- 學位論文
以氮化鋁材料作為矽基板上閘極介電層之研製與特性分析
Characteristic Study of MIS Capacitors Using Sputtered AlN Film as Gate Dielectrics
摘要
在半導體製程微縮的過程中，除了水平方向的縮減外，垂直方向也必須作等比例縮減來維持元件的基本操作。所以在65及45奈米時代，傳統的二氧化矽絕緣層厚度將需要縮小到約奈米左右，此時閘極之電子藉由穿隧(Tunneling)效應通過閘極氧化層流入元件之汲極，產生元件之大量漏電流及遷移率下降問題。為了降低閘極漏電流，必須將閘極絕緣層的實際厚度增加以減少穿隧電流，但是又要維持在電性操作時之等效氧化層厚度(Effective Oxide Thickness; EOT)不變。於是使用高介電常數(k)材料作為絕緣層，以同時兼顧閘極絕緣層實際厚度與電性等效厚度便成為眾所矚目之課題。 近來氮化物由於有堅固的機械性質、熱穩定性、寬能隙(6.2 eV)等特性，已被視為最具潛力的新一代電子材料。其中，氮化鋁是所有材料當中，具有良好的電絕緣性又同時具有良好的熱傳導性且與其它金屬共存性佳的少數材料之一，此外還具有高介電常數(ε= 8.5)、高體電阻、低介電損失等優點，而其製程與IC發展相容。此外由於本實驗室使用具有類MBE成長機制之迴旋濺鍍系統(Helicon sputtering system)成長氮化鋁薄膜已有多年經驗，使得氮化鋁成為本研究中的高介電值材料。 本研究以氮化鋁(AlN)薄膜作為MIS電容器中的閘極介電層，並透過I-V、C-V等電性量測，觀察其介電常數在厚度50~135Å下，k值約介於7.6~9.9；而在等效氧化層(EOT)方面，氮化鋁可微縮至25Å；閘極漏電流密度約為10-5~10-8 A/cm-2左右@ -1V。至於與陷捕電荷數相關的遲滯曲線寬度則以厚度為50Å下的ΔVh=100 mV (8.75x1011cm-2)為最佳值；而介面態密度值則約為1012 cm-2eV-1左右。 由實驗結果可知，在透過改善製程及回火條件之下，均可得到不錯的氮化鋁薄膜品質及其電性表現，尤其在微縮等效氧化層厚度及抑制漏電流方面的優點；對於在未來65或45奈米技術節點的應用上，若能更好地控制製程及基板表面環境，氮化鋁薄膜將可能成為具有潛力的閘極介電層。
並列摘要
In the downscaling process of the semiconductor industry , besides reduction in the horizontal direction , the basic operation that such proportions as the vertical direction must be done to reduce and maintain the properties of the component . Therefore , in 65 and 45 nm technology node , the thickness of the traditional insulator SiO2 will need to be reduced to about 1nm . However , the electrons of the gate can flow through gate oxide into drain by tunneling in this case , and produce large leakage current and thus the degradation of mobility . To decrease the leakage current , one must increase the physical thickness of the gate insulator to reduce the tunneling current , while keeping the EOT (equivalent oxide thickness) to maintain the characteristics of the devices . Using insulators with high dielectric constant is one of the attractive and popular method to research the problem . Recently the nitrides have already been considered as the most potential electronic material of a new generation , because of its firm mechanical nature , excellent thermal stability and wide bandgap (6.2 eV) . Aluminium nitride among the all material have good insulating in electricity , excellent thermal conduction and superior coexisting with other metal at the same time . In addition , it has high many advantages of dielectric constant (ε=8.5) , high body resistance and low dielectric loss , and which is comparable to IC process . Because our laboratory use helicon sputtering system that is MBE-like to deposit aluminium nitride film experience for many years , and control to the understanding and quality of the aluminium nitride film has sutible confidence . Comprehensive above-mentioned material advantages , we choose aluminium nitride as the high dielectric constant material in our research . In this research , the I-V、C-V electrical characteristics of MIS capacitors using AlN thin film deposited by Helicon sputtering system has been reported. The dielectric constant of 7.6~9.9 , and the leakage current density of 10-5~10-8 A/cm2 at -1V were obtained for physical thickness of around 50~135 Å , as the EOT scaled down to 25 Å . The optimized hysteresis(ΔVh) is about 100mV (8.75x1011cm-2) for 50Å . The Dit is about 1012 cm-2eV-1 . The experimental results showed that AlN thin film with acceptable electrical properties , especially in downscaling the equivalent oxide thickness and suppressing the leakage current, can be obtained using improved and optimized process . This makes AlN film as the potential gate dielectrics in 65 or 45 node technology in the future .