Test Structure for Pitch Walking Measurement in Multiple Patterning
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Solution Overview
Problem
Current metrology techniques face difficulties in accurately measuring and controlling the 'pitch walking' effect, an overlay error in multiple patterning lithography processes, especially in self-aligned double patterning techniques, due to limitations in standard overlay measurement methods and the asymmetry of modern measurement techniques.
Innovation Solution
A novel test structure design with a pair of gratings having different feature and space dimensions is used, which provides a differential optical response indicative of the pitch walking effect, allowing for accurate measurement and control of the multiple patterning process through optical critical dimension measurements without modifying existing scatterometry systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard overlay measurement techniques (IBO or DBO) are used, then measurement capability is provided, but they cannot accurately measure pitch walking effect due to lack of asymmetry and minimal periods/CDs
Solution Approach 1:
The patent applies asymmetry by designing a test structure where one grating has asymmetric spacing relative to the other, creating intentional asymmetry in the differential optical response. This asymmetry enables the measurement system to detect pitch walking effects that would otherwise be invisible in symmetric structures, directly resolving the measurement difficulty for minimal periods and CDs.
Solution Approach 2:
The patent implements local quality by creating specific test structures with different local properties (different grating periods, different spacing relationships) within the overall test site. These localized variations in structure quality enable targeted measurement of pitch walking effects at specific regions, overcoming the limitations of standard techniques that cannot handle minimal periods and CDs.
2Ease of operation
If larger features are created for measurement, then standard overlay techniques become applicable, but it is difficult to create features much larger than design rules in multiple patterning schemes
Solution Approach 1:
The patent resolves this contradiction by transitioning from measuring absolute overlay in a single dimension to measuring differential optical response across multiple gratings with different local properties. This dimensional approach to measurement enables the use of standard techniques while maintaining compliance with design rule constraints, as the measurement sensitivity comes from the differential response rather than feature size alone.
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
Enables fast and accurate interpretation of pitch walking and other parameters, facilitating precise monitoring and control of multiple patterning processes, even in cases where standard techniques fail, by utilizing special algorithms and data processing techniques.
Implementation Method 1
differential optical response from said test structure is indicative of the pitch walking effect
Implementation Method 2
utilizing special algorithms and data processing techniques
Data Source
AI summary
An article is presented configured for controlling a multiple patterning process, such as a spacer self-aligned multiple patterning, to produce a target pattern. The article comprises a test site carrying a test structure comprising at least one pair of gratings, wherein first and second gratings of the pair are in the form of first and second patterns of alternating features and spaces and differ from the target pattern by respectively different first and second values which are selected to provide together a total difference such that a differential optical response from the test structure is indicative of a pitch walking effect.