Hybrid extreme ultraviolet imaging spectrometer
Inventors
Sanford, Norman A. • CHIARAMONTI DEBAY, ANN • GORMAN, BRIAN P. • DIERCKS, DAVID R.
Assignees
Colorado School of Mines • United States Department of Commerce
Publication Number
US-9899197-B2
Publication Date
2018-02-20
Expiration Date
2036-08-02
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Abstract
A hybrid extreme ultraviolet (EUV) imaging spectrometer includes: a radiation source to: produce EUV radiation; subject a sample to the EUV radiation; photoionize a plurality of atoms of the sample; and form photoions from the atoms subject to photoionization by the EUV radiation, the photoions being desorbed from the sample in response to the sample being subjected to the EUV radiation; an ion detector to detect the photoions: as a function of a time-of-arrival of the photoions at the ion detector after the sample is subjected to the EUV radiation; or as a function of a position of the photoions at the ion detector; an electron source to: produce a plurality of primary electrons; subject the sample to the primary electrons; and form scattered electrons from the sample in response to the sample being subjected to the primary electrons; and an electron detector to detect the scattered electrons: as a function of a time-of-arrival of the scattered electrons at the electron detector after the sample is subjected to the EUV radiation or the primary electrons; or as a function of a position of the scattered electrons at the electron detector.
Core Innovation
The invention described is a hybrid extreme ultraviolet (EUV) imaging spectrometer that integrates a radiation source producing EUV radiation to photoionize atoms of a sample, forming photoions that are radiatively desorbed in the presence of an external electric field. This spectrometer includes an ion detector that detects photoions based on their time-of-arrival or position at the detector, an electron source producing primary electrons that scatter from the sample, and an electron detector that detects these scattered electrons also based on their time-of-arrival or position.
The problem addressed is the limitations in conventional atom probe microscopy techniques that rely on thermally assisted field evaporation using ultraviolet (UV) radiation, which produces significant thermal transients and element-dependent variations in evaporation rates. These techniques can generate multiply charged photoions, complex molecular ions, and lack uniform photoionization across different elements, reducing the accuracy and spatial resolution of chemical mapping. The hybrid EUV imaging spectrometer resolves these issues by using EUV radiation which provides higher photon energies to achieve direct photoionization with sub-nanometer spatial resolution and more uniform elemental detection sensitivity.
The hybrid EUV imaging spectrometer also integrates real-time electron imaging using primary electrons and electron detectors capable of transmission, diffraction, secondary, and backscattered electron detection, enabling continuous measurement of the sample shape during data acquisition. This combined approach allows precise three-dimensional chemical mapping and tomographic reconstruction of the sample, with the capability to alternate between electron imaging and ion detection modes, enhancing data accuracy and eliminating the need to remove the sample or interrupt vacuum conditions during analysis.
Claims Coverage
The patent claims include 4 independent claims that cover a hybrid EUV imaging spectrometer apparatus with combined ion and electron detection, and a process for performing hybrid EUV imaging spectrometry.
Hybrid EUV imaging spectrometer apparatus
The apparatus includes: a radiation source producing EUV radiation that photoionizes single atoms at distinct sample locations sequentially to form photoions; an ion detector detecting the photoions based on their time-of-arrival or position; an electron source producing primary electrons to scatter from the sample; and an electron detector detecting the scattered electrons based on their time-of-arrival or position.
Extraction electrode for photoion transmission
An extraction electrode disposed proximate to the sample and interposed between the sample and ion detector, comprising an aperture that transmits photoions from the sample to the ion detector.
Electron detection modes for scattered electrons
Electron detectors configured to detect various scattered electrons including transmitted primary electrons (transmission electron imaging detector), diffracted primary electrons (diffraction detector), secondary electrons emitted by the sample (secondary electron detector), and backscattered electrons from the sample (backscatter electron detector) to acquire shape or distance information of the sample or its relation to the extraction electrode.
Process for performing hybrid EUV imaging spectrometry
A process comprising producing EUV radiation; sequentially photoionizing single atoms at distinct locations on the sample; forming photoions; detecting the photoions by time-of-arrival or position at an ion detector; subjecting the sample to primary electrons from an electron source; detecting scattered electrons by an electron detector similarly by time or position; and acquiring data from both detectors with an analyzer to image and reconstruct the sample shape and chemical composition.
The independent claims define a hybrid EUV imaging spectrometer system and method combining EUV photoionization-based ion detection with electron scattering imaging, facilitated by an extraction electrode, enabling three-dimensional chemical mapping with high spatial resolution and tomographic reconstruction of samples.
Stated Advantages
Provides quantitative three-dimensional chemical maps with sub-nanometer spatial resolution for elemental constituents of samples.
Achieves substantially uniform photoionization across elements reducing element-to-element variation compared to conventional UV laser atom probes.
Reduces formation of multiply charged photoions and complex ions, yielding clearer, more interpretable mass spectra.
Enables in-situ, real-time electron imaging for accurate shape measurement during data acquisition without interrupting vacuum or removing the sample.
Combines ion and electron detection to improve accuracy and provide fast, standards-quality chemical composition and tomographic shape data.
Documented Applications
Metrology instrument for accurate, subnanometer three-dimensional chemical mapping of hard or soft matter materials including metals, polymers, ceramics, glasses, semiconductors, insulators, and hybrid materials.
Determination of local structure and chemical composition at interfaces in materials to inform structure-properties-processing relationships.
Use as an atom probe tomograph with integrated electron imaging to enhance three-dimensional spatial reconstruction and analysis.
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