Characteristics of a phosphorus liquid‐metal ion source (LMIS) for use in focused ion beam systems was investigated because of its potential as ann‐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 &mgr;m 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‐&mgr;m 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.