Memory Deterioration Detection Using Dual Reference Voltages
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Solution Overview
Problem
Current memory devices lack an effective method to accurately determine the type of deterioration condition, which affects their reliability, as existing techniques fail to discriminate between different deterioration states, leading to errors during data read operations.
Innovation Solution
A method involving the use of first and second reference voltages to calculate specific information about memory cells' threshold voltages, followed by a predetermined equation to determine the deterioration condition, utilizing a support vector machine algorithm to discriminate between types of deterioration based on experimentally measured data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reference voltage is used for read operations, then the operation is simple and fast, but the deterioration condition cannot be accurately determined
Solution Approach 1:
The read operation is segmented into multiple modes: a normal read mode using a first reference voltage for regular operations, and a deterioration detection mode using a second reference voltage for determining memory device health status. This segmentation allows the system to maintain simplicity during normal operation while enabling accurate deterioration detection when needed.
Solution Approach 2:
The reference voltage is made dynamic by selecting between a first reference voltage (lower value) for normal reads and a second reference voltage (higher value) for deterioration detection. The system dynamically switches between voltage levels based on the operational mode, enabling both simple normal operations and accurate deterioration determination without permanent complexity.
2Measurement precision
If multiple read operations with different reference voltages are performed, then the deterioration condition can be accurately determined, but the operation time increases
Solution Approach 1:
The system performs only the necessary read operations based on the detection need. For normal operations, only a single read with the first reference voltage is performed. For deterioration detection, an additional read with the second reference voltage is performed. This partial action approach minimizes time loss while maintaining the capability for accurate deterioration determination when required.
3Measurement precision
If the first reference voltage is set to distinguish erase state from program state, then state discrimination is accurate, but deterioration types cannot be differentiated
Solution Approach 1:
The system adds another dimension to the measurement by introducing a second reference voltage that operates at a higher level. While the first reference voltage provides one-dimensional discrimination between erase and program states, the second reference voltage adds a second dimension that enables differentiation between types of deterioration by detecting shifts in threshold voltage distributions at higher voltage levels.
Data Source
AI summary
A method is provided for determining a deterioration condition of a memory device. The method includes calculating first information corresponding to a number of bits having a first logic value from data obtained by performing a first read operation on target storage region of the memory device using a first reference voltage as a read voltage, and calculating second information corresponding to a number of bits having a second logic value from data obtained by performing a second read operation on the target storage region using a second reference voltage as the read voltage. A deterioration condition of the target storage region is determined based on the first and second information. The first reference voltage is less than a first read voltage by which an erase state of the memory device is distinguished from an adjacent program state, and the second reference voltage is higher than the first read voltage.