Multicrystalline silicon (mc-Si) grown by cast method has been most widely used for solar cell application. The improvement of mc-Si quality is the crucial issue for photovoltaics. There exist two directions for this purpose. One is the seed cast technique which can grow mono Si ingot free from GBs. The other is the controlled mc-Si growth, which is called high performance mc-Si. However, it is still not clear how the grain structure in mc-Si evolves and to which extent GBs can be controlled. In this study of Takashi Sekiguchi and coworkers (pp. 1094–1098), the authors have grown mc-Si from microcrystalline template. The grain evolution (low left) and electron backscattered diffraction (EBSD) pattern (low right) are analyzed and a three-step mechanism of grain growth was proposed.

The layout of electronic systems of the next generation will be mainly three-dimensional. For vertical interconnections so-called TSVs (through silicon vias) are used. These are vertical holes filled with metal, e.g. copper. Resulting stress can affect the functionality of electronic devices and, a keep-out zone has to be defined. The integrity of TSV structures has to be tested by non-destructive analytical tools (see the paper of Martin Herms and coworkers on pp. 1085–1089). The figure shows a map of optical birefringence of a group of 6 × 6 single TSVs (ca. 500 μm × 500 μm) recorded with a photo-elastic microscope SIREX (Scanning Infrared Explorer). SIREX is a reflection-based plane polarimeter specially developed for the high-resolution stress state visualization in silicon-based electronic and mechanic devices. The diameter of a single TSV shown in the figure is 5 μm. Optical birefringence does occur if the silicon crystal matrix around the single TSV is optically anisotropic. The anisotropy revealed is caused by a radial stress field which is typical for point-like stress sources. The visualized “butterflies” represent the in-plane shear stress which can be converted into stress units in the order of a few kPa. The color sequence indicates the stress direction. Here, the TSVs generate a radial tensile stress component in the silicon matrix. Generally, magnitude, direction and lateral distribution of stress are determined by size and shape of a TSV but also by the presence of defects like voids.