Selective Copper Deposition Research Articles

Selective Metallization on Ordinary Polymer Substrates by Laser Direct Activation of Copper Phosphate or Nickel Phosphate

In recent years, selective metallization on polymer surfaces has attracted considerable attention due to its excellent properties and wide applications. This paper reports that copper phosphate (Cu3(PO4)2) or nickel phosphate (Ni3(PO4)2) was selected as laser-active material to successfully fabricate metallic patterns on ordinary polymer substrates by laser direct activation and electroless plating. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the interaction mechanism between a nanosecond-pulsed laser (355 and 1064 nm wavelengths) and Cu3(PO4)2 or Ni3(PO4)2. It was found that after 355 or 1064 nm laser activation with appropriate parameters, Cu+ was generated from Cu3(PO4)2, and NiO was generated from Ni3(PO4)2. At the same time, Cu+ or NiO adsorbed on the porous sponge-like microstructure of modified polycarbonate (PC), respectively, and acted as catalytic active centers to realize selective copper deposition in the laser-activated zone. Furthermore, the obtained copper layers were confirmed to possess good selectivity, electrical conductivity, and high adhesion strength (the highest grade of 5B). Moreover, from comparisons of Cu3(PO4)2 with Ni3(PO4)2 and of 355 nm laser activation with 1064 nm laser activation, the 1064 nm laser activation of Cu3(PO4)2 produced the most catalytic seeds (Cu+) and had the best catalytic effect.

Fabrication of metallic patterns on ordinary polymer substrates by laser direct activation and electroless plating

In recent years, the fabrication of metallic patterns on polymer substrates has been given increasing attention because of its wide and important applications in many fields. This paper reported a selective metallization technology on ordinary polymer substrates basing on laser direct activation of copper hydroxyl phosphate [Cu2(OH)PO4] and electroless deposition of copper. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the interaction mechanism between nanosecond-pulsed fiber laser (1064 nm wavelength) and Cu2(OH)PO4. It was found that after laser modification and activation by appropriate parameters, the special surface microstructure (e.g., porous sponge-like) appeared and explained the good adhesion strength (the highest grade of 5B) between the copper layer and substrate. At the same time, Cu+ was generated from the Cu2(OH)PO4, adsorbed on the microstructure, and acted as catalytic active centers to realize the selective copper deposition in the laser-activated zone. In addition, the copper layer possessed good selectivity (< 3% error of line space and width) and electrical conductivity (10−6 Ω·cm volume electrical resistivity). By comparison with laser direct structuring (LDS) technology and with palladium chloride as laser sensitive material, this was a more universal and less-cost technical pathway to fabricate planar and/or three dimensional (3D) metallic patterns on more kinds of ordinary polymer substrates.

Selective Deposition of Copper on Self-Assembled Block Copolymer Surfaces via Physical Vapor Deposition.

Block copolymer (BCP) self-assembly produces chemically and topographically patterned surfaces which are used to guide the formation of Cu nanostructures by exploiting differences in the mobility of vapor-deposited species on each microdomain. Cu metal films a few nm thick were deposited on three different BCP surfaces self-assembled from poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP). For PS-b-PMMA, the effects of chemical heterogeneity dominate over the effects of the 2 nm peak-to-valley topography, and sputtered Cu preferentially wets the PS block. PS-b-P2VP has greater chemical and topographical contrast and shows a wider process window for selective deposition. Cu grown by evaporation has less surface mobility, and shadowing effects are believed to dominate pattern formation. The hierarchical self-assembly process of thin metal films on BCP surfaces provides a route to fabricating heterogeneous metallic nanostructures.

Versatile bifunctional building block for in situ synthesis of sub-20 nm silver nanoparticle and selective copper deposition

In this work, a new bifunctional building block is presented for the development of versatile photosensitive resists, which enable in situ synthesis of sub-20 nm silver nanoparticles (AgNPs). In addition, practical adaptation to a palladium (Pd)-free electroless plating process verifies the facile fabrication of a metallic grid-based transparent conductive film. The building block is an aromatic small molecule with α,β-unsaturated acryloyl group and para-hydroxyl group protected by an acid-labile group (i.e., Di-tert-dicarbonate (referred to as Boc anhydride)). Spectroscopy analysis verifies the ease of photopolymerization as well as deprotection of Boc from the para-hydroxyl group where plays a key role in Ag+ reduction. The studies on plasmon absorption, morphology and elemental analysis confirm that the in situ synthesized AgNPs are sub-20 nm with a uniform distribution in the polymer matrix, which is important for efficient catalytic performance in electroless copper (Cu) deposition. In addition, the photosensitive resist exhibited excellent process reliability with respect to photolithographic patterning process and electroless plating under strong alkaline solutions (pH 10–12). Finally, the present work demonstrates the successful fabrication of sub-3 μm Cu metal grids on a polyethylene naphthalate (PEN) film.

Selective Electroless Copper Deposition by Using Photolithographic Polymer/Ag Nanocomposite

This paper presents a novel, direct, selective, vacuum-free, and low-cost method of electroless copper deposition, allowing additive patterning of nonconductive surfaces. Ag nanoparticles (NPs) synthesized inside a photosensitive polymer are acting as seeds for electroless copper deposition. The resulting copper film surface morphology was studied with scanning electron microscopy. Copper films were shown to display a rough grainlike structure, covering substrate uniformly with good metal-substrate adhesion. Copper thickness was studied as a function of the plating time, temperature, and Ag NPs seed concentration. A maximal copper thickness of ${0.44}\,\pm \,{0.05}~\mu \text{m}$ was achieved when plated at 30 °C with 0.4 M Ag(I). The minimum feature resolution of copper patterns, grown with 0.025- and 0.1-M silver salt, is attained down to ${10}~\mu \text{m}$ . The maximum electrical conductivity of the copper film prepared with 0.025-, 0.1-, and 0.4-M Ag(I) approaches ( ${0.8}\,\pm \,0.1) \times {10}^{{7}}$ S/m, ( ${1.1}\,\pm \,{0.1}) \times {10}^{{7}}$ S/m and ( ${1.6}\,\pm \, {0.4}{)} \times {10}^{{7}}$ S/m, respe- ctively. Electroless copper interconnections and LED circuit on glass substrate were fabricated as a proof of concept demonstrators.

Electrochemical and in situ SERS study of the role of an inhibiting additive in selective electrodeposition of copper in sulfuric acid

The role of an inhibiting additive in selective copper (Cu) deposition was investigated using linear sweep and cyclic voltammetry and in situ SERS. Both the normalized SERS peak intensity of Basic Red 12 and the Cu deposition current showed hysteresis. These results indicate that Basic Red 12 desorbs or decomposes on the surface during electrodeposition of Cu. Therefore the concentration of Basic Red 12 on the patterned area decreases more than that on the flat area. This inhomogeneity of concentration leads to the preferential growth of Cu on the patterned area.

Laser-assisted selective copper deposition on commercial PA6 by catalytic electroless plating – Process and activation mechanism

Results of in-depth experimental analysis of the laser-assisted local copper deposition on commercial Polyamide6 (PA6) are presented. Pico- and nanosecond lasers were validated for surface modification of the polymer followed by silver(I) activation and finished by autocatalytic electroless copper plating on the laser-modified areas. Detailed investigations were dedicated to finding out the origin of selective metal plating, including the surface profiling and wettability dynamics, XPS analysis and electric resistance measurements of the deposited copper layer. Based on the experimental data, the mechanism of the polymer surface activation by the laser modification is proposed.

Selective deposition of plasmonic copper on few layers graphene with specific defects for efficiently synchronous photocatalytic hydrogen production

Abstract： Graphene from chitosan (CG) with wrinkle, few layers and specific defects was prepared via a simple method of low carbonization temperature and high KOH activation temperature. At the activation temperature of 1100 °C, the obtained CG-1100 has the specific surface of 1212 m2·g−1 and the total volume of 1.02 cm3·g−1 at the optimized activation temperature. The results show that the CG-1100 is similar to another two graphenes: graphene nanoparticles (GNP) and multilayer graphene powders (MGP), which contain less defects. The Cu/CG-1100 composite photocatalyst was prepared from CG-1100 and Cu(Ac)2 solution with surface plasmon resonance (SPR) effect by in-situ synthesis method under illumination. When the binary composite contains 10 wt% of Cu NPs, the hydrogen evolution rate of Cu/CG-1100 photocatalyst reached 3.94 mmol·g−1·h−1, which is 3.2 times as high as that of pure Cu NPs. Interestingly, the defect sites of the graphene can influence the photocatalytic hydrogen production rate which was observed by depositing Cu NPs on GNP and MGP. The results showed that more defects on the graphene presented higher photocatalytic hydrogen evolution rate.

Maskless copper electroplating on stainless steel using DPSS green laser

ABSTRACTIn this paper selective deposition of copper on the steel substrate is described by the laser enhanced electroplating method from liquid phase i.e. aqueous copper sulphate solution. The present study involves (i) identification of suitable laser wavelength (i.e. frequency doubled Nd: YAG laser at 532 nm) with low absorption in the electrolyte, (ii) determination of threshold voltage for selective deposition with laser, (iii) experiments on laser-assisted selective copper electroplating and (iv) characterisation based on dimensions, surface topography, residual stresses and phases present. Thus formed deposits can be controlled by incident laser power density and build up growth increases with plating time.

Fabrication of Double-Sided FPC by Hydrolyzing-Doping-Plating Additive Process

A one-step fully additive chemical process to fabricate double-sided flexible printed circuit (FPC) is reported, the process includes the drilling of through-holes, hydrolysis of PI surface, adsorption of catalyst and selective copper deposition by electroless plating. The process mentioned in this paper requires simple operating procedure and mild reacting condition. The conductive copper patterns show a resistivity of 1.95 μΩ·cm, and a high adhesion of 5B. Surface roughening can increase the mechanical anchor between deposited copper and PI, guaranteeing the good adhesion of copper patterns with high thickness about 12 μm. With faster manufacture, less pollution, lower cost and double-sided patterns accessible, this process shows high development potential and a good application prospect in FPC fabrication.

Selective precipitation of Cu in manganese-copper chloride leaching liquor

Recovery of valuable metal from industrial waste is critically important for wastewater treatment and recycling. In the present work, we developed a new method for selective copper extraction from the actual industrial manganese-copper chloride leaching liquor, which was produced in wet extraction of cobalt. The theoretical pH value for selective copper precipitation was calculated, which was in the range of 2.80–4.71. Manganese carbonate was used for selective copper deposition, and the factors that could affect the precipitation performance were investigated. The procedure for selective precipitation of copper was optimized as follows: the amount of manganese carbonate was twice the theoretical amount of neutralization acid; the reaction temperature and time were 60°C and 4.0h, respectively. Under the optimal conditions, the copper deposition rate was higher than 90%, while the deposition rates of other ions were lower than 10%. The XRD and SEM results showed that the copper-rich precipitate was granular and its main component was Cu2(OH)3Cl.

Selective Copper Electrodeposition to a 3D Copper Nanostructure

Introduction Three-dimensional (3D) copper nanostructures are expected to be applied as current collectors for lithium ion battery anodes due to their high electrical conductivity and large specific surface area. The production of 3D copper nanostructures usually requires complicated fabrication steps; however, we have developed a simple method for the production of 3D copper nanostructures.1) There is a disadvantage with this method in that the 3D copper nanostructure is likely to collapse due to low mechanical strength. Reinforcement of the 3D structures is thus considered to be one of the most effective methods to address this problem. This study aims to develop a reinforcement technology using a plating method that is applied after fabrication of the 3D copper nanostructures. The reinforcement technology employed here was viafilling plating technology. This technology is also expected to improve the adhesion to the substrate by selectively depositing copper to the bottom of the 3D nanostructure.Experimental A 3D copper nanostructure plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + 3×10-4 M polyacrylic acid) and a selective copper plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + additives) were prepared. A copper sulfate bath that does not contain additives was also employed for comparison. Pure copper and phosphorus-containing copper plates were used as the cathode and anode, respectively. Electrodeposition was conducted under galvanostatic conditions (1 A dm-2) without agitation at 25 °C. In addition, the influence of agitation on selective copper deposition was also investigated. Air agitation, magnetic stirring and a cathode rocker were used. The phase structure and microstructure of the deposits were analyzed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Results and discussion Figures 1a and 1d show a surface and cross-sectional SEM images of the 3D copper nanostructure before selective copper electrodeposition. Figure 1b shows a surface SEM image of the 3D copper nanostructure after electrodeposition without additives. The 3D nanostructure was not observed, because copper was deposited on the surface of the 3D nanostructure. The 3D nanostructure seems to have been deformed by the copper deposited on the surface, according to cross-sectional observations (Fig. 1e).Figure 1c shows a surface SEM image of the 3D copper nanostructure after electrodeposition with additives. The surface morphology is almost the same as the bare 3D nanostructure shown in Figure 1a because copper deposition at the surface of the 3D nanostructure is suppressed. Thus, the 3D nanostructure was maintained, and copper was deposited selectively at the boundary of the 3D nanostructure and the substrate, according to cross-sectional observations (Fig. 1f). Agitation also affected the selective copper deposition, and the results of agitation tests will be discussed at the meeting. References S. Arai and T. Kitamura, ECS Electrochem. Lett., 3(5), D7-D9 (2014). Figure 1

Improved Efficiency for Partial Oxidation of Methane by Controlled Copper Deposition on Surface-Modified ZSM-5.

The mono(μ‐oxo) dicopper cores present in the pores of Cu‐ZSM‐5 are active for the partial oxidation of methane to methanol. However, copper on the external surface reduces the ratio of active, selective sites to unselective sites. More efficient catalysts are obtained by controlling the copper deposition during synthesis. Herein, the external exchange sites of ZSM‐5 samples were passivated by bis(trimethylsilyl) trifluoroacetamide (BSTFA) followed by calcination, promoting selective deposition of intraporous copper during aqueous copper ion exchange. At an optimum level of 1–2 wt % SiO2, IR studies showed a 64 % relative reduction in external copper species and temperature‐programmed oxidation analysis showed an associated increase in the formation of methanol compared with unmodified Cu‐ZSM‐5 samples. It is, therefore, reported that the modified zeolites contained a significantly higher proportion of active, selective copper species than their unmodified counterparts with activity for partial methane oxidation to methanol.

The preparation of pH-sensitive Pd catalyst ink for selective electroless deposition of copper on a flexible PET substrate

We report on the preparation of a pH-sensitive styrene (St)-co-N, N-dimethyl-dimethylaminoethyl methacrylate (DMAEMA)/Pd ink for fabrication of copper pattern on a flexible PET substrate. The St-co-DMAEMA oligomers are synthesized via free radical polymerization using potassium persulfate as the initiator. The synthesized St-co-DMAEMA copolymer is utilized to self-reduce Pd nanoparticles. The pH-sensitive DMAEMA segments function as stabilizing agent for noble metal nanoparticles in acidic ink solution. On the other hand, ink-jet printing St-co-DMAEMA oligomers become hydrophobic during the electroless plating of copper with a basic bath. Therefore, a copper film with dramatically enhanced adhesion is formed on the PET surface without special pretreatment step before electroless deposition of copper film. This process yields Cu conductor formed by plating for 15 min on PET substrate with resistance 2.5 times that of bulk copper. The cyclic bending test results show that electrical resistance increases only slightly after 1000 cycles and is remained low enough for use in practical applications.

Selective electrodeposition of copper on stainless steel using laser irradiation

This paper proposes a novel selective metal deposition process that uses a combination of laser irradiation and electrodeposition. Via the selective electrodeposition using laser irradiation (SELI) process, metal can be deposited selectively on a metal surface without a special mask, which is in contrast to conventional deposition processes that routinely require a metal mask or a photo-resist. The SELI process consists of three steps: laser irradiation, electrodeposition, and ultrasonic vibration cleaning. In the course of experimentation, a recast layer was formed via the laser irradiation process, which acts as the sacrificial layer in the SELI process. The sacrificial layer was removed after the cleaning step. The separation of the sacrificial layer was due to the hydrogen evolution effects of the hydrogen embrittlement via the hydrogen bubbles and the hydrogen absorption. The results were observed via focused ion beam (FIB) analysis of the cross-sectional images. Electron probe X-ray micro-analyzer (EPMA) analysis was used to detect the surface components. Through the SELI process, selective copper deposition was successfully performed with various micro-patterns of the approximately 4μm thick deposited copper.

Selective Electroless Deposition of Copper on Organic Thin Films with Improved Morphology

We have investigated the selective electroless deposition (ELD) of Cu on functionalized self-assembled monolayers (SAMs). Previous studies have demonstrated that Cu deposits on -COOH and -CH(3) terminated SAMs using ELD. However, the deposited films were rough and contained irregular crystallites. Further, the copper penetrated through the film. In this Article, we demonstrate that copper can be selectively deposited on -COOH terminated SAMs with improved morphology and without penetration of copper through the organic layer. The method employs a Cu(II) seed layer and an additive, adenine or guanine. We demonstrate the efficacy of the technique on photopatterned -CH(3)/-COOH SAMs. Copper is observed to deposit only atop the -COOH terminated SAM area and not on the -CH(3) terminated SAM. The use of a Cu(II) seed layer increased the Cu ELD rate on both -COOH and -CH(3) terminated SAMs. The deposited copper layer strongly adheres to the -COOH terminated SAMs because the copper layer nucleates at Cu(2+)-carboxylate complexes. In contrast, the deposited copper layer can easily be removed from the -CH(3) terminated SAM surface because there is no specific copper-surface interaction. The additives adenine and guanine mediate the interaction of Cu(2+) and the deprotonated -COOH terminated SAMs via the formation of additive-carboxylate complexes. These complexes lead to significantly reduced copper penetration through the SAM. In the case of adenine, the diffusion of copper through the organic film was eliminated. This new technique for copper deposition will facilitate the development of inexpensive molecular electronics, sensors, and other nanotechological devices.

Preparation and characterization of copper patterns on polyethylenimine-modified flexible substrates

We report a simple and low-cost method to fabricate copper circuit patterns on flexible polymeric substrates. This method relies on crosslinked branched polyethylenimine (PEI) films that incorporate palladium (Pd) catalysts, which are employed as adhesive interlayers for the fabrication of copper circuit patterns on polymeric substrates. Patterned Pd catalysts are immobilized on the polymeric substrates and subsequently initiate the selective deposition of copper in an electroless plating solution. We demonstrated the fabrication of patterned copper films on a variety of flexible polymers with minimum feature sizes of 200 μm. The films were characterized by ATR FT-IR, contact angle, XPS, XRD, TEM, SEM, EDX, and AFM. The adhesion between the flexible polymeric substrate and the copper film was also investigated. Our results indicate that this novel and facile fabrication method possesses great potential for applications in the electronics industry.

Selective Deposition of Copper with Iodine Assisted Growth of MOCVD on an MPTMS Monolayer Surface at a Low Temperature

We have investigated the selective deposition of Cu films on the mercaptopropyltrimethoxysilane-ocatadecyltrichlorosilane (MPTMS-OTS) patterned glass substrate using (hfac)Cu(DMB) and C2H5I as precursors at 110°C. The low temperature deposition of Cu without iodine exhibited the difficulties of Cu nucleation on MPTMS with its low Cu growth rate of 22 nm/min and long induction period of approximately 4 min at 110°C. The addition of iodine significantly enhanced the surface diffusion of Cu adatoms on the MPTMS surface and thus led to increased nucleation and growth rate (28 nm/min) at 110°C. With these advantages, we successfully increased the maximum thickness of Cu selectively deposited on the MPTMS patterned lines from 57 nm to 140 nm without selectivity loss by adding iodine to (hfac)Cu(DMB)(3,3-dymethyl-1-butene) at 110°C. Consequently, the low temperature process for the selective deposition of Cu on the MPTMSOTS patterned surface can be utilized for the fabrication of flexible electronics.

Selectively Metallized Polymeric Substrates by Microcontact Printing an Aluminum(III) Porphyrin Complex

We report a simple, low-cost method for the fabrication of copper wires and contacts on a wide range of flexible, rigid, and inert polymeric substrates. This method relies on procedures to oxidize the polymeric substrates to form surface-bound carboxylic acid groups. Patterning of an aluminum porphyrin ink using microcontact printing results in the formation of an aluminum porphyrin monolayer that is covalently anchored to the oxidized polymer surface via an aluminum-carboxylate bond. We characterize this monolayer using ultraviolet-visible absorption spectra, reflection-absorption infrared spectroscopy, and contact angle measurements. Patterned aluminum porphyrin monolayers bind a Pd/Sn colloidal catalyst from solution that subsequently initiates the selective deposition of copper in an electroless plating solution. We demonstrate the fabrication of patterned copper films on a variety of both flexible and rigid polymers with minimum feature sizes of 2 microm over 2 cm(2) substrates. Measurements of electrical resistivity of copper wires fabricated on flexible poly(ethylene naphthalate) (PEN) substrates as a function of the bending radius show no negative impact on electrical performance at bending radii as small as 500 microm. Permanently damaging the PEN substrate by creasing (corresponding to a bending radius of 100 microm) results in only a modest increase in resistivity.

Selective Electroless Copper Deposition on Self-Assembled Dithiol Monolayers

The paper reports the use of self-assembled monolayers (SAMs) of dithiols to induce electroless copper deposition on a gold substrate. The metallization catalyst, palladium nanoparticles, is bound on the dithiol SAM. The assembly process is followed by IR and X-ray photoelectron spectroscopies to confirm the formation of a monolayer with bound catalyst. Electroless metallization is then carried out with a steady deposition rate of 130 nm/min. Additionally, microcontact printing of the catalyst on the SAM by poly(dimethylsiloxane) stamps is used to localize copper deposits. Resulting metallization is selective and allows for a high resolution.