Structural defects formed on ͕111͖ planes of BaTiO 3 during the degradation of high performance multilayer Ni-BaTiO 3 X7R ceramic capacitors are studied using transmission electron microscopy and electron energy loss spectroscopy ͑EELS͒. Regular pseudocubic barium titanate grains are present in as-produced ͑virginal͒ base-metal electrode capacitors. However, there is a coexistence of regular, modulated, and long-range ordered structures in intentionally electrically degraded devices. The EELS analysis demonstrates that the concentration of oxygen vacancies in barium titanate with modulated or ordered structures is higher than that in the regular perovskite grains. The clustering or accumulation of oxygen vacancies in the structural framework of BaTiO 3 gives rise to the formation of new metastable structures. These observations are consistent with earlier models for degradation, but demonstrate that the details of the process may be more complex than originally assumed. Here we introduce new details on the nature of the reduction process and the manner in which the lattice accommodates the enhanced oxygen vacancy concentration towards the failed regions of the capacitors and in the vicinity of the ''blocking'' cathodic electrodes.
There is an ongoing need to develop new technologies to enable further down‐scaling of layer thicknesses in multilayer ceramic devices, for example, in multilayer capacitors (MLC). Microcontact printing of chemical solutions of both the dielectric and electrode layers was explored as an economical means of preparing patterned thin films for MLC without requiring photolithography. For this purpose, methanol/acetic acid‐based BaTiO3 solutions were spun onto polydimethylsiloxane stamps, printed onto substrates, pyrolyzed, and crystallized. LaNiO3 was used as a prototype electrode that could also be microcontact printed. The line edge roughness produced this way was on the order of a tenth of a micrometer, which should enable very small margins. The printed layer thickness was also very uniform. Microcontact printed capacitors with a single dielectric layer were fabricated and found to have dielectric constants >800 with loss tangents <2%. Alignment between subsequent layers is readily achieved. Multilayer dielectric/electrode stacks could be fabricated without cracking or delaminations. Consequently, microcontact printing appears to be a viable potential means of preparing MLC with layer thicknesses in the range of ≤0.2 μm.
A microwave sintering technique has been developed for base-metal electrode (BME) multilayer ceramic capacitors (MLCCs). Commercial green chips of size 0603 MLC with nickel electrodes were sintered in a microwave field. With a specially designed susceptor/insulation package to optimize coupling and uniformity of heating, a number of sintering experiments were conducted in the temperature range of 1200 to 1250 • C in a multimode microwave cavity operating at 2.45 GHz under a partially reducing atmosphere. Microstructure of the microwave processed MLCCs was investigated with both SEM and TEM techniques. The dielectric properties of the microwave sintered MLCCs were measured and compared with those sintered using conventional process at 1320 • C and lower pO 2 's ≈ 10 −9 atms. The results demonstrate that nickel electrodes remain metallic after microwave sintering even though the pO 2 's were relatively high and would thermodynamically favor NiO. The microwave sintered samples showed a dense, fine and uniform microstructure. The properties of the microwavesintered samples were comparable to the conventionally sintered samples. The microwave processing was found to have enhanced sintering kinetics of the BME MLCCs, lowering sintering temperature by about 100 • C and also the processing time by about 90%.
Metallization layers with thicknesses well below a micron are needed for future generation multilayer ceramic devices such as capacitors and integrated passive components. In many cases, the limiting thickness for the electrode is governed by dewetting of the metals from the oxide surface. Therefore, thin, stable metallization layers with low electrical resistivities that can survive high processing temperatures are of interest for these applications. For this purpose, Cu films prepared from 2-methoxyethanol-based solutions were developed using adhesion promoters such as Ti, Zn, and Zr. The solutions were spun onto BaTiO 3 /SiO 2 /Si or SiO 2 /Si substrates, pyrolyzed, and annealed in a reducing ambient. The microstructure of films prepared in this way was found to be uniform and continuous at thicknesses as low as 80 nm. Cu films modified with 15 mol% Zr had electrical resistivities of about 16-17 μΩ-cm after 500°C annealing and 5-6 μΩ-cm after annealing at 900°C in a reducing ambient.
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