Common Metallization Research Articles

Multimaterial 3D Printing Technique for Electronic Circuitry Using Photopolymer and Selective Metallization

Herein, a 3D printing technique to enable the manufacturing of selectively plated polymer objects by photopolymer printing and copper metallization is presented. Metallized plastic has become popular in a number of industries due to its lightweight, flexibility of design, and cost‐effective fabrication. Common metallization techniques require multiple pretreatment steps, such as surface etching, sensitization/activation, and acceleration. The proposed method, by eliminating the sensitization step, allows selective metallization of 3D‐printed samples by direct plating. The method relies on the inclusion of silver seeds into a mixture of acrylate‐ and methacrylate‐based monomers and oligomers, which enables direct electroless copper metallization following 3D printing. Ag(I) ions act as catalytic sites for copper deposition. Copper films grown with embedded 2 and 4 wt% Ag(I) seeds reach thicknesses of 5.7 ± 1.2 and 7.7 ± 1.3 μm, respectively. Furthermore, printing with pristine and silver‐modified resins on the same sample allows selective plating: only the modified resin is plated leaving the pristine resin unaffected. A proof‐of‐concept temperature sensor is manufactured to demonstrate the performance of the printed interconnects.

Die-attach on nickel substrate by pressureless sintering a trimodal silver paste

Most of the reported sintered-silver bonding was done on substrates metallized with silver or gold. There is lacking in reports of strong sintered-silver bonding on nickel (Ni), a common and low-cost metallization on substrates, due to nickel oxidation at sintering temperature. In this study, we proposed a die-attach method on nickel by pressureless in-air sintering a trimodal hybrid-silver paste. Thanks to the strong cohesion of densification bond-line from close packing of trimodal-silver particles and adhesion from metallic bonds at Ag-Ni interface by prevention nickel from extensive oxidation, strong die-shear strength above 40 MPa was achieved. The results presented in this study open a way to achieve strong sintered-silver bonding on nickel metallization.

Extrinsic Spin Hall Effect in Cu1−xPtx

We have experimentally studied the effects on the spin Hall angle due to systematic addition of Pt into the light metal Cu. We perform spin torque ferromagnetic resonance measurements on Py/CuPt bilayer and find that as the Pt concentration increases, the spin Hall angle of CuPt alloy increases. Moreover, only 28% Pt in CuPt alloy can give rise to a spin Hall angle close to that of Pt. We further extract the spin Hall resistivity of CuPt alloy for different Pt concentrations and find that the contribution of skew scattering is larger for lower Pt concentrations, while the side-jump contribution is larger for higher Pt concentrations. From technological perspective, since the CuPt alloy can sustain high processing temperatures and Cu is the most common metallization element in the Si platform, it would be easier to integrate the CuPt alloy based spintronic devices into existing Si fabrication technology.

Metalizowanie bezpradowe tworzyw polimerowych

This article is a review of the literature related to the electroless metallization of plastics. The basic methods of electroless metallization by: displacement, metal reduction, and autocatalysis have been described. The importance of proper preparation of the surface layer of metallized materials, which enables the deposition and activation of metallization precursors, as well as the dominant role of palladium as a common metallization catalyst have been discussed. The role of organometallic complexes as precursors of electroless metallization has also been described. The possible applications of electroless metallized plastics and most recent research trends have been presented.

Laser-assisted Electroless Metallization of Polymer Materials: A Critical Review

A significant boost to basic research and experimentation in metallization of polymers was caused by several factors, including rapid developments in manufacturing of electronic and microelectronic circuits, coupled with pursuit of miniaturization in electronic devices, as well as material requirements in automation and robotics, not to mention the ongoing demand in many other areas of modern technology. Industrially, electroless metallization is the most common metallization method for polymers. However, in this method surface activation is required prior to metallization. This article presents a review on the application of lasers in electroless metallization of polymer materials. Various approaches for laser induced surface activation are discussed. The discussion is comprehensively supported by experimental results and numerous references.

Fracture toughness of intermetallic Cu6Sn5 in lead-free solder microelectronics

Even though lead-free Sn-Ag-Cu based solder alloys are emerging as promising candidates to replace well-established but hazardous lead-containing solders, they suffer from limited knowledge about their mechanical performance. To ensure the high reliability demands in microelectronics, fracture properties need to be quantified with respect to crucial microstructural elements like Cu6Sn5 intermetallic compounds formed at common Cu metallization interfaces. While indentation fracture testing methods have shown varying fracture toughness values, micro-cantilever fracture testing is applied in this work on FIB-prepared single-crystalline Cu6Sn5 cantilevers to clarify on the microstructure-fracture relationship.

Embedded Ceramic Capacitors in LTCC

The integration of passive elements in ceramic interconnect devices promises higher package densities and reliability. LTCC compatible high-k dielectrics are commercially available with k-values up to 250. Barium titanate dielectrics stand out for their high permittivity even at low sintering temperatures. This fact allows the co-firing with common metallization and commercially available tapes. In this study we investigate the co-firing of barium titanate LTCC tapes with commercially available standard tapes. Pressure assisted sintering and constraint sintering is used for the manufacturing of buried capacitors. Crucial process parameters are worked out using a statistical set up according to Taguchi. High k-values up to 2300 are obtained for embedded dielectric tape patches. Beside of the capacitor properties the process constancy is observed.

Influence of the cooling method on the structure of 55AlZn coatings

In metallization processes, metals or metal alloys are used which have a low melting point and good anticorrosion properties. Moreover, they must form durable intermetallic compounds with iron or its alloys. The most common hot-dip metallization technology involves galvanizing, however, molten multi-component metal alloys are used as well. An addition of aluminium to the zinc bath causes an increase in corrosion resistance of the obtained coatings. The article presents results of tests of obtaining coatings by the batch hot-dip method in an 55AlZn bath. Kinetics of the coating growth in the tested alloys were determined in the changeable conditions of bath temperature, dip time and type of cooling. The structure of coatings and their phase composition were revealed. As a result of the tests performed, it has been found that an increase in total thickness of the coatings as a function of the dipping time at a constant temperature is almost of a parabolic nature, whereas an increase in the transient layer is of a linear nature. The structure was identified by the XRD analysis and the morphology of the coatings was tested by means of SEM. It has been found that the cooling process with the use of higher rates of cooling causes a size reduction of the structure in the outer layer and a reduction of thickness of both the intermediate diffusion layer and the whole coating by ca. 25 %.

The effect of Cr barrier on interfacial reaction of Au/Zn/Au/Cr/Au contacts to p-type InGaAs/InP

Alloy-type metal is widely used to reduce contact resistance in optoelectronic devices. Among the alloy-types, Au/Zn is one of the most common metallization systems. In this paper, we studied the alloy morphology of p-InP/p-InGaAs/Au/Zn/Au/Cr/Au systems. We found that the amount of Au–Zn alloy depended upon the thickness of the Cr layer. When Cr thickness was reduced to 135 Å, both Au-rich and GaAs-rich excessive compound formation started to occur. The Au diffusion punched through the InGaAs layer and penetrated into the InP. Comparison of Au/Zn/Au and Au/Zn/Au/Cr/Au suggested that the top Au layer maybe very influential during the alloy reaction. The Au–Zn alloy was significantly less in the Au/Zn/Au than that in the Au/Zn/Au/Cr/Au.

The effect of Cr barrier on interfacial reaction of Au/Zn/Au/Cr/Au contacts to p-type InGaAs/InP

Alloy-type metal is widely used to reduce contact resistance in optoelectronic devices. Among the alloy-types, Au/Zn is one of the most common metallization systems. In this paper, we studied the alloy morphology of p-InP/p-InGaAs/Au/Zn/Au/Cr/Au systems. We found that the amount of Au–Zn alloy depended upon the thickness of the Cr layer. When Cr thickness was reduced to 135 Å, both Au-rich and GaAs-rich excessive compound formation started to occur. The Au diffusion punched through the InGaAs layer and penetrated into the InP. Comparison of Au/Zn/Au and Au/Zn/Au/Cr/Au suggested that the top Au layer maybe very influential during the alloy reaction. The Au–Zn alloy was significantly less in the Au/Zn/Au than that in the Au/Zn/Au/Cr/Au.

High density plasma via hole etching in SiC

Throughwafer vias up to 100 μm deep were formed in 4H-SiC substrates by inductively coupled plasma etching with SF6/O2 at a controlled rate of ∼0.6 μm min−1 and use of Al masks. Selectivities of >50 for SiC over Al were achieved. Electrical (capacitance–voltage: current–voltage) and chemical (Auger electron spectroscopy) analysis techniques showed that the etching produced only minor changes in reverse breakdown voltage, Schottky barrier height, and near surface stoichiometry of the SiC and had high selectivity over common frontside metallization. The SiC etch rate was a strong function of the incident ion energy during plasma exposure. This process is attractive for power SiC transistors intended for high current, high temperature applications and also for SiC micromachining.

Microstructural stability of ohmic contacts to InxGa1−xN

The microstructural properties and interdiffusion reactions of some common metallization schemes (Au/Ge/Ni, Ti/Pt/Au, WSix, and AuBe) on GaN and In0.5Ga0.5N have been examined using scanning electron microscopy and Auger electron spectroscopy. The objective of this study was to investigate thermally stable and uniform contacts to both materials. The WSix contacts were found to possess excellent thermal stability and retained good structural properties at annealing temperatures as high as 800 °C on GaN. These contacts on In0.5Ga0.5N had a minimum specific contact resistivity of 1.48×10−5 Ω cm2 and an excellent surface morphology following annealing at 700 °C. The increase in contact resistance observed at higher temperatures was attributed to intermixing of metal and semiconductor. By contrast the Ti/Pt/Au and Au/Ge/Ni contacts showed lower stabilities, but also showed little Au penetration into the underlying GaN. AuBe contacts had the poorest thermal stability of all four schemes investigated, with substantial reaction with GaN occurring even at 400 °C. The WSix contact appears to be an excellent choice for application in high temperature GaN electronics.

Admittance properties of thin/thick metal-oxide-semiconductor structures. I. Experiment and equivalent network

A metal-oxide-semiconductor structure with a stepped oxide under a common gate metallization is investigated. The G(V) and C(V) curves strongly deviate from those of wafers with uniform oxide thicknesses: Three sharp G(V) maxima and a well structured C(V) curve are seen. A general equivalent network has been established for the description of the behavior of the structure. By choosing special bias conditions, the network can be reduced to simpler configurations. In this case all the network elements are accessible from independent measurements (secondary electron microscopy, control samples), so that the C(V) curve can be reconstructed solely from geometrical and technological data for its essential portions. The network is exploited for a separate determination of the surface-state density underneath the thin and the thick oxide regions. This has been done for a series of thin/thick oxide combinations. A lateral field induced p-i junction is found underneath the thick/thin oxide boundary for appropriate biases, V. The G (ω;V=const.) and C(ω;V=const.) analysis delivers the (forward)conductance and capacitance of the junction.

A high performance Josephson binary counter implemented in Nb and NbN technology

A Josephson binary counter with nondestructive readout has been implemented and tested in both niobium and niobium nitride technology. Successful operation of the Nb version has been observed. The design incorporates an additional tapered-edge SiO/sub 2/ level in the Nb processing sequence, which increases interferometer inductance, decreases capacitance, and ensures that geometric resonances are as high in frequency as possible. This level has the added advantage of providing mask compatibility with the NbN process, as this level is skipped in the NbN flow, thereby compensating in part for the larger penetration depth of NbN. The counter cell is designed to be as compact as possible to minimize stray inductance and maximize top count rate and high count rate bias margins. A novel readout SQUID coupling layout that allows low read SQUID inductance and requires no holes in the groundplane is used. Coupling to the adjacent count SQUID is provided by a common control line level metallization, which directs count SQUID flux through the read SQUID loop. Nb versions of the circuit functioned as expected, but low device yield limited the longest chain of functioning stages to five. The NbN circuits did not function due to higher than predicted inductance values.