Formation Of Copper Films Research Articles

Unraveling the multilayer structure formation mechanism of copper coating for the metallization of poly para-phenylene terephthalamide fibers

The Cu-clad PPTA fibers (Cu@PPTA), which combined conductive coating with high-performance fibers, have been successfully prepared through a simple and controllable chemical copper deposition process. Chemical phase analysis indicated that carboxyl group was successfully obtained by breaking amide bond via ultrasonic etching (UE), and Pd element after sensitization and activation was adsorbed on the surface of PPTA fibers, and the catalytic palladium accounted for 50 at%. Moreover, it was also confirmed that the state of metal coating was pure metal. Microstructure characterization demonstrated that the nanoscale cracks were achieved after UE treatment and the copper nanoparticles were nearly spherical but irregular in shape. Additionally, the growth of copper crystal was nonlinear, and the formation of copper film might be controlled by capillary force. The possible formation mechanism of copper film on the surface of PPTA fibers was proposed, including nucleation stage, planar growth stage and multiplanar growth stage.

Stainless steel substrate pretreatment effects on copper nucleation and stripping during copper electrowinning

The effects of surface pretreatment of 304 stainless steel (SS) substrates on copper film formation, adhesion, and purity obtained by galvanostatic electrodeposition at a current density of – 30 mA cm−2 are presented. The polished substrate produced more copper nuclei, resulting in an increase of the adhesion as compared to chemically oxidized SS substrate. The adhesion of the copper deposits was characterized by a Nano-scratch tester (NST). The nucleation behavior is associated with the flatband potential of the SS surface, which was derived from capacitance measurements. The grain size of copper deposits was characterized by field emission scanning electron microscopy (FESEM). Copper grains were smaller on the polished SS with a size of less than 1 µm after 5 min of electrodeposition. High-purity copper deposits with < 1 ppm S (detection limit) were obtained on the oxidized SS substrate compared to 2.5 ppm for the polished SS substrate. Atomic force microscopy (AFM) measurements showed that the copper deposits were 25% less rough on the polished SS as compared to the oxidized SS. The results indicate that the obtained purity of the copper deposit relates to the grain size of the deposit, rather than the initial surface roughness. In the context of industrial electrowinning, high adherence to the polished substrate could increase the operation time of the copper cathode stripping. Hence for electrowinning from copper sulfate electrolytes, oxidizing the SS surface prior to deposition could lead to higher purity along with enhanced stripping.

Copper film formation on metal surfaces with 100 W blue direct diode laser system

In laser cladding, in the wavelength range of blue, light absorptivity of copper is much higher than that in the wavelength range of infrared. The authors developed the laser cladding system with the continuous wave blue direct diode laser (blue DDL). The system consists of a number of fiber-coupled blue DDLs with a maximum power of 20 W at a wavelength of 445 nm, a focusing lens, and a powder feeding nozzle. In this study, the authors investigated the fundamental characteristics of the multiple blue DDL system and formed copper film on 304 stainless steel plate using the system.

In-Situ Electrochemical-AFM and CV Measurement Study on the Nucleation and Growth in Reduced Graphene Oxide Electrode Contacts

Electrochemical atomic force microscopy (EC-AFM) is a composite electrochemical analysis method. A lot of researches have been done on this, and it has been applied in many fields. EC-AFM was composed of EC-Cell, electrochemical analysis system, AFM and so on. For electrochemical analysis system and AFM to be analyzed at the same time, EC-Cell with a suitable structure is required. In this study, we made an electrochemical system in AFM with CV measurement system for in-situ observation of the elctrochemical reaction. Based on the developed EC-Cell, EC-AFM experiment system which was developed by constructing EC-AFM analysis system and numerical analysis method were proposed and tested and studied. First, we confirmed the EC-AFM analysis procedure and analysis method developed by observing copper electrochemical corrosion process. Second, electrochemical reduction characteristics of graphene oxide were studied using electrochemical analysis. An electrochemical atomic force microscope (EC-AFM) was used to study the reaction of wet electrode in various electrolyte, when the reaction corresponding to what occurs at the electrode of an electrode deposition. We observed wet plated solar electrode process during cyclic-voltammetry (CV) measurement with atomic force microscopy, and then were obtained useful continuous in situ images of the surface morphology. These AFM images dynamically showed the surface morphology change during the electro deposition. It was confirmed that initial nucleation of electrode crystals occurs after supersaturation, and that the slow dissolving on CV. AFM images of the electrode crystal morphology were compared with those in a different potential sweeping rate and electrolyte concentration at CV. We also compared the difference in AFM images and SEM images that were observed on the same electrode sample. Finally, we investigated the copper electrochemical deposition process in reduced graphene oxide using EC-AFM and observed the copper film formation process on reduced graphene oxide surface. As a result, the EC-AFM analysis system was constructed and tested, and the electrochemical characteristics on the reduce graphene oxide surface were observed.

Formation of copper film using various powders by aerosol deposition method

Formation of copper film using various powders by aerosol deposition method

Synergetic Effect of Blended Alkylamines for Copper Complex Ink To Form Conductive Copper Films.

Cu(II) complex ink consisting of copper formate (Cuf) and a primary alkylamine could yield highly conductive copper films at low heating temperatures without a reducing atmosphere. A synergetic effect of the blended alkylamines on the formation of conductive films was observed. It was found that blending two types of amines with different alkyl chain lengths as ligands could improve the conductivity of copper films, compared with using one of these amines alone. The decomposition mechanism of the Cuf-amine complex and the role of amines with different alkyl chain lengths were investigated. It was found that the decrease in the decomposition temperature and the formation of copper films were attributed to the activating effect and capping effect of the amine, and these two effects were dependent on the alkyl chain length. The relative intensity of the dual effects determined the decomposition rate of the complex and the nucleation and growth of particles. The use of blended amines with different alkyl chain lengths as ligands could balance the two effects and lead to appropriate nucleation and growth rates, so that densely packed copper films with low resistivity could be obtained at low heating temperature in a short time. The Cuf-butylamine-octylamine (Cuf-butyl-octyl) ink with 1:1 molar ratio of the amines showed the best performance. The understanding of the synergetic effect could provide guidance to the design of copper complex inks to control the morphology of the films.

Chiral surface formation of copper films by magnetoelectrochemical etching

Chiral surface formation of copper films by magnetoelectrochemical etching

Using an Office Inkjet Printer to Define the Formation of Copper Films on Paper

A low-cost fabrication process for forming conductive copper lines on paper is presented. An office inkjet printer was used to deposit desired patterns of silver nitrate and tannic acid solutions sequentially on paper. Silver nitrate was instantaneously reduced in situ on paper by tannic acid at room temperature to form silver nanoparticles, which acted as catalysts for the subsequent electroless deposition of copper. The copper films were 1.8 μm thick, and the sheet resistance of the copper film on paper was 9 Ω/□. A dual monopole ultrawide band antenna was fabricated on paper and its performance was equivalent to that of a similar antenna fabricated on a copper-film covered Kapton substrate using conventional lithographic processes. The paper-based conductive copper films fabricated using the facile process presented herein will aid the development of low-cost flexible circuits and sensors.

Preparation of Nanostructured Superhydrophobic Copper and Aluminum Surfaces

Preparation of nanostructured superhydrophobic surfaces requires both an optimum roughness and low surface energy. Application of a direct voltage between two copper plates immersed in a dilute ethanolic stearic acid solution transforms the surface of the anodic copper electrode to superhydrophobic due to the formation of micro-nanofibrous low surface energy flower-like copper stearate as confirmed by scanning electron microscope (SEM). Nanostructured superhydrophobic aluminum surfaces have also been prepared by electrodeposition of copper films on aluminum surfaces followed by electrochemical modification by ethanolic stearic acid. The X-ray diffraction (XRD) analyses confirmed the formation of copper films on aluminum substrates. The electrodeposited copper films are composed of microdots of copper whose density increases with the decrease of deposition potential as observed by SEM. The deposited copper microdots on aluminum substrates were electrochemically modified to low surface energy copper stearate nanofibres to obtain superhydrophobicity. The copper films deposited at potentials above-0.6 V did not exhibit superhydrophobic properties. However, the copper films deposited at potential-0.6 V and below exhibited superhydrophobic properties with water drop rolling-off those surfaces.

Is the (hfac)Cu(I)–(tmvs) bond intrinsically weak?

Density functional theory studies were performed to study the structure and bonding of (hexafluoroacetylacetonate)-copper(I)-(trimethylvinylsilane) [Cu(hfac)(tmvs)], an ideal and important Cu(I)-CVD compound. A popular three-parameter hybrid density functional (B3LYP) with 6-311+G(d,p) and an effective core potential included LanL2DZ basis set was utilized for this purpose. The (hfac)Cu–(tmvs) bond energy of approximately 30 kcal mol−1 obtained at the B3LYP/6-311+G(d,p) level of theory reveals that the Cu–olefin bond in Cu(hfac)(tmvs) is not as weak as previously estimated/assumed and, hence, that the substrate plays a vital role in copper film formation from Cu(hfac)(tmvs). Bonding analysis reveals that fairly strong (hfac)Cu–(tmvs) bonding is the result of DCD-model σ-donation and π-back-bonding between the copper and tmvs in Cu(hfac)(tmvs).

Seedless micropatterning of copper by electroless deposition on self-assembled monolayers

A novel approach for direct electroless (EL) patterning of copper films without catalysts has been developed. In a special electroless solution employed in the present study, the formation of copper particles was observed and the negatively charged surfaces were confirmed by zeta potential measurements. The conditions of the solution (ionic strength, pH, temperature, additives etc.) greatly affected the composition of the resulting precipitates. Results showed that pure copper films formed in EL solutions with pH higher than 7.3. A self-assembled monolayer (SAM) terminated with either NH2 or OH headgroups was employed as a template to enhance the selective adhesion of copper particles. As expected, many particles were deposited on the positive NH2-SAM by electrostatic attraction, while few particles were deposited on the negative OH-SAM due to repulsive interaction. The measurement results obtained by AFM, QCM, XRD and optical microscopy confirmed the selective formation of copper films on the NH2-SAM. Subsequently, micropatterns of copper films with high resolution were successfully produced. The deviation in the thickness of the deposit reached 110 nm between the NH2-SAM and OH-SAM after 90 min soaking in the EL solution. Current–voltage characteristics revealed relatively high resistivity (0.3 mΩ cm) of the formed copper film on the NH2-SAM, which can be ascribed to the poor connectivity among particles.

A novel Cu(II) chemical vapor deposition precursor: Synthesis, characterization, and chemical vapor deposition

A nonfluorinated β-diketonate precursor, bis(t-butylacetoacetato)Cu(II) or Cu(tbaoac)2, was synthesized by modifying bis(dipivaloylmethanato)Cu(II) or Cu(dpm)2 for chemical vapor deposition (CVD) of copper. The complex was characterized by a variety of techniques, such as melting point determination, mass spectrometry, infraredspectroscopy, elemental analysis, thermogravimetric and differential thermal analysis, and x-ray diffraction. Cu(tbaoac)2 has a higher sublimation rate than Cu(dpm)2 over the temperature range 90–150 °C. Pyrolysis of Cu(tbaoac)2 leads to the formation of copper films at 225 °C, compared to 330 °C for Cu(dpm)2. As-deposited copper films ere highly dense, mirror-bright, adhered strongly to SiO2, and showed a resistivity of less than 2.9 μΩ-cm at a thickness as low as 1300 Å. A possible mechanism for the decomposition of the ligand tbaoac has been proposed.

Low-Pressure Chemical Vapor Deposition of Cu−Pd Films: Alloy Growth Kinetics

We have examined the formation of copper films alloyed with small quantities of palladium. Independent control studies of palladium and copper deposition from palladium bis(hexafluoroacetylacetonate) [Pd(hfac)2] and (hexafluoroacetylacetonato)copper(I)(vinyltrimethylsilane) [(hfac)Cu(I)(vtms)], both in the presence and absence of H2, were carried out. The growth kinetics for both metals were feed-rate-limited under similar reactor conditions. No significant variation in deposition rate (100 nm/min, Pd; 100−500 nm/min, Cu), morphology, resistivity, and purity of the copper films was observed due to the addition of H2. Simultaneous introduction of both precursors yielded Cu−Pd alloy films. The absence of pure palladium grains was confirmed by X-ray diffraction analysis which showed binary solid solutions (Cu99.5Pd0.5−Cu80Pd20) as the only crystalline phases. Auger electron spectroscopy analysis showed a significant reduction in the palladium content of the films as compared to that expected on the basis of ...

Copper film formation using electron cyclotron resonance plasma sputtering and reflow method

A subhalf-micron gap filling process for copper (Cu) films was developed by using an electron cyclotron resonance (ECR) plasma sputtering method. The achieved Cu film had a resistivity as low as that of bulk Cu and an excellent, void-free filling property in a 0.5-μm-wide trench. This result is because the distance between the target and wafer was longer than conventional sputtering; the plasma could be generated at low pressure (&amp;lt;1 mTorr); and the ECR plasma sputtering method generates a highly anisotropic particle flux of Cu. Then, a reflow process of the Cu films deposited by using an ECR plasma sputtering method was tried. The reflow phenomenon was observed and the filling property was improved; void-free filling in a 0.4-μm-wide trench was achieved. Moreover, a Cu interconnection of 0.5 μm linewidth was fabricated by a chemical mechanical polishing method without dishing, scratching, and erosion.

Formation of CVD copper films investigated by surface analysis and reflectivity

In this contribution we investigate the formation of copper films by chemical vapor deposition on silicon using the copper (II) bis(acetylacetonate) precursor. From Auger spectroscopy and ion sputtering, the chemical composition of the film is determined. We show that the carbon is on the CVD copper surface and plays an important role in stabilizing the silicon copper interface. The formation at 300 o C of a metallic copper film on silicon instead of copper silicide is explained by the presence of carbon. The resistivity versus temperature has a behavior similar to the one observed on an evaporated copper film. Its value is for the best film two times higher than for pure copper. We present the evolution of the reflectivity of the film measured in situ during the MOCVD growth. Following the evolution of the reflectivity during the MOCVD process can give information on the nucleation process, the growth rate and the evolution of the roughness of the film

Formation and properties of copper film on Tl-(Pb, Bi)-Sr-Ca-Cu-O superconductor by electrodeposition from aqueous solution

A new process of electrodeposition in saturated cupric sulphate aqueous solution was successfully developed for the formation of copper film on a high-Tc, three Cu-O layered Tl-(Bi, Pb)-Sr-Ca-Cu-O superconductor substrate surface for the first time. Scanning electron microscopy and electron micro-probe analysis were used to investigate the morphology of the substrate surface and the composition of the copper superconductor interface. After the electrodeposition process, no evident changes in the temperature dependence of electrical resistivity were found by four-point probe measurement. The difference of magnetic properties before and after electrodeposition was investigated from magnetization measurements. Almost no degradation of the bulk properties was observed from the susceptibility data. The copper-superconductor contact was confirmed to show Ohmic behaviour by two-pointI–V characterization at liquid nitrogen boiling temperature.

Plasma-Enhanced Chemical Vapor Deposition of Copper

Plasma enhanced copper chemical vapor deposition (CVD) using acetyl-acetonato copper as a source compound is investigated for VLSI metallization. Results show that electrical resistivity and film morphology are greatly dependent on substrate temperature, and that plasma enhancement results in smooth copper film formation. Hydrogen is essential for reducing oxygen and carbon incorporation of copper film. A smooth surface film of low electrical resistivity (1.8 µΩcm) is obtained by plasma-enhanced CVD with hydrogen carrier gas at the substrate temperatures between 200°C and 280°C. Investigation of the step coverage of the film results in the coverage of the trench being superior to that of the sputtering method.

Ultrahigh-Vacuum Measurement of the Optical Properties of Copper*

An ultrahigh-vacuum system has been designed and built in which metallic films may be evaporated and their optical properties measured in situ. This system has been used in the formation of copper films and the study of their aging histories. A control sample formed and held at 10−5 Torr displayed a relatively constant value for the dielectric constant with time. Samples held at 10−8 Torr showed a sharp decrease in this parameter during the first 5 h after evaporation.