In the present work, the effect of rapid thermal annealing (RTA) on the electrical and structural properties of poly-Si thin films, grown by the crystallization of a-Si films deposited by rapid thermal low-pressure chemical vapor deposition, has been studied. Structural and electrical results were obtained using atomic force microscopy, transmission electron microscopy, electron spin resonance, electrical resistivity, and Hall mobility techniques. The effects of the grain size, grain boundaries, and surface roughness on the electrical characteristics of poly-Si films have been investigated. Amorphous Si (a-Si) films crystallized by RTA at 850 °C for 45 s result in the formation of poly-Si with small grains, an electron spin density Ns=5.2×1016 cm−3, and a Hall mobility μH=30 cm2 V−1 s−1. A two-stage annealing, involving low-temperature annealing at 600 °C for 6 h, followed by RTA at 850 °C in five steps of 30 s each, results in the formation of poly-Si films with large grains free of in-grain defects, low surface roughness, and higher Hall mobility μH=43 cm2 V−1 s−1, characteristics rendering such poly-Si films suitable for the fabrication of good performance thin film transistors.
The phase transformation of amorphous silicon-aluminum thin films with 16 at.% and 30 at.% aluminum was characterized by TEM during an in-situ anneal at 500°C. No crystallization was observed in the samples having 16 at.% Al even after a 10 hour anneal at 500°C. In contrast, nucleation of crystallites was observed in the samples having 30 at.% Al after a 40 min anneal. The size of these crystallites grew during annealing. Single crystal regions were also observed and were identified as aluminum having <111> orientation.
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