Cobalt UBM for fine pitch microbump applications in 3DIC

2015 IEEE International Interconnect Technology Conference and 2015 IEEE Materials for Advanced Metallization Conference (IITC/MAM) Pub Date : 2015-05-18 DOI:10.1109/IITC-MAM.2015.7325652

J. Derakhshandeh, I. de Preter, K. Vandersmissen, D. Dictus, L. di Piazza, L. Hou, S. Guerrieri, G. Vakanas, S. Armini, R. Daily, A. Lesniewska, Yannick Vandelaer, M. Van De Peer, J. Slabbekoorn, K. Rebibis, Andy Miller, G. Beyer, E. Beyne

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引用次数: 9

Abstract

In this paper we report results and challenges of replacing Cu with Co as UBM (under bump metallization) in microbumps for 3D technology applications. Cobalt has softer and single IMC (intermetallic compounds) and according to calculations using Cobalt as UBM can reduce consumption of UBM material by solder which is attractive for sub 10um pitches of microbumps. However, cobalt oxidizes very fast which results in poor wetting by solder as shown in Figure 1. This Figure shows two SEM images of cross section of 20um (left) and 50um (right) pitches microbumps from IMEC test vehicles where poor solder wetting is observed. It can be seen than in both cases Sn is deformed during TCB (thermo-compression bonding) bonding but due to oxide formation on cobalt bumps there is no reaction between Sn and Co. Such a joints may have weak electrical connection however, it is not suitable for a reliable device. Therefore surface treatment/passivation is required for cobalt bumps.

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钴UBM用于3DIC中的细间距微凸点应用

在本文中，我们报告了用Co代替Cu作为微凸点金属化(在凸点金属化下)用于3D技术应用的结果和挑战。钴具有较软的单一IMC(金属间化合物)，根据计算，使用钴作为UBM可以通过焊料减少UBM材料的消耗，这对于小于10um间距的微凸起是有吸引力的。然而，钴氧化非常快，导致焊料润湿不良，如图1所示。该图显示了IMEC测试车辆上20um(左)和50um(右)间距微凸起的横截面的两张SEM图像，观察到焊料润湿不良。可以看出，在这两种情况下，Sn在TCB(热压键合)键合过程中都发生了变形，但由于钴凸起处形成了氧化物，因此Sn和Co之间没有发生反应。这种接头可能具有弱的电气连接，但不适合用于可靠的器件。因此，需要对钴凸起进行表面处理/钝化。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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2015 IEEE International Interconnect Technology Conference and 2015 IEEE Materials for Advanced Metallization Conference (IITC/MAM)

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