Margined Neighbor Reading for Non-Volatile Memory Coupling Compensation
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Solution Overview
Problem
In non-volatile memory systems, floating gate to floating gate coupling causes erroneous readings due to shifts in apparent charge storage, particularly in multi-state devices with narrower threshold voltage ranges, as memory cells shrink and coupling between adjacent cells increases.
Innovation Solution
The read process for a memory cell includes compensating for adjacent cell coupling by determining the condition of adjacent memory cells and using margined reference voltages to adjust the read voltage, ensuring accurate data retrieval by accounting for shifts in threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory cell size is reduced to increase storage density, then storage capacity is improved, but coupling between adjacent floating gates increases causing reading errors
Solution Approach 1:
The patent applies preliminary action by performing a first read operation on the adjacent memory cell before the main read operation on the target memory cell. This first read determines the state of the adjacent cell, and based on this information, a compensation value is calculated and applied to the read voltage or reference voltage in the subsequent main read operation. This preliminary determination of adjacent cell state allows the system to pre-compensate for the coupling effect that will interfere with the target cell reading.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the read voltage or reference voltage based on the determined state of the adjacent memory cell. Different voltage parameters are applied depending on whether the adjacent cell is in a programmed or erased state, thereby compensating for the varying coupling effects and maintaining accurate reading despite reduced cell spacing.
2Quantity of substance
If threshold voltage ranges are narrowed to increase data states in multi-state devices, then storage capacity is improved, but susceptibility to coupling-induced reading errors increases
Solution Approach 1:
The patent implements feedback by using the read result from the adjacent memory cell to adjust the reading parameters for the target memory cell. The state determination of the adjacent cell provides feedback information that is used to modify the read voltage or reference voltage, thereby compensating for the coupling effect and improving the precision of threshold voltage detection in multi-state devices with narrow voltage ranges.
Solution Approach 2:
The patent applies parameter changes by selecting different read voltage levels or reference voltage levels based on the adjacent cell's state. This dynamic parameter adjustment ensures that even with narrow threshold voltage ranges for multiple data states, the coupling-induced shifts do not cause misinterpretation of the target cell's actual state.
3Adaptability or versatility
If adjacent memory cells are programmed at different times, then data storage flexibility is improved, but coupling effects cause apparent charge shifts leading to erroneous readings
Solution Approach 1:
The patent applies preliminary action by reading the adjacent memory cell's state before reading the target memory cell. This preliminary read captures the final state of the adjacent cell regardless of when it was programmed, and this information is then used to compensate for the coupling effect in the subsequent target cell read, thereby preventing data loss or misinterpretation.
Solution Approach 2:
The patent uses the adjacent memory cell's state information as an intermediary to mediate the reading process of the target cell. By determining the adjacent cell's state first and using it to adjust the read parameters, the system indirectly compensates for the coupling effect, maintaining data reading accuracy despite flexible programming timing.
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 errors in data reading by compensating for coupling effects, maintaining data integrity and reliability in multi-state memory systems, even as memory cell sizes decrease and coupling between adjacent cells intensifies.
Implementation Method 1
Shifts in the apparent charge stored on a floating gate or other charge region can occur because of the coupling of an electric field based on the charge stored in adjacent floating gates.
Data Source
AI summary
Shifts in the apparent charge stored on a floating gate (or other charge storing element) of a non-volatile memory cell can occur because of the coupling of an electric field based on the charge stored in adjacent floating gates (or other adjacent charge storing elements). The problem occurs most pronouncedly between sets of adjacent memory cells that have been programmed at different times. To account for this coupling, the read process for a particular memory cell will provide compensation to an adjacent memory cell in order to reduce the coupling effect that the adjacent memory cell has on the particular memory cell. When reading the adjacent cell to determine the appropriate compensation, margined read voltages can be used.