Oxidized Polysilicon Etch Stop Protection in 3D Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In memory cells with a nitride structure, charges can become trapped in portions not directly between the control gate and floating gate, altering the threshold voltage and causing issues during etch processes, particularly affecting the nitride material and etch stop materials.
Innovation Solution
A protective layer of oxidized polysilicon is used to prevent damage to etch stop materials during nitride removal processes, ensuring selective etching that maintains the integrity of both materials by employing an In Situ Steam Generation oxidation process and conformal deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride structure is used in memory cells, then charge storage capability is improved, but charge trapping in portions not directly between CG and FG occurs, altering threshold voltage and affecting etch stop materials
Solution Approach 1:
An oxidized polysilicon layer is introduced as an intermediary between the nitride structure and the etch stop material. This intermediate layer serves as a protective barrier that prevents charge from trapping in the etch stop material and protects the etch stop material during removal processes, thereby resolving the harmful effects of charge trapping while maintaining the charge storage capability of the nitride structure
Solution Approach 2:
The etch stop material is removed before forming the nitride structure, and an oxidized polysilicon layer is deposited in advance to protect the underlying layers. This preliminary removal and protection approach prevents subsequent damage to the etch stop material during nitride removal processes and eliminates charge trapping issues that would otherwise occur
2Ease of manufacture
If etch stop material is used during nitride removal, then selective etching is enabled, but the etch stop material is damaged by the removal process
Solution Approach 1:
The etch stop material is removed in advance before the nitride structure formation and subsequent removal processes. This preliminary removal eliminates the risk of damage to the etch stop material while maintaining the benefits of selective etching during nitride removal, as the etch stop material is no longer present to be damaged
Solution Approach 2:
An oxidized polysilicon layer is deposited as an intermediate protective layer before nitride removal. This intermediate layer protects the underlying structure during the nitride removal process, enabling selective etching of the nitride while preventing damage to the layers below, including any remaining etch stop material
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces charge trapping, maintains charge density, and improves the uniformity of memory cell programming and erase performance by minimizing Vt shifts and enhancing FG to CG alignment, thereby reducing erase saturation and ISPP degradation.
Implementation Method 1
A protective layer of oxidized polysilicon is used to prevent damage to etch stop materials during nitride removal processes
Implementation Method 2
employing an In Situ Steam Generation oxidation process and conformal deposition techniques
Data Source
AI summary
Protective dielectrics are discussed generally herein. In one or more embodiments, a three-dimensional vertical memory may include a protective dielectric material. A device may include an etch stop material, a first control gate (CG) over the etch stop material, a first CG recess adjacent the first CG, a trench adjacent the first CG recess, and an at least partially oxidized polysilicon on at least a portion of the etch stop material. The at least partially oxidized polysilicon may line a sidewall of the trench and may line the first CG recess.