Tantalum nitride (TaN) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

, a

nitride In chemistry, a nitride is an inorganic compound of nitrogen. The "nitride" anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occuring. Some nitrides have a find applications, such as wear-resistant ...

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

. There are multiple phases of compounds, stoichimetrically from Ta₂N to Ta₃N₅, including TaN. As a thin film TaN find use as a diffusion barrier and insulating layer between copper interconnects in the back end of line of computer chips. Tantalum nitrides are also used in thin film resistors.

Phase diagram

The tantalum -

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

system includes several states including a nitrogen

solid solution A solid solution, a term popularly used for metals, is a homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The wor ...

in Tantalum, as well as several nitride phases, which can vary from expected stoichiometry due to lattice vacancies. Annealing of nitrogen rich "TaN" can result in conversion to a two phase mixture of TaN and Ta₅N₆. Ta₅N₆ is thought to be the more thermally stable compound - though it decomposes in vacuum at 2500C to Ta₂N. It was reported the decomposition in vacuum from Ta₃N₅ via Ta₄N₅, Ta₅N₆, ε-TaN, to Ta₂N.

Preparation

TaN is often prepared as thin films. Methods of depositing the films include RF-magnetron-reactive sputtering, Direct current (DC)

sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ca ...

, Self-propagating high-temperature synthesis (SHS) via 'combustion' of Tantalum powder in Nitrogen, low‐pressure

metalorganic chemical vapor deposition Metalorganic vapour-phase epitaxy (MOVPE), also known as organometallic vapour-phase epitaxy (OMVPE) or metalorganic chemical vapour deposition (MOCVD), is a chemical vapour deposition method used to produce single- or polycrystalline thin films. ...

(LP‐MOCVD),

ion beam assisted deposition Ion beam assisted deposition or IBAD or IAD (not to be confused with ion beam induced deposition, IBID) is a materials engineering technique which combines ion implantation with simultaneous sputtering or another physical vapor deposition techniq ...

(IBAD), and by electron beam evaporation of tantalum in concert with high energy nitrogen ions. Depending on the relative amount of N₂, the deposited film can vary from (fcc) TaN to (hexagonal) Ta₂N as nitrogen decreases. A variety of other phases have also been reported from deposition including bcc and hexagonal TaN; hexagonal Ta₅N₆; tetragonal Ta₄N₅; orthorhombic Ta₆N_2.5, Ta₄N, or Ta₃N₅. The electrical properties of TaN films vary from metallic conductor to insulator depending on the relative nitrogen ratio, with N rich films being more resistive.

Uses

It is sometimes used in integrated circuit manufacture to create a diffusion barrier or "glue" layers between

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

, or other conductive metals. In the case of BEOL processing (at c. 20 nm), copper is first coated with tantalum, then with TaN using physical vapour deposition (PVD); this barrier coated copper is then coated with more copper by PVD, and infilled with electrolytically coated copper, before being mechanically processed (grind/polishing). It also has application in thin film resistors. It has the advantage over nichrome resistors of forming a passivating oxide film which is resistant to moisture.

References

{{Nitrides Nitrides Tantalum compounds