dislocation nucleation
A study of conditions for dislocation nucleation in coarser-than-atomistic scale models
Akanksha Garg, Amit Acharya, Craig E. Maloney
Tension-Compression Asymmetry in Homogeneous Dislocation Nucleation
Abstract. This letter addresses the dependence of homogeneous dislocation nucleation on the crystallographic orientation of pure copper under uniaxial tension and compression. Molecular dynamics simulation results with an embedded-atom method potential show that the stress required for homogeneous dislocation nucleation is highly dependent on the crystallographic orientation and the uniaxial loading conditions; certain orientations require a higher stress in compression (e.g., <110> and <111>) and other orientations require a higher stress in tension (<100>). Furthermore, the resolved shear stress in the slip direction is unable to completely capture the dependence of homogeneous dislocation nucleation on crystal orientation and uniaxial loading conditions.
Split singularities and dislocation injection in strained silicon
By Martijn Feron, Zhen Zhang and Zhigang Suo
The mobility of charge carriers in silicon can be significantly increased when silicon is subject to a field of strain.In a microelectronic device, however, the strain field may be intensified at a sharp feature, such as an edge or a corner, injecting dislocations into silicon and ultimately failing the device. The strain field at an edge is singular, and is often a linear superposition of two modes of different exponents. We characterize the relative contribution of the two modes by a mode angle, and determine the critical slip systems as the amplitude of the load increases. We calculate the critical residual stress in a thin-film stripe bonded on a silicon substrate.
Spacing effect on dislocation injection from sharp features in strained silicon structures
In practice, the SiN stripes or pads are periodically patterned on silicon, so the spacing effect on dislocation injection from sharp features deserves attention. As in Figure 1, the SiN stripes with residue stress, of width L and thickness h, are periodically patterned with spacing S. In the numerical calculation, we take shear modulus and Poisson’s ratio of Si3N4 to be 54.3 GPa and 0.27, and those of silicon 68.1GPa and 0.22, the same as in Ref.[1].
A method to analyze dislocation injection from sharp features in strained silicon structures
Stresses inevitably arise in a microelectronic device due to mismatch in coefficients of thermal expansion, mismatch in lattice constants, and growth of materials. Moreover, in the technology of strained silicon devices, stresses have been deliberately introduced to increase carrier mobility. A device usually contains sharp features like edges and corners, which may intensify stresses, inject dislocations into silicon, and fail the device. On the basis of singular stress fields near the sharp features, this letter describes a method to obtain conditions that avert dislocations.