Flash Memory GSL Voltage Control for Error Recovery Reads
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Solution Overview
Problem
The complexity of manufacturing flash memory devices leads to difficulties in individually controlling lines such as string selection, word, and ground selection lines, resulting in reduced reliability and performance.
Innovation Solution
Implementing a coded GSL structure where ground selection transistors of cell strings are connected in units of rows, allowing individual control by setting different threshold voltages and controlling ground selection lines, thereby enabling normal and special read operations to enhance data reading reliability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cell strings are controlled individually by manufacturing separate lines, then reliability and performance are improved, but manufacturing complexity increases
Solution Approach 1:
The ground selection lines are segmented into multiple lines (first ground selection line and second ground selection line) that can be controlled independently. This allows different cell strings to be selectively activated without requiring complete redesign of the manufacturing process, thus improving reliability while managing complexity through functional segmentation rather than structural segmentation.
Solution Approach 2:
The patent introduces dynamic voltage control where the first voltage is applied to the first ground selection line and the second voltage (higher than first) is applied to the second ground selection line. This dynamic voltage differentiation enables flexible control of cell string activation states, allowing the system to adapt to different reading requirements without increasing manufacturing complexity.
2Reliability
If higher voltage is applied to all ground selection lines, then all ground selection transistors are turned on ensuring data reading, but performance deteriorates due to increased power consumption and interference
Solution Approach 1:
Different voltages are applied to different ground selection lines based on local requirements. The first ground selection line receives the first voltage while the second ground selection line receives the second voltage (higher than first). This local differentiation ensures that only the necessary cell strings are activated, improving data reading reliability for specific blocks while maintaining overall reading performance by avoiding unnecessary activation of all transistors.
Solution Approach 2:
Instead of applying high voltage to all ground selection lines (excessive action), the patent applies high voltage only to the second ground selection line when needed (partial action). This selective partial activation ensures sufficient voltage for reliable reading in affected blocks while avoiding the performance penalty of excessive voltage application across the entire array.
3Reliability
If error correction operation is performed, then data integrity is improved, but time consumption increases
Solution Approach 1:
The patent performs preliminary voltage differentiation before reading operations by applying the first voltage to the first ground selection line and the second voltage to the second ground selection line. This preliminary action prepares the memory structure in advance to handle potential errors more effectively during reading, improving data integrity without requiring excessive time-consuming error correction operations afterward.
Data Source
AI summary
Disclosed are storage devices and operation methods thereof. A method includes performing a normal read operation on a memory block of the memory device to read first user data, performing an error correction operation on the first user data, and performing a special read operation on the memory block to read second user data when an error of the first user data fails to be corrected. The memory block includes cell strings, and the cell strings share ground selection lines. In the normal read operation, the memory device applies a first voltage to at least one ground selection line of the ground selection lines and applies a second voltage higher than the first voltage to remaining ground selection lines. In the special read operation, the memory device applies the second voltage or a third voltage higher than the second voltage to the ground selection lines.