Effective Model for Conductive Pattern Metrology
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Solution Overview
Problem
Conventional optical metrology techniques struggle to accurately measure complex sample structures with overlying orthogonally arranged periodic patterns, such as copper interconnects, due to structural complexity and large parameter spaces.
Innovation Solution
A model is developed using TE and TM polarized light to characterize samples with periodic or non-periodic patterns, employing an effective medium layer with combined optical properties of conductive and transparent materials, allowing for the determination of sample characteristics without needing detailed physical descriptions of all layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical metrology techniques are used to measure complex sample structures with overlying orthogonally arranged periodic patterns, then measurement capability is provided, but measurement precision deteriorates due to structural complexity and large parameter spaces
Solution Approach 1:
The patent changes the parameter space by switching from TE to TM polarization and selecting specific wavelengths. This transforms the measurement approach to exploit the optical properties of the effective medium layer, allowing accurate measurement of complex periodic patterns by measuring at wavelengths where the structure behaves as an effective medium rather than resolving individual features
Solution Approach 2:
The patent introduces an effective medium layer as an intermediary concept between the actual complex periodic structure and the measurement process. This effective medium layer with combined optical properties of conductive and transparent materials serves as a simplified representation that captures the essential optical behavior without requiring detailed modeling of the complex underlying structure
2Reliability
If detailed physical descriptions of all layers are used to model complex structures, then model accuracy is improved, but device complexity increases due to the need to model all underlying layers
Solution Approach 1:
The patent extracts only the essential optical properties needed for measurement by using TM polarization, which makes the measurement sensitive to the effective medium layer properties while being insensitive to the detailed structure of underlying layers. This extraction approach obtains the necessary information without requiring complete modeling of all layers
Solution Approach 2:
By changing to TM polarization and selecting specific wavelengths, the patent transforms the measurement to depend primarily on the effective medium layer parameters rather than requiring accurate parameters for all underlying layers. This parameter change simplifies the modeling requirement while maintaining measurement accuracy
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 simplifies the measurement of complex structures by using effective models for both TE and TM polarizations, providing accurate characterization of periodic patterns and their dimensions, even when underlying layers are opaque, thus improving dimensional control in semiconductor processing.
Implementation Method 1
employing an effective medium layer with combined optical properties of conductive and transparent materials
Implementation Method 2
A model is developed using TE and TM polarized light to characterize samples with periodic or non-periodic patterns
Implementation Method 3
Metrology solutions using scatterometry based techniques require 3D modeling for these structures
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A~4B
AI summary
A model (150, 160,460,550,560) of a sample (100, 400, 500) with a periodic or nonperiodic pattern of conductive and transparent materials is produced based on the effect that the pattern has on TE polarized incident light The pattern may include a uniform film (154e, 162e, 462e, 552e, 562e) of the transparent material and an underlying uniform film (154m, 162m, 462m, 552m, 562m) of the conductive material When the pattern has periodicity in two directions, the model may include a uniform film of the transparent material and an underlying portion that based on the physical characteristics of the periodic pattern in the TM polarization direction When the sample 100 includes an underlying periodic pattern (104) that is orthogonal to the top periodic pattern (102), the sample (100) may be modeled (160) by modeling the physical characteristics of the top periodic pattern (164) and the effect of the bottom periodic pattern (162).