Liquid Metal Jet X-Ray Source for Metrology
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Solution Overview
Problem
Current x-ray metrology techniques face challenges in producing a small, high-brightness beam spot, which is essential for accurate measurement of integrated circuits, especially at grazing incidence angles, and are hindered by the large and expensive nature of synchrotron radiation sources, making them unsuitable for in-line metrology in production environments.
Innovation Solution
A compact x-ray metrology tool utilizing a liquid metal source with an electron beam to generate a bright, focused x-ray beam, capable of producing a small spot size with high brightness, suitable for various x-ray metrology techniques like reflectometry, scattering, and fluorescence, using a liquid metal jet source and collector with optional multiple metal elements to tailor photon energies and wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchrotron radiation sources are used to achieve high brightness and small spot size, then measurement precision and signal-to-noise ratio are improved, but device size and cost increase significantly
Solution Approach 1:
The patent replaces the expensive, complex synchrotron radiation source with a compact, cost-effective laboratory-based x-ray source that uses a liquid metal jet target. This disposable-like approach uses readily available materials (liquid metal alloys) and simple electron beam excitation to achieve synchrotron-like brightness without the massive infrastructure, thereby resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent changes the fundamental parameters of x-ray generation by using a liquid metal jet target instead of conventional solid targets. This parameter change enables continuous target rotation and optimal electron beam interaction, achieving high brightness and small spot size in a compact configuration, thus improving measurement precision without increasing device size
2Device complexity
If conventional solid anode x-ray sources are used, then device complexity is reduced, but beam brightness and spot size are insufficient for accurate metrology
Solution Approach 1:
The patent applies hydraulic principles by using a liquid metal jet instead of a solid anode. The liquid metal is pumped through a nozzle to create a continuous jet that can be easily replaced and optimized. This hydraulic approach allows for better heat dissipation and target rotation, achieving high beam brightness while keeping the overall device complexity low compared to synchrotrons
Solution Approach 2:
The patent exploits the phase transition properties of liquid metal alloys, maintaining them in a liquid state at controlled temperatures. This phase state allows the target material to be continuously replenished and optimized during operation, achieving high brightness output while using simple laboratory equipment rather than complex synchrotron facilities
3Measurement precision
If beam spot size is reduced to measure small features, then measurement precision improves, but signal-to-noise ratio decreases unless brightness is increased
Solution Approach 1:
The patent segments the x-ray generation process into distinct components: electron beam source, liquid metal jet target, and x-ray optics. This segmentation allows independent optimization of each component, particularly enabling the liquid metal jet to be focused to a small spot size while maintaining high brightness, thus achieving both measurement precision and reliable signal-to-noise ratio simultaneously
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
The tool achieves a brightness comparable to synchrotron sources but in a smaller, more cost-effective format, enabling precise, high-signal-to-noise ratio measurements of integrated circuits with shorter acquisition times and improved sensitivity for nano-scale metrology.
Implementation Method 1
an electron beam source for directing an electron beam at the liquid metal jet, thereby producing an incident x-ray beam
Implementation Method 2
a liquid metal source for heating and melting at least one metal and producing a liquid metal jet
Data Source
AI summary
An x-ray metrology tool having only one x-ray source. The x-ray source includes a liquid metal source for heating and melting at least one metal and producing a liquid metal jet, a liquid metal collector for acquiring the liquid metal jet, a liquid metal circulation system for returning liquid metal from the liquid metal collector to the liquid metal source, and an electron beam source for directing an electron beam at the liquid metal jet anode, thereby producing an incident x-ray beam that is directable towards a sample. A detector receives emissions from the sample in response to the incident x-ray beam, and produces signals indicative of properties of the sample. A controller controls the x-ray source, acquires the signals from the detector, and determines the properties of the sample based at least in part on the signals.