Anti-fuse Circuit Rupture Screening for Impedance Stability
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Solution Overview
Problem
Conventional semiconductor memory devices with anti-fuse circuits face reliability issues due to increasing impedance over time after the rupture process, as the broken gate oxide layer of NMOS transistors is slowly restored, potentially leading to abnormal anti-fuse status detection signals.
Innovation Solution
Incorporating a sensing current supplying unit that supplies sensing current to the sensing node in response to a rupture sensing signal, allowing for a test mode operation to filter out anti-fuses that do not reach a predetermined rupture level by comparing impedance, ensuring only functional anti-fuses are used in normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anti-fuse rupture process is performed to program the anti-fuse, then the anti-fuse changes from open state to short-circuit state achieving programming function, but the impedance of the anti-fuse increases over time as the broken gate oxide layer slowly restores, leading to reliability degradation
Solution Approach 1:
The patent applies preliminary action by performing a test mode operation before normal operation to detect and filter out anti-fuses that have not achieved sufficient rupture. The test mode supplies a test current and measures voltage to identify anti-fuses with impedance below a threshold, ensuring only properly ruptured anti-fuses are used in normal operation, thus preventing future reliability issues
Solution Approach 2:
The patent implements feedback by measuring the voltage across the anti-fuse during test mode, comparing it against a threshold value, and using this information to determine whether the anti-fuse has ruptured sufficiently. This feedback mechanism allows the system to identify and exclude defective anti-fuses before they cause reliability problems in normal operation
2Reliability
If a test mode operation is implemented to filter anti-fuses with insufficient rupture, then the reliability of normal operation is improved, but the device complexity increases due to additional circuit components and operation modes
Solution Approach 1:
The patent applies universality by designing the anti-fuse circuit to perform multiple functions using the same basic components. The anti-fuse circuit can operate in both test mode (for filtering) and normal mode (for data storage), with the sense amplifier and current supply serving dual purposes in both modes, thereby reducing the need for separate dedicated test circuitry
Solution Approach 2:
The patent implements self-service by using the anti-fuse circuit's own components to perform the test and filtering function. The sense amplifier that is already part of the normal operation circuitry is reused to detect anti-fuse impedance during test mode, and the same current supply is used for both testing and normal operation, eliminating the need for external or separate test equipment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach secures operational reliability by screening out anti-fuses that may malfunction due to increased impedance over time, ensuring normal operation and maintaining the anti-fuse in a low resistivity state effectively.
Implementation Method 1
the anti-fuse is physically changed into a conductor by applying a voltage greater than a predetermined level to an insulator between electrodes, i.e., two conductors, and breaking down the insulator
Data Source
AI summary
An anti-fuse circuit includes an anti-fuse coupled to a sensing node, a driving unit configured to rupture the anti-fuse in response to a rupture enable signal, an anti-fuse status detecting unit configured to output an anti-fuse status detecting signal in response to a voltage at the sensing node corresponding to a rupture status of the anti-fuse, and a sensing current supplying unit configured to supply sensing current to the sensing node in response to a rupture sensing signal.