Kumar, C Hemanth and Vanjari, Siva Rama Krishna and Singh, Shiv Govind et. al.
(2017)
WoW Post-CMOS compatible Cu-Cu Low temperature, Low pressure thermocompression bonding with Pd passivation Engineering.
In: 19th International Workshop on Physics of Semiconductor Devices, IWPSD, 11-15 December 2017, New Delhi, India.
Abstract
Surface passivation of Copper plays vital role in accomplishing low temperature, low pressure Wafer-on-Wafer (WoW) Cu-Cu thermocompression bonding, as it not only helps in protecting the Cu surface from oxidation but also smoothen the surface. Ultra-thin Palladium (Pd) layer is regarded as one of the promising passivation layer which can prevent oxidation of copper and in addition it can also minimize the roughness of Cu surface. The thickness of Pd layer plays an important role in achieving good and reliable bonding. In this endeavor, we have optimized the Pd passivation thickness to achieve low temperature (150 ˚C) and low pressure (4 bar) WoW Cu-Cu thermocompression bonding. The optimum thickness of Pd for achieving a good bonding is found out to be 3 nm. Our optimized result yielded an excellent bond interface confirms the reliability of Cu-Cu bonding with Pd passivation.
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