Bonding Mechanisms of Roughened Nanotwinned-Cu Surface at Temperature as Low as 120 °C
YewChung Sermon Wu, Tung‐Yen Lai, Meiyi Li, Tsan-Feng Lu, Yu Hsiang Wang, Tzu Yen Tseng
Abstract
Cu direct bonding has been achieved at 150 °C by using (111)-oriented nanotwinned Cu (nt-Cu) because it has the fastest surface diffusivity. In this study, nt-Cu was bonded at even lower temperature of 120 °C by roughening one of the nt-Cu surfaces. However, the flat-to-flat nt-Cu could not be bonded at the same temperature. This result violates a bonding concept that “for good wafer bonding, the contact area must be as large as possible”. This paper discusses in detail two possible bonding mechanisms: diffusion and creep/plastic deformation.
Topics & Concepts
Materials scienceDiffusion bondingCreepWaferThermal diffusivityAnodic bondingComposite materialThermocompression bondingWafer bondingDiffusionDirect bondingMetallurgyNanotechnologyThermodynamicsLayer (electronics)Physics3D IC and TSV technologiesElectronic Packaging and Soldering TechnologiesCopper Interconnects and Reliability