标题: | 高介电系数介电质材料应用于金氧金电容之研究 The Investigation of Metal-Insulator-Metal Capacitor Applying High-k Dielectrics Material |
作者: | 黄靖谦 Huang, Ching-Chien 荆凤德 Chin, Feng-Der 电子研究所 |
关键字: | 高介电系数材料;金氧金电容;高频;high-k dielectric material;Metal-Insulator-Metal capacitor;RF |
公开日期: | 2008 |
摘要: | 根据国际半导体技术蓝图制定会(ITRS),元件尺寸必须不断的缩微,为了配合现今类比、射频通讯和记忆体元件的发展,金氧金电容(MIM Capacitor)的研发是刻不容缓的。在各种不同的被动元件中,金氧金电容经常被广泛的应用在射频电路里的阻抗匹配与直流滤波器中;然而,它们通常却占据了很大的电路面积。此外,金氧金电容也是发展高密度动态记忆体中所面临的重要挑战之一。因此,为了有效降低晶片的面积与节省成本,提高单位面积的电容值是极为需要的。为了达到未来记忆体元件的高电容密度要求,高介电系数介电质材料的开发似乎是唯一的选择。当使用高介电质材料时,在增加材料的介电常数和减少元件厚度所伴随而来的高漏电,更是目前主要的研究议题之一。 目前高介电材料应用于金氧金电容从氮氧化矽(k~4-7)、氧化铝(k~10)、氧化铪(k~22)、氧化钽(k~25),一直发展到氧化铌(k~40)。但是目前在这些材料中还无法同时达到在高电容密度下金氧金电容所需要的特性,例如:低漏电、低电压和低电容变化系数。因此,我们发展出新的制程和高介电系数的材料来改进金氧金电容,例如氧化镍(k~30-40)、氧化镨(k~26-32)和钛酸锶(k>50)。为了进一步改善介电质低能隙的缺点,我们利用较高功函数金属铂或铱当作上电极,可以得到较佳的元件特性。 虽然,钛酸锶具有高介电系数,但较低的导带不连续(conduction band discontinuity)和能带宽度(bandgap),会造成较大的电流。钛酸锶必须要形成结晶相才能具有较高的介电系数(k~150-170),而要形成奈米结晶(nano-crystal)的钛酸锶,则需要较高的制程温度(>450oC),这不适用于后段制程。此外,钛酸锶具有电压电容系数(Voltage coefficient of capacitance)较高的缺点。因此,我们利用氧化钽具有降低漏电流以及改善电压电容系数的特性,将氧化钽以一定比例掺入钛酸锶中,可有效降低整体元件的漏电流和电压电容系数。此外,我们也成功发展出一种电浆处理(Plasma treatment)介电质的方法,不但在漏电流上有明显的改善,也同时改良了电压电容系数和温度电容系数(Temperature coefficient of capacitance)。 除了基本的漏电流与低频量测以外,我们也量测了射频电容的高频散射參數。并利用模拟软体,淬取出元件在不同频率所具有的电容大小。除此,我们还深入探讨电容的传导机制与电容变化跟电压和温度相关的成因,相信本篇论文对未来发展高效能金氧金电容会有很大的助益。 According to International Technology Roadmap for Semiconductor (ITRS), continuous increasing the capacitance density is required to scale down the device size and the cost of Metal-Insulator-Metal (MIM) capacitors which are widely for Analog, RF and DRAM functions. However, they often occupy a large fraction of circuit area. To meet these requirements, high dielectric constant (k) materials provide the only solution since decreasing the dielectric thickness (tk) degrades both the leakage current and ΔC/C performance. To achieve this goal, the only choice is to increase the k value of the dielectrics, which have evolved from SiON (k~4-7), Al2O3 (k=10), HfO2 (k~22), Ta2O5 (k~25) to Nb2O5 (k~40). To further achieve the properties of MIM such as low leakage current, low voltage coefficient of capacitance and low temperature coefficient of capacitance. Thus, we have developed novel process and high-k dielectric materials, such as TiNiO (k~30-40), TiPO (k~26-32) and SrTiO3 (k>50) to achieve this technology. To further improve the small bandgap (EG) of these dielectrics, we apply the higher work-function Pt (5.7 eV) and Ir (5.3 eV) top electrode are used to give better device performance. Although SrTiO3 has large dielectric (k~50-200), the small conduction band offset (ΔEc) and bandgap leading to larger leakage current is a larger drawback. Besides, SrTiO3 shows its higher k values by forming nano-crystals, which is only practicable at a higher process temperature > 450oC. Furthermore, the high voltage coefficient of capacitance of SrTiO3 is also an important issue. Because Ta2O5 has very low voltage coefficient of capacitance and can considerably suppressed the leakage current, the overall electrical characteristics of MIM device could be improved by doping Ta2O5 into SrTiO3 MIM capacitor. Otherwise, we have developed a plasma treatment on dielectric to repair the defect of the dielectric to improve leakage current, voltage coefficient of capacitance and temperature coefficient of capacitance at the same time. Therefore, not only high capacitance and low leakage current, but also small voltage/temperature dependence of capacitance are obtained under limited thermal budget for back-end-integration. In addition to the measurement of capacitance at low frequency and the leakage current, the measurement of the S-parameters to investigated the characteristics of the MIM capacitors at RF regime are also demonstrated. By using the simulation software, the capacitance density of MIM capacitors at different frequencies was extracted. Besides, the related factors such as understandings of the mechanism of conductivity, the voltage/temperature dependence of capacitances, barrier height, and interfacial layer were investigated, and these are also useful in the development of advanced MIM capacitors. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT009311513 http://hdl.handle.net/11536/77985 |
显示于类别: | Thesis |
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