| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 96 === Abstract
Since the Si will be preferentially oxidized during the high-temperature oxidation of SiGe alloy or annealing of SiGeO alloy and the segregated Ge atom will pile-up along the SiGe/SiO2 interface, it could be expected that the Ge nanocrystals would be tentatively formed with the Ge atom segregation and agglomeration. In this thesis, the multilayer a-SiGe/a-SiON, a-SiGe/a-SiN, and a-SiGeO/a-SiN thin-films have been prepared with a plasma enhanced chemical vapor deposition system, then with a thermal oxidation for a-SiGe/a-SiON and a-SiGe/a-SiN or a thermal annealing for a-SiGeO/a-SiN thin-films, the single /multilayer nano-meter scale Ge crystal dots have been obtained. The multilayer, well-separated, and 5 nm-sized Ge nanocrystals could be obtained with a thermal annealing technique. The crystallinity of Ge nanodots has been checked with a Raman spectroscopy.
The metal-oxide-semiconductor (MOS) capacitors ( MOS-Cs ) with Ge nanocrystals embedded in oxide have been fabricated to investigate the charge trapping effect of Ge nanocrystals. A current spike phenomenon in I-V curve has been observed. This was ascribed to the transient current of hole charging from p-type Si substrate. In addition, the hysteresis phenomenon has also been observed in C-V measurement. This indicated that the charge storage effect resulted from the formed Ge nanocrystals. The highest obtainable memory window with multilayer Ge nanocrystals was 3 V. Furthermore, the charge storage effects have been investigated by using the C-V measurement at various frequencies.
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