Non-Volatile Memory Judgment Strings for Selective Pre-Programming
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Solution Overview
Problem
Conventional pre-programming operations before erasing in NAND flash memory cause additional burden on memory cells, leading to increased erasing time and reduced service life due to shallow erase issues, especially in advanced processes with reduced cycling capabilities.
Innovation Solution
A non-volatile memory system with judgment memory cell strings determines if memory cells have undergone programming in an isolated state, performing pre-programming only when necessary, using judgment memory cells to assess the need for pre-programming operations and adjusting the page range based on the number of erase cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-programming operation is performed on all pages before erasing, then shallow erase problem is prevented, but memory cell damage increases and service life decreases
Solution Approach 1:
The patent applies pre-programming operation selectively to specific pages that require it, rather than uniformly to all pages. The controller identifies pages with shallow erase issues through judgment memory cells and applies pre-programming only to those specific pages, making the operation localized rather than global.
Solution Approach 2:
The patent performs pre-programming operation only on the necessary subset of pages that have shallow erase problems, rather than performing the operation on all pages. This partial action approach reduces unnecessary memory cell stress while still addressing the shallow erase issue where it actually occurs.
2Reliability
If pre-programming operation is performed before erasing, then shallow erase is prevented, but erasing time increases
Solution Approach 1:
The patent applies pre-programming operation selectively to specific pages that require it, rather than uniformly to all pages. The controller identifies pages with shallow erase issues through judgment memory cells and applies pre-programming only to those specific pages, making the operation localized rather than global.
Solution Approach 2:
The patent performs pre-programming operation only on the necessary subset of pages that have shallow erase problems, rather than performing the operation on all pages. This partial action approach reduces unnecessary memory cell stress while still addressing the shallow erase issue where it actually occurs.
3Reliability
If pre-programming operation is performed on all pages, then shallow erase is prevented, but programming/erasing cycling capability is reduced
Solution Approach 1:
The patent applies pre-programming operation selectively to specific pages that require it, rather than uniformly to all pages. The controller identifies pages with shallow erase issues through judgment memory cells and applies pre-programming only to those specific pages, making the operation localized rather than global.
Solution Approach 2:
The patent performs pre-programming operation only on the necessary subset of pages that have shallow erase problems, rather than performing the operation on all pages. This partial action approach reduces unnecessary memory cell stress while still addressing the shallow erase issue where it actually occurs.
Data Source
AI summary
A non-volatile memory and an operating method thereof are provided. The non-volatile memory includes a memory array and a controller. Each main memory cell string, a first judgment memory cell string, and a second judgment memory cell string of the memory array respectively includes a plurality of main memory cells, a plurality of first judgment memory cells and a plurality of second judgment memory cells. During a programming operation, the controller determines, according to a data level of each main memory cell, a data level of the corresponding first judgment memory cell, determines, according to data levels of each first judgment memory cell and its preceding first judgment memory cell, a data level of the corresponding second judgment memory cell, and accordingly determines whether to perform a pre-programming operation during an erasing operation.