An anomalous ring-shaped distribution of oxygen precipitates in Czochralski-grown Si is investigated, using x-ray-diffraction topography and Fourier transform infrared spectroscopy. The appearance of the ring area, corresponding to a region of oxidation-induced stacking faults, strongly depends on the preanneal before the precipitation anneal at 1000 °C. The single precipitation anneal at an elevated temperature without any preanneal maintains the distribution of precipitation nuclei formed at 450 °C during cooling from crystal growth; however, the ring-shaped distribution is not affected by the existence of thermal donors. Therefore, it is concluded that the precipitation nuclei formed at 450 °C do not have any relationship to thermal donors.
Poly-Si films are grown by ultrahigh vacuum chemical vapor deposition (UHV-CVD) with plasma-seeding on SiO2. The preferred grain orientations are investigated as a function of thickness, source gas flow rate, and growth temperature. The poly-Si fills show (100) preferred orientation in a wide range of growth conditions. The (100) orientation increases as thickness and flow rate increases and decreases as temperature increases. UHV-CVD and other deposition methods are compared in order to estimate the role of hydrogen and oxygen as factors controlling the preferred grain orientation.
The lattice strain in excimer laser crystallized polycrystalline Si (poly-Si) thin films reflects the grain growth induced by the laser irradiation. In this report, the measurement of the lattice strain is made by using the energy-dispersive grazingincidence X-ray diffraction with synchrotron radiation. The excimer laser crystallized poly-Si thin films show tensile lattice strain in the directions parallel to the substrate surface. The { 111 } strain increases from 2.2 x iO to 5.0 x iO when the grain size increases from 40 to 200 nm. The strain is anisotropic between the { 111 } strain and the {220} strain in the layer near the substrate interface when the grain size is small. Carrier mobility in a thin film transistor tends to increase when the strain increases and the anisotropy decreases.
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