Memory Device Threshold Voltage Control via Segmented Programming
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Solution Overview
Problem
Current memory devices face reliability issues due to the variability in threshold voltage distributions during programming operations, which can lead to data retention problems and inefficiencies in programming processes.
Innovation Solution
The memory device employs a method that includes a first program operation with an intermediate and additional program step, and a second program operation to ensure that memory cells have threshold voltages corresponding to specific target program states, using page buffers and a data conversion controller to manage logical page bits and distinguish between even and odd program states, thereby optimizing threshold voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single program operation is used to program memory cells, then the programming process is simple and fast, but the threshold voltage distribution becomes wide and unreliable
Solution Approach 1:
The programming operation is divided into multiple distinct phases: an initial program operation that programs memory cells to intermediate threshold voltage states, followed by a final program operation that adjusts threshold voltages to precise target states. This segmentation allows each phase to focus on specific aspects of threshold voltage control, improving overall precision while managing complexity through structured multi-step processing.
Solution Approach 2:
The initial program operation performs preliminary programming of memory cells to intermediate threshold voltage states before the final program operation refines them to target states. This preliminary action prepares the memory cells in advance, making the subsequent fine-tuning more effective and reducing the complexity of achieving precise threshold voltage control in a single operation.
2Measurement precision
If threshold voltage distributions are narrow to improve read accuracy, then data retention improves, but programming becomes more difficult and time-consuming
Solution Approach 1:
The programming process is segmented into an initial program operation that quickly establishes intermediate threshold voltage distributions, and a final program operation that narrows these distributions to precise target values. This segmentation enables the system to balance programming speed and precision by performing coarse programming first, then fine-tuning threshold voltages to achieve narrow distributions required for accurate read operations.
Solution Approach 2:
The initial program operation performs preliminary programming to intermediate states, preparing memory cells for subsequent refinement. This preliminary action allows the system to achieve narrow threshold voltage distributions for high read accuracy without requiring the entire programming process to be optimized for precision from the start, thus maintaining reasonable programming speed.
3Quantity of substance
If multiple program states are distinguished using more logical page bits, then data storage capacity increases, but the complexity of data conversion and programming increases
Solution Approach 1:
The data conversion process is segmented into distinct operations: converting input data to intermediate values during the initial program operation, and adjusting these values to final target states during the final program operation. This segmentation allows the data conversion controller to manage complex multi-state programming by breaking down the conversion process into manageable stages, reducing overall controller complexity while maintaining high storage capacity.
Solution Approach 2:
The data conversion controller performs preliminary conversion of input data to intermediate values that correspond to intermediate threshold voltage states. This preliminary data conversion prepares the data for subsequent refinement in the final program operation, allowing the system to support multiple program states and high storage capacity while managing conversion complexity through staged processing.
Data Source
AI summary
A memory device comprises a plurality of memory cells each having a threshold voltage corresponding to any one of a plurality of program states according to target data to be stored by performing a program operation, page buffers configured to store data provided from a memory controller, a data conversion controller configured to control the page buffers to convert the data into the target data including a plurality of logical page bits and a program operation controller configured to perform the program operation to store the target data in the plurality of memory cells, wherein the plurality of logical page bits include at least one logical page bit distinguishing even program states from odd program states among the plurality of program states and remaining logical page bits other than the at least one logical page bit having a same value as at least one program state among adjacent program states.