3D NAND Tunneling Structure With Local High-κ Regions for Vth Stability
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Solution Overview
Problem
The unintentional loss of charge from the charge trap structure in 3D NAND memory devices leads to unstable select gate threshold voltages, affecting the operation and data storage ability of electronic apparatus.
Innovation Solution
Incorporating a high-κ material in the first tunneling structure adjacent to the word line tiers and an oxide-only structure in the second tunneling structure adjacent to the select gate tier, which inhibits charge loss and stabilizes the threshold voltage of the select gate tier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a uniform high-κ material tunneling structure is used throughout the vertical structure, then the charge storage capability is improved, but the select gate threshold voltage becomes unstable due to charge loss
Solution Approach 1:
The patent applies different material compositions to different regions of the tunneling structure: a first tunneling structure with high-κ material is used adjacent to word line tiers for enhanced charge storage, while a second tunneling structure with oxide-only material is used adjacent to select gate tiers to prevent charge loss and stabilize threshold voltage. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The tunneling structure is divided into distinct segments: a first tunneling structure region with high-κ material and a second tunneling structure region with oxide-only material. This segmentation allows independent optimization of charge storage (in the first region) and charge retention/stability (in the second region), resolving the technical contradiction between these competing requirements.
2Quantity of substance
If high-κ material is used in the tunneling structure adjacent to select gate tier, then charge storage is enhanced, but charge loss occurs leading to threshold voltage instability
Solution Approach 1:
The patent implements local quality differentiation by using high-κ material only in the first tunneling structure adjacent to word line tiers where charge storage is needed, while using oxide-only material in the second tunneling structure adjacent to select gate tiers where charge retention is critical. This prevents charge loss at the select gate interface while maintaining enhanced charge storage elsewhere.
Solution Approach 2:
The oxide-only material in the second tunneling structure acts as an intermediary barrier between the charge trap structure and the select gate tier, preventing charge loss to the select gate while allowing the high-κ material in the first tunneling structure to provide enhanced charge storage capability in other regions.
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
The solution effectively maintains the initial charged state of select gate tiers, reducing unwanted changes in threshold voltage and enhancing the stability and reliability of 3D NAND memory devices.
Implementation Method 1
The first tunneling structure comprises a composite structure including a high-κ material
Implementation Method 2
an oxide-only structure in the second tunneling structure adjacent to the select gate tier, which inhibits charge loss and stabilizes the threshold voltage
Data Source
AI summary
A vertical structure extends through a tiered structure of alternating conductive and insulative materials. The vertical structure includes a channel structure and a tunneling structure. At least one of the conductive materials of the tiered structure provides a select gate tier (e.g., including a control gate for a select gate drain (SGD) transistor). Adjacent the select gate tier of the tiered structure, the tunneling structure consists of or consists essentially of an oxide-only material. Adjacent the word line tiers of the tiered structure, the tunneling structure comprises at least one material that is other than an oxide-only material, such as a nitride or oxynitride. The oxide-only material adjacent the select gate tier may inhibit unintentional loss of charge from a neighboring charge storage structure, which may improve the stability of the threshold voltage (Vth) of the select gate tier.