Strain engineering based on Si/Ge heterostructures enables us to control band structures and boost advanced device performances. Recently, the uniaxial strain has attracted attentions owing to its high potential to further widen the possibility of band engineering and consequently enhance device performances more than the biaxial one. Particularly, the uniaxial compressive stress induced along the channel length direction is highly expected to effectively increase the hole mobility. And hence, new technologies to induce the uniaxial stress are strongly required to be established. We proposed selective ion implantation technique to induce uniaxial strain into the SiGe layer [1]. In this method, strain of the SiGe is locally relaxed in the region where ions are implanted into the Si substrate prior to the SiGe growth. Implantation induced defects play an important role in this facilitation of the strain relaxation. In proper configurations of the selective implantation, the anisotropic strain can be introduced into SiGe layers in the unimplanted regions, where the neighboring relaxed SiGe on the ion-implanted region provides the shear stress and causes the anisotropic strain to the unrelaxed SiGe in the unimplanted region. In previous works [1, 2], we obtained a SiGe (Ge: 27%) buffer layer where the strain relaxation around 40% took place only one direction and almost no relaxation did along the orthogonal direction. In this study, we examine uniaxial strain states induced in Si/Ge heterostructures with various Ge concentrations including (111) as well as (100) substrate orientation. In experimental, Ar ion implantation was performed on a Si(100), Si(111) or SiGe virtual substrate through the SiO2 mask with a stripe pattern consisting of several-mm-wide lines and spaces. After this selective ion implantation, a SiGe layer was grown and followed by thermal annealing at 900 °C for strain relaxation, where an uniaxially strained SiGe buffer layer was created. On some of the uniaxially strained SiGe buffers, SiGe layers with the higher Ge contents were grown as uniaxially strained channels. X-ray diffraction reciprocal space mapping (XRD RSM) and micro-Raman mapping measurements were carried our for evaluation of strain states of the structures. XRD RSM was performed with incident X-ray beam directions both perpendicular and parallel to the stripe line pattern direction, which can precisely determine the amount of the strain along the both direction independently. As a results we show the anisotrorpic strain states for SiGe with various Ge concentrations. Concerning the substrate orientation, it is found that the anisotropy of the strain for SiGe(111) is much smaller than that of SiGe(100). This can be explained by difference in dislocation structures. It has been shown that the uniaxial strain is realized when the misfit dislocations generated are aligned only one direction and resultantly strain is relieved along one direction. In the case of SiGe(100), dislocations are likely to be aligned perpendicular to the stripe line. By contrast in the case of SiGe(111), since intersections of (111) planes and interface create triangular shape, dislocations are not likely to be formed along one direction. It is also found that the SiGe channel layer is pseudomorphically grown on the SiGe buffer and the asymmetric strain state is realized in the channel as well as in the buffer layer. From these results it can be said that this technique is very promising for applications to the high mobility uniaxially strained Si/Ge channel MOSFETs. This work was partly supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities 2009-2013, by Grant-in-Aid for Scientific Research (Grant No. 21246003) from MEXT, Japan, by Industrial Technology Research Grant Program from NEDO, and by the Strategic Information and Communications R&D Promotion Programme (SCOPE) from MIC, Japan. References [1] K. Sawano et al., Appl. Phys. Express 1, 121401 (2008). [2] Y. Hoshi et al., Appl. Phys. Express 4, 095701 (2011).

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