Memory die containing stress reducing backside contact via structures and method of making the same

Abstract

A three-dimensional memory device includes a pair of alternating stacks of insulating layers and electrically conductive layers located over a semiconductor region, and laterally spaced from each other by a backside trench, memory stack structures extending through the pair of alternating, each memory stack structure containing a vertical semiconductor channel and a memory film, and a backside contact assembly located in the backside trench. The backside contact assembly includes an isolation dielectric spacer contacting the pair of alternating stacks, a conductive liner contacting inner sidewalls of the isolation dielectric spacer and a top surface of the semiconductor region, and composite non-metallic core containing at least one outer dielectric fill material portion that is laterally enclosed by a lower portion of the conductive liner and a dielectric core contacting an inner sidewall of the at least one outer dielectric fill material portion.