Nonvolatile Memory Programming via Bit Line Voltage Segmentation
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Solution Overview
Problem
The reliability of data stored in nonvolatile memory devices deteriorates due to memory cell characteristics, leading to issues with programming speed and threshold voltage distribution in programmed states.
Innovation Solution
A method and device that divide memory cells into multiple groups based on threshold voltage, applying specific programming voltages to each group to improve programming speed and reduce the width of threshold voltage distribution, including first and second programming loops with different voltage levels and inhibition voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a programming voltage pulse is provided to memory cells using ISPP method, then programming operation can be performed, but the reliability of data stored in memory cells deteriorates due to memory cell characteristics
Solution Approach 1:
The patent divides memory cells into multiple groups based on their threshold voltage characteristics (first group with higher Vth, second group with lower Vth). This segmentation allows different programming strategies to be applied to each group, improving overall reliability while maintaining programming speed. The verification operation identifies cells in each group, and subsequent programming pulses are selectively applied based on group classification.
Solution Approach 2:
The patent applies different programming voltages and verification strategies to different memory cell groups. Specifically, memory cells in the first group receive different programming treatment compared to cells in the second group. This local quality approach ensures that each cell group is programmed according to its specific characteristics, thereby improving data reliability without sacrificing overall programming efficiency.
2Measurement precision
If verification operation is performed after programming, then programmed state can be verified, but the width of threshold voltage distribution of memory cells increases
Solution Approach 1:
The patent segments memory cells into multiple groups based on threshold voltage distribution and applies targeted programming to each segment. By dividing cells into first and second groups with distinct Vth characteristics and applying group-specific programming voltages, the overall threshold voltage distribution width is reduced while maintaining verification accuracy through selective programming approaches.
3Productivity
If programming operation is performed on all memory cells, then all cells can be programmed, but programming speed decreases due to uniform treatment of all cells
Solution Approach 1:
The patent implements local quality by applying different programming voltages and verification procedures to different memory cell groups. Memory cells in the first group (higher Vth) and second group (lower Vth) receive tailored programming treatment based on their specific characteristics. This approach accelerates programming speed by avoiding uniform treatment while ensuring programming accuracy through group-specific optimization.
Data Source
AI summary
A nonvolatile memory device includes multiple memory cells including first memory cells and second memory cells. A method of programming the nonvolatile memory device includes: performing first programming to apply a programming forcing voltage to a bit line of each of the first memory cells; and dividing the second memory cells into a first cell group, a second cell group, and a third cell group, based on a threshold voltage of the second memory cells after performing the first programming. The method also includes performing second programming to apply a programming inhibition voltage to the bit line of each of the first memory cells and a bit line of each of memory cells of the first cell group. A level of the programming forcing voltage is lower than that of the programming inhibition voltage.