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A method for alleviating the effect of pinhole defects in inter-metal dielectric films
摘要： As the insulation layers between two metal layers, inter-metal dielectric (IMD) films are widely used in integrated circuits (IC) and micro-electromechanical-systems (MEMS) devices. Commonly used IMD materials, such as silicon dioxide and silicon nitride, can be deposited on the metal surface using either physical vapor deposition (PVD) or chemical vapor deposition (CVD). However, due to the imperfections of deposition processes and surface cleanliness, defect-free of an IMD film cannot be guaranteed. As a common defect of an IMD film, pinhole is a tiny via of IMD film that can result in failures of short-circuit or current leakage between two metal layers and therefore decrease the fabrication yield. Reported methods for healing the pinhole defect require light-transmitting substrate, suspended structures, high-temperature annealing processes and none of them is universal. Therefore, we propose a metal etching method that uses metal etchants to etch the underlying metals through the pinholes of the IMD film. The etched area is reasonably larger than the pinhole; therefore, although the following upper metal deposition fills the pinhole, there is no electrical connection between the lower and upper metal features through the pinhole. Results of a series of experiments prove that the proposed method is feasible, valid, operable and reliable. Therefore, the proposed method is promising to be used for many IMD-based applications for either discovering pinholes or healing pinhole induced defects.
关键词： defect healing,thin film,inter-metal dielectric,pinhole,metal etching
更新于2025-09-23 15:23:52
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European Microscopy Congress 2016: Proceedings || Defects in as-grown vs. annealed rutile titania nanowires and their effect on properties
摘要： Semiconducting metal oxides play a key role in electrochemical and photo physical applications like photo catalysis and as electrode material in solar cells and Li-ion batteries. Among these metal oxides, hydrothermally grown rutile TiO2 nanowire arrays are promising as the 1 D structure possesses a large surface area and a directed electron path towards the substrate. However, the efficiency of these devices is also influenced by the defects inside the nanowires (dislocations, stacking faults, titanium interstitials and oxygen vacancies). A previous study showed that as-grown nanowires have a high density of lattice defects.[1] However, these defects can be removed by an additional annealing step. Latest findings demonstrate that hybrid solar cells where those annealed nanowires are incorporated have significantly higher power-conversion efficiency.[2] However, the removal of the defects is not fully understood so far. In our present work, transmission electron microscopy (TEM) was used to study the changes within the nanowire during annealing. TEM investigations were performed at 200 kV using a JEOL JEM-2200FS and at 300 kV using a FEI Titan Themis 60-300. First results were obtained by ex-situ TEM analysis of as-grown TiO2 nanowires and nanowires, which were annealed at 500 °C for 4 h. These ex-situ analysis confirm that both, as-grown and annealed nanowires, have the rutile crystal structure. Defects, present in the as-grown state, can be removed by the thermal treatment. Concurrently, a structural transformation inside the nanowires occurs resulting in faceted voids of several nanometer in diameter. Using tilt series from -70° to +70° in high-angle annular dark-field (HAADF) scanning (S)TEM mode and the discrete iterative reconstruction technique (DIRT)[3], a TEM tomograph was obtained, which proved that these voids are solely formed inside the nanowire and not at the nanowire surface (Fig. 1). Further analysis including electron energy loss spectroscopy revealed changes of the oxidation state at the surface region of the voids during annealing, whereas the rutile TiO2 crystal structure was maintained. HAADF-STEM in-situ heating experiments, performed in a JEOL JEM-2200FS with a DENSsolutions heating holder, enabled the direct observation of the structural changes inside the rutile TiO2 nanowires (Fig. 2). Using a slow heating ramp of 3.3°C/min, a sudden formation of these voids at around 500 °C could be observed. Heating at lower temperatures did not affect the structure of the nanowire and also an additional heating after the transformation (600°C, 1h) did not change the size and shape of the voids. These ex-situ and in-situ observations are a decisive step to explain the mechanisms involved in this process in more detail. The results of our TEM investigation were correlated to the properties of as-grown and annealed TiO2 nanowires. Here, we could show that the healing of the lattice defects upon annealing not only increased the performance of hybrid solar cells but also affects other properties of the nanowires e.g. chemical stability.
关键词： in-situ TEM,TiO2 nanowire,defect healing
更新于2025-09-16 10:30:52