Memory Device Program Operation Strobe Time Control
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Solution Overview
Problem
Nonvolatile memory devices face reliability issues due to source line degradation, leading to under-programming of memory cells, which affects data integrity and storage capacity, particularly in fast cells with higher program speeds.
Innovation Solution
The solution involves adjusting the current amount on bit lines during program operations by varying the strobe time in the page buffer control signals, allowing for incremental step pulse programming with different current amounts to ensure threshold voltages reach the target voltage accurately, thereby preventing under-programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of strings included in each block increases, then the storage capacity increases, but the electrical characteristics of the source lines are degraded and reliability is lowered
Solution Approach 1:
The patent applies dynamics by making the strobe time variable rather than fixed. The control logic dynamically adjusts the strobe time based on the program loop number and cell type (fast or slow cells). In early program loops, a first strobe time is used, and in later loops, a second strobe time is used. This dynamic adjustment compensates for source line degradation effects, allowing reliable programming even as the number of strings per block increases and storage capacity expands.
2Device complexity
If the strobe time is kept constant during program operations, then the control logic is simple, but under-programming occurs in fast cells affecting data integrity
Solution Approach 1:
The patent segments the program operation into multiple program loops, where each loop uses a different strobe time value. The control logic determines whether to use a first strobe time or a second strobe time based on the current program loop number and the identified cell type (fast or slow cells). This segmentation allows the system to address different cell programming characteristics separately, preventing under-programming in fast cells while maintaining simplicity in the overall control structure.
3Ease of operation
If the program operation uses a fixed current amount, then the process is simple, but threshold voltages do not reach the target voltage accurately
Solution Approach 1:
The patent implements periodic action by using different strobe times in different program loops. The program operation cycles through multiple loops, with each loop applying a specific strobe time pattern. This periodic variation in strobe time allows the threshold voltage to be incrementally adjusted to reach the target voltage accurately, while maintaining relative simplicity in the program operation structure through systematic repetition of the looped process.
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 the reliability of program operations by preventing under-programming, ensuring accurate data storage and maintaining the integrity of memory cells across varying cell types, thus improving overall memory device performance.
Implementation Method 1
increasing threshold voltages of selected memory cells
Implementation Method 2
sensing currents of the bit lines varying according to threshold voltages of the memory cells
Data Source
AI summary
Provided herein is a memory device including a plurality of memory blocks comprising a plurality of memory blocks each comprising a plurality of memory cells; a peripheral circuit coupled to the memory cells through bit lines, and suitable for sensing currents of the bit lines varying according to threshold voltages of the memory cells; and a control logic suitable for controlling the peripheral circuit so that the current amount of the bit lines vary during a program operation of the memory cells.