标题: | 介孔洞二氧化矽超低介电薄膜在积体电路技术之应用 Mesoporous Silica Thin Films as Ultralow-k Dielectrics for ULSI Applications |
作者: | 陳致宇 Jr-Yu Chen 潘扶民 張立 Fu-Ming Pan Li Chang 材料科學與工程學系 |
关键字: | 介孔洞二氧化矽;超低介电材料;氢化碳化矽;金属化;铜镶嵌;三甲基矽化作用;Mesoporous silica;Ultralow-k dielectrics;Hydrogenated silicon carbide;Metallization;Copper damascene;Trimethylsilylation |
公开日期: | 2005 |
摘要: | 本研究将进行有机模板分子介孔洞二氧化矽(mesoporous SiO2)超低介电薄膜之制备,期能应用于半导体65奈米以下之IC制程。研究中乃利用模板分子之自我组装(self-assembly)方式制备出具有4-6 nm大小之孔径,且呈高规则孔道结构的介孔洞二氧化矽薄膜。由于其孔洞呈现规则性排列且孔洞尺寸具有一致性,因此经由此种方法可以制作出具有较佳之机械性质与介电特性的多孔性二氧化矽薄膜。此薄膜若再经由三甲基矽化作用(trimethylsilylation)之疏水化改质,不但可使多孔性二氧化矽薄膜具有k~2.1之超低介电常数,且因薄膜内有序性的微孔洞结构,以及孔洞表面上的三甲基矽化结构所产生的回弹效应(spring-back effect),因此利用此一方式亦能有效地提升多孔性二氧化矽薄膜之机械强度。 此外,本研究亦对于多孔性二氧化矽薄膜以及其与非晶相氢化碳化矽(a-SiC:H)薄膜的叠层,进行薄膜应力方面的研究与探讨。在多孔性二氧化矽薄膜的制备过程中,因薄膜内所含有的溶剂与模板分子,于烘烤与煅烧阶段不断地被移除,使得二氧化矽薄膜产生体积收缩,衍生张应力。研究中发现,薄膜经过HMDS (Hexamethyldisilazane)蒸气处理后,在回弹效应的作用下,薄膜张应力将可得以舒缓。非晶相氢化碳化矽薄膜本身具高压应力,与多孔性二氧化矽薄膜形成叠层后,藉由应力补偿与其镀膜时烷氧基化诱生的回弹效应,同样可舒缓多孔性二氧化矽薄膜的张应力,甚至形成轻微的压应力。 最后,金属化后多孔性二氧化矽薄膜叠层的热稳定性与化学结构的稳定性亦将被探讨。研究结果显示以HMDS蒸气处理过后,薄膜内的三甲基矽化结构其热稳定性可达400oC,并能持续稳定保持极佳之疏水性与介电特性达50天以上。然而经高温(>400oC)退火后,三甲基矽化薄膜的化学结构被发现有劣化的现象,位于孔洞表面上的甲基会因高温而产生裂解脱附。不过在高温退火之下并未发现到有金属离子穿隧过Ta(N)阻障层到介电层中,薄膜叠层也显示具有很好的附着性。本研究之结果显示经三甲基矽化改质后的多孔性二氧化矽薄膜具有卓越的热与介电稳定性,利于将来进行铜镶嵌之后段制程整合。 Organic templated mesoporous silica ultralow-k films were prepared as the intermetal dielectric for sub-65 nm IC technology nodes. The films have a pore size of 4-6 nm and a well-ordered pore channel structure formed in a self-assembly process of the surfactant. The self-assembled molecularly templated mesoporous silica films have better mechanical and dielectric properties than many other porous low-k dielectrics, because of an ordered pore structure and uniform pore size distribution. Trimethylsilylation of the mesoporous silica thin film by HMDS vapor treatment greatly improves the hydrophobicity of the mesoporous dielectric, and a dielectric constant ~2.1 can be obtained for the thin film. Also, trimethylsilylation effectively increases the mechanical strength of the mesoporous silica films. Moreover, the nanoindentation measurements are discussed in terms of the pore microstructure of the mesoporous silica network and the spring-back effect due to the trimethylsilyl groups in the nanopores. The film stress of the mesoporous silica thin film and the a-SiC:H/mesoporous silica film stack was also studied. The as-calcined mesoporous silica exhibits a tensile film stress caused by its contraction during bake and calcination. Trimethylsilylation of the mesoporous film causes the spring-back effect, thereby improving its mechanical properties and relieving the tensile stress. Deposition of a plasma-assisted a-SiC:H layer on the mesoporous silica thin film can also relieve the tensile stress, and even cause the film stack to become compressively stressed. This finding follows from the stress compensation and alkoxylation during the deposition of a-SiC:H. Finally, the thermal and chemical stability of the Cu/nitrided Ta/mesoporous silica film stack on the Si wafer are considered. The trimethylsilylated mesoporous silica dielectric is thermally stable up to 400oC, and its dielectric and chemical properties are reliably maintained over 50 days. Decomposition of trimethylsilyl groups on the pore surface becomes significant at temperatures of over 400oC. However, when the metallized film stack is annealed at temperatures of over 400oC, the film stack exhibits only slight delamination between layers and retains smooth interfaces. A bias-temperature stress test of the metallized film stack reveals little Cu diffusion into the mesoporous dielectric layer. This work reveals that the trimethylsilylated mesoporous silica thin film is thermally and electrically stable up to 400oC, and is a candidate ultralow-k dielectric for incorporation into a Cu damascene structure. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT008918524 http://hdl.handle.net/11536/77757 |
显示于类别: | Thesis |
文件中的档案:
If it is a zip file, please download the file and unzip it, then open index.html in a browser to view the full text content.