3D Memory Program Disturb Prevention via Staged Line Discharge
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Solution Overview
Problem
In three-dimensional memory devices, program disturbance occurs in unselected memory strings due to voltage decreases, leading to unintended programming of memory cells, which affects the reliability and accuracy of data storage.
Innovation Solution
The solution involves applying positive voltages to the bit line and source line connected to unselected memory strings before programming, and discharging the word lines and select lines at different times to maintain the channel voltage of unselected memory strings, preventing voltage drops and thus minimizing program disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a program voltage is applied to a selected word line to program a selected memory cell, then the programming operation is performed, but voltage decreases occur in unselected memory strings causing program disturbance
Solution Approach 1:
The method applies positive voltages to bit lines and source lines connected to unselected memory strings before the program voltage is applied to the selected word line. This preliminary voltage application maintains the channel voltage of unselected memory strings at a higher level, preventing program disturbance when the selected memory cell is programmed.
Solution Approach 2:
The method changes the voltage parameters of bit lines and source lines connected to unselected memory strings by applying positive voltages before programming. This parameter change maintains the channel voltage at an appropriate level, preventing unintended programming of unselected memory cells while allowing the selected memory cell to be programmed accurately.
2Speed
If word lines and select lines are discharged simultaneously to prepare for programming, then the operation speed is improved, but the channel voltage of unselected memory strings decreases causing program disturbance
Solution Approach 1:
The discharge operation of word lines and select lines is segmented into different time stages. Word lines are discharged first, followed by the discharge of select lines after a predetermined time period. This staged discharge maintains the channel voltage of unselected memory strings at an appropriate level, preventing program disturbance while maintaining operation speed.
3Reliability
If positive voltage is applied to bit line and source line before programming, then program disturbance is prevented, but the operation complexity increases
Solution Approach 1:
The control logic is designed to universally manage voltage application to multiple bit lines and source lines connected to unselected memory strings. By using a unified control approach that applies positive voltages to all relevant lines before programming, the method prevents program disturbance across all unselected memory strings without requiring separate complex control circuits for each line.
Data Source
AI summary
A memory device and an operating method thereof are provided. The memory device includes: a plurality of memory strings connected between a bit and source lines, the plurality of memory strings connected to a first select line, a plurality of word lines, and a second select line, which are disposed between the bit line and the source line; a peripheral circuit for programming a selected memory cell included in a selected memory string among the memory strings; and control logic for controlling the peripheral circuit to program the selected memory cell. The control logic controls the peripheral circuit to apply a positive voltage to the bit and source lines, which are connected to an unselected memory string, before a program voltage is applied to a selected word line connected to the selected memory cell, and discharge the word lines and the first and second select lines at different times.