Nonvolatile Memory Write Control Boost Coupling Ratio
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Solution Overview
Problem
As the number of memory cells increases in nonvolatile semiconductor memory devices, the boost coupling ratio decreases, leading to easier erroneous writing, which is stabilized by channel isolation methods, but these methods can be inefficient and prone to errors.
Innovation Solution
The implementation of a nonvolatile semiconductor memory device with a write control unit and isolation control unit that applies specific voltages to word lines to separate channels between written and unwritten memory cells, using program, intermediate, isolation, and electric field relaxing voltages to prevent erroneous writing by stabilizing the boost level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of memory cells is increased, then the storage capacity is improved, but the boost coupling ratio decreases leading to easier erroneous writing
Solution Approach 1:
The patent segments the word lines into selected word lines (for active writing) and unselected word lines (for isolation). By applying different voltages to different segments of word lines, the system maintains reliable writing operation even as the total number of memory cells increases. The isolation control unit specifically segments unselected word lines into those requiring isolation voltage and those requiring electric field relaxing voltage based on their position relative to the selected word line.
Solution Approach 2:
The patent introduces intermediary voltage control mechanisms - specifically the isolation control unit that applies isolation voltages and electric field relaxing voltages to unselected word lines. These intermediary voltage applications prevent harmful electric field coupling between selected and unselected memory cells, thereby maintaining writing reliability as memory capacity scales up.
2Reliability
If channel isolation is applied to stabilize boost level, then erroneous writing is reduced, but the device complexity and number of voltages required increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment of unselected word lines based on their specific position relative to the selected word line. Word lines adjacent to the selected word line receive electric field relaxing voltage, while other unselected word lines receive isolation voltage. This localized differentiation stabilizes the boost level with minimal voltage complexity.
Solution Approach 2:
The patent changes voltage parameters dynamically based on the writing operation state. The isolation control unit adjusts the voltage applied to unselected word lines according to whether they are adjacent to the selected word line or not. This parameter change approach maintains boost level stability while minimizing the number of distinct voltage levels required compared to uniform isolation schemes.
3Reliability
If isolation voltage is applied to unselected word lines, then channel separation is achieved, but hot electron generation may occur without proper electric field relaxation
Solution Approach 1:
The patent applies preliminary action by proactively applying electric field relaxing voltage to word lines adjacent to the selected word line before or during the writing operation. This preliminary relaxation of the electric field prevents the accumulation of energy that would otherwise generate hot electrons, while still maintaining channel separation through isolation voltage on other unselected word lines.
Solution Approach 2:
The patent converts the potentially harmful electric field concentration into a beneficial effect by applying targeted electric field relaxing voltage. The isolation voltage creates strong electric fields for channel separation, while the adjacent word lines receive relaxing voltage that converts this strong field into a controlled, non-harmful distribution, preventing hot electron generation while maintaining the separation benefit.
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 reduces erroneous writing by maintaining a stable boost level and simplifies the write operation, reducing the generation of hot electrons and the number of voltages required, thereby enhancing the reliability and efficiency of data storage.
Implementation Method 1
an isolation control unit that makes to apply an isolation voltage to any word line of unselected rows to separate the channels between a written memory cell and an unwritten memory cell
Implementation Method 2
makes to apply an electric field relaxing voltage to a word line adjacent to a word line to which the isolation voltage is applied, and makes the isolation voltage and the electric field relaxing voltage equal to the intermediate voltage so that the channels are connected
Data Source
AI summary
According to one embodiment, in a write control unit that performs writing on a selected memory cell connected to a selected word line by making to apply a program voltage to the selected word line while making to apply an intermediate voltage to unselected word lines, an isolation voltage is controlled to be applied to any word line of the unselected word lines at a time of applying the program voltage and the isolation voltage is controlled to increase before the intermediate voltage is removed after applying the program voltage.