Multi-Pitch Overlay Measurement for Distortion-Resistant Alignment
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Solution Overview
Problem
As the semiconductor industry advances to nanometer technology process nodes, accurately determining overlay errors between photo resist layout patterns and underlying layout patterns in lithography operations becomes increasingly challenging due to distortion and asymmetry in overlay measurement patterns caused by manufacturing process steps, which can lead to gross errors in overlay error measurement.
Innovation Solution
The implementation of an overlay measurement pattern with additional features and sub-patterns having different pitches, where the first order diffracted light is used to determine overlay errors, and extra features are added to protect the overlay measurement pattern from process effects, ensuring the pitch size becomes comparable to the layout pattern dimensions, thereby reducing line width and avoiding distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If overlay measurement patterns are used in nanometer technology process nodes, then overlay error determination is enabled, but distortion and asymmetry occur in the measurement patterns due to manufacturing process steps
Solution Approach 1:
The overlay measurement pattern is segmented into multiple sub-patterns with different pitch values. By dividing the measurement pattern into distinct segments with varying pitches, the system can selectively use certain pitch segments that are less susceptible to manufacturing-induced distortion, thereby maintaining measurement accuracy despite process variations.
Solution Approach 2:
The invention changes the pitch parameter of the measurement pattern sub-patterns to create a multi-pitch structure. By varying the pitch values across different sub-patterns, the system can identify and utilize pitch ranges that minimize the impact of manufacturing process steps on pattern symmetry and measurement accuracy.
2Measurement precision
If overlay measurement patterns with larger pitch are used, then measurement capability is provided, but the pitch size becomes significantly larger than layout pattern dimensions causing vulnerability to process effects
Solution Approach 1:
The measurement pattern is divided into multiple sub-patterns with different pitch values. This segmentation allows the system to incorporate smaller pitch sub-patterns that are less vulnerable to manufacturing process effects while maintaining the overall measurement capability through the combination of multiple pitch segments.
Solution Approach 2:
The overlay measurement pattern functions as a composite structure combining multiple sub-patterns with different pitch characteristics. This composite approach allows the system to leverage the advantages of different pitch values, creating a robust measurement pattern that maintains accuracy while reducing sensitivity to process variations.
3Reliability
If additional features and sub-patterns with different pitches are added to overlay measurement pattern, then protection from process effects and reduced distortion are achieved, but device complexity increases
Solution Approach 1:
The measurement pattern is segmented into multiple sub-patterns with different pitches, where each segment serves a specific function in combating process effects. While this increases structural complexity, the segmented approach provides systematic protection against manufacturing variations through the diverse pitch characteristics of different segments.
Solution Approach 2:
The multi-pitch measurement pattern structure serves multiple functions simultaneously: it provides overlay measurement capability, reduces sensitivity to process effects, and enables identification of optimal pitch ranges. This multi-functionality justifies the increased complexity by delivering comprehensive measurement reliability.
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 allows for precise determination of overlay errors by isolating first order diffracted light and reducing the impact of process steps on overlay measurement accuracy, ensuring accurate alignment and minimizing errors in semiconductor manufacturing.
Implementation Method 1
directing a beam of light onto a lower-layer overlay measurement pattern and an upper-layer overlay measurement pattern to generate a combination of diffracted light
Data Source
AI summary
An overlay error measurement method includes disposing a lower-layer pattern over a substrate that includes disposing a first pattern having a first plurality of first sub-patterns extending in a first interval along a first direction and being arranged with a first pitch in a second direction crossing the first direction. The method includes disposing a second pattern having a second plurality of second sub-patterns extending in a second interval along the first direction and being arranged with a second pitch, smaller than the first pitch, in the second direction crossing the first direction. The second sub-patterns are disposed interleaved between the first sub-patterns. The method includes disposing an upper-layer pattern including a third pattern having the first pitch and at least partially overlapping with the lower-layer pattern over the lower-layer pattern and determining an overlay error between the lower-layer pattern and the upper-layer pattern.