Memory Device Program Voltage Adjustment for MLC Storage
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Solution Overview
Problem
Memory devices face challenges in managing threshold voltages of multi-level cell (MLC) methods, where the increasing number of bits stored in a memory cell leads to narrower intervals between threshold voltage distributions, causing program operation times to increase and potentially resulting in overlapping distributions, which affects data retention and read accuracy.
Innovation Solution
A memory device and method that include an operation code generator, verify counter, and verify determiner to adjust the program voltage by comparing the count value of verify operations with a reference value, allowing for incremental step pulse programming (ISPP) to ensure proper voltage increments and prevent threshold voltage distribution overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bits stored in a memory cell is increased (MLC method), then the storage capacity is improved, but the interval between threshold voltage distributions becomes narrower, causing program operation time to increase and potentially resulting in overlapping distributions
Solution Approach 1:
The patent applies dynamics by making the program voltage increment amount variable rather than fixed. The verify determiner dynamically adjusts the program voltage increment based on the verify operation results, using larger increments when verify operations pass quickly and smaller increments when verify operations take longer, thereby optimizing program operation time while maintaining reliable threshold voltage distribution separation for high-capacity MLC storage
Solution Approach 2:
The patent changes the parameter of program voltage increment amount based on verify operation characteristics. By monitoring whether verify operations pass and adjusting the program voltage increment accordingly, the system adapts to different memory cell programming speeds, resolving the contradiction between maintaining narrow voltage distribution intervals for high capacity and achieving fast program operation
2Quantity of substance
If the number of bits stored in a memory cell is increased (MLC method), then the storage capacity is improved, but the interval between threshold voltage distributions becomes narrower, causing threshold voltage distributions to potentially overlap and affecting data retention and read accuracy
Solution Approach 1:
The patent implements feedback by using verify operation results to control subsequent program voltage application. The verify determiner continuously monitors verify operation outcomes and adjusts the program voltage increment amount accordingly, ensuring that threshold voltage distributions remain properly separated even when storing multiple bits per cell, thus maintaining data retention and read accuracy while achieving high storage capacity
Solution Approach 2:
The system dynamically adjusts the program voltage increment based on real-time verify operation feedback. This dynamic control ensures that even with narrow threshold voltage distribution intervals required for high-capacity MLC storage, the distributions remain properly separated, preventing overlap and maintaining reliability
3Adaptability or versatility
If memory cells with different electrical characteristics are present in the array, then device variability is inherent, but program operation time increases due to slow cells requiring more verification cycles
Solution Approach 1:
The patent applies dynamics by making the program voltage increment amount adaptive rather than fixed. The verify determiner adjusts the increment size based on verify operation results, allowing fast cells to be programmed quickly with larger increments while slow cells receive smaller increments that ensure proper programming, thereby reducing overall program operation time while handling electrical characteristic variability
Solution Approach 2:
The system changes the program voltage increment parameter based on verify operation characteristics. By adapting the increment amount to the actual programming progress indicated by verify operations, the system efficiently handles memory cells with different electrical characteristics, preventing excessive program operation time while ensuring all cells are properly programmed
Data Source
AI summary
Provided herein may be a memory device and a method of operating the memory device. The memory device includes an operation code generator configured to generate a program code and a verify code in response to a program control code and to output an operation code using the program code and the verify code, a verify counter configured to store a count value acquired by counting the number of verify operations that are performed depending on the verify code, a verify determiner configured to compare the count value with a reference value depending on the result of the verify operation and to generate the program control code to change a step voltage for raising a program voltage depending on the comparison result, and a voltage generator configured to generate the program voltage and a verify voltage depending on the operation code.