Non-Volatile Memory Program Verify Skipping Unnecessary Sensing
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Solution Overview
Problem
The increasing complexity of multi-level memory cells in NAND-type flash memory devices requires more precise control during programming and verification operations, which slows down the programming process due to the need for multiple sensing operations.
Innovation Solution
A method and circuit that skip the second sensing operation if the measured voltage of a source line is lower than a reference voltage, allowing for a balance between precision and speed by selectively performing only the necessary sensing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensing operations are performed to enhance verification precision, then measurement precision is improved, but programming speed deteriorates
Solution Approach 1:
The patent implements dynamic sensing operation selection based on memory cell state. The system performs a first sensing operation and uses its result to dynamically determine whether a second sensing operation is necessary. This dynamic approach adapts the verification process to actual cell conditions, performing multiple sensing operations only when needed for MLC/TLC cells while using single sensing for SLC cells, thereby resolving the contradiction between verification precision and programming speed.
Solution Approach 2:
The patent changes the sensing operation parameters (number of sensing steps) based on the type of memory cell being verified. By adjusting the verification process parameters according to cell type (SLC, MLC, TLC), the system achieves appropriate verification precision for each cell type without uniformly applying multiple sensing operations that would slow down all programming operations.
2Manufacturing precision
If more sensing operations are performed to verify multi-bit cells, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The system dynamically adjusts the number of sensing operations based on the verified state from the first sensing operation. When the first sensing operation confirms adequate verification (as in SLC cells), the system skips the second sensing operation, thereby maintaining programming precision when needed while maximizing programming throughput when verification is already sufficient.
Solution Approach 2:
The patent implements a skipping mechanism where the second sensing operation is omitted when the first sensing operation result indicates adequate verification. This allows the system to rush through the verification process for cells that don't require multiple sensing operations, thereby improving overall programming productivity while maintaining precision for cells that do require thorough verification.
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 reduces the overall programming time while maintaining adequate precision by skipping unnecessary sensing operations based on the initial voltage measurement, thereby enhancing the efficiency of program verify operations in non-volatile memory.
Implementation Method 1
The program verify operation may be performed, for example, by sensing the current flowing through a target cell, i.e., a cell that has been programmed
Data Source
AI summary
Provided herein may be a method for controlling program verify operations of a non-volatile memory and a corresponding circuit thereof. The method for controlling a program verify operation of a non-volatile memory, comprising: selecting a source line among source lines coupled to a plurality of planes respectively; measuring a voltage of the selected source line associated with target cells of the non-volatile memory to be verified in a first sensing operation; comparing the measured voltage of the selected source line with a reference voltage; and skipping the second sensing operation if the measured voltage of the selected source line is lower than the reference voltage.