Adhesion Of Copper Films Research Articles

Autocatalytic deposition of copper from modified electrolytes and its characteristics

The electroless deposition process of copper plating consisting of TEA and EDTA as complexing agents, paraformaldehyde as reducing agent, and 2-mercaptobenzothiozole as stabilizer and gelatin and animal glue as additives was investigated. The stability of the electroless copper solution was monitored by measuring the absorbance of the solution with a UV-Visible spectrophotometer and the solution was quite stable up to 15 h. The adhesion of copper films on mild steel foil was assessed by standard bend test and exhibited good adhesion. The XRD results indicate that the copper films have a (111) texture. Moreover, the additives suppress the predominant (111) plane crystal growth and increase the rate of (220) texture crystal growth. The crystal size of the copper films was calculated using the Scherrer formula from the predominant peak. SEM and AFM studies reveal that these two additives modify the crystal structure, grain size and surface morphology of the copper films. The cyclic voltammetry studies reveal that the additives are adsorbed on the electrode surface and inhibit the rate of deposition. Potentiodynamic polarization and electrochemical impedance studies reveal that the deposits produced in the presence of additives display higher corrosion resistance.

Influence of the interface width on the adhesion strength of copper films deposited on negatively biased carbon steel substrates

In order to improve the adhesion of copper films deposited by DC magnetron sputtering on carbon steel substrates, a negative bias voltage was applied to the substrate during the film deposition process. The scratch test was used to evaluate the adhesion strength of the films on the substrates. Chemical element identification and interface width measurement were carried out by Auger electron spectroscopy. The experimental results show that a variation of the bias voltage causes a change in the behaviour of the interface width similar to that of the critical load. The size of the interface width is obtained from Auger elemental depth profiles by measuring the depth of the interface between the coating and the substrate. It had a value of 45 min for an unbiased substrate and increased to 310 min at a bias of 450 V. In the latter case, the interface is relatively wide and the effects of diffusion and physical mixing of materials at the interface become preponderant. Then, the interface width decreased to 130 min at 600 V in which case it gets narrower and the phenomenon of film densification becomes prominent. In all cases, the substrate temperature generated by the bias voltage also has an effect. Moreover, it was observed in this study that the critical load increases with the size of the interface width. As a result, the application of a bias voltage contributes positively to the enlargement of the interface and consequently enhances the adhesion strength.

Adhesion Property of Copper Paste on Ceramic Radiator Fins

Ceramic radiator fins were produced by screen-printing copper paste on ceramic substrate, which could replace the traditional technique of direct bestrow copper and meet the requirements of surface mounted technology. This method could be used to manufacture high density, superior thin and micro-sized molectrons. The key processes were screen-printing copper paste, sintering and electroless plating of nickel. The adhesion of copper film onto the ceramic substrate was often reduced after the process of electroless plating of nickel, resulting in the low quality of manufacturing. In this study, we analyzed the ceramic radiator fins which were obtained by the screen-printing copper paste method and using scanning electron microscopy to examine the surface and the cross-sections of copper film and Cu/Ni film. The adhesive properties of copper film during electroless plating was studied. The corrosion resistance of copper film and sintering glass phase on alumina substrate (96%) was also studied in an electroplating bath. The study revealed that the glass phase of acidity of silicon, softening temperature, the interaction conjunction between glass phase and ceramics were important factors.

Effect of Pretreatment on the Adhesion of Copper Film on PET Substrate Prepared by ECR-MOCVD Coupled with a Periodic DC Bias

Effect of Pretreatment on the Adhesion of Copper Film on PET Substrate Prepared by ECR-MOCVD Coupled with a Periodic DC Bias

Adhesion evaluation of immersion plating copper films on silicon by microindentation measurements

Adhesion of copper films on silicon is investigated by microindentation measurements. Load–displacement tests with loads in the range of 1–1000 mN are performed on immersion plating copper films deposited on Si(100) from fluoride containing solutions, with or without adhesion-promoting additives. The results are analyzed with the aid of a composite hardness model for soft films on hard substrates. The composite Vickers microhardness is influenced by the adhesion of the copper film to the substrate: stronger adhesion corresponds to higher composite hardness and more extended deformation zone at the film/substrate interface. Thus, microhardness measurements provide a useful way to quantify the effect of solution additives (such as ascorbic acid or sodium sulfite) and heat treatment on copper film adhesion, and to rank additives accordingly.

Effects of Process Parameters on the Adhesion of Copper Film on Polyethylene Tetrephthalate(Pet) Substrate Prepared by ECRMOCVD Coupled with a Periodic DC Bias

ABSTRACTCharacteristics of Cu/C:H films on the PET substrate prepared by ECR-MOCVD coupled with a DC bias under Cu(hfac)2-Ar-H2 was investigated with special attention to process parameters. Our results showed that the Cu/C:H film has strongly adhere with the polymer substrate by chemical bonding and exhibited wide range of electrical conductivity that could be controlled by process parameters. The increase in H2/Ar ratio, microwave power and negative DC bias voltage brought on the higher pulling strength between Cu/C:H films and PET substrate. The effects of surface pretreatments of polymer substrate on pulling strength were insignificant in the range of our experimental range.

The adhesion of copper films deposited onto aluminum nitride

Good adhesion between copper film and AlN substrate is obtained when the surface of AlN is laser-irradiated prior to copper film deposition and post deposition annealing is conducted. Surface chemistry of AlN substrates before and after laser irradiation and the interfacial reactions of copper film/AlN couples were studied with Auger Electron Spectroscopy (AES) to understand the adhesion mechanisms. The surface of as-received AlN substrates was covered with a thin sheath of Al2O3. Laser irradiation removed the surface Al2O3 layers, smoothened the surface, and decomposed AlN leaving metallic aluminum on the surface. The interfacial reactions in the copper film/AlN couple are affected by the amounts of oxygen and metallic aluminum available at the interface. The adhesion mechanism is the formation of a Cu-O-Al compound at the interface of copper film/AlN couple. Since copper does not react with AlN, laser induced decomposition of AlN seems to be the driving force for the formation of the compound.

Interface structure between polyimide film substrate and copper film prepared by ion beam and vapor deposition (IVD) method

The effects of improvement of copper film adhesion prepared on polyimide film substrate were investigated. The copper thin films on polyimide films were prepared by evaporation of copper metal and simultaneous irradiation of argon gas ions with energies in the range of 0.5 to 10.0 keV. The structures at the interface between the copper films and polyimide substrates were analyzed by transmission electron microscopy (TEM). TEM analysis showed that the ion bombardment formed the mixed layer which consisted of the polyimide elements and copper atoms at the interface. The thicknesses of the intermixed layers were evaluated by using energy dispersive X-ray spectroscopy (EDXS) analysis. The thicknesses of the mixed layers were increased with an increase of ion dose and ion energy. The adhesion of copper films was evaluated by means of a peel test. The test showed that the film adhesion was dependent on the conditions of the ion bombardment, the adhesion was improved by the formation of the intermixed layer, but high energy ions, which increased the thicknesses of the intermixed layers, decreased the film adhesion. It is revealed that the high energy ions caused the carbonization at the polyimide surfaces. The improvement of the film adhesion depends on the formation of intermixed layer but also on the carbonization at the polyimide surface.

Improvement of the adhesion to polyimide substrates of copper films prepared by an ion beam and vapor deposition (IVD) method

Copper films were prepared by evaporation of copper metal and simultaneous bombardment by nitrogen ions with ion energy in the range 0.2 keV to 2.0 keV. The adhesion of copper films was improved by increasing the ion energy of the nitrogen ions. The copper film prepared with 2.0 keV nitrogen ions had the strongest adhesion. The structure of the interlayer between the copper film and the polyimide substrate was evaluated by transmission electron microscopy. The copper atoms were diffused into the polyimide substrate by nitrogen ion bombardment. The chemical states of the polyimide film surface and the chemical binding states at the interlayer were analyzed by X-ray photoelectron spectrometry. Nitrogen ion bombardment caused carbonization of the polyimide surface, and the irradiated nitrogen ions combined with the carbon atoms of the polyimide film. At the interlayer, X-ray photoclcctron spectrometry showed that copper compounds were formed by nitrogen ion bombardment. It was considered that the increase in adhesion due to nitrogen ion bombardment could be attributed to a combination of the anchor effect caused by the diffusion of copper atoms into the substrate and the formation of copper compounds at the interlayer.

The deposition and adhesion of copper films on smooth polymer surfaces

Electroless copper plating (ECP) of polymeric surfaces has found several important applications, such as the metallization of epoxy glass laminates (EGL) employed in the production of printed circuits. In this process EGL boards are degreased and then prepared for metallization by preliminary oxidative etching with chromic acid and then surface activation for ECP. Such activation is typically achieved with catalysts derived from palladium and stannous chlorides or by the use of different photochemical processes [1-4]. The activated boards are then metallized in an electroless copper bath, which contains a copper source, a complexing agent, a reducing agent, a stabilizer and a pH buffer [5]. In order to produce printed circuits on microscopically smooth polymer surfaces, capable of high-frequency signal transmission, we have investigated the possibility of forming adherent copper films on polymer surfaces, which have not been subjected to chemical or mechanical roughening. In this study we have evaluated the suitability of several commercial polymers and blends of polymers for this purpose. We have been able to demonstrate that chemical interaction between the copper film and certain polymer surfaces contributes to the adhesion exhibited by the copper. The substrates chosen for electroless copper plating were thin glossy polymeric films cured on EGL boards. Brominated epoxy and Novolac resins (DER-531 from DOW Chemical Co. and EPIPHEN ER-825-A from Monomer Polymer Laboratories) were used as unblended polymer coatings. These epoxy resins were also blended with poly(4-vinylpyridine) (P4VP) (molecular mass 20 000) at weight ratios of epoxy to P4VP of 10:1, 5:1, 2:1, 1:1, 1:2 and 1:4 and these blends were then spin-coated on EGL boards and cured. The addition of P4VP to the epoxy resin aimed at increasing the copper adhesion to the smooth surface, since the pyridine group was expected to be the preferred binding site for copper [6, 7]. The resulting coatings were glossy and without microdefects as observed by optical and scanning electron microscopy (SEM). The thickness of the layers were estimated by SEM analysis to be about 5 gm. Freshly cured coatings were activated for electroless plating by a photochemical process [3, 4]: a solution of the metal salt (e.g. copper acetylacetonate), photosensitizer and solvent was applied to the polymer surface, which was then irradiated with

Enhanced Adhesion of Copper Films to SiO2, PSG and BPSG by Refractory Metal Additions

ABSTRACTCopper films generally exhibit poor adhesion on dielectrics. It has been shown that the addition of refractory metals promotes adhesion via an interfacial reaction or better wetting to the dielectric. We investigate the adhesion of Cu-refractory metal (Cr, Ti) alloy films and bilayers on various silicon oxide substrates (SiO2, PSG, BPSG) after annealing in the temperature range 400-600°C by conventional furnace using N2/H2 forming gas. Rutherford backscattering spectrometry (RBS) was used to determine the interfacial reaction characteristics. The efficacy of a variation of the standard Scotch™ tape testing was evaluated. We found that the combined Scotch™ tape/scribe adhesion test revealed excellent qualitative bonding information and could be correlated well to RBS characterization. We were able to optimize the sample configurations and chemical compositions to achieve the best adhering film.

Optimised Nitrogen‐based Atmospheres for Copper Thick Film Manufacture

This paper reports the results of development work conducted on nitrogen‐based atmospheres in order to improve the firing of copper thick film systems through continuous furnaces. The proposed solution is particularly suitable for industrial production conditions since it allows variations of the material quantity processed per unit time, resulting not only in an improvement in quality but also in productivity. Such improvements have been achieved by using a new gas distribution system which provides both zone control and regulation of oxygen additions in the nitrogen furnace atmosphere. An efficient set‐up of this system has become possible thanks to precise control of the oxygen profile in relation to the temperature cycle, taking into account various inks' characterisation, and owing to an extensive study of the effects of oxygen additions on copper thick film properties. The solution was tested in a muffle‐lined belt furnace with several commercial dielectric and copper inks, and for increasing oxygen additions into the furnace preheat zone. Different sample patterns were designed to test both monolayer and multilayer systems. The test programme includes measurements of resistivity, bondability, solderability, dielectric breakdown voltage and adhesion of copper films on alumina and on dielectric layers before and after ageing. Ink characterisation by thermogravimetry and by several gas analyses has confirmed that the organic vehicle removal mechanism under nitrogen atmospheres doped with oxygen is a burnout. Indeed, significant oxygen consumption occurs within the temperature range of the removal, as a function of the amount of ink processed. Oxygen additions in the furnace burnout zone greatly improve both the dielectric breakdown voltage and the adhesion of copper on alumina and on dielectric (especially after ageing), while sheet resistivity, wire bondability and soft solderability are not altered below a defined O2 level. It is therefore possible to determine an optimum oxygen addition range for which the thick films fired under such conditions will have the best characteristics. This optimum oxygen window is achieved thanks to a new regulation system which operates whenever variations occur in the quantity of paste processed.

Oxygen Reactive Ion Beam Etching on Polyimide to Enhance Copper Film Adhesion

AbstractPolyimide(PI) films were modified by O2 reactive ion beam etching(RIBE) to make special surface features which enhance the adhesion of copper films. The top plane and the cross-sectional plane of PI films were changed to a grass-like structure and a plate-like structure, respectively. The reason for these surface morphological changes is presumably due to the structural inhomogeniety of PI. XPS studies show that the O2 RIBE oxygenates the PI, resulting in an increase in oxygen and a decrease in carbon and nitrogen. The adhesion of evaporated copper on the O2 RIBE modified PI was substantially increased. In this study, the maximum peel strength of modified PI, 70 grams/mm, is more than 25 times larger than that of the unmodified PI, 2.5 grams/mm. Two types of failure mechanisms were observed with various ion doses:adhesive failure at the Cu/PI interface and at very large doses cohesive failure at the roots of the thin and long grass blades of PI.

Adhesion of copper films on ABS polymers deposited in an internal magnet magnetron sputtering system

Adhesion of copper films on ABS polymers deposited in an internal magnet magnetron sputtering system

Adhesion of copper films on ABS polymers deposited in an internal magnet magnetron sputtering system

In order to metallize ABS polymer surfaces without electroless plating, thin copper films were deposited by an internal magnet, coaxial cylindrical magnetron sputtering system. The adhesion of the metallized layers was evaluated by measuring peel strength. Average strength higher than 1 kg/cm was obtained with an appropriate process of metallizing. Several factors, which might influence the adhesion, such as conditions of sputtering, pretreatment of the polymer before sputtering, and the constitution of the polymer were studied. Oxygen plasma treatment before the metallization was found to improve the adhesion. Topographical change of the polymer surface was observed with SEM for the oxygen-plasma-treated substrate. Also, surface change in atomic constitution and chemical bonding energies were detected by ESCA and ir spectroscopy. It was found that the peel strength was higher for substrates of smaller butadiene content, which implied that tensile strength of polymer affected the peel strength of the metallized layer.