Three-dimensional memory device having non-uniform spacing among memory stack structures and method of making thereof

Abstract

An alternating stack of insulating layers and sacrificial material layers is formed over a substrate. Memory stack structures including a memory film and a vertical semiconductor channel are formed through the alternating stack in an array configuration. Backside trenches extending along a lengthwise direction are formed through the alternating stack. Backside recesses are formed by removing the sacrificial material layers. Filling of the backside recesses with electrically conductive layers can be performed without voids or with minimal voids by arranging the memory stack structures with a non-uniform pitch. The non-uniform pitch may be along the direction perpendicular to the lengthwise direction such that the nearest neighbor distance among the memory stack structures is at a minimum between the backside trenches. Alternatively or additionally, the pitch may be modulated along the lengthwise direction to provide wider spacing regions that extend perpendicular to the lengthwise direction.