Method of making a vertical NAND device using sequential etching of multilayer stacks

摘要

A method of making a vertical NAND device includes forming a lower portion of a memory stack over a substrate, forming a lower portion of memory openings in the lower portion of the memory stack, and at least partially filling the lower portion of the memory openings with a sacrificial material. The method also includes forming an upper portion of the memory stack over the lower portion of the memory stack and over the sacrificial material, forming an upper portion of the memory openings in the upper portion of the memory stack to expose the sacrificial material in the lower portion of the memory openings, removing the sacrificial material to connect the lower portion of the memory openings with a respective upper portion of the memory openings to form continuous memory openings, and forming a semiconductor channel in each continuous memory opening.

主权项

1. A method of making a vertical NAND device, comprising:
forming a lower portion of a memory stack over a substrate; forming a lower portion of memory openings in the lower portion of the memory stack; at least partially filling the lower portion of the memory openings with a sacrificial material; forming an upper portion of the memory stack over the lower portion of the memory stack and over the sacrificial material; forming an upper portion of the memory openings in the upper portion of the memory stack to expose the sacrificial material in the lower portion of the memory openings; removing the sacrificial material to connect the lower portion of the memory openings with a respective upper portion of the memory openings to form continuous memory openings extending through the upper and the lower portions of the memory stack; and forming a semiconductor channel in each continuous memory opening, wherein at least partially filling the lower portion of the memory openings with the sacrificial material comprises forming a non-conformal sacrificial layer over the lower portion of the memory openings such that the sacrificial layer pinches off a top of the lower portion of the memory openings and leaves an air gap below it in the lower portion of the memory openings.