TSV-Cu protrusion induced by thermal cycling test

Abstract

Current densities of 1.5ASD and additive concentrations of 15ml/L were used to electroplate the copper into TSV to fabricate the test samples. The samples were annealed at 425°C for 30 minutes in a vacuum furnace with the heating rate of 10°C /min. The annealed samples were thermal cycled with temperature range (25~325°C), heating & cooling rate (10 °C/min), dwell time of 2 min at the peak and bottom temperature in each cycle. The copper protrusion and microstructure evolution are examined during the thermal cycling. The results show that, the protrusion value increases gradually with the thermal cycling number increases, and reaches stable value of 2.152μm after the cycling number increases to 30 cycles. The average copper grain size grows larger as the thermal cycling number accumulates, suggesting grain growth occurs during the thermal cycling. The sample with greater copper grain size has a greater protrusion after the thermal cycling test.