Non-volatile Memory Adaptive Voltage Control
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Solution Overview
Problem
Existing non-volatile semiconductor memory devices, such as EEPROM and flash memory, face inefficiencies due to the use of fixed programming, verifying, and reading voltages that do not account for variations in threshold voltage distribution caused by issues like program disturb, leading to non-optimized performance.
Innovation Solution
A non-volatile storage system that measures threshold voltage distributions for multi-level storage elements, determines customized voltage sets based on these distributions, and stores these voltages for use in write, read, and verify operations to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed programming, verifying, and reading voltages are used, then device complexity is reduced, but performance is not optimized due to threshold voltage distribution variations
Solution Approach 1:
The patent measures threshold voltage distributions before programming operations and determines optimal programming voltages in advance. This preliminary characterization allows the system to use customized voltage levels for each memory device, optimizing programming efficiency and reliability while avoiding the need for complex real-time voltage adjustment during operations.
Solution Approach 2:
The patent changes the voltage parameters (programming voltage, verify voltage, read voltage) based on the measured threshold voltage distribution of each memory device. By adjusting these electrical parameters according to actual device characteristics, the system achieves optimized performance without requiring complex structural modifications.
2Reliability
If fixed verify voltages are used, then ease of operation is improved, but errors increase due to program disturb effects
Solution Approach 1:
The patent implements a feedback mechanism where threshold voltage distributions are measured, and verify voltages are determined based on these measurements. This feedback loop ensures that verify voltages are appropriately adjusted to account for program disturb effects and other variations, reducing errors while maintaining ease of operation through automated voltage selection.
Solution Approach 2:
The verify voltage parameter is changed based on the measured threshold voltage distribution. By adjusting the verify voltage to match actual device characteristics, the system reduces verification errors caused by program disturb without requiring manual intervention.
3Reliability
If fixed read voltages are used, then device complexity is reduced, but reliability decreases due to threshold voltage distribution variations
Solution Approach 1:
The patent performs preliminary measurement of threshold voltage distributions and determines optimal read voltages before actual read operations. This advance preparation allows the system to use customized read voltages that account for device-specific variations, improving read accuracy without requiring complex real-time voltage adjustment mechanisms.
Solution Approach 2:
The read voltage parameter is adjusted based on the measured threshold voltage distribution of each memory device. By changing this electrical parameter to match actual device characteristics, the system achieves improved read reliability while keeping the overall system manageable through automated voltage determination.
Data Source
AI summary
A non-volatile memory device is accessed using voltages which are customized to the device, and/or to portions of the device, such as blocks or word lines of non-volatile storage elements. The accessing can include programming, verifying or reading. By customizing the voltages, performance can be optimized, including addressing changes in threshold voltage which are caused by program disturb. In one approach, different sets of storage elements in a memory device are programmed with random test data. A threshold voltage distribution is determined for the different sets of storage elements. A set of voltages is determined based on the threshold voltage distribution, and stored in a non-volatile storage location for subsequent use in accessing the different sets of storage elements. The set of voltages may be determined at the time of manufacture for subsequent use in accessing data by the end user.