Non-volatile Memory Programming Voltage Sequencing to Reduce HCI
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Solution Overview
Problem
Non-volatile memory devices, such as flash memory devices, are susceptible to disturbances during memory operations, leading to changes in threshold voltage distribution and deterioration of memory characteristics due to hot carrier injection (HCI).
Innovation Solution
A method and device for improving threshold voltage distribution in non-volatile memory devices by controlling the rising times and levels of voltages applied to word lines during programming operations, where the voltage for a selected cell is increased to a program voltage level after a non-selected cell's voltage has risen to a predetermined level, thereby reducing variations in threshold voltage due to HCI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage is applied to a word line connected with a cell to be programmed during a programming operation, then the cell can be programmed, but hot carrier injection (HCI) causes variation in threshold voltage of the cell
Solution Approach 1:
The method applies a preliminary voltage to a non-selected word line before applying the programming voltage to the selected word line. This preliminary voltage preparation reduces the threshold voltage variation caused by HCI by establishing appropriate voltage conditions in advance, thereby improving the reliability of the programming operation while maintaining threshold voltage distribution precision.
Solution Approach 2:
The method changes the voltage parameters applied to word lines during the programming operation. By adjusting the voltage level and timing for both selected and non-selected word lines, the method optimizes the programming efficiency while minimizing HCI-induced threshold voltage variation, thus resolving the contradiction between programming reliability and threshold voltage distribution.
2Productivity
If the voltage rising time is shortened to improve programming speed, then productivity increases, but hot carrier injection effects worsen causing greater threshold voltage variation
Solution Approach 1:
The method prepares the voltage conditions for non-selected word lines before the programming voltage is applied to the selected word line. This preliminary voltage setup allows for faster programming speeds by reducing the overall voltage rising time, while simultaneously controlling HCI effects through proper voltage sequencing, thus maintaining threshold voltage distribution precision.
Solution Approach 2:
The method optimizes voltage parameters including the level and timing of voltages applied to both selected and non-selected word lines. By carefully controlling these parameters, the method achieves high programming speed while minimizing threshold voltage variation caused by HCI, effectively resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If a voltage is applied to a non-selected word line before the selected word line voltage rises, then hot carrier injection is reduced, but the operation complexity increases
Solution Approach 1:
The method applies voltage to non-selected word lines in advance before the selected word line voltage rises. This preliminary action reduces HCI effects and improves threshold voltage distribution. The voltage control operation, while requiring multiple steps, is systematically managed through defined sequencing that balances the increased operational complexity with improved manufacturing precision.
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 decreases the variation of threshold voltage in memory cells due to HCI, enhancing the distribution characteristics and operational stability of non-volatile memory devices.
Implementation Method 1
disturbances due to hot carrier injection (HCI), etc., may result in changes in the distribution of threshold voltages of the memory cells
Data Source
AI summary
In a method of programming a non-volatile memory device, a first voltage is applied to a selected memory cell for programming, and a second voltage is applied to a non-selected memory cell. Before the second voltage rises to a predetermined voltage level, which is less than a program voltage level, the first voltage is greater than the second voltage or the second voltage is maintained at greater than a ground voltage level. Related non-volatile memory devices and memory systems are also discussed.