雙重電漿處理下二氧化鉿金屬-絕緣層-半導體電容器的電流傳導機制以及可靠度之研究

Abstract

非結晶形態的二氧化矽閘極介電質在金氧半場效電晶體元件的製造上提供了許多的優點，像是熱穩定性，高品質的矽基板與二氧化矽的界面以及優良的電絕緣性。因此，二氧化矽在過去40年已經被普遍地應用在積體電路製程技術上。為了提升金氧半場效電晶體元件的特性，極薄的閘極介電質是必須的。由於氧化層厚度在65奈米製程之後將會小於1奈米，造成太高的閘極直接穿隧漏電流。因此，閘極介電質的微縮無法永遠持續下去。高介電常數閘極介電質能夠有效降低漏電流而且維持好的元件特性。在許多的高介電常數閘極介電質材料之中，由於較大的介電常數，相對大的能隙以及與矽之間良好的熱穩定性，二氧化鉿是最有潛力的。在本篇論文中，以Al/Ti/HfO2/Si金屬-絕緣層-半導體電容器作為控制樣品。結合沉積前氟電漿處理以及沉積後氮電漿處理的製程，我們稱為雙重電漿處理。此論文記述雙重電漿處理下的二氧化鉿金屬-絕緣層-半導體電容器電流傳導機制以及可靠度特性。所有經過雙重電漿處理的樣品都表現出電容密度的提升以及漏電流的降低。雙重電漿處理也能大大地降低表面狀態的數量以及抑制界面層的成長。電流傳導機制歸因於蕭基發射(Schottky emission),弗崙克爾-普爾發射(Frenkel-Poole emission)以及福勒-諾德海姆穿隧(Fowler-Nordheim tunneling)。蕭基發射主導於中低電(1.7-3.0 MV/cm)與高溫(>348K)時，弗崙克爾-普爾發射主導於中高電場 (4.0-6.0MV/cm)，福勒-諾德海姆穿隧則是在高電場(>7MV/cm)下具有主導性。

Amorphous silicon dioxide gate dielectric proffered many advantages in fabrication of MOSFET device,such as thermodynamically stable,high-quality Si/SiO2 interface and excellent electrical isolation properties.Therefore silicon dioxide has been applied popularly in the integrated circuit process technology in the past 40 years.In order to promote the performance of MOSFET device,ultrathin gate dielectric was needed.Oxide thickness would be less than 1.0 nm for 65 nm technology node,leading to high gate direct tunneling leakage current.Therefore,the scaling down of gate dielectric could not go on forever.High-κ gate dielectric could effectively reduced leakage current and maintained good device performance.Among many dielectric materials,HfO2 is the most promising material due to its high dielectric constant,relatively large band gap,and good thermal stability with Si.In this thesis, Al/Ti/HfO2/Si metal-insulator-semiconductor capacitors were used as control samples.The process which combined pre-deposition plasma fluorination and post-deposition plasma nitridation, we called it dual plasma treatment.This thesis reported current conduction mechanisms and reliability properties of HfO2 MIS capacitors with dual plasma treatment.It indicated that all samples with dual plasma treatment showed the promotion of capacitance density and reduction of leakage current.Dual plasma treatment could also greatly reduce the number of interface states and suppress the growth of interfacial layer.The current conduction mechanisms could be attributed to Schottky emission(SE),the Frenkel-Poole (FP)emission,and Fowler-Nordheim(FN) tunneling in different ranges of electric field.Schottky emission(SE) dominated in low to medium electric field(1.7-3.0MV/cm) and at high temperature(>348K),Frenkel-Poole(FP) emission dominated in medium to high electric field(4.0-6.0MV/cm) and Fowler-Nordheim(FN) tunneling dominated in electric field(>7MV/cm).