Flash Memory Programming Method Using Dynamic Voltage Control
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Solution Overview
Problem
Flash memory devices face slower program speeds due to widened threshold voltage distributions when memory cells are integrated more densely, requiring methods to reduce program pulse numbers while maintaining sufficient read margins.
Innovation Solution
A method involving increased verify voltages and decreased program voltage increments in a log-scale progression to reduce the number of program pulses, allowing for faster programming and narrower threshold voltage distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory cells are integrated more densely, then more memory cells per unit area are achieved, but threshold voltage distribution becomes widened requiring more program pulses
Solution Approach 1:
The patent applies dynamics by making the program voltage increment variable rather than constant. The increment is dynamically adjusted based on the current threshold voltage distribution width, allowing the programming process to adapt to the widened distribution caused by dense integration. This resolves the contradiction by enabling effective programming of densely integrated cells without requiring excessive fixed-number of pulses.
Solution Approach 2:
The patent changes the parameter of program voltage increment from a fixed constant to a variable value that depends on the threshold voltage distribution width. By monitoring the distribution width and adjusting the increment accordingly, the system can maintain effective programming even as integration density increases and distribution widens, thus resolving the contradiction between higher integration and maintained programming precision.
2Manufacturing precision
If program voltage increment is reduced to accommodate widened threshold voltage distribution, then read margin is improved, but number of program pulses increases remarkably
Solution Approach 1:
The patent implements feedback by monitoring the threshold voltage distribution width during the programming process and using this information to adjust the program voltage increment. This closed-loop approach allows the system to reduce the number of pulses needed while maintaining adequate read margin, resolving the contradiction between programming precision and speed by adapting to actual distribution conditions rather than using a fixed pulse count.
Solution Approach 2:
The patent makes the program voltage increment dynamic based on real-time distribution width measurement. Instead of using a constant increment that would require many fixed pulses, the system dynamically adjusts the increment size according to the actual threshold voltage distribution, thereby reducing the total number of pulses while maintaining programming precision and read margin.
3Device complexity
If constant increment program voltage is applied, then programming process is simple, but threshold voltage distribution cannot be effectively narrowed when integrated densely
Solution Approach 1:
The patent changes the program voltage increment parameter from constant to variable, where the increment is determined by the current threshold voltage distribution width. This parameter change enables the programming process to effectively narrow widened distributions caused by dense integration, while the added complexity is managed through automated measurement and adjustment mechanisms.
Solution Approach 2:
The patent introduces dynamic adjustment of the program voltage increment based on real-time distribution width measurement. This dynamic approach allows the programming process to adapt to the actual state of the memory cells, effectively narrowing threshold voltage distributions in densely integrated devices while maintaining manageable process complexity through systematic measurement and control.
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 enhances program speed and reduces the number of pulses needed, effectively narrowing the threshold voltage distribution and improving overall programming efficiency.
Implementation Method 1
The threshold voltage may be shifted through F-N tunneling in the case of a NAND flash memory
Implementation Method 2
through CHE injection in the case of a NOR flash memory device
Data Source
AI summary
A method of programming a plurality of memory cells in a flash memory device from a first state to a second state includes verifying the plurality of memory cells using a verify voltage having a level increased according to an increase in a program loop number; and programming the plurality of memory cells using a program voltage having an increment decreased according to an increase in the program loop number, wherein the verifying and programming steps constitute a program loop, the program loop being terminated at a point in time when a level of the verify voltage reaches to a voltage range of the second state.