Metal Spiral PUF Circuit Layout for Stronger Random Code Generation

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Solution Overview

Problem

Existing hardware security measures in IoT devices are insufficient to prevent unauthorized access and duplication of chips, as software-based security designs are vulnerable to hacking and physical equipment threats.

Innovation Solution

A circuit pattern with metal spiral and dummy metal spiral patterns is introduced to enhance process variation, increasing resistance range and random code generation in physically unclonable functions (PUF) by using a PUF cell array with metal and dummy metal spiral patterns arranged alternately, enhancing resistance variation and random coding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If software-based security design is used, then implementation is simple and cost-effective, but security against physical attacks and chip duplication is insufficient

Engineering Contradiction:

Improveimplementation simplicityVSAvoidsecurity against physical attacks

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces a physically unclonable function (PUF) circuit as an intermediary layer between software security and physical hardware. The PUF circuit generates unique cryptographic keys based on inherent manufacturing variations in the semiconductor structure, providing hardware-level security without requiring complex physical security measures. This mediator combines the simplicity of software implementation with the reliability of hardware security.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If traditional PUF circuits are used, then hardware security is improved, but resistance variation and random code generation capability are limited

Engineering Contradiction:

Improvehardware securityVSAvoidresistance variation range

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the physical parameters of the PUF circuit by introducing metal spiral patterns with varying geometries. The spiral patterns have different numbers of turns, radii, and line widths, which create significant resistance variations due to the skin effect and proximity effect at high frequencies. This parameter variation enhances the random code generation capability while maintaining hardware security.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses spiral patterns instead of straight lines or simple geometric shapes. The curved spiral structure increases the effective path length and creates more sensitive resistance variations due to the skin effect. The curvature of the spiral patterns amplifies the impact of manufacturing variations on resistance, thereby enhancing the randomness and uniqueness of the generated codes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Manufacturing precision

If metal spiral patterns are added to enhance resistance variation, then random code generation is improved, but circuit complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveresistance variation rangeVSAvoidcircuit pattern complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent uses metal spiral patterns that are all formed from the same metal layer and follow a consistent design rule set. Although the spirals have different geometries, they are homogeneous in terms of fabrication process, material composition, and structural characteristics. This homogeneity simplifies manufacturing while still achieving the desired resistance variation through geometric differences.

Inventive Principle:

Principle #33Homogeneity

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 increases the randomness, uniqueness, and robustness of PUF chips, making them less susceptible to read errors and environmental distortions, thereby improving hardware security in IoT devices.

Implementation Method 1

a metal spiral pattern, including multiple connected horizontal line segments extending in a horizontal direction and multiple connected vertical line segments extending in a vertical direction and with one end connected to a constant voltage and the other end connected to a ground voltage; and a dummy metal spiral pattern

Methodology Applied

Scientific EffectElectromagnetic interaction: Electromagnetic Induction

Data Source

PatentUS20250348625A1Circuit patterns for physically unclonable function and method of achieving physically unclonable function through circuit patterns

Publication Date: 2025.11.13 UNITED MICROELECTRONICS CORP

AI summary

A circuit pattern for physically unclonable function (PUF) is provided in the present invention, including a metal spiral pattern composed of multiple horizontal line segments connected with vertical line segments and a dummy metal spiral pattern composed of multiple dummy horizontal line segments connected with dummy vertical line segments, wherein the horizontal line segments and dummy horizontal line segments are adjacent and alternately arranged in a vertical direction, and the vertical line segments and dummy vertical line segments are adjacent and alternately arranged in a horizontal direction.