Controller Read-Voltage History for Memory Reliability
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Solution Overview
Problem
Semiconductor memory devices face challenges in maintaining read performance due to errors in data retrieval, particularly when error correction fails, leading to inefficiencies in read operations.
Innovation Solution
A controller system that utilizes a read-history table to adjust read voltages based on previous successful operations, allowing for retry operations with different voltages to improve data retrieval accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction is performed using a fixed read voltage, then the read operation can be completed quickly, but read performance deteriorates when errors occur due to voltage drift or cell degradation
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed read voltage to a dynamic voltage selection mechanism. The read voltage is no longer static but is selected from multiple candidate voltages based on real-time conditions such as error correction outcomes and read history. This dynamic adjustment allows the system to adapt to voltage drift and cell degradation, improving reliability without significantly sacrificing read operation efficiency.
Solution Approach 2:
The patent implements parameter changes by modifying the read voltage parameter from a single fixed value to multiple candidate values stored in a read-history table. When error correction fails with the initial read voltage, the system changes to a different read voltage from the table that was successful in previous operations. This parameter variation enables the system to overcome errors caused by voltage drift or cell degradation while maintaining efficient read operations.
2Reliability
If multiple read voltages are tried sequentially when error correction fails, then read performance improves, but read operation time increases
Solution Approach 1:
The patent applies preliminary action by pre-storing multiple candidate read voltages in a read-history table during normal operations. These voltages are recorded when they successfully retrieve data under various conditions. When error correction fails, the system immediately retrieves a pre-validated voltage from the table rather than performing extensive searches or trials, thus improving data retrieval accuracy without significant time penalty.
Solution Approach 2:
The patent implements feedback by using the outcomes of error correction operations to guide subsequent read voltage selection. When error correction succeeds or fails, this feedback information is used to select an appropriate read voltage from the read-history table. The system learns from previous read operations and adjusts voltage selection based on actual performance, improving accuracy while minimizing additional read operation time.
3Reliability
If a read-history table is implemented to store successful read voltages, then read performance improves through voltage adjustment, but device complexity increases
Solution Approach 1:
The patent applies copying by creating a read-history table that stores copies of successful read voltage values from previous operations. Instead of implementing complex real-time analysis or extensive voltage sweeping, the system copies and stores validated voltage values that can be quickly retrieved and applied when needed. This copying approach improves read operation success rate while adding minimal complexity to the controller structure.
Solution Approach 2:
The patent implements discarding and recovering by selectively storing only the successful read voltages in the read-history table and discarding unsuccessful attempts. When error correction fails, the system recovers a suitable voltage from the stored successful values. This selective retention and recovery strategy improves read operation success rate while keeping the table size and overall device complexity manageable.
Data Source
AI summary
The present technology includes a method of operating a controller that controls a semiconductor memory device including a plurality of memory blocks. The method includes receiving a read request for data included in any one memory block among the plurality of memory blocks from a host, and controlling the semiconductor memory device to read data corresponding to the read request using a read-history table. The read-history table includes read voltages used for a plurality of read pass operations for the any one memory block, respectively.