Local Self-Boost Using Cut-Off Cells on Single Side of Memory String
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Solution Overview
Problem
In flash memory devices, a large capacitance on the source-side of a series string of memory cells leads to leakage current during programming operations, increasing the likelihood of programming errors due to reduced voltage in the selected memory cell channel.
Innovation Solution
Implementing at least two cut-off memory cells on a single side of a selected memory cell, either on the source-side or drain-side, to reduce local channel capacitance by splitting the total capacitance into smaller areas, thereby boosting the local channel voltage and minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single cut-off cell is used for program inhibit, then the structure is simple, but the channel capacitance is too large causing leakage current
Solution Approach 1:
The patent divides the single cut-off cell into multiple cut-off cells (first cut-off cell and second cut-off cell) positioned at different locations adjacent to the selected memory cell. This segmentation reduces the channel capacitance by distributing it across multiple smaller units, thereby minimizing leakage current and improving programming reliability.
2Reliability
If multiple cut-off cells are used on both sides of the selected cell, then the capacitance is reduced effectively, but the device complexity increases
Solution Approach 1:
The patent applies local quality by placing cut-off cells selectively at specific locations (adjacent to the selected cell on one or both sides) rather than uniformly throughout the memory array. This localized approach reduces capacitance where it matters most while minimizing the overall increase in device complexity.
3Productivity
If erased memory cells are present between the selected cell and source select gate, then the memory array is fully utilized, but the capacitance increases causing voltage reduction
Solution Approach 1:
The patent introduces cut-off cells as intermediary elements between the selected memory cell and the source select gate. These intermediary cells act as capacitive buffers that isolate the selected cell from the large capacitance of erased cells, preventing voltage reduction and maintaining programming reliability while allowing full memory array utilization.
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 effectively reduces leakage current and minimizes the risk of programming errors by maintaining a higher voltage on the selected memory cell channel, enhancing programming accuracy and reliability.
Implementation Method 1
a large capacitance C exists in the channel of the source-side memory cells. The large capacitance causes a leakage current (ILEAK) from the selected memory cell channel to the large capacitance C
Data Source
AI summary
Methods for local self-boost of a selected memory cell channel, memory devices, and systems are disclosed. One such method generates a cut-off channel under each of a plurality of memory cells on one of either a source side or a drain side of a selected memory cell.