Shotaro Yamamoto

Examination of phonon deformation potentials for accurate strain measurements in silicon–germanium alloys with the whole composition range by Raman spectroscopy

The phonon deformation potentials (PDPs), p and q, of Si1−xGex with the whole range of the Ge concentration x were examined in detail in pursuit of accurate strain measurements by Raman spectroscopy. An oil-immersion Raman technique was adopted to extract the PDPs of Si1−xGex, in which a complex sample preparation process or a stress-introduction device is not necessary. The strain-shift coefficients bLO and bTO, which can be calculated using the obtained PDPs, were compared with the values in the literature, and we suggested which values were best for application to accurate strain measurements. Ab initio calculation was also performed to understand the behavior of the PDPs throughout the whole range of x in Si1−xGex.

Pattern-dependent anisotropic stress evaluation in SiGe epitaxially grown on a Si substrate with selective Ar+ion implantation using oil-immersion Raman spectroscopy

Biaxial stress states in SiGe stripes on Si substrates fabricated by a novel selective Ar+ ion implantation technique were evaluated by oil-immersion Raman spectroscopy. The oil-immersion technique is appropriate for the measurement of strain induced in nanostructure devices, because it has a higher spatial resolution than conventional Raman spectroscopy and can evaluate anisotropic stress states owing to the excitation of multiple optical phonon modes. Results indicate that quasi-uniaxial stress states exist in SiGe layers in unimplanted Si areas, which depends on the stripe-width ratio of implanted and unimplanted areas, and that quasi-uniaxial stress states are successfully induced in SiGe by the present technique, which can be considered as the channel materials of high-performance transistors.