Interfacial reactions in single-crystal-TiN (100)/Al/polycrystalline-TiN multilayer thin films

Abstract

The thermal stability of Al/polycrystalline-TiN and Al/single-crystal-TiN couples was investigated using Auger electron spectroscopy (AES) and cross-sectional transmission electron microscopy (XTEM) with energy-dispersive X-ray spectroscopy (EDX). The trilayer samples consisted of a 100 nm thick epitaxial TiN layer grown on MgO(100) substrates, a 100 nm thick aluminium layer, and a 100 nm thick polycrystalline TiN layer. The multilayer films were grown in a dual-magnetron sputter-deposition system and then annealed in a reducing atmosphere at temperatures between 500 and 600 °C for up to 90 min. AES and EDX showed extensive penetration of titanium into the aluminum layer, but only limited interdiffusion of aluminum into both single-crystal and polycrystalline TiN. However, aluminum segregation occurred at both Al/TiN interfaces. XTEM examination revealed the formation of the ordered aluminum-rich AlTi intermetallic compoundssuch as Al 3Ti in the aluminum layer, while cubic-structure AIN formed at the AlTiN interfaces. Only small differences were observed in the reaction paths and product formation rates of Al/polycrystalline-TiN and Al/single-crystal-TiN couples. AlTi intermetallic compounds formed more rapidly in the former while AIN formation proceeded more rapidly at the Al/single-crystal-TiN interface.