Nonvolatile Memory Channel Precharge Method for Program Disturbance
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Solution Overview
Problem
Nonvolatile memory devices face a program disturbance phenomenon due to inadequate bit line pre-charging, especially as power supply voltage decreases, leading to increased probability of memory cell programming errors.
Innovation Solution
A two-step channel pre-charge method is implemented, where the channel of a nonvolatile memory device is pre-charged under a first word line bias condition and then further pre-charged under a second word line bias condition different from the first, allowing for increased channel pre-charge potential by controlling voltages of word lines to prevent program disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power supply voltage is decreased to reduce power consumption, then energy efficiency is improved, but program disturbance phenomenon occurs more frequently
Solution Approach 1:
The patent applies preliminary action by performing bit line pre-charge operation before the programming operation. The bit line is pre-charged to a first voltage level before programming, and then further pre-charged to a second voltage level (higher than the first) immediately before programming. This preliminary pre-charging action ensures that the bit line reaches the necessary voltage threshold to prevent program disturbance, even when the overall power supply voltage is reduced for energy efficiency.
2Reliability
If bit line pre-charge voltage is increased to prevent program disturbance, then programming reliability is improved, but power consumption increases
Solution Approach 1:
The patent applies segmentation by dividing the bit line pre-charge operation into two distinct stages: a first pre-charge stage where the bit line is charged to an initial voltage level, and a second pre-charge stage where the bit line is charged to a higher final voltage level. This segmentation allows the system to perform pre-charging in steps rather than all at once, enabling better control over voltage levels and reducing overall power consumption while still achieving the necessary programming reliability.
3Ease of operation
If single-step pre-charge operation is used, then operation simplicity is maintained, but program disturbance occurs
Solution Approach 1:
The patent applies dynamics by making the pre-charge operation adaptive and conditional. The control circuit dynamically determines when to perform the second pre-charge stage based on the data being programmed. Specifically, the second pre-charge stage is performed only when the data to be programmed requires it (e.g., when programming a '0' that needs the bit line to reach a higher voltage). This dynamic approach maintains operational simplicity for common cases while ensuring reliability when 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
The two-step pre-charge method effectively reduces or prevents program disturbance by maintaining higher channel voltages, ensuring accurate programming of memory cells even at lower power supply voltages.
Implementation Method 1
pre-charging a channel of the cell string according to a first word line bias condition and pre-charging the channel of the cell string according to a second word line bias condition
Implementation Method 2
each selection transistor being connected to a corresponding word line, the method including moving electrons from each channel of the cell strings to the corresponding bit line
Data Source
AI summary
A channel pre-charge method of a nonvolatile memory device including a cell string includes pre-charging a channel of the cell string according to a first word line bias condition and pre-charging the channel of the cell string according to a second word line bias condition, different than the first word line bias condition.