Surface Flatness and Interface Stability of Ni-P Film using New Electroless Plating Method with the Emulsion of Supercri
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0968-V07-10
Surface Flatness and Interface Stability of Ni-P Film using New Electroless Plating Method with the Emulsion of Supercritical CO2 Hiroki Uchiyama, Masato Sone, Chiemi Ishiyama, and Yakichi Higo Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuda, Midoriku, Yokohama, 226-8503, Japan
ABSTRACT This paper proposes a novel coating method combining supercritical fluid technology and electroless plating in a hybrid technique. The electroless plating reactions are carried out in an emulsion of supercritical carbon dioxide (sc-CO2) and an electroless plating solution with surfactants. The Ni-P film obtained by this proposed technique was a uniform and conformal film without the pinholes and nodules. The Ni-P film fabricated by our technique was smoother and more uniform than the substrate after pretreatment and the conventional electroless plating. INTRODUCTION In recent years, the miniaturization and sophistication of electronic devices have been advancing remarkably. The thin-film formation technology is certainly a vital element in the microelectronics. Yet the increasing complexity and decreasing dimensions of devices for microelectronics are placing stringent demands on this technology—demands that have yet to be fully satisfied [1]. Electroless plating is widely used in microelectronics [2-5]. The disadvantages of electroless plating are the high viscosity of the solution and anomalous growth in the plating film because of the pretreatment condition. These disadvantages have interfered with the formation of microstructures for electronic devices and Micro-Electro-Mechanical Systems (MEMS). The key requirement for forming a uniform, conformal thin film over a complex 3-D micro/nanostructure will be to improve the transport properties. To this end, our group has developed a new technique based on the criteria mentioned above. The technique is a new electroless plating method using sc-CO2 as a solvent. Sc-CO2 enables excellent control of the intermolecular interactions, and the high density and diffusivity of the material give it an outstanding ability to convey materials to nano scale areas. Chemical Fluid Deposition (CFD) and Nano-scale Casting with Supercritical Fluid (NC-SCF) are typical technologies that exploit those features [6,7]. Sc-CO2, however, has been found to be unsuitable as a medium for plating reactions. Metal salts are generally soluble in water, but water and carbon dioxide (CO2) tend to mix poorly. The problem can be solved by emulsifying sc-CO2 and a plating solution, then adding a nonionic surfactant [8,9]. In this study we propose a novel technique for electroless plating using a dense CO2 beyond the critical point. The electroless plating reaction in this technique is conducted in an emulsion containing dense CO2. We discuss the properties of the film obtained by this method in comparison with properties of a plated film fabricated by a conventional method of electroless plating using the same electroless plating solution.
EXPERIMENT CO2 with a minim
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