Modeling Germanium-Silicon Interdiffusion in Silicon Germanium/Silicon Super Lattice Structures

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Intermixing at heterointerfaces and the broadening of the SiGe layer in SiGe/Si super-lattice (SL) structures can be detrimental to device performance. Thus it is important to develop predictive model for interdiffusion in SL structures. In this work, the diffusion of the host Si and Ge atoms are modeled considering the vacancy exchange mechanism, kick-out mechanism and the recombination mechanism. The model was implemented using the FLOOPS-ISE process simulator and was used to simulate previously published data on Si/Ge interdiffusion in SiGe/Si SL structures with Ge fraction in the SiGe layer varying in the range 7.5-20%. Experimental data spans a temperature range of 850-1125°C for different anneal times in either inert, oxidizing or nitriding ambient. During the implementation of the model we took into account the variations of intrinsic equilibrium vacancy and interstitial concentrations and the variations of the intrinsic self-diffusivities of Si and Ge as a function of the Ge fraction. Our implementation of the model also took into account the conservation of lattice sites to relate the vacancy flux with the diffusing Si and Ge fluxes. In all the cases, the values of the intrinsic self diffusivities of Si and Ge were fitted to match the inert diffusion profiles and these values were very close to the previously reported results. Once these values were fixed for inert anneals, the diffusion behavior under oxidizing and nitriding anneals were completely accounted for by the model with no additional fitting parameters. We were able to get excellent fits in all the cases.

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Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2008: Microsystems, Photonics, Sensors, Fluidics, Modeling, and Simulation – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: June 1, 2008
Pages: 576 - 579
Industry sectors: Advanced Materials & Manufacturing | Sensors, MEMS, Electronics
Topic: Informatics, Modeling & Simulation
ISBN: 978-1-4200-8505-1