NAND MEMORY STRINGS AND METHODS OF FABRICATION THEREOF

摘要

Methods of making monolithic three-dimensional memory devices include performing a first etch to form a memory opening and a second etch using a different etching process to remove a damaged portion of the semiconductor substrate from the bottom of the memory opening. A single crystal semiconductor material is formed over the substrate in the memory opening using an epitaxial growth process. Additional embodiments include improving the quality of the interface between the semiconductor channel material and the underlying semiconductor layers in the memory opening which may be damaged by the bottom opening etch, including forming single crystal semiconductor channel material by epitaxial growth from the bottom surface of the memory opening and/or oxidizing surfaces exposed to the bottom opening etch and removing the oxidized surfaces prior to forming the channel material. Monolithic three-dimensional memory devices formed by the embodiment methods are also disclosed.

主权项

1. A method of fabricating a memory device, comprising:
forming a material layer stack over a major surface of a semiconductor substrate; etching the stack through a mask to the semiconductor substrate using a first etching process to form a memory opening having a sidewall defined at least in part by the stack and a bottom surface that is defined by the semiconductor substrate; etching through the memory opening using a second etching process that is different from the first etching process to remove a damaged portion of the semiconductor substrate from the bottom surface of the memory opening; forming a single crystal semiconductor material over the semiconductor substrate on the bottom surface of the memory opening using an epitaxial growth process; forming at least one memory film on at least a portion of the sidewall of the memory opening and over the single crystal semiconductor material on the bottom surface of the memory opening; forming a layer of semiconductor material over the at least one memory film on at least a portion of the sidewall of the memory opening and on the bottom surface of the memory opening; etching through the memory opening using a third etching process to remove a portion of the layer of semiconductor material and a portion of the at least one memory film from over the bottom surface of the memory opening and expose the single crystal semiconductor material on the bottom surface of the memory opening; and forming a semiconductor channel material over the layer of semiconductor material on the sidewall of the memory opening and over the single crystal semiconductor material on the bottom surface of the memory opening.