【作者】 聂王焰；

【导师】 徐洪耀；

【作者基本信息】 安徽大学 ， 无机化学， 2010， 博士

【摘要】 随着超大规模集成电路(ULSI)的迅速发展,器件的集成度逐步提高,半导体芯片特征尺寸不断减小。当特征尺寸降低到亚微米时,线间和层间寄生电容引起的RC延迟、串扰、功耗已经成为限制器件性能的主要因素。研究和开发综合性能优异的低介电常数材料,以取代传统的Si02介电材料是解决上述问题的有效方法。根据2005年国际半导体发展规划预测,2013年将进入32 nm线宽的纳电子器件时代,要求介电常数k<2.0的超低介电常数材料作为线间和层间介质。而目前,性能优越的符合ULSI制作要求的超低介电常数材料尚未出现。本文的目的在于研究和探索新型超低介电常数材料的设计和制备方法,具体研究内容如下：(1)详细综述了国内外低介电常数材料的发展现状。针对目前低介电常数材料研究的不足,提出了课题研究内容。(2)设计并合成了一种多功能团的POSS分子(T8H8)及三种不同结构的二烯功能团有机小分子,通过FT-IR,1H-NMR和13C-NMR对其结构进行了表征。并通过DSC和POM等对合成的三种二烯单体进行了热性能及液晶性能的分析,发现其中二种单体具有较高的热稳定性和良好的液晶性质,呈现向列相液晶织构。另一种单体受柔性烷基链的影响使其热稳定性降低并失去液晶性质。该研究为功能型高分子液晶材料的分子设计奠定了基础。(3)选择以笼型多面低聚倍半硅氧烷T8H8为结构构造基元,以具有刚性液晶基元的二烯分子为有机连接链,通过硅氢化加成反应,将所有的POSS笼以共价键的形式连接起来,合成了三种POSS基有机-无机杂化交联聚合物,优化了制备条件。利用FTIR和29Si NMR对合成产物的结构进行了表征,证明成功合成了POSS均匀分散的有机-无机杂化交联聚合物。(4)杂化交联聚合物TGA分析结果表明,三种杂化聚合物均表现出较高的热稳定性,聚合物的热稳定性与有机成分二烯的刚性有关,随着有机碳链刚性增强,Td增大；且聚合物的热性能受分子交联密度的影响,交联密度越大,聚合物的热稳定性越高。(5)AFM和SEM观察结果均显示,三种杂化交联聚合物薄膜均具有较好的均一性和平整度；不同放大倍数的SEM照片显示,在薄膜表面未发现任何裂纹和破损区域,证明合成的杂化交联聚合物具有较好的成膜性。三种杂化交联聚合物的XRD图谱未出现POSS的结晶峰,表明聚合物中的POSS组分未发生物理聚集,而呈现均匀分散状态。(6)采用纳米压痕法对杂化交联聚合物薄膜的力学性能进行表征。结果发现,三种聚合物薄膜具有较高的硬度和弹性模量,硬度在0.13-0.20GPa、弹性模量在5.37-8.08GPa之间。硬度和弹性模量随着连接POSS的有机碳链的刚性增大而增大。(7)通过氧化-裂解工艺制备了POSS基多孔低介电常数薄膜。HRTEM和BET分析结果表明,三种薄膜均具有丰富的多孔性,孔径在23-88 nm之间,比表面积为307-612m2/g,孔体积为0.03-0.37 cm3/g。研究表明,连接POSS的有机碳链的长度和刚性适中,可得到孔径大小分布均匀、比表面积和孔体积大的多孔薄膜材料。(8)接触角测试结果发现：三种杂化交联聚合物薄膜的接触角θ值均大于100°,表现出较强的疏水性。随着连接POSS的碳链刚性增强,它们的吸水性依次减弱。(9)采用椭圆偏振测量技术测定薄膜的介电常数。结果发现,三种多孔薄膜的介电常数在1.69-2.10之间,k值小于2.2,属于超低介电常数材料。薄膜的孔隙率影响材料的介电常数大小,随着多孔薄膜孔隙率的增大,薄膜的介电常数减小。更多还原

【Abstract】 With the rapid development of the ultra-large-scale integration(ULSI). continuing increase in device density has markedly made the feature size of integrated circuit(IC) device continue to decrease. As feature size approach beyond submicron, the resistance-capacity (RC) delay, cross-talking and power dissipation of the interconnect structure become limiting factors for the overall performance of integrated system. In order to improve circuit performance, new materials with low dielectric constant and excellent properties are required to replace the traditional silicon dioxide(k=4.0) as interlayer dielectrics. According to the International Technology Roadmap for Semiconductors(ITRS 2005), nano-electronic times with 32 nm of wiring dimension may appear in 2013. Ultra-low-dielectric-constant materials (k<2.0) should be achieved for the insulator between interconnect. However, ultra-(?)-k materials which satisfy the requirement of ULSI fabrication have not emerged so far. Therefore, ultra-low-k materials are extremely important in the current microelectronic industry. This dissertation is devoted to the exploration and investigation of the design and preparation of novel ultra-low-k materials. The major contents are as follows:(1) The recent development of low-k materials was systematically reviewed. Based on the existing problems in research and application, the contents of our research were put forward.(2) A POSS molecule (T8H8) with multiple functional groups and three diene monomers which contain different structures with olefin bond in the molecular end were designed and synthesized. Their structures were characterized by FT-IR. ’H-NMR and 13C-NMR. The thermodynamic properties and liquid crystalline characters of three diene monomers were analyzed by DSC and POM. The results showed that two of them exhibited nematic phase with high thermal stability. But the other one showed us nothing because of the effect of alkyl chain. This work paves the way for designing new functional liquid crystalline polymers. (3) Three organic-inorganic hybrid polymers based on POSS were prepared via hydrosilylative addition reaction between octahydridosilsesquioxane (T8H8) and linear dienes with rigid liquid crystalline mesogenic unit, and the synthetic conditions were optimized and their structures were characterized by FTIR,29Si-NMR. The results confirmed that the hybrid polymers with POSS cages uniformly dispersed in the networks were successfully synthesized.(4) The TGA results showed that three hybrid polymers have good thermal stability. The Tds increase with increasing the rigidity of linking chains between POSS cages, and the thermal properties are affected by molecular cross-linking density.(5) AFM and SEM observation shows that the surfaces of the hybrid polymer films are smooth and free of cracks or flaws at multiple magnifying scale, indicating that the synthesized hybrids have good film formability. No crystalline peaks appearing on the XRD spectra showed that POSS cages were well dispersed in the polymeric matrix and no POSS aggregation occurred.(6) The mechanical properties of the hybrid polymer films were measured using a nanoindenter (Hysitron Tribolndenter) with a Berkowich diamond tip. All the three films show good mechanical properties with their hardness around 0.13-0.20 GPa and elastic modulus in the range of 5.37～8.08 GPa. Both hardness and elastic modulus increase with increasing the rigidity of linking chains between POSS cages.(7) Nanoporous silica films based on POSS were prepared via oxidation-decomposition process. HRTEM observation and BET characterization show that porous silica films had evenly dispersed nanopores with 23～88 nm in pore diameter, 307-612m2/g of surface area and 0.03～0.37 cm3/g of pore volume.By changing the length and rigidity of organic linking chain in the hybrids, porous silica films with various porosities can be achieved.(8) The contact angle tests showed that three hybrid polymer films had contact angles bigger than 100°, standing for considerable hydrophobic property. The moisture adsorption of films decreases with increasing the rigidity of linking chains between POSS cages.(9) The electrical properties of nanoporous films were analyzed by variable-angle spectroscopic ellipsometry. The results show that porous films had low dielectric constant values around 1.69-2.10.The porosity of films had much influence on dielectric constants, which showed an obvious decreasing trend with increasing porosities.更多还原