Kaushik Kumar

Tantalum Nitride Films Grown by Inorganic Low Temperature Thermal Chemical Vapor Deposition Diffusion Barrier Properties in Copper Metallization

Key findings are presented from a systematic study which evaluated the performance of chemical vapor deposited (CVD) nitrogen-rich tantalum nitride (TaN x , x ∼ 1.8) films as a diffusion barrier in copper (Cu) based metallization schemes. For this purpose, 3800 A thick Cu films were grown by physical vapor deposition (PVD) on 550 A thick TaN x films which were deposited by low temperature (<425°C) thermal CVD (TCVD) using tantalum pentabromide (TaBr 5 ), ammonia, and hydrogen as coreactants. The resulting stacks were annealed in argon ambient at 450, 500, 550, and 650°C for 30 min each, along with similar PVD Cu/PVD TaN x bilayers of identical thickness. Both types of pre- and postannealed stacks were characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, nuclear reaction analysis for hydrogen profiling, X-ray diffraction, stack sheet resistance measurements, and Secco chemical treatment and etch-pit observation by scanning electron microscopy. The resulting findings showed that the PVD TaN x films provided an excellent barrier against Cu diffusion throughout the annealing window investigated. Altematively, the TCVD TaN x films exhibited similar stability up to 550°C. Barrier failure occurred, however, at temperatures between 550 and 600°C, as revealed by the formation of etch pits after Secco etch treatment. The failure of the TCVD TaN x films could not be attributed to bromine incorporation, given that residual bromine (∼0.5 atom %) in the TCVD TaN x films was highly stable against thermal diffusion in the temperature window investigated. Instead, the higher thermal stability of the PVD TaN x was attributed to differences in film microstructure and crystalline phase, or the location of excess nitrogen within the film matrix.

Integration of PECVD Tungsten Nitride as a Barrier Layer for Copper Metallization

Amorphous tungsten nitride (WN x ) is a promising diffusion barrier for extending Cu metallization beyond 0.18 μm. This study evaluates the barrier performance, adhesion, and step coverage of PECVD WN 0.5 integrated with a CVD Cu seed layer. The WN 0.5 films exhibit amorphous structure with 33% bottom and side-wall step coverage in 0.14 μm wide structures with 9:1 aspect ratio. The potential of 50 A WN 0.5 as an effective Cu barrier is shown by the absence of Secco etch-pits in the Si substrate after a 30 min anneal at 500°C. When deposited on PECVD WN 0.5 the CVD Cu films exhibit uniform nucleation, and as deposited resistivity of 2.5 μΩ-cm. Step coverage of the CVD Cu is better than 95% in 0.14 μm structures. Adhesion exceeding epoxy strength of the CVD Cu seed layer even to air-exposed WN 0.5 is demonstrated using stud-pull adhesion tests.

Integration of chemical vapor deposition Al interconnects in a benzocyclobutene low dielectric constant polymer matrix: A feasibility study

Results are presented from a proof-of-concept study that examined the integration of damascene-processed thermal chemical vapor deposited (TCVD) aluminum (Al) interconnects in a benzocyclobutene (BCB) polymer matrix. In a first phase, the study identified baseline deposition conditions for the formation of structurally and chemically compatible blanket Al/titanium nitride (TiN)/BCB stacks on two types of blanket BCB substrates utilized to simulate the actual surfaces encountered in typical damascene processing: (1) blanket BCB films capped with a silicon dioxide SiO2 layer (SiO2-BCB), and (2) plasma reactive ion etched blanket BCB films. The TiN diffusion barrier was grown in two stages. A first (bottom) layer was deposited by physical vapor deposition (PVD), followed by a CVD-grown top layer. The resulting TCVD Al/CVD TiN/PVD TiN/BCB stacks were stable under thermal stressing up to 325u200a°C for 1 h. In a second phase, an optimized TCVD Al process flow was developed for void-free filling of TiN-coated 320-n...

Integrated plasma-promoted chemical vapor deposition route to aluminum interconnect and plug technologies for emerging computer chip metallization

A low temperature plasma-promoted chemical vapor deposition (CVD) process was developed for the formation of reliable aluminum interconnect and plug metallization schemes for applications in and beyond 0.25 μm integrated chip device technology. The process employs aluminum source precursors that are based on amine adducts of alane, such as dimethylethylamine alane, where the lack of a direct aluminum–carbon bond provides a clean chemical pathway by which to eliminate the precursor’s hydrocarbon groups at relatively low temperatures and yield pure aluminum films. The formation of dense and thick aluminum films at low temperature and that have a smooth surface morphology is achieved by combining a radio-frequency hydrogen plasma at low power densities (below 0.1 W/cm2) with a low frequency (<400 kHz) substrate bias. The use of a low power density plasma is designed to activate a uniform nucleation of aluminum grains, thus eliminating the inherent problem of surface roughness that plagues thermal CVD process...

Low Temperature CVD Route to Binary and Ternary Diffusion Barrier Nitrides for Cu Metallization

The identification of viable diffusion barrier/adhesion promoter material and associated deposition processes is a critical factor in the successful development of structurally and electrically reliable copper based metallization schemes. As feature sizes continue shrinking, such materials are expected to delivery enhanced performance at increasingly thinner layers to allow maximum space utilization by the actual conductor. In this respect, Ta and W based binary and ternary nitrides present promising solutions in view of their hardness, chemical inertness, and thermal stability to high temperatures. Additionally, their availability in amorphous form provides the added benefit of inherent absence of grain boundaries, which usually serve as a primary diffusion path. This paper presents finds from the development of low0temperature (,350°C) CVD processes for the growth of ultrathin Ta, W, Ta-Si, and WSinitride layers for sub−0.18 micron device structures. These processes employ novel inorganic and metal-organic source precursors which allow for the in-situ, one-step, growth of binary and ternary nitrides from appropriate mixtures of the corresponding source precursors. Results will also be discussed from diffusion barrier studies which established performance metris for the applicability of such materials in copper interconnect technologies.