Memory System Stabilizing Word Line Potentials to Prevent Electron Trapping
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Solution Overview
Problem
Three-dimensionally stacked semiconductor memory systems face challenges in maintaining accurate data reading due to potential variations in word line voltages caused by coupling effects, leading to incorrect readings and reduced operation reliability.
Innovation Solution
The implementation of a memory system that includes a semiconductor memory with a row decoder and driver circuit, which asserts a block selection signal to transfer specific voltages to word lines during data read operations, and continues to apply a discharge voltage to word lines after data is read to prevent electron trapping and threshold variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If word lines are left floating after data read, then device complexity is reduced, but threshold variation increases due to electron trapping
Solution Approach 1:
The block decoder continues to assert the block selection signal for a predetermined period after data reading completes, proactively preventing electron trapping before it can cause threshold variation. This preliminary action maintains word line voltage stability without requiring complex additional circuitry.
2Reliability
If block selection signal is asserted continuously, then word line voltage stability is improved, but energy consumption increases
Solution Approach 1:
The block selection signal is asserted periodically for a predetermined time duration after data reading, rather than continuously. This periodic assertion maintains sufficient voltage stability to prevent electron trapping while reducing overall power consumption compared to continuous assertion.
3Speed
If voltage is applied to all word lines during read, then reading speed is improved, but interference between adjacent blocks increases
Solution Approach 1:
The driver circuit applies different voltages to different word lines based on their selection status: high voltage to the selected word line for fast reading, and low voltage to unselected word lines to minimize interference. This localized voltage application achieves both fast reading speed and reduced crosstalk.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves data reading accuracy by stabilizing word line potentials and reducing the occurrence of incorrect readings, thereby enhancing the reliability of the memory system.
Implementation Method 1
the first transistors transfer a first voltage to a selected first word line, and a second voltage higher than the first voltage to unselected other first word lines
Data Source
AI summary
According to one embodiment, a memory system includes a semiconductor memory and a controller. The semiconductor memory includes: first memory cells, first word lines, a first row decoder, and a driver circuit. The first row decoder includes first transistors capable of coupling the first word lines to first signal lines, and a first block decoder supplying a first block selection signal to the first transistors. When the controller issues a data read command, the first block decoder asserts the first block selection signal to allow the first transistors to transfer a first voltage to a selected first word line, and a second voltage to unselected other first word lines. After data is read, the first block decoder continues asserting the first block selection signal, and the driver circuit transfers a third voltage.