Lattice strain analysis of transistor structures with silicon–germanium and silicon–carbon source∕drain stressors

Abstract

We report the characterization of strain components in transistor structures with silicon–germanium (Si0.75Ge0.25) and silicon–carbon (Si0.99C0.01) stressors grown by selective epitaxy in the source and drain regions. The spacing between the source and drain stressors is 35nm. Lattice strain analysis was performed using high-resolution transmission electron microscopy (HRTEM) and diffractograms obtained by fast Fourier transform of HRTEM images. The lateral strain component εxx and the vertical strain component εzz were derived from the (220) and (002) reflections in the diffractogram, respectively. SiGe source and drain stressors lead to lateral compressive strain and vertical tensile strain in the Si channel. On the other hand, the SiC source and drain stressors give rise to lateral tensile strain and vertical compressive strain in the Si channel, an effect complementary to that of SiGe source∕drain stressors. The results of this work will be useful for channel strain engineering in complementary metal-oxide-semiconductor transistors.

Mechanics of silicon nitride thin-film stressors on a transistor-like geometry

“…The elastic constants defined for the cubic system of Si where x, y, and z are orthogonal {001} directions are C 11 = 165.7 GPa, C 12 = 63.9 GPa, C 44 = 79.6 GPa. In our system, the observation axis y corresponds to the [1][2][3][4][5][6][7][8][9][10] direction. Hence, to calculate the strains in the substrate, the stiffness matrix has to be rotated by 45 • around the [001] direction.…”

“…Strain and stress field maps will be presented hereafter using the symbols ε ij and σ ij with i, j = x, z being coordinates in the image plane, perpendicular to the observation axis y. With respect to the Si substrate, we define the coordinate system as x//[110],y// [1][2][3][4][5][6][7][8][9][10] and z//[001], where the z-axis corresponds to the direction normal to the surface of the substrate.…”

“…[2][3][4] Different manners of implementation have been proposed. Source and drain regions can be built of epitaxial alloys such as silicon-carbon (Si x C 1-x ) [5][6][7][8] and silicon-germanium (Si x Ge 1-x ), [9][10][11][12] that have lattice parameters different from those of the Si matrix. The channel region is therefore confined between two strained pockets, and deforms to an equilibrium configuration.…”

Features of electronic transport in relaxed Si/Si1−XGeX heterostructures with high doping level

“…1) studied in the present work were characterized by the value of the surface carrier concentration n cr > 10 12 cm -2 , and a relatively low values of electron mobility in the system (µ e ≈ 3000-5000 cm 2 /Vs at liquid helium temperature) [5]. The details of sample preparation is presented elsewhere [7].…”

“…Much less works are devoted to studying the properties of relaxed heterostructures with an electron transport channel in the silicon layers. Earlier the main efforts were concentrated on the analysis of the structural defect features in the grown heterocompositions [4,5] and on low-temperature magnetotransport measurements of two-dimensional electrons in the elastic -strained layers of Si [6,7]. Problems arising from the formation of conductive Si channels with high-mobility electron gas in the surface layer of the solid solution Si 1-х Ge х , are connected to the necessity of introduction a plastic deformation area in the structure.…”