Nonvolatile Memory Device Threshold Voltage Control
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Solution Overview
Problem
Current nonvolatile memory devices face challenges in efficiently writing data due to limitations in controlling threshold voltage of floating-gate transistors, which affects the storage capacity and reliability of data retention.
Innovation Solution
A nonvolatile memory device and method that utilize a first and second latch unit to selectively program and verify data in a nonvolatile memory cell through incremental step pulse programming, allowing for precise control of threshold voltage and repeated writing operations to ensure data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the threshold voltage of the floating-gate transistor is controlled to have multiple different values to increase storage capacity, then the data storage capacity per cell is improved, but the precision and reliability of threshold voltage control becomes more difficult to maintain
Solution Approach 1:
The patent segments the data writing process into multiple iterative steps (ISPP - Incremental Step Pulse Programming). Instead of attempting to program the threshold voltage to its final value in a single step, the method divides the programming process into multiple incremental steps, each adjusting the threshold voltage by a small amount. This segmentation allows for precise control of the threshold voltage even when targeting multiple different values for increased storage capacity.
Solution Approach 2:
The patent employs periodic verification and adjustment cycles during the programming process. After each incremental programming step, the threshold voltage is verified, and if necessary, additional programming pulses are applied in a periodic manner until the desired threshold voltage is achieved. This periodic action ensures precise control while accommodating the complexity of multi-level cell programming.
2Reliability
If incremental step pulse programming is used to precisely control threshold voltage, then the data storage reliability is improved, but the time required to complete the writing operation increases
Solution Approach 1:
The patent applies preliminary verification checks at each incremental step of the programming process. Rather than completing the full programming sequence and then verifying, the method performs preliminary verification at intermediate stages to detect and correct programming errors early. This preliminary action prevents the need for complete re-programming, thereby reducing the overall time while maintaining high reliability.
Solution Approach 2:
The patent incorporates feedback mechanisms where the verification results from each incremental step are used to adjust subsequent programming actions. If the threshold voltage reaches the desired value or if verification fails, the feedback loop terminates or adjusts the programming sequence accordingly. This feedback-driven approach avoids unnecessary programming steps, reducing writing time while ensuring data retention reliability.
3Reliability
If multiple verification steps are performed to ensure data accuracy, then the data storage reliability is improved, but the complexity of the writing process increases
Solution Approach 1:
The patent employs a universal verification and control mechanism that functions across all incremental programming steps. The same verification circuitry and control logic are reused iteratively for each step, rather than implementing separate specialized verification processes for each stage. This multi-functional approach maintains high verification accuracy while avoiding the need for additional complex dedicated circuits or processes.
Solution Approach 2:
The verification process is designed to be self-regulating, where the verification results automatically determine the next programming action without requiring external intervention or complex control logic. The system self-adjusts the programming sequence based on verification outcomes, simplifying the overall process complexity while maintaining rigorous verification standards for data accuracy.
Data Source
AI summary
A nonvolatile memory device, including a first latch unit and a nonvolatile memory cell, and a method of writing data in a nonvolatile memory device are provided. The method includes receiving a first writing command or a second writing command from outside of the nonvolatile memory device, and writing first data stored in the first latch unit in the nonvolatile memory cell in response to the first or second writing command. The first data is retained in the first latch unit until the writing of the first data stored in the first latch unit in the nonvolatile memory cell is completed.