Non-Volatile Memory Read Compensation for Temperature Variations
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Solution Overview
Problem
Non-volatile memory devices face challenges in maintaining accurate read and verify operations due to temperature changes, which affect the threshold voltage of memory cells, leading to reduced read margins and incorrect state determination.
Innovation Solution
The method involves sensing the temperature of memory cells and adjusting the bit line voltage levels and evaluation times accordingly, using a first and second voltage setting for precharging and data sensing, to compensate for temperature-induced changes in the read and verify operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed read voltage is used for sensing memory cell threshold voltage, then the read operation is simple and fast, but the read margin is reduced and reading accuracy deteriorates due to temperature changes
Solution Approach 1:
The patent applies dynamics by making the read voltage adjustable rather than fixed. The read voltage is dynamically changed according to temperature conditions, allowing the system to adapt to temperature variations and maintain accurate reading operations across different thermal environments
Solution Approach 2:
The patent changes the voltage parameter based on temperature. By adjusting the read voltage level according to sensed temperature conditions, the system compensates for temperature-induced threshold voltage shifts in memory cells, thereby maintaining reading accuracy without requiring complex additional hardware
2Measurement precision
If the read voltage is increased to compensate for high temperature effects, then the reading accuracy is improved, but the harm to memory cell state is increased
Solution Approach 1:
The patent applies local quality by using different read voltage levels for different temperature conditions. Instead of using a uniformly high voltage that could harm memory cells, the system applies appropriately sized voltage adjustments localized to specific temperature ranges, compensating for threshold voltage shifts while minimizing harmful effects on memory cell states
3Reliability
If temperature compensation is implemented by adjusting read voltage, then reading accuracy is maintained across temperature ranges, but the control complexity increases
Solution Approach 1:
The patent implements feedback by sensing the temperature condition and using this information to adjust the read voltage accordingly. The temperature sensor provides feedback about the current thermal state, which is then used to select the appropriate read voltage level, creating a closed-loop system that maintains reading reliability automatically
Solution Approach 2:
The patent applies preliminary action by pre-defining multiple read voltage levels corresponding to different temperature ranges. Before performing the actual read operation, the system determines the appropriate voltage level based on temperature, preparing the optimal voltage in advance to ensure accurate reading without requiring complex real-time calculations
Data Source
AI summary
A method of reading data in a non-volatile memory device compensates for a change in a reading/verifying result in accordance with a change of temperature. The method includes sensing a temperature of memory cells, setting a first voltage and a second voltage of a bit line sensing signal in accordance with the sensed temperature, precharging a bit line in accordance with the set first voltage, evaluating a change of a voltage level of the bit line based on whether a memory cell for a read operation is programmed, and sensing data of the memory cell in accordance with the set second voltage. The method may read/verify data constantly even though a temperature is changed.