Test structures for electrical evaluation of high aspect ratio TSV arrays fabricated using planarised sacrificial photoresist

An improved bottom-up electroplating technique has been successfully developed for the fabrication of TSV arrays with 9.5:1 aspect ratios. 125,500 TSVs have been fabricated in an area of 6×6 cm with a horizontal and vertical pitch of 240 μm. A method of visually inspecting the via yield is presented, and Kelvin test structures and contact chain test structures have been fabricated to electrically evaluate single and multiple TSVs respectively. The average resistance of the Cu vias was measured as of 9.1 mΩ using the Kelvin contact resistance structures.