X-Ray Reflectance Scatterometry for 3D Periodic Structure Metrology
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Solution Overview
Problem
Current metrology techniques, such as CD-SEM and OCD, struggle to accurately measure three-dimensional profiles of nanostructured surfaces 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 from only the top surfaces of 3D structures.
Innovation Solution
A method and system using multi-angle X-ray reflectance scatterometry (XRS) with a conical X-ray beam providing multiple incident angles and azimuthal angles to measure periodic structures, allowing for the detection of scattered light in two angular directions and inferring the shape and pitch of 3D structures.
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 uses X-ray radiation as an intermediary probe instead of electron beams. X-rays penetrate low-k dielectrics without causing charging effects or radiation damage to the resist, enabling non-destructive measurement of 3D structures while maintaining high resolution
Solution Approach 2:
The patent replaces the mechanical electron beam system with an X-ray optical system. This substitution eliminates charging effects and radiation damage while enabling measurement through multi-angle X-ray reflectance scatterometry (XRS) to obtain 3D structural information
2Measurement precision
If optical critical dimension (OCD) metrology is used, then measurement can be performed, but the long wavelength is significantly larger than device feature size requiring extensive modeling and interpolation
Solution Approach 1:
The patent changes the fundamental parameter of radiation wavelength from optical range to X-ray range. This wavelength reduction enables direct measurement of nanoscale features without requiring extensive modeling and interpolation, as the X-ray wavelength is comparable to or smaller than the feature dimensions being measured
3Loss of information
If GISAS techniques are used to measure 3D structures, then top surface information can be obtained, but information from deeper structures is limited due to small incident angles
Solution Approach 1:
The patent extends the measurement from single-angle grazing incidence to multi-angle X-ray reflectance scatterometry. By varying the incident angle in another dimension, the X-ray beam penetrates to different depths, enabling comprehensive 3D structural characterization including both top surface and deeper structures
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 by obtaining higher order scattering orders, providing direct sensitivity to structural dimensions critical for device performance, and overcoming the limitations of existing techniques.
Implementation Method 1
System and method for measuring a sample by x-ray reflectance scatterometry
Implementation Method 2
a monochromator positioned between the X-ray source and the sample holder. The monochromator is for focusing the X-ray beam
Implementation Method 3
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.