Ruthenium is one of the most promising candidates to replace tantalum and titanium based diffusion barrier layers in microelectronics. Its unique properties allow the deposition of ultrathin layers with controlled thickness by means of a wide variety of different techniques. Ruthenium barriers are characterized by good thermal stability, low resistivity and great adherence. Moreover, the copper filling deposited during the Damascene process can be directly applied on the barrier without the need of a seed layer. As a consequence of the industrial interest in developing new ruthenium based interconnects technologies, a significant literature has been produced in the last few years. The scope of the present work is to collect and analyze the literature on the topic, investigating in this way the technologies developed in the past and the current development stage of ruthenium based barrier layers. Due to their multiple advantages, a special focus is devoted to the manufacturing of ruthenium diffusion limiters by mean of wet electrochemical processes.

Drop‐on‐demand inkjet printing of highly viscous fluids represents a highly attractive emerging technology for advanced material deposition. The jetting of viscous inks, such as concentrated polymer solutions and nanoparticle suspensions, is a key enabling technology for many industrial applications, ranging from microelectronics to biomedicine and ceramics manufacturing. Currently available standard inkjet printers typically operate in a relatively narrow viscosity range (up to 16 mPa s), and alternative drop‐on‐demand printing techniques (such as laser‐induced forward transfer) present limited industrial applicability. In this context, the development of a piezoelectric‐driven printhead capable of jetting high‐viscosity fluids is of great interest. Herein, a prototype of such a device is presented and its performance is evaluated using model fluids at increasing viscosities. Specifically, the dependence of emitted droplets’ properties on jetting parameters is evaluated and linked to the physical characteristics of the system. In optimal conditions, piezoelectric jetting of solutions characterized by viscosities in excess of 200 cP is achieved. Finally, as an applicative example, the jetting of functional inks is attempted. A ZnO suspension and a poly(3,4‐ethylenedioxythiophene) (PEDOT) based solution are successfully jetted to demonstrate the applicability of the developed printhead to the deposition of ceramic suspensions and concentrated polymer solutions.

The present work follows the trend to develop non-aqueous electrolytes for the deposition of corrosion resistant ZnNi alloys. It investigates the use of the choline chloride/ethylene glycol (1:2 molar ratio) eutectic mixture and of pure ethylene glycol as solvents for ZnNi electroplating. The electrochemical behavior of Zn and Ni is investigated via cyclic voltammetry, and potentiostatic ZnNi deposition is performed. Ni content is found to be precisely tunable in the 10–20% wt range, which presents the highest industrial interest for corrosion protection. ZnNi coatings obtained are characterized from the morphological and phase composition point of view. Evidence of the formation of a metastable γ ZnNi phase is observed for both choline chloride/ethylene glycol and pure ethylene glycol. Finally, potentiodynamic corrosion tests are performed to assess their corrosion properties.

In the present paper the electroless metallization of 3D printed devices using stereolithography is investigated. Two different photocurable resins from a commercial supplier and a self-formulated one are used as starting materials for printing. A first metal layer of NiP or Cu, obtained by an optimized pretreatment and plating process, is subsequently applied on the parts. The possibility of obtaining multilayers through the successive electrodeposition of different metals on the electroless treated parts is demonstrated as well. From the applicative point of view, the use of 3D printing, coupled with electroless deposition of mono or multilayers, can be employed to manufacture functional microstructures for use in the fields of microrobotics, MEMS, metamaterials and others. For this reason, the realization of a prototypical magnetic actuator is presented as an example of possible application.

This paper starts with a short review of smart materials, which can be 4D printed and whose properties can be modified over time through specific stimuli such as heat, light, temperature, electric and magnetic fields. In the second part of the paper, a new polymer material for 4D printing was presented. The material was a thermally activated shape memory polymer (SPM), capable of memorizing a temporary shape and restoring the original one by means of a thermal stimulus. A self-healing behavior was introduced into the polymer, to enhance its durability and make it suitable for application in the fields of soft robotics and actuators. A polycaprolactone (PCL) was selected to provide a shape memory effect, taking into account its molecular weight and the possibility of chemically modifying it in order to make it photo-curable. Self-healing properties were provided by an ureidopyrimidinone (UPy) methacrylate monomer, capable of forming four hydrogen bonds with a self-complementary unit, favored by temperature. This new material was thus 4D printed by a digital liquid processing (DLP) printer. Both the shape memory effect and the self-healing feature were demonstrated, enabling this new material to be used as a raw material for new generation soft robotic actuators.