Dummy vertical structures for etching in 3d nand memory and other circuits

Abstract

A memory device comprises a stack of patterned conductor layers, at least a plurality of the layers comprising conductive strips including strips continuous with a pad and other strips isolated from the pad. An array of vertical pillars extends through the stack of patterned conductor layers, wherein memory cells are disposed at cross-points between the vertical pillars and patterned conductor layers. The array has an array boundary proximal to the pad. A first set of isolation blocks extends through the plurality of patterned conductor layers separating the strips continuous with the pad from the other strips isolated from the pad. A second set of isolation blocks inside the array boundary extends through the plurality of patterned conductor layers isolating the other strips from the pad.