Articles you may be interested inEnergy spread of boron palladium liquid metal ion source and characterization with focused ion beam system Rev.Design of a high resolution focused ion beam system using liquid metal ion source Summary Abstract: Liquid metal ion sources and applications in focused ion beam systems J. Vac. Sci. Technol. B 6, 936 (1988); 10.1116/1.584327 Characterization of phosphorus liquid-metal ion source as a dopant source in focused ion beam systemsBoron liquid metal ion sources (LMIS) for the recently acquired VG focused ion beam system have been developed, and Pd 73 Bn binary eutectic alloy was selected as the p-type dopant source. A lifetime of more than 120 h has been recorded and three different emitter tip radii were used to test boron ion beam stability. Microstructure examination of the Pd73B27 binary alloy proved that boron LMIS instability was caused primarily by the formation of solid precipitates due to a change in alloy stoichiometry. Auger electron spectroscopy (AES) analysis of boron beam deposited on a flat silicon substrate shows rhenium emitter erosion as well as other elements (Fe, Ni, and Cr) resulting from extractor sputtering. In this paper, greater attention is placed on the metallurgical aspects of LMIS in order to develop more reliable boron LMIS.
Energy spread in liquid metal ion sources at low currents
Characteristics of a phosphorus liquid-metal ion source (LMIS) for use in focused ion beam systems was investigated because of its potential as an n-type dopant for integrated circuit device fabrication. A continuous lifetime of more than 33 h was recorded as a part of the source stability measurement. Short-term stability measurements indicated a very stable beam emission during its operation. Three different emitter tip radii of 2.5, 5.0, and 10 μm were selected to examine phosphorus beam emission characteristics. Mass spectrum measurements were used to examine phosphorus ion content and beam stability by repeat scanning. Steep current-voltage characteristics were observed for 5.0- and 10-μm emitter tip radii. The beam purity was characterized with Auger electron spectroscopy and a scanning electron microprobe by analysis of the deposited beam on a flat silicon substrate. Microstructure analysis by optical metallography indicated no liquid-metal corrosion on the emitter tip. A thorough analysis was carried out on beam purity and metallurgical aspects of LMIS in order to develop a more reliable phosphorus liquid-metal ion source.
Characteristics of a eutectic boron platinum (Pt58B42) liquid-metal ion source (LMIS) were analyzed and investigated with a quadrupole mass spectrometer (QMS), Auger electron spectroscopy (AES), and Rutherford backscattering spectroscopy (RBS). The source characteristics can be explained by the hydrodynamic model, particularly for needle geometry LMIS. Surface analysis with RBS and AES indicated that more boron is produced in the ion beam than left in the liquid alloy reservoir and more droplets are produced with a 10-μm emitter tip radius, which reduced boron current in the beam. The source instability was associated with droplet formation. AES results show that substantial neutral ions were produced which was not detected by QMS. RBS results on the depleted residual alloy remaining on the carbon ribbon heater indicated that the cause of the alloy system’s short lifetime (33 h) is due to a change in alloy stoichiometry to a higher platinum content. Three different emitter tip radii (2.5, 5, and 10 μm) made of graphite were used in the present investigation. Higher boron current and high stability during ion emission was recorded with 2.5-μm graphite emitter tip radius than with the 5- or 10-μm tip radii.
It has been found that by utilizing a sharp needle for the extractor electrode in close proximity to the source tip wetted with Cu3P liquid alloy, a large increase (factor ∼300) in ion current is observed in comparison to standard liquid metal ion sources (LMIS’s). In standard previously used LMIS’s the extractor electrode was a flat plane with a circular hole centered on the source needle tip. This new high current source has important applications in focused and broad ion beam deposition systems.
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