Method of forming a stepped surface in a three-dimensional memory device and structures incorporating the same

Abstract

A method includes forming a first-tier alternating stack of first insulating layers and first sacrificial material layers, forming a joint dielectric layer over the first-tier alternating stack, such that the joint dielectric layer is thicker than each of the first insulating layers and the first sacrificial material layers, forming a second-tier alternating stack of second insulating layers and second sacrificial material layers over the joint dielectric layer and the first-tier alternating stack, performing a level-shift anisotropic etch process to form a recess trench or via cavities vertically extending through the second-tier alternating stack and down to the joint dielectric layer, and performing an extension etching process to extend the recess trench or the via cavities through at least the joint dielectric level. At least one of etching time or etching power used during the extension etching process is different from that used during the level-shift anisotropic etch process.