NAND Flash HV Switch Sequencing for Fast Word Line Programming
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Solution Overview
Problem
Existing technologies face challenges in providing high voltages required for programming operations in NAND flash memory, particularly in achieving fast and reliable programming of memory cells, which necessitates voltages higher than the power supply voltage.
Innovation Solution
A high voltage switch system comprising multiple MOSFET switches is employed to transfer boost and regulated voltages to selected word lines during different time periods, allowing for precise control of voltages applied to memory cells, with the system including a first switch for boost voltage, a second switch for a target regulated voltage, and a third switch for a pre-target regulated voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single switch is used to transfer high voltage to word lines, then the device complexity is low, but the programming speed and reliability are insufficient
Solution Approach 1:
The patent divides the single switch into multiple switches (first switch, second switch, third switch) that operate at different time periods. The first switch transfers boost voltage during a first time period, while the second and third switches transfer regulated voltages during a second time period. This segmentation allows optimized voltage control for different programming stages, improving programming speed and reliability without requiring a completely complex new system.
Solution Approach 2:
The patent applies preliminary action by first transferring the boost voltage to the selected word lines before transferring the regulated voltage. The first switch operates during a first time period to establish the initial high voltage condition, and then the second and third switches operate during a second time period to apply the final programming voltage. This sequential preliminary action ensures proper voltage sequencing for reliable programming.
2Reliability
If multiple switches are used to transfer different voltages at different time periods, then the programming reliability is improved, but the device complexity increases
Solution Approach 1:
The patent implements dynamic operation by controlling the switches to operate at different time periods based on the programming stage. The first switch is activated during the first time period for boost voltage transfer, while the second and third switches are activated during the second time period for regulated voltage transfer. This dynamic time-multiplexed approach allows the system to adapt voltage levels to programming requirements, improving reliability while managing complexity through temporal separation of functions.
3Productivity
If high voltage is applied continuously to word lines, then the programming speed is fast, but the risk of voltage damage and interference increases
Solution Approach 1:
The patent employs periodic action by dividing the voltage application into distinct time periods. The first switch transfers boost voltage during a first time period, and then the second and third switches transfer regulated voltages during a second time period. This periodic, time-separated voltage application maintains fast programming speed while reducing the risk of continuous voltage exposure that could cause damage or interference to non-selected memory cells.
Solution Approach 2:
The patent uses the switches as intermediary components that control and mediate the voltage transfer to word lines. Rather than applying high voltage directly and continuously, the switches act as intermediaries that selectively transfer voltage during specific time periods. This intermediary control prevents harmful continuous voltage exposure while maintaining the necessary high voltage conditions for fast programming during the appropriate time windows.
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
The system enables efficient and reliable programming of NAND flash memory cells by accurately applying the necessary high voltages, enhancing programming speed and reliability.
Implementation Method 1
a first switch configured to transfer a boost voltage during a first time period to a first set of selected word lines or a second set of selected word lines of the memory device; a second switch configured to transfer a target regulated voltage during a second time period to the first set of selected word lines
Data Source
AI summary
The present disclosure provides a high voltage (HV) switch system for a memory device that includes a first switch configured to transfer a boost voltage during a first time period to a first set of selected word lines or a second set of selected word lines of the memory device; a second switch configured to transfer a target regulated voltage during a second time period to the first set of the selected word lines when programming a first set of memory cells coupled to the first set of the selected word lines; and a third switch configured to transfer the target regulated voltage during the second time period to the second set of the selected word lines that is different from the first set of word lines when programming a second set of memory cells coupled to the second set of the selected word lines.