3D NAND Stacked Connections With Etch-Stop Alignment Layers

The patent introduces an intermediary etch-stop layer (aluminum oxide) between the conductor layers and the memory strings. This etch-stop layer acts as a mediator that provides precise alignment references during fabrication and enables selective etching processes. The etch-stop layer with specific etch selectivity allows for controlled formation of connections between stacked memory strings while maintaining alignment tolerance, thus resolving the contradiction between manufacturing precision and process complexity.

The patent transitions from planar memory architecture to three-dimensional stacked architecture, where multiple memory string layers are vertically stacked and interconnected. This dimensional change enables significant increase in bit density by utilizing the vertical dimension. The conductor layers and etch-stop layers are arranged in alternating stacked configurations, allowing multiple memory strings to be connected vertically while maintaining manageable device complexity through systematic layering.

The patent implements preliminary alignment by forming etch-stop layers with specific patterns and dimensions before forming the memory strings. These pre-formed etch-stop layers serve as alignment templates that guide subsequent fabrication steps. By performing alignment-critical operations early in the fabrication process and using the etch-stop layers as permanent references, the patent achieves high alignment precision without requiring expensive real-time alignment systems or multiple costly rework steps.