难混溶系（铜—钨、钼、铌）复合膜及多层膜的结构与性能研究

发布时间：2018-04-17 15:21

  本文选题：Cu-W(Mo + Nb)复合薄膜　； 参考：《昆明理工大学》2016年博士论文

【摘要】：Cu薄膜具有良好的导电性、电迁移抗性及塑韧性,被广泛用于微电子和微机械领域。但因其粘附性差、强度和硬度不高,因此Cu薄膜的改性成为必然。难熔金属与铜在性质上有互补性,且铜-难熔金属复合薄膜常呈现特殊结构及优良的综合性能。本文选择Cu-W、Cu-Mo及Cu-Nb三个难混溶体系作研究对象,通过正交试验优化工艺,采用磁控溅射方法,以组合靶共溅射成功制备了宽成分Cu-W.Cu-Mo及Cu-Nb复合薄膜,并用单质靶交替沉积制备Cu/W纳米多层膜。通过结构与性能分析测试,研究W、Mo及Nb添加量对Cu复合薄膜结构与性能及热稳定性的影响,考察Cu/W纳米多层膜结构与性能与调制参数的关系。这些研究不仅为铜-难熔金属薄膜的应用提供了实验依据和重要支持,而且对新颖结构-功能型薄膜的设计和研发深具指导意义。提出了合理的评价指标优化工艺,即靶功率密度PD为8 W/cm2、溅射气压P为2 Pa、靶基距Drs为140 mm。统一用该工艺制备薄膜,为探讨组元含量的影响规律提供了保证。自行设计了镶嵌和叠加型组合靶,调整靶面积分数即能有效控制成分,工艺简单且稳定性和重复性好,为铜基复合薄膜的制备提供了一条新路径。利用磁控溅射非平衡技术,制备出了具有亚稳和非晶结构的Cu复合薄膜,其结构与W、Mo及Nb含量有关：(1)在W、Mo及Nb低含量区(含(2.12～16.19)at.%W、 (2.19～15.12)at.%Mo及(1.16～23.43)at.%Nb),复合薄膜呈现亚稳准混溶态均质化结构,存在fcc Cu(W).Cu(Mo)及Cu(Nb)亚稳准固溶体。(2)在中间含量区(含(24.65～38.2)at.%W.(20.26～35.15)at.%Mo及(35.32～48.1)at.%Nb),Cu-W和Cu-Mo膜呈亚稳准混溶态高度均质化结构,分别存在(fcc Cu(W)+bcc W(Cu)).(fcc Cu(Mo)+bcc Mo(Cu))两种亚稳准固溶体；Cu-Nb膜则为非晶Nb与晶态Cu混合结构。(3)在高含量区(含(53.14～55.92)at.%W.(58.6-74.91)at.%Mo及(53.36～60.4)at.%Nb)),Cu-W和Cu-Mo膜也呈亚稳准混溶均质化结构,并存在bcc W(Cu)和bcc Mo(Cu)亚稳准固溶体；Cu-Nb膜为完整非晶结构。适量添加W、Mo及Nb可细化Cu复合薄膜的晶粒,并提高薄膜的表面光洁度：随含量增加,晶粒尺寸逐渐减至小于4 nm,RMS值低达1.93 nm。这是因W、Mo、Nb原子形核率高扩散率低,均匀弥散的核心可有效阻止Cu原子的扩散迁移。含W、Mo及Nb的Cu复合薄膜存在102MPa量级的本征应力,处于弹性压应力状态。Cu复合薄膜电学性能和力学性能也与W、Mo及Nb含量有关：随含量增加,Cu复合薄膜的电阻率ρ、屈服强度σ0.2、弹性模量E及硬度H逐渐增加,裂纹萌生临界应变8。和摩擦系数μk逐渐减小。高W、Mo含量的薄膜ρ、σ0.2及εc值减小,其余值增加；中、高Nb含量的Cu-Nb膜ρ和μk值明显增加,其余值均降低。电学和力学性能的这种变化均与结构变化密切相关。总体上,Cu-Nb膜电阻率最高而Cu-W膜最低,Cu-Nb膜弹性模量和硬度最低,体现了组元本征性质的影响。Cu-2.12at.%W膜电阻率最低(11.4 μΩ·cm), Cu-35.15at.%Mo膜屈服强度最高(1.302 GPa)而摩擦系数最低(0.089), Cu-1.16at.%Nb膜裂纹萌生临界应变最大(1.95%), Cu-74.91at.%Mo膜弹性模量和硬度最高(分别为168.85和9.19 GPa)。添W、Mo及Nb明显影响Cu复合薄膜的膜基结合力,结合力随其含量增加先增后减,Cu-38.2at.%W膜结合力最强(31.07 N)。热处理使Cu复合薄膜结构发生不同程度的改变。200～400℃的退火通常只发生回复和初始再结晶；临界退火温度为650℃,中、高W、Mo及Nb含量的复合薄膜分别发生相分离及晶化转变,形成(富Cu+富W、Mo及Nb)两相并存结构。退火温度为650℃时,随退火时间延长,相分离更为彻底而两相结构趋于完整。退火时Cu复合薄膜应变弛豫并减弱本征压应力。热稳定性评估表明Cu复合薄膜结构基本稳定的温度上限约在400～650℃范围。退火的Cu复合薄膜形貌明显改变,出现凸出表面的Cu偏聚粒子,表面粗糙度显著增加。一些偏聚粒子表观形状为六边形或准对称八边形,归因于其结构为能量最低的截角八面体。退火改变薄膜力学和电学性能,随退火温度升高或时间延长,其E和H值通常降低,但Cu-Nb膜在晶化转变后有所提高；电阻率则单调递减。650℃-5 h退火后,Cu-74.91at.%Mo膜E和H值仍最高(分别为162.5和7.24 GPa), Cu-2.12at.%W膜电阻率仍最低(5.47 μΩ·cm)。Cu/W纳米多层膜的Cu和W层均呈纳米细晶结构,随λ增加Cu{111}和W{110}织构减弱或消失,W(110)晶面间距随λ减小或η增加而减小。混合过渡层存在于Cu/W层间界面。厚厚增加时,Cu层晶粒明显增大且表面更光洁,W层晶粒尺寸和表面光洁度无明显改变。调制参数λ和η显著影响多层膜力学和电学性能。总体而言,当λ或η增加时,多层膜的屈服强度、弹性模量、硬度及电阻率趋于减小,裂纹萌生临界应变ε。则随λ减小或η增加而增加。调制参数改变引起层厚、层间界面数量及子层(尤其Cu层)微结构的变化,使层内和层间的位错运动和电子散射情况以及W层应力强度因子改变,因此多层膜性能发生变化并呈规律性。
[Abstract]:Cu thin film has good conductivity, electromigration resistance and toughness, is widely used in microelectronics and micro mechanical field. But because of the poor adhesion strength, and hardness is not high, so the Cu film modified inevitable. Refractory metal and copper in nature are complementary, and refractory copper - gold a composite film often has special structure and excellent comprehensive performance. This paper chooses Cu-W, Cu-Mo and Cu-Nb three immiscible system as the research object, through the orthogonal test method, the use of magnetron sputtering, sputtering successfully with a combination of wide component Cu-W.Cu-Mo and Cu-Nb composite films were prepared, and the elemental target alternate preparation Cu/W nano multilayer film deposition. By analyzing the structure and properties of W, Mo test, and effects of Nb content on the structure and properties of Cu composite films and thermal stability, relationship between structure and properties of Cu/W nano multilayers and the modulation parameters. These studies Not only is the Cu to provide experimental basis and important support for application of molten metal films, and has guiding significance to design and research and development of novel functional thin film structure is proposed. The evaluation index to optimize the reasonable process, namely the target power density of PD was 8 W/cm2 P 2 Pa, sputtering pressure, target substrate distance Drs as for the process of 140 mm. unified film provides a guarantee effect, to discuss the rule of component content. The mosaic and superimposed composite target was designed to adjust the target area fraction that can effectively control the composition, simple process and good stability and repeatability, for copper based composite film preparation provides a new path. By using unbalanced magnetron sputtering technology, preparation of Cu composite films with metastable and amorphous structure, and the structure of W, Mo and Nb contents: (1) in W, Mo and Nb (with low content area (2.12 ~ 16.19) at.%W (2.19 ~ 15.12) at.%Mo and (from 1.16 to 23.4 3)at.%Nb),澶嶅悎钖勮啘鍛堢幇浜氱ǔ鍑嗘贩婧舵，

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