标题: 高介电系数介电质在金氧金电容之研究
The Investigation of Metal-Insulator-Metal Capacitor Using High-k as Dielectrics
作者: 江国诚
Kuo-Cheng Chiang
荆凤德
Albert Chin
电子研究所
关键字: 金氧金;高介电;电容;混和讯号;类比;高频;动态记忆体;高功函数;MIM;High-k;Capacitor;Mixed-signal;analog;RF;DRAM;High work function
公开日期: 2006
摘要: 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电路里的去耦合、阻抗匹配与直流滤波器中;而且它们通常占据了很大比例的电路面积。此外金氧金电容也是发展高密度动态记忆体中面临的重要挑战。记忆体电容是决定检测讯号电压、速度还有防止软件误差影响资料保存时间和耐久性的重要参数。而根据国际半导体技术蓝图制定会(ITRS),为了元件尺寸缩微和节省成本,金氧金电容的面积必须不断的减少。
因为减低电容的厚度会增加不必要的漏电流以及恶化电容变化系数,所以使用高介电常数的介电层是唯一的解决方法。此外技术的趋势在于发展同一种高介电材料应用于类比、射频和动态记忆体嵌入式系统单晶片。所以高介电材料应用在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,例如低电压和低电容变化系数。因此在这里,我们发展出新的制程和超高介电系数的材料来改进金氧金电容,例如氧化钛和氧化钽的混合物、氧化钛和氧化铪的混合物(k~45-50)与钛酸锶(k~50-300) 。为了进一步改善这些介电质低能隙的缺点,应用高功函数镍或铱的上电极可得到较佳的特性。如此在有限的热预算下,不只高电容密度和低漏电还有低电容变化系数都可以同时实现。
除了基本的漏电流与低频量测以外,我们另外量测了射频电容的高频散射参数。并运用数学模拟软体,淬取出元件在不同频率所具有的电容大小。除此我们还深入研究电容的传导机制与电容变化跟电压和温度相关的成因,一些重要的因素如介电质跟电极间的介面层、能障、和表面粗糙度还有相关材料特性都在这篇论文中有透彻的讨论,相信这对发展高特性金氧金电容会有很大的帮助。
Among various passive devices, metal-insulator-metal(MIM) capacitors are widely used for decoupling, impedance
matching and direct current (DC) filtering; they occupy a large fraction of circuit area. Moreover, one of the most critical challenges which gigabit density DRAM’s face will be MIM memory cell capacitance. Memory cell capacitance is the crucial parameter which determines the sensing signal voltage, sensing speed, data retention times and endurance against the soft error event. According to International Technology Roadmap for Semiconductors (ITRS), continuous down-scaling of the size of MIM capacitors is required to reduce chip size and the cost.
To meet these requirements high dielectric constant (k) materials provide the only solution, since decreasing the dielectric thickness to increase the capacitance density degrades both the leakage current and dC/C performance. Furthermore, it is also desirable to use the same high-k □ dielectric to meet all the Analog, RF and DRAM functions for embedded SoC. Therefore the high-k dielectrics used in MIM capacitors have evolved from SiON (k~4-7), Al2O3 (k=10), HfO2 (k~22), Ta2O5 (k~25) to Nb2O5 (k~40). However, the demonstration of MIM with these films is yet able to achieve properties such as nondispersive, good linearity and high breakdown with low leakage concomitantly, at high unit capacitance. Hence, we have developed novel process and very high-k materials, such as TiTaO, TiHfO (k~45-50) and STO (k~50-300) to advance this technology. To further improve small bandgap (Eg) in these dielectrics, a high work-function Ir or Ni (5.2 eV) electrode is used to give better performance. Therefore, not only high capacitance density, and low leakage current, but also small voltage- and temperature- dependence of capacitance are achieved under limited thermal budget for back-end integration.
In addition to the measurements of leakage current density and capacitance at low frequency, we also measured the S-parameters to investigate the characteristics of the MIM capacitors at RF regime. Using the simulation software, the capacitance of the device at different frequencies was extracted. Moreover, understandings of the mechanism of conductivity, voltage- and temperature-dependence of capacitance were studied, which are also useful in the development of advanced MIM devices. The related factors, such as barrier height, surface roughness, interfacial layer, and dielectric material properties should be concerned for improving MIM performance, which were also investigated in this thesis.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009311809
http://hdl.handle.net/11536/78173
显示于类别:Thesis


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