Foggy and Fine Programming for Non-Volatile Memory Threshold Voltage Control
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Solution Overview
Problem
Existing non-volatile memory devices face challenges in efficiently programming and verifying data, particularly in ensuring that memory cells reach the correct threshold voltage states during programming operations, which affects data retention and storage efficiency.
Innovation Solution
The proposed solution involves a non-volatile memory device with a foggy operation and a fine operation, each comprising specific application and verification voltage levels, where the foggy operation raises threshold voltages and the fine operation further adjusts them to precise levels, using a control logic circuit to determine completion based on predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single programming operation is used to set threshold voltage, then the programming process is simple, but the precision of threshold voltage control is insufficient
Solution Approach 1:
The programming operation is divided into two distinct segments: foggy programming operation that raises threshold voltage to a preliminary level, and fine programming operation that precisely adjusts threshold voltage to the target level. This segmentation allows each operation to be optimized for its specific function, achieving high precision without excessive overall complexity.
Solution Approach 2:
The foggy programming operation is performed as a preliminary action before the fine programming operation. This preliminary action brings the threshold voltage close to the target value, reducing the adjustment range needed in the subsequent fine programming operation and improving overall efficiency.
2Reliability
If verification voltage is set higher than target threshold voltage, then verification is more robust, but power consumption increases
Solution Approach 1:
The verification voltage level is dynamically changed based on the programming stage: a higher verification voltage is used during foggy programming verification for robustness, while a lower verification voltage matching the target threshold voltage is used during fine programming verification to reduce power consumption.
Solution Approach 2:
The verification process transitions from a static single-voltage approach to a dynamic multi-voltage approach, where verification voltage levels are adjusted according to the programming stage and requirements, optimizing both reliability and power efficiency.
Data Source
AI summary
An operating method of a non-volatile memory device comprises: performing a foggy operation applying a first application voltage to a word line and applying a first verification voltage having a same level as or a higher level than a target threshold voltage to the word line, determining whether the foggy operation is completely performed according to whether a number of memory cells each having a threshold voltage higher than the first verification voltage is equal to or greater than a first number, performing a fine operation applying a second application voltage to the word line and applying a second verification voltage having the same level as the target threshold voltage, and determining whether the fine operation is completely performed, according to whether a number of memory cells each having a threshold voltage lower than the second verification voltage is less than or equal to a second number.