High-density through-wafer copper via array in insulating glass mold using reflow process

Abstract

A high-density through-wafer vertical copper via array in insulating glass interposer is demonstrated. The glass reflow and bottom-up filling copper electroplating process enables fabrication of a vertical through-wafer copper via array with high aspect ratio and high density. The minimum diameter of the copper vias and the gaps in between are 20 and 10 µm, respectively. Three failures among one hundred measurement points were detected within a 1 cm2 area of the via array, and the resistance of the 20-µm-diameter copper via was measured to be 153 ± 23 mΩ using the four-probe method. The optical transmittance and RF performance of the reflowed glass substrate were compared with those of bare glass. The reliability of the copper via in harsh environments was evaluated through thermal shock and pressure cooker tests.