OTP Fuse Programming Circuit with Closed-Loop Voltage Monitoring
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Solution Overview
Problem
Existing methods for programming one-time programmable (OTP) memory fuses face challenges in achieving consistent high resistance values with minimal errors, as variations in post-trimmed resistances can lead to errors in read-out and require redundant memories or complex programming methods.
Innovation Solution
A closed-loop programming control circuit that monitors the voltage across the fuse during programming, detects a drop in voltage to trigger the end of the programming period, and includes a baking delay to ensure a well-defined void forms without refilling, thereby achieving consistent high resistance values with reduced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed programming period is used to program the fuse, then the programming process is simple and fast, but the post-trimmed resistance varies widely leading to high error rates
Solution Approach 1:
The patent implements a closed-loop feedback control system where the programming current is continuously monitored during the programming process. When the current drops below a threshold (indicating void formation), the system adjusts the programming duration by adding a baking period. This feedback mechanism ensures consistent post-trimmed resistance values while adapting to real-time fuse state changes, resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent applies preliminary action by detecting the void formation event during programming and preemptively extending the programming period with a baking phase. This preliminary detection and response prevents resistance variation before it occurs, ensuring consistent high resistance values without requiring complex post-programming adjustments or redundant memory structures.
2Manufacturing precision
If the programming current is applied for a longer duration to ensure complete fuse breakdown, then the resistance becomes more consistent, but the fuse and surrounding structures suffer more damage
Solution Approach 1:
The patent employs dynamic control of the programming process by transitioning from a fixed static programming period to a dynamic adaptive period. The programming duration is adjusted in real-time based on monitored current characteristics, extending the period only as needed to achieve void formation and desired resistance. This dynamic approach ensures consistent resistance while minimizing excessive programming time that would cause damage to surrounding structures.
3Manufacturing precision
If monitoring and control circuits are added to improve programming precision, then resistance consistency improves, but the device complexity and error rates increase
Solution Approach 1:
The patent implements a feedback control mechanism that monitors programming current characteristics and adjusts the programming duration accordingly. By detecting the void formation event through current monitoring and responding with a controlled baking period, the system achieves high programming precision and consistency. This feedback approach reduces errors by adapting to actual fuse conditions rather than relying on fixed predetermined parameters.
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
The solution ensures consistent post-trimmed resistances of ≥1 MΩ with ≤5% programming errors, minimizing damage to the fuse and surrounding structures, and adapts to different technologies and voltage variations, providing reliable and efficient programming.
Implementation Method 1
a programming current to flow through the fuse... a portion of the fuse is polysilicon at a start of a programming period and changes to amorphous silicon
Implementation Method 2
The trigger circuit is configured to receive a voltage from a fuse during programming and to generate a trigger signal upon detecting a drop in the voltage from the fuse during programming
Implementation Method 3
The delay circuit is configured to delay the trigger signal from the trigger circuit for a baking period
Data Source
AI summary
Programming a fuse for a one-time programmable (OTP) memory can require applying a programming current for a programming period to increase a resistance of the fuse. It may be desirable for the resistance to be very high. A very high resistance may be achieved by applying a high programming current to form a void in the fuse. Applying the high programming current too long after the void is formed, however, may lead to uncontrolled variations and ultimately damage. Accordingly, it may be desirable to end the programming period sometime after the void is formed but before the uncontrolled variations begin. Ideally the programming period is ended at a time at which the programming current is minimum. The disclosed circuits and method provide a means to estimate this time without requiring the complexity of sensing very low levels of programming current.