The adhesion between the electroless seed layer and the buildup film substrates was studied. After the buildup film was laminated, the buildup film surface was modified by a desmear treatment from 0 to 30 min, and electroless Cu or electroless Ni-P was plated as the seed layer on the buildup film. The Cu was then electroplated, and the post curing was carried out at 180 • C for 2 h before or after Cu electroplating. The adhesion strength between the electroless seed layers and the buildup film substrates was measured by the 90 • peel test. Increasing the desmear treatment time made the buildup film surface rougher, and consequently enhanced the adhesion strength of the electroless Cu and electroless Ni-P to the film. Under the same conditions, the electroless Ni-P specimen showed a higher peel strength than the electroless Cu specimens. Post curing significantly increased the adhesion strength due to the increased ductility of the metal layer after heat-treatment. In addition, the peel strength decreased as the thickness of the seed layer increased, which was also related to the mechanical properties of each metal layer.Electroless metallization is widely used for the fabrication of circuit patterns in microelectronics because electroless plating can deposit on wide variety of materials including insulating surfaces such as glass, oxides, and polymers, without the need for any electrical equipment. 1,2 However, the electroless plating of metal on polymer substrates is often limited by weak adhesion strength caused by structural incompatibility between the substrate and the metal layer. The finer dimensions of the typical interconnection pattern obtained from the buildup film has made even the reliability of packages critical; therefore, good adhesion of the metal on the buildup insulating films is essential. 3,4 Cu metal has been widely used in semiconductor manufacturing due to its high conductivity and low cost, 5,6 and electroless copper is usually deposited on the buildup insulating film as a conducted seed layer for subsequent Cu electroplating. In order to improve the adhesion of plated copper on the polymer film, many processes involving plasma activation followed by surface graft polymerization have been carried out. 7,8 However, compared to plasma processes wet chemical treatments are preferred industrially due to the much lower cost. 3,9 A typical wet chemical processes for the pretreatment of buildup film consist of three steps: swelling, desmear and neutralization. 10 After pretreatment, mechanical interlocks that utilize anchoring sites on the roughened surface of the buildup insulating film enhance adhesion. 3,9,10 Electroless nickel has also been studied as a potential conducted seed layer deposited on buildup film for Cu electroplating. 8,11 However, even though many techniques has been developed to enhance the adhesion of the metal layer to the insulating substrate, previous research has mainly focused on the interfacial energy effect such as chemical bonding. However, the mechanical effect of th...

Nanocomposites consisting of Cu or Cu2O nanoparticles in various polyimide (PI) films were successfully prepared using polyamic acid (PAA) and Cu powders. Cu powders were dissolved into PAA solutions, and the solutions were spin-coated onto the substrates. Cu or Cu2O nanoparticles were formed in PI film by curing in a reducing or inert atmosphere, respectively. The Cu nanoparticles were transformed to Cu2O nanoparticles by post-heat treatment in an oxidizing atmosphere after curing in a reducing atmosphere. Transmission electron microscopy showed that uniform, round Cu2O nanoparticles 6.0 nm in diameter were dispersed in the PI film by post-heat treatment. The addition of Cu2O nanoparticles in the 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-4,4'-oxydianiline (6FDA-ODA) PI film enhanced the refractive index of the 6FDA-ODA PI film from 1.60 to 1.72 at 633 nm, and the transparency of the nanocomposite film was about 70-90% in the visible region and remained around 90% beyond 550 nm.

Cu and Cu2O nanoparticles were fabricated in polyimide by curing the stacked polyamic acid/Cu/polyamic acid on Si wafer and post heat treatment. Nanoparticle distribution in polyimide (a monolayer of vertically aligned nanoparticles or the randomly dispersed nanoparticles) can be controlled by changing the reactivity of Cu with PAA and curing atmosphere. About 6-7 nm sized Cu or Cu2O nanoparticles were observed in the polyimide film. The capacitance-voltage curves were measured with Al/particles in polyimide/p-Si(100) specimens at 300 K, and the capacitance hystereses were observed at different sweep voltage ranges, which indicates that Cu2O or Cu nanoparticles can be utilized in next generation flash memories.

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