A Novel Method for Low-Resistivity Metal-Interconnection by Using Metallic Functional Liquids and Catalytically Generate
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A Novel Method for Low-Resistivity Metal-Interconnection by Using Metallic Functional Liquids and Catalytically Generated Hydrogen Atoms Nguyen T. T. Kieu1, Keisuke Ohdaira1, Tatsuya Shimoda1, Hideki Matsumura1 1 School of Materials Science, Japan Advanced institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan. ABSTRACT A novel method to make low-resistivity metal lines in assembled silicon (Si) integrated circuit (IC) chips or other semiconductor chips with high-speed and low-cost is demonstrated. In the method, functional silver (Ag)-liquid (Ag-ink) which contains Ag nanoparticles (NPs) in organic solution is used to draw metal-lines in trenches formed on a plastic substrate by imprint technology. Surface energy of trenches is modified by exposing the substrate to ultra-violet (UV) light with the purpose of concentrating the functional Ag-ink into trenches by capillary effect in order to connect with electrodes of Si chips. The resistivity of such metal-lines can be lowered to 4×10-6 Ωcm by exposing the Ag metal-lines to hydrogen (H) atoms generated by catalytic cracking reaction with a heated tungsten catalyzer. X-ray photoelectron spectroscopy (XPS) proves that H atoms can remove organic compounds surrounding Ag NPs, resulting in the lowtemperature sintering of NPs as confirmed by scanning electron microscopy (SEM). The method is promising for low-cost fabricating of IC cards or other electronic devices utilizing assemble of many semiconductor chips. INTRODUCTION Low temperature formation of low-resistivity metal-lines with high speed has collected attentions for forming metal-interconnection in the assembling process of electronic devices such as IC-chips. It can be used for making IC cards, and also, it can be used in metal-line formation among many light-emitting diode (LED) chips delivered at pixel positions in large area LED displays. In addition, the metal interconnection is also significant in a rising technology for the fabrication of ultra-large flat panel displays (FPD) such as liquid crystal display (LCD) or organic LED (OLED) display in which millions of Si IC chips embedded at pixel positions control the pixels instead of conventional thin film transistors. We have investigated the formation of metal lines at trenches on a plastic substrate by using metallic functional liquid containing metal NPs dispersed in an organic solvent [1]. In particular, Ag NPs are used due to their specific advantages such as high electrical conductivity and chemical durability [2,3]. The metallic functional liquid is concentrated inside trenches for forming metal lines by covering the substrate with a hydrophobic polytetrafluoroethylene (PTFE) film and converting only trench surface to hydrophilic by ultra-violet (UV) light irradiation. However, the Ag lines obtained after drying at 40 oC have a high electrical resistivity due to remaining organic compounds in the lines. As a novel solution to lower the resistivity, hydrogen (H) atoms generated catalytically from hydrogen molecules in
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