TiSi2

TiSi2, or titanium disilicide, is an intermetallic compound with the formula TiSi2. It is of interest for both materials science and microelectronics due to its electrical conductivity, thermal stability, and compatibility with silicon substrates. TiSi2 is formed in silicon devices through silicidation, often by depositing titanium on silicon and annealing to drive a reaction between titanium and silicon at the interface, creating a low-resistance contact.

The material exists in two main crystallographic forms, commonly referred to as C49 and C54. The C49 phase forms at lower temperatures and is less conductive, while the C54 phase is more ordered and exhibits lower resistivity and greater thermal stability. During processing, the C49 phase can transform into the C54 phase upon further annealing.

Electrical and physical properties of TiSi2 are favorable for metallization. The C54 phase yields low resistivity, typically around a few tens of microohm-centimeters, enabling efficient current transport in contacts. TiSi2 also offers a high melting point and good adhesion to silicon, contributing to device reliability under thermal cycling.

Applications and significance: TiSi2 has been widely used as a self-aligned silicide (salicide) in CMOS and other silicon-based devices to reduce contact resistance and improve performance. Its processing is compatible with standard silicon fabrication, but in advanced nodes it is often supplanted by other silicides (such as NiSi or CoSi2) due to lower resistivity, lower formation temperatures, and improved long-term stability. TiSi2 remains an important reference silicide in the history and study of semiconductor metallization.