Recent Progress in the Development of High-Density TSV for 3-Layers CMOS Image Sensors

Copper TSV in a via last approach were developed for advanced imaging applications. An aspect ratio of 10:1 was targeted with a diameter/space of 1 mu m/1 mu m (pitch 2 mu m) associated to a depth of 10 mu m. A test vehicle made of a single metal level on each side of a thinned Si substrate bonded onto a thick carrier was used to develop and optimize a process flow compatible with the constraints of a subsequent hybrid bonding process. An electrical resistance of 0.7 O (median value) was measured on Kelvin patterns and a yield of 100% was obtained on daisy chains made of 10 000 TSV. No failure was observed after 2000 h of HTS at 150 degrees C nor after 2000 cycles of TCT between -55 degrees C and +150 degrees C.