The Optics and Photonics Department of CEA/LETI is involved in the assembly of imaging components (such as Infrared detectors or microdisplays) on CMOS circuits. In this area one of the driving element for a better resolution is the pitch reduction. If some interconnection technologies exist, the assembly of components with an ultrafine pitch (<5-10µm) requires new development. The goal is to achieve a vertical interconnection between chips that guarantees mechanical, electrical and thermal cohesion. One of the foreseen technique for this development is the interconnection using copper pillar structures and microbumps. Understanding and controlling this technological step will significantly help increase the interconnection density, and produce more performing display in smaller format (Moore’s Law). The objective of this thesis is therefore to analyze the physical and chemical mechanisms as well as the kinetics governing the interconnection with micro-bumps, in order to define the best interconnection technology suited for ultrafine pitch and apply it to future generations of components. For this study the student will use some modeling for understanding the electromigration phenomenon, work with 200mm wafer fabrication, to design and fabricate the components and finally achieve the assembly of the components. Some characterization techniques such as SEM, and FIB will be used to observe the connections between the bumps and the pads, and to understand the brazing mechanism as well as the intermetallic formation.

This position is open until it is filled.

Département: Département d’Optronique (LETI)
Laboratory: Laboratoire Packaging et Assemblage
Start Date: 01-05-2015
ECA Code: SL-DRT-15-0971
Contact: gilles.lasfargues<στο>cea.fr