Depth profile analysis of aluminium metallization in microelectronics: Optimization of depth resolution

Abstract

Depth protiling of aluminium metallization in microelectronics devices by Auger or S I M S analysis is impeded by the severe sputter-induced roughening which causes a serious loss in depth resolution. This paper discusses strategies to avoid this deteriorating eflect : optimization of the bombardment angle, sample rotation during sputtering and the use of heavy or reactive ions. The best depth resolutions were achieved by sputtering with normal incidence 15 keV 02+ ions. In this case, an interface width of 12 nm was measured for a film of 1 p m thickness. This is an improvement by more than a factor of 10 compared to the extremely poor depth resolution of 160 nm resulting from routine analysis parameters (Ar+ ions incident at 55"). ~~

Towards the ultimate limits of depth resolution in sputter profiling: Beam‐induced chemical changes and the importance of sample quality

“…the best depth resolution, was observed using oxygen bombardment at normal incidence, in which case the near-surface regionis are converted to A l z 0 3 . 84 The beneficial effect of oxygen bombardment shows up even at angles between 310" and 40" (cf. Fig.…”

Oxygen Exchange Processes between Oxide Memristive Devices and Water Molecules

“…The interfaces (i.e., the transition regions between individual layers) appear relatively broad in these SIMS depth profiles. This broadening is due to ion‐beam‐induced roughening of the polycrystalline metal layers, the sputter rate in metals being dependent on the grain orientation . Careful examination of the data, and data obtained at other ion‐beam energies, suggested that the beginning of a new layer could be reasonably defined as the intensity offset of a characteristic secondary ion (e.g., the TiO − offset will be referred to as the begin of the SrTiO 3 layer).…”

Improved sputter depth resolution in Auger thin film analysis using in situ low angle cross-sections

“…A pyramidal surface topography has developed during sputtering. A more grazing incident sputter ion beam is more effective in terms of depth resolution [4,5]. Hence the depth resolution is improved to ∆z/z = 11.5 %.…”

“…To enhance depth resolution the sputter conditions can be optimised. In particular this is done by choosing the appropriate primary ion, reducing the primary ion energy, selecting a more grazing incidence ion impact angle [4,5] or rotating the sample around its surface normal during sputtering to avoid permanent ion channelling on single grains [6,7]. In literature even more complex approaches are reported [8,9].…”