【作者】 尹翔；

【导师】 吴春艳；

【作者基本信息】 合肥工业大学 ， 集成电路工程（专业学位）， 2022， 硕士

【摘要】 为了达到低温互连、高温服役的目的,一般利用Sn基无铅焊料通过固-液互扩散技术实现Cu-Cu键合。在键合界面处产生均匀、连续和致密的Cu-Sn金属间化合物（IMCs）层是可靠键合的必要条件,但在高温下IMCs层的过度不规则生长以及良性高强度的Cu₆Sn₅向恶性较脆的Cu₃Sn的转变将导致键合可靠性的降低。为了提高Cu-Cu键合的可靠性,提出采用低温键合工艺和利用还原氧化石墨烯（rGO）薄膜作为键合中间层来抑制IMCs的过度不规则生长,具体内容如下:1.利用同步还原自组装方法直接在Cu衬底表面制备连续的厚度约为14 nm的rGO薄膜,并采用N₂H₄进行二次化学还原以进一步提高rGO的还原程度。结果表明,rGO薄膜表面连续且平整,石墨烯结构较完整,含氧官能团被有效去除,C原子的共轭结构得到了恢复。2.采用低温键合技术,利用Sn-3.0 Ag-0.5 Cu（SAC）焊料在150℃的温度下实现了Cu/rGO/SAC/rGO/Cu键合结构,并将样品置于高温环境下持续老化以研究rGO中间层对IMCs过度不规则生长的抑制作用。在150℃环境中老化72 h后,Cu/rGO/SAC/rGO/Cu键合结构依旧保持较高的剪切强度和低的接触电阻,且Cu/rGO/SAC/rGO/Cu键合结构的剪切强度下降速率和接触电阻上升速率均小于Cu/SAC/Cu键合结构。在Cu/rGO/SAC界面形成了一层薄而均匀、连续且致密的IMCs,其层厚较Cu/SAC界面降低了30%以上,平均投影面积降低了80%以上。3.为了验证rGO薄膜作为键合中间层的可靠性及低温键合工艺的通用性,再利用Sn-57 Bi-1.0 Ag（SBA）焊料在100℃的温度下实现了Cu/rGO/SBA/rGO/Cu键合结构,得到了与前述研究类似的结果。通过对比总结与计算,分析了rGO薄膜抑制IMCs过度不规则生长的机理,得出了键合界面原子扩散模型。综上,rGO薄膜作为键合中间层及低温键合工艺可以有效抑制键合界面IMCs的过度不规则生长,延长器件服役时间,同时该键合工艺具有温度低、操作方便、可靠性高的优点,具有广泛的应用前景。更多还原

【Abstract】 In order to achieve the purpose of low temperature interconnection and high temperature service,Cu-Cu bonding is generally realized by solid-liquid interdiffusion technology using Sn-based lead-free solder.The formation of uniform,continuous and dense Cu-Sn intermetallic compound（IMCs）layer at the bonding interface is a necessary condition for reliable bonding,but the immoderate irregular growth of the IMCs layer and the transformation of benign and high-strength Cu₆Sn₅into malignant and brittle Cu₃Sn at high process temperatures will lead to the decrease of bonding reliability.For the sake of improve the reliability of Cu-Cu bonding,a low temperature bonding process and the use of reduced graphene oxide（rGO）film as the bonding interlayer are proposed to inhibit the excessive irregular growth of IMCs.The details are as follows:1.Continuous rGO film with thickness of about 14 nm were fabricated directly on Cu substrate surface by synchronous reduction and self-assembly method,and the reduction degree of rGO was further improved by secondary chemical reduction with N₂H₄.The results show that the surface of rGO film is continuous and smooth,the graphene structure is relatively complete,the oxygen-containing functional groups are effectively removed,and the conjugated structure of C atoms is restored2.Sn-3.0 Ag-0.5 Cu（SAC）was used to realize Cu/rGO/SAC/rGO/Cu bonding structure at 150℃by low temperature bonding technology.The samples were subjected to continuous aging at high temperature to study the inhibitory effect of rGO interlayer on the immoderate irregular growth of IMCs.After aging at 150℃for 72 h,the Cu/rGO/SAC/rGO/Cu bonding structure still maintains high shear strength and low contact resistance,and the shear strength decline rate and contact resistance increase of Cu/rGO/SAC/rGO/Cu bonding structure were both lower than that of the Cu/SAC/Cu bonding structure.A thin,uniform,continuous and dense IMCs layer was formed at the Cu/rGO/SAC interface.The thickness of the IMCs layer is more than 30%lower than that at the Cu/SAC interface,and the average projection area is more than 80%lower.3.In order to verify the reliability of rGO film as bonding interlayer and the universality of low temperature bonding process,Cu/rGO/SBA/rGO/Cu bonding structure was realized by Sn-57 Bi-1.0 Ag（SBA）solder at 100℃,and similar results were obtained.Through comparison,summary and calculation,the mechanism of rGO film inhibiting the immoderate irregular growth of IMCs was analyzed,and the atomic diffusion model of bonding interface was obtained.In conclusion,rGO film as bonding interlayer and low temperature bonding process can effectively inhibit the immoderate irregular growth of IMCs on bonding interface and prolong the service time of devices.Meanwhile,this bonding process has the advantages of low temperature,convenient operation and high reliability,and has a wide application prospect.更多还原