Copper silicide also called pentacopper silicide, is a binary compound of silicon with copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

. It is an intermetallic compound, meaning that it has properties intermediate between an ionic compound

Ionic compound

In chemistry, an ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Usually, the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion. Ions in ionic compounds are held together...

 and an alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

. This a solid crystalline material is a silvery solid that is insoluble in water. It forms upon heating mixtures of copper and silicon.

Applications

Copper silicide thin film

Thin film

A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....

 is used for passivation

Passivation

Passivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...

 of copper-based chips

Copper-based chips

Copper-based chips are semiconductor integrated circuits, usually microprocessors, which use copper for interconnections. Since copper is a better conductor than aluminium, chips using this technology can have smaller metal components, and use less energy to pass electricity through them...

, where it serves to suppress diffusion

Diffusion

Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

 and electromigration

Electromigration

Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in...

 and serves as a diffusion barrier

Diffusion barrier

A diffusion barrier is a thin layer of metal usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other....

.

Copper silicides are invoked in the Direct process

Direct process

The Direct Process, also called the Direct Synthesis, Rochow Process, and Müller-Rochow Process is the most common technology for preparing organosilicon compounds on an industrial scale. It was first reported independently by Eugene G. Rochow and Richard Müller in the 1940s...

, the industrial route to organosilicon compounds. In this process, copper, in the form of its silicide, catalyses the addition of methyl chloride to silicon. An illustrative reaction affords the industrially useful dimethyldichlorosilane

Dimethyldichlorosilane

Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains...

:

2 CH₃Cl + Si → (CH₃)₂SiCl₂