Dummy Word Line Pre-Charge in Non-Volatile Memory Programming
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Solution Overview
Problem
In non-volatile memory systems, certain conditions can prevent effective pre-charging of unselected memory cells, leading to disturb issues during programming, particularly when portions of the memory lack access to a source of pre-charging.
Innovation Solution
Implementing overdrive voltage on word lines for a sub-block between the selected word line and the source of pre-charging, maintaining the dummy word lines at a low voltage to isolate memory cells, and applying program voltage pulses while boosting pre-charged channels to prevent disturb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-charging is applied to unselected memory cells, then disturb issues during programming are prevented, but portions of memory lacking access to pre-charging source experience programming disturbances
Solution Approach 1:
The memory block is divided into sub-blocks with dummy word lines separating them. This segmentation allows independent voltage control of different regions, enabling pre-charging of unselected cells in one sub-block without affecting other regions that lack pre-charging access.
Solution Approach 2:
Dummy word lines are introduced as intermediary elements between sub-blocks. These dummy word lines are maintained at low voltage to isolate and block voltage propagation, preventing programming disturbances from reaching unselected memory cells in regions without pre-charging access.
2Object-affected harmful factors
If dummy word lines are maintained at low voltage to isolate memory cells, then voltage propagation is blocked, but additional control complexity is introduced
Solution Approach 1:
The dummy word lines serve multiple functions: they act as isolation barriers to block voltage propagation, define sub-block boundaries, and provide additional control nodes for precise voltage management. This multi-functionality reduces the need for separate isolation structures.
Solution Approach 2:
Dummy word lines are pre-configured at low voltage states before programming operations begin. This preliminary voltage setup creates ready-to-block isolation barriers, eliminating the need for dynamic voltage switching during operations and reducing control complexity.
3Reliability
If overdrive voltage is applied to word lines for sub-block pre-charging, then unselected memory cells are properly charged, but energy consumption increases
Solution Approach 1:
Overdrive voltage is applied selectively only to word lines within sub-blocks that require pre-charging, rather than uniformly across the entire memory block. This localized voltage application ensures effective pre-charging of unselected cells while minimizing energy consumption in regions where pre-charging is not needed.
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
Effectively prevents unwanted programming of unselected memory cells by ensuring proper pre-charging and boosting, enhancing data retention and reliability in non-volatile memory systems.
Implementation Method 1
maintaining the dummy word lines at a low voltage to isolate memory cells
Implementation Method 2
applying one or more overdrive voltages to word lines connected to memory cells of the first sub-block to provide a conductive path from memory cells of the second sub-block through the first sub-block to a source line
Implementation Method 3
boosting the pre-charged channels of unselected memory cells
Data Source
AI summary
Memory cells of a second sub-block are programmed by pre-charging channels of unselected memory cells connected to the selected word line, boosting the pre-charged channels of unselected memory cells and applying a program voltage to selected non-volatile memory cells connected to the selected word line. The pre-charging includes applying one or more overdrive voltages to word lines connected to memory cells of a first sub-block to provide a conductive path from memory cells of the second sub-block through the first sub-block to a source line and maintaining the word lines connected to memory cells of the first sub-block at one or more overdrive voltages while ramping down signals at the end of the pre-charging. Dummy word lines, positioned between sub-blocks, are maintained at a resting voltage during the boosting in order to cut-off channels of memory cells in the second sub-block from channels of memory cells in the first sub-block.