Three-dimensional memory device including a deformation-resistant edge seal structure and methods for making the same

A method of forming a three-dimensional memory device, wherein the method comprises forming a memory die using processing steps of:

• forming a vertically alternating stack of insulating layers and dielectric spacer material layers over a semiconductor substrate;
• patterning the vertically alternating stack into a first alternating stack of first insulating layers and sacrificial material layers and a second alternating stack of second insulating layers and spacer dielectric layers, wherein the second alternating stack laterally encloses, and is laterally spaced from, the first alternating stack;
• forming memory stack structures comprising vertical stacks of memory elements through the first alternating stack;
• replacing the sacrificial material layers with electrically conductive layers while retaining the second alternating stack intact;
• forming at least one metallic wall structure vertically through the second alternating stack;
• forming memory-die bonding pads within dielectric material layers over the first alternating stack;
• and
• forming an edge seal assembly comprising at least one vertical stack of metallic seal structures, wherein each of the at least one vertical stack of metallic seal structures vertically extends from a top surface of the semiconductor substrate to a bonding-side surface of the dielectric material layers, and comprises a respective one of the at least one metallic wall structure.