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Open Access Nano Express

STEM nanoanalysis of Au/Pt/Ti-Si3N4 interfacial defects and reactions during local stress of SiGe HBTs

Ali Alaeddine*, Cécile Genevois, Laurence Chevalier and Kaouther Daoud

Author Affiliations

Université de Rouen, GPM, UMR CNRS 6634, BP 12, Avenue de l'Université, 76801 Saint Etienne de Rouvray, France

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Nanoscale Research Letters 2011, 6:574  doi:10.1186/1556-276X-6-574

Published: 31 October 2011

Abstract

A new insight on the behavior of metal contact-insulating interfaces in SiGe heterojunction bipolar transistor is given by high-performance aberration-corrected scanning transmission electron microscopy (STEM) analysis tools equipped with sub-nanometric probe size. It is demonstrated that the presence of initial defects introduced during technological processes play a major role in the acceleration of degradation mechanisms of the structure during stress. A combination of energy-filtered transmission electron microscopy analysis with high angle annular dark field STEM and energy dispersive spectroscopy provides strong evidence that migration of Au-Pt from the metal contacts to Ti/Si3N4 interface is one of the precursors to species interdiffusion and reactions. High current densities and related local heating effects induce the evolution of the pure Ti initial layer into mixture layer composed of Ti, O, and N. Local contamination of Ti layers by fluorine atoms is also pointed out, as well as rupture of TiN thin barrier layer.

Keywords:
HBT; STEM-HAADF; EDS; EFTEM; failure; reliability