Optical Metrology Selective Modeling Underlayer Complexity
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Solution Overview
Problem
Current Optical Critical Dimension (OCD) metrology faces challenges in accurately modeling the optical response of patterned semiconductor structures, particularly when underlayers are complex and unknown, leading to increased modeling complexity and overhead, especially as device dimensions shrink.
Innovation Solution
The Selective Modeling approach disregards underlayer modeling by utilizing preliminary measurements of their complex spectral response to describe the optical response of the entire structure, using a general function to relate theoretical and measured data, allowing for the determination of top layer parameters without needing to model the underlayers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complete description of underlayers is used for modeling optical response, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the necessary optical response characteristics of the underlayer (complex spectral response) without requiring complete geometric and material description. This selective extraction maintains measurement precision while reducing modeling complexity by ignoring unnecessary underlayer details.
Solution Approach 2:
The patent performs preliminary measurement of the underlayer's complex spectral response before conducting the main OCD measurement. This preliminary action captures the essential optical characteristics that need to be accounted for, enabling subsequent top-layer parameter extraction without repeated complex underlayer modeling.
2Measurement precision
If underlayer details are modeled, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent extracts only the complex spectral response of the underlayer through preliminary measurement, avoiding the time-consuming process of complete underlayer geometric and material modeling. This extraction maintains precision by capturing essential optical characteristics while dramatically reducing calculation overhead.
Solution Approach 2:
The patent performs the underlayer characterization in advance through preliminary measurement, separating this time-consuming task from the main measurement process. The pre-acquired complex spectral response is then reused in the top-layer parameter extraction, eliminating redundant calculations and reducing total measurement time.
3Measurement precision
If underlayers are measured and modeled, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential optical response (complex spectral response) of the underlayer through preliminary measurement, avoiding the need to model complete underlayer geometry and material properties. This selective approach maintains precision while reducing the complexity of the overall modeling task.
Solution Approach 2:
The patent performs preliminary measurement of the underlayer's optical response before the main measurement process. This preliminary characterization captures all necessary underlayer information in advance, simplifying the subsequent top-layer analysis and reducing overall system 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
This method simplifies the modeling process by accurately describing the optical response of multi-layer structures, reducing calculation overhead and enabling precise parameter determination of top layers without requiring detailed underlayer information, thus addressing the complexity and variability of underlayers in OCD metrology.
Implementation Method 1
measuring a complex spectral response of the underneath structure
Implementation Method 2
measuring... spectral intensity and phase data
Data Source
AI summary
Determining parameters of a patterned structure located on top of an underneath layered structure, where input data is provided which includes first measured data PMD being a function ƒ of spectral intensity Iλ and phase ϕ, PMD=ƒ(Iλ; ϕ), corresponding to a complex spectral response of the underneath layered structure, and second measured data Smeas indicative of specular reflection spectral response of a sample formed by the patterned structure and the underneath layered structure, and where a general function F is also provided describing a relation between a theoretical optical response Stheor of the sample and a modeled optical response Smodel of the patterned structure and the complex spectral response PMD of the underneath layered structure, such that Stheor=F(Smodel; PMD), where the general function is then utilized for comparing the second measured data Smeas and the theoretical optical response Stheor, and determining parameter(s) of interest of the top structure.