THREE-DIMENSIONAL MEMORY DEVICE AND METHOD OF MAKING THEREOF USING ION IMPLANTED ETCH STOP LAYER ON A SACRIFICIAL FILL MATERIAL

A method includes forming a first alternating stack of first insulating layers and first sacrificial material layers over a substrate, forming a first in-process inter-tier dielectric layer over the first alternating stack, forming a first memory opening through the first in-process inter-tier dielectric layer and the first alternating stack, forming a sacrificial memory opening fill structure in the first memory opening, doping an upper portion of the sacrificial memory opening fill structure with atoms of at least one dopant species, forming a second alternating stack of second insulating layers and second sacrificial material layers over the first alternating stack, forming a second memory opening through the second alternating stack by performing an anisotropic etch process, and removing the sacrificial memory opening fill structure.