Ground Selection Transistor Threshold Voltage Adjustment
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Solution Overview
Problem
Nonvolatile memory devices face challenges in accurately adjusting the threshold voltage of ground selection transistors, leading to potential read errors and inefficiencies in data storage and retrieval.
Innovation Solution
A method and device for adjusting the threshold voltage of ground selection transistors in a nonvolatile memory device by applying specific voltages to the gates of first and second ground selection transistors during read operations, using ion implantation and adaptive bias conditions to optimize voltage levels without causing read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single voltage is applied to ground selection transistors, then the device structure is simple, but read errors occur due to inaccurate threshold voltage adjustment
Solution Approach 1:
The ground selection transistor gate control is segmented into two independent voltage lines (first ground selection line and second ground selection line), allowing separate voltage application to different regions of the gate. This enables differential threshold voltage adjustment based on local requirements, improving read accuracy without requiring complete redesign of the transistor structure.
Solution Approach 2:
Different voltage levels are applied to different portions of the ground selection transistor gate according to local threshold voltage requirements. The first voltage is applied to the first ground selection line and the second voltage to the second ground selection line, creating localized electrical characteristics that match the specific needs of different memory cell regions.
2Reliability
If threshold voltage adjustment is performed during read operation, then read errors are minimized, but additional voltage control steps are required
Solution Approach 1:
The first and second ground selection lines serve dual functions: they act as standard selection lines during normal read operations and simultaneously function as threshold voltage adjustment lines by applying appropriate voltage levels. This multi-functionality allows threshold voltage calibration to be integrated into the existing read operation workflow without requiring completely separate control mechanisms.
Solution Approach 2:
The threshold voltage of ground selection transistors is dynamically adjusted by changing the voltage parameter applied to their gates. During read operations, specific voltage levels (first voltage and second voltage) are applied to the first and second ground selection lines respectively, modifying the electrical characteristics of the transistors to optimize read accuracy for different memory cell states.
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 effectively adjusts the threshold voltage of ground selection transistors, enhancing data storage reliability and retrieval efficiency by minimizing leakage currents and read errors, while maintaining compatibility with existing memory device structures.
Implementation Method 1
the first and second ground selection transistors are formed by ion implantation
Data Source
AI summary
A method of adjusting a threshold voltage of a ground selection transistor in a nonvolatile memory device includes providing a first voltage to a gate of a first ground selection transistor in a read operation and providing a second voltage to a gate of a second ground selection transistor in the read operation. The nonvolatile memory device includes at least one string, the string having string selection transistors, memory cells and the first and second ground selection transistors connected in series and stacked on a substrate.