Electrodeposition of Silver in Sub-Micron-Sized Features

Journal of The Electrochemical Society, 2006

The influence of a catalyst deactivating leveling additive in electrodeposition is explored in the context of the previously developed curvature enhanced accelerator coverage model of superconformal film growth. Competitive adsorption between a rapidly adsorbed suppressor, rate accelerating catalyst, and catalyst-deactivating leveler is examined. Rate equations are formulated where the leveling agent is capable of deactivating the adsorbed catalyst by either direct adsorption from the electrolyte or by deactivation/displacement during surface area reduction that accompanies advancing concave surfaces. The influence of a prototypical cationic surfactant leveler on electrochemical kinetics and feature filling is examined for copper electrodeposition from an electrolyte containing polyethylene glycol-chloride-bis͑3-sulfopropyl͒disulfide ͑PEG-Cl-SPS͒.

Journal of The Electrochemical Society, 2002

Superconformal deposition of silver in vias was studied. The observed experimental fill behavior is compared with predictions from a model based on the curvature-enhanced accelerator coverage mechanism of superconformal deposition. Superconformal copper deposition and conformal nickel deposition results are also modeled. The previously published model predicts via filling behavior using the dependence of deposition rate kinetics on the coverage of adsorbed catalyst. The requisite kinetic parameters are obtained from independent current-voltage and current-time transient studies conducted on planar substrates.

Electrochemical and Solid-State Letters, 2003

Superconformal filling of submicrometer trenches was achieved using substrates that were catalyzed with KSeCN prior to metal deposition in a catalyst-free, silver-cyanide electrolyte. The degree of superfill was dependent on the time the specimen spent in the KSeCN-containing solution prior to electrodeposition. Longer derivatization times correspond to higher initial catalyst coverages. The feature filling results were consistent with the curvature enhanced accelerator coverage mechanism of superconformal deposition. This mechanism implies that area changes during deposition in a feature lead to higher catalyst coverage at the bottom of the feature, thus enhancing the deposition rate and allowing bottom-up fill.

Electrochemical and Solid-State Letters, 2002

This paper demonstrates superconformal electrodeposition of copper in trenches using a two-step process. The substrate is first derivitized with a submonolayer coverage of catalyst and then transferred for electroplating in a cupric sulfate electrolyte containing an inhibitor. For an optimum catalyst coverage, superconformal, ''bottom-up'' filling of trenches and vias is observed. If the catalyst coverage is too low or too high, conformal or subconformal deposition occurs, resulting in void formation during feature filling. The filling behavior of the derivitized electrodes is analogous to that obtained using a single ͑conventional͒ electrolyte containing both catalytic and inhibiting species. Restricting the catalyst to the surface by derivitization prior to metal deposition provides strong support for the curvature-enhanced accelerator coverage mechanism of superconformal film growth. From a technical perspective, the two-step process offers an interesting solution to the difficult control issues associated with catalyst destruction and related aging effects known to occur in the ''conventional'' single-electrolyte superfilling process.

Electrochemical and Solid State Letters, 2001

A model of superconformal electrodeposition is presented based on a local growth velocity that is proportional to coverage of a catalytic species at the metal/electrolyte interface. The catalyst accumulates at the interface through reaction with the electrolyte. More importantly, if the concentration of the catalyst precursor in the electrolyte is dilute, then surface coverage within small features can change far more rapidly due to changing interface area. In such a case, the catalyst effectively floats on the interface during deposition, with changes in coverage coupled to alterations in arc-length of the moving surface. The local coverage therefore increases during conformal growth on a concave surface, resulting in a corresponding increase in the local deposition rate. The opposite is true for a convex surface. The model is supported by experiments and simulations of superconformal copper deposition in 350-100 nm wide features. The model also has significant implications for understanding the influence of adsorbates on the evolution of surface roughness during electrodeposition.

Physical Review Letters, 2001

Superconformal electrodeposition is explained based on a local growth velocity that increases with coverage of a catalytic species adsorbed on the copper-electrolyte interface. For dilute concentration of the catalyst precursor in the electrolyte, local coverage in fine features changes more ...

ECS Transactions, 2018

Superconformal electrodeposition utilizing additives that adsorb on the deposit surface and either enhance or suppress metal deposition enabled the implementation of Cu damascene interconnects in microelectronics. The filling process is a consequence of the Curvature Enhanced Accelerator Coverage (CEAC) mechanism, which captures the interplay between adsorbate coverage and the metal deposition rate during area change that necessarily accompanies growth on nonplanar surfaces. CEAC-based models have successfully predicted superconformal deposition using a variety of different chemistries that yield void-free filling of fine features, as well as optically smooth, surfaces of metals such as Cu, Ag and Au. Herein a brief review of advances in the superconformal Au deposition will be detailed. Of particular interest are additives whose behavior is non-monotonic with adsorbate coverage that present new challenges for understanding as well as interesting opportunities for application.

The Journal of Physical Chemistry B, 2001

The influence of the electrode surface quality and surface morphology on the silver electrocrystallization process onto a carbon substrate from 10-2 M Ag(NH 3) 2 + /1.6 M NH 3 , 1 M KNO 3 (pH) 11) electrolyte solution was studied. Three substrates with different types of surface morphology and surface roughness were used: highly oriented pyrolitic graphite (HOPG), mechanically polished vitreous carbon (MPVC), and fractured vitreous carbon (FVC). Before the silver deposition process, the electrode surface was examined and characterized by means of Atomic Force Microscopy (AFM) analysis. Evaluation of the kinetic parameters of the silver nucleation and the growth behavior, as well as other characteristics of the silver electrocrystallization process onto carbon substrates, were based on cyclic voltammetry and chronoamperometric measurements. Cyclic voltammetry data also show that silver deposition efficiency is proportional to the increase of electrode surface roughness (from HOPG, via MPVC to FVC). The silver bulk deposition process on all three carbon substrates was characterized as 3D nucleation and diffusion-controlled growth. However, this process proceeds with different overpotentials on different substrates: the lowest for HOPG and the highest for MPVC electrode surface. The major electrocrystallization parameters, such as nucleation rate, number of active sites, and number of formed silver nuclei, strictly related to the electrode surface conditions, seem to not follow the same trends as the cyclic voltammetry data. It is clearly indicated in the nonlinear relationship between number of active sites and the surface features (recognized in AFM images). As pointed out in the discussion, it opens new questions regarding the nature of the active sites for deposition on the electrode surface and their identification by microscopic techniques.

Journal of The Electrochemical Society, 2003

Superconformal deposition enables the void-free filling of high aspect ratio features such as trenches or vias in the Damascene metallization process. Superconformal electrodeposition, also known as superfill, occurs when particular combinations of chemical additives are included in the electrolyte. The additives enable preferential metal deposition at the bottom surface which leads to bottom up filling before the sidewalls close off. Two crucial mechanisms by which the additives enable superfill to occur are ͑i͒ accelerator behavior increasing the copper deposition rate as a function of coverage and ͑ii͒ conservation of accelerator coverage with increasing/decreasing interface area. Thus, the adsorbed catalytic accelerator species floats upon the growing metal/ electrolyte interface. An effective modeling approach must accurately track the position of the interface as well as preserving surfactant coverage while the interface is advancing. This must be achieved in an Eulerian framework due to the necessity of modeling the diffusion of electrolyte species. To this end, the level set method is used to track the interface while a scalar variable approach governs the surfactant coverage. Modeling of additive accumulation and conservation on a deforming interface in conjunction with the level set method presents areas for novel numerical approaches. Several test cases are examined to validate the surface coverage model. Comparison of superfilling simulations with experimental results is also presented.

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