3D NAND Inverted Staircase Vias for Layer Contact Precision

The fabrication process is segmented into multiple sequential steps: forming sacrificial material layers at different heights, creating lateral isolation trenches, forming access via cavities at different depths, performing isotropic recessing to create inverted staircase structures, and forming contact via structures. This segmentation allows precise control over the three-dimensional arrangement of memory elements and conductive pathways while managing process complexity through systematic progression.

The patent transitions from conventional two-dimensional planar structures to three-dimensional vertical structures by forming memory openings that extend vertically through alternating insulating and sacrificial material layers. The contact via structures vertically extend through subsets of dielectric and insulating layers to contact horizontal surfaces of conductive layers at different elevations, creating a multi-level three-dimensional architecture that improves integration precision.

Sacrificial material layers are formed preliminarily at different heights within the alternating stack before memory openings are created. These sacrificial layers serve as placeholders that define the future positions of conductive pathways. The preliminary formation of these structures at controlled elevations enables precise integration of memory elements while the sacrificial materials are subsequently removed and replaced with conductive materials in later fabrication steps.

Sacrificial material layers act as intermediary structures during fabrication. They are temporarily formed to establish the three-dimensional geometry of the device, then removed and replaced with conductive materials. This intermediary approach allows the fabrication process to achieve complex three-dimensional integration precision without requiring direct formation of final conductive structures in difficult-to-access locations.