Super-Conformal Electrodeposition

Super-Conformal Electrodeposition of Copper into Nanometer Vias and Trenches 

Defect-free deposits in vias and trenches known as super-conformal electrodeposition, may be achieved in the presence of certain additives. In super-conformal deposition, electrodeposition inside vias and trenches occurs preferentially at the bottom. 

Sub-conformal and conformal electrodeposition of copper in vias and trenches, on the other hand, occurs in an additive-free acid sulfate solution. These deposits have two types of defects voids and seams (Fig. 3 in Ref. 22). 

Two mechanisms for super-conformal deposition in the presence of additives have been proposed the differential-inhibition mechanism and the inhibition-acceleration mechanism. 

It was proposed by Andricacos et al This mechanism considers one-additive system. It is noted in Ref. 47 (Ch. 10, Sections 10.4 and 10.5) that in general, adsorption of additives (inhibitor) at the cathode affects the kinetics and growth mechanism of electrodeposition. The surface coverage of the additive (inhibitor), 0, is a function of the diffusion controlled rates of the adsorption-desorption processes. In the differential-inhibition mechanism it is assumed that a very wide range of additive fluxes over the micro-profile (vias and trenches) exists, that is, extremely low flux in deep interior comers, low flux at the bottom center, moderate flux at the sidewalls, and high flux at shoulders. 

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The inhibition factor used in the interpretation of leveling cannot describe the shape-change behavior in super-conformal electrodeposition of copper (see Refs. 22, and 47 Ch. 10, Section 10.6). 

Moffat et al." proposed the inhibition-acceleration mechanism in order to explain the experimentally observed comer rounding (inversion of curvature, Ref. 41, Fig 19) and general shape evolution in super-conformal electrodeposition of copper in vias and trenches of nanometer dimensions." These authors studied as well a three-additive system composed of two inhibitors and one accelerator. They concluded that super-conformal deposition and comer rounding might be attributed to competitive adsorption of inhibitor and accelerator. This model is based on the assumption of curvature enhanced accelerator coverage in vias and trenches. 

Two types of modeling have been used to interpret and optimize super-conformal electrodeposition of copper the deterministic modeling and the stochastic modeling... 

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