The mainstream planar technology is marked by physical and technological limitations, which have a severe impact on system characteristics. The performance, the multi-functionality and the reliability of microelectronic systems will be mainly limited by the wiring between the ICs and subsystems. The “on-chip” wiring also leads to a critical performance bottleneck for future IC generations which can be solved only temporarily by the introduction of additional metallization layers and innovative materials (copper, low-ε-dielectrics). 3D IC fabrication creates a basis to overcome these drawbacks and to pave the way for system approaches of an entirely new quality. We realized a three dimensional metallization for Vertically Integrated Circuits (VIC) using a newly developed technology that allows stacking and vertical interchip wiring of completely processed and electrically tested wafers using available microelectronic processes. Wafers are stacked by an aligned bonding process. Vertical electrical connections are formed between the uppermost metal levels of the bonded wafers by fabrication and metal refill of high aspect ratio interchip vias. This interchip via (ICV) concept allows the formation of multiple wafer stacks using CMOS compatible materials and process steps exclusively and avoids wafer back processes. The potential of the ICV technology is the realization of some 100 000 vertical interconnects per cm2 with 1–4 μm2 interchip vias, arbitrarily selectable.

Fullyc-axis oriented thin films of YBa2(Cu1−x57Fe x )3O7 on 〈100〉 SrTiO3 substrate (x=0.15%, 1%, 3%, and 6%) were investigated by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX-analysis), inductiveTc measurement, and conversion electron Mößbauer spectroscopy (CEMS). For all iron concentrations the films are fullyc-axis oriented and iron is homogeneously distributed in the film. Forx=0.15%, 1%, and 3% thec-axis length is the same as for undoped films, forx=6% it is enlarged. With increasingx the surface of the films, which shows an undulated structure, gets smoother. TheTc values forx=0.15% and 1% are the same as for the undoped films, forx=3% and 6%Tc is reduced. CEMS spectra for allx values can satisfactorily be fitted with only three quadrupole doubletsA, B, andC, but with different relative intensities for differentx values. The quadrupole splitting of doubletB decreases with increasingx values. The Debye Waller factor does not change significantly withx.

Fullyc-axis oriented thin films of YBa2 (Cu0.9757Fe0.03)3O7 on <100> SrTiO3 substrate were irradiated with different fluences ϕ of 500 MeV127I parallel to thec-axis. The samples were investigated by means of x-ray diffraction, resistiveTc measurements and conversion electron Mößbauer spectroscopy (CEMS). Irradiation results in the appearance of a fourth quadrupole doubletE in the CEMS-spectra (EQ=1.1 mm/s, IS=0.26 mm/s), whose intensity increases with increasing ϕ. The Debye Waller factor of the new Fe-speciesE is only about 60% of that of the speciesA, B, andC proving that irradiation with high energy heavy ions results in latent tracks of lower density. from the hyperfine parameters of speciesE we conclude that the latent tracks are mainly formed by the “green phase” Y2BaCuO5. We derived the radius of the latent tracks to be about 26 Å.

Fullyc-axis oriented thin films of YBa2(Cu1−x 57Fe x )3O7−y were studied by varying the Fe- and O-content and the substrate. For the two substrates MgO and SrTiO3 no difference in the CEMS spectra was observed. Measurements for differentx andy values and their comparison with results from powder samples proved that the solubility of iron is the same in the films and powders. The substitution of Cu(2) by Fe in the films is the highest ever reported. The CEMS spectrum of a reduced film shows that the direction of the magnetic hyperfine field for doubletC is perpendicular to thec-axis.