A Ge thin film deposited by chemical vapor deposition (CVD) was used to obtain a uniform bonding between Au and Ge films for applications of wafer level packages (WLPs). This Ge CVD thin film showed selective growth on Au and Cu metals when the substrate has both metal and oxide. A one-step and two-step Ge deposition followed by eutectic bonding method was employed to bond the wafers. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy equipped with an energy dispersive spectroscopy (FESEM-EDS), atomic force microscopy, high resolution Field emission transmission electron microscopy, IR inspection tool and secondary ion mass spectroscopy (SIMS). According to the IR inspection results, the two-step Ge deposited sample showed more uniform film compared to one-step deposition after eutectic bonding. Moreover, an improved bonding quality was obtained from the two-step process. Based on FESEM observations, a uniform and crater-free interface was detected between the bonded 4-inch wafers, in which the presence of Ge beside Au and Si was confirmed by EDS. SIMS profiles proved the formation of a thin Au-Ge interlayer at the bonded interface, which enhanced the bonding conditions. (C) 2016 Elsevier B.V. All rights reserved.

The diffusion barrier property of directly grown graphene-graphite films between Al2O3 films and Si substrates was evaluated using metalinsulator-semiconductor (MIS) structures. The roughness, morphology, sheet resistance, Raman spectrum, chemical composition, and breakdown field strength of the films were investigated after rapid thermal annealing. About 2.5-nm-thick graphene-graphite films effectively blocked the formation of the interfacial layer between Al2O3 films and Si, which was confirmed by the decreased breakdown field strength of graphene-graphite film structures. After annealing at 975 degrees C for 90 s, the increase in the mean breakdown field strength of the structure with the similar to 2.5-nm-thick graphene-graphite film was about 91% (from 8.7 to 16.6MV/cm), while that without the graphene-graphite film was about 187% (from 11.2 to 32.1MV/cm). Si atom diffusion into Al2O3 films was reduced by applying the carbon-based diffusion barrier. (C) 2016 The Japan Society of Applied Physics

We evaluated the effects of H-2 plasma and thermal treatment on current-voltage (I-V) and capacitance-voltage ( C-V) characteristics using Al/Al2O3/Si. H-2 plasma treatment reduced the concentration of C and enhanced the diffusion of Si and O atoms and the mean breakdown field strength. The breakdown field increased significantly after rapid thermal annealing (RTA) due to crystallization and the formation of an interface layer between Si and Al2O3, which was confirmed by TEM, secondary ion mass spectroscopy (SIMS), and three-dimensional (3D) atom probe tomography. H-2 plasma treatment produced a negative fixed charge due to the outgassing of C and H-2, and RTA produced a positive fixed charge. (C) 2015 The Japan Society of Applied Physics

Electroless-plating Ni-B films have been evaluated for the application as the diffusion barrier and metal cap for copper integration. The effect of post plasma treatment in a hydrogen environment on the characteristics of Ni-B films such as chemical composition, surface roughness, crystallinity, and resistivity was investigated. By treating electroless-plating Ni-B films with H2 plasma, the resistance and the roughness of the films decreased. The leakage current of Ni-B bottom electrode/30-nm-thick Al2O3/Al top electrode structures improved after the H2 plasma treatment on the Ni-B films. 40 nm-thick electroless-plating Ni-B film was able to block Cu diffusion up to 350 degrees C.

We have evaluated the conformality and electrical properties of Al2O3 films deposited by atomic layer deposition at temperatures below 300 °C for through-silicon via (TSV) applications. Al2O3 films were able to be conformally deposited on the scallops of 50-μm-wide, 100-μm-deep TSV at the temperature range between 200 and 300 °C. The median breakdown fields of the metal–insulator–metal device with 30-nm-thick Al2O3 layer were above 6 MV/cm for the films deposited at 250 and 300 °C, while that at 200 °C was inferior due to residual carbon impurities in the oxide layer.