溶膠凝膠法製備CaCu3Ti4O12 (CCTO)薄膜之電特性探討

Abstract

因為動態隨機存取記憶體(dynamic random access memory, DRAM)在不斷微縮下，其電容值也隨之微縮，進而造成內部儲存電荷量減少。所以需要利用高介電材料，藉由高介電常數並降低其漏電進而可應用於DRAM。本論文利用溶膠凝膠法製作CaCu3Ti4O12(CCTO)高介電材料薄膜並研究其電學性質及相關物理、化學特性。討論不同CCTO厚度與其不同退火製程，如單次爐管退火(single-cycle furnace annealing, SFA)和多次爐管退火(multi-cycle furnace annealing, MFA)；發現CCTO介電常數隨著厚度之增加而降低，歸究其原因並利用內部孔洞(void)與介面層(interlayer)等一些模型。此外，CCTO內部導電機制在低電場是Ohmic conduction，高電場為Frenkel-Poole emission主導。

Electrical behaviors, physical and chemical properties of the high dielectric constant material CaCu3Ti4O12 (CCTO) derived from sol-gel methods is investigated in this study. The effects of thicknesses and annealing conditions on the electrical properties of CCTO thin films are discussed as well. The dielectric constant of CCTO thin films decreases with increasing film thicknesses. Both the dielectric constant of CCTO thin films and interlayer are calculated based on the equivalent circuit models, which are explored to explain the thickness dependence of the dielectric constant of CCTO films. Carrier conduction mechanisms of CCTO thin films at low and high electric fields are Ohmic conduction and Frenkel-Poole emission, respectively.