Philippe M. Vereecken

Liner materials for direct electrodeposition of Cu

We identified a family of materials which can be directly electroplated with Cu in acidic plating baths commonly found in the microelectronics industry. Details are presented illustrating a number of important properties of the electroplated Cu/linear material system. These include the adhesion of the plated film to liner material, the recrystallization behavior of the plated film, the texture of the plated film, and the resistivity of the plated film after high-temperature anneals. Finally, an example is presented illustrating the direct plating of Cu across an 8 in. wafer without the use of a Cu seed layer.

Chemical vapour deposition of zeolitic imidazolate framework thin films

Integrating metal-organic frameworks (MOFs) in microelectronics has disruptive potential because of the unique properties of these microporous crystalline materials. Suitable film deposition methods are crucial to leverage MOFs in this field. Conventional solvent-based procedures, typically adapted from powder preparation routes, are incompatible with nanofabrication because of corrosion and contamination risks. We demonstrate a chemical vapour deposition process (MOF-CVD) that enables high-quality films of ZIF-8, a prototypical MOF material, with a uniform and controlled thickness, even on high-aspect-ratio features. Furthermore, we demonstrate how MOF-CVD enables previously inaccessible routes such as lift-off patterning and depositing MOF films on fragile features. The compatibility of MOF-CVD with existing infrastructure, both in research and production facilities, will greatly facilitate MOF integration in microelectronics. MOF-CVD is the first vapour-phase deposition method for any type of microporous crystalline network solid and marks a milestone in processing such materials.

Electrochemical Deposition of Copper on n‐Si/TiN

In this paper we report on the electrochemical deposition of copper onto n‐type silicon with a 30 nm TiN barrier film. We show that the mechanism of nucleation and growth is dependent on the applied potential. At potentials more negative than −0.35 V, instantaneous nucleation of hemispherical clusters is followed by diffusion‐limited growth. In this potential regime, the nucleus density is essentially constant at about . At potentials more positive than −0.35 V, the nucleation and growth kinetics are more complex, and clusters consisting of several nuclei are formed. The cluster density decreases to about at −0.05 V.

Plasma-enhanced chemical vapour deposition growth of Si nanowires with low melting point metal catalysts: an effective alternative to Au-mediated growth

Au nanoparticles are efficient catalysts for the vapour?solid?liquid (VLS) growth of semiconductor nanowires, but Au poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts for Si nanowire growth can be broadened when the need for catalytic precursor dissociation is eliminated through the use of plasma enhancement. However, in this regime the incubation time for the activation of VLS growth must be minimized to avoid burying the catalyst particles underneath an amorphous Si layer. We show that the combined use of plasma enhancement and the use of a catalyst such as In, already in a liquid form at the growth temperature, is a powerful method for obtaining Si nanowire growth with high yield. Si nanowires grown by this method are monocrystalline and generally oriented in the direction.

Measuring the electrical resistivity and contact resistance of vertical carbon nanotube bundles for application as interconnects

Carbon nanotubes (CNT) are known to be materials with potential for manufacturing sub-20 nm high aspect ratio vertical interconnects in future microchips. In order to be successful with respect to contending against established tungsten or copper based interconnects, though, CNT must fulfil their promise of also providing low electrical resistance in integrated structures using scalable integration processes fully compatible with silicon technology. Hence, carefully engineered growth and integration solutions are required before we can fully exploit their potentialities. This work tackles the problem of optimizing a CNT integration process from the electrical perspective. The technique of measuring the CNT resistance as a function of the CNT length is here extended to CNT integrated in vertical contacts. This allows extracting the linear resistivity and the contact resistance of the CNT, two parameters to our knowledge never reported separately for vertical CNT contacts and which are of utmost importance, as they respectively measure the quality of the CNT and that of their metal contacts. The technique proposed allows electrically distinguishing the impact of each processing step individually on the CNT resistivity and the CNT contact resistance. Hence it constitutes a powerful technique for optimizing the process and developing CNT contacts of superior quality. This can be of relevant technological importance not only for interconnects but also for all those applications that rely on the electrical properties of CNT grown with a catalytic chemical vapor deposition method at low temperature.

Particle Codeposition in Nanocomposite Films

Nanocomposite films can be deposited by electrochemical deposition of a material from a solution containing a suspension of nanometer size particles. We show that the kinetics of nanometer size particle incorporation into a growing film can be described by a model that takes into account the convective diffusion of particles to the surface and treats particle incorporation in terms of the residence time at the surface. Experimentally, particle transport can be controlled using a rotating disk electrode. We show that incorporation of 300 nm Al 2 O 3 particles into nickel films can be described by this model.

Kinetics of Particle Codeposition of Nanocomposites

In this paper we describe a kinetic model for electrochemical deposition of nanocomposites composed of a metal matrix and inert particles. The model takes into account both the diffusion force as well as the gravitational force acting on the particles. The gravitational force is shown to he important for the codeposition of 300 nm Al 2 O 3 particles in Ni, but negligible for codepositing 50 nm particles.

Synthesis and characterization of particle-reinforced Ni/Al2O3 nanocomposites

Nanocomposite Ni/Al 2 O 3 films were electrodeposited from a suspension of Al 2 O 3 nanoparticles in aqueous nickel sulfamate solution. The volume fraction of particles incorporated increased with electrode rotation rate and decreased with deposition current density. The composition, microstructure, hardness, and magnetic properties of these nanocomposite films were characterized. The mechanical strengthening due to particle dispersion in the films was interpreted by considering an Orowan dislocation bowing mechanism. The coercivity of the films increased with increasing particle concentration in the film. The saturation magnetization showed a weak dependence on particle concentration.

Electrochemical Characterization of Adsorption-Desorption of the Cuprous-Suppressor-Chloride Complex during Electrodeposition of Copper

The deposition of copper metallization is achieved from acidic copper sulfate solution containing small concentrations of chloride, suppressor, accelerator, and leveler. Void-free filling of trenches and vias results from the complex interplay between the additives in the solution. Here we report on the adsorption/desorption of the copper-suppressor-chloride complex in solutions without accelerator or leveler. We show that desorption of the suppressor complex occurs at a critical potential that is dependent on the pH, chloride concentration, cupric ion concentration, and suppressor concentration. We derive an expression for the critical potential from which we determine the composition of the complex. In addition, the solubility product of the complex is determined to be log K s = -14.4.

Solvent-free synthesis of supported ZIF-8 films and patterns through transformation of deposited zinc oxide precursors

Film processing and patterning techniques are a prerequisite to fully exploit the potential of metal–organic frameworks (MOFs) in integrated applications. We report a solvent-free approach for the synthesis of ZIF-8 thin films and patterns through the reaction of ZnO films with melted 2-methylimidazole.