Large-grain polycrystalline silicon films with low intragranular defect density by low-temperature solid-phase crystallization without underlying oxide
The solid-phase crystallization of an amorphous silicon film to polycrystalline silicon by a low-temperature (⩽600 °C) furnace anneal has been investigated in a suspended cantilever structure without underlying silicon oxide by transmission electron microscopy and Raman spectroscopy. The grain size of polysilicon increases up to ∼3.0 μm and the density of intragranular defects decreases one order of magnitude in the samples without underlying oxide, compared with those with underlying oxide. The main reasons for the high quality of the suspended structures are thought to be due to the lower stress in the films during crystallization and a reduced grain nucleation rate.
Low Temperature Polysilicon Materials and Devices
In this paper, we essentially discuss the material aspects of low temperature (≤ 600 °C) polysilicon technologies. Emphasis is put on the properties of polysilicon films, depending on the way they are obtained. Solid phase crystallisation as well as pulsed laser crystallisation processes are presented in some detail, together with thin film transistor characteristics. Although not yet stabilised and despite uniformity and reproducibility problems, laser crystallisation will probably end up being the technology of choice for the manufacture of large area electronics products, because it allows the fabrication of devices exhibiting superior properties, with a reduced thermal budget.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.