應用於金氧半電晶體閘極氧化層的高介電常數薄膜之電性研究

An Investigation on the Electrical Properties of High Dielectric Constant Films for the Application of Gate Dielectric of Metal-Oxide-Semiconductor Field Effect Transistors

張銀谷(Ingram Yin-Ku Chang)

指導教授 ： 李雅明

國立清華大學/電機資訊學院/電子工程研究所/博士(2009年)

https://doi.org/10.6843/NTHU.2009.00052

摘要

本實驗製作利用氧化鋁鑭 (LaAlO3)、堆疊式氧化鉿 (HfO2)/氧化鍶 (CeO2)、與氧化釤 (Sm2O3)介電材料做為絕緣層的金氧半電容器與電晶體並探討電流傳導機制、薄膜與矽基材的接面特性與電子遷移率衰減的機制。所有的介電薄膜都是利用高頻磁控濺鍍器濺鍍而成。物性分析採用X光繞射儀 (XRD)、二次質譜分析儀 (SIMS)、X光電子頻譜儀 (XPS)與穿隧式電子示波器 (TEM)。氧化鋁鑭具有很高的結晶溫度，經過濺鍍後退火溫度1000度5秒後依然保持非晶態。在電容器的電性分析上，氧化鋁鑭的介電係數為17.5。其有相對低的漏電流密度，在電壓為-1 V時為7.6×10-5 A/cm2，這是因為氧化鋁鑭與鋁電極有很大的電子障礙高度1.8 eV。而電子障礙高度與電子有效質量是利用電流傳導機制中的蕭基發射Schottky emission與Fowler-Nordheim 穿隧計算出來的，其值為分別為1.12 eV 與0.27 倍的真空電子質量 (m0)。在氧化鋁鑭與矽基材間的接面特性上，表面的復合速度 (surface-recombination velocity, s0)、少數載子的生命時間 (minority carrier lifetime, τ0,FIJ)、還有有效的表面缺陷截面積 (effective capture cross section of surface state, σs)參數都是利用分析電晶體的閘極二極體特性而得到的。在電子遷移率的研究上，利用變溫從11K 到300 K對電晶體的影響，臨界電壓 (threshold voltage) (VT/T)會隨著溫度上升而下降，變化率為-1.38 mV/K，而電子遷移率會因材料與矽基材間的粗糙度限制而變差，隨著電場強度有著Eeff-0.66的關係。 而聲子散射 (phonon scattering) 在溫度變化從300 K到400 K有著T-5.6的關係。
利用堆疊式氧化鉿 (HfO2)/氧化鍶 (CeO2)與矽基材的接面研究上，表面缺陷密度(Dit) 為9.78x1011 cm-2 ∙ eV-1，表面的復合速度(s0)與少數載子的生命時間(τ0,FIJ)分別為6.11×103 cm/s 與1.8×10-8 s。有效的表面缺陷截面積(σs)為7.69×10-15 cm2。
利用氧化釤 (Sm2O3)薄模制作的電容器，分析其電流傳導機制，在溫度從325 K到500 K間，電場從0.08 到 0.81 MV/cm間，主要的電流傳導機制為蕭基發射Schottky emission，在溫度為77 K電場大於 0.9 MV/cm時，主要的電流傳導機制為Fowler-Nordheim 穿隧機制，而電子障礙高度與電子有效質量則是利用蕭基發射Schottky emission與Fowler-Nordheim 穿隧分析中計算出來的，其值為分別為0.82 eV 與0.13 倍的真空電子質量 (m0)。

關鍵字

氧化鋁鑭 ； 堆疊式氧化鉿/氧化鍶 ； 電流傳導機制 ； 電子遷移率衰減 ； 閘極二極體 ； 氧化釤

並列摘要

In our work, metal-oxide-semiconductor capacitors and transistors with LaAlO3 (LAO), laminated HfO2/CeO2, and Sm2O3 gate dielectrics were fabricated. The current conduction mechanisms, the interfacial properties, and the electron mobility degradation mechanisms were studied. The dielectric films were deposited by radio frequency magnetron sputtering and examined by x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The LaAlO3 films remained amorphous with post-deposition annealing up to 1000 °C for 5 s. The dielectric constant of LAO capacitors was 17.5. The leakage current density was relatively low at 7.6×10-5 A/cm2 for a voltage bias of -1 V due to the high electron barrier height of 1.8 eV at the Al/LaAlO3 interface. The Al/LaAlO3 barrier height and the effective electronic mass calculated from from Schottky emission and Fowler-Nordheim tunneling were 1.12 eV and 0.27 m0, respectively. The interfacial properties such as the surface-recombination velocity, the minority-carrier lifetime, and the effective capture cross section of surface states were extracted from the gated-diode measurement. The temperature dependence of electron mobility degradation mechanisms was studied from 11 K to 400 K. The rate of threshold voltage change with temperature (VT/T) was -1.38 mV/K. The electron mobility limited by surface roughness was proportional to Eeff-0.66 in the electric field of 0.93 MV/cm

並列關鍵字

LaAlO3 ； laminated HfO2/CeO2 ； conduction mechanisms ； electron mobility degradation ； gated diode ； Sm2O3

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