超薄(Ta2O5)1-x-(TiO2)x介電薄膜之研究

Abstract

利用磁控射頻濺鍍法製備結晶性與非結晶性超薄(Ta2O5)1-x-(TiO2)x介電薄膜，分別以Pt與IrOx為底電極，以Al為上電極得到MIM電容結構，作物性與電性之分析。非結晶性薄膜初始厚度為14Å~160Å，利用n&k及TEM量測薄膜厚度，可知薄膜厚度與鍍膜時間成正比，薄膜成長初期需要約五秒鐘成核成長。探討不同成長溫度以及不同退火溫度下，薄膜的漏電流特性及介電特性及表面形態關係。 由I-V及C-V量測顯示，非結晶性薄膜在電場為1MV/cm下，初始厚度50Å薄膜其漏電流密度可達到1*10-6(A/cm2)，退火溫度越高，介電常數隨之升高；結晶性薄膜在電場為1MV/cm下，初始厚度96Å薄膜其漏電流密度可達到5*10-6(A/cm2)。經對薄膜漏電流機制進行預測，可以發現非結晶性(Ta2O5)1-x-(TiO2)x介電薄膜主要為蕭特基發射，而結晶性(Ta2O5)1-x-(TiO2)x介電薄膜主要為普勒-法蘭克發射。

Crystalline and amorphous ultra thin (Ta2O5)1-x(TiO2)x films were prepared by magnetron rf sputtering in this study. The amorphous films thickness, varying from 14 Å to 160 Å obtained by n&k and TEM measurements, shows a linear increase with deposition time and indicates an incubation time of around 5 seconds. The physical and electrical properties of the dielectric films, sandwiched in a MIM structure with Pt and IrO2 as bottom electrode and Al as top electrode, were investigated. The leakage current, dielectric behavior and surface morphology of the films deposited and subsequently annealed at various temperatures were measured and their correlations were studied. For typical amorphous films of thickness 50 Å, the leakage current density under an field of 1MV/cm is 1*10-6(A/cm2) and its dielectric constant increases with the annealing temperature. For crystalline films of 90 Å, the leakage current density under the same field is 5*10-6 (A/cm2). The charge transport in the former follows the Schottky Emission model, and Poole-Frenkel model in the latter.