Non-uniform Programming Voltage Control for 3D NAND Flash Memory Cells
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Solution Overview
Problem
3D NAND flash memory devices face inefficiencies in program time due to varying cell diameters, leading to a broad program threshold voltage distribution, making it challenging to control programming time across cells in a string.
Innovation Solution
Applying non-uniform programming voltages to cells within a string, where cells with larger diameters receive higher voltages and those with smaller diameters receive lower voltages, thereby reducing the variation in threshold voltages and optimizing program time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform programming voltage is applied to all cells in a string, then the programming operation is simplified, but the program threshold voltage distribution becomes broad due to varying cell diameters
Solution Approach 1:
The patent applies different programming voltages to different cells within the same string based on their specific diameter characteristics. Cells with larger diameters receive higher programming voltages while cells with smaller diameters receive lower voltages, optimizing the programming process for each cell's local characteristics and achieving narrow Vt distribution without excessive complexity
Solution Approach 2:
The patent changes the programming voltage parameter dynamically based on cell diameter measurements. By adjusting the voltage parameter according to each cell's specific diameter, the system achieves precise control over threshold voltage distribution while adapting to manufacturing variations
2Manufacturing precision
If higher programming voltage is applied to cells with larger diameters, then the program threshold voltage distribution narrows, but the programming operation becomes more complex
Solution Approach 1:
The patent implements local quality control by measuring the diameter of each cell and applying customized programming voltages accordingly. This approach narrows the Vt distribution by addressing each cell's specific characteristics rather than applying a one-size-fits-all voltage, achieving precision without requiring complete redesign of the programming architecture
Solution Approach 2:
The patent employs feedback mechanisms where cell diameter measurements are obtained and used to determine the appropriate programming voltage for each cell. This closed-loop approach enables precise control of Vt distribution while automating the complexity management through measurement-based voltage selection
3Quantity of substance
If 3D NAND flash memory structure is used to increase storage capacity, then the storage density improves, but the program time control becomes difficult due to non-uniform cell diameters
Solution Approach 1:
The patent addresses the 3D NAND challenge by applying local quality control to cells at different heights and positions within the vertical stack. By measuring and compensating for diameter variations across multiple layers, the system achieves uniform programming times and Vt distributions while maintaining the high storage density benefits of 3D architecture
Solution Approach 2:
The patent dynamically adjusts programming parameters including voltage magnitude and pulse duration based on the specific diameter measurements of cells in the 3D structure. This adaptive parameter control enables precise programming time management across the complex multi-layer architecture, ensuring consistent performance throughout the vertical stack
Data Source
AI summary
The present invention provides methods and associated devices for controlling the voltage threshold distribution corresponding to performing a function on cells of non-volatile memory device. In one embodiment, a method is provided. The method may comprise providing the non-volatile memory device. The device comprises one or more strings, each string comprising a plurality of cells, the plurality of cells comprising a first cell and a second cell. The method further comprises performing a function of the non-volatile memory device by applying a first function voltage to the first cell and a second function voltage to the second cell. The first function voltage and the second function voltage are different.