With the maximum operating temperature of semiconductor devices becomes higher, novel die attach methods for high temperature application are required. Cu–Cu direct bonding provides a simple solution that eliminates the use of die attach materials and the related reliability issues. However, the easy oxidation of copper is the main obstacle for Cu–Cu direct bonding. In this study, a simple and efficient method for Cu–Cu direct bonding in minutes at low pressure and low temperature in air without complex pre-treatment was developed. The problem of copper oxidation was solved by rapid in-situ reduction and temporary passivation of glycerol. The bonded samples show very high shear strength. The surface leveling effect of the glycerol reduction was verified, which is beneficial for bonding. The bonded samples showed little change in shear strength after 1000 h of aging at 250 °C in air, demonstrating a long-term high temperature service capability. This new bonding method has great potential in power devices packaging and flip chip bonding.

中文翻译：

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通过甘油原位还原氧化铜在空气中直接键合 Cu-Cu

随着半导体器件的最高工作温度变得更高，需要用于高温应用的新型芯片贴装方法。 Cu-Cu 直接键合提供了一种简单的解决方案，消除了芯片连接材料的使用以及相关的可靠性问题。然而，铜的易氧化是Cu-Cu直接键合的主要障碍。在这项研究中，开发了一种简单有效的方法，无需复杂的预处理，即可在低压和低温的空气中在几分钟内实现铜-铜直接键合。通过甘油的快速原位还原和暂时钝化解决了铜氧化的问题。粘合的样品显示出非常高的剪切强度。验证了甘油还原的表面流平效果，有利于粘接。在250℃空气中老化1000小时后，粘合样品的剪切强度几乎没有变化，表现出长期的高温使用能力。这种新的键合方法在功率器件封装和倒装芯片键合方面具有巨大的潜力。