Method for forming a memory structure

Abstract

A method of forming a semiconductor structure. A memory structure is formed on a substrate in the memory array region. A dielectric layer is deposited over the memory array region and peripheral region to cover the memory structure. A reverse etching process is performed to remove part of the dielectric layer from the central area of the memory array region, thereby forming an upwardly protruding wall structure along perimeter of the memory array region. The remaining thickness of the dielectric layer in the central area is equal to the sum of a polishing buffer thickness and a target thickness. A first polishing process is performed to remove the upwardly protruding wall structure from the memory array region. A second polishing process is performed to remove upper portion of the dielectric layer with the polishing buffer thickness from the memory array region.