3D NAND Selector Device Stabilization via Erase Pulse
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Solution Overview
Problem
3D NAND memory devices face reliability issues due to instability in selector devices caused by charge loss and lateral migration of holes, leading to unstable threshold voltage, which affects consistent operation and increases bit error rates.
Innovation Solution
Applying a selector stability pulse after each erase operation to neutralize holes near the selector device region, stabilizing the threshold voltage of selector devices through program and erase cycles, thereby reducing maintenance needs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gating structures are fabricated similar to memory cell structures to streamline processing, then manufacturing complexity is reduced, but reliability of selector devices deteriorates due to charge loss and lateral migration
Solution Approach 1:
The patent applies different fabrication characteristics to the selector device compared to memory cells. The selector device uses a wider channel width (e.g., 20nm vs 10nm for memory cells) and adjusted threshold voltage settings to compensate for the lateral migration effects, while still using the same basic stacked gate structure fabrication process. This local differentiation maintains manufacturing simplicity while improving selector reliability.
Solution Approach 2:
The patent modifies key parameters of the selector device including channel width, threshold voltage, and gate material composition to address reliability issues. By changing these parameters within the same fabrication framework, the patent maintains ease of manufacture while improving selector device stability against charge loss and lateral migration.
2Productivity
If selector devices undergo repeated program and erase cycles, then memory device productivity is improved, but threshold voltage stability deteriorates due to hole accumulation and lateral migration
Solution Approach 1:
The patent performs preliminary stabilization actions during the erase cycle by applying specific voltage patterns to the selector device before it undergoes normal operation. This preliminary action neutralizes accumulated holes and prevents lateral migration, thereby maintaining threshold voltage stability even after repeated program and erase cycles, enabling sustained high productivity.
Solution Approach 2:
The patent implements periodic stabilization pulses during erase operations to counteract hole accumulation and lateral migration effects. These periodic actions reset the selector device threshold voltage at regular intervals, maintaining stability throughout extended operation and enabling sustained productivity over many program-erase cycles.
3Device complexity
If no stabilization procedure is applied to selector devices, then device complexity is reduced, but bit error rate increases due to threshold voltage instability
Solution Approach 1:
The patent enables the selector device to self-stabilize through integrated stabilization circuits and algorithms that automatically detect and correct threshold voltage drift. This self-service approach maintains low operational complexity while significantly reducing bit error rates, as the system autonomously manages selector device stability without requiring external intervention or complex management protocols.
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 selector stability pulse procedure enhances the stability of selector devices, reducing bit error rates and eliminating the need for frequent system-level maintenance, resulting in improved reliability and performance of 3D NAND memory devices.
Implementation Method 1
applying a program pulse to a select line coupled to the selector device and to an access line coupled to a memory cell of multiple memory cells of the string with the memory cell being adjacent to the selector device in the string
Data Source
AI summary
A variety of applications can include memory devices designed to provide stabilization of selector devices in a memory array of the memory device. A selector stabilizer pulse can be applied to a selector device of a string of the memory array and to a memory cell of multiple memory cells of the string with the memory cell being adjacent to the selector device in the string. The selector stabilizer pulse can be applied directly following an erase operation to the string to stabilize the threshold voltage of the selector device. The selector stabilizer pulse can be applied as part of the erase algorithm of the memory device. Additional devices, systems, and methods are discussed.