集成电路铜互连中硅碳氮介质阻挡层的制备与特性研究

【作者】 石之杰；

【导师】 周继承；

【作者基本信息】 中南大学 ， 凝聚态物理， 2009， 硕士

【摘要】 随着集成电路技术不断发展,互连RC（R为电阻,C是介质电容）延迟却逐步增大。从130nm技术阶段开始,其已成为影响电路速度的主要矛盾。为提高互连性能,采用新的低电阻率金属互连材料（Cu）和低介电常数互连介质材料的铜互连技术应运而生。Si₃N₄常被用作大马士革工艺中的电介质阻挡层,在其成型过程中也被用作刻蚀停止层,同时也是其下方铜导线的覆盖层,器件的稳定性受其影响较大,而Si₃N₄是一种高介电常数（k=7～8）介质,会增加互连系统的有效介电常数,影响互连延迟的降低。于是新型三元材料SiCN（k=4～5）作为铜互连大马士革工艺中的电介质扩散阻挡层的应用受到了人们的广泛关注。在综合分析比较了各类阻挡层制备方法、性能特征的基础上,本文采用磁控溅射法在n型Si（111）衬底上制备出了SiCN薄膜和Cu/SiCN/Si纳米薄膜,并对薄膜样品进行了快速热退火（RTA）。用四探针电阻测试仪（FPP）、原子力显微镜（AFM）、X射线衍射（XRD）、扫描电镜（SEM）、EDS能谱、傅里叶变换红外光谱（FTIR）等测试分析方法对各样品的方块电阻、表面形貌、晶体结构、成分、化学键等特性进行了表征分析。实验结果表明,射频磁控反应溅射方法可以制备出表面光滑致密的无定形非晶SiCN薄膜。对其化学成分分析表明所得薄膜为富Si的SiCN薄膜,样品中存在Si—N、Si—C、C—N、C=N、C—Si—N键,说明SiCN薄膜不是二元薄膜的简单结合,而是形成了复杂的无规网络结构。样品中有少量的C团簇成分,并含有微小的Si颗粒。SiCN薄膜具有非常优异的热稳定性,其晶化温度在1200℃左右。通过C-V特性曲线的分析,所得SiCN非晶薄膜的相对介电常数为4.22,略小于晶体SiCN的相对介电常数5。SiCN薄膜作为Cu的介质阻挡层有很好的阻挡效果,其失效温度在600℃左右。Cu/SiCN/Si薄膜体系的界面稳定性好,Cu膜与SiCN薄膜之间附着性良好。对Cu/SiCN/Si结构热稳定性的研究发现其主要失效机制为:Cu通过非晶层的结构缺陷向内部扩散,同时与SiCN膜发生反应消耗Si、N等元素,耗尽阻挡层后,与Si层反应并生成Cu₃Si。更多还原

【Abstract】 The interconnect resistance-capacitance （RC） delay is a dominant factor in determining the performance of ultra large-scale integrated circuits as critical dimension below 130 nm. Although many low-k materials have been used as interlayer dielectrics （ILD）, high dielectric constant （k =7-8） of silicon nitride （Si₃N₄） film is still the primary candidate for the Cu cap barrier and etch stop layer （ESL） required in the Cu damascene process. Thus, this increases the effective k value of stack dielectric films, and limits the reduction of the RC delay in ultra large-scale integration. As a result, amorphous silicon nitricarbide （SiCN） have received much attention for applications as Cu dielectric diffusion barrier and ESL in Cu damascene process.On the basis of a comparative study of the diffusion barriers on their fabrication methods and characteristics, SiCN thin films and Cu/SiCN thin films were deposited on n-type Si（111） substrates by magnetron reactive sputtering. Then rapid thermal annealing （RTA） was performed on the samples. The sheet resistance, surface morphology, crystalline structures, chemical composition and chemical bonding status of the films were characterized by four-point probe （FPP） sheet resistance measurement, atomic force microscopy （AFM）, scanning electron microscope （SEM）, X-ray diffraction method （XRD）, energy disperse spectroscopy （EDS）, and fourier transform infrared spectroscopy（FTIR）, respectively.The results revealed the formation of complex networks among the three elements, Si, C and N, and the existence of different chemical bonds in the SiCN films such as Si-C, Si-N, C-N, C=N and C-Si-N. Further more, there are C and Si clusters in the samples. The as-deposited SiCN thin-films were amorphous structure with smooth and compact surfaces, and their crystallization temperature is about 1200℃, which shows their good thermal stability. The sheet resistance measurement and C-V measurement results shows that the dielectric constant of the as-deposited SiCN thin-films is 4.22.The SiCN thin-films play a good performance as Cu dielectric diffusion barriers and they can prevent the diffusion reaction between Cu and Si interface after 5min RTA processing below 600℃. The Cu/SiCN thin films have a good thermal stability and the adhension of Cu with SiCN is strong, and no Cu film falling is observed. The failure of the barriers is mainly attributed to Cu diffusion and reactions among multilayered films. Cu atoms diffuse through the flauts of the amorphous structure of SiCN layers directly, and react with Si and N of SiCN barriers untill the barriers fail, and finally react with Si substrates to form the Cu₃Si phase.更多还原