Zener Diode Reverse Breakdown Voltage for IC Traceability
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Solution Overview
Problem
Current methods for uniquely identifying integrated circuits during fabrication and post-fabrication are inadequate, as they require additional process steps, substantial die space, and are not tamper-proof, and often rely on digital identifiers that are not easily detectable using common test equipment.
Innovation Solution
The use of Zener diodes as identifier devices, which are tested for reverse breakdown voltage to create a unique analog identifier for each integrated circuit, allowing for stable and tamper-proof identification without additional process steps or significant die space, using Automated Test Equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional process steps are used to create identifiers during fabrication, then identification capability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent utilizes natural process variations that occur during standard fabrication to create unique identifiers. Each integrated circuit develops its own characteristic Zener diode behavior based on random variations in the fabrication process, eliminating the need for additional identifier creation steps. The circuits essentially identify themselves through their inherent manufacturing variations.
Solution Approach 2:
The patent changes the measurement parameter from digital presence/absence to analog characteristic values. By measuring the continuous analog parameters of Zener diodes (such as breakdown voltage and current characteristics), the system captures the natural variations introduced during fabrication, converting manufacturing variability into useful identification data without adding process steps.
2Ease of operation
If digital identifiers are used for identification, then identification is simplified, but detectability with common test equipment is reduced
Solution Approach 1:
The patent replaces digital identification methods with analog electrical measurement. Instead of using digital codes that require specialized decoders, the system uses continuous electrical parameter measurements (current, voltage) that can be performed with standard semiconductor test equipment, making identification accessible with common tools while maintaining simplicity.
3Ease of manufacture
If natural process variations are used for identification, then additional process steps are eliminated, but measurement precision requirements increase
Solution Approach 1:
The patent measures continuous analog parameters rather than discrete digital values. By capturing the full range of analog variations in Zener diode characteristics (breakdown voltage, current ratios), the system achieves high measurement precision using standard equipment, converting the challenge of natural variations into an advantage for unique identification.
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 provides a reliable and efficient method for die-level traceability, enabling accurate identification of integrated circuits through their unique analog identifiers, facilitating root cause analysis of defects and reducing costs associated with defect resolution.
Implementation Method 1
the use of Zener diodes to provide analog identifiers for use in identifying integrated circuits
Data Source
AI summary
Devices, systems and methods for uniquely identifying integrated circuits are provided. For at least one embodiment, an identifiable integrated circuit in a lot of integrated circuits includes a plurality of identifier devices. Each of the identifier devices, when tested, returns a series of first test results that form an analog identifier for the integrated circuit. For one embodiment, the identifier devices is a Zener diode. The test results may be based on reverse breakdown voltage measurements determined prior to packaging of the integrated circuit. Later testing of the integrated circuit returns a second series of reverse breakdown voltage measurements that monotonically vary over time and temperature, as compared to the first series of test results. Such monotonical variation facilitates correlation of the first series of test results with the second series of test results and, thereby, identification of the integrated circuit.