Process for word line connections in 3d memory

Abstract

A 3D memory has multiple memory layers stacked on top of a substrate. Word lines in different memory layers are connected respectively to different columns of contact pads in the substrate directly under the multiple memory layers. The connection is accomplished by creating vertical shifts above each contact pad and creating a vertical word line VIA connecting to the contact pad. For a given memory layer and its column of vertical word line VIAs, an auxiliary vertical shaft down to the memory layer is formed between each vertical word line VIA and an adjacent word line. The auxiliary vertical shaft is contiguous with the vertical shift allowing access to the vertical word line VIA. The auxiliary vertical shaft also enables excavating a lateral space between the word line and the vertical word line VIA. Filling the space with a conductive material completes a conductive path from the word line to the contact pad.