Sector Erase Operation for Flash Memory Suspend-Resume
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Solution Overview
Problem
Conventional flash memory erase operations require substantial time and steps to correct over-erased memory cells, particularly due to variations in threshold voltages within a block, leading to inefficiencies in the erase process.
Innovation Solution
The proposed solution involves a sector erase operation where memory cells are erased in groups by sector rather than blocks, allowing for a suspend-resume function that interrupts the erase process to perform other operations, and utilizes a Fowler-Nordheim programming pulse to prevent leakage and complete the erase procedure efficiently, reducing the time required for the erase process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional block erase operation is used to ensure complete erasure of all memory cells, then erasure reliability is improved, but erase time increases substantially due to multiple cycles and soft program correction
Solution Approach 1:
The patent divides the memory block into multiple sectors and performs erase operations on individual sectors rather than the entire block. This segmentation allows the erase operation to be completed more quickly by processing smaller units, while still achieving complete erasure of all memory cells through systematic sector-by-sector treatment.
2Reliability
If voltage-stepping or time-stepping procedure is used during erase cycle to handle threshold voltage variations, then erasure completeness is improved, but process complexity and erase time increase
Solution Approach 1:
The patent applies different erase voltages to different sectors based on their specific threshold voltage characteristics. By tailoring the erase voltage locally to each sector's needs rather than using a uniform approach, the method achieves complete erasure while avoiding the complexity of systematic voltage-stepping procedures across the entire block.
3Reliability
If multiple erase cycles with verification are performed to ensure all cells are erased, then erasure reliability is improved, but the number of operation steps and time increase
Solution Approach 1:
The patent extracts the verification step from the traditional multi-cycle erase process and performs it selectively after each sector erase rather than requiring multiple complete erase cycles. This allows early termination when all sectors are successfully erased, reducing the total number of operation steps while maintaining reliability.
4Productivity
If sector erase with suspend-resume function is implemented to allow interruptions for other operations, then productivity is improved, but control complexity increases
Solution Approach 1:
The patent implements a dynamic suspend-resume capability that allows the erase operation to be paused and resumed based on system needs. The controller can interrupt the sector-by-sector erase process to handle other operations, then resume the erase from the specific sector where it left off, providing flexible resource management while maintaining overall system productivity.
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 the time and steps needed to erase blocks by erasing memory cells in sectors, minimizing the risk of leakage and ensuring compliance with timing requirements, thereby enhancing the efficiency of the erase operation.
Implementation Method 1
utilizes a Fowler-Nordheim programming pulse to prevent leakage and complete the erase procedure efficiently
Data Source
AI summary
A method of erasing memory cells of a memory device includes programming memory cells if the erasing procedure is suspended. The erasing procedure can include pre-programming, erasing, and soft-programming of memory cells in a selected memory unit. If a suspend command is received, for example to allow for a read operation of memory cells of another unit of memory, the erasing procedure stops the pre-programming, erasing, or soft-programming, and proceeds with programming one or more memory cells of the memory unit that was being erased.