Non-Volatile Memory Read Voltage Coupling Compensation
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Solution Overview
Problem
Non-volatile memory devices face issues in accurately sensing the threshold voltage of selected memory cells due to the coupling effect of read voltage on unselected word lines, leading to erroneous data reading and potential read disturbance.
Innovation Solution
A non-volatile memory device that applies a variable pass voltage to unselected word lines adjacent to the selected word line, with a power supplying section generating multiple read and pass voltages to accurately sense the threshold voltage of the selected memory cell, thereby minimizing read disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a read voltage is applied to a selected word line to perform a read operation, then data can be read from the memory device, but the threshold voltage of memory cells connected to unselected word lines increases due to coupling effect, causing erroneous data reading
Solution Approach 1:
The patent applies a pass voltage to unselected word lines before and during the read operation to counteract the coupling effect of the read voltage. This preliminary anti-action prevents the threshold voltage shift in memory cells connected to unselected word lines, thereby maintaining sensing accuracy while enabling the read operation to proceed.
Solution Approach 2:
The patent dynamically adjusts the pass voltage level based on the read voltage being applied. By changing the parameter (pass voltage) in response to the read operation conditions, the system compensates for the coupling effect and maintains accurate threshold voltage sensing throughout the read process.
2Measurement precision
If the pass voltage applied to unselected word lines is increased to compensate for coupling effect, then threshold voltage sensing accuracy improves, but a read disturbance phenomenon occurs due to increased voltage difference between gate and substrate
Solution Approach 1:
The patent employs dynamic pass voltage adjustment rather than a fixed high pass voltage. The pass voltage is modulated to match the read voltage levels, providing just enough compensation to maintain sensing accuracy without excessive voltage that would cause read disturbance. This dynamic approach balances accuracy and disturbance prevention.
Solution Approach 2:
The system uses feedback mechanisms to adjust the pass voltage based on the actual read operation conditions and the observed coupling effect. By monitoring the threshold voltage shifts and adjusting the pass voltage accordingly, the system achieves accurate sensing while avoiding the read disturbance that would result from overly aggressive pass voltage application.
3Loss of information
If multiple read voltages are applied in sequence to a selected word line for multilevel cell reading, then more states can be sensed, but the coupling effect on unselected word lines becomes more complex, requiring adjusted pass voltage
Solution Approach 1:
The patent implements dynamic pass voltage adjustment that adapts to each read voltage level applied during multilevel cell reading. For each sequential read voltage, the pass voltage is adjusted to the appropriate level to compensate for the coupling effect, enabling accurate sensing of multiple states while managing the complexity through systematic voltage coordination.
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
The solution enables accurate sensing of the threshold voltage of the selected memory cell, reducing erroneous data reading and mitigating read disturbance by dynamically adjusting voltages to compensate for voltage differences.
Implementation Method 1
The threshold voltage of memory cells connected to the unselected word line that is adjacent to the selected word line increases due to coupling effect of the read voltage applied to the selected word line
Data Source
AI summary
A non-volatile memory device and a read method thereof are disclosed. The read method includes providing a memory block having memory cells connected to word lines and connected in serial to a bit line, sensing potential of the bit line by applying a first read voltage to a selected word line of the word lines and providing a first pass voltage to an unselected word line adjacent to the selected word line, sensing potential of the bit line by applying a second read voltage higher than the first read voltage to the selected word line and providing a second pass voltage lower than the first pass voltage to the unselected word line adjacent to the selected word line, and sensing potential of the bit line by applying a third read voltage higher than the second read voltage to the selected word line and providing a third pass voltage lower than the second pass voltage to the unselected word line adjacent to the selected word line.