Intrinsic Properties and Barrier Behaviors of Thin Films of Sputter-Deposited Single-Layered and Alternately Layered Tantalum Nitrides (Ta[sub 2]N/TaN)

Abstract

This work employs X-ray diffraction, X-ray reflectivity, and transmission electron microscopy, along with electrical ͑sheet resistance and resistivity͒ and bending-beam stress analyses, to characterize the intrinsic properties and barrier behavior of 40 nm thick thin films of sputter-deposited single-layered Ta 2 N, single-layered TaN, and alternately layered Ta 2 N/TaN having various period thicknesses ͑͒ from 4 to 40 nm. The thermal stability of each of these barriers interposed between silicon and copper at a high temperature regime ͑500-900°C͒ is closely related to variations of intrinsic properties of the barriers, particularly microstructure and residual stress ͑͒. Failure of the barriers is explained in terms of a previously reported mass transport mechanism, which suggests that the free short-diffusion paths ͑grain boundaries͒ created by anneal-induced crystallization/grain growth in the single-layered Ta 2 N and TaN barriers ͑ ϭ 3-5 GPa͒ are a key factor in deteriorating the diffusion barriers. Conversely, an adequately layered Ta 2 N/TaN barrier with down to approximately 5 nm is nearly free of residual stress and can maintain a very stable quasi-amorphous microstructure against annealing. Therefore, this quasi-superlattice novel design has the capability to further improve thermal stability and reliability of tantalum nitride diffusion barriers for copper metallization.

Studies on phase dependent mechanical properties of dc magnetron sputtered TaN thin films: evaluation of super hardness in orthorhombic Ta4N phase

“…Tantalum nitride (TaN) thin films have been studied rather extensively in view of their interesting physical properties and for their applications in several areas such as diffusion barriers in microelectronics, hard protective coatings and as bio-compatible coatings [1][2][3]. The TaN films possess high melting point, excellent mechanical properties and resistance to most of the chemical environments.…”

Barrier properties of ultrathin VN films of low resistivity and high density for Cu interconnects

“…For example, the conventional barrier of TaN x for Cu interconnects is 180-270 µΩ cm in resistivity. [17][18][19] The VN barrier of low resistivity is favorable for reducing the wiring resistance and interwire capacity product (RC) time constant for signal transmission.…”

“…This VN film, an interesting transition metal nitride, has a resistivity of 50 µΩ cm, which is extremely lower than that of the TaN film deposited by reactive sputtering (180-270 µΩ cm). [17][18][19] Recently, VN has been considered an interesting material that attracts attention for electrodes in energy storage devices such as batteries and supercapacitors. [20][21][22] For these applications, a thinner film is required to maintain its performance.…”

Characterization of Ultrathin Electroless Barriers Grown by Self-Aligned Deposition on Silicon-Based Dielectric Films

“…[2][3][4] However, copper is ready to diffuse ͑or drift͒ into surrounding dielectrics when thermally treated ͑or biased under thermal stress͒, even at low temperatures ͑ϳ200°C͒, 5,6 so a highly conducting barrier layer with a markedly reduced thickness of typically less than ϳ20 nm must be used to separate the copper from the dielectric films. 7 Apart from the sputter and chemical vapor deposited transition metal nitride/carbide thin films ͑e.g., TiN, TaN, TiSiN, and TaC͒, [8][9][10][11] electrolessly plated metal-based ͑nickel and cobalt͒ barriers are attracting extensive attention because of the proven barrier characteristics for copper and dielectric layers, improved gap-filling capability, reduced electrical resistivity, and simplified flow in the deposition of copper. 2,4,12 However, because the dissimilar surfaces of the substrates ͑dielectric and nitride/ carbide barriers͒ generally lack catalytic properties, a seeding treatment or surface modification must be invoked to initiate the deposition of electroless barriers or copper.…”