Memory Sub-System Threshold Voltage Modification
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Solution Overview
Problem
The existing memory sub-systems face challenges in efficiently utilizing memory dice due to varying threshold voltage windows, leading to increased costs and waste from rejecting dice that do not meet reliability standards, and affecting data retention at high temperatures.
Innovation Solution
A threshold voltage modification component adjusts the threshold voltage and voltage window of memory dice during manufacture or testing to increase the reliability margin by expanding the threshold voltage window of dice that fall below the standard, allowing for better incorporation and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory dice are manufactured with standard threshold voltage windows, then manufacturing process is simple and fast, but reliability margin is insufficient and data retention at high temperatures deteriorates
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage modification during the manufacturing or testing phase before the memory dice are deployed. The controller proactively adjusts the threshold voltage window of memory dice that fall below standard specifications, ensuring they meet reliability requirements before entering service. This prevents future reliability issues without requiring complex real-time adjustments during operation.
Solution Approach 2:
The patent directly changes the electrical parameter (threshold voltage) of memory dice to improve reliability. By modifying the threshold voltage window through controlled electrical operations, the system transforms memory dice that initially failed to meet specifications into reliable components. This parameter change approach resolves the contradiction by improving reliability margin without fundamentally changing the manufacturing process structure.
2Reliability
If memory dice with varying threshold voltage windows are accepted, then manufacturing cost is reduced and waste is minimized, but data retention at high temperatures deteriorates
Solution Approach 1:
The patent enables memory dice to self-correct their threshold voltage characteristics through controlled electrical operations. Rather than requiring manual selection or rejection during manufacturing, the system allows borderline dice to self-improve their threshold voltage windows automatically. This self-service approach maintains ease of manufacture while ensuring data retention reliability, as the memory dice themselves perform the adjustment rather than requiring complex external intervention.
Solution Approach 2:
The system implements feedback by measuring the threshold voltage window of each memory die during testing and comparing it against specification standards. Dice that fall below the threshold are identified and subjected to modification operations. This feedback loop ensures that only dice meeting reliability requirements (or capable of meeting them through modification) are accepted, resolving the contradiction between manufacturing ease and data retention reliability.
3Reliability
If strict threshold voltage window standards are enforced, then reliability margin is ensured, but manufacturing waste increases and costs increase
Solution Approach 1:
The patent applies discarding and recovering by identifying memory dice that initially fail to meet threshold voltage specifications and subjecting them to recovery operations. Instead of discarding these borderline dice as waste, the system recovers them through threshold voltage modification, transforming them into reliable components. This approach dramatically reduces manufacturing waste while maintaining reliability standards, as dice that were previously rejected are now salvaged and utilized.
4Reliability
If threshold voltage window is increased for all memory dice, then reliability margin is improved, but manufacturing time and energy consumption increase
Solution Approach 1:
The patent applies local quality by selectively applying threshold voltage modification only to memory dice that require it, rather than uniformly processing all dice. The system identifies individual dice or small groups with threshold voltage windows below specifications and applies modification operations only to those specific units. This localized approach improves reliability margin for affected dice while minimizing impact on overall manufacturing throughput, as the majority of compliant dice proceed through normal manufacturing without additional processing time.
Data Source
AI summary
A method includes determining, for a plurality of memory dice, binning information relating to quality characteristics of each of the plurality of memory dice. The method further includes performing a select gate scan to determine a first threshold voltage and a first threshold voltage window of each of the plurality of memory dice, and, based on the determined quality characteristics of each of the plurality of memory dice, perform an erase and program operation to set a second threshold voltage with a second threshold voltage window of a subset of memory dice among the plurality of memory dice where the second threshold voltage window is greater than the first threshold voltage window.