Memory Device Blind Program Operations Stabilize Threshold Voltage
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Solution Overview
Problem
Nonvolatile semiconductor memory devices face challenges in maintaining data reliability due to excessive erase phenomena during program-erase cycles, leading to variations in erase threshold voltage distributions and reduced memory cell reliability.
Innovation Solution
The implementation of blind program operations, including first, second, and third blind program operations, are performed before and after erase voltage applications to stabilize threshold voltages, mitigate excessive erase issues, and refine the erase threshold voltage distribution, thereby enhancing memory device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple program-erase cycles are performed to store data in memory cells, then data storage capacity is improved, but excessive erase phenomena occur leading to variations in erase threshold voltage distributions and reduced reliability
Solution Approach 1:
A first blind program operation is performed before the erase operation to preliminarily set the threshold voltages of memory cells to a predetermined range. This preliminary action ensures that when the erase operation is subsequently performed, the threshold voltage distribution remains controlled and excessive erase phenomena are prevented, thereby maintaining reliability while enabling repeated program-erase cycles for data storage.
Solution Approach 2:
An erase verify operation is performed after the erase operation to detect whether the threshold voltage distribution has become excessive. Based on the verification result, a second blind program operation is conditionally performed to adjust and re-stabilize the threshold voltages. This feedback mechanism ensures that reliability is maintained throughout multiple program-erase cycles by dynamically correcting threshold voltage deviations.
2Productivity
If erase voltage is applied to memory block to erase data, then data erasure is achieved, but threshold voltage distribution becomes excessive leading to reduced reliability
Solution Approach 1:
The first blind program operation is performed before the erase operation to preliminarily stabilize threshold voltages within a predetermined range. This preliminary stabilization ensures that when the erase voltage is subsequently applied for efficient data erasure, the threshold voltage distribution remains controlled and excessive variations are prevented, thereby maintaining reliability while achieving effective erasure.
Solution Approach 2:
The erase verify operation is performed after erase voltage application to detect excessive threshold voltage distribution. When excessive distribution is detected, the second blind program operation is executed as a corrective feedback action to re-stabilize the threshold voltages, ensuring reliability is restored while maintaining erasure efficiency.
3Reliability
If blind program operations are performed before and after erase operations, then threshold voltage stability is improved, but additional operations increase processing time
Solution Approach 1:
The erase verify operation serves as a feedback mechanism that detects whether threshold voltage distribution has become excessive after the erase operation. The second blind program operation is conditionally executed only when excessive distribution is detected, rather than being performed unconditionally. This feedback-based approach maintains threshold voltage stability while minimizing unnecessary additional operations and their associated time overhead.
Solution Approach 2:
Instead of performing blind program operations in every program-erase cycle, the second blind program operation is performed selectively only when the erase verify operation detects excessive threshold voltage distribution. This partial action approach applies the corrective measure only when necessary, thereby maintaining reliability while reducing the overall time loss compared to unconditional repeated operations.
Data Source
AI summary
Provided herein may be a method of operating a memory device. The method may include applying an erase voltage to a memory block. The method may include performing an erase verify operation on the memory block. The method may include performing a first blind program operation based on a result of the erase verify operation.