Characterization of Thin Titanium and Titanium Nitride Layers Using Sims

Abstract

Titanium (Ti) and titanium nitride (TiN) films are widely used as barrier stack to prevent junction spiking. It is also an important material for an anti-reflection coating (ARC) on aluminum (Al) films to facilitate lithography processes during multilevel metallization for the manufacture of integrated circuits on silicon-based (Si) semiconductor devices. Secondary Ion Mass Spectrometry (SIMS) is proven to be very powerful analytical technique for the semiconductor materials. However, quantitative analysis of very thin structures using SIMS constitutes an ultimate challenge since a large fraction of the profile is located in the transient region where a stable concentration of primary beam species has not been established.

This paper reports a SIMS technique for advanced characterization of very thin titanium and titanium nitride layers. Improvements in depth resolution were achieved by reducing the angle of incidence and the impact energy maintaining enhanced ionization yield associated with oxygen bombardment. Significant improvements in characterization of the film surface were developed by using oxygen flooding technique. Optimized oxygen pressure was used to achieve a stable ion yield due to the complete surface oxidation of titanium and titanium nitride layers during the analysis. The method was employed in the SIMS characterization of multiple Ti/TiN films deposited on silicon substrate. The example presents dramatic enhancement in depth resolution due to minimized matrix related ion yield variations at the interfaces.