Soutenance de thèse de Ting LUO - 16/11/2018: Study of the mechanism of silicide formation by isotope diffusion and atom probe tomography

Salle des thèses, campus de Saint-Jérôme

16/11/2018

Annonce de soutenance de thèse

Madame Ting LUO

Study of the mechanism of silicide formation by isotope diffusion and atom probe tomography

Date: Vendredi 16 novembre 2018 à 10:00
Lieu: Salle des thèses, Campus St Jérôme, 13397 Marseille

Composition du jury:

M. Christian LAVOIE	Professeur, IBM/Ecole Polytech. Montreal	Rapporteur
Mme Marie-Laurence GIORGI	Professeur, CentraleSupélec, Paris-Saclay	Rapporteur
Mme Magali GREGOIRE	Docteur, STMicroelectronics, Crolles	Examinateur
M. Fiqiri HODAJ	Professeur, SIMaP, Grenoble	Examinateur
M. Lijun ZHANG	Professeur, Central South University, Changsha	Examinateur
M. Dominique MANGELINCK	Directeur de Recherche, IM2NP, Marseille	Directeur de thèse
M. Christophe GIRARDEAUX	Professeur, IM2NP, Marseille	Co-Directeur de thèse

Abstract:
With the downscaling of microelectronic devices, NiSi has been widely used in complementary-metal-oxide-semiconductor (CMOS) transistors as contact on source, drain and gate. However, the Nickel monosilicide suffers from degradation upon annealing at high temperatures. Adding alloying elements is an effective method to increase the stability of nickel monosilicide but the formation sequence of Ni silicides is substantially modified. Therefore, the studies of the phase formation sequence and the stability of monosilicide are of great importance.
The solid state reactions between Ni films alloyed with W and/or Pt and Si substrates were studied by using combinatorial analysis of co-deposited gradient films. The phase sequence was monitored mainly by in-situ X-ray diffraction (XRD) and atom probe tomography (APT) was used to examine the silicides and reveal the redistribution of alloying elements. The content of alloying elements (W and Pt) has a large impact on the phase sequence of Ni silicides and the kinetics of phase formation.
The basic agglomeration mechanism of NiSi thin films was studied. A 15nm pure Ni film was deposited on a Si substrate enriched with isotope multilayers. APT analyses were performed on the sample of Ni/Si (isotope) after an annealing at 600°C. By observing the distribution of Si isotopes (³⁰Si, ²⁹Si and ²⁸Si), whether they are maintained in a multilayer structure or became mixed together, a mechanism of the agglomeration of NiSi was proposed. This was possible because of the unique capability of APT to observe isotopes in 3D at atomic scale and it allows a better understanding and to control of the agglomeration of poly-crystalline compound thin films.

Keywords: Ni silicide, Alloying elements, Reactive diffusion, Agglomeration, Isotope, Atom probe tomography