Photochemical Nucleation of Copper on Polyimide Surface with 10ns Laser Irradiation - Growth of Copper Metal on Copper N
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Photochemical Nucleation of Copper on Polyimide Surface with 10ns Laser Irradiation - Growth of Copper Metal on Copper Nuclei and Deposition of SiO2 film on Copper Metal -
H. Tokunaga, Y. Ogawa and M. Murahara
Department of Electrical Engineering, Tokai University, 1117 Kitakaname, Hiratuka, Kanagawa 259-1292, Japan Abstract Copper atoms were substituted on the polyimide surface in the presence of CuSO4 solution with only 10ns single shot of ArF laser. Then, we have succeeded in substituting copper atoms with dangling bonds of carbon cross- linking with oxygen atoms. In this study, we placed fused silica glass on the polyimide surface firstly, and poured the sulfate solution into the gap between the silica glass and the film, forming a thin liquid layer. Then, one shot of circuit patterned ArF laser light having 42mJ/cm2 was irradiated vertically onto the sample. The photon is dissociating and exciting the copper sulfate solution and the polyimide surface. The dissociated copper atoms form the C-O-Cu bond with active oxygen on the polyimide surface. However, we were able to grow a copper thin film of about 24µm after immersing the sample into the electro less plating solution for 15 minutes at 60℃. On the other hand, we have laminated transparent and low dielectric constant SiO 2 film at room temperature on polyimide surface by using Xe2 * excimer lamp. Then, the copper film deposited on polyimide film and the piece of silicon were placed in the reaction chamber with mixing NF3 and O2 gasses in the ratio of 10:1 ; total pressure 330 Torr. Then, Xe2 * excimer lamp was irradiated for 20 minutes. By the photochemical reaction, SiF 4 and NO2 were produced. The adsorbed SiF 4 on copper and polyimide surface of one molecule layer and NO2 up react with NO 2 , and growth SiO 2 film on the sample surface. A chain reaction of film formation is brought about by these two chemical reactions of adsorption and oxidization. By this film formation film thickness was not more than 600Å after 20 minutes with the Xe2* excimer lamp irradiation in order to lose in SiF 4 . Then, the silicon was supplied, and insufficient SiF 4 was filled by ablating the silicon wafer by focused ArF excimer laser beam.
Introduction All aromatic group polyimide have characteristics of chemical resistance, heat resistance and radiation resistance and it has been extensively used for printed circuit board. This printed board has been fabricated by either sticking the copper foil with adhesive agents or heat welding after making the copper foil surface rough. Thus, even the printing board might generate high
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frequency wavelength noise due to rough interface between copper and polyimide or irregularity or dielectric constant between copper and adhesive agents. Therefore, flat interface between copper and polyamide have been insisted. Then, we have succeeded in substitution of copper atoms on polyimide with photochemical reaction of ArF excimer laser. And, Cu film was grown on the Cu nuclei with this polyimide immersing in electro less plating solu
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