Metrology Test Structure With Blocking Layer For Pattern Segmentation
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Solution Overview
Problem
Accurate metrology measurements of complex microelectronic patterns with multiple critical dimensions are challenging due to tool instability and overlay errors in advanced patterning techniques like LELE and SADP, requiring improved sensitivity and calibration methods.
Innovation Solution
A novel test structure design that splits complex sample patterns into simpler patterns using a block/cut layer, allowing for focused metrology measurements and self-calibration by modifying unit cells with a blocking layer to enhance measurement sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If optical scatterometry is applied to complex patterns with multiple critical dimensions, then measurement information content increases, but measurement accuracy and sensitivity deteriorate due to parameter correlations and tool instability
Solution Approach 1:
The complex pattern is segmented into multiple simplified test patterns, each designed to measure a specific critical dimension. By applying a block/cut layer to create distinct measurement regions, each pattern isolates specific geometric parameters, reducing parameter correlations and enabling accurate individual CD measurements even in complex multi-patterning structures
Solution Approach 2:
Different regions of the test structure are assigned different local qualities through selective blocking. The block/cut layer creates regions with different optical responses tailored to specific measurement needs, allowing each region to optimize sensitivity for its target critical dimension while maintaining overall measurement accuracy across multiple CDs
2Manufacturing precision
If advanced patterning techniques like LELE and SADP are used to achieve smaller pitch, then manufacturing capability improves, but measurement difficulty increases due to overlay errors and tool instability
Solution Approach 1:
The invention creates simplified copies of the complex pattern features in the form of test patterns. These test patterns replicate the critical dimension information needed for process control but in a simplified geometric form that is less sensitive to overlay errors and tool instability, enabling accurate measurement of the actual manufacturing results
Solution Approach 2:
The test structure is prepared in advance with predetermined block/cut patterns that are applied to the substrate before final measurements. This preliminary structuring creates known reference geometries that account for expected overlay errors and tool variations, allowing for accurate CD extraction even when the actual patterning process introduces deviations
3Device complexity
If conventional test structures are used for multi-CD measurement, then device complexity remains low, but measurement sensitivity and correlation reduction are insufficient
Solution Approach 1:
The test structure is divided into multiple discrete test patterns, each optimized for measuring specific critical dimensions. This segmentation allows each pattern to maximize sensitivity to its target parameter while minimizing sensitivity to other parameters, achieving high measurement precision without requiring excessively complex overall device structure
Solution Approach 2:
Each test pattern region is designed with local quality optimized for its specific measurement function. The block/cut layer creates regions with tailored optical properties and geometric configurations that enhance sensitivity to specific CD parameters, allowing the overall test structure to achieve high multi-CD measurement precision with moderate complexity
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 measurement of multiple critical dimensions and space parameters with improved sensitivity and reduced correlations, facilitating effective process control without modifying existing measurement hardware.
Implementation Method 1
Optical scatterometry (including spectral reflectometry and spectral ellipsometry, etc.) is an extremely effective method for obtaining information on the geometry and material properties of such structures. In this method, broadband light is shone on a sample and collected after being returned from it. By analyzing the returned light of different wavelengths and polarization components of the incident light, incident at different directions, it is possible to obtain information about the structure/sample.
Data Source
AI summary
A test structure and method of its manufacture are presented for use in metrology measurements of a sample pattern. The test structure comprises a test pattern comprising a portion of the sample pattern including at least one selected feature and a blocking layer at least partially covering regions of the test structure adjacent to the at least one selected region.