LOW TEMPERATURE BONDING OF AU-AU IN NON-VACUUM ENVIRONMENT USING SURFACE ACTIVATED METHOD

摘要

Plasma treatment, using argon and hydrogen mixed gas, was studied as pretreatment of gold surface for Au-Au interconnection. Ion bombardment and chemical reactions of Ar/H_2 plasma with gold surface were used for both surface activation and removal of surface contaminants. XPS was used to evaluate the cleaning effect of the plasma treatment. Relationships of surface roughness, shear strength and plasma treatment time were also studied. As contaminants content decreased and surface roughness increased with increasing plasma treatment time, shear strength of Au-Au interconnection became stronger except the plasma treatment time exceeded thirty minutes. In addition, the relationships between bonding parameters, such as bonding pressure and bonding temperature, and shear strength were also investigated in this paper. After optimizing the plasma treatment time and bonding parameters, we can obtain Au-Au interconnection with low temperature (150°C) and low pressure (13.3 MPa) in non-vacuum environment compared with traditional thermocompression. Finally, the reliability of 30 um pitch chip on chip (COC) interconnections was tested in -55°C～125°C thermal shock test (TST) for 500 cycles. According to the results, it is possible to get reliable joint and stable contact resistance of Au-Au interconnection at low temperature in non-vacuum environment using surface activated method, even in 30μm pitch COC applications.