Coaxial ion micro-source for VP/ESEM - E-beam impact mode

The coaxial ion micro-source was developed as a part of the multi-functional equipment for SEM. This equipment contains a quadruple BSE ionization detector for 3D imaging and an axial SE detector serving optionally as the ion micro-source. The ion micro-source may be made as an independent unit as well. The source has been designed in the form of extended Pressure Limiting Aperture (PLA) used commonly in Variable Pressure/Environmental Scanning Electron Microscopes (VP/ESEM), so no additional vacuum arrangements are needed. Additionally, the vacuum-detector head was developed to provide an intermediate vacuum space necessary to apply the source in a classic SEM. The source operates at argon pressure of 100 Pa and delivers an ion current of a few μA at ions energy of 4 keV, which enables drilling or stripping away layers of material with lateral resolution of about 10 μm. The ion micro-source may work in two regimes: the glow discharge mode or the electron beam impact mode. Preliminary experiments were conducted on JSM 840 microscope equipped with the mentioned vacuum-detector head extending its capabilities to 3D VP/ESEM. The paper presents and roughly explains some noticed regularities in the source functioning basing on its simple and intuitive model.