Strain mapping of tensiley strained silicon transistors with embedded Si1−yCy source and drain by dark-field holography

Abstract

Dark-field holography, a new transmission electron microscopy technique for mapping strain distributions at the nanoscale, is used to characterize strained-silicon n-type transistors with a channel width of 65 nm. The strain in the channel region, which enhances electron mobilities, is engineered by recessed Si0.99C0.01 source and drain stressors. The strain distribution is measured across an array of five transistors over a total area of 1.6 μm wide. The longitudinal tensile strain reaches a maximum of 0.58%±0.02% under the gate oxide. Theoretical strain maps obtained by finite element method agree well with the experimental results.

Strain Measurement in Semiconductor Heterostructures by Scanning Transmission Electron Microscopy

“…Owing to Bragg's law~1!, none but the local lattice parameter determines the measured signal in diffraction-based techniques so that the precision is to be discussed rather by means of the analyzing procedure applied to the diffraction patterns than by inaccurately known specimen parameters, such as its thickness, orientation, composition, and crystal potential Fourier components @which are sensitive to bonding~Rosenauer et al, 2005!, thermal~Waller, 1927 The highest precisions for strain measurements at large fields of view the authors are aware of are based on darkfield holography~Hÿtch et al, Hüe et al, 2009;Koch et al, 2010!. It turned out that it is extremely difficult to compare with these reports for two reasons, one physical and one methodical.…”

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

“…[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.…”

“…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.…”

“…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.…”

Channel-Length-Dependence of Strain Field in Transistor Studied via Scanning Moire Fringe Imaging

“…Thus, a compressive stress is formed in the source/drain region, which in turn induces a tensile strain in the n-type channel. 4 Since the electrical performance of the device is greatly influenced by the strain field induced in the channel region, it is required to control the strain field for optimum manufacturing processing. Furthermore, with decrease in the size of modern semiconductor devices, the strain field in the semiconductor devices tends to be strongly influenced by layout design parameters such as the channel length and the geometry of the source and drain regions.…”