Study of dopant deactivation in advanced metal/semiconductor contact stacks

The downscaling of metal-oxide-semiconductor field effect transistors has dramatically increased the parasitic contribution of contacts to their output characteristics. For this reason, contact resistances must be minimized. The physical properties of the different layers and interfaces composing metal/semiconductor contact stacks (namely the in situ doped epitaxial source/drain (S/D), the metal -silicide- contact and the interface between them) therefore need to be perfectly understood and accurately controlled. 

To achieve low contact resistances, S/D layers with high active doping concentrations are of prime importance. Recent simulation work identified stress-induced deactivation of dopants as a possible root-cause for contact performance degradation. These results still require experimental verification for the variety of considered material stacks but could open avenues for further contact engineering.

The Master thesis candidate will concentrate on the (de)activation of dopants in n-type and p-type epitaxial S/D layers deposited on blanket wafers. First, these materials will be subjected to different annealing treatments to document their doping behavior as a function of the applied thermal budget. Afterwards, contact stacks containing several metals/silicides in addition to these S/D layers will be subjected to the same annealing treatments and de-processed (i.e., the top layers will be removed) to extract the resulting active doping concentration. Comparing these results will allow the candidate to assess the impact of the metals/silicides deposition/formation process(es), and, in particular, the strain induced by these steps, on the S/D active doping concentration. Finally, the electrical characteristics of the fabricated stacks will be studied to correlate the doping and contact properties.
 

Type of Project: Combination of internship and thesis 

Master's degree: Master of Science 

Master program: Materials Engineering; Chemistry/Chemical Engineering; Nanoscience & Nanotechnology; Physics 

Duration: 6 months or more 

Supervisor: Clement Merckling 

For more information or application, please contact Clement Porret (clement.porret@imec.be)

Only for self-supporting students.