Method for reducing via resistance in small high aspect ratio holes filled using aluminum extrusion

Abstract

A method of forming an electrical interconnect through a via to electrically couple two electrically conductive layers and the device. There are provided a pair of electrically conductive layers and an electrically insulating layer between the pair of electrically conductive layers having a via extending between the pair of electrically conductive layers. A layer of titanium is formed covering the walls of the via and extending onto one of the pair of electrically conductive layers. A thin layer of titanium nitride with a poor step ?? technique is formed covering the titanium on the walls but not covering the titanium on the one of the pair of electrically conductive layers. The remainder of the via is filled with aluminum. The layer of titanium and the layer of titanium nitride preferably extend out of the via and between the electrically insulating layer and at least one of the pair of electrically conductive layers. The aluminum is substantially everywhere spaced from the portion of the layer of titanium covering the walls of the via. The filling of the remainder of the via with aluminum can include deposition of aluminum in the via, heating the aluminum to a temperature at which it is plastically deformable and applying pressure to the aluminum to cause the aluminum to substantially fill voids within the aluminum.