Using Thermal Oxidation and Rapid Thermal Annealing on Polycrystalline-SiGe for Ge Nanocrystals
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1071-F03-21
Using Thermal Oxidation and Rapid Thermal Annealing on Polycrystalline-SiGe for Ge Nanocrystals Chyuan-Haur Kao1, C. S. Lai1, M. C. Tsai1, C. H. Lee1, C. S. Huang1, and C. R. Chen2 1
Electronics Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan, 333, Taiwan 2
Material Science Service Corporation, Hsin Chu, 300, Taiwan
ABSTRACT In this paper, simple techniques were proposed to fabricate germanium nanocrystal capacitors by one-step thermal oxidation and/or rapid thermal annealing on polycrystalline-SiGe (poly-SiGe) deposited with a LPCVD (low pressure chemical vapor deposition) system. This thermal oxidation method can directly result in the top-control oxide layer via the oxidation of amorphous-Si film and the formation of Ge nanocrystals from the poly-SiGe film. Otherwise, the rapid thermal annealing method can be also used to form Ge nanocrystals as comparison. INTRODUCTION The first NC Flash memory device was demonstrated using Si-NC embedded in SiO2 [1]. Since then, various materials such as Ge and metals have been used to form NC FG on SiO2 [2-3] and various storage mechanisms have been proposed. Therefore, silicon (Si) or Germanium (Ge) nanocrystals are promising candidates for flash electrically erasable and programmable read only memories (EEPROMs), and the reduction of charge leakage from weak spots in tunneling oxide. In this work, simple techniques were proposed to fabricate germanium nanocrystal capacitors by one-step thermal oxidation and/or rapid thermal annealing on polycrystalline-SiGe (poly-SiGe) deposited with a LPCVD (low pressure chemical vapor deposition) system. This thermal oxidation method can directly result in the top-control oxide layer via the oxidation of amorphous-Si film and the formation of Ge nanocrystals from the poly-SiGe film. Otherwise, the rapid thermal annealing method can be also used to form Ge nanocrystals as comparison. EXPERIMENTAL DETAILS The Ge nanocrystal capacitors were fabricated using with two different oxidation methods.
(a). Ge Nanocrystal formation by Using One Step Thermal Oxidation At first, a tunneling oxide of 3nm was grown on a (100)-oriented p-type Si substrate via thermal oxidation at 9500C in a dry O2 ambient. Then, 1nm thickness amorphous Si (a-Si) and 5nm thickness poly-SiGe film were deposited on the tunneling oxide by the LPCVD system at 4750C under the pressure of 100 mtorr. The gas flows of GeH4 and Si2H6 are 5 sccm, and 40 sccm, respectively. After that, a 10 nm thickness of amorphous-Si film was deposited on the sample by the LPCVD system in a Si2H6 gas flow rate of 40 sccm, and then performed at 9000C thermal oxidation in a dry O2 ambient to grow about 20 nm thick oxide layer. This one-step oxidation resulted in the top-control oxide layer via the oxidation of amorphous-Si (α-Si) film and the formation of Ge nanocrystals from the deposited poly-SiGe film. Finally, a 500 nm thickness of Al metal film was deposited and patterned to form the capacitor structures followed by a hydrogen sintering process at
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