NAND Flash Programming Bias Control for Hot Electron Disturb
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Solution Overview
Problem
During programming operations in NAND flash memory, the injection type of disturb, specifically hot electron threshold voltage disturb, affects the threshold voltage of selected memory cells due to residue electrons from previously programmed cells, reducing the read window budget and negatively impacting data storage reliability.
Innovation Solution
Implementing measures to mitigate hot electron threshold voltage disturb by controlling the flow of residue electrons during programming operations, such as adjusting the channel potential and voltage levels to minimize electron injection into selected memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If programming operations are performed in NAND flash memory, then data is written to memory cells, but hot electron threshold voltage disturb occurs due to residue electrons from previously programmed cells, reducing read window budget and data storage reliability
Solution Approach 1:
The patent applies preliminary anti-action by performing a read operation before the programming operation to detect and compensate for the hot electron threshold voltage disturb. The read operation measures the threshold voltage shift caused by residue electrons, and this information is used to adjust subsequent programming parameters or compensate for the predicted disturb, thereby preventing the harmful effect from degrading data storage reliability
Solution Approach 2:
The patent implements feedback by using the threshold voltage measurements obtained during read operations to inform and adjust subsequent programming operations. The system continuously monitors the threshold voltage of memory cells and uses this feedback to optimize programming parameters, compensate for hot electron disturb effects, and maintain accurate data states, thereby improving data storage reliability
2Productivity
If residue electrons flow to selected memory cells during programming, then programming speed is maintained, but threshold voltage of selected memory cells is disturbed, reducing read window budget
Solution Approach 1:
The patent applies partial action by performing a preliminary read operation that does not require full programming completion to detect threshold voltage disturbances. This partial action allows the system to identify hot electron effects early in the programming process and adjust parameters accordingly, maintaining programming speed while improving threshold voltage accuracy through intermediate monitoring and adjustment
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
Enhances the read window budget and improves data storage reliability by reducing the impact of hot electron threshold voltage disturb, thereby maintaining accurate data states in memory cells.
Implementation Method 1
the injection type of disturb, specifically hot electron threshold voltage disturb, affects the threshold voltage of selected memory cells due to residue electrons from previously programmed cells
Data Source
AI summary
A memory device includes an array of memory cells, a plurality of access lines, and a controller. The array of memory cells includes a plurality of strings of series-connected memory cells. Each access line is connected to a respective memory cell of each string of series-connected memory cells. The controller is configured to access the array of memory cells to program a selected memory cell of the array of memory cells connected to a first access line of the plurality of access lines. The selected memory cell is within a selected string of the plurality of strings of series-connected memory cells. The controller is further configured to, during a program operation, bias the first access line to a first voltage level and bias remaining access lines of the plurality of access lines to reduce the flow of residue electrons within the selected string to the selected memory cell.