Non-volatile Memory Read Method for Coupling Error Reduction
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Solution Overview
Problem
Non-volatile memory devices face read errors due to parasitic capacitance coupling between subsequently programmed memory cells, which widens threshold voltage distributions and affects data storage reliability.
Innovation Solution
The method involves performing multiple read operations with different time periods and using specific read voltages to differentiate between coupled and uncoupled memory cells, reducing read errors by applying read voltages DR1 and DR2 to discriminate memory cells within uncoupled and coupled threshold voltage distributions, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple read operations are performed with different time periods to distinguish coupled and uncoupled memory cells, then read error reduction is achieved, but read operation time increases
Solution Approach 1:
The read operation is divided into multiple distinct phases: a first read operation performed at a first time period to detect coupled memory cells, and a second read operation performed at a second time period to read uncoupled memory cells. This segmentation allows the system to handle different memory cell states separately, improving overall read reliability by reducing read errors caused by coupling effects.
Solution Approach 2:
The first read operation is performed as a preliminary step before the second read operation. By first identifying which memory cells are coupled through the initial read operation, the system can then selectively perform the second read operation only on uncoupled cells or adjust reading parameters accordingly, thereby reducing subsequent read errors while managing total read time efficiently.
2Measurement precision
If read voltages are adjusted to discriminate between coupled and uncoupled memory cells, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent employs dynamic adjustment of read voltages based on the coupling state of memory cells. Different read voltages (first read voltage for coupled cells, second read voltage for uncoupled cells) are applied at different time periods. This dynamic voltage adjustment enables precise discrimination between coupled and uncoupled memory cells, significantly improving measurement precision in threshold voltage detection.
Solution Approach 2:
The system uses feedback from the first read operation to determine the coupling state of memory cells, then adjusts the reading strategy for the second read operation accordingly. This feedback mechanism allows the system to adaptively select appropriate read voltages and timing, achieving high measurement precision while managing control complexity through intelligent decision-making based on detected states.
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 read errors caused by word line coupling, enhancing the reliability of data retrieval in non-volatile memory devices by accurately distinguishing between coupled and uncoupled memory cells.
Implementation Method 1
parasitic capacitance coupling between subsequently programmed memory cells, which widens threshold voltage distributions
Data Source
AI summary
In one embodiment, the method includes receiving a request to read data stored in a first memory cell associated with a first word line, and performing a first read operation on at least one memory cell associated with a second word line in response to the request. The second word line follows the first word line in a word line programming order, and the first read operation is performed over a first time period. The method further includes performing a second read operation on the first memory cell based on output from the first read operation. The second read operation is performed for a second time period, and the first time period is shorter than the second time period if output from performing the first read operation indicates the first memory cell is not coupled.