Self-Moiré Grating Layout for Precise Device-Pitch Metrology
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Solution Overview
Problem
Existing metrology techniques struggle to accurately measure device-like pitches due to their unresolved nature, limiting the precision of measurements in semiconductor manufacturing.
Innovation Solution
A grating design comprising periodic sub-structures with device-like pitches that generate a measurable Moiré pitch through evanescent modes, allowing for accurate metrology measurements by optical tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional self-moiré gratings are used, then device complexity is reduced, but measurement precision deteriorates due to sensitivity to misalignment and non-linearity errors
Solution Approach 1:
The grating structure is segmented into multiple zones with different pitch values. Each zone has a specific pitch designed to compensate for errors in that region, dividing the overall measurement function into manageable segments that collectively improve precision
Solution Approach 2:
Different regions of the grating are assigned different local properties (pitch values) based on their specific measurement requirements. The pitch varies locally across the grating surface to optimize measurement accuracy for each region while accounting for systematic errors
2Measurement precision
If conventional gratings with uniform pitch are used, then manufacturing precision is simplified, but measurement precision deteriorates due to non-linearity errors
Solution Approach 1:
The pitch parameter is deliberately changed across different zones of the grating rather than maintaining uniformity. This parameter variation compensates for non-linearity errors and improves measurement precision, accepting that the pitch will not be uniform across the entire grating surface
3Measurement precision
If conventional self-moiré gratings are used, then ease of operation is improved, but measurement precision deteriorates due to sensitivity to misalignment
Solution Approach 1:
The grating is pre-configured with multiple zones of different pitches during manufacturing, so that when misalignment occurs, at least one zone will provide accurate measurements. This preliminary structuring compensates for alignment issues without requiring precise adjustment during operation
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 grating design enables precise measurement of misregistration between semiconductor layers by resolving device-like pitches, enhancing measurement accuracy and relevance to real devices.
Implementation Method 1
Improved self-moiré grating design for use in metrology
Implementation Method 2
When the grating is illuminated, a moiré pattern is produced
Data Source
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AI summary
A grating for use in metrology including a periodic structure including a plurality of units having a pitch P, at least one unit of the plurality of units including at least a first periodic sub-structure having a first sub-pitch P1 smaller than the pitch P, and at least a second periodic sub-structure arranged along-side and separated from the first periodic sub-structure within the at least one unit and having a second sub-pitch P2 smaller than the pitch P and different from the first sub-pitch P1, P1 and P2 being selected to yield at least one Moir pitch Pm = P1•P2/(P2 - P1), the pitch P being an integer multiple of the first sub-pitch P1 and of the second sub-pitch P2.