Kinetics of solid phase crystallization in amorphous silicon

Secondary grain growth in thin films can lead to grain sizes much greater than the film thickness. Surface energy anisotropy often provides an important fraction of the driving force for secondary grain growth, especially in the early stages of growth. Surface‐energy‐driven secondary grain growth leads to the development of large grains with restricted crystallographic textures. A model is presented for growth of secondary grains into a uniform matrix of columnar normal grains. The model indicates that secondary grain growth rates should increase with grain boundary energy, surface energy anisotropy, grain boundary mobility, and temperature. While final secondary grain sizes will decrease with film thickness, their growth rates will increase. The final secondary grain sizes and orientations will be strongly affected by grain sizes and orientations in the initial film. The models presented here provide analytical tools for experimental study of secondary grain growth in thin films. They will be used in for...

Secondary grain growth in thin films of semiconductors: Theoretical aspects

Growth of grains with sizes many times (>50×) larger than the film thickness and with uniform (111) texture, has been achieved in ultrathin (<100 nm) films of Si on SiO2. Growth of these secondary grains is driven by minimization of anisotropic surface energy. As a result, the secondary grain growth rate increases with decreasing film thickness. The time required for growth of large secondary grains decreases with increasing temperature.

Surface‐energy‐driven secondary grain growth in ultrathin (<100 nm) films of silicon

A silicon-filament vacuum-sealed incandescent light source has been fabricated using IC technology and subsurface micromachining. The incandescent source consists of a heavily doped p/sup +/ polysilicon filament coated with silicon nitride and enclosed in a vacuum-sealed ( approximately=80-mT) cavity in the silicon-chip surface. The filament is formed beneath the surface and later released using sacrificial etching to obtain a microstructure that is protected from the external environment. The filament is electrically heated to reach incandescence at a temperature near 1400 K. The power required to achieve this temperature (for a filament 510*5*1 mu m) is 5 mW. The emitted optical power is 250 mu W, and the peak in the spectrum distribution is near 2.5 mu m. The radiation approximately follows Lambert's cosine law. The subsurface micromachining technique used to produce the evacuated cavity has applications in other micromechanical devices. >

Electrical and optical characteristics of vacuum-sealed polysilicon microlamps

We demonstrate that fine‐grained polycrystalline Si films obtained by chemical vapor deposition can be aligned expitaxially with respect to the underlying (100) Si substrate upon furnace annealing at temperatures of 1000–1150 °C. The alignment proceeds basically by the formation of epitaxial columns which subsequently grow laterally to consume the remaining polycrystalline Si. The rates of alignment are measured to be 20–200 A/min in the temperature interval of annealing with an activation energy of 4.7 eV. The epitaxial layers so obtained are of reasonably good crystal quality and contains only a small amount of planar crystallographic defects.

Epitaxial alignment of polycrystalline Si films on (100) Si

Recrystallization processes in polycrystalline silicon made by a chemical vapor deposition technique have been investigated. Primary recrystallization has been observed between 1150 and 1250 °C, secondary recrystallization occurred above 1350 °C. By this procedure, grains of about 100 μm have been obtained. Recrystallized silicon can in principle be used as a substrate for making relatively inexpensive solar cells.

H. Heijligers

Papers

Recrystallization processes in polycrystalline silicon