Dynamic Program Start Voltage Control for Nonvolatile Memory
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Solution Overview
Problem
The existing incremental step pulse programming (ISPP) method for nonvolatile memory devices fixes the program start voltage, leading to widened threshold voltage distributions as the number of program and erase operations increases, resulting in decreased program speed and inefficiency.
Innovation Solution
A method that allows for variable setting of the program start voltage based on the programmed state, using a program start voltage storage unit and controller to update the voltage information after each successful program operation, ensuring optimal voltage levels for each memory cell regardless of the number of program/erase cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the program start voltage is fixed to a specific value, then the programming process is simple, but the threshold voltage distribution widens as the number of program/erase operations increases
Solution Approach 1:
The patent implements dynamic adjustment of the program start voltage based on the number of program/erase operations performed on each memory block. The controller automatically increases the program start voltage in response to detected program pass events, transforming the static voltage approach into a dynamic one that adapts to wear conditions, thereby maintaining threshold voltage distribution precision without excessive complexity
Solution Approach 2:
The patent employs feedback mechanisms where the controller monitors program verify results and detects program pass events. Based on this feedback information, the controller adjusts the program start voltage for subsequent operations on the same memory block, creating a closed-loop control system that maintains precision while managing complexity
2Manufacturing precision
If the program start voltage is increased to compensate for worn cells, then the threshold voltage distribution is maintained, but the program speed decreases due to higher voltages required
Solution Approach 1:
The patent applies different program start voltages to different memory blocks based on their individual wear states. Each memory block maintains its own program start voltage that is adjusted according to its specific program/erase history, allowing worn blocks to receive higher voltages while fresh blocks continue using lower voltages, thus maintaining overall program speed while ensuring precision for all blocks
Solution Approach 2:
The patent divides the memory device into multiple independently managed memory blocks, each with its own program start voltage stored in dedicated storage units. This segmentation allows differential voltage adjustment per block rather than a global voltage increase, preserving program speed for blocks that don't require higher voltages while maintaining precision for worn blocks
3Manufacturing precision
If dummy pulses are applied to maintain threshold voltage distribution, then the precision is improved, but the programming time increases
Solution Approach 1:
The patent eliminates the need for dummy pulses by directly adjusting the program start voltage to achieve the desired threshold voltage distribution. The controller detects program pass events and immediately adjusts the voltage for subsequent operations, skipping the time-consuming dummy pulse steps that were previously necessary to maintain precision, thereby reducing programming time while preserving threshold voltage distribution
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 maintains consistent threshold voltage distributions and improves program speed by dynamically adjusting the program start voltage according to the number of program/erase operations, preventing the need for dummy pulses and ensuring efficient data storage.
Implementation Method 1
The nonvolatile memory cell is an element enabling electrical program/erase operations, and is configured to perform the program and erase operations by changing its threshold voltage as electrons migrate in response to a strong electric field applied to a thin oxide layer of 100 angstrom or less.
Implementation Method 2
in the program operation, the controller supplies a program voltage raised by a step voltage from a program start voltage based on the program start voltage information
Data Source
AI summary
A method of 4-bit MLC programming a nonvolatile memory device includes inputting an mth program operation command and sequentially executing first to fourth logical page program operations according to first to fourth logical page program start voltages, each stored in first to fourth logical page program start voltage storage units, wherein a program voltage, which is applied at a time point at which a memory cell programmed higher than a lowest verify voltage while a program operation of each logical page is performed occurs for a first time, is updated to each logical page program start voltage.