Memory Cell Read Voltage Timing for Disturbance-Resistant Reads
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Solution Overview
Problem
Semiconductor devices experience read disturbance due to changes in the threshold voltage levels of memory cells over time, leading to incorrect identification of data states and reduced reliability.
Innovation Solution
Adjusting the level of the read voltage based on elapsed time since the previous write or read operation, using time stamps to determine the appropriate voltage level for accurate data state identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed target level read voltage is used for read operations, then the read operation is simple and fast, but read disturbance occurs due to threshold voltage changes over time leading to incorrect data state identification
Solution Approach 1:
The patent applies dynamics by making the read voltage level adjustable based on elapsed time. Instead of using a fixed target level read voltage, the system dynamically selects between a first level read voltage (when elapsed time exceeds first setting time) and a second level read voltage (when elapsed time is within the first setting time). This dynamic adjustment resolves the contradiction by adapting the read voltage to the actual state of memory cells, improving data state identification accuracy while maintaining operational simplicity through automated time-based selection.
Solution Approach 2:
The patent changes the parameter of read voltage level based on elapsed time conditions. The control logic monitors the time since the last write or read operation and adjusts the read voltage parameter accordingly. When the elapsed time exceeds a threshold, a first level read voltage is applied; otherwise, a second level read voltage is used. This parameter change approach directly addresses the threshold voltage drift issue without complicating the read operation流程, as the adjustment is automatically managed by the control logic.
2Reliability
If the read voltage level is adjusted based on elapsed time, then read disturbance is minimized and data identification accuracy is improved, but additional time stamp storage and comparison operations are required
Solution Approach 1:
The patent implements self-service by having the control logic automatically manage the entire process of timestamp storage, retrieval, comparison, and read voltage selection. The control logic stores timestamps during write and read operations, automatically retrieves them when needed, compares the elapsed time against thresholds, and selects the appropriate read voltage level without external intervention. This self-service mechanism resolves the contradiction by embedding the complexity within the control logic itself, improving read operation reliability while keeping the overall system operation simple and automated.
3Measurement precision
If a higher read voltage is always used to ensure accurate detection, then data state identification is more reliable, but read disturbance increases causing threshold voltage shifts
Solution Approach 1:
The patent changes the read voltage parameter dynamically based on elapsed time conditions rather than always using a high voltage. When the elapsed time since the last write or read operation exceeds a first setting time, the system uses a first level read voltage (higher for better detection). When the elapsed time is within the first setting time, it uses a second level read voltage (lower to minimize disturbance). This conditional parameter change resolves the contradiction by optimizing the read voltage level according to the actual memory cell state, ensuring accurate detection when needed while minimizing read disturbance during recent operations.
Solution Approach 2:
The patent applies dynamics by making the read voltage level adaptive to the temporal state of memory cells. The control logic continuously monitors elapsed time and adjusts the read voltage accordingly, creating a dynamic system that responds to changing conditions. This dynamic approach resolves the contradiction between detection precision and read disturbance by applying higher voltage only when necessary (after sufficient time has passed) and using lower voltage when memory cells are still in a stable recent state, thus maintaining precision while reducing harmful effects.
Data Source
AI summary
An operating method of a semiconductor device may include checking an operation time stamp when receiving a read command, calculating an elapsed time based on the operation time stamp that has been stored and a time when the read command has been received, comparing the elapsed time and a first setting time, selecting a read voltage having a first level instead of a target level when the elapsed time is greater than the first setting time, and performing a read operation based on the read voltage that has been selected.