Nonvolatile Memory Programming with Shared Bitline Voltage Control
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Solution Overview
Problem
Nonvolatile memory devices with shared bitline structures face programming disturbances due to insufficient voltage boosting in unselected cell strings, leading to unintended programming of memory cells.
Innovation Solution
A method is introduced where both channels of cell strings are precharged with a first voltage, and a selected cell string is programmed using a second voltage greater than ground but less than the power supply voltage, reducing leakage current and preventing programming disturbances by ensuring sufficient voltage boosting in unselected cell strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one cell string is selected from multiple cell strings coupled to the same bitline for programming, then the selected memory cell can be programmed, but the unselected cell string experiences programming disturbance due to insufficient voltage boosting
Solution Approach 1:
The patent applies preliminary action by precharging the channel of the unselected cell string to a first voltage (e.g., power supply voltage) before the programming operation. This precharge ensures that when the programming voltage is subsequently applied to the selected cell string, the unselected cell string's channel already has sufficient voltage level, preventing programming disturbance and ensuring reliable non-programming of unselected cells.
2Power
If ground voltage is applied to the bitline during programming of selected cell string, then programming can be performed, but leakage current increases causing voltage boosting failure in unselected cell strings
Solution Approach 1:
The patent changes the voltage parameter of the bitline from ground voltage to a voltage greater than ground voltage (e.g., second voltage level between ground and power supply voltage) during the programming operation. This parameter change reduces the voltage differential that drives leakage current in unselected cell strings, thereby minimizing energy loss and preventing voltage boosting failure while still allowing programming of the selected cell string.
3Quantity of substance
If multiple cell strings share one bitline to increase density, then storage capacity increases, but programming disturbance occurs in unselected cell strings
Solution Approach 1:
The patent applies local quality by differentiating the voltage treatment between selected and unselected cell strings. The selected cell string receives the programming voltage on its bitline, while unselected cell strings receive a different voltage level (greater than ground but less than power supply voltage) on their shared bitline. This localized voltage differentiation allows multiple cell strings to share the bitline for increased density while maintaining programming precision by preventing disturbance in unselected strings.
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 prevents programming disturbances in unselected cell strings by ensuring sufficient voltage boosting and reducing leakage current, thereby improving the accuracy and reliability of memory cell programming.
Implementation Method 1
a first channel of a first cell string and a second channel of a second cell string are precharged by applying a first voltage to a bitline
Data Source
AI summary
In method of programming a nonvolatile memory device including first and second cell strings that are coupled to one bitline, a first channel of the first cell string and a second channel of the second cell string are precharged by applying a first voltage to the bitline, one cell string is selected from the first and second cell strings, and a memory cell included in the selected cell string is programmed by applying a second voltage greater than a ground voltage and less than the first voltage to the bitline.