Polychromatic Soft X-Ray Diffraction for Semiconductor Metrology
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Solution Overview
Problem
Current semiconductor metrology systems face challenges in accurately measuring both low and high aspect ratio structures with limited prior information, particularly in high volume manufacturing environments, due to limitations in measurement precision, accuracy, and throughput, especially when dealing with complex geometries and diverse material properties.
Innovation Solution
The implementation of high-brightness, polychromatic, reflective small angle x-ray scatterometry (RSAXS) metrology systems that utilize soft x-ray radiation and graded multi-layer optics to achieve precise measurements over a range of wavelengths, angles of incidence, and azimuth angles with a small illumination beam spot size, enabling deeper penetration and improved measurement information content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical metrology systems are used, then measurement capability is maintained for standard structures, but measurement sensitivity and capability decrease as device critical dimensions shrink
Solution Approach 1:
The patent changes the fundamental measurement parameter from optical wavelengths to soft X-ray wavelengths. This parameter change enables deeper penetration into semiconductor structures and provides enhanced sensitivity for measuring shrinking critical dimensions, directly resolving the contradiction between maintaining measurement precision and adapting to smaller device dimensions.
Solution Approach 2:
The patent transitions from surface-only measurement capabilities to three-dimensional measurement capability by utilizing the penetration depth of soft X-rays. This dimensional change allows measurement of both surface and subsurface features, maintaining measurement precision across varying device dimensions including high aspect ratio structures.
2Length of stationary object
If hard X-ray T-SAXS systems are used, then penetration capability is improved, but scattering from shallow structures becomes weak limiting measurement resolution
Solution Approach 1:
The patent selects soft X-ray photon energies (100-2000 eV) as an optimal parameter range that balances penetration depth and scattering intensity. This intermediate energy range provides sufficient penetration for deep structures while maintaining strong scattering signals from shallow features, resolving the contradiction between penetration capability and measurement resolution.
3Length of stationary object
If grazing angle illumination is used, then penetration into structures is improved, but beam footprint on wafer becomes large
Solution Approach 1:
The patent utilizes the unique property of soft X-rays to achieve both grazing angle illumination for deep penetration and small beam footprint by employing focused beam delivery systems. This enables precise localization of the measurement volume while maintaining deep penetration capability, resolving the contradiction between penetration depth and beam footprint area.
4Measurement precision
If prior dimensional and material composition information is obtained through TEM imaging, then measurement model accuracy is improved, but imaging time increases and process is destructive
Solution Approach 1:
The patent enables the metrology system to determine material composition and dimensional parameters directly from the diffraction measurements themselves, without requiring separate TEM imaging. The soft X-ray diffraction signals provide direct information about material composition (through absorption edges) and structure, making the system self-sufficient and eliminating the time-consuming, destructive TEM characterization step.
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 enhances measurement precision, accuracy, and throughput by allowing for the estimation of shape and edge placement parameters of high aspect ratio structures, reducing the need for prior dimensional and material composition information, and enabling efficient operation in high volume manufacturing environments.
Implementation Method 1
a polychromatic x-ray illumination source is configured to generate soft x-ray radiation
Implementation Method 2
x-ray radiation scattered from the semiconductor wafer is detected
Implementation Method 3
reflective small angle x-ray scatterometry (RSAXS) metrology systems that utilize soft x-ray radiation and graded multi-layer optics
Implementation Method 4
focused onto the semiconductor wafer as an x-ray illumination beam incident on the semiconductor wafer at a nominal grazing incidence angle
Data Source
AI summary
Methods and systems for performing measurements of semiconductor structures based on high-brightness, polychromatic, reflective small angle x-ray scatterometry (RSAXS) metrology are presented herein. RSAXS measurements are performed over a range of wavelengths, angles of incidence, and azimuth angles with small illumination beam spot size, simultaneously or sequentially. In some embodiments, RSAXS measurements are performed with x-ray radiation in the soft x-ray (SXR) region at grazing angles of incidence in the range of 5-20 degrees. In some embodiments, the x-ray illumination source size is 10 micrometers or less, and focusing optics project the source area onto a wafer with a demagnification factor of 0.2 or less, enabling an incident x-ray illumination spot size of less than two micrometers. In another aspect, active focusing optics project programmed ranges of illumination wavelengths, angles of incidence, and azimuth angles, or any combination thereof, onto a metrology area, either simultaneously or sequentially.