Low Temperature and Pressureless Microfluidic Electroless Bonding Process for Vertical Interconnections
Low Temperature and Pressureless Microfluidic Electroless Bonding Process for Vertical Interconnections
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DOI：
10.1109/ectc.2019.00265
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
H. Hung;Sean Yang;I. Weng;Yan-Hao Chen;C. Kao
中科院分区：
文献类型：
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作者：
H. Hung;Sean Yang;I. Weng;Yan-Hao Chen;C. Kao
热压键合（TCB）工艺现已被用于高密度互连，但施加力和热的必要性会导致很多问题，例如翘曲引起的缺陷、精致芯片的破裂和热漂移。为了解决上述问题，我们提出了一种新的键合技术，称为微流体无电互连（MELI）工艺，在低于80°C的温度下直接制造Cu柱之间的互连，而无需对芯片施加任何压力。在我们先前的研究中已经表明，使用化学镀镍和化学镀Au的MELI工艺可以在受控的流动下键合垂直互连。为了将MELI的应用范围扩展到细间距，在本研究中，我们分析了通过在化学镀镍和化学镀Au溶液中添加稳定剂来在微通道中选择性化学沉积的可行性。化学镀可以在已经被催化活化的表面的所有部分上提供均匀的保形涂层。然而，从Cu柱凸块的侧面延伸的涂层缩短了互连节距，这可能导致桥接的风险。在本文中，我们成功地实现了选择性化学镀镍在微通道中添加1.5 ppm的醋酸铅到镀液。对于无电Au镀覆，可以通过使差距变窄来实现微通道中的选择性沉积。总之，创新的MELI工艺提供了一种低温无压的细间距键合技术。
Thermocompression bonding (TCB) process is now being adopted for high density interconnections but the necessity of applying force and heat causes a lot of problems, such as warpage-induced defects, cracking of delicate chips and thermal drift. To address the above issues, we proposed a novel bonding technique called microfluidic electroless interconnection (MELI) process to directly fabricate interconnection between Cu pillars at the temperature below 80°C and without applying any pressure on the chips. It has been shown in our previous researches that the MELI process using electroless Ni and electroless Au could bond vertical interconnection under controlled flow. In order to extend the application range of the MELI to fine pitch, in this study we analyze the feasibility of selective electroless deposition in microchannel by adding stabilizers into electroless Ni and electroless Au solution. Electroless plating can provide a uniform conformal coating on all parts of the surface that have been catalytically activated. However, the extended coating from the sides of the Cu pillar bump shortens the interconnect pitch, which may cause the risk of bridging. In this paper, we successfully achieve selective electroless Ni plating in microchannel by adding 1.5 ppm of lead acetate into the plating bath. As for electroless Au plating, selective deposition in the microchannel can be accomplished by narrowing the gap. In summary, the innovative MELI process provides a low-temperature and pressureless fine pitch bonding technique.