高介電係數材料鈦酸鍶鋇BaxSr1-xTiO3在動態隨機存取記憶體電容器之研究

Abstract

隨著次微米元件從超大型積體電路到極大型積體電路尺寸之縮小,電容面 積也隨之縮小,但儲存電荷仍需維持在一臨界值(~25fF/cell).高介電係數 材質作為動態隨機記憶體中電容器益形重要.氧化鉭雖比傳統ONO提高了較 高的介電係數,但對十億位元DRAM,仍嫌不足.鈦酸鍶鋇提供了下列優點:高 介電係數,低漏電流,長使用壽命,高製程缺陷的抵抗性,好的電性,化性,熱 穩定性及低損耗因子.用濺鍍加熱來形成鈦酸鍶鋇介電質,易於控制結構, 適用平面堆疊電容器的製造.其應用範圍大概在十億位元至四十億位元 DRAM.本論文將針對不同O2和Ar氣氛混合比例濺鍍在不同基座溫度上成長 之鈦酸鍶鋇層,探討其電性和物性,薄膜沉積後在N2中退火效應也將討論. As device dimensions are scaled down into the deep-submicron regime, the demand for small capacitor area while still maintaining a certain critical charge for DRAM capacitors become more stringent. Ta2O5 films are suitable for 256M to 1G bit DRAM application. However, higher dielectric constant materials are required for 1 Gbit DRAMs and beyond. Recently the BST (BaxSr1-xTiO3) film has attracted great attentions due to its high dielectric constant, low leakage current, TDDB over 10 years, resistance to process induced damage, good chemical and thermal stability and low dissipation factor. In this study, we present the physical and electrical properties of BST films deposited by RF magnetron sputtering. The effect of deposition temperature, the sputtering oxygen partial pressure and film thickness on the physical properties (grain size, orientation) electrical (leakage current, breakdown voltage, polarization, dielectric conatant) properties were investigated in details. In addition, a post-deposition thermal treatment by furnace annealing in N2 ambient was used to improve the electrical characteristics.