  A new module concept for future ATLAS pixel detector upgrades is presented,
where thin n-in-p silicon sensors are connected to the front-end chip
exploiting the novel Solid Liquid Interdiffusion technique (SLID) and the
signals are read out via Inter Chip Vias (ICV) etched through the front-end.
This should serve as a proof of principle for future four-side buttable pixel
assemblies for the ATLAS upgrades, without the cantilever presently needed in
the chip for the wire bonding.
  The SLID interconnection, developed by the Fraunhofer EMFT, is a possible
alternative to the standard bump-bonding. It is characterized by a very thin
eutectic Cu-Sn alloy and allows for stacking of different layers of chips on
top of the first one, without destroying the pre-existing bonds. This paves the
way for vertical integration technologies.
  Results of the characterization of the first pixel modules interconnected
through SLID as well as of one sample irradiated to $2\cdot10^{15}$\,\neqcm{}
are discussed.
  Additionally, the etching of ICV into the front-end wafers was started. ICVs
will be used to route the signals vertically through the front-end chip, to
newly created pads on the backside. In the EMFT approach the chip wafer is
thinned to (50--60)\,$\mu$m.
