Ge Diffusion in Strained Si / Relaxed SiGe Heterostrucutures

We have studied the Ge diffusion in strained silicon (sSi) layers deposited on SiGe virtual substrates. Two Ge concentrations have been used to induce strain in the Si layers: 30 and 40%, corresponding to a 1.8 and 2.5 GPa strain level respectively. Ge diffusion in highly strained layers has been understudied, whereas these layers are of great interest since they allow mobility gains for both electrons and holes. Therefore, quantifying the impact of Ge diffusion within the sSi layer (sSi consumption, Ge doping and piling...) is of great importance if one wants to use such layers for CMOS transistors or for the realization of strained Silicon On Insulator wafers using the SmartCut technology. The samples consist in a deposited SiO2 / sSi / relaxed SiGe / graded buffer / Si substrate stack. Thermal treatments have been performed in a horizontal furnace with temperatures ranging from 750 up to 1000°C. The Ge diffusion in sSi has been characterized by Secondary Ion Mass Spectrometry (SIMS). Figure 1 shows the Ge concentration depth profile in a sSi layer deposited on relaxed Si0.7Ge0.3 for the various thermal treatments investigated.