Multiple plasma ion source for inline secondary ion mass spectrometry
Inventors
YANG, Ming Hong • KOUZMINOV, Dimitry • SRIVATSA, Arun Ramaswamy
Assignees
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Publication Number
US-12452988-B2
Publication Date
2025-10-21
Expiration Date
Abstract
Methods leverage premixed gas mixtures to perform a metrology process on a substrate using an inline secondary ion mass spectrometry (SIMS) process. The premixed gas mixture of two or more gases is injected into a plasma chamber that is configured to produce sputtering ions for the inline SIMS process. The two or more gases produce non-metallic ion species which are compatible with downstream substrate fabrication processes and allow further fabrication to be performed on the substrate after the inline SIMS process has completed. The sputtering ions are ejected from the plasma chamber into a magnetic field. The intensity of the magnetic field is altered to select a single species of ions. The single species of ions are directed towards a surface of the substrate and secondary ions sputtered from the surface of the substrate by the selected species of ions are detected and analyzed.
Core Innovation
The invention relates to inline secondary ion mass spectrometry (SIMS) for a metrology process on a substrate that is compatible with downstream substrate fabrication processes. A premixed gas mixture of two or more gases is injected into a plasma chamber configured to produce sputtering ions for the inline SIMS process. The two or more gases are selected to produce only non-metallic ion species for both positive ion detection and negative ion detection.
Sputtering ions are ejected from the plasma chamber into a magnetic field, where the intensity of the magnetic field is altered to select a single species of ions formed from only one of the two or more gases of the premixed gas mixture. The selected single species of ions is directed towards a surface of the substrate, and secondary ions sputtered from the surface are detected by the single species of ions.
The disclosed approach supports dynamically switching the selected ion species without gas purging or equipment downtime by altering the magnetic field. A controller automates injection and ion-species selection using recipes, and the inline SIMS process is tuned using parameters such as gas ratio, ion intensity, plasma stability, and material sensitivity to improve yields and data quality while reducing maintenance and cesium contamination.
Claims Coverage
The independent claims cover three aspects of the same inline SIMS concept: a metrology method, a computer-readable medium implementing the method, and an apparatus configured to perform the method. Across these independent claims, the core inventive features are the use of a premixed non-metallic gas mixture for both positive and negative ion detection, and ion selection by adjusting a magnetic field to choose a single ion species from the premixed mixture.
Injecting a premixed gas mixture producing only non-metallic ion species
A method where a premixed gas mixture of two or more gases is injected into a plasma chamber, wherein the two or more gases produce only non-metallic ion species for both positive ion detection and negative ion detection.
Selecting a single ion species by altering magnetic field intensity
Sputtering ions are ejected into a magnetic field and the intensity of the magnetic field is altered to select a single species of ions formed from only one of the two or more gases of the premixed gas mixture.
Directing selected ions to the substrate and detecting secondary ions
The single species of ions is directed towards a surface of the substrate, and secondary ions sputtered from the surface are detected by the single species of ions.
Instructions for performing the inline SIMS method
A non-transitory, computer readable medium storing instructions that cause injecting a premixed gas mixture, selecting a single species by altering magnetic field intensity, directing the single species towards a substrate surface, and detecting secondary ions sputtered from the surface.
Apparatus using premixed non-metallic gas plasma and magnetic primary mass filter
An apparatus with a premixed gas mixture source providing a premixed gas mixture of two or more gases producing only non-metallic ion species, a plasma chamber producing two or more ion species from the premixed gas mixture, a primary mass filter selecting a sputtering ion species by adjusting a magnetic field, and a controller configured to inject the premixed gas mixture, eject ions into the magnetic field, and alter magnetic field intensity to select a single non-metallic ion species for both positive ion detection and negative ion detection.
Across the independent claims, the claims center on producing non-metallic ion species from a premixed gas mixture compatible with downstream substrate fabrication processes, selecting a single ion species by adjusting the intensity of a magnetic field in a primary mass filter, and detecting secondary ions from the substrate using that selected non-metallic ion species for both positive and negative ion detection.
Stated Advantages
Enable positive and negative ion detection using only non-metallic ion species.
Enable dynamic on-the-fly ion-species switching without gas purging or equipment downtime.
Improve yields and data quality.
Reduce maintenance.
Reduce cesium contamination.
Documented Applications
Inline SIMS metrology process on a semiconductor substrate performed in a cleanroom-compatible manner compatible with downstream substrate fabrication processes.
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