【作者】 李超；

【导师】 陈明祥；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2017， 硕士

【摘要】 为适应半导体集成电路技术的发展趋势,电子封装技术逐步进入三维封装和系统封装集成时代。三维封装的发展离不开先进键合技术,Cu-Cu键合保留了金属铜的众多优良性能,包括高导电导热性、高强度、低成本以及抗电迁移性能,是十分有潜力的三维封装键合技术。但普通Cu-Cu键合温度较高,对封装产生不可忽略的损害,实现Cu-Cu低温键合是一个急需解决的问题。纳米多孔铜具有高表面能以及小尺寸效应带来的低熔点,是一种实现Cu-Cu低温键合的潜在材料。去合金法制备的纳米多孔铜具有结构可控、工艺简单、成本低廉等优点。本文利用去合金法在陶瓷基片上制备纳米多孔铜,并以此为键合层材料实现了Cu-Cu低温键合。主要研究内容如下:首先分析了以纳米多孔铜为键合层材料实现Cu-Cu低温键合的理论依据,纳米多孔铜具有小尺寸效应带来的低熔点、高孔隙率带来的低杨氏模量,是实现Cu-Cu低温键合的理想材料。然后以铜锌合金为前驱体,用去合金法在陶瓷基片表面制备了一层1μm厚的纳米多孔铜薄膜,并系统地分析了去合金温度、腐蚀剂种类、前驱体成分对纳米多孔铜结构的影响。通过综合以上参数设计去合金实验,制备了韧带特征尺寸在20nm以下的纳米多孔铜薄膜。另外开展了以纳米多孔铜为键合层材料的纳米热压键合实验,通过键合界面分析、键合层超声检测以及键合层抗拉强度检测对键合质量进行评估,并分析了各种键合工艺参数对键合质量的影响。以纳米多孔铜薄膜作为键合层材料,在200℃条件下键合90min,实现了Cu-Cu低温键合,键合层抗拉强度高达8.4MPa,而普通铜薄膜在相同情况下未能实现键合,证实了纳米多孔铜可以作为键合层材料实现Cu-Cu低温键合。最后,用分子动力学模拟了纳米铜颗粒键合过程,分析了各键合参数影响纳米热压键合的微观机制。更多还原

【Abstract】 In order to meet the development of semiconductor technology,electronic packaging gradually moves into a new era of three-dimensional packaging and system-in-packaging.Bonding is an important process for three-dimensional packaging.Among many bonding methods,Cu-Cu bonding has huge advantages,such as high electrical and thermal conductivity,extraordinary strength,low cost and high electromigration resistance,which make it a very promising bonding technology for achieving three-dimensional packaging.However,a high bonding temperature required by normal Cu-Cu bonding does a lot damages to the package,which gives much importance to Cu-Cu low-temperature bonding technology.Considered as a potential bonding material,nanoporous copper has many unique properties,such as small size effect,high surface energy and low melting temperature.To prepare size-controllable nanoporous copper,dealloying method stands out from the rest for its simple process and low cost.In this paper,ceramic substrates were covered by thin nanoporous copper films,with which as bonding layers Cu-Cu low-temperature bonding was achieved.The main contents are listed as follows:Firstly,light was cast on the theoretical foundation for Cu-Cu low-temperature bonding with nanoporous copper as bonding layers.Properties like small size effect and good softness make nanoporous copper feasible to lower the temperature of Cu-Cu bonding.Secondly,nanoporous copper was fabricated by dealloying method,and the key process parameters affecting the nanoporous structure including annealing temperature,choice of etchant and precursor composition were studied.With all parameters above considered,ligament feature size of nanoporous copper was shrink as fine as 20 nanometers.Thirdly,bonding experiments with various process parameters were carried out.To analyze how much those parameters effect bonding,the bonding qualities were evaluated by three kinds of methods.An excellent bonding quality with a tensile strength as high as 8.4MPa was achieved by bonding nanoporous copper at 200℃ for 90 minutes,while the control groups with normal copper films failed to be bonded under the same conditions,which verified the feasibility of Cu-Cu low-temperature bonding with nanoporous copper as bonding layers.Last but not the least,in order to understand the micro-mechanism of bonding with nanoporous copper,molecular dynamics simulation was carried out to simulate the bonding process of two copper nano-particles.The key factors which contribute to a successful bonding with nanoporous copper were analyzed,too.更多还原