Dynamic Pass Voltage Adjustment for Memory Read Reliability
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Solution Overview
Problem
The reliability of read operations in memory devices is compromised due to interference from voltage differences between read and pass voltages, which affects the accuracy of determining memory cell states in multi-level cell methods.
Innovation Solution
The solution involves setting a read voltage for a selected word line and a first pass voltage for adjacent word lines, with the pass voltage adjusted based on the read voltage's level relative to a reference voltage, and using a voltage generator to output read and pass voltages with offset codes to optimize voltage differences and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a read voltage is applied to a selected word line and a fixed pass voltage is applied to adjacent word lines, then the read operation can be performed, but voltage interference occurs due to voltage difference between read voltage and pass voltage, reducing read operation reliability
Solution Approach 1:
The pass voltage is made dynamic rather than fixed. The voltage generator adjusts the pass voltage level based on the read voltage level according to stored voltage code information. When the read voltage is high, the pass voltage is set higher; when the read voltage is low, the pass voltage is set lower. This dynamic adjustment reduces the voltage difference between read and pass voltages, minimizing voltage interference and improving read operation reliability.
Solution Approach 2:
The patent changes the parameter of pass voltage from a fixed reference value to a variable value that depends on the read voltage level. The voltage generator modifies the pass voltage parameter based on voltage code information, creating a correlated relationship between read voltage and pass voltage levels. This parameter change strategy reduces voltage interference by ensuring the pass voltage adapts to the read voltage condition.
2Measurement precision
If multiple read voltages are used to determine program states in multi-level cell method, then data storage capacity increases, but voltage interference from voltage difference between read and pass voltages increases, affecting measurement precision
Solution Approach 1:
The patent implements parameter changes by adjusting the pass voltage level according to the read voltage level. The voltage generator uses voltage code information to determine appropriate pass voltage levels that correlate with read voltage levels. This ensures that even when multiple read voltages are used for multi-level cell reading, the pass voltage adapts to minimize interference, maintaining measurement precision for accurate program state determination.
Solution Approach 2:
The system employs feedback through voltage code information that stores the relationship between read voltage and pass voltage levels. The voltage generator uses this feedback information to adjust pass voltage levels dynamically, ensuring optimal voltage conditions for each read operation. This feedback mechanism maintains measurement precision by compensating for voltage interference across different read voltage levels.
Data Source
AI summary
A memory device and a method of operating the memory device include setting a read voltage to be applied to a selected word line among word lines connected to a memory block and setting a first pass voltage to be applied to an adjacent word line adjacent to the selected word line among the word lines. The method also includes applying the first pass voltage to the adjacent word line and applying the read voltage to the selected word line. The first pass voltage is set higher than a reference pass voltage when the read voltage is lower than a reference voltage. The first pass voltage is set lower than the reference pass voltage when the read voltage is higher than the reference voltage.