Ambient and High Temperature STM Investigations of the Growth of Titanium Suicide on Silicon Substrates

A variable temperature scanning tunnelling microscope (STM) in UHV has been used to investigate the growth, morphology and surface atomic structure of ultrathin titanium suicide films on Si(100) and Si(111) substrates. Three stages of suicide growth have been identified based on microstructural considerations. They occur over similar temperature ranges for both substrates and may be summarised as: agglomeration and the formation of disordered islands, crystallite formation, and crystallite growth. Additionally, island burial is found for Si(100) substrates (950°C), and preferential crystallite growth is observed for high temperature processing (1200°C) of titanium silicide on Si(111). Methods for STM crystallography have been developed and used to identify possible epitaxial silicide/silicon relationships based on morphological considerations. Atomic resolution images of titanium silicide crystallites have identified a 2×2 silicon termination of a C54-TiSi2(111) surface, a 2×2 silicon terminated C54-TiSi2(010) surface, and a reconstructed C54-TiSi2(311) surface. It has been concluded that unambiguous identification of epitaxial relationships requires images of the atomic structure of the silicide crystallite surfaces in addition to morphological information.