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Chemical compound that combines silicon and a more electropositive element

A silicide is a type of chemical compound that combines silicon and a usually more electropositive element. Silicon is more electropositive than carbon. In terms of their physical properties, silicides are structurally closer to borides than to carbides. Because of size differences however silicides are not isostructural with borides and carbides.

Most silicides are produced by direct combination of the elements. A silicide prepared by a self aligned process is called a salicide. This is a process in which silicide contacts are formed only in those areas in which deposited metal (which after annealing becomes a metal component of the silicide) is in direct contact with silicon, hence, the process is self aligned. It is commonly implemented in MOS/CMOS processes for ohmic contacts of the source, drain, and poly Si gate.

The transition metal silicides are usually inert to aqueous solutions. At red heat, they react with potassium hydroxide, fluorine, and chlorine. Mercury, thallium, bismuth, and lead are immiscible with liquid silicon.

Silicide thin films have applications in microelectronics due to their high electrical conductivity, thermal stability, corrosion resistance, and compatibility with photolithographic wafer processes. For example silicides formed over layers of polysilicon, called polycides, are commonly used as an interconnect material in integrated circuits for their high conductivity. Silicides formed through the salicide process also see use as a low work function metal in ohmic and Schottky contacts. High work function metals are often not ideal for use in metal–semiconductor junctions directly due to fermi–level pinning where the Schottky barrier potential of the junction becomes locked around 0.7–0.8V. For this reason low forward voltage Schottky diodes and ohmic interconnects between a semiconductor and a metal often utilize a thin layer of silicide at the metal–semiconductor interface.