Multi-Angle X-Ray Reflectance Scatterometry for 3D IC Profiles
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Solution Overview
Problem
Current metrology techniques, such as CD-SEM and OCD, struggle to accurately measure three-dimensional profiles of integrated circuit features due to limitations like charging issues, radiation damage, incompatibility with low-k dielectrics, and the need for extensive modeling, while GISAS techniques provide limited information on 3D structures due to incident beams being directed mostly along top surfaces.
Innovation Solution
A method and system using multi-angle X-ray reflectance scatterometry (XRS) that impinges an incident X-ray beam with multiple angles and azimuthal angles on a sample to collect scattered X-ray beams, allowing for precise measurement of periodic structures, including 2D and 3D profiles, by utilizing low-energy X-rays and a monochromator to focus the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD-SEM metrology is used to measure IC features, then surface topology can be observed, but charging problems limit achievable resolution and radiation damage causes dimensional shrinking
Solution Approach 1:
The patent replaces electron-based CD-SEM metrology with X-ray based scatterometry. X-rays have different interaction mechanisms with matter compared to electrons, avoiding charging effects and radiation-induced dimensional changes. The X-ray beam interacts with the sample through scattering and absorption processes that do not cause the same harmful effects as electron beams, enabling non-destructive high-precision measurements.
Solution Approach 2:
The patent changes the fundamental measurement parameter from electron beam energy to X-ray wavelength and energy. By using X-rays with specific wavelengths (typically 0.1-10 nm range) and controlling the incident energy, the measurement process avoids the charging and radiation damage issues inherent in electron microscopy while maintaining high resolution capability through the shorter wavelength of X-rays.
2Measurement precision
If optical critical dimension (OCD) metrology is used, then measurement can be performed with longer wavelengths, but the wavelength is significantly larger than device feature size requiring extensive modeling and interpolation
Solution Approach 1:
The patent changes the wavelength parameter from optical range (400-700 nm) to X-ray range (0.1-10 nm). This wavelength reduction brings the probing wavelength closer to or smaller than the device feature size, enabling direct measurement without extensive modeling and interpolation. The shorter X-ray wavelengths provide inherent sensitivity to nanoscale dimensions while reducing the complexity of inverse modeling required.
3Measurement precision
If GISAS technique is used with incident angles less than a few degrees, then scattering can be measured, but information on 3D structures is limited since beam is directed mostly along top surfaces
Solution Approach 1:
The patent implements dynamic angle variation in the X-ray scatterometry system. Instead of using fixed grazing incidence angles as in GISAS, the system varies the incident angle dynamically to optimize information extraction from different depths and orientations of the sample structure. This angular diversity enables comprehensive 3D structural characterization while maintaining measurement flexibility.
Solution Approach 2:
The patent extends the measurement from primarily surface-level scattering (2D information) to include deeper penetration and多角度 scattering (3D information). By using X-rays with appropriate energies and varying incident angles, the system accesses scattering information from multiple depths and orientations, providing comprehensive three-dimensional structural information that overcomes the surface-limited nature of GISAS.
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 precise measurement of complex 2D and 3D periodic structures with improved sensitivity and stability, providing critical dimension information for semiconductor devices, especially fin-FETs, by using higher order scattering orders and interference fringes.
Implementation Method 1
The monochromator is for focusing the X-ray beam to provide an incident X-ray beam to the sample holder
Implementation Method 2
impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam
Data Source
AI summary
A system and method for measuring a sample by X-ray reflectance scatterometry. The method may include impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam, the incident X-ray beam simultaneously providing a plurality of incident angles and a plurality of azimuthal angles; and collecting at least a portion of the scattered X-ray beam.