lithography tool to electromagnetic radiation transferred through a lens and a photomask to form a first plurality of features and a second plurality of features that are latent in the resist
Data Source
AI summary
Structures for detecting and correcting an overlay inaccuracy and methods of detecting and correcting an overlay inaccuracy. An overlay target includes a first plurality of features arranged along a first longitudinal axis in a first line-space pattern having a first line width, and a second plurality of features arranged along a second longitudinal axis in a second line-space pattern having a second line width that is less than the first line width. The second longitudinal axis is aligned substantially parallel to the first longitudinal axis.