Semiconductor Refresh Controller Redundancy Cell Malfunction
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Solution Overview
Problem
Semiconductor memory devices face malfunctions during refresh operations due to the use of redundancy cells, especially when multiple word lines are enabled, leading to data loss and reduced data retention times as the technology scales down.
Innovation Solution
A semiconductor device is designed with a refresh counter, check signal generator, redundancy checker, and refresh controller to selectively enable word lines and redundancy word lines based on the logic level of refresh addresses, ensuring proper usage of redundancy cells and preventing malfunctions during refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple word lines are enabled during refresh operation to increase refresh capacity, then refresh efficiency is improved, but malfunction risk due to redundancy cell usage increases
Solution Approach 1:
The refresh controller monitors which word lines are enabled during refresh operations and receives feedback about redundancy cell usage status. Based on this feedback, the controller dynamically adjusts the refresh operation to prevent malfunctions while maintaining high refresh capacity. The system continuously checks the state of redundancy cells and modifies subsequent refresh cycles accordingly.
Solution Approach 2:
The refresh controller dynamically changes the refresh operation parameters based on real-time conditions. When redundancy cells are detected as used, the controller adapts by adjusting which word lines are enabled in subsequent refresh cycles. This dynamic adaptation allows the system to maintain high refresh efficiency while avoiding the malfunction conditions that arise from static, fixed refresh patterns.
2Ease of manufacture
If redundancy cells are used to replace defective cells, then manufacturing yield is improved, but refresh operation malfunction risk increases
Solution Approach 1:
The system performs preliminary checks to detect when redundancy cells have been used before executing refresh operations. By identifying redundancy cell usage in advance, the refresh controller can pre-adjust the refresh pattern to avoid malfunctions. This preliminary detection and preparation prevents the malfunction issue from occurring during the actual refresh operation.
Solution Approach 2:
The refresh controller acts as an intermediary between the redundancy cell array and the refresh operation. It monitors the state of redundancy cells and mediates the refresh process by selectively enabling or disabling word lines based on redundancy cell usage status. This intermediary control layer prevents direct conflicts between redundancy cell usage and refresh operations.
3Duration of action of stationary object
If refresh operation is performed on all memory banks simultaneously, then data retention is improved, but control complexity increases
Solution Approach 1:
The refresh operation is segmented into multiple independent controllable units (word lines and memory banks). The refresh controller can selectively enable or disable specific word lines and banks based on redundancy cell usage status. This segmentation allows parallel refresh of multiple banks while maintaining simple control logic for each individual unit, avoiding the need for complex centralized control.
Solution Approach 2:
Different control strategies are applied to different local regions (word lines and memory banks) based on their specific needs. When redundancy cells are used in certain regions, the controller applies localized adjustments to those specific word lines or banks while maintaining normal operation in other regions. This local quality approach maintains data retention across all banks without requiring complex global control.
Data Source
AI summary
A semiconductor device may include a refresh counter configured to output a plurality of refresh addresses by counting a refresh signal; a check signal generator configured to generate a check signal according to a logic level of any one specific refresh address among the plurality of refresh addresses during a refresh operation, and output the check signal in response to a redundancy check pulse signal; a redundancy checker configured to store information on whether a redundancy cell was used, in response to the check signal, the redundancy check pulse signal and the plurality of refresh addresses, and output a word line control signal according to whether the redundancy cell was used; and a refresh controller configured to control a row address for selectively enabling a word line and a redundancy word line of a cell array in response to the word line control signal.