In microelectronics, 3D integration consists in vertically stacking 2D chips to build up 3D devices. Once realized, thermal treatments linked to fabrication process, e.g. annealing, may induce delamination between chips, defects in the 3D stack or local voids in interconnects. These defects can be as small as few tens of nanometers and are deeply «buried» in the 3D silicon stack. Electrical characterization can be used to evidence failures; however, no direct high-resolution imaging method exist today that allow for the investigation of a 3D chip in a rapid and non-destructive way, in order to couple electrical and 3D morphological coupling for instance. With respect to the state of the art, the goal is to switch from 3D imaging of a single, isolated object, to the 3D imaging of an integrated and functional device using a laboratory system. In this context, X-ray nanotomography appears to be a technique of choice. At CEA LETI, the ?Silicium Department’ owns such a tool. However, the current signal to noise ratio and the penetration depth (linked to the beam energy, 8keV) prevent rapid investigation of thick samples. The use of a more brilliant laboratory x-ray source with x-rays of higher energies (up to 20keV while it is only 8keV so far), associated to an optimized data collection scheme (sampling and detection) will allow to reach sub-100nm resolution on 3D objects of sub-millimetric size, for the first time. This constitutes the goal of the post-doc position. More specifically, after a minimalist sample preparation, the acquisition sampling, the rigorous hardware and software pre/post alignment (using Python or Matlab, typically), associated to in-house advanced 3D reconstruction will have to be developed and optimized. The critical point will be to preserve the 2D spatial resolution when going to 3D images. Applications include CMOS stack, copper pillars, solid oxide fuel cells or porous materials.

This position is open until it is filled.

Département: Département Technologies Silicium (LETI)
Laboratory: Autre laboratoire
Start Date: 01-03-2015
ECA Code: PsD-DRT-15-0006
Contact: pierre.bleuet<στο>cea.fr