Silicon germanium interdiffusion in SiGe device fabrication: A calibrated TCAD model

SiGe alloys are used in many types of electronic devices. For upcoming FinFET technologies, there is interest in the use of SiGe heterostructures in the complete mole fraction range (0–100% Ge atoms). For high Ge mole fraction and small device dimensions, interdiffusion of Si and Ge atoms can lead to critical changes in the distribution of Si and Ge atoms, impacting channel strain and carrier mobility. A process model for Si–Ge interdiffusion has been developed which covers the needs for actual device fabrication processes. Interdiffusion is understood to be correlated with the diffusion of vacancies, self-interstitials, and dopant-defect pairs. We consider the impact of non-equilibrium point defect concentrations (such as interstitial super-saturation after ion implantation), the impact of compressive or tensile strain, and a twofold impact of doping: first, doping determines the local electron concentration and thereby the abundance of charged point defects, and second, the diffusion of dopant-defect pairs can contribute to the interdiffusion of Si and Ge atoms. The model covers the full range of possible Ge mole fractions (0–100%). For undoped SiGe, it has been calibrated against a broad range of published experimental data for radio-tracer diffusion in SiGe and for interdiffusion in biaxially strained SiGe heterostructures grown on Si, stress-relaxed SiGe, or Ge. The extensions for doped SiGe are presented with a reference to few interdiffusion data for heavily doped SiGe heterostructures. Finally, the model has been consistently integrated into a set of models for the continuum process simulation of point defects and dopants in pure Si, SiGe, and pure Ge, in Sentaurus Process.