Antifuse Sensing Circuit for DRAM Yield Improvement
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Solution Overview
Problem
Incorrect judgment of high or low resistance in antifuses used in DRAMs leads to wrong identification of redundant rows and columns, adversely affecting yield.
Innovation Solution
An antifuse circuit comprising a current generator and an antifuse sense unit, where the electronic device specifications are matched to improve sensing accuracy, including a voltage divider, PTAT current source, and CTAT resistor to simulate temperature and process changes, and a current mirror to stabilize gate-to-source voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the antifuse sensing circuit uses simple resistance measurement, then the circuit complexity is low, but the sensing accuracy is insufficient to correctly judge high or low resistance states
Solution Approach 1:
The patent employs copied electronic devices (transistors with identical specifications) in the sensing circuit to create matched reference paths. These copied devices replicate the electrical characteristics of the antifuse being tested, enabling accurate differential measurement that correctly distinguishes between high and low resistance states without excessive circuit complexity
Solution Approach 2:
The patent utilizes PTAT (Proportional To Absolute Temperature) and CTAT (Complementary To Absolute Temperature) current sources that dynamically adjust their output parameters based on temperature. This compensation mechanism maintains sensing accuracy across varying temperature conditions while keeping the overall circuit design manageable through systematic parameter control
2Measurement precision
If the sensing circuit does not compensate for temperature effects, then the circuit complexity is low, but the sensing accuracy deteriorates under temperature variations
Solution Approach 1:
The patent implements PTAT and CTAT current sources whose output parameters automatically change with temperature in compensating directions. The PTAT current increases with temperature while CTAT decreases, creating a balanced compensation effect that maintains sensing accuracy across temperature ranges without requiring complex external control circuits
Solution Approach 2:
The sensing circuit incorporates feedback mechanisms where the output of the sensing operation feeds back to adjust the reference currents. This feedback loop continuously compensates for temperature drift by comparing the antifuse state against temperature-adjusted references, maintaining precision while using standard circuit blocks
3Reliability
If incorrect judgment of antifuse resistance occurs, then the sensing speed is fast, but the DRAM yield is adversely affected due to wrong redundant row and column identification
Solution Approach 1:
By using copied electronic devices with matched specifications in the sensing circuit, the patent creates highly accurate reference paths that enable correct differentiation between blown and unblown antifuse states. This copying approach ensures that the sensing decision is based on reliable comparative measurements, directly improving DRAM yield through accurate redundancy mapping
Solution Approach 2:
The patent establishes equipotential reference points and matched impedance paths in the sensing circuit to eliminate measurement errors caused by circuit asymmetry. This ensures that the voltage and current distributions during sensing are balanced and accurate, preventing misjudgment of antifuse states and protecting yield
Data Source
AI summary
An antifuse circuit includes a current generator and an antifuse sense unit. The current generator has at least one electronic device. The antifuse sense unit is electrically connected to the current generator, and the antifuse sense unit has at least one copied electronic device. An electronic device specification of the at least one electronic device of the antifuse sense unit is equal to an electronic device specification of the at least one copied electronic device of the current generator. The current generator supplies a current to the antifuse sense unit that senses an antifuse.