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Physical modelling of junction fabrication processes on FDSOI substrate for the 10 nm node and below

Abstract : The junction fabrication involve numerous technological challenges as the devices shrink. To alleviate issues brought by the aggressive device scaling, Fully Depleted SOI substrates as well as strained silicon-germanium (SiGe) have been introduced in advanced nodes. They however require a highly-activated abrupt junction achievable with solid phase epitaxial regrowth (SPER) and a low thermal budget (500°C-5h).In this manuscript, the SPER of silicon, germanium and SiGe alloys is investigated using Kinetic Monte Carlo (KMC) and Molecular Dynamics (MD) methods. The KMC model of SPER uses an Arrhenius equation and distinguishes local configurations at the amorphous-crystalline interface to simulate the SPER rate dependence on substrate orientations. In MD simulations, the SPER rate on {111} orientations is found to heavily depends on the cell size, anneal temperature and time.The KMC model is furthermore refined to consider the effect of boron during SPER. Boron is known to create complexes in both amorphous and crystalline phases and increase the SPER rate. This increase however saturates at high boron concentrations. A defect reaction model handling the complexes has been conjoined to the SPER model to correctly simulate the SPER rate behaviour for all boron concentrations.In relaxed (100)SiGe alloys, the SPER activation energy possesses a maximum at 40% of Ge concentration. The KMC model introduces in addition to Si-Si and Ge-Ge bonds, the Si-Ge bond to correctly simulate alloy recrystallisation. The model is also used to hypothesise the rates on other orientations. MD simulations also confirm the activation energy behaviour in SiGe alloys.Finally, X-ray diffractions following in real-time the recrystallisation of strained SiGe alloys are performed with synchrotron radiations. The strain is lost in Ge-rich alloys. The strain relaxation can be related to the anneal temperature. The interface roughness could be the link between the strain relaxation and the temperature, as MD simulations exhibit an influence of the anneal temperature on the interface roughness and strain relaxing defects are associated to a rough interface.In summary, the SPER and its several dependencies are investigated in this manuscript with atomistic approaches. The drawn conclusions increase the current understanding of SPER, allowing a better optimisation of junction fabrication.
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Anthony Payet. Physical modelling of junction fabrication processes on FDSOI substrate for the 10 nm node and below. Micro and nanotechnologies/Microelectronics. Université Grenoble Alpes, 2017. English. ⟨NNT : 2017GREAY034⟩. ⟨tel-01699426⟩

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