Use of an SF5+ polyatomic primary ion beam for ultrashallow depth profiling on an ion microscope secondary ion mass spectroscopy instrument

A magnetic sector secondary ion mass spectrometry (SIMS) instrument has been fitted with a modified hot filament duoplasmatron ion source for generation of ${\mathrm{SF}}_5^{+}$ primary ion beams for SIMS depth profiling applications. The ${\mathrm{SF}}_5^{+}$ primary ion beam has been evaluated by depth profiling of several low energy boron ion implants, boron delta-doped structures and a Ni/Cr metal multilayer depth profiling standard reference material. Using 3.0 keV impact ${\mathrm{SF}}_5^{+}$ bombardment at a 52° impact angle with oxygen flooding gives a trailing edge decay length $\text{(1/e)}$ for the boron implants and delta-doped layers of 1.3 nm. Under the same conditions, ${\mathrm{O}}_2^{+}$ bombardment gives a trailing edge decay length $\text{(1/e)}$ of 2.3 nm. The use of the ${\mathrm{SF}}_5^{+}$ beam without oxygen flooding gives a substantial increase in decay length that is related to the formation of ripples as determined by atomic force microscopy. In the case of the Ni/Cr reference material, a significant reduction in sputter-induced topography is observed with ${\mathrm{SF}}_5^{+}$ bombardment.