Study On Micro-nano Metal Wires Interconnect By Nanoimprint Lithography With Pseudoplastic Metal Nanoparticles Fluids

Pattern transfer is one of the core technology of the microelectronic industry and it has been realized by using optical lithography of decades. However, the resolution of optical lithography is limited by the Rayleigh formula. With the decrease of feature sizes, especially in under 14 nm node, optical lithography has been difficult to achieve the high resolution requirement. Among the next generation of alternative patterning method put forward by the Technology Roadmap for Semiconductors(ITRS), nanoimprint lithography has strong competitiveness and broad development prospects, due to its high resolution, high fidelity, high yield and low cost features.Metal micro-nano structure has been widely used in recent years. Metal nanoparticles can realize metallization at low temperature due to its high surface energy, which can avoid the high temperature process damage of the flexible substrate. The combine of metal and nanoimprint process has the obvious advantages in production, costs, and resolution in the preparation of metal microstructure. In the pseudoplastic metal nanoparticles fluid imprint, thermal treatment is needed to translate the metal nanoparticles to continuous metal structure after the demolding process. It is important or ensure the integrity of metal microstructure morphology and good electrical conductivity during the thermal treatment.Various analytical methods such as theoretical derivation, computer simulation and experimental research are used to investigate the morphology and electrical conductivity of the metal micro-nano structure after the thermal treatment. The thermal treatment process can be divided into two stages: solvent evaporation and metal nanoparticles sintering. Through the theoretical derivation and analysis of two-sphere sintering model, the optimal parameters for the materials property and thermal treatment are provided. Grain boundary diffusion causes the shrinkage of sintered body, which reduces the fidelity of imprinted micro-nano structure. In order to avoid the shrinkage in horizontal direction, uniaxial stress is proposed to load on the sintered body during sintering process. The sintering behavior of metal nanoparticles is studied through the molecular dynamics simulation. It has been proved that, the sintered body won’t shrink or expand in the horizontal direction by adjusting the sintering time and the magnitudes of uniaxial stress.Ag nanoparticles prepared by chemical reduction method are deposited onto a Si substrate to form Ag microwires. The particles are coated by organic shells to prevent aggregation or agglomeration and the mean size of it is 30 nm. After sintering at 200 oC for 1 h, the grain size increases to 130 nm, the Ag wires exhibit a low resistivity of 2.29???cm, which is 1.5 times that of the bulk, and the corresponding grain boundary reflection coefficient is 0.4.