Multilayer Substrate Metrology Using Scatterometry and RCWA
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Solution Overview
Problem
Conventional imaging and metrology methods are inadequate for accurately measuring multilayer structures with critical dimensions due to limitations in resolution and complexity, particularly in the semiconductor industry, where existing methods are either too intensive or unsuitable for process monitoring and series production.
Innovation Solution
A method and device utilizing a combination of measurement technologies such as VUV/UV/VIS/NIR variable angle spectral ellipsometry, IR variable angle spectral ellipsometry, polarized reflectometry, scatterometry, and spectroscopy, along with rigorous coupled-wave analysis (RCWA) for simulation, to characterize multilayer systems with structured surfaces, enabling high-accuracy measurements of optical properties and structural parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional imaging methods (optical microscopy) are used to measure structures, then the measurement process is simple and non-destructive, but the resolution is limited to structural dimensions above half the optical wavelength (above 100 nm) due to the Abbe resolution limit
Solution Approach 1:
The patent replaces conventional optical microscopy with scatterometry, which uses optical scattering principles rather than direct imaging to measure structural dimensions. This substitution enables measurement of critical dimensions below the optical wavelength limit by analyzing scattering patterns rather than relying on diffraction-limited image resolution.
Solution Approach 2:
The patent changes the measurement approach from direct optical imaging to scatterometric measurement, utilizing the scattering of light by periodic structures to extract dimensional information. This parameter change in the measurement methodology enables resolution beyond the Abbe limit while maintaining non-destructive measurement.
2Measurement precision
If transmission electron microscopy (TEM), scanning electron microscopy (SEM), or atomic force microscopy (AFM) are used to measure structures with critical dimensions below optical wavelength, then the measurement precision is sufficient, but the measurement process becomes too time-intensive for process monitoring and series production
Solution Approach 1:
The patent replaces slow, time-intensive electron microscopy and atomic force microscopy with scatterometry, which uses optical scattering to rapidly characterize periodic structures. This substitution maintains the ability to measure sub-wavelength critical dimensions while achieving measurement speeds suitable for industrial process monitoring and series production.
Solution Approach 2:
The patent creates a computational model that simulates the scattering behavior of periodic structures and compares it with experimental scatterometric data to extract dimensional information. This copying approach allows rapid virtual characterization without requiring physically intensive measurement processes.
3Measurement precision
If conventional imaging methods are combined with non-imaging optical scatterometric measuring methods, then the measurement capability is enhanced, but the device complexity and difficulty of detecting and measuring increase
Solution Approach 1:
The patent integrates scatterometry with existing optical measurement systems, enabling a single device to perform both imaging and non-imaging scatterometric measurements. This multi-functionality approach enhances characterization accuracy while managing device complexity by consolidating measurement capabilities rather than requiring separate systems.
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 high-accuracy characterization of complex multilayer systems with structured surfaces, providing detailed information on refractive index, layer thickness, and structural dimensions, suitable for process monitoring and optimization in the semiconductor industry.
Implementation Method 1
Classic ellipsometry is used in the prior art in order to measure layer thicknesses and optical material properties, such as refractive index and reflectance
Implementation Method 2
In the prior art, conventional imaging methods, such as optical microscopy are combined with non-imaging optical scatterometric measuring methods
Implementation Method 3
A device and a method for measuring a multilayer on a substrate is specified for example in U.S. Pat. No. 6,912,056B2
Data Source
AI summary
A method for measuring a multilayered substrate, particularly with at least one structure with critical dimensions, the method including the steps of (a) producing the substrate with a plurality of layers, particularly with a structure, wherein the dimensions of the layers and in particular the structures are known, (b) measuring the substrate using at least one measuring technology, (c) creating a simulation of the substrate using the measurement results from the measurement of the substrate, (d) comparing the measurement results with simulation results from the simulation of the substrate, and (e1) optimizing the simulation and renewed creation of a simulation of the substrate using the measurement results from the measurement of the substrate, in the event that there is a deviation of the measurement results from the simulation results, or (e2) calculating parameters of further substrates, in the event that the measurement results correspond to the simulation results.