“Seedless” electrochemical deposition of copper on physical vapor deposition-W2N liner materials for ultra large scale integration (ULSI) devices

Abstract

Electrochemical studies are designed to identify processes that provide adequate nucleation and thin film growth directly on ultrathin, air-exposed physical vapor deposition (PVD)-tungsten nitride diffusion barriers. In this study, it is shown that very thin copper films can be nucleated directly on a conducting PVD-W 2 N liner surface. A complex chemistry model based on mass balance and thermodynamic equilibrium has been applied to numerous ammoniacal platting bath compositions and the resulting concentration profiles inserted into the Nernst equation. Comparing the experimental results with the predicted model indicates that a strong adhesion is associated with the reduction of several copper-ammonia complexes at the metal nitride surface. Nucleation, growth mechanisms, and film resistivity are found to be dependent on the reduction potential, electrolyte velocity, and platting bath chemistry.

Homogeneous Decomposition of Aryl- and Alkylimido Precursors for the Chemical Vapor Deposition of Tungsten Nitride: A Combined Density Functional Theory and Experimental Study

“…To overcome the problem of copper contamination, thin films acting as diffusion barriers are used. , Besides having good resistance to diffusion, barrier films should be structurally and thermally stable, exhibit good adhesion to both copper and dielectric layers, be nonreactive with copper, have low resistivity, and be resistant to thermal and mechanical stresses. Tungsten nitride (WN x ) − and tungsten carbonitride (WN x C y ) − are promising candidates for barrier materials based on these criteria. Recently, we reported metal−organic chemical vapor deposition (MOCVD) growth of WN x and WN x C y thin films using a series of related single source precursors: the phenylimido complex Cl 4 (CH 3 CN)W(NPh) ( 1 ), the isopropylimido complex Cl 4 (CH 3 CN)W(N i Pr) ( 2 ), and the allylimido complex Cl 4 (CH 3 CN)W(NC 3 H 5 ) ( 3 ) .…”

Tungsten Allylimido Complexes Cl4(RCN)W(NC3H5) as Single-Source CVD Precursors for WNxCy Thin Films. Correlation of Precursor Fragmentation to Film Properties

“…Excess nitrogen present in these materials can migrate to grain boundaries, helping to block these potential diffusion pathways through repulsive Cu−N interactions. , An example of a refractory metal nitride that has found applications in IC technology is tantalum nitride (TaN), which has been used as a barrier material for intermediate and upper level wiring in some IC devices . Another metal nitride that is a promising candidate for thin film barrier materials is tungsten nitride (WN x ). − This material has the additional advantages of increased adhesion to copper, potential seedless copper electrodeposition, − and facile processing (e.g., more efficient chemical mechanical polishing) . In addition to these binary nitrides, the ternary material tungsten carbonitride (WN x C y ) has also shown promise for diffusion barrier applications.…”

“…4 Another metal nitride that is a promising candidate for thin film barrier materials is tungsten nitride (WN x ). [5][6][7] This material has the additional advantages of increased adhesion to copper, 8 potential seedless copper electrodeposition, [9][10][11] and facile processing (e.g., more efficient chemical mechanical polishing). 12 In addition to these binary nitrides, the ternary material tungsten carbonitride (WN x C y ) has also shown promise for diffusion barrier applications.…”

Surface Morphology Evolution of Cu Thin Films Electrodeposited Directly on Ti Diffusion Barrier in Citric Acid

“…Citric acid is dissociated into C 6 H 5 O 7 3− (Cit 3− ) and 3H + in aqueous solution. Theoretically the pH of 0.5 M citric acid solution is 1.72 when calculating it from a dissociation equilibrium constant of citric acid, K a = 7.45 × 10 −4 .…”