Tantalum nitride

The tantalum - nitrogen system includes several states including a nitrogen solid solution in Tantalum, as well as several nitride phases, which can vary from expected stoichiometry due to lattice vacancies.{{Cite encyclopedia|encyclopedia = Concise Encyclopedia of Self-Propagating High-Temperature Synthesis - History, Theory, Technology, and Products | year = 2017 | pages = 370–371 | chapter = Tantalum Nitride | first = Inna P. | last = Borovinskaya| doi = 10.1016/B978-0-12-804173-4.00150-2 | isbn = 9780128041734 }} 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 2500 °C to Ta₂N. It was reported the decomposition in vacuum from Ta₃N₅ via Ta₄N₅, Ta₅N₆, ε-TaN, to Ta₂N.{{citation|title = Structure of Tantalum Nitrides | first = Nobuzo | last = Terao | year =1971 | journal = Japanese Journal of Applied Physics | volume = 10 | pages = 248–259 | number = 2 | doi = 10.1143/JJAP.10.248 | bibcode = 1971JaJAP..10..248T | s2cid = 122356023 }}

TaN is often prepared as thin films. Methods of depositing the films include RF-magnetron-reactive sputtering,{{citation| title = Microstructure and Mechanical Properties of TaN Thin Films Prepared by Reactive Magnetron Sputtering | first1 = Anna | last1 = Zaman| first2 = Efstathios I. | last2 = Meletis |date = 23 November 2017 | journal = Coatings| doi = 10.3390/coatings7120209 | volume = 7 | issue = 12 | pages = 209 | doi-access = free }} Direct current (DC) sputtering,{{citation| title = Tantalum Nitride as Promising Gate Electrode for MOS Technology | first1 = Lucas | last1 = Lima | first2 = Milena D. | last2 =Moreiraa | first3 = Fred | last3 =Cioldin | first4 = José Alexandre | last4 = Diniza | first5 = Ioshiaki | last5 = Doi | doi = 10.1149/1.3474175| journal = ECS Trans. |year=2010 | volume = 31 | issue = 1|pages= 319–325| bibcode = 2010ECSTr..31a.319L | s2cid = 97901262 }} Self-propagating high-temperature synthesis (SHS) via 'combustion' of tantalum powder in nitrogen, low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD),{{citation|title= Metalorganic chemical vapor deposition of tantalum nitride by tertbutylimidotris(diethylamido)tantalum for advanced metallization | journal = Appl. Phys. Lett. | volume = 67| issue = 8 | page = 1128 | year = 1995| doi = 10.1063/1.114983 | first1 = M. H.|last1 = Tsai |first2= S. C.| last2 = Sun | bibcode = 1995ApPhL..67.1128T }} ion beam assisted deposition (IBAD),{{citation| journal = Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms | volume = 127–128| date = 2 May 1997 | pages = 841–845 | title = Structure and properties of NbN and TaN films prepared by ion beam assisted deposition | first1 = K. |last1 = Baba | first2 = R.| last2 = Hatada | first3= K.|last3 = Udoh | first4 = K. | last4 = Yasuda | doi = 10.1016/S0168-583X(97)00018-9 | bibcode = 1997NIMPB.127..841B}} and by electron beam evaporation of tantalum in concert with high energy nitrogen ions.{{citation | title = Low-temperature formation of metastable cubic tantalum nitride by metal condensation under ion irradiation | journal = Journal of Applied Physics | volume = 77 | issue = 12 | page = 6630 | year = 1995 | doi = 10.1063/1.359073 | first1 = W. | last1 = Ensinger| first2 = M. | last2 = Kiuchi | first3 = M. | last3 = Satou | bibcode = 1995JAP....77.6630E }}

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.{{citation| title =Electrical and mechanical properties of tantalum nitride thin films deposited by reactive sputtering | journal = Journal of Crystal Growth | volume = 283 |issue = 3–4 | pages = 404–408 | date = October 2005 | doi = 10.1016/j.jcrysgro.2005.06.017 | first1 = Deok-kee | last1 = Kim | first2 = Heon | last2 = Lee | first3 = Donghwan | last3 = Kim | first4 = Young Keun | last4 = Kim | bibcode = 2005JCrGr.283..404K }}

It is sometimes used in integrated circuit manufacture to create a diffusion barrier or "glue" layers between copper, 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).{{citation| url = https://semiengineering.com/challenges-mount-for-interconnect/ |first = Mark | last = LaPedus | title = Challenges Mount For Interconnect | date =26 June 2012 | work = semiengineering.com }}

It also has application in thin film resistors.{{citation | doi = 10.1541/ieejsmas.125.182 |title=Fabrication of a Tantalum-Nitride Thin-Film Resistor with a Low-Variability Resistance |last =Akashi |first =Teruhisa | year=2005 |journal = IEEJ Transactions on Sensors and Micromachines | volume = 125 | issue = 4 | pages = 182–187 | bibcode = 2005IJTSM.125..182A | doi-access = free }} It has the advantage over nichrome resistors of forming a passivating oxide film which is resistant to moisture.{{citation| at= § 2.5 Characteristics of Tantalum Nitride Resistors, pp.83-4 | title = Hybrid Microcircuit technology Handbook| edition = 2nd |first1 = James J. | last1 = Licari | first2= Leonard R. |last2 = Enlow | publisher = Noyes Publications | year = 1998 }}

{{reflist}}

{{Tantalum compounds}}

{{Nitrides}}

Category:Nitrides

Category:Tantalum compounds