Effect of thermal shock on Cu extrusion of TSV for three-dimensional packaging

Through-silicon-via (TSV) is a core technology that enables vertical stacking of several semiconductor chips for 3-demensional packaging. However, thermo-mechanical problems of the TSV technology, such as Cu extrusion, cracks between the Cu and Si substrate, and voids within Cu become important issues. In this study, Cu-filled TSV with a diameter of 30 μm and depth of 70 μm was fabricated by electroplating, and the effect of thermal shock on Cu extrusion of the TSV was investigated. A thermal shock test was conducted from -65 °C to 150 C for 250, 500, and 1000 cycles. The experimental results showed that a defect free Cu-filled TSV was obtained by electroplating using periodic pulse-reverse current form. Cu extrusion occurred after the thermal shock test, and the average height of the pumped Cu increased from -0.3 to 0.78 um with increasing thermal shock cycles from 0 to 1000. An interfacial crack between Cu and Si was observed after 1000 cycles. The average grain size of Cu during the thermal shock test from 0 to 1000 cycles increased from 0.65 to 0.83 μm.