NAND Flash Select-Line Voltage Control for Leakage Suppression
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Solution Overview
Problem
NAND-type flash memory experiences increased leakage current and hot carriers in non-conductive select transistors during data read operations, which affect the reliability and efficiency of the memory device.
Innovation Solution
A semiconductor memory device is designed with a driver module that applies a difference in voltages to selection lines, ensuring that non-selected select transistors remain in a non-conductive state by using a first non-selection voltage for some transistors and a second non-selection voltage for others, thereby reducing leakage current and hot carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If select transistors are used in NAND-type flash memory for data read operations, then data read capability is improved, but leakage current and hot carriers increase in non-conductive select transistors
Solution Approach 1:
The selection lines are divided into multiple groups (first selection lines and second selection lines) corresponding to different string units. By segmenting the control structure, the patent applies different voltage levels to different groups of select transistors, allowing selective suppression of leakage current and hot carriers in non-conductive transistors while maintaining read capability in selected transistors.
Solution Approach 2:
Different voltage levels (first non-selection voltage and second non-selection voltage) are applied to different groups of select transistors based on their specific operational state and position. This local differentiation in voltage application optimizes each group's performance, minimizing leakage and hot carriers in non-selected transistors while preserving read functionality in selected transistors.
2Device complexity
If non-conductive select transistors are maintained in a single voltage state, then device complexity is reduced, but leakage current and hot carriers cannot be effectively minimized
Solution Approach 1:
The voltage control system is segmented into multiple levels (first non-selection voltage and second non-selection voltage) applied to different groups of select transistors. This segmentation enables differentiated control without requiring complex individual control for each transistor, achieving effective leakage and hot carrier suppression through grouped voltage application.
Solution Approach 2:
The patent changes the voltage parameter applied to select transistors based on their selection state and group assignment. By introducing multiple voltage levels (first non-selection voltage and second non-selection voltage) instead of a single voltage state, the system effectively controls leakage current and hot carriers while maintaining manageable device complexity through systematic parameter differentiation.
Data Source
AI summary
A semiconductor memory device includes strings each including memory cells connected in series; first select transistors connected to one end of the strings; second select transistors connected to the other end of the strings; first control lines commonly provided to the strings and connected to gates of the memory cells; first selection lines connected to gates of the first select transistors and each corresponding to a first unit having one string; second selection lines connected to gates of the second select transistors and corresponding to a second unit including a plurality of the first units; and a driver configured to provide a voltage for the plurality of first selection lines, causing a difference between a first non-selection voltage and a second non-selection voltage.