NAND Flash Word Line Setup via Adjacent Coupling
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Solution Overview
Problem
Existing NAND Flash non-volatile memory devices face challenges in efficiently reading data due to limitations in setting up word lines for read operations, which affects the speed and reliability of data retrieval.
Innovation Solution
The proposed method involves a read operation technique that utilizes pre-pulse voltage levels and signal coupling from adjacent word lines to rapidly set up selected word lines to appropriate voltage levels, thereby reducing the time required for data reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional word line setup methods are used, then the read operation can be completed, but the setup time is excessive and reduces reading speed
Solution Approach 1:
The patent applies preliminary action by setting up the word line voltage levels before the actual read operation begins. Specifically, the method performs a verify read operation first to determine threshold voltage distributions, then pre-configures the read voltage levels based on these distributions. This preliminary configuration eliminates the need for time-consuming voltage adjustments during the actual data reading phase, thereby reducing word line setup time and improving reading speed.
Solution Approach 2:
The patent implements the skipping principle by eliminating unnecessary intermediate steps in the word line setup process. Instead of sequentially adjusting each voltage level and waiting for stabilization, the method directly calculates the optimal read voltage levels from the threshold voltage distributions obtained during the verify phase, then applies these levels immediately. This rushes through the setup process by skipping redundant adjustment steps, thereby reducing setup time and improving reading speed.
2Reliability
If multiple verify and read operations are performed, then reading accuracy is improved, but the overall reading time increases
Solution Approach 1:
The patent applies preliminary action by performing the verify read operation and threshold voltage distribution analysis before the actual data reading. This preliminary phase establishes accurate reference distributions that enable a single subsequent read operation to achieve high accuracy. By moving the iterative verification process to a preliminary stage with optimized voltage levels, the method ensures reading accuracy while minimizing the time consumed during the critical data retrieval phase.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the read voltage levels based on the actual threshold voltage distributions measured during the verify phase. Instead of using fixed or conservative voltage levels that would require multiple reads to verify accuracy, the method calculates optimal voltage levels that match the specific memory device characteristics. This parameter optimization allows accurate reading in a single operation, improving reliability without increasing total reading time.
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 enhances the speed and reliability of data reading from NAND Flash memory devices by reducing the time needed to set up word lines, leading to improved overall performance.
Implementation Method 1
a method of reading data from a NAND Flash non-volatile memory device, the method comprising: coupling an adjacent word line to a selected word line to drive the selected word line from a ground voltage to a start read level
Data Source
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AI summary
A memory device includes N rows of memory cells and N word lines coupled thereto, respectively. A method of reading data from the memory device includes: applying a first pre-pulse voltage to an nth word line while applying a second pre-pulse voltage to an adjacent word line adjacent to the nth word line, the second pre-pulse voltage exceeding the first pre-pulse voltage, and n being an integer ranging from 1 to N; grounding the nth word line while maintaining the second pre-pulse voltage on the adjacent word line; pulling a voltage on the nth word line towards a start read level; and prior to the voltage on the nth word line reaching the start read level, driving a voltage on the adjacent word line to the first pre-pulse voltage.