Asymmetric relaxation of SiGe in patterned Si line structures

High resolution X-ray diffraction (HRXRD) measurements were performed using a commercially-available X-ray metrology tool, the BedeMetrix (TM)-L, on small test pads containing arrays of SiGe line structures selectively deposited in Si recesses with various window dimensions. Reciprocal space maps (RSMs) were performed in two orthogonal < 110 > directions in order to determine the lattice parameter parallel and perpendicular to the lines. With narrow lines, asymmetric relaxation effects were seen: the SiGe was fully strained along the long dimension of the lines while there was significant relaxation along the short dimension of the lines. The magnitude of the relaxation increased significantly for lines with short dimension below about 1 mu m. We show how to determine the lattice parameters, and hence the strain of the SiGe in the [110] and [-110] directions, the Ge composition and the relaxation initially using RSMs, but with an extension to measurements more suitable for in-fab metrology.