■ Topic : No TSV pumping occurs for electrodeposited copper
■ Speaker : Dr. Kazuo Kondo (Osaka Prefecture University, Department of Chemical Engineering)
■ Date : June 16 (Tue), 16:00
■ Venue : Education 3.0 Classroom (W1-1, Room No. 2427)
■ Abstract :
We have found that the copper electrodeposit thermal expansion coefficient(TEC) reduces to half, or sometimes shows negative TEC. This electrodeposit not only fills the PCB via but also fills through silicon via. Some additives are effective.
The difference in TEC between silicon and copper causes serious failures with annealing. For the via middle process of TSV formation, the electrodeposited copper encounters with the annealing temperature of 450℃. This annealing temperature causes pumping of the electrodeposited copper and cut the wiring above the TSV. The warpage causes serious C4 interconnection failures at the second annealing of 230℃ for few ten seconds.
With an in situ high temperature annealing stage, the pumping has been measured. Pumping samples are tilted 70°to the incident electron beam. Thermal expansion coefficients of electrodeposited copper have been measured by as follows. Coppers are electrodeposited on aluminum substrate pipes sputtered with gold and the aluminum pipes are dissolved in NaOH solution. Hence, copper foil pipes form. Thermal expansion coefficient of these copper pipes have been measured in cylindrical rod of TD5020SA (NETZSCH).