Evaluation of electron irradiated embedded SiGe source/drain diodes by Raman spectroscopy

The stress evolution of Si0.75Ge0.25 layers for Si0.75Ge0.25 source/drain (S/D) diodes, which have been irradiated at room temperature with 2-MeV electrons, is investigated using Raman spectroscopy measurements. According to Raman results for Si0.75Ge0.25/Si hetero-structures before and after irradiation, tensile stress was induced in the silicon substrate under the Si0.75Ge0.25 layer. Before irradiation, the range of tensile stress estimated by the peak shift of the Raman spectrum was −110 to −10 MPa for several measurement patterns. After irradiation, the tensile stress was relaxed in all measurement patterns though the compressive stress status in the Si0.75Ge0.25 layer was not changed. The stress relaxation in the silicon substrate amounted to about 10 MPa as a maximum. The influence of the irradiation on the stress relaxation in the silicon substrate, could be explained because the electron irradiation at 2-MeV can easily penetrate through the studied 140 nm Si0.75Ge0.25 layers.