Studies on electrical , structure and crystallization characteristics of Se-doped Sb70Te30 alloy

• Main Authors: Ying-Da Liu, 劉應達
• Other Authors: 何永鈞
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/25765830301718171191

碩士 === 國立中興大學 === 材料工程學系所 === 95 === Abstract Chalcogenide phase-change materials exhibiting a large difference in resistance between crystalline and amorphous states have a great potential to be applied for the phase-change memory. The eutectic Sb70Te30 alloy is a growth-controlled phase-change material. Since the crystallization rate of Sb70Te30 alloy will increase when the size of recording area is reduced, Sb70Te30 alloy is considered as one of the promising materials for the high density and high data transfer rate memories. However, the Sb70Te30 thin film showed a disadvantage of poor thermal stability which can be improved by adding specific foreign elements. In this work, we studied the effects of Se doping on the structure and electrical properties of Sb70Te30 thin film. Based on the experimental results, adding small amount of Se (2.1~6.6 at.%) into the Sb70Te30 film resulted in the increases of the crystallization temperature and activation energy for crystallization which would increased from 138.5 to 163.6 ℃ and 2.23 ± 0.05 to 3.40 ± 0.04 eV as the Se content was increased from 0 to 6.6 at.%. The electrical conduction activation energies of Se-doped Sb70Te30 films also increased with the doping concentration of Se, where Ea were equal to 0.291eV at amorphous state and 0.051eV at crystalline state for the non-doped Sb70Te30 film, and were increased to 0.299~0.438eV at amorphous state and 0.052 ~ 0.092eV at crystalline state as the Se contents were in the range form 2.1 to 6.6 at.%. These may be attributed to the increases of bonding energy and electrical defects in the film. The resistivity of Sb70Te30 film showed a slightly increase with the Se doping concentration. When 6.6 at.% of Se was doped into the film, the sheet resistance increased about 1 order compared with the non-doped Sb70Te30 film. For phase-change random access memory, the increase in resistance is helpful for the reduction of writing current, while the increases in crystallization temperature and activation energy for crystallization will improve the thermal stability and life time.