Flash Memory Read Method Using Coupling Compensation
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Solution Overview
Problem
Flash memory devices face challenges in reliably reading data due to electric field coupling between adjacent memory cells, which causes variations in threshold voltage distributions and narrows the interval between program states, leading to inaccurate data retrieval, especially as the number of bits stored per cell increases.
Innovation Solution
A read method for flash memory devices that involves reading adjacent memory cells connected to a different word line, applying coupling compensation parameters such as varying pre-charge voltage levels or sensing periods based on the program states of adjacent memory cells to compensate for coupling effects, and selectively latching the read results from selected memory cells using appropriate compensation parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bits stored per cell is increased, then the storage capacity is improved, but the interval between adjacent program states is narrowed due to coupling effects
Solution Approach 1:
The patent applies preliminary action by performing a read operation on adjacent memory cells before reading the selected memory cells. This preliminary read obtains coupling compensation parameters from adjacent cells that are used to compensate for coupling effects during the subsequent read of selected cells, thereby maintaining measurement precision while enabling higher storage capacity
Solution Approach 2:
The patent changes parameters by adjusting read operations based on coupling compensation parameters obtained from adjacent memory cells. The system modifies sensing conditions and timing parameters dynamically to compensate for coupling effects, allowing reliable reading even when program state intervals are narrowed due to increased bits per cell
2Reliability
If coupling compensation is applied to all selected memory cells, then reading reliability is improved, but reading time increases
Solution Approach 1:
The patent applies local quality by selectively applying coupling compensation only to selected memory cells that are adjacent to cells containing specific data values (e.g., '1' states). Not all memory cells require compensation - only those affected by coupling from neighboring cells with particular data patterns. This selective approach maintains reading reliability while minimizing the time penalty
Solution Approach 2:
The patent uses partial action by applying coupling compensation to only a subset of selected memory cells rather than all of them. The system identifies which cells need compensation based on adjacent cell states and applies compensation selectively, achieving sufficient reading reliability without the full time cost of universal compensation
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 enhances the reliability of data reading by effectively compensating for the coupling effects between adjacent memory cells, ensuring accurate data retrieval even with increased bit storage, by adjusting sensing times or pre-charge voltage levels according to the program states of adjacent memory cells.
Implementation Method 1
The coupling causes widening of each of threshold voltage distributions each corresponding to program states and narrowing of an interval between adjacent program states. Such coupling is referred to as the electric field coupling or F-poly coupling.
Data Source
AI summary
A read method of a flash memory device is provided which comprises reading a plurality of adjacent memory cells connected with a word line different from a plurality of selected memory cells; reading the plurality of selected memory cells one or more times using a plurality of coupling compensation parameters; and selectively latching the read result of the selected memory cells based on the read result of the adjacent memory cells.