Variable Compensating Pass Bias for Wordline Interference Correction
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Solution Overview
Problem
Non-volatile memory devices face errors due to word line interference, which affects the reliability of data reading, especially as memory cells are packed more densely, leading to increased operational errors and data corruption.
Innovation Solution
A variable compensating pass bias is applied to adjacent memory cells based on the state being sensed at the selected word line, adjusting compensating pass biases to account for shifts in threshold voltage caused by word line interference, thereby reducing errors during read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory cells are packed more densely to increase memory capacity, then memory capacity per die area is improved, but operational errors such as word line interference increase
Solution Approach 1:
The patent applies preliminary anti-action by sensing the state of adjacent memory cells before reading the target cell. Based on this preliminary sensing, a compensating pass bias is applied to adjacent cells during the read operation to counteract the word line interference that would otherwise affect the target cell. This proactive approach prevents reading errors caused by densely packed memory cell interference.
2Quantity of substance
If memory cells are packed more densely to increase memory capacity, then memory capacity per die area is improved, but data corruption increases
Solution Approach 1:
The patent prevents data corruption by proactively sensing adjacent cell states and applying compensating biases before the read operation completes. This preliminary anti-action ensures that word line interference does not cause threshold voltage shifts that would lead to incorrect data interpretation, thereby maintaining data integrity in densely packed memory arrays.
3Reliability
If a fixed compensating pass bias is applied to adjacent memory cells, then word line interference is partially compensated, but reading accuracy deteriorates due to varying interference levels based on adjacent cell states
Solution Approach 1:
The patent implements dynamics by making the compensating pass bias adaptive rather than fixed. The bias applied to adjacent memory cells is dynamically adjusted based on the sensed state of those cells. If adjacent cells are in a programmed state, a higher compensating bias is applied; if they are in an erased state, a lower or zero bias is applied. This dynamic adjustment maintains high reading accuracy across varying interference conditions.
Solution Approach 2:
The patent changes the parameter of compensating pass bias based on the state of adjacent memory cells. The bias level is modified according to whether adjacent cells contain programmed or erased data, allowing the system to adapt the compensation strength to match the actual interference conditions, thereby maintaining reading accuracy.
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 errors by compensating for word line interference, improving the reliability of data reading and maintaining data integrity in densely packed memory devices.
Implementation Method 1
word line interference, which affects the reliability of data reading, especially as memory cells are packed more densely
Data Source
AI summary
A variable compensation pass bias based on a state being sensed in non-volatile memory based is provided. Shifts in the apparent charge stored by a memory cell can occur because of coupling based on charge stored by adjacent cells. To account for the shift, compensations can be applied to an adjacent word line when reading based on the different possible conditions of an adjacent cell. The effects of coupling may be more pronounced for memory cells in lower states corresponding to lower threshold voltages. A compensation pass bias can be reduced as the state being sensed at a selected word line increases to account for the different effects. A compensation pass bias for an adjacent word line may be reduced with the application of larger read reference voltages to a selected word line. Other variations to a compensation pass bias are provided.