SSD Memory Module Isolation for Yield Recovery
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Solution Overview
Problem
NAND flash memory modules with defective dies are typically discarded, leading to the unnecessary disposal of functional dies and increased costs due to low yield in solid state drives.
Innovation Solution
A solid state drive system and method that isolates defective memory units within memory modules, allowing for the use of modules with one or more defective dies by utilizing switching logic to disconnect power and communication signals of defective units, thereby enabling the use of all functional dies and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a memory module with defective dies is discarded, then the reliability of the solid state drive is maintained, but the productivity and cost efficiency deteriorate due to loss of functional dies
Solution Approach 1:
The memory module is segmented into individually addressable memory units, each with separate power and communication signals. This allows the system to isolate and disable only the defective units while keeping functional units operational, thereby maintaining drive reliability while improving effective yield by utilizing all good dies in the module
Solution Approach 2:
The defective memory units are extracted from the module through logical isolation using switching logic. By removing only the problematic units from the operational configuration rather than discarding the entire module, the system maintains reliability while recovering and utilizing the remaining functional dies
2Reliability
If all dies in a memory module must be functional, then the reliability is ensured, but the cost increases due to low yield requirements
Solution Approach 1:
The system dynamically configures which memory units are active based on their functional status. Through switching logic controlled by the memory controller, the operational configuration adapts to accommodate defective units, allowing modules with lower yield to be manufactured at reduced cost while maintaining required reliability through selective unit activation
3Device complexity
If defective memory modules are discarded, then the quality control is simplified, but the loss of functional dies increases
Solution Approach 1:
The system performs preliminary testing and identification of defective memory units during manufacturing or initialization. By pre-characterizing each unit's functionality and configuring the switching logic accordingly before deployment, the system simplifies quality control while maximizing utilization of functional dies through advance isolation of defective units
Data Source
AI summary
A method and system to facilitate the usage of memory modules that have one or more defective memory dies. In one embodiment of the invention, a memory module is packaged with a number of dies and the memory module is tested and sorted according to the number of dies that pass testing. Each signal of each die in the memory module has an unique bond-out or connection point in the package of the memory module. By separating the signals of each die in the memory module, any defective die can be easily isolated and this allows a significant cost reduction in products that use a large number of dies.